Applied Operating Conditions Research Articles

Supramolecular tunnelling junctions with robust high rectification based on assembly effects.

The performance of large-area molecular diodes can in rare cases approach the lower limit of commercial semiconductor devices but predictive structure-property design remains difficult as the rectification ratio (R) achieved by self-assembled monolayer (SAM) based diodes depends on several intertwined parameters. This paper describes a systematic approach to achieve high rectification in bisferrocenyl-based molecular diodes, HSCnFc-CC-Fc (n = 9-15) immobilised on metal surfaces (Ag, Au and Pt). Experiments supported by molecular dynamics simulations show that the molecular length and bottom electrode influence the SAM packing, which affects the breakdown voltage (VBD), the associated maximum R (Rmax), and the bias at which the Rmax is achieved (Vsat,R). From the electrical characterisation of the most stable Pt-SCnFc-CC-Fc//GaOx/EGaIn junctions, we found that VBD, Vsat,R, and Rmax all scale linearly with the spacer length of Cn, and that Rmax for all the SAMs consistently exceeds the "Landauer limit" of 103. Our data shows that the robust switching of M-SCnFc-CC-Fc//GaOx/EGaIn junctions is the result of the combined optimisation of parameters involving the molecular structure, the type of metal substrate, and the applied operating conditions (bias window), to create stable and high-performance junctions.

Purification of monoethylene glycol by melt crystallization

Separation of glycols with close boiling points and relatively high viscosity at their melting point is a challenge in the production of high purity products downstream of biorefinery processes. In this work, the efficiency of the layer melt crystallization process with acetone as the assisting solvent was evaluated for a mixture of monoethylene glycol and 1,2-pentanediol. Solid-liquid equilibrium was measured and modelled with the NRTL and modified UNIFAC group-contribution models to evaluate the thermodynamic driving force of crystallization. Layer melt crystallization was conducted to determine the effect of solvent composition on purity, distribution coefficient of impurity, crystal growth rate, and yield at different operating conditions. Addition of the solvent altered the thermodynamics and kinetics of crystallization, thereby altering the purity level of the final product. An effective distribution coefficient of impurity between 0.1 and 0.6 in one-step crystallization was obtained, depending on the solvent composition and the applied operating conditions.

Electrocatalytic oxidation of antidiabetic drug metformin adsorbed on intercalated MXene

Two-dimensional (2D) Ti3C2Tx transition metal carbide (MXene) nanosheets intercalated with sodium ions (SI–Ti3C2Tx MXene) were used in the adsorption and electrochemical regeneration process for removal of the antidiabetic drug metformin (MF) as a model emerging pollutant. After MF adsorption, SI–Ti3C2Tx MXene oxidized the MF on its surface through its electrocatalytic activity at very low current density and cell potential. For complete oxidation the optimum parameters were 0.525 C g−1, 0.005 mA cm−2, and pH 6 in absence of NaCl or 26.25 C g−1 and 0.5 mA cm−2 in the presence of 2.5 w/v% NaCl. The overall regeneration of SI–Ti3C2Tx is governed by a combined mechanism, i.e., desorption followed by degradation. The degradation mechanism, such as direct electron transfer or indirect oxidation, depends on the applied operating conditions. Thus, the investigation suggests that these 2D sheets are good nanoadsorbents as well as good electrocatalysts and proves their usefulness in practical water-treatment applications.

Design and fabrication of polyamine nanofiltration membrane by constituting multifunctional aliphatic linear amine and trifunctional cyanuric chloride for selective organic solvent nanofiltration

BackgroundThin film composite nanofiltration (TFC-NF) membranes have been developed for organic solvent nanofiltration. Most of the polyamide TFC-NF membranes are vulnerable to nucleophilic hydrolysis. MethodsA multifucntional amine was crosslinked with a trifucntional non-aqueous monomer namely cyanuric chloride (CC) on surface of self-fabricated polysulfone/polyester terephthalate (PS/PET) membarne support leading to a new polyamine active layer containing TFC-NF membrane named as PA@PS/PET. The fabricated PA@PS/PET membrane was thoroughly characterized by several characterization techniques such as ATR-FTIR, XPS, FE-SEM, Water Contact Angle (WCA), and EDX analysis. Significant FindingsPA@PS/PET TFC-NF membrane showed remakable perfomance in terms of solvent flux for all tested solvents including water, methanol, ethanol and isopropanol. The highest flux was found to be 29.58 L m−2h−1 at 8 bar for methanol. The flux of solvents was found to be inversly related to the viscosity of the solvents. The PA@PS/PET membrane showed remarkably high rejection of solute (Congo Red) reaching to a value of ∼98%. Moreover, the PA@PS/PET membrane showed permanant flux of 8.45 L m−2 h−1 at 2 bar during solute separation (CR dye rejection) tests which hinted the stability of the membrane under the applied operating conditions.

