This invention relates to a process for the production of lower aliphatic esters by reacting a lower olefin with a saturated lower aliphatic mono-carboxylic acid in the vapor phase in the presence of a heteropolyacid catalyst characterized in that an amount of water in the range from 1-10 mole % based on the total of the olefin, aliphatic monocarboxylic acid and water is added to the reaction mixture during the reaction. The presence of water enhances the yield of the desired ester. The reaction mixture may optionally contain a di-ether to minimize the by-products.
The process is particularly suitable for producing ethyl acetate from ethylene and acetic acid in the presence of water.
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1. A process for the production of lower aliphatic esters said process comprising reacting a lower olefin and a di-ether with a saturated lower aliphatic monocarboxylic acid in the vapour phase in the presence of a free acid silico-tungstic heteropolyacid catalyst supported on a siliceous support characterized in that an amount of water in the range from 1-10 mole % based on the total of the olefin, aliphatic mono-carboxylic acid and water is added to the reaction mixture during the reaction and the amount of di-ether is in the range from 1 to 6 mole % based on the total reaction mixture comprising the olefin, aliphatic carboxylic acid, water, and di-ether.
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The present invention relates to a process for the synthesis of esters by reacting an olefin with a lower carboxylic acid in the presence of an acidic catalyst.
It is well known that olefins can be reacted with lower aliphatic carboxylic acids to form the corresponding esters. One such method is described in GB-A-1259390 in which an ethylenically unsaturated compound is contacted with a liquid medium comprising a carboxylic acid and a free heteropolyacid of molybdenum or tungsten. This process is a homogeneous process to which the heteropolyacid catalyst is unsupported. A further process for producing esters is described in JP-A-05294894 in which a lower fatty acid is esterified with a lower olefin to form a lower fatty acid ester. In this document, the esterification reaction is carried out in the gaseous phase in the presence of a catalyst consisting of at least one heteropolyacid salt of a metal e.g. Li, Cu, Mg or K, being supported on a carrier. The heteropolyacid used is phosphotungstic acid and the carrier described is silica.
It has now been found that the process efficiency can be improved significantly by co-feeding water to the reaction mixture.
Accordingly, the present invention is a process for the production of lower aliphatic esters said process comprising reacting a lower olefin with a saturated lower aliphatic mono-carboxylic acid in the vapour phase in the presence of a heteropolyacid catalyst characterised in that an amount of water in the range from 1-10 mole % based on the total of the olefin, aliphatic mono-carboxylic acid and water is added to the reaction mixture during the reaction.
A feature of the invention is the addition of water as a component of the reaction mixture. Surprisingly, it has been fond that the presence of water in the reaction mixture in an amount of 1-10 mole %, preferably from 1 to 7 mole %, e.g. 1 to 5 mole %, based on the total feed enhances the stability of the catalyst and thereby enhances the efficiency of the process. Furthermore, the presence of water also reduces the selectivity of the process to undesired by-products such as e.g. oligomers and other unknowns, excluding diethyl ether and ethanol.
It has further been found that dosing the reaction mixture with amounts of di-ether such as e.g. diethyl ether, as a co-feed also reduces the formation of undesirable by-products. The amount of di-ether co-fed is suitably in the range from 1 to 6 mole %, preferably in the range from 1 to 3 mole % based on the total reaction mixture comprising the olefin, the aliphatic carboxylic acid, water and diethyl ether. The di-ether co-fed may correspond to the by product di-ether from the reaction generated from the reactant olefin. Where a mixture of olefins is used, e.g. a mixture of ethylene and propylene, the di-ether may in turn be an unsymmetrical di-ether. The di-ether co-feed may thus be the by-product of the reaction which by-product is recycled to the reaction mixture.
The term “heteropolyacids” as used herein and throughout the specification is meant to include the free acids. The heteropolyacids used to prepare the esterification catalysts of the present invention therefore include inter alia the free acids and coordination type salts thereof in which the anion is a complex, high molecular weight entity. Typically, the anion is comprises 2-18 oxygen-linked polyvalent metal atoms, which are called peripheral atoms. These peripheral atoms surround one or more central atoms in a symmetrical manner. The peripheral atoms are usually one or more of molybdenum, tungsten, vanadium, niobium, tantalum and other metals. The central atoms are usually silicon or phosphorus but can comprise any one of a large variety of atoms from Groups I-VIII in the Periodic Table of elements. These include, for instance, cupric ions; divalent beryllium, zinc, cobalt or nickel ions; trivalent boron, aluminium, gallium, iron, cerium, arsenic, antimony, phosphorus, bismuth, chromium or rhodium ions; tetravalent silicon, germanium, tin, titanium, zirconium, vanadium, sulphur, tellurium, manganese nickel, platinum, thorium, hafnium, cerium ions and other rare earth ions; pentavalent phosphorus, arsenic, vanadium, antimony ions; hexavalent tellurium ions; and heptavalent iodine ions. Such heteropolyacids are also known as “polyoxoanions”, “polyoxometallates” or “metal oxide clusters”. The structures of some of the well known anions are named after the original researchers in this field and are known e.g. as Keggin, Wells-Dawson and Anderson-Evans-Perloff structures.
Heteropolyacids usually have a high molecular weight e.g. in the range from 700-8500 and include dimeric complexes. They have a relatively high solubility in polar solvents such as water or other oxygenated solvents, especially if they are free acids and in the case of several salts, and their solubility can be controlled by choosing the appropriate counter-ions. Specific examples of heteropolyacids that may be used as the catalysts in the present invention include:
The heteropolyacid catalyst whether used as a free acid or as a salt thereof is suitably supported, preferably on a siliceous support. The siliceous support is suitably in the form of extrudates or pellets.
