CA1060467A - Process for producing acetic acid, ethanol, and acetaldehyde from synthesis gas - Google Patents
Process for producing acetic acid, ethanol, and acetaldehyde from synthesis gasInfo
- Publication number
- CA1060467A CA1060467A CA218,756A CA218756A CA1060467A CA 1060467 A CA1060467 A CA 1060467A CA 218756 A CA218756 A CA 218756A CA 1060467 A CA1060467 A CA 1060467A
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/10—Preparation of carboxylic acids or their salts, halides or anhydrides by reaction with carbon monoxide
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
- C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
- C07C29/1512—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by reaction conditions
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
- C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
- C07C29/153—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used
- C07C29/154—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used containing copper, silver, gold, or compounds thereof
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
- C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
- C07C29/153—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used
- C07C29/156—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used containing iron group metals, platinum group metals or compounds thereof
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
- C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
- C07C29/153—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used
- C07C29/156—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used containing iron group metals, platinum group metals or compounds thereof
- C07C29/157—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used containing iron group metals, platinum group metals or compounds thereof containing platinum group metals or compounds thereof
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
- C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
- C07C29/153—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used
- C07C29/156—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used containing iron group metals, platinum group metals or compounds thereof
- C07C29/157—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used containing iron group metals, platinum group metals or compounds thereof containing platinum group metals or compounds thereof
- C07C29/158—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used containing iron group metals, platinum group metals or compounds thereof containing platinum group metals or compounds thereof containing rhodium or compounds thereof
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
- C07C45/49—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by reaction with carbon monoxide
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/10—Preparation of carboxylic acids or their salts, halides or anhydrides by reaction with carbon monoxide
- C07C51/12—Preparation of carboxylic acids or their salts, halides or anhydrides by reaction with carbon monoxide on an oxygen-containing group in organic compounds, e.g. alcohols
Abstract
ABSTRACT
A process for the selective preparation of tow-carbon atom oxygenated hydrocarbons, namely acetic acid, ethanol, and acetaldehyde, by continuously contacting a reaction mixture containing hydrogen and carbon monoxide with a rhodium metal catalyst, at a combination of reaction conditions correlated so as to favor the formation of a substantial proportion of these products.
A process for the selective preparation of tow-carbon atom oxygenated hydrocarbons, namely acetic acid, ethanol, and acetaldehyde, by continuously contacting a reaction mixture containing hydrogen and carbon monoxide with a rhodium metal catalyst, at a combination of reaction conditions correlated so as to favor the formation of a substantial proportion of these products.
Description
1060467 :-..: .'.
BACKGROUND
This invention concerns the selective preparation of two-carbon atom oxygenated hydrocarbons, namely acetic acid~ ethanol~ and/or acetaldehyde, from synthesis gas.
More particularly, the invention concerns reaction of synthesis gas in the presence of a heterogeneous catalyst to produce such products.
The preparation of hydrocarbons and oxygenated hydrocarbons from synthesis gas (essentially a mixture of carbon monixide with varying amounts of carbon dioxide and hydrogen) has received extensive study and has achieved c~mmercial adoption. Reaction conditions generally involved temperatures on the order of 150-450C, pressures of from atmospheric to about 10,000 psig, and hydrogen-to-carbon monixide ratios in the range of 4:1 to about 1:4, with an iron group or a noble metal group hydrogenation catalys~.
--~ D-9406-1 i O ~0 ~ 6'7 One serious disability of most synthesis gas processes has been the non-selective or non-specific nature of the product distribution. Catalysts which possess acceptable activity generally tend to give a wide spectrum of products--hydrocarbons and oxygenated hydrocarbons--having a broad distribution of carbon atom contents. This not only complicates the recovery of desired products, but results in the wastage of reactants to commercially uninteresting byproducts.
SUMMARY OF INVENTION
In accordance with the invention, a process is provided for the reaction of carbon monoxide with hydrogen to prepare, selectively, oxygenated hydrocarbons of two carbon atom~ per molecule. Synthesis gas is continuously contacted with a catalyst essentially comprising rhodium metal, at a c~mbination of reaction conditions correlated so as to favor the formation of a substantial proportion of acetic acid, ethanol, and/or acetaldehyde.
The reaction is conducted at reactive conditions of temperature, pressure, gas composition and space velocity correlated so as to collectively produce acetic acid, ethanol, and/or acetaldehyde in an amount which is at least about 50 weight percent, preferably at least about 75 weight percent, of the two and more carbon atom compounds obtained by the reaction, Desirably, the reaction is conducted at these correlated conditions to achieve product efficiencies based on carbon consumption in excess of 10%, ~~~ D-9406-1 10~iO4~
and frequently in excess of 50%. Ethyl esters and acetates formed are included as ethanol and acetic acid in determining productivities and selectivities as used in data presented herein. At optimum reaction conditions, and particularly at relatively low conversions, there is little conversion to three carbon atom and higher hydrocarbons and oxygenated hydrocarbons, and conversion to methane and methanol may readily be minimized. As will appear, it is also possible, through variations in catalyst composition and reaction conditions, to direct the selectivity toward only one of the three products, e.g. acetic acid or ethanol.
REL~TION TO PRIOR ART
The literature on synthesis gas conversion i~
extensive. While it is rare to find a metal that has not been investigated as a catalyst for the reaction, most efforts to date have focused on the iron group metals, on ruthenium, and on various metal oxide systems.
Extensive literature surveys have revealed that five prior workers have investigated the use of rhodium metal as a synthesis gas conversion ~atalyst. Their publications, identified in Table I below, report results which are no more impressive than are obtained with iron group catalysts. In view of these recults and the relatively high price of rhodium, it is not surprising to find there has been so little interest in the use of rhodium as a catalyst for synthesis gas conversion.
~o60467 o ~ i ~, f g W
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z ~ r ~ ~ 2 ~2 8 ;~ Y -Bl E r ~ 9 ¦ 9~ ' ~ 2 , 4_ , :
~0467 D-9406-1 The relationship between reaction conditions employed and the results achieved by prior workers are well summarized in the above Table. None reported or found more than 3.4 mole percent of two carbon atom oxygenated compounds in the reaction products. This contrasts with as much as 80 mole percent two carbon atom oxygenated compounds in the presently described process. There is evidently an importance in associating a rhodium metal catalyst with correlated reaction conditions to favor the formation of a substantial proportion of acetic acid, ethanol, and/or acetaldehyde.
A more detailed illustration of the difference ~etween Soufi's results and those obtained by the practice of the present invention is shown in Table II.
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~iO~7 DETAILED DESCRIPTION
_ In keeping with the invention, a synthesis gas containing carbon monoxide and hydrogen is contacted with a rhodium metal catalyst under reactive conditions of temperature, pressure, gas composition and space velocity correlated so as to favor as stated previously, the formation of a substantial proportion of acetic acid, ethanol, and/or acetaldehyde. The reaction efficiency, or selectivity, to these two-carbon atom compounds is invariably at least about 10%, and is usually upwards of about 25%;
under the preferred conditions it exceeds 50% and, under -~-optimum conditions, has reached 90% or more. Selectivity is deined herein as the percentage of carbon atoms converted from carbon monoxide to a speci~ied compound or compounds.
Thus, the independent reaction variables are correlated so as to favor the formation of a substantial ~ -proportion of the desired two carbon atom oxygenated hydrocarbons (acetic acid, ethanol, and/or acetaldehyde).
This proportion, expressed as carbon conversion efficiency, is usually upwards of 25% and frequently exceeds 50%.
In one aspect of the invention, this correlation is a combination of conditions which result in maintaining moderate reaction conditions to thereby limit the conversion of CO to not more than about one fourth, preferably not more than about one eighth. As will be discussed in detail below, this may be achieved primarily by a combination of high space velocity and low temperature, but other ~ ~4,~j,7 D- 9406 -1 factors (e.g. H2/CO ratio, catalyst activity, pressure, bed ge~metry, etc.) also affect the conversion. At high conversions, it has been noted that higher carbon ntImber hydrocarbons and oxygenated hydrocarbons are produced in excess, with a resulting loss in efficiency to two-carbon atom compounds.
Conditions of temperature, of pressure, and of gas composition are usually ~ithin the ranges that are essentially conventional for synthesis gas conversions, particularly those employed in the production of methanol.
Thus, existing technology and, in some instances, existing equipment may be used to effect the reaction, The reaction is highly exothermlc, with both the thermodynamic equilibrium and the kinetic reaction rates being governed by the reaction temperature Average catalyst bed temperatures are usually within the range of about 150-450C., but for optimum conversions, bed temperatures are kept within the range of about 200-400C., typically about 250-350C.
The reaction temperature is an important process variable, affecting not only total productivity but selectivity toward one or more of the desired two carbon atom products. Over relatively narrow temperature ranges, as for example 10 or 20C., an increase in temperature may somewhat increase total synthesis gas conversion, tending to increase the efficiency of ethanol production but decreases the efficiency of acetic acid and acetaldehyde production. At the same time, however, higher temperatures ~ ;0~;()4~i7 favor methane production, and apparently methane production increases much more rapidly at higher temperatures than do conversions to the more desirable two carbon atom products.
l~us, for a given catalyst and with all other variables held constant, the optimum temperature will depend more on product and process economics than on thermodynamic or kinetic considerations, with higher temperatures tendin~
to increase the production of oxygenated products but disproportionately increasing the co-production of methane.
In the discussions above the indicated temperatures are expressed as average, or mean, reaction bed temperatures.
Because of the highly exothermic nature of the reaction, ~t is desirable that the temperature be controlled so as not to produ~e a runaway methanation, in which methane formation i8 increased with higher temperature, and the resulting exotherm increases the temperature further. To accomplish this, conventional temperature control techniques are utilized, as for example the use of fluidized bed reaction zones, the use of multi-stage fixed bed adiaba~ic reactors with interstage cooling, or relatively small (1/16th inch or less) catalyst particles placed in tube-and-shell type reactors with a coolant fluid surrounding the catalyst-filled tubes.
The reaction zone pressure is desirably within the range of about 15 psig to about 10,000 psig, economically w~thin the range of about 300-5,000 psig. Higher reaction zone pressures increase the total weight of product obtained per unit time and likewise improve the selectivity _g_ ~ D-9406-l ~ 0~04~7 toward two carbon atom compounds.
