Introduction to the Alkylation Unit in the Petroleum Refining Technology

1. PETROLEUM REFINING TECHNOLOGY
CHE441
PRESENTATION ON: ALKYLATION UNIT
BY
GROUP 9
DEPARTMENT OF CHEMICAL ENGINEERING
400 LEVEL
6TH FEBRUARY, 2013

3. ALKYLATION
The addition of an alkyl group to any compound is an alkylation reaction but in
petroleum refining terminology the term alkylation is used for the reaction of low
molecular weight olefins with an isoparaffin to form higher molecular weight
isoparaffins.
ALKYLATION UNIT
It is simply the unit in the petroleum refining process where alkylation take place.

4. LEARNING OUTCOMES
1. ALKYLATION/ ALKYLATION UNIT
2. ALKYLATION REACTIONS
3. PROCESS VARIABLES
4. ALKYLATION FEEDSTOCKS
5. ALKYLATION PRODUCTS
6. CATALYSTS
7. HYDROLUORIC ACID ALKYLATION PROCESSES
-Philips Process
-UOP
8. SULPHURIC ACID ALKYLATION PROCESSES
-Auto Refrigeration Process
-Effluent Refrigeration Process
9. COMPARISON OF PROCESSES
10. ALKYLATION YIELDS AND COST
11. HAZARDS AND SAFETY MEASURES

5. ALKYLATION REACTIONS
• The principal reactions which occur in alkylation are the
combinations of olefins with isoparaffins as follows:
• The first step is the addition of a proton to the olefin to form a
t-butyl cation.

6. This reaction with sulfuric acid results in the production of alkyl
sulfates. Occasionally alkyl sulfates are called esters. Propylene
tends to form much more stable alkyl sulfates than either C4 or
C5 olefins.
With either 1-butene or 2-butene, the sec-butyl cation formed
may isomerize via methyl shift to
give a more stable t-butyl cation.

7. These initiation reactions are required to generate
a high level of ions but become less important at
steady state. Typically, this can be observed as a
higher rate of acid consumption initially when
using fresh acid.
The t-butyl cation is then added to an olefin to
give the corresponding C8 carbocation:

8. These C8 carbocations may isomerize via
hydride transfer and methyl shifts to form
more stable cations…

10. Then the C8 cations undergo rapid hydride transfer as
isobutane, or other species, regenerates the t-butyl
cation to perpetuate the chain sequence…
Unfortunately, these are not the only reactions occurring
during alkylation. There are a number of secondary
reactions that, in general, tend to reduce the quality of
the alkylate.

11. PROCESS VARIABLE OF ALKYLATION
ALKYLATION PROCESS
Sulfuric acid process
Hydrofluoric acid process
ESSENTIAL PROCESS VARIABLE OF ALKYLATION
Reaction Temperature
Acid Strength
Isobutane Concentration
Reactor Pressure
Olefin Space Velocity

12. PROCESS VARIABLES
The most important process variables are reaction temperature, acid strength,
isobutane concentration, and olefin space velocity. Changes in these variables
affect both product quality and yield.
Reaction temperature has a greater effect in sulfuric acid processes than in those using
hydrofluoric acid. Low temperatures mean higher quality and the effect of changing sulfuric
acid reactor temperature from 25 to 55°F (4 to 13°C) is to decrease product octane from one
to three numbers depending upon the efficiency of mixing in the reactor. In hydrofluoric acid
alkylation, increasing the reactor temperature from 60 to 125°F (16 to 52°C) degrades the
alkylate quality about three octane numbers [16]. In sulfuric acid alkylation, low
temperatures cause the acid viscosity to become so great that good mixing of the reactants
and subsequent separation of the emulsion is difficult. At temperatures above 70°F (21°C),
polymerization of the olefins becomes significant and yields are decreased. For these reasons
the normal sulfuric acid reactor temperature is from 40 to 50°F (5 to 10°C) with a maximum
of 70°F (21°C) and a minimum of 30°F (1°C).
For hydrofluoric acid alkylation, temperature is less significant and reactor
temperatures are usually in the range of 70 to 100°F (21 to 38°C).

