Activated Carbon Support Research Articles

Deactivation mechanism of catalyst in long-period experiment of 1,1,2-TCE dehydrochlorination

ABSTRACT VDC, as an important raw material for high barrier material PVDC and lithium-ion battery binder PVDF, had an increasing demand. The catalytic dehydrochlorination of 1,1,2-TCE to generate VDC was a green process route that was expected to replace the heavily polluting sodium hydroxide saponification process in industry. There was a certain research foundation for the catalytic dehydrochlorination of 1,1,2-TCE, among which the core problem was that the catalyst was prone to deactivation. Previous studies had calculated the average molecular structure of the spent catalyst surface species when coconut shell activated carbon was used as the support. In subsequent studies, alumina support had been proven to be a better carrier for dehydrochlorination of 1,1,2-TCE, and the selected catalyst had been used in long-period laboratory experiments. The results indicated that the catalyst life had been significantly improved. In the early stage of the reaction, the activity of the catalyst decreased rapidly. In the first 20 h, the conversion of 1,1,2-TCE decreased from 49.35% to 40.36%. From 21 h to 120 h, the conversion of 1,1,2-TCE decreased from 39.96% to 36.18%, tending to stabilize. After 120 h of reaction, the catalyst was extracted and elemental analysis, FTIR, and GPC characterization were performed on the spent catalyst surface species. The average molecular formula of the carbon deposits was obtained as C96.08H50.29Cl36.53. Compared with coconut shell activated carbon support, under the action of activated alumina support, the route of catalyst carbon deposition had changed, and the sediment was more composed of polyvinylidene chloride components. Under certain conditions, sediment formed a dynamic equilibrium, which explained why the activity of the catalyst gradually stabilized. This study revealed the catalytic mechanism of active alumina supported catalyst and the pathway of carbon deposits generation, which was of great significance for improving the lifespan of improved catalyst.

Carbon-Supported Fe-Based Catalyst for Thermal-Catalytic CO2 Hydrogenation into C2+ Alcohols: The Effect of Carbon Support Porosity on Catalytic Performance

Carbon materials supported Fe-based catalysts possess great potential for the thermal-catalytic hydrogenation of CO2 into valuable chemicals, such as alkenes and oxygenates, due to the excellent active sites’ accessibility, appropriate interaction between the active site and carbon support, as well as the excellent capacities in C-O bond activation and C-C bond coupling. Even though tremendous progress has been made to boost the CO2 hydrogenation performance of carbon-supported Fe-based catalysts, e.g., additives modification, the choice of different carbon materials (graphene or carbon nanotubes), electronic property tailoring, etc., the effect of carbon support porosity on the evolution of Fe-based active sites and the corresponding catalytic performance has been rarely investigated. Herein, a series of porous carbon samples with different porosities are obtained by the K2CO3 activation of petroleum pitch under different temperatures. Fe-based active sites and the alkali promoter Na are anchored on the porous carbon to study the effect of carbon support porosity on the physicochemical properties of Fe-based active sites and CO2 hydrogenation performance. Multiple characterizations clarify that the bigger meso/macro-pores in the carbon support are beneficial for the formation of the Fe5C2 crystal phase for C-C bond coupling, therefore boosting the synthesis of C2+ chemicals, especially C2+ alcohols (C2+OH), while the limited micro-pores are unfavorable for C2+ chemicals synthesis owing to the sluggish crystal phase evolution and reactants’ inaccessibility. We wish our work could enrich the horizon for the rational design of highly efficient carbon-supported Fe-based catalysts.

