Dimethyl Ether Synthesis Research Articles

Optimal reaction pathways of carbon dioxide hydrogenation using P-graph attainable region technique (PART)

The attainable region interpretation of the thermodynamic principles has indicated that carbon dioxide (CO2) can be either hydrogenated directly to form dimethyl ether (DME) or gasoline. The process that converts CO2 to DME is more thermodynamically favourable at lower temperature. A certain thermodynamic temperature range (25 to 300 °C) is suggested for the conversion of CO2 to DME via a methanol intermediate pathway without addition of work. Optimal synthesis routes derived from P-graph's mutual exclusion solver were compared with reactions reported in literature and showed great correlation. The reactions collectively possess Gibbs free energy of less than zero, and negative enthalpy of reaction. With P-graph attainable region technique, the case studies have demonstrated that the synthesis of DME and gasoline using CO2 hydrogenation via methanol intermediate and carbon monoxide intermediate from Fischer–Tropsch synthesis is feasible with no work and heat requirement. Both case studies have demonstrated visual advantage of P-graph and data-driven applications. The benefit of integrating the P-graph framework with machine learning model like decision tree classifier was also demonstrated in the second case study as it solves topological optimisation problems without scaling constraints.

Effect of Microwave Drying of Alumina Support on Properties of Cu/Al2O3 Catalyst for Synthesis of Dimethyl Ether via CO2 Hydrogenation

Effect of Microwave Drying of Alumina Support on Properties of Cu/Al2O3 Catalyst for Synthesis of Dimethyl Ether via CO2 Hydrogenation

Temperature-dependent synthesis of dimethyl ether (DME) from methanol over beta zeolite: a novel approach to a sustainable fuel.

Crystalline beta zeolite molecular sieve with SiO2/Al2O3 molar ratio of 28.5 was synthesized by the hydrothermal crystallization method and examined for methanol dehydration reaction. The micro-mesoporous beta zeolite was active between 280 and 450°C. Dimethyl ether (DME) was observed as the predominant product at all reaction temperatures, with a maximum selectivity of 47.9% at 300°C and a methanol turnover frequency (TOFMeOH) of 741.9 h-1. At increased reaction temperatures, beta zeolite showed enhanced strong acid site fraction, promoting higher hydrocarbon formation following the olefin-based cycle. It was revealed that the crystallinity, porosity and acidity of beta zeolite change in the reaction environment. Amorphous carbon deposition occurred on beta zeolite, which involved a loss in crystallinity to some extent. The temperature increase showed a pore-broadening phenomenon at elevated temperature regions. Regeneration cycle testing demonstrated beta zeolite activity maintained stable throughout a 280 h time-on-stream period.

Infrared action spectroscopy as tool for probing gas-phase dynamics: protonated dimethyl ether, (CH3)2OH+, formed by the reaction of CH3OH2 + with CH3OH

Methanol is one of the most abundant interstellar Complex Organic Molecules (iCOMs) and represents a major building block for the synthesis of increasingly complex oxygen-containing molecules. The reaction between protonated methanol and its neutral counterpart, giving protonated dimethyl ether, ( CH 3 ) 2 OH + , along with the ejection of a water molecule, has been proposed as a key reaction in the synthesis of dimethyl ether in space. Here, gas phase vibrational spectra of the ( CH 3 ) 2 OH + reaction product and the [ C 2 H 9 O 2 ] + intermediate complex(es), formed under different pressure and temperature conditions, are presented. The widely tunable free electron laser for infrared experiments, FELIX, was employed to record these vibrational fingerprint spectra using different types of infrared action spectroscopy in the 600-1700 cm − 1 frequency range, complemented with measurements using an OPO/OPA system to cover the O − H stretching region 3400 − 3700 c m − 1 . The formation of protonated dimethyl ether as a product of the reaction is spectroscopically confirmed, providing the first gas-phase vibrational spectrum of this potentially relevant astrochemical ion.

