Catalytically active membranes for esterification:A review

Esterification is an important process in the food industry and can be carried out via homogeneous or heterogeneous catalysis.The homogeneous catalyst,despite providing high conversion,can cause corrosion in reactors,which is not observed with the use of heterogeneous catalysts.However,some of these catalysts require a high process temperature and may lose their catalytic activity with reuse.Thus,catalytic membranes have been proposed as a promising alternative.The combination of catalysis and separation in a single module provides greater conversion,reduction of excess reagents,compact industrial plant,making the process more efficient.Within this context,this work aims to present a literature review on the catalytic membrane for the synthesis of esters,improving the understanding of the production and development.This review examines the materials,catalysts used,and synthetic pathways.A comparison between the methods,as well as limitations and gaps in the literature,are highlighted.

Electrifying Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ) for focalized heating in oxygen transport membranes

Industry decarbonization requires the development of highly efficient and flexible technologies relying on renewable energy resources,especially biomass and solar/wind electricity.In the case of pure oxygen production,oxygen transport membranes(OTMs)appear as an alternative technology for the cryogenic distillation of air,the industrially-established process of producing oxygen.Moreover,OTMs could provide oxygen from different sources(air,water,CO_(2),etc.),and they are more flexible in adapting to current processes,producing oxygen at 700^(-1)000℃.Furthermore,OTMs can be integrated into catalytic membrane reactors,providing new pathways for different processes.The first part of this study was focused on electrification on a traditional OTM material(Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)),imposing different electric currents/voltages along a capillary membrane.Thanks to the emerging Joule effect,the membrane-surface temperature and the associated O_(2) permeation flux could be adjusted.Here,the OTM is electrically and locally heated and reaches 900℃on the surface,whereas the surrounding of the membrane was maintained at 650℃.The O_(2)permeation flux reached for the electrified membranes was~3.7 NmL min^(-1)cm^(-2),corresponding to the flux obtained with an OTM non-electrified at 900℃.The influence of depositing a porous Ce_(0.8)Tb_(0.2)O_(2-δ) catalytic/protective layer on the outer membrane surface revealed that lower surface temperatures(830℃)were detected at the same imposed electric power.Finally,the electrification concept was demonstrated in a catalytic membrane reactor(CMR)where the oxidative dehydrogenation of ethane(ODHE)was carried out.ODHE reaction is very sensitive to temperature,and here,we demonstrate an improvement of the ethylene yield by reaching moderate temperatures in the reaction chamber while the O_(2) injection into the reaction can be easily fine-tuned.

Reduction of nitrate from groundwater:powder catalysts and catalytic membrane

The reduction of nitrate contaminant in groundwater has gained renewed and intensive attention due to the environmental problems and health risks. Catalytic denetrification presents one of the most promising approaches for the removal of nitrate from water. Catalytic nitrate reduction from water by powder catalysts and catalytic membrane in a batch reactor was studied. And the effects of the initial concentration, the amounts of catalyst, and the flux H 2 on the nitrate reduction were also discussed. The results demonstrated that nitrate reduction activity and the selectivity to nitrogen gas were mainly controlled by diffusion limitations and the mass transfer of the reactants. The selectivity can improved while retaining a high catalytic activity under controlled diffusion condition or the intensification of the mass transfer, and a good reaction condition. The total nitrogen removal efficiency reached above 80%. Moreover, catalytic membrane can create a high effective gas/liquid/solid interface, and show a good selectivity to nitrogen in comparative with the powder catalyst, the selectivity to nitrogen was improved from 73 4% to 89 4%.

A bifunctional MnO_x@PTFE catalytic membrane for efficient low temperature NO_x-SCR and dust removal

Low-temperature selective catalytic reduction of NOx combined with dust removal technique due to its energy conservation characteristic has been attracted much attention for fume purification.In this work,the MnOx wrapped PTFE membrane with efficient dust removal and low-temperature NH3-SCR has been prepared with a facile route.MnOxwith different crystal structures was uniformly grown around the PTFE fibrils through water bath.The flower-sphere-like MnOx@PTFE(O-MnOx@PTFE)and lamellar-interlaced ripple-like MnOx@PTFE(W-MnOx@PTFE)have large specific surface area which is favorable for enhancing catalytic performance.Also,the uniformly wrapped W-MnOxaround the PTFE fibrils optimized the pore structure for ultrafine dust capture.The membrane can almost 100%reject particles that are smaller than 1.0μm with a low filtration resistance.Meanwhile,W-MnOx@PTFE with more surface chemisorbed oxygen has the best NO conversion efficiency of 100%at a comparatively low and wide activity temperature window of 160–210°C,which is far to the thermal limitation of the PTFE.Therefore,this efficient and energy conserving membrane has a bright application prospects for tail gas treatment compared to the original treatment process.

MOF-Like 3D Graphene-Based Catalytic Membrane Fabricated by One-Step Laser Scribing for Robust Water Purification and Green Energy Production

Increasing both clean water and green energy demands for survival and development are the grand challenges of our age.Here,we successfully fabricate a novel multifunctional 3D graphene-based catalytic membrane(3D-GCM)with active metal nanoparticles(AMNs)loading for simultaneously obtaining the water purification and clean energy generation,via a“green”one-step laser scribing technology.The as-prepared 3D-GCM shows high porosity and uniform distribution with AMNs,which exhibits high permeated fluxes(over 100 L m^(−2) h^(−1))and versatile super-adsorption capacities for the removal of tricky organic pollutants from wastewater under ultra-low pressure-driving(0.1 bar).After adsorption saturating,the AMNs in 3D-GCM actuates the advanced oxidization process to self-clean the fouled membrane via the catalysis,and restores the adsorption capacity well for the next time membrane separation.Most importantly,the 3D-GCM with the welding of laser scribing overcomes the lateral shear force damaging during the long-term separation.Moreover,the 3D-GCM could emit plentiful of hot electrons from AMNs under light irradiation,realizing the membrane catalytic hydrolysis reactions for hydrogen energy generation.This“green”precision manufacturing with laser scribing technology provides a feasible technology to fabricate high-efficient and robust 3D-GCM microreactor in the tricky wastewater purification and sustainable clean energy production as well.

