| Organic solid waste can be converted into gas,oil and char through pyrolysis,providing flexible means for further utilization.However,the high value utilization of pyrolysis oil was limited by the high oxygen content and complexity component of oil for the fact that conventional catalysts would be deactivated due to coke deposition.Molten salt,with good fluidity and thermal conductivity coefficient,can improve the effective interface surface area between alkali metal cations and reactants and alleviate the coke deposition process.In recent years,molten salt has been widely used in the thermal conversion of biomass and organic solid waste.Researches showed that molten salt could catalyze thermal conversion of biomass and organic solid waste.At present,the researches on molten salt thermal conversion mainly focus on the direct pyrolysis of biomass or organic solid waste.The conversion mechanism of pyrolysis oil in molten salt is still unclear.Accordingly,ternary carbonate eutectics（Li2CO3-Na2CO3-K2CO3）were selected as catalyst and heat storage medium to investigate the thermal conversion behavior of organic solid waste pyrolysis oil,in order to explore the influence of molten salt on the thermal conversion mechanism of main components of pyrolysis oil.The main conclusions are as follows:（1）Thermal conversion characteristics of simulated organic solid waste pyrolysis oil in molten salt:Experiment of simulated pyrolysis oil in molten salt under N2 atmosphere was carried out.The results showed that molten salt inhibited the decomposition of simulated pyrolysis oil,and the gas yield was decreased by 62.1%at 850°C.The reaction amounts of toluene,phenol and furfural in simulated pyrolysis oil were increased and the formation of coke was alleviated.The results of simulated pyrolysis oil reforming in molten salt under CO2 atmosphere showed that coke deposition process of pyrolysis oil thermal conversion could also be attenuated under CO2.The yield of liquid products was increased,retaining more material and energy in liquid products.Both molten salt and CO2 could increase the water content of the liquid product of the thermal conversion of simulated pyrolysis oil,showing a good performance in the upgrading of pyrolysis oil.（2）Mechanism of thermal conversion of phenol-methanol in molten salt:The main products of thermal conversion of phenol-methanol in molten salt were anisole and cresol.The introduction of alkali metal cations changed the electron distribution of phenol and promoted the formation of cresol.The contents of cresol in molten salt were increased by60.2%（650°C）,55.4%（750°C）and 48.8%（850°C）,respectively.CO2 could occupy the reaction site where phenol reacted with methanol to form anisole,resulting in the decrease of anisole and the increase of cresol content.（3）Influence of mall molecule gases on toluene thermal conversion:The influences of H2,CO and CH4 on the thermal conversion behavior of toluene were explored.It was found that H2 could increase the gas production of toluene decomposition in salt free environment,while CO and CH4 could reduce the gas production.The influence of H2 in molten carbonate on gas production was dominant,and the influence order of small molecule gas on toluene reforming was H2>CH4>CO.In this paper,the thermal conversion characteristics of organic solid waste pyrolysis oil in molten salt were investigated.The influence of molten salt on the thermal conversion reaction of main components of pyrolysis oil was clarified.It was found that molten salt could alleviate the coke deposition in the thermal conversion of pyrolysis oil and improve the yield of liquid products.Meanwhile,the thermal conversion behaviors of phenol and toluene in molten salt were discussed.The results showed that the introduction of molten salt and the change of atmosphere would affect the thermal conversion pathway of phenol or toluene,which provided a potential for realizing the control of thermal conversion of pyrolysis oil by adjusting the reaction conditions. |