Structural and Tribological Properties of Heat-Treated Stainless Steels against Abrasive and Lubricant Wear Conditions

The current paper investigates the effect of the heat treatment process on three grades of stainless steel alloys against the abrasive and the lubricant wear conditions, using 25 wt.% glucose solution for the industrial agriculture applications. The heat treatment process was carried out for one hour at 900 ± 10 °C, followed by quenching with monograde motor oil and tempering for more than two hours at 200 ± 10 °C. Several analyses were conducted to estimate the final mechanical, surface morphological and tribological properties for the studied materials, before and after the heat treatment process. The heat-treated martensitic stainless steel grade exhibited superior wear resistance and higher hydrophobicity compared to the other two heat-treated austenite stainless steel grades. Therefore, the mechanism of the heat treatment process, the chemical and physical nature of the parent material, and the viscosity of the selected lubricant all influence the final behaviour of the studied material against the applied operating conditions for the selected application.

The Relationship Between the Biokinetic Parameters of an Aerobic Granular Sludge System and the Applied Operating Conditions

Biokinetic parameters help to describe the rate of substrate utilization and biomass production or growth by microbial action, which is important to the design process and performance optimization of wastewater treatment. Although studies of the biokinetic parameters of aerobic granular sludge (AGS) systems have been increasing lately, the significance for each value in terms of maximum specific growth rate (μ<sub>max</sub>), substrate concentration at one-half of the maximum specific growth rate (K<sub>S</sub>), and cell yield (Y) in relation to the applied operating conditions are rarely discussed. Therefore, this study investigates the relationship and significance between the above-stated biokinetic parameters with organic loading rate (OLR) and reactor height/diameter (H/D) ratio from five different batches of AGS treated sewage, using the independent t-test. The biokinetic parameters are summarized as biomass production (<i>Y</i> and <i>μmax</i>) and relied upon the relative increase in the OLR and reactor H/D ratios. Additionally, aerobic granules developed in reactors with a high H/D ratio have a shorter setup time and are more active in contrast with low H/D ratio reactors.

Development of mathematical transfer functions correlating Solid Oxide Fuel Cell degradation to operating conditions for Accelerated Stress Test protocols design

This work presents an innovative model-based approach for the development of mathematical transfer functions capable of correlating Solid Oxide Fuel Cells (SOFCs) degradation rate to the applied operating conditions. Such functions can be used for fuel cell lifetime prediction and Accelerated Stress Test (AST) protocols design. The proposed approach relies on multiscale modelling methodology and links local degradation to high level performance models to evaluate the key operating variables accelerating voltage decay over time. A thorough simulation analysis is performed to convey the correlation among operating variables and degradation rate into mathematical transfer functions. To better illustrate the overall design and application process of such functions, a case study accounting for Ni agglomeration is addressed. The multiscale modelling framework is applied to correlate microscale (i.e., Ni particles size change) and macroscale (i.e., SOFC voltage reduction) levels through the most affected mesoscale parameters. The model is then used to simulate voltage decay over time and link degradation rates to the applied operating conditions. Afterwards, a parametric analysis is performed to investigate the influence exerted by each operating variable on the degradation rate and derive the transfer functions. An example of application for Accelerated Stress Test (AST) protocols design is then given.

Waste oil/crambe oil blends for ethyl ester production under supercritical conditions

The objective of this study was to evaluate the ethyl esters (EE) production obtained with waste oil (WO) and crambe oil (CO) blends using supercritical ethanol. Experiments were carried out to evaluate the effect of temperature, residence time and water concentration (in the ethanol) on the EE yield. Reactions were also conducted with pure oils for comparison purposes. The results show that an increase in temperature and residence time favors the production of esters; however, with an increase in decomposition. The EE yields obtained followed the order CO>blend 25/75 (WO/CO)>blend 50/50 (WO/CO)>WO. It was found that the degree of decomposition is related to the content of polyunsaturated fatty acids. The addition of water to the ethanol promoted an increase in the EE yield in the initial reaction time, but from 30 min the observed effect was minimal. Ethyl linoleate and linolenate underwent degradation under the applied operating conditions. Therefore, the blend with 25/75 (WO/OC) and the addition of 5 wt% of water provided a better yield, with ∼70 % esters at 300 °C and ∼10 wt% unreacted compounds.

