Investigations Into Preparation Characteristics Of Sulfur Doped Porous Carbon Material From Waste Tire Char Via Heat Treatment With Double Metal Salts

Waste tire（WT）is a municipal solid waste with huge production capacity.It is urgent to develop efficient resource treatment and utilization method of WT.Pyrolysis can achieve the large-scale treatment of WT,and many pyrolytic chars generated.This work has innovatively proposed the preparation of sulfur doped porous carbon material from waste tire char（WTC）with high sulfur content via heat treatment with double metal salts.The main research contents and conclusions are as below:As the most important parameter of pyrolysis,temperature would obviously affect structures of WTCs.Therefore,the structures of WTCs at different temperatures and their effects on activation for preparing sulfur doped porous carbon material（activated char）were firstly analyzed.The results showed that when the pyrolysis temperature increased from 400℃to 1000℃,the disordered carbon skeleton turned to ordered graphitic structure,WTC was more difficult to be oxidized by K₂FeO₄,the yield of activated waste tire char（AWTC）（mass yield of AWTC compared to WTC）increased from 24.3%to 44.8%.With the pyrolysis temperature rising from 400℃to 800℃,sulphide and sulphone bridges in AWTC decreased,thus the sulfur doping content decreased.As the pyrolysis temperature rose to 1000℃,micropores in AWTC massively disappeared,mesopores and macropores destroyed,the specific surface area obviously decreased.Thus,the specific capacitance of AWTC decreased from 92.6 F/g to 54.1 F/g.Then,the characteristics and mechanisms of WTC activation with K₂FeO₄ were deeply studied.It was found that during activation process,K atom and lattice oxygen burned and etched WTC to promote pores formation,which were mainly mesopores and macropores,Fe atom promoted the formation of more micropores.K and Fe atoms promoted amorphous carbon to graphitic microcrystals,but lattice oxygen could lead to form more defects.Lattice oxygen promoted sulphide bridge to be sulphone bridge,Fe atom can react with lattice oxygen and inhibit the conversion pathway,and Fe atom can promote sulphone bridge to inorganic sulfur.When 3 times of mass ratios of K₂FeO₄activated WTC at 1000℃,specific capacitance of AWTC was largest（111.9 F/g）,the total yield（mass yield of activated char compared to WT）was only 6.8%,every gram WT can only produce capacitance of 7.6 F/g _WT via heat treatment.Furthemore,in order to improve resource degree of WT heat treatment,ZnCl₂ was used to adjust WTC structure and instead Fe（OH）₃ from decomposition of K₂FeO₄,KOH was coupled to modify activation process.ZnCl₂-KOH heat treatment method was innovatively developed to treat WT,sulfur doped porous carbon material with high yield and large specific capacitance was thus acquired.During pyrolysis process,ZnCl₂ promoted polymerization reactions,pores’massive formation,graphitic microcrystals generation.During activation process,ZnCl₂ inhibited the oxidations of KOH on WTC,promoted mesopores and macropores formations,conversion of inorganic sulfur to doped sulfur,weakened the reactions between KOH and doped sulfur.When the mass ratio of ZnCl₂ and KOH to WT were both 1,every gram WT can produce capacitance of 25.7F/g _WT via heat treatment.Lastly,with Feedforward Artificial Neural Network,the correlation models between physical/chemical structures with total yield/specific capacitance for sulfur doped porous carbon materials from WT were built respectively.The results showed that the single Feedforward Neural Network model commonly showed severe overfitting,leading to the predicted values deviated from the actuals,but the generalization effects would tend to be stronger after multiply averaged.As for two predicted conditions,when the prediction worked best,the relative errors of predicted total yields and specific capacitances for Feedforward Neural Network average models were 6.4%/12.7%and 4.2%/9.5%.The built Feedforward Neural Network average models can achieve reliable predictions of total yield and specific capacitance based on the physical/chemical structures with a small number of experimental data.The research can benefit for efficient pyrolysis treatment of WTs and high-value utilization of pyrolytic chars,and further make guidance for preparing sulfur doped porous carbon materials with high yield and large specific capacitance from WTCs via activation.