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1. EXPERIMENTAL INVESTIGATION OF THE APPLICATION OF IONIC LIQUIDS TO METHANOL SYNTHESIS IN MEMBRANE REACTORS

   https://doi.org/10.1021/acs.iecr.9b01178  

   Sadat Zebarjad, Fatemeh; Hu, Sheng; Li, Zhongtang; Tsotsis, Theodore (June 2019, Industrial engineering chemistry research)

   In this study a high-pressure membrane reactor (MR) was employed to carry-out the methanol synthesis (MeS) reaction. Syngas was fed into the MR shell-side where a commercial MeS catalyst was used, while the tube-side is swept with a high boiling point liquid with good solubility towards methanol. A mesoporous alumina ceramic membrane was utilized, after its surface had been modified to be rendered more hydrophobic. The efficiency of the MR was investigated under a variety of experimental conditions (different pressures, temperatures, sweep liquid flow rates, and types of sweep liquids). The results reveal improved per single-pass carbon conversions when compared to the conventional packed-bed reactor. An ionic liquid (IL), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) was utilized in the MR as the sweep liquid. The experimental results are compared to those previously reported by our Group (Li and Tsotsis, J. Membrane Sci., 2019) while using a conventional petroleum-derived solvent as sweep liquid, tetraethylene glycol dimethyl ether (TGDE). Enhanced carbon conversion (over the petroleum-derived solvent) was obtained using the IL. 

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2. Investigation of CO2 and Methanol Solubility at High Pressure and Temperature in the Ionic Liquid [EMIM][BF4] Employed During Methanol Synthesis in a Membrane-Contactor Reactor

   https://doi.org/10.1016/j.ces.2021.116722  

   Zebarjad, Fatemeh; Wang, Zi; Li, Hao; Hu, Sheng; Tang, Yongchun; Tsotsis, Theodore (January 2021, Chemical engineering science)

   In this paper, the solubility properties of the ionic liquid (IL), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) were studied using a high-pressure, high-temperature set-up employing the pressure-drop technique. [EMIM][BF4] was selected for study because it is used as the sweep liquid in a membrane reactor (MR)-based methanol synthesis (MR-MeS) process recently proposed and studied by our group. The MR-MeS studies indicated high methanol (MeOH) solubilities in the IL under typical MeS reaction conditions, which then motivated this study to measure such solubilities directly under non-reactive conditions to validate the findings of the MR study. In addition, during the MR-MeS studies a concern existed about the solubility of CO2 in [EMIM][BF4], since it is a reactant in the MeS process and its dissolution in the sweep liquid would be detrimental for reactor performance. Studies, therefore, were also carried out to investigate the solubility of CO2, in addition to MeOH, in the IL. Our investigation indicates that though CO2 solubilities in the [EMIM][BF4] are high at room temperature, they become negligible at the typical MeS operating conditions (i.e., temperatures above 200 ⁰C). 

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3. Numerical Simulation of a Novel H ₂ /O ₂ Co-Transport Membrane Reactor for Combined H ₂ O/H ₂ Removal and Ethylene Production

   https://doi.org/10.1149/1945-7111/acfc6b  

   Shoukry, Yasser M. M.; Huang, Kevin; Jin, Xinfang (October 2023, Journal of The Electrochemical Society)

   To cut CO₂emissions, we propose to directly convert shale gas into value-added products with a new H₂/O₂co-transport membrane (HOTM) reactor. A Multiphysics model has been built to simulate the membrane and the catalytic bed with parameters obtained from experimental validation. The model was used to compare C2 yield and CH₄conversion rate between the membrane reactor and the state-of-the-art fixed-bed reactor with the same dimensions and operating conditions. The results indicate that (1) the membrane reactor is more efficient in consuming CH₄for a given amount of fed O₂. (2) The C2 selectivity of the membrane reactor is higher due to the gradual addition of O₂into the reactor. (3) The current proposed membrane reactor can have a decent proton molar flux density but most of the proton molar flux will contribute to producing H₂O on the feed side under the current operating conditions. The paper for the first-time projects the performance of the membrane reactor for combined H₂O/H₂removal and C2 production. It could be used as important guidance for experimentalists to design next generation natural gas conversion reactors. 

