Optimization Design And Application Of Acidity Function And Hydrogenation Function Of The Hydro-upgrading Catalysts

Subject to the drive of the environmental regulations and more and more strict fuel qualityrequirements of the automobile industry, in recent years, China quickened the pace of dieselquality upgrading. FCC diesel accounts for30%in the diesel pool in China, FCC diesel ischaracterized by high sulfur, high nitrogen and high aromatics content, low cetane number,high density, so it is crucial for diesel quality upgrading.Diesel hydro-upgrading technology can effectively decrease aromatics content,substantially increase Cetane Number, and HDS, HDN, decrease the density of the FCCdiesel, it is one of the most effective methods to improve the diesel quality. As the core ofdiesel hydro-upgrading technology, hydro-upgrading catalyst is the significance and difficultyof hydro-upgrading technology research. Hydro-upgrading catalyst is a kind of dualfunctional catalyst with acidity function and hydrogen function, the acidity function isprovided by zeolites, the hydrogen function is provided by metals. This paper focused onsecondary structure design of acid components for hydro-upgrading catalysts based on theknowledge of hydro-upgrading reaction mechanism, optimizated and utilized novel acidcomponents for hydro-upgrading catalysts, so the technology foundation for developing a newgeneration hydro-upgrading catalyst was established.Firstly, the modifications of NaY zeolites and Beta zeolites were carried out, respectively.Characterization and performance evaluation of USY zeolites and modified Beta zeolites wereconducted, the results revealed that modified USY zeolites and modified Beta zeolites showedsome secondary pores, as the SiO2/Al2O3ratio of USY increased, the weak acidity strength ofUSY had little change, medium and strong acidity strength of USY decreased, the weakacidity concentration, medium-strong concentration decreased. But as the SiO2/Al2O3ratio ofBeta increased, the weak acidity strength and concentration, medium-strong acidity strength and concentration of modified Beta decreased. Different crystal sizes of NaY zeolites andBeta zeolites were modified at the same time.Hydro-upgrading catalysts using USY zeolite and (or) Beta zeolite as acidic component,Ni-W and Ni-Mo-P as hydrogen component were prepared by pore volume co-impregnationmethod, respectively. The selective ring opening evaluation of tetralin revealed thathydro-upgrading catalyst with USY zeolite which had framework SiO2/Al2O3ratio of13.2showed best hydro-upgrading performance. Hydro-upgrading catalyst with small crystal sizeUSY zeolite had high tetralin conversion and better hydro-upgrading performance for FCCLCO with higher diesel yield, therefore USY zeolite with smaller crystal size is more suitablefor preparation of hydro-upgrading catalysts compared with larger crystal size USY zeolite.As the SiO2/Al2O3ratio of Beta increased, hydro-upgrading performance increased,hydro-upgrading catalyst with Beta zeolite which had SiO2/Al2O3ratio of86showed besthydro-upgrading performance. Beta zeolites with different crystal sizes influencedhydrodearomatization andcetane number improvement performance, had a little effect on thediesel yield.The preparation process of hydro-upgrading catalysts containing modified USY andmodified Beta zeolites was also optimized, the effect of the content of modified USY andmodified Beta zeolites, the hydrogenation metals of Ni-W type, Ni-Mo-P type, respectively,the impregnation sequences of Ni, W salt solution, and the atom ratio of Ni to W onhydro-upgrading performance were examined in detail, successfully developed PRIOR-1hydro-upgrading catalyst. The research found that PRIOR-1catalyst had a good metaldispersion; the pore distribution was very centralized, pore diameter of4～10nm accountedfor90%of total pore diameter; the tungsten species had a weak interaction with carrier,so it iseasy to form more hydrogenation activity center; PRIOR-1catalyst had no nickel aluminumspinel which had the lower activity, however, the octahedral nickel species were produced,which showed that the Ni-W-O bonds were formed between nickel species and tungstenspecies, the Ni-W-O bonds would contribute to the improvement of the hydrogenationfunction of PRIOR-1catalyst.The hydro-upgrading performance evaluation of PRIOR-1catalyst was carried out usingFCC diesel as feedstocks in the single stage, once through process, the results exhibited thatdiesel yield was more than97.6wt%, and cetane number improvement was more than10.9,the sulfur content and the nitrogen content decreased to less than23.9μg·g-1and4μg·g-1,respectively. Using FCC diesel as feedstocks, and under the same operating conditions, PRIOR-1catalyst had high cetane number and high diesel yield compared to domesticreference catalyst and abroad reference catalyst. The performance of PRIOR-1catalyst in thecombined processes of hydrorefining/hydro-upgrading/hydrodewaxing and hydrorefining/hydro-upgrading was also examined, the results showed that PRIOR-1catalyst had betterhydro-upgrading performance and good feedstocks adaptability.Regenation experiment of PRIOR-1catalyst was carried out, most of residual carbon andresidual sulfur were burned, the better recovery of physical properties and chemicalcomponents of PRIOR-1catalyst was achieved during regenation process.