Catalysts Supported Research Articles

Closed-loop recylcing of thermoset poly(vinylogous urethane) foams

Foams are an intriguing class of porous and lightweight materials which have found widespread applications in thermal insulation, pollutant adsorption, catalyst support, and energy storage. However, their covalently cross-linked structure makes foam unable to be recycled resulting in serious environmental burden. To address this challenge, we report the first example of closed-loop chemically recyclable foam. A simple, catalyst-free cryo-polymerization process with multifunctional amines and acetoacetates was utilized to successfully prepare a series of poly(vinylogous urethane) foams, containing dynamic covalent bonds which can selectively be cleaved on demand. The resulting foams exhibit macroporous structure with diameters exceeding 14 μm, pronounced thermal stability (Td,5% > 262.5 °C), robust hydrophobicity (WCA > 93°) and unique reactivity. Applications have been demonstrated for efficient adsorption of organic solvents and anionic dyes. More importantly, the foams show excellent recyclability under acidic conditions with high monomer recovery yields of up to 97 % and high purity levels. Fresh foams could be regenerated from the retrieved building blocks, thus demonstrating efficient closed-loop recycling. This work provides a new “monomer-foam-monomer” ecological chain and may inspire the advancement of next-generation closed-looped recyclable foam materials.

Valorization of dairy waste scum oil and rice husk ash-supported CuO nanocatalyst towards cleaner production of biodiesel: A waste-to-energy approach

This study surveys the valorization of dairy waste scum oils (DWSO) to synthesis biodiesel using a novel rice husk ash-supported CuO nanocatalyst. The rice husk ash-supported CuO nanocatalyst was synthesized through a facile impregnation method and characterized by BET, XRD, FTIR, EDX, CO2/TPD, TEM, and FESEM to confirm its structural and morphological features. Transesterification of DWSO was conducted under optimized conditions, achieving a maximum biodiesel yield of 97.42% at temperature of 62.36°C, methanol/DWSO proportion of 11:12, and nanocatalyst loading of 2.76wt.% within 2.85h. Kinetic studies revealed that the transesterification reaction follows a pseudo-first-order model with an activation energy of 100.34kJ/mol. Thermodynamic analysis indicated that the reaction is endothermic (ΔH = 100.26kJ/mol) and non-spontaneous (ΔG = -11043.6kJ/mol) at the studied temperature range, suggesting the requirement of external heat to drive the process. Reusability tests demonstrated that the rice husk ash-supported CuO nanocatalyst retains over 86% of its initial activity after seven cycles, highlighting its potential for practical applications. This study highlights the dual benefits of utilizing agro-industrial waste for both feedstock and catalyst support, promoting a cleaner and economically viable approach for biodiesel generation.

Application of Corn Oil Derived Carbon Nano-onions Using Flame Pyrolysis as Durable Catalyst Support for Polymer Electrolyte Membrane Fuel Cells

Application of Corn Oil Derived Carbon Nano-onions Using Flame Pyrolysis as Durable Catalyst Support for Polymer Electrolyte Membrane Fuel Cells

Pore Expansion of N-Doped Carbon as Support of Pd Catalyst for Accelerated Formic Acid Dehydrogenation

Pore Expansion of N-Doped Carbon as Support of Pd Catalyst for Accelerated Formic Acid Dehydrogenation

Insights into pore structure-activity relationships of iron catalysts supported on fluorine–cerium nanosheets for heterogeneous Fenton oxidation

Two-dimensional (2D) structural materials as catalyst supports is crucial for improving the heterogeneous catalytic activity, while the relationships between their porous structure and catalytic performance are still not very clear. Herein, four kinds of porous 2D Fluorine-Cerium (F-Ce) nanosheets were fabricated and used as catalyst support, aiming to investigate the effect of porous structure on the catalytic properties by heterogeneous Fenton oxidation and unveil the structure-activity relationships. Compared with 2D non-porous GO, Ti3C2, and porous g-C3N4, F-Ce nanosheets exhibited superior catalytic activity. Specifically, FeOOH/F-Ce-3 catalysts achieved 95.5 % phenol removal within 40 minutes, with the deposition sites and electronic structures of the loaded Fe-active species being modulated by tuning the pore structures. In addition, we demonstrated that large pore size and high pore volume are more conducive to high catalytic performance, as well as the uniform pore shape and well-ordered pore distribution are more favorable for mass transfer during catalysis. This work emphasizes the great advantage of using porous 2D F-Ce nanosheets as support in the construction of heterogeneous Fenton catalysts while elaborating the relationship between pore structure and catalytic activity.