(Invited) Designing SOC for Power-to-X Applications: A Multi-Physical Modelling Approach

In the current global energy transition, the Solid Oxide Cell (SOC) represents a promising technology for stationary energy generation and storage, since it facilitates highly efficient and low-emission energy conversion. Besides converting hydrogen or hydrocarbon fuels directly into electricity in fuel cell mode, the SOC can also be operated in a reverse mode as a Solid Oxide Electrolyzer Cell (SOEC). By operating the SOC as an electrolyzer, any surplus electrical energy produced from fluctuating renewable energy sources (e.g. solar or wind energy) can be utilized to synthesize syngas and subsequently hydrocarbon fuels. The outlet syngas composition is directly correlated to the applied operating conditions as H2O/CO2-ratio, temperature and current. Therefore, it is of utmost importance to gain a deep understanding of these relationships in order to establish optimal operational strategies for different applications.During electrolyzer operation the key component of the SOC is the fuel electrode (anode), since it facilitates the (i) electrochemical charge transfer reaction and (ii) the chemical reaction kinetics (cf. Fig. 1(c)). In state-of-the-art, anode-supported SOCs the anode relies on two porous, Ni / stabilized zirconia layers with specified phase compositions and microstructural characteristics: (i) the highly porous and catalytically active anode substrate (AS) and (ii) the electrochemically active anode functional layer (AFL) (cf. Fig. 1(a)). To raise fuel conversion efficiency, we must first gain a profound understanding of the optimal double-layer design for the desired application. Numerical simulations enable an efficient variation of geometrical, microstructural and material parameters over wide ranges and provide correlations between anode design and SOEC performance.In this contribution, we demonstrate a multi-physical modelling approach to predict the SOC performance in both fuel cell and electrolyzer operation. To do so, we combine two of our recently published modelling approaches: (i) the physically meaningful, three-channeled transmission line model for double-layered cermet anodes [1,2] and (ii) the non-isothermal FEM stacklayer model [3,4]. For the first time, a powerful mode framework is realized (cf. Fig. 1(b)), which is capable of spatially resolving all of the above mentioned processes, in both anode layers, within a complete stacklayer. The model considers the complex interplay of (i) multi-component gas transport coupled with (ii) catalytic reforming reactions, (iii) charge carrier transport, (iv) electrochemical charge transfer, (v) coupled heat release and consumption as well as (vi) heat transport in the individual stack components.We demonstrate a comprehensive, model-based optimization of Ni-based cermet anodes in a SOC stack layer with respect to (i) the selection of the electrolyte material, (ii) the modification of the microstructure and (iii) adapting of the layer thicknesses. Furthermore, the impact of the operating conditions on the optimal cell configuration will be discussed. Finally, we derive operational strategies for efficient SOEC operation by investigating the impact of (i) the inlet gases, (ii) the operating temperature and (iii) the applied current on the produced syngas composition.[1] S. Dierickx, J. Joos, A. Weber, E. Ivers-Tiffée, Advanced impedance modelling of Ni/8YSZ cermet anodes, Electrochim. Acta. 265 (2018) 736–750.[2] S. Dierickx, T. Mundloch, A. Weber, E. Ivers-Tiffée, Advanced impedance model for double-layered solid oxide fuel cell cermet anodes, J. Power Sources. 415 (2019) 69–82.[3] H. Geisler, A. Kromp, A. Weber, E. Ivers-Tiffée, Stationary FEM Model for Performance Evaluation of Planar Solid Oxide Fuel Cells Connected by Metal Interconnectors, J. Electrochem. Soc. 161 (2014) F778–F788.[4] N. Russner, S. Dierickx, A. Weber, R. Reimert, E. Ivers-Tiffée, Multiphysical modelling of planar Solid oxide fuel cell stack layers, J. Power Sources (in press). Figure 1

