Selective synthesis of propylene oxide through liquid-phase epoxidation of propylene with H2O2 over formed Ti-MWW catalyst

Recent Advances in Greener and Energy Efficient Alkene Epoxidation Processes

The chemical industry is considered to be one of the largest consumers of energy in the manufacturing sector. As the cost of energy is rising rapidly, coupled with the increasingly stringent standards for the release of harmful chemicals and gases into the environment, more attention is now focused on developing energy efficient chemical processes that could significantly reduce both operational costs and greenhouse gas emissions. Alkene epoxidation is an important chemical process as the resultant epoxides are highly reactive compounds that are used as platform chemicals for the production of commercially important products for flavours, fragrances, paints and pharmaceuticals. A number of epoxidation methods have been developed over the past decade with the ultimate aim of minimising waste generation and energy consumption. In this review paper, some of the recent advances in epoxides synthesis using energy efficient processes are discussed. The epoxidation methods may provide sustainability in terms of environmental impact and energy consumption.

Clean Synthesis of Ti-MWW by Utilizing the Recycled Mother Liquor

This article introduces a clean and efficient method for the synthesis of Ti-MWW by utilizing the recycled mother liquor. The effects of titanium and silicon sources on the synthesis of Ti-MWW and the recycling of the mother liquor are discussed in detail. Precipitated silica prepared with Na₂SiO₃ and CO₂ was selected as the silicon source, and TiCl₃ was selected as the titanium source. The mother liquor was recycled five times, and the obtained samples showed good catalytic activity in cyclohexanone ammoximation. This work can be conducive to reducing the influence on the environment and economizing on materials for the industrial production of Ti-MWW.

Improved Catalytic Propylene Epoxidation for Extruded Micrometer TS-1: Introducing Mesopores and Macropores Insides the Crystals

In the paper, mesopores and macropores are introduced inside the crystals of micrometer microporous titanium silicate-1 (TS-1) to solve the problem of active site coverage and mass transfer during extrusion. Hierarchically porous titanium silicalite-1 (HPTS-1) was acquired by treating micrometer microporous TS-1 with TPABr and ethanolamine. Extruded HPTS-1 maintained greatly superior catalytic performance and possessed high mechanical strength. Characterization results showed that extruded HPTS-1 possessed macroporous, mesoporous structure inside the crystals. These abundant pores are not only beneficial for diffusion reactants, but also make Ti-peroxo species (η2), active oxidation sites in TS-1/H2O2 system become much more reactive. The formula of extruded HPTS-1 was optimized using an orthogonal experiment. The maximum strength of extruded HPTS-1 was up to 200 N/cm, the highest yield of propylene oxide was 92.5% and the specific rate was up to 41.9%. The research provides a scientific basis for producing extruded catalysts with excellent catalytic performance and high mechanical strength in industrial applications.

Al-Modified Ti-MOR as a robust catalyst for cyclohexanone ammoximation with enhanced anti-corrosion performance

The skeleton desilication accompanied by Ti active sites leaching accounts for the dominant chemical deactivation reasons in the alkali liquid-phase ammoximation, which could be retarded by creating a protective Al-rich shell.

Identification of key oxidative intermediates and the function of chromium dopants in PKU-8: catalytic dehydrogenation of sec-alcohols with tert-butylhydroperoxide

t-BuOO* activated by Cr-PKU-8 from TBHP is the key intermediate to the highly selective dehydrogenation of sec-alcohols.

Selective synthesis of epichlorohydrin via liquid-phase allyl chloride epoxidation over a modified Ti-MWW zeolite in a continuous slurry bed reactor

The epoxidation of allyl chloride (ALC) to epichlorohydrin (ECH) with H₂O₂ using a piperidine (PI)-modified Ti-MWW catalyst (Ti-MWW-PI) in a continuous slurry reactor was investigated to develop an efficient reaction system for the corresponding industrial process.

Highly stable TS-1 extrudates for 1-butene epoxidation through improving the heat conductivity

The stability of TS-1 extrudates in 1-butene epoxidation was significantly improved by introducing different substances with high heat conductive rates.

Highly selective 1-pentene epoxidation over Ti-MWW with modified microenvironment of Ti active sites

The hexa-coordinated Ti active sites with the piperidine molecules as ligand significantly accelerate H₂O₂ activation, which effectively improve the catalytic performance of Ti-MWW in the 1-pentene epoxidation reaction.

Hydrothermal synthesis of Sn-Beta zeolites in F−-free medium

Sn-Beta zeolites, with high Sn content and smaller crystal size, hydrothermally synthesized in F⁻-free medium using N-cyclohexyl-N,N-dimethylcyclohexanaminium hydroxide as the structure-directing agent with the assistance of Na⁺ and seed, are highly active as Lewis acid catalysts.

Synthesis of two titanosilicates with distinct interlayer connections from similar gels

Ti-SSZ-70 and Ti-ECNU-6, with identical intralayer structures but distinct interlayer connections, were prepared from similar synthetic gels free of alkali metal ions and boric acid. Ti-SSZ-70, composed of vertically misaligned MWW layers, was transferred to Ti-ECNU-6, structurally analogous to the Ti-MWW zeolite with a well-aligned layer stacking, upon the addition of an appropriate amount of hexamethyleneimine to the gel. These two titanosilicate catalysts exhibited outstanding catalytic activities in the liquid-phase alkene epoxidation.

Enhancing ethylene epoxidation of a MWW-type titanosilicate/H2O2 catalytic system by fluorine implanting

SiO_3/2F units in the framework of Ti-MWW generate stronger hydrogen-bonding between Hend in Ti–O^α–O^β–H^end intermediates and the adjacent Si–F species, which effectively improves the catalytic performance of Ti-MWW for the liquid-phase epoxidation of ethylene.

Epoxidation of 1-octene under harsh tail-end conditions in a flow reactor I: a comparative study of crystalline vs. amorphous catalysts

The crystalline Ti-UCB-4 epoxidation catalyst is more active, selective, and stable than the amorphous Ti–SiO₂.