Amines

AMINES
Contents
Historical perspective
Background
(MMA, DMA and TMA)
Stereochemistry and Structure
Reaction Mechanisms and Thermodynamics
CATALYSTS FOR AMINATION
Non-Zeolitic Catalysts for Amination
Mordinite (MOR) Catalysts for Amination
Zeolite Catalysts for Amination
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AMINES
Contents
Amines Production
Amines: Markets and Applications
Gas Separation
Conventional Amines Treating System
Amine System for Gas Sweetening
APPENDIX
Structures
Ethyleneamines Production

AMINES
Historical Perspective
Industrially the synthesis of methylamines in batch mode from
methanol and ammonia, using zinc chloride, was first reported
in 1884.
The first report of amination of alcohols in the gas phase was in 1909
Methylamines were first made commercially in the 1920s for use in
the tanning industry for the dehairing of animal skins by
Commercial Solvents Corporation in Terra Haute, Indiana.

AMINES
Historical Perspective
The process used at that time and the current
processes [are essentially the contact of gaseous
methanol and ammonia over dehydrating catalysts
(e.g. silica-alumina), followed by collection and
separation of the products.
For higher aliphatic amines, catalysts having hydrogenating and
dehydrogenating properties have also become important

Amines Background
(MMA, DMA and TMA)

Mono-methyamine (MMA)
Mono-methylamine is the organic compound
with the chemical formula CH3NH2.
This colorless gas is a derivative of ammonia,
but with one H atom replaced by a methyl
group.
It is the simplest primary amine.
It is sold as a solution in methanol, ethanol, and
water or as the anhydrous gas in pressurized
metal containers.

Di-methylamine (DMA)
Dimethylamine is an organic compound with the chemical
formula (CH3)2NH.
This secondary amine is a colorless, flammable liquefied gas
with an ammonia-like odor.
Dimethylamine is generally encountered as a solution in
water at concentrations up to around 40%.
Dimethylamine is a precursor to several industrially
significant compounds.
It reacts with carbon disulfide to give dimethyldithiocarbamate, a
precursor to a family of chemicals widely used in the vulcanization
of rubber.

Tri-methylamine (TMA)
Trimethylamine is an organic compound with the chemical
formula N(CH3)3.
This colorless, hygroscopic, and flammable tertiary amine
has a strong "fishy" odor in low concentrations and an
ammonia-like odor at higher concentrations.
It is a gas at room temperature but is usually sold in
pressurized gas cylinders or as a 40% solution in water.
Tri-methylamine is used in the synthesis of choline, tetramethylammonium
hydroxide, plant growth regulators, strongly basic anion exchange resins,
dye leveling agents and a number of basic dyes [1]. Gas sensors to test for
fish freshness detect trimethylamine.

Physical Properties of MMA, DMA and TMA

The electron structure of amines

Reaction Mechanisms and
Thermodynamics

Chemical reactions and catalysts
The reaction of ammonia and methanol in the presence of a solid
acid catalyst forms a mixture of mono-, di- and trimethylamine
(MMA, DMA and TMA, respectively).

Reactions and Thermodynamics
Table I shows the different classes of reactions that play a role in
the amination of alcohols over solid acid catalysts.
Alkylation of Ammonia with Alcohols

The alkylation reactions are exothermic and are
regarded as Irreversible due to their high equilibrium
constant.
They proceed in sequential order to yield the mono-,
di- and tri-substituted amines.
The transalkylation reactions are regarded as being
reversible and are held responsible for the amine
product distribution at higher alcohol conversion.

Dependence of the equilibrium amine distribution on (a) the NH
/MeOH ratio and Reaction temperature
(‫)ם‬ MMA, (Δ) DMA, (ο) TMA

The equilibrium distribution of the reactants and products in
methanol and ethanol amination:
Dependence of the equilibrium product distribution on: (a) and (b)
NH3/EtOH ratio at 573 K and p=1 bar
(‫)ם‬ MEA, (Δ)DEA, (ο) TEA, (♦) ethene

The equilibrium distribution of the reactants and products in
methanol and ethanol amination:
Dependence of the equilibrium product distribution on reaction
temperature at NH /EtOH=4 and p=1 bar
Bar.
(‫)ם‬ MEA, (Δ)DEA, (ο) TEA, (♦) ethene

OBSERVATIONS
The equilibrium distribution of the reactants and
products in methanol and ethanol amination given in
the previous three slides suggest the following:
 The necessity to shift the reactions away from
equilibrium
 In ethylamine synthesis this need arises from the
necessity to avoid the formation of ethene and its
oligomerization products and thus to increase catalyst
and equipment lifetime

