Mechanism Of Hydrogen Production By Catalytic Pyrolysis Of Tire Rubber

In today’s rapid energy consumption,traditional energy can no longer meet the needs of human beings for energy.At the same time,traditional energy will bring environmental pollution and other problems.Therefore,it is imperative to develop and utilize new clean energy.As one of kind high-efficiency,clean and renewable secondary energy source,hydrogen energy is used more and more widely,so the demand for hydrogen is increasing,and the development of new hydrogen production methods has received extensive attention.With the rapid development of the automobile industry,the ever-increasing waste tires have caused serious pollution to the environment,and its reasonable disposal is imminent.Using waste tires to produce hydrogen by pyrolysis can not only solve the problems of environmental pollution caused by waste tires,but also produce new energyhydrogen energy.In this paper,natural rubber,styrene-butadiene rubber and cis-butadiene rubber,which are the most widely used in waste tires were used as raw materials.The tire rubber was subjected to conventional and microwave pyrolysis by means of molecular dynamics supplemented by experiments,Ni,ZSM-5,and Ni/ZSM-5 catalysts were used for catalytic pyrolysis,and the microscopic mechanism of hydrogen production from tire rubber pyrolysis was studied.Firstly,Materials Studio software was used to simulate and calculate the H· reaction path before and after catalysis,and the reaction energy barriers of all paths were compared to find the reaction path and catalyst for catalytic hydrogen production.Based on the possible paths of hydrogen production from the three monomers,Ni and Ni/ZSM-5 have better catalytic effects for H2 generation,indicating that Ni has a good effect on hydrogen production.At the same time,the addition of Ni increases the energy barrier for CH4 generation,and the addition of ZSM-5 increases the energy barrier to generate C2H4.Therefore,loading Ni on ZSM-5 not only does not reduce the effect of Ni on hydrogen production,but also provides ZSM-5 with an active site for hydrogen production,and combines the advantages of Ni inhibiting methane and ZSM-5 inhibiting ethylene.It shows that Ni/ZSM-5 catalyst can better improve the hydrogen production effect.Then,the pyrolysis process of tire rubber before and after adding Ni and Ni/ZSM-5 catalysts was simulated by Materials Studio software.The results show that the addition of catalyst in the low temperature stage is mainly manifested in accelerating the pyrolysis process and increasing the number of monomers in the low temperature stage.In the high temperature stage,the pyrolysis termination temperature is decreased after the catalyst is added,it mainly changes the distribution of gas products.The addition of Ni increases the H2 ratio,especially the tire rubber:catalyst=1:1 ratio has the highest H2 content,while reducing the C1 and C3 ratios.Comparing the catalyst pyrolysis simulation of Ni/ZSM-5 with 1wt.%Ni,5wt.%Ni,and 10wt.%Ni,the results show that the higher the Ni content,the higher the hydrogen production.Comparing the pyrolysis simulations of Ni/ZSM-5 with Ni,1wt.%Ni,5wt.%Ni,and 100t.%Ni,the results show that the 10wt.%Ni/ZSM-5 catalyst has a better hydrogen production effect.From the comprehensive path simulation and pyrolysis simulation results,it is Ni that plays a major role in hydrogen production.The combination of Ni and ZSM-5 has further improved the catalytic hydrogen production.The microwave pyrolysis and Ni-catalyzed microwave pyrolysis of tire rubber were simulated by LAMMPS software.The results show that the main performance of microwave pyrolysis can accelerate the cracking of three rubber monomers at high temperature and generate more small molecular gases,especially the target product hydrogen.After adding the catalyst,it is found that the hydrogen content will be further increased,which is similar to the conventional pyrolysis law,indicating that the Ni-catalyzed hydrogen production has obvious effects in these two pyrolysis methods.Finally,the pyrolysis process of tire rubber was studied by experimental method.Ni/ZSM-5 catalysts with different Ni loadings were prepared by impregnation method,and the prepared catalysts were characterized.The results of TG experiments show that Ni,ZSM-5 and Ni/ZSM-5 catalysts can reduce the pyrolysis temperature range of tire rubber,increase the pyrolysis rate,and increase the gas production rate.The results of conventional pyrolysis experiments show that the main gas-phase products of tire rubber pyrolysis are H2,CH4,C2H4.The addition of Ni,ZSM-5 and Ni/ZSM-5 catalysts have no change the gas species.Among them,the Ni/ZSM-5 catalyst has the best hydrogen production effect,followed by Ni,and finally ZSM-5.With the increase of catalyst ratio,the higher the hydrogen content,the more obvious the increase of hydrogen with high Ni content in Ni/ZSM-5 catalyst.The results of microwave pyrolysis gas chromatography showed that microwave heating increased the hydrogen content,and the hydrogen content increased further after adding the catalyst compared with conventional pyrolysis.