Heterogeneous Photooxidation of Phenol by Catalytic Membranes

In this work the heterogenization in polymeric membranes of decatungstate,a photocatalyst for oxidation reactions,was reported.Solid state characterization techniques confirmed that the catalyst structure was preserved within the polymeric membranes.The catalytic membranes were successfully applied in the aerobic photo-oxidation of phenol,one of the main organic pollutants in wastewater,providing stable and recyclable photocatalytic systems.The dependence of the phenol degradation rate by the catalyst loading and transmembrane pressure was shown.By comparison with homogeneous reaction,the catalyst heterogenized in membrane appears to be more efficient concerning the rate of phenol photodegradation and mineralization.

A Kinetic Approach to Photomineralization of Methane in Air by Membranes Based on TiO2/WO3

Photomineralization of methane in air(10.0-1,000 ppm(mass/volume)of C)at 100%relative humidity(dioxygen as oxygen donor),was systematically studied at 318±3 K,in an annular laboratory-scale reactor,by photocatalytic membranes immobilising titanium dioxide and tungsten trioxide as co-photocatalysts.Kinetics of both substrate disappearance,to yield intermediates,and total organic carbon(TOC)disappearance,to yield carbon dioxide,were followed.A kinetic model was employed,from which,by a set of differential equations,four final optimised parameters,k1 and K1,k2 and K2,were calculated,able to fit the whole kinetic profile adequately.Modelling of quantum yields,as a function of substrate concentration and irradiance,as well as of concentration of photocatalysts,was carried out very satisfactorily.Kinetics of hydroxyl radicals reacting between themselves,leading to hydrogen peroxide,other than with substrate or intermediates leading to mineralization,were considered,paralleled by second competition kinetics involving superoxide radical anion.When using appropriate blends of the two photocatalysts,limiting quantum yieldsF∞values increase considerably and approach the maximum allowable value for the investigated molecule,in a much wider range of irradiances than that shown by the single catalysts mainly at low irradiances.This may be interpreted by strong competition kinetics of superoxide radicals generated by the catalyst defects,in the corresponding range of high irradiances.By this way,operation at high irradiance values is possible,without losing any efficiency for the mineralization process.

Interlayer-confined two-dimensional manganese oxide-carbon nanotube catalytic ozonation membrane for efficient water purification

Catalytic ozonation technology has attracted copious attention in water purification owing to its favorable oxidative degradation of pollutants and mitigation of membrane fouling capacity.However,its extensive industrial application has been restricted by the low ozone utilization and limited mass transfer of the short-lived radical species.Interlayer space-confined catalysis has been theoretically proven to be a viable strategy for achieving high catalytic efficiency.Here,a two-dimensional MnO_(2)-incorporated ceramic membrane with tunable interspacing,which was obtained via the intercalation of a carbon nanotube,was designed as a catalytic ozonation membrane reactor for degrading methylene blue.Benefiting from the abundant catalytic active sites on the surface of two-dimensional MnO_(2) as well as the ultralow mass transfer resistance of fluids due to the nanolayer confinement,an excellent mineralization effect,i.e.,1.2 mg O_(3)(aq)mg^(-1) TOC removal(a total organic carbon removal rate of 71.5%),was achieved within a hydraulic retention time of 0.045 s of pollutant degradation.Further,the effects of hydraulic retention time and interlayer spacing on methylene blue removal were investigated.Moreover,the mechanism of the catalytic ozonation employing catalytic ozonation membrane was proposed based on the contribution of the Mn(III/IV)redox pair to electron transfer to generate the reactive oxygen species.This innovative twodimensional confinement catalytic ozonation membrane could act as a nanoreactor and separator to efficiently oxidize organic pollutants and enhance the control of membrane fouling during water purification.

Highly active iridium catalyst for hydrogen production from formic acid

Formic acid（FA） dehydrogenation has attracted a lot of attentions since it is a convenient method for H_2 production. In this work, we designed a self-supporting fuel cell system, in which H_2 from FA is supplied into the fuel cell, and the exhaust heat from the fuel cell supported the FA dehydrogenation. In order to realize the system, we synthesized a highly active and selective homogeneous catalyst Ir Cp＊Cl_2 bpym for FA dehydrogenation. The turnover frequency（TOF） of the catalyst for FA dehydrogenation is as high as7150 h^（-1）at 50°C, and is up to 144,000 h^（-1）at 90°C. The catalyst also shows excellent catalytic stability for FA dehydrogenation after several cycles of test. The conversion ratio of FA can achieve 93.2%, and no carbon monoxide is detected in the evolved gas. Therefore, the evolved gas could be applied in the proton exchange membrane fuel cell（PEMFC） directly. This is a potential technology for hydrogen storage and generation. The power density of the PEMFC driven by the evolved gas could approximate to that using pure hydrogen.