Abstract
Ethylene epoxidation with hydrogen peroxide was studied in a laboratory-scale trickle bed reactor under a broad range of experimental conditions (15–80 °C, 2.5–8.5 bar) utilizing a commercial titanium-silicate catalyst (TS-1). The catalyst was very stable and selective over 150 h time-on-stream. The main reaction product was ethylene oxide, while 2-methoxyethanol and ethylene glycol were observed as kinetic byproducts. In most of the experiments, ethylene glycol was not detected at all. An increase in temperature and pressure affected negatively the ethylene oxide selectivity, while an increase in the hydrogen peroxide concentration improved both the ethylene oxide selectivity and ethylene conversion. Ethylene epoxidation was comparable with propylene epoxidation, displaying, however, important differences in activity and selectivity, which were attributed to the partial pressures studied in the present work. It was demonstrated that TS-1 is a very selective and active catalyst for the selective epoxidation of ethylene with hydrogen peroxide.
Highlights
Ethylene oxide is an important compound used as a key intermediate for the production of many chemicals including ethylene glycol and ethoxylates.[1]
The scientific literature on propylene epoxidation is extensive, covering in detail several aspects, such as reaction conditions, catalyst modifications, and reactor technology.[3−14] even if the propylene epoxidation over TS-1 has been successfully implemented in the industrial scale,[15] the open literature devoted to the epoxidation of ethylene with hydrogen peroxide on the TS-1 catalyst is limited
Most of the previous studies were carried out in batch reactors only.[16−18] The epoxidation of ethylene over the TS-1 catalyst at 0.2 MPa and 40 °C in methanol has displayed a product yield of 13% and an ethylene oxide selectivity of 15.5% after 2 h, while the propylene epoxidation under similar conditions has exhibited an 89.3% product yield and 82.8% propylene oxide selectivity.[16]. These results suggest that ethylene epoxidation on TS-1 is much more challenging than propylene epoxidation
Summary
Ethylene oxide is an important compound used as a key intermediate for the production of many chemicals including ethylene glycol and ethoxylates.[1] The global production volume of ethylene oxide is about 30 million metric tons per year.[1] The production of ethylene oxide is a well-stablished gas-phase process where heterogeneous silver catalysts are applied.[1,2] A very high selectivity of ca. 90% of ethylene oxide is achieved only at low conversion levels, calling for an improvement of the proven technology.[1,2]. These results suggest that ethylene epoxidation on TS-1 is much more challenging than propylene epoxidation
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