Selective Conversion Of Methanol Research Articles

Electrocatalysis Boosts the Methanol Thermocatalytic Dehydrogenation for High-Purity H2 and CO Production.

Hydrogen production from methanol represents an energy-sustainable way to produce ethanol, but it normally results in heavy CO2 emissions. The selective conversion of methanol into H2 and valuable chemical feedstocks offers a promising strategy; however, it is limited by the harsh operating conditions and low conversion efficiency. Herein, we realize efficient high-purity H2 and CO production from methanol by coupling the thermocatalytic methanol dehydrogenation with electrocatalytic hydrogen oxidation on a bifunctional Ru/C catalyst. Electrocatalysis enables the acceleration of C-H cleavage and reduces the partial pressure of hydrogen at the anode, which drives the chemical equilibrium and significantly enhances methanol dehydrogenation. Furthermore, a bilayer Ru/C + Pd/C electrode is designed to mitigate CO poisoning and facilitate hydrogen oxidation. As a result, a high yield of H2 (558.54 mmol h-1 g-1) with high purity (99.9%) was achieved by integrating an applied cell voltage of 0.4 V at 200 °C, superior to the conventional thermal and electrocatalytic processes, and CO is the main product at the anode. This work presents a new avenue for efficient H2 production together with valuable chemical synthesis from methanol.

Promoted electro-oxidation kinetics in chromium-doped α‑Ni(OH)2 nanosheets for efficient selective conversion of methanol to formate

Owing to the elusive pathways of methanol oxidation reaction (MOR) and the lack of applicable catalysts, the selective electro-oxidation of methanol to formate remains a challenging topic. Herein, we present a chromium-doping strategy to promote the MOR performance of α-Ni(OH)2 nanosheets with a high selectivity towards formate generation. Taking chromium-doped α-Ni(OH)2 nanosheets as an example, we further highlight the role of doping atoms in MOR by combining theoretical calculations with experimental measurements. It reveals that chromium doping can not only enhance the conductivity of α-Ni(OH)2 nanosheets, but also endow the catalyst with optimized kinetics for electroactive NiOOH formation and methanol absorption, thus resulting in a remarkable MOR current density of 141 mA cm−2 at 0.50 V vs. Ag/AgCl with a faradaic efficiency of 92.1% for formate. Furthermore, in situ infrared spectroscopy demonstrates that methanol is selectively oxidized to formate without further oxidation to CO2 over chromium-doped α‑Ni(OH)2 nanosheets in alkaline media.

Relay Catalysis for Highly Selective Conversion of Methanol to Ethylene in Syngas.

The precise C-C coupling is a challenging goal in C1 chemistry. The conversion of methanol, a cheap and easily available C1 feedstock, into value-added and largely demanded olefins has been playing a game-changing role in the production of olefins. The current methanol-to-olefin (MTO) process, however, suffers from limited selectivity to a specific olefin. Here, we present a relay-catalysis route for the high-selective conversion of methanol to ethylene in syngas (H2/CO) typically used for methanol synthesis. A bifunctional catalyst composed of selectively dealuminated H-MOR zeolite and ZnO-TiO2, which implemented methanol carbonylation with CO to acetic acid and selective acetic acid hydrogenation to ethylene in tandem, offered ethylene selectivity of 85% at complete methanol conversion at 583 K. The selective removal of Brønsted acid sites in the 12-membered ring channel of H-MOR favors the selectivity of acetic acid in CH3OH carbonylation. The high capabilities of ZnO-TiO2 in the adsorption of acetic acid and the activation of H2 play key roles in selective hydrogenation of acetic acid to ethylene. Our work provides a promising relay-catalysis strategy for precise C-C coupling of C1 to C2 molecules.

Dry-gel conversion synthesis of SAPO-14 zeolites for the selective conversion of methanol to propylene

High-crystalline SAPO-14 zeolites were efficiently synthesized through dry-gel conversion (DGC) for the first time. Further using as a catalyst, the optimal SAPO-14 with proper acidity showed superior MTP performance with not only a very high propylene selectivity (76.2%) but also a large P/E ratio (7.19).

