Methanol Catalyst Research Articles

Synthesis of hierarchical ZSM-11 and its catalytic performances during methanol to propylene

To solve the easy deactivation of zeolite catalyst in methanol to propylene (MTP) reaction, hierarchical ZSM-11 zeolite composed of loosely aggregating ultra-small nanocrystals (∼10 nm) were prepared using vinyltrimethoxysilane-methyl methacrylate (VTMS-MMA) copolymer latex as a “bond blocker”. The structure and texture properties of the as-synthesized zeolite were systematically characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption desorption, NH3-TPD, and thermogravimetric analysis (TG). The results showed that as compared with the parent ZSM-11-0 without adding the latex, the hierarchically porous ZSM-11-x (1 ≤ x ≤ 3) zeolite synthesized with VTMS-MMA copolymer latex had a higher surface area, mesopore volume, and moderate acidity. Due to the nanocrystallization of the primary grain in the polycrystalline aggregates, the micropores channels in the as-synthesized ZSM-11-x (1 ≤ x ≤ 3) were effectively shortened and abundant intercrystalline mesopores resulted from loosely aggregating of the ultrasmall primary crystals were therefore introduced, which offered the optimized ZSM-11-1 catalysts with a longer catalyst life (46 h) and a higher propylene yield (∼40.5 %) in MTP.

One-pot catalytic conversion of sugars to methyl lactate over acid-base bifunctional Sn/MgO catalysts

Alkyl lactates represent such green added-value chemicals that commonly used as biodegradable green solvents, detergents, pharmaceutical intermediates et al. Catalytic conversion of carbohydrates to methyl lactate (MLA) is a representative way for high-value utilization of biomass and the key lies in the development of highly efficient catalysts. In methanol, strong acid or alkaline catalysts are usually used under high temperature and high pressure, suffering from problems such as low selectivity, high cost or contamination of environment. This study aims to develop an acid-base bifunctional heterogeneous catalyst for the one-pot conversion of sugars to MLA under mild conditions. Sn/Mg composite oxides was synthesized by a coprecipitation method and further modified by poly (vinyl imidazole) ([PVIM]) to tune the hydrophilicity. Effect of polymer and Sn amount, calcination temperature, reaction temperature, catalyst dosage, and substrate concentration were investigated. The acid-base properties were characterized by NH3-TPD, pyridine-FTIR and CO2-TPD analysis. It was found that the presence of medium acid sites and medium base sites played an important role to the cascade reactions of carbohydrates to MLA. An optimum MLA yield of 55.4% was achieved over 10[PVIM]-5Sn/MgO (0.05 g) with complete conversion of glucose (28 mM) at 140 ℃, 2 MPa N2 for 10 h. The reaction conditions are mild and no strong acid or strong base catalyst is required. Furthermore, a possible reaction mechanism was proposed that the introduction of [PVIM] effectively regulated the local microenvironment of active sites and the acid base synergism greatly promoted the retro-aldol condensation, dehydration and hydrogen transfer reactions during the conversion of glucose to MLA.

CO2 Hydrogenation to CH3OH on Metal-Doped TiO2(110): Mechanisms, Strain Effect and a New Thermodynamic-Kinetic Relation.

Surface strain and linear thermodynamic-kinetic relation are interesting topics in catalysis. Development of low temperature methanol catalysts of high activity and selectivity is of particularly importance for conversion of CO2 to methanol. In the present paper CO2 hydrogenation to methanol on Znx@TiO2(110) (x=0-2) was explored using density functional calculations and microkinetic simulations. The reaction mechanisms on the three model systems were determined and it is shown that Zn2@TiO2(110) is the most active. The most favorable pathway on Zn2@TiO2(110) is identified and CO2+H to HCOO is found to be the rate-controlling step. It is demonstrated that there is a linear relation (named AEB relation) between the adsorption energies of the initial states and the barriers for the controlling step on the 18 systems studied. Calculations on strained surfaces show that the AEB relation exists within ±1 % strain. Sr2@TiO2(110) and -1 % strained CaZn and ZnCu doped TiO2(110) are potential good low temperature catalysts and deserve experimental testing.

