Catalytic Conversion of Biomass-derived Compounds to Fuels and Chemicals.

摘要

Among the potential routes for production of fuels and chemicals from lignocellulosic biomass, fast pyrolysis accompanied by or followed by catalytic upgrading offers excellent potential because the number of conversion steps is small and the processing may be cost effective. Lignin-derived bio-oils can be converted into fuels and aromatic chemicals, with a key processing challenge being the removal of oxygen. The literature of bio-oils conversion is largely lacking in fundamental chemistry, which limits the usefulness of the available data for predicting catalyst performance.;To determine a quantitative reaction network, we designed and constructed four identical tubular flow reactor systems with flexibility to produce data at high and at low conversions and with ability to identify and quantify even trace products by GC-MS and GC-FID. Higher conversion data are necessary to determine trace products formed in the conversions of the individual reactants and enable reaction networks that are more detailed than any previously published to be elucidated. Low conversion data are required to determine quantitative kinetics of reactions that lead to the most abundant products. These reactor systems also enabled mass balance closures of greater than 95%.;Reaction networks were elucidated to account for the reactions of a group of compounds prototypical of lignin and compounds derived from it, incorporating the representative functional groups, such as aromatic rings and ether linkages---the compounds are anisole, 4-methylanisole, and furan. These reactants are converted in the presence of catalysts representative of important catalyst classes, including solid acid (HY zeolite), supported metal (platinum on gamma-Al 2O3, Pt/gamma-Al2O3), and bifunctional (platinum of SiO2-Al2O3, Pt/SiO2-Al 2O3) catalysts.;The results show that one of the dominant classes of reactions observed with anisole and 4-methylanisole is transalkylation. When the catalyst was HY zeolite, transalkylation was the only kinetically significant reaction class. Hydrogenation, dehydrogenation, hydrogenolysis (C-O bond cleavage reactions that did not remove oxygen from the organic reactant), and hydrodeoxygenation (C-O bond cleavage reactions that removed oxygen from the organic reactant) were also observed in the conversion of each reactant (anisole, 4-methylanisole, and furan) with the supported-platinum catalysts. The data determine quantitative conversions and selectivities of the products that were formed in relatively high yields at conversions 10%. The data also determine approximate kinetics of the primary reactions.;The data imply that a supported-metal catalyst and H2 will be necessary for selective removal of oxygen bonded to aromatic rings. Identification of the role of the acid function in transalkylation and the metal function in HDO (hydrodeoxygenation) presents an opportunity for tuning the catalyst functions to increase the activity and selectivity for the desired reaction pathways. Understanding such as that provided by this reaction network is potentially important for the design of catalysts and processes for the conversion of biomass to fuels and chemicals.