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Aqueous-Phase Reforming and BioForming Process
Published in Yatish T. Shah, Water for Energy and Fuel Production, 2014
Thus, C–C coupling (i.e., condensation reactions) can be employed along with oxygen removal to obtain larger hydrocarbons starting from biomass-derived C5 and C6 sugar compounds. Ketones are coupled via aldol condensation using basic catalysts such as MgAlOx, MgAl, Pd–MgO/ZrO2, MgZrO2, La/ZrO2, Y/ZrO2, and Mg/TiO2[4,32,48,58,59,65,68–86]. Furthermore, the introduction of bifunctional metal basic catalysts allows for the coupling of secondary alcohols in the presence of hydrogen. More condensation reactions are also driven for ketones in the presence of hydrogen [32]. C–C coupling can also be enhanced by ketonization of carboxylic acid [4]. The complete hydrogenations of monofunctional groups can also produce alcohols. The alcohols can then be converted to gasoline using methanol-to-gasoline (MTG) technology of Mobil Oil Co. that uses H-ZSM-5 catalyst [4,32,48,58,59,65,68–86]. Alcohols can also be dehydrated to produce olefins.
Advances in sustainable biofuel production from fast pyrolysis of lignocellulosic biomass
Published in Biofuels, 2023
Denzel C. Makepa, Chido H. Chihobo, Downmore Musademba
In the residual ash of biomass, alkali and alkaline-earth metals (AAEMs) including Ca, K, Mg, and Na are typically present. These metals can be deposited on the acid sites of the catalyst easily, which immediately deactivates the acid catalyst [181]. On the other hand, catalysts with base sites, as opposed to acid sites, withstand deactivation by AAEMs much better. With acid sites, the base active sites display several reaction pathways, such as carbon coupling (C-C) reactions. Carbon coupling processes transform low molecular weight substances like organic acids, ketones, and aldehydes into gasoline and diesel range products. Base catalysts that produce CO2 during the ketonization of acids, such as MgO [182] and CaO [183], facilitate the deoxygenation of pyrolysis products. With regard to preserving carbon, the deoxygenation pathway is more effective than the acid catalyst pathway since the latter encourages the creation of CO [184]. Base catalysts also reduce H2O generation to preserve the hydrogen level in the bio-oil, hence improving the energy and quality of the bio-oil [181, 184].