3. Table of Content
Chapter 1 Cyclopentene Overview
Definition…………………………………………………………………………………………………..06
1.1 Origin and History…………………………………………………………………………………….06
1.2.1 Mechanism ……………….…………………………………………………………………………08
1.2.2 Methodology Development…………………………………………………………………………11
1.2.3 Use in total synthesis..………………………………………………………………………………14
1.2.3.1 Trost's synthesis of aphidicolin…………………………………………………………………..15
1.2.3.2 Piers' synthesis of zizaene (1979)…………………………………………………………….…15
1.2.3.3 Hudlicky's synthesis of hirstuene (1980) and isocomene (1984)……………………..……...16
1.2.3.4 Paquette's synthesis of alpha-Vetispirene (1982)……………………………………………...16
1.2.3.5 Corey's synthesis of Antheridiogen-An (1985)………………………………………………….17
1.2.3.6 Njardarson's synthesis of biotin (2007)………………………………………………………….17
1.2.3.7 Majetich's's synthesis of salviasperanol (2008)………………………………………………...18
1.3 Cyclopentene properties………………………………………………………………………………18
1.4 Method of producing cyclopentene and description ……………………………………………….18
1.4.1 Examples……………………………………………………………………………………………..24
1.4.2 Comparatives Examples…………………………………………………………………………….26
1.4.3 Brief Description of Drawing………………………………………………………………………...26
1.4.4 Background of the Invention………………………………………………………………………..26
1.4.5 Summary of the Invention…………………………………………………………………………..27
1.4.6 Claims……………………………………………………….………………………………………..28
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4. Chapter 2 Cyclopentene uses
2. 1 Cyclopenetene used in monomer synthesis of Plastic………………………………….…………31
2.2. Monomer ……………...……………..…………………………………………………….…………..31
2.1.1 Polymers ……………...……………..…………………………………………………….…………31
2.1.2 Examples of Polymers ……………...……………..………………………………….….…………31
2.1.3 How Polymers Form ……………...……………..…………………………………………………..31
2.1.4 Monomer word Derived ……………...……………..………………………………………………31
2.1.5 Natural Monomers ……………...……………..……………………………………………………32
2.1.6 Molecular Weight ……………...……………..……………………………………………………..32
2.1.7 Industrial Use ……………...……………..…………………………………………………….……32
2. 2 Plastics ……………...……………..…………………………………………………….…………….33
2. 2.1 What is Plastics ……………...……………..…………………………………………………….…33
2.2.2 How to make Plastic ……………...……………..…………………………………………………..34
2.2.3 Polymers are everywhere ……………...……………..…………………………………………….34
2.2.4 Thermoplastics and Thermosets..……………...……………..……………………………………35
2.2.5 Better catalysts improve plastics…………………………………………………...37
Chapter 3 Safety Procedures of Cyclopentene
3.1 Product Identification ……………...…………………………………………………………………..40
3.2 Physical and Chemical Properties……………………………………………………………………40
3.3 First Aid Measures……………………………………………………………………………………..40
3.4 Handling and Storage………………………………………………………………………………….41
3.5 Hazards Identification……………………………………………………………………………..…...41
3.6 Exposure Controls/Personal Protection……………………………………………………………...41
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5. 3.7 Fire Fighting Measures………………………………………………………………………………..42
3.8 Accidental Release Measures………………………………………………………………………..43
3.9 Stability and Reactivity…………………………………………………………………………………43
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7. Cyclopentene Definitions:
1. Cyclopentene is a chemical compound with the formula C5H8. It is a colorless liquid with a petrollike odor. It is one of the cycloalkenes. Cyclopentene is produced industrially in large amounts. It is
used as a monomer for synthesis of plastics, and in a number of chemical syntheses. It can be
obtained from vinylcyclopropane in the vinylcyclopropane-cyclopentene (Source Wikipedia).
2. The term cyclopenetene is used in reference to a chemical compound that is colourless with
petrol like smell. It is produced industrially in large amounts and it is mainly used as a monomer for
synthesizing plastics (Wikipedia on Ask.com)
Origins and History:
The vinylcyclopropane rearrangement or cyclopentene rearrangement is a ring expansion
reaction, converting a vinyl-substituted cyclopropane ring into a cyclopentene ring.
Intense experimental as well as computational investigations have revealed that mechanistically,
the vinylcyclopropane rearrangement can be thought of as either a diradical-mediated two-step
and/or orbital-symmetry-controlled pericyclic process. The amount by which each of the two
mechanisms is operative is highly dependent on the substrate. Due to its ability to form
cyclopentene rings the vinylcyclopropane rearrangement has served several times as a key
reaction in complex natural product synthesis.
Origins and History:
In 1959, a young research chemist with Humble Oil and Refining (Esso, now Exxon) named
Norman P. Neureiter was instructed to find new uses for the excess butadiene produced from one
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8. of the refinery processes. Discussions about carbine chemistry with one of the company's most
respectable consultants at the time, William von Eggers Doering, then a professor at Yale, led the
young Ph.D. graduate from Northwestern University to follow a recent procedure combining both,
carbenes and butadiene. In particular the procedure described the reaction of 1,3-butadiene with
carbenes generated from the action of base on chloroform or bromoform, which had been studied
previously by Doering. Neureiter then took the resulting 1,1-dichloro-2,2-dimethylcyclopropane and
under
pyrolysis
conditions
(above
400 °C)
discovered
a
rearrangement
to
4,4-
dichlorocyclopentene which today is considered to be the first thermal vinylcyclopropanecyclopentene rearrangement in history.
The corresponding all-carbon version of the reaction was independently reported by Emanuel
Vogel and Overberger & Borchert just one year after the Neureiter publication appeared.
Interestingly Doering, although actively interacting with Humble Oil and Refining - and therefore
also with Neureiter - as a consultant, in a 1963 publication stated the following : "CREDIT for
discovery that vinylcyclopropane rearranges to cyclopentene is due to Overberger and Borchert,
and Vogel et al., who appear to have developed several examples of the rearrangement
independently. "The development of further vinylcyclopropane rearrangement variants didn't take
long as demonstrated by Atkinson & Rees in 1967, Lwowski in 1968 and Paladini & Chuche in
1971.
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9. It is remarkable that the classical vinylcyclopropane rearrangement was discovered after two of its
heteroatom variants had already been reported for almost 30 years and 12 years, respectively.
Although it is believed that the vinylcylcopropane rearrangement must have occurred during
Nikolay Demyanov's preparation of vinylcyclopropane by Hofmann elimination at elevated
temperatures in 1922 the cyclopropylimine-pyrroline rearrangement by Cloke in 1929 and Wilson's
cyclopropylcarbaldehyde-2,3-dihydrofuran rearrangement in 1947 are really the only examples of
vinylcyclopropane-like rearrangements.