Synergistic effect of CaCO3 particles and porous carbon towards the removal of Zn2+ ions in aqueous solutions

This work describes the preparation of an adsorbent containing CaCO3 particles dispersed in activated carbon and its use for the removal of Zn2+ ions from aqueous solutions. The combination of the large porosity of the activated carbon support with the easy ion exchange occurring at the surface of the carbonate particles led to the achievement of fast adsorption kinetics and excellent ion removal capacity for the composite adsorbent. The material was synthesized by wet impregnation of the porous carbon support with an aqueous solution of Ca(NO3)2, followed by evaporation of the solvent with subsequent heat treatment in an inert atmosphere. X-ray diffraction results demonstrated the presence of CaCO3 crystals in the material, but with broad and low intensity diffraction peaks, corresponding to an average crystallite size of 20 nm; solid-state 13C NMR spectroscopy confirmed the presence of this phase by means of the identification of the signal relative to the 13C nuclei of the CO32− group at ∼170 ppm. The carbon-based adsorbent containing the CaCO3 particles showed excellent ability to remove Zn2+ ions from aqueous solutions, with essentially all ions removed after 30 min of contact time. In addition, the kinetic analysis data were properly fitted using the pseudo-second order model, pointing to the occurrence of chemisorption as the rate limiting of the process. The equilibrium adsorption isotherms were correctly described by the Langmuir model, indicating that the adsorption takes place with the formation of a monolayer on the adsorbent surface. The results evidenced a synergistic effect of the porous carbon and the CaCO3 particles regarding the Zn2+ ions removal, with a fast adsorption kinetics at the initial stage of adsorption attributed to the high availability of the dispersed CaCO3 particles on the carbon surface.

Ru and Ruδ+ synergistic catalysis efficiently promotes 2,2,6,6-Tetramethyl-4-Piperidone hydrogenation for 2,2,6,6-Tetramethyl-4-Piperidinol preparation

The catalytic hydrogenation of nitrogen-containing heterocyclic compounds is a crucial process; however, nitrogen removal severely restricts product selectivity. Consequently, this study utilized a simple heat treatment method to synthesize ruthenium (Ru)-based catalysts supported on N-doped activated carbon for application in the selective catalytic hydrogenation of 2,2,6,6-Tetramethyl-4-piperidone (TAA). The results show that the selectivity of 2,2,6,6-Tetramethyl-4-piperidinol (TMP) is as high as 99.87 % under the premise of almost complete TAA reaction. The catalyst was characterized using N2-physisorption-desorption, XRD, TEM, Raman, XPS, ICP-OES, and H2-TPR techniques. N-doped activated carbon introduced numerous defect sites to the catalyst, improved the surface wettability of the activated carbon support, provided abundant active metal anchoring sites, which results in highly uniform dispersion of Ru nanoparticles (NPs) on the carrier surface, forms relatively smaller nanoparticles, and enhances the catalyst's activity. Additionally, a strong interaction exists between the active metal Ru and N-doped activated carbon support. Thus, the transfer of free electrons from Ru to N species was facilitated, and the relative content of Ruδ+ in the catalyst was increased, and the synergistic effect between Ru and Ruδ+ contributes to improving the catalyst's performance. This work holds significant potential for controlling the selectivity of nitrogen-containing heterocyclic compounds in the catalytic hydrogenation process.

Adsorption and degradation of tetracycline hydrochloride in aqueous solutions using activated carbon with Fe/Ag nanoparticles

In this study, a new adsorbent denoted as nAg/nZVI/AC was developed using activated carbon (AC) loaded with nanosized zero-valent iron (nZVI) and nanosilver (nAg). Then, the adsorption and degradation of tetracycline hydrochloride (TCH) in aqueous solutions using nAg/nZVI/AC was examined. At pH 3.8, the adsorbed amount of TCH on nAg/nZVI/AC was 191.18 mg/g, which is 78.95 mg/g higher than that adsorbed on the pristine AC support. The adsorption process could be explained adequately using the Freundlich (R2 = 0.9641) and pseudo-second-order kinetic models (R2 = 0.9967). Thermodynamic analyses revealed that TCH removal is a spontaneous chemisorption-dominated process. Free-radical-quenching experiments and electron paramagnetic resonance spectroscopic studies revealed that hydroxyl (·OH) and superoxide (·O2−) radicals are the main species involved in the degradation of TCH. Finally, the intermediates generated during the degradation were examined using liquid chromatography-mass spectrometry, and possible deterioration pathways are proposed.

