Preparation And Study Of Acid-modified Low-ruthrenium Content Mercury Free Catalyst

Mercury-containing catalysts are widely used in the calcium carbide method which is one of the main methods to produce vinyl chloride,an important chemical raw material.But mercury,as a poisonous material,is do harm to both people and the environment,so that looking for free-mercury containing and high-performance catalysts to replace the mercury catalysts becomes one of the most essential areas of the acetylene conversion research.Recently,materials like Au?Ru?Cu are focused because of their favorable performance in the conversion of acetylene by replacing Hg in the mercury-containing catalysts.And in these materials,Ru,cheaper than Au and higher performance than other non-noble metals,are on the rise.However,it is impossible to replace the mercury-containing catalysts in the acetylene conversion industries because both of the high containing of Ru?1 wt%Ru?in most of Ru-containing catalysts and the high cost of Ru.Thus,it is necessary to develop a low-content Ru-based catalyst.In our study,a low-content Ru-based catalyst?0.25 wt%Ru?was prepared by impregnation method firstly,then it was modified by three different auxiliaries of phosphoric acid,acetic acid and boric acid,next the phase composition,surface structure properties,redox properties,and valence state of the Ru species of the fresh and reacted catalyst samples were analyzed by XRD,BET,SEM,TEM,H₂-TPR,TG.Because of those facts,we can reach the following conclusion:1?A low content Ru-based catalyst?0.25 wt%Ru?was developed by impregnation method successfully,and it was modified by varying levels of phosphoric acid,acetic acid and boric acid.And we focused the optimum catalysts that were 0.25 wt%Ru/4 wt%PAC,0.25 wt%Ru/5wt%HAc-AC,0.25 wt%Ru/20wt%BAC under the reaction conditions of T=150°C,GHSV=1222h^-1,V_HCl:V_C2H2=1.15 and the 0.25 wt%Ru/20wt%BAC under the reaction conditions of T=150°C,GHSV=770h^-1,V_HCl:V_C2H2=1.15;2?The optimum low ruthenium catalyst modified by phosphoric acid0.25 wt%Ru/4 wt%PAC had an almost same original catalytic efficiency to the 0.25 wt%Ru catalysts,about 72%.And after a 7-hour reaction for the hydrochlorination of acetylene,the catalytic efficiency of0.25 wt%Ru/4 wt%PAC declined to 63%,which down 12.9 percent,while the 0.25 wt%Ru to 42%from 71%,which down 40.8 percent and higher than modified catalysts largely;3.The optimum low ruthenium catalyst modified by acetic acid 0.25wt%Ru/5 wt%HAc-AC had a higher original catalytic efficiency of86%and it was 15%higher than the 0.25 wt%Ru catalysts.And after a7-hour reaction for the hydrochlorination of acetylene,the catalytic efficiency of 0.25 wt%Ru/5 wt%HAc-AC declined to 63%,which down 26.7 percent but still lower than the initial 0.25 wt%Ru catalyst;4.The optimum low ruthenium catalyst modified by boric acid 0.25wt%Ru/20wt%BAC had a lower original catalytic efficiency of 66%,but it had a higher stability than the 0.25 wt%Ru catalyst,which still kept the catalytic efficiency of 48%after a 7-hour reaction for the hydrochlorination of acetylene,which down 27.3 percent which lower than the initial 0.25 wt%Ru catalyst.Above all,the catalysts stability of 0.25 wt%Ru/4 wt%PAC,0.25wt%Ru/5 wt%HAc-AC,0.25 wt%Ru/20wt%BAC are all improved in a 7-hour reaction for the hydrochlorination of acetylene compared to the0.25 wt%Ru catalyst.The stability and catalytic efficiency of 0.25 wt%Ru/5 wt%HAc-AC were both improved because the increases of high-valent ruthenium species and content of oxygen-containing functional groups on the surface of activated carbon which inhibited the carbon deposition after adding acetic acid.And more interestingly,the catalyst of 0.25 wt%Ru/5 wt%HAc-AC for a 7-hour reaction for the hydrochlorination of acetylene had a lower efficiency than high-mercury catalysts in the industries of Acetylene conversion slightly and up 10percent to the low-mercury catalysts in the industries of Acetylene conversion.The stability of 0.25 wt%Ru/4 wt%PAC was improved also because the increases of high-valent ruthenium species and content of oxygen-containing functional groups on the surface of activated carbon inhibited the carbon deposition after adding phosphoric acid.The stability of 0.25 wt%Ru/20wt%BAC was improved because the increase of high-valent ruthenium species and the formation of B-C-O structure on the catalyst surface inhibited the carbon deposition and promoted the dispersion of active components after adding boric acid.