An evaluation of direct dimethyl ether (DME) synthesis from hydrogen and carbon dioxide based on CFD reactor simulations

To mitigate the effects of anthropogenic climate change, various options for decarbonizing the transport sector are under investigation. One promising approach is the chemical production of energy carriers and fuels from renewable sources. Among various options, dimethyl ether (DME) is discussed as one of the top candidates. However, the production of DME from a renewable raw material supply is associated with certain challenges. This study analyzes the direct synthesis of DME from CO2 and H2 based on computational fluid dynamics (CFD) simulations of the relevant reactors. For the CFD simulations, the software ANSYS Fluent was applied. Kinetic models were integrated by user-defined functions to describe the multiple heterogeneous catalyzed reactions in the synthesis reactor. Several kinetic models were tested with respect to their accuracy and applicability with regard to describing DME formation. A quasi-isothermal reactor model was implemented as base case. It is shown that the progressive formation of water slows down the reaction of direct DME formation. Moreover, a model for a membrane reactor was developed and analyzed in detail. In comparison to the base case, a significant increase in reactor performance was obtained. In conclusion, it can be stated that, for the direct conversion of CO2 to DME, techniques for reducing the accumulation of water need to be adopted such as in-situ water removal or implementing an upstream reverse water-gas shift reactor.

Direct synthesis of liquid hydrocarbons from CO2 over CuZnAl/Zn-HZSM-5 combined catalyst in a single reactor

BackgroundFor the direct CO2 conversion to liquid hydrocarbons, a combination of the CuZnAl/Al2O3 and Zn-HZSM-5 catalysts was used, which made it possible to combine the oxygenates (methanol and dimethyl ether) synthesis and the subsequent formation of liquid hydrocarbons from them. MethodsWith this purpose, the performance of CuZnAl/Al2O3 metallic oxides was compared by using them in tandem with a Zn-HZSM-5. The catalysts were analysed by means of N2 adsorption-desorption, XRD, XRF, H2-TPR and NH3-TPD. Significant findingsThe CO2 conversion was demonstrated to be controlled by controlling the mass ratio of CuZnAl:Al2O3 in the Ox-component, the mass ratio of Ox:Zeo-components, the loading scheme of the Ox- and Zeo-components in the reactor, and the GHSV in reaction zone. The best results were achieved when this process was carried out in the tail-gas recirculation mode on a CuZnAl-Al2O3/Zn-HZSM-5 combined catalyst in a physical mixture form of oxide and zeolite components in a 1:1 wt ratio. At H2/CO2=3 molar ratio, 10 MPa, and 340 °C, the CO2 conversion and selectivity for C5+–hydrocarbons were 20% and 47 wt% (78 wt% based on total hydrocarbons), respectively, for more than 60 h of operation. The selectivity for methane did not exceed 2 wt%. The liquid hydrocarbon mixture was characterized by a high content of isoalkanes (66 wt%), the durene content did not exceed 1 wt%.

Cerium sulfate doped ZrO2 as a solid acid catalyst for the synthesis of polyoxymethylene dimethyl ethers: Influence of Brønsted acidity on the catalytic activity and product selectivity

Cerium sulfate doped ZrO2 solid acid catalyst was prepared by a simple wet impregnation method and tested its efficiency for the synthesis of polyoxymethylene dimethyl ethers (PODE). The surface Brønsted acidity contributed significantly for improved selectivity of desired PODE3–5 and higher PODEn>5. The overall acidity of the catalyst was directly related to the dispersion of CeO2 and the sulfate moiety. The polymerization of dimethoxymethane (DMM) and 1, 3, 5-trioxane (TOX) is in direct correlation with the surface Brønsted acid sites present on the cerium sulfate doped zirconia catalyst surface. The recovered catalyst showed consistent activity up to four catalytic cycles. The structural properties of the catalyst were rationalized by using p-XRD, BET-surface area, NH3-TPD, TGA, UV-DRS, IR, pyridine adsorbed IR, XPS and SEM analyses.

Oxymethylene Ether (OME) Fuel Catalyst Screening Using in-situ NMR spectroscopy.

Online NMR measurements are introduced in the current study as a new analytical setup for investigation of the oxymethylene dimethyl ether (OME) synthesis. For the validation of the setup, the newly established method is compared with state-of-the-art gas chromatographic analysis. Afterwards, the influence of different parameters, such as temperature, catalyst concentration and catalyst type on the OME fuel formation based on trioxane and dimethoxymethane is investigated. As catalysts, AmberlystTM 15 (A15) and trifluoromethanesulfonic acid (TfOH) are utilized. A kinetic model is applied to describe the reaction in more detail. Based on these results, the activation energy (A15: 46.3 kJ mol -1 and TfOH: 79.8 kJ mol-1) and the order in catalyst (A15: 0.8 and TfOH: 2.2) are calculated and discussed.

