CH3OH Conversion Research Articles

SIMULATION STUDY ON THE TUBULAR MICROREACTOR FOR HYDROGEN PRODUCTION BY STEAM REFORMING OF METHANOL

In order to reduce the carbon emissions of fuel vehicles, hydrogen has received extensive attention as a new clean energy. In this paper, a packed-bed microreactor for hydrogen production from methanol steam is designed for use in hydrogen fuel cells. By considering the heating gas velocity in the heating tubes, the inlet temperature of the microreactor, the size and number of heating tubes, inlet pressure, pellet porosity and thermal conductivity, parameters such as methanol conversion rates and hydrogen concentration were evaluated. First, the rate at which the gas is heated has a great influence on the reaction results. Choosing a larger heating gas velocity leads to an increase in the temperature inside the microreactor, thereby increasing the CH3OH conversion, resulting in a higher H2 concentration at the outlet. Changing the inlet temperature of the microreactor affects the reaction speed, but has little effect on the H2 concentration at the outlet. By studying the radius and number of heating tubes, we selected three different sets of data to compare the conversion rate of reactants and the concentration of products, and finally determined the optimal parameters as R = 4 mm and N = 8. Second, the inlet pressure has little effect on the H2 concentration at the outlet, but has a significant effect on the reaction speed. Particle porosity has no effect on the reaction results. Finally, the larger the thermal conductivity, the higher the temperature in the microreactor, which is more conducive to the reaction.

Nickel-Organic Frameworks as Highly Efficient Catalyst for Electrochemical Conversion of Ch3oh into Formic Acid

Nickel-Organic Frameworks as Highly Efficient Catalyst for Electrochemical Conversion of Ch3oh into Formic Acid

Enhanced methanol production by two-stage reaction of CO2 hydrogenation at atmospheric pressure

Methanol can be produced from CO2 hydrogenation. CO2 was hydrogenated to CH3OH in one-stage reaction at atmospheric pressure. The result was highly selective to CH3OH but insufficient conversion of CO2 using Cu/Zn/Al2O3. A two-stage reaction was carried out with high and low temperatures, respectively. CO2 was hydrogenated to carbon monoxide (CO) and H2O in the first-stage at high temperatures. Subsequently, after removing H2O, CO was further hydrogenated to CH3OH in the second-stage at low temperatures. The CH3OH yield was 3.4 times higher than that of single-stage reaction. This concept achieves CO2 hydrogenation towards more CH3OH production.

Selective Methane Oxidation to Methanol on ZnO/Cu2O/Cu(111) Catalysts: Multiple Site-Dependent Behaviors.

Because of the abundance of natural gas in our planet, a major goal is to achieve a direct methane-to-methanol conversion at medium to low temperatures using mixtures of methane and oxygen. Here, we report an efficient catalyst, ZnO/Cu2O/Cu(111), for this process investigated using a combination of reactor testing, scanning tunneling microscopy, ambient-pressure X-ray photoemission spectroscopy, density functional calculations, and kinetic Monte Carlo simulations. The catalyst is capable of methane activation at room temperature and transforms mixtures of methane and oxygen to methanol at 450 K with a selectivity of ∼30%. This performance is not seen for other heterogeneous catalysts which usually require the addition of water to enable a significant conversion of methane to methanol. The unique coarse structure of the ZnO islands supported on a Cu2O/Cu(111) substrate provides a collection of multiple centers that display different catalytic activity during the reaction. ZnO-Cu2O step sites are active centers for methanol synthesis when exposed to CH4 and O2 due to an effective O-O bond dissociation, which enables a methane-to-methanol conversion with a reasonable selectivity. Upon addition of water, the defected O-rich ZnO sites, introduced by Zn vacancies, show superior behavior toward methane conversion and enhance the overall methanol selectivity to over 80%. Thus, in this case, the surface sites involved in a direct CH4 → CH3OH conversion are different from those engaged in methanol formation without water. The identification of the site-dependent behavior of ZnO/Cu2O/Cu(111) opens a design strategy for guiding efficient methane reformation with high methanol selectivity.

