Al Catalyst Research Articles

Catalytic cracking of methane to H2 and carbon over hydrotalcite-derived sintering-resistant NiVAl catalysts

Catalytic methane cracking produces pure H2 and high value-added carbon, a potentially environmentally friendly process for hydrogen production, but challenges remain in the designing of high-performance catalysts. NiVAl catalysts were obtained by reducing the hydrotalcite precursor, and the samples were analyzed by XRD, ICP, N2 adsorption-desorption, SEM, XPS, and the impacts of reaction temperature and V/Ni ratio on the production of H2 by cracking methane were studied. The results showed that the V doping could promote the reduction of Ni species, improve the specific surface area of the catalyst and inhibit the sintering of Ni particles. The methane cracking hydrogen yield curve illustrates that the performance of NiVAl catalyst shows a volcanic relationship with the V/Ni ratio. The Ni2.4V0.6Al catalyst exhibits optimal performance, with a stable hydrogen yield of about 80% for 210 min at 700 °C. In addition, the reaction temperature also significantly affects the catalyst performance, with high temperatures favoring increased catalytic activity and low temperatures tending to improve stability. The Ni2.4V0.6Al catalyst was reacted at 600 °C for 300 min with 68% hydrogen yield without deactivation.

Fe–Ce–Al Catalysts for Decomposition of Methane to High Purity Hydrogen and High-Value Carbon

Fe–Ce–Al Catalysts for Decomposition of Methane to High Purity Hydrogen and High-Value Carbon

Enhancing glycerol dry reforming performance through metal promoters: A study on 10Ni/La.Al catalyst with Mo, Sn, and Cd additions

The effect of metal promoters (Mo, Sn, and Cd) on the performance of the 10Ni/La.Al nanocrystalline catalyst in Glycerol Dry Reforming (GDR) was investigated. 2x.10Ni/La.Al (x = Mo, Sn, and Cd) catalysts were prepared using the solid-state method and 10 wt.% Ni and 2 wt.% Mo, Sn, and Cd were added to the catalyst using the impregnation method. The catalysts were characterized by BET, X-ray diffraction, temperature-programmed reduction (TPR), oxidation (TPO), Raman, and scanning electron microscopies (SEM) techniques. It was found that adding Mo caused an increase in glycerol conversion and improved the long-term stability of the 10Ni/La.Al. Furthermore, catalysts with different amounts of promoter loading (2, 4, and 6 wt%) were synthesized to evaluate the optimum amount of Mo. 4Mo.10Ni/La.Al was selected to achieve 58 % glycerol conversion and the best stability.

Oxygen evolution reaction activity of carbon aerogel supported Pd–Ni–Al catalysts synthesized by microwave irradiation method

The oxygen evolution reaction (OER) is a critical step for oxygen production during the electrochemical splitting of water. Effective OER catalysts support the development of clean energy technologies by increasing the energy efficiency of these processes. In this study, carbon aerogel (CA) was first synthesized as a catalyst support material using sol-gel, supercritical drying, and pyrolysis process. Then, mono-metallic (Pd/CA, Al/CA), bi-metallic (Pd–Al/CA, Pd–Ni/CA), and tri-metallic (Pd–Ni–Al/CA) catalysts were synthesized by microwave irradiation method. Inductively coupled plasma-mass spectrometry (ICP-MS), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy have been made to examine the structural properties of the synthesized catalysts. Electrochemical analysis was carried out through cyclic voltammetry (CV), chronoamperometry, and electrochemical impedance spectroscopy (EIS) in alkaline media (1 M KOH: Methanol) to examine the effect of metal loading of CA support material towards OER performance. All the compositions showed excellent activity toward OER, among all Pd–Ni/CA catalysts showed the highest activity. The OER peak current increased remarkably up to 48 mA cm−2 with methanol addition, which signifies the substantial application of carbon aerogel supported-Pd-Ni-Al catalysts in direct methanol fuel cells (DMFCs). Pd–Ni/CA display high OER performance with maximum diffusion coefficient, Do (6.6 × 10−8 cm2 s−1) and heterogeneous rate constant, ko (4.706 × 10−4 cm s−1), and smaller value of Tafel slope (128 mV dec−1). Electrochemical studies predicted that all the prepared carbon aerogel supported-Pd-Ni-Al catalysts can be used as efficient catalysts for OER and other related electrocatalysis applications.