13. At temperatures above 70°F (21°C), polymerization of the olefins becomes significant and
yields are decreased. For these reasons the normal sulfuric acid reactor temperature is from 40
to 50°F (5 to 10°C) with a maximum of 70°F (21°C) and a minimum of 30°F (1°C). For
hydrofluoric acid alkylation, temperature is less significant and reactor temperatures are
usually in the range of 70 to 100°F (21 to 38°C).
Acid strength has varying effects on alkylate quality depending on the effectiveness of
reactor mixing and the water content of the acid. In sulfuric acid alkylation, the best quality
and highest yields are obtained with acid strengths of 93 to 95% by weight of acid, 1 to 2%
water, and the remainder hydrocarbon diluents. The water concentration in the acid lowers its
catalytic activity about 3 to 5 times as much as hydrocarbon diluents, thus an 88% acid
containing 5% water is a much less effective catalyst than the same strength acid containing
2% water. The poorer the mixing in a reactor, the higher the acid strength necessary to keep
acid dilution down [16]. Increasing acid strength from 89 to 93% by weight increases alkylate
quality by one to two octane numbers. In hydrofluoric acid alkylation the highest octane
number alkylate is attained in the 86 to 90% by weight acidity range. Commercial operations
usually have acid concentrations between 83 and 92% hydrofluoric acid and contain lessthan
1% water. increasing the reactor temperature from 60 to 125°F (16 to 52°C) degrades the
alkylate quality about three octane numbers [16].In sulfuric acid alkylation, low temperatures
cause the acid viscosity to become so great that good mixing of the reactants and subsequent
separation of the emulsion is difficult.

14. Isobutane concentration is generally expressed in terms of isobutane/olefin ratio. High
isobutane/olefin ratios increase octane number and yield, and reduce side reactions and
acid consumption. In industrial practice the isobutane/olefin ratio on reactor charge varies
from 5:1 to 15: 1. In reactors employing internal circulation to augment the reactor feed ratio,
internal ratios from 100:1 to 1000:1 are realized.
Olefin space velocity is defined as the volume of olefin charged per hour divided by the volume
of acid in the reactor. Lowering the olefin space velocity reduces the amount of high-
boiling hydrocarbons produced, increases the product octane, and lowers acid
consumption. Olefin space velocity is one way of expressing reaction time; another is by
using contact time. Contact time is defined as the residence time of the fresh feed and
externally recycled isobutane in the reactor. Contact time for hydrofluoric acid alkylation
ranges from 5 to 25 minutes and for sulfuric acid alkylation from 5 to 40 minutes . Although
the
relationship is only approximate, Mrstik, Smith, and Pinkerton developed a correlating
factor, F, which is useful in predicting trends in alkylate quality where operating variables are
changed.
F= IE(I/O)F
100(SV)O
where
IE = isobutane in reactor effluent, liquid volume %
(I/O)F = volumetric isobutane/olefin ratio in feed
(SV)O = olefin space velocity, v/hr/v
The higher the value of F, the better the alkylate quality. Normal values of F
range from 10 to 40.

15. SUMMARY (Alkylation process variable)
Reaction temperature: If too low, increases acid
viscosity & hinder good mixing of reactant. If too
high, side reaction set in.
Acid strength: Its effect depends on the
effectiveness of reactor mixing & H2O content of
the acid.
Isobutane concentration: It’s express interms of
isobutane/olefin ratio. The higher the ratio the
better the octane number.
Olefin space velocity: It’s the ratio of volume of
olefin per hour to volume of acid in the reactor.
The lower the ratio the higher the octane number.
Reactor Pressure: The reactor pressure at which the reactant
are maintain in the liquid phase is sufficient.

16. ALKYLATION FEEDSTOCK
A feedstock is the basic material from which a
good is manufactured or made.
Olefins (ranging from C3-C5) and isobutane are
used as alkylation unit feedstock
Olefin feed originates from the FCC Unit.
The olefin feed is also likely to contain diluents
(such as propane, n-butane and n-pentane), non-
condensable (such as ethane and hydrogen) and
contaminants.
Olefins can also be produced by dehydrogenation
of paraffins.