Impingement cooling using different arrangements of conical nozzles in a film cooled blade leading edge

Abstract In this paper, a combined internal and external blade cooling system is conducted numerically to study the effect of different nozzles arrangements on flow and heat transfer performance. The applied operating conditions are different values of Reynolds number ranging from 5000 to 25,000 and different temperature ratios varied from 0.5 to 0.85. Results indicate that Nusselt number increases with the increase of Reynolds number at constant temperature ratio for all cooling models. The staggered normal cooling model achieves the highest overall Nusselt number with a maximum increase of 14.3% compared to the other cooling models. Overall film cooling efficiency increases with the increase in the corresponding blowing ratios. The staggered normal cooling model achieves superior overall cooling performance compared with the other cooling models. A correlation for overall Nusselt number is derived as a function of Reynolds number and temperature ratio.

A new physisorption power generation system using advanced adsorbent materials

A large number of people worldwide lack access to secure power systems, particularly in developing countries. The abundant solar energy and waste heat energy can be used to generate electric power cleanly using absorption and adsorption systems to build small localized power generation units. The inclusion of a turbine within the physisorption system opens great opportunities to use low-grade and medium-grade heat sources, such as solar energy, geothermal energy and industrial waste heat, for power generation. In this numerical study, the water adsorption system for cooling and electricity (ASCE) is utilized for the first time to generate electric power only using advanced metal organic framework (MOF) materials. The main components of the physisorption power generation cycle (PPGC) are similar to those of ASCE, where the only difference is in the applied operating conditions. In PPGC, the water temperature entering the evaporator is relatively high, so that no cooling effect within the normal range can be obtained. This helps to increase the adsorption uptake in some adsorbent materials like MIL101-Cr, which increases the mass flow rate of the working fluid and improves the power generation process. According to these considerations, the two-bed PPGC system adopted in this study can generate electricity of up to 5.24 kW utilizing about 14.28 kg of MIL101-Cr with heating temperature of 320 ºC. This study highlights the potential of using advanced physical adsorbent materials like MOFs (e.g. MIL101-Cr) in power generation utilizing two-bed PPGC under a range of operating conditions.

Multivariate Chemometric Analysis of Membrane Fouling Patterns in Biofilm Ceramic Membrane Bioreactor

Membrane fouling highly limits the development of Membrane bioreactor technology (MBR), which is among the key solutions to water scarcity. The current study deals with the determination of the fouling propensity of filtered biomass in a pilot-scale biofilm membrane bioreactor to enable the prediction of fouling intensity. The system was designed to treat domestic wastewater with the application of ceramic microfiltration membranes. Partial least squares regression analysis of the data obtained during the long-term operation of the biofilm-MBR (BF-MBR) system demonstrated that Mixed liquor suspended solids (MLSS), diluted sludge volume index (DSVI), chemical oxygen demand (COD), and their slopes are the most significant for the estimation and prediction of fouling intensity, while normalized permeability and its slope were found to be the most reliable fouling indicators. Three models were derived depending on the applied operating conditions, which enabled an accurate prediction of the fouling intensities in the system. The results will help to prevent severe membrane fouling via the change of operating conditions to prolong the effective lifetime of the membrane modules and to save energy and resources for the maintenance of the system.

Can CabECO® technology be used for the disinfection of highly faecal-polluted surface water?

In this work, the disinfection of highly faecal-polluted surface water was studied using a new electrochemical cell (CabECO® cell, manufactured by CONDIAS) specifically designed to produce ozone in water with very low conductivity. The disinfection tests were carried out in a discontinuous mode to evaluate the influence of the electrode current charge passed. The effect of the current density was also studied in order to optimize the disinfection conditions and to simultaneously prevent the formation of undesirable by-products (chlorates and perchlorates) during the electrolysis. The results demonstrate that this technology is robust and efficient, and it can suitably disinfect water. During electrolysis, the chloride contained in the water was oxidized to hypochlorite, and this compound was combined with ammonia to form chloramines. Both hypochlorite and chloramines (formed by the well-known break point reaction) promoted persistent disinfection and seemed to be mainly responsible for the disinfection attained during the electrochemical process. Chlorate and perchlorate could also be produced, although the low concentrations of chloride in the tested water made them irrelevant. The removal of the total organic carbon under the applied operating conditions was not very efficient (although it reached 50% in 2 h) and the production of trihalomethanes was very low, below 100 ppb for all tests.