Catalytic Activity of Cellulose-supported Platinum andPalladium Nanoparticles for Allylbenzene Hydrogenation.

Platinum and palladium nanoparticles were successfully deposited on tunicate cellulose via the photodeposition or microemulsion deposition method. Evenly distributed, small and narrow-sized particles in the range of 2‑3 nmwere obtained for microemulsion-prepared cellulose catalysts. The photodeposition method led to larger particle sizes, broader size distribution, and occasional agglomerations. The catalysts were tested in the allylbenzene hydrogenation reaction and the results were compared to commercially available catalysts. Because of smaller particles, both microemulsion-prepared catalysts and photodeposited ones show better activity than commercial catalysts. Even platinum and palladium nanoparticles were active for the hydrogenation, only cellulose-supported platinum nanoparticles showed good stability. For palladium nanoparticles, stronger leaching from the surface of cellulose was observed. Cellulose-supported catalysts were recycled, and reusability is comparable to commercial catalysts. Therefore, cellulose could be used as an alternative catalyst support.

Influence of MIL-53 on the catalytic performance of metallocene in propylene polymerization

In this study, we investigate the application of metal-organic frameworks (MOFs) as a support for metallocene catalysts in the polymerization of propylene. MOFs such as MIL-53 and other conventional supports, SBA-15 and SiO2, were employed to immobilize the Me2Si(2-Me-4-PhInd)2ZrCl2 catalyst activated with methylaluminoxane (MAO). The effects of the physicochemical properties of these supports on catalytic performance and polymer properties were investigated. MIL-53, characterized by its channel structure, facilitated higher molecular weight polypropylene production and exhibited double the catalytic activity of SBA-15 and SiO2 supports. The MIL-53/MAO/Me2Si(2-Me-4-PhInd)2ZrCl2 catalyst also demonstrated higher comonomer incorporation and lower polymer melting points. The higher activity, elevated molecular weight, and increased reactivity towards 1-hexene of the MIL-53/MAO/Me2Si(2-Me-4-PhInd)2ZrCl2 catalyst are attributed to the electronic and steric effects of MIL-53. This study underscores the significant role of MOF structure in influencing polymerization behavior and highlights the potential of MOF-supported catalysts for tailored polymer properties.

In-situ formation of boehmite and ammonium aluminum carbonate hydroxide for facile synthesis of γ-Al2O3 as industrial catalyst support used for hydrodesulfurization

Alumina-supported CoMo catalysts have been widely used for hydrodesulfurization of various kinds of feeds. In the current research, γ-Al2O3 was synthesized through the simultaneous formation of boehmite and ammonium aluminum carbonate hydroxide (AACH) precursors under controlled pH and temperature conditions. After optimization of the textural properties, γ-Al2O3 was utilized as catalyst support for the immobilization of catalytically active species and obtaining CoMo/γ-Al2O3-n (concentration of Al(NO3)3.9H2O solutions (n) = 30, 40, 50, 60, 70, 80, 90, and 100 g/L) catalysts via wet impregnation technique. Moreover, this preparation method was applied for the successful large-scale synthesis of CoMo/γ-Al2O3-n. The catalyst was characterized by FT-IR, powder X-ray diffraction (XRD), thermogravimetric analysis, inductively-coupled plasma (ICP), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and Brunauer–Emmett–Teller (BET). The conversion of thiophene over CoMo/γ-Al2O3 was studied to assess the catalytic performance. The catalytic activity and stability of our reported catalyst were comparable with that of KATALCOJM 41-6 T commercial catalyst. Highlights Mixture of boehmite and AACH precursors was synthesized by co-precipitation method The precursors were thermally decomposed to extruded γ-Al2O3 as catalyst support The properties of γ-Al2O3 were tuned by various concentrations of Al solution CoMo/γ-Al2O3 was prepared by the impregnation of γ-Al2O3 in the Co and Mo solutions CoMo/γ-Al2O3 catalyst was sulfided and used for hydrodesulfurization of thiophene