The siliceous support used is most preferably derived from an amorphous, non-porous synthetic silica especially fumed silica, such as those produced by flame hydrolysis of SiCl4. Specific examples of such siliceous supports include Support 350 made by pelletisation of AEROSIL® 200 (both ex Degussa). This pelletisation procedure is suitably carried out by the process described in U.S. Pat. No. 5,086,031 (see especially the Examples) and is incorporated herein by reference. Such a process of pelletisation or extrusion does not involve any steam treatment steps and the porosity of the support is derived from the interstices formed during the pelletisation or extrusion step of the non-porous silica. The silica support is suitably in the form of pellets or beads or are globular in shape having an average particle diameter of 2 to 10 mm, preferably 4 to 6 mm. The siliceous support suitably has a pore volume in the range from 0.3-1.2 ml/g, preferably from 0.6-1.0 ml/g. The support suitably has a crush strength of at least 2 Kg force, suitably at least 5 Kg force, preferably at least 6 Kg and more preferably at least 7 Kg. The crush strengths quoted are based on average of that determined for each set of 50 beads/globules on a CHATTILLON tester which measures the minimum force necessary to crush a particle between parallel plates. The bulk density of the support is suitably at least 380 g/l, preferably at least 440 g/l.
The support suitably has an average pore radius (prior to use) of 10 to 500 Å preferably an average pore radius of 30 to 100 Å.
In order to achieve optimum performance, the siliceous support is suitably free of extraneous metals or elements which might adversely affect the catalytic activity of the system. The siliceous support suitably has at least 99% w/w purity, i.e. the impurities are less than 1% w/w, preferably less than 0.60% w/w and more preferably less than 0.30% w/w.
Other pelleted silica supports are the Grace 57 and 1371 grades of silica. In particular, Grace silica No. 1371 has an average bulk density of about 0.39 g/ml, an average pore volume of about 1.15 ml/g and an average particle size ranging from about 0.1-3.5 mm. These pellets can be used as such or after crushing to an average particle size in the range from 0.5-2 mm and sieving before being used as the support for the heteropolyacid catalyst.
The impregnated support is suitably prepared by dissolving the heteropolyacid, which is preferably a tungstosilicic acid, in e.g. distilled water, and then adding the support to the aqueous solution so formed. The support is suitably let to soak in the acid solution for a duration of several hours, with periodic manual stirring, after which time it is suitably filtered using a Buchner funnel in order to remove any excess acid.
The wet catalyst thus formed is then suitably placed in an oven at elevated temperature for several hours to dry, after which time it is allowed to cool to ambient temperature in a desiccator. The weight of the catalyst on drying, the weight of the support used and the weight of the acid on support was obtained by deducting the latter from the former from which the catalyst loading in g/liter was determined.
Alternatively, the support may be impregnated with the catalyst using the incipient wetness technique with simultaneous drying on a rotary evaporator.
This supported catalyst (measured by weight) can then be used in the esterification process. The amount of heteropolyacid deposited/impregnated on the support for use in the esterification reaction is suitably in the range from 10 to 60% by weight, preferably from 30 to 50% by weight based on the total weight of the heteropolyacid and the support.
In the esterification reaction, the olefin reactant used is suitably ethylene, propylene or mixtures thereof Where a mixture of olefins is used, the resultant product will inevitably a mixture of esters. The source of the olefin reactant used may be a refinery product or a chemical grade olefin which invariably contain some alkanes admixed therewith.
The saturated, lower aliphatic mono-carboxylic acid reactant is suitably a C1-C4 carboxylic acid and is preferably acetic acid.
The reaction mixture suitably comprises a molar excess of the olefin reactant with respect to the aliphatic monocarboxylic acid reactant. Thus the mole ratio of olefin to the lower carboxylic acid in the reaction mixture is suitably in the range from 1:1 to 15:1, preferably from 10:1 to 14:1.
The reaction is carried out in the vapour phase suitably above the dew point of the reactor contents comprising the reactant acid, any alcohol formed in situ, the product ester and water as stated above. The amount of water is in the range from 1-10 mole %, suitably from 1-7 mole %, preferably from 1-5 mole % based on the total amount of olefin, carboxylic acid and water. Dew point is the temperature at which condensation of a vapour of a given sample in air takes place. The dew point of any vaporous sample will depend upon its composition. The supported heteropolyacid catalyst is suitably used as a fixed bed which may be in the form of a packed column. The vapours of the reactant olefins and acids are passed over the catalyst suitably at a GHSV in the range from 100 to 5000 per hour, preferably from 300 to 2000 per hour.
The esterification reaction is suitably carried out at a temperature in the range from 150°-200° C. using a reaction pressure which is at least 400 KPa, preferably from 500-3000 Kpa depending upon the relative mole ratios of olefin to acid reactant and the amount of water used.
The water added to the reaction mixture is suitably present in the form of steam and is capable of generating a mixture of esters and alcohols in the process. The products of the reaction are recovered by e.g. fractional distillation. Where esters are produced, whether singly or as mixture of esters, these may be hydrolysed to the corresponding alcohols or mixture of alcohols in relatively high yields and purity. By using this latter technique the efficiency of the process to produce alcohols from olefins is significantly improved over the conventional process of producing alcohols by hydration of olefins.