Mechanism:
The mechanistic discussion on whether the vinylcyclopropane rearrangement proceeds through a
diradical-mediated two-step or a fully concerted orbital-symmetry-controlled mechanism has been
going on for more than half a century. Kinetic data together with the secondary kinetic isotope
effects observed at the vinyl terminus of the vinylcyclopropane suggest a concerted mechanism
whereas product distribution indicates a stepwise-diradidal mechanism. In the 1960s, shortly after
the rearrangement was discovered, it was established that the activation energy for the
vinylcyclopropane rearrangement is around 50kcal/mol. The kinetic data obtained for this
rearrangement were consistent with a concerted mechanism where cleavage of the cyclopropyl
carbon-carbon bond was rate-limiting. Albeit a concerted mechanism seemed likely it was shortly
recognized that the activation energy to break the carbon-carbon bond in unsubstituted
cyclopropane was with 63kcal/mol exactly 13kcal/mol higher in energy than the parent activation
energy, a difference remarkably similar to the resonance energy of the allyl radical.
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10. Immediately people started to appreciate the possibility for a diradical intermediate arising from
homolytic cleavage of the weak C1-C2-cyclopropane bond under thermal conditions.
The discussion on whether the vinylcyclopropane rearrangement proceeds via a fully concerted or
a two-step, non-concerted mechanism was given further careful consideration when Woodward
and Hoffmann used the vinylcyclopropane rearrangement to exemplify [1,3]- sigmatropic concerted
alkyl shifts in 1969. They hypothesized that if a concerted mechanism was operative the
consequences of orbital-symmetry controlled factors would only allow the formation of certain
products. According to their analysis of a vinylcyclopropane substituted with three R groups the
antarafacial [1,3]-shift of bond 1,2 to C-5, with retention at C-2, leading to the ar-cyclopentene and
the suprafacial [1,3]-shift of bond 1,2 to C-5, with inversion at C-2, leading to cyclopentene are
symmetry allowed whereas the suprafacial [1,3]-shift of bond 1,2 to C-5, with retention at C-2,
leading to cyclopentene sr and the antarafacial [1,3]-shift of bond 1,2 to C-5, with inversion at C-2,
leading to the ai cyclopentene are symmetry-forbidden. It is important to note that Woodward and
Hoffmann based their analysis solely on the principles of the conservation of orbital symmetry
theory without however making any mechanistic or stereo chemical prediction.
The attention directed towards the vinylcyclopropane rearrangement by Woodward and Hoffmann
as a representative example for [1,3]-carbon shifts clearly enhanced the interest in this reaction.
Furthermore their analysis revealed potential experiments that would allow distinguishing between
a concerted or stepwise mechanism. The stereo chemical consequences of a concerted reaction
pathway on the reaction outcome suggested an experiment where one would correlate the
obtained reaction stereochemistry with the predicted reaction stereochemistry for a model
substrate. Observing the formation of ai- and sr-cyclopentene products would support the notion
that a stepwise, non-concerted mechanism is operative whereas their absence would point towards
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11. a fully concerted mechanism. As it turned out finding an appropriate substituted model substrate to
study the stereo chemical outcome of the vinylcyclopropane rearrangement was much more
challenging than initially thought since side reaction such as the homodienyl [1,5]-hydrogen shifts
and more so thermal stereo mutations tend to scramble stereochemical distinctions much faster
than rearrangements lead to the cyclopentene products.
Even though deconvolution of the complex kinetic scenarios underlying these rearrangements was
difficult there have been several studies reported where exact and explicit deconvolutions of kinetic
and stereochemical raw data to account for the stereochemical contributions arising from
competitive stereomutations was possible.
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12. Thereby rate constants for all four stereochemically distinct pathways of the vinylcyclopropane
rearrangement could be determined.
The data clearly indicated that the mechanistic preferences of the rearrangements are system
dependent. Whereas trans-vinylcyclopropanes tend to form more of the symmetry-allowed ar- and
si-cyclopentenes supportive of a concerted mechanism, the cis-vinylcyclopropanes preferentially
yield the symmetry-forbidden ai- and sr- products suggesting a more stepwise, diradical
mechanism. The influence of substituent effects on the reaction stereochemistry also becomes
apparent from the data. Substituents with increased radical stabilizing ability not only lower the
rearrangements activation energy but also reclosure of the initially formed diradical species
becomes slower relative to the rate of cyclopentene formation resulting in an overall more
concerted mechanism with less stereomutation (e.g. entry 6 & 7). In all cases though all the four
products were formed indicating that both orbital-symmetry controlled pericyclic, as well as
diradical-mediated two-step mechanisms are operative either way. The data is consistent with the
formation of biradical species on a relatively flat potential energy surface allowing for restricted
conformational flexibility before the products are formed. The amount of conformational flexibility
and therefore conformational evolution accessible to the diradical species before forming product
depends on the constitution of the potential energy surface. This notion is also supported by
computational work. One transition state with a high diradicaloid character was found. Following
the potential energy surface of the lowest energy path of the reaction it was found that a very
shallow regime allows the diradical species to undergo conformational changes and
stereoisomerization reactions with minor energetic consequences. Furthermore it was shown that
substituents can favor stereoselective pathways by destabilizing species that allow stereochemical
scrambling.
Methodology development:
Arguably the biggest drawback of the vinylcyclopropane rearrangement as a synthetic method is its
intrinsically high activation barrier resulting in very high reaction temperatures (500-600°C). Not
only do these high temperatures allow side reactions with similar activation energies, such as
homodienyl-[1,5]-hydrogen shifts, to occur but also do they significantly limit the functional groups
tolerated in the substrates. It was well recognized by the chemical community that in order for this
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13. reaction to become a useful synthetic method, hopefully applicable in complex natural product
settings at some point, some reaction development had to be done. Some of the earliest attempts
to improve the vinylcyclopropane rearrangement as a synthetic method came from the Corey group
in 1972. They found that the reaction temperature could be lowered drastically when the
cyclopropane ring contained a dithiane group. Even though the dithiane-substituted
vinylcyclopropane substrates required two synthetic steps starting from the corresponding 1,3dienes the method proved itself successful for the synthesis of a variety of substituted
cyclopentenes. The immediate rearrangement products could be easily converted to the
corresponding cyclopentenones.
Only a year later Simpson and co-workers demonstrated that also simple methoxy-substituted
vinylcyclopropanes show significantly faster reaction rates allowing the rearrangement to take
place at 220°C.
A big improvement came in the mid-1970s from Barry M. Trost's group. It was found that siloxyvinyl
cyclopropanes as well as the analogous sulfinylvinyl cyclopropanes could be used as substrates to
build interesting annulated cyclopentene structures. Albeit these reactions still required reaction
temperatures above 300°C they were able to make really useful products arising from the
annulation of cyclopentene to a present ring system.
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14. Paquette demonstrated that vinylcyclopropane rearrangements can also be mediated
photochemically. In a particularly intriguing example he was able to show that vinylcyclopropanes
embedded within a cyclooctane core can be converted to the corresponding [5-5]-fused ring
systems.
Further reaction improvement came when Hudlicky and Brown proved that vinylcyclopropane
rearrangements are amenable to transition metal catalysts. Using a Rh (I) acetate catalyst they
were able to promote rearrangements from room temperature to 80°C.
Analogous to the rate acceleration observed in the anionic-oxy-Cope rearrangement Danheiser
reported a very similar effect for vinylcyclopropane substrates bearing [alkoxy] substituents.
Another intriguing result was reported by Larsen in 1988. He was able to promote
vinylcyclopropane rearrangements with substrates such as the one shown in the reaction below at
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15. temperatures as low as -78°C. The substrates were generated in situ upon ring contracting
thiocarbonyl Diels-Alder adducts under basic conditions. This methodology allowed the formation
of numerous highly functionalized cyclopentenes in a stereoselective manner.