Effect of Contact Time on Carbon Deposition and Catalytic Activity of Nickel Alumina Catalysts for Dry Reforming of Methane

AbstractDry reforming of methane (DRM) reaction is advantageous in producing syngas with a low H2/CO, relevant to many industries. Effect of contact time on catalytic activity and carbon deposition is studied for DRM using Ni−Al catalysts, along with the effect of metal loading, reaction temperature, and reactant partial pressure (CO2/CH4). Maximum CH4 conversion (58 %) and CO2 (59 %) were achieved at a higher contact time of 4.009 kg‐cat . h/kgCH4. A maximum of 46 % CH4 conversion was achieved at 1023 K with a contact time of 0.134 kg‐cat . h/kgCH4. Higher CH4 and CO2 conversion were achieved with an excellent H2 and CO yield due to the RWGS reaction with increased metal (Ni) loading (10–30 wt . %). When the reactant partial pressure (CO2) changed from 0.1–0.3, the CH4 conversion increased whereas CO2 conversion decreased. FESEM images revealed the formation of whisker‐like carbon fibers for all loadings. For the best syngas output and stability in a Ni‐based catalyst, a combination of a basic support (alumina) at a higher contact time (~4.009 kg‐cat . h/kgCH4) and a CO2/CH4 ratio of 1–1.5 at a moderate temperature of 873 K may provide best CO2 adsorption with minimal coking.

Effect of TiO2 on Acidity and Dispersion of H3PW12O40 in Bifunctional Cu-ZnO(Al)-H3PW12O40/TiO2 Catalysts for Direct Dimethyl Ether Synthesis

The performance of bifunctional hybrid catalysts based on phosphotungstic acid (H3PW12O40, HPW) supported on TiO2 combined with a Cu-ZnO(Al) catalyst in the direct synthesis of dimethyl ether (DME) from syngas has been investigated. In this work, different types of TiO2 were used as a support to study the effect of changes in the structure of the TiO2 support on the acidity and dispersion of HPW. Various TiO2 supports with different structural and surface characteristics have been studied and the results indicate that: (i) the crystallinity and crystallite size of the primary particles of the HPW units depend on the TiO2 support; (ii) the pore size distribution of the TiO2 support affects the surface segregation of the heteropolyacids; and (iii) changes in the supported HPW acid catalysts do not significantly alter the crystal structure of the CuO and ZnO phases after contact with CZA in bifunctional catalysts. The activity results indicate that the variation in the intrinsic activity of the Cu-ZnOx centers in the bifunctional catalysts for direct DME synthesis is minimal due to the limited alteration of the crystal structure of the centers.

Efficient synthesis of 1,6-Hexanediol via the hydrogenation of dimethyl adipate on CuZn nanoparticles with balanced Cu+-Cu0 sites

In this paper, Cu-based catalyst was prepared by co-precipitation method with DMA hydrogenation as a probe reaction. Compared to the binary Cu-ZnO catalyst, the Cu-ZnO-MxOy (M=Ce, Ti, Zr and Al) catalyst modified with the addition of a third component showed a significant increase in 1,6-Hexanediol (HDO) selectivity. Especially, the dimethyl adipate (DMA) conversion, HDO selectivity and yield of the CZZ catalyst were up to 75.7 %, 53.6 % and 40.6 %, respectively, higher than others. Combining the results of XPS and N2O titration, HDO selectivity was adjusted by varying the Cu+/(Cu0+Cu+) ratio via the third component. The addition of ZrO2 prevented further reduction of Cu+ due to the formation of Cu/ZrO2 or Cu/ZnO species, thus maintaining a constant Cu+/(Cu0+Cu+) ratio and realizing the efficient selectivity of HDO. Furthermore, higher alkaline site density on the CZZ catalyst facilitated CO bond activation further favored the formation of 1,6-hexanediol. In addition, CZZ catalyst had better hydrogen dissociation capacity and smaller catalyst particle size, which will further promote the hydrogen dissociation and thus the hydrogenation process of DMA.

