Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Patent
1984-07-20
1986-04-29
Trousof, Natalie
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
560190, 560193, 568909, C07C 6736, C07C 2700, C07C 2948
Patent
active
045858918
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the production of dihydrocarbyl oxalates.
Dialkyl oxalates have various industrial uses, such as for example, reagents for analysis, solvents, and starting materials for oxamide, orotic acid, etc production. By far their greatest potential use is as an intermediate in the production of ethylene glycol by hydrogenation. Specific dialkyl oxalates are also intermediates in the production of other valuable products. For example di-t-butyl oxalate is known to undergo a facile and efficient decomposition to i-butene and oxalic acid, which latter product is used in industry as a mordant in cloth printing, for the manufacture of dyes, dextrin, ink, as a bleaching agent for straw and as a precipitant for the rare-earths.
Early methods for preparing dialkyl oxalates involved heating anhydrous oxalic acid with an aliphatic alcohol in the presence of concentrated sulphuric acid. Thereafter, in keeping with the trend towards the utilisation of carbon monoxide, either alone or in combination with hydrogen, in the synthesis of bulk organic chemicals, several patents describe the production of dialkyl oxalates by reacting an aliphatic alcohol with carbon monoxide and oxygen in the presence as catalyst of a mixture of a salt of a platinum group metal and a salt of copper or iron. Such patents include U.S. Pat. Nos. 3,391,136 and 3,994,960. Of necessity water is formed when an alcohol is reacted with carbon monoxide and molecular oxygen. It is recognised that the formation of water is undesirable, because it can deactivate the catalyst, it can depress the yield of dihydrocarbyl oxalate and it can complicate product separation. For this reason steps have been taken to remove the water as it is formed by the addition of a dehydrating agent, for example an alkyl orthoformic ester.
More recently, integrated processes for the production of ethylene glycol via the intermediate formation of dialkyl oxalates have been disclosed. Typically, GB 2083032A describes a process for continuously preparing ethylene glycol by (1) a first step of contacting a gas containing carbon monoxide and an ester of nitrous acid with a solid catalyst of the platinum group metal series in the gaseous phase thereby to obtain a product containing a diester of oxalic acid, (2) a second step of condensing the product of the first step thereby to separate a non-condensed gas containing nitrogen monoxide formed by the catalytic reaction of the first step from a condensed liquid containing the diester of oxalic acid, (3) a third step of contacting the non-condensed gas of the second step with a gas containing molecular oxygen and an alcohol, and recycling the resulting gas containing an ester of nitrous acid to the first step, (4) a fourth step of contacting the condensed liquid of the second step containing the diester of oxalic acid and hydrogen with a catalyst for hydrogenation in the gaseous phase thereby to obtain a product containing ethylene glycol, (5) a fifth step of distilling the product of the fourth step thereby to distil out the alcohol and to obtain ethylene glycol, and (6) a sixth step of recycling the alcohol of the fifth step as an alcohol source for the third step. In this process nitrogen monoxide functions essentially as a carrier for oxygen. Whilst nitrogen monoxide may be effective as an oxygen carrier, it can under certain conditions, eg the presence of water, cause corrosion of plant and associated equipment with which it comes into contact.
Canadian Pat. No. 743559 describes a method of producing a tertiary ester of a carboxylic acid comprising contacting with agitation carbon monoxide and a di-t-hydrocarbyl peroxide of the formula (RR'R") C--O--O--C(RR'R") wherein R, R' and R" are hydrocarbyl radicals selected from the group consisting of alkyl, aryl, alkaryl and aralkyl having up to nine carbon atoms, said contacting being conducted at an elevated temperature and carbon monoxide pressure and in the presence of inert organic liquid diluent. The use of transition metal salts as catalysts i
REFERENCES:
patent: 3393136 (1968-07-01), Fenton et al.
patent: 3994960 (1976-11-01), Yamazaki et al.
patent: 4005128 (1977-01-01), Zehner et al.
patent: 4076949 (1978-02-01), Zehner
patent: 4160107 (1979-07-01), Agnes et al.
Clarke Vera C.
The British Petroleum Company p.l.c.
Trousof Natalie
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