Process Simulation and Environmental Aspects of Dimethyl Ether Production from Digestate-Derived Syngas

The production of dimethyl ether from renewables or waste is a promising strategy to push towards a sustainable energy transition of alternative eco-friendly diesel fuel. In this work, we simulate the synthesis of dimethyl ether from a syngas (a mixture of CO, CO2 and H2) produced from gasification of digestate. In particular, a thermodynamic analysis was performed to individuate the best process conditions and syngas conditioning processes to maximize yield to dimethyl etehr (DME). Process simulation was carried out by ChemCAD software, and it was particularly focused on the effect of process conditions of both water gas shift and CO2 absorption by Selexol® on the syngas composition, with a direct influence on DME productivity. The final best flowsheet and the best process conditions were evaluated in terms of CO2 equivalent emissions. Results show direct DME synthesis global yield was higher without the WGS section and with a carbon capture equal to 85%. The final environmental impact was found equal to −113 kgCO2/GJ, demonstrating that DME synthesis from digestate may be considered as a suitable strategy for carbon dioxide recycling.

Kinetics of the direct DME synthesis from CO2 rich syngas under variation of the CZA-to-γ-Al2O3 ratio of a mixed catalyst bed

Experimental and numerical kinetic investigations for the direct DME synthesis resulted in one of the predictive models with the broadest range of validity in the open literature for the CZA/γ-Al2O3 system.

The high-yield direct synthesis of dimethyl ether from CO2 and H2 in a dry reaction environment

Highly efficient DME synthesis from CO2 and H2 was realized in a dry reaction environment via the incorporation of a water-conduction membrane.

Direct DME synthesis on CZZ/H-FER from variable CO2/CO syngas feeds

Catalyst systems for the conversion of synthesis gas, which are tolerant to fluctuating CO/CO2 gas compositions, have great potential for process-technical applications, related to the expected changes in the synthesis gas supply.

The Techno-Economic Benefit of Sorption Enhancement: Evaluation of Sorption-Enhanced Dimethyl Ether Synthesis for CO2 Utilization

Dimethyl ether (DME) is an important platform chemical and fuel that can be synthesized from CO2 and H2 directly. In particular, sorption-enhanced DME synthesis (SEDMES) is a novel process that uses the in situ removal of H2O with an adsorbent to ensure high conversion efficiency in a single unit operation. The in situ removal of steam has been shown to enhance catalyst lifetime and boost process efficiency. In addition, the hydrogen may be supplied through water electrolysis using renewable energy, making it a promising example of the (indirect) power-to-X technology. Recently, major advances have been made in SEDMES, both experimentally and in terms of modeling and cycle design. The current work presents a techno-economic evaluation of SEDMES using H2 produced by a PEM electrolyzer. A conceptual process design has been made for the conversion of CO2 and green H2 to DME, including the purification section to meet ISO fuel standards. By means of a previously developed dynamic cycle model for the SEDMES reactors, a DME yield per pass of 72.4 % and a carbon selectivity of 84.7% were achieved for the studied process design after optimization of the recycle streams. The production costs for DME by the power-to-X technology SEDMES process at 23 kt/year scale are determined at ∼€1.3 per kg. These costs are higher than the current market price but lower than the cost of conventional DME synthesis from CO2. Factors with the highest impact on the business cases are the electricity and CO2 cost price as well as the CAPEX of the electrolyzer, which is considered an important component for technology development. Furthermore, as the H2 cost constitutes the largest part of the DME production cost, SEDMES is demonstrated to be a powerful technology for efficient conversion of green H2 into DME.

Enhanced Direct Dimethyl Ether Synthesis from CO2-Rich Syngas with Cu/ZnO/ZrO2 Catalysts Prepared by Continuous Co-Precipitation

The manufacturing of technical catalysts generally involves a sequence of different process steps, of which co-precipitation is one of the most important. In this study, we investigate how continuous co-precipitation influences the properties of Cu/ZnO/ZrO2 (CZZ) catalysts and their application in the direct synthesis of dimethyl ether (DME) from CO2/CO/H2 feeds. We compare material characteristics investigated by means of XRF, XRD, N2 physisorption, H2-TPR, N2O-RFC, TEM and EDXS as well as the catalytic properties to those of CZZ catalysts prepared by a semi-batch co-precipitation method. Ultra-fast mixing in continuous co-precipitation results in high BET and copper surface areas as well as in improved metal dispersion. DME synthesis performed in combination with a ferrierite-type co-catalyst shows correspondingly improved productivity for CZZ catalysts prepared by the continuous co-precipitation method, using CO2-rich as well as CO-rich syngas feeds. Our continuous co-precipitation approach allows for improved material homogeneity due to faster and more homogeneous solid formation. The so-called “chemical memory” stamped during initial co-precipitation is kept through all process steps and is reflected in the final catalytic properties. Furthermore, our continuous co-precipitation approach may be easily scaled-up to industrial production rates by numbering-up. Hence, we believe that our approach represents a promising contribution to improve catalysts for direct DME synthesis.

CO2 Utilization Process Simulation for Enhancing Production of Dimethyl Ether (DME)

Increase in the world energy demand also increases the concentration of CO2 in the atmosphere, which contributes to global warming and ocean acidification. This study proposed the simulation process to utilize CO2 released from the acid gas removal unit in one of gas processing plants in Indonesia to enhance the production of dimethyl ether (DME) through unreacted gas recycle that can be beneficial in reducing CO2 emission to the atmosphere. Simulation was developed in Unisim R390.1 using Peng–Robinson–Stryjek–Vera (PRSV) as a fluid package. Simulation was validated by several studies conducted by many researchers and giving satisfactory results especially in terms of productivity, conversion, and selectivity as a function of reactor temperatures in the indirect and the direct DME synthesis processes. Simulation results show that the DME production was enhanced by around 49.6% and 65.1% for indirect and direct processes, respectively, at a recycling rate of 7 MMSCFD. Compressor is required to increase the unreacted gas pressure to the desired pressure in the methanol reactor or dual methanol-DME reactor in both processes. Specific power consumption (SPC) was used as a tested parameter for the effectiveness of recycling unreacted gas. Based on the simulation, the direct DME synthesis process is superior over the indirect process in terms of DME and methanol productions, SPCs, and system energy efficiencies.