Studyon The Effect Of Carrier Modificationand Promoterontheperformance Ofnon-Mercurylow-Gold Acetylene Hdrochlorination Catalyst

In this paper,the main low content of active components Au(content of 0.25%)was used as the active ingredient,the performance of acetylene hydrogenation catalyst was researched from two aspects,that is,the use of carrier modification and adding additives.N2 physical adsorption,XPS,H2-TPR,C2H2-TPD,TG,TEM and SEM were used to compare and analysis the phase composition,structural properties,redox properties,adsorption of reactant gas HCl and C2H2 of the fresh and reacted catalyst samples.The effects of carrier modification and addition of additives on the catalytic performance of low-content Au-based supported catalysts were investigated.The following conclusions were drawn.1.A series of boron-modified low-content Au(0.25wt.%)-based catalysts were prepared by impregnation method and their catalytic performance was tested in acetylene hydrogenation.The performance of the catalysts before and after B modification was compared.The results show that the acetylene conversion rate is increased by 21.4%and the selectivity of vinyl chloride is upgraded about 2%when the space velocity is 770h-1 and the reaction temperature is 150℃,compared with the unmodified catalyst.The results showed that the B-C-O bond could be formed by the addition of B species,which could reduce the electron cloud density of Au3 + and inhibit the reduction of Au3 + → Au0.The addition of B species could significantly reduce the amount of carbon in the reaction process and improve the stability of the catalyst.It was found that the B-modified catalyst had smaller particle size and higher activity of the catalyst than that of the unmodified catalyst.It indicated that Au nanoparticles could contribute to the hydrogenation of acetylene;The adsorption capacity of acetylene is not the main reason for the stability and the activity of the catalyst.Instead,the adsorption capacity of the catalyst to hydrogen chloride is the main factor affecting the stability and activity of the catalyst.The addition of B can significantly improve the adsorption capacity of the catalyst sample on HCl gas,thus enhancing the stability of the catalyst.2.A series of B and N doped Au 0.25%/AC catalysts were prepared by impregnation method using B and N to modify the activated carbon carrier.The effects of different proportions of B and N doped catalyst samples on the hydrogenation of acetylene is studied.The conversion of acetylene was 83.5%,The results showed that the conversion of acetylene was 83.5%Which is increased by 22.5%compared with that of undoped samples,and is about 1.6%higher than that of the B-doped catalyst,which indicated that the existence of the N species has a great influence on the catalyst performance.In general,the effects of the N species to the catalyst is in the order of pyrrolic N>graphitic N>pyridinic N.3.Au 0.25%X Ta/AC(X = 1,3,5,7)bimetallic catalysts and Au 0.25%/AC single Au catalysts o were prepared by impregnation method,and the their influence on the hydrogenation of acetylene was studied in order to select the most outstanding catalyst(Au 0.25%-5Ta/AC bimetallic catalyst).The optimum conversion rate of Au 0.25%-5Ta/AC bimetallic catalyst was 85.8%,and the selectivity of vinyl chloride could reach more than 99%.Through various characterization methods,it was found that there existed a obvious interaction between the active component Au and Ta species,resulting in the the reductive peak of Au34 species shift to the high temperature,making the Au1U species more difficult to be reduced,thereby improving the stability of the catalyst;The number of micropores in 3-5 nm of the Au 0.25%-5Ta/AC bimetallic catalyst is also slightly greater than that of the Au 0.25%/AC catalyst.It can be seen that the decrease in the specific surface area of the catalyst sample is due to the addition of the metal Ta,which blocks a portion of the catalyst structure.4.The Au-Ce bimetallic catalyst with the active component Au was prepared by impregnation method.The results showed that when the content of Au was 0.25%and the content of Ce was 7%,Au 0.25%7Ce/AC catalyst showed great catalytic activity.When the reaction temperature was 150℃,the conversion rate of acetylene could reach 78%at the space velocity of 770 h-1,the ratio of hydrogen chloride and acetylene in the feed gas was 1:1.15,Which is about 17%higher than that of single component Au 0.25%/AC catalyst.At the same time,the selectivity of Au 0.25%/AC catalyst for acetaldehyde is low,and the method of calculation and experiment is adopted.We believe that the lower selectivity of the vinyl 0.25%/AC catalyst for the hydrochlorination of Acetylene is likely to result in the formation of the by-product 1,2-dichloroethane.And the electron cloud density of the active component Au3+ species can be increased by adding the rare earth additive Ce,which makes the active component Au3+ species more stable and difficult to be reduced,thus enhancing the stability of the catalyst.