Preparation Of Catalytic Porous Ceramic Balls And Catalytic Pyrolysis Of Corn Stover

The bio-oil produced by pyrolysis-liquefaction of biomass has problems such as high oxygen content,high acidity,and complex components.Therefore,it is necessary to improve the quality of bio-oil.Based on the self-heating stover pyrolysis liquefaction technology,the ceramic ball heat carrier can enhance the heat transfer process of the stover in the pyrolysis reactor,but its composition regulation ability is relatively weak and must be loaded with active metals to enhance the catalytic effect of the ceramic ball heat carrier.The preparation process of catalytic porous ceramic balls was achieved by optimizing the preparation process parameters of the porous ceramic balls and modifying the porous ceramic balls with active metal components,a batch of catalytic porous ceramic balls with the directional regulation function was obtained,and the influence of catalytic porous ceramic balls loaded with different active metals on the characteristics of three-phase products from corn stover pyrolysis was investigated in a fixed-bed reactor.The main experimental results and conclusions are as follows:（1）Calcium carbonate and pseudo-boehmite were selected as ceramic aggregates,and porous ceramic balls（PCB）was prepared by adding a pore-forming agent and rolling molding process,a reasonable sintering system was established by TG-DTG curve analysis to research the effect of different formulas on PCB performance.The results showed when the PCB prepared with the ratio of pseudo-boehmite and calcium carbonate is 1:3,the apparent porosity can reach 54.5%,the crushing stress is 56.6N,and the thermal conductivity is 1.075W/（m·K）.Considered and determined that the PCB prepared by pseudo-boehmite and calcium carbonate at 1:3 is the best carrier for the preparation of catalytic porous ceramic balls.（2）A fixed-bed reactor was selected to carry out PCB catalyzed pyrolysis of corn stover to investigate the effect of temperature on the composition and distribution of pyrolysis products.The results showed that the highest bio-oil yield of 38.59%was obtained by PCB at 500°C.The acid content of the bio-oil was reduced to varying degrees compared to the pyrolysis of corn stover alone with a reduction of up to 22.47%at 450°C,the phenolic content increased firstly and then the aldehyde content decreased with increasing temperature.The volume fractions of CO,CH₄,and H₂ in the non-condensable gas increased with increasing temperature,while the volume fractions of C_nH_m tended to decrease,and the volume fractions of propane were all higher than those of corn stover alone.Meanwhile,the observation of SEM showed that cylindrical pores and a small number of cracked pores appeared on the surface of biochar,and the specific surface area and pore volume also increased with the increase of temperature.（3）At the pyrolysis temperature of 500°C,the influence of material ratio on the composition and distribution of pyrolysis products of corn stover was investigated.The results showed that the content of acids in bio-oil was the lowest when PCB:corn stover was 3,which was only 29.61%,and the types of acids were the least when PCB:corn stover was 3-5.The content of ketones increased with PCB as the content of phenols and furans increased firstly and then decreased,but both were higher than those of corn stover pyrolysis alone.The volume fractions of CO and CH₄ in non-condensable gas decreased with increasing PCB dosage,and the volume fractions of C_nH_m（n≥2）were higher than those of corn stover pyrolysis alone,while the alkanes and olefins increased significantly,At the same time,the specific surface area and pore volume of biochar increased to varying degrees with the continuous increase of PCB dosage.（4）The Catalytic porous ceramic balls were obtained by impregnating and loading five metal oxides（Zn O,Ni O,Ce O₂,Cr₂O₃,Fe₂O₃）,the catalytic effect of the PCBs on the pyrolysis of corn stover was investigated when the temperature was 500℃,and the ratio of PCB to corn stover was 3.The experimental results indicated that all modified PCBs improved the production rate of bio-oil,and the Ni-based PCB made the highest production rate,which gained 41.62%.Porous ceramic balls loaded with five metal oxides can be promoted the content of phenols and furans increased obviously.The acid substances in bio-oil and its types were both reduced,and the acid reduction effect of Ce-based porous ceramic balls was significant,which decreased 37.15%.The addition of catalytic porous ceramic balls promotes the production of C_nH_m（n≥2）in non-condensable gases,and the ethylene among the olefins increased the most,which gained 50.53%.Meanwhile,the physicochemical properties of biochar were improved.The content of this study provides a significant reference for targeted product regulation and bio-oil quality enhancement during autothermal cracking and liquefaction.