Preparation, Characterization Of Solid Acid Of Montmorillonite Doped With Zr And Ti And Their Properties Of Aromatic Ring Opening And Cracking

As the fuel oil contains a certain amount of aromatics, it will reduce the quality of the fuel and bring more pollution to the environment. It is of great significance to develop the new type of high efficient solid acid catalysts with superior ring opening to remove the aromatics. In this paper, using the natural clay montmorillonite（MMT） as the precursors, the solid acid catalysts of MMT doped by Zr, Ti and Al were prepared by the hydrothermal reaction. Combined with the results of UV-DRS, XRD and XRF, the doping behaviors and species of the elements doped into the framework of MMT were researched. The acidities of MMT doped with Zr, Ti and Al were characterized by FT-IR and NH₃-TPD. The effects of calcination temperature, calcination atmosphere, ion-exchange method on the acidities of MMT doped with Zr, Ti and Al were also studied. Using tetralin and decalin as the model compounds, the properties of ring opening and cracking of the prepared catalysts were researched. The results show that:（1） Zr element can be doped into the framework of MMT in the form of oxide species by hydrothermal reaction and the solid acid catalyst of MMT doped by Zr is obtained. On the hydrothermal reaction conditions（ 200 ℃,24h）, zirconium oxychloride dissolved in water are mainly doped into the framework of MMT by isomorphous substitution of Al element in the skeleton of MMT. The amount of the doped Zr O₂ is 23.29 wt%. The acidity of the catalyst is promoted by doping Zr into MMT. And the acidity of the catalyst is improved further by calcining at 550℃ and exchanged with ammonium ion. The acidity of MMT doped with Zr is mainly B acid.（2） Ti element can also be doped into the framework of MMT in the from of oxide species by hydrothermal reaction and the solid acid catalyst of MMTdoped by Ti is obtained, but the degree of Ti doping is higher than Zr element, the same condition of doping is introduced for the Ti O₂ loading amount is 53.47%, and The acidity of MMT doped with Zr is mainly L acid. However, Al element can’t be doped into the framework of MMT by hydrothermal reaction, which is mainly in the form of ion exchange with the interlayer of MMT, and the acidity of the catalyst can’t be promoted.（3）The solid acid catalysts of MMT doped with Zr and Ti show the superior performances for ring cracking and especially ring opening of the aromatics. For tetralin, compared with ZSM-5, the activities of MMT doped with Zr and Ti are improved greatly. Doped montmorillonite had a significant increase in the activity, as well as the superior performance of the C₁₀ ring product selectivity, the activity of Zr doped montmorillonite had increases 5%, acquire a high selectivity of C₁₀ relatively, while it is not in favor of reducing the selectivity of naphthalene. For decalin, ZSM-5 almost have no activity, the activity of Zr and Ti doped montmorillonite compared to four hydrogen naphthalene has close to 2 times increase, at the same time, the selectivity of C₁₀ open loop product was also greatly improved, especially for Ti doped Montmorillonite solid acid catalyst, the selectivity of C₁₀ is as high as 77.8% and have no dehydrogenation products.