Another low temperature vinylcyclopropane rearrangement was obtained by the Hudlicky group.
The scope of this particular methodology is impressively broad and allows the formation of various
[5-5]- as well as [5-6]-carbon scaffolds.
Use in total synthesis:
Five-membered carbon rings are ubiquitous structural motifs in natural products. In contrast to the
larger, fully "consonant" cyclohexane scaffold cyclopentanes and their derivatives are "dissonant"
according to the Lapworth-Evans model of alternating polarities. The dissonance in polarity clearly
limits the ways by which cyclopentanes can be disconnected which become evident in the
decreased number of general methods available for making five-membered rings versus the
corresponding six-membered rings. Especially the fact that there is no Diels-Alder-equivalent for
the synthesis of five-membered rings has been bothering synthetic chemists for many decades.
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16. Consequentially, after the vinylcyclopropane rearrangement was discovered around 1960 it didn't
take long for the synthetic community to realize the potential inherent to form cyclopentenes by
means of the vinylcyclopropane rearrangement. As the vinylcyclopropane rearrangement
progressed as a methodology and the reaction conditions improved during the 1970s, first total
syntheses making use of the vinylcycopropane rearrangement started to appear around 1980. Key
figures to apply this reaction in total synthesis were Barry M. Trost, Elias J. Corey, Thomas
Hudlicky, Leo A. Paquette,
Trost's synthesis of aphidicolin (1979):
In 1979 Trost reported the synthesis of Aphidicolin using methodology around the
vinylcyclopropane rearrangement developed in their laboratory. In one of their key steps they were
able to convert a late stage siloxyvinyllcyclopropane into a cyclopentene that contained the [6-65]-fused carbon skeleton found within the natural product. They were able to convert the
rearranged product into the natural product by further manipulations.
Piers' synthesis of zizaene (1979):
Piers' synthesis of zizaene is another early example for the application of a vinylcyclopropane
rearrangement as a key disconnection.
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17. Hudlicky's synthesis of hirstuene (1980) and isocomene (1984):
Hudlicky has been one of the key figures in pushing the vinylcyclopropane rearrangements
forwards as a method and has used in multiple times in complex natural product synthesis. A
particularly elegant piece of work is the chemistry developed to access both, linear as well as
angular triquinanes starting from similar precursors. He has been able to apply this strategy to
hirsuteneHirsutene and isocomene.
Paquette's synthesis of alpha-Vetispirene (1982):
Paquette used a vinylcyclopropane rearrangement to build the spirocyclic natural product alphaVetispirene in 1982.
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18. Corey's synthesis of Antheridiogen-An (1985):
Elias J. Corey has contributed heavily to the development of the vinylcyclopropane rearrangement
as a synthetic method. In 1985, Corey and his student, Andrew G. Myers, published an impressive
synthesis of Antheridiogen-an using a Lewis-acid mediated late-stage vinylcyclopropane
rearrangement.
Njardarson's synthesis of biotin (2007):
More recently a copper-catalyzed heteroatom-vinylcyclopropane rearrangement was used to form
the tetrahydrothiophene core of biotin and the thiophene unit of Plavix respectively.
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19. Majetich's's synthesis of salviasperanol (2008):
In 2008, an acid-mediated vinylcyclopropane rearrangement was used to synthesize the natural
product salviasperanol.
Cyclopentene properties:
Nature: a colorless liquid and have 0.7720 g/cm3 density (20 °C). Melting point -135%, Boiling
Point 44.2 °C 1.4225 refractive index. A flash point of -34 ° C Dissolved in alcohol, ether, benzene,
acetone and chloroform. Do not dissolve in water. Exist in the pyrolysis oil C5 fraction (about 2%).
From cracking C5 extraction fraction obtained, or by Cyclopentene dehydrated to produce.
Industrial mainly by C5 fraction isolated from the selective hydrogenation Cyclopentadiene
obtained. Failed to polymerization can also stimulated the two olefin copolymer conjugate. Used in
various organic synthesis.
Method of producing cyclopentene:
A method of producing cyclopentene comprising the steps of depolymerizing dicyclopentadiene to
produce raw cyclopentadiene; feeding the raw cyclopentadiene to a distillation tower having an
upper part cooled to a temperature near the boiling point of the cyclopentadiene and an outlet
maintained at 35 of 40 cyclopentadiene at the top outlet and impure components having high
boiling point at the lower outlet which are removed continuously; mixing the highly pure
cyclopentadiene obtained thereby with hydrogen and reacting in a first hydrogenation reactor using
a palladium containing catalyst, then mixing the resulting product with hydrogen and reacting in a
second hydrogenation reactor with a palladium containing catalyst; cooling the resulting product
and separating the liquid phase from the gas phase and recirculating the gas phase for use in the
hydrogenation reactions.
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21. After extensive study, the inventors have discovered a method of removing substantially all
impurities of high boiling point from the raw cyclopentadiene obtained from decomposing
dicyclopentadiene, and then supplying same for hydrogenation using a palladium containing
catalyst. In other words, the present invention encompasses a method of producing cyclopentene
combining two subprocesses, one involving purifying cyclopentadiene obtained from thermal
decomposition or depolymerization of dicyclopentadiene, and another involving the hydrogenation
reaction of the purified cyclopentadiene by mixing with hydrogen and reacting in the presence of a
palladium containing catalyst.
The invention can be better understood with reference to the drawing in which raw material
containing a substantial portion of raw dicyclopentadiene may be supplied through pipe or inlet 1,
into a depolymerization or thermal decomposition reactor 2, thereby to decompose or depolymerize
the dicyclopentadiene into raw cyclopentadiene containing various impurities, such as unreacted
dicyclopentadiene, co-dimer of cyclopenten, etc, which have a high boiling point. The reactor is
maintained at 170 250 slightly higher pressure. The raw dicyclopentadiene is in gaseous state. The
raw cyclopentadiene produced by the depolymerization or decomposition is gaseous and contains
the above mentioned impurities, and is fed through pipe 3, which cools the gas somewhat, into the
midpoint 4-1 of distillation tower 4. The tower 4 comprises an upper heat exchanger 4-2 and a
lower heat exchanger 4-3 and an inlet at the midpoint between the upper and lower portions 4-1,
and also the tower has an upper outlet (not labeled) connected to pipe 6 and a lower outlet (not
labeled) connected to pipe 5. The upper part 4-2 may be filled with packing material and is rapidly
cooled to a temperature of 30 outlet is maintained at 35 material and is maintained at 40 distillation
tower acts upon the raw cyclopentadiene to separate the high boiling point impurities from the
cyclopentadiene. The high boiling point impurities or components are fractionated in the distillation
tower 4 and is removed continuously from the lower outlet 5. The gaseous cyclopentadiene is
removed continuously from the upper outlet 6, and is passed through pipe 6 and is then mixed with
a controlled stream of hydrogen gas passing through pipe 7. The ratio of hydrogen to purified
cyclopentadiene at this stage is 1 to 2, preferably 1 to 1.5 mol hydrogen per mol of
cyclopentadiene. The mixture is then supplied to reactor 8 to be selectively hydrogenated in the
presence of a palladium containing catalyst. The hydrogenation reactor 8 is at 50 preferably 70
slightly higher. A conversion rate of 90 to 98% cyclopentene from the highly purified
cyclopentadiene was obtained.
