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• Several kinds of MOFs/GFM were prepared, including ZIF-8/GFM, PdZIF-8/GFM and FeBDC/GFM. • MOFs/GFM-based microreactor was fabricated, and the rough surface and porous structure of gfm were regarded as microchannels for liquid reactions. • Continuous catalysis was performed to evaluate the efficiency and lifetime of MOFs/GFM-based microreactors and they showed high efficiency and stability. Reactions within the confined spaces of a microreactor often yield higher conversion and better selectivity as a result of enhanced transport processes. Traditional microfluidic reactors often constrain the fluid flow within fabricated microchannels leading to a large pressure gradient. This work employs the network of interconnecting channels defined by the strands of glass fibers in a glass fiber membrane as conduits for fluid flow, with the glass fibers as support for the MOF catalysts. Thus, a microreactor with a low pressure drop was obtained despite the narrow width of the flow channels (< 100 µm). The large contact surface (i.e. , 200,000 m2/m3) is ideal for catalyst deposition and ZIF-8 for Knoevenagel condensation reaction, PdZIF-8 for selective hydrogenation reaction and FeBDC for acetalization reaction were successfully prepared. A new synthesis approach enables each strand of glass fibers to be completely cladded with an intergrown layer of MOF catalysts ensuring good adhesion and catalyst stability. Indeed, these MOF catalysts display higher yield and better stability compared to MOF catalyst powder in batch reactor and fixed-bed microreactor. [ABSTRACT FROM AUTHOR]

Abstract: A multichannel membrane microreactor for continuous selective oxidation of aniline by hydrogen peroxide on TS-1 nanoparticles was successfully demonstrated. The high surface area to volume ratio that can be attained in the microreactor (3000m2/m3) facilitates the selective removal of water by-product, which reduces the effect of catalyst deactivation during the reaction. An improvement in the product yield and selectivity towards azoxybenzene was also observed. Azobenzene was obtained as by-product and its formation was attributed to homogeneous reaction of nitrosobenzene with aniline. Increasing temperature was beneficial for both yield and selectivity, but beyond 340K, microreactor operation was ineffective due to bubble formation and hydrogen peroxide decomposition. [Copyright &y& Elsevier]

Abstract: Zeolites are increasingly used in fuel cell, from fuel conversion and conditioning to membrane additives as well as support for electrocatalysts. Zeolites’ ionic conductivity and capacity for water adsorption and retention were exploited to create zeolite and zeolite-PFSA proton conducting membranes for PEMFC. HZSM-5 micromembranes of different Si/Al ratios (from ∞ for Sil-1 to 30) were fabricated in a regular array on silicon followed by assembly and test for fuel cell performance. HZSM-5 with high aluminum content exhibits good proton conductivity and better PEMFC performance that approaches that of Nafion MEA. A rational approach in the design of structured HZSM-5-PFSA composite membrane was demonstrated. The PFSA was confined in subnanoliter volumes within zeolite sleeves to obtain self-humidifying membrane and enhanced PEMFC performance (i.e., up to nine-fold in MPD) at elevated temperatures (i.e., up to 100°C) and dry conditions. Higher water retention and improved membrane thermomechanical properties are believed to be responsible. [Copyright &y& Elsevier]

Abstract: Freestanding Sil-1 and ZSM-5 micromembranes of Si/Al ratios ranging from 14 to ∞ were fabricated on silicon. The zeolite synthesis was adjusted to obtain micromembranes of similar microstructures (i.e., thickness, orientation, crystal grain size, morphology and intergrowth) and prepared membranes display comparable helium gas permeance. The low temperature removal of the organic TPA+ molecules by ozone enabled the preparation of low defect zeolite micromembranes that exhibit superb H2/nC4 (i.e., ≥100) and nC4/iC4 (i.e., ≥30) permselectivity ratios. The effects of aluminum content of the ZSM-5 micromembranes were investigated for single, binary and ternary gas permeation. Surface diffusion is important at low temperature and the single gas permeances of hydrogen, argon, nitrogen and methane were larger than Knudsen. The deviation from Knudsen increased with the Si/Al ratio and was largest for Sil-1. Propane–nitrogen separation in the zeolite micromembranes is mainly molecular sieving and display weak dependence on the aluminum content of the zeolite, where the separation of the ternary H2–CH4–CO2 mixture is by preferential adsorption and shows strong dependence on the Si/Al ratio of the zeolite. [Copyright &y& Elsevier]