The ratio of hydrogen to carbon monoxide in the synthesis gas may vary widely, and in large measure is dictated by the process or processes employed to make the gas~. Normally the mole ratio of hydrogen to carbon monoxide is within the range of 20:1 to 1:20, or preferably within the range of about 5:1 to about 1:5. In most of the experimental work reported herein the mole ratio of the hydrogen pressure to the carbon monoxide pressure is somewhat less than 1:1. Increasing the ratio ~ends to increase the total rate of reaction, sometimes quite significantly, and has a small but favorable effect on production of two carbon atom products, but concurrently lncrea8e8 sele~tivity to methane. Increasing the hydrogen to carbon monoxide ratio also favors the formation of more highly reduced products, that i8, ethanol rather than acetaldehyde or acetic acid.
Impurities in the synthesis gas may or may not have an effect on the reaction, depending on their nature and concentration. Carbon dioxide, normally present in an amount of up to about 10 mole percent, has essentially no effect. ~f a recycle operation is conducted, in which all or part of the reacted gas is recycled to the catalyst zone, it is desirable to remove oxygenated hydrocarbons before recycling To provide empirical orientation, a set of ten experiments, in the form of a two-level, fractional factorial ,. ., - . . , - ; .
~ 0~04~
design plus centerpoints, was conducted. The independent variables were temperature (275 and 300C.), hydrogen and carbon monoxide partial pressures (350 and 500 psig), and gas hourly space velocities (3600 and 4700 volumes of gas at standard conditions per volume of catalyst per hour).
All variables, with the exception of space velocity, proved to be significant in their influences on the rates and efficiencies to the principal products, i.e., acetic acid, ethanol, acetaldehyde, and methane.(Note, ~owever, that space velocity was varied over a comparatively narrow range, and in each instance was quite high.) Qualitatively, the8e responses are indicated in Table III below. In each instance, the effect of an increase in the specified variab~e is represented by either one or more positive or negative signs to characterize the degree of response of the rate and/or of the efficiency.
10~04~7 ~1 ++ ., + I ''.
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10ti04~7 The results of Table IIT, above, suggest that the conditions most favorable to high selectivity toward acetic acid and acetaldehyde are the lowest practical operating temperature, low hydrogen partial pressure, and high carbon monoxide partial pressure. Verification of this prediction is provided in the following data (here and in Table III
utilizing a 5% rhodium on silica catalyst) presented in Table IV below.
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i,o4f~7 One of the features of the present invention is the recognition that a low conversion--preferably less than 20% of the CO--favors the formation or production of a substantial proportion of acetic acid, ethanol and/or acetaldehyde, generally in excess of 10% as compared with a maximum of 3 4% in the prior art (Table I). This conversion is conveniently achieved by employing a high space velocity correlated with other reaction variables (e.g. temperature, pressure, gas composition, catalyst, etc ). Space velocities in excess of about 10 gas hourly space velocity (volumes of reactant gas, at 0C and 760mm mercury pressure, per volume of catalysts per hour) are generally employed, although it is preferable that the space velocity bs within the range of about 104 to about 106 per hour. Excessively high space velocity result in an uneconomically low conversion, while excessively low space velocities cause the production of a more diverse spectrum of reaction products, including higher boiling hydrocarbons and oxygenated hydrocarbons.
The rhodium catalyst is rhodium metal provided in the reaction zone by a number of techniques, or a combination of a number of these techniques. One technique is to coat the reaction zone (or reactor) walls with rhodium metal. Another is to coat a porous screen or screens with a thin coating of the metal. Still another way involves placing particles of rhodium in the reaction zone, generally supported by an inert porous packing material.
--~ D-9406-1 ~O~ ~ 4 ~7 Another way is to deposit rhodium onto a particulate support material and place the supported rhodium into the reaction zone. Any combination of these techniques can be employed.
However, important advantages within the scope of the invention are achieved when the rhodium metal catalyst is in a highly dispersed form on a particulate support. ~n the basis of experience to date the amount of catalysts on the support should range from about 0.01 weight percent to about 25 weight percent, based on the combined weight of the metal catalyst and the support material. Preferably, the amount of catalyst is within the range of about 0.1 to about 10 weight percent.
A wide variety of support materials has been tested. A relatively high surface area particulate support, e.g. one having a surface area upwards of about 1.0 square meters per gram (BET low temperature nitrogen adsorption isotherm method), is preferred, desirably upwards of about 1.5 square meters per gram, although surface area alone is not the sole determinative variable. Based on research to date, silica gel is preferred as the catalyst base or support, with alpha alumina, magnesia, eta alumina, gamma alumina, and active carbon being progressively less desirable. Zeolitic molecular sieves, primarily the higher silica-to-alumina crystalline zeolites, also have promise.
The rhodium metal may be deposited onto the base or support by any of the techniques commonly used for .
.. . .. ~; . . . .
`` D-9406-1 4~7 catalyst preparation, as for example impregnation from an organic or inorganic solution, precipitation, coprecipitation, or cation exchange (on a zeolite).
Numerous specific embodiments of catalysts preparatory techniques are described in the Examples below; it suffices for the present to say that an inorganic or organic rhodium compound is appropriately contacted with the support material, and the support then dried and heated, the latter advantageously under reducing conditions, to form the finely dispersed rhodium metal.
The invention in its various aspects is illustrated in the different "Series" of experiments presented below. In each instance it will be appreciated that the tests are exemplary only, and are not intended to be wholly definitive or exclusive with respect to scope or conditions of the invention.
SERIES A
This Series illustrates the preparation and testing of supported rhodium metal catalysts on a variety of high surface area supports. It also contrasts supported rhodium with supported iridium, supported ruthenium, supported palladium, supported platinum, supported copper, and supported cobalt.
Preparation of Catalysts Catalysts tested in this study were all prepared by essentially the same sequence of steps: An aqueous solùtion of the desired component was impregnated on the ~ D-9406-1 1(3~04~7 support; the impregnated support was carefully dried;
the metal salt was reduced slowly in a flowing hydr~gen atmosphere. When metal components were impregnated as nltrate salts, a pyrolysis step preceeded the hydrogen reduction step. In most cases, rhodium was impregnated as a RhCl3 solution.
The description below illustrates this procedure for the catalyst used in Tests 1-7(5% rhodium on Davison TM
Grade 59 Silica Gel). Table V summarized preparative details for the catalysts whose activities are described in this Series.
Thodium trichloride (22.58 gm, 41.93% Rh) was dissolved in 240 ml of distilled water at ambient temperature.
Davison TM Grade 59 si~ica gel (200.0 gm, 3-6 mesh) was placed in a vacuum flask. The top of the flask was sealed with a rubber septum, and the flask was evacuated through the side arm. A syringe needle was then used to inject the rhodium solution onto the evacuated support. When addition was complete, the impregnated support was allowed to stand at one atmosphere for ca. 30 minutes. It was then carefully dried in a nitrogen atmosphere: 80C (l hr); 110C (2 hrs);
150C (2 hrs). The dried, impregnated support was placed in a quartz tube through which hydrogen was continuously ., passed. The temperature was raised to 450C and held at that value for 2 hours. The reduced catalyst was cooled to ambient temperature in an atmosphere of flowing nitrogen.
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N N
.
~ D-9406-1 04~7 De~scr~ of Test Reactor The reactor used in these studies was a bottom-agitated "Magnedrive" autoclave of the J. M. Berty design with a centrally positioned catalyst basket and a side product effluent line. It is of the type depicted in Figure 1 of the paper by Berty, Hambrick, Malone and Ullock, entitled "Reactor for Vapor-Phase Catalytic Studies", presented as Preprint 42E at the Symposium on Advances in High-Pressure Technology - Part II, Sixty Four~h National Meeting of the American Institute of Chemical Engineers (AlChE), at New Orleans, Louisiana, on March 16-20, 1969 and obtainable from AlChE at 345 East 47 Street, New York, N.Y. 10017. A variable æpeed, magnetically driven, fan continuously rccirculated the reaction mixture over the catalyst bed. The following modifications were found to facilitate operation and inhibit run-away methanation reactions.
1. Hydrogen feed gas was introduced c~ntinuously at the bottom of the autoclave through the well for the shaft of the Magnedrive agitator.
BACKGROUND
This invention concerns the selective preparation of two-carbon atom oxygenated hydrocarbons, namely acetic acid~ ethanol~ and/or acetaldehyde, from synthesis gas.
More particularly, the invention concerns reaction of synthesis gas in the presence of a heterogeneous catalyst to produce such products.
The preparation of hydrocarbons and oxygenated hydrocarbons from synthesis gas (essentially a mixture of carbon monixide with varying amounts of carbon dioxide and hydrogen) has received extensive study and has achieved c~mmercial adoption. Reaction conditions generally involved temperatures on the order of 150-450C, pressures of from atmospheric to about 10,000 psig, and hydrogen-to-carbon monixide ratios in the range of 4:1 to about 1:4, with an iron group or a noble metal group hydrogenation catalys~.
--~ D-9406-1 i O ~0 ~ 6'7 One serious disability of most synthesis gas processes has been the non-selective or non-specific nature of the product distribution. Catalysts which possess acceptable activity generally tend to give a wide spectrum of products--hydrocarbons and oxygenated hydrocarbons--having a broad distribution of carbon atom contents. This not only complicates the recovery of desired products, but results in the wastage of reactants to commercially uninteresting byproducts.
SUMMARY OF INVENTION
In accordance with the invention, a process is provided for the reaction of carbon monoxide with hydrogen to prepare, selectively, oxygenated hydrocarbons of two carbon atom~ per molecule. Synthesis gas is continuously contacted with a catalyst essentially comprising rhodium metal, at a c~mbination of reaction conditions correlated so as to favor the formation of a substantial proportion of acetic acid, ethanol, and/or acetaldehyde.
The reaction is conducted at reactive conditions of temperature, pressure, gas composition and space velocity correlated so as to collectively produce acetic acid, ethanol, and/or acetaldehyde in an amount which is at least about 50 weight percent, preferably at least about 75 weight percent, of the two and more carbon atom compounds obtained by the reaction, Desirably, the reaction is conducted at these correlated conditions to achieve product efficiencies based on carbon consumption in excess of 10%, ~~~ D-9406-1 10~iO4~
and frequently in excess of 50%. Ethyl esters and acetates formed are included as ethanol and acetic acid in determining productivities and selectivities as used in data presented herein. At optimum reaction conditions, and particularly at relatively low conversions, there is little conversion to three carbon atom and higher hydrocarbons and oxygenated hydrocarbons, and conversion to methane and methanol may readily be minimized. As will appear, it is also possible, through variations in catalyst composition and reaction conditions, to direct the selectivity toward only one of the three products, e.g. acetic acid or ethanol.
