Study On 1,2,4-Trimethylbenzene Hydrogenation Transformation

1,2,4-TMB is an important component of C9+ heavy aromatics,accounted for mass fraction 30.0% 40.0%.Light aromatics are important chemical raw materials,which can be used as pharmaceutical preparation,pesticide intermediates,dye synthesis,production of surfactants and others.Benzene,toluene and xylene（BTX）are the most important materials in the industrial and agricultural production.Due to the shortage of petrochemical resources,the efficient utilization of C9+ heavy aromatics become an practical significance.As a result,hydrogenation transformation of heavy aromatics with catalysts is a way of the green economy.In the article,we focused on the hydrogenation transformation of 1,2,4-TMB to BTX.We prepared a series of Ni/SiO₂ catalysts system.According to the influence of catalyst acidity in the reaction,we carried on some discussions,included the structure of catalyst,the loading,calcination temperature,nickel source,the influence of reaction temperature and the pressure.The main content of the paper is as follows:1.Producing the Ni/SiO₂ catalysts by the sol-gel method,we researched the influence of catalysts in the reaction in the hydrogenation transformation of 1,2,4-TMB.Firstly,to study the influence of the pore structure and specific surface,we changed the amount of CA.The result show that the CA had a great influence on the pore and the overall structure of catalysts,and the quantity of the CA influenced the dispersion of the active species.Secondly,we studied the loaded mass of Ni,roasted temperature,and the Ni source in it.Finally,according to change the reaction temperature and pressure,we found the most suitable method.The result showed that,the catalyst which loaded of 10（wt）% Ni,n（Ni）/ n（CA）= 1:2,and the Ni source was Ni（NO3）2·6H2O,was roasted at 773 K in 3 h,and in the condition of 723 K,3.0 MPa,the conversion rate of 1,2,4-TMB reached 29.4%,the selectivity of BTX closed to 100%.2.Using varieties of characterization methods to investigate the effect of acid sites in the hydrogenation transformation of 1,2,4-TMB.The focus in this reaction is to improve the BTXs’ selectivity.Therefore,we chose the SiO₂ as the carrier to make the Ni/SiO₂ catalysts with weak acid,and studied the catalytic performance.According to the researching report,the main acid site was Lewis acid without Bronsted acid.Combined with other characterization results,we found that hydrodealkylation reaction was mainly related to the catalysts’ Lewis acid except Ni.3.The influence of ZSM-5 catalysts in the hydrogenation transformation of 1,2,4-TMB.We made the Co/ZSM-5 catalysts,and determined the synthesis conditions.As the best experimental results,the conversion of 1,2,4-TMB to 73.2%,and the selectivity of BTX reached 87.8%.