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Three meso-SiO2 (RB-MSN, HMS, and MCM-41) supported Ni3P catalysts to be used in gas-phase hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG) are prepared via the impregnation method ...

Ethylene in principle can be obtained via oxidative coupling of methane (OCM), but it is urgently calling for a low-temperature active and selective catalyst. To accomplish this goal, the CexZr1-xO2 solid solutions with varied Ce/Zr molar ratio were modified with Mn2O3-Na2WO4 to fabricate OCM catalysts. The effects of Ce/Zr ratio and Mn2O3-Na2WO4 doping were investigated on the catalyst reactivity for the OCM, showing that the reaction light-off temperature, activity and selectivity are subject to the Ce/Zr molar ratio and Mn2O3-Na2WO4 doping. The promising catalyst with Ce/Zr molar ratio of 0.15/0.85 achieves 25% CH4 conversion with 67% selectivity to C2-C3 at 660 °C and is stable for at least 100 h. The catalysts were systematically studied by CH4-TPSR, O2-TPO/-TPD, CH4-pulse, in-situ FT-IR, EPR and XPS, showing that the Mn2O3-Na2WO4 doped Ce0.15Zr0.85O2 can generate more O2– species thereby leading to a markedly improved activity and selectivity at much lowered reaction temperature.

A series of Zn-incorporated nano-ZSM-5 zeolites were synthesized by a dry gel conversion (DGC) method using tetrapropylammonium hydroxide (TPAOH) as a single template, and their activity in methanol to aromatics (MTA) process was investigated. The characterization results revealed that the introduction of Zn species slightly decreased the crystal size with the formation of some agglomerated particles. We also demonstrated that new Lewis acid sites formed in Zn-incorporated nano-ZSM-5 zeolite at the expense of Bronsted acid sites. The amount of medium acid sites in Zn-modified samples increased with increasing of Zn contents. Catalytic evaluation results revealed that the selectivity of BTX and aromatics for the sample synthesized via direct synthesis (Zn-NZ5-3) is increased from 24.0% and 37.9% to 27.9% and 46.4%, respectively. In addition, the lifetime of the sample prepared by the direct synthesis (Zn-NZ5-3) was 33% longer than that of the impregnated sample, while the selectivity of BTX and aromatics was slightly higher.

The free-standing Ni-Al2O3 ensemble derived from NiAl-layered double hydroxides (NiAl-LDHs) grown onto a Ni-foam has been developed for the exothermic gas-phase acetone hydrogenation to isopropanol. This approach works effectively and efficiently to achieve a unique combination of high activity/selectivity and enhanced heat/mass transfer stemmed from the Ni-foam. The outstanding catalyst is obtained by direct reduction of the un-calcined NiAl-LDH/Ni-foam, with a high turnover frequency of 0.90 s-1, being capable of converting 90.8% acetone into isopropanol with almost 100% selectivity under stoichiometric H2/acetone molar ratio, atmospheric pressure at 80 °C, and a WHSVacetone of 10 h-1. The catalyst derivation using the un-calcined NiAl-LDH/Ni-foam enables the Ni nanoparticles to be intertwined with Al2O3 to form a large Ni-Al2O3 interface, without interruption of impurities such as irreducible NiO (in the case of calcined NiAl-LDH/Ni-foam samples), which markedly improves the strong acetone adsorption next to the Ni0 hydrogenation sites, thereby leading to a dramatic improvement of catalyst activity.

The efficient utilization of renewable biogas has attracted ever-increasing interest in the past few decades. Ni–Ce1−xZrxO2 supported on monolithic SiC-F (named Ni–Ce1−xZrxO2/SiC-F) is developed and applied in biogas reforming. Monolithic Ni–Ce1−xZrxO2/SiC-F catalysts were comprehensively characterized by ICP-AES, XRD, SEM, HR-TEM, CO2-TPD, etc. The promotional roles of Ce1−xZrxO2 in coke elimination as well as CO2 activation were deeply analyzed via in situ CH4-TPSR/CO2-TPO and in situ H2-TPR/CO2-TPSR. Ni–Ce1−xZrxO2/SiC-F exhibits satisfactory catalytic activity and ability to inhibit sintering and coke-deposition due to (a) the homogeneous dispersion of Ni nanoparticles (NPs) and (b) the strong interaction between Ce1−xZrxO2 solid solutions and Ni NPs. At 900 °C and a weight hourly space velocity (WHSV) of 24 000 mL gcat−1 h−1, an excellent CH4/CO2 conversion of 90/92% was initially achieved over the Ni–Ce1−xZrxO2/SiC-F catalyst, followed by a slight decrease after 150 h, but remained basically stable for the next 250 h.

Thin-felt ZSM-11/stainless-steel(SS)-fiber composites are successfully prepared via a combined washcoating and steam-assisted crystallization (SAC) method. Pre-aging of synthesis sol at a lower temperature of 80 °C can facilitate the zeolite nucleation and subsequent SAC growth at 180 °C. Such synthesis approach realizes the flexible tuning of acidity via adjusting SiO2/Al2O3 molar ratio in a wide range, including but not limited from 105 to 425. The as-synthesized ZSM-11/SS-fiber composites are employed as catalysts for the methanol-to-propylene reaction, and the promising thin-felt catalyst with SiO2/Al2O3 molar ratio of 200 shows remarkable stability improvement in comparison with its powdered counterpart, due to enhanced zeolite utilization efficiency and heat/mass transfer by the microfibrous-structured design.

