SBIR-STTR Award

Ethanol is a versatile chemical with many industrial uses, but most ethanol is used as a fuel or fuel additive. Ethanol is produced primarily by fermentation of grains, but if it could instead be made from the syngas produced thermochemically from biomass gasification, a valuable fuel could potentially be made using a wide variety of cellulosic feedstocks. In Phase I, TDA will prepare and test a novel catalytic process for the conversion of syngas to ethanol. Mainly due to its projected use as an oxygenate in gasoline, ethanol demand is projected to grow by as much as 10% per year until 2012. Currently, as much as 83% of the ethanol in the U.S. is produced by fermentation processes of corn. As a result, food prices spiked in 2008, in part driven by the fact that farmers were growing corn for ethanol production instead of for food crops. As an alternative, intensive R&D efforts are underway to develop biochemical methods to convert cellulosic biomass into ethanol, but technologies are not yet mature. Conversion of syngas produced from gasification of cellulosic biomass to high value ethanol would be an advantage for both the fuels and chemical industries. TDA Research, Inc. (TDA) has identified a novel catalyst for converting syngas to ethanol. In Phase I, TDA will synthesize and test new catalysts using our automated reactor equipment to determine the combination of catalyst formulation and operating conditions that give the best selectivity for converting syngas to ethanol. In Phase II, we will optimize the catalyst formulation further and test the best catalyst in a bench-scale reactor. We will then work with our commercialization partner to test our process at the pilot plant scale. Commercial Applications and Other

Benefits:
This project will develop a new route to ethanol from a cheap, abundant (domestic supply), cellulosic feedstock that will help meet the rapidly growing demand for fuel ethanol.

Synthesis gas, a mixture of H2 and CO, is one of the top-ten platform chemicals produced from biomass and can be used to produce fuel-ethanol. However, existing heterogeneous catalysts have only a low selectivity for ethanol and produce too much low-value methane. As a result, the production of ethanol from syngas with heterogeneous catalysts is uneconomical. Our major breakthrough is the discovery of a homogeneous catalytic system that exhibits high selectivity for ethanol and produces one tenth the amount of methane as do heterogeneous catalysts. TDA Research has developed a homogeneous catalytic system that can produce ethanol from syngas at rates comparable to the best heterogeneous catalysts while producing less than 2-3% methane (heterogeneous catalysts produce 20-40% CH4). Our catalysts first convert syngas to methanol, which is homologized in-situ to ethanol. Acetic acid formed by CO-insertion into methanol reacts with methanol to form methyl acetate, which is subsequently hydrogenated to ethanol and methanol. The alcohols are separated downstream and the methanol is recycled. The only products exiting the reactor are ethanol, a small amount of 1-propanol, methanol (which is recycled) and a small amount of methane. At the same time, the water-gas shift reaction consumes water produced during alcohol synthesis to produce additional hydrogen. The goal of the Phase IIB project is to scale up our homogeneous syngas to ethanol process by a factor of 50 by designing and building a continuous flow reactor system. We have chosen a bubble column reactor to dissipate the large exothermic heat of reaction of ethanol synthesis. The bubble column will hold approximately 250 mL of homogeneous catalyst solution with another 250 mL in the circulation system. While obviously much smaller than an industrial reactor, this scale of reactor will sufficiently simulate a full scale bubble column so that we can make the kinetic and steady state measurements, and determine the heat and mass transfer characteristics of the system needed to perform a preliminary pilot plant design at the end of the Phase IIB project. Also, we will work with our industrial partners and perform a detailed techno-economic analysis of the process. Commercial Applications and Other

Benefits:
Corn based ethanol plants use a food to produce fuel. Thermochemical methods (such as our syngas-to-ethanol process) for making ethanol are attractive because they can use agricultural and other renewable (non-edible) waste streams to make ethanol.