CA1144940A - Process for the preparation of esters of oxalic acid - Google Patents
Process for the preparation of esters of oxalic acidInfo
- Publication number
- CA1144940A CA1144940A CA000330654A CA330654A CA1144940A CA 1144940 A CA1144940 A CA 1144940A CA 000330654 A CA000330654 A CA 000330654A CA 330654 A CA330654 A CA 330654A CA 1144940 A CA1144940 A CA 1144940A
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/36—Preparation of carboxylic acid esters by reaction with carbon monoxide or formates
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
- C07C69/34—Esters of acyclic saturated polycarboxylic acids having an esterified carboxyl group bound to an acyclic carbon atom
- C07C69/36—Oxalic acid esters
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
The invention relates to a process for the prepa-ration of alkyl esters of oxalic acid, wherein said esters are obtained by reaction, in a gaseous phase, of an alkyl nitrite having the formula R-ONO, wherein R represents an alkyl having from 1 to 10 carbon atoms, with carbon monoxide in the presence of at least one catalyst selected from the group consisting of:
a) rhodium, iridium, platinum , gold and the salts thereof, with or without a co-catalyst selected from the group consisting of iron, copper and the salts thereof, and b) palladium in combination with a co-catalyst selected from the group con-sisting of iron, copper and the salts thereof, the salts of the hereinabove defined metals being selected from the group consisting of chlorides, sulphates, nitrates, acetates and acetylacetonates, at a temperature between 50 and 500°C, under at least atmospheric pressure. This process allows a simple an unexpensive preparation of oxalic acids ester in high yields and high quality.
The invention relates to a process for the prepa-ration of alkyl esters of oxalic acid, wherein said esters are obtained by reaction, in a gaseous phase, of an alkyl nitrite having the formula R-ONO, wherein R represents an alkyl having from 1 to 10 carbon atoms, with carbon monoxide in the presence of at least one catalyst selected from the group consisting of:
a) rhodium, iridium, platinum , gold and the salts thereof, with or without a co-catalyst selected from the group consisting of iron, copper and the salts thereof, and b) palladium in combination with a co-catalyst selected from the group con-sisting of iron, copper and the salts thereof, the salts of the hereinabove defined metals being selected from the group consisting of chlorides, sulphates, nitrates, acetates and acetylacetonates, at a temperature between 50 and 500°C, under at least atmospheric pressure. This process allows a simple an unexpensive preparation of oxalic acids ester in high yields and high quality.
Description
O'.
The present invention concerns a process for the pre-paration of oxalic acid esters. More particularly, the present invention relates to a catalytic process for the preparation of esters of oxalic acid by the reaction of carbon monoxide with alkyl nitrites in the presence of metals of Group VIII of the Periodic System. From the esters, if desired, the acid is ob-tained accordiny to conventional methods, e.g., hydrolysis, etc.
Oxalic acid and the oxalic acid esters are important compounds having known and wide applicational possibilities of considerable industrial interest. In fact, they may find an application (oxalic acid) in the textile industry as an auxi-liary agent for stripping in the dyeing of wool, as a bleaching agent for natural fibers, as a pickling agent for metal surfaces, especially of copper. In industry its use is also known as a dehydrogenating agent in condensation reactions, etc.
The oxalic acid esters are known solvents, such as, for instance, the diethylester as a solvent for cellulose.
It is known to prepare oxalic esters by the oxidation reaction of carbon monoxide and monobasic alcohols with oxygen and also with quinones, preferably in a medium substantially anhydrous for the presence of dehydrating substances, this reac-tion being catalyzed by Redox-systems, in general, consisting of a finely subdivided metal or of soluble salts or complexes (citrates, chelates) of a noble metal of the Pt group, such as for instance Pd, Os and of a salt and/or a complex of another metal that is more electro-positive than the preceding ones, such as Fe, Co, Ni, Cu, Mn, etc., as chlorides, acetates, etc., having several oxidative states.
The reaction is preferably carried out in the presence of catalysts and/or complexing agents consisting of soluble salts of alkaline me-tals (LiCl, KCl, etc.).
:' 1144~0 Nevertheless, processes of this type, because of the contemporaneous occurrence of secondary reactions leading to the formation of carbonates, C02, esters (acetates, formiates, etc.) cannot be considered fully satisfactory from the indus-trial point of view because of the low yields and because of the relatively burdensome separation, purification, etc., operations.
Moreover, the use of gaseous CO+O2 mixtures, with its corresponding risk of explosions, represents a further heavy hindrance for the realization of the process on an industrial scale.
On the other hand, the other priGr art processes, for instance, by hydrogenation of the sodium formiate successively converted to calcium oxalate, acidified, etc., or by oxidation of the propylene with HNO3, catalyzed by Fe, Cr, etc., do not ensure better results while showing considerable technical and operational difficulties that make those processes little accept-able from the economical point of view, especially for produc-tion on a large scale.
Lastly, there has been suggested a process for the preparation of dialkyloxalates by a liquid phase reaction of aliphatic alcohol with carbon monoxide under pressure, in the presence of a metal of the platinum group and of a reaction ac-celerator consisting of nitric acid and/or nitrogen oxides.
Finally, in order to obtain reasonable yields, the reaction is conducted preferably in the presence also of mole-cular oxygen. This method substantially aims to the overco~ing the existing difficulty, discusses above in connection with the prior art, of maintaining the reaction medium under anhydrous conditions also by the use of dehydrators, since the formation of oxalic ester is hindered by the water that forms during the reaction itself, even if in modest amounts.