Conversion of methane to methanol on C-doped boron nitride: A DFT study

Computational modeling of the methane-to-methanol catalytic conversion reaction on the carbon-boron nitride nanosheet (C-BNN) was reported with the density functional theory. The charge density on C-BNN was displayed with the electron density difference map and investigated with the Bader charge analysis. The reaction mechanism was constituted according to the Eley Rideal model. CH4 → CH3OH conversion reaction were analyzed through the interaction of CH4 with O or O2 on the surface. The calculated energy barrier of the CH4 + O* → CH3OH and CH4 + O2 → CH3OH + O on C-BNN is 0.97 eV and 0.20 eV respectively. Our calculation results showed that the C-BNN surface was a highly active catalyst for the conversion reaction of methane to methanol. This information can provide different strategies for new catalyst researches with low cost and high catalytic activity.

Combined steam and dry reforming of methanol over Fe‐Mn‐Cu / ZrO 2 catalyst to syngas formation: Study about kinetic and fuzzy model approaches

Combined steam and dry reforming of methanol (CSDRM) experiments were applied to measure the responses of CH3OH conversion, H2/CO ratio, H2 and CO yield at a temperature range of 300°C to 900°C, CO2/H2O ratio of 0.5 to 2.5 and (CO2 + H2O)/CH3OH ratio of 1 to 3 on Fe-Mn-Cu/ZrO2 catalyst in a fixed bed reactor. Fe-Mn-Cu/ZrO2 catalyst was synthesized via the co-precipitation approach, and its physicochemical properties were examined through X-ray diffractometer, X-ray fluorescence, temperature-programmed reduction, N2 adsorption/desorption and thermal gravimetric analysis tests. A kinetic model for CSDRM reaction was derived via the Langmuir-Freundlich method and the proposed mechanism included three reversible reactions on three types of active sites. A Mamdani-type fuzzy model was also developed for comparison purposes, as there was no need for detailed knowledge of the process. The error of the kinetic and Mamdani-type fuzzy model approaches obtained 12.69% and 16.42%, respectively. H2 yield obtained from kinetic model values was closer to the experimental data compared to other responses. However, for the fuzzy model approach, the difference between experimental and calculated methanol conversion was lower.

Two-in-One Catalyst Turns Carbon Dioxide in Base Chemicals

Cascading chemical reactions can be realized when the local structure and composition of two catalytically active phases are fine-tuned and combined in one material. In this issue of Chem, Fan et al. report an innovative approach for the conversion of carbon dioxide into light olefins with a metal oxide-zeolite tandem catalyst.

Visible-Light-Driven Methane Conversion with Oxygen Enabled by Atomically Precise Nickel Catalyst

It remains an extreme challenge to activate thermodynamically unfavorable, chemically inert methane molecules under mild conditions. Herein, we report a molecular-like nickel-thiolate hexameric clu...

Hydrogen production from partial oxidation and autothermal reforming of methanol from a cold start in sprays

Hydrogen is a noticeable clean fuel that can be applied in power generation and transport. Hydrogen production from methanol via thermochemical methods has been widely studied and used. In these methods, autothermal reforming (ATR) simultaneously contains endothermic steam reforming and exothermic partial oxidation of methanol (POM), The latter can help start the experiment and provide heat for the former. This study aims to perform methanol ATR by sprays via an h-BN-Pt catalyst without preheating, mainly focusing on the effects of operating conditions on hydrogen production and methanol conversion. Meanwhile, the comparison between ATR and POM of methanol is also carried out. The results of POM indicate that the highest H2 and CO concentrations are obtained at the air-to-methanol molar ratio (O2/C) of 0.7, and the CH3OH conversion can reach 100%. However, through the ATR process, the methanol conversion reaches 60% at O2/C = 0.7 with steam-to-methanol molar ratio (S/C) of 1.5. At S/C = 0.5, it is observed that the CH3OH conversion is up to 100% with increasing the O2/C ratio, and the H2 yield is higher than that of POM. The effects of S/C and O2/C ratios on ATR indicate that the CH3OH conversion and reaction temperature are significantly increased with decreasing the S/C ratio and increasing the O2/C ratio. Overall, the H2 yield from ATR at S/C of 0.5 and O2/C of 0.7 is highest with 1.697 mol (mol CH3OH)−1.