The present invention is further illustrated with reference to the following Examples and Comparative Tests.
In all the Examples, the reaction conditions used and the results achieved are tabulated below. In these tables, the following abbreviations have been used:
HOS
Hours on stream
Bed (T/M/B)
Bed (top/middle/bottom)
HAC
Acetic Acid
C2H4
Ethylene
H2O
Water
EtAc
Ethyl acetate
EtOH
Ethanol
DEE
Diethyl ether
GHSV
Gas hourly space velocity
g/Lcat/h
Gram per liter of catalyst per hour
STP
Standard temperature & pressure
STY
Space time yield
A. Catalyst Preparations
Catalyst 1
Silica granules (Grace 1371 grade, 530 m2/g, bulk density 0.39 g/ml, pore volume 1.15 ml/g, ca. 1-3 mm, 70 g, ex W R Grace) were soaked over 24 hours with intermittent stirring in a solution of silicotungstic acid [H4SiW12O40.26H2O] (65.53 g, ex Japan New Metals) dissolved in 250 mlo distilled water in order to impregnate the silica support with the silicophosphoric acid catalyst. After this duration, excess catalyst solution was decanted and filtered off. The resultant catalyst impregnated support was then dried in flowing nitrogen gas overnight at 120° C. The supported catalyst so formed was then left in a desiccator to cool and was finally reweighed. The resultant support catalyst had a heteropolyacid catalyst loading of 92 g/liter.
Catalyst 2: Silica granules (Grace 57 grade, surface area 510 m2/g, bulk density 0.649 g/ml, pore volume 1.0267 ml/g, ca. 5-8 mm, 57.7 g, ex W R Grace) was soaked in a solution of 12-tungstosilicic acid [H4SiW12O40.26H2O] (ex Johnson Matthey, 69.4 dissolved in 200 ml distilled water) for 24 hours with intermittent stirring in order to impregnate the support with the catalyst. Thereafter the excess solution of the silicotungstic acid catalyst was removed by decantation and filtration. The resultant catalyst impregnated support was then dried overnight under flowing nitrogen at 120° C. The dried supported catalyst so formed was cooled in a desiccator and had a heteropolyacid catalyst loading of 190g/liter.
Catalyst 3: The above process of Catalyst 2 was repeated and was found to have a heteropolyacid catalyst loading of 192 g/liter.
B. Catalyst Forming
All the catalysts produced above were broken down and sieved to obtain the desired pellet size for loading into the esterification reactor.
C. Catalyst Testing
The reactor used was a three-zone Severn Sciences reactor constructed of Hastelloy C-276 capable of withstanding glacial acetic acid up to 300° C. and 15000 Kpa (150 barg) pressure (length 650 mm, outer diameter 22 mm, internal diameter 16 mm). It had a thermowell running the entire reactor length (5 mm outer diameter) and 1.77 cm outer diameter Swagelock VCR joints at each end. Gas from cylinders of ethylene and nitrogen were taken off at 1000 Kpa (10 barg) and then compressed to 5000-12000 Kpa (50-120 barg), via Haskel boosters, before being regulated and fed to mass-flow controllers. The liquid feed systems had 2 dm3 reservoirs maintained under a nitrogen blanket of 10 KPa-80 KPa (0.1-0.8 barg).
A cooling jacket was provided to condense products in the gas stream back to liquids prior to collection in a receiver. The majority of the liquid product was collected at room temperature.
A pre-heating zone was located upstream of the catalyst bed. The pre-heating zone was separated from the catalyst bed by a plug of glass wool. Another plug of gas wool was used downstream of the catalyst bed to reduce dead volume and help maintain the catalyst bed in the centre section of the reactor.
The reaction was started up by pressurising the reactor to 1000 KPa (10 barg) with nitrogen, establishing the desired flow rate (which is the same as that used later for the olefin feed) and then increasing the reactor temperature to the desired operating conditions (170° C. or 180° C.) over a one hour period. The liquid pump for the mixture of acetic acid/water mixture was switched on initially at the desired flow rate and the olefin admitted into the reactor on liquid breakthrough at the collection pots, usually after 2 to 3 hours. The flows were then adjusted to give the desired feed molar ratios and GHSVs. The reactor effluent was collected at regular intervals. Liquid product was drained off, weighed and then analysed by GC. The gas stream was sampled downstream of the liquid collection points and also analysed by GC. Total gas out during a test period was measured using a wet-gas meter.
The above process/catalysts were used to esterify ethylene with acetic acid. The relative amounts of each of the Catalysts 1 to 3 used, their bed size and bed length in performing the esterification reaction were as follows:
Parameter
Catalyst 1
Catalyst 2
Catalyst 3
Volume (cm3)
25
25
25
Weight (g)
11.3
(11.4*)
12
12
Pellet size (mm)
1-2
(0.5-1*)
0.5-1
0.5-1
Bed length
8.75
(14*)
14
14
*Parameters of Catalyst 1 used for the Runs in Table 2
TABLE 1
Run Conditions: (1 Mole % Water added to feed) using Catalyst 1:
Parameters
Run No. 1
Run No. 2
Run No. 3*
HOS
17-20
42-45
70-73
(21-24)
Temperature (° C.)
