Study On Preparation Of Camellia Oleifera Abel Shell Biochar Pretreated With Acid/alkali Solution And Its Catalytic Pyrolysis Of Waste Cooking Oil For Aromatic-rich Bio-oil

Camellia oleifera Abel will produce a large number of by-product Camellia oleifera Abel shell（COAs）during processing.The commonly used treatment methods of COAs are to incinerate or throw away,which is easy to cause waste of resources and environmental pollution.COAs is rich in lignocellulose and developed pore structure,which can be used as an important raw material in the process of preparing biochar.Waste cooking oil（WCO）comes from food processing industry,catering industry and home cooking,etc.The main component is fatty acid,which has the potential to prepare ecological fuel.If the two kinds of waste are comprehensively utilized,it can"turn waste into treasure".Microwave-assisted catalytic pyrolysis of WCO has good prospects for the preparation of high-value liquid fuels.Using biochar as a catalyst can reduce oxy-compounds in bio-oil,resulting in improved bio-oil quality.However,compared with biochar prepared after pretreatment of biomass,the direct modification of biochar has the drawbacks high cost and unsuitability for broad-scale production,with smaller specific surface area,mesopore and micropore volume.Therefore,in this study,the biochar prepared by pretreatment of COAs with Na OH and HNO₃ solutions was used as a catalyst,and microwave-assisted pyrolysis of WCO combined with ex-situ catalytic technology was used to prepare high-quality aromatic-rich bio-oil,the effects of Na OH and HNO₃ pretreatment on the catalytic performance of the prepared biochar,and the influence of process parameters on pyrolysis products distribution and bio-oil components during the catalytic pyrolysis of WCO were studied.The main results are as follows:1.In the microwave-assisted pyrolysis up-flow system,the COAs was pretreated with HNO₃/Na OH solution to prepare biochar catalyst to conduct catalytic pyrolysis experiments on WCO.In terms of bio-oil yield,HNO₃-biochar<untreated-biochar<Na OH-biochar.The catalytic performance of HNO₃-biochar was superior to that of untreated-biochar and Na OH-biochar in catalytic conversion of WCO into aromatic-rich bio-oil.When catalyzed by HNO₃-biochar,the relative contents of monocyclic aromatic hydrocarbons（MAH）and polycyclic aromatic hydrocarbons（PAH）in bio-oil increased,but the relative contents of alkenes,alkanes and oxy-compounds decreased.The pyrolysis temperature and catalytic temperature were both 450℃,and the catalyst-to-feedstock ratio was 1:8,the relative content of MAH can reach up to 66.86%.The bio-oil components catalyzed by Na OH-biochar and untreated-biochar were mainly distributed in C₆-C₁₃,and the main peak was at C₇.The bio-oil components catalyzed by HNO₃-biochar are mainly distributed in C₆-C₁₇,with two main peaks of C₇ and C₁₀,and the peak of C₁₀ was the highest peak.Moreover,with the decrease of the solid-liquid ratio of immersion during the pretreatment of COAs,the carbonization temperature of biochar could significantly affect the carbon number distribution of the bio-oil components.2.The biochar catalysts were characterized by Scanning Electron Microscopy,Brunauer-Emmett-Teller,and Fourier Transform Infrared Spectroscopy.The results showed that HNO₃-biochar had a higher specific surface area,the highest is 392.65m²/g,which is approximately 677 times that of untreated-biochar.HNO₃-biochar was applied in microwave-assisted pyrolysis and ex-situ catalytic systems.Besides,the distribution of WCO pyrolysis products and the chemical components of bio-oil were analyzed.Results showed that when the temperature of pyrolysis and catalytic,the ratio of catalyst-to-feedstock were 450℃and 1:8,respectively,compared with no catalyst,the relative content of oxy-compounds in the bio-oil was greatly reduced by63.04%,showing a significant deoxygenation ability.The relative content of total aromatics was 69.21%when the catalyst-to-feedstock ratio was 1:4,which is 13.57times than that when there was no catalyst（5.10%）.When the catalyst-to-feedstock ratio was 1:8 and the catalytic temperature was 600°C,the relative content of MAH was as high as 78.82%,and the relative content of green naphtha（C₅–C₉）was 76.32%.3.The effects of catalyst-to-feedstock ratio,Si C dosage,and pyrolysis temperature on the distribution of WCO pyrolysis products and the chemical composition of bio-oil were studied in the microwave-assisted pyrolysis downdraft reaction system.Results showed that when the catalyst-to-feedstock ratio was 1:4,the catalytic temperature was 450℃,the amount of Si C was 90 g,and the pyrolysis temperature was 600℃,the relative content of the total aromatic compounds and oxy-compounds in the bio-oil were 98.82%and 0.11%.Lower pyrolysis temperature is not conducive to deoxygenation and aromatization of biochar catalysts.Properly increasing the Si C dosage or the pyrolysis temperature is conducive to the formation of hydrocarbons with low carbon numbers.However,an excessively high Si C dosage or pyrolysis temperature can lead to the formation of high carbon number hydrocarbons.The mechanism of biochar catalyzing the conversion of waste cooking oil pyrolysis gas into aromatic hydrocarbons was briefly analyzed.