Effect of I- ligand and surface oxygen-containing groups on catalytic activity and stability of activated carbon-supported Pd catalysts in acetylene dicarbonylation

The support and ligand play a crucial role in regulating the catalytic performance, selectivity, and stability of heterogeneous catalysis. Herein, activated carbon (AC) supported palladium (Pd) catalysts (2.0 wt%) were prepared by impregnation for acetylene dicarbonylation. The oxygen-containing groups on the surface of the AC support were modulated by nitric acid (HNO3) to investigate metal–support interactions on the catalytic performance and stability of the Pd/AC. The characterization of the chemical composition and structure of the supports and catalysts demonstrates that high concentrations of oxygen-containing groups on the surface of the carbon support lead to the fine dispersion of Pd nanoparticles. Notably, the finely dispersed Pd/AC70 catalyst exhibited good activity and stability for acetylene dicarbonylation under high-pressure CO conditions after several rounds of regeneration. Furthermore, operational parameters including the type of support, co-catalyst (KI), and reaction time and temperature were identified for their impact on the reaction. It was found that I- anions serve as a co-catalyst and can ligate with Pd species, thereby preventing the leaching of Pd and improving reaction selectivity. This study presents a straightforward and sustainable modulation strategy to improve the dispersion of active metals, as well as to prevent the leaching and sintering of these metals during high-pressure CO reactions.

Production of Biodiesel from Candlenut Seed Oil (Aleurites Moluccana Wild) Using a NaOH/CaO/Ca Catalyst with Microwave Heating

Oil fuels derived from fossils are non-renewable, so over time, they will run out and have a negative impact on air pollution. To overcome this, there is a need for environmentally friendly alternative fuels from renewable sources such as biodiesel. This research used microwave heating with a CaO catalyst. NaOH-impregnated snail shells and active carbon support. This research aims to determine the effect of power on the conversion of candlenut seed oil into biodiesel using the NaOH/CaO/CA catalyst both in terms of compliance with the SNI 7182-2015 standard and analysis using GC-MS (Gas Chromatography-Mass Spectrometry). The synthesis of the NaOH/CaO/CA catalyst was carried out through wet impregnation and calcination at a temperature of 500°C and analyzed using gas sorption analysis (GSA). Then proceed to the transesterification process, where the power for microwave heating was varied to 300, 450, and 600 watts with a mole ratio of esterified oil and methanol, namely 1:10 for 3 minutes. The analysis results of the NaOH/CaO/CA catalyst using the GSA instrument have a surface area of 9.306 m2/g, pore volume of 0.033 cc/g, and pore diameter of 14.043 nm. Meanwhile, the results of the biodiesel analysis showed that the optimum biodiesel yield was 85.625% at 600 watts of power and had a kinematic density and viscosity that met the SNI 7182-2015 biodiesel standards. Analysis of biodiesel characteristics using GC-MS showed that the three most optimum biodiesel components were hexadecanoic acid, methyl ester (22.664%), 9,12-Octadedecadienoic acid (Z,Z)-, methyl ester (30.176%) and 9-Octadecenoic acid (Z)-, methyl ester (38.656%).