Applied
170
170
170
Bed (T/M/B)
173/—/170
172.5/—/169.5
173/—/168
Pressure (Kpa)
1000
1000
1000
Total feed GHSV/h
980
980
974
(@ STP)
C2H4 GHSV/h
905
905
905
HAC GHSV/h
66
66
69
H2O GHSV/h
9
9
9
C2H4 (g/Lcat/h)
1131
1131
1131
HAC (g/Lcat/h)
177
177
185
H2O (g/Lcat/h)
8
8
0
Feed contact time
4
4
4
[1/GHSV](secs)
C2H4/HAC/H2O
92.3/6.7/1.0
92.3/6.7/1.0
92.9/14.1/0
mole % ratio
C2H4/HAC/H2O wt % ratio
85.9/13.5/0.6
85.9/13.5/0.6
85.9/14.1/0
C2H4/HAC mole ratio
13.7
13.7
13.1
*No added water used in this comparative test (not according to the
invention)
Product Analysis
Products/Analysis
Run No. 1
Run No. 2
Run No. 3*
HAC Conversion
66
64
27
Product Selectivity (wt %)
EtAc
97.3
97.8
91.6
EtOH
0.4
0.3
0.1
DEE
1.8
1.3
0.0
Acetaldehyde
0.0
0.0
0.0
Oligomers
0.3
0.6
1.4
Others
0.1
0.04
6.8
EtAc Yield
95
59
25
EtAc STY (g/Lcat/h)
180
160
44
Carbon Balance (mol %)
104
105
100
Oxygen Balance (mol %)
95
102
81
Mass Balance
103
105
99
Water recovered (%)
69
73
—
*No water used and is hence a comparative test (not according to the invention)
TABLE 2
Run Conditions: (1 Mole % Water added to feed) using Catalyst 1:
Parameters
Run No. 4
Run No. 5
Run No. 6
Run No. 7
HOS
19-22
44-77
68.75-73.75
91-94
Temperature (° C.)
Applied
180
180
180
180
Bed (T/M/B)
181.5/186/182.5
181.5/185/183
181.3/184.5/181.2
181.4/184/181.1
Pressure (Kpa)
1000
1000
1000
1000
Total feed GHSV/h (@ STP)
980
980
980
980
C2H4 GHSV/h
905
905
905
905
HAC GHSV/h
66
66
66
66
H2O GHSV/h
9
9
9
9
C2H4 (g/Lcat/h)
1131
1131
1131
1131
HAC (g/Lcat/h)
177
177
177
177
H2O (g/Lcat/h)
8
8
8
8
Feed contact time [1/GHSV](secs)
4
4
4
4
C2H4/HAC/H2O mole % ratio
92.3/6.7/1.0
92.3/6.7/1.0
92.3/6.7/1.0
92.3/6.7/1.0
C2H4/HAC/H2O wt % ratio
86/13.4/0.6
86/13.4/0.6
86/13.4/0.6
86/13.4/0.6
C2H4/HAC mole ratio
13.7
13.7
13.7
13.7
Product Analysis
Products/Analysis
Run No. 4
Run No. 5
Run No. 6
Run No. 7
Ethylene conversion (%)
5.3
3.9
4.1
6.0
HAC Conversion
71
64
60
54
Product Selectivity (wt %)
EtAc
95.9
97.2
97.8
98.1
EtOH
0.7
0.6
0.5
0.6
DEE
2.3
1.8
1.3
1.0
Acetaldehyde
0.0
0.0
0.0
0.0
Oligomers
0.8
0.3
0.6
0.2
Others
0.3
0.1
0.0
0.0
EtAc Yield
68
63
59
53
EtAc STY (g/Lcat/h)
194
183
164
148
Carbon Balance (mol %)
100
199
100
97
Oxygen Balance (mol %)
94
89
93
88
Mass Balance
100
99
99
96
Water recovered (%)
53
56
62
65
TABLE 3
Run Conditions: (1 Mole % Water added to feed) using Catalyst 2:
Parameters
Run No. 8
Run No. 9
Run No. 10
HOS
14.75-17.5
38.5-41.5
62.5-65.5
Temperature (° C.)
Applied
180
180
180
Bed (T/M/B)
179.5/189/
179.6/187.5/
179.4/186.5/
182.8
182.9
182.8
Pressure (Kpa)
1000
1000
1000
Total feed GHSV/h (@ STP)
981
981
981
C2H4 GHSV/h
905
905
905
HAC GHSV/h
66
66
66
H2O GHSV/h
10
10
10
C2H4 (g/Lcat/h)
1131
1131
1131
HAC (g/Lcat/h)
177
177
177
H2O (g/Lcat/h)
8
8
8
Feed contact time
4
4
4
[1/GHSV](secs)
C2H4/HAC/H2O
92.3/6.7/1.0
92.3/6.7/1.0
92.9/6.7/1.0
mole % ratio
C2H4/HAC/H2O wt % ratio
85.9/13.5/0.6
85.9/13.5/0.6
85.9/13.5/0.6
C2H4/HAC mole ratio
13.7
13.7
13.7
Product Analysis
Products/Analysis
Run No. 8
Run No. 9
Run No. 10
Ethylene Conversion
7.3
3.9
3.3
HAC Conversion
81
77
75
Product Selectivity (wt %)
EtAc
92.7
95.2
96.0
EtOH
0.8
0.7
0.7
DEE
3.8
2.8
2.2
Acetaldehyde
0.0
0.0
0.0
Oligomers
1.6
0.9
0.8
Others
1.1
0.5
0.3
EtAc Yield
75
73
72
EtAc STY (g/Lcat/h)
213
211
201
Carbon Balance (mol %)
100
102
103
Oxygen Balance (mol %)
99
96
98
Mass Balance
100
102
103
Water recovered (%)
45
43
51
TABLE 4
Run Conditions: (5 Mole % Water added to feed) using Catalyst 2:
Parameters
Run No. 11
Run No. 12
Run No. 13
HOS
90.5-95.5
134.5-137.5
158.5-161.5
Temperature (° C.)
