Catalysts Supported Research Articles

Construction of dual Z-scheme ternary carbon nitride homojunction pectin microspheres as a multifunctional photocatalyst for tetracycline degradation, H2O2 production, and N2 fixation

Graphitic carbon nitride (GCN) has gathered phenomenal research interest as a metal-free, safe, and affordable photocatalyst. However, GCN suffers several problems, such as lower utilization of visible light, higher recombination ratio, slower electron immobility, poor reusability, and a tedious recovery process. Herein, a ternary homojunction (OPACN) was effectively constructed between oxidized GCN (OCN), amino-rich GCN (ACN), and phosphorylated GCN (PCN) and then formulated into 3D hydrogels (OPACN) using pectin as the catalyst support via a crosslinking strategy using FeCl3. The photocatalytic studies using OPACN hydrogel reported 88 % degradation of tetracycline in 30 min with a maximum reusability of 15 cycles. The ternary homojunction hydrogel photocatalyst produced 1204 µM of H2O2 and 404 µM of ammonia in 60 min of visible light irradiation. The phenomenal catalytic activity of the OPACN hydrogel is ascribed to the effective construction of homojunction between the OCN, PCN, and ACN, which facilitated the separation efficiency and boosted the visible light utilization. This study affirmed that the utilization of pectin as a catalytic support enhanced the visible light utilization, reusability, stability, and easiness in recoverability. In addition to this, pectin can act as an electron mediator, and the robust interactions between the GCN components via hydrogen bonding can also facilitate H2O2 production and nitrogen fixation. Overall, this study illuminates the usage of pectin as ideal photocatalytic support for environmental applications.

Influence of Ni concentration on α-MnO2 catalyst support and its potential application for benzene hydrogenation to cyclohexane

Herein, we report the influence of Ni at different concentrations on manganese oxide catalyst support (Ni/α-MnO2) prepared by the combined wet-impregnation and chemical reduction methods. A correlated dependence of Ni concentration was observed on the structural, surface, and morphological properties of the catalyst. The catalytic activity of Ni/α-MnO2 was evaluated for benzene hydrogenation to cyclohexane. Ni/α-MnO2 shows superior catalytic activity, and benzene conversion efficiency achieves 96.1%, which is 2.4 times greater compared to α-MnO2. Interestingly, high Ni species concentration on α-MnO2 results in an increased benzene conversion percentage. The result is synergistically attributed to the highly dispersed Ni species on the surface of α-MnO2, increased acidity, and the improved pore diameter of the Ni/α-MnO2. This work provides a facile and convenient method to develop α-MnO2 doped by Ni at various concentrations for enhanced catalytic performance as an alternative strategy to cope with the presence of aromatic compounds in fossil fuels.

Si-pillared MFI zeolites as promising supports for HDS catalysts

Si-pillared MFI zeolites as promising supports for HDS catalysts

Surface and physicochemical characteristics of KSF-clay in a liquid esterification process: The boundaries between heterogeneous catalyst and precatalysts support

Surface and physicochemical characteristics of KSF-clay in a liquid esterification process: The boundaries between heterogeneous catalyst and precatalysts support

Microwave initiated synthesis of carbon nanosphere from plastic and its application as anode electrocatalyst support in direct methanol fuel cell

The term plastisphere was coined to describe the human-made plastic environment, addressing the challenges of plastic waste. This study presents a rapid method using microwave susceptor catalysts (Co/Mo/Biochar, Ni/Mo/Biochar, Fe/Mo/Biochar) for the catalytic degradation of polystyrene into valuable carbon in microwave synthesizer. Using SEM, we found that active metal nanoparticles are uniformly distributed and the sizes of the active porous sites varied depending upon the catalyst used where the porous active sites of catalyst Co/Mo/biochar, Ni/Mo/biochar and Fe/Mo/biochar ranges between 300 nm and 700 nm, 2.21 μm and 4.05 μm, and 5 μm to larger pore size respectively. The microwave initiated catalytic synthesis process transforms uniform-sized polystyrene pellets into carbon nanospheres within 90 s. From XRD characterization, the broadened peaks at (002) plane resulted from the graphitic flakes' waving structure, confirming that the carbon nanospheres formed are graphitic in nature which is in agreement with results obtained from Raman spectroscopy. This study also explores polystyrene as an energy feedstock, utilizing Co/Mo/Biochar synthesized carbon nanospheres (CNS) which is mesoporous in nature with BET average surface area about 1428.3 m2/g as anode electro catalyst support for methanol oxidation in direct methanol fuel cells. The Pt Ru (1:1) supported on CNS catalyst exhibited higher electro catalytic activity compared to commercial PtRu/C, as indicated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS).

