Hollow Titanium Silicalite Zeolite: From Fundamental Research to Commercial Application in Environmental-Friendly Catalytic Oxidation Processes

Abstract

The systematical investigation on the synthesis, characterization, formation mechanism, and catalytic application of hollow titanium silicalite (HTS) zeolite has been reviewed. HTS is prepared through a "dissolution-recrystallization" post-treatment in the presence of template under hydrothermal conditions. Compared with TS-1, HTS is of unique hollow voids and with high framework Ti content, which significantly increase the mass diffusion and the amount of active sites, respectively. Thus, HTS zeolite displays high catalytic activity and stability in many oxidation processes with H 2 O 2 oxidant, that is, cyclohexanone ammoximation, phenol hydroxylation, propylene epoxidation, Baeyer-Villiger oxidation of cyclohexanone, and selective oxidation of aromatics and cycloalkanes. The former three ones have been commercialized and run smoothly, which have promising economic and environmental significance.

On the key role of aluminium and other heteroatoms during interzeolite conversion synthesis

“…The synthesis and commercialization of stannosilicates ( e.g. TS-1, ([Ti]MFI)) 160 and silicoaluminophospates ( e.g. SAPO-34 (CHA)) 26 for selective oxidation catalysts and methanol to olefins (MTO) respectively, has expanded the field of zeolites to contain heteroatoms other than Al (zeotypes).…”

Environmental-Friendly Catalytic Oxidation Processes Based on Hierarchical Titanium Silicate Zeolites at SINOPEC

“…Up to now, HTS zeolite had been already commercially manufactured at SINOPEC, and successfully applied in many selective catalytic oxidation processes, i.e., cyclohexanone ammoximation, propylene epoxidation, and phenol hydroxylation, presenting desirable economic and social benefits via reducing cost and waste production. To the best of our best knowledge, HTS is the first and only hierarchical titanium-based zeolite applied in industry, and the detailed synthesis, characterization, and application have been summarized in our previous chapter [37].…”

Preparation of core–shell-like zeolites by diffusion controlled chemical etching

“…During the preparation of hierarchical zeolites, the persistence of crystal surface is commonly observed but often ignored [7][8][9][10][11] . This surface of zeolite crystals is characterized by the universal formation of a "crust" on the outermost layer, no matter the post synthesis treatment including desilication-biased caustic leaching [12][13][14][15][16] , dealumination-biased acidic treatment [7][8][9] , or Si and Al unbiased NH 4 F etching [11] .…”