Applied
180
180
180
Bed (T/M/B)
179.3/188.5/
179.6/188.5/
179.5/188.5/
182.4
183.4
183.4
Pressure (Kpa)
1000
1000
1000
Total feed GHSV/h (@ STP)
975
975
975
C2H4 GHSV/h
866
866
866
HAC GHSV/h
61
61
61
H2O GHSV/h
48
48
48
C2H4 (g/Lcat/h)
1083
1083
1083
HAC (g/Lcat/h)
164
164
164
H2O (g/Lcat/h)
38
38
38
Feed contact time
4
4
4
[1/GHSV](secs)
C2H4/HAC/H2O
88.8/6.3/4.9
88.8/6.3/4.9
88.8/6.3/4.9
mole % ratio
C2H4/HAC/H2O wt % ratio
84.2/12.8/3
84.2/12.8/3
84.2/12.8/3
C2H4/HAC mole ratio
14.2
14.2
14.2
Product Analysis
Products/Analysis
Run No. 11
Run No. 12
Run No. 13
Ethylene Conversion
4.4
4.0
4.3
HAC Conversion
68
72
72
Product Selectivity (wt %)
EtAc
85.2
82.9
82.0
EtOH
3.7
3.7
3.9
DEE
10.5
13.0
13.6
Acetaldehyde
0.0
0.0
0.0
Oligomers
0.6
0.4
0.5
Others
0.01
0.02
0.07
EtAc Yield
58
60
59
EtAc STY (g/Lcat/h)
203
215
210
Carbon Balance (mol %)
102
103
103
Oxygen Balance (mol %)
87
87
89
Mass Balance
101
102
102
Water recovered (%)
43
39
42
TABLE 5
Run Conditions: (5 Mole % Water added to feed) using Catalyst 3:
Parameters
Run No. 14
Run No. 15
Run No. 16
HOS
16-19
40-43
112.5-115.5
Temperature (° C.)
Applied
180
180
180
Bed (T/M/B)
179.1/191/
179.1/190.5/
179.2/190/
183.2
183.5
183.8
Pressure (Kpa)
1000
1000
1000
Total feed GHSV/h (@ STP)
980
980
980
C2H4 GHSV/h
866
866
866
HAC GHSV/h
64
64
64
H2O GHSV/h
50
50
50
C2H4 (g/Lcat/h)
1083
1083
1083
HAC (g/Lcat/h)
170
170
170
H2O (g/Lcat/h)
40
40
40
Feed contact time
4
4
4
[1/GHSV](secs)
C2H4/HAC/H2O
88.4/6.5/5.1
88.4/6.5/5.1
92.3/6.7/1.0
mole % ratio
C2H4/HAC/H2O wt % ratio
83.7/13.2/3.1
83.7/13.2/3.1
86/13.4/0.6
C2H4/HAC mole ratio
13.6
13.6
13.6
Product Analysis
Products/Analysis
Run No. 14
Run No. 15
Run No. 16
Ethylene Conversion
6.6
7.6
6.3
HAC Conversion
86
85
83
Product Selectivity (wt %)
EtAc
73.4
74.0
73.2
EtOH
3.7
3.7
3.5
DEE
22.0
21.5
22.9
Acetaldehyde
0.0
0.0
0.0
Oligomers
0.6
0.7
0.5
Others
0.2
0.1
0.0
EtAc Yield
63
63
60
EtAc STY (g/Lcat/h)
219
221
224
Carbon Balance (mol %)
106
104
105
Oxygen Balance (mol %)
103
101
95
Mass Balance
105
104
104
Water recovered (%)
40
40
36
TABLE 6
Run Conditions: (5 Mole % Water added to feed) using Catalyst 3:
Parameters
Run No. 17
Run No. 18
Run No. 19
HOS
160.5-163.5
208.5-211.5
285.5-288.5
Temperature (° C.)
Applied
180
180
180
Bed (T/M/B)
179.2/190/
179.3/190/
179.3/190/
184.1
184.3
184.2
Pressure (Kpa)
1000
1000
1000
Total feed GHSV/h (@ STP)
980
980
980
C2H4 GHSV/h
866
866
866
HAC GHSV/h
64
64
64
H2O GHSV/h
50
50
50
C2H4 (g/Lcat/h)
1083
1083
1083
HAC (g/Lcat/h)
170
170
170
H2O (g/Lcat/h)
40
40
40
Feed contact time
4
4
4
[1/GHSV](secs)
C2H4/HAC/H2O
88.4/6.5/5.1
88.4/6.5/5.1
88.4/6.5/5.1
mole % ratio
C2H4/HAC/H2O wt % ratio
83.7/13.2/3.1
83.7/13.2/3.1
83.7/13.2/3.1
C2H4/HAC mole ratio
13.6
13.6
13.6
Product Analysis
Products/Analysis
Run No. 17
Run No. 18
Run No. 19
Ethylene Conversion
8.8
8.7
8.4
HAC Conversion
85
86
88
Product Selectivity (wt %)
EtAc
73.2
73.0
73.7
EtOH
3.6
3.9
3.7
DEE
22.6
22.6
22.1
Acetaldehyde
0.0
0.0
0.0
Oligomers
0.5
0.5
0.5
Others
0.1
0.1
0.1
EtAc Yield
62
63
65
EtAc STY (g/Lcat/h)
217
217
225
Carbon Balance (mol %)
104
104
104
Oxygen Balance (mol %)
103
103
103
Mass Balance
103
104
104
Water recovered (%)
40
41
38
TABLE 7
Run Conditions: (5 Mole % Water added to feed) using Catalyst 3:
Parameters
Run No. 20
Run No. 21*
Run No. 22*
HOS
375.5-378.5
448.5-451.5
472.5-475.5
Temperature (° C.)