Synthesis of Tertiary Aliphatic Amines

CATALYSTS FOR
AMINATION

Non-Zeolitic Catalysts for
Amination

Variety of catalysts for the vapor phase methanol-ammonia reaction
has been reported:
 Aluminas,
 Silicas,
 Zirconia,
 Thoria
 Phosphates.
*other materials that perform dehydration chemistry have
been used for methylamines synthesis

Among the more exotic candidates are a
photocatalytic Pt/titania system where at
MeOH conversion of < 0.1% only TMA is
produced and a heteropoly acid catalyst
that suppresses TMA completely at 477°C
and N/C=2.
It was recognized early on that a high N/C ratio favored
MMA formation.
The temperature range employed was, as expected, large
250-500°C.
Photocatalytic Pt/titania

Silica-alumina (SA) is currently the most widely used
catalyst for methylamines synthesis.
Silica-alumina (SA)
It is usually made by
coprecipitation.

A SA (46.9 wt% SiOa) was compared to
a boron phosphate and an SA-boron
phosphate hybrid, SA was found to be
the preferred catalyst; it had a higher
selectivity to amines.
Reduced coking and improved rates are
obtained by using a high alumina
(94 wt%) content SA catalyst.
Silica-alumina (SA)
*at the same conditions, conversion and selectivity to amines
increased with increasing surface area and acidity.

MORDENITE (MOR) CATALYSTS
FOR AMINATION

Mordenite (MOR) CATALYSTS FOR AMINATION
Among the zeolites seen suitable for shape selective alkylamine
synthesis, mordenite is industrially the most widespread applied.
Mordenite consists of a one dimensional system
of large channels (12-ring, 6.5 x 7.0 Å) lined with
so-called side pockets, which have an aperture of
approx. 4.8 x 3.7 Å [14,15], these side pockets are
separated by a restriction of 2.6 x 5.7 Å, as shown
in the Figure to the Right, in which the
accessibility of the MOR structure to ammonia is
represented (obtained using the Insight II
program from Biosym/MSI).

Mordenite (MOR) CATALYSTS FOR AMINATION

ZEOLITE CATALYSTS FOR
AMINATION

ZEOLITE CATALYSTS FOR AMINATION
The primary building blocks of zeolites are {SiO4}4- and
{AlO4}5- tetrahedra.
As a result of the difference
in charge between these
tetrahedra, the total
framework charge is
negative and hence must be
balanced by cations,
typically protons, alkali, or
alkaline earth metal ions.

Generally in the protonic or acid form, these materials
behave as solid acids and as such are excellent
candidates as catalysts for methylamines synthesis.

Zeolite Properties 1
 Zeolites have uniform pore systems of a size that is
comparable to a number of organic molecules.
 Zeolites are crystalline materials that are composed of a three
dimensional network of metal oxygen tetrahedral with:
- a one-dimensional channel system
- a two-dimensional channel system
- a three-dimensional channel system
* Depending on the way these tetrahedral are
linked together.

Zeolites can be classified according to their largest pore size.
'Small pore' zeolites are those containing 8-membered ring
openings,
'medium' containing 10-membered rings and
'large' containing 12-membered rings
Zeolites of all three classes have been tested for amine synthesis.
The pore openings of these zeolites range from 3 to 7.5Å and
allow for exclusion of molecules based on their minimum kinetic
diameter and shape.

Mechanistically, different reasons for the occurrence of
shape selectivity are distinguished:
(i) Reactant shape selectivity (a consequence of one
reactant being too large to pass through the zeolite
channel) and
(ii)Product selectivity (when only certain products are of
the proper size and shape are able to diffuse out of the
channels.
(iii)Transition state selectivity occurs when the
corresponding transition state of a certain reaction
requires more space than available in the framework of
the zeolite.

Zeolites can contain high concentrations of localized acid
sites.
The acid sites of zeolites are an integral part of the
microporous structure resulting from an imbalance between
the metal oxygen stoichiometry and the formal charges of the
cations.
In zeolites the tetrahedral are based on silicon and oxygen. In
this network of tetrahedral a Si atom has a charge of +4, an O
atom of -2.
As every O atom belongs to two tetrahedral, a purely siliceous
lattice is neutral and possesses no acidity.

Substituting part of the Si atoms by Al (+3), creates a negative charge
at the Al-O tetrahedra, which is balanced by a metal cation (Lewis
acid site) or a proton (Brønsted acid site).
Thus these acid sites are localized and their concentration is
proportional to the aluminum concentration in the lattice.
Due to their open structure, the accessibility of acid sites is much
larger than for amorphous materials of similar composition.
High surface concentration of reactants and longer residence times
of reactants in the pores generally additionally enhance the activity of
zeolites.