Surface Redox Reaction for the Synthesis of NiPt Catalysts for the Upgrading of Renewable Ethanol/Methanol Mixtures

Mixtures of ethanol and methanol being synthesized from CO2 and green H2 can serve as sustainable base chemicals for a number of chemical processes. Amongst these processes, the catalytically supported synthesis of CO2-neutral C4 to C10 alcohols is of increasing importance as, e.g., iso-butanol can be used as a drop-in fuel or after dehydration to produce iso-butene as a feedstock for the synthesis of plastics. 2-ethyl-hexanol can be further refined into solvents, tensides, or monomers. In this respect, NiPt alloys on an activated carbon support were found to be active and stable catalysts for the synthesis of iso-butanol following the Guerbet reaction scheme. In this study, two different routes are applied to the synthesis of these NiPt catalysts: a more conventional one based on the impregnation of Ni and Pt salts and an advanced path with a surface redox reaction between elemental Ni on the support and Pt ions in a polar solution. The experimental evaluation shows that the Pt particles from the surface redox reaction being exposed on the Ni particles are more active than those on the impregnated catalysts due to their high surface energy. Their specific space-time yields are 10–20 times higher.

Engineered ionic liquids supported on activated carbon as a sustainable and selective catalyst for viable fixation of CO2 into valuable chemicals

The use of ionic liquids (ILs) based materials in catalysis, especially for CO2 conversion has been attracted great scientific attention due to green catalytic approach and eco-friendliness of the material. In this effort, especially engineered NH2-functionalized imidazolium based ILs with different anions were prepared to develop new covalent ILs functionalized activated carbon (AC) catalysts. All different AC-ILs namely AC-IL-Br, AC-IL-BF4, AC-IL-NTf2 and AC-IL-HSO4 was successfully synthesized by metathesis reaction, and characterized using various analytical and spectroscopic techniques. With the maximum immobilization of the NH2-functionalized ILs on the AC support, the immobilized AC-ILs showed superior structural advantages such as high thermal stability and appreciable surface area. The newly developed AC-ILs as bi-functional catalysts were applied in the fixation of CO2 into epoxide and it displayed high catalytic activity during the catalytic screening. Various reaction variables were surveyed wherein especially, 10.0 wt% of AC-IL-NTf2 catalyst demonstrated the best catalytic activity with 100 % conversion of styrene oxide and 83 % selectivity towards styrene carbonate at 120 °C, 20 bar CO2 pressure in 13 h under solvent-free conditions. The enhanced performance by AC-IL-NTf2 catalyst was achieved as a result of least co-ordination of the NTf2− anion with the NH2-functionalized imidazolium cation which helped in the opening and stabilization of epoxide ring and increased the reaction rate. The best performing AC-IL-NTf2 catalyst was found to be compatible with a broad substrate scope and could effectively produce the respective cyclic carbonates in good to quantitative yields with different substituted epoxides. Most significantly, AC-IL-NTf2 catalyst could be easily separated from the reaction mixture and recycled it for number of cycles. It maintained its catalytic activity without any evident leaching and structural damage up to six recycles. Additionally, plausible reaction mechanism also has been proposed with AC-IL-NTf2 catalyst with the help of catalytic activity results and characterization support.

Electrochemical Performances of PtCrCo Alloy/Nitrogen-Doped Activated Carbon for Proton Exchange Membrane Fuel Cell Catalyst

Proton Exchange Membrane Fuel Cell is a promising green energy conversion machine. However, some drawbacks, such as Pt corrosion on the cathode side, the high price of Pt, Nafion membrane, and the need for the high precision assembly process, limit their commercialization. In this study, PtCrCo alloy which is supported by nitrogen-doped activated carbon was synthesized by facile method to increase electrochemical performance as a cathode catalyst and reduce Pt catalyst usage. Nitrogen-doped Activated Carbon/PtCrCo/Nitrogen-doped Carbon (NAC/PtCrCo/N) catalyst was investigated to analyze the effect of increasing the composition of nitrogen-doped activated carbon in the synthesis process on the morphology and electrochemical performances of the catalyst. Polyaniline (PANI) as Nitrogen precursor was added to Activated Carbon (AC) powder with ratio of AC to PANI; 1:0, 3:1, 1:1, 1:3, as called AC, NAC1, NAC2, and NAC3 respectively. The catalyst synthesis process is carried out with the four activated carbon supports. Material characterizations were carried out using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Brunauer-Emmett-Teller (BET), Cyclic Voltametry (CV), and Linear Sweep Voltametry (LSV). The XRD measurement shows that the addition of nitrogen doping tends to reduce the diffraction peak intensity of nitrogen-doped activated carbon compared to the pristine carbon. The doping also increases the surface area of the activated carbon as measured by the BET method. Nitrogen doping increases the conductivity and the addition of alloys can add better stability and catalytic activity for cyclic voltammetry results of the four catalysts cannot be calculated. The NAC3/Pt-Cr-Co/N electrocatalyst exhibited the highest initial potential at ~1 mAcm-2 of 0.997 V compared to the other four samples. On the other hand, AC/Pt-Cr-Co/N catalyst has the highest current density value of 22.156 mAcm-2.