Study of Catalytic Properties of the HoxMg1-xAl2O4 Modified HZSM-5 Zeolite in Conversion of Methanol to C2-C4 Alkenes and p-Xylene

Selective conversion of methanol to C2-C4 alkenes and p-xylene is one of the appealing chemical routes. Currently, there are no effective catalysts for the co-production of C2-C4 alkenes and p-xylene from methanol. To date, modified medium-pore ZSM-5 zeolites are considered one of the excellent candidates for the development of selective catalysts for the conversion of methanol to lower alkenes and aromatic hydrocarbons. In this paper, nanosized (30-33nm) powders of HoхMg1-хAl2O4 spinel structure were obtained by the method of combustion of nitrate solutions of aluminium, magnesium, holmium, diethylmalonate and hydrazine monohydrate with the further calcination of nanopowders at 1000 °C. Obtained nanopowders used in the preparation of a solid-phase catalytic composition of HoхMg1-хAl2O4-HZSM-5. Various physico-chemical properties of the catalytic composition were investigated using X-ray diffraction (XRD), pyridine adsorption (BİO-RAD FTS 3000 MX) and low-temperature nitrogen adsorption (BET) techniques. The textural properties and acidity of the catalysts were altered by adjusting the nanopowder concentration (1.0-5.0 wt.%) in the catalytic composition. The conversion of methanol in the presence of the catalytic compositions was carried out in flow-type fixed-bed catalytic reactor at 400 °C, in the presence of nitrogen carrier gas with 1.0 h-1 flow rate. A correlation between the selectivity to C2-C4 alkenes and p-xylene with a ratio of Lewis (L) and Brønsted (B) acid sites and the volume of the catalyst pore, the amount of the modifier in the catalytic system has been established. As the amount of HoхMg1-хAl2O4 nanopowder increases, the ratio of B/L acid sites and the volume of the catalyst pore decrease, which play a significant role in the increase of the selectivity to C2-C4 alkenes and p-xylene. Maximum yield of C2-C4 alkenes (31.6%) and selectivity to p-xylene (80.5%) is achieved on a catalytic composition containing 5.0 wt.% HoxMg1-xAl2O4. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Short-Range Diffusion Enables General Synthesis of Medium-Entropy Alloy Aerogels.

Medium-entropy alloy aerogels (MEAAs) with the advantages of both multimetallic alloys and aerogels are promising new materials in catalytic applications. However, limited by the immiscible behavior of different metals, achieving single-phase MEAAs is still a grand challenge. Herein, a general strategy for preparing ultralight 3D porous MEAAs with the lowest density of 39.3 mg cm-3 among the metal materials is reported, through combining auto-combustion and subsequent low-temperature reduction procedures. The homogenous mixing of precursors at the ionic level makes the short-range diffusion of metal atoms possible to drive the formation of single-phase MEAAs. As a proof of concept in catalysis, as-synthesized Ni50 Co15 Fe30 Cu5 MEAAs exhibit a high mass activity of 1.62 A mg-1 and specific activity of 132.24 mA cm-2 toward methanol oxidation reactions, much higher than those of the low-entropy counterparts. In situ Fourier transform infrared and NMR spectroscopies reveal that MEAAs can enable highly selective conversion of methanol to formate. Most importantly, a methanol-oxidation-assisted MEAAs-based water electrolyzer can achieve a low cell voltage of 1.476 V at 10 mA cm-2 for making value-added formate at the anode and H2 at the cathode, 173 mV lower than that of traditional alkaline water electrolyzers.

Selective conversion of methanol to aromatics with superior catalytic stability by relay catalysis over quadruple ZSM-5 sequence beds with gradient-increasing acidity

