Upgrading Bio-Oil From Copyrolysis Of Lignin And Food Waste Soapstock Over Activated Carbon Catalyst

Lignin is the second largest renewable resource after cellulose and the most abundant aromatic biopolymer in nature,which could potentially be converted into biofuel and high value-added chemicals.However,it is very difficult to achieve lignin conversion and utilization since lignin is a natural high molecular weight polymer,its molecular weight is generally between several hundred and several million,and the chemical structure of lignin is complicated and insoluble in water.In addition,there is a large amount of food waste soapstock from China's food industry and catering industry every year.The resulting soapstock is not only difficult to handle,but also cause serious environmental pollution and energy waste.Therefore,the current study mainly employed the ex-situ catalytic co-pyrolysis combined with pretreatment technology to comprehensively thermochemically convert lignin and food waste soapstock.The main goal of this study is to prepare bio-based green phenolic chemicals and aromatic-rich high-grade liquid fuel using the synergistic effect between phenylpropane structure of lignin molecular and hydrogen-rich food waste soapstock.In current study,the effects of raw material pretreatment on the structural characterization and pyrolysis properties of lignin were studied.The effects of key parameters and co-pyrolysis process on the product distribution and the composition and content of liquid fuels were investigated.The enrichment and regulation mechanism of phenol during pyrolysis was explored.The regulation method and theoretical basis for the preparation of high quality liquid biofuel by catalytic pyrolysis of lignin and food waste were obtained.1.Microwave-assisted acid pretreatment of alkali ligninThis study performed microwave-assisted acid pretreatment on pure lignin.The effects of microwave temperature,microwave time,and hydrochloric acid concentration on characteristics and pyrolysis behavior of lignin were examined.Results of ultimate analysis revealed better properties of all pretreated samples than those of raw lignin.Fourier transform infrared spectroscopy analysis showed breakage of?-O-4 bond and aliphatic side chain,decrease in-OH groups,and formation of C=O groups after pretreatment.Microwave temperature exerted more significant influence on lignin structure than microwave time and acid concentration,possibly due to mild microwave conditions considered.Thermal stability of treated lignin was improved and therefore insensitive to short microwave time and acid concentration under mild conditions.Resulting from improved alkyl-phenols and decreased alkoxy-phenols,microwave-assisted acid pretreatment of lignin yielded bio-oil with excellent thermal stability and quality.2.Microwave-assisted co-pyrolysis of pretreated lignin and soapstock for upgrading bio-oil:Effect of pretreatment parameters on pyrolysis behaviorThe co-pyrolysis of pretreated lignin and soapstock was carried out to upgrade vapors under microwave irradiation.Results showed that the yield of 29.92-42.21 wt.%of upgraded liquid oil was achieved under varied pretreatment conditions.Char yield decreased from 32.44 wt.%for untreated control to 24.35 wt.%for the 150 ^oC pretreated samples.The increased temperature,irradiation time and acid concentration were conducive to decrease the relative contents of phenols and oxygenates in the bio-oils.The main components of the bio-oil were gasoline fraction?mono-aromatics and C5-C12 aliphatics?,which ranged from 57.38 to 71.98%under various pretreatment conditions.Meanwhile,the diesel fraction?C12+aliphatics?ranged from 13.16 to 22.62%from co-pyrolysis of pretreated lignin and soapstock,comparing with 10.18%of C12+aliphatics from co-pyrolysis of non-pretreated lignin and soapstock.A possible mechanism was proposed for co-pyrolysis of pretreated lignin and soapstock for upgraded bio-oils.3.Ex-situ catalytic pyrolysis lignin to prepare phenol-rich bio-oilIn this section,the agricultural waste corn stover was used as materials to prepare the activated carbon by H₃PO₄ activation via microwave heating.The resulted corn stover derived activated carbon was then employed as catalyst during ex-situ catalytic pyrolysis lignin process to produce phenol-rich bio-oil.The CCD was used to analyze the effects of pyrolytic temperatures and catalyst/lignin ratios on the products yield and chemical profiles of the bio-oil.The results showed that the concentration of H₂produced from lignin pyrolysis was improved when use the corn stover derived activated carbon as catalyst.Up to 95.5%relative content of total phenols in the upgraded bio-oil derived from unpretreated lignin pyrolysis was obtained at the pyrolytic temperature of 550oC with a catalyst/lignin ratio of 0.7.In addition,during the deactivation test,the catalyst exhibited a benign catalytic performance after using four times.4.Ex-situ catalytic pyrolysis pretreated lignin to upgrade bio-oilAccording to the optimal experimental condition in previous study,the ex-situ catalytic pyrolysis of pretreated lignin was carried out,the corn stover derived activated carbon was used as catalyst.Under the same condition,the pyrolysis of untreated lignin was employed as control.The results showed that when compared with the control,the water content of the bio-oil produced from ex-situ catalytic pyrolysis of the pretreated lignin decreased,and the phenol concentration increased from 0.6 to 7.0 mg/mL.The pyrolytic temperature of 150oC was the optimal pretreatment condition.Finally,the“phenol pool”and free radical were proposed to reveal the mechanism of phenol generation from catalytic conversion of pretreated lignin.5.Ex-situ catalytic co-pyrolysis of lignin and soapstock to upgrade bio-oil.In order to further understand the products produced from lignin pyrolysis when there were both catalyst and hydrogen donor,in this section,according to previous study,the ex-situ catalytic co-pyrolysis of lignin and soapstock over corn stover derived activated carbon was carried out.The effects of pyrolytic temperature,lignin/soapstock ratio and catalyst/feedstock ratio on the co-pyrolytic products were discussed.The results showed that the activated carbon has the catalytic ability to convert pyrolysis vapors into high-density jet fuel-ranged aromatic hydrocarbons rather than phenol during ex-situ catalytic pyrolysis process with hydrogen donor existence.Soapstock,as hydrogen donor,exhibited a positive synergistic effect with lignin to accelerate the generation of valuable aromatics in the obtained bio-oil during catalytic co-pyrolysis process.