Research On Pyrolysis And Oil Catalytic Reforming Of Typical Components Of Waste Rubber

As rubber products are used more and more widely in modern society,the production of waste rubber has increased rapidly,which has made it become the solid waste in urgently needing of disposal.At present,pyrolysis is regarded as one of the most thorough and effective methods for waste rubber recycling.The high complexity of waste rubber pyrolysis process makes it difficult to analyze the pyrolysis process and mechanism of waste rubber by directly research on its pyrolysis.Therefore,this article studied the pyrolysis and catalytic reforming of pure rubbers and its vulcanized rubbers,to avoid the influence of various secondary additives.Firstly,three kinds of typical rubber,including natural rubber(NR),butadiene rubber(BR)and styrene-butadiene rubber(SBR)were chose,and the corresponding vulcanized rubber(NR-S,BR-S,SBR-S)were prepared by vulcanizing with elemental sulfur.Thermogravimetric analysis was used to study the pyrolysis characteristics of three rubbers.The results showed that NR had only one major pyrolysis stage(300-460 °C),while the pyrolysis of BR and SBR could be divided into two sections(350-450 °C and 450-500 °C).Based on the thermogravimetric results,three different kinetic methods,including ModelBased method,Model-Free method and Distribution Activation Energy Model method,were used to simulate the kinetics of the pyrolysis process of three rubbers.It could be inferred that the pyrolysis of rubbers followed the free radical reaction mechanism by analyzing the activation energy distribution of rubber pyrolysis reaction.Then,four characteristic temperatures were chosen respectively as the final pyrolysis temperature,based on the thermogravimetric results.The three kinds of rubbers and their corresponding vulcanized rubbers were pyrolysed in fixed bed reactor to study the pyrolysis process of rubbers and the effect of vulcanization on rubber pyrolysis.The results showed that the degree of the rubber sample pyrolysis increased with the increase of final pyrolysis temperature.While the vulcanization process reduced the polymerization degree of rubber molecules,which promoted their decomposition at low temperatures.The main components of the rubber sample pyrolysis oils were dimers and trimers of the corresponding rubber monomers.However,the vulcanized rubber pyrolysis oil contained more complex components with larger molecular weight and stronger aromaticity.In addition,the sulfur in the vulcanized rubber was mainly released at a low temperature,and the sulfur-containing components in pyrolysis oil would partially decompose into pyrolysis gas at high temperature.Finally,pyrolysis-catalytic reforming of three vulcanized rubber samples on a two-stage fixed-bed reactor were carried out to study the effects of catalysts on the vulcanized rubber pyrolysis and the desulfurization process.The microporous molecular sieve HZSM-5 and mesoporous molecular sieve MCM-41 were chosen as catalysts.And the transition metal copper and zinc were supported on two molecular sieves respectively by incipient wetness impregnation to prepare four kinds of metal modified catalysts: Cu/ZSM-5,Zn/ZSM-5,Cu/MCM-41 and Zn/MCM-41.The results showed that the catalyst could promote the cracking,dehydrocyclization and aromatization reactions of vulcanized rubber volatiles.As results,the content of polar aromatics in pyrolysis oil decreased,while the content of anthracene and naphthalene components increased.Besides,the metal-modified catalysts removed the sulfur-containing components in the pyrolysis oil by forming stable metal sulfide,and the Zn-modified catalysts showed better desulfurization effect comparing to corresponding Cu-modified catalysts.