17. Isobutane feed obtained from the
hydrocracker.
The Isobutane feed to an alkylation unit can
be either low or high purity.
 The isobutane feed does not normally contain
any significant level of contaminants.
Hydrocrackers produce a great deal of the
isobutane used in alkylation but it is also
obtained from catalytic reformers, crude
distillation, and natural gas processing

18. CATALYST
Concentrated sulfuric and hydrofluoric acids are the only catalysts used
commercially today for the production of high octane alkylate gasoline .
The desirable reactions are the formation of C8 carbonium ions and the
subsequent formation of alkylate. The main undesirable reaction is
polymerization of olefins. Only strong acids can catalyze the alkylation
reaction but weaker acids can cause polymerization to take place.
Therefore, the acid strengths must be kept above 88% by weight H2SO4 or
HF in order to prevent excessive polymerization. Sulfuric acid containing
free SO3 also causes undesired side reactions and concentrations greater
than 99.3% H2SO4 are not generally used.
Isobutane is soluble in the acid phase only to the extent of about 0.1% by
weight in sulfuric acid and about 3% in hydrofluoric acid. Olefins are more
soluble in the acid phase and a slight amount of polymerization of the
olefins is desirable as the polymerization products dissolve in the acid and
increase the solubility of isobutane in the acid phase. If the concentration
of the acid becomes less than 88%, some of the acid must be removed
and replaced with stronger acid.

19. In hydrofluoric acid units, the acid removed is
redistilled and the polymerization products removed as
a thick, dark ‘‘acid soluble oil’’ (ASO). The concentrated
HF is recycled in the unit and the net consumption is
about 0.3 lb per barrel of alkylate produced. Unit
inventory of hydrofluoric acid is about 25–40 lb acid
per BPD of feed.
The sulfuric acid removed usually is regenerated in a
sulfuric acid plant which is generally not a part of the
alkylation unit. The acid consumption typically ranges
from 13 to 30 lb per barrel of alkylate produced.
Makeup acid is usually 98.5 to 99.3 wt% H2SO4.

20. ALKYLATION PRODUCTS
In addition to the alkylate stream, the products leaving the alkylation unit include
the propane and normal butane that enter with the saturated and unsaturated feed
streams as well as a small quantity of tar produced by polymerization reactions.
The product streams leaving an alkylation unit are:
1. LPG grade propane liquid
2. Normal butane liquid
3. C5 alkylate
4. Tar
Theoretical Yields and Isobutane
Requirements Based on Olefin Reacting
Alkylate Isobutane
vol% vol%
Ethylene 188 139
Propene 181 128
Butenes (mixed) 172 112
Pentenes (mixed) 165 96
Only about 0.1% by volume of olefin feed is converted into tar. This is not truly a tar but a thick dark
brown oil containing complex mixtures of conjugated cyclopentadienes with side chains

21. HYDROFLUORIC ACID ALKYLATION PROCESSES

22. Phillips and UOP are the two common types of hydrofluoric acid
alkylation processes in use.
THE PHILLIPS PROCESS
In the Phillips process, olefin and isobutane feedstock are dried and
fed to a combination reactor/settler system. Upon leaving the reaction
zone, the reactor effluent flows to a settler (separating vessel) where
the acid separates from the hydrocarbons. The acid layer at the
bottom of the separating vessel is recycled. The top layer of
hydrocarbons (hydrocarbon phase), consisting of propane, normal
butane, alkylate, and excess (recycle) isobutane, is charged to the main
fractionator, the bottom product of which is motor alkylate. The main
fractionator overhead, consisting mainly of propane, isobutane, and
hydrogen fluoride (HF), goes to a depropanizer. Propane with trace
amount of HF goes to an HF stripper for HF removal and is then
catalytically defluorinated, treated, and sent to storage. Isobutane is
withdrawn from the main fractionator and recycled to the
reactor/settler, and alkylate from the bottom of the main fractionator
is sent to product blending.

23. REACTOR
SETTLER
SETTLER
MAIN FRACTIONATOR
ALKYLATE
`
OLEFINS AND ISOBUTANE
PROPANE N-BUTANEISOBUTANE
ISOBUTANE
RECIRCULATION
PUMP
HYDROCARBONLAYER
HF
UOP HYDROFLUORIC ACID ALKYLATION PROCESS
OLEFINS AND ISOBUTANE
HF
HF

24. THE UOP
The UOP process uses two reactors with separate settlers. Half of
the dried feedstock is charged to the first reactor, along with
recycle and makeup isobutane. The reactor effluent then goes to
its settler, where the acid is recycled and the hydrocarbon
charged to the second reactor. The other half of the feedstock
also goes to the second reactor, with the settler acid being
recycled and the hydrocarbons charged to the main fractionator.
Subsequent processing is similar to the Phillips process.
Overhead from the main fractionator goes to a depropanizer.
Isobutane is recycled to the reaction zone and alkylate is sent to
product blending.

