Comparison of Gas–Liquid–Liquid–Solid Four-Phase Trickle-Bed Reactor with Upflow Reactor under High Liquid Flow Rate

Abstract

The hydrogenation of carbobenzoxy phenylalanine was investigated in order to better understand the influence of mass transfer effects in four-phase fixed-bed reactor systems. In this reaction, the carbobenzoxy phenylalanine is dissolved in an organic solvent and is reacted with a gas in the presence of a hydrophilic catalyst (Pd/Al2O3). An aqueous phase is also required to dissolve the reaction product, leading to a four-phase gas–liquid–liquid–solid system. Results indicate that higher liquid flow rates lead to faster rates of reaction due to improved contact efficiency between the organic phase and catalyst. Similar performance was observed through experiment and modeling in two fixed-bed reactor configurations (trickle-bed reactor and gas–liquid cocurrent upflow reactor) at higher liquid flow rates.

Continuous Hydrogenation of Cinnamaldehyde: Gas–Liquid–Liquid–Solid Helical Coil Reactor

“…In some cases, the difference in the solubility of the desired product in two liquid phases can lead to increased selectivity of the desired product. For instance, in the case of benzene to cyclohexene hydrogenation, the desired partial hydrogenated product is separated from the reactive liquid phase by virtue of its solubility difference in the two liquid phases, and further hydrogenation is inhibited, also reducing the mass transfer of reactants to catalyst surface after addition of the fourth phase, playing a major role in promotion. − For hydrogenation of carbobenzoxy phenylalanine, the product phenylalanine is strongly adsorbed on the catalyst surface which reduces the catalytic activity, it can be separated effectively in GLLS by adding an aqueous phase . A similar mechanism can be beneficial in the case of hydrogenation of aniline to cyclohexylamine in GLLS, while in situ rearrangements of the intermediate hydrogenation product, because of the presence of aqueous acid (as the fourth phase), leads to the formation of p -aminophenol as the major product for hydrogenation of nitrobenzene. − In the case of hydrogenation of unsaturated aldehydes to alcohols, for instance, cinnamaldehyde to cinnamyl alcohol, the selectivity of cinnamyl alcohol is increased by the presence of alkaline aqueous phase .…”

“…10−13 For hydrogenation of carbobenzoxy phenylalanine, the product phenylalanine is strongly adsorbed on the catalyst surface which reduces the catalytic activity, it can be separated effectively in GLLS by adding an aqueous phase. 14 A similar mechanism can be beneficial in the case of hydrogenation of aniline to cyclohexylamine in GLLS, 15 while in situ rearrangements of the intermediate hydrogenation product, because of the presence of aqueous acid (as the fourth phase), leads to the formation of p-aminophenol as the major product for hydrogenation of nitrobenzene. 16−18 In the case of hydrogenation of unsaturated aldehydes to alcohols, for instance, cinnamaldehyde to cinnamyl alcohol, the selectivity of cinnamyl alcohol is increased by the presence of alkaline aqueous phase.…”

Hydrodynamic analysis of gas‐liquid‐liquid‐solid reactors using the XDEM numerical approach

“…Many attempts have been devoted to studying the three‐phase reactors, while four‐phase reactors such as gas‐liquid‐liquid‐solid have received fewer investigations. Some examples of this kind of multiphase systems are the multiphase catalytic reactions in agrochemicals, pharmaceuticals, and polymers,,] and the flow of gas, slag, and molten iron through a pile of coke particles in the dripping zone of a blast furnace …”