Synergistic Study On Gold-based Acetylene Hydrochlorination Catalysts

In this thesis,a supported gold-based catalyst was prepared by ultrasonic assisted impregnation technique and its catalytic activity in acetylene hydrochlorination was tested.Firstly,the effects of catalysts?Au0.25Ru0.75/Coconut AC?Au0.25Ru0.75/Granular AC and Au0.25Ru0.75/Columnar AC?formed by three activated carbon supports on the catalytic performance of acetylene hydrochlorination catalysts were investigated to select the best activated carbon carrier.Subsequently,the loading of the active component,the loading sequence of the active component,and the synergistic effect between the active components on the catalytic performance of the catalyst were explored.XRD,BET,TEM,XPS,H₂-TPR,TG and other characterization methods were used to compare the phase composition,texture properties,redox capacity and valence state of the active components.Get the following results:?1?A supported gold-based catalyst Au-Ru/AC?Coconut AC,Granular AC,Columnar AC?was prepared by ultrasonic assisted impregnation technique.It was found that the Au0.25Ru0.75/Coconut AC catalyst prepared by using coconut shell activated carbon as the carrier has the best catalytic performance in the acetylene hydrochlorination reaction.Its specific surface area?787.5m²/g?was also significantly greater than that of Au-Ru/Granular AC catalyst?664.6m²/g?and Au-Ru/Columnar AC catalyst?635.4m²/g?.Therefore,coconut shell type activated carbon is the best acetylene hydrochlorination catalyst 0.25Au0.75Ru/AC support.?2?Three different Au,Ru ratio Au-Ru/Coconut AC acetylene hydrochlorination catalysts?Au0.25Ru0.75/Coconut AC?Au0.5Ru0.5/Coconut AC and Au0.75Ru0.25/Coconut AC?were prepared by ultrasonic assisted impregnation technique.It was found that the catalytic performance of the catalyst for acetylene hydrochlorination was best when Au and Ru ratios were Au:Ru=0.75%:0.25%.At this time,the prepared Au0.75Ru0.25/Coconut AC catalyst had a vinyl chloride selectivity of 99.8%and an acetylene conversion rate of 95.6%in the acetylene hydrochlorination reaction.It is significantly higher than the single gold Au1%/Coconut AC catalyst,and also higher than the single ruthenium Ru1%/Coconut AC catalyst.?3?The effects of simultaneous loading and step loading of the active components Au and Ru on the catalytic performance of the catalyst were investigated.It was found that the catalyst obtained when the active components Au and Ru were simultaneously loaded at a step load of Au and Ru exhibited better acetylene hydrochlorination catalytic properties,and it had a larger specific surface area?801.6m²/g?.According to the XPS results,the active species Au³⁺and Ru⁴⁺in the catalyst obtained by simultaneous Au and Ru loading are present on the surface of the catalyst.On this basis,the influence of the order of the raw materials acetylene and hydrogen chloride on the catalytic performance of the catalyst was also explored.It was found that the first pass of hydrogen chloride and then the passage of acetylene would better improve the catalytic performance of acetylene hydrochlorination.?4?The synergy between Au and Ru was investigated.It was found that the Au0.75Ru0.25/Coconut AC catalyst was at a temperature of 150°C,the ratio of feed gas acetylene to hydrogen chloride was 1:1.15,and the total space velocity was 1224h^-1.Under the reaction conditions,the conversion of acetylene can reach 95.65%,and the selectivity of vinyl chloride has been stable at about 99%.Compared with Au1%/Coconut AC,Ru1%/Coconut AC,the catalytic activity is higher and stable.The H₂ reduction peak of Au³⁺and RuO₂ in Au0.75Ru0.25/Coconut AC catalyst shifted to high temperature,indicating that Au³⁺and RuO₂ are more difficult to be reduced.It can be seen from the XPS analysis that the content of Au³⁺and high-valent cerium oxide in the Au0.75Ru0.25/Coconut AC catalyst is more.?5?On the basis of the above,the Au metal loading in the Au0.75-Ru0.25/Coconut AC catalyst with a total total loading of 1%was reduced to0.1%,and the total loading was formed into Au0.1Ru0.25/Coconut AC of 0.35.It was found that its catalytic activity is higher and more stable than the single gold Au0.1/Coconut AC of the same gold content and the single ruthenium Ru0.25/Coconut AC of the same ruthenium content,and also higher than the industrial high mercury and low mercury catalysts.Subsequently,Cu²⁺4%was substituted for Ru0.25%,and Au0.1Cu4/Coconut AC catalyst was prepared by ultrasonic assisted impregnation technique.The conversion of acetylene could also be similar to that of industrial low mercury catalyst.