Sorption-enhanced chemical looping oxidative steam reforming of methanol for on-board hydrogen supply

Hydrogen is an indispensable energy carrier for the sustainable development of human society. Nevertheless, its storage, transportation, and in situ generation still face significant challenges. Methanol can be used as an intermediate carrier for hydrogen supplies, providing hydrogen energy through instant methanol conversion. In this study, a sorption-enhanced, chemical-looping, oxidative steam methanol-reforming (SECL-OSRM) process is proposed using CuO–MgO for the on-board hydrogen supply, which could be a promising method for safe and efficient hydrogen production. Aspen Plus software was used for feasibility verification and parameter optimization of the SECL-OSRM process. The effects of CuO/CH3OH, MgO/CH3OH, and H2O/CH3OH mole ratios and of temperature on H2 production rate, H utilization efficiency, CH3OH conversion, CO concentration, and system heat balance are discussed thoroughly. The results indicate that the system can be operated in auto-thermal conditions with high-purity hydrogen (99.50 vol%) and ultra-low-concentration CO (< 50 ppm) generation, which confirms the possibility of integrating low-temperature proton-exchange membrane fuel cells (LT-PEFMCs) with the SECL-OSRM process. The simulation results indicate that the CO can be modulated in a lower concentration by reducing the temperature and by improving the H2O/CH3OH and MgO/CH3OH mole ratios.

Mathematical modelling of the solar-driven steam reforming of methanol for a solar thermochemical micro-fluidized bed reformer: thermal performance and thermochemical conversion

A solar thermochemical reformer/receiver which combines a ST-μFB reformer and a catalytic bed of micro-sized particles offers a novel approach for the solar-driven catalytic steam reforming of methanol (SDCSR-MeOH) method. Heat transfer, mass transfer and solar thermochemical conversion performance have a great significance on the SDCSR-MeOH method due to high interfacial absorption surface of micro-sized particles. The solar radiation has been coupled to the ST-μFB reformer as a novel driving energy for conducting the endothermic reactions of methanol (CH3OH) inside ST-μFB reformer to produce solar H2. Solar H2 had won an important role as renewable feedstocks for different chemical processes and particularly in fuel cells applications. A non-isothermal mathematical model was described by a set of partial differential equations (PDEs) that couples to a complex kinetic model of the SDCSR-MeOH employing the Cu/ZnO/Al2O3 catalyst. The system of novel PDEs has been transformed into simpler system of ordinary differential equations using the coupled integral equation approach. Validation results demonstrate that the two validated cases for the reaction temperature against the simulated results by authors had reached a good fit as well as the solar thermochemical conversion of CH3OH. The temperature profiles of the gas phase, solid phase and ST-μFB reformer wall were simulated at three different positions from ST-μFB reformer. The reactant and product distributions inside ST-μFB reformer were analysed at two different reaction temperatures. The effect of the reaction temperature was studied on the conversion of CH3OH and yield of H2. In addition, the action of the weight hourly space velocity has been analysed on the conversion of CH3OH.

