Research On Catalytic Fast Pyrolysis Of Biomass To Produce Value-added Chemicals

Fast pyrolysis is one of the important thermal-chemical technologies for the utilization of biomass. During fast pyrolysis process, the biomass is mainly converted into liquid, which is usually called bio-oil. Bio-oil is considered as a potential raw material for chemical recovery due to the fact that many kinds of valuable chemicals are formed during biomass fast pyrolysis process. However, conventional bio-oil is the complex mixture with low concentrate of these chemicals. Based on this background, experiments were conducted in this dissertation to produce value-added chemicals from catalytic fast pyrolysis of biomass, and the works can be divided into three sections.The researches on catalytic fast pyrolysis of biomass to selectively produce anhydrosugars:A new technology was proposed to produce levoglucosenone by catalytic pyrolysis of biomass (or cellulose) using solid phosphoric acid. The catalytic behaviors of several solid phosphoric acid with different catalysts carries were investigated using Pyrolysis-gas chromatograpgy/mass spectrometry (Py-GC/MS) experiments and the solid phosphoric acid prepared using SBA-15 carrier showed the highest selectivity for levoglucosenone. The presence of catalyst could promote the formation of levoglucosenone from cellulose and inhibit the decomposition of hemicellulose and lignin to form organic compounds. Lower temperature and proper catalyst ratio favored the formation of levoglucosenone, and the maximal yields of levoglucosenone obtained from biomass and cellulose were 8.2 wt% and 16.1 wt%, respectively.Zixc-aluminium layered double oxide catalysts were prepared and used for catalytic fast pyrolysis of cellulose to produce 1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one. Zixc-aluminium layered double oxide catalysts with different metal molar ratios were investigated using Py-GC/MS experiments. All four catalysts could inhibit the generation of levoglucosan and promote the formation of 1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one, and the catalyst with the metal molar ratio of 2 exhibited the best catalytic capacity. The highest content of 1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one was 21.9%, obtained at lower pyrolysis temperature and proper catalyst ratio.The researches on catalytic fast pyrolysis of biomass to selectively produce phenolic compounds:A new technology was proposed to produce phenolic-rich bio-oil by catalytic fast pyrolysis of biomass using phosphate. The catalytic behavior of three kinds of phosphate (K3PO4, K2HPO4, KH2PO4) were investigated using Py-GC/MS experiments. The presence of K3PO4 showed the best catalytic ability to promote the decompositon of lignin to form phenolic compounds and inhibit the formation of holocellulose-derived products. Moderate temperature was benefit for the formation of phenolic compounds, and the highest content with the peak area% over 60% was obtained under higher catalyst ratio.Solid base catalyst (K.3PO4/Fe3O4) was prepared and used for catalytic fast pyrolysis of biomass to produce phenolic-rich bio-oil. Similar with impregnation of K3PO4, the presence of solid base catalyst could promote the decompositon of lignin to form phenolic compounds. Meanwhile, the catalyst could also inhibit the formation of anhydrosugars, linear aldehydes, linear acids and other compounds from holocellulose. By means of external standard method, major phenolic compounds were quantified. The highest yield of twelve major phenolic compounds reached 43.9 mg/g under the optimal condition. Moreover, solid base catalyst possessed promising recycling properties.The researches on catalytic pyrolysis of biomass to selectively produce specific single phenolic compounds:Pd/SBA-15 catalyst was prepared and used for catalytic upgrading of herbaceous biomass vapors to produce 4-ethyl phenol. Low temperature non-catalytic pyrolysis of herbaceous biomass could produce large amount of 4-vinyl phenol, while Pd/SBA-15 could selectively hydrogenate the 4-vinyl phenol into 4-ethyl phenol. Several compounds derived from holocellulose could serve as hydrogen-donor for the formation of 4-ethyl phenol. Lower temperature and proper catalyst ratio favored the formation of 4-ethyl phenol, and the highest 4-ethyl phenol yield reached 2.0 wt%.Pd/SBA-15 catalyst could be also used for catalytic fast pyrolysis of softwood to produce 4-ethyl guaiacol. The presence of catalyst could promote the 4-ethyl guaiacol formation from lignin, and meanwhile inhibit the generation of other products derived from lignin and holocellulose.4-Ethyl guaiacol was formed from the decomposition/hydrogenation of lignin and several holocellulose-derived products could serve as hydrogen-donor. The formation of 4-ethyl guaiacol was favored by lower temperature, proper catalyst ratio and proper Pd content of Pd/SBA-15 catalyst. The highest 4-ethyl guaiacol yield reached 1.8 wt%under the optimal condition.A new technology was proposed to produce 4-ethyl phenol from catalytic fast pyrolysis of herbaceous biomass using activated carbon. The effects of pyrolysis temperature and catalyst-to-biomass ratio on 4-ethyl phenol selectivity were invesitaged using Py-GC/MS experiments. The presence of activated carbon could selectively convert 4-vinyl phenol or its precursor into 4-ethyl phenol during catalytic fast pyrolysis process. The highest 4-ethyl phenol yield was 2.1 wt%, obtained at lower temperature and proper catalyst ratio.