Methanol Dehydration Catalyst Research Articles

Direct Synthesis of Dimethyl Ether from Syngas Over Hybrid Catalyst with Hierarchical ZSM-5 as the Methanol Dehydration Catalyst

Commercial ZSM-5 zeolites were submitted to alkaline treatment in order to prepare hierarchical ZSM-5 zeolites with hierarchical porosity and moderate acidity. Hybrid bifunctional catalyst comprising a CuO-ZnO-Al₂O₃ (CZA) and zeolite was prepared by physical mixing method, used for the direct synthesis of dimethyl ether (DME) from syngas. The correlation between the textural and acid properties of the zeolite and the catalytic performance of hybrid catalyst has been assessed from the combined results of N₂ physisorption, FTIR of adsorbed pyridine, elemental analysis ICP, online-GC and other characterization techniques. The results indicate that the hybrid catalyst with hierarchical ZSM-5 zeolite exhibits higher activity and stability than that with parent ZSM-5 zeolite due to the synergy effect of moderated acidity and enhanced mass transport capability of the hierarchical ZSM-5 sample. Under 260 °C, 2.0 MPa and 3600 h-1, the conversion of CO and the DME selectivity to DME over hybrid catalyst CZA-ZSM-5(25)-A achieved 65.2% and 67.8%, respectively.

Zirconium Oxide Sulfate-Carbon (ZrOSO4@C) Derived from Carbonized UiO-66 for Selective Production of Dimethyl Ether.

Methanol dehydration process to dimethyl ether (DME) has been considered as one of the main routes to produce clean fuel, that is, DME. Thus, efficient catalysts are highly required for selective production of DME. Herein, UiO-66 was used as a precursor for the synthesis of zirconium oxide sulfate embedded carbon (ZrOSO4@C). The synthesis method involves a one-step carbonization of UiO-66 in the presence of sulfuric acid (10 wt %). Material characterizations using X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared, and Raman spectroscopy approve the formation of the high crystalline phase of ZrOSO4@C. Nitrogen adsorption-desorption isotherms and high-resolution transmission electron microscopy confirm the mesopore structure of the materials. Acidity analysis using pyridine temperature-programmed desorption and isopropanol dehydration corroborates that ZrOSO4@C has weak and intermediate acidic sites making ZrOSO4@C an effective catalyst for methanol dehydration to DME. The materials offered full conversion (100%) with excellent selectivity (100%) at a relatively low temperature (250 °C). The catalyst exhibited a long-term stability for 120 h. Based on these results, DME is produced efficiently in terms of conversion, selectivity, and long-term stability.

Effect of Pressure and Syngas Composition on Direct Synthesis of Dimethyl Ether using Dual Bed Catalyst

National General Energy Plan of Indonesia 2017 (RUEN 2017) stated that dimethyl ether (DME) is appointed as a blending of LPG to reduce LPG imports. DME can be made with two reaction pathways, namely direct synthesis and indirect synthesis. The objective of this study was to determine the effect of pressure and syngas composition on the direct synthesis of DME using dual fixed bed catalyst. The research was carried out with two types of catalyst: M-xxx as a commercial catalyst for methanol synthesis and γ-Al2O3 as catalyst for dehydration of methanol to DME. The later was prepared in our Laboratory of Chemical Reaction Engineering and Catalysis, ITB. The dual catalyst experiment was carried out at 5 and 7 bars, and a fixed temperature of 240oC. The mass ratio of the M-xxx to γ-Al2O3, so-called M/D ratios, were varied from 1/9 to 9/1. Two type of syngas were used, i.e. SA containing only H2 and CO with a SN of 2,3 and SB containing 4% CO2 with SN of 1,8. The dual bed with a M/D ratio of 1/4 gave a CO conversion up to 62% at 5 bars and 240oC (SA). As pressure increased, the conversion of CO and H2 increases to 85% and 83% at 7 bar and 240oC (SA). The presence of CO2 (SB) decreases catalyst activity, as indicated by the decrease in conversion of CO and H2 to 56% and 54%, at 7 bar and 240oC.

