Study On The Performance Of Bismuth-based Catalysts For Low-temperature Catalytic Removal Of Hydrogen From Tail Chlorine

Chlor alkali industry is an important basic chemical industry.Because its products are widely used in various fields such as chemical materials,it is related to the development of national economy and society.A large amount of chlorine produced by chlor alkali enterprises needs to be compressed and liquefied,and steel cylinders are used for storage and transportation.In the process of compression liquefaction,a part of incompressible non condensable tail gas containing chlorine will be produced,which is called tail chlorine in industry,mixed with some gases such as nitrogen,oxygen and hydrogen.Once the volume content of enriched hydrogen reaches 4%,there will be explosion risk,so the tail chlorine can not continue to liquefy and be used in downstream chlorine consumption process products.In this experiment,bismuth based catalyst was selected in fixed bed reactor to effectively remove hydrogen from tail chlorine by catalytic hydrogen-oxygen reaction and hydrogen-chloride reaction.Metal Bi and Bi₂O₃catalysts were used to test the dehydrogenation performance of tail chlorine at different reaction temperatures,while supported Bi₂O₃/γ-Al₂O₃and Bi₂O₃/silica catalysts were used to test the dehydrogenation performance of tail chlorine by changing the reaction temperature,calcination temperature and loading content.XRD,SEM,EDS,FT-IR and N₂adsorption desorption were used to characterize the crystal form,morphology,element content,skeleton structure and pore structure of the catalysts before and after the reaction.The conclusion is as follows:1.Metal bismuth catalyzes the dehydrogenation of tail chlorine at a reaction temperature of 50°C,with an average hydrogen conversion rate of 88.89%,and bismuth oxide catalyzes the dehydrogenation of tail chlorine at a reaction temperature of 70°C,with an average hydrogen conversion rate of 94.69%.XRD showed that bismuth oxychloride was produced as a by-product in the catalyst after the reaction,and the EDS element analysis showed that the content of chlorine in bismuth oxide after the catalytic tail chlorine dehydrogenation was small,so the catalytic performance was relatively stable.By mechanically mixing bismuth oxide with activated alumina,titania,white carbon black,and molecular sieves,the carrier with better catalytic dehydrogenation effect of tail chlorine-activated alumina and white carbon black are screened out..2.The optimal process conditions for the supported Bi₂O₃/γ-Al₂O₃catalyst to catalyze the dehydrogenation of tail chlorine are:the catalyst with 3%active components is calcined at450°C and the dehydrogenation of tail chlorine is carried out at 80°C.The average hydrogen conversion rate can reach 95.8%.The analysis and characterization results show that the surface of the catalyst after the catalytic reaction is rough,the content of active components is reduced,and the production of hydrogen chloride and water causes corrosion of the catalyst,which reduces its specific surface area and increases its pore size.The catalytic activity of the catalyst after the reaction is reduced to a certain extent.The results of the catalysis experiment are consistent.3.The optimal process conditions of the supported Bi₂O₃/silica catalyst for the catalytic dehydrogenation of tail chlorine are:the catalyst loaded with 3%active component Bi₂O₃is calcined at 550°C and undergoes catalytic dehydrogenation of tail chlorine at 50°C,and its average hydrogen conversion rate Can reach 97.8%.Analysis based on the characterization results shows that Bi₂O₃is uniformly dispersed on the surface of the silica support.Although the product water,hydrogen chloride and trace by-products produced during the catalysis process,as well as the strong chlorine oxidation and strong corrosive atmosphere,the catalyst is damaged,resulting in a decrease in performance.However,the crystal type,morphology and overall framework structure of the catalyst are basically not changed,and the catalyst has good stability..4.All the bismuth-based catalysts explored in the experiment have lower hydrogen-oxygen reaction selectivity in catalytic reactions than hydrogen-chlorine reactions.Therefore,we can conclude that they are more inclined to catalyze the hydrogen-chlorine reaction in the catalytic dehydrogenation of tail chlorine.Comparing the catalytic activity of the above-mentioned Bi₂O₃/γ-Al₂O₃and Bi₂O₃/silica supported catalysts,the latter not only reduces the reaction temperature to a certain extent,but also shows more excellent catalytic activity and stable catalytic performance.