Silicon-glass microreactors with TS-1 catalyst wall coatings were fabricated and used for 1-pentene epoxidation with hydrogen peroxide in continuous flow. Seeding of the microchannels before zeolite growth was necessary to obtain a small crystal size and a sufficient zeolite film thickness. Crystal size was further reduced by adjusting synthesis conditions and utilizing triethoxymethylsilane (TEMS) as a crystal growth inhibitor. Zeolite film morphology and crystal orientation did not show any significant effect on reactor performance. However, reaction rate was found to increase with decreasing TS-1 crystal size in the zeolite films and with increasing amount of tetrahedrally coordinated Ti(IV). Catalyst deactivation was observed, caused by the presence of organic compounds and Ti leaching from the microporous framework. [Copyright &y& Elsevier]

A ZIF-8/NaA composite membrane microreactor was fabricated on multi-channel stainless steel plate. NaA zeolite membrane was first introduced into the microchannel as a modification layer via a secondary growth. Subsequently, a layer of ZIF-8 membrane was grown over the NaA zeolite layer as a catalytic layer by using ZnO-induced synthesis method. Such ZIF-8/NaA composite membrane microreactor was applied in continuous flow Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate. Nearly 100% product yield was achieved in a short residence time under mild conditions. Importantly, no obvious deactivation was observed even after 50 h, indicating its excellent stability. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel Fe3O4@ZIF-8 core–shell microsphere is synthesized by a new facile method. [•] The microspheres are easily loaded/unloaded into/out a capillary microreactor. [•] The microreactor filled with the Fe3O4@ZIF-8 catalyst shows excellent performances. [Copyright &y& Elsevier]

Abstract: A catalytic layer of CsNaX zeolite film was deposited on quartz capillary tube by flow synthesis method under hydrothermal conditions. The procedure involved seeding of the capillary tube with zeolite nanocrystals followed by controlled zeolite regrowth and crystallization under flow conditions. The CsNaX capillary microreactor was employed in Knoevenagel condensation reaction of benzaldehyde and ethyl cyanoacetate. The sensitivity of the catalyst to water produced by the condensation reaction was remedied with the use of solvents. Ninety nine percent benzaldehyde conversions were obtained using a traditional solvent DMSO, but decreased with time as water accumulates and poisons the catalyst. Replacing the solvent with an ionic liquid (IL-BMIC) improves water absorption and the catalyst displayed better (i.e., >99%) and stable conversions. [Copyright &y& Elsevier]

The performance of a membrane microreactor was tested and compared with that of a microreactor, a packed bed reactor (PBR) and a packed bed membrane reactor (PBMR) for the Knoevenagel condensation reaction of benzaldehyde and ethyl cyanoacetate to produce ethyl 2-cyano-3-phenylacrylate. Cs-exchanged NaX faujasite zeolite was used as the base catalyst for this equilibrium-limited reaction. Hydrophilic ZSM-5 membranes were employed in both the membrane microreactor and the PBMR for the selective removal of water byproduct from the reaction. The product yield per pass was low for the packed bed reactor. Higher yields were observed for the microreactor and PBMR, but the best performance belongs to the membrane microreactor, which displayed both supra-equilibrium conversion and better product purity. [Copyright &y& Elsevier]

Using a new fabrication method based on microelectronic fabrication and zeolite thin film technologies, MFI-type zeolites with engineered structures were incorporated as catalyst, membrane and structural material within the design architecture of a microreactor, membrane microseparator and microeletrochemical cell. Complex microchannel geometry and network (<5 μm), as well as zeolite arrays (<10 μm) were successfully fabricated onto highly orientated supported zeolite films. The zeolite micropatterns were stable even after repeated thermal cycling between 303 and 873 K for prolonged period of time. Blueprints for zeolite-based microchemical systems were presented, and test units were fabricated and the structural details of the microdevices’ architecture were analysed. [Copyright &y& Elsevier]