Structured catalysts for the direct synthesis of dimethyl ether from synthesis gas: A comparison of core@shell versus hybrid catalyst configuration

Abstract The direct synthesis of dimethyl ether (DME) from synthesis gas via methanol as an intermediate is a promising process for realizing a decentralized, small-scale Power-to-X concept. The efficient realization of this coupled process depends to a large extent on the appropriate catalyst configuration, i.e. the combination of the catalyst for methanol formation with the one for the subsequent dehydration step. In this work, two catalyst configurations were compared in terms of CO-conversion and DME-selectivity using modelling and experiments. Catalysts for methanol formation (Cu/ZnO/Al2O3, CZA) and dehydration (Zeolite H-ZSM-5, Z) prepared via flame spray pyrolysis and hydrothermal synthesis, respectively, were combined in the form of hybrid pellets (CZA&Z) and CZA-core@zeolite-shell (CZA@Z) particles. During the synthesis of the CZA@Z system, alteration of the CZA core in terms of CuO-reducibility and activity in methanol synthesis were found after individual steps of calcination and hydrothermal shell synthesis. In contrast, the preparation of the CZA&Z system presents an easy and tunable method with promising catalytic properties in terms of CO-conversion and DME-selectivity, once the proper mass ratio of the two catalysts was set. From modelling, for the same CZA/Z ratio in general higher CO-conversion was found for the CZA&Z system as compared to the CZA@Z, while the latter system shows higher DME-selectivity.

Modified vermiculites as effective catalysts for dehydration of methanol and ethanol

Abstract Two series of catalysts for the reactions of methanol and ethanol dehydration were obtained from vermiculite. The first series of the catalysts were obtained by treatment of raw clay with nitric acid solution. Such modification of vermiculite resulted in a significant increase of its specific surface area and also partial leaching of Al3+ and Fe3+ cations from clay layers. Acid treatment of vermiculite resulted in its activation in the processes of methanol and ethanol dehydration. The second series of the catalysts were obtained by intercalation of vermiculite with alumina pillars. Prior to the pillaring process, raw vermiculite was treated with nitric acid solution followed by complexation of Al3+ and Fe3+ cations, leached from clay layers, with oxalic acid or citric acid. Alumina pillared vermiculites, characterized by increased specific surface area, porosity and acidity, were found to be very active catalysts of alcohols dehydration. Catalytic performance of modified vermiculites was related mainly to the concentration and strength of acid sites present in the samples.

Zn and Si transport in dual-functioning catalyst for conversion of synthesis gas to dimethyl ether

Dimethyl ether (DME) is traditionally produced from synthesis gas, i.e., CO, CO2, and H2, with methanol as an intermediate before the final dehydration to DME. However, DME may also be produced in a one-stage synthesis from synthesis gas using a combi-catalyst with both methanol synthesis and methanol dehydration functionalities in a single catalyst. In this work, two combi-catalysts consisting of co-tableted methanol synthesis catalyst (Cu/ZnO/Al2O3) and methanol dehydration catalyst domains (silica-alumina) were tested in synthesis gas as 6 mm in diameter pellets in a single-pellet configuration for 700–850 h at 235–310 °C and 60 bar. The catalyst domain sizes were 50–100 μm in a fine particle catalyst A and 600–1000 μm in a coarse particle catalyst B. Surprisingly, the finer particle combi-catalyst A(fine) showed a markedly faster deactivation of the dehydration activity and slightly faster deactivation of the methanol activity than the coarser combi-catalyst B(coarse). Electron microprobe analysis of the spent catalyst B(coarse) showed that Zn had migrated from the methanol active material and 10 μm into the DME active particles. Similarly, silicon from the silica-alumina methanol dehydration catalyst particles had diffused several hundred µm into the methanol catalyst particles. Based on these experimental results, it is concluded that the methanol dehydration catalyst domains in combi-catalyst A(fine) were poisoned faster than those in combi-catalyst B(coarse) due to the larger contact area between the two catalyst materials, easing the transport of Zn and leading to a faster deactivation. Similarly, silicon migration from the silica-alumina catalyst to the methanol synthesis catalyst might decrease the formation rate of methanol in catalyst A(fine) more than in catalyst B(coarse).