Activated carbon supported Ni, Fe, and bimetallic NiFe catalysts for COx-free H2 production by microwave methane pyrolysis

The goal of this study was to test the effect of metal-impregnated carbon-based catalysts on the conversion of methane to hydrogen gas and solid carbon using microwave reactor technology. Monometallic and bimetallic catalysts on activated carbon supports (Ni/AC, Fe/AC, NiFe/AC) are compared during methane pyrolysis testing. Catalytic methane pyrolysis was carried out in a microwave reactor at reaction temperatures of 600 °C and 800 °C. For comparison, one of the catalysts (NiFe/AC) was tested in a conventionally heated reactor at 800 °C. The prepared catalysts were characterized by X-ray diffraction (XRD), while post-reaction catalysts were characterized by XRD and SEM. During reaction testing, the monometallic Ni/AC catalyst exhibited the best catalytic activity (CH4 conversion: 46.0 and H2 yield: 46.9 %) when reacted in the microwave reactor, however, it suffered from rapid deactivation from carbon deposition (carbon yield: 0.39 g C/g catalyst). The bimetallic NiFe/AC catalyst was slightly less active (CH4 conversion: 36.9 and H2 yield: 40.5 %) but it was more resistant to carbon formation (carbon yield: 0.27 g C/g catalyst) suggesting it may have greater long-term stability. The NiFe/AC catalyst was also the most energy efficient as it required the least microwave power to maintain the 800 °C reaction temperature compared to the other catalysts tested. Methane conversion of the bimetallic NiFe/AC at 800 °C under microwave irradiation was three times the conversion under conventional heating at the same reaction temperature. This work demonstrates the use of microwave-specific catalysts for catalytic methane pyrolysis in a microwave reactor, and can be used as a foundation for further methane pyrolysis process and catalyst optimization for COx-free H2 production.

Enhancing electron interaction between Pt and support for superior electrochemical performance through atomic layer deposition of tungsten oxide

The stabilization of platinum (Pt) catalysts through strong metal-support interactions is crucial for their successful implementation in fuel cell applications. Tungsten oxide (WO3) has demonstrated excellent CO tolerance and has been recognized as a promising substrate for anchoring and stabilizing Pt nanoparticles (NPs). However, the limited specific surface area of conventional tungsten oxide restricts its effectiveness in dispersing noble metal NPs. In this study, we present a pioneering approach by employing atomic layer deposition (ALD) to create a WO3 interlayer between Pt NPs and a carbon substrate. Using nitrogen-doped carbon nanotubes (NCNT) as the foundation, WO3 nanoparticles (2–5 nm) were selectively synthesized, followed by the subsequent deposition of Pt NPs using a bottom-up approach. The Pt-WO3-NCNT catalyst, with a WO3 bridge layer effectively inserted between the active site and carbon support, has displayed a notable augmentation in electrocatalytic activity and notable stability when compared to commercial Pt catalysts in oxygen reduction reaction (ORR). The detailed microstructure and the enhanced electrochemical reaction mechanism of Pt-WO3-NCNT catalyst has been investigated by X-ray adsorption spectrum and density functional theory (DFT) calculations. This work presents an innovative approach for enhancing the stability of Pt catalysts through the utilization of the ALD technique.