REL~TION TO PRIOR ART
The literature on synthesis gas conversion i~
extensive. While it is rare to find a metal that has not been investigated as a catalyst for the reaction, most efforts to date have focused on the iron group metals, on ruthenium, and on various metal oxide systems.
Extensive literature surveys have revealed that five prior workers have investigated the use of rhodium metal as a synthesis gas conversion ~atalyst. Their publications, identified in Table I below, report results which are no more impressive than are obtained with iron group catalysts. In view of these recults and the relatively high price of rhodium, it is not surprising to find there has been so little interest in the use of rhodium as a catalyst for synthesis gas conversion.
~o60467 o ~ i ~, f g W
~ o ~i 2 E ; ~ ~r - ~ ~8 Y R 7, a ~ O ~~ ~--9 ; 2 '~ 9 I ~ OU ~ O
z ~ r ~ ~ 2 ~2 8 ;~ Y -Bl E r ~ 9 ¦ 9~ ' ~ 2 , 4_ , :
~0467 D-9406-1 The relationship between reaction conditions employed and the results achieved by prior workers are well summarized in the above Table. None reported or found more than 3.4 mole percent of two carbon atom oxygenated compounds in the reaction products. This contrasts with as much as 80 mole percent two carbon atom oxygenated compounds in the presently described process. There is evidently an importance in associating a rhodium metal catalyst with correlated reaction conditions to favor the formation of a substantial proportion of acetic acid, ethanol, and/or acetaldehyde.
A more detailed illustration of the difference ~etween Soufi's results and those obtained by the practice of the present invention is shown in Table II.
~06V4~7 o U~ ~o V
t- ~ ~ ~ ~ . O . "~
R ~ ~ o o o ~ - ~
~ ~ ~ o ~ ~ y o ~ ~o 8 _ ,,, ~; , , , $~
g ~, 3 ~.,J, ~Y_ ~1 ~ a ~y C~ y ~ a ..1 ~ .
'~
~iO~7 DETAILED DESCRIPTION
_ In keeping with the invention, a synthesis gas containing carbon monoxide and hydrogen is contacted with a rhodium metal catalyst under reactive conditions of temperature, pressure, gas composition and space velocity correlated so as to favor as stated previously, the formation of a substantial proportion of acetic acid, ethanol, and/or acetaldehyde. The reaction efficiency, or selectivity, to these two-carbon atom compounds is invariably at least about 10%, and is usually upwards of about 25%;
under the preferred conditions it exceeds 50% and, under -~-optimum conditions, has reached 90% or more. Selectivity is deined herein as the percentage of carbon atoms converted from carbon monoxide to a speci~ied compound or compounds.
Thus, the independent reaction variables are correlated so as to favor the formation of a substantial ~ -proportion of the desired two carbon atom oxygenated hydrocarbons (acetic acid, ethanol, and/or acetaldehyde).
This proportion, expressed as carbon conversion efficiency, is usually upwards of 25% and frequently exceeds 50%.
In one aspect of the invention, this correlation is a combination of conditions which result in maintaining moderate reaction conditions to thereby limit the conversion of CO to not more than about one fourth, preferably not more than about one eighth. As will be discussed in detail below, this may be achieved primarily by a combination of high space velocity and low temperature, but other ~ ~4,~j,7 D- 9406 -1 factors (e.g. H2/CO ratio, catalyst activity, pressure, bed ge~metry, etc.) also affect the conversion. At high conversions, it has been noted that higher carbon ntImber hydrocarbons and oxygenated hydrocarbons are produced in excess, with a resulting loss in efficiency to two-carbon atom compounds.
Conditions of temperature, of pressure, and of gas composition are usually ~ithin the ranges that are essentially conventional for synthesis gas conversions, particularly those employed in the production of methanol.
Thus, existing technology and, in some instances, existing equipment may be used to effect the reaction, The reaction is highly exothermlc, with both the thermodynamic equilibrium and the kinetic reaction rates being governed by the reaction temperature Average catalyst bed temperatures are usually within the range of about 150-450C., but for optimum conversions, bed temperatures are kept within the range of about 200-400C., typically about 250-350C.
The reaction temperature is an important process variable, affecting not only total productivity but selectivity toward one or more of the desired two carbon atom products. Over relatively narrow temperature ranges, as for example 10 or 20C., an increase in temperature may somewhat increase total synthesis gas conversion, tending to increase the efficiency of ethanol production but decreases the efficiency of acetic acid and acetaldehyde production. At the same time, however, higher temperatures ~ ;0~;()4~i7 favor methane production, and apparently methane production increases much more rapidly at higher temperatures than do conversions to the more desirable two carbon atom products.
l~us, for a given catalyst and with all other variables held constant, the optimum temperature will depend more on product and process economics than on thermodynamic or kinetic considerations, with higher temperatures tendin~
to increase the production of oxygenated products but disproportionately increasing the co-production of methane.
In the discussions above the indicated temperatures are expressed as average, or mean, reaction bed temperatures.
Because of the highly exothermic nature of the reaction, ~t is desirable that the temperature be controlled so as not to produ~e a runaway methanation, in which methane formation i8 increased with higher temperature, and the resulting exotherm increases the temperature further. To accomplish this, conventional temperature control techniques are utilized, as for example the use of fluidized bed reaction zones, the use of multi-stage fixed bed adiaba~ic reactors with interstage cooling, or relatively small (1/16th inch or less) catalyst particles placed in tube-and-shell type reactors with a coolant fluid surrounding the catalyst-filled tubes.
The reaction zone pressure is desirably within the range of about 15 psig to about 10,000 psig, economically w~thin the range of about 300-5,000 psig. Higher reaction zone pressures increase the total weight of product obtained per unit time and likewise improve the selectivity _g_ ~ D-9406-l ~ 0~04~7 toward two carbon atom compounds.
The ratio of hydrogen to carbon monoxide in the synthesis gas may vary widely, and in large measure is dictated by the process or processes employed to make the gas~. Normally the mole ratio of hydrogen to carbon monoxide is within the range of 20:1 to 1:20, or preferably within the range of about 5:1 to about 1:5. In most of the experimental work reported herein the mole ratio of the hydrogen pressure to the carbon monoxide pressure is somewhat less than 1:1. Increasing the ratio ~ends to increase the total rate of reaction, sometimes quite significantly, and has a small but favorable effect on production of two carbon atom products, but concurrently lncrea8e8 sele~tivity to methane. Increasing the hydrogen to carbon monoxide ratio also favors the formation of more highly reduced products, that i8, ethanol rather than acetaldehyde or acetic acid.
Impurities in the synthesis gas may or may not have an effect on the reaction, depending on their nature and concentration. Carbon dioxide, normally present in an amount of up to about 10 mole percent, has essentially no effect. ~f a recycle operation is conducted, in which all or part of the reacted gas is recycled to the catalyst zone, it is desirable to remove oxygenated hydrocarbons before recycling To provide empirical orientation, a set of ten experiments, in the form of a two-level, fractional factorial ,. ., - . . , - ; .
~ 0~04~
design plus centerpoints, was conducted. The independent variables were temperature (275 and 300C.), hydrogen and carbon monoxide partial pressures (350 and 500 psig), and gas hourly space velocities (3600 and 4700 volumes of gas at standard conditions per volume of catalyst per hour).
All variables, with the exception of space velocity, proved to be significant in their influences on the rates and efficiencies to the principal products, i.e., acetic acid, ethanol, acetaldehyde, and methane.(Note, ~owever, that space velocity was varied over a comparatively narrow range, and in each instance was quite high.) Qualitatively, the8e responses are indicated in Table III below. In each instance, the effect of an increase in the specified variab~e is represented by either one or more positive or negative signs to characterize the degree of response of the rate and/or of the efficiency.
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10ti04~7 The results of Table IIT, above, suggest that the conditions most favorable to high selectivity toward acetic acid and acetaldehyde are the lowest practical operating temperature, low hydrogen partial pressure, and high carbon monoxide partial pressure. Verification of this prediction is provided in the following data (here and in Table III
utilizing a 5% rhodium on silica catalyst) presented in Table IV below.
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i,o4f~7 One of the features of the present invention is the recognition that a low conversion--preferably less than 20% of the CO--favors the formation or production of a substantial proportion of acetic acid, ethanol and/or acetaldehyde, generally in excess of 10% as compared with a maximum of 3 4% in the prior art (Table I). This conversion is conveniently achieved by employing a high space velocity correlated with other reaction variables (e.g. temperature, pressure, gas composition, catalyst, etc ). Space velocities in excess of about 10 gas hourly space velocity (volumes of reactant gas, at 0C and 760mm mercury pressure, per volume of catalysts per hour) are generally employed, although it is preferable that the space velocity bs within the range of about 104 to about 106 per hour. Excessively high space velocity result in an uneconomically low conversion, while excessively low space velocities cause the production of a more diverse spectrum of reaction products, including higher boiling hydrocarbons and oxygenated hydrocarbons.
The rhodium catalyst is rhodium metal provided in the reaction zone by a number of techniques, or a combination of a number of these techniques. One technique is to coat the reaction zone (or reactor) walls with rhodium metal. Another is to coat a porous screen or screens with a thin coating of the metal. Still another way involves placing particles of rhodium in the reaction zone, generally supported by an inert porous packing material.
--~ D-9406-1 ~O~ ~ 4 ~7 Another way is to deposit rhodium onto a particulate support material and place the supported rhodium into the reaction zone. Any combination of these techniques can be employed.
However, important advantages within the scope of the invention are achieved when the rhodium metal catalyst is in a highly dispersed form on a particulate support. ~n the basis of experience to date the amount of catalysts on the support should range from about 0.01 weight percent to about 25 weight percent, based on the combined weight of the metal catalyst and the support material. Preferably, the amount of catalyst is within the range of about 0.1 to about 10 weight percent.
A wide variety of support materials has been tested. A relatively high surface area particulate support, e.g. one having a surface area upwards of about 1.0 square meters per gram (BET low temperature nitrogen adsorption isotherm method), is preferred, desirably upwards of about 1.5 square meters per gram, although surface area alone is not the sole determinative variable. Based on research to date, silica gel is preferred as the catalyst base or support, with alpha alumina, magnesia, eta alumina, gamma alumina, and active carbon being progressively less desirable. Zeolitic molecular sieves, primarily the higher silica-to-alumina crystalline zeolites, also have promise.
The rhodium metal may be deposited onto the base or support by any of the techniques commonly used for .
.. . .. ~; . . . .