Applied
180
180
180
Bed (T/M/B)
179.3/190/
179.3/186.5/
179.3/186.5/
184.4
183.4
183.4
Pressure (Kpa)
1000
1000
1000
Total feed GHSV/h
980
1001
1001
(@ STP)
C2H4 GHSV/h
866
866
866
HAC GHSV/h
64
64
64
H2O GHSV/h
50
50
50
DEE GHSV/h
0
21
21
C2H4 (g/Lcat/h)
1083
1083
1083
HAC (g/Lcat/h)
170
170
170
H2O (g/Lcat/h)
40
40
40
DEE (g/Lcat/h)
0
71
71
Feed contact time
3.7
3.6
3.6
[1/GHSV](secs)
C2H4/HAC/H2O/DEE
88.4/6.5/5.1§
86.5/6.4/2.1§
86.5/6.4/5/2.1
mole % ratio
C2H4/HAC/H2O/DEE
83.7/13.2/3.1§
79.4/12.5/2.9/
79.4/12.5/2.9/
wt % ratio
5.2
5.2
C2H4/HAC mole ratio
13.6
13.6
13.6
Product Analysis
Products/Analysis
Run No. 20
Run No. 21
Run No. 22
Ethylene Conversion
8.7
2.7
2.4
HAC Conversion
85
81
80
Product
Selectivity (wt %)
EtAc
74.1
71.9
70.8
EtOH
3.6
5.0
5.4
DEE
21.6
22.9
23.3
Acetaldehyde
0.0
0.0
0.0
Oligomers
0.5
0.2
0.5
Others
0.1
0.0
0.0
EtAc Yield
63
59
57
EtAc STY (g/Lcat/h)
226
226
222
Carbon Balance
103
105
105
(mol %)
Oxygen Balance
98
101
98
(mol %)
Mass Balance
102
105
104
Water recovered (%)
38
60
63
*co-fed additionally with 2 Mole % DEE.
§No diethyl ether used in this Run
TABLE 8
Run No. 23
Run No. 24
Run Conditions: (5 Mole % Water + 2 Mole % DEE added to feed)
using Catalyst 3:
Parameters
HOS
479.5-500.5
544.5-547.5
Temperature (° C.)
Applied
180
180
Bed (T/M/B)
179.3/186.5/183.4
179.4/187/183.4
Pressure (Kpa)
1000
1000
Total feed GHSV/h (@ STP)
1001
1001
C2H4 GHSV/h
866
866
HAC GHSV/h
64
64
H2O GHSV/h
50
50
DEE GHSV/h
21
21
C2H4 (g/Lcat/h)
1083
1083
HAC (g/Lcat/h)
170
170
H2O (g/Lcat/h)
40
40
DEE (g/Lcat/h)
71
71
Feed contact time [1/GHSV](secs)
3.6
3.6
C2H4/HAC/H2O/DEE mole % ratio
86.5/6.4/5/2.1
86.5/6.4/5/2.1
C2H4/HAC/H2O/DEE wt % ratio
79.4/12.5/2.9/5.2
79.4/12.5/2.9/5.2
C2H4/HAC mole ratio
13.6
13.6
Product Analysis
Products/Analysis
Ethylene Conversion
1.4
1.3
HAC Conversion
84
82
Product
Selectivity (wt %)
EtAc
70.6
71.1
EtOH
5.1
5.2
DEE
23.9
23.5
Acetaldehyde
0.0
0.0
Oligomers
0.3
0.3
Others
0.0
0.0
EtAc Yield
59
58
EtAc STY (g/Lcat/h)
226
224
Carbon Balance (mol %)
107
106
Oxygen Balance (mol %)
103
99
Mass Balance
106
105
Water recovered (%)
61
63
TABLE 9
LIQUID PRODUCT DATA
GCMS
180° C., 1000 Kpa (10 barg), ethylene/acetic acid = 14
Run No.
Organics (% by Wt)
7
17
23
Water (mole % in feed)
1
5
5
(+2% DEE)
Acetic acid (unreacted feed)
52.3
21.2
16.3
Ethyl acetate
46.5
67.3
69
Diethylether
0.05
3
3.3
Ethanol
0.65
7.8
11
Acetaldehyde
0.002
0.04
0.009
C6 oligomers
0.0015
0
0
C8 oligomers
0.0055
0
0
Miscellaneous oxygenates
0.0065
0
0
Aromatic hydrocarbons
0.045
0
0
Unknowns
0.11
0.01
0
BALANCE: others
(Hydrocarbons & oxy
compounds)
Catalyst Preparations
Catalyst 4. 12-Tungstophosphoric acid [H3PW12O40.24H2O] (175 g) was dissolved in distilled water (250 ml). Lithium nitrate [LiNO3.2H2O] (0.652 g) was dissolved in distilled water (˜5 ml). The lithium nitrate solution was added dropwise to the tungstophosphoric acid solution to form Solution “A”.
