This project deals with production of methyl ethyl ketone (MEK) from corn fiber. Corn fiber is consisted of mostly hemicellulose that can be hydrolyzed to produce a mixture of sugars. Extensive work has been done on fermentation by Klebsiela oxytoca that can metabolize all hemicellulose sugars and give a 50% weight yield of a compound called 2,3-butanediol (BDO). BDO has a boiling point of 180 E C. To recover BDO from fermented broth involves energy intensive evaporation of a large amount of water and then vacuum distillation. BDO can be converted into MEK by dehydration. MEK with a boiling point of 79.6 E C can be purified by simple distillation. Work has been done on dehydration of pure BDO to MEK with sulfuric acid as a catalyst. This project has its objective of testing the use of crude BDO in fermented broth, without first being purified, directly in dehydration. If successful, a 2-step process will be possible for conversion of corn fiber first to BDO by fermentation and then to MEK by acidic dehydration. Impurities in the fermented broth including residual sugars and proteins have been reported to interfere with the dehydration reaction. This Phase I project work is to eliminate such possible interferences by different methods including complete sugar metabolism, pretreatment of ion exchange resins and/or activated carbon, etc. Work will also be done using solid acids such as zeolite ZSM-5 to replace sulfuric acid in dehydration. The zeolite cage structures may reject large molecules such proteins from interfering. Use of solid acid also avoids otherwise a waste sulfuric acid stream. The activity half-life of zeolite in an aqueous reaction will be carefully determined.
Anticipated Results/Potential Commercial Applications of Research: With the greatly expanded ethanol production, new uses are needed to dispose the excessive byproduct, corn fiber. MEK, at $0.46 per pound, is a bulk chemical with an annual worldwide consumption of 1.2 million tons, growing at a rate of about 2% per year. Corn fiber is currently marketed as an ingredient in animal feed. Feed products are priced according to protein contents and corn fiber is disposed by this outlet but brings no financial benefits to the processor. With the cheap corn fiber and the high efficiency, MEK by the new method is competitive. Preliminary analysis shows a direct production cost of less than 20 cents per pound. Shell Chemical Company, the world's largest MEK producer by petrochemical synthesis, endorses a feasibility study of this new hybrid biological/chemical method of MEK production.