The use of the accelerator (HNO3 and/or of the nitrogen ~1~4~9~0 oxides) seems to allow the avoidance of the use of dehydrating substances.
Nevertheless, this method also shows drawbacks that make appear the real industrial applicational interest thereof rather uncertain.
In fact, the reaction is conducted by having the catalyst dispersed in the liquid reaction medium, a circumstance that causes some technological problem for the recovery and re-cycling of the catalyst. The presence, that is practically necessary, of molecular oxygen in order to obtain better yields, makes again arise the risks already indicated with respect to the use of gaseous C0+02 mixtures. Finally, the use of nitric acid and/or nitrogen oxides, poses problems of corrosion for the equipment.
The drawbacks indicated above, even if in part techni-cally solvable, already by themselves create at any rate consi-derable economical and operational burdens which make the method little acceptable for use on an industrial scale.
It is an object of this invention to provide a process for the preparation of oxalic acid esters which is simple and inexpensive.
It is another object of this invention to provide a process for the preparation of oxalic acid esters which is free of the drawbacks of the prior art and which represents an ad-` vance thereover.
It is still another object of this invention to provide a process for the preparation of oxalic acid esters which will ensure that these derived end products are obtained in high yields and high purity.
These and other objects which will be apparent from the fo~lowing description are obtained by the invention described.
According to this invention, there is provided a pro-_3_ ., .
11L~4~lO
cess for the preparation of alkyl esters of oxalic acid, wherein said esters are obtained by reaction, in a gaseous phase, of an alkyl nitrite having the formula R-ONO, wherein R represents an alkyl having from 1 to 10 carbon atoms, with carbon monoxide in the presence of at least one catalyst selected from the group consisting of:
a) rhodium, iridium, platinum, gold and the salts thereof, with or without a co-catalyst selected from the group consisting of iron, copper and the salts thereof, and b) palladium in combination with a co-catalyst selected from the group consisting of iron, copper and the salts thereof, the salts of the hereinabove defined metals being selected from the group consisting of chlorides, sulphates, nitrates, acetates and acetylacetonates, C
at a temperature between 50 to 500C, under at least atmospheric pressure.
The reaction may be represented schematically by the following equation:
(1) 2 R-ONO (gas) ~ 2CO (gas)----~ COOR
¦ + 2NO (gas) COOR
As will easily be noticed, the reaction does not include the formation of water and, thus, there do not exist the corresponding problems of the hindrance of the reaction or ` of the high formation of by-products such as the diester of carbonic acid, etc. In other words, reaction (1) does by itself provide sufficiently anhydrous conditions.
As stated above, the reaction is conducted in the gaseous phase and, thus, the operative alkyl nitrites are - evidently those containing a low number of carbon atoms, that is from 1 to 3. Usually there is used methyl nitrite.
~ r~ - 4 -.i ~,~1 ll9L4~40 Obviously, depending on.the conditions of tempe-rature and pressure that have been chosen, there may also be used alkyl nitrites having a higher number of carbon atoms.
Thus, for instance, there may be considered as operational alkyl nitrites those having up to 10 carbon atoms.
~ he alkyl nitrites necessary for the reaction are known, easily available compounds or at any rate easily prepared from nitrous acid and R-OH alcohols in which R has the meaning pre-viously indicated. The alkyl nitrite is separated by distilla-tion, etc.
As a catalyst is used at least one metal. In fact, also catalysts formed by more than one of the hereunder indi-cated metals of the group comprising palladium, rhodium, iridium, platinum and gold, either as a metal or as a salt, are effective.
Suitable salts are chlorides, sulphates, nitrates, acetates, acetylacetonates, etc.
The catalyst is used according to the known fixed-bed technique and is thus preliminarily placed on carrier according to any of the many available conventional techniques.
As a carrier material it is posqible to use, for instance, silica, magnesium oxide or aluminum oxide, zinc oxide, chromium sesquioxide (Cr203), brimstone (pumice), etc. Or, alternatively, the carrier may consist of a metal or of its salt used together with the above-mentioned metals: palladium, rhodium, iridium, platinum, gold, as a co-catalyst, as more closely defined as follows.
The catalyst chosen from among palladium, rhodium, iridium, platinum and gold, either in the metal state or as salts as defined above, may in fact be accompanied, according to a further preferred aspect of this invention, by at least one further element with a co-catalytic function chosen from among iron and copper, in the metallic state, or as a salt such as chlorides, sulphates, acetates, etc., analogously to the primary catalyzing element. The use of the co-catalyzing element permits higher yields and an improved selectivity in obtaining the oxalic ester.
The catalyst is thus, preferably, formed by at least one element chosen from among palladium, rhodium, iridium, platinum, gold, as above defined, and by at least a co-catalyzing , element chosen between iron and copper, either as a metal or a ~4~40 slat which may also act as a carrier, or otherwise they may be supported on conventional carriers as above defined.
The global content of active catalytic elements on a conventional carrier ¦MgD~ A1203, etc.) is preferably comprised between 0.1% and 50% by weight with respect to the carrier.
These are just indicative values and at any rate not essential for the purposes of a correct carrying on of the reaction accord-ing to the invention.
Analogously, the global quantity of active catalytic elements used is comprised between 0.1 g and 10 g per mol of alkyl nitrite used, but preferably between 0.5 g and 5 g per mol of alkyl nitrite.
