The Schwank Group

-Aromatic Chemical Synthesis from Synthesis Gas-

Benjamin Harris and Johannes Schwank

Zeolite activity under typical FTS reaction conditions

Activity of Ga-Zeolite in the conversion of propylene under
Fischer-Tropsch Synthesis reaction conditions

The use of synthesis gas, composed of carbon monoxide and hydrogen and derived from natural gas or coal, has been used for fuel and chemical production for over half a century in the Fischer-Tropsch Synthesis (FTS) process. Countries have used the technology as an alternative to oil at times when oil resources were limited. With increasing oil prices, production of fuel from natural gas (with natural gas reforming as an intermediate step) has begun to become appealing in an economic sense. An alternative use for the synthesis gas derived from natural gas is the production of commodity chemicals that are typically derived from oil sources. Aromatic chemicals such as benzene and p-xylene have large markets for use in polymer production, as an example. My research is based on the use of an FTS catalyst and a gallium-incorporated zeolite for the one-step production of aromatic chemicals from synthesis gas.

The FTS process forms a wide range of typically straight-chained olefin and paraffin compounds. These chemicals must be separated after the reactor and then sent to further reactors for the production of other desired compounds. My research is attempting to remove the need of a second reactor and separation unit by reacting the products of the FTS process over a gallium-incorporated zeolite present in the same reactor. To do this, I am currently testing the use of the zeolite under conditions typically found in an FTS reactor. These conditions differ from the conditions typically found in reactors used for the zeolite. Such changes include, the presence of water, lower operating temperatures, potentially higher pressures, longer operating times, reduction under hydrogen prior to reaction, and a wide range of reactive chemicals. Based on my results from these experiments, I will match an FTS catalyst capable of operating at the needed pressure and temperature to ideally form a product stream with a high aromatic content.

Early results have shown that the zeolite performs under conditions similar to the FTS process. The use of 3% propylene (balance nitrogen) stream as a model reactant was chosen for this experiment due to propylene's high molar fraction as a product of the FTS process. In this sample experiment, the zeolite was reduced under hydrogen, operated at 300 C (a temperature 100 C lower than typically used), and analyzed over a timeframe of 23 hours (typical timeframes of zeolite reactions are less than 1 hour). The experiment shows that the reaction is sustained over the timeframe with a fairly constant product distribution. The production of aromatic compounds appears to be low in this experiment, however the composition of the C9+ fraction is currently unknown. It is also believed that the product distribution is partially controlled by the chemical, propylene, being used as the reactant, and that use of higher carbon hydrocarbons may produce a more concentrated aromatic product fraction. This hypothesis has yet to be tested, but it is planned that this hypothesis will be tested in the near future.

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