`` D-9406-1 4~7 catalyst preparation, as for example impregnation from an organic or inorganic solution, precipitation, coprecipitation, or cation exchange (on a zeolite).
Numerous specific embodiments of catalysts preparatory techniques are described in the Examples below; it suffices for the present to say that an inorganic or organic rhodium compound is appropriately contacted with the support material, and the support then dried and heated, the latter advantageously under reducing conditions, to form the finely dispersed rhodium metal.
The invention in its various aspects is illustrated in the different "Series" of experiments presented below. In each instance it will be appreciated that the tests are exemplary only, and are not intended to be wholly definitive or exclusive with respect to scope or conditions of the invention.
SERIES A
This Series illustrates the preparation and testing of supported rhodium metal catalysts on a variety of high surface area supports. It also contrasts supported rhodium with supported iridium, supported ruthenium, supported palladium, supported platinum, supported copper, and supported cobalt.
Preparation of Catalysts Catalysts tested in this study were all prepared by essentially the same sequence of steps: An aqueous solùtion of the desired component was impregnated on the ~ D-9406-1 1(3~04~7 support; the impregnated support was carefully dried;
the metal salt was reduced slowly in a flowing hydr~gen atmosphere. When metal components were impregnated as nltrate salts, a pyrolysis step preceeded the hydrogen reduction step. In most cases, rhodium was impregnated as a RhCl3 solution.
The description below illustrates this procedure for the catalyst used in Tests 1-7(5% rhodium on Davison TM
Grade 59 Silica Gel). Table V summarized preparative details for the catalysts whose activities are described in this Series.
Thodium trichloride (22.58 gm, 41.93% Rh) was dissolved in 240 ml of distilled water at ambient temperature.
Davison TM Grade 59 si~ica gel (200.0 gm, 3-6 mesh) was placed in a vacuum flask. The top of the flask was sealed with a rubber septum, and the flask was evacuated through the side arm. A syringe needle was then used to inject the rhodium solution onto the evacuated support. When addition was complete, the impregnated support was allowed to stand at one atmosphere for ca. 30 minutes. It was then carefully dried in a nitrogen atmosphere: 80C (l hr); 110C (2 hrs);
150C (2 hrs). The dried, impregnated support was placed in a quartz tube through which hydrogen was continuously ., passed. The temperature was raised to 450C and held at that value for 2 hours. The reduced catalyst was cooled to ambient temperature in an atmosphere of flowing nitrogen.
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~ D-9406-1 04~7 De~scr~ of Test Reactor The reactor used in these studies was a bottom-agitated "Magnedrive" autoclave of the J. M. Berty design with a centrally positioned catalyst basket and a side product effluent line. It is of the type depicted in Figure 1 of the paper by Berty, Hambrick, Malone and Ullock, entitled "Reactor for Vapor-Phase Catalytic Studies", presented as Preprint 42E at the Symposium on Advances in High-Pressure Technology - Part II, Sixty Four~h National Meeting of the American Institute of Chemical Engineers (AlChE), at New Orleans, Louisiana, on March 16-20, 1969 and obtainable from AlChE at 345 East 47 Street, New York, N.Y. 10017. A variable æpeed, magnetically driven, fan continuously rccirculated the reaction mixture over the catalyst bed. The following modifications were found to facilitate operation and inhibit run-away methanation reactions.
1. Hydrogen feed gas was introduced c~ntinuously at the bottom of the autoclave through the well for the shaft of the Magnedrive agitator.
2. Carbon monoxide feed gas was introduced continuously through a separate port at the bottom of the autoclave, in order to avoid a hydrogen-rich zone in the autoclave. When carbon dioxide was fed, it was added with the carbon monoxide feed stream Experimentsl Rhodium catalysts supported on silica gel, gamma-A1203, and carbon were tested for synthesis activity ~ 0~04~7 in a backmixed autoclave described above. Reaction conditions and salient features of the product distribution are described in Table VI below. In all cases, the feed gases included a quantity of carbon dioxide; the nominal leve] of carbon dioxide in the feed was 5% by volume, but the actual feed rates achieved probably varied widely from this value. There was no indication that carbon dioxide had any effect on the activity or selectivity of any of the catalysts studied.
Under the conditions of these studies, rhodium catalysts supported on silica gel had a selective activity for production of two-carbon, oxygenated compounds.
Carbon efficiency tata are given for ethanol and acetic acid. Methyl-, ethyl-, and propyl-acetate esters are also formed (Other work had shown that acetaldehyde was also produced by these catalysts. Acetaldehyde production was very poorly reflected in the results reported here, because the analytical system did not distinguish acetaldehyde fr~m methanol.) A number of relatively minor products were also formed. m ese included methanol, propanol, and propanal. The major inefficiency in these syntheses was methane.
Those rhodium catalysts for which the support was gamma-A1203 or carbon also showed significant selectivities to ethanol and acetic acid. However, these catalysts were much less active than silica gel supported catalysts at closely similar reaction conditions, despite the fact that the Rh dispersion was much higher.
D-9406-l 1C~j0 ~ 7 A brief study of the RPM of the fan in the backmixed autoclave was made in Tests 1-4 to determine the effect of RPM on productivity. Dropping RPM fr~m 1500 to 750 did not affect the productivity; however, decreasing RPM to 400 did decrease the productivity, An RPM of 800 was used in all later work.
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Under the conditions of these studies, rhodium catalysts supported on silica gel had a selective activity for production of two-carbon, oxygenated compounds.
Carbon efficiency tata are given for ethanol and acetic acid. Methyl-, ethyl-, and propyl-acetate esters are also formed (Other work had shown that acetaldehyde was also produced by these catalysts. Acetaldehyde production was very poorly reflected in the results reported here, because the analytical system did not distinguish acetaldehyde fr~m methanol.) A number of relatively minor products were also formed. m ese included methanol, propanol, and propanal. The major inefficiency in these syntheses was methane.
Those rhodium catalysts for which the support was gamma-A1203 or carbon also showed significant selectivities to ethanol and acetic acid. However, these catalysts were much less active than silica gel supported catalysts at closely similar reaction conditions, despite the fact that the Rh dispersion was much higher.
D-9406-l 1C~j0 ~ 7 A brief study of the RPM of the fan in the backmixed autoclave was made in Tests 1-4 to determine the effect of RPM on productivity. Dropping RPM fr~m 1500 to 750 did not affect the productivity; however, decreasing RPM to 400 did decrease the productivity, An RPM of 800 was used in all later work.
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~ ' : ' 1CNj04~7 D-9406-1 Table VI also reports data on iridium, ruthenium, palladium, platinum, copper, and cobalt catalysts supported on silica gel. Testing of these catalysts was carried out under substantially the same conditions described above for the rhodium catalysts. Although two-carbon products were detected, in no case was the productivity comparable to that observed with rhodium catalys~s.
The iridium catalyst was very inactive. Under the conditions used, it produced primarily methane.
The ruthenium catalyst was active, but it produced large quantities of hydrocarbon oil. This oil production was not surprising; an extensive literature has documented the use of ruthenium catalysts for synthesis of high molecular weight hydrocarbons. The results of Table VI reflect the analysis of the gaseous and aqueous layer products only.
The copper catalyst was inactive under these conditions.
The cobalt catalyst produced methane as the ma;or product.
The data obtained for the platinum and palladium catalysts showed only very low activity for two-carbon products. These data were of low quality, - . - . . . .
.
-~~ D-9406-l 1()~i04~7 SERIES B `
This Series illustrates the preparation and testing of a group of supported rhodium metal catalysts, employing a variety of rhodium c~mpounds and catalyst supports In the tests, the reaction was carried out in a one gallon Berty autoclave.
The procedure described below was used in Tests 1-15 recited-in Table VII below. The carbon monoxide used contained a few percent carbon dioxide. It and the hydrogen were fed to the reactor in the desired molar ratio from 4,500 psig headers The carbon monoxide stream to the reactor was purified in all but tests 1-4~
inclusive, using 1/8 inch activated carbon pellets which had bee~ dried at 250C in a nitrogen flow overnight.
~ ne hundred eighty milliliters (ml) of catalyst were placed in the reactor in a perforated basket having a capacity of approximately 200 ml. The reactor was pressurized with hydrogen to 2,000 psig and the flows of carbon monoxide and hydrogen were adjusted to achieve the desired composition. During the pressurization of the reactor, the reactor temperature was adjusted to approximately 25C below that desired for that particular run.
The pressure was then raised to 2500 psig and the temperature raised to the desired reaction temperature.
Approxlmately one hour was allowed for the reactor to come to a steady state before beginning to measure actual .. . ...
~ ................................ .
~ 7 time of reaction. After one hour of reaction, a sample of liquid product was collected by cooling the product-containing gals through a brine condenser and then trapping the liquid product in a series of four traps having a capacity of approximately one liter per trap. The traps were maintained in a low temperature bath containing a mixture of dry-ice and acetone The liquid products from all the traps and the condenser were then combined to obtain a single liquid sample, which was then analyzed and the results reported in the Table below. The non-condensable gases were metered through a wet-test meter to determine the volume of gas, and a gas sample was collected to determine its composition.
After the desired time of reaction, the reactor was shut down overnight and the catalyst maintained under a slight hydrogen flow at 600 psig. When testing was resumed the following day, the reactor was again brought to the selected set of reaction conditions in the manner described previously. m erefore the catalyst of Test 1 was stored overnight in hydrogen and then used the following day under the reaction conditions of Test 2, then stored overnight under hydrogen, and used the following day for Test 3 and the same procedure repeated through Test 4.
The period for the reaction of the examples was one hour except for Tests 9 and 11 where the reactions in Tests 8 and 10 respectively, were allowed to continue three additional hours ~efore a second sample was taken.
10~4~7 The fourth hour sample of Tests 8 and 10 are reported as Tests 9 and 11 respectively.
The following illustrate the preparation and compositions of the catalysts used in the Table below.
Catalyst A:
Three grams of rhodium carbonyl acetylacetonate were dissolved in 66 ml o toluene preheated to about ,0~.
The toluene-catalyst solution was added to 200 grams of an alpha-alumina support in the form of l/8-inch cylindrical pellets having a surface area characteristic of about 3.5 square meters/gram (m /gm.) The alpha-alumina support was prepared by heating CONOC ~ N-alumina, obtained from Continental Oil Co. of New York, N.Y., to 1,200C.
for about 24 hours. The toluene was evaporated from the impregnated support by drying in a nitrogen purged oven at 100C.