Numerous zeolites have been tested as catalyst
ranging in size from 'small pore' to 'large pore' zeolites.
 ZK-5
 Rho
 Chabazite
 Erionite
 Offretite
 ZSM-5
 Mordenite

 Mordenite (MOR)
 Faujasite (FAU)
 Mazzite (MAZ)
 Beta (BEA)
Large Pore zeolites

LargePorezeolites Zeolite structures, emphasizing the diameter of the 12-ring;
(a) BEA, (b) FAU, (c) MOR, and (d) MAZ.

Amines Production

Amines Production
When ammonia is reacted with methanol, the products
MMA, DMA and TMA are formed in consecutive reactions.
The most widely used method for the production of
methylamines is the reaction of methanol with ammonia at
temperatures of about 400°C in the presence of acidic solid
catalysts.
These catalysts are capable of dehydrating and aminating
methanol.
These catalysts are capable of dehydrating and aminating
methanol. For example, modified γ-alumina, aluminosilicate
and thorium oxide catalysts.

Amines Production
Largest Producers of methylamines and their method of
production

Amines Production
Process Constraints
As a result of the increasing demand for DMA all major
producers and researchers are looking for a catalyst that
increases the yield of DMA.
Therefore, in many processes MMA and TMA are converted
into DMA by being recycled into the feedstock.
There are also byproducts that are produced during the
catalytic reaction and they include ethanol, ethylamine,
dimethylether, methane and etc.

Amines Production
Process Overview
Fresh methanol and ammonia feed are combined with
recycled ammonia and methylamines (mainly MMA and TMA)
are fed to a reactor containing a solid acid catalyst.
The amorphous silica alumina catalysts produced by
Albemarle are those most commonly used in the
methylamine production process.
These catalysts are highly active and stable but have no
specific product selectivity.
Various catalysts are available in the market under
commercial names.

Amines Production
Typical properties of KDC-6 catalyst
produced by Albemarle

AMINE PRODUCTION
PROCESSES
The Nitto Chemical Methylamines Process
Methylamines are produced conventionally by
reacting gaseous methanol and ammonia in the
presence of a catalyst such as silica-alumina.
The reaction products have the thermodynamic
equilibrium composition of monomethylamine,
dimethylamine, and trimethylamine.
To produce a product mix different from the
equilibrium composition, unwanted methylamines
recovered downstream must be recycled to the
reaction to suppress their formation.

AMINE PRODUCTION
PROCESSES
Nitto Chemical (Japan) has developed a process
that can produce a non-equilibrium product mix
having a high dimethylamine content, e.g., 86%
dimethylamine and 7% each of mono- and
trimethylamines.
The process is based on zeolite-type catalysts.
A commercial methylamines plant based on it
has been in operation since 1984.

AMINE PRODUCTION
PROCESSES
A conventional process to produce a product
mix consisting of 34wt% monomethylamine,
46wt% dimethylamine, and 20wt%
trimethylamine would require a total fixed
capital about 14%higher and a product value
about 7% higher than that of the Nitto Chemical
process.

AMINE PRODUCTION
PROCESSES
To produce a product mix similar to the one
prescribed for the Nitto Chemical process, the
conventional process would be even more
costly, because larger portions of the
monomethylamine and trimethylamine product
streams must be recycled to the reactor to
suppress the formation of these two
methylamines.

Amines: Markets and
Applications

Amines: Markets and Applications

Amines: Gas Separation
Solvents
Amine scrubbing technology was established over 60 years ago in the
oil and chemical industries, for removal of hydrogen sulfide and CO2
from gas streams Commercially, it is the most well established of the
techniques available for CO2 capture although practical experience is
mainly in gas streams which are chemically reducing, the opposite of
the oxidizing environment of a flue gas stream. and desorption
characteristics.

Amines: Gas Separation
Solvents
There are several facilities in which amines are used to capture CO2
from flue gas streams today, one example being the Warrior Run coal
fired power station in the USA where 150 t/d of CO2 is captured.
Mono-ethanolamine (MEA) is a widely used type of amine for CO2
capture. CO2 recovery rates of 98% and product purity in excess of
99% can be achieved. There are, however, questions about its rate of
degradation in the oxidizing environment of a flue gas and the amount
of energy required for
Regeneration.
Improved solvents could reduce energy requirements by as much as
40% compared to conventional MEA solvents. There is considerable
interest in the use of sterically-hindered amines which are claimed to
have good absorption and desorption characteristics.

Conventional Amines Treating
System

US 7,626,058 Scheme1

US 7,626,058 Scheme 2

US 7,626,058 Scheme 3

Ethyleneamine Profiles
Typical Physical Properties

Ethyleneamines Applications
Ethyleneamines are utilized in a wide variety of applications
because of their unique combination of reactivity, basicity,
and surface activity.
They are predominantly used as intermediates in the
production of functional products.
The following table lists the major end-use applications for
these versatile materials.

Amines

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