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4. Production of renewable alcohols from maple wood using supercritical methanol hydrodeoxygenation in a semi-continuous flowthrough reactor

   https://doi.org/10.1039/d0gc03218b  

   Galebach, Peter H.; Soeherman, Jimmy K.; Gilcher, Elise; Wittrig, Ashley M.; Johnson, Jillian; Fredriksen, Thomas; Wang, Chengrong; Lanci, Michael P.; Dumesic, James A.; Huber, George W. (December 2020, Green Chemistry)

   null (Ed.)

   Biomass conversion to alcohols using supercritical methanol depolymerization and hydrodeoxygenation (SCM-DHO) with CuMgAl mixed metal oxide is a promising process for biofuel production. We demonstrate how maple wood can be converted at high weight loadings and product concentrations in a batch and a semi-continuous reactor to a mixture of C 2 –C 10 linear and cyclic alcohols. Maple wood was solubilized semi-continuously in supercritical methanol and then converted to a mixture of C 2 –C 9 alcohols and aromatics over a packed bed of CuMgAlO x catalyst. Up to 95 wt% of maple wood can be solubilized in the methanol by using four temperature holds at 190, 230, 300, and 330 °C. Lignin was solubilized at 190 and 230 °C to a mixture of monomers, dimers, and trimers while hemicellulose and cellulose solubilized at 300 and 330 °C to a mixture of oligomeric sugars and liquefaction products. The hemicellulose, cellulose, and lignin were converted to C 2 –C 10 alcohol fuel precursors over a packed bed of CuMgAlO x catalyst with 70–80% carbon yield of the entire maple wood. The methanol reforming activity of the catalyst decreased by 25% over four beds of biomass, which corresponds to 5 turnovers for the catalyst, but was regenerable after calcination and reduction. In batch reactions, maple wood was converted at 10 wt% in methanol with 93% carbon yield to liquid products. The product concentration can be increased to 20 wt% by partially replacing the methanol with liquid products. The yield of alcohols in the semi-continuous reactor was approximately 30% lower than in batch reactions likely due to degradation of lignin and cellulose during solubilization. These results show that solubilization of whole biomass can be separated from catalytic conversion of the intermediates while still achieving a high yield of products. However, close contact of the catalyst and the biomass during solubilization is critical to achieve the highest yields and concentration of products. 

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5. Mechanistic understanding of methane-to-methanol conversion on graphene-stabilized single-atom iron centers

   https://doi.org/10.1039/D1CY00826A  

   Hong, Sungil; Mpourmpakis, Giannis (January 2021, Catalysis Science & Technology)

   null (Ed.)

   The functionalization of methane to value-added liquid chemicals remains as one of the “grand challenges” in chemistry. In this work, we provide insights into the direct methane-to-methanol conversion mechanisms with H 2 O 2 as an oxidant on single Fe-atom centers stabilized on N-functionalized graphene, using first principles calculations. By investigating a series of different reaction paths on various active centers and calculating their turnover frequencies, we reveal that a H 2 O 2 -mediated radical mechanism and a Fenton-type mechanism are energetically the most plausible pathways taking place on di- and mono-oxo centers, respectively. Due to the thermodynamic preference of the mono-oxo center formation over the di-oxo under reaction conditions, the Fenton-type mechanism appears to determine the overall catalytic activity. On the other hand, the hydroxy(oxo) center, which is thermodynamically the most favorable center, is found to be catalytically inactive. Hence, the high activity is attributed to a fine balance of keeping the active centers as oxo-species during the reaction. Moreover, we reveal that the presence of solvent (water) can accelerate or slow down different pathways with the overall turnover of the dominant Fenton-type reaction being decreased. Importantly, this work reveals the nature of active sites and a gamut of reaction mechanisms for the direct conversion of methane to methanol rationalizing experimental observations and aiding the search for room temperature catalysts for methane conversion to liquid products. 

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