Study On Fast Pyrolysis Of Sawdust Catalyzed By Refining Catalyst And Blast Furnace Ash

Biomass resource utilization is an important way to deal with energy crises and environmental problems.Fast catalytic pyrolysis of biomass can promote the decomposition of organic matter and directionally acquire high value-added products,which is an efficient way of biomass energy utilization.However,catalytic pyrolysis usually faces the problems of complex catalyst preparation,high price,hard recovery,and low economic benefit.It is difficult to guide the development and optimization of industrial reactors for the lack of data on catalytic pyrolysis mechanism and reaction kinetics.In view of the above problems,two typical cheap industrial wastes with different acid-base activities,e.g.,spent FCC catalyst（s FCCc）and blast furnace ash（BFA）,were selected as catalysts for sawdust pyrolysis experiments.Firstly,catalytic pyrolysis kinetics was analyzed based on different analytical methods.Secondly,the fixed-bed reactor was used to explore the distribution and composition variation of fast pyrolysis products of sawdust catalyzed by acid-base industrial waste catalyst in situ.Finally,the characteristic metal compound components were selected to carry out the catalytic mechanism research.The obtained char was used for the ex-situ conversion catalyst of pyrolysis volatiles to explore its action law and product distribution,providing reference for large-scale industrial applications.Friedman method,Flynn-Wall-Ozawa（FWO）method and distributed activation energy model（DAEM）method were used to analyze the kinetics of sawdust catalytic pyrolysis,respectively,and three methods had high fitting accuracy.According to the kinetic parameters,the activation energy（E_a）of sawdust pyrolysis was generally distributed from 140 k J/mol to 220 k J/mol.The E_a of the sawdust pyrolysis reaction was reduced by industrial waste catalysts,and the E_a of pyrolysis by acidic s FCCc catalyst was the smallest.Average E_a calculated by FWO method and Friedman method was173.20 k J/mol and 182.16 k J/mol,respectively.DAEM method was used to deeply analyze the pyrolysis kinetics of three components of biomass.It was found that the activation energies of CNT1（hemicellulose）and CNT3（lignin）were reduced by acidic catalysts,while those of CNT1（hemicellulose）and CNT2（cellulose）were reduced by alkaline catalysts.By comparing the iso-conversion method and the DAEM method,the DAEM method supplemented the kinetic information of biomass component decomposition at high temperature,and the iso-conversion method could better highlight the effect of catalyst on the pyrolysis process.The results of in-situ catalytic pyrolysis of sawdust showed that both acidic and alkaline catalysts promoted the conversion of liquid products to gas products,which reached 52.60%at 700°C using BFA.s FCCc had stronger deoxidation activity at 500-600°C,and the gas yields of CO and CO₂ were higher;BFA had higher polycondensation dehydrogenation activity at 600-700°C,resulting in more polycyclic aromatic hydrocarbons and H₂.Pyrolysis oil was mainly composed of phenols,and acidic s FCCc promoted the conversion of methoxyphenol to hydroquinone.At 700°C,s FCCc had higher saturated hydrocarbon selectivity,and more polycyclic aromatic hydrocarbons were generated under BFA catalytic conditions.The FT-IR results of pyrolysis oil showed that the bio-oil catalyzed by BFA at 700°C contained more heavy phenolic compounds.Finally,the results of in-situ catalytic pyrolysis experiments showed that the semi-coke catalyst promoted the conversion of liquid products to gas products.Compared with the alkaline char catalysts（BFA and Fe₂O₃）,the acidic char catalysts（s FCCc and Al₂O₃）had a higher gross yield of oil and gas and gas yield.Semi-coke catalyst loaded with alumina had the lowest oil yield（10.10%）and the highest gas yield（47.18%）.The yield of hydrocarbons and the content of monocyclic aromatic hydrocarbons in tar increased with char catalyst,and the s FCCs loaded char had the highest total hydrocarbon yield（peak area 33.94×10⁷）and monocyclic aromatic hydrocarbons content（47.00%of total hydrocarbon content）.Compared with the alkaline-based char catalyst,the acidic-based char catalyst had higher tar conversion efficiency and deoxygenation activity,and the contents of-OH,C=O and C-O three oxygen-containing functional groups in tar were significantly reduced.