Continuous multi-column sorption-enhanced dimethyl ether synthesis (SEDMES):Dynamic operation

In this work the continuous production of dimethyl ether (DME) by sorption-enhanced DME synthesis (SEDMES) technology has been demonstrated for the first time with a multi-column test-rig. A continuous single-pass carbon yield up to 95%, higher than ever reported before, has been achieved. The multi-column experiments have also shown that SEDMES can be operated at lower temperatures (220°C) than previously reported. This allows a higher temperature rise, making higher conversions possible while allowing even larger reactor tube diameters. Whereas the anticipated multi-tubular reactor concept is complex and costly, larger reactors could facilitate the economic valorisation. The SEDMES reactor model cannot only describe the transient behaviour of the process during the cyclic steady-state well, but also the dynamic approach towards the cyclic steady-state is adequately captured. Capturing the dynamic operation is of large interest with respect to process flexibility, especially for Power-to-X systems.</p

The Association Between Cytomegalovirus Infection and Cardiac Allograft Vasculopathy in the Era of Antiviral Valganciclovir Prophylaxis

Background. Previous studies on the association between cytomegalovirus (CMV) infection and cardiac allograft vasculopathy (CAV) were conducted on patients transplanted in the prevalganciclovir prophylaxis era. The aim of our study is to evaluate this relation in heart transplantation (HTx) recipients treated according to current prophylactic and immunosuppressive regimens. Methods. This single-center retrospective study included all consecutive adult patients that underwent HTx between January 1, 2000, and May 31, 2018. Clinically relevant CMV infection was defined as either plasma CMV DNAemia ≥ 1000 IU/mL with/without clinical symptoms or <1000 IU/mL with symptoms. The primary endpoint was first manifestation of CAV diagnosed by coronary angiography. For statistical analysis, the cause-specific hazard regression model was applied, with clinically relevant CMV infection and any CMV infection as time-dependent variables. Results. In total, 260 patients were included in the analysis. The median (interquartile range) follow-up was 7.88 (4.21–12.04) years. During the follow-up, clinically relevant CMV infection was diagnosed in 96 (37%) patients and CAV in 149 (57%) patients. In the multivariate regression analysis, independent predictors of CAV were: number of rejection episodes (cause-specific hazard ratio [95% confidence interval]: 1.18 [1.04-1.34], P = 0.01), hypertension (1.61 [1.11-2.34], P = 0.01), treatment with mycophenolate mofetil (0.68 [0.47-0.97], P = 0.03). No significant association was observed between CMV infection and CAV, except for patients who experienced a breakthrough CMV infection (n = 24) during prophylaxis (1.94 [1.11-3.40], P = 0.02). Conclusions. In the era of contemporary immunosuppression and valganciclovir prophylaxis, a signifi

Steam adsorption on molecular sieve 3A for sorption enhanced reaction processes

Steam adsorption enhanced reaction processes are a promising process intensification for many types of reactions, where water is formed as a byproduct. To assess the potential of these processes, adequate models are required that accurately describe water adsorption, particularly under the desired elevated temperatures and pressures. In this work, an adsorption isotherm is presented for H2O adsorption at 200–350 °C and 0.05–4.5 bar partial pressure on molecular sieve (LTA) 3A. The isotherm has been developed on the basis of experimental data obtained from a thermogravimetric analysis and integrated breakthrough curves. The experimental data at lower steam partial pressures can be described with a Generalized Statistical Thermodynamic Adsorption (GSTA) isotherm, whereas at higher steam partial pressures the experimental data can be adequately captured by capillary condensation. Based on the characteristics of the adsorbent particles, a linear driving force relation has been derived for the adsorption mass transfer rate and the apparent micropore diffusivity is determined. The isotherm and mass transport model presented here prove to be adequate for modelling and improved evaluation of steam adsorption enhanced reaction processes.Steam adsorption enhanced reaction processes are a promising process intensification for many types of reactions, where water is formed as a byproduct. To assess the potential of these processes, adequate models are required that accurately describe water adsorption, particularly under the desired elevated temperatures and pressures. In this work, an adsorption isotherm is presented for H2O adsorption at 200–350 °C and 0.05–4.5 bar partial pressure on molecular sieve (LTA) 3A. The isotherm has been developed on the basis of experimental data obtained from a thermogravimetric analysis and integrated breakthrough curves. The experimental data at lower steam partial pressures can be described with a Generalized Statistical Thermodynamic Adsorption (GSTA) isotherm, whereas at higher steam partial pressures the experimental data can be adequately captured by capillary condensation. Based on the characteristics of the adsorbent particles, a linear driving force relation has been derived for the adsorption mass transfer rate and the apparent micropore diffusivity is determined. The isotherm and mass transport model presented here prove to be adequate for modelling and improved evaluation of steam adsorption enhanced reaction processes