Steam reforming of toluene over Ni–Co/modified-activated carbon catalyst for hydrogen production: Thermodynamic and experimental analysis

An integrated thermodynamic and experimental analysis of steam reforming of toluene (SRT) over Ni–Co/modified-palm kernel shell activated carbon (AC) catalysts for H2 production has been investigated. The catalyst samples, synthesized with different AC support modifications methods (i.e., HNO3 reflux and H2O2 aging) and impregnation, are characterized by BET, TGA, FESEM-EDX, TEM, XRD, H2-chemisorption and TPO spectroscopies. Aspen Plus® simulation software is employed to perform the thermodynamic analysis to investigate the effect of wide range of operating parameters such as temperature (373–1473 K), pressure (1–30 atm) and steam-to-carbon (S/C) molar ratio (1–9) on product distribution using Gibbs free energy minimization. Optimum conditions of SRT with 86.4% H2 yield and complete toluene conversion are attained at 973 K, S/C ratio of 5 and atmospheric pressure. Next, the catalytic performance of Ni–Co/modified-AC for enhancing SRT to H2 is conducted in a fixed-bed reactor at selected conditions. It is revealed that Ni–Co/ACP catalyst confers 82.0% and 91.7% of H2 yield and toluene conversion, respectively. The results of thermodynamic simulation and experimental testing strongly corroborate the role of Ni–Co/ACP as a high-performance catalyst to enhance catalytic conversion of SRT.

(Digital Presentation) Ethanol Electro-Oxidation Kinetics Using Activated Carbon-Supported Pt-Ag Catalysts in Alkaline Media

Due to scarcity of fossil fuels and their severe environmental consequences, the development of high efficiency energy conversion devices such as fuel cells (FCs) have gained considerable attention. The specific energy conversion efficiency of FC is highly influenced by the activity of the electrocatalysts. The Pt is widely used as an electrocatalyst due to its high activity and stability, but its high cost and depletion of resources hinder its commercialization. One of the workable strategies for the practical application of Pt is to reduce its content by alloying with some non-precious metals and simultaneously maintain its electrochemical performance. In this context, we developed a low Pt-loaded Pt-Ag/C alloy electrocatalyst via a gradual reduction process. The electrochemical performance of the as-synthesized catalyst was investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) using the three-electrode electrochemical workstation at room temperature. The electrocatalytic investigations reveal that the resultant alloy has an activity of 32.7 mA cm-2, which is significantly higher than that of Pt/C (17.6 mA cm-2) in an alkaline electrolyte and makes it a very efficient electrocatalyst for the ethanol oxidation reaction (EOR). The partial electron transfer from Ag to Pt in Pt-Ag alloy, which weakens the CO binding and poisoning effect on the surface, may be partly responsible for the enhanced catalytic activity of Pt-Ag/C. The activated carbon support also favors charge transport by transferring charge from catalytic active sites to external circuits. The stability and durability studies reveal that Pt-Ag/C performs significantly better than Pt/C, making it a viable electrocatalyst for EOR. Keywords: Direct Ethanol Fuel Cell, Electrochemical Impedance Spectroscopy, Cyclic Voltammetry, Alloy.

Construction of surface oxygen vacancy active sites upon MnOx/AC composite catalysts for efficient coupling adsorption and oxidation of toluene

