Combined Superbase Ionic Liquid Approach to Separate CO2 from Flue Gas

[Image: see text] Superbase ionic liquids (ILs) with a trihexyltetradecylphosphonium cation and a benzimidazolide ([P(66614)][Benzim]) or tetrazolide ([P(66614)][Tetz]) anion were investigated in a dual-IL system allowing the selective capture and separation of CO(2) and SO(2), respectively, under realistic gas concentrations. The results show that [P(66614)][Tetz] is capable of efficiently capturing SO(2) in preference to CO(2) and thus, in a stepwise separation process, protects [P(66614)][Benzim] from the negative effects of the highly acidic contaminant. This results in [P(66614)][Benzim] maintaining >53% of its original CO(2) uptake capacity after 30 absorption/desorption cycles in comparison to the 89% decrease observed after 11 cycles when [P(66614)][Tetz] was not present. Characterization of the ILs post exposure revealed that small amounts of SO(2) were irreversibly absorbed to the [Benzim](−) anion responsible for the decrease in CO(2) capacity. While optimization of this dual-IL system is required, this feasibility study demonstrates that [P(66614)][Tetz] is a suitable sorbent for reversibly capturing SO(2) and significantly extending the lifetime of [P(66614)][Benzim] for CO(2) uptake

Biobutanol as Fuel for Direct Alcohol Fuel Cells-Investigation of Sn-Modified Pt Catalyst for Butanol Electro-oxidation

Direct alcohol fuel cells (DAFCs) mostly use low molecular weight alcohols such as methanol and ethanol as fuels. However, short-chain alcohol molecules have a relative high membrane crossover rate in DAFCs and a low energy density. Long chain alcohols such as butanol have a higher energy density, as well as a lower membrane crossover rate compared to methanol and ethanol. Although a significant number of studies have been dedicated to low molecular weight alcohols in DAFCs, very few studies are available for longer chain alcohols such as butanol. A significant development in the production of biobutanol and its proposed application as an alternative fuel to gasoline in the past decade makes butanol an interesting candidate fuel for fuel cells. Different butanol isomers were compared in this study on various Pt and PtSn bimetallic catalysts for their electro-oxidation activities in acidic media. Clear distinctive behaviors were observed for each of the different butanol isomers using cyclic voltammetry (CV), indicating a difference in activity and the mechanism of oxidation. The voltammograms of both n-butanol and iso-butanol showed similar characteristic features, indicating a similar reaction mechanism, whereas 2-butanol showed completely different features; for example, it did not show any indication of poisoning. Ter-butanol was found to be inactive for oxidation on Pt. In situ FTIR and CV analysis showed that OHads was essential for the oxidation of primary butanol isomers which only forms at high potentials on Pt. In order to enhance the water oxidation and produce OHads at lower potentials, Pt was modified by the oxophilic metal Sn and the bimetallic PtSn was studied for the oxidation of butanol isomers. A significant enhancement in the oxidation of the 1° butanol isomers was observed on addition of Sn to the Pt, resulting in an oxidation peak at a potential ?520 mV lower than that found on pure Pt. The higher activity of PtSn was attributed to the bifunctional mechanism on PtSn catalyst. The positive influence of Sn was also confirmed in the PtSn nanoparticle catalyst prepared by the modification of commercial Pt/C nanoparticle and a higher activity was observed for PtSn (3:1) composition. The temperature-dependent data showed that the activation energy for butanol oxidation reaction over PtSn/C is lower than that over Pt/C

The addition of CO2 to four superbase ionic liquids: a DFT study

The addition of carbon dioxide to four superbase ionic liquids, [P3333][Benzim], [P3333][124Triz], [P3333][123Triz] and [P3333][Bentriz] was studied using a molecular DFT approach involving anions alone and individual ion pairs. Intermolecular bonding within the individual ion pairs is characterised by a number of weak hydrogen bonds, with the superbase anion geometrically arranged so as to maximize interactions between the heterocyclic N atoms and the cation. The pairing energies show no correlation to the observed CO2 adsorption capacity. Addition of CO2 to the anion alone clearly resulted in the formation of a covalently-bound carbamate function with the strength of binding correlated to experimental capacity. In the ion pair however the cation significantly alters the nature of the bonding such that the overall cohesive energy is reduced. Formation of a strong carbamate function occurs at the expense of weakening the interaction between anion and cation. In the more weakly absorbing ion pairs which contain [123Triz](-) and [Bentriz](-), the carbamate-functionalised systems are very close in energy to adducts in which CO2 is more weakly bound, suggesting an equilibrium between the chemi- and physisorbed CO2

