Liquid Catalyst Research Articles

Task-Specific Ionic Liquids Catalysts Efficiently Catalyze Atmospheric CO2 Gas Mixture to Cyclic Carbonates Under Mild Conditions

Task-Specific Ionic Liquids Catalysts Efficiently Catalyze Atmospheric CO2 Gas Mixture to Cyclic Carbonates Under Mild Conditions

Nickel ion-containing DABCO based ionic liquid: An efficient catalyst for the convenient chemoselective reduction of nitroarenes, N-acetylation of arylamines, and one-pot reductive acetylation of nitroarenes

The present paper describes convenient, green, and efficient approaches for the chemoselective reduction of nitroarenes, N-acetylation of arylamines, and one-pot reductive acetylation of nitroarenes in the presence of a new nickel ion-containing DABCO based ionic liquid, formulated as [C4(DABCO)2].NiCl4. The prepared catalyst was examined using FT-IR, FESEM, XRD, EDS, ICP-OES, TGA, DRS and TEM analyses. The reported protocols are accompanied with several advantages including the introduction of a novel nontoxic ionic liquid catalyst, green reaction conditions, chemoselectivity, short reaction times and high yields of the products. Significantly, the used Lewis acidic catalyst could be successfully recycled for at least six times without the considerable lose in its catalytic efficiency.

Thermo- and Photocatalytic Activation of CO2 in Ionic Liquids Nano-domains.

Ionic liquids (ILs) are considered to be potential material devices for CO2 capturing and conversion to energy-adducts. They form a cage (confined-space) around the catalyst providing an ionic nano-container environment which serves as physical-chemical barrier that selectively controls the diffusion of reactants, intermediates, and products to the catalytic active sites via their hydrophobicity and contact ion pairs. Hence, the electronic properties of the catalysts in ILs can be tuned by the proper choice of the IL-cations and anions that strongly influence the residence time/diffusion of the reactants, intermediates, and products in the nano-environment. On the other hand, ILs provide driving force towards photocatalytic redox process to increase the CO2 photoreduction. By combining ILs with the semiconductor, unique solid semiconductor-liquid commodities are generated that can lower the CO2 activation energy barrier by modulating the electronic properties of the semiconductor surface. This mini-review provides a brief overview of the recent advances in IL assisted thermal conversion of CO2 to hydrocarbons, formic acid, methanol, dimethyl carbonate, and cyclic carbonates as well as its photo-conversion to solar fuels.

An Efficient and Super Stable Immobilized Ionic Liquid Catalyst Application in the Catalytic Synthesis of Carbonates

An Efficient and Super Stable Immobilized Ionic Liquid Catalyst Application in the Catalytic Synthesis of Carbonates

One-pot synthesis of cyclic carbonates from olefins and CO2 catalyzed by silica-supported imidazolium hydrogen carbonate ionic liquids

The direct synthesis of cyclic carbonates by catalytic oxidative carboxylation of olefins with CO2 has become an essential topic, but the development of highly active metal- and halogen-free heterogeneous single catalysts is still a huge challenge. Herein, a series of [Im][HCO3]@SBA-15 supported ionic liquids (SILs) catalysts are prepared by using anion exchange and solvent-free mehcanochemical grafting strategies for the direct synthesis of cyclic carbonates from olefins and CO2. As-prepared [Im][HCO3]@SBA-15 catalysts exhibit excellent catalytic activity and selectivity for the one-pot synthesis of cyclic carbonates from various olefins and CO2 under metal- and halogen-free conditions, providing moderate to excellent yields of cyclic carbonates. Furthermore, the catalysts can be easily regenerated at least five times without significant loss of catalytic activity, exhibiting excellent reusability and stability. This work presents an efficient and green method for the design and preparation of SILs catalysts for CO2 conversion.

About Some Fundamental Aspects of the Growth Mechanism Vapor-Liquid-Solid Nanowires

This study provides the formation of semiconductor nanowires (NWs) with a singular facet and a curved end surface by the vapor-liquid-solid (VLS) process that is analyzed and explained in details. Given the evidence, it is confirmed that the wettability of a liquid catalyst droplet on a crystal surface and the contact angle between the droplet and crystal play an essential role in the VLS process of NWs development. It is shown that for the VLS mechanism, the formation of NWs depends on the reduction in activation barrier to crystallization caused by the release of surplus-free energy by a spheroidizing drop in the region of the triple junction during the process of lowering surface area. This decreases the necessary supersaturation for the development of NW vertex facets at a fixed growth rate. The source of the extra free energy that drives the catalyst droplet movement during the steady-state development of NWs is the droplet’s outer surface. During the formation of NWs, those angles of inclination of the lateral surface NWs and droplet contact are obtained at which the solid/vapor, solid/liquid, and liquid/vapor interfaces experience the smallest increase in free energy. The wetting hysteresis is demonstrated to occur at the vertex of NWs, and the contact angle of a catalyst droplet may be regarded as an independent and fully-fledged thermodynamic parameter of the system’s state.

