Studies On Regeneration Methods Of The Pd/C Catalyst And Estimating Its Effectiveness Factor For The Purification Of Crude Terephthalic Acid

The macrokinetics of purification of terephthalic acid by hydrogenation has been studied on the two kind of different radius Pd/C catalyst (0.5%(wt%),4-8 mesh and 12-20mesh) which was put into a special-made basket in a high-pressure stirred stainless batch reactor. The research enunciate, if the radius of the catalyst was varied, effect of the internal diffusion also is varied. The radius of catalyst let up, the effectiveness factor increase, the rate of hydrogenation also increase. The reaction is a first order reaction. On the basis of it, the internal diffusion effectiveness factor of two kind of different radius Pd/C catalyst on the different temperature was estimated . At 275# ,285# ,295# the reaction temperature ,the catalyst(4-8 mesh) effectiveness factor is 0.931,0.68,0.35, the fitting data is 0.92,0.63,0.32.The effectiveness factor of calculative result accord with the fitting data of the dynamics equation. Its opposite error margin is not over 10%.The research of Pd/C catalyst deactivation reason is some the microcosmic analysis, such as XPS, TEM, EPMA. The deactivation reason of Pd/C catalyst include (1) the palladium crystal grow up,(2) the impurity covered activity center,(3) the palladium content reduce,(4) the catalyst specific surface area reduce. According to all the kind of the deactivation reason of the Pd/C catalyst, the way of the Pd/C catalyst regeneration was studied. The deactivation Pd/C catalyst was washed by the water, acid and alkali, then it was loaded palladium again. The result suggest there is the regeneration probability of the deactivation Pd/C catalyst. The hydrogenation activity of the regeneration Pd/C catalyst is good , it almost is the same as fresh Pd/C catalyst. There is the specific regeneration method, the first, the heat water washes the deactivation Pd/C catalyst for 5 hours. The second, the normal temperature alkali washes the deactivation Pd/C catalyst for 5 hours. The third, the catalysts which have been washed load 0.2% palladium again, then restored with the hydrogen. The hydrogenation of the catalyst of the rebirth empress activity is good, basic attain the hydrogenation of the fresh catalyst the activityThe fresh Pd/C catalyst, the deactivation Pd/C catalyst and the regeneration Pd/Ccatalyst are token, including content of Pd, the specific surface area, the distribution of pore size and the volume of pore. The phenomenon of the specific surface area increase is discussed.