Methanol to aromatics (MTA) process is an attractive non-petroleum route for producing high-valued aromatics, but simultaneously achieving high catalytic stability and high aromatics selectivity remains a challenging research target. Herein, we present a highly efficient MTA process by quadruple tandem relay catalysis containing four layers of nanosized ZSM-5 with different acidity features in series. Specifically, four ZSM-5 catalysts with gradient-increasing acid density were sequentially packed in the tubular fixed bed reactor for reaction. Among them, ZSM-5 with a high SiO2/Al2O3 ratio as 480 was packed in top layer to convert methanol into light alkanes and alkenes intermediates, then these reaction intermediates and a small amount of unreacted methanol were transported on other two ZSM-5 layers with lower SiO2/Al2O3 ratio as 240 and 120 respectively for stepwise converting to aromatics. In particular, Zn doped ZSM-5 with a low SiO2/Al2O3 ratio of 60 was packed in the bottommost layer which further promoted aromatization of upstream light hydrocarbons. Accordingly, aromatics selectivity was significantly increased to 32.6% using the sequence beds, much higher than 17.6% for the widely recognized two-step MTA. Based on deliberate analysis of methanol conversion and coke formation behavior in different beds, we demonstrate that a methanol concentration gradient existed along the sequence beds which remarkably decreased alkylation of aromatics induced by methanol. So, the catalyst stability of the ZSM-5 located in the bottommost layer was significantly enhanced to 238 h, which was 3-folds compared with the traditional two-step methanol conversion. The present work offers a promising strategy for MTA via tandem ZSM-5 catalysis systems, which has an active impact on the solving of the energy and environmental problems existing in the production process of aromatics.

Hierarchical trace copper incorporation activated cobalt layered double hydroxide as a highly selective methanol conversion electrocatalyst to realize energy-matched photovoltaic-electrocatalytic formate and hydrogen co-production

Hierarchical CuxCoCo-LDH as a highly selective methanol conversion electrocatalyst realizes energy-matched photovoltaic-electrocatalytic formate and hydrogen co-production.

Selective conversion of methanol to propylene over highly dealuminated mordenite: Al location and crystal morphology effects

The growing consumption of light olefins has stimulated intensive researches on methanol to olefin (MTO) process which possesses great advantages for coal conversion to value-added chemicals in an environmentally benign way. The catalysts commonly used for MTO process faces several challenges such as poor selectivity control, low hydrothermal stability and short lifetime. In the present study, we prepared a series of mordenite zeolites with variable Al contents (Si/Al molar ratios of 51−436) by a sequential dealumination treatment of air-calcination and acid leaching. The textural properties, acidity and Al location before and after the dealumination treatment have been systematically studied and their effect on MTO especially the methanol to propylene (MTP) performance was thoroughly investigated. The mordenite zeolites with the Si/Al ratios over 150 selectively catalyzed methanol conversion in the MTP pathway, providing a high propylene selectivity of 63% and propylene/ethylene ratio of > 10. Compared to the low-silica MOR catalysts, highly dealuminated MOR showed much higher stability and longer lifetime, which can be further enhanced via harsh hydrothermal pretreatment. Furthermore, the lifetime was highly related to the crystal size along c-axis. The excellent performance of highly dealuminated MOR is likely ascribed to the mesopores formed upon dealumination and the scarce Al sites located in the T sites shared by the 8-member ring (MR) side pockets and 12-MR pore channels.

Nickel Iron Diselenide for Highly Efficient and Selective Electrocatalytic Conversion of Methanol to Formate.

The electro-oxidation of methanol to formate is an interesting example of the potential use of renewable energies to add value to a biosourced chemical commodity. Additionally, methanol electro-oxidation can replace the sluggish oxygen evolution reaction when coupled to hydrogen evolution or to the electroreduction of other biomass-derived intermediates. But the cost-effective realization of these reaction schemes requires the development of efficient and low-cost electrocatalysts. Here, a noble metal-free catalyst, Ni1- x Fex Se2 nanorods, with a high potential for an efficient and selective methanol conversion to formate is demonstrated. At its optimum composition, Ni0.75 Fe0.25 Se2 , this diselenide is able to produce 0.47 mmolcm-2 h-1 of formate at 50 mAcm-2 with a Faradaic conversion efficiency of 99%. Additionally, this noble-metal-free catalyst is able to continuously work for over 50000 s with a minimal loss of efficiency, delivering initial current densities above 50 mAcm-2 and 2.2 Amg-1 in a 1.0 m KOH electrolyte with 1.0 m methanol at 1.5V versus reversible hydrogen electrode. This work demonstrates the highly efficient and selective methanol-to-formate conversion on Ni-based noble-metal-free catalysts, and more importantly it shows a very promising example to exploit the electrocatalytic conversion of biomass-derived chemicals.