Ionic liquid supported on mesoporous Pd/SBA-15 during the manufacture of 1,3-butadiene using ethanol at lower temperature reaction

Investigating the heterogeneous organo-catalysts such as 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate upon SBA-15, which includes one percent palladium, and their ability to produce 1,3-butadiene from ethanol while supporting them on mesoporous materials. SBA-15 and metal precursors were mixed together and crushed in solid state. By using the TGA, N2 adsorption–desorption, TEM, and XRD procedures, the produced catalysts were studied. Once an organic motif was added to SBA-15, the solid-state grinding procedure produced more accessible acid sites on the catalyst and increased the dispersion of Pd metal. In a fixed-bed reactor, the catalytic performance was assessed, and a selectivity of up to 82% for 1,3-butadiene was achieved. This is brought on by the coupling activity of Pd and ionic liquid species in the porous structure of SBA-15, where the ionic liquid catalyst promotes ethanol dehydrogenation while Pd promotes aldol condensation The solvent-free method also served as the inspiration for a fresh way of synthesizing catalysts for the formation of 1,3-butadiene using ethanol.

Development and catalytic mechanism of ionic liquid catalysts for polyoxymethylene dimethyl ethers

In this paper, Gaussian calculation and acid strength determination were used to analyze the acid strength of ionic liquid catalysts, and to design ionic liquids with different anions and cations. The synthesis experiment of polyoxymethylene dimethyl ether (PODEn) using paraformaldehyde and methanol as raw materials was used as the catalyst evaluation experiment. Among them, the ionic liquid catalyst [PY-PS][PA] had the best catalytic performance, the conversion rate of methanol was 96%, and the selectivity of PODE3-5 was 49%. The chemical reactivity of the ionic liquid [PY-PS][PA] was analyzed using DFT theory, and the reaction mechanism and rate constant of the process were calculated at the molecular level. Paraformaldehyde is decomposed into formaldehyde and water by chain scission under the action of a catalyst; Formaldehyde and methanol are catalyzed to form hemiacetal (CH3OCH2OH); The hemiacetal is chain-extended by formaldehyde and then dehydrated with methanol to form PODEn with different degrees of polymerization. On the basis of the transition state, the kinetic parameters of the PODE3 synthesis process were calculated.

Supported Ionic Liquid Catalysts for the Oxidation of S- and N-Containing Compounds—The Effect of Bronsted Sites and Heteropolyacid Concentration

In this article, a series of effective catalysts based on betaine and sulfuric or phosphomolybdic acids was obtained. These compositions were characterized by various physicochemical methods and tested in the oxidation of sulfur- and nitrogenous-containing compounds by H2O2. An increase in the amount of heteropolyacid (HPA) leads to a non-linear change in acidity, and the degree of removal of sulfur-containing compounds correlates with the concentration of Bronsted acid sites on the surface. On the contrary, the degree of pyridine removal is determined primarily by the content of heteropolyacids in the catalyst.

Process optimization and technoeconomic assessment of biodiesel production by one-pot transesterification of Ricinus communis seed oil

In the present study, Ricinus communis seed oil with high free fatty acid content was utilized for the one-pot biodiesel production using 1-(2,3-dihydroxy)-propyl-3-methylimidazolium hydroxide, a basic ionic liquid catalyst. The 97.83% biodiesel yield was obtained at the optimized conditions of 6.26 % (w/w) of catalyst concentration, 10.51:1 M ratio of methanol to oil, 57.87 °C temperature and reaction time of 61.01 min. The transesterification of Ricinus communis seed oil to biodiesel exhibited an activation energy of 37.60 kJ/mol. The technoeconomic analysis, the profitability and the sensitivity analysis were investigated for the simulated process design. The technoeconomic analysis reported a total revenue of 20,455,431 $/yr, with gross margins, ROI, payback period, IRR, and NPV of 23.54%, 35.72%, 2.8 years, 28.20%, and 19,287,000 $, respectively. According to the sensitivity analysis, the two most important factors determining the economic viability of the simulated process are Ricinus communis seed oil cost and biodiesel selling price.