25. SULPHURIC ACID ALKYLATION PROCESS
This is an alkylation process which uses sulphuric acid(H₂SO₄) as a catalyst to yield paraffinic
products with high octane blending components which make them suitable for automobile fuel
and aviationfuel.
Basically the major processes involving the use of sulphuric acid asa catalyst in the unit are
•AUTO-REFRIDGERATION PROCESS
•EFFULENT REFRIDGERATION PROCESS
AUTO REFRIGERATION
This process uses a multistage cascade reactor with mixers ineach stage to emulsify the
hydrocarbon–acid mixture. An olefin feed or a mixture of olefin feed and isobutane feed is
introduced into the mixing compartments with enough mixing energy is introduced to obtain
sufficient contact of the hydrocarbon reactants and the sulphuric acid catalyst to obtain good
reaction selectivity.The reaction is held at a pressure of approximately 10 psig (69 kPag) in order
to maintain the temperature at about 40˚F (5˚C). To prevent vaporization of the hydrocarbons,
the gases are vaporized,compressed and liquefied. A portion of this liquid is vaporized in an
economizer to cool the olefin hydrocarbon feed before it is sent to the reactor. The vapors are
returned for recompression. The remaining liquefied hydrocarbon is sent to a depropanizer
column for removal of the excess propane whichaccumulates in the system. The liquid isobutane
from the bottom of the depropanizer is pumped to the first stage of the reactor. The acid–
hydrocarbon emulsion from the last reactor stage is separated into acid and hydrocarbon phases
in a settler.

26. The acid is removed from the system for reclamation, and the hydrocarbon phase is
pumped through a caustic wash followed by a water wash (or a fresh acid wash
followed by either caustic or alkaline water washes) to eliminate trace amounts of acid
and then sent to a deisobutanizer. The deisobutanizer separates the hydrocarbon feed
stream into isobutane (which is returned to the reactor), n-butane, and alkylate
product

27. EFFULENT REFRIGERATION PROCESS: The effluent refrigeration process uses a single-stage reactor in which
the temperature is maintained by cooling coils.This process is the divided into four processes
•REACTION SECTION
•REFRIGERATION SECTION
•EFFLUENT TREATING SECTION
•FRACTIONATION SECTION
REACTION SECTION:In the reaction section, olefins and isobutane are alkylated in the presence ofsulfuric
acid catalyst.The olefin feed is initially combined with the recycle isobutane. The olefin and recycle isobutane
mixed stream is then cooled to approximately 60°F (15.6°C) by exchanging heat with the net effluent stream
in the feed/effluent exchangers.
REFRIGERATION SECTION:This a sectionwhere the heatof reaction is removedandlight hydrocarbon are
purged from the unit
NET EFFLUENT TREATING SECTION:The net effluent stream from the reaction section contains traces of free
acid, alkylsulfates and di-alkyl sulfates formed by the reaction of sulfuric acid with olefins. Thesealkyl sulfates
are commonly referred to as “esters.” Alkyl sulfates are reactionintermediates found in all sulfuric acid
alkylation units, regardless of the technology utilized. If the alkyl sulfates are not removed they can cause
corrosion in downstream equipment.
FRACTIONATION SECTION:The fractionation section configuration of grassroots alkylation units, either
autorefrigeratedor effluent refrigerated, is determined by feed composition to the unit andproduct
specifications. As mentioned previously, the alkylation reactions are enhancedby an excess amount of
isobutane. In order to produce the required I/O volumetric ratioof 7:1 to 10:1 in the feed to the Contactor
reactors, a very large internal recycle stream is required. Therefore, the fractionation section stream.
BLOW DOWN SECTION: The spent acid is degassed,waste water ph is adjusted and acid vent
stream are neutralised before been sent off-site.