The ponderal ratio between the primary catalytic element or elements (Pd, Rh, Ir, Pt, Au) and the co-catalysts is not binding and may vary from 1:100 to 25:100, but preferably from 1:100 and 5:100, expressed as metal.
Examples of catalysts effective according to the in-vention may be the following: consisting of Pd (2%), Au ~1%) and deposited on ZnO and Cr203, ad~ixed to Cu(OCH3)Cl, Pd (5~) deposited on CuCl, Pd (5%) deposited on FeC12: Rh (5%) deposited on alumina, Rh (5%) and Pd (5%) deposited on alumina, Pd (5%) deposited on metallic Fe.
As indicated above, the catalyst is supported on a conventional carrier, otherwise on the co-catalyzing element which also acts as a carrier, according to substantially conventional methods, and the obtained catalyst is then used according to the Xnown fixed bed technique.
Just for illustrative purposes, without being a con-ditioning aspect for the execution of the invention, a method suitable for the preparation of the supported catalyst of the invention is as follows.
Into a small flask is introduced the pre-fixed quantity 9~0 of the substance tha~ will form the carrier for~the catalyst, and this substance is then covered with a solution containing the salt of the noble metal to be deposited on the carrier. The concentration of the salt in the solution depends on the total amount of noble metal to be deposited on the carrier.
Once said suspension has been achieved, under stirring, the solvent is distilled under vacuum up to dryness.
If one wished to add as a catalyst another noble metal different from the first one, the operation so far described is repeated once again, etc.
The same may be said for the co-catalyzing metal.
Once there has been obtained the solid consisting of the carrier with the metal salt or salts, the carrier is heated to 200C., under hydrogen, for about two hours.
At the end of this operation, the catalyst is ready for use and, of course, is kept in an atmosphere of ~2.
The process conditions of temperature, pressure and contacting times are variable within wide ranges, depending on the mutual choice.
Advantageous results have been achieved uqing tempera-tures comprised between 50C. and 500C., but preferably 150C.
and about 350C.
The contacting times are comprised between 0.1 and 10 seconds, but preferably between 0.1 and 1 second.
The partial pressure of the reacting gases may vary between atmospheric pressure and about 200 atmospheres, but preferably between atmo~pheric pressure and about 50 atm., without being, however, an essential aspect of the invention.
Where desired, the use of CO in admixture with inert gases or of synthesis gases (CO and H2) is compatible. The separation of the oxalic ester is achieved suitably according to known methods, for instance by conventional distillation,etc.
4~'340 From the ester it is easy to obtain the acid by hydro-lysis, etc., likewise by mean~ of conventional known methods.
The NO gas that develops from the reaction may be re-covered, and, after oxidation, may be re-used for the prepara-tion of the alkyl nitrite.
In one embodiment, the process of the invention is conducted as follows.
Into a vessel fitted with reactant feeding systems, and provided with a flow regulator and a temperature regulating system, is placed the prepared catalytic bed. Thereupon the gaseous stream o the reactants is made to flow through the reactor in the desired ratio, quantity and for the desired contact time. At the outlet of the reactor there condenses a liquid from which the oxalic ester i~ recovered by distillation, etc.
Thankq to the simple operational conditions, the in-vention proves to be particularly advantageous. Other advantage3 consist of the selectivity in the formation of the oxalic ester in by them~elves anhydrous conditions of the reaction and in the ~ 20 exclusion of the operational risks of explosions due to the lack j of possible CO+O2 mixtures.
The "fixed bed" technique allows one to have a localized catalyst, not dispersed in the reacting mass, and moreover, ensures a much simpler and more economical operational effective-ness of the renewal, recovery operations, etc.
i Finally, the possibility of employing C~ and hydrogen mixtures as such as coming from the synthesis gas preparation is ` of particular intere~t, without sub~tantially involving the pro-; cess effectiveness.
~ The invention will now be described in more detail in the following examples given for purely illustrative and not limiting purposes.
.. , 49~0 EXAMPLE
-Into a glass reactor for heterogeneous catalysis, provided with a porous diaphragm, there were introduced 1.5 g of a catalyst consisting of Pd (5%) deposited on CuCl. The reactor was then inserted into a muffle furnace with a known thermal dia~ram and maintained at a temperature of 200C. On the cataly t there was then allowed to flow a gas thus composed:
CO (4 N lt~hr) - CH30NO (3 ~ lt/hr).
Under these conditions, the dwelling time o the reaction mix-ture and the contact with the catalyqt amounted to 0.5 second.
At the outlet of the reactor there had been placed a gathering trap maintained at 0C. After two hours from the start of the test, the liquld deposited in the trap was collected and subjected to analysis. The analysis was carried out both by gas-chromatography as well as by directly titering the precipitated calcium oxalate.
There were thus ascertained 100 mg of methyl oxalate in the gathered liquid.
EXAMPL~ 2 In the same equipment and following the same procedures a~ those described in Example 1, there was used a catalyst con-sisting of Pd (2%), Au (1%), deposited on ZnO and Cr203 admixed to Cu(OCH3)Cl.
The reaction temperature amounted to 180C., while the test lasted 3 hours.
At the end of the test, at the outlet of the reactor, there was gathered a liquid in which were found 20 mg of methyl-oxalate.