Sustainable methyl formate generation by dehydrogenation of green methanol over Cu_SiO2/MgO

Copper impregnated SiO2 and MgO catalysts were prepared, characterised, and tested for the synthesis of methyl formate (MF) from methanol by dehydrogenation. Compared to the Cu-impregnated pure oxides, MF formation was improved when SiO2/MgO mixtures were used as support. For further comparison, a silver impregnated mixed oxide catalyst, known for its dehydrogenation ability, and a typical methanol catalyst (Cu/ZnO/Al2O3) were tested. Both catalysts displayed non or poorer performance under tested reaction conditions. High catalytic activity was assigned, besides the Cu content, to the presence of both medium acidic and basic sites. At 240 °C and 1 bar, the highest MF yield of 34 % has been obtained with the mixture of oxides containing the highest MgO ratio of 35 mol%. By exposing the prepared catalyst to a methanol/water mixture (36 wt% water), methanol conversion drops to 5 %, but compared to the reference Cu/ZnO/Al2O3 catalyst, two times the selectivity towards MF was obtained. With respect to sustainable technology development, direct coupling of green methanol synthesis from CO2/H2 gas feed and MF production without water removal is not recommended, since the yield to MF is below 2 % in this case.

Mg enhanced the performance of Cu/ZnO/ZrO2 for CO2 hydrogenation to methanol and the mechanism investigation

Optimizing the microstructure of copper-based catalysts for CO2 hydrogenation to methanol is an attractive and widely reported strategy, but there are still certain barriers to improving both carbon dioxide conversion rate and methanol product selectivity. Herein, Cu/ZnO/ZrO2/MgO (CZZ1-xMx) catalysts were synthesized by co-precipitation method for CO2 hydrogenation to methanol. Furthermore, the structural features and reaction processes were systematically characterized by XRD, TEM, nitrogen adsorption/desorption, H2-TPR, CO2-TPD and in-situ DRIFT. The results showed that Mg species optimized the microstructure of the catalyst, increased the dispersion of active species and constructed appropriate basic sites. This further enhanced the capture of reactive species and improved the CO2 hydrotreating to methanol reaction performance, which was accompanied by a simultaneous increase in CO2 conversion and methanol yield. It could be convinced that the highest space time yield (STY) of methanol (305.3 gMeOH kgcat−1 h−1) was obtained at 220 °C, WHSV = 18,000 mL gcat−1 h−1 and 3 MPa (XCO2 = 7.28%, SMeOH = 71.8%) for the optimized CZZ0.8M0.2 catalyst, which exhibited twice the CO2 conversion than Cu/ZnO/ZrO2. This work elaborated a scheme for the preparation of efficient methanol catalysts. providing reference for the research of CO2 hydrogenation to methanol process.

Heterointerface engineering of rhombic Rh nanosheets confined on MXene for efficient methanol oxidation

Although metallic rhodium (Rh) is regarded as a promising platinum-alternative anode catalyst of direct methanol fuel cell (DMFC), the conventional “particle-to-face” contact model between Rh and matrix largely limits the overall electrocatalytic performance due to their insufficient cooperative effects. Herein, we report a controllable and robust heterointerface engineering strategy for the bottom-up fabrication of rhombic Rh nanosheets in situ confined on Ti3C2Tx MXene nanolamellas (Rh NS/MXene) via a convenient stereoassembly process. This unique design concept gives the resulting 2D/2D Rh NS/MXene heterostructure intriguing textural features, including large accessible surface areas, strong “face-to-face” interfacial interactions, homogeneous Rh nanosheet distribution, ameliorative electronic structure, and high electronic conductivity. As a consequence, the as-prepared Rh NS/MXene nanoarchitectures exhibit exceptional electrocatalytic methanol oxidation properties in terms of a large electrochemically active surface area of 126.2 m2 g−1Rh, a high mass activity of 1056.9 mA mg−1Rh, and a long service life, which significantly outperform those of conventional particle-shaped Rh catalysts supported by carbon black, carbon nanotubes, reduced graphene oxide, and MXene matrixes as well as the commercial Pt nanoparticle/carbon black and Pd nanoparticle/carbon black catalysts with the same noble metal loading amount. Density functional theory calculations further demonstrate that the direct electronic interaction at the well-contacted 2D/2D heterointerfaces effectively enhances the adsorption energy of Rh nanosheets and induces a left shift of the d-band center, thereby making the Rh NS/MXene configuration suffer less from CO poisoning. This work highlights the importance of rational heterointerface design in the construction of advanced noble metal/MXene electrocatalysts, which may provide new avenues for developing the next-generation DMFC devices.

