Study On The Position Of Coke Deposition On Catalyst During Residue Hydrogenation

Catalyst deactivation has always been one of the difficulties restricting its economy and energy consumption,during residue hydrogenation.and coke is the main cause of catalyst deactivation.Therefore,it is very important to understand the initial formation process,especially the initial formation location of the coke deposit on the catalyst.By investigating the process of residual oil hydrogenation on catalyst and support to form coke,and comparing the amount of coke on the two surfaces,it is found that the initial coke on both the active site and the support surface.At the same time,the formation of this part of initial coke is mainly from the adsorption of the heavy components in the raw material on the surface of the catalyst,but this adsorption process is not completely random,and the adsorption effect of the active site on this part of the raw material is obviously stronger than that of the support.At the same time,the active sites contribute greatly to bond breaking and free radical generation,relative to the support surface activity of a nearby is a rich hydrogen env ironment and rich free radicals of the environment,so under the low hydrogen condition,it is more likely to generate coke activity and high hydrogen for conditions,raw materials are easily hydrogenated,hydrogenation effect of raw material depends on the size of the materials of free radical fragments,but relative to the support,even if is the generation of coke,active sites also tend to produce soft coke reactivity.At the same time,there was no significant difference in the content of aromatic components between soft coke and hard coke,and the main factors that determined the difficulty of reaction were the size of aromatic structure and the average length of side chain.And a considerable part of the hard coke in the catalyst forms directly from the deposition in the feedstock.By comparing the amount of coke between different temperatures,it can be concluded that the increase of temperature is conducive to the breaking of bonds,so that more free radicals will be generated.For the support in a hydrogen-rich environment,the high temperature simultaneously promotes the generation of hydrogen and raw material free radical fragments,making hydrogenation easier.Therefore,in the case of hydrogen rich,there is little difference in the amount of coke of the support at different temperatures,but at the same time,there is basically no soft coke formation on the surface of the support,indicating that the support itself basically has no hydrogenation ability,and the hydrogenation process described above completely occurs in the liquid phase.However,for the higher active site of hydrogen donor,it means that the free radicals around it have a greater chance of hydrogenation.However,for the case of more raw materials in the initial stage,the hydrogenation advantage is not shown basically,because the generation rate of hydrogen free radical fragments is much lower than that of raw material free radical fragments.The rate of hydrogenation matches the rate of free radical formation only after the concentration of the heavy part of the feedstock drops.Hydrogenation is what makes it work.