Thereupon the feeding of the reactants was resumed under the same conditions for an additional 6 hour~. At the end there was recovered another 40 mg of methyl oxalate.
It was then proceeded for another 16 hours to feed _g_ ~1~4~0 into the reactor the given reactants. At the end there were obtained another 230 mg of methyl oxalate.
In the same equipment and following the same procedures as those described in Example 1, there was used a catalyst con-sisting of Pd (~%) deposited on FeC12.
The reaction temperature was 200C. The duration of the test was 4 hours. At the end of the test there was reco-vered a liquid containing 500 mg of methyl oxalate, thereupon feeding of the reactants wa~ re~umed for a further hour.
At the end there were gathered 50 mg of methyl oxalate.
Proceeding as in the previous examples, there was used a catalyst consisting of Rh (5%) deposited on aluminum. The reaction temperature was 200C., while the duration of the test was 4 hours. The flow of CO wa~ 2 N lt/hr. At the end of the test there was recovered a liquid containing quantities of methyl oxalate traced by means of gas-ghromatography.
Proceeding as in the previous examples, there was used a catalyst consisting of Rh (5%) and Pd (5%) depo~ited on alumina, and there obtained the same re~ults.
-Operating as in the previous examples, there was used a catalyst consisting of Pd (5%) deposited on Fe. The reaction temperature was 200C., while the duration of the test was 4 hours. At the end of ~aid test there was recovered a liquid containing 460 mg of methyl oxalate.
~XAMPLE 7 Following the same procedures as those of the previous examples, there was used a catalyst consisting of Pd (5%) on FeC12. Into the reactor were fed 3 ~.lt/hour of ethyl nitrite ~4~
and 4 N.lt/hour of carbon monoxide. The temperature was 200C., while the duration of the test was S hours. At the end of the test there was recovered a liquid containing 50 mg of ethyl oxalate.
It was operated as in Example 6, but at 300C. Thereby were obtained 20 mg of ethyl oxalate.
E~AMPLE 9 On the same equipment and with the same procedures described in Example 1, there was used a catalyst consisting of Pt (5%) on FeC12. The reaction temperature was 210C. and the duration of the test was 3 hours.
At the end of the test, at the outlet of the reactor there was gathered a liquid containing 130 mg of methyl oxalate.
In this instance there was repeated the test of Example 9, but using as a catalyst: Rh (5%) on FeC12 for a period of 3 hours, thereby obtaining 450 mg of oxalate.
Again Exam~le 9 was repeated, but using as a catalyst:
Ir (5%) on FeC12, for a reaction time of 3 hours. Thereby were obtained 100 mg of oxalate.
The present invention concerns a process for the pre-paration of oxalic acid esters. More particularly, the present invention relates to a catalytic process for the preparation of esters of oxalic acid by the reaction of carbon monoxide with alkyl nitrites in the presence of metals of Group VIII of the Periodic System. From the esters, if desired, the acid is ob-tained accordiny to conventional methods, e.g., hydrolysis, etc.
Oxalic acid and the oxalic acid esters are important compounds having known and wide applicational possibilities of considerable industrial interest. In fact, they may find an application (oxalic acid) in the textile industry as an auxi-liary agent for stripping in the dyeing of wool, as a bleaching agent for natural fibers, as a pickling agent for metal surfaces, especially of copper. In industry its use is also known as a dehydrogenating agent in condensation reactions, etc.
The oxalic acid esters are known solvents, such as, for instance, the diethylester as a solvent for cellulose.
It is known to prepare oxalic esters by the oxidation reaction of carbon monoxide and monobasic alcohols with oxygen and also with quinones, preferably in a medium substantially anhydrous for the presence of dehydrating substances, this reac-tion being catalyzed by Redox-systems, in general, consisting of a finely subdivided metal or of soluble salts or complexes (citrates, chelates) of a noble metal of the Pt group, such as for instance Pd, Os and of a salt and/or a complex of another metal that is more electro-positive than the preceding ones, such as Fe, Co, Ni, Cu, Mn, etc., as chlorides, acetates, etc., having several oxidative states.
The reaction is preferably carried out in the presence of catalysts and/or complexing agents consisting of soluble salts of alkaline me-tals (LiCl, KCl, etc.).
:' 1144~0 Nevertheless, processes of this type, because of the contemporaneous occurrence of secondary reactions leading to the formation of carbonates, C02, esters (acetates, formiates, etc.) cannot be considered fully satisfactory from the indus-trial point of view because of the low yields and because of the relatively burdensome separation, purification, etc., operations.
Moreover, the use of gaseous CO+O2 mixtures, with its corresponding risk of explosions, represents a further heavy hindrance for the realization of the process on an industrial scale.
On the other hand, the other priGr art processes, for instance, by hydrogenation of the sodium formiate successively converted to calcium oxalate, acidified, etc., or by oxidation of the propylene with HNO3, catalyzed by Fe, Cr, etc., do not ensure better results while showing considerable technical and operational difficulties that make those processes little accept-able from the economical point of view, especially for produc-tion on a large scale.
Lastly, there has been suggested a process for the preparation of dialkyloxalates by a liquid phase reaction of aliphatic alcohol with carbon monoxide under pressure, in the presence of a metal of the platinum group and of a reaction ac-celerator consisting of nitric acid and/or nitrogen oxides.