Lanthanum-Doped Ceria Nanocomposite: A Highly Stable Monolithic Catalyst for Direct Synthesis of Dimethyl Carbonate

That dimethyl carbonate is directly synthesized from methanol and carbon dioxide is an effective and environmental approach to solve the greenhouse effect. For the sake of solving the problems of low DMC productivity and poor catalysts stability in presence of the formed water. Here we design and prepare a serial of spherical La-doped ceria nanoparticles (Ce1-xLaxOδ nanocomposites, x=0.00, 0.05, 0.10, 0.15, and 0.20) via a co-precipitation method. These Ce1-xLaxOδ composites are ground into slurry by ball milled and then coated on cordierite honeycomb ceramics to obtain Ce1-xLaxOδ monolithic catalysts. These Ce1-xLaxOδ composites are characterized extensively by TEM, XRD, Raman spectroscopy, N2 adsorption-desorption isotherms, H2-TPR and XPS. The characterization results show that the Ce1-xLaxOδ composites nanoparticles possesses richer surface oxygen vacancies, higher BET surface area and smaller particle size than that of pure CeO2 nanoparticle. Besides, catalytic activity test shows these Ce1-xLaxOδ monolithic catalysts exhibit better catalytic performance than that of pure CeO2 nanoparticles. Among them, Ce0.95La0.05Oδ monolithic catalyst exhibits the highest CH3OH conversion and DMC yield, which is in good line with the oxygen vacancy content measured by XPS. Finally, the Ce0.95La0.05Oδ monolithic catalyst also shows an excellent durability of more than 100 hours, which is mainly due to the doping effect of lanthanum into the ceria oxides tailoring the structure and surface properties of the catalyst.

Thiolation of methanol with H2S using core-shell structured ZSM-5@t-ZrO2 catalyst

Core-shell structured ZSM-5@t-ZrO2 catalysts were prepared by a hydrothermal coating method, and their physicochemical properties, catalytic performance, and deactivation behavior in thiolation reactions were studied using a ZSM-5/t-ZrO2 physically-blended catalyst as a comparison. Reactions using the core-shell ZSM-5@t-ZrO2 catalyst were carried out at a pressure of 0.7 MPa, 370 °C, a H2S:CH3OH molar ratio of 2:1, and a N2 flow rate of 90 ml·min−1. The conversion of CH3OH, and the selectivity and yield of CH3SH under these conditions were 92.07%, 90.89%, and 83.68%, respectively, and the catalytic lifetime was longer than 30 h. Compared with the ZSM-5/t-ZrO2 physically-blended catalyst, the CH3SH yield and the catalytic lifetime of the core-shell structured ZSM-5@t-ZrO2 catalyst were higher by 5.37% and 150%, respectively. The unique reaction pathway of the shell (t-ZrO2, Lewis (L) base active site)-core (ZSM-5, Brǿnsted (B) acid active site) and the Lewis-Brønsted acid active center based on a composite solid-solution interface were mainly responsible for the high activity of the thiolation reaction. Meanwhile, the formation of a micro-mesoporous system increased the diffusion of molecules and reduced the deactivation rate of carbon- and sulfur-containing deposits. Generally, carbon- and sulfur-containing substances deposited on catalysts were mainly composed of polymethylbenzene, polymethyl naphthalene, cyclic elemental sulfur, and other compounds containing CS and SS bonds. Finally, the core-shell structured catalysts showed excellent resistance to deactivation by carbon- and sulfur-containing deposits.

CO2 Hydrogenation on Cu/Al2 O3 : Role of the Metal/Support Interface in Driving Activity and Selectivity of a Bifunctional Catalyst.

Selective hydrogenation of CO2 into methanol is a key sustainable technology, where Cu/Al2 O3 prepared by surface organometallic chemistry displays high activity towards CO2 hydrogenation compared to Cu/SiO2 , yielding CH3 OH, dimethyl ether (DME), and CO. CH3 OH formation rate increases due to the metal-oxide interface and involves formate intermediates according to advanced spectroscopy and DFT calculations. Al2 O3 promotes the subsequent conversion of CH3 OH to DME, showing bifunctional catalysis, but also increases the rate of CO formation. The latter takes place 1) directly by activation of CO2 at the metal-oxide interface, and 2) indirectly by the conversion of formate surface species and CH3 OH to methyl formate, which is further decomposed into CH3 OH and CO. This study shows how Al2 O3 , a Lewis acidic and non-reducible support, can promote CO2 hydrogenation by enabling multiple competitive reaction pathways on the oxide and metal-oxide interface.