Thin-sheet microfibrous-structured Pd–MgO–Al2O3/Al-fiber catalysts were developed for high-throughput catalytic methane combustion with 3–15 vol% water vapor in feed gas. The catalysts were obtained by hydrothermally growing Mg–Al mixed-oxide precursors (e.g., layered double hydroxides (LDHs) plus MgCO3) on Al-fiber surfaces followed by placing 0.5 wt% Pd on the as-obtained substrates by impregnation. Transformation of Pd/MgAl-LDH–MgCO3 mounted on the Al-fiber into Pd-MgO-Al2O3 via in situ reaction activation markedly enhances the catalyst basicity and electron density of metallic Pd, thus weakening support electrophilicity and stabilizing PdO against the formation of inactive Pd4+ species. This preferred catalyst with high intrinsic activity (turnover frequency 135 h−1 at 290 °C and 3 vol% water vapor) achieves a very low Ea of only 57 kJ mol−1, a third that (170 kJ mol−1) for the Pd/AlOOH/Al-fiber. This catalyst can stably run for feed gases of 1 vol% methane and 3–15 vol% water vapor in air.

Microfibrous-structured Pd/brass-fiber catalysts are developed for the selective hydrogenation of acetylene in the front-end configuration. The brass fibers are pre-calcined in air to create an endogenously growing ZnO-CuOx composite layer, and 0.25 wt% Pd is loaded on the brass fibers via the impregnation method. The activity and selectivity of our Pd/brass-fiber catalysts are primarily governed by the alloying degree of active sites regarded as Pd-Zn-Cu ensembles with the PdCu(alloy)-PdZnCu(alloy) twin structure, which are strongly sensitive to both the brass-fiber calcination and the catalyst reduction temperatures. For the preferred catalyst obtained using brass fibers calcined at 500 °C and reduced in H2 at 250 °C, over 90% selectivity is achieved at nearly 100% acetylene conversion with promising stability. Additionally, due to the weakened ethylene hydrogenation ability at high reaction temperature over the Pd-Zn-Cu ensembles, the catalysts tend to present higher ethylene selectivity as the reaction temperature increases.

The fabrication of qualified catalysts is a key issue to implement gas-phase aerobic alcohol oxidation but necessarily requires understanding the structures of catalytic active sites and the supply of active oxygen species. Herein, we present one example of the Ag–CoO/Ti- powder catalyst for gas-phase benzyl alcohol aerobic oxidation. The first interesting observation is that the Ag–Co3O4 ensembles on the fresh catalyst could be transformed into Ag–CoO due to the presence of reductive benzyl alcohol. The preferred catalyst with 3 wt% Ag and 3 wt% CoO exhibits 93% benzyl alcohol conversion and 99% benzaldehyde selectivity at a weight hourly space velocity of 20 h−1 and a temperature of 240 °C. The structures of Ag–CoO ensembles and oxygen species supply were probed and identified by electron microscopy and other spectroscopy techniques in combination with temperature-programmed thermal analyses, pulse experiments, and kinetic studies. In nature, the oxygen species is generated at the Ag–CoO interfacial sites in the form of atomic oxygen with appropriate chemisorption strength on these sites to achieve a high oxidation activity of benzyl alcohol. Moreover, the Co3O4 ↔ CoO cycle is promoted by Ag at low temperature such as 240 °C to endow the Ag–CoO ensembles with excellent catalytic performance.

We report a Ni-foam-structured MoNi4-MoOx nanocomposite catalyst derived from NiMoO4 spinel in situ grown on Ni-foam, which is highly active, selective (>93%) and stable for the gas-phase hydrogenation of dimethyl oxalate to ethanol. Such a reaction proceeds mainly through ethylene glycol formation, whereas a pathway through methyl acetate (MA) formation also occurs. Catalyst activity and selectivity are primarily governed by the MoNi4 nanoalloy but can be further improved by an MoOx modifier, due to the synergistic MoNi4-MoOx interaction that markedly promotes the MA hydrogenation to EtOH.

Improving the low-temperature water-resistance of methane combustion catalysts is of importance for industrial applications and it is challenging. A stepwise strategy is presented for the preparation of atomically dispersed tungsten species at the catalytically active site (Pd nanoparticles). After an activation process, a Pd-O-W

Oxygen-deficient oxide supports enhance the electron density of InNi3C0.5, enabling efficient CO2 hydrogenation to methanol., Direct CO2 hydrogenation to methanol using renewable energy–generated hydrogen is attracting intensive attention, but qualifying catalysts represents a grand challenge. Pure-/multi-metallic systems used for this task usually have low catalytic activity. Here, we tailored a highly active and selective InNi3C0.5/ZrO2 catalyst by tuning the performance-relevant electronic metal-support interaction (EMSI), which is tightly linked with the ZrO2 type–dependent oxygen deficiency. Highly oxygen-deficient monoclinic-ZrO2 support imparts high electron density to InNi3C0.5 because of the considerably enhanced EMSI, thereby enabling InNi3C0.5/monoclinic-ZrO2 with an intrinsic activity three or two times as high as that of InNi3C0.5/amorphous-ZrO2 or InNi3C0.5/tetragonal-ZrO2. The EMSI-governed catalysis observed in the InNi3C0.5/ZrO2 system is extendable to other oxygen-deficient metal oxides, in particular InNi3C0.5/Fe3O4, achieving 25.7% CO2 conversion with 90.2% methanol selectivity at 325°C, 6.0 MPa, 36,000 ml gcat−1 hour−1, and H2/CO2 = 10:1. This affordable catalyst is stable for at least 500 hours and is also highly resistant to sulfur poisoning.