Construction of MOF-5 derived ZnO composites porous carbon supported Pd nanoparticles as highly stable catalyst for methanol and ethanol oxidation

The preparation of highly active and stable Pd-based catalysts for direct alcohol fuel cells (DAFC) is hampered by inefficient utilization of the active sites, susceptibility to CO poisoning, poor stability, and relatively slow reaction kinetics. Herein, the stability and anti-toxicity of the catalysts (Pd/ZnO/MDC) are tuned by loading Pd nanoparticles on the carbon-coated ZnO support, achieving efficient electrocatalysis for methanol and ethanol oxidation reaction (MOR and EOR). TEM result shows the ZnO is covered by the carbon layer formed outside of MOF-5 derived porous carbon, which can prevent it from dissolving under harsh conditions. The mass activities of the well-tuned catalyst Pd/ZnO/MDC(800) for MOR and EOR are 931.83 mA/mg and 1838.30 mA/mg, respectively. It is due to the improved electron transport efficiency between the Pd and ZnO, and the enhanced stability by carbon layer outside the ZnO. It is also found that the onset potential and the peak potential of Pd/ZnO/MDC(800) (−0.813 V, −0.228 V) in CO stripping experiment in MOR are more negative than Pd/MDC(800) (−0.261 V, −0.215 V). This result indicates that the existence of ZnO helps to provide surface hydroxyl group, which promotes the oxidation of the intermediates. This work indicates provides a feasible idea for DAFC catalyst design and construction.

Grinding synthesis of SAPO-44 in the presence of dual templates: a promising catalyst for methanol to propylene reaction

Grinding synthesis of SAPO-44 in the presence of dual templates: a promising catalyst for methanol to propylene reaction

Dual-function macroalgae biochar: Catalyst for hydrogen production and electrocatalyst

In the current study, Enteromorpha intestinalis, a green macroalgae, has been utilized as a substrate to synthesise a new environmentally friendly and cheap dual-functional (catalyst and electrocatalyst) material. The catalyst was used for efficient hydrogen production from alcoholises sodium borohydride and as an anode catalyst for direct methanol fuel cell applications. At the catalyst synthesis stage, orthogonal arrays of Taguchi is used to find the optimum levels of independent variables for the superior catalyst performance that bears the modest kinetics. The experiments performed in accordance with the L16(45) type orthogonal array. The samples treated at relatively moderate acid, impregnation temperature, impregnation time, burning temperature and burning time showed higher catalytic activities with Exp(5) presenting the optimal catalytic activity followed by Exp(1), Exp(15), Exp(8) and Exp(12), respectively. The experimental levels of coded variables (acid molarity, impregnation temperature and time, burning temperature and time) for Exp(5) were 3 M, 50 °C, 24 h, 500 °C and 2 h., respectively. These finding suggest that providing maximum levels of each of independent variable will not provide high catalytic activity. Taking into account the binary and ternary interactions is an efficient way to determine optimal level of each parameter with regards to maximum hydrogen production rate. The morphological and structural characterization of the optimal catalyst was finally carried out with SEM- EDS, XRD and FT-IR. CV and EIS measurements were taken to determine the electrocatalytic activity of final biochar. Experimental studies revealed that the utilization of E. intestinalis-based electrocatalyst as an anode catalyst for direct fuel cell applications is promising. By employing advanced Taguchi-based experimentation, this research establishes the optimum levels of independent variables, enhancing the catalyst's performance, and highlighting a novel approach to modest kinetics improvement.