Preparation of Catalyst Cu-ZnO-MgO-Al2O3 for Direct Synthesis of DME

Direct synthesis of DME catalyst was prepared using the co-precipitation method. The catalyst contained CuO/ZnO/Al2O3 about 40/27/33 (%-wt). Two types of catalyst were prepared, i.e. CZMA0 (Mg 0%-wt) and CZMA20 (Mg 20%-wt). Both of catalysts were activated using reducing gas (5% H2 and N2). The activity test was conducted by syngas model which contained (%-mole) 65% H2, 28% CO and 7% N2. The reaction was carried out in a fixed bed reactor at 5 bar, and temperature of 240, 250 and 260°C. Synthesis shown CZMA20 catalyst gave the highest catalytic activity with 73% of CO conversion and 66% of H2 conversion (5 bar and 260°C). Direct synthesis of DME was also carried out using a dual-catalyst, i.e. catalyst for methanol synthesis (M151, the commercial catalyst of methanol synthesis) and methanol dehydration (γ-Al2O3-ITB). The activity of dual catalyst shown 93% of CO conversion and 91% of H2 conversion. This activity was more stable than two other catalysts (CZMA0 and CZMA20).

Sulfonated catalysts for methanol dehydration to dimethyl ether (DME)

Sulfonic acids grafted on inorganic support such as SiO2 and MCM41 was used as catalysts for conversion of methanol to dimethyl ether. In this experimental work the catalysts were compared for their catalytic properties in a continuous flow fixed-bed reactor at temperatures between 180 and 320 °C and 1 bar. It was found that all SO3H-functionalized materials in this study were active, selective and stable for DME synthesis.According to the experimental results MCM-41-(CH2)3-SO3H exhibited the best performance, related to its higher surface area and acidity.

Development of Heterogeneous Catalysts for Dehydration of Methanol to Dimethyl Ether: A Review

Dimethyl ether (DME) is a promising multisource and multipurpose clean fuel and value-added chemical synthesized from syngas. This process can be either performed in a single stage (direct process) using a dual catalysis system or a two stage (indirect process) where syngas is first converted into methanol and then dehydrated to produce DME. While the dehydration reaction has been studied extensively over multiple decades, to date no review has been conducted on the catalysts involved in the methanol dehydration reaction. This work demonstrates the state of the art in catalyst preparation and analysis for this application. The dominant catalysts are studied extensively in this work, including γ-Al2O3 and various zeolites, such as ZSM-5, Y, beta and mordenite as well as their relevant modifications. Additionally, silica-alumina, mesoporous silicates, alumina phosphate, silicoaluminophosphates, heteropoly acids (HPAs), metal oxides, ion exchange resins and quasicrystals are discussed in this work, owing to the wide variety of catalysts available and studied for the purposes of methanol dehydration to DME.

Synthesis of dimethyl ether using a fixed bed of dual catalyst for methanol synthesis and its dehydration

Experimental study on direct synthesis of DME (dimethyl ether) has been conducted using tubular reactor. The synthesis of DME was performed with two commercial catalysts, ie methanol synthesis catalyst (M151, Cu-based) and methanol dehydration catalyst (γAl2O3). A mixture of H2, CO, and N2 was used as a model for synthesis gas. Gas flow rate was set at 20 mL/min (5 bar and 240oC). The reaction held at: pressure of 5 bar and a temperature of 240°C. This experiment was conducted by arranging a series of two types of catalysts in a fixed bed reactor. The methanol synthesis catalyst was placed in the upstream to ensure the reaction of methanol formation, then proceed with dehydration of methanol to DME. The objective of this experiment was to find out the best dual catalyst composition to produce a high concentration of DME. The experiment has shown that the best combination of methanol catalyst to dehydration catalyst was a mixture of 20% methanol catalyst (ratio 1/4). CO conversion was 62% and the product ratio of DME/methanol was 40%.