Summary Large-scale shale gas exploitation greatly enriches ethane resources, making the oxidative dehydrogenation of ethane to ethylene quite fascinating, but the qualified catalyst with unique combination of enhanced activity/selectivity, enhanced heat transfer, and low pressure drop presents a grand challenge. Herein, a high-performance Nb2O5-NiO/Ni-foam catalyst engineered from nano- to macroscale for this reaction is tailored by finely tuning the performance-relevant Nb2O5-NiO interaction that is strongly dependent on NiO-precursor morphology. Three NiO-precursors of different morphologies (clump, rod, and nanosheet) were directly grown onto Ni-foam followed by Nb2O5 modification to obtain the catalyst products. Notably, the one from the NiO-precursor of nanosheet achieves the highest ethylene yield, in nature, because of markedly diminished unselective oxygen species due to enhanced interaction between Nb2O5 and NiO nanosheet. An advanced catalyst is developed by further thinning the NiO-precursor nanosheet, which achieves 60% conversion with 80% selectivity and is stable for at least 240 h., Graphical Abstract, Highlights • A series of Nb2O5-NiO/Ni-foam catalysts are developed for the ODE reaction • Catalysts are obtained by Nb2O5 modification of NiO-precursors grown onto Ni-foam • Thinning NiO-precursors dramatically improves the ethylene selectivity • Non-selective O2- species are markedly reduced with enhanced Nb2O5-NiO interaction, Catalysis; Organic Reaction; Nanomaterials; Nanostructure

Methyl glycolate (MG) is a versatile platform molecule to produce numerous important chemicals and materials, especially new-generation biocompatible and biodegradable poly(glycolic acid). In principle, it can be massively produced from syngas (CO + H2) via gas-phase hydrogenation of CO-derived dimethyl oxalate (DMO), but the groundbreaking catalyst represents a grand challenge. Here, we report the discovery of a Ni-foam-structured nanoporous Ni3P catalyst, evolutionarily transformed from a Ni2P/Ni-foam engineered from nano- to macro-scale, being capable of nearly fully converting DMO into MG at >95% selectivity and stable for at least 1000 h without any sign of deactivation. As revealed by kinetic experiments and theoretical calculations, in comparison with Ni2P, Ni3P achieves a higher surface electron density that is favorable for MG adsorption in a molecular manner rather than in a dissociative manner and has much higher activation energy for MG hydrogenation to ethylene glycol (EG), thereby markedly suppressing its overhydrogenation to EG.

Thin-sheet Al-fiber-felt-structured Pd/AlOOH/Al-fiber catalysts are developed for the back-end process of semihydrogenation of acetylene. A series of AlOOH/Al-fiber substrates were synthesized by endogenous growth and subsequent annealing in air. Palladium was then dispersed onto the as-obtained substrates by impregnation. The catalyst activity and stability show interesting substrate annealing temperature dependence. The preferred catalyst, obtained by dispersing lower than 0.05 wt % Pd onto the AlOOH/Al-fiber annealed at 100 °C, exhibits a high specific activity with the turnover frequency (measured at 40 °C) of 0.0167 s–1, being two times as high as that (0.0083 s–1) for the catalyst using a high substrate annealing temperature of 600 °C. Low AlOOH/Al-fiber annealing temperature enables the catalysts with hydroxyl-rich surfaces that not only promote the hydrogen activation on Pd but also strengthen the adsorption of acetylene. Notably, the Pd–hydroxyl interaction obviously suppresses carbonaceous depos...

Summary: CO2 circular economy is urgently calling for the effective large-scale CO2 reutilization technologies. The reverse water-gas shift (RWGS) reaction is the most techno-economically viable candidate for dealing with massive-volume CO2 via downstream mature Fischer-Tropsch and methanol syntheses, but the desired groundbreaking catalyst represents a grand challenge. Here, we report the discovery of a nano-intermetallic InNi3C0.5 catalyst, for example, being particularly active, selective, and stable for the RWGS reaction. The InNi3C0.5(111) surface is dominantly exposed and gifted with dual active sites (3Ni-In and 3Ni-C), which in synergy efficiently dissociate CO2 into CO* (on 3Ni-C) and O* (on 3Ni-In). O* can facilely react with 3Ni-C-offered H* to form H2O. Interestingly, CO* is mainly desorbed at and above 400°C, whereas alternatively hydrogenated to CH3OH highly selectively below 300°C. Moreover, this nano-intermetallic can also fully hydrogenate CO-derived dimethyl oxalate to ethylene glycol (commodity chemical) with high selectivity (above 96%) and favorable stability. : Chemical Reaction; Catalysis; Nanomaterials Subject Areas: Chemical Reaction, Catalysis, Nanomaterials