28. Block Flow Diagram of a STRATCO® Effluent
Refrigerated Sulfuric acid alkylation.
RECYCLE ISOBUTANE
PROPANE
PRODUCT
n-butane
PRODUCT
ACID
OLEFIN FEED
MAKEUP ISOBUTANE ACID
SPENT ACID
FRESH ACID
PROCESS ALKYLATE PRODUCT
WATER
REFINERY SPENT ACID
WASTEWATER
TREATMENT
REFIGERATION
ALKYLATION
REACTION EFFLUENT
TREATING
F
R
A
C
T
I
O
N
A
T
I
O
N
BLOWDOWN

29. DEISOBUTANIZER OPERATION (DIB)
The DIB is a part of the fractionation column it is basically used for
purification and separation of liquids into various components. The
feed into the DIB contains excess isobutene, n- butane, C8
+ alkylate,
and residual olefinic C4’s. Figure 1 below illustrates a typical DIB.
When the feed enters the DIB it is being heated and evaporation takes
place. The isobutane in the mixture having the lowest boiling point (-
11.7OC 0r 10.9oF) is evaporated first and it comes out as the overhead
product. Some of the isobutane is refluxed back to the DIB with a
reflux ratio of 11.588 for further purification and it is being recycled
back to the feed stream of the alkylation unit. The n-butane having a
boiling point of -0.5oC (31.1o
F) comes out at the side stream of the
column. The final and most important product which is the alkylate
comes out at the base of the column.

31. COMPARISION OF THE ALKYLATION PROCESSES
Commercial alkylation catalyst options for refiners today consist of hydrofluoric
(HF) and sulfuric (H2SO4) acids. In some areas of the world, HF is no longer
considered an acceptable option for a new unit due to concerns over safety;
however, this is not the case everywhere. Due to site-specific differences in utility
economics, feed and product values, proximity to acid regeneration facilities, etc.,
both H2SO4 and HF alkylation technologies should be evaluated. The evaluation
criteria can be divided into the following categories: Feed Availability and Product
Requirements, Safety and Environmental Considerations, Maintenance, Operating
Costs (Utilities and Catalyst/Chemical Costs) and Capital Investment.
 Feed Availability and Product Requirements
Historically, butylenes from the FCC were the traditional olefins fed to the
alkylation unit. Today, alkylation units are using a broader range of light olefins
including propylene, butylenes and amylenes. Alkylate composition and octane
number from pure olefins are quite different for each catalyst as shown in table 1

32. Table 1. Light Olefin Alkylate Octanes
RON MON
HF H2SO4 HF H2SO4
Propene 91-93 91-92 89-91 90-92
Butene-1 90-91 97-98 88-89 93-94
Butene-2 96-97 97-98 92-93 93-94
Isobutene 94-95 94-95 91-92 92-93
Amylene 90-92 89-92 88-89 88-90

33. • Safety & Environmental Considerations
• Maintenance
• Operating Costs
• Utility Costs
• Catalyst and Chemical Costs
• Capital Investment
In summary, a process comparison of the alkylation processes
shows that neither has an absolute advantage over the other. From
a safety and environmental standpoint, H2SO4 has a clear
advantage over HF. Economics of the processes are sensitive to
base conditions for feedstocks and operating conditions, as well as
refined product pricing. Thus, the actual choice for a particular
refinery is governed by a number of site-specific factors, which
require a detailed analysis.

34. HAZARDS AND SAFETY MEASURES IN
ALKYLATION UNIT
There are two main hazards inherent in the alkylation unit, which are:
1. Large volumes of light hydrocarbon which are highly flammable and are
potential explosives if released.
2. The acid catalyst (H2SO4 and HF) which is corrosive and toxic are used.
Both sulfuric acid and HF contains similar volume and similar risk
but the risk associated with HF is more severe than sulfuric acid and as
such HF demands stricter precautions. For this, the American petroleum
institute (API) issued a recommended practice specifically for HF
alkylation unit. The publication recommends that access to an HF
alkylation unit be restricted due to the potential hazards of HF. No
similar specification was recommended for sulfuric acid alkylation.
The major risk-related differences of sulfuric acid and HF as a catalyst
in the alkylation unit lies in each compound’s VOLATILITY. HF has a
boiling point of 19.4oC at atmospheric pressure and vaporizes in the
event of any leak to the atmosphere.