SiO2-Al2O3 catalysts for methanol to olefins: Comparative study with SAPO34 and ZSM5

The conversion of methanol to olefins (MTO, T = 400 and 450 °C, WHSV=4 h-1) was studied using ZSM5, SAPO34 and amorphous silica-aluminas (different percentages of SiO2, 40%, 60% and 70%) (commercial catalysts) treated or not by HCl. All the catalysts studied present type IV adsorption/desorption isotherms of N2. The incorporation of HCl decreased the surface area, increased the pore size, the total acidity and the quantity and strength of Brønsted acid sites. The increase in the reaction temperature favors the yield of ethylene to a greater extent than that of propylene. The highest light olefins yield was obtained with catalysts containing 60% SiO2 at 400ºC. Its good performance is attributed to the combination of adequate acidity, high specific surface area, and small pore size. Catalysts with 40% SiO2 are not suitable for MTO. The addition of HCl to the aluminosilicates cause further deactivation.

Efficient synergism of concentric ring structures and carbon dots for enhanced methanol electro-oxidation.

Developing affordable and reliable electrocatalysts with high activity and stability is crucial for enhancing the practicality of direct methanol fuel cells (DMFCs). An effective and simple strategy of combining the carbon point of N-CDs (0.4 mg mL-1) with NiO/Ni for the fabrication of NiO/Ni-N-CDsV nanocomposites with a three-dimensional concentric core-shell structure was proposed to successfully prepare the electro-oxidation catalyst of methanol. The low cost of Ni-based materials and the conductive N-CDs that improve methanol catalytic performance make the composites an excellent choice as electrode materials for direct methanol fuel cells (DMFCs). The electrocatalytic behavior of methanol oxidation was studied using cyclic voltammetry and chronoamperometry. The results indicated that the catalytic activity of NiO/Ni-N-CDsV increased by 3.02 times, and the current density was stable during the operation for 83 hours, implying strong electrocatalytic stability. Furthermore, the electrocatalytic performance for ethanol, ethylene glycol, and glycerol electro-oxidation reactions was impressive. This study provides a novel foundation for the development of high-performance, cost-effective, non-noble metal catalysts for DMFC applications, contributing to the formation of commercially competitive electro-oxidation catalysts with enhanced efficiency and stability.

Restructuring of Ag catalysts for methanol to formaldehyde conversion studied using in situ X-ray ptychography and electron microscopy

Dynamic restructuring of Ag catalysts was visualised in real time using in situ X-ray ptychography. Formation of pores and cavities was observed upon heating under various gas environments, allowing quantitative assessment of material redistribution.

GBL/BDO pair as a bio-based liquid organic carrier: Kinetic modeling of liquid phase hydrogenation and dehydrogenation over copper-based catalyst

The use of liquid organic hydrogen carriers (LOHC) for hydrogen storage has technical, economical, and environmental advantages. The γ-butyrolactone (GBL)/1,4-butanediol (BDO) pair is used in this work as a bio-based LOHC. Reaction kinetics of liquid phase GBL hydrogenation and BDO dehydrogenation have been studied using a semi-batch reactor filled with a copper based methanol catalyst with the experiments have been performed in the temperature range of 458–503 K with a constant pressure of 50 and 3 bar for hydrogenation and dehydrogenation respectively. Based on analytical results, a reaction pathway including the formation of side products was proposed. This pathway includes the formation of two side-products: 4-hydroxybutyl 4-hydroxybutanoate (4-HHB) is produced from the transesterification of GBL by BDO in both reactions; and dibutyleneglycol (DG) from the etherification of BDO in dehydrogenation. Based on experimental results, kinetic models were established for hydrogenation and dehydrogenation reactions. In these models, balanced reactions with a first order were used. Estimation of kinetic parameters for both reactions allows a good prediction of the experimental data and results in a temperature extrapolation by an Arrhenius law. Activation energies for GBL hydrogenation and BDO dehydrogenation were determined to be respectively 104 kJ/molLOHC and 98.3 kJ/molLOHC. Furthermore, models are valid at short (up to 5 h) and long (up to 20 h) reaction times and the estimation results display acceptable uncertainties for all the reaction temperatures.