CO2 Hydrogenation on Cu/Al2O3: Role of the Metal/Support Interface in Driving Activity and Selectivity of a Bifunctional Catalyst

AbstractSelective hydrogenation of CO2 into methanol is a key sustainable technology, where Cu/Al2O3 prepared by surface organometallic chemistry displays high activity towards CO2 hydrogenation compared to Cu/SiO2, yielding CH3OH, dimethyl ether (DME), and CO. CH3OH formation rate increases due to the metal–oxide interface and involves formate intermediates according to advanced spectroscopy and DFT calculations. Al2O3 promotes the subsequent conversion of CH3OH to DME, showing bifunctional catalysis, but also increases the rate of CO formation. The latter takes place 1) directly by activation of CO2 at the metal–oxide interface, and 2) indirectly by the conversion of formate surface species and CH3OH to methyl formate, which is further decomposed into CH3OH and CO. This study shows how Al2O3, a Lewis acidic and non‐reducible support, can promote CO2 hydrogenation by enabling multiple competitive reaction pathways on the oxide and metal–oxide interface.

Cu-Exchanged Ferrierite Zeolite for the Direct CH4 to CH3OH Conversion: Insights on Cu Speciation from X-Ray Absorption Spectroscopy

The direct stepwise transformation of CH4 to CH3OH over Cu-exchanged zeolites has been an intensively researched reaction as it can provide a solution for the utilization of this abundant feedstock. Up to date a commercial process is far from realization, which is why an understanding of the Cu speciation in zeolites as a function of reaction conditions as well as the development of a mechanistic view of the reaction are necessary to further advance the field. Herein we study Cu-exchanged ferrierite zeolite for the direct CH4 to CH3OH conversion by utilizing X-ray absorption spectroscopy (XAS), in order to assess the local structure and electronic properties of Cu through the reaction. A Cu-FER sample with a Cu/Al = 0.20 and Si/Al = 11 was subjected to three reaction cycles yielding ultimately 96 µmol $$_{{{\text{C}}{{\text{H}}_3}{\text{OH}}}}/{{\text{g}}_{{\text{zeolite}}}}$$ . Normalized to the Cu loading, this accounts for 0.33 mol $$_{{{\text{C}}{{\text{H}}_3}{\text{OH}}}}$$ /molCu, making the sample comparable to very active Cu-MOR materials reported in the literature. During O2 activation, a transient self-reduction regime of CuII to CuI ions was identified; eventually leading to mostly framework interacting CuII species. CH4 loading leads to a reduction of these CuII containing species; which are finally partially reoxidized during H2O-assisted CH3OH extraction. The speciation after CH4 activation as well as H2O-assisted CH3OH extraction was assessed via linear combination fitting analysis of the XAS data.

Understanding and Optimizing the Performance of Cu‐FER for The Direct CH4 to CH3OH Conversion

AbstractCu‐exchanged zeolites with the Ferrierite topology were investigated in the direct CH4 to CH3OH conversion. Samples with a systematic compositional variation in terms of Na/Al and Cu/Al ratios where synthesized by liquid ion exchange. The presence of Na is observed to be beneficial for the Cu exchange and thereby higher Cu loadings were achieved. The overall performance of Cu‐FER samples depends on Cu loading as well as the conditions of the reaction. Elevated O2 activation temperature as well as long CH4 loading times are proven to enhance the CH3OH yield of the Cu‐FER sample with Cu/Al=0.2. In addition, the productivity depends on the Cu/Al ratio, at low values the sample is almost inactive indicating a Cu threshold that needs to be surpassed. We employed X‐ray absorption and IR of adsorbed CO spectroscopies in order to rationalize the performance as well as the effect of Cu/Al ratio. From the in situ spectroscopies we ultimately establish structure‐activity relationships between the reducibility of Cu species and the CH3OH yield.

