Preparation Of TS-1 Monolithic Catalysts And Use For The Reaction Of Cyclohexanone Ammoximation

Monolithic catalyst possesses distinguish advantages over traditional particle catalysts in small pressure-drop, low mass-transfer resistances, unremarkable scale-up effect and so on. Not only improving the efficiency and selectivity of catalytic reaction, it is also contributed to the achievement of low energy, zero emission and safe operation process.As an incoming catalyst with MFI topological structure, Titanium silicalite-1 molecular sieve (TS-1), has been drawn more attention of domestic and abroad researchers because of its excellent catalytic-oxidation performance in H2O2/TS-1 system with mild reaction conditions. Since using powder TS-1 in slurry reactor, it is difficult to separate such a small crystal from liquid, the unavoidable loss of expensive catalyst increases the operation cost. In this paper the TS-1 molecular sieve was synthesized on honeycomb-shaped cordierites pretreated by acid liquid with hydrothermal method, the aim was at solving the problem mentioned.My research was focus on pretreatment of cordierite support, growth of TS-1 on cordierite and evaluation of catalytic activity in cyclohexanone ammoximation.First of all, the cordierite supports were pretreated by acid solution. The results showed that the specific surface area of support pretreated with hydrochloride acid was larger 2 times than that pretreated by nitric acid, and the former was superior in planting the TS-1 molecular sieve on cordierite. Then the mixed templates were used to synthesize TS-1 monolithic catalysts, crystal size of molecular sieves was larger in micron scale. The mole ratio of tetrabutylammonium hydroxide (TBAOH) to tetraethylammonium hydroxide (TEAOH) in mixed templates affected the purity of TS-1 crystal obviously. When mixed TS-1 and TS-2 crystals were formed, a triplet-peak would appear at 2θ=45.5°in XRD patterns. Based on the FT-IR analysis of molecular sieve film on the cordierite supports, a shoulder peak at 1050cm-1 should be the vibration of out framework Si-O, and not strong interrelated with the size and shape of TS-1 crystal.After investigating the calcination process of catalyst with TG-DTA, the temperature range, 550 800℃is suitable to removal of the templates. Actual calcination temperatures of TS-1 powder and monolithic catalyst were chosen as 550℃and 600℃respectively. Comparing the XRD patterns of TS-1 catalysts before and after calcination, the low angle diffraction peaks were evidently changed to partial overlap and split, however, almost no impact was observed in higher angle. According to the calculation TS-1 relative crystallinity became larger after calcination, which meant that the calcination could lead to perfect structure and good stability of crystal.When tetrapropylammonium hydroxide (TPAOH) was used as template, TS-1 crystal shape gradually changed from cylinder to ellipse with the increase of Ti content, and increase in the amount of template or H₂O/SiO₂ ratio would benefit the formation of TS-1 crystal. Crystallization temperature was a key factor for synthesis of TS-1 monolithic catalysts, proper one is 170℃, below it the precursor had not been completely crystallized on cordierite supports. The dense film of TS-1 catalysts on support was uneven because of the effects of gravity. When the TS-1 catalyst was crystallized step by step on a honeycomb cordierite surface by using hydrothermal method, a branch-like TS-1 film was formed evenly, which was self-assembly of crystalline rather than oriented grown of crystalline.A monolithic reactor self designed was used to test the catalytic performance of TS-1 monolithic catalysts in the cyclohexanone ammoximation reaction. After TS-1 catalyst was activated by acid, the cyclohexanone conversion decreased, but oxime selectivity increased. Comparing the activity of TS-1 catalysts synthesized by different templates, the TS-1 catalyst by single template had higher activity than that by mixed templates, which maybe caused by different particle size. Compared to TS-1 powder, the reuse of monolithic catalysts could be convenient although its activity was somewhat low. When the branch-like TS-1 film on supports, dense film on supports and TS-1 powder were used to catalyze cyclohexanone ammoximation reaction, the branch-like TS-1 film was easy to diffuse reactants, thus improve the utilization of monolithic catalyst, and finally made catalytic activity almost as the same as the TS-1 powder.