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22. The reaction product from reactor 8 is then again mixed at junction 10 with a controlled stream of
hydrogen gas passing through pipe 9 in the ratio of 1 to 20, preferably 1 to 7, mol of hydrogen to
one mol of unreacted cyclopentadiene and the unreacted cyclopentadiene contained in the
reaction product coming from reactor 8, is then selectively hydrogenated in the second
hydrogenation reactor 11, using a palladium containing catalyst. The reactor 11 is at 50 70 slightly
higher pressure.
Although shown herein to be mixed prior to hydrogenation reaction in reactors 8 and 11, the mixing
can be done within the reactors. Also, in place of the second hydrogenation reactor 11, the reaction
product of reactor 8, may be once liquified by cooling and then separated into gaseous and liquid
parts by a knock out pot. The liquid portion may then be sent to an evaporator using a dosing pump
and the evaporated gas may be mixed with a controlled stream of hydrogen gas through pipes 9
and then introduced to the second hydrogenation reactor 11.
The catalyst used in the hydrogenation reactions is a palladium containing catalyst, carried, for
example on alumina, silica or magnesium oxide and used together with iron, chromium, etc. The
same or different catalysts may be used in the different hydrogenation reactors 8 and 11.
The reaction product from reactor 11 contains only a minute amount of cyclopentadiene monomer,
about less than several hundred parts per million (ppm). It is cooled down by passing through a
cooling pipe 12 and then separated into two phases, gas and liquid, by a knock out pot 13. The
separated gases are sent via pipes 14 and are recycled through pipes 7 and 9 for use in the first
and second hydrogenation reactions. The liquid portion containing the purified cyclopentene
passes through an outlet 15 and may be stored or sent to a further distillation process for further
use or treatment.
As the distillation tower for fractionating of the raw material, although it is possible to use any type
of distillation tower, it is preferable to use one comprising an upper heat exchanger filled with
packing material and maintained at 30 at the upper side of an inlet used to feed in the raw
cyclopentadiene having impurities therein, and a lower heat. Heat exchanger located below the
inlet and filled with packing material and maintained at 40 150 gaseous state. The upper outlet is
maintained at 35 C, and more preferably 35 cyclopentadiene having various other impurities is
reacted to separate the impurities from the cyclopentadiene. The impurities have high boiling point
and are direct to the lower outlet where such impurities are continuously removed. The purified
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23. gaseous cyclopentadiene is taken out continuously from the top outlet. In this manner a
cyclopentadiene monomer of high purity, in the range over 99% is obtained in gaseous state.
Comparing the 99% purity to that degree of purity obtained by prior art methods will distinctly show
that by use of the invention an unexpected result was obtained. In U.S Plant No. 2,913,504, a
distillation column of 30 plates was used. The inlet temperature of raw cyclopentadiene was 150 38
of reboiler being 143 produced of a purity of 95.2 to 97.8%. As will be discussed hereinafter
impurities of, for example 4.8 to 2.2%, as present in the prior art cyclopentadienes, will adversely
affect the catalytic activity and lifetime of the catalyst when used in the production of cyclopentene
by hydrogenation of the impurities containing cyclopentadiene. On the other hand, the present
invention produces impurities of less than 1%, which extra degree of purity makes possible
industrial use of the process which would not have been previously possible.
This unexpected purity of cyclopentadiene which is produced by the rectifying tower of the present
invention results, it is thought, from first, retaining the cyclopentadiene in the tower for a relatively
short time, by rapid elimination of excess heat of raw material by maintaining the temperature of
the upper portion heat exchanger at 30 80 cyclopentadiene at a desired temperature; and second,
the retaining of the high boiling point components for a relatively short time by removing it
continuously from the bottom of the tower by providing a heat exchanger at the lower side of the
inlet and maintaining its temperature at a temperature higher than the boiling point of
cyclopentadiene monomer but lower than the boiling point of the impurities such as
dicyclopentadiene, such as within the range of 40.
When cyclopentadiene is partially hydrogenated to produce cyclopentene, it inevitably contains
several percent of cyclopentadiene remaining unreacted therein. However, in case cyclopentene is
used as a monomer to produce, for example, trans-polypentenamer, which is a polymer becoming
more important industrially, the content of cyclopentadiene in cyclopentene should be less than
several hundred ppm, since the existence of diolefine, especially such as cyclopentadiene, disturbs
smooth polymerization reaction of cyclopentene.
There are known various processes for purification of raw cyclopentene, such as distillation,
dimerization, and treatment with maleic acid anhydride, adsorption method, ion exchange method
and hydrogenation method. The method involving dimerization of cyclopentadiene to
dicyclopentadiene is deficient in that it is impossible to remove cyclopentadiene completely since
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24. there exists a chemical equilibrium between the monomer and the dimer. The method involving
treatment with maleic acid anhydride is also deficient in that the acid remains in the purified
cyclopentene in a small amount. The adsorption method or the ion exchange method, such as
disclosed in U.S. Plant No. 3,506,732 wherein an adsorbent of zinc oxide-silica-alumina system is
used, or Japanese Plant. No. 4963/1972 wherein an ion exchanger of basic property is used is
deficient in that it is necessary to use a large amount of absorbent or ion exchanger, compared
with the amount of cyclopentadiene to be removed and moreover there is the problem of
reactivating these materials.
Also in the art, U.S. Plant No. 3,565,963, for example, discloses a method of hydrogenating
cyclopentadiene in two stages in the presence of a nickel catalyst to obtain cyclopentene. The
method is deficient in that the nickel catalyst is poisoned by sulfur and thus requires further
treatment. Moreover the method's hydrogenation reaction is carried out at a high temperature
under pressure.
The inventors solved such difficulties as mentioned above by the two stage hydrogenation of
cyclopentadiene in the presence of palladium containing catalyst, as set forth hereinabove.
As the raw material used for conversion to cyclopentadiene, a dicyclopentadiene whose purity is
about 95% may be used in the present invention and even if the purity of dicyclopentadiene to be
used is lower than this, such as 80 to 95%, it is sufficient for the method of the present invention to
add the inventive distillation apparatus to obtain a cyclopentene of sufficiently high purity for
polymerization use.
In producing cyclopentene from dicyclopentadiene, various problems arise due to the thermal
instability of cyclopentadiene monomer. The inventive method carries out the entire process in the
gaseous system, thus eliminating these problems, since cyclopentadiene monomer is relatively
stable in the gaseous form. Moreover, the inventors have simplified the industrial plant needed to
work the process. The inventive method has produced an unexpectedly low content of unreacted
cyclopentadiene in cyclopentene, to an amount of less than several hundred ppm.
Thus, the present invention has overcome difficulties and deficiencies which previously prevented
large-scale industrial production of cyclopentene from dicyclopentadiene, and moreover, the
invention has provided a simiplified process. To summarize some of the difficulties and deficiencies
of the prior art, which have been overcome by the invention: (1) it was necessary to purify
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25. cyclopentadiene rapidly due to its thermal instability. (2) It was necessary to prevent the
dimerization or further polymerization of cyclopentadiene by protecting it from heating or
compressing after thermal decomposition of dicyclopentadiene and use of a short retention time.