Finally, in order to obtain reasonable yields, the reaction is conducted preferably in the presence also of mole-cular oxygen. This method substantially aims to the overco~ing the existing difficulty, discusses above in connection with the prior art, of maintaining the reaction medium under anhydrous conditions also by the use of dehydrators, since the formation of oxalic ester is hindered by the water that forms during the reaction itself, even if in modest amounts.
The use of the accelerator (HNO3 and/or of the nitrogen ~1~4~9~0 oxides) seems to allow the avoidance of the use of dehydrating substances.
Nevertheless, this method also shows drawbacks that make appear the real industrial applicational interest thereof rather uncertain.
In fact, the reaction is conducted by having the catalyst dispersed in the liquid reaction medium, a circumstance that causes some technological problem for the recovery and re-cycling of the catalyst. The presence, that is practically necessary, of molecular oxygen in order to obtain better yields, makes again arise the risks already indicated with respect to the use of gaseous C0+02 mixtures. Finally, the use of nitric acid and/or nitrogen oxides, poses problems of corrosion for the equipment.
The drawbacks indicated above, even if in part techni-cally solvable, already by themselves create at any rate consi-derable economical and operational burdens which make the method little acceptable for use on an industrial scale.
It is an object of this invention to provide a process for the preparation of oxalic acid esters which is simple and inexpensive.
It is another object of this invention to provide a process for the preparation of oxalic acid esters which is free of the drawbacks of the prior art and which represents an ad-` vance thereover.
It is still another object of this invention to provide a process for the preparation of oxalic acid esters which will ensure that these derived end products are obtained in high yields and high purity.
These and other objects which will be apparent from the fo~lowing description are obtained by the invention described.
According to this invention, there is provided a pro-_3_ ., .
11L~4~lO
cess for the preparation of alkyl esters of oxalic acid, wherein said esters are obtained by reaction, in a gaseous phase, of an alkyl nitrite having the formula R-ONO, wherein R represents an alkyl having from 1 to 10 carbon atoms, with carbon monoxide in the presence of at least one catalyst selected from the group consisting of:
a) rhodium, iridium, platinum, gold and the salts thereof, with or without a co-catalyst selected from the group consisting of iron, copper and the salts thereof, and b) palladium in combination with a co-catalyst selected from the group consisting of iron, copper and the salts thereof, the salts of the hereinabove defined metals being selected from the group consisting of chlorides, sulphates, nitrates, acetates and acetylacetonates, C
at a temperature between 50 to 500C, under at least atmospheric pressure.
The reaction may be represented schematically by the following equation:
(1) 2 R-ONO (gas) ~ 2CO (gas)----~ COOR
¦ + 2NO (gas) COOR
As will easily be noticed, the reaction does not include the formation of water and, thus, there do not exist the corresponding problems of the hindrance of the reaction or ` of the high formation of by-products such as the diester of carbonic acid, etc. In other words, reaction (1) does by itself provide sufficiently anhydrous conditions.
As stated above, the reaction is conducted in the gaseous phase and, thus, the operative alkyl nitrites are - evidently those containing a low number of carbon atoms, that is from 1 to 3. Usually there is used methyl nitrite.
~ r~ - 4 -.i ~,~1 ll9L4~40 Obviously, depending on.the conditions of tempe-rature and pressure that have been chosen, there may also be used alkyl nitrites having a higher number of carbon atoms.
Thus, for instance, there may be considered as operational alkyl nitrites those having up to 10 carbon atoms.
~ he alkyl nitrites necessary for the reaction are known, easily available compounds or at any rate easily prepared from nitrous acid and R-OH alcohols in which R has the meaning pre-viously indicated. The alkyl nitrite is separated by distilla-tion, etc.
As a catalyst is used at least one metal. In fact, also catalysts formed by more than one of the hereunder indi-cated metals of the group comprising palladium, rhodium, iridium, platinum and gold, either as a metal or as a salt, are effective.
Suitable salts are chlorides, sulphates, nitrates, acetates, acetylacetonates, etc.
The catalyst is used according to the known fixed-bed technique and is thus preliminarily placed on carrier according to any of the many available conventional techniques.
As a carrier material it is posqible to use, for instance, silica, magnesium oxide or aluminum oxide, zinc oxide, chromium sesquioxide (Cr203), brimstone (pumice), etc. Or, alternatively, the carrier may consist of a metal or of its salt used together with the above-mentioned metals: palladium, rhodium, iridium, platinum, gold, as a co-catalyst, as more closely defined as follows.
The catalyst chosen from among palladium, rhodium, iridium, platinum and gold, either in the metal state or as salts as defined above, may in fact be accompanied, according to a further preferred aspect of this invention, by at least one further element with a co-catalytic function chosen from among iron and copper, in the metallic state, or as a salt such as chlorides, sulphates, acetates, etc., analogously to the primary catalyzing element. The use of the co-catalyzing element permits higher yields and an improved selectivity in obtaining the oxalic ester.
The catalyst is thus, preferably, formed by at least one element chosen from among palladium, rhodium, iridium, platinum, gold, as above defined, and by at least a co-catalyzing , element chosen between iron and copper, either as a metal or a ~4~40 slat which may also act as a carrier, or otherwise they may be supported on conventional carriers as above defined.
The global content of active catalytic elements on a conventional carrier ¦MgD~ A1203, etc.) is preferably comprised between 0.1% and 50% by weight with respect to the carrier.
These are just indicative values and at any rate not essential for the purposes of a correct carrying on of the reaction accord-ing to the invention.