Activated carbon (AC) has been widely used as adsorbent and support of noble metal catalysts for the elimination of VOCs, owing to its high specific surface area and effective regulation of interfacial properties of catalysts via metal-support interaction. Herein, a series of MnOx/AC composite catalysts are prepared by in-situ redox precipitation method using KMnO4 as manganese source, ethylene glycol (EG) as reducing agent and coconut shell-based AC as active carrier. The obtained MnOx/AC catalysts have been fully characterized by XRD, SEM, TEM, N2 adsorption-desorption, FT-IR, XPS, EPR, H2-TPR, TPD-MS and toluene-TPSR-Ms (with and without O2) and their catalytic properties are evaluated for low temperature oxidation of toluene. It is found that the introduction of AC support significantly enhanced the adsorption capacity of toluene upon the MnOx/AC composite catalysts. Amongst, the MnOx/AC-0.3 shows excellent low-temperature catalytic activity (T90 = 193 °C), which can be related to highly efficient synergy of AC and MnOx species in toluene combustion. Especially, the construction of efficient MnOx/AC interfaces with more oxygen vacancy active sites, better lattice oxygen mobility, and stronger molecular oxygen activation ability, makes MnOx/AC-0.3 composite catalyst possess the best coupling adsorption oxidation capacity of toluene, and thus resulting in significant improvement in catalytic performance. Additionally, the obtained MnOx/AC-0.3 catalyst has also exhibited good catalytic stability and water resistance (5 vol%). This work deepens the understanding of the metal-support interaction in MnOx/AC composite catalysts and provides new ideas for the design of environmentally friendly catalysts.

COx -free H2 Production via Catalytic Decomposition of CH4 over Fe Supported on Tungsten oxide-activated Carbon Catalyst: Effect of Tungsten Loading

Production of COx-free H2 from CH4 (a major global warming contributor) over cheap catalysts is a dominant task for the scientific community to accomplish environmental-friendly clean H2 energy sources. Herein, a tungsten oxide-activated carbon-supported Fe catalyst is prepared by impregnation method, characterized by X-ray diffraction, surface area-porosity measurement, temperature programmed reduction/oxidation and thermogravimetry analysis. 30wt.%Fe supported tungsten oxide incorporated activated carbon catalyst is found superior to 30 wt% Fe supported on activated carbon incorporated tungsten oxide due to higher surface area and high concentration of reducible catalytic active sites. 30wt.%Fe impregnated over 25 wt%WO3-75 wt%activated carbon support catalyst has the highest concentration of reducible surface-active species and it had excellent performance among other tungsten oxide incorporated catalysts. The catalyst showed 66.04% CH4 conversion, 63.12% H2 yield and YH2 /CCH4 > 0.9 initially which didn’t fall below 35 % up to 160-minutes. Improper matching between the rate of carbon formation and the rate of diffusion over a highly crystalline 30Fe50W50Ac catalyst resulted in rapid deactivation.

Mechanistic Insight into Favorable Aldehyde Hydrogenation over Hydroxymethyl Hydrogenolysis in 5-Hydroxymethylfurfural by Formic Acid over Single-Atom Co-N3/C

Although the Co–N–C catalyst exhibits good catalytic performance toward the hydrogenation of 5-hydroxymethylfurfural (HMF) with formic acid (FA) as the H source, its catalytic mechansim is still unclear at the molecular level, including competitive hydrogenation of the aldehyde (−CHO) group and hydrogenolysis of the hydroxymethyl (−CH2OH) group. Here, a single-atom Co-N3/C surface was modeled as a Co–N–C catalyst with an armchair model of activated carbon support. Over Co-N3/C, the catalytic mechanism for the hydrogenation/hydrogenolysis of HMF with FA has been theoretically investigated in 1,4-dioxane solution at the GGA-PBE/DNP level. The hydrogenation product, i.e., 2,5-dihydroxymethylfuran (DHMF), should be predominant, whereas the hydrogenolysis products, i.e., 5-methylfurfuryl alcohol (5-MFA), 5-methylfurfural (5-MF), and 2,5-dimethylfuran (DMF), should be minor. The rate-determining steps are concerned with the cleavage of the C–H bond in the FA moiety through an intermolecular H-shift. For the crucial transition states, compared with the Co–C group in the hydrogenolysis of the −CH2OH group, the Co–O–C group in the hydrogenation of the −CHO group can more efficiently promote the cleavage of the C–H bond in the FA moiety, which stems from the electrophilic properties of aldehyde oxygen. Kinetically, Co-N3/C boosts the hydrogenation of the −CHO group to a −CH2OH group and selectively hampers the hydrogenolysis of the −CH2OH group to a −CH3 group.

