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CO2 capture performance of two imidazolium-based ionic liquids 1-Butyl-3-methylimidazolium Acetate [BMIM][Ac] and 1-propyl-3-methylimidazolium bis(trifluoro -methylsulfonyl)imide [PMIM][Tf2N] supported on a commercial Cu-BTC metal organic framework (HKUST-1) was investigated. The thermogravimetric analysis (TGA) was employed to analyse the impacts of ILs impregnation on the thermal stability of the composites. Furthermore, other characterization techniques such as powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) were used to confirm the successful incorporation of the ILs within the cages of HKUST-1. The as-synthesized ILs@HKUST-1 composites exhibited a stable crystal structure after the encapsulation of the ILs indicating that the structural features of the HKUST-1 support were retained and not impacted by the presence of ILs inside the pores. Moreover, the BET surface area and total pore volume of the ILs@HKUST-1 composites decreased considerably with the increase in IL loading in the composite which suggests the efficient incorporation of the ILs into the porous surface of the HKUST-1 support. Remarkably, the composite sorbent prepared with 5 wt% [bmim][Ac] exhibited the highest CO2 capacity in the low pressure region with almost double that of the pristine HKUST-1 at 303 K and 0.15 bar. On the other hand, the introduction of [pmim][Tf2N] into the pores of HKUST-1 did not show any enhancement in the CO2 uptake at all IL loadings. The samples also displayed a fast adsorption kinetics and a stable adsorption-regeneration performance up to ten cycles. The developed IL@HKUST-1 composites provide a great opportunity to design sorbent materials with excellent merits for potential industrial gas separation applications.

The potential advantage of using supported ionic liquids (SILs) for CO2 capture applications has been investigated in this work. The impregnation of 1-ethyl-3-methylimidazolium Acetate [emim][Ac] into two voluminous metal–organic frameworks (MOF-177 and MIL-101) is evaluated using different synthesis methods. The performance of the composite sorbents for CO2 capture has been evaluated using various characterization techniques. The successful incorporation of [emim][Ac] into the pores of MOF-177 and MIL-101 have been confirmed using thermogravimetric analysis and Fourier transform infrared spectroscopy results. Furthermore, the porosity of the as-synthesized samples using different synthesis methods have been measured using N2 adsorption experiments to evaluate the changes in the specific surface areas and pore volumes upon the introduction of [emim][Ac] to the support materials. A significant decrease in the porosity was realized for the [emim][Ac]-confined samples especially when using wet impregnation synthesis method compared to the dry mixing approach. The crystal structures of the MOF-177 and MIL-101 were found to be maintained after the synthetic steps, with some reductions in the X-ray diffraction peak intensities. No improvements in the CO2 uptakes could be achieved for the MIL-101 samples using both synthesis strategies, whereas the [emim][Ac]@MOF-177 samples prepared using wet impregnation method, has shown a remarkable enhancement in the CO2 capacity up to 0.3 mmol/g at 0.15 bar and 303 K. Moreover, the adsorption kinetics in MOF-177 based samples was found to be significantly fast as depicted from the first order rate constant values. The [emim][Ac]@MOF-177 samples exhibited a substantially stable cyclic adsorption–desorption performance up to 10 successive cycles with a considerably fast desorption kinetics.

The use of mixed metal oxides as oxygen carriers for chemical looping with oxygen uncoupling (CLOU) applications has shown great potential compared to single metal oxide-based oxygen carriers. In this work, the effects of adding WO3 to CuO/ZrO2 oxygen carriers on the oxygen capacity and rate indices for CLOU applications are investigated using nitrogen gas environment. Two synthesis methods were used to prepare the CuO-WO3/ZrO2 oxygen carriers, namely the coimpregnation and sequential impregnation, to evaluate the role of the oxygen carriers’ preparation method. The resulting oxygen carriers were thoroughly characterized using XRD, ICP-OES, SEM-EDS and H2-TPR characterization techniques to evaluate the physicochemical properties of the mixed oxide oxygen carriers. The oxygen transport capacity was found to significantly increase for the WO3-modified oxygen carriers compared with the single metal oxide CuO/ZrO2 which was due to the formation of a Cu-W intermediate phases that was found to enhance the redox characteristics of the oxygen carriers. Moreover, the sample synthesized via coimpregnation method displayed higher oxygen release capacity than the sequentially impregnated sample. This was ascribed to the formation a Cu-rich intermediate phase (Cu3WO6) possessing higher Cu/W ratio on the coimpregnated sample compared with a CuWO4-x phase with lower Cu/W ratio and larger crystallite structure formed on the sequentially impregnated oxygen carrier. The mixed metal oxide oxygen carriers also showed a stable redox performance which highlights the potential of WO3 as a modifier to Cu-based oxygen carriers to enhance the oxygen capacity and subsequently decrease the solids inventory. The proposed WO3-based promotors offer significant trait to synthesize Cu-based oxygen carriers with excellent properties for CLOU applications.

