Study On Process For Acidic Gas Presulfidation And Passivation Of Hydrogenation Catalyst

The article introduced the progress inland and abroad of presulfidation and passivation, defined the necessity, mechanism and factors of presulfiding and passivating reaction; based on these a low cost method to presulfide hydrogenation catalyst was determined. The sulfided catalyst was passivated with gas and liquid passivating agents to get high activity and stability catalyst.The feasibility of presulfidation with model acidic gas that was composed of H₂S,H₂,N₂,CO₂ and NH₃ was studied by means of fixed-bed reactor at atmosphere. The effects of different factors on presulfidation such as sulfiding temperature, sulfiding time, GHSV and the proportion of acidic gas were studied. The best condition and the suitable proportion of acidic gas were confirmed by orthogonal design. The activity of catalyst was measured using actual material in high pressure micro-reactor. The results indicated that: It was feasible to presulfide hydrogenation catalyst with acidic gas. The effect of CO₂ was weak in low concentration, NH3 must be removed. The proper condition as follows: sulfiding temperature at 370℃, sulfiding time≥2.5to, H₂S concentration=5v%, H₂ concentration=5v%, CO₂ concentration =7.5v%, GHSV=1000h^-1. The fitting proportion of model acidic gas: H₂S:H₂:CO₂= 1:1:1.5.The method that the concentration of oxygen transforms regularly with the reaction time was used to passivate sulfided catalyst. Sulfided catalyst was passivated with a liquid oxygen-containing hydrocarbon and paraffin wax without water or aromatic hydrocarbon. The effects of different factors on passivation such as the quantity of passivating agent, passivating time, temperature and so on were studied. The self-heating maximum temperature of passivated catalyst was tested in ONU. The activity of catalyst was measured using actual material in micro-reactor and 15mL reactor under high pressure. The results showed that the gas passivation can cause the catalyst surface to form the more compact oxide compound protector which made catalyst stabilize in the air. It was feasible to passivate sulfided catalyst with oxygen-containing hydrocarbon and paraffin wax. The passivating process of oxygen-containing hydrocarbon as follows: the quatity of the oxygen-containing hydrocarbon was 40v% of the hole volume of the catalyst, passivating temperature at 40℃, passivating time=10min, unsaturated hydrocarbon was compelet. The passivating process of paraffin wax as follows: the rate of paraffin wax to catalyst was 15wt%, passivating time=10¹5min, passivating temperature at 60℃. The catalyst can activate in the course of raising temperature under the hydrogen atmosphere normally. The gas passivation mechanism was studied by Pyridine-TPD and XRD. The acid strength and density of passivated catalyst were more than sulfided catalyst. The gas passivated catalyst from outside to inward is M_xO_y, M_xS_yO_z and M_xS_y.