Preparation and Synergy of Supported Ru0 and Pd0 for Rapid Chlorate Reduction at pH 7.

Chlorate (ClO3-) is a common water pollutant due to its gigantic scale of production, wide applications in agriculture and industry, and formation as a toxic byproduct in various water treatment processes. This work reports on the facile preparation, mechanistic elucidation, and kinetic evaluation of a bimetallic catalyst for highly active ClO3- reduction into Cl-. Under 1 atm H2 and 20 °C, PdII and RuIII were sequentially adsorbed and reduced on a powdered activated carbon support, affording Ru0-Pd0/C from scratch within only 20 min. The Pd0 particles significantly accelerated the reductive immobilization of RuIII as >55% dispersed Ru0 outside Pd0. At pH 7, Ru-Pd/C shows a substantially higher activity of ClO3- reduction (initial turnover frequency >13.9 min-1 on Ru0; rate constant at 4050 L h-1 gmetal-1) than reported catalysts (e.g., Rh/C, Ir/C, Mo-Pd/C) and the monometallic Ru/C. In particular, Ru-Pd/C accomplished the reduction of concentrated 100 mM ClO3- (turnover number > 11,970), whereas Ru/C was quickly deactivated. In the bimetallic synergy, Ru0 rapidly reduces ClO3- while Pd0 scavenges the Ru-passivating ClO2- and restores Ru0. This work demonstrates a simple and effective design for heterogeneous catalysts tailored for emerging water treatment needs.

Green preparation of self-supporting platinum nanoflower catalyst and its electrocatalytic oxidation performance of methanol

The three-dimensional (3D) self-supporting Pt nanoflower catalyst was prepared by using Pt organic compounds as precursors in a low-temperature molten salt system. The obtained Pt nanoflower nanoparticle can reach 400–500 nm with a face-centered cubic structure, which has the structural characteristics of a loose framework and more exposed active sites. The surfactant-free Pt nanoflower was directly used as methanol electrooxidation reaction (MOR) electrocatalysts without any pretreatment and activated carbon support. The results of electrochemical catalytic oxidation of methanol showed that the Pt nanoflower catalyst exhibit more enhanced electrocatalytic oxidation performance toward methanol compared with the commercial platinum black catalyst. The green and effective method can be developed and expected to enable mass production of fuel cell catalysts.

MOF-based heterogeneous catalysis in continuous flow via incorporation onto polymer-based spherical activated carbon supports.

We present an approach to harnessing the tuneable catalytic properties of complex nanomaterials for continuous flow heterogeneous catalysis by combining them with the scalable and industrially implementable properties of carbon pelleted supports. This approach, in turn, will enable these catalytic materials, which largely currently exist in forms unsuitable for this application (e.g. powders), to be fully integrated into large scale, chemical processes. A composite heterogeneous catalyst consisting of a metal-organic framework-based Lewis acid, MIL-100(Sc), immobilised onto polymer-based spherical activated carbon (PBSAC) support has been developed. The material was characterised by focused ion beam-scanning electron microscopy-energy dispersive X-ray analysis, powder X-ray diffraction, N2 adsorption, thermogravimetric analysis, atomic absorption spectroscopy, light scattering and crush testing with the catalytic activity studied in continuous flow. The mechanically robust spherical geometry makes the composite material ideal for application in packed-bed reactors. The catalyst was observed to operate without any loss in activity at steady state for 9 hours when utilised as a Lewis acid catalyst for the intramolecular cyclisation of (±)-citronellal as a model reaction. This work paves the way for further development into the exploitation of MOF-based continuous flow heterogeneous catalysis.