From CO2 to DME: Enhancement through Heteropoly Acids from a Catalyst Screening and Stability Study.

The direct synthesis of dimethyl ether (DME) via CO2 hydrogenation in a single step was studied using an improved class of bifunctional catalysts in a fixed bed reactor (T R: 210-270 °C; 40 bar; gas hourly space velocity (GHSV) 19,800 NL kgcat -1 h-1; ratio CO2/H2/N2 3:9:2). The competitive bifunctional catalysts tested in here consist of a surface-basic copper/zinc oxide/zirconia (CZZ) methanol-producing part and a variable surface-acidic methanol dehydration part and were tested in overall 45 combinations. As dehydration catalysts, zeolites (ferrierite and β-zeolite), alumina, or zirconia were tested alone as well as with a coating of Keggin-type heteropoly acids (HPAs), i.e., silicotungstic or phosphotungstic acid. Two different mixing methods to generate bifunctional catalysts were tested: (i) a single-grain method with intensive intra-particular contact between CZZ and the dehydration catalyst generated by mixing in an agate mortar and (ii) a dual-grain approach relying on physical mixing with low contact. The influence of the catalyst mixing method and HPA loading on catalyst activity and stability was investigated. From these results, a selection of best-performing bifunctional catalysts was investigated in extended measurements (time on stream: 160 h/7 days, T R: 250 and 270 °C; 40 bar; GHSV 19,800 NL kgcat -1 h-1; ratio CO2/H2/N2 3:9:2). Silicotungstic acid-coated bifunctional catalysts showed the highest resilience toward deactivation caused by single-grain preparation and during catalysis. Overall, HPA-coated catalysts showed higher activity and resilience toward deactivation than uncoated counterparts. Dual-grain preparation showed superior performance over single grain. Furthermore, silicotungstic acid coatings with 1 KU nm-2 (Keggin unit per surface area of carrier) on Al2O3 and ZrO2 as carrier materials showed competitive high activity and stability in extended 7-day measurements compared to pure CZZ. Therefore, HPA coating is found to be a well-suited addition to the CO2-to-DME catalyst toolbox.

Prospect of Direct Dimethyl Ether Production from CO2: Reactor Design Development

The increasing emissions of carbon dioxide (CO2) and volatile hydrocarbons via burning of fossil fuels result in a significant amount of global warming and air pollution. With the concern over the impact of fossil fuel to the environment, the interest in alternative fuel production from the CO2 generated through utilization of new technologies has risen rapidly. Several clean alternative fuels, including dimethyl ether (DME) have been investigated for a more sustainable and greener environment. DME has a high cetane number but produces much lower NOx emission upon combustion. DME is typically synthesized using syngas based on conventional indirect DME route, where the process begins with conversion of syngas into methanol and subsequently dehydrated to DME in separate units. Recently, a direct single-step route to produce DME through dehydrogenation of CO2 and dehydration of methanol by utilising a novel bifunctional catalyst has been investigated. In direct DME, the dehydrogenation and dehydration occur simultaneously in a single reactor, which eliminate the need for a methanol production plant. However, the use of conventional fixed-bed reactor (FBR) for the direct DME synthesis causes many challenges including catalyst deactivation, where water appears in the reaction area, limiting the conversion of CO2 reactants into DME and consequently, the DME yield. It is also essential to manage the exothermic heat generated from the catalyst for better DME yield. In order to overcome these hurdles, several types of reactors have been proposed such as fluidized bed reactor, slurry reactor, microreactor and catalytic membrane reactor. In this paper, different types of reactors are first discussed and its applications related to the direct DME production from CO2 are highlighted. Finally, the challenges and difficulties of reactor development are addressed and future direction is outlined.