Dynamic Activation of Ga Sites by Pt Dopant in Low-Temperature Liquid-Metal Catalysts.

Liquid GaPt catalysts with Pt concentrations as low as 1×10-4 atomic % have recently been identified as highly active for the oxidation of methanol and pyrogallol under mild reaction conditions. However, almost nothing is known about how liquid state catalysts support these significant improvements in activity. Here, ab initio molecular dynamics simulations are employed to examine GaPt catalysts in isolation and interacting with adsorbates. We find that persistent geometric features can exist in the liquid state, given the correct environment. We postulate that the Pt dopant may not be limited to direct involvement in catalysis of reactions, but rather that its presence can also enable Ga atoms to become catalytically active.

Dynamic Activation of Ga Sites by Pt Dopant in Low‐Temperature Liquid‐Metal Catalysts

AbstractLiquid GaPt catalysts with Pt concentrations as low as 1×10−4 atomic % have recently been identified as highly active for the oxidation of methanol and pyrogallol under mild reaction conditions. However, almost nothing is known about how liquid state catalysts support these significant improvements in activity. Here, ab initio molecular dynamics simulations are employed to examine GaPt catalysts in isolation and interacting with adsorbates. We find that persistent geometric features can exist in the liquid state, given the correct environment. We postulate that the Pt dopant may not be limited to direct involvement in catalysis of reactions, but rather that its presence can also enable Ga atoms to become catalytically active.

Ch][TAPSO] As an Efficient Ionic Liquid Catalyst for One‐Pot Synthesis ofTetrahydro‐4H‐chromenes and 3,4‐Dihydropyrano[c]chromenes

AbstractCholinium N‐Tris(hydroxymethyl)methyl‐3‐amino‐2‐hydroxypropanesulfonate [Ch][TAPSO] has been found as an efficient ionic liquid catalyst for the synthesis of tetrahydro‐4H‐chromenes and 3,4‐dihydropyrano[c]chromenes in water and EtOH : Water (3 : 2) respectively. [Ch][TAPSO] being a basic IL has also been observed to extract acidic compounds such as rhodamine B from IL‐ immiscible organic solvent such as acetone through acid‐base interaction. The extraction process of fluorescent dye rhodamine B was determined by ultraviolet‐visible (UV‐Vis) spectroscopy. The observed percentage extraction rate is 100 % upto 6 mM solution of rhodamine in acetone. This method results in faster reaction with operational simplicity and excellent yields of the products. Furthermore, the catalyst has a great capacity for reutilisation.

Self-separation ionic liquid catalyst for the highly effective conversion of H2S by α,β-unsaturated carboxylate esters under mild conditions

The deep-processing utility of pure hydrogen sulfide (H2S) is a significant direction in natural gas chemical industry. Herein, a brand-new strategy of H2S conversion by α,β-unsaturated carboxylate esters into thiols or thioethers using task-specific carboxylate ionic liquids (ILs) as catalyst has been developed, firstly accomplishing the phase separation of product and catalyst without introducing the third component. It can be considered as a cascade reaction in which the product selectivity can be controlled by adjusting the molar ratio of H2S to α,β-unsaturated carboxylate esters. Also, the effects of ILs with different anions and cations, intermittent feeding operations, as well as pressure−time kinetic behaviors on cascade reaction were investigated. Furthermore, the proposed interaction mechanism of H2S conversion using butyl acrylate catalyzed by [Emim][Ac] was revealed by DFT-based theoretical calculation. The approach enables the self−phase separation promotion of catalyst and product and achieves 99% quantitative conversion under mild conditions in the absence of solvent, making the entire process ecologically benign. High-efficiency reaction activity can still be maintained after ten cycles of the catalyst. Therefore, the good results, combined with its simplicity of operation and the high recyclability of the catalyst, make this green method environmentally friendly and cost−effective. It is anticipated that this self-separation method mediated by task-specific ILs will provide a feasible strategy for H2S utilization, which will guide its application on an industrial scale.