Low-field 2D NMR relaxation and DRIFTS studies of glucose isomerization in zeolite Y: New insights into adsorption effects on catalytic performance

Sn and Ga doped zeolite Y catalysts were tested for the isomerization of glucose to fructose carried out in different solvents (water, methanol and ethanol). Therein, ethanol favoured a Lewis acid site catalyzed pathway that promotes glucose isomerization to fructose, whereas methanol resulted in an equal distribution of products (mannose, fructose and alkyl fructoside). In contrast, the catalysts were totally inactive in water solvent. NMR relaxation measurements, including solvent displacement experiments, suggested that the lack of catalytic activity in water is due to the strong adsorption of this solvent within the zeolite pores blocking reactants from the Lewis acid sites active for the sugar isomerization. In comparison, ethanol adsorbs relatively more strongly than methanol, hence is retained in the pores where solvated fructose is preferentially prevented from the further reaction on Bronsted acid sites situated outside of the pore space. NMR relaxation measurements using pyridine and tetrahydrofuran (THF) and pyridine-DRIFTS measurements suggest metal doping had little effect on the overall relative acid strength of the zeolites but resulted in zeolites with increased Lewis acid strength relative to the non-doped zeolites. The results reported provide direct experimental evidence on the importance of adsorption properties of solvents within zeolites used for glucose to fructose isomerization and may serve as a starting point for a new approach towards designing and optimizing such catalytic systems. & COPY; 2023 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

Probing the dynamics and structure of confined benzene in MCM-41 based catalysts

A combination of Molecular Dynamics (MD) simulations and Quasielastic Neutron Scattering (QENS) experiments has been used to investigate the dynamics and structure of benzene in MCM-41 based catalysts. QENS experiments of benzene as both an unconfined liquid and confined in the catalyst Pt/MCM-41 find that the mobility of benzene decreases upon confinement as shown by the decreased diffusion coefficients. Complementary MD simulations on benzene in MCM-41 show agreement with the QENS experiments when using a novel fully flexible model of MCM-41. Structural information from the MD simulations show that benzene in MCM-41 has a significantly different structure from that of the bulk liquid; with benzene molecules closer together and no prefered orientation

A kinetic analysis methodology to elucidate the roles of metal, support and solvent for the hydrogenation of 4-phenyl-2-butanone over Pt/TiO<inf>2</inf>

The rate and, more importantly, selectivity (ketone vs aromatic ring) of the hydrogenation of 4-phenyl-2-butanone over a Pt/TiO₂ catalyst have been shown to vary with solvent. In this study, a fundamental kinetic model for this multi-phase reaction has been developed incorporating statistical analysis methods to strengthen the foundations of mechanistically sound kinetic models. A 2-site model was determined to be most appropriate, describing aromatic hydrogenation (postulated to be over a platinum site) and ketone hydrogenation (postulated to be at the platinum–titania interface). Solvent choice has little impact on the ketone hydrogenation rate constant but strongly impacts aromatic hydrogenation due to solvent-catalyst interaction. Reaction selectivity is also correlated to a fitted product adsorption constant parameter. The kinetic analysis method shown has demonstrated the role of solvents in influencing reactant adsorption and reaction selectivity.We acknowledge EPSRC for funding as part of the CASTech grant (EP/G011397/1) and the Department of Employment and Learning for a studentship (IM). NSB was funded by a PhD scholarship from the University of Birmingham. SKW was supported by an Engineering Doctorate Studentship in Formulation Engineering at the University of Birmingham sponsored by the EPSRC (EP/G036713/1) and Johnson Matthey.This is the final version of the article. It was first available from Elsevier via http://dx.doi.org/10.1016/j.jcat.2015.06.00

