Ethylene epoxidation over supported silver catalysts – influence of catalyst pretreatment on conversion and selectivity

Abstract

BACKGROUND Ethylene oxide is a key intermediate in the chemical industry. It is produced through catalytic epoxidation of ethylene. Significant economic benefits can be achieved by small improvements in catalyst activity and selectivity. The aim of this work was to study how different preparation methods and pretreatments affect the catalyst performance under industrially relevant reaction conditions. The influence of pretreatment strategy on the selectivity and reaction temperature was for the first time investigated at a constant ethylene conversion of 7%. RESULTS Epoxidation of ethylene to ethylene oxide was studied over a range of silver catalysts which were prepared with different thermal treatments. The influence of catalyst preparation method and catalyst pretreatment strategy on the catalytic performance was investigated. It was found that calcination resulted in lower ethylene conversion compared with pre‐drying. In the latter case an induction period was observed, absent for the calcined catalyst. This induction period can be eliminated by oxidative or reductive pretreatment of the catalyst. CONCLUSIONS The most promising pretreatment strategy was carried out by first treating the catalyst with 1 ppm of DCE for 5 h at 230 °C followed by overnight pre‐treatment in 20% ethylene at 250 °C. With this pretreatment it was possible to achieve a target ethylene conversion of 7% at 232.6 °C with a selectivity to ethylene oxide of 82.1%. © 2018 Society of Chemical Industry

Kinetics of the Ag/KNO3/CaCO3 Catalyzed Aerobic Propylene Epoxidation and Effects of CO2

“…[62] Other reports in the literature have examined the pretreatment of Ag catalysts using CO 2 resulting in shorter induction periods or higher initial selectivity of the catalyst. [63] Based on the findings herein along with prior literature reports, we postulate that a similar phenomenon is occurring in the system reported herein for propylene epoxidation.…”

Influence of the specific surface area and silver crystallite size of mesoporous Ag/SrTiO3 on the selectivity enhancement of ethylene oxide production

“…The ethylene pretreatment was carried out in order to remove oxygen adsorbed on the catalyst surface . Aho et al ., however, have recently reported that the most promising thermal pretreatment for ethylene epoxidation was first treating the catalyst with 1 ppm of dichloroethane (DCE) followed by overnight pre‐treatment in 20 vol% ethylene. Nevertheless, all the experiments of the presents study were carried out with the same pretreatment method and confident comparisons between different catalysts performances are still possible.…”

Synthesis of Silver Nanocomposites for Stereolithography: In Situ Formation of Nanoparticles

“…In particular, the optical properties of Ag NPs have been historically exploited in decorative pigments for jewellery/handicrafts, staining glass, or ceramics [ 26 , 27 , 28 , 29 ]. Over the last decades, Ag NPs have found use in many areas, such as catalysis [ 30 , 31 ], optical and electro-optical devices [ 23 , 32 ], surface-enhanced Raman spectroscopy (SERS) [ 33 , 34 ], and antimicrobial agents [ 14 , 35 ]. Ag NPs are promising nanofillers to obtain composites with electrical and optical properties to extend the applicability of SLA including the electronic or biomedical fields [ 13 , 14 , 36 , 37 , 38 , 39 ].…”