Analogously, the global quantity of active catalytic elements used is comprised between 0.1 g and 10 g per mol of alkyl nitrite used, but preferably between 0.5 g and 5 g per mol of alkyl nitrite.
The ponderal ratio between the primary catalytic element or elements (Pd, Rh, Ir, Pt, Au) and the co-catalysts is not binding and may vary from 1:100 to 25:100, but preferably from 1:100 and 5:100, expressed as metal.
Examples of catalysts effective according to the in-vention may be the following: consisting of Pd (2%), Au ~1%) and deposited on ZnO and Cr203, ad~ixed to Cu(OCH3)Cl, Pd (5~) deposited on CuCl, Pd (5%) deposited on FeC12: Rh (5%) deposited on alumina, Rh (5%) and Pd (5%) deposited on alumina, Pd (5%) deposited on metallic Fe.
As indicated above, the catalyst is supported on a conventional carrier, otherwise on the co-catalyzing element which also acts as a carrier, according to substantially conventional methods, and the obtained catalyst is then used according to the Xnown fixed bed technique.
Just for illustrative purposes, without being a con-ditioning aspect for the execution of the invention, a method suitable for the preparation of the supported catalyst of the invention is as follows.
Into a small flask is introduced the pre-fixed quantity 9~0 of the substance tha~ will form the carrier for~the catalyst, and this substance is then covered with a solution containing the salt of the noble metal to be deposited on the carrier. The concentration of the salt in the solution depends on the total amount of noble metal to be deposited on the carrier.
Once said suspension has been achieved, under stirring, the solvent is distilled under vacuum up to dryness.
If one wished to add as a catalyst another noble metal different from the first one, the operation so far described is repeated once again, etc.
The same may be said for the co-catalyzing metal.
Once there has been obtained the solid consisting of the carrier with the metal salt or salts, the carrier is heated to 200C., under hydrogen, for about two hours.
At the end of this operation, the catalyst is ready for use and, of course, is kept in an atmosphere of ~2.
The process conditions of temperature, pressure and contacting times are variable within wide ranges, depending on the mutual choice.
Advantageous results have been achieved uqing tempera-tures comprised between 50C. and 500C., but preferably 150C.
and about 350C.
The contacting times are comprised between 0.1 and 10 seconds, but preferably between 0.1 and 1 second.
The partial pressure of the reacting gases may vary between atmospheric pressure and about 200 atmospheres, but preferably between atmo~pheric pressure and about 50 atm., without being, however, an essential aspect of the invention.
Where desired, the use of CO in admixture with inert gases or of synthesis gases (CO and H2) is compatible. The separation of the oxalic ester is achieved suitably according to known methods, for instance by conventional distillation,etc.
4~'340 From the ester it is easy to obtain the acid by hydro-lysis, etc., likewise by mean~ of conventional known methods.
The NO gas that develops from the reaction may be re-covered, and, after oxidation, may be re-used for the prepara-tion of the alkyl nitrite.
In one embodiment, the process of the invention is conducted as follows.
Into a vessel fitted with reactant feeding systems, and provided with a flow regulator and a temperature regulating system, is placed the prepared catalytic bed. Thereupon the gaseous stream o the reactants is made to flow through the reactor in the desired ratio, quantity and for the desired contact time. At the outlet of the reactor there condenses a liquid from which the oxalic ester i~ recovered by distillation, etc.
Thankq to the simple operational conditions, the in-vention proves to be particularly advantageous. Other advantage3 consist of the selectivity in the formation of the oxalic ester in by them~elves anhydrous conditions of the reaction and in the ~ 20 exclusion of the operational risks of explosions due to the lack j of possible CO+O2 mixtures.
The "fixed bed" technique allows one to have a localized catalyst, not dispersed in the reacting mass, and moreover, ensures a much simpler and more economical operational effective-ness of the renewal, recovery operations, etc.
i Finally, the possibility of employing C~ and hydrogen mixtures as such as coming from the synthesis gas preparation is ` of particular intere~t, without sub~tantially involving the pro-; cess effectiveness.
~ The invention will now be described in more detail in the following examples given for purely illustrative and not limiting purposes.
.. , 49~0 EXAMPLE
-Into a glass reactor for heterogeneous catalysis, provided with a porous diaphragm, there were introduced 1.5 g of a catalyst consisting of Pd (5%) deposited on CuCl. The reactor was then inserted into a muffle furnace with a known thermal dia~ram and maintained at a temperature of 200C. On the cataly t there was then allowed to flow a gas thus composed:
CO (4 N lt~hr) - CH30NO (3 ~ lt/hr).
Under these conditions, the dwelling time o the reaction mix-ture and the contact with the catalyqt amounted to 0.5 second.
At the outlet of the reactor there had been placed a gathering trap maintained at 0C. After two hours from the start of the test, the liquld deposited in the trap was collected and subjected to analysis. The analysis was carried out both by gas-chromatography as well as by directly titering the precipitated calcium oxalate.
There were thus ascertained 100 mg of methyl oxalate in the gathered liquid.
EXAMPL~ 2 In the same equipment and following the same procedures a~ those described in Example 1, there was used a catalyst con-sisting of Pd (2%), Au (1%), deposited on ZnO and Cr203 admixed to Cu(OCH3)Cl.
The reaction temperature amounted to 180C., while the test lasted 3 hours.
At the end of the test, at the outlet of the reactor, there was gathered a liquid in which were found 20 mg of methyl-oxalate.
