Catalytic reactions, pyrolysis products

The catalytic pyrolysis of R22 over metal fluoride catalysts was studied at 923K. The catalytic activities over the prepared catalysts were compared with those of a non-catalytic reaction and the changes of product distribution with time-on-stream (TOS) were investigated. The physical mixture catalysts showed the highest selectivity and yield for TFE. It was found that the specific patterns of selectivity with TOS are probably due to the modification of catalyst surface. Product profiles suggest that the secondary reaction of intermediate CF2 with HF leads to the formation of R23. 

The pyrolysis gas chromatogram of ABS at 550°C changes considerably when the pyrolysis products are passed over zeolite catalysts. The specific activity towards certain reactions, e.g., cycliza-tion, aromatization, or chain cleavage is somewhat dependent on the nature of the individual zeolite. In general, enhanced benzene, toluene, ethylbenzene at the cost of dimer, trimer formation is observed. Nitrogen containing compounds do not appear in the pyrolysis oil after catalytic conversion. However, the product gas is rich in nitriles (132). 

Catalytic pyrolysis is the conversion of biomass via pyrolysis in the presence of a catalyst [27]. In this process, the catalyst can react in a secondary reactor directly with the vapors produced by pyrolysis, or the catalyst can be mixed with the biomass in a fluidized bed pyrolysis reactor [28], In either system, catalysts with high selectivity to diesel and gasoline range hydrocarbons are often preferred [29-31], Because the pyrolysis products are upgraded by additional deoxygenation reactions on the catalyst, the resulting catalyticaUy produced bio-oil is generally more stable than noncatalytic pyrolysis bio-oil. 

The objective of this chapter is to present a survey of the open literature to examine the various methods of PTFE pyrolysis so as to build a coherent image of the art, and to present and evaluate the known catalytic reactions of the pyrolysis products, with emphasis on those of TEE. This is essential to direct any research concerning the selective beneficiation of PTFE waste to high value chemicals. In areas where the information on the reactions of perfluorocarbons are lacking or nonexistent, reference is made to the reactions of fluorochlorocarbons or simple hydrocarbons for by analog information. 

Distribution of pyrolysis products and specific compounds produced (particularly in the liquid fraction) can be greatly affected by the introduction of a catalyst to the pyrolysis reaction system. Catalytic pyrolysis, the main subject of this chapter, is not so different to standard pyrolysis but has a significant effect on pyrolysis products by enhancing potential biofuel or higher-value chemical production. Catalytic pyrolysis is covered in depth below. 

Thermochemical Liquefaction. Most of the research done since 1970 on the direct thermochemical Hquefaction of biomass has been concentrated on the use of various pyrolytic techniques for the production of Hquid fuels and fuel components (96,112,125,166,167). Some of the techniques investigated are entrained-flow pyrolysis, vacuum pyrolysis, rapid and flash pyrolysis, ultrafast pyrolysis in vortex reactors, fluid-bed pyrolysis, low temperature pyrolysis at long reaction times, and updraft fixed-bed pyrolysis. Other research has been done to develop low cost, upgrading methods to convert the complex mixtures formed on pyrolysis of biomass to high quaHty transportation fuels, and to study Hquefaction at high pressures via solvolysis, steam—water treatment, catalytic hydrotreatment, and noncatalytic and catalytic treatment in aqueous systems. 

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