Kinetic Study Of Acetylene Selectivity Hydrogenation

In the industry,the main producing method of ethylene was petroleum steam pyrolysis.The production of petroleum hydrocarbon steam cracking contained 0.5%?2.5%(volume fraction)acetylene.Ethylene polymerization catalyst could be toxic by trace acetylene,so the content of acetylene in ethylene should be lower than 1 ppm.In recent years,many researchers had studied this project,optimized the catalyst,and studied the kinetics of acetylene hydrogenation.In this paper,the kinetic study of front-end acetylene hydrogenation was studied by using an internal recycle gradientless reactor.In the approximate condition of industrial application,an industrial catalyst was tested and the dynamic experimental data was gotten using a reactant gas close to the industrial raw gas of front-end acetylene hydrogenation.The reaction kinetics model was fitted by the mathematical software Matlab.The steady-state and dynamic simulation of acetylene hydrogenation were carried out by the Aspen(chemical process simulation software).The influence of inlet temperature and CO content in raw materials on the performance of catalyst in front-end acetylene hydrogenation reactor was analyzed.Based on the operating conditions of the industrial acetylene hydrogenation reactor,the optimum inlet temperature was 58.72 ? when the acetylene conversion was 60% in the first reactor;and the optimum inlet temperature was 59.95 ? when the acetylene total conversion was 95% in the second reactor;the optimum inlet temperature was 60.36% when the acetylene content in the third reactor outlet was less than 1 ppm.At the same time,in order to make sure the temperature of first reactor was not “run-away”,the feed temperature should be controlled to be less than 70.98 ?.The simulation analysis showed that when the CO content of the reactor inlet changed,the acetylene conversion could be maintained at 60% by adjusting the inlet temperature.Based on the data of the industrial acetylene hydrogenation reactor in the stable period of the catalyst,the kinetics model was fitted.The effect of the inlet temperature of the reactor,the content of acetylene,the content of acetylene,the content of CO,the total molar flow and the pressure of the reactor on the acetylene conversion were analyzed by Aspen Plus dynamic and steady-state simulation.The inlet temperature had the biggest influence on the conversion of acetylene.It was found by simulation that the stability of industrial catalyst was a little worse,so the catalyst was modified.Pd catalysts were prepared by step impregnation method.The catalysts with different promoters,supporters,Pd-Ag ratios and supporter calcination temperature were evaluated.The experimental results showed that the ethylene selectivity could be most enhanced by Ag adding.After Ag modification,the hydrogenation activity would be decreased,but the temperature window was increased from 20 ? to 27 ?.When the small ball Al2O3 supporter of was used,the most suitable supporter calcination temperature was 1300 ?,and the optimum ratio of Pd and Ag was 2:1,and the temperature window was 34 ?.Through experimental evaluation and Aspen Plus simulation,it was found that the self-made catalyst had better reaction stability than the industrial catalyst.