(4) The selective activity of catalyst for hydrogenation must be increased to prevent the formation
of saturated compound, that is, cyclopentene, and the removal of cyclopentadiene contained in
cyclopentene as an impurity when the cyclopentene was used as a monomer for production of
polymers. (5) It was necessary to remove impurities of high boiling point, such as
dicyclopentadiene, co-dimers of cyclopentadiene, etc., which shorten the life and retard the
catalytic activity of catalysts for hydrogenation. By resolving the foregoing problems, the present
invention has made an important contribution to the art.
The invention will be further illustrated by an actual example, which is for illustrative purposes and
is not to be construed to be limiting.
1.4.1 Examples
As the thermal depolymerization apparatus 2, a tubular type reactor comprising four tubes
connected to each other was used. Each tube had a heating jacket with a heating medium and an
inner diameter of 21.6 mm φ, and a length of 1 m. When it was desired to have packing material,
such was packed only in the last one meter. The obtained results are shown in Table 1.
TABLE 1______________________________________Feed Rate of Raw Material
Degree of (purity 95%)
Temperature
Decomposition (kg/hr)
(%)
Jacket
Packing
Material__________________________________________________2.031091.6none2.031096.7
filled______________________________________
As the distillation tower 4, there was used one comprising an upper heat exchanger 4-2 situated at
the upper side of inlet 4-1 into which the raw material comprising cyclopentadiene was fed, and
having pipes whose dimension were 2 cm of diameter and 30 cm of length, filled with packing
material, and maintained at 50 lower heat exchanger 4-3 situated at the lower side of inlet 4-1,
having 7 pipes whose dimensions were 2 cm diameter and 30 cm length, filled with packing
material and maintained at 100 The high boiler component fractionated in the tower was
continuously removed from the bottom 5 of the tower. The raw material cyclopentadiene obtained
24
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26. from the depolymerization reactor 2 was introduced continuously in a gaseous state. The obtained
results are shown in Table 2.
TABLE2____________________________________________________High boiling Cyclopenta
High Boiling Cyclopenta-Feed Amount point compon-diene at point compon-diene at top Amount
removed at inlet end at inlet inlet end at top outlet from bottom(kg/hr) (%)(%) outlet (%)(%)
(kg/hr)________________________________________________________2.08.490.90.299.0
0.32.03.395.90.199.10.2___________________________________________________________
As the hydrogenation reaction vessels 8, 11, a heat exchanger type reactor comprising 20 tubes
whose dimensions were 1.8 cm diameter, was used. The outside temperature was 120 ml at the
first step of hydrogenation and 17 ml at the second step of hydrogenation, such amount being for
each reaction tube. The reaction times of gas were 1.0 sec and 1.3 sec respectively. The results
are shown in Table 3.
TABLE 3________________________First step of hydrogenation High Boiling Pt.Feed CycloCyclo-Cyclopen-Components, and at inletH.sub.2 /cyclo-pentane pentenetadiene other C.sub.5,
C.sub.6
im-(kg/hr)
pentadiene
(%)
(%)
(%)
purities
(%)________________________________________________________1.81.1.690.04.4
1.0_____________________________________________Second
of
hydrogenation
High Boiling Pt. Cyclo-Cyclo-Cyclopen-Components, and H.sub.2 /cyclo-pentane
pentene
tadiene other C.sub.5, C.sub.6 im-pentadiene (%)
(%)
step
(%)
purities (%) 2.4
5.49.3.61301.03.06.093.070
1.0_____________________________________________________________________
The catalysts used in the Example were prepared by the following method. After immersing a
magnesium oxide whose surface area was 1 m.sup.2 /g, into a 3.5% aqueous solution of
hydrochloric acid containing palladium chloride and ferrous chloride, reduction of metallic ions
contained in the magnesium oxide was carried out for 2 hours using an aqueous solution
containing 10% hydrazine and 10% caustic soda and the product was washed with water until the
chloride ion did not exist in the filtrate and dried at 150 carried on magnesium oxide contained
0.48% palladium and 0.32% iron.
1.4.2 Comparative Example
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27. In the first step of hydrogenation, a cyclopentadiene whose purity was 95.2% and which had 4.0%
of high boiling point components was used as raw material. The experimental results are shown
below in Table 4, using the above conditions. The life time of the catalyst was also decreased to 12
hours.
TABLE 4_______________________________________________High Boiling Pt.Feed at CycloCyclo-Cyclopent-component andinletH.sub.2 /cyclo-pentane pentene adiene
C.sub.5,
C.sub.6,
im-(kg/hr)
pentadiene
(%)
(%)
(%)______________________________________________________1.81.1
other
(%)
purities
9.077.1
9.1
4.8_____________________________________________________________________
The foregoing description is for purposes of illustrating the principles of the invention. Numerous
other variations and modifications thereof would be apparent to the worker skilled in the art. All
such variations and modifications are to be considered to be within the spirit and scope of the
invention.
1.4.3 Brief Description of Drawing:
The single FIGURE depicts an illustrative apparatus in which the method of the invention may be
practiced.
1.4.4 Background of the Invention:
The present invention relates to a method of producing cyclopentene.
Cyclopentene is useful for example, as a raw material for producing cyclic aldehydes, alcohols and
chlorinated compounds, and also as fuel. Recently cyclopentene has been used as a monomer
which is polymerized to a high molecular weight polymer. However, the amount of cyclopentene
available on the commercial market is so small and the cost thereof is so expensive that use
thereof in industrial quantities is unrealistic. There are other reasons for its lack of widespread
industrial use. For example, there have been many difficulties encountered in the production of
cyclopentene such as during thermal depolymerization of dicyclopentadiene, during selective
hydrogenation of cyclopentadiene monomer and during purification of hydrogenated cyclopentene.
There is yet no known method which combines these processes into a smooth and economical
procedure to produce substantially pure cyclopentene from dicyclopentadiene.
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28. To combine thermal decomposition of dicyclopentadiene and hydrogenation of cyclopentadiene,
many problems arise due to the thermal instability of cyclopentadiene monomer. Accordingly, after
thermal decomposition of dicyclopentadiene, it is necessary to send the diene monomer to a
hydrogenation zone as soon as possible after a quick purification of the monomer. Moreover to
prevent dimerization of the monomer, it is necessary to prevent exposure thereof to pressure or to
heat before the hydrogenation.
One of the important problems to be solved in the hydrogenation of cyclopentadiene is the
decrease of catalytic activity and concurrent decrease of catalytic life time by the adsorption of
impurities of high boiling point contained in cyclopentadiene, such as dicyclopentadiene, co-dimers
of cyclopentadiene and isoprene or pentadiene, etc.
1.4.5 Summary of the Invention:
An object of the invention is to eliminate the deficiencies and disadvantages of the prior art
methods. Another object of the invention is to provide a process which combines the
depolymerization of dicyclopentadiene and purification of the cyclopentadiene produced thereby
and the hydrogenation in at least one step thereby to produce a highly pure cyclopentene. A further
object of the invention is to reduce the unwanted reduction of catalytic activity and life time
resulting from the presence of unwanted impurities in the cyclopentadiene.