After removing the toluene, the impregnated support was heated to 150C. and the temperature held therefor 1-1/2 hours. The impregnated support was then oxidized by air at 500C. in a tubular furnace for a sufficient time to remove any remaining organic residue from the catalyst.
The oxidized catalyst was then reduced in the presence of hydrogen at 300C. to yield a catalyst having a metal dispersion characteristic of 3.4 percent. (Although 0.6 percent rhodium is the intended metal composition of the finished catalyst, the actual metal dispersion may be somewhat higher and the total metal content proportionately ~ D-9406-1 O4~7 lower depending ~pon the fraction ~f rhodium lost during the decomposition step by partial vaporization of the rhodium carbonyl acetylacetonate. Therefore, the metal composition of the finished catalyst is very likely somewhere on the order of 0.5 percent rather than the intended 0.6 percent.) Catalyst B:
The equipment and techniques used in this preparation were the same as those used in the preparation of Catalyst A, except that the metal salt rhodium chlori~e, RhC13 3H2O, containing 41.4 weight percent rhodium, was used in place of the rhodium carbGnyl acetylacetonate used in making Catalyst A. About 3.1 grams of the rhodium chloride salt were dissolved in approximately 66 ml of distilled water at room temperature. Inasmuch as the rhodium chloride c~mpletely dissolved in the water, there was no need to preheat the water or the support. Impregnation of the support was done as previously described in the making of Catalyst A. The support used was a commercially available alpha-alumina (AL-3920) from Harshaw Chemical Company of Cleveland, Ohio of 3/16 inch size and cylindrical shape, having a surface area of approximately 5 m2/g. The impregnated support was then dried in three successive stages: 85C. for two hours, 200~. for two hours. The impregnated support was then heated in air at 500C. for two hours and reduced at 500C. in hydrogen for 1.5 hours. me catalyst showed no loss of rhodium metal, D-9406-l ~0~04~7 which is believed due to the use of the inorganic rhodium salt. The finished catalyst had a rhodium metal concentration of about 0 6 percent.
Catalyst C:
This involved the use of the rhodium organic salt of Catalyst A on the Harshaw alpha-alumina support of Catalyst B. The preparation procedure was the same as that used in Catalyst A except that the mixture was reduced, after the oxidation step, at 500C. for two hours before charging it to the reactor. The finished catalyst showed a percent dispersion of 7.5 per cent and a rhodium content of 0 6 percent.
Catal~st D:
12.46 grams of the metal salt rhodium chloride was dissolved in 120 ml of distilled water at room temperature. m is solution was then used to impregnate 100 gms. of DavisonTM, grade 59, silica gel, obtained from Davison Chemical Co. of Baltimore, Maryland. The support ;~ was then dried sequentially, at 80C. for 1-1/2 hours, 110C.
for 1.5 hours, and 150C for 3.0 hours. me dried, impregnated support was then heated at 400C. for two hours, cooled in air at 100C., and then heated in hydrogen up to 300C. for 3.0 hours. me finished catalyst had a rhodium content of 5 per cent on the DavisonTM, grade 59, silica gel and a percent dispersion of 15,6 percent.
~ D-9406-1 CatalYst E: 1CHj0~7 This involved the use of the rhodium organic salt of Catalyst A on the silica gel support of Catalyst D. The preparation and procedure used are the same as that used in Catalyst A except that the catalyst was dried at 105C.
for 2.5 hours and then heated immediately to 150~C. for 3 hours. The dried catalyst was then oxidized at 500C. for 1.5 hours and reduced in the presence of hydrogen at 500C.
for 1.5 hours. The finished catalyst should have a rhodium content of 0.6 percent on DavisonTM, grade 59, ~ilica gel and a percent metal dispersion of 15.3 percent.
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1~04~7 Percent metal dispersion, as used herein, is defined as the percentage of metal atoms exposed on the cata-lyst surface as ¢ompared to the totalnumb~r of metal atoms deposited. The per cent metal dispersion was obtained by determining the chemisorption of carbon monoxide at room temperature on a clean metal catalyst surface, and then calculating the number of exposed surface atoms by assuming that one carbon monoxide molecule is chemisorbed per surface metal atom. These analytical pr~cedures can be found in S. J. Gregg and K. S. W. Sing~
Adsorp ion Surface Area And Porosity, where C0 adsorption is described at pages 263-267 and the dynamic gas chromatographic technique is described at pages 339-343.
The surface purity of the catalyst was measured by Auger Spectroscopic Analysis. The analysis of product and unreacted gases was accomplished by the use of gas chromatographic analysis of the various liquids and gases.
Tests 1 through 15 of Table VII were conducted at an early investigative stage of the present invention when reproduceability of metal catalyst activity was a problem. Auger Spectroscopic Analysis of the various fresh and used catalysts of the examples indicated that the inability consistently to produce a particular product distribution could be attributed to the presence of iron and/or nickel impurities on the surface of the used catalyst. There is no direct evidence that iron and/or ~04~7 nickel impurities preferentially attached themselves tO
the surface of the metal catalyst; however, it appears to be highly probable that this did occur. For example, the ùse of argon ion sputtering of an impure catalyst indicated that as the iron signal decreased several fold the rhodium signal increased ~omewhat. If the iron did il.
fact attach itself to the surface of the metal catalyst, it very likely would be in the form of iron metal or iron oxide as a result of its reaction with water. The presence of iron on the metal surface woùld explain the low values of rhodium dispersion measured by carbon monoxide chemisorption. Inasmuch as iron and nickel are known methanation catalysts, this could possibly account for the high amount of methane found in some of the examples.
Installation of activated carbon traps in the carbon monoxide feed gas stream helped reduce the amount of iron and nickel present during the reaction.
The effect of increasing reaction temperature, studied in Tests 1 through 4 of Table VII was to increase overall productivity, to increase methane formation, and to increase the ratio of ethanol to methanol obtained while the ratio of the yield to acetic acid plus ace~ates remained about constant.
Changing the source ofthe rhodium on the cataly~t support from carbonyl acetylacetonate to rhodium chloride did not alter the product spectrum nor did it appear to affect the level of conversion of products as illustrated ~0~()4~7 by Tests S and 6 in Table VII. The lower overail activity of the catalyst derived from rhodium carbonyl acetylacetonate can be explained in terms of its lower dispersion and/or lower rhodium metal content. The lower yield of acetates in the rhodium chloride preparation run is primarily due to the lower partial pressure of carbon monoxide, which tends to favor the production of ethanol over acetic acid andacetates.
Increasing the rhodium concentration from 0.6 percent to 5 percent on the support increased the reaction rate and the product yield, The effect of carbon monoxide and hydrogen partial pressures and of c~talyst aging are illustrated in Tests 7 through 11. The tests show that a high ratio of carbon monoxide to hydrogen favors the formation of acetic acid while a low ratio of carbon monoxide to hydrogen favors the formation of ethanol. Production of higher alcohols was minimal in both cases. Increasing the partial pressure of carbon monoxide from 25% to approximately 75% decreased methane formation while increasing the yield of total acetic acid and acetates substantially. Carbon efficiency to useful liquid products at high carbon monoxide partial pressures (75%) was about 64% while carbon efficiency at low carbon monoxids partial pressures (25%) was about 35%
as shown in Tests 7 through 11.
It can be seen fr~m Tests 8, 9 and 12 that the activities of catalysts containing different levels of rhodium 1 0t~ 7 but having similar metal dispersions increase as the amount of rhodium present increases.
1o~i0 4 SERIES C
This Series illustrates the effects of reaction temperature and catalyst age on product distribution.
The same procedure and equipment used for the tests in Table VIII were used for all the tests in Table VIII
except for the following conditions which were held constant:
the pressure was 2500 psia; feed gas c~mposition was 77%
volume CO, 20% H2 and 3% CO2; reactant feed rate was 600 liters/hour; and there was a one (1) hour reaction time.
The catalyst used in Tests 16 through 33 of Table VIII was Catalyst D, above, i.e., rhodium, at a concentration of 5 percent, on a DavisonTM, grade 59, silica gel 8upport. In Table VIII, after tests 18 and 21, the catalyst was stored overnight at 250C in a 600 p8ig carbon monoxide atmosphere. After Test 23, the catalyst was stored for two days at 285C in a 2000 psig carbon monoxide atmosphere. After Test 26, the catalyst was stored overnight at 300C in a 600 psig hydrogen atmosphere.
The catalysts used in Tests 16 and 29 are freshly prepared and were then reduced with hydrogen in the reactor before the reaction was commenced. The catalyst used in each test, other than for Tests 16 and 29, was obtained from the preceeding test.
The results reports in Table VIII indicate a substantial shift in catalyst performance as time progressed.
The catalyst became more selective to the production of ethanol and less selective toward methane production lC~04~7 D-94~6-]
with age. The molar ratio of acetic aci~ to ethanol producecl decreased from a high of 63 in Test 16 to less t:han one (1) in Tests 24 through 28. This change in catalyst selectivity can perhaps best be explained by th~ presence of iron found in the recovered catalyst.
Sur~ace lron of 1.2 atomic percent was detected by Auger atomic analysis on the recovered catalyst of Test 28 while no iron was detected on the unused catalyst. The atomic percent ratio of rhodium to iron for the used catalyst of Test 28 was 12.2, The atomic percent ratio of Rh to Fe for the used catalyst from Test 33 was 40. The iron contamination probably arises through the generation of iron carbonyl from the reactor walls and its subsequent decomposition on the catalyst surface. This suggests that by purposely contaminating the catalyst with iron one provides a process which favors ethanol production.
me decrease in methane production in the results reported in Table VIII as compared with that of Table VII
is perhaps due to the absence of nickel on the surface of the catalysts of Table VIII.
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10~04~7 D-9406-1 SERIES D
A series of studies were designed to determine the effect of space velocity on the product distribution over rhodium catalysts. These experiments were directed toward the more inclusive goal of a better definition of the reasons for the differences between the process of this invention and descriptions in the prior art.
Modifications to the reactant gas feed system to the Berty reactor permitted operation in a well-controlled manner at space velocities of about 400-500 hr 1. Most previous experlmentations hsd been with space velocities in the range 800-3000hr 1.
Additionally, it was found possible to operate the back-mixed Berty reactor (internally goldplated) in a quasi-static mode. This involved manually closing valves to stop all flow of reactants into the reactor. Flow of gas out of the reactor was controlled by a pressure-actuated valve whose leakage rate proved to be low (0.5-3.0 STP l/hr). Several experiments were conducted with the reactor sealed in this manner and maintained at reaction conditions of pressure and temperature.