Energy‐Efficient Methanol to Dimethyl Ether Processes Combined with Water‐Containing Methanol Recycling: Process Simulation and Energy Analysis

AbstractTwo methanol‐to‐dimethyl ether (MTD) process scenarios were proposed to develop new MTD processes with improved energy efficiency by recycling water‐containing methanol to the MTD reactor. In both scenarios, a water‐tolerant K‐modified H‐ZSM‐5 was used in the MTD reactor as the methanol dehydration catalyst. Process modeling was implemented by using Aspen Plus to obtain the quantitative energy analysis results. Both scenarios are mainly comprised of a methanol preheating unit, a methanol dehydration unit, a DME separation unit, a methanol separation unit, and a methanol recycling unit. The two modelled scenarios have differing flow paths of the methanol recycle stream. That is, in option 1, after separating DME, a portion of the water‐containing methanol was recycled directly to the MTD reactor without entering the methanol separation unit. Whereas, in option 2, all of the water‐containing methanol was sent to the methanol separation unit. However, the less‐purified methanol was obtained and recycled. The process performance of both proposed scenarios was investigated by varying the recycle ratio or the recycled methanol purity in scenarios 1 and 2, respectively. Compared with the conventional γ‐Al2O3 based MTD process, both of the proposed scenarios were found to be more beneficial in saving both energy and capital cost, which can be seen from the high energy saving rate and smaller equipment size of the separation units in the newly proposed MTD process scenarios 1 and 2.

Development of Heterogeneous Catalysts for Dehydration of Methanol to Dimethyl Ether: a Review

Dimethyl ether (DME) is a promising multisource and multipurpose clean fuel and value-added chemical synthesized from syngas. This process can be either performed in a single stage (direct process) using a dual catalysis system or a two stage (indirect process) where syngas is first converted into methanol and then dehydrated to produce DME. While the dehydration reaction has been studied extensively over multiple decades, to date no review has been conducted on the catalysts involved in the methanol dehydration reaction. This work demonstrates the state of the art in catalyst preparation and analysis for this application. The dominant catalysts are studied extensively in this work, including γ-Al2O3and various zeolites, such as ZSM-5, Y, beta and mordenite as well as their relevant modifications. Additionally, silicaalumina, mesoporous silicates, aluminum phosphate, silicoaluminophosphates, heteropoly acids (HPAs), metal oxides, ion exchange resins and quasicrystals are discussed in this work, owing to the wide variety of catalysts available and studied for the purposes of methanol dehydration to DME.

Porous clay heterostructures intercalated with multicomponent pillars as catalysts for dehydration of alcohols

Abstract Montmorillonites intercalated with silica, silica-alumina, silica-titania and silica-zirconia pillars by surfactant directed method were studied as catalysts for dehydration of methanol and ethanol to dimethyl ether as well as diethyl ether and ethylene, respectively. Moreover, the samples of montmorillonite intercalated with silica pillars were doped with aluminum using template ion-exchange method. In the case of all the samples deposited metal (Al, Ti, Zr) species were present in highly dispersed forms and resulted in generation of acid sites catalytically active in dehydration of methanol and ethanol. The best catalytic results in both studied processes were obtained for the samples doped with aluminum, especially introduced by using template ion-exchange method (first time applied for deposition of metal cations into PCHs), which were more catalytically active in the process of methanol to dimethyl ether conversion than γ-Al2O3 (one of the most important commercial catalysts of this process). High catalytic activity of the aluminum doped samples was related to the nature and strength of acid sites active in the processes of alcohols dehydration.

Lifetime of the H3PW12O40 heteropolyacid in the methanol-to-DME process: A question of pre-treatment

