Method of producing lower alcohols from glycerol

Abstract

A reactive-separation process converts glycerin into lower alcohols, having boiling points less than 2000 C, at high yields. Conversion of natural glycerin to propylene glycol through an acetol intermediate is achieved at temperatures from 150° to 2500 C at pressures from 1 and 25 bar. The preferred applications of the propylene glycol are as an antifreeze, deicing compound, or anti-icing compound. The preferred catalyst for this process in a copper-chromium.

Description

RELATED APPLICATIONS[0001]This application is a continuation-in-part of U.S. application Ser. No. 11 / 510,992 filed Aug. 28, 2006 claiming benefit of priority to U.S. provisional application Ser. No. 60 / 731,673 filed Oct. 31, 2005, and is a continuation-in-part of U.S. application Ser. No. 11 / 088,603 filed Mar. 24, 2005, which claims benefit of priority to U.S. provisional patent application Ser. No. 60 / 556,334 filed Mar. 25, 2004 and is a continuation-in-part of U.S. patent application Ser. No. 10 / 420,047 filed Apr. 21, 2004, which claims benefit of priority to U.S. provisional patent application Ser. Nos. 60 / 374,292, filed Apr. 22, 2002 and 60 / 4103,24, filed Sep. 13, 2002, all of which are incorporated by reference herein.BACKGROUND[0002]1. Field of The Invention[0003]This invention relates generally to a process for value-added processing of fats and oils to yield glycerol and glycerol derivatives. More particularly, the process converts glycerol to acetol and / or propylene glycol,...

AI Technical Summary

Benefits of technology

[0011]In one aspect, a process for converting glycerol to acetol with high selectivity, commences with providing a glycerol-containing material that has 50% or less by weight water. This material may be, for example, a byproduct of biodiesel manufacture. The glycerol-containing material is contacted with a catalyst that is capable of hydrogenating glycerol, in order to form a reaction mixture. Conditions for reaction of the reaction mixture are established to include a temperature within a range from 150° C. to 250° C. and a pressure within a range from 0.1 bar to 25 bar. The reaction mixture is reacted under the conditions for reaction to dehydrate the glycerol with resultant formation of acetol as a reaction product. The reaction may be performed at temperatures of up to 270° C., 280° C. or even 290° C. or 300° C.; however, the use of these increased temperature results in thermal degradation of the reaction product together with die-reactions, and so is not recommended for applications where high purity of the reaction product is required. The inclusion of increased amounts of water in the reagent stream facilitates improved selectivity It is possible by use of this process according to one or more of the embodiments described below to achieve, for example, propylene glycol that is 90% pr even 98% pure at a high yield of better than 85% or even 95%. The lower end of this range is preferably at least 150° C. to fully activate the catalyst and accelerate the reaction, but in some embodiments it is feasible to conduct the reaction in the range less than 150° C., such as down to 80° C.

[0015]It is possible to use a gas flow for stripping the reaction products from the reaction mixture, where such reaction product may include acetol and propylene glycol. In one embodiment, the glycerol-containing material is in liquid phase and the process entails removing the reaction product(s) during the step of reacting. This may be done by facilitating selective release of acetol as vapor from the reaction mixture by action of partial pressure through contact with a gas, such as nitrogen or a noble gas, that is essentially inert to the reaction mixture and the acetol reaction product.

[0017]In another embodiment, the gas that strips reaction [products from the initial reaction mixture may be reactive with the acetol reaction product, such as hydrogen gas is reactive with the acetol. Accordingly, the stripper gas may be supplemented with hydrogen for this effect, such that a different reaction product is condensed. This different reaction product may be propylene glycol. Unused hydrogen may be recycled from the condenser back to the reactor vessel.

[0018]A more preferred temperature range for facilitating the reaction is from 180° C. to 220° C. A more preferred pressure range is from 1 to 20 bar, where low pressures of from 1 to 15 bar and 1 to 5 bar may yield especially pure products. The reaction may persist for a duration in a slurry phase with reaction limited by catalyst within a range from 0.1 hour to 96 hours, such as from 4 to 46 hours or from 4 to 28 hours. It is possible to operate the reaction at higher catalyst loadings and even in a gas phase with much shorter reaction times within the range from 0.001 to 8 hours, or more-preferably 0.002 to 1 hour, or even more preferably from 0.05 to 0.5 hours.

Problems solved by technology

Existing processes for the hydrogenation of glycerol to form other products are generally characterized by requirements for excessively high temperatures and pressures.

For example, high temperatures may degrade the reaction products.

Working pressures of several hundred bar create safety concerns and increase the capital costs of implementing these processes.

Most of such processes yield substantial impurities that may necessitate costly purification steps to isolate the desired reaction products.

None of the processes shown by these patents provide a direct reaction product mixture that is suitable for use as antifreeze.

None provide process conditions and reactions that suitably optimize the resultant reaction product mixture for direct use as antifreeze.

None address the use of unrefined crude natural glycerol feed stock, and none of these processes are based on reactive distillation.

The reaction may be performed at temperatures of up to 270° C., 280° C. or even 290° C. or 300° C.; however, the use of these increased temperature results in thermal degradation of the reaction product together with die-reactions, and so is not recommended for applications where high purity of the reaction product is required.

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