Solution “A” was added to pelleted silica support (Grace 1371 grade, 1-3 mm, 99.5 g, ex W R Grace) and left to soak over 24 hours with occasional stirring in order to impregnate the silica with the tungstophosphoric acid catalyst. After this duration, excess solution “A” was decanted and filtered off. The resultant catalyst impregnated support was then dried in flowing nitrogen gas initially at 150° C. for 3 hours and then raised to 200° C. and maintained at that temperature for 5 hours. The supported catalyst so formed was then left in a desiccator to cool and was finally reweighed. The resultant supported catalyst had a final weight of 164.4 g, a net catalyst loading of 64.9 g and had the formula Li0.1H2.9PW12O40.24H2O/SiO2 corresponding to a loading of 255 g/l.
Catalyst 4. Pelleted silica support (Grace 1371 grade, 1-3 mm, 70 g, ex W R Grace) was soaked in a solution (250 ml) of 12-tungstosilicic acid [H4SiW12O40.26H2O] (65.53 g in distilled water) for 24 hours with intermittent stirring in order to impregnate the support with the catalyst. Thereafter the excess solution of the tungstosilicic acid was removed by decantation and filtration. The resultant catalyst impregnated support was then dried overnight under flowing nitrogen at 120° C. The dried supported catalyst so formed was cooled in a desiccator and had a final weight of 86.2 g, a net catalyst loading of 16.2 g and had the formula H4SiW12O40.26H2O/SiO2 corresponding to a loading of 92 g/l.
The above catalysts were used to esterify ethylene with acetic acid. The relative amounts of each of these catalysts used, their bed size and bed length in performing the esterification reaction were as follows:
Parameter
Catalyst 4
Catalyst 5
Volume (cm3)
25
25
Weight (g)
15.5
11.2-11.4
Pellet size (mm)
1-2
1-2
(Table 11) &
0.5-1
(Tables 12, 13 and 14)
Bed length
8.5
8.75
TABLE 10
Run No. 25
Run No. 26
Run No. 27
(Catalyst 4-15.5 g)
Run Conditions:
Parameters
HOS
1-3
19-21
25-27
Temperature (° C.)
Applied
170
170
170
Bed (T/M/B)
173.5/—/170.5
172/—/169
172/—/169
Pressure (Kpa)
1000
1000
1000
Total feed GHSV/h
979
979
979
(@ STP)
C2H4 GHSV/h
905
905
905
HAC GHSV/h
65
65
65
H2O GHSV/h
9
9
9
C2H4 (g/Lcat/h)
1131
1131
1131
HAC (g/Lcat/h)
173
173
173
H2O (g/Lcat/h)
8
8
8
Feed contact time
4
4
4
[1/GHSV](secs)
C2H4/HAC/H2O mole
92.4/6.6/1.0
92.4/6.6/1.0
92.4/6.6/1.0
% ratio
C2H4/HAC/H2O wt % ratio
86.2/13.2/0.6
86.2/13.2/0.6
86.2/13.2/0.6
C2H4/HAC mole ratio
14.0
14.0
14.0
Product Analysis (Table 10 continued)
Products/Analysis
HAC Conversion
51
47
45
Product Selectivity (wt %)
EtAc
89.7
98.0
97.7
EtOH
0.5
0.5
0.4
DEE
0.9
0.7
1.0
Acetaldehyde
0.0
0.0
0.0
Oligomers
7.0
0.4
0.7
Others
1.90
0.49
0.26
EtAc Yield
45
46
44
EtAc STY (g/Lcat/h)
128
122
118
Carbon Balance (mol %)
102
102
105
Oxygen Balance (mol %)
86
89
100
Mass Balance
101
101
104
Water recovered (%)
90
70
81
TABLE 11
Run No. 28
Run No. 29
Run No. 30
(Catalyst 5-11.3 g)
Run Conditions:
Parameters
HOS
1-2
17-20
21-24
Temperature (° C.)
Applied
170
170
170
Bed (T/M/B)
176/—/174
173/—/170
173/—/170
Pressure (Kpa)
1000
1000
1000
Total feed GHSV/h (@ STP)
980
980
980
C2H4 GHSV/h
905
905
905
HAC GHSV/h
66
66
66
H2O GHSV/h
9
9
9
C2H4 (g/Lcat/h)
1131
1131
1131
HAC (g/Lcat/h)
177
177
177
H2O (g/Lcat/h)
8
8
8
Feed contact time
4
4
4
[1/GHSV](secs)
C2H4/HAC/H2O mole % ratio
92.3/6.7/1.0
92.3/6.7/1.0
92.4/6.6/1.0
C2H4/HAC/H2O wt % ratio
85.9/13.5/0.6
85.9/13.5/0.6
86.2/13.2/0.6
C2H4/HAC mole ratio
13.7
13.7
13.7
Product Analysis:
Products/Analysis
HAC Conversion
62
66
64
Product Selectivity (wt %)
EtAc
86.0
97.3
97.6
EtOH
2.4
0.4
0.4
DEE
3.3
1.8
1.4
Acetaldehyde
0.0
0.0
0.0
Oligomers
2.4
0.3
0.6
Others
5.9
0.1
0.1
EtAc Yield
53
65
62
EtAc STY (g/Lcat/h)
151
180
171
Carbon Balance (mol %)
101
104
105
Oxygen Balance (mol %)
98
95
99
Mass Balance
101
103
105
Water recovered (%)
70
69
67
TABLE 12
Run No. 31
Run No. 32
Run No. 33
(Catalyst 5-11.2 g)
Run Conditions:
Parameters
HOS
19.25-22.5
23-26
43.25-46.25
Temperature (° C.)