Reactant gases were added as needed by manual manipula-tion in order to maintain the total pressure near the desired nominal value. Liquid samples were collected by purging small volumes of gas from the reactor through the '~ D-9406-1 ~ 4 ~7 condenser in the product gas line.
Three catalysts were studied in both the low space velocity and the quasi-static operating modes. Many of these esperiments attempted to study the product distri-bution obtained at low synthesis temperatures and low reaction rates. Moreover, the major objective was to study the product distribution at conditions of high conversion. The relevant catalysts studied wPre:
(1) 5% rhodium on Davison 59 silica gel; and (2) powder-ed, bulk rhodium metal prepared by in situ reduction ofrhodium oxyhydrate (prepared by Soufi's method for making "Catalyst D", pagè 23 of dissertation). The rhodium oxyhydrate was charged to the reactor in a "jelly-roll"
of glass wool and ~tainless steel screen.
The silica-gel-supported rhodium catalyst was studied at 2500 psi and temperatures of 200, 250, 300, ~nd 325C. Several (7 out of 34) of the liquid product samples contained measurable quantities of hydrocarbon oil. Here too the product distributions were generally similar to the usual experience with two-carbon products greatly exceeding longer chain organics. However, in two cases (out of 34), the yield of heavies exceeded the yield of two-carbon products, and in several more cases the yield of heavies was more than 20% of the yield of two-carbon products (weight basis). In general, these results provide only weak support for the original hypo-, 1 0~ 0 4 ~ ~
thesis that longer c~ain products result from long contact times and high conversions.
Unsupported rhodium was studied at 2500 psi and temperatures of 160, 200, 300, and 325C. Quæsi-static experiments were made at 300 and 325C. The experiments at 160 and 200C produced only very small qusntities of products ~nd these products contained m~ch more two-carbon products thsn heavies. The experiment~ at 300 and 325C were distinctly different. The productivities were greater, and the quantities of heavies were almost always ~ubstantially (2- to 8-fold) greater than the quantities of two-carbon products. Fiv~ out of 22 s~mples contained me~surable quantitie8 of oil. Ihe proportlon of heavles W~8 very ~ubstantially le88 than that reported by Soufi, however. It would appe~r that the form in which the rhodium ig introduced is spparently not the only factor which dete~mines the product distribution. Comparison of these results to those reported by Soufi implies that either reaction condition~ (notably temperature, GHSV, and extent of conversion) or other unitent~fied factors also strongly influence the product distributlon.
The Table below summa~izes results in a somewhst over-simplified form.
D-9406-l 04~7 Comparison of Product Distributions Catalyst C3 1 2 (wel~t ~atio)***
5% Rh on D 59 ca. 0.5 to 0.05*
Rh black (UCC) ca. 5.*
~h black (Soufi Thesis) ca. 170.**
* ca. 2H2 per C0 at 2500 psi. Temperature ca. 300C -** 2H2 per C0 at 7500 psi. Temperature 160C
***The ratio of the sum of the weights of three and higher number carbon products and the sum of the weights of acetaldehyde, ethanol and acetic acid.
10~0467 SERIES E
This series illustrates prelLminary tests, utilizing a silver plated reactor of the type employed in the previous Series, to study the effect of reaction temperature on product di~tribution.
Except for the silver plating of the reactor, and for the following recited conditions, the equipment and procedure in experiments A through J were the same as those used in the previous Series above. All of the experiments A-J were made using a fresh 60 gram sample of Catalyst D above, i.e., 5 percent rhodium on Davison TM, grade 59, silica gel, at 2,500 psig, a feed gas composition of 3 moles of carbon monoxide per mole of hydrogen and a feed ga~ rate of 450 liters/hour. The C0 feed gas of experiments A through K contained about 3 to 5 mole percent C02 In each experiment the reaction was allowed to proceed for one hour before a sample was taken for analysis or the reactor was shut down overnight. Experiments A
and B were consecutive one hour runs, i.e., there was no shut down of the reactor after the first sample but the reaction was allowed to proceed for one more additional hour before sample B was taken. A~ter experiment B, the reactor was shut down and the catalyst was stored overnight in the reactor at 250C., under a 600 psig H2 atmosphere and a slight H2 flow through the reactor before being used in experiment C. Experiments C through F were four consecutive one hour runs. After experiment F, the catalyst was removed from the reactor and heated at 350C.
in air for 2.5 hours and then reduced overnight in the .
1()~04f~'7 reactor at 200C. and a H2 pressure of 500 psig. The cata-lyst from experiment F was then used to make the consecutive ~.~
one hour runs of experiments G and H. A fresh sample -of Catalyst D above was used on the two consecutive one hour runs of experiments I and J.
Auger analysis of the used catalyst of experiment F showed sulfur at levels of 10 to 15 atomic percent of that surface. rhodium. The reason for the presence of sulfur is presently unaccounted for. .-.:
.
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~ ' : ' 1CNj04~7 D-9406-1 Table VI also reports data on iridium, ruthenium, palladium, platinum, copper, and cobalt catalysts supported on silica gel. Testing of these catalysts was carried out under substantially the same conditions described above for the rhodium catalysts. Although two-carbon products were detected, in no case was the productivity comparable to that observed with rhodium catalys~s.
The iridium catalyst was very inactive. Under the conditions used, it produced primarily methane.
The ruthenium catalyst was active, but it produced large quantities of hydrocarbon oil. This oil production was not surprising; an extensive literature has documented the use of ruthenium catalysts for synthesis of high molecular weight hydrocarbons. The results of Table VI reflect the analysis of the gaseous and aqueous layer products only.
The copper catalyst was inactive under these conditions.
The cobalt catalyst produced methane as the ma;or product.
The data obtained for the platinum and palladium catalysts showed only very low activity for two-carbon products. These data were of low quality, - . - . . . .
.
-~~ D-9406-l 1()~i04~7 SERIES B `
This Series illustrates the preparation and testing of a group of supported rhodium metal catalysts, employing a variety of rhodium c~mpounds and catalyst supports In the tests, the reaction was carried out in a one gallon Berty autoclave.
The procedure described below was used in Tests 1-15 recited-in Table VII below. The carbon monoxide used contained a few percent carbon dioxide. It and the hydrogen were fed to the reactor in the desired molar ratio from 4,500 psig headers The carbon monoxide stream to the reactor was purified in all but tests 1-4~
inclusive, using 1/8 inch activated carbon pellets which had bee~ dried at 250C in a nitrogen flow overnight.
~ ne hundred eighty milliliters (ml) of catalyst were placed in the reactor in a perforated basket having a capacity of approximately 200 ml. The reactor was pressurized with hydrogen to 2,000 psig and the flows of carbon monoxide and hydrogen were adjusted to achieve the desired composition. During the pressurization of the reactor, the reactor temperature was adjusted to approximately 25C below that desired for that particular run.
The pressure was then raised to 2500 psig and the temperature raised to the desired reaction temperature.
Approxlmately one hour was allowed for the reactor to come to a steady state before beginning to measure actual .. . ...
~ ................................ .
~ 7 time of reaction. After one hour of reaction, a sample of liquid product was collected by cooling the product-containing gals through a brine condenser and then trapping the liquid product in a series of four traps having a capacity of approximately one liter per trap. The traps were maintained in a low temperature bath containing a mixture of dry-ice and acetone The liquid products from all the traps and the condenser were then combined to obtain a single liquid sample, which was then analyzed and the results reported in the Table below. The non-condensable gases were metered through a wet-test meter to determine the volume of gas, and a gas sample was collected to determine its composition.
After the desired time of reaction, the reactor was shut down overnight and the catalyst maintained under a slight hydrogen flow at 600 psig. When testing was resumed the following day, the reactor was again brought to the selected set of reaction conditions in the manner described previously. m erefore the catalyst of Test 1 was stored overnight in hydrogen and then used the following day under the reaction conditions of Test 2, then stored overnight under hydrogen, and used the following day for Test 3 and the same procedure repeated through Test 4.
The period for the reaction of the examples was one hour except for Tests 9 and 11 where the reactions in Tests 8 and 10 respectively, were allowed to continue three additional hours ~efore a second sample was taken.
10~4~7 The fourth hour sample of Tests 8 and 10 are reported as Tests 9 and 11 respectively.
The following illustrate the preparation and compositions of the catalysts used in the Table below.
Catalyst A:
Three grams of rhodium carbonyl acetylacetonate were dissolved in 66 ml o toluene preheated to about ,0~.
The toluene-catalyst solution was added to 200 grams of an alpha-alumina support in the form of l/8-inch cylindrical pellets having a surface area characteristic of about 3.5 square meters/gram (m /gm.) The alpha-alumina support was prepared by heating CONOC ~ N-alumina, obtained from Continental Oil Co. of New York, N.Y., to 1,200C.
for about 24 hours. The toluene was evaporated from the impregnated support by drying in a nitrogen purged oven at 100C.
After removing the toluene, the impregnated support was heated to 150C. and the temperature held therefor 1-1/2 hours. The impregnated support was then oxidized by air at 500C. in a tubular furnace for a sufficient time to remove any remaining organic residue from the catalyst.
The oxidized catalyst was then reduced in the presence of hydrogen at 300C. to yield a catalyst having a metal dispersion characteristic of 3.4 percent. (Although 0.6 percent rhodium is the intended metal composition of the finished catalyst, the actual metal dispersion may be somewhat higher and the total metal content proportionately ~ D-9406-1 O4~7 lower depending ~pon the fraction ~f rhodium lost during the decomposition step by partial vaporization of the rhodium carbonyl acetylacetonate. Therefore, the metal composition of the finished catalyst is very likely somewhere on the order of 0.5 percent rather than the intended 0.6 percent.) Catalyst B:
The equipment and techniques used in this preparation were the same as those used in the preparation of Catalyst A, except that the metal salt rhodium chlori~e, RhC13 3H2O, containing 41.4 weight percent rhodium, was used in place of the rhodium carbGnyl acetylacetonate used in making Catalyst A. About 3.1 grams of the rhodium chloride salt were dissolved in approximately 66 ml of distilled water at room temperature. Inasmuch as the rhodium chloride c~mpletely dissolved in the water, there was no need to preheat the water or the support. Impregnation of the support was done as previously described in the making of Catalyst A. The support used was a commercially available alpha-alumina (AL-3920) from Harshaw Chemical Company of Cleveland, Ohio of 3/16 inch size and cylindrical shape, having a surface area of approximately 5 m2/g. The impregnated support was then dried in three successive stages: 85C. for two hours, 200~. for two hours. The impregnated support was then heated in air at 500C. for two hours and reduced at 500C. in hydrogen for 1.5 hours. me catalyst showed no loss of rhodium metal, D-9406-l ~0~04~7 which is believed due to the use of the inorganic rhodium salt. The finished catalyst had a rhodium metal concentration of about 0 6 percent.