Thin-felt microfibrous-structured Pd-Co-MnOx/Al2O3/Al-fiber catalysts (named Pd-Co-MnOx-Al) with low Pd-loading engineered from micro- to macro-scale are developed for the high-throughput catalytic decomposition of high level gaseous ozone (O3) under humid conditions. The catalysts are obtained by highly dispersing Pd-Co-Mn active components onto the γ-Al2O3 nanosheets endogenously grown on the thin-felt microfibrous structure consisting of 10 vol% 60 μm-Al-fiber and 90 vol% voidage, using impregnation method. This approach effectively and efficiently couples the unique form factor, thin-sheet feature, and high permeability with the high activity, markedly improved stability, and enhanced moisture resistance. The most promising 0.1Pd-Co-MnOx-Al (0.1 wt% Pd, 0.36 Co/Mn molar ratio, Co2O3 + MnO2 loading of 5 wt%) catalyst remains full O3 conversion for at least 4 h at 25 °C for a feed gas containing 1500 ± 45 ppm O3 even at a high relative humidity (RH) of 70%, using a high gas hourly space velocity of 48,000 mL gcat.–1 h–1; the full O3 conversion quickly slides to a flat of ~96% during 4 h testing at 90% RH whereas it is retrievable immediately after switching the feed gas to a dry one. The remarkable improvement of activity, stability and moisture resistance by Pd-doping of Co-MnOx-Al is, in nature, due to the highly improved and stabilized low-valent-Mn related oxygen vacancies (i.e., active sites) and markedly weakened H2O adsorption on the catalyst surface, which are verified by XRD, H2-TPR, O2-TPD, H2O-TPD and XPS measurements.

A high-performance, low Pd-loading and highly thermal conductive catalyst is developed by carburizing a thin-felt Pd/AlOOH/Al-fiber (0.25 wt% Pd) using ethylene. Carbon dissolving into the subsurface of Pd nanoparticles to form surface PdCx species (i.e., Pd@PdCx) leads to at least 2-fold improvement of the intrinsic activity (expressed by turnover frequency, TOF) for the CO oxidative coupling to dimethyl Oxalate, in nature, remarkably promoting the generation of key reaction intermediate of COCOOCH3* (*, a surface site).

A carbon-decorated Pd@C/ns-AlOOH/Al-fiber catalyst (0.24 wt% Pd) is engineered from nano- to macro-scales, which is promising for the vapor-phase synthesis of dimethyl carbonate (DMC) from methyl nitrite (MN) and CO. A high MN conversion of 99.9% with MN-based DMC selectivity of 39.1% and 70.6% CO conversion with CO-based DMC selectivity of 39.6% can be obtained at 220 °C for a feed of MN/CO/N2 (10/7/83) at a high gas hourly space velocity of 25,000 L kg−1 h−1. Moreover, the carbon decoration shows ability to improve the formation of electron-deficient Pd species, which is paramount for the enhanced selectivity to DMC.

A hollow-B-ZSM-5/SS-fiber catalyst is developed through alkali leaching of the full-silica core of the silicalite-1@B-ZSM-5 in situ structured onto a thin-felt stainless-steel fiber (20 μm SS-fiber), which is synthesized by a seed-assisted dry-gel vapor-phase transport method. As-obtained catalyst shows marked improvement in the mesoporosity-dependent diffusion (by o-xylene diffusion measurement). Boron incorporation is essential for preventing the framework dealumination during alkali leaching treatment due to the increased framework negative charges. The hollow-B-ZSM-5/SS-fiber catalyst shows remarkable stability improvement in the methanol-to-propylene (MTP) reaction because of the enhanced diffusion of the nano-hollow-structure and the boron-incorporation stabilized framework aluminum. A boron-free hollow-ZSM-5/SS-fiber is also obtainable with the textural properties comparable to the hollow-B-ZSM-5/SS-fiber but shows undesired degeneration of the tetra-coordinated aluminum. The preferential generation of coke in the micropores of the hollow-ZSM-5/SS-fiber causes a rapid deactivation even compared to the parent silicalite-1@ZSM-5/SS-fiber, due to the existence of extra-framework aluminum.

Atomic-level insight into the unique catalytic capability of single-atom catalysts that distinguished from nanometer-sized counterparts is highly desirable for catalyst design and catalysis research. By synthesizing single Pd atoms supported on TiO2 as a catalyst, here we demonstrate a steric hindrance effect of single atoms induced by the unique isolation of single-atom active sites to achieve a remarkable enhancement on catalytic performance in the synthesis of dimethyl carbonate. Experimental results and density functional theory calculations reveal that such steric hindrance effect of single atoms favors the yield of the desired product dimethyl carbonate against further reacting with intermediates to form byproduct, because no extra Pd species around single Pd atoms provide active sites to further adsorb and activate substrates directly. The discovery of such steric hindrance effect is a valuable supplement to single-atom catalysis, and may promote single-atom catalysts to be widely applied in selective catalytic reactions.

Chemical looping concept paves way toward intrinsically safe and efficient oxidative coupling of methane (CL-OCM) process, because it permits the reaction to proceed via repeating reduction-oxidation cycle in two reactors. It is calling for a ground-breaking catalyst with enough high selective CH4-converting lattice-oxygen carrying capacity but represents a grand challenge. Herein, we report an efficient catalyst obtainable by decorating an oxygen carrier FeMnO3 with Na2WO4, with good cycling performance, achieving a high space time yield of 29.8 gC2-C3 kgcat.-1 h-1 with 20% CH4 conversion and 80% C2-C3 selectivity at 800 oC and a low catalyst/CH4 weight ratio of 13.5. CL-OCM process is established by “FeMnO3↔[MnFe2O4 + MnO]” red-ox cycle. Na2WO4-decoration gets lattice oxygen stored in FeMnO3 transformed from non-selective to selective due to mitigation of lattice-oxygen evolution. Scaled up CL-OCM testing with 10-gram catalyst also yields comparable results seen in the case of using 1-gram catalyst, validating great application potential.

