Combining catalysis and computational fluid dynamics towards improved process design for ethanol dehydration

Abstract

Combining computational fluid dynamics with catalysis gives significant insights into reactor design for sustainable solid acid catalysed processes.

Designing Multi-Dopant Species in Microporous Architectures to Probe Reaction Pathways in Solid-Acid Catalysis

“…To investigate the crystallinity of the system scanning electron microscopy (SEM) was used to explore the particle morphology, showing smooth cubic crystals of around 1-2 µm in length (Figure 2). Again this is in good agreement with previous observations (Potter et al, , 2018a. ICP analysis (Table S3) shows similar levels of Al, P and Si in the MgSiAlPO-34 and SiAlPO-34 catalysts, as variations are within experimental error.…”

“…• C, however similar systems are hampered by the formation of longer-chain by-products, leading to coking (Phung et al, 2015;Li X. et al, 2018). In our previous work with SAPO-34 we did not see any products aside from diethyl ether and ethylene, suggesting that the smaller pore may play a significant role in ethylene formation (Potter et al, , 2018a. The benefits of smaller pores have been investigated by others, comparing RHO and MFI zeolites, where the smaller pore of RHO lead to superior ethylene selectivity, alongside a higher quantity of medium-strong acid sites (Masih et al, 2019).…”

“…This led to the synthesis of a novel Mg 2+ Si 4+ AlPO-5 catalyst, which outperformed the analogous mono-dopant Mg 2+ AlPO-5 and Si 4+ AlPO-5 for the both alkylation of benzene, and the Beckmann rearrangement of cyclohexanone oxime, despite the reactions requiring differing acid strengths Gianotti et al, 2014). The findings from this study were instrumental in the predictive design of solid catalysts for the acid catalyzed dehydration of ethanol (Potter et al, , 2018a, where we have shown that SiAlPO-34 is a promising catalyst for converting ethanol to ethylene at low (<250 • C) temperatures. This is partially attributed to the isolated silicon sites creating effective acid centers, but also the constricting micropores of , that promote the formation of ethylene over the larger diethyl ether intermediate.…”

“…In our previous work (Potter et al, , 2018a we have developed synthesis methods to create a phase-pure crystalline SiAlPO-34 catalysts, utilizing tetraethylammonium hydroxide as the structure directing (templating) agent. To synthesize MgSiAlPO-34 we modified this protocol to incorporate a small fraction of magnesium (molar ratio Mg:Si = 1:15), with the aim of limiting extra-framework Mg, promoting isomorphous substitution.…”

“…We therefore intend to see the influence of incorporating small quantities of Mg 2+ ions into the framework of SiAlPO-34, using a unique synthesis procedure, to promote isomorphous substitution of Mg 2+ and Si 4+ ions, as single-site entities. In line with our previous work, we have carried out in-depth kinetic analysis of solid acid catalyzed dehydration of ethanol to ethylene, as a function of time and temperature, to directly probe the effect of adding magnesium to the framework (Potter et al, 2018a). We will then use these findings as an input for the experimentally defined CFD simulations, to explore local variations in the chemical concentrations across the catalyst bed, with the intention of simultaneously optimizing catalyst and reactor design (Potter et al, 2018a).…”