Roles of Metal‐Organic Framework Supports in Base‐Free Oxidation of 5‐Hydroxymethylfurfural to Furan‐2,5‐Dicarboxylic Acid over Pt‐Based Catalysts

AbstractThe catalytic oxidation of 5‐hydroxymethylfurfural (HMF) is an important process for producing a renewable furan‐2,5‐dicarboxylic acid (FDCA). Although several Pt‐based catalysts have been reported to efficiently catalyze the oxidation of HMF, the functional roles of catalyst supports, as corroborated by spectroscopic techniques, have not been fully described. Here, we report on Pt nanoparticles supported on metal‐organic frameworks (MOFs) that catalyze the oxidation of HMF to FDCA in the absence of base. Several catalysts are prepared by immobilizing pre‐synthesized Pt nanoparticles on supports, allowing for the investigation of the role of the supports without the influence of the size of Pt nanoparticles (Pt NPs). By analyzing the catalytic performances along with the electronic properties using X‐ray photoelectron spectroscopy and surface properties of the catalysts using in situ infrared spectroscopy of adsorbed CO2, we find that the presence of Pt NPs in the metallic phase and basic hydroxyl groups on the support promote the HMF oxidation.

Synthesis and characterization of bagasse cellulose-based quaternary ammonium peroxyphosphotungstate and their catalytic properties for cyclohexene oxidation in the absence of any solvent

Bagasse cellulose, an industrial waste byproduct of sugar production, was demonstrated to be a viable solid support for a solid-phase ionic oxidation catalyst enabling organic solvent-free aqueous reaction conditions and facile catalyst recovery. Bagasse cellulose-supported quaternary ammonium peroxyphosphotungstate was synthesized from bagasse cellulose-supported quaternary ammonium chloride, phosphotungstic acid, and hydrogen peroxide. The chemical structure of this material was characterized by SEM, XRD, FT-IR, XPS, and 13C NMR, revealing stability of the cellulose matrix to the catalyst loading conditions and effective dispersion of the acicular catalyst crystals throughout the matrix. High catalytic activity of this synthetic complex was demonstrated in the oxidation of cyclohexene to 1,2-cyclohexanediol with hydrogen peroxide in the absence of solvent. Optimized conditions providing trans-1,2-cyclohexanediol with 86.2 % selectivity were 12 wt% catalyst and 4 mL/g 30 % H2O2 (vs. cyclohexene) at 50 °C for 10 h.

Reaction synergy of bimetallic catalysts on ZSM-5 support in tailoring plastic pyrolysis for hydrogen and value-added product production

Hydrogen, viz. a green energy carrier, is poised to considerably contribute to the empowerment of a sustainable society. By valorizing plastics, catalytic pyrolysis was envisaged as a promising route to produce green hydrogen and value-added product here. Firstly, the screening of optimal catalyst support (from activated carbon and four zeolites: M-zeolite, B-zeolite, Y-zeolite, ZSM-5) was executed by studying catalytic polypropylene (PP) pyrolysis over supported Ni catalysts. In view of the highest H2 yield (19.2 mmol/gPP) of Ni/ZSM-5, ZSM-5 was put forth as the optimal catalyst support. Then, the identification of optimal active metal (from Ni, Fe, Co, FeNi, FeCo, and NiCo) was performed by running the catalytic PP pyrolysis over ZSM-5 supported catalysts. For catalytic PP pyrolysis, NiCo/ZSM-5 was the optimal catalyst with the highest H2 yield (28.7 mmol/gPP), while the resulting pyrolysis oil demonstrated potential for use as jet fuel. From catalytic pyrolysis of various plastics over NiCo/ZSM-5, polystyrene gave the highest H2 composition (83.2 vol%) of pyrolysis gas and high composition (52.8 area%) of benzocyclobutene (useful chemicals for semiconductor and microelectronics fields) in pyrolysis oil. Lastly, the catalytic mechanism was discussed based on the results, revealing NiCo's remarkable enhancement in H2 yield to 28.7 mmol/g, which surpassed the individual yields of Ni (19.2 mmol/g) and Co (10.2 mmol/g), thereby underscoring the synergistic effect of NiCo. This study supports the recycling of plastics waste into hydrogen energy and valuable products, contributing to environmental pollution mitigation.