Performance of novel dielectric barrier discharge reactor for biodiesel production from palm oil and ethanol

The disadvantages of conventional biodiesel synthesis trigger the birth of new biodiesel synthesis methods using the DBD plasma reactor. The conventional methods with homogeneous and heterogeneous catalysts have significant constraints that the formation of glycerol compounds in large enough quantities that require considerable energy. The aim of present experiment is to design DBD non-thermal plasma reactor coaxial pipe type and to do its performance test in converting biodiesel The feed stock used are palm oil, ethanol, and argon gas as plasma carrier. Such a chemical reactor, this plasma reactor is also influenced by reaction kinetics and hydrodynamic factors. From this research, it can be seen that the optimum feed and gas flowrate being operated is 1.64 and 41.67 mL/s. The plasma reactor is used in the form of a quartz glass tube surrounded by a SS-314 spiral coil as an outer electrode. The applied operating conditions are 1 : 1 molar ratio of methanol/oil, ambient temperature of 28 - 30 °C, and pressure 1 bar. From this performance test, it is found that this plasma reactor can be used to synthesize biodiesel from palm oil and methanol without catalyst, no formation of soap, and minimal byproducts.

Spark discharge generation of superparamagnetic Nickel Oxide nanoparticles

The unique properties of superparamagnetic nanoparticles offer many potential applications in various fields, especially in biomedicine. We have synthesized nickel oxide nanoparticles using spark discharge method in the argon gas followed by oxidation at atmospheric conditions. At applied operating conditions, the production rate of the nanoparticles was about 7 mg/h. The produced nanoparticles were characterized in terms of morphology, size, purity, structure, and magnetic property using field emission scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, x-ray and electron diffraction, as well as vibrating sample magnetometer analysis. All the characterization techniques suggested the formation of ∼6nm size nickel oxide nanoparticles and some scarce larger size nickel nanoparticles with a high chemical purity and superparamagnetic behaviour. The results indicate that spark discharge in the gas phase is a facile and powerful method for the generation of chemically pure superparamagnetic nanoparticles as candidate for biomedical applications.

Thermo-mechanical strength analysis for energy storage improvement of horizontal storage tanks integrating evacuated tube collectors

In the present paper, a two dimensional axisymmetric Finite Element Method (FEM) is developed to carry out a thermo-mechanical analysis on a horizontal storage tank intended to storage hot water for a domestic application. The purpose of these numerical simulations is to assess the thermo-mechanical behavior of a horizontal tank with evacuated tube collectors, and consequently to suggest a new design which ensures an optimum mechanical strength according to severe applied operating conditions in terms of temperature and pressure. To achieve this goal, a thermo-mechanical 1-way sequential coupling has been used as a solving method. The physical model suggested in this study and the simulations procedure was described under detailed assumptions. In fact, the main hypotheses in the current formulation were the thermo-elastic behavior of the tank's materials and the steady state assumption analysis.This paper outlines three studies that were performed to extend the lifespan of the horizontal storage tank, through the definition of a suitable material and an optimal design. The main conclusions of the assessment are that the optimal configuration which avoid the appearance of the stress concentration zones is the configuration (c), where Ri = 11 mm and Re = 14 mm, because the stress on the tank's shell was better applied. Moreover, the effect of the material's selection was carried out, and it was found that stainless steel is the optimal material. Last but not least, a set of simulations were conducted to investigate the tank shell thickness on which the thermo-mechanical constraints were applied. The thickness t=2 mm was presenting an optimal mechanical behavior with regard to the studied operating conditions.

Assessment of the impact of post-injection on exhaust pollutants emitted from a diesel engine fueled with biodiesel

This paper reports the effect of post-injection on pollutant emissions from a four-cylinder, direct-injection diesel engine fueled with biodiesel. Characteristics of exhaust pollutants were measured and evaluated for different main-post intervals (MPIs) and post-injection rates (PIRs). Measurements included emissions of carbon monoxide (CO), total hydrocarbons (THC), nitrogen oxides (NOx) and particulate matter (PM), the particle number concentration distribution, and the reactivity and graphitization degree of the soot particles. Increasing the MPI or PIR increased the emissions of CO and THC but decreased those of NOx. At both low and high MPI values, higher PM emissions and particle number concentrations were observed for the 12 and 20% PIRs. At a PIR of 4%, PM emissions and particle number concentration increased with the increase in MPI. The size distributions of exhaust particulates exhibited a trimodal character under the applied operating conditions. The particle geometric mean diameter decreased with the increase in MPI, probably as a result of an increased yield of soluble organic compounds. Post-injection significantly impacted the reactivity of emitted soot particles, as evidenced by changes in the graphitization degree of soot.