Sulphated zirconia on cyclodextrin nanosponge: A carbohydrate-based catalyst for conversion of mono-saccharides to 5-hydroxymethylfurfural

To expand the utility of cyclodextrin nanosponges for catalytic purpose, β-cyclodextrin nanosponge was prepared via melting method and then utilized as a catalyst support for the stabilization of sulphated zirconia. The resulting catalyst, denoted as CDNS-SO42−/ZrO2, was then applied as a heterogeneous acidic catalyst for conversion of fructose to 5-hydroxymethylfurfural. The results, underpinned that the catalytic activity of CDNS-SO42−/ZrO2, was superior to that of ZrO2 and SO42−/ZrO2, confirming the role of sulfonation of ZrO2 and immobilization of SO42−/ZrO2 on CDNS in catalysis. To optimize the reaction parameters and achieve maximum yield of the desired product, Response Surface Method that is an accurate procedure for appraising the impacts of the reaction variables was employed and it was found that using 35 wt% CDNS-SO42−/ZrO2 at 80 °C, HMF in 93 % yield was achieved in 45 min. Kinetic study also showed that the activation energy was 13.28 kJ/mol. Furthermore, thermodynamic parameters, i.e. enthalpy, entropy and Gibbs free energy were estimated as 10.46 kJ/mol, −150.40 J/mol and 63.58 kJ/mol respectively. Noteworthy, the catalysis was true heterogeneous, as confirmed by Hot filtration test and the catalyst could be recycled several times with low leaching of SO42−/ZrO2.

Thermo‐Mechanical Study on Auxetic Shape Memory Periodic Open Cellular Structures—Part I: Characterization of Reentrant Geometry and Effective Heat Conductivity

Periodic open cellular structures (POCS) are additively manufactured supports for heterogeneous catalysts in the field of chemical reaction engineering. Constructed from a repeated unit cell, POCS offer excellent heat transport characteristics due to heat conduction in the continuous solid matrix. However, when inserted into tubular reactors, a loose fit between structure and tube wall results. This considerably hinders heat transfer across the wall. The novel POCS concept presented in this work aims at an intensified wall heat transfer by utilizing a reentrant structure design to ensure auxetic behavior. If the POCS is made of shape memory alloy, it can recover its original shape. Combining these two effects with an initial radial oversize, an interference fit with the tube is established. This contribution comprises the geometric description of reentrant POCS and heat conduction simulations for characterization of the effective heat conductivity, yielding scaling correlations dependent on geometric parameters. Moreover, the effective radial heat conductivity of POCS in cylindrical shape is explicitly investigated. The influencing factor identified is the ratio of tube diameter and cell size: while the ratio increases, the effective radial heat conductivity decreases, but remains well above the effective heat conductivity of the unit cell.

State of the Art and Challenges in Complete Benzene Oxidation: A Review.

Increased levels and detrimental effects of volatile organic compounds (VOCs) on air quality and human health have become an important issue in the environmental field. Benzene is classified as one of the most hazardous air pollutants among non-halogenated aromatic hydrocarbons with toxic, carcinogenic, and mutagenic effects. Various technologies have been applied to decrease harmful emissions from various sources such as petrochemistry, steel manufacturing, organic chemical, paint, adhesive, and pharmaceutical production, vehicle exhausts, etc. Catalytic oxidation to CO2 and water is an attractive approach to VOC removal due to high efficiency, low energy consumption, and the absence of secondary pollution. However, catalytic oxidation of the benzene molecule is a great challenge because of the extraordinary stability of its six-membered ring structure. Developing highly efficient catalysts is of primary importance for effective elimination of benzene at low temperatures. This review aims to summarize and discuss some recent advances in catalyst composition and preparation strategies. Advantages and disadvantages of using noble metal-based catalysts and transition metal oxide-based catalysts are addressed. Effects of some crucial factors such as catalyst support nature, metal particle size, electronic state of active metal, redox properties, reactivity of lattice oxygen and surface adsorbed oxygen on benzene removal are explored. Thorough elucidation of reaction mechanisms in benzene oxidation is a prerequisite to develop efficient catalysts. Benzene oxidation mechanisms are analyzed based on in situ catalyst characterization, reaction kinetics, and theoretical simulation calculations. Considering the role of oxygen vacancies in improving catalytic performance, attention is given to oxygen defect engineering. Catalyst deactivation due to coexistence of water vapor and other pollutants, e.g., sulfur compounds, is discussed. Future research directions for rational design of catalysts for complete benzene oxidation are provided.

