Methanol coke-forming process

Figure 12.13 Coke-forming process occurring during the methanol-to-hydrocarbon process over H-ZSM-5 zeolites, and a corresponding in situ UV-vis spectrum measured under reaction conditions. (Reproduced with permission from Ref. [121].)...

J. Marchi at Ryksuniversiteit Gent (Belgium) provide a comprehensive review of zeolite catalysis for the methanol-to-olefin reaction. He examines small, medium, and large-pore zeolites, the important role of acidity and shape selectivity on product distribution, and, like several of the other Reporters, the importance of understanding the coke-forming deactivation processes. 

CO2 reforming of methane can be used to adjust the H/CO ratio and provide the correct H2/CO ratio for Fischer-Tropsch synthesis and could potentially be used to reduce CO2 emissions from other processes however, it is even more endothermic than steam reforming. Partial oxidation is exothermic and has the correct H2/CO ratio for methanol synthesis, but requires a pure oxygen source, adding to the cost. In addition to the individual drawbacks, all of these processes must be run with 0/C ratios of greater than 1 to prevent coking of the catalyst. This makes the processes more expensive in practice than would be expected under optimized conditions for the stoichiometric reactions. The propensity of these processes to form carbon at low 0/C ratios is even more pronounced at... 

In 1923 two German scientists, Franz Fischer (1877-1947) and Hans Tropsch (1889-1935) developed a process whereby coke exposed to steam in the presence of catalysts forms a variety of organic compounds (hydrocarbons, aldehydes, ketones, alcohols) depending upon the catalyst and other specific conditions. Around this time, Alwin Mittasch (1869-1953), who developed the catalyst for the Haber-Bosch Process (chapter 1), introduced a related reaction in which carbon monoxide and hydrogen are combined in the presence of chromium oxide and zinc oxide (and similar combinations) to form methanol. The Fischer-Tropsch process played an important role in the synthesis of fuels... 

Methanol is obtained in another process, by oxidizing coke with steam to form a mixture of carbon monoxide and hydrogen, as follows ... 

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