| Facing the increasingly serious energy crisis and environmental pollution problems,the comprehensive utilization of waste cooking oil to produce high calorific value hydrocarbon biofuels has always been a hot research topic.How to reduce the acid value of pyrolysis oil and improve the oil performance is the focus of research.Based on the shortcomings of single acid and single base catalysis,this research proposed that biodiesel with low acid value,high calorific value and high H/Ceff was prepared from WCO by acid-base bifunctional catalyst,which provided powerful guidance for effective deoxygenation in the catalytic cracking process of WCO in the future.The specific research results were as follows:(1)By investigating the influence of different acid and base active components on the catalytic performance,combined with the physical properties of the material itself,the rule of oil performance with the acid and base amount was obtained.On this basis,the acid-base dual-functional catalyst SBA-15@CaO@Mn was synthesized.Compared with the single acid SBA-15@Mn and the single base SBA-15@CaO,SBA-15@CaO@Mn has higher catalytic activity,and the acid value of the prepared biodiesel can reach 16.8 mg KOH·g-1,and the oxygen content can be reduced to 4.86%,and the calorific value can reach 43.17 MJ/kg.And by analyzing the physical and catalytic properties of the three catalysts,the rationality of the acid-base synergy law was verified.(2)Further exploring the optimal process conditions and optimal acid and base loading of SBA-15@CaO@Mn.The results showed when the temperature was 430?,the ratio of catalyst to WCO was 1:30,the Si/Ca was 6,and the Mn loading was 15%,the catalyst had higher catalytic deoxidation activity.The gas and liquid components obtained in the catalytic process of SBA-15@CaO@Mn were analyzed by GC-MS,and the carbon coupling mechanism of acid-base cooperative cracking was obtained.The reusability of SBA-15@CaO@Mn was investigated,and it was found that after repeated use for 5 times,the mesoporous structure of the molecular sieve remained intact,but the acidic and alkaline active components were lost,resulting in the yield of biodiesel decreased slightly.(3)In order to further improve the stability of mesoporous molecular sieves,Ca-ZSB micro-mesoporous composite molecular sieves with acid-base coexistence were synthesized.The effects of alkali concentration and SiO2/Al2O3 of ZSM-5 on the structure and properties of the composite molecular sieves were investigated.The results showed that different alkali concentration and SiO2/Al2O3 had great influence on the structure and acid-base of the catalyst,and further affected the catalytic activity.The catalytic activity of the catalyst first increased and then decreased with the increase of alkali concentration,and decreased with the increase of SiO2/Al2O3.When the SiO2/Al2O3 was 21 and the alkali concentration was 1.5 mol/L,the catalytic activity of the composite molecular sieve was the highest.Analyzing liquid fuels collected in different temperature ranges by GC-MS,it was found that biodiesel with acid value close to zero and hydrocarbon content of 89%could be obtained when the temperature was controlled between 420?and 440?.Finally,the stability of Ca-ZSB micro-mesoporous composite molecular sieves with acid-base coordination was investigated.It was found that the catalyst still had strong catalytic activity after repeated use for 5times,and the stability of the micro-mesoporous molecular sieves prepared by ZSM-5and SBA-15 was greatly improved.In short,the design of acid-base synergistic catalyst overcame the shortcomings of single acid and single base catalysis,reduced the acid value of oil,and improved its calorific value and H/Ceff. |
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