H3PW12O40 is a Keggin heteropolyacid (HPA) that nowadays attracts more and more attention as catalyst for the gas phase dehydration of methanol to dimethylether. Here, we investigate its performance in the latter reaction at 250–300°C, namely under coking conditions. Actually, we address the question whether the elsewhere elucidated procedure allowing to activate the bulk of the H3PW12O40 solid is beneficial or not under conditions leading to the rapid coking/deactivation of H3PW12O40’s surface (through which the bulk gets accessed). Unprecedented, our results show that pre-activating the bulk is actually crucial in the latter conditions, as it allows drastically increasing H3PW12O40’s lifetime (up to 5 times at 300°C). Indeed, once activated, the bulk stays accessible beyond the deactivation of the surface. However, with its 24 times more protons than provided by the surface, and with the conversion over the latter protons being diffusion-limited, it then contains continuously enough fresh protons being able to take over the job of the other bulk protons that are deactivated (in the sense that they are capped within coke molecules) until having all been solicited/deactivated. As a consequence, the catalyst bed gets fully exploited until the last of its available bulk protons has contributed to the reaction, instead of getting only scarcely exploited as it is the case when the reaction is purely surface-type. So, the results of this work bring considerable insight on how to use a Keggin HPA-based catalyst in a more sustainable way. Furthermore, they allow understanding the performance obtained upon submitting a Keggin HPA to a temperature programmed reaction of methanol from 25 to 300°C. Indeed, throughout such a reaction, the deactivation profile (e.g. drastic conversion drops vs slow ones) is governed by the nature of the protons (surface vs bulk-type) that are getting deactivated.

Catalyst Deactivation During One-Step Dimethyl Ether Synthesis from Synthesis Gas

Catalysts for direct synthesis of dimethyl ether (DME) from synthesis gas should essentially contain two functions, i.e., methanol synthesis and methanol dehydration. In the present work, the deactivation of both functions of hybrid catalysts during direct DME synthesis under industrially relevant conditions has been investigated with special focus on the influence of each reaction step on the deactivation of the catalyst function corresponding to the other step. A physical mixture of a Cu–Zn-based methanol synthesis catalyst and a ZSM-5 methanol dehydration catalyst was used. The metallic catalyst appears to deactivate due to Cu sintering, with no apparent effect from the methanol dehydration step under the conditions applied. The acid catalyst deactivates due to accumulation of hydrocarbon species formed in its pores. Synthesis gas composition, i.e., $$\text{{H}}_{2}$$ /CO ratio and $$\text{{CO}}_{2}$$ -content (which directly affects partial pressure of water), seems to influence the zeolite deactivation.

Specifics of dimethyl ether synthesis from syngas over mixed catalysts

Dimethyl ether (DME) synthesis from syngas over a mixture of a methanol synthesis catalyst (ZnO, 25.10 wt %; AuO, 64.86 wt %; Al2O3, 10.04 wt %) and a methanol dehydration catalyst (γ-A12O3) has been investigated for one-, two-, and three-layer catalyst beds. There is a common regularity for these three variants: with an increasing temperature, the total CO conversion decreases, the CO-to-methanol conversion decreases, and the CO-to-DME conversion increases. The largest values of DME selectivity and DME yield have been attained with the three-layer bed. The highest DME yield has been obtained at 250–285°C. Use of a mechanical mixture of the methanol synthesis catalyst and alumina makes it possible to efficiently obtain DME from syngas ballasted with nitrogen (20 vol %) at an H2/CO ratio of 1, which is unfavorable for methanol synthesis. The DME yield on the syngas input basis in this case with the ballast gas (nitrogen or CO2) taken into account can be about 10 wt %.

Mesoporous silica materials modified with alumina polycations as catalysts for the synthesis of dimethyl ether from methanol

Mesoporous silica materials (SBA-15 and MCF) were used as catalytic supports for the deposition of aggregated alumina species using the method consisting of the following steps: (i) anchoring 3-(mercaptopropyl)trimethoxysilane (MPTMS) on the silica surface followed by (ii) oxidation of SH toSO3H groups and then (iii) deposition of aluminum Keggin oligocations by ion-exchange method and (iv) calcination. The obtained samples were tested as catalysts for synthesis of dimethyl ether from methanol. The modified silicas were characterized with respect to the ordering of their porous structure (XRD), textural properties (BET), chemical composition (EDS, CHNS), structure (27Al NMR, FTIR) and location of alumina species (EDX-TEM), surface acidity (NH3-TPD, Py-FTIR) and thermal stability (TGA). The obtained materials were found to be active and selective catalysts for methanol dehydration to dimethyl ether (DME) in the MTD process (methanol-to-dimethyl ether).