Applied
170
170
180
Bed (T/M/B)
172.5/176/—
172.5/175.5/—
182/187/—
Pressure (Kpa)
1000
1000
1000
Total feed GHSV/h
980
980
980
(@ STP)
C2H4 GHSV/h
905
905
905
HAC GHSV/h
66
66
66
H2O GHSV/h
9
9
9
C2H4 (g/Lcat/h)
1131
1131
1131
HAC (g/Lcat/h)
177
177
177
H2O (g/Lcat/h)
8
8
8
Feed contact time
4
4
4
[1/GHSV](secs)
C2H4/HAC/H2O mole %
92.3/6.7/1.0
92.3/6.7/1.0
92.3/6.7/1.0
ratio
C2H4/HAC/H2O wt % ratio
86/13.4/0.6
86/13.4/0.6
86/13.4/0.6
C2H4/HAC mole ratio
13.7
13.7
13.7
Product Analysis:
Products/Analysis
HAC Conversion
72
72
72
Product Selectivity (wt %)
EtAc
96.0
94.4
94.9
EtOH
0.5
0.5
0.7
DEE
2.9
2.7
3.3
Acetaldehyde
0.0
0.0
0.0
Oligomers
0.4
1.6
0.7
Others
0.2
0.3
0.8
EtAc Yield
69
68
78
EtAc STY (g/Lcat/h)
203
194
210
Carbon Balance (mol %)
101
103
108
Oxygen Balance (mol %)
91
97
104
Mass Balance
100
103
108
Water recovered (%)
47
48
48
TABLE 13
Run No. 34
Run No. 35
Run No. 36
(Catalyst 5-11.2 g)
Run Conditions:
Parameters
HOS
47-50
67.25-70.25
71-74
Temperature (° C.)
Applied
180
190
190
Bed (T/M/B)
181.5/186.5/—
191.5/196/—
191.5/195.5/—
Pressure (Kpa)
1000
1000
1000
Total feed GHSV/h
980
980
980
(@ STP)
C2H4 GHSV/h
905
905
905
HAC GHSV/h
66
66
66
H2O GHSV/h
9
9
9
C2H4 (g/Lcat/h)
1131
1131
1131
HAC (g/Lcat/h)
177
177
177
H2O (g/Lcat/h)
8
8
8
Feed contact time
4
4
4
[1/GHSV](secs)
C2H4/HAC/H2O mole
92.3/6.7/1.0
92.3/6.7/1.0
92.3/6.7/1.0
% ratio
C2H4/HAC/H2O wt %
86/13.4/0.6
86/13.4/0.6
86/13.4/0.6
ratio
C2H4/HAC mole ratio
13.7
13.7
13.7
Product Analysis:
Products/Analysis
HAC Conversion
79
74
72
Product
Selectivity (wt %)
EtAc
95.2
94.7
94.9
EtOH
0.7
0.7
0.7
DEE
3.2
2.8
2.2
Acetaldehyde
0.0
0.0
0.0
Oligomers
0.6
1.4
1.3
Others
0.2
0.3
0.8
EtAc Yield
75
70
68
EtAc STY (g/Lcat/h)
206
202
191
Carbon Balance
105
102
104
(mol %)
Oxygen Balance
102
94
99
(mol %)
Mass Balance
105
102
104
Water recovered (%)
47
52
54
TABLE 14
Run No. 37
Run No. 38
Run No. 39
(Catalyst 5-11.4 g)
Run Conditions:
Parameters
HOS
19-22
44-47
68.75-71.75
Temperature
(° C.)
Applied
180
180
180
Bed (T/M/B)
181.5/186/182.5
181.5/185/182
181.3/184.5/181.2
Pressure (Kpa)
1000
1000
1000
Total feed
980
980
980
GHSV/h
(@ STP)
C2H4 GHSV/h
905
905
905
HAC GHSV/h
66
66
66
H2O GHSV/h
9
9
9
C2H4 (g/Lcat/h)
1131
1131
1131
HAC (g/Lcat/h)
177
177
177
H2O (g/Lcat/h)
8
8
8
Feed contact time
4
4
4
[1/GHSV](secs)
C2H4/HAC/H2O
92.3/6.7/1.0
92.3/6.7/1.0
92.3/6.7/1.0
mole % ratio
C2H4/HAC/H2O
86/13.4/0.6
86/13.4/0.6
86/13.4/0.6
wt % ratio
C2H4/HAC mole
13.7
13.7
13.7
ratio
Product Analysis:
Products/Analysis
HAC Conversion
71
64
60
Product
Selectivity (wt %)
EtAc
95.9
97.2
97.8
EtOH
0.7
0.6
0.5
DEE
2.3
1.8
1.3
Acetaldehyde
0.0
0.0
0.0
Oligomers
0.8
0.3
0.3
Others
0.3
0.1
0.0
EtAc Yield
68
63
59
EtAc STY
194
183
164
(g/Lcat/h)
Carbon Balance
100
100
100
(mol %)
Oxygen Balance
94
89
93
(mol %)
Mass Balance
100
99
99
Water recovered
53
56
62
(%)
Atkins, Martin P., Sharma, Bhushan
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