The CO2 capture performance of a novel amino acid ionic liquid (AAIL), 1-aminopropyl-3-methylimidazolium lysine ([APMIM][Lys]), impregnated into a mesoporous silica pore-expanded SBA-15 (PE-SBA-15) and a commercial poly(methyl methacrylate) (PMMA) supports was evaluated. The thermogravimetric analysis (TGA) was conducted to analyze the effect of AAIL impregnation on the thermal stability of the sorbents. X-ray diffraction (XRD) compared the intrinsic structure of PMMA with and without AAIL loading. Additionally, the surface area and pore volume decreased, when the AAIL loading increased, which suggests the effective impregnation of AAIL into the porous surface of the supports. Moreover, kinetics analysis was carried out using a double exponential model. The analysis indicates the CO2 uptake of the sorbents was affected not only by the AAIL loading, but also the AAIL dispersion on the surface of supports. According to the CO2 isotherms, the isosteric enthalpy of adsorption was calculated based on the Freundlich model and Clausius-Clapeyron equation. The best sorbent was 50 wt%[APMIM][Lys]-based PMMA, since it had the highest CO2 capacity, a fast adsorption kinetics and an enhanced chemisorption of CO2.

The solubility of carbon dioxide (CO2) in four ionic liquids, 1-ethyl-3-methylimidazolium L-(+)-lactate ([EMIM][LACTATE]), 3-methyl-1-propylpyridinium bis[(trifluoromethylsulfonyl]imide ([PMPY] [TF2N]), 1-(4-sulfobutyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([(CH2)4SO3HMIm][TF2N]), 1-(4-sulfobutyl)-3-methylimidazolium hydrogen sulfate ([(CH2)4SO3HMIm][HSO4]), has been experimentally studied using the gravimetric microbalance method. (Carbon dioxide + IL) systems were studied at (313.15, 323.15 and 333.15)K over a pressure range of 100 mbar–20000 mbar. Experimental densities, Henry's Law constants, entropies and enthalpies of absorption were also reported. The results obtained showed that CO2 solubility diminished in the following sequence: [PMPY][Tf2N]>[EMIM][LACTATE] > [(CH2)4SO3HMIm][TF2N] > [(CH2)4SO3HMIm][HSO4]. It was found that [PMPY][Tf2N] shows comparable CO2 solubility with ionic liquids that are considered promising such as [HMIM] [Tf2N], which makes this ionic liquid an attractive solvent for gas separation processes. CO2 solubility in the ionic liquids was well correlated using Peng–Robinson equation of state with a quadratic mixing rule and the nonrandom two-liquid (NRTL) model.

The conversion of methane to fuel and value-added chemicals such as syngas and oxygenated hydrocarbons is an attractive proposition for the energy and chemical industry. The conventional technologies for methane conversion are energy-intensive, costly, and major sources of greenhouse gas emissions. Low-temperature direct methane valorization is an attractive energy solution to significantly reduce dependency on current commercial technologies. Amongst the wide portfolio of the direct methane conversion processes is the photocatalytic liquefaction of methane to oxygenated hydrocarbons, which utilizes solar radiation to stimulate methane activation for methanol production. The low activity, selectivity, and low efficiency of the photocatalytic route, compared to other well-established technologies for the conversion of methane, limited their wide-scale applications. Therefore, a review of the existing literature is required to give a perspective of this promising technology, to discuss challenges and to identify potential areas for research and development and ultimately contribute to promoting green methane conversion processes. This review aims to highlight the state-of-the-art and the progress achieved in the catalyst development studies of the photocatalytic conversion of methane to oxygenated hydrocarbons. A special focus is given to WO3, bismuth-based, and zeolite photocatalysts used in the direct photocatalytic conversion of methane under moderate conditions. The catalyst structure-property relationship, the effect of operating conditions on reactivity, and reaction mechanism studies are discussed to highlight the challenges and opportunities for future research work. A perspective and outlook of the direct methane liquefaction technology are presented which emphasize the potential areas for improvements of catalytic activity and selectivity.

