| Oxygenated chemicals are industrially important intermediates in petrochemical and finechemical field, whose corresponding synthesis processes are needed to be greener urgently. The goal is to realize environment-friendly green chemistry and chemical processes instead of the noncatalytic and stoichiometric ones. As excellent catalytic materials for selective oxidation of hydrocarbons, titanium-containing molecular sieves attract more and more attention of reserach. However, it is a challenge to realize the industrial manufacture of TS-1 with high and stable catalytic activity, whereas the cost of TS-1 is still high. Those problems seriously hinder the further industrial application of TS-1. At the same time, the medium-size pore of TS-1 does not meet the demand of bulky molecular reactions. Hence, the efforts have been made in this thesis to resolve the problems. At first, the study has been carried out to overcome the problem in the industrialization of TS-1, then to develop new molecular sieves and new synthesis method to meet the demand of bulky molecular reactions. The relationship between their structures and catalytic performance has also been established. The main contents are as follows:In the first part, based on the full understanding the factors affecting the catalytic activity of TS-1 in the preparation process, effective optimization was carried out and the industrialization of TS-1 with high and stable catalytic activity was realized readily. The TS-1 catalyst thus manufactured has been applied to the industrial unit (70,000 t per year) of the new SINOPEC caprolactam process successfully. Then in order to reduce the cost of TS-1 which hinder its further industrial application, an improved process for the lower cost synthesis of TS-1 has been provided through hydrolyzation of TEOS and TBOT under lower OH" content and crystallization under higher TPAOH content. Compared with the previous process, the new process showed higher efficiency, that is, the production increased from 18 Kg/(m3·d) to 70 Kg/(m3·d), and the TS-1 product retained the activity comparable to the previous one. On the other hand, a new modification of TS-1 to enhance its catalytic activity remarkably was provided. That is, as-synthesized TS-1 was refluxed in an acid solution to remove non-framework Ti species selectively before calcination. It showed that the catalytic activity of modified TS-1 in the phenol hydroxylation was up to 39.2% at the standard condition ( phenol /H2O2 =3:1 (mol), phenol/acetone=1.25:l(wt), phenol /TS-l=20:l(wt), 80℃,6 h), to our bestknowledge, it is so far the highest catalytic activity reported on TS-1 at the same condition. Finally, the synthesis of TS-1 using inorganic precursors was attempted. Using mixture of Ti(SO4)2 and solid silica gel as inorganic precursor, TS-1 with good catalytic performance was prepared by the calcination of the mixture at a proper temperature before crystallization.In the second part, AEL structure molecular sieves were studied. Many factors in the sol-gel process affecting its unit cell structure were investigated, and SAPO-11 molecular sieve with a stable cell unit structure was obtained, which showed the highest C8° isomerization selectivity compared with others with an unstable unit cell structure. On the basis of synthesis of SAPO-11, TAPO-11 molecular sieve with the stable unit cell structure was successfully synthesized simply by controlling its crystallization temperature. Other transition metal-containing AEL structure molecular sieves, such as CoAPO-11, MnAPO-11, FAPO-11, NAPO-11, were also prepared, which showed higher unit cell structure stability than that of AIPO4-11.In the third part, Ti-MWW was synthesized for the first time by the dry gel conversion (DGC), namely Ti-MWW-DGC, and a novel titanosilicate, Del-Ti-MWW, was successfully prepared by delaminating the Ti-MWW precursor.Ti-MWW-DGC was synthesized from the colloidal and fumed silica sources with the assistance of boric acid by using piperidine or hexametheleneimine as a structure-directing agent (SDA)...
|
PDF Full Text Request