Better Together: Synergic Effect of Gallium‐Based Catalyst and Porous Support for Reduction Reactions

Liquid metal solutions are a new class of catalysts with outstanding properties in terms of catalytic conversion and resistance to coking. Finding the perfect combination of catalytic particles with homogeneous size distribution and support material able to stabilize them during catalysis is key for preparing model systems to gain understanding of these complex catalytic processes. In this work, we present a method for the preparation of small and narrowly distributed gallium‐palladium particles supported on inverse opals, interconnected 3‐dimensional porous networks with a very narrow pore size distribution. Our platform is a promising candidate as supported liquid metal catalytic system thanks to its permeability to fluids and its confined pore environment, which prevents the coalescence of the metal alloy, thus maximizing the surface area available for the catalytic reaction. We demonstrate their enhanced performance when compared to other state of the art systems giving a proof of concept of their application as catalysts for a simple model reaction, the reduction of methylene blue.

Precision Macroporous Monoliths Made Using High‐Throughput Microfluidic Emulsification

Materials with pore sizes ranging from micrometers to millimeters find use in thermal insulation, acoustics, separation, and energy‐related applications. While several routes have been developed to manufacture such macroporous materials, current fabrication technologies remain limited in either scalability or pore size control. Herein, a scalable microfluidic approach is reported to create macroporous materials with precisely controlled pore sizes from monodisperse emulsion templates. Emulsion droplets produced in a parallelized step emulsification device are assembled by gravity and converted into macroporous monoliths by polymerization and drying. Microstructural analysis and model filtration experiments show that the pore windows of the bulk macroporous material can be tightly controlled and used for the size‐selective separation of particles from suspensions. By heat treating macroporous structures of selected compositions, one can also create bulk carbon and silica glass monoliths with unique cellular architectures for potential applications as filters, separation membranes, or catalyst supports.

Performance and Durability of Heavy-Duty Fuel Cell Systems with an Advanced Ordered Intermetallic ORR Alloy Catalyst and Novel Support

Abstract Ordered PtCo intermetallic (OIM) catalyst (L10-PtCo/C) is a promising candidate as the oxygen reduction reaction (ORR) catalyst in hybrid fuel cell systems (FCS) for class-8 heavy duty (HD) trucks. Compared to a baseline annealed Pt on high surface area carbon (a-Pt/HSC) catalyst, its mass activity (MA) is 71% higher initially and 144% higher after 90,000 potential cycles in an accelerated stress test (AST). Analysis of the AST data indicates that the ORR kinetic constants do not change with aging and the degradation in the OIM catalyst activity is linearly proportional to the loss in the electrochemically active surface area (ECSA). Several operational strategies are investigated to mitigate catalyst degradation and achieve 25,000-h electrode lifetime and 2.5 kW/g Pt utilization on a HD truck duty cycle including load sharing with the hybrid battery, regulating the radiator fan power to maintain the coolant temperature close to 60oC, clipping the maximum cell voltage below 850 mV, limiting the ECSA loss to 55%, and oversizing the membrane active area by 20%. Drive cycle simulations indicate that the lifetime average voltage degradation rate is about 1.8 V/h and the integrated stack and FCS drive cycle efficiencies decrease by 3.5 to 3.9%.

Influencing Factors on the Wet Impregnation of Additive‐Manufactured Catalyst Support Structures

AbstractThe wet impregnation of additive manufactured aluminum oxide cylinders with platinum is investigated. The influence of five parameters on the penetration depth and the platinum loading is evaluated. A smaller penetration depth is obtained by increasing pH, sodium chloride concentration in the impregnation solution, decreasing impregnation solution volume, heating rate during subsequent calcination, and no vacuum during prewetting before the impregnation. A pH range of 2 to 4, a low chloride concentration, a small liquid volume, and no vacuum drawing lead to high platinum uptake. This investigation is crucial in understanding and optimizing the wet impregnation process, providing practical guidance for future research with more complex structures.