The MnOx-Na2WO4 catalyst for oxidative coupling of methane (OCM) is highly attractive but its high light-off temperature (>800 °C) is a major obstacle for commercialization. In-depth understanding of reaction light-off relevant chemistry is particularly desirable. We explored the OCM light-off over several metal-oxide-supported MnOx-Na2WO4 catalysts. As CH4 conversion above 15% with acceptable C2-3 selectivity is considered as the sign of OCM light-off, support-dependent OCM light-off is clearly observed over MnOx-Na2WO4 supported on SnO2 (660 °C), TiO2 (670 °C), MgO (690 °C), and ZnO (720 °C), being tightly linked with the redox rate of Mn3+(or Mn4+) ↔ Mn2+ cycle governed by support oxides.

The efficient conversion of renewable biogas has attracted ever-increasing interest in past decades. Ni-CeO2-Al2O3 supported on monolithic SiC-foam (denoted as Ni/CeO2-Al2O3/SCF) is designed and applied in biogas reforming. The monolithic Ni/CeO2-Al2O3/SCF catalysts were deeply characterized by XRD, ICP-AES, SEM, HR-TEM, CO2-TPD, etc. The cycle between CeO2-Al2O3 and CeAlO3 was verified by in-situ CH4/CO2-TPSR, and the catalytic role of CeAlO3 in coke elimination and CO2 activation was further confirmed. Due to the uniform distribution of Ni nanoparticles (NPS) and the activation of CO2 by CeAlO3, Ni/CeAlO3-Al2O3/SCF shows excellent catalytic stability to inhibit sintering and eliminate carbon deposition. At 900 °C and a gas hourly space velocity (GSHV) of 24000 mL gCat-1h−1, excellent CH4/CO2 conversion of 86/99% are initially achieved over Ni/CeAlO3-Al2O3/SCF catalyst, followed by slight decrease after 140 h, and remain basically stable for the next 260 h.

Catalytic distillation (CD) has received inviting interests due to the green chemical process with a unique integration of catalytic reaction and distillative separation. This approach opens a promising way towards one-step cyclohexyl acetate production and cyclohexene-cyclohexane separation via esterification of cyclohexene (cyclohexene-cyclohexane mixture as feed) with acetic acid in a CD column, which can overcome many of the drawbacks encountered in the conventional reaction/separation processes. We present a microfibrous-structured Nafion-SiO2/SS-fiber solid acid catalyst as CD packings and demonstrate its high efficiency and effectiveness for synthesizing cyclohexyl acetate and separating cyclohexene/cyclohexane mixture in one-step. The Nafion-SiO2/SS-fiber catalytic packings achieved as-expected catalytic properties with respect to stability, adequate acidic sites and high mass/heat transfer, and therefore worked efficiently and effectively in the titled CD system. The operation parameters, including reboiler duty, molar ratio of acetic acid to cyclohexene, reflux ratio, and weight hourly space velocity (WHSV), were optimized with the aid of the factorial design based on response surface methodology (RSM). High actual yield of cyclohexyl acetate (78.1%) and high recovery of cyclohexane (93.0%) with 94.3% of cyclohexane purity were achievable, while such microfibrous-structured Nafion catalyst was stable for at least 200 h consecutive batch runs.

A series of Ni5Ga3/m-SiO2/Al2O3/Al-fiber (m = 0, 0.5, 1.0, 3.0 and 5.0 wt%) catalysts have been developed for CO2 hydrogenation to methanol at ambient pressure. Microfibrous-structured SiO2/Al2O3/Al-fiber supports are obtained though endogenous growth of free-standing boehmite (AlOOH) nanosheets onto a three-dimensional (3D) network of 60 μm-Al-fiber thin felt with the aid of steam-only hydrothermal oxidation reaction between Al metal and H2O (2 Al + 4H2O → 2 AlOOH + 3H2), followed by calcination and SiO2-modification using silica sol. The bimetallic Ni5Ga3 nanoparticles are then placed onto the pore surface of as-obtained SiO2/Al2O3/Al-fiber support by co-impregnation method using Ni and Ga nitrates as precursors followed by reduction in H2 at 630 °C. The promising Ni5Ga3/1-SiO2/Al2O3/Al-fiber catalyst is capable of converting 2.3% CO2 into CH3OH with a high selectivity of 86.7% as well as 10.3%/3.0% selectivities to CO/CH4 at 210 °C, for a feed of CO2/H2/N2 (2/6/1, molar ratio). Such microfibrous-structured catalyst design combines the promising catalytic performance of Ni5Ga3 with the enhanced heat transfer and high permeability of the Al2O3/Al-fiber support. The effect of SiO2 loading on the formation of Ni5Ga3 alloy nanoparticles is also discussed.

A promising thin-felt stainless-steel-fiber (SS-fiber) structured hollow-ZSM-5/SS-fiber catalyst is developed through alkali leaching of the full-silica core from the silicalite-1@ZSM-5/SS-fiber. A silicalite-1 seeded dry-gel/SS-fiber is obtained by dip-coating technique and is then transformed into the silicalite-1@ZSM-5/SS-fiber (overall SiO 2 /Al 2 O 3 molar ratio of 93) via seed-assisted dry gel conversion method. Such catalyst shows marked enhancement of mesoporosity development because of the abundant hollow structures left behind after the silicalite-1 core removal by alkali treatment in a mild Na 2 CO 3 media. The effect of alkali-treated time length on catalyst structure, textural and acidic properties as well as methanol-to-propylene (MTP) performance is systematically investigated. As-obtained catalyst, with well-maintained Bronsted acid sites after alkali treatment, shows hollow-structure-dependent stability improvement in the MTP and n-hexane cracking processes due to markedly enhanced diffusion.