Enhancing the Carbon Monoxide Oxidation Performance through Surface Defect Enrichment of Ceria-Based Supports for Platinum Catalyst.

Effective synthesis and application of single-atom catalysts on supports lacking enough defects remain a significant challenge in environmental catalysis. Herein, we present a universal defect-enrichment strategy to increase the surface defects of CeO2-based supports through H2 reduction pretreatment. The Pt catalysts supported by defective CeO2-based supports, including CeO2, CeZrOx, and CeO2/Al2O3 (CA), exhibit much higher Pt dispersion and CO oxidation activity upon reduction activation compared to their counterpart catalysts without defect enrichment. Specifically, Pt is present as embedded single atoms on the CA support with enriched surface defects (CA-HD) based on which the highly active catalyst showing embedded Pt clusters (PtC) with the bottom layer of Pt atoms substituting the Ce cations in the CeO2 surface lattice can be obtained through reduction activation. Embedded PtC can better facilitate CO adsorption and promote O2 activation at PtC-CeO2 interfaces, thereby contributing to the superior low-temperature CO oxidation activity of the Pt/CA-HD catalyst after activation.

Preparation of easily-stripped and high-purity carbon nanotubes from various waste plastics

The conversion of waste plastics to carbon nanotubes (CNTs) through catalytic pyrolysis technology marks a significant advancement in environmental sustainability. This process not only mitigates environmental pollution but promotes the effective use of solid waste. However, the use of powder particle catalysts still faces a separation challenge after carbon deposition. To address this, a carbon paper-based catalyst has been introduced in this study, which possesses a milk thistle-like structure. The results shows that this catalyst facilitated the generation of easily-stripped CNTs on the surface of carbon paper. Around 9 wt% CNTs was collected from 1 g of polyethylene (PE), followed by polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC). Thermogravimetric analysis revealed that CNTs constituted over 95 % of carbon deposition. The harvested CNTs-PE exhibited a more uniform diameter of around 15 nm, which is smaller compared to that of CNTs-PP, CNTs-PS, and CNTs-PVC. Further cyclic experiments confirmed the reusability of carbon paper as a catalyst support, with the yield of CNTs remaining nearly constant over five cycles. This innovative approach paves the way for recycling plastic waste into high-valued CNTs that can be easily-stripped from the support materials with simple physical operations such as pickling.

Nickel ferrite decorated noble metal containing nitrogen-doped carbon nanotubes as potential magnetic separable catalyst for dinitrotoluene hydrogenation

The 2,4-toluenediamine (TDA) is one of the most important chemicals in the polyurethane industry, produced by the catalytic hydrogenation of 2,4-dinitrotoluene (DNT). The development of novel catalysts that can be easily recovered from the reaction mixture is of paramount importance. In our work, a NiFe2O4/N-BCNT supported magnetic catalyst was prepared by a modified coprecipitation method. The catalyst support alone also showed activity in the synthesis of TDA. Platinum nanoparticles were deposited on the catalyst support surface by a fast, relatively simple, and efficient sonochemical method, resulting in a readily applicable catalytically active system. The prepared catalyst exhibited high activity in hydrogenation tests, which was proved by the exceptionally high DNT conversion (100% for 120 min at 333 K) and TDA yield (99%). Furthermore, the magnetic catalyst can be easily recovered from the reaction medium by the action of an external magnetic field, which can greatly reduce catalyst loss during separation.

