Catalytic Hydrogenation Process For Synthesis Of Decalin From Crude Naphthalene

Decalin is a versatile chemical raw material, which is mainly produced by hydrogenation of naphthalene. Now China relies heavily on imports of decalin, and doesn't achieve its domestic industrial production. In the early 1950s, China mastered the hydrocracking technology, and since then hydrocracking process, catalysts and equipment have made great progress in the oil refining industry. Catalyst is the key to hydrocracking technology, therefore this paper is mainly focused on the hydrogenation performance of traditional hydrogenation catalyst in the presence of organic nitrogen, and catalyst's composition and structure are also modified to produce decalin more effectively. Conventional hydrocracking catalyst is mainly formed by the carrier and the hydrogenation metal, and hydrogenation metal can be divided into non-noble metals and noble metals. In this paper hydrogenation and denitrification of non-noble metals were studied, and hydrogenation and anti-N performance of noble metals were studied as well. Then the silica-alumina used as the carrier, we prepared a series of Pt-Pd catalysts using excessive impregnation. The impact of impregnating solution's composition on catalyst's pore structure and distribution of active metal was studied, and the correlation of reactivity and distribution of active metal was also investigated. Three kinds of hydrocracking process were used to synthesize decalin through the hydrogenation of naphthalene, thus make it clear how to choose the proper hydrocracking process according to the differences of catalysts and raw materials.The main conclusions of this paper are as follows:(1) The Mo-Ni catalyst with lower metal load has pretty good hydrogenation activity only at 360℃, but the activity can't be kept. The hydrogenation performance improves as Mo load increase. W-No-Ni catalyst possess the best hydrogenation activity of the three none-noble metal catalysts due to its highest metal load, and its best denitrification activity is derived from larger surface area and pore volume.(2) For catalysts with poor performance of anti-N, organic nitrogen compounds can significantly reduce the conversion of naphthalene hydrogenation. For catalysts with nice performance of anti-N, organic nitrogen compounds can barely reduce the conversion of naphthalene hydrogenation, but the tetralin to decalin reaction is severely inhibited. (3) When the Pt-Pd catalyst is used to synthesize decalin from naphthalene or tetralin. the reaction temperature should not be higher than 320℃, otherwise the tetralin to naphthalene reaction occurs, which will reduce the decalin production. As Pt mass fraction of impregnating solution increases, the actual Pt load increases, and the actual Pd load drops. But Pd mass fraction's increase will make almost no differences of Pt and Pd load.(4) The distribution of reactive species in the noble catalysts has high impact on hydrogenation activity and anti-N performance. The eggshell-type catalyst has high hydrogenation activity, but its anti-N performance is poor. The egg white-type catalyst has medium anti-N performance, but its hydrogenation activity is low. When Pt forms "thick eggshell-type" distribution and Pd forms egg white-type distribution in a catalyst, the catalyst's hydrogenation activity and anti-N performance will be significantly improved due to interaction between Pt and Pd.(5) The three common hydrocracking process can be applied to synthesis of decalin through naphthalene hydrogenation, but the composition of raw material and catalyst properties be considered seriously.