Breaking azeotropes by reactive adsorption:A case for sorption-enhanced dimethyl carbonate synthesis

This work investigates the direct production of dimethyl carbonate (DMC) from CO2 by sorption-enhanced DMC (SEDMC) synthesis, employing modelling techniques. SEDMC synthesis is shown to be an exemplary case for reactive separation, as it enhances the reaction and simplifies downstream processing through in-situ separation. By incorporating in-situ water adsorption, SEDMC achieves significantly higher methanol conversions compared to other direct synthesis routes. Simultaneously, the formation of two azeotropes can be avoided, leading to a drastic simplification of downstream separation, requiring only one-step conventional distillation. By increasing the methanol conversion to 45%, the formation of a DMC-methanol azeotrope is prevented, and the in-situ water adsorption effectively avoids the DMC-water azeotrope. Based on these findings, further research should focus on identifying suitable materials and (reactive) adsorbents, while also incorporating a more detailed process layout and cycle design. These efforts will unlock the full potential of SEDMC synthesis in the production of renewable materials.</p

Separation enhanced methanol and dimethyl ether synthesis

Separation enhanced reaction processes are promising process intensification strategies for carbon dioxide utilisation. In recent years, major improvements have been made in adsorption and membrane technology for the direct production of methanol and dimethyl ether from carbon dioxide rich feedstock and hydrogen. In situ water removal results in high single-pass conversions, thereby circumventing the disadvantages of conventional routes, such as the low carbon efficiency, energy intensive downstream separation and large recycles. In situ water removal by adsorption results in extremely high single-pass conversion and yield, especially in direct DME production. Membrane reactors allow for high single-pass conversion and yield, especially for methanol production. Here, we highlight recent advances in membrane and adsorption-enhanced synthesis of methanol and DME

Sorption enhanced dimethyl ether synthesis under industrially relevant conditions: experimental validation of pressure swing regeneration

Dimethyl ether (DME) is one of the most attractive alternative fuel solutions under consideration worldwide. However, its production from CO2-rich feedstock or CO2 directly is limited via conventional processes and therefore considered unattractive. For CO2 utilisation, the production and efficient handling of steam remains a major bottleneck. Sorption enhanced DME synthesis (SEDMES), which combines heterogeneous catalysis with in situ water adsorption, is a promising process intensification strategy for the direct production of DME from CO2. In this work, SEDMES is demonstrated experimentally on a bench-scale reactor with pressure swing regeneration under industrially relevant conditions. Pressure swing regeneration, rather than the time and energy intensive temperature swing regeneration, shows high performance with over 80% single-pass carbon selectivity to DME. This already allows for a factor four increase in productivity, with further optimisation still possible. With the proposed Sips working isotherm for the water adsorbent, and the methanol synthesis and dehydration kinetics, the validated dynamic cycle model adequately describes the SEDMES bench-scale data. Applying shorter cycle times, made possible by pressure swing regeneration, allows optimisation of the DME productivity while maintaining the high single-pass yield typical for SEDMES. The experimental confirmation shown in this paper unlocks the full potential of the high efficiency carbon and hydrogen utilisation by SEDMES technology