Selective Conversion of Methanol to Aromatics with Superior Catalytic Stability by Relay Catalysis Over Quadruple ZSM-5 Sequence Beds with Gradient-Increasing Acidity

Selective Conversion of Methanol to Aromatics with Superior Catalytic Stability by Relay Catalysis Over Quadruple ZSM-5 Sequence Beds with Gradient-Increasing Acidity

Metal-substituted sponge-like MFI zeolites as high-performance catalysts for selective conversion of methanol to propylene

Abstract In this study, sponge-like and M-substituted (M: Mn, W and Ce) sponge-like MFI zeolites were successfully synthesized by seed-assisted hydrothermal technique. The special bi-functional organic surfactant of C22-6-6Br2 with multi-ammonium groups was separately synthesized and used as structure directing agent (SDA). The prepared catalyst samples were examined in methanol to propylene (MTP) process and demonstrated superior catalytic performance compared to conventional H-ZSM-5 and M-substituted MFI zeolite nanosheets. The W-substituted sponge-like MFI zeolite effectively showed the most enhanced catalytic activity with complete methanol conversion, propylene selectivity of 56.3%, total selectivity of light olefins of 88.3% and catalytic life-span of 161 h. Moreover, to increase propylene selectivity, bi-metallic and tri-metallic sponge-like MFI zeolites were successfully synthesized via seed-assisted hydrothermal method by utilizing central composite design (CCD) strategy. For optimizing promoter compositions in lattice of bi-metallic and tri-metallic sponge-like MFI zeolites, the incorporated response surface methodology (RSM)-CCD technique and also an intelligent approach namely neuro-genetic method were applied. It was deduced that optimal bi-metallic sponge-like MFI zeolite suggested by neuro-genetic approach approved the highest propylene selectivity (66.7%). Synthesized catalysts were appropriately characterized by XRD, FE-SEM, EDX, TEM, FT-IR, N2 adsorption/desorption and NH3-TPD analyses which comparatively approved high specific surface area and dominant meso-porosity.

Performance of niobium catalysts in a one-pot system for selective methanol conversion to dimethoxymethane under mild conditions

In this work, the synthesis and application of catalysts based on niobium oxide were carried out in order to modify their acid and redox properties and make them active for the synthesis of dimethoxymethane (DMM), considered an excellent additive for diesel, in a single step. The materials were characterized by several techniques, where functionalization was confirmed by elemental analysis, infrared spectroscopy, XPS and TPR analysis. The functionalization with sulphate groups in the materials did not promote significant surface area losses. In addition, acid sites quantification showed that the modification of materials with sulfate groups led to increased acidity. Depending on the conditions used, such as 1 wt% catalyst and 10 wt% hydrogen peroxide, in relation to the methanol mass used (1.98 g), for 5 h at 100 °C the functionalized catalysts provided methanol conversion above 80% with almost 100% of DMM selectivity.

Solvent-Free Synthesis of Core–Shell Zn/ZSM-5@Silicalite-1 Catalyst for Selective Conversion of Methanol to BTX Aromatics

We report the synthesis of Zn/ZSM-5 particles coated with a silicalite-1 zeolite shell (core–shell Zn/ZSM-5@silicalite-1) via grinding of the raw silica source materials with TPAOH and Zn/ZSM-5, fo...

Highly selective conversion of methanol to propylene: design of an MFI zeolite with selective blockage of (010) surfaces.

As an important catalyst of methanol-to-propylene (MTP) conversion, the ZSM-5 zeolite has an anisotropic diffusion path and a large pore size, resulting in the formation of undesirable heavy aromatic by-products. Herein, we developed a surface-specific silica deposition method to block straight channels of nanosized ZSM-5 crystals selectively. By such a coating method, we can selectively suppress the yield of aromatics from the original 13% to 2.4% at 100% conversion of methanol. Trapped hydrocarbon pool species are directly confirmed by aberration-corrected S/TEM for the first time. Such a method of trapping and restricting hydrocarbon pool species in a multiscale zeolite with 10-membered rings would significantly increase its catalytic efficiency and olefin diffusion. Moreover, this provides new methodologies for zeolite structure construction and will be greatly beneficial for the industrial MTP process.

