Hydrogen Production and Organic Synthesis in Photocatalytic Membrane Reactors: A Review

Abstract

Photocatalytic Membrane Reactors (PMRs) are green and promising technologies for sustainable applications. The recent scientific literature on PMRs is reviewed with a particular focus on the photocatalytic hydrogen production from water splitting, CO2 conversion to solar fuels (CH3OH, C2H5OH, CH4 and HCOOH) and organic synthesis such as oxidation (benzene to phenol, cyclohexane to cyclohexanol, ferulic acid to vanillin) and reduction reactions (acetophenone to phenylethanol). Different types of PMRs, synthesis of various photocatalytic membranes and modification of some semiconductors, to improve selectivity and yield also under visible light, are discussed. The described results show that combination of photocatalysis and a membrane process to build PMRs is a promising approach in view of large-scale application and use of solar energy.

Valorization of refinery flue gas through tri‐reforming and direct hydrogenation routes

“…The ethanol production process follows a similar scheme as that of the MET production process except for additional distillation columns required for the separation of the product. In the flowsheet (Figure 2C), the reactor named ethanol synthesis reactor (ETOH-RX) utilizes the plug flow reactor (RPLUG) module and operates at 300 C and 50 atm, [34] where reactions occur as per Equations ( 17)- (19). To model these reactions, the Langmuir-Hinshelwood (LH) kinetics have been utilized, and the kinetic equations have been considered based on the LH kinetic model developed by Gunturu et al [34] The product from the reactor has been subjected to cooling at À15 C and then flashed in separator FD-2.…”

“…Direct hydrogenation is a promising technology for transforming CO 2 into valuable chemicals [7,8] as it is a one-step process that can operate at moderate temperatures and pressures, resulting in a lower energy demand than traditional carbon capture and utilization methods. [16,17] A detailed feasibility study and parametric analysis on CO 2 hydrogenation via various catalysts has been presented by García-Hurtado et al, [18] Pietro et al, [19] Marcos et al, [20] and Frei et al [21] In this analysis, the hydrogen stream required in the hydrogenation process has been produced via an electrolysis unit powered by renewable energy, such as wind electricity. [7,8] The two approaches mentioned above have been evaluated based on their performance related to economic parameters and CO 2 valorization via defining suitable performance metrics: gross margin and percentage of CO 2 valorized, respectively.…”

Hydrogen Production as a Clean Energy Carrier through Heterojunction Semiconductors for Environmental Remediation

“…Photocatalytic processes have the potential to develop renewable and eco-friendly energy carriers such as H 2 and O 2 by water splitting [12,13]; they can also degrade various organic pollutants [14][15][16][17][18], convert energy conversion, be used in material storage by photocatalytic CO 2 reduction [19][20][21], synthesize organic substances [14,22,23], and even reduce iron ore with hydrogen [24]. In this regard, both energy issues and environmental pollution treatment can be economically solved by semiconductor-mediated photocatalysis procedures, and hydrogen, as an ideal green fuel, can be produced through the photocatalytic reduction of protons by the photoinduced electrons; hence, toxic organic pollutants can be degraded by utilization of multi-step photocatalytic oxidation reactions [25].…”