Catalyst C:
This involved the use of the rhodium organic salt of Catalyst A on the Harshaw alpha-alumina support of Catalyst B. The preparation procedure was the same as that used in Catalyst A except that the mixture was reduced, after the oxidation step, at 500C. for two hours before charging it to the reactor. The finished catalyst showed a percent dispersion of 7.5 per cent and a rhodium content of 0 6 percent.
Catal~st D:
12.46 grams of the metal salt rhodium chloride was dissolved in 120 ml of distilled water at room temperature. m is solution was then used to impregnate 100 gms. of DavisonTM, grade 59, silica gel, obtained from Davison Chemical Co. of Baltimore, Maryland. The support ;~ was then dried sequentially, at 80C. for 1-1/2 hours, 110C.
for 1.5 hours, and 150C for 3.0 hours. me dried, impregnated support was then heated at 400C. for two hours, cooled in air at 100C., and then heated in hydrogen up to 300C. for 3.0 hours. me finished catalyst had a rhodium content of 5 per cent on the DavisonTM, grade 59, silica gel and a percent dispersion of 15,6 percent.
~ D-9406-1 CatalYst E: 1CHj0~7 This involved the use of the rhodium organic salt of Catalyst A on the silica gel support of Catalyst D. The preparation and procedure used are the same as that used in Catalyst A except that the catalyst was dried at 105C.
for 2.5 hours and then heated immediately to 150~C. for 3 hours. The dried catalyst was then oxidized at 500C. for 1.5 hours and reduced in the presence of hydrogen at 500C.
for 1.5 hours. The finished catalyst should have a rhodium content of 0.6 percent on DavisonTM, grade 59, ~ilica gel and a percent metal dispersion of 15.3 percent.
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1~04~7 Percent metal dispersion, as used herein, is defined as the percentage of metal atoms exposed on the cata-lyst surface as ¢ompared to the totalnumb~r of metal atoms deposited. The per cent metal dispersion was obtained by determining the chemisorption of carbon monoxide at room temperature on a clean metal catalyst surface, and then calculating the number of exposed surface atoms by assuming that one carbon monoxide molecule is chemisorbed per surface metal atom. These analytical pr~cedures can be found in S. J. Gregg and K. S. W. Sing~
Adsorp ion Surface Area And Porosity, where C0 adsorption is described at pages 263-267 and the dynamic gas chromatographic technique is described at pages 339-343.
The surface purity of the catalyst was measured by Auger Spectroscopic Analysis. The analysis of product and unreacted gases was accomplished by the use of gas chromatographic analysis of the various liquids and gases.
Tests 1 through 15 of Table VII were conducted at an early investigative stage of the present invention when reproduceability of metal catalyst activity was a problem. Auger Spectroscopic Analysis of the various fresh and used catalysts of the examples indicated that the inability consistently to produce a particular product distribution could be attributed to the presence of iron and/or nickel impurities on the surface of the used catalyst. There is no direct evidence that iron and/or ~04~7 nickel impurities preferentially attached themselves tO
the surface of the metal catalyst; however, it appears to be highly probable that this did occur. For example, the ùse of argon ion sputtering of an impure catalyst indicated that as the iron signal decreased several fold the rhodium signal increased ~omewhat. If the iron did il.
fact attach itself to the surface of the metal catalyst, it very likely would be in the form of iron metal or iron oxide as a result of its reaction with water. The presence of iron on the metal surface woùld explain the low values of rhodium dispersion measured by carbon monoxide chemisorption. Inasmuch as iron and nickel are known methanation catalysts, this could possibly account for the high amount of methane found in some of the examples.
Installation of activated carbon traps in the carbon monoxide feed gas stream helped reduce the amount of iron and nickel present during the reaction.
The effect of increasing reaction temperature, studied in Tests 1 through 4 of Table VII was to increase overall productivity, to increase methane formation, and to increase the ratio of ethanol to methanol obtained while the ratio of the yield to acetic acid plus ace~ates remained about constant.
Changing the source ofthe rhodium on the cataly~t support from carbonyl acetylacetonate to rhodium chloride did not alter the product spectrum nor did it appear to affect the level of conversion of products as illustrated ~0~()4~7 by Tests S and 6 in Table VII. The lower overail activity of the catalyst derived from rhodium carbonyl acetylacetonate can be explained in terms of its lower dispersion and/or lower rhodium metal content. The lower yield of acetates in the rhodium chloride preparation run is primarily due to the lower partial pressure of carbon monoxide, which tends to favor the production of ethanol over acetic acid andacetates.
Increasing the rhodium concentration from 0.6 percent to 5 percent on the support increased the reaction rate and the product yield, The effect of carbon monoxide and hydrogen partial pressures and of c~talyst aging are illustrated in Tests 7 through 11. The tests show that a high ratio of carbon monoxide to hydrogen favors the formation of acetic acid while a low ratio of carbon monoxide to hydrogen favors the formation of ethanol. Production of higher alcohols was minimal in both cases. Increasing the partial pressure of carbon monoxide from 25% to approximately 75% decreased methane formation while increasing the yield of total acetic acid and acetates substantially. Carbon efficiency to useful liquid products at high carbon monoxide partial pressures (75%) was about 64% while carbon efficiency at low carbon monoxids partial pressures (25%) was about 35%
as shown in Tests 7 through 11.
It can be seen fr~m Tests 8, 9 and 12 that the activities of catalysts containing different levels of rhodium 1 0t~ 7 but having similar metal dispersions increase as the amount of rhodium present increases.
1o~i0 4 SERIES C
This Series illustrates the effects of reaction temperature and catalyst age on product distribution.
The same procedure and equipment used for the tests in Table VIII were used for all the tests in Table VIII
except for the following conditions which were held constant:
the pressure was 2500 psia; feed gas c~mposition was 77%
volume CO, 20% H2 and 3% CO2; reactant feed rate was 600 liters/hour; and there was a one (1) hour reaction time.
The catalyst used in Tests 16 through 33 of Table VIII was Catalyst D, above, i.e., rhodium, at a concentration of 5 percent, on a DavisonTM, grade 59, silica gel 8upport. In Table VIII, after tests 18 and 21, the catalyst was stored overnight at 250C in a 600 p8ig carbon monoxide atmosphere. After Test 23, the catalyst was stored for two days at 285C in a 2000 psig carbon monoxide atmosphere. After Test 26, the catalyst was stored overnight at 300C in a 600 psig hydrogen atmosphere.
The catalysts used in Tests 16 and 29 are freshly prepared and were then reduced with hydrogen in the reactor before the reaction was commenced. The catalyst used in each test, other than for Tests 16 and 29, was obtained from the preceeding test.
The results reports in Table VIII indicate a substantial shift in catalyst performance as time progressed.
The catalyst became more selective to the production of ethanol and less selective toward methane production lC~04~7 D-94~6-]
with age. The molar ratio of acetic aci~ to ethanol producecl decreased from a high of 63 in Test 16 to less t:han one (1) in Tests 24 through 28. This change in catalyst selectivity can perhaps best be explained by th~ presence of iron found in the recovered catalyst.
Sur~ace lron of 1.2 atomic percent was detected by Auger atomic analysis on the recovered catalyst of Test 28 while no iron was detected on the unused catalyst. The atomic percent ratio of rhodium to iron for the used catalyst of Test 28 was 12.2, The atomic percent ratio of Rh to Fe for the used catalyst from Test 33 was 40. The iron contamination probably arises through the generation of iron carbonyl from the reactor walls and its subsequent decomposition on the catalyst surface. This suggests that by purposely contaminating the catalyst with iron one provides a process which favors ethanol production.
me decrease in methane production in the results reported in Table VIII as compared with that of Table VII
is perhaps due to the absence of nickel on the surface of the catalysts of Table VIII.
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10~04~7 D-9406-1 SERIES D
A series of studies were designed to determine the effect of space velocity on the product distribution over rhodium catalysts. These experiments were directed toward the more inclusive goal of a better definition of the reasons for the differences between the process of this invention and descriptions in the prior art.
Modifications to the reactant gas feed system to the Berty reactor permitted operation in a well-controlled manner at space velocities of about 400-500 hr 1. Most previous experlmentations hsd been with space velocities in the range 800-3000hr 1.
Additionally, it was found possible to operate the back-mixed Berty reactor (internally goldplated) in a quasi-static mode. This involved manually closing valves to stop all flow of reactants into the reactor. Flow of gas out of the reactor was controlled by a pressure-actuated valve whose leakage rate proved to be low (0.5-3.0 STP l/hr). Several experiments were conducted with the reactor sealed in this manner and maintained at reaction conditions of pressure and temperature.
Reactant gases were added as needed by manual manipula-tion in order to maintain the total pressure near the desired nominal value. Liquid samples were collected by purging small volumes of gas from the reactor through the '~ D-9406-1 ~ 4 ~7 condenser in the product gas line.
Three catalysts were studied in both the low space velocity and the quasi-static operating modes. Many of these esperiments attempted to study the product distri-bution obtained at low synthesis temperatures and low reaction rates. Moreover, the major objective was to study the product distribution at conditions of high conversion. The relevant catalysts studied wPre:
(1) 5% rhodium on Davison 59 silica gel; and (2) powder-ed, bulk rhodium metal prepared by in situ reduction ofrhodium oxyhydrate (prepared by Soufi's method for making "Catalyst D", pagè 23 of dissertation). The rhodium oxyhydrate was charged to the reactor in a "jelly-roll"
of glass wool and ~tainless steel screen.
The silica-gel-supported rhodium catalyst was studied at 2500 psi and temperatures of 200, 250, 300, ~nd 325C. Several (7 out of 34) of the liquid product samples contained measurable quantities of hydrocarbon oil. Here too the product distributions were generally similar to the usual experience with two-carbon products greatly exceeding longer chain organics. However, in two cases (out of 34), the yield of heavies exceeded the yield of two-carbon products, and in several more cases the yield of heavies was more than 20% of the yield of two-carbon products (weight basis). In general, these results provide only weak support for the original hypo-, 1 0~ 0 4 ~ ~
thesis that longer c~ain products result from long contact times and high conversions.