Understanding the reactivity of unsaturated alcohols: Experimental and kinetic modeling study of the pyrolysis and oxidation of 3-methyl-2-butenol and 3-methyl-3-butenol

The reactivity of unsaturated alcohols with a C=C double bond in the β- and γ-positions to the hydroxyl group is not well established. The pyrolysis and oxidation of two such unsaturated alcohols have been studied, i.e. 3-methyl-2-butenol (prenol) and 3-methyl-3-butenol (isoprenol). Experiments at three equivalence ratios, i.e. φ=0.5, φ=1.0 and φ=∞ (pyrolysis), were performed using an isothermal jet-stirred quartz reactor at temperatures ranging from 500 to 1100K, a pressure of 0.107MPa and a residence time of 2s. The reactant and product concentrations were quantified using gas chromatography. A kinetic model has been developed using the automatic network generation tool “Genesys”. Several important rate coefficients are obtained from new quantum chemical calculations. Overall, there is a good agreement between model calculated mole fraction profiles and experimental data. Reaction path analysis reveals that isoprenol consumption is dominated by a unimolecular reaction to formaldehyde and isobutene. At the applied operating conditions, the equivalence ratio has no effect on the isoprenol conversion profile. Pyrolysis and oxidation of prenol is dominated by radical chemistry, with hydrogen abstractions from prenol forming resonantly stabilized radicals as dominating conversion path. Oxidation and decomposition of the resulting radicals are predicted to form 3-methyl-2-butenal and 2-methyl-1,3-butadiene, which have been detected as important products in the reactor effluent.

Investigating natural organic carbon removal and structural alteration induced by pulsed ultrasound

The application of pulsed ultrasound for DOC removal from natural water samples has been thoroughly investigated in this work. Natural water samples were treated with ultrasound at power levels of 48 and 84 W with treatment times of 5 and 15 min. Chemical fractionation was conducted for both untreated and treated samples to clearly identify the change in DOC structure caused by ultrasonic treatments. Statistical analyses applying 2(3) factorial design were performed to study the behaviour of the response (i.e. DOC removal) under different operating conditions. Overall, ultrasonic treatments resulted in DOC removal of 7-15% depending on the applied operating conditions. The treated water had high microbial loading that interfered with DOC removal due primarily to the release of microbial products when exposed to ultrasound. Pulse ultrasound was found to be more effective than the continuous mode for DOC removal at the same effective power level. A regression model was developed and tested for DOC removal prediction. The model was adequate in predicting DOC removal with a maximum deviation from the experimental data of <11%. Pulsed ultrasound at low power levels and short treatment times was found to be the most energy efficient treatment for DOC removal.

Direct dimethyl ether synthesis from synthesis gas: The influence of methanol dehydration on methanol synthesis reaction

Direct dimethyl ether (DME) synthesis from synthesis gas is studied with regard to potential effects of methanol dehydration on methanol formation and copper-based catalyst performance. For this, the influence of the operating conditions (space velocity, temperature, pressure, time-on-stream and syngas composition) on activity, selectivity and stability of the catalyst was studied and compared for methanol synthesis and direct DME synthesis. The advantage of the direct over the two-step DME synthesis is apparent at conditions where syngas conversion to methanol is thermodynamically limited. However, under the applied operating conditions, results suggest that combining methanol synthesis and dehydration has a negative effect on the methanol formation kinetics. The origin of the observed phenomena is investigated by varying dehydration catalyst and by introducing dehydration products (DME and water) into the methanol synthesis feed. Choice of the solid acid catalyst does not seem to affect methanol formation, and DME is also found to be practically inert over the methanol synthesis catalysts. Water injection, on the other hand, led to a significant decrease in the methanol synthesis rate. Thus, formation of an additional amount of water through methanol dehydration might be an explanation for the lower methanol formation rate in the direct DME synthesis.