A versatile electrospinning method to fabricate ZSM-5-decorated MgO nanofibers as a catalyst for methanol to light olefins: Toward remarkable stability and superior performance

In response to the increasing concerns about climate change and the depletion of fossil fuel reserves, the application of zeolite ZSM-5 as a catalyst in the methanol to olefin (MTO) process is considered a promising chemical technique. It holds the potential to produce essential chemical building blocks, such as light olefins, using sustainable raw materials. In this study, electrospun MgO/ZSM-5 nanofibers were synthesized to enhance mass/heat transfer limits during the MTO process and improve catalyst stability. In this synthesis, ZSM-5 nanoparticles with a mean diameter of 600 nm were arranged on magnesium oxide nanofibers with a mean diameter of 200 nm. The catalysts were characterized using various techniques, including XRD, SEM, TEM, EDX-Mapping, NH3-TPD, BET, and TGA. The electrospinning technique prevented nanoparticle accumulation and improved the morphology of the catalyst. In an isothermal fixed-bed reactor, the catalysts were tested at 450 °C, 1 atm, WHSV = 4.5 hr−1, with a methanol-water solution in a 1:1 (v/v) ratio as the feed. The stability of the nanofibers was found to be enhanced compared to ZSM-5 nanoparticles. MgO/ZSM-5-50 nanofibers (50 wt% zeolite), MgO/ZSM-5-80 nanofibers (80 wt% zeolite), and ZSM-5 nanoparticles exhibited methanol conversion rates of 99 %, 88 %, and 76 %, respectively, after 430 min of continuous operation. Furthermore, the amount of coke formed after 10 h for MgO/ZSM-5-50, MgO/ZSM-5-80, and ZSM-5 was 11.83 wt%, 13.63 wt%, and 20.98 wt%, respectively. The reduced coke formation on the electrospun samples compared to ZSM-5 nanoparticles demonstrates improved performance and stability for nanofiber catalysts.

Conversion of methanol and ethanol into hydrocarbons over zeolites with different pore structure and acid properties

Methanol and ethanol are converted into hydrocarbons over zeolites with different pore structures and acid properties. It is an alternative technology for generating petrochemical feedstocks, particularly ethene and propene. Thus, the search for catalysts with physicochemical properties that maximize activity and selectivity to products of interest in the reaction has increased. In this study, ZSM-5 and MCM-22 zeolites in their acid form (HZSM-5 and HMCM-22), as well as ITQ-2, the delaminated form of MCM-22, were investigated as catalysts for methanol (MeOH) and ethanol (EtOH) conversion. All samples were characterized by X-ray diffractometry (XRD), X-ray fluorescence spectrometry (XRF), 27Al magic angle spinning nuclear magnetic resonance spectrometry (27Al MAS/NMR), N2 physisorption and temperature programmed desorption of ammonia (TPD of NH3). A comparison of the catalytic performance at 500 °C and atmospheric pressure showed that the product distribution and catalyst stability were significantly influenced by the studied alcohol, suggesting that these results reflected the differences in the mechanism for the formation of hydrocarbons.

Preparation of H-[B]- ZSM -5 zeolites by hydrothermal method as a highly stable and selective catalyst for methanol to propylene (MTP) conversion

A series of high-silica boron-containing H-ZSM-5 zeolites were prepared employing the hydrothermal method. Subsequently, the physico-chemical characteristics of prepared catalysts were comprehensively studied through diverse analytical methods, followed by evaluation of catalytic performance in the methanol-to-propylene (MTP) reaction. The results demonstrated that incorporation of boron into the H-ZSM-5 zeolite induced the reduction in the total surface area and pore volume, accompanied by a raise in the density of weak acid sites. Also, the optimal point for boron content has been recognized at molar coefficient of B2O3/SiO2 = 0.025 for obtaining the highest H-[B]-ZSM-5 performance in MTP process. In comparison to unmodified H-ZSM-5, the optimized H-[B]-ZSM-5 yielded the higher selectivity towards propylene (42.9 % versus 40.1 %) and total light olefins (72.1 % versus 69.5 %), as well as propylene to ethylene ratio (8.1 versus 7.8) with a considerable reduction in selectivity toward C1–C4 alkanes (3.9 % versus 4.2 %) and heavy hydrocarbons (24.1 % versus 26.4 %). Also, the optimized H-[B]-ZSM-5 catalyst exhibited an extended lifetime of 988 h in the MTP process, surpassing the lifetime of unmodified H-ZSM-5 (936 h). These results suggest the optimal point for boron content at B2O3/SiO2 = 0.025 to attain the superior catalytic performance, specifically in terms of propylene yield and catalyst lifetime during MTP process.