Self-catalyzed GaP nanowire MOVPE growth on Si

Typically, vapour liquid solid (VLS)-grown nanowires via metal–organic vapour phase epitaxy (MOVPE) use gold as a liquid growth catalyst. However, incorporating gold as an impurity during growth is disadvantageous. Therefore, we introduce the self-catalyzed VLS growth of GaP nanowires on Si (111) substrates via MOVPE, utilizing (deposited) Ga droplets as seed particles. To understand and optimize the growth process, the influence of various growth parameters such as Ga precursor preflow, growth temperature, growth time and V/III ratio are studied. As main findings we show that nanowire growth without strong tapering is possible. By varying the V/III gas phase ratio the tapering of nanowires can be manipulated during growth via droplet consumption. In addition, nanowires with lengths up to 10 µm and an aspect ratio of around 20 are demonstrated, showing only slight tapering. High-resolution scanning transmission electron microscopy measurements prove the zincblende crystal structure of the GaP nanowires in horizontal and vertical ultramicrotomy cuts. In vertical cross sections, a high number of microtwin boundaries perpendicular to the growth direction are found.

HDBU]Br@P-DD as Porous Organic Polymer-Supported Ionic Liquid Catalysts for Chemical Fixation of CO2 into Cyclic Carbonates

The chemical fixation of CO2 into high value-added cyclic carbonates is of significant potential and sustainability to address the energy and ecological issues. [HDBU]Br@P-DD-m/n, a series of porous organic polymer-supported ionic liquids (PSILs), were fabricated in this work through a one-pot four-component reaction of DMAEMA, DVB, 4-bromobutyric acid, and DBU. The formation of [HDBU]Br and construction of the P-DD polymer network proceeded concurrently with the support of the in situ-formed IL being achieved simultaneously. Characterization of the PSILs by IR, ICP, BET, SEM, and TGA etc. showed that the as-prepared catalysts possessed versatile hierarchical porosity with varying ionic densities and excellent thermostability. The porosity of the copolymer skeleton was found to be affected by the accompanying formation of [HDBU]Br. The PSILs were then evaluated as catalysts for the cycloaddition reaction of CO2 with epoxides, among which [HDBU]Br@P-DD-4/1 showed the optimal performance under atmospheric pressure and solvent-/cocatalyst-free conditions (95% yield and 99% selectivity for CO2 cycloaddition with epichlorohydrin). By correlating the performance and structures of the catalysts, the synergistic effect of the tertiary amine, [HDBU]Br, and pore distribution was demonstrated. In addition, the catalyst was found to be applicable in synthesizing a range of differently substituted carbonates in good to excellent yields. Finally, the catalyst could be recovered readily and good catalytic activity was still observed after use for 6 runs. The work not only provided an active, reusable, and metal-free heterogeneous catalyst for the fixation of CO2 into cyclic carbonates but also developed a facile one-step multicomponent strategy for constructing PSIL catalysts, which would be promising to find wide applications in catalysis and organic synthesis field.

Catalytic methane pyrolysis for simultaneous production of hydrogen and graphitic carbon using a ceramic sparger in a molten NiSn alloy

Catalytic methane pyrolysis (CMP) for simultaneous hydrogen and carbon production has been achieved in molten NiSn liquid alloys, with the additional benefit of spontaneous separation of solid carbon from the liquid catalyst. Here, the use of ceramic spargers for the injection of CH4 bubbles into the molten liquid has shown to be advantageous not only in enhancing the CH4 conversion above 90%, but also in producing graphitic carbon. When a quartz tube was used to feed CH4 bubbles into the molten alloy, the conversation was limited to about 15–25% and the quality of the graphitic carbon product was more defective and disordered. Regardless of the use of the spargers, carbon precipitates preferentially accumulate at the top of the molten alloy, and steady-state conversion over 24 h with high selectivity towards H2 was achieved under a constant flow rate of pure CH4 without any pressure increase. The synergistic effect of the ceramic sparger on molten NiSn may be the result of a controlled bubble size of CH4 and a catalytic role of zirconia surfaces in contact with the molten alloy. Our results imply that there is a great opportunity to improve CMP in molten alloy catalysts further toward a scalable production of H2 and graphitic carbon with a nearly complete conversion of CH4.