Pd-N-doped carbons for chemoselective hydrogenation of cinnamaldehyde: Unravelling the influence of particle size and support in multiphase batch and continuous-flow systems

The chemoselective hydrogenation of the CC bond of cinnamaldehyde (CAL) was investigated under batch and continuous flow conditions, by comparing the performance of two ad-hoc prepared palladium-based catalysts supported on N-doped carbons to that of a commercial Pd/C system. An impregnation (I) and a solution-mediated (S) protocols were used for the synthesis of the catalytic materials, Pd-N/Ci and Pd-N/Cs, respectively, in the presence of chitin as a precursor of the support. The S method afforded palladium nanoparticles of 2.0±0.5 nm, while by impregnation, a wider size distribution was achieved with particles mostly belonging to two groups displaying a mean radius of 3.0±0.5 nm and 8.4±0.5 nm, respectively. A parametric analysis of the hydrogenation reaction showed that both the reaction conditions and the nature of the catalysts played a role to steer the selectivity towards the formation of the desired product, 3-phenylpropanal (hydrocinnamaldehyde, HCAL). At 50 °C and 1 bar H2, in a triphasic (liquid-liquid-liquid) batch reactor where the catalyst was compartmentalized in an ionic liquid layer, Pd-N/Ci and commercial Pd/C were almost equally active and allowed to obtain HCAL in a 90–96 % selectivity at complete conversion. On the other hand, at the same T and p (50 °C/1 bar), Pd-N/Cs was more effective in the continuous-flow mode: the process was quantitative yielding HCAL with a selectivity and a productivity of 91 % of 16 mmol (gcat h)−1, respectively, while the catalyst proved highly stable showing no loss of activity over 300 min of time on-stream. The reaction environment, the size and dispersion of the metal active sites, and the nature of the catalyst support were major contributors to such results, acting synergistically to each other to tune the energetics of adsorption/desorption of reactants/products, of the interfacial interactions/ barriers, and in the last analysis, of the process kinetics/selectivity.

Effect of Carbon Support on the Properties of Fe, N, S Co-Doped ORR Catalysts Prepared by Molten Salt Method

In recent years, the development of sustainable and environmentally friendly catalysts for various electrochemical processes has become a major focus in the fields of energy storage and fine chemicals. Efficient and cost-effective oxygen reduction reaction (ORR) catalysts are crucial for the advancement of fuel cells and metal-air batteries. This study explores the use of rice husk-based porous carbon (RHPC) with a hierarchically porous structure as a support material for sustainable ORR catalysts. The performance of RHPC was compared with other commercial carbon materials, such as acetylene black (AB) and coconut shell carbon (YP-50), evaluating key properties including particle size, specific surface area, oxygen-containing functional groups, degree of graphitization, and hydrophilicity/hydrophobicity. Compared to AB, which has higher conductivity, and YP-50, which has a greater abundance of oxygen functional groups, RHPC demonstrated significant advantages as a catalyst support. The resulting Fe-NS/RHPC catalyst exhibited high activity (E1/2 = 0.858 V vs RHE, J = 4.83 mA cm−2), outperforming the standard Pt/C (E1/2 = 0.844 V vs RHE, J = 4.99 mA cm−2). When tested in a liquid Zn-air battery, the Fe-NS/RHPC catalyst achieved a peak power density of 116.2 mW cm−2 and a capacity of up to 792.5 mAh g−1.

