Poison Resistant Water-Gas-Shift Catalyst for Biomass and Coal Gasification

The U.S. has estimated 24 billion tonnes of coal, which at current rates of consumption is enough to last about 200 years. The general problem is how to prevent the 80+ billions tonnes of carbon dioxide from being emitted into the atmosphere when using this resource. One way to decrease the amount of CO2 generated when using coal, and to increase U.S. energy security, is to co-feed biomass with the coal using gasification to make synthetic fuels. Biomass is carbon neutral, since the CO2 released when the "biomass portion" of the fuel is burned or gasified eventually ends up being used to grow more biomass. Biomass is an indirect way of utilizing solar energy (which provides the energy needed by the plants to convert CO2 into cellulose) and has the potential to reduce CO2 emissions by 50% or more depending on the ratio of biomass to coal fed to the gasifier. Sulfur free diesel and other middle distillate fuels can be made from synthesis gas (CO + H2) produced by biomass and coal gasification using the Fischer Tropsch (FT) process. Unfortunately, current catalysts needed for both FT synthesis and the required upstream water gas shift (WGS) reactions are sensitive to a variety of poisons that are not normally present when coal alone is gasified. Thus, the development of poison resistant catalysts that function with both coal and biomass gasification, will significantly advance coal-biomass-to-liquids (CBTL) technology. Coal gasification followed by Fischer-Tropsch synthesis has been commercially demonstrated for producing sulfur-free diesel and other middle distillate fuels for over 50 years in South Africa by SASOL. Because coal contains both organic and inorganic sulfur, hydrogen sulfide is produced during gasification. Also, raw synthesis gas has too low of a hydrogen to carbon monoxide ratio to be directly used for Fischer-Tropsch synthesis. To increase the H2/CO ratio the synthesis gas is shifted over a catalyst where CO reacts with water to produce CO2 and H2 (the water gas shift reaction). Unfortunately, hydrogen sulfide poisons conventional water gas shift catalysts, and therefore a series of commercial sulfur tolerant WGS catalysts have been developed. While these catalysts have been in service for over 30 years, they require higher operating temperatures than conventional WGS catalysts, and consequently give lower CO conversions (because of equilibrium limitations). In addition, when biomass is added to the feed, mineral matter present in the ash can end up in the gas; for example alkali chloride vapors such as KCl. Chlorine is a severe poison of sweet LT shift catalysts forming volatile copper chlorides. TDA Research Inc. (TDA) has developed a new water gas shift catalyst that is as active as conventional high and low temperature water-gas-shift catalysts that is not poisoned by sulfur and other contaminants present in syngas produced during biomass and coal gasification. Because our catalyst is poison resistant and active, it improves the energy efficiency and economics of coal-biomass-to-liquids. Commercial Applications and Other Benefit: This project will develop a new catalyst that will allow more efficient fuels production from coal and biomass while minimizing the number of steps involved