A series of thin-felt SS-fiber@HZSM-5 catalysts are fabricated via the seed-assisted vapor-phase transport (VPT) method. The crystal size and mesoporosity of zeolite shell are controllably tuned toward enhanced diffusion by increasing the silicalite-1 seeding gel (SG) amount used. The microstructured catalyst obtained with a high SG amount of 50% contains a smaller crystal size of ∼70 nm and higher mesopore volume of 0.21 cm3 gzeolite−1, which markedly prolonged single-run lifetime with a remarkable decrease in the coking rate in the MTP process. The adverse effect of non-uniform aluminum in the zeolite shell on the MTP stability is revealed. The use of aluminum-containing SG to replace the pure-silica one makes the acid sites of as-obtained ZSM-5 mounted on SS-fiber distributed homogeneously thereby leading to a marked suppression of hydrogen transfer, and as a result, the catalyst single-run lifetime is further increased by ∼40%. This promising SS-fiber@HZSM-5 catalyst is stable for at least 1600 h (>94% conv.) with a high propylene selectivity of ∼36% at 450 °C using a WHSV of 1 h−1 for a feed of MeOH/H2O molar ratio of 1:1, by taking advantage of improved diffusion from mesoporosity development and uniform aluminum distribution as well as our distinctive microfibrous-engineered design.

Gold nanoparticles supported on Fe2O3 are a promising type of catalyst for CO oxidation. One challenge for their application in the real world is developing novel monolithic catalytic packings to meet the fundamental criteria (for example, high catalyst utilization efficiency and low pressure drop) needed for such high-throughput reaction process. Herein, a highly active and efficient thin-felt microfibrous-structured Au-α-Fe2O3/ns-γ-Al2O3/Al-fiber catalyst with unique form factor and high permeability is fabricated for the low-temperature CO oxidation. Initially, thin-felt Al-fiber felt (60 μm diameter; 85 vol% voidage) undergoes a steam-only oxidation and calcination to create a 0.7 μm mesoporous layer of γ-Al2O3 nanosheets (ns-γ-Al2O3) along with the Al-fiber. Subsequently, α-Fe2O3 is hydrothermally grown onto the ns-γ-Al2O3 layer followed by Au nanoparticle deposition via urea-assistant deposition-precipitation method. As-resulted microfibrous-structured Au-α-Fe2O3/ns-γ-Al2O3/Al-fiber catalysts effectively and efficiently couple the low-temperature activity and improved water vapor tolerance with enhanced catalyst accessibility and high permeability. The promising microfibrous-structured catalyst with only 0.14 wt% Au and 1.4 wt% α-Fe2O3 is capable of fully or 40% oxidizing CO into CO2 at 25 °C or 0 °C for a feed gas of 2 vol% CO and 0.3 vol% water vapor in air at a high linear velocity of 0.7 cm s−1, using a high gas hourly space velocity of 25,200 mL g−1 cat h−1. Moreover, the microfibrous-structured catalyst performs robustly for at least 232 h under the changeable temperature conditions. Interestingly, 3D hierarchical porous flake structure of α-Fe2O3 nano-sheets is detected other than the irregular micron-sized particles, leading to a 3-fold increase in the intrinsic activity (TOF of 0.46 s-1 for the Au-α-Fe2O3/ns-γ-Al2O3/Al-fiber vs. 0.11 s−1 for the Au-α-Fe2O3 powder at 25 °C).

A Nb2O5–NiO/Ni-foam catalyst engineered from nano- to macro-scale is developed by hydrothermal growth of NiC2O4 onto a Ni-foam and subsequent (niobium ammonium oxalate)-modification and calcination, which is highly active/selective and stable for the oxidative dehydrogenation of ethane to ethylene. External and partial coverage of the NiC2O4-derived NiO nanorods with Nb2O5 lumps, coupled with a foam-structure enhanced heat transfer, is paramount for high-efficiency ethylene production.

From macro- to nano-engineering of a promising CeO2-ZrO2-doped NiO-Al2O3/Ni-foam catalyst has been demonstrated for the oxidative dehydrogenation of ethane to ethylene (ODE), through facial wet chemical etching of a Ni-foam followed post modification with CeO2 and ZrO2. The NiO-Al2O3/Ni-foam (denoted as NANF) achieved a high ethane conversion of 25.2% but with a very low ethylene selectivity of 43.1% at 450 °C. ZrO2-doping of the NANF led to a remarkable improvement in the ethylene selectivity but serious deterioration of activity while the CeO2-doping showed an opposite effect. Co-doping of the NANF using optimal amount of CeO2 and ZrO2 markedly promoted not only the activity but also the selectivity to ethylene. For example, over the 1CeO2-5ZrO2-NANF (CeO2:1 wt%, ZrO2:5 wt%) catalyst, a high ethane conversion of 40.3% was obtained with a 60.6% ethylene selectivity for a feed gas of C2H6/O2/N2 = 1/1/8 at 500 °C and a gas hourly space velocity of 18,000 cm3 g−1 h−1, corresponding to a high ethylene productivity of 510 gEthylene kgcat−1 h−1. In nature, co-doping with CeO2 and ZrO2 synergistically tamed the NiO for selective H-abstraction of the ethane molecules other than over oxidation of them.