Unsupported rhodium was studied at 2500 psi and temperatures of 160, 200, 300, and 325C. Quæsi-static experiments were made at 300 and 325C. The experiments at 160 and 200C produced only very small qusntities of products ~nd these products contained m~ch more two-carbon products thsn heavies. The experiment~ at 300 and 325C were distinctly different. The productivities were greater, and the quantities of heavies were almost always ~ubstantially (2- to 8-fold) greater than the quantities of two-carbon products. Fiv~ out of 22 s~mples contained me~surable quantitie8 of oil. Ihe proportlon of heavles W~8 very ~ubstantially le88 than that reported by Soufi, however. It would appe~r that the form in which the rhodium ig introduced is spparently not the only factor which dete~mines the product distribution. Comparison of these results to those reported by Soufi implies that either reaction condition~ (notably temperature, GHSV, and extent of conversion) or other unitent~fied factors also strongly influence the product distributlon.
The Table below summa~izes results in a somewhst over-simplified form.
D-9406-l 04~7 Comparison of Product Distributions Catalyst C3 1 2 (wel~t ~atio)***
5% Rh on D 59 ca. 0.5 to 0.05*
Rh black (UCC) ca. 5.*
~h black (Soufi Thesis) ca. 170.**
* ca. 2H2 per C0 at 2500 psi. Temperature ca. 300C -** 2H2 per C0 at 7500 psi. Temperature 160C
***The ratio of the sum of the weights of three and higher number carbon products and the sum of the weights of acetaldehyde, ethanol and acetic acid.
10~0467 SERIES E
This series illustrates prelLminary tests, utilizing a silver plated reactor of the type employed in the previous Series, to study the effect of reaction temperature on product di~tribution.
Except for the silver plating of the reactor, and for the following recited conditions, the equipment and procedure in experiments A through J were the same as those used in the previous Series above. All of the experiments A-J were made using a fresh 60 gram sample of Catalyst D above, i.e., 5 percent rhodium on Davison TM, grade 59, silica gel, at 2,500 psig, a feed gas composition of 3 moles of carbon monoxide per mole of hydrogen and a feed ga~ rate of 450 liters/hour. The C0 feed gas of experiments A through K contained about 3 to 5 mole percent C02 In each experiment the reaction was allowed to proceed for one hour before a sample was taken for analysis or the reactor was shut down overnight. Experiments A
and B were consecutive one hour runs, i.e., there was no shut down of the reactor after the first sample but the reaction was allowed to proceed for one more additional hour before sample B was taken. A~ter experiment B, the reactor was shut down and the catalyst was stored overnight in the reactor at 250C., under a 600 psig H2 atmosphere and a slight H2 flow through the reactor before being used in experiment C. Experiments C through F were four consecutive one hour runs. After experiment F, the catalyst was removed from the reactor and heated at 350C.
in air for 2.5 hours and then reduced overnight in the .
1()~04f~'7 reactor at 200C. and a H2 pressure of 500 psig. The cata-lyst from experiment F was then used to make the consecutive ~.~
one hour runs of experiments G and H. A fresh sample -of Catalyst D above was used on the two consecutive one hour runs of experiments I and J.
Auger analysis of the used catalyst of experiment F showed sulfur at levels of 10 to 15 atomic percent of that surface. rhodium. The reason for the presence of sulfur is presently unaccounted for. .-.:
.
.
:
1()~04~'7 ~: D-9406-1 o ~U~
o o C`~ ~ ~ o ~ ~ ~ o ~ ~ U-~
O ~
,,~ O
0 C ~
I *
~ ~ O ~ O ~ ~ O~
O :~
O O ~ ~ -~
I ~ a~ o o ~ _l ~ oo c~
P~ ~
~rl ,~ ~
, c~ ~ ~ u~
P~ m ~1 _ ~ I o o ~ ;g 6 ~3 ~ c) ~o co o ~ 0 ~ ,:
_1 ~ ~ ~ e~i ~ ~i 0 0 o O I u~ r~ o u~
~ 1 C~l ~
_ $ t~ N
~.
00 ~ O~ 0 ~O r~ O ~ 0 J- O ~
Ul ~c~l o o ~ ~ u~ u~ ~ o o o o J~
~ Z
Claims (7)
1. In a process for the reaction of a synthesis gas containing carbon monoxide and hydrogen in the pres-ence of a hydrogenation catalyst, the improvement whereby oxygenated hydrocarbon products of two carbon atoms are selectively produced, which comprises continuously con-tacting said synthesis gas with a heterogeneous catalyst comprising rhodium metal and at reaction conditions correlated to achieve such product in efficiencies, based on carbon consumption, in excess of 10% and obtain the formation of acetic acid, ethanol, and/or acetaldehyde in an amount which is at least about 50 weight percent of the two or more carbon atom compounds obtained by the reaction, which reaction conditions include a temp-erature within the range of 150-450°C., a pressure within the range of about 15-10,000 psig, and a mole ratio of hydrogen to carbon monoxide within the range of 20:1 to 1:20.
2. Process of claim 1 wherein said reactive conditions include a temperature within the range of about 250-350°C., a pressure within the range of about 300-5,000 psig, and a mole ratio of hydrogen to carbon monoxide within the range of about 5:1 to 1:5.
3. Process of claim 1 wherein said rhodium metal is present on a support in amounts within the range of about 0.1 to about 25 weight percent based on the combined weight of the metal and support.
4. Process of claim 1 wherein said support is selected from the group consisting of alpha alumina, gamma alumina, and silica gel.
5. Process of claim 1 wherein the space velocity of the snythesis gas is in excess of about 103 GHSV.
6. Process of claim 5 wherein said space velocity is within the range of about 104 to 106 GHSV.
7. Process of claim 1 wherein said two carbon atom oxygenated hydrocarbons are at least 50 percent of the reacted carbon atoms.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US43714174A | 1974-01-28 | 1974-01-28 | |
| US54166175A | 1975-01-16 | 1975-01-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1060467A true CA1060467A (en) | 1979-08-14 |
Family
ID=27031196
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA218,756A Expired CA1060467A (en) | 1974-01-28 | 1975-01-27 | Process for producing acetic acid, ethanol, and acetaldehyde from synthesis gas |
Country Status (7)
| Country | Link |
|---|---|
| CA (1) | CA1060467A (en) |
| DE (1) | DE2503233C3 (en) |
| FR (1) | FR2259077B1 (en) |
| GB (1) | GB1501892A (en) |
| IT (1) | IT1031173B (en) |
| NL (1) | NL7500916A (en) |
| SE (1) | SE428682B (en) |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4014913A (en) * | 1975-06-26 | 1977-03-29 | Union Carbide Corporation | Process for producing oxygenated two carbon compounds |
| US4101450A (en) * | 1977-05-09 | 1978-07-18 | Celanese Corporation | Catalyst for production of acetic acid |
| US4268689A (en) * | 1978-12-11 | 1981-05-19 | Texaco Development Corp. | Manufacture of vicinal glycol esters from synthesis gas |
| US4235798A (en) * | 1979-06-28 | 1980-11-25 | Union Carbide Corporation | Process for producing two-carbon atom oxygenated compounds from synthesis gas with minimal production of methane |
| US4471075A (en) * | 1979-06-28 | 1984-09-11 | Union Carbide Corporation | Process for producing two-carbon atom oxygenated compounds from synthesis gas with minimal production of methane |
| US4446251A (en) * | 1980-02-15 | 1984-05-01 | Union Carbide Corporation | Process for producing two-carbon atom oxygenated compounds from synthesis gas with minimal production of methane |
| CA1146592A (en) * | 1979-06-28 | 1983-05-17 | Thomas P. Wilson | Process for producing two-carbon atom oxygenated compounds from synthesis gas with minimal production of methane |
| US4444909A (en) * | 1980-04-07 | 1984-04-24 | Mobil Oil Corporation | Synthesis gas conversion to oxygenates |
| ZA814981B (en) * | 1980-08-01 | 1983-02-23 | British Petroleum Co | Process for the production of c1 to c4 oxygenated hydrocarbons by the catalytic conversion of synthesis gas |
| US4312955A (en) | 1980-12-01 | 1982-01-26 | Union Carbide Corporation | Process for the production of methanol from synthesis gas |
| US4882360A (en) * | 1984-07-30 | 1989-11-21 | The Dow Chemical Company | Process for producing alcohols from synthesis gas |
| US4831060A (en) * | 1984-07-30 | 1989-05-16 | The Dow Chemical Company | Mixed alcohols production from syngas |
| US4762858A (en) * | 1985-09-16 | 1988-08-09 | The Dow Chemical Company | Syngas conversion to oxygenates by reduced yttrium/lanthanide/actinide-modified catalyst |
| DE69206070T2 (en) * | 1991-06-21 | 1996-06-20 | Tokyo Gas Co Ltd | Process for the production of acetic acid. |
| JP2660880B2 (en) * | 1991-06-21 | 1997-10-08 | 東京瓦斯株式会社 | Acetic acid production method |
| DE102007055024A1 (en) | 2007-11-15 | 2009-05-20 | Rolf-Dieter Riesbeck | Fire protection device for e.g. cultivated building area, has pipe system with pipes that are force-fitly connected with each other and arranged at intended location, where outlet devices are designed as groove shaped openings |
| CN115636739A (en) * | 2022-09-27 | 2023-01-24 | 厦门大学 | Method for preparing acetone by synthesis gas one-step method |
-
1975
- 1975-01-27 DE DE19752503233 patent/DE2503233C3/en not_active Expired
- 1975-01-27 FR FR7502461A patent/FR2259077B1/fr not_active Expired
- 1975-01-27 SE SE7500857A patent/SE428682B/en not_active IP Right Cessation
- 1975-01-27 IT IT1961375A patent/IT1031173B/en active
- 1975-01-27 NL NL7500916A patent/NL7500916A/en not_active Application Discontinuation
- 1975-01-27 GB GB337075A patent/GB1501892A/en not_active Expired
- 1975-01-27 CA CA218,756A patent/CA1060467A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| SE7500857L (en) | 1975-07-29 |
| SE428682B (en) | 1983-07-18 |
| DE2503233B2 (en) | 1977-07-28 |
| FR2259077B1 (en) | 1978-07-13 |
| IT1031173B (en) | 1979-04-30 |
| NL7500916A (en) | 1975-07-30 |
| GB1501892A (en) | 1978-02-22 |
| DE2503233A1 (en) | 1975-07-31 |
| DE2503233C3 (en) | 1978-03-16 |
| FR2259077A1 (en) | 1975-08-22 |
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