Ordered mesoporous silica MCM-41 and SBA-15 were impregnated by two imidazolium-based ionic liquids 1-Butyl-3-methylimidazolium Acetate [bmim][Ac] and 1-propyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide [pmim][Tf2N] using a facile impregnation-evaporation approach. The immobilization of ILs into the mesoporous silica supports was found to reduce the derivative decomposition temperatures (Tonset) by about 30 °C compared to the bulk ILs, however the decomposition process was found to occur over a wider temperature range for the IL-immobilized samples. These observations are indicative of interionic interactions between the ILs and the surface of the mesoporous silica supports, which was further corroborated by the shifts in the FTIR bands. The X-ray diffraction patterns (XRD) of the pristine MCM-41, SBA-15 and the IL-modified samples have shown that no textural or morphological changes were observed for the IL-impregnated samples and that the crystal structure of the mesoporous silica supports remained intact. The BET surface area and pore volumes of the composite sorbents have remarkably decreased after the incorporation of the ILs due to the occupation of the pore surface. All the composite sorbents modified with [bmim][Ac] ILs have shown a substantial increase in CO2 sorption capacity especially in the low pressure region up to 6 times higher CO2 uptake at 0.2 bar and 30 °C. On the other hand, the immobilization of [pmim][Tf2N] did not show any improvements in the sorption capacity for all impregnation amounts used. Furthermore, unlike the slow adsorption kinetics in the bulk ILs, the supported ILs exhibited significantly rapid sorption rates, with a stable cyclic adsorption-regeneration performance.

The potentiometric titration method was used to measure pKa values of nine amines [2-(diisopropylamino)ethanol [2-DIPA], N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine [THPEDA], 2-{[2-(dimethylamino) ethyl]methyl amino} ethanol [2-DMAEMAE], tris[2-(2-methoxyethoxy)ethyl]amine [TMEEA], N-(2-hydroxyethyl) aniline [2-HEAN], 1-(2-hydroxyethyl)piperazine [HEP], piperazine [PZ], monoethanolamine [MEA], and N-methyldiethanolamine [MDEA] at (298.15, 303.15, 313.15, 323.15, and 333.15) K. pKa values of the last three amines were compared with published data to validate the procedure and assess the accuracy of the instrument. Thermodynamic quantities, such as standard enthalpy (ΔH°·kJ–1·mol–1) and entropy (ΔSo·kJ–1·mol–1) for the dissociation process, were determined at 298.15 K using the van’t Hoff equation. From the experimental results, the values of the standard state thermodynamic properties were derived and compared to the values of commercially available amines used as absorbents for CO2 capture. Among t...

Over the past few years, great attention is paid to syngas production processes from different resources especially from abundant sources, such as methane. This review of the literature is intended for syngas production from methane through the dry reforming (DRM) and the steam reforming of methane (SRM). The catalyst development for DRM and SRM represents the key factor to realize a commercial application through the utilization of more efficient catalytic systems. Due to the enormous amount of published literature in this field, the current work is mainly dedicated to the most recent achievements in the metal-oxide catalyst development for DRM and SRM in the past five years. Ni-based supported catalysts are considered the most widely used catalysts for DRM and SRM, which are commercially available; hence, this review has focused on the recent advancements achieved in Ni catalysts with special focus on the various attempts to address the catalyst deactivation challenge in both DRM and SRM applications. Furthermore, other catalytic systems, including Co-based catalysts, noble metals (Pt, Rh, Ru, and Ir), and bimetallic systems have been included in this literature review to understand the observed improvements in the catalytic activities and coke suppression property of these catalysts.