Enhanced catalytic stability of non-stoichiometric Cu–Al spinel catalysts for dimethyl ether synthesis from syngas: Effect of coordination structure

Cu–Al spinel catalysts were synthesized by various preparation methods, and its CO hydrogenation performance was evaluated. Characterization results showed that different preparation methods can effectively regulate the coordination distribution of cations in surface spinel structure. The sustained release property of Cu–Al spinel was related to its coordination structure. The catalyst containing a large amount of octahedral spinel Cu2+ ions was capable of delaying the reduction of copper, and small Cu nanoparticles (Cu NPs) were produced and highly dispersed on the defective spinel surface, which may be that the vacancy derived on the surface of defective spinel anchored small Cu NPs, which was the key to improve catalytic stability. We also discussed the real reason for poor catalytic stability, and this was due to that the easily-reducible spinel possessed extensive tetrahedral spinel Cu2+, which accelerated the reduction and release of copper, resulting in that the formed copper was unstable and aggregated readily. The Cu–Al spinel catalyst prepared by the solid phase method included octahedral coordination Cu2+ ratio as high as 59%, and the corresponding average size of Cu particles produced from spinel was measured as about 11.3 nm by N2O titration method, exhibiting enhanced stability and excellent catalytic performance.

Design framework for dimethyl ether (DME) production from coal and biomass‐derived syngas via simulation approach

AbstractA comprehensive thermodynamic study was conducted to evaluate the comparative efficacy of methanol and dimethyl ether (DME) synthesis using CO2 rich syngas feed. The first part of our study included assessing the relative performances of the methanol synthesis system, two step DME synthesis system, and one step DME synthesis system in terms of the COx conversion and product yield (methanol/DME) based on the Gibbs free energy minimization approach. The wide range of composition of CO2‐enriched syngas feed produced by the coal and biomass gasification was simulated using Aspen Plus and the following evaluation parameters were analyzed for a broad parameter range: reaction temperature (180–280°C), reaction pressure (10–80 bar), stoichiometry number (SN) (0–11), and CO2/(CO2 + CO) molar feed ratio (0–1) for isothermal as well as adiabatic conditions. Based on the equilibrium yield, one‐step DME synthesis was discovered as the most viable process to utilize the co‐gasification derived syngas effectively. In the second part of our study, the overall process efficiency was inspected through the process design of 1 tonnes per day (TPD) DME plant inclusive of heat integration, resulting in significant CO2 abatement and DME production with high product purity and minimum energy consumption. Consequently, one‐step DME production via CO2‐enriched syngas obtained through the coal or biomass gasification process is identified as the leading technology based on energy utilization and CO2 abatement.

Is Direct DME Synthesis Superior to Methanol Production in Carbon Dioxide Valorization? From Thermodynamic Predictions to Experimental Confirmation

CO2 valorization is a key measure to reach climate neutrality. Thermodynamics suggest direct conversion of CO2 into dimethyl ether (DME) to have greater potential than the indirect route via methanol synthesis, followed by purification of methanol and then a separate dehydration into DME. In this work, we introduce heteropoly acids as a capable class of dehydration catalysts for direct DME synthesis from CO2 and H2. To clarify if direct DME synthesis is in fact superior to sole MeOH synthesis, accurate thermodynamic equilibrium calculations are performed and pose as the base of our argumentation. An efficient Cu/ZnO/ZrO2 (CZZ) methanol catalyst is used to compare the methanol synthesis using a feedstock with stoichiometric CO2/3H2 mixture against bifunctional catalysts, containing CZZ and a dehydration component. The dehydration components include a commercial ferrierite (FER) and heteropoly acid (HPA) coated alumina and zirconia. For direct DME synthesis, the CO2 feed gas at gas hourly space velocities (GHSVs) between 1,250 and 158,400 NL kgcat–1 h–1, at temperatures of 210–270 °C and 40 bar pressure, was investigated. Based on the wide parameter window investigated, the following can be concluded at 250 °C: under a thermodynamic regime, CO2 conversion is close to the theoretical limit (30%exp/32%theo) and the direct DME synthesis is superior to sole methanol synthesis (+20%exp/+33%theo). The amount of valuable products (methanol, DME) profits significantly more (+70%exp/+88%theo) from the direct DME synthesis than CO2 conversion indicates. Under a kinetic regime, HPA-coated catalysts show superior apparent activation energies for DME production than the widely used ferrierite (HPA: 45 kJ mol–1/FER: 80 kJ mol–1), making HPA coatings a great option for highly capable dehydration catalysts under CO2- and water-rich conditions.