Efficient esterification over hierarchical Zr-Beta zeolite synthesized via liquid-state ion-exchange strategy

The eco-friendly zeolite-based solid acid catalysts constitute an important alternative to the liquid acid catalyst for the production of plasticizer tributyl citrate (TBC), due to their non-corrosive, high hydrothermal stability and easiness to recycle. Herein, a simple acid treatment to the H-Beta zeolite and subsequent incorporation of ZrIV ions into the vacated Al sites were conducted by liquid-state ion-exchange of ZrO(NO3)2 aqueous solution. The ZrIV ions were incorporated into the framework by the expand of the unit cell size, verified by XRD patterns, the emerging new band at ∼198 nm on UV–vis spectra, the enhanced binding energies of the Zr 3d5/2 and Zr 3d3/2 on XPS spectra, as well as the variations of isolated terminal silanol groups (Si-OH) by FTIR and the change of integrated intensity ratio of Q3/Q4 by 29Si MAS NMR. It was illustrated that the Lewis acid sites was the main active sites for esterification reaction and the produced abundant mesopores in the Zr-Beta-x catalysts would facilitate the transportation of TBC. The maximum conversion of citric acid as high as 80 % was obtained on Zr-Beta-128 (SiO2/ZrO2 molar ratio = 128) catalyst with the highest Lewis acid amount. Furthermore, the Zr-Beta-128 zeolite exhibited high stability without any detectable deactivation after 6 cycles with the 100 % selectivity to TBC. The efficient Zr-Beta catalyst could supply a novel possibility for the development of an environmentally-friendly solid acid catalyst with good performance for the TBC production.

Preparation of di-[EMIM]CoCl3 Ionic Liquid Catalyst and Coupling with Oxone for Desulfurization at Room Temperature

The intermediate di-[EMIM]Cl was synthesized from methyl imidazole and 1,4-dichlorobutane and then reacted with cobalt chloride at 105 °C to prepare a bi-[EMIM]CoCl3 ionic liquid catalyst. The di-[EMIM]CoCl3 catalyst coupled with oxone to remove sulfur-containing organics in octane. The di-[EMIM]CoCl3 catalyst was characterized by HNMR, FTIR, TG, and SEM–EDS. The dibenzothiophene (DBT) was dissolved in octane to prepare a model oil with an initial sulfur content of 500 ppm. Six grams of the model oil was added. The results showed that the optimal dosages of di-[EMIM]CoCl3, oxone (20 wt%), and [BMIM]BF4 extractant were 1 g, 2 g, and 2 g, respectively. At the optimum temperature of 45 °C, 100% of sulfur was removed after 40 min. After di-[EMIM]CoCl3 was recycled five times, the sulfur removal percentage remained above 91%. The sulfur removal percentages for different sulfur-containing organics followed the order of dibenzothiophene (DBT) > benzothiophene (BT) > 4,6-dimethyldibenzothiophene (4,6-DMDBT). The oxidation product was determined to be DBTO2 by GC–MS analysis, and the oxidation mechanism was discussed. The active oxygen atoms of oxone oxidized DBT to form DBTO, and then persulfate oxidized DBTO to DBTO2 via an identical oxidation mechanism.

Methane pyrolysis and carbon formation mechanisms in molten manganese chloride mixtures

Molten manganese chloride (MnCl2) is attractive as a high-temperature liquid catalyst for methane pyrolysis (CH4 → C + 2H2). Nevertheless, the mechanism of this reaction for continuously producing high-purity hydrogen and graphitic carbon from CH4 has not been fully elucidated. In this work, we investigated the reaction kinetics and mechanism of CH4 pyrolysis in mixtures of molten MnCl2 with various monovalent or divalent chlorides. The apparent activation energies of the molten MnCl2 mixtures for CH4 pyrolysis (<230 kJ mol−1) were much lower than that of the uncatalyzed reaction (400 kJ mol−1). Among the MnCl2 mixtures, only MnCl2–KCl showed a lower apparent activation energy than pure MnCl2 (152 and 172 kJ mol−1, respectively). In addition, MnCl2–KCl produced the largest amount of CH2* and the final solid carbon product with the highest crystallinity, suggesting that this system has unique CH4 dehydrogenation and carbon formation pathways. Density functional theory calculations also predicted high concentrations of CH2* in MnCl2–KCl, as confirmed by CH2 formation being more thermodynamically favorable in MnCl2–KCl than in MnCl2. Furthermore, the generation of C2+ unsaturated intermediates from CHx* (x < 3) was thermodynamically favored, suggesting a more facile pathway for the formation of graphitic carbon layers in molten MnCl2–KCl. In addition, an NVT ab initio molecular dynamics simulation suggested that gas-phase C–C coupling was facilitated in MnCl2–KCl by the frequent reversible desorption and adsorption of CHx* intermediates. These fundamental insights into the origins of the enhanced CH4 pyrolysis performance in MnCl2–KCl could aid in the development of molten salt catalysts with enhanced reactivity.