35. A scientific HF tests conducted in 1986 in the Nevada desert surprised the
researchers when 100% of the HF liquid released formed a dense white
rolling cloud of toxic gas. The cloud expanded rapidly and toxic
concentrations were measured at a distance of 5-10km from the released
point. Thus, unless mitigated, an HF released in a refinery will place
workers and the surrounding community in severe danger. Sulfuric acid on
the other hand, is a non-volatile liquid with a boiling point of over 290oC at
atmospheric pressure. A test of its behaviour when combined with
isobutane in an alkylation condition were carried out in 1990, the test
shows that sulfuric acid consistently remained in its liquid state and no
aerosols or vapours were observed during any portion of the test. Other Oil
Company like Exxon Mobil, Chevron, Amaca, Texaco etc. also carried out
test on sulfuric acid which was concluded that sulfuric acid does not
vapourize.
MITIGTION PROCESS OF HF
1. RAPID DEINVENTORY SYSTEM: The main aim here is to reduce the
amount of HF that would be released during an accident. In the cause of an
accident the acid is transferred to an empty vessel by an available system
pressures or pumps. The total time to transfer the acid will depend on the
size of the unit, transfer mechanism and the pipe diameters.

36. 2. WATER SPRAY SYSTEM: There are two main benefits to a water spray
system for HF, the first is derived from the ability of water to absorb HF,
thus removing the HF from the released cloud. The second benefit comes
from the enhanced turbulence generated by the water mixing with the
released cloud. The increased turbulence adds air to the system, thereby
reducing the concentration of HF in the cloud. There different types of
water spray that can be used for this function they are; water curtains, fixed
water monitors, portable water cannons etc.
3. ADDITION OF ADDITIVE: Over the years several efforts have been
made to identify a material(s) that when added to HF would reduce the
potential size of the hazard zone following a release. In general, a
desirable additive would have the following characteristics :
The additive increases the ratio of HF that falls to the ground versus the
HF that remains airborne during a release.
The additive dilutes the acid thereby reducing its concentration.
The additive works to reduce the vapour pressure of the HF phase, thus
making the HF/ additive mixture less volatile.
The additive does not affect the alkylation efficiencies.

37. NOTE:
The additive reduces the amount of HF that remains airborne following a
release when compared to the non-additive release. This will reduce the risk
of inhalation of the compound.
PERSONAL PROTECTIVE EQUIPMENT (PPE)
These are pieces of equipment or apparel used or worn to protect an
individual working in an alkylation unit. Within both HF and sulfuric acid
alkylation units, readily available safety showers, water hydrant and hose,
and eye wash fountains should be provided and regularly inspected to assure
good working order.
Other PPE to be provided includes:
 Face shield, goggles or acid resistance gauntlets- To protect the eyes from
HF and sulfuric acid.
 Acid resistance gloves- to protect the hands from HF and sulfuric acid in the
alkylation unit.
 Acid resistance boots and coverall- To protect the feet and body from acid
burns.
 Air-supplied respirator (self-contained breathing apparatus)- It supplies
oxygen or compressed air to personnel exposed to alkylation unit
environment.

39. CONCLUSION.
 Definition of Alkylation unit.
 Alkylation reaction.
 Effects of the process variables: temperature,
acid strength, isobutane concentrations, olefins
space velocity.
 Feed stocks in alkylation unit
 Products of Alkylation units
 Catalysts used in Alkylation units

40. Comparison of processes.
 Hydrofluoric Acid (HF):
I. Smaller and simpler reactor designs are feasible
II. Cooling water can be used instead of refrigerator
III. Smaller settlling devices are needed for emulsion.
IV. Essentially complete regeneration of hydrofluoric
acid catalyst occurs.
V. There is increased flexibility of operations relative
to temperature, external ratio of isobutane to
olefins
VI. There is decreased need for turbulence or agitation
when acid and hydrocarbon streams are combined

41.  Sulphuric acid
I. The entire effluents hydrocarbon stream is neutralized,
no additional equipment needed unlike in hydrofluoric
acid process.
II. Drying is not required, whereas in hydrofluoric acid
process, drying equipment is needed.
III. Maintenance costs and the amount of safety
equipment in hydrofluoric acid process are greater.
IV. Capital cost is lesser because there is no mitigation
equipment.
V. Isobutane is fully used for production of Alkylate.
VI. There are greater limitations on obtaining Alkylates
with high octane numbers with HF acid process
VII. Safety and environmental restrictions limit the use of
hydrofluoric system in highly populated Areas.

42. HAZARDS AND SAFETY
• Large volumes of light hydrocarbon which are
highly flammable and are potential explosives
if released.
• The acid catalyst (H2SO4 and HF) which is
corrosive and toxic are used.
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