Catalytic gasification

This section concerns catalytic processes that transform chemicals from renewables by C-C bond breaking. Among these are thermochemical processes, such as pyrolysis and also gasification, catalytic reactions, such as catalytic cracking and different reforming reactions, and decarbonylation and decarboxylation reactions. Many of these reactions occur simultaneously, particularly in the thermochemical processes. Another technically important class of C-C bond breaking reactions is the fermentation processes, however, they will not be considered in this section since they do not involve heterogeneous catalysis. 

Coal gasification is accelerated by the components of ash such as potash and iron oxide sometimes, to promote gasification, catalytically active... 

At Pacific Northwest Laboratory we have been testing the use of high-moisture biomass (marine and fresh-water biomass, post-harvest field residues and food processing wastes) in a thermochemical conversion system to produce useful fuels. Although the main focus of the work (19) has been gasification (catalytic production of methane) we have also performed a limited number of tests under high-pressure liquefaction conditions. 

Gasification technologies for the production of high heat-value gas do not all depend entirely on catalytic methanation, that is, the direct addition of hydrogen to coal under pressure to form methane. 

Liquid Fuels. Liquid fuels can be obtained as by-products of low temperature carbonization by pyrolysis, solvent refining, or extraction and gasification followed by catalytic conversion of either the coal or the products from the coal. A continuing iaterest ia Hquid fuels has produced activity ia each of these areas (44—46). However, because cmde oil prices have historically remained below the price at which synthetic fuels can be produced, commercialization awaits an economic reversal. 

Hydrocarbons from Synthesis Gas and Methanol. Two very important catalytic processes in which hydrocarbons are formed from synthesis gas are the Sasol Eischer-Tropsch process, in which carbon monoxide and hydrogen obtained from coal gasification are converted to gasoline and other products over an iron catalyst, and the Mobil MTG process, which converts methanol to gasoline range hydrocarbons using ZSM-5-type 2eohte catalysts. 

Gasification. Gasification of coal is used to provide gaseous fuels by surface and underground appHcations, Hquid fuels by indirect Hquefaction, ie, catalytic conversion of synthesis gas, and chemicals from conversion of synthesis gas. There are also appHcations in steelmaking (see Coal conversion PROCESSES, gasification). 

Methanol. Methanol is produced by stoichiometric reaction of CO and H2. The syngas produced by coal gasification contains insufficient hydrogen for complete conversion to methanol, and partial CO shifting is required to obtain the desired concentrations of H2, CO, and CO2. These concentrations are expressed in terms of a stoichiometric number, ((H2 — CO)/(H2 + CO2), which has a desired value of 2. In some cases CO2 removal is required to achieve the stoichiometric number target. CO and H2 are then reacted to form methanol in a catalytic methanol synthesis reactor. 

Whilst the basic process for generation and conversion of syngas is well established, production from biomass poses several challenges. These centre on the co-production of tars and hydrocarbons during the biomass gasification process, which is typically carried out at 800 °C. Recent advances in the production of more robust catalysts and catalytic membrane reactors should overcome many of these challenges. 

J.M. Lee, Non-catalytic and Catalytic Coal Gasification in an Internally Circulating Fluidized... 

Heterogeneous catalysts are used to convert solid coal into gasoline and other chemicals. Solid coal is not easily transformed into hydrocarbon chains, so the conversion requires two general steps gasification followed by catalytic hydrocarbon-forming reactions. Coal is first gasified by reaction with steam ... 

Chemistries such as gasification, carboxylation, carbonylation, partial oxidation, and salt splitting may see much greater emphasis in manufacturing. These chemistries will need concurrent development of more selective catalytic and biocatalytic systems and promoters, as well as processes requiring much less ex-... 

Mudge, L. K. Baker, E. G. Mitchell, D. H. Brown, M. D., Catalytic steam gasification of biomass for methanol and methane production. Journal of Solar Energy Engineering 1985, 107, 88-92. 

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