Influence of Impurities in a Methanol Solvent on the Epoxidation of Propylene with Hydrogen Peroxide over Titanium Silicalite-1

Gang Wang,Chao Zhang,Yue Li,Hongchen Guo,Gang Li,Quanren Zhu

doi:10.3390/catal10010015

Gang Wang, Chao Zhang + Show 4 more

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https://doi.org/10.3390/catal10010015

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Abstract

The recycled methanol solvent of the HPPO (liquid-phase epoxidation of propylene and hydrogen peroxide to propylene oxide) process usually contains many kinds of trace impurities, such as fusel alcohol, aldehyde, ketone, ester, acetal, and amine. In this study, the influence of these impurities on the catalytic performance of titanium silicalite-1 (TS-1) in the liquid-phase epoxidation of propylene with H2O2 was investigated with a batch reactor and simulated methanol solvents. The results show that amine and acetone are the most hazardous impurities, as they could remarkably suppress the conversion of H2O2. Furthermore, competitive adsorption experiments and IR and UV-Raman spectroscopic studies indicate that the suppression effect of impurities on the catalytic activity of TS-1 can be attributed to the competitive adsorption of the impurities on the tetra-coordination framework Ti sites. With this funding, the suppression mechanism of different impurities in a methanol solvent on the catalytic activity of TS-1 in the liquid-phase epoxidation of propylene was discussed.

Highlights

Propylene oxide (PO) is a vital chemical intermediate, which is widely used for producing varieties of commercial and industrial products, such as polyether polyols, propylene glycol, and propylene glycol ethers [1]
The conversion of H2 O2 remained higher than 98% until 700 h in the fresh methanol solvent
The selectivity of PO was still lower than 97% when the time-on-stream was extended to 500 h in the case of using a recycled methanol solvent, whereas it was already higher than 98% after 264 h when fresh methanol was used

Summary

Introduction

Propylene oxide (PO) is a vital chemical intermediate, which is widely used for producing varieties of commercial and industrial products, such as polyether polyols, propylene glycol, and propylene glycol ethers [1]. The chlorohydrin methods have disadvantages, such as large volumes of waste solid, waste water, and harmful byproducts, resulting in a badly contaminated environment, while co-production processes produce huge amounts of co-products that depend on market demand [2]. To eliminate these problems, great efforts have been made to develop alternative technologies. Owing to its unique oxidation properties, TS-1 led to the HPPO (liquid-phase epoxidation of propylene and hydrogen peroxide to propylene oxide) process, which can produce PO at mild conditions with a titanium silicalite-1 (TS-1) catalyst, using H2 O2 as an oxidant and methanol as a solvent [3,11,17,18,19]

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