The foregoing and other objects of the invention are attained in a method of producing
cyclopentene, comprising the steps of feeding raw dicyclopentadiene to a thermal reactor for
depolymerization at 170 to 400 substantially ordinary atmospheric pressure, into cyclopentadiene;
then feeding the raw cyclopentadiene to the middle part of a distillation tower having an upper part
at 30 the top thereof at 35 45 produce highly pure, over 99%, cyclopentadiene in gaseous form
through the upper outlet, and at the lower part outlet higher boiling point components which are
continuously drained off; and then, feeding the highly pure cyclopentadiene to a first hydrogenation
chamber wherein hydrogen gas is reacted therewith in the ratio of 1 to 2 mol, preferably 1 to 1.5,
mol hydrogen per 1 mol of cyclopentadiene, in the presence of a palladium containing catalyst
thereby to produce a conversion rate of 90 to 98%; and thereafter feeding the unreacted
cyclopentadiene to a second hydrogenation chamber wherein 1 to 20, preferably 1 to 7, mol of
hydrogen is employed per mol of unreacted cyclopentadiene in the presence of a palladium
containing catalyst, and thereafter cooling the resulting product, separating the liquid and gas
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29. portions and recirculating the gas portion for use in the hydrogenation steps. The hydrogenation
reaction temperature is 50 in substantially ordinary atmospheric pressure.
A feature of the invention is the use of a distillation tower having an upper part at 30 35 lower part
at 40 by supplying same to the midpoint between the upper and lower parts and having high boiling
point impurities removed continuously from the lower part and removing gaseous high purity
cyclopentadiene from the upper outlet after fractionating in the tower.
A further feature of the invention is the use of the purified cyclopentadiene as raw material for use
in hydrogenation with hydrogen in a mol ratio of 1 to 2 mol, preferably 1 to 1.5 mol, hydrogen to 1
mol cyclopentadiene in a first hydrogenation reactor at 50 200 substantially ordinary atmospheric
pressure in the presence of a palladium containing catalyst.
Another feature of the invention is the use of a second hydrogenation reactor immediately after the
first hydrogenation reactor wherein unreacted cyclopentadiene is reacted with hydrogen mixed in
the ratio of 1 to 20, preferably 1 to 7, mol of hydrogen and 1 mole of unreacted cyclopentadiene in
the presence of a palladium containing catalyst, and the subsequent cooling of the resulting
product and the separation of the liquid and gas parts with the gaseous part being recirculated for
use in the first and second hydrogenation reactors. Another feature is the use of a palladium
containing catalyst carried on alumina, silica or magnesium oxide together with use of iron or
chromium.
1.4.6 Claims:
What is claimed is:
1. A method of producing cyclopentene, comprising the steps of A. thermal decomposition or
depolymerization of dicyclopentadiene in a gaseous state at 170 to 400 atmospheric pressure to
produce cyclopentadiene and other high boiling point impurities;
B. Feeding the raw cyclopentadiene and impurities produced in step (A) into a two part distillation
tower, the upper part being maintained at 30 150 maintained at 35 purity of 99% or more is
continuously removed from said top outlet, and said high boiling point impurities are removed
continuously from a lower part outlet of said tower;
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30. C. Reacting the purified cyclopentadiene of step (B) with hydrogen gas in the ratio of 1 to 1.5 mol
hydrogen to 1 mol cyclopentadiene, in the presence of a palladium catalyst on a carrier and at a
temperature of 50 pressure thereby to produce a conversion ratio of 90 to 98% cyclopentene,
remainder unreacted cyclopentadiene;
D. Reacting the unreacted cyclopentadiene of step (C) with hydrogen gas in the mol ratio of 1 to 7
mol hydrogen to 1 mole of unreacted cyclopentadiene, in the presence of a palladium containing
catalyst, at a temperature of 50 atmospheric pressure, thereby to produce cyclopentene; and
E. Cooling the resulting product of step (D), and separating the liquid part from the gaseous part
and recirculating the gaseous part to steps (C) and (D) above.
2. The method of claim 1, wherein said depolymerization or decomposition temperature is 250
outlet is 35 reaction of steps (C) and (D) is 70
3. The method of claim 1, wherein said palladium containing catalyst comprises palladium and iron
or chromium carried on a carrier of alumina, silica or magnesium oxide.
4. Process of purifying cyclopentadiene comprising the steps of feeding raw gaseous material
containing cyclopentadiene and impurities of high boiling point to the middle part of a distilling
tower having an upper heat exchanger, an upper outlet, a middle part, a lower heat exchanger, and
a lower outlet, said upper heat exchanger maintained at 30 80 and said lower heat exchanger
maintained at 40 to 150 substantially pure cyclopentadiene of over 99% purity is removed
continuously from said upper outlet in gaseous form, and said higher boiling point impurities is
removed continuously from said lower outlet.
5. The process of claim 4, wherein said upper outlet is maintained at 35
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32. 2.1 Cyclopentene Uses: It’s used as a monomer for synthesis of plastics. Further details
as follow.
2. 1.0 Monomer
Monomers are the building blocks of more complex molecules, called polymers. Polymers consist
of repeating molecular units which usually are joined by covalent bonds. Here is a closer look at
the chemistry of monomers and polymers. Monomers are small molecules which may be joined
together in a repeating fashion to form more complex molecules called polymers.
2.1.1 Polymers
A polymer may be a natural or synthetic macromolecule comprised of repeating units of a smaller
molecule (monomers). While many people use the term 'polymer' and 'plastic' interchangeably,
polymers are a much larger class of molecules which includes plastics, plus many other materials,
such as cellulose, amber, and natural rubber.
2.1.2 Examples of Polymers
Examples of polymers include plastics such as polyethylene, silicones such as silly putty,
biopolymers such as cellulose and DNA, natural polymers such as rubber and shellac, and many
other important macromolecules.
2.1.3 How Polymers Form
Polymerization is the process of covalently bonding the smaller monomers into the polymer. During
polymerization, chemical groups are lost from the monomers so that they may join together. In the
case of biopolymers, this is a dehydration reaction in which water is formed.
2.1.4 Monomer word Derived: A monomer, pronouced mŏn'ə-mər, or MON-uh-mer, (from
Greek mono "one" and meros "part") is a molecule that may bind chemically to other molecules to
form a polymer.[1][2] The term "monomeric protein" may also be used to describe one of the proteins
making up a multi protein complex. The most common natural monomer is glucose, which is linked
by glycosidic bonds into polymers such as cellulose and starch, and is over 77% of the mass of all
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33. plant matter. Most often the term monomer refers to the organic molecules which form synthetic
polymers, such as, for example, vinyl chloride, which is used to produce the polymer polyvinyl
chloride (PVC).
2.1.5 Natural Monomers
Amino acids are natural monomers that polymerize at ribosomes to form proteins. Nucleotides,
monomers found in the cell nucleus, polymerize to form nucleic acids – DNA and RNA. Glucose
monomers can polymerize to form starches, glycogen or cellulose; xylose monomers can
polymerise to form xylan. In all these cases, a hydrogen atom and a hydroxyl (-OH) group are lost
to form H2O, and an oxygen atom links each monomer unit. Due to the formation of water as one of
the products, these reactions are known as dehydration. Isoprene is a natural monomer and
polymerizes to form natural rubber, most often cis-1,4-polyisoprene, but also trans-1,4polyisoprene.