Production of green diesel from waste cooking oil via catalytic deoxygenation reaction using metal doped eggshell catalyst

Abstract Green diesel production via catalytic deoxygenation of waste cooking oil (WCO) over metal doped eggshell catalyst was investigated in this work. The catalyst was prepared through liquid-liquid precipitation of 5 transition metal solutions and ground eggshell (ES) as the catalyst support. The prepared catalyst, Fe-ES, Cu-ES, Co-ES, Zn-ES, and Ni-ES were characterized using BET surface area and Scanning Electron Microscopy (SEM) analysis. BET surface area data and SEM images of the catalyst shows a promising catalyst physical properties that tailor to the deoxygenation reaction. Gas Chromatography Mass Spectrometry (GCMS) was used to determine the hydrocarbon composition of the oil yield product from the reaction. The reaction also produces gas, soap and liquid acid phase while the remaining unreacted WCO becomes coke. The percentage of all products and coke were calculated using mass balance. Deoxygenation of WCO with Ni-ES catalyst produced highest oil yield at 61.6% with the hydrocarbon content of 56.11%. Ni-ES also produced 22.9% coke; the least percentage compared to other catalyst. The findings proved that Ni-ES catalyst exhibited the highest conversion of WCO into gas and liquid product with a greater yield of oil and minimal coke formation. These findings demonstrate the feasibility and practicality of using eggshell catalysts as substitutes for commercial catalysts in green diesel production.

Fischer-Tropsch synthesis: Platinum promoted Co@HCS catalysts

Hollow carbon sphere (HCS) nanoreactors were used as a catalyst support for Co, with Pt as a promoter. The hollow morphology of the HCSs nanoreactor was exploited to study the influence of the Pt promoter nanoparticle location relative to that of the Co3O4 (Co 10 wt%) nanoparticles (dCo = 3.5 – 12.5). Furthermore, the effect of Pt on the reduction behaviour and activity of the Co FTS catalyst was evaluated. The synthesis and use of Pt nanoparticles supported on/in Co@HCS FT catalysts to give CoPt@HCS and Pt/(Co@HCS) catalysts are reported. Electron microscopy, ex situ PXRD, BET, and TPR studies revealed that the prepared catalysts were successfully synthesized with well dispersed Co nanoparticles. It was observed that the proximity between the Co and Pt influenced the Co hcp/fcc ratios. A secondary hydrogen spillover effect was invoked to account for the reduction of Co3O4 on 1Pt/(10Co@HCS) at 335 °C. The complete reduction of Co3O4 to Co metal on 10Co1Pt@HCS at 350 °C was attributed to a primary hydrogen spillover effect. Following catalyst activation at 350 °C, the primary spillover process resulted in a catalyst exhibiting higher Fischer–Tropsch activity (approximately 2×) compared to both the unpromoted catalyst and catalysts where Pt and Co were separated by the HCS. This enhanced activity was partially attributed to the Co phases formed on the carbon support during reduction and the degree of catalyst reduction, which depended on the type of hydrogen spillover process. A comparison of the reduction ability of Os, Ru and Pt on the reduction of Co supported on/in HCSs and the impact of the promoter on Co hcp/fcc ratios is reported.

Stabilizing alkaline fuel cells with a niobium-doped brookite titanium dioxide catalyst support

Stabilizing alkaline fuel cells with a niobium-doped brookite titanium dioxide catalyst support

The direct synthesis of H2O2 and in situ oxidation of methane: An investigation into the role of the support

The selective oxidation of methane to methanol, using H2O2 generated in situ from H2 and O2 has been investigated using bimetallic gold-palladium catalysts, prepared via an industrially relevant wet co-impregnation protocol on a range of zeolite and metal oxide supports. The choice of catalyst support was found to drastically influence catalyst performance, through control of both nanoparticle dispersion and Pd speciation. Notably in the case of those formulations prepared on metal oxides a direct correlation between catalytic performance towards H2O2 synthesis and methane valorisation exists, whereas in the case of the zeolitic-based analogues, no clear correlation could be drawn between activity towards individual reaction pathways.

