Continuous preparation of methyl formate

Details Continuous preparation of methyl formate Continuous preparation of methyl formate

1997-07-30

1999-06-29

Barts, Samuel

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acid esters

C07C 6736

Patent

active

059170859

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to an improved continuous process for preparing methyl formate by reaction of carbon monoxide and methanol under elevated pressure and elevated temperature in the presence of an alkali metal methoxide as catalyst.
The principle of this method of preparing methyl formate has long been known.
Methyl formate is processed into formic acid on an industrial scale. For this purpose, methyl formate is, prior to a hydrolysis step, separated by distillation from the catalyst and higher-boiling byproducts. The bottom product formed in the distillation cannot be recirculated to the reaction. In the case of sodium methoxide being used as catalyst, it contains sodium hydroxide, sodium formate, sodium carbonate and sodium oxalate, as well as other compounds. In continuously operated plants, these salts have to be disposed of, which incurs considerable costs because of the organic compounds present in the distillation bottoms (content of total organic carbon, TOC), which compounds have to be degraded in an effluent treatment plant.
DE-A 926 785 teaches a process for preparing methyl formate from methanol and carbon monoxide in the presence of at most 0.25% by weight of sodium, corresponding to 0.59% by weight of sodium methoxide, based on methanol used. The document discloses a reaction pressure of 300 bar. However, the space-time yields achievable under these conditions are unsatisfactory. A further disadvantage is that the reaction mixture obtained has to be pumped in a circuit outside the reactor to remove heat.
DE-A 11 47 214 teaches the splitting of the carbon monoxide stream in the preparation of methyl formate into two substreams which are fed to the reactor at different levels.
According to this document, from 0.12 to 0.3 mol% of catalyst are used, corresponding to over 0.2% by weight of sodium methoxide or 0.26% by weight of potassium methoxide, based on methanol used. The reaction pressure is from 150 to 200 bar. After prolonged operation, this procedure too results in encrustations of decomposition products of the catalyst on heat exchangers and reactor walls.
DE-A 43 09 731 relates to a process method according to which methanol and carbon monoxide are partially reacted in a mixing zone, the mixture thus obtained is saturated with carbon monoxide and the reaction is then completed in a post-reaction zone without a further supply of starting compounds. The reaction pressure is preferably a typical pressure for low-pressure processes of from 40 to 100 bar. The alkali metal methoxide concentration is preferably from 0.4 to 1.5% by weight, based on methanol used.
The reaction procedures described lead to the above-described formation of distillation bottoms which require cost-intensive disposal.
It is an object of the invention to keep the disposal costs for said distillation bottoms as low as possible. In particular, a way is to be found of reducing the formation of organic salts in these distillation bottoms.
We have found that this object is achieved by a continuous process for preparing methyl formate by reaction of methanol and carbon monoxide under elevated pressure and elevated temperature in the presence of alkali metal methoxide, wherein the reaction is carried out at a pressure of from 210 to 250 bar in the presence of from 0.05 to 0.2% by weight of alkali metal methoxide, based on methanol used.
The carbon monoxide used in the process of the invention can be mixed with inert gases such as nitrogen. However, the carbon monoxide content of the mixture of carbon monoxide and inert gases is preferably at least 93% by volume. To keep the hydrolytic decomposition of the catalyst low, the water content of the gas should be less than 100 ppm.
The catalyst used is an alkali metal methoxide such as sodium methoxide, preference being given to potassium methoxide. The catalyst is used in an amount of from 0.05 to 0.2% by weight, based on methanol used. The catalyst is advantageously introduced into the reaction zone in methanol solution.
Carbon monoxide, methanol and catalyst are mixed

REFERENCES:
patent: 4661624 (1987-04-01), Chang et al.
patent: 5401873 (1995-03-01), Zehner et al.

Affiliated with

Also associated with

Rating

Continuous preparation of methyl formate does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Continuous preparation of methyl formate, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Continuous preparation of methyl formate will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1376680