2.1.6 Molecular Weight
The lower molecular weight compounds built from monomers are also referred to as dimers,
trimers, tetramers, pentamers, octamers, 20-mers, etc. if they have 2, 3, 4, 5, 8, or 20 monomer
units, respectively. Any number of these monomer units may be indicated by the appropriate Greek
prefix; e.g. a decamer is formed from 10 monomers. Larger numbers are often stated in English or
numbers instead of Greek. Molecules made of a small number of monomer units, up to a few
dozen, are called oligomers.
2.1.7 Industrial Use
Considering the current tight monomers market, particularly in propylene, and the benefits of
membrane-based recovery processes, major polyolefin producers around the world already employ
them in new state-of-the-art plants. In order to enhance the competitiveness of older plants, the
use of a recovery solution is becoming mandatory.
2. 2 Plastics
Look around you, and chances are high that a variety of the things you can see are made of
plastics. There are hard plastics and soft plastics, clear ones and colorful ones, and plastics that
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34. look like leather, wood, or metal. Developed during the twentieth century, plastics have changed
the world.
All plastics were soft and moldable during their production - that's why they're called plastics. The
Greek word plasticós means "to mold." You can form nearly any object out of plastics from bristles
on toothbrushes to bulletproof vests to fibers for making textiles for clothes. Soon, tiny plastic
projectiles may be used as carriers of vaccine, making it possible to swallow the vaccine instead of
getting an injection!
2. 2.1 What is Plastics?
Plastics are a synthetic material, which means that they are artificial, or manufactured. Synthesis
means that "something is put together," and synthetic materials are made of building blocks that
are put together in factories.
The building blocks for making plastics are small organic molecules - molecules that contain
carbon along with other substances. They generally come from oil (petroleum) or natural gas, but
they can also come from other organic materials such as wood fibers, corn, or banana peels! Each
of these small molecules is known as a monomer ("one part") because it's capable of joining with
other monomers to form very long molecule chains called polymers ("many parts") during a
chemical reaction called polymerization. To visualize this, think of a single paper clip as a
monomer, and all the paper clips in a box chained together as a polymer.
1. Crude oil, the unprocessed oil that comes out of the ground, contains hundreds of different
hydrocarbons, as well as small amounts of other materials. The job of an oil refinery is to
separate these materials and also to break down (or "crack) large hydrocarbons into
smaller
ones.
2. A petrochemical plant receives refined oil containing the small monomers they need and
creates
polymers
through
chemical
reactions.
3. A plastics factory buys the end products of a petrochemical plant - polymers in the form
of resins - introduces additives to modify or obtain desirable properties, then molds or
otherwise forms the final plastic products.
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35. 2.2.2 How to make Plastic: First, find a suitable molecule. One such molecule is the
ethylene monomer, the starting point for a variety of plastics. Ethylene is a small hydrocarbon
consisting of four hydrogen atoms and two carbon atoms.
Polymerization is often started by combining the monomers through the use of a catalyst - a
substance that aids a chemical reaction without undergoing any permanent chemical change itself.
During the chemical reaction, hundreds or thousands of monomers combine to form a polymer
chain, and millions of polymer chains are formed at the same time. The mass of polymers that
results is known as a resin. Resins are sold to plastics factories, usually in the form of powder, tiny
granules, or pellets. The plastics manufacturer adds coloring agents and other additives that
modify the properties of the material for the intended product. Finally, the resin is formed into the
body of a cell phone, fibers for a sweater, or one of a myriad of other plastic products.
When you polymerize ethylene you get a polyethylene resin. There are a number of polyethylene
resins families that differ by such properties as density and molecular weight, and they can be
made into a huge variety of plastic products. One of the most common is the plastic grocery bag.
Polyethylene is made from just ethylene monomers - but it's also possible to create polymers from
two or more different monomers. You can make hundreds of different polymers depending on
which monomers and catalysts you use.
2.2.3 Polymers are everywhere
Plastics are polymers, but polymers don't have to be plastics. The way plastics are made is actually
a way of imitating nature, which has created a huge number of polymers. Cellulose, the basic
component of plant cell walls is a polymer, and so are all the proteins produced in your body and
the proteins you eat. Another famous example of a polymer is DNA - the long molecule in the
nuclei of your cells that carries all the genetic information about you.
People have been using natural polymers, including silk, wool, cotton, wood, and leather for
centuries. These products inspired chemists to try to create synthetic counterparts, which they
have done with amazing success.
2.2.4 Thermoplastics and Thermosets
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36. Plastics are classified into two categories according to what happens to them when they're heated
to high temperatures. Thermoplastics keep their plastic properties: They melt when heated, and
then harden again when cooled. Thermosets, on the other hand, are permanently "set" once
they're initially formed and can't be melted. If they're exposed to enough heat, they'll crack or
become charred.
80% of the plastics produced are thermoplastics and of these Polyethylene, Polypropylene,
Polystyrene and Polyvinylchoride (PVC) are the most commonly used (70%).
Thermoplastics
Thermosets
Plastics that can be reshaped
Plastics that can't be reshaped
When ice is heated, it melts. When a
Just as a raw egg has the potential to
thermoplastic object is heated, it melts
become a boiled egg, a fried egg, and
as well.
so on, thermosetting polymers have
Analogies
the potential to become all sorts of
different objects.
The melted ice can be formed into a
new shape, and it will keep that shape
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37. when it's cooled. Similarly, a melted
thermoplastic object can be formed
into a different shape, and it will keep
Once an egg has been boiled,
however, you can't make it into a fried
that new shape when it's cooled.
egg. In the same way, once a
thermosetting plastic object has been
formed, it can't be remade into a
different object.
Reasons
for
the
reactions
when
heated
linear
The linear chains are cross linked -
polymer chains that are only weakly
strongly chemically bonded. This
chemically bonded, or connected, to
prevents a thermoplastic object from
each other. When a thermoplastic
being melted and reformed.
Thermoplastics
have
long,
object is heated, these bonds are
easily broken, which makes the
polymers able to glide past each other
like
strands
of
freshly
cooked
spaghetti. That's why thermoplastics
can readily be remolded.
The
weak
bonds
between
the
polymers reform when the plastic
object is cooled, which enable it to
keep its new shape.
How
The most common method for making
plastic
plastics is molding. To make a
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Thermosets are produced in two steps:
Prepared by Waqas Akram Muhammad
38. objects
thermoplastic object, plastic granules
are
known as resin are forced into a mold
formed
under high heat and pressure. When
1. Linear polymers are formed.
the material has cooled down, the
mold is opened and the plastic object
is complete. When making plastic
fibers, the molten resin is sprayed
through a strainer with tiny holes.
2. The linear polymers are forced into
a mold where "curing" takes place.
This may involve heating, pressure,
and the addition of catalysts. During
this
process,
a
cross-linked
or
networked structure forms, creating a
permanently hard object that is no
longer meltable or moldable.
Uses
There is a huge range of uses
Thermosets are good to use for things
including plastic wrap, food containers,
that will be warmed up such as
lighting panels, garden hoses, and the
spatulas and other kitchen tools.
constantly encountered plastic bag.
They're also used in glues, varnishes,
and in electronic components such as
circuit boards.
Recycling
Thermoplastics are easy to recycle
Thermosets are hard to recycle, but
since they can be melted and
today there are methods of crushing
reshaped into other products. For
the objects into a fine powder form for
example, a plastic bottle that contained
use as fillers in reinforced thermosets.
a soft drink could be reformed into the
fibres of a fleece jacket.