Thereupon the feeding of the reactants was resumed under the same conditions for an additional 6 hour~. At the end there was recovered another 40 mg of methyl oxalate.
It was then proceeded for another 16 hours to feed _g_ ~1~4~0 into the reactor the given reactants. At the end there were obtained another 230 mg of methyl oxalate.
In the same equipment and following the same procedures as those described in Example 1, there was used a catalyst con-sisting of Pd (~%) deposited on FeC12.
The reaction temperature was 200C. The duration of the test was 4 hours. At the end of the test there was reco-vered a liquid containing 500 mg of methyl oxalate, thereupon feeding of the reactants wa~ re~umed for a further hour.
At the end there were gathered 50 mg of methyl oxalate.
Proceeding as in the previous examples, there was used a catalyst consisting of Rh (5%) deposited on aluminum. The reaction temperature was 200C., while the duration of the test was 4 hours. The flow of CO wa~ 2 N lt/hr. At the end of the test there was recovered a liquid containing quantities of methyl oxalate traced by means of gas-ghromatography.
Proceeding as in the previous examples, there was used a catalyst consisting of Rh (5%) and Pd (5%) depo~ited on alumina, and there obtained the same re~ults.
-Operating as in the previous examples, there was used a catalyst consisting of Pd (5%) deposited on Fe. The reaction temperature was 200C., while the duration of the test was 4 hours. At the end of ~aid test there was recovered a liquid containing 460 mg of methyl oxalate.
~XAMPLE 7 Following the same procedures as those of the previous examples, there was used a catalyst consisting of Pd (5%) on FeC12. Into the reactor were fed 3 ~.lt/hour of ethyl nitrite ~4~
and 4 N.lt/hour of carbon monoxide. The temperature was 200C., while the duration of the test was S hours. At the end of the test there was recovered a liquid containing 50 mg of ethyl oxalate.
It was operated as in Example 6, but at 300C. Thereby were obtained 20 mg of ethyl oxalate.
E~AMPLE 9 On the same equipment and with the same procedures described in Example 1, there was used a catalyst consisting of Pt (5%) on FeC12. The reaction temperature was 210C. and the duration of the test was 3 hours.
At the end of the test, at the outlet of the reactor there was gathered a liquid containing 130 mg of methyl oxalate.
In this instance there was repeated the test of Example 9, but using as a catalyst: Rh (5%) on FeC12 for a period of 3 hours, thereby obtaining 450 mg of oxalate.
Again Exam~le 9 was repeated, but using as a catalyst:
Ir (5%) on FeC12, for a reaction time of 3 hours. Thereby were obtained 100 mg of oxalate.
Claims (16)
1. A process for the preparation of alkyl esters of oxalic acid, wherein said esters are obtained by reaction, in a gaseous phase, of an alkyl nitrite having the formula R-ONO, wherein R represents an alkyl having from 1 to 10 carbon atoms, with carbon monoxide in the presence of at least one catalyst selected from the group consisting of:
(a) rhodium, iridium, platinum, gold and the salts thereof, with or without a co-catalyst selected from the group consiting of iron, copper and the salts thereof, and (b) palladium in combination with a co-catalyst selected from the group consisting of iron, copper and the salts thereof, the salts of the hereinabove defined metals being selected from the group consisting of chlorides, sulphates,nitrates, acetates and acetylacetonates, at a temperature between 50 and 500°C, under at least atmospheric pressure.
(a) rhodium, iridium, platinum, gold and the salts thereof, with or without a co-catalyst selected from the group consiting of iron, copper and the salts thereof, and (b) palladium in combination with a co-catalyst selected from the group consisting of iron, copper and the salts thereof, the salts of the hereinabove defined metals being selected from the group consisting of chlorides, sulphates,nitrates, acetates and acetylacetonates, at a temperature between 50 and 500°C, under at least atmospheric pressure.
2. A process according to claim 1, characterized in that the alkyl nitrite is selected from among methyl-, ethyl-and propyl nitrites.
3. A process according to claim 1, characterized in that the catalyst is used supported on a carrier selected from among silicon,magnesium oxide, aluminum oxide and zinc oxide, chromium sesquioxide, pumice and their mixtures.
4. A process according to claim 3, characterized in that the carrier consits of the co-catalytic metal element chosen between iron and copper or` from among their salts.
5. A process according to claim 3, characterized in that the global amount in catalytic active elements on the carrier is in the range between 0.1 and 50% by weight with respect to the carrier.
6. A process according to claim 1, characterized in that the global amount of catalytic active elements used is in the range between 0.1 and 10 grams per mol of alkyl nitrite.
7. A process according to claim 6, wherein said catalytic active elements are used in an amount between 0.5 and 5 grams per mol of alkyl nitrite.
8. A process according to claim 1, characterized in that the weight ratio expressed as metal between the total of the elements selected from among Pd, Rh, Ir, Pt, Au and the total of the elements chosen from between Fe and Cu, is between 1:100 and 25:100.
9. A process according to claim 8, wherein said weight ratio is between 1:100 and 5:100.
10. A process according to claim 1, characterized in that the reaction is conducted at a temperature between about 150°C and 350°C.
11. A process according to claim 1, characterized in that the contact times of the gaseous reactants with the catalyst is between 0.1 and 10 seconds.
12. A process according to claim 11, wherein said contact time is between 0.1 and 1 second.
13. A process according to claim 1, characterized in that the partial pressure of the reacting gases varies between about atmospheric pressure and about 200 atm.