Hydrogen production from the oxidative steam reforming of methanol over Au[sbnd]Cu nanoparticles supported on Ce1-xZrxO2 in a fixed-bed reactor

Oxidative steam reforming of methanol over monometallic gold (Au) and bimetallic Au-copper (Cu) supported on ceria-zirconia (CeO2ZrO2) was examined over the temperature range of 200–400 °C in a fixed-bed reactor. The composition of CeO2ZrO2 supports was also studied for their catalytic activity. The Au/Ce0.75Zr0.25O2 catalyst exhibited the highest methanol (CH3OH) conversion level (96.7%) and hydrogen (H2) yield (59.7%) due to the formation of a homogeneous Ce1-xZrxO2 solid solution. When Cu was introduced in the Au catalysts, all of the bimetallic catalysts presented a better stability for CH3OH conversion as well as H2 yield in comparison to the monometallic catalysts, which was due to the partial electron transfer from Cu to Au metals. The performance of the AuCu/Ce0.75Zr0.25O2 catalysts, which was evaluated under identical conditions, was ranked in the order: 3Au1Cu > 1Au3Cu > 1Au1Cu.

Synthesis of Methanethiol from Methanol and Carbon Disulfide over CoKW/Al2O3 Catalysts: The Possible Reaction Network and Reaction Mechanism

AbstractSynthesis of methanethiol from methanol and carbon disulfide was catalyzed by KW/γ‐Al2O3 catalysts under different reaction conditions. A possible reaction network was put forward by investigating the effects of the molar ratio of reactants, the reaction pressure, the reaction temperature, the residence time, and in the presence of water and hydrogen sulfide on the catalytic performance. Furthermore, the relationship between the conversion of CH3OH, the yield of CH3SH and the surface acid‐base properties was discussed in detail. The catalytic results measured in the laboratory scale (2 ml catalysts) and those obtained in the scaling‐up tests (50 ml original grain catalysts) are well matched. Combined with pyridine adsorption Fourier Transform Infrared (FT‐IR), CO2/NH3‐Temperature Programmed Desorption (CO2/NH3‐TPD), and the catalytic results, it was found that the conversion of CH3OH can be chiefly correlated with weak and moderate acid sites, while the selectivity toward CH3SH is mainly related to the weak basic sites, and the possible reaction mechanism was put forward.

Improvement of dimethyl carbonate formation via methanol carbonation over vanadium-doped Cu–Ni/AC catalyst

In present study, Cu–Ni/AC and V-doped Cu–Ni/AC were prepared using an impregnation and co-impregnation methods respectively for dimethyl carbonation (DMC) formation from CH3OH carbonation at various temperatures (110, 170, and 220°C) and CO2/N2 volumetric flow ratios (1/4, 1/7, and 1/9). Effects of vanadium addition on Cu–Ni/AC intrinsic properties and catalytic performances were investigated. Decrease of Cu–Ni/AC surface acidity with vanadium addition was found with NH3–temperature programmed desorption (NH3–TPD) at 25–450°C. Furthermore, the valence shifts of metallic atoms in catalysts were found by X–ray absorption near–edge structure/extended X–ray absorption fine structure (XANES/EXAFS). Optimal reaction conditions (170°C and CO2/N2 = 1/7) with the highest CH3OH conversion (8.1%), DMC selectivity (93.2%), and DMC yield (7.5%) were confirmed in a fixed-bed column reactor. Linear regressions of the pseudo-first-order, pseudo-second-order, and third-order models referred that the largest CH3OH consumption rate constant (15.56 × 10−3 1/min, 9.29 L/mol-min), turnover number (TON = 17.89), and turnover frequency (TOF = 3.73 × 10−2 1/min) of DMC formation were acquired with V-doped Cu–Ni/AC at optimal reaction conditions. A reaction mechanism over Cu–Ni/AC or V-doped Cu–Ni/AC active sites was proposed.