Process intensification of biodiesel production using pilot-scale continuous multiple baffle reactor with feed distribution

This study aims to enhance biodiesel production through a pilot-scale continuous multiple baffle reactor. This reactor incorporates a baffle array with suitable dimension ratio into the conventional CSTR to create a series of complex flows that increase turbulence and mixing intensity, leading to an increased overall reaction rate. Additionally, this reactor also employed a method of distributing MeOH-KOCH3 solution into 5 streams to enhance mass transfer, reduce catalyst entrapment and ensure the reaction progression throughout the reactor. The investigated variables were the number of baffles, agitation speed, oil to methanol molar ratio, catalyst concentration, and residence time. Ester content of 97.70 wt. % was obtained with residence time of 10 min from single-step transesterification process. This achievement represents 6 times residence time reduction and 75 % reactor cost reduction compared to conventional CSTR with similar reaction conditions and equivalent production capabilities while maintaining simple and highly scalable design of traditional counterparts.

Biodiesel production from microalgal biomass by Lewis acidic deep eutectic solvent catalysed direct transesterification

Traditional two steps biodiesel production process generally involves corrosive sulfuric acid in the transesterification step, which is not environmentally benign. In this work, a novel procedure was presented for the direct production of biodiesel using Lewis acid deep eutectic solvent (LADES) to avoid using sulfuric acid. Synergy between the Lewis site of the LADES catalyst and the Brønsted site from biomass pretreated by Brønsted acidic deep eutectic (BADES) has resulted in the development of a bifunctional medium considered to be appropriate for high biodiesel formation and increase the FAMEs weight. The mechanism of biodiesel formation was anticipated through the experimental and computational studies of Lewis and/or Brönsted acid sites in the reaction process. The potential interference factors of the extraction process such as time of reaction, temperature, LADES catalyst concentration in methanol, and solvent volume were further optimized experimentally, followed by the Box–Behnken method. The highest amount (39.86 mg/g) of fatty acid methyl esters (FAMEs) was obtained from Chlorella pyrenoidosa biomass at 120 °C for 90 min, 5 mL solvent volume, and 5% concentration of LADES (ChCl-CrCl3.6 H2O) catalyst in methanol. The predominant FAMEs were C16:0 (9.47 mg/g), C18:2 (12.42 mg/g), and C18:3 (8.68 mg/g), and obtained biodiesel qualities meet international standards. The recyclability of LADES was tested, and satisfactory results of FAME weight were observed up to three cycles, and the FTIR peaks of LADES catalyst after four cycles of reusing have shown the structure of DES remain stable. Despite the existence of sustainable, efficient, and less toxic ways for microalgae transesterification, further investigation is required to assess the scalability of these methods for large-scale use.

Preparation and optimization of eggshell-type Cu/Zn/Al2O3 pellet catalysts for methanol reforming

The pellet-type catalyst demonstrates a usable region for the chemical reaction based on the reaction rate and reactant diffusivity. Therefore, achieving selective metal infiltration on the outer region of the support enhances the catalyst's efficiency. To address this issue, we prepared the eggshell-type Cu/ZnO/Al2O3 catalysts using the repulsion between a hydrophobic solution and a hydrophilic solution. For the methanol steam reforming reaction, the eggshell-type catalysts outperformed the homogeneously metal distributed catalysts. By analyzing the elemental distribution at both the pellet-scale and nanoscale of the catalyst, we revealed that the improved performance of the eggshell-type catalyst resulted from the selective distribution of copper particles on the outer region of the catalysts.

Methanol catalyst market to reach $8.0 bn, globally, by 2032 at 3.2% CAGR

Methanol catalyst market to reach $8.0 bn, globally, by 2032 at 3.2% CAGR