14. A process according to claim 13, wherein said partial pressure is between atmospheric and 50 atmospheres.
15. A process according to claim 1, characterized in that the carbon monoxide is fed in admixture with gases inert under reaction conditions.
16. A process according to claim 15, wherein the carbon monoxide is fed in admixture with H2 coming from the industrial preparation of the synthesis gas.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT24903A/78 | 1978-06-23 | ||
| IT24903/78A IT1097268B (en) | 1978-06-23 | 1978-06-23 | PROCESS FOR THE PREPARATION OF ESTERS OF OXALIC ACID |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1144940A true CA1144940A (en) | 1983-04-19 |
Family
ID=11215084
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000330654A Expired CA1144940A (en) | 1978-06-23 | 1979-06-22 | Process for the preparation of esters of oxalic acid |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS5522666A (en) |
| BE (1) | BE877206A (en) |
| CA (1) | CA1144940A (en) |
| DE (1) | DE2925336A1 (en) |
| FR (2) | FR2429198A1 (en) |
| GB (1) | GB2025950B (en) |
| IT (1) | IT1097268B (en) |
| NL (1) | NL7904824A (en) |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5980630A (en) * | 1982-11-01 | 1984-05-10 | Ube Ind Ltd | Preparation of oxalic acid diester |
| AU545415B2 (en) * | 1980-08-26 | 1985-07-11 | Ube Industries, Ltd. | Oxalic esters from carbon monoxide and nitrous acid ester |
| JPS5742656A (en) * | 1980-08-29 | 1982-03-10 | Ube Ind Ltd | Continuous preparation of oxalic acid diester |
| JPS57120175U (en) * | 1981-01-21 | 1982-07-26 | ||
| JPS57122043A (en) * | 1981-01-23 | 1982-07-29 | Ube Ind Ltd | Preparation of oxalic acid diester |
| JPS57122529U (en) * | 1981-01-23 | 1982-07-30 | ||
| US4629806A (en) * | 1981-01-23 | 1986-12-16 | Union Carbide Corporation | Vapor state formation of diesters of oxalic acid |
| EP0057629B1 (en) * | 1981-01-23 | 1986-03-26 | Union Carbide Corporation | Vapor state process for the preparation of diesters of oxalic acid |
| US4616093A (en) * | 1981-01-23 | 1986-10-07 | Union Carbide Corporation | Process for preparing a diester of oxalic acid in the vapor phase |
| US4410722A (en) * | 1981-01-23 | 1983-10-18 | Ube Industries, Ltd. | Process for preparing oxalic acid diesters using platinum group metals supported on alumina |
| JPS58126836A (en) * | 1982-01-26 | 1983-07-28 | Ube Ind Ltd | Preparation of oxalic acid diester |
| JPS5982233A (en) * | 1982-11-01 | 1984-05-12 | Hitachi Ltd | Operating method of unloader |
| JPS6366674U (en) * | 1986-10-21 | 1988-05-06 | ||
| US20130150617A1 (en) * | 2010-06-04 | 2013-06-13 | Xinbin MA | Monolithic structured catalyst for carbon monoxide gase-phase coupling to dialkyl oxalate & preparation method and application thereof |
| WO2012124616A1 (en) * | 2011-03-11 | 2012-09-20 | 宇部興産株式会社 | Catalyst for production of oxalic acid diester, and method for producing oxalic acid diester using catalyst |
| WO2020082200A1 (en) * | 2018-10-22 | 2020-04-30 | Pujing Chemical Industry Co., Ltd | Carbonylation catalyst and preparation thereof |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5315313A (en) * | 1976-07-27 | 1978-02-13 | Ube Ind Ltd | Production of oxalic acid diesters |
| GB2003872B (en) * | 1977-09-07 | 1982-05-19 | Ube Industries | Process for preparing a diester of oxalic acid |
-
1978
- 1978-06-23 IT IT24903/78A patent/IT1097268B/en active
-
1979
- 1979-06-20 NL NL7904824A patent/NL7904824A/en not_active Application Discontinuation
- 1979-06-22 CA CA000330654A patent/CA1144940A/en not_active Expired
- 1979-06-22 BE BE0/195915A patent/BE877206A/en not_active IP Right Cessation
- 1979-06-22 DE DE19792925336 patent/DE2925336A1/en not_active Withdrawn
- 1979-06-22 FR FR7916113A patent/FR2429198A1/en active Granted
- 1979-06-22 JP JP7824979A patent/JPS5522666A/en active Pending
- 1979-06-25 GB GB7922056A patent/GB2025950B/en not_active Expired
-
1981
- 1981-04-23 FR FR8108103A patent/FR2477141A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| NL7904824A (en) | 1979-12-28 |
| FR2429198B1 (en) | 1984-05-11 |
| IT1097268B (en) | 1985-08-31 |
| IT7824903A0 (en) | 1978-06-23 |
| FR2477141A1 (en) | 1981-09-04 |
| DE2925336A1 (en) | 1980-01-10 |
| GB2025950A (en) | 1980-01-30 |
| FR2429198A1 (en) | 1980-01-18 |
| FR2477141B1 (en) | 1983-02-25 |
| JPS5522666A (en) | 1980-02-18 |
| BE877206A (en) | 1979-12-24 |
| GB2025950B (en) | 1983-04-27 |
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