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

Abstract

Background Ethylene oxide, which is industrially produced by ethylene epoxidation, is an important versatile chemical intermediate, thus its selectivity enhancement can bring substantial economic profits. In this work, the effects of two important, but still debatable, factors, i.e. catalyst specific surface area and active phase crystallite size, on the catalyst selectivity enhancement were investigated. Surfactant assisted sol–gel method with good control ability on the pores structure was selected to produce mesoporous strontium titanate (SrTiO3) nanocrystals with various specific surface area. The SrTiO3 nanocrystals were used as the supports of silver (Ag) for ethylene epoxidation. Results The Ag/SrTiO3 catalysts with various surface areas were obtained by changing the surfactant‐alkoxide ratio and the calcination time. The ethylene oxide selectivity of the prepared catalysts was examined in a laboratory‐scale fixed bed reactor. The best performance was observed at the lowest surfactant–alkoxide ratio of 0.2 and calcination time of 4 h, with the surface area of 1.7 m2/g and Ag crystallite size of 15 nm. Conclusion The best catalyst selectivity was observed at the lowest surface area and the highest average Ag crystallite size. In this condition, the selectivity of the Ag/SrTiO3 catalyst without any modifier was superior to a commercial Ag/Al2O3 catalyst with 3.7m2/g surface area and alkaline earth metal modifiers. © 2019 Society of Chemical Industry

Tailoring morphology of hierarchical catalysts for tuning pore diffusion behaviour: a rational guideline exploiting bench-top pulsed-field gradient (PFG) nuclear magnetic resonance (NMR)

“…7-13 nm) 6,7 are required to allow diffusion and access of larger molecules to the catalyst active sites. Conversely, certain highly selective processes such as the partial epoxidation of ethylene to ethylene oxide 8,9 and the selective oxidation or selective hydrogenation of acetylene 10 require catalysts with large pores and low surface areas. This acts to limit the residence time of substrate on the catalyst, thereby boosting selectivity to the desired products by limiting further reactions on the catalyst surface.…”

Metal Titanate (ATiO3, A: Ni, Co, Mg, Zn) Nanorods for Toluene Photooxidation under LED Illumination

“…Metal titanates (ATiO 3 , where A: Ni, Co, Zn, Mn, Mg, Fe, Ca, Ba, Sr) have been extensively studied for photooxidation applications, due to their unique physical and chemical properties. According to the literature, ATiO 3 has been prepared by various methods such as sonochemical method [12][13][14][15], precipitation method [16], sol-gel method [17][18][19], wet chemical method [20], auto-ignited combustion method [21], through conventional solid-state reaction route [22], and through hydrothermal method [23,24]. However, polyol process [25,26]-that is followed in our work-offers a low-cost and simple way of fabricating metal titanates.…”