Effect of substrate type on structural and electrochemical performance of vertical graphene nanosheets deposited by HWP-CVD

Vertical graphene nanosheets (VGs) were synthesized on Cu, Ti, Si, and C substrates by helicon wave plasma chemical vapor deposition (HWP-CVD) method using CH4/Ar as precursors. The obtained samples formed vertical orientation structures of nanosheets-graphene as the scanning electron microscopy and TEM images indicated. Specifically, the VGs grown on Cu substrate exhibit a parallel arrangement with a wall spacing of approximately 450 nm. This structural characteristic facilitates efficient ion exchange channels and promotes low resistance for electron transport. The effect of substrate type on the growth mechanism of VGs was discussed. The relationship between the microstructure and electrochemical performance of the VGs grown on different substrates was investigated. The charge transfer resistance of the VGs/Cu is 20.75 Ω, and the value of VGs/Ti, VGs/C and VGs/Si are 23.51 Ω, 33.76 Ω and 66.40 Ω, respectively. The robust vertical orientation structure of VGs holds promise for various applications, including catalyst support in fuel cells, conductive electrodes in photovoltaic cells, and energy storage devices like lithium-ion batteries and supercapacitors. This structural characteristic plays a pivotal role in advancing the development of next-generation energy storage technologies.

Supported phenylalanine on core-shell mesoporous microsphere as a catalyst for the synthesis of triazolo[1,2-a] indazole-triones and spiro triazolo[1,2-a] indazole-tetraones

In recent years, mesoporous silica materials have gained attention due to their unique properties, such as high surface area, pore volume, size, and chemical stability. These characteristics make them effective in various fields, particularly efficient supports in heterogeneous catalytic reactions. The present study developed a novel type of core-shell mesoporous microsphere material by anchoring phenylalanine on a core-shell SiO2@NiO@MS support. The catalyst support (SiO2@NiO@MS) was synthesized through homogeneous precipitation and sol-gel methods, with NiO encapsulated within the porous silica. The catalyst was characterized using various techniques, including Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), Elemental mapping analysis, N2 adsorption-desorption, Transmission electron microscopy (TEM), Vibrating sample magnetometer (VSM), and Thermogravimetric analysis (TGA). It was then employed for the synthesis of triazolo[1,2-a]indazole-trione and spiro triazolo[1,2-a]indazole-tetraones compounds from 4-phenyl urazole, dimedone, and aromatic aldehydes or isatin derivatives. This synthetic approach offers multiple advantages, including high yields, faster reaction times, low catalyst requirements, and environmentally sustainable conditions.

Insights into the effect of various supports on hydrothermal liquefaction of food waste over iron-oxide nano-catalysts

This work investigates the effect of supported iron-oxide nano-catalysts for hydrothermal conversion of food waste. The studied supports were Vulcan carbon (VC), CeO2, ZSM-5 and amorphous SiO2-Al2O3. Catalytic hydrothermal liquefaction experiments were carried out in a batch reactor at 16 MPa and 300 °C maintained for 1 h. Different fractions of Fe(0), Fe2+ and Fe3+ alter its tendency toward deoxygenation, hydrogenations and condensation reactions, which influence the bio-crude yield, elemental compositions, and energy recoveries. The fresh and spent catalysts were characterized using X-ray photoelectron spectroscopy, physisorption analysis, thermogravimetric analysis, transmission and scanning electron microscopy. It was found that the change in catalyst support influences HTL pathways and product compositions. The results reveal that the inclusion of FeOx catalyst on Vulcan carbon, SiO2-Al2O3 and ZSM-5 supports can increase the bio-crude yield by ~7–9 wt% compared to their FeOx-free yields. The increase in bio-crude yield was associated with the decrease in the surface ratios of Fe3+/Fe2+ at the range of 0.8–1.6. In overall, catalysts that had higher tendencies in converting amines into oil-soluble compounds increased the bio-crude yield, while catalysts that promoted dehydration and decarboxylation route decreased the bio-crude yield. The maximum energy recovery in bio-crude was obtained using FeOx/SiO2-Al2O3 catalyst with values ~95 %. The deactivation of catalysts was associated with the increase in Ca and P poisonous elements on catalytic sites, which decreased the energy recovery of recycled FeOx/SiO2-Al2O3 to ~85 % after three cycles.

