Research On Thermochemical Conversion Of Waste Biomass To Biofuels

The world is facing the problem of fossil energy depletion and greenhouse gas emissions,and the energy and chemicals mainly come from fossil fuels,so it’s an urgent need to find an alternative resource to meet the demand.Biomass,as the only renewable carbon source in nature,had a wide range of sources and was considered to be the most potential alternative resource.Common biomass resources include agricultural and forestry waste/residues,food processing waste,and municipal solid waste.Hyperaccumulator plants（rich in heavy metals）contain a large amount of lignocellulose,livestock manure was rich in lipid,protein and lignocellulose,and peanut residue as food waste was rich in protein and lipid,was considered a potential biomass resource.Thermochemical method was an important technology for converting waste biomass into biofuel,which could convert hyper-accumulated plants,livestock manure and food waste into high-quality biofuel under confined conditions.And each component can be collected without causing environmental pollution.The research of this topic mainly focuses on the following two aspects:（1）For the first time,A multi-functional homogeneous catalyst was used to catalyze the hydrogenolysis of the heavy metal-rich hyperaccumulator plant（PVL）into a high-quality biofuel,so as to realize the effective treatment and high-value utilization of the hyperaccumulator.After PVL pretreatment to remove lipids and lignin,more than 64%of heavy metals were transferred to water,and the As content in solid biomass was reduced from 1328 mg/kg to 483 mg/kg.Under the multifunctional catalyst Rh Cl₃/Na I/HCl/H₂and biphasic reaction system,PVL was converted into biofuel with high selectivity,and the main products were C5,C6furans and hypoxic ketones with high HHV.Under the optimal reaction conditions（160°C,4 h,300 psi H₂,4 mmol Na I,H₂O/toluene=1:1）,the biofuel yield was 18.8wt.%.After the reaction,more than 50%of heavy metals（Cu,Pb,Zn,Cd,As）remain in biochar,while less than 20%of heavy metals in bio-oil（As content is less than 55mg/kg）,which was conducive to obtaining high-quality bio-fuel and arsenic recovery.（2）Our study firstly co-liquefaction livestock manure（cattle manure）and food waste（peanut residue）,aiming to obtain high-quality bio-oil and bio-char to maximize resource utilization.By adjusting the ratios of the two biomasses in a closed system,the contents of different components in the reaction were controlled to obtain biofuel with high hydrocarbons,low oxygen and low nitrogen.Under the optimal reaction conditions（270℃,30 min,CM/PR=1/3）,the overall yields of bio-oil（23.5 wt.%）and biochar（18.5 wt.%）were the highest,and the oil HHV value was the highest of 31.74 MJ/kg.Maillard and Mannich reactions occurred during the co-liquefaction process,and the experimental values of biochar yield,carbon,hydrogen and nitrogen were all higher than the calculated values,indicating the synergistic effect of biochar.The migration and transformation of carbon,nitrogen and energy recovery rate were also explored,and it was found that nitrogen in bio-oil and water phase was transferred to biochar,which was beneficial to improve the quality of bio-oil and the subsequent utilization of biochar.