Catalytic conversion processes

Catalytic conversion processes include naphtha catalytic reforming, catalytic cracking, hydrocracking, hydrodealkylation, isomerization, alkylation, and polymerization. In these processes, one or more catalyst is used. A common factor among these processes is that most of the reactions are initiated hy an acid-type catalyst that promotes carhonium ion formation. 

San Francisco, Ca., Spring 1997, p.578-9. 012 CATALYTIC CONVERSION PROCESS FOR RECYCLING NAVY SHIPBOARD PLASTIC WASTES... 

The Fischer-Tropsch (FT) catalytic conversion process can be used to synthesize diesel fuels from a variety of feedstocks, including coal, natural gas and biomass. Synthetic diesel fuels can have excellent autoigitition characteristics. The Fischer-Tropsch diesel is composed of only straight-chain hydrocarbons and has no aromatics or sulfur. The synthetic Fischer-Tropsch diesel fuel can provide benefits in terms of both PM and NO, emissions. 

Layered zeolites offer new possibilities for catalytic conversion processes, as well as for petrochemicals production. Finally, new possibilities for zeolites will be opened in separation processes and for combined reaction/separation. 

Highlights the economic advantages of using catalytic conversion processes and their ability to refine lower quality crude oils... 

Thus, control of nitrogen oxides has traditionally been achieved with staged combustion and with catalytic conversion processes using ammonia or urea. Catalytic processes using ammonia or urea have proven to be quite effective, but they are very expensive to implement and operate. Staged combustion has provided some control of nitrogen oxides formed from the volatiles, but it has had little effect on the formation of nitrogen oxides formed from the char. 

Biomass has a comparatively low sulphur content with respect to coal less than 0.1% by weight for lignocellulosic biomass, less than 1% for refuse-derived fuels. A large part of the sulphur is removed with the ashes and as a consequence the sulphur compound content of raw syngas rarely exceeds the order of lOOppmv. Nevertheless, the tolerance limit may be of the order of 1 ppmv, or even lower in downstream gas catalytic conversion processes and for high-temperature fuel cell operations below 1000 °C [43]. 

Importantly, all the catalytic conversion processes described in the investigations reported above follow green chemistry requirements. 

The thermal and catalytic conversion processes described in this chapter involve the chemical reaction of one or more gas phase species, including the impurities to be removed, to form new species, which remain in the gas. In thermal processes the desired reaction occurs at an acceptably high rate as a result of operating the reactor at an elevated temperature. Ill catalytic processes the reaction rate is accelerated at a low or moderate temperature by the presence of an active catalyst. 

The new compounds formed by the conversion reactions are either unobjectionable and therefore permitted to remain in the gas, or more readily removed than the initial impurities. In the first case, the thermal or catalytic conversion process constitutes the entire purification operation while, in the second case, additional steps, such as absorption or adsorption, are... 

Thermal and catalytic conversion processes that are not covered in this chapter include (I) processes associated with the removal of SO2, which are covered in Chapter 7 (2) processes used for converting H2S to elemental sulfur, including treatment of sulfur plant tail gas. which are covered in Chapter 8 and (3) processes for reducing NO, which are covered in Chapter 10. 

Much of the progress in catalytic conversion processes has been in the development of catalysts, systems, and operating procedures that minimize the effects of these phenomena. Commercial cataly.sts must not only have the required activity and resistance to deactivation, but mu.st also be available in shapes that provide effective contact with the gas at low pressure drop and meet installation and operating requirements. such as recharging and regeneration. 

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