Zeolitic Upgrading of Cellulosic Feedstocks

and water [26], A large amount of coke forms during the upgrading of glucose and starch. The coke formation is attributed to the decomposition of glucose monomers at the reaction temperature and pressure (510°C, 1 atm). However, the addition of methanol during the reaction increases hydrocarbon yields and decreases coke formation by promoting decarboxylation reactions [26], 

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. 

Based on results with HZSM-5, researchers have investigated the use of metal additives on HZSM-5 to improve aromatics production or tune selectivity. The Huber group has shown marked improvement with the use of gallium exchanged HZSM-5 for the catalytic fast pyrolysis of furans. In this report, the gallium should be incorporated by exchange rather than incipient wetness or framework substitution to 

FIGURE 9.4 Thermochemical catalytic conversion of cellulose to biofuels [35]. 

FIGURE 9.5 Metal additives of HZSM-5 to alter selectivity and activity. 

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