A high-performance Ni-foam-structured nano-intermetallic InNi3C0.5 catalyst is developed for the gas-phase hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG). The InNi3C0.5/Ni-foam catalyst is obtainable by hydrothermal growth of NiC2O4 onto the Ni-foam, impregnation with In2O3 precursor, subsequent calcination and carburization in a syngas. Despite DMO cascade hydrogenation to MG, then to EG, and finally to EtOH, such catalyst hydrogenates DMO dexterously until to EG with a high turnover frequency of 636 h−1, because the 3Ni-In and 3Ni-C sites on InNi3C0.5(1 1 1) effectively activate DMO but hinder EG over-hydrogenation to EtOH. Favorable reaction pathway on the InNi3C0.5(1 1 1) surface predicted theoretically is DMO* → CH3OCOCO* → CH3OCOCHO* → CH3OCOCHOH* → MG* → CH3OCHOCH2OH* → CHOCH2OH* → HOCHCH2OH* → EG*. Moreover, the neutral Ni-foam diminishes the formation of ethers and diols. This catalyst achieves full DMO conversion with 96–98% EG selectivity and is stable for at least 2500 h under industrial-relevant conditions, and can also hydrogenate a broad scope of carbonyl compounds to corresponding alcohols with high yields.

Monolithic SiC-foam-structured Mn2O3-Na2WO4-TiO2 catalysts are developed via a binder-free dip-coating method for the oxidative coupling of methane reaction. MnTiO3-assisted growth of coating from nanoparticles to nanorods proceeds spontaneously to form interpenetrating nano-structure in the presence of alkali (such as Na2WO4) during the high-temperature calcination treatment, which grants the coating strong robustness. This catalyst involves the effective and efficient coupling of advanced catalysis of Mn2O3-Na2WO4-TiO2 coating with enhanced heat/mass transfer stemmed from SiC-foam substrate. The preferred catalyst is the one with 40 wt% coating at Mn2O3/Na2WO4/TiO2 weight ratio of 2.2%/5.1%/32.7%, giving 26% CH4 conversion and 69% C2-3 selectivity at 800 °C and 0.1 MPa for a feed gas of CH4/O2 of molar ratio of 5/1 at gas hourly space velocity of 4000 h−1. The SiC-foam-structured Mn2O3-Na2WO4-TiO2 catalyst can also be used for this reaction in the form of bead string reactor, and the highest C2-3 yield of 13% is obtained with 18% CH4 conversion and 72% C2-3 selectivity at 0.35 MPa, 20,000 h−1, CH4/O2 molar ratio of 6.5/1, and 800 °C.

Development of efficient catalyst for conversion of benzyl alcohol to benzaldehyde using molecular oxygen is of great importance in virtue of the economic and environmentally friendly superiority. In this study, a cobalt-based zeolitic imidazolate framework, ZIF-67, has been used as precursor to synthesize different catalysts for study in benzyl alcohol oxidation by air. The catalysts were characterized by XRD, SEM, ICP-MS, N2 adsorption-desorption and XPS. The cobalt oxide catalyst, which was obtained via calcination of ZIF-67 in air, showed low activity and selectivity toward benzaldehyde. While the Co@CN, prepared from pyrolysis in argon, exhibited good activity and recyclability under mild conditions. The results suggested that the cobalt species, either metallic cobalt or Co2+, were the main active sites. In addition, the nitrogen species also played a role for the efficient conversion of benzyl alcohol.

A facile strategy is reported for engineering layered double hydroxides (LDHs)-derived nanocomposite catalysts from nano-to macro-scales in one step, via the Al 2 O 3 /water interface-assisted method to embed LDHs onto monolithic substrates (such as thin-felt microfibrous structure using 22 μm FeCrAl fibers or 20 μm stainless steel fibers and SiC foam) followed by calcination to transform LDHs to nanocomposites. Such approach achieves unique integration of tunability and homogeneous distribution of catalytic components, enhanced heat/mass-transfer, self-supported feature, and high permeability, thus exhibiting tremendous potential for application in harsh reactions. For example, the thin-felt NiO MgO Al 2 O 3 /FeCrAl-fiber catalyst derived from NiMgAl-LDHs/Al 2 O 3 /FeCrAl-fiber offers high activity and stability for the high throughput and exothermic catalytic oxy-methane reforming: 87–90% methane conversion and 91–93/90–92% H 2 /CO selectivities at 700 °C within 300 h testing, using a high gas hourly space velocity of 72 L g −1 h −1 .

Self-supported NiO-MOx-Al2O3 (M = Ce or Mg) nanocomposites mounted on a Ni-foam (110 PPI) as the monolithic structured catalyst have been developed for the high throughput catalytic partial oxidation of methane to syngas. The catalysts are obtainable by direct growth of NiAl layered double hydroxides nanosheets and subsequent impregnation with boehmite sol containing Al-Ce or Al-Mg nitrates. Such catalysts are highly active and selective with promising stability in the title reaction, for example, the NiO-CeO2-Al2O3/Ni-foam achieves a high methane conversion of 86.4% with 91.2%/89.0% selectivities to H2/CO and is stable for at least 100 h at 700 °C and a high gas hourly space velocity of 100 L g−1 h−1. Thanks to a feasible CeO2↔CeAlO3 chemical cycling that is able to promote the O2 activation to create an oxidative environment around Ni particles, carbon formation rate is dramatically suppressed by a factor of at least 5 compared to the base catalyst.