Carbon nanofibers@NiSe core/sheath nanostructures as efficient electrocatalysts for integrating highly selective methanol conversion and less-energy intensive hydrogen production

In situ synthesized carbon nanofibers@NiSe core/sheath nanostructures act as robust and stable electrocatalysts for highly selective methanol conversion to value-added formate and boosting hydrogen production with less energy consumption.

Efficient and selective conversion of methanol to para-xylene over stable H[Zn,Al]ZSM-5/SiO2 composite catalyst

A highly shape-selective H[Zn,Al]ZSM-5/SiO2 composite catalyst was prepared by direct incorporating Zn species via isomorphous substitution into the zeolite framework and subsequent SiO2 deposition on zeolite surface. Its catalytic performance in methanol to aromatics (MTA) was compared with Zn/HZSM-5/SiO2 prepared by impregnation of Zn species and subsequent SiO2 deposition. The textural properties and acidic properties as well as the subsequent catalytic performances of the resultant catalysts in MTA reaction were obviously influenced by the introduction method of Zn species. H[Zn,Al]ZSM-5/SiO2 prepared by isomorphous substitution contained more inter-crystalline voids, which provided much space to resist deposition of coke and avoided quick blockage of micropore entrances. In contrast, Zn/HZSM-5/SiO2 prepared by impregnation contained sub-nanometric ZnO clusters at the pore entrances, which might restrict large molecule products diffusion and deteriorated the catalyst deactivation. Moreover, the sum of strong and medium acid sites in H[Zn,Al]ZSM-5/SiO2 was more than that in Zn/HZSM-5/SiO2, which meant there were more active sites for cyclization and aromatization steps in MTA reaction in the former. As a result, the lifetime of H[Zn,Al]ZSM-5/SiO2 was almost twice that of Zn/HZSM-5/SiO2. In addition, the enhancement in catalytic activity by Zn introduction and the improvement in para-selectivity in xylene by SiO2 deposition were also studied. Finally, nearly 100% methanol conversion, 95.6% para-selectivity in xylene and 18.2% para-xylene yield were simultaneously obtained over the stable H[Zn,Al]ZSM-5/SiO2 (with 24 h lifetime) in MTA reaction.

Graphene Oxide and Polyelectrolyte Composed One-Way Expressway for Guiding Electron Transfer of Integrated Artificial Photosynthesis

A novel photocatalyst/biocatalyst integrated artificial photosynthesis system (APS) based on polyurethane hollow nanofibers doped with graphene oxide (GO) and poly(allylamine hydrochloride) (PAH) was developed and employed for selective methanol conversion from CO2. The biocatalysts, including formate, formaldehyde, and alcohol dehydrogenases, as well as NAD+, were in situ coencapsulated inside the lumen of the GO-PAH-doped PU nanofibers (G-Fiber) by simply predissolving them in the core-phase solution for coaxial electrospinning, while the precise assembling of the photocatalyst parts involving visible light active photosensitizer (PS) and electron mediator (M) on the surface of the G-Fiber was realized by their π–π interactions with the GO doped in the shell of fibers. By using this highly integrated APS, about 10-times higher methanol yield was accomplished as compared with the solution-based system. The significantly enhanced reaction efficiency of the G-Fiber-based APS is considered predominately due...

Direct and selective conversion of methanol to para-xylene over Zn ion doped ZSM-5/silicalite-1 core-shell zeolite catalyst

We successfully designed Zn ion doped ZSM-5/silicalite-1 core-shell zeolite catalyst. On methanol to para-xylene (MTpX) over the core-shell catalyst, p-xylene yield was 40.7C-mol% and para-selectivity (para-xylene selectivity in xylene isomers) was higher than 99C-mol%, which substantially exceeds the other results reported in the literature.

Investigating the mixing sequence and the Si content in SAPO-34 synthesis for selective conversion of methanol to light olefins using morpholine &/ TEAOH templates

SAPO-34 as the commercialized catalyst of methanol to olefin (MTO) process was synthesized by single and mixed-template methods using TEAOH and morpholine. The mixing sequence in gel preparation and the optimum Si content were investigated.