MECHANICAL PROPERTIES OF POROUS SILICON CARBIDE CERAMICS: A REVIEW

Porous silicon carbide (SiC)-based ceramics exhibit exceptional structural and functional properties, such as excellent mechanical, chemical, and thermal stability, and controlled electrical resistivity. Owing to their superior properties, porous SiC ceramics are suitable for various industrial applications, including heatable filters, heating elements, thermoelectric energy converters, fusion reactors, thermal insulators, water purifiers, molten metal and hot gas filters, diesel particulate filters, membrane supports, and catalyst supports. A deeper understanding of the mechanical properties of porous SiC ceramics, coupled with the development of new strategies for tuning these properties, will enable the realization of numerous new applications. In this review, important factors known to determine the mechanical strength of porous SiC ceramics, such as microstructures (necking area) and pore characteristics (porosity, pore size), have been analyzed. With increasing porosity and pore size of porous SiC ceramics, the flexural strength tends to decrease. The flexural strength increases with decreasing pore size at a constant porosity, whereas the flexural strength decreases with increasing porosity at a constant pore size. In addition, the flexural strength of porous SiC ceramics is primarily influenced by the developed necking area between SiC grains, which can be obtained through the doping of soluble atoms into the SiC lattice. Based on these critical factors affecting the mechanical properties, a novel strategy for tuning the flexural strength of porous SiC ceramics is proposed.

Highly dispersed BiVO4 nanoparticles supported by pseudoboehmite for effective removal of antibiotics

BiVO4/pseudoboehmite (PB) composite catalysts were innovatively prepared using the cost-effective PB as support by a facile hydrothermal method. BiVO4 nanoparticles with an average size of 12 nm are highly dispersed on the surface of PB. Compared to pure BiVO4, the composite BiVO4/6 %PB exhibits high specific surface area (32.9 m2/g) about double that of pure BiVO4 (15.1 m2/g) which can provide more adsorption and photocatalytic reaction sites. Meanwhile, the composite has enhanced photogenerated electron-hole separation and transfer efficiency. As a result, it has a superior performance of antibiotics removal in water than pure BiVO4. The tetracycline hydrochloride (TCH) removal efficiency of BiVO4/6 %PB can reach 87 % within 2 h with high stability (<7 % decay after four cycles) under LED lamp (380–780 nm) irradiation as well as high selectivity. Specifically, the adsorption efficiency and photocatalytic rate constant are respectively triple and double that of pure BiVO4. Simultaneously, the BiVO4/6 %PB also possesses high removal efficiency of amoxicillin (76 %). Our results indicate that the selection of cost-effective PB as catalyst support offers a new solution to solve the aggregation problem of BiVO4 nanoparticles and the composite obtained contributes to an economic and efficient BiVO4-based photocatalyst for antibiotics removal in sewage treatment.

Effect of Photoreactor Design on the Degradation of Thiamethoxam by Pure/Supported Titanium Dioxide

The environmental persistence of thiamethoxam (THX), a commonly used neonicotinoid insecticide, raises concerns about its long-term effects. This study explored the photocatalytic degradation of THX using pure and perlite supported TiO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; photocatalysts in two distinct UV photoreactor configurations. Our investigation aimed to identify some optimal conditions for efficient THX removal while considering cost-effectiveness and sustainability for potential industrial applications. The results revealed that horizontal UV irradiation (System 1) significantly surpassed vertical irradiation (System 2) in both THX degradation rate and energy efficiency. This highlights the importance of photoreactor design for maximizing light utilization and mass transfer. While pure TiO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; exhibited superior performance in both systems compared to perlite-supported TiO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; (PST), the latter demonstrated an intriguing temperature dependence. PST achieved enhanced degradation at higher temperatures, suggesting its potential for industrial applications where waste heat is available. Furthermore, we discovered that low pH conditions substantially boosted THX degradation with PST, opening a promising avenue for optimizing industrial processes and minimizing chemical usage. This finding underscores the crucial role of operational parameters in tailoring photocatalytic performance. In conclusion, this study provided strong evidence for the effectiveness of TiO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; photocatalysis in degrading THX, a persistent organic pollutant. We emphasized the impact of catalyst support, photoreactor design, and operational parameters, such as temperature and pH, on treatment efficiency. Notably, the enhanced performance of PST at higher temperatures and its responsiveness to low pH conditions suggest its potential for cost-effective and sustainable THX treatment in industrial settings. These findings pave the way for further research and development of optimized photocatalytic systems for mitigating environmental contamination by THX and other persistent organic pollutants.