Alternative Strategies for Effective Utilization of Carbon Dioxide in Dimethyl Ether Synthesis

AbstractConverting CO2 into chemicals, e.g., methanol and dimethyl ether (DME), has been an attractive way to protect the global environment. In this process, the total catalyst volume of the methanol reactor was split into two sections to load the reactors. The catalyst volume of each reactor was optimized by the differential evolution technique. It was concluded that the indirect route yields a higher DME production rate than the direct one, as it produces higher amounts of methanol. CO2 conversions increased by 79 % in the indirect two‐stage process, which resulted in the highest DME production rate of 343 t per day. The results demonstrate how the concept of a two‐stage process in the indirect conversion of CO2 is feasible and beneficial for fuel production.

Mesostructured γ-Al2O3-Based Bifunctional Catalysts for Direct Synthesis of Dimethyl Ether from CO2

In this work, we propose two bifunctional nanocomposite catalysts based on acidic mesostructured γ-Al2O3 and a Cu/ZnO/ZrO2 redox phase. γ-Al2O3 was synthesized by an Evaporation-Induced Self-Assembly (EISA) method using two different templating agents (block copolymers Pluronic P123 and F127) and subsequently functionalized with the redox phase using an impregnation method modified with a self-combustion reaction. These nanocomposite catalysts and their corresponding mesostructured supports were characterized in terms of structural, textural, and morphological features as well as their acidic properties. The bifunctional catalysts were tested for the CO2-to-DME process, and their performances were compared with a physical mixture consisting of the most promising support as a dehydration catalyst together with the most common Cu-based commercial redox catalyst (CZA). The results highlight that the most appropriate Pluronic for the synthesis of γ-Al2O3 is P123; the use of this templating agent allows us to obtain a mesostructure with a smaller pore size and a higher number of acid sites. Furthermore, the corresponding composite catalyst shows a better dispersion of the redox phase and, consequently, a higher CO2 conversion. However, the incorporation of the redox phase into the porous structure of the acidic support (chemical mixing), favoring an intimate contact between the two phases, has detrimental effects on the dehydration performances due to the coverage of the acid sites with the redox nanophase. On the other hand, the strategy involving the physical mixing of the two phases, distinctly preserving the two catalytic functions, assures better performances.

Increasing carbon efficiency for DME production from wheat straw and renewable electricity – Analysis of 14 system layouts

Liquid fuels like dimethyl-ether (DME), produced from biomass and electricity are crucial for decarbonizing the shipping industry. In this work, the production of DME from wheat straw through gasification is presented. It was shown how the process can be optimized by using 1) two-stage instead of one-stage DME synthesis, 2) partial oxidation of the produced gas and 3) a hydrogen quench for high-temperature reverse water gas shift reactions. The investigation was conducted by stepwise introducing the different process steps, leading to investigating 14 different plant layouts. This enabled a systematic analysis of the influence of different process steps by looking at the changes in carbon efficiency and energy efficiency. In all plants, DME and bio-ash, which acts as a soil amendment and carbon sink, were produced. 10 of the 14 plants additionally produced high-quality bio-oil. The analysis showed that all the introduced measures increased the carbon efficiency of the plants. At the same time, they increased the net electricity consumption. The highest energy efficiency reached was 57.5 %. A different plant reached the highest carbon efficiency with 84.0 %.,while having the highest net electricity consumption (45.2 MW at a biomass input of 50 MW (LHV)).

Direct Synthesis of Dimethyl Ether from CO2 Hydrogenation over Core-Shell Nanotube Bi-Functional Catalyst