2.2.5 Better catalysts improve plastics
For most applications, the ideal polymer is a long, straight chain with a highly regular molecular
structure. Early synthetic polymers, however, often exhibited odd little branches and other
irregularities. In the 1950s, German chemist Karl Ziegler (1898–1973) discovered that an entirely
different type of catalyst - a combination of aluminum compounds with other metallic compounds could solve some of these annoying problems and increase the length of a polymer chain,
producing superior plastics. Ziegler became a wealthy man as a result of patents for plastics such
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39. as high density polyethylene (HDPE), which is used to manufacture a variety of products such as
bottles or pipe.
Polymers often have short side chains, which can occur on either side of the main chain. If side
branches occur randomly to the left or right, the polymer has an irregular structure. Italian chemist
Giulio Natta (1903–1979) discovered that some Ziegler catalysts led to a uniform structure in which
all the side branches are on the same side. This structure results in stiffer and tougher plastics that
are also lightweight, which proved to be of significant economic importance, especially for
polypropylene. Almost immediately, new and better plastic products were produced. For their
innovative work in the polymerization of plastics, Karl Ziegler and Giulio Natta shared the Nobel
Prize in Chemistry in 1963. Today, Ziegler-Natta catalysts are used throughout the world to
produce a variety of polymers.
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40. Chapter 3 Safety Procedures of Cyclopentene
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41. 3.1 Product Identification:
Product Name:
Cyclopentene
Formula:
c5h8
Formula Wt:
68.12
Case no.:
00142-29-0
Niosh/Rtecs no.: Gy5950000
Product Codes:
G101
3.2 Physical and Chemical Properties:
Physical State: Clear liquid
Appearance: clear, colorless
Odor: None reported.
PH: Not available.
Vapor Pressure: 1.2 mbar @ 50 C
Vapor Density: 2.3
Evaporation Rate: Not available.
Viscosity: Not available.
Boiling Point: 44 deg C @ 760.00mm Hg
Freezing/Melting Point:-94 deg C
Decomposition Temperature: Not available.
Solubility: Insoluble.
Specific Gravity/Density:.7740g/cm3
Molecular Formula: C5H8
Molecular Weight: 68.11
3.3 First Aid Measures
Eyes: Flush eyes with plenty of water for at least 15 minutes, occasionally lifting the upper and
lower
eyelids.
Get
medical
aid.
Skin: Get medical aid. Flush skin with plenty of water for at least 15 minutes while removing
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42. contaminated
clothing
and
shoes.
Wash
clothing
before
reuse.
Ingestion: Never give anything by mouth to an unconscious person. Get medical aid. Do NOT
induce vomiting. If conscious and alert, rinse mouth and drink 2-4 cupfuls of milk or water.
Inhalation: Get medical aid immediately. Remove from exposure and move to fresh air
immediately. If not breathing, give artificial respiration. If breathing is difficult, give oxygen.
Notes to Physician: Treat symptomatically and supportively.
3.4 Handling and Storage
Handling: Wash thoroughly after handling. Use only in a well-ventilated area.
Ground and bond containers when transferring material. Avoid contact with eyes,
skin, and clothing. Empty containers retain product residue, (liquid and/or vapor),
and can be dangerous. Keep container tightly closed. Keep away from heat, sparks
and flame. Avoid ingestion and inhalation. Do not pressurize, cut, weld, braze,
solder, drill, grind, or expose empty containers to heat, sparks or open flames.
Storage: Keep away from heat, sparks, and flame. Keep away from sources of
ignition. Store in a tightly closed container. Store in a cool, dry, well-ventilated area
away from incompatible substances. Flammables-area. Refrigerator/flammables.
3.5 Hazards Identification
According to Regulation (EC) No1272/2008
Flammable liquids (Category 2)
Acute toxicity, Dermal (Category 4)
Acute toxicity, Oral (Category 4)
Skin irritation (Category 2)
Eye irritation (Category 2)
Specific target organ toxicity - single exposure (Category 3)
Aspiration hazard (Category 1)
Highly flammable. It is Harmful in contact with skin and if swallowed. Cyclopentene Irritating to
eyes, respiratory and skin system. Harmful: may cause lung damage if swallowed
3.6 Exposure Controls/Personal Protection
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43. Engineering Controls: Use adequate ventilation to keep airborne concentrations low. Use
process enclosure, local exhaust ventilation, or other engineering controls to control airborne
levels.
Exposure Limits
Chemical Name
ACGIH
Cyclopentene
NIOSH
none listed
OSHA - Final PELs
none listed
none listed
OSHA Vacated PELs: Cyclopentene: No OSHA Vacated PELs are listed for this chemical.
Personal
Protective
Equipment
Eyes: Wear appropriate protective eyeglasses or chemical safety goggles as described by OSHA's
eye and face protection regulations in 29 CFR 1910.133 or European Standard EN166.
Skin:
Wear
appropriate
protective
gloves
to
prevent
skin
exposure.
Clothing: Wear a chemical apron. Wear appropriate protective clothing to prevent skin exposure.
Respirators: Wear a NIOSH/MSHA or European Standard EN 149 approved full-face piece airline
respirator in the positive pressure mode with emergency escape provisions. Follow the OSHA
respirator regulations found in 29 CFR 1910.134 or European Standard EN 149. Use a
NIOSH/MSHA or European Standard EN 149 approved respirator if exposure limits are exceeded
or if irritation or other symptoms are experienced.
3.7 Fire Fighting Measures
General Information: As in any fire, wear a self-contained breathing apparatus in pressuredemand, MSHA/NIOSH (approved or equivalent), and full protective gear. Vapors may form an
explosive mixture with air. Vapors can travel to a source of ignition and flash back. Use water spray
to keep fire-exposed containers cool. Containers may explode in the heat of a fire. Liquid will float
and may reignite on the surface of water. Flammable liquid and vapor. Vapors may be heavier than
air. They can spread along the ground and collect in low or confined areas. Will be easily ignited by
heat,
Extinguishing Media: For small fires, use dry chemical, carbon dioxide, water spray or alcoholresistant foam. For large fires, use water spray, fog, or alcohol-resistant foam. Use water spray to
cool fire-exposed containers. Water may be ineffective. Do NOT use straight streams of water.
Flash Point: -29 deg C ( -20.20 deg F) Auto ignition Temperature: 395 deg C ( 743.00 deg F)
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44. Explosion Limits, Lower:1.50 vol % Upper: .00 vol % NFPA Rating: 1 - health, 3 - flammability,
1 – instability
3.8 Accidental Release Measures
Spills/Leaks: Absorb spill with inert material (e.g. vermiculite, sand or earth), then place in suitable
container. Clean up spills immediately, observing precautions in the Protective Equipment section.
Remove all sources of ignition. Use a spark-proof tool. Provide ventilation. A vapor suppressing
foam may be used to reduce vapors.
3.9 Stability and Reactivity
Chemical
Stability:
Stable
under
normal
temperatures
and
pressures.
Conditions to Avoid: Incompatible materials, ignition sources, excess heat, strong oxidants.
Hazardous Decomposition Products: Carbon monoxide, carbon monoxide, carbon dioxide.
Hazardous Polymerization: Has not been reported.
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