Influence of Fluorination on the Solubilities of Carbon Dioxide, Ethane, and Nitrogen in 1‑n‑Fluoro-alkyl-3-methylimidazolium Bis(n‑fluoroalkylsulfonyl)amide Ionic Liquids

International audienceThe effect on gas solubilities of adding partially fluorinated alkyl side chains either on imidazolium-based cations or on bis(perfluoroalkylsulfonyl)amide anions was studied. The aim was to gain knowledge of the mechanisms of dissolution of gases in fluorinated ionic liquids and, if possible, to improve physical absorption of carbon dioxide in ionic liquids. We have determined experimentally, in the temperature range of 298–343 K and at pressures close to atmospheric pressure, the solubility and thermodynamics of solvation of carbon dioxide, ethane, and nitrogen in the ionic liquids 1-octyl-3-methylimidazolium bis[trifluoromethylsulfonyl]amide ([C8mim][NTf2]), 1-octyl-3-methylimidazolium bis[pentafluoroethylsulfonyl]amide ([C8mim][BETI]), 1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-3-methylimidazolium bis[trifluoromethylsulfonyl]amide ([C8H4F13mim][NTf2]), and 1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-3-methylimidazolium bis[pentafluoroethylsulfonyl]amide ([C8H4F13mim][BETI]). Ionic liquids with partial fluorination on the cation were found to exhibit higher carbon dioxide and nitrogen mole fraction solubilities but lower ethane solubilities, compared to those of their hydrogenated counterparts. Molecular simulation provided insights about the mechanisms of solvation of the different gases in the ionic liquids

Assessing the surface modifications following the mechanochemical preparation of a Ag/Al2O3 selective catalytic reduction catalyst

The surface modification of a mechanochemically prepared Ag/Al2O3 catalyst compared with catalysts prepared by standard wet impregnated methods has been probed using two-dimensional T1–T2 NMR correlations, H2O temperature programmed desorption (TPD) and DRIFTS. The catalysts were examined for the selective catalytic reduction of NOx using n-octane in the presence and absence of H2. Higher activities were observed for the ball milled catalysts irrespective of whether H2 was added. This higher activity is thought to be related to the increased affinity of the catalyst surface towards the hydrocarbon relative to water, following mechanochemical preparation, resulting in higher concentrations of the hydrocarbon and lower concentrations of water at the surface. DRIFTS experiments demonstrated that surface isocyanate was formed significantly quicker and had a higher surface concentration in the case of the ball milled catalyst which has been correlated with the stronger interaction of the n-octane with the surface. This increased interaction may also be the cause of the reduced activation barrier measured for this catalyst compared with the wet impregnated system. The decreased interaction of water with the surface on ball milling is thought to reduce the effect of site blocking whilst still providing a sufficiently high surface concentration of water to enable effective hydrolysis of the isocyanate to form ammonia and, thereafter, N2

Effect of solvent on the hydrogenation of 4-phenyl-2-butanone over Pt based catalysts

In part I of this study, experimental data were presented for the hydrogenation of 4-phenyl-2-butanone with a 4% Pt/TiO2 catalyst where the reaction rate and selectivity (ketone vs. aromatic ring) varied with solvent. In this paper, a rigorous kinetic model is presented utilising these data, incorporating statistical analysis methods to strengthen the foundations of mechanistically sound kinetic models. A fundamental kinetic model for the system is presented and a 2-site model was determined to be most appropriate, describing aromatic hydrogenation (postulated to be over a platinum site) and ketone hydrogenation (at the platinum titania interface). Solvent choice has little impact on the ketone hydrogenation rate constant but strongly impacts aromatic hydrogenation due to solvent-catalyst interaction. Reaction selectivity is also correlated to a fitted product adsorption constant parameter. This kinetic analysis method is the first of its kind demonstrating the role of solvents in influencing reactant adsorption and reaction selectivity.We acknowledge EPSRC for funding as part of the CASTech grant (EP/G011397/1) and the Department of Employment and Learning for a studentship (IM). NSB was funded by a PhD scholarship from the University of Birmingham. SKW was supported by an Engineering Doctorate Studentship in Formulation Engineering at the University of Birmingham sponsored by the EPSRC (EP/G036713/1) and Johnson Matthey.This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.jcat.2015.06.00