Enhancement of CO2 adsorption and oxygen transfer properties on γ-Al2O3 support through surface modification with MgO-ZrO2 for coke suppression over Ni catalyst in CO2 reforming of methane

This work focuses on employing commercial γ-Al2O3 for surface modification with MgO-ZrO2 mixed oxide to enhance the potential of CO2 adsorption and oxygen mobility. This enhancement facilitates its application as a support in catalysts for CO2 utilization such as CO2 reforming of methane (CRM). To achieve this perspective, γ-Al2O3 was modified with 10 wt.% of various MgO and ZrO2 contents (MgO:ZrO2= 10:0, 9:1,7:3, 5:5, 3:7, 1:9 and 0:10) using the impregnation method. All samples including unmodified γ-Al2O3 (Al) were characterized. Due to the increase in basicity and oxygen transfer around the surface, the improvement of the CO2 adsorption was observed on γ-Al2O3 modified with 9 wt.% MgO-1 wt.% ZrO2 (9Mg1ZrAl) and 10 wt.% MgO (10MgAl), respectively. An application of these two superior samples as a support of 10 wt.% Ni (10Ni) catalysts for CRM was investigated and compared with an unmodified γ-Al2O3. Characterization results suggest the formation of NiO-MgO solid solution at the surface due to the decrease in metal-support interaction and the increase in metal dispersion. The Ni catalysts with the surface-modified support show higher CO2 activity that raises carbon deposition resistance. The greatest coke prevention was observed on 10Ni/9Mg1ZrAl that lowers the coke deposition by 42 % compared to 10Ni/Al. It indicates that the composition of this modification allowed very low ZrO2 portion to merge with MgO and MgO to form solid solution with NiO. This enables the 10Ni/9Mg1ZrAl catalyst to generate labile oxygens which can be conveyed to the Ni metal sites on the catalyst.

Hexagonal boron nitride fibers as ideal catalytic support to experimentally measure the distinct activity of Pt nanoparticles in CO2 hydrogenation

Catalytic studies aim to design new catalysts to eliminate unwanted by-products and obtain 100 % selectivity for the preferred target product without losing activity. For this purpose, understanding the role of each component building up the catalyst is essential. However, determining the intrinsic catalytic activity of pure metals, especially precious metals in the CO2 hydrogenation reaction under ambient conditions is complex. This is because the catalyst supports used thus far always influence the catalytic process either directly or indirectly due to interface formation that modifies the electronic and morphological structure of the metals. Even SiO2, regarded as inert shows some activity owing to the hydroxyl groups on its surface. In this work, we propose chemically inert and defect-free hexagonal boron-nitride fibers (BNF) synthesized via a co-precipitation method with wide band gap and robust covalent bonds as an uncommon reference catalyst support to evaluate the catalytic activity of size-controlled Pt nanoparticles (4.7 ± 0.6 nm) in the hydrogenation of CO2. The fibers alone show no catalytic activity; however, Pt/BNF exhibited low but notable activity of 377 nmol/g at 400 °C and the catalyst can achieve nearly 100 % CO selectivity. X-ray photoelectron spectroscopy, transmission electron microscopy, and diffuse reflectance infrared Fourier transform spectroscopy measurements were used to indicate that hexagonal boron-nitride affects neither the metal nanoparticles nor the reaction itself; the measured catalytic activity stems from the activity of Pt deposites without the effect of the support, as they were alone. CO vibration spectroscopy studies suggest that due to the lack of substrate-metal interaction, Pt nanoparticles adopt an ideal spherical structure, resulting in several low coordination sites capable of CO2 conversion. Thus, BNF is proposed in the present article to be used as a reference catalyst support material. It can be efficiently used in investigations involving the proposed metal and reaction or under varying conditions with different metal nanoparticles and reaction systems.