Catalytic Dehydration of Methanol to Dimethyl Ether Over Mesoporous γ-Al2O3

This study focused on the preparation of a high surface area mesoporous γ-Al2O3 as a catalyst for methanol dehydration. The catalysts were characterized using NH3- temperature-programmed desorption, X-ray diffraction, Brunauer-Emmett-Teller, and transmission electron microscopy techniques and evaluated in a fixed-bed reactor at 250°C at a gas hourly space velocity of 1,000 h−1 under atmospheric pressure. A three-factor uniform design was utilized to determine the optimal conditions. The catalyst prepared under optimal conditions showed a time-space yield of 0.659 g dimethyl ether/(g cat·h) with selectivity of about 99.99%. The activity showed a significant dependence on the textural properties and enhanced weak acid strength of the alumina.

Dehydration of methanol to dimethyl ether over modified vermiculites

Vermiculite materials pillared with alumina and modified with titanium were tested as catalysts for methanol dehydration to dimethyl ether. The different samples were characterized by powder XRD, TG, nitrogen adsorption, and pyridine adsorption followed by FTIR. Catalytic activity was evaluated in the temperature range 250–450 °C using different hourly space velocities, in the absence and in the presence of water in the feed. Modified vermiculites were shown to be active and selective in methanol dehydration. Al pillaring was found to result in more active catalysts than in the case of the modification with TiO2. The influence of methanol hourly space velocity did not have a significant effect on methanol conversion, but it changed drastically selectivity to dimethyl ether at the beginning of the reaction. The addition of water had a negative effect on the catalysts’ activity and led to a faster catalyst deactivation. Les vermiculites à piliers d’alumine et modifiées avec du titane ont été testées comme catalyseurs pour la déshydratation du méthanol en diméthyléther. Les différents échantillons ont été caractérisés par diffraction des rayons X (DRX), TG, FTIR de la pyridine adsorbée et par adsorption d’azote à basse température. Les vermiculites modifiées se sont avérées être actives et sélectives dans la déshydratation du méthanol à 450 °C. De plus, l’influence de la vitesse spatiale horaire et de l’addition d’eau sur l’activité et la distribution des produits a également été étudiée. Cette dernière n’a pas eu d’effet significatif sur la conversion du méthanol, mais elle change considérablement la sélectivité en diméthyléther au début de la réaction. L’addition d’eau, quant à elle, a eu un effet négatif sur l’activité des catalyseurs.

Effect of metal precursor on Cu/ZnO/Al2O3 synthesized by flame spray pyrolysis for direct DME production

Cu/ZnO/Al2O3 catalysts were synthesized by flame spray pyrolysis (FSP). The effect of different metal precursor types, i.e. metal nitrates and organometallics, on the catalytic properties was investigated. Organometallic precursors are commonly used for flame spray pyrolysis because small nanoparticles can be produced. In this study, we have obtained nanosized copper and zinc oxide clusters also from the nitrate precursors. Characterization was applied to reveal the difference between the clusters obtained from the different precursor types. Both precursors allowed the formation of well-ordered Cu/ZnO/Al2O3 particles with similar size according to TEM investigations.However, the catalyst from metal nitrate precursors possessed a lower reduction temperature, a higher active copper surface area, and a lower overall BET surface area than the one from the organometallic precursor. The catalytic performance of the obtained catalysts was investigated in the direct DME synthesis from synthesis gas. Methanol dehydration catalyst, H-ZSM-5, was therefore admixed to the FSP powders in a pre-defined amount; the FSP powders served as methanol synthesis catalyst in the mixture. The catalyst from metal nitrate precursors showed higher conversion of syngas than the catalyst from the organometallic precursors at same reaction conditions. This effect can be explained mainly by the higher copper surface area. Catalysts with different Cu/Zn ratio were also tested and the best catalyst was further studied by variation of the reaction conditions. In conclusion, we have demonstrated an efficient utilization of less expensive precursor materials for flame spray pyrolysis for production of Cu/ZnO/Al2O3 catalysts.