A promising Ni-MoOx bifunctional catalyst for halide-free methanol carbonylation is developed by H2-reduction of NiO-MoO3/SiO2 obtained via facile impregnation method. Catalyst performance is strongly dependent on the calcination/reduction temperature. Over the preferable NiMo-350-600/SiO2 catalyst obtained by calcining at 350 °C and subsequently reducing at 600 °C, a methanol conversion of 4.2 % and acetyls space-time yield of 1.37 mol kgcat−1 h−1 are achieved with 22.1 % selectivity to acetyls at 290 °C and 3 MPa. Co-existence of Ni0 and MoOx (especially MoO2) markedly decreases formation of dimethyl ether (DME) and reversely increases acetyls formation, in nature, due to the catalyst acidity modulation and the partial electron transfer from Ni0 to MoOx that tunes the CO adsorption strength on Ni0 sites. MoO3 and NiMoO4 are both favorable for formation of acetyls and DME whereas the latter mainly accounts for DME formation. MoNi4 alone favors methyl formate formation while together with MoO2 enhancing DME production.

Sustainable transformation of methane into methanol feedstock syngas is a promising direction in future energy generation. A monolithic SiC-foam (SiC-foam, denoted as SCf) supported structured Ni-SrO composite nanomaterial was prepared via reducing the SrNiO3 perovskite. The Ni-SrO/SCf displays a stronger resistance to Ni-sintering/coke-deposition than the unmodified Ni/SCf due to its uniform Ni distribution as well as the strong Ni-SrO interaction. In the presence of Ni-SrO/SCf sample at a gas hourly space velocity (GHSV) of 24,000 mLCH4 CO2 gCat−1 h − 1 and an operating temperature of 850 °C, the initial conversion rate of biogas (CH4/CO2) was 70/94%, which gradually dropped to 55/72% within 40 h, but its activity remained stable for the next 60 h. By contrast, the conversion rate of biogas (CH4/CO2) in the presence of Ni/SCf sample was decreased rapidly from 60/80 to 50/65% within 20 h, due to the severe coke deposition and Ni-sintering.

BACKGROUND Catalytic distillation (CD) has been received as an inviting green chemical process for numerous catalytic esterification reactions. Rendering novel structured CD packings is particularly desirable but remains challenging. RESULTS We present a microfibrous-structured HZSM-5 solid acid catalyst as CD packings and demonstrate its separation and esterification reaction efficiency for producing ethyl acetate from acetic acid and ethanol. The factorial design based on response surface methodology is employed for fast determination of optimum reaction conditions, which is working effectively and efficiently. Such structured catalyst packings are obtained by direct growth of zeolite onto the θ-ring analogues shaped from a microfibrous-structure consisting of 15 vol% 20 µm stainless-steel-fiber (SS-fiber) and 85 vol% voidage. CONCLUSION The SS-fiber@HZSM-5 packings provide a unique combination of instantaneous distillation and desired catalytic properties with respect to stability, adequate acidic sites and high mass/heat transfer, and therefore work efficiently and effectively. High total (95.9%) and actual (90.9%) yields of ethyl acetate with 89.8% purity are achievable while the high CD efficiency was well-preserved after at least 240 h over 30 consecutive batch runs.

The Mn2O3-Na2WO4/SiO2 catalyst is the most promising one among the enormous catalysts for the oxidative coupling of methane (OCM) but only at above 800 °C. No doubt that lowering temperature of the OCM process is at the forefront of this catalysis field. A promising low-temperature active and selective TiO2-doped Mn2O3 Na2WO4/SiO2 catalyst, consisting of 6 wt% TiO2, 6 wt% Mn2O3, 10 wt% Na2WO4 and SiO2 in balance, is developed by solution combustion synthesis (SCS) method. This catalyst is capable of converting 20% CH4 with 70% selectivity to C2-C3 hydrocarbons even at 700 °C (catalyst bed temperature) and is stable for at least 250 h without deactivation sign, for a feed gas of 50% CH4 in air using a gas hourly space velocity of 8000 mL gcat.−1 h−1. In contrast, the non-TiO2-doped SCS catalyst is almost inactive at 700 °C whereas it can achieve reactivity (∼24% CH4 conversion and ∼74% C2-C3 selectivity) comparable to the TiO2-doped one at 800 °C. XRD and Raman results evidently reveal that the formation of MnTiO3 during the OCM process appears to be important for the low-temperature OCM activity improvement by TiO2-doping.

A foam-structured Ag-CuOx nanocomposite catalyst obtained by sequential galvanic-deposition of 0.4 wt% Ag and 28 wt% Cu onto a Ni-foam, is highly active, selective and stable for the gas-phase hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG). The best catalyst 0.4-Ag-28-CuOx/Ni-foam was capable of converting more than 96% DMO into MG with a high selectivity of more than 96% and was stable for at least 200 h at 210 °C and a WLHSVDMO of 0.25 h− 1 for a feed of 13 wt% DMO dissolved in MeOH. Silver is responsible to apportion the proportion of Cu+ and Cu0 to an appropriate scale of optimal potency for converting DMO-to-MG.