Effect of triethylamine treatment of titanium silicalite-1 on cyclohexanone ammoximation in a continuous system

Abstract

TS-1 has been hydrothermally treated by aqueous solutions of triethylamine, characterized by a number of techniques and studied in the ammoximation of cyclohexanone with NH 3 and H 2 O 2 in a continuous system. Some irregular hollow cavities are created after the treatment by desilication. The catalytic activities of TS-1 are not affected, but the catalyst stabilities significantly increase after the treatment, which can be attributed to the generation of the cavities. The treatment conditions are optimized, with the catalyst stability being extended to ten times of the conventional TS-1. After the treatment, triethylamine can be separated simply through distillation and recycled. The causes of deactivation are elucidated to be the deposition of higher weight byproducts formed on the surface of the catalysts and the deactivated TS-1 can be effectively regenerated through calcination in air.

Inter-connected and open pore hierarchical TS-1 with controlled framework titanium for catalytic cyclohexene epoxidation

“…Although sodium hydroxide can create mesopores in MFI zeolites it also decreases their relative crystallinity, and in addition increases the amount of extra-framework titanium in the TS-1 [20][21][22] . Recently, organic templates such as tetrapropyl ammonium hydroxide (TPAOH) [23][24][25][26] and a mixture of TPAOH and NaOH 27 have been used to treat TS-1 after synthesis to obtain hollow TS-1. The TPAOH acts as an alkaline and dissolves the zeolite crystals to create mesopores in the TS-1 crystals.…”

“…Due to the above dissolution-recrystallization process, the relative zeolite crystallinity is preserved better than what is obtainable with sodium hydroxide treatment. However, the above methods inevitably break the Si-O-Ti bonds in the crystal and convert part of the framework titanium to extra-framework titanium 10,23,25 . Furthermore, the above methods produce a closed-pore meso-/macropore in the zeolites, with a dense shell around the crystal.…”

Highly efficient synthesis of cumene via benzene isopropylation over nano-sized beta zeolite in a submerged ceramic membrane reactor

“…During six cycles, the conversion of benzene decreased from 25.1% to 2.8%, while the selectivity of cumene increased from 92.7% to 98.1%. Such decrease in the catalytic activity could be due to catalyst deactivation by the deposition of organic matters, especially the byproduct of DIPB, and other polymeric species inside the zeolite pores [32,33]. This was verified by the BET analysis of the recovered catalyst.…”

Hierarchically Structured Zeolites: From Design to Application

“…Titanosilicates are highly active and environmentally friendly catalysts used in a series of industrially important organic oxidation reactions using peroxide as an oxidant, such as the epoxidation of linear alkenes ,,− and cyclic olefins, ,− the oxidative desulfurization, ,− ,− the hydroxylation of phenol, ,,,− and the ammoxidation of cyclohexanone. ,− ,− The most common titanosilicate zeolites are titanium Silicalite-1 (TS-1). , However, they are limited in catalytic oxidation reactions of the substrates with relatively small molecular sizes due to the medium pores of the 10-membered ring (about 0.5–0.6 nm pore diameter). The relatively narrow micropores in the TS-1 zeolite limit the diffusion of reactants and products.…”