Directly synthesising dimethyl ether (DME) from CO2 hydrogenation is a promising technique for efficiently utilising CO2 as a feedstock to produce clean fuel. The main challenges in this process are the low CO2 conversion and DME selectivity of the catalyst and its deactivation over time due to sintering, aggregation, coke formation, and water adsorption. This study aimed to develop a dual-functional, halloysite nanotube-supported CuZnO-PTA catalyst with a core-shell structure and investigate the effects of the active site mass ratio CuZnO/PTA on CO2 conversion and DME selectivity. A dual-functional core-shell mesopores halloysite nanotube (HNT) catalyst was developed, and both active sites were co-hosted on one support. The co-impregnation method was used to synthesise CuZnO and 12-phosphotungstic acids (PTA) that were then supported by a mesoporous core-shell (HNT). BET surface area, N2 physisorption, FE-SEM, SEM, XRD, H2-TPR, and NH3-TPD of the core-shell catalyst characterised physio-chemical properties of the prepared hybrid catalyst. The experimental results showed that the synthesised CuZn-PTA@HNT core-shell bifunctional catalyst was promising; the CO2 conversion was almost the same for all four catalysts, with an average of 22.17%, while the DME selectivity reached 68.9%. Furthermore, the effect of both active sites on the hybrid catalyst was studied, and the metal Cu wt% mass ratio loading was not significant. In contrast, the PTA acid sites positively affected DME selectivity; they also showed an excellent tolerance towards the water generated in the methanol dehydration reaction. In addition, the effect of the temperature and reusability of the CZ-PTA@HNT catalyst has also been investigated, and the results show that increasing the temperature improves CO2 conversion but decreases DME selectivity. A temperature of less than 305 °C is a good compromise between CO2 conversion and DME selectivity, and the catalyst also showed good stability and continuous activity/stability over five consecutive cycles. In conclusion, this study presents a novel approach of using a core-shell halloysite nanotube-supported CuZnO-PTA catalyst to directly synthesise dimethyl ether (DME) from CO2 hydrogenation which exhibits promising results in terms of CO2 conversion and DME selectivity.

Influence of the Distance between Two Catalysts for CO2 to Dimethyl Ether Tandem Reaction

AbstractTandem reactions, with their great potential for reduction of capital and operational costs, reaction time, and byproducts are becoming more prominent. Among possible tandem reaction systems for direct conversion of CO2 to green fuel, dimethyl ether synthesis via methanol route is of vital importance. However, there are several parameters which must be considered for the combination of two catalysts to achieve promising performance, of those, the distance between the two catalysts is a crucial one. This distance can affect the overall performance of the tandem system by causing external mass transfer limitations or the poisoning of the catalysts. This work presents a systematic study on the influence of the distance between the two catalysts for the CO2 to dimethyl ether tandem system.

Dimethyl ether synthesis on clinoptilolite zeolite and HZSM5-based hybrid catalysts in a fixed-bed reactor

In this study 4 different acid catalysts were prepared and mixed with commercial CZA catalysts and investigated in direct DME synthesis. Some of the used acid catalysts were not investigated in the literature therefore the work involves novelty. In a fixed-bed reactor, dimethyl ether (DME) was synthesized from the synthesis gas on two catalysts from, natural clinoptilolite and zeolite catalysts. The clinoptilolite (HK and DK) and two (HZSM5(117) and HZSM5(360)) catalysts mixed with commercial CuO/ZnO/Al2O3 (CZN) catalysts. The catalysts were also characterized by analytical chemistry techniques such as XRD, BET, TGA, and FTIR. Four different catalysts (HK, DK, HZSM5(117) and HZSM5(360)) and CZA catalysts were mixed at a ratio of 3/1, respectively, and studies were carried out in a fixed-bed reactor. Four different catalyst composition activity tests were made at temperatures 250, 275, and 300 °C. At the same time, the pressure was 30 and 40 bar and four different times (30, 60, 90, and 120 min). The composition of the gases fed to the system for DME was adjusted to N2/CO2/CO/H2 = 36/10/18/36 by volume. DME selectivity (SDME) and total carbon (XC) conversion were calculated for each condition. The experimental results showed that the highest DME selectivity of 96.50% was observed in the reaction of the DK + CZA catalyst mixture at 250 °C and 30 min at 40 bar. In addition, high DME selectivity was obtained in all reactions of DK + CZA and HK + CZA catalyst compositions at three different temperatures. The highest DME selectivity obtained is 89.69% for the reaction of the HK + CZA catalyst mixture at 300 °C and 60 min at 30 bar. Experimental results gave insights into Dimethyl ether synthesis from syngas on clinoptilolite zeolite and HZSM5-based hybrid catalysts in a fixed-bed reactor.

Present and Future Perspectives of Liquid-Phase Slurry Processes Involved in Methanol and Dimethyl Ether Synthesis Using Biomass-Derived Syngas

Present and Future Perspectives of Liquid-Phase Slurry Processes Involved in Methanol and Dimethyl Ether Synthesis Using Biomass-Derived Syngas