Correction to: Synthesis of MIL-68 (Al) Catalyst and Optimization of Green Biodiesel Production from Waste Cooking Oil

Correction to: Synthesis of MIL-68 (Al) Catalyst and Optimization of Green Biodiesel Production from Waste Cooking Oil

Enhanced predictive optimization of methane dry reforming via ResponseSurface methodology and artificial neural network approaches: Insights using a novel nickel-strontium-zirconium-aluminum catalyst

This study investigates the molecular dynamics of methane dry reforming catalyzed by a novel nickel-strontium-zirconium-aluminum (5Ni+3Sr/10Zr+Al) catalyst, leveraging both Response Surface Methodology (RSM) and Radial Basis Function Neural Network (RBFNN) for predictive optimization. Focusing on the impact of operational parameters—hourly space velocity, reaction temperature, and CO2:CH4 mole ratio—on the conversion rates and formation of reaction components, we aim to predict optimal conditions and corresponding process variables. Through a comparison of a three-layer Feed Forward Neural Network, optimized at a 3:10:1 topology, with traditional RSM approaches, our findings highlight the superior predictive capabilities of ANN models. Notably, ANN demonstrated exceptional performance with Radj2and F_Ratio values significantly surpass those of RSM, alongside lower statistical error terms. This superiority is attributed to ANN's robust handling of nonlinear relationships between inputs and outputs, asserting its potential for enhancing predictive accuracy in chemical process optimization. At optimum predicted conditions like 1 CH4/CO2,750 °C reaction temperature, 12000 cm3g−1h−1 space velocity, NiSrZrAl outperformed with > 85 % CH4 and CO2 conversion with H2/CO ∼1 up to 20 h time on stream. Our research underscores the importance of integrating advanced modeling techniques for the efficient and accurate prediction of catalytic reactions, offering valuable insights for future applications in chemical engineering and catalysis.

Synthesis of MIL-68 (Al) Catalyst and Optimization of Green Biodiesel Production from Waste Cooking Oil

Synthesis of MIL-68 (Al) Catalyst and Optimization of Green Biodiesel Production from Waste Cooking Oil

Atomically Dispersed p‐Block Aluminum‐Based Catalysts for Oxygen Reduction Reaction

AbstractThe main group metals are commonly perceived as catalytically inert in the context of oxygen reduction reactions (ORR) due to the delocalized valence orbitals. Regulating the local environment and structure of metal center coordinated by nitrogen ligands (M‐Nx) is a promising approach to accelerate catalytic dynamics. Herein, we, for the first time, report the atomically dispersed Al catalysts coordinated with N and C atoms for 4‐electron ORR. The axial coordinated pyrrolyl N group (No) is constructed in the Al‐N4‐No moiety to regulate the p‐band structure of Al center, effectively steering the local environment and structure of the square planar Al‐N4 sites, which typically exhibit too strong interaction with ORR intermediates. The dynamic covalency competition of axial Al‐No and Al‐O bonding could endow the Al center with moderate hybridization between Al 3p orbital and O 2p orbital, alleviating the binding energy of ORR intermediates. The as‐prepared Al‐N4‐No electrocatalyst exhibits excellent ORR activity, selectivity, and durability, along with the rapid kinetics as demonstrated by in situ Raman spectroscopy. This work offers a fundamental comprehension of the fine regulation on p‐band and guides the rational design of main‐group metal‐based single atom catalysts.

Atomically Dispersed p-Block Aluminum-Based Catalysts for Oxygen Reduction Reaction.

The main group metals are commonly perceived as catalytically inert in the context of oxygen reduction reactions (ORR) due to the delocalized valence orbitals. Regulating the local environment and structure of metal center coordinated by nitrogen ligands (M-Nx) is a promising approach to accelerate catalytic dynamics. Herein, we, for the first time, report the atomically dispersed Al catalysts coordinated with N and C atoms for 4-electron ORR. The axial coordinated pyrrolyl N group (No) is constructed in the Al-N4-No moiety to regulate the p-band structure of Al center, effectively steering the local environment and structure of the square planar Al-N4 sites, which typically exhibit too strong interaction with ORR intermediates. The dynamic covalency competition of axial Al-No and Al-O bonding could endow the Al center with moderate hybridization between Al 3p orbital and O 2p orbital, alleviating the binding energy of ORR intermediates. The as-prepared Al-N4-No electrocatalyst exhibits excellent ORR activity, selectivity, and durability, along with the rapid kinetics as demonstrated by in situ Raman spectroscopy. This work offers a fundamental comprehension of the fine regulation on p-band and guides the rational design of main-group metal-based single atom catalysts.

SrCaAl mixed metal oxides derived from LDH precursor as a novel and efficient solid base catalyst for Knoevenagel condensation reaction: Multivariate optimization study

The Knoevenagel condensation reaction is one of the most important reactions in the industry for the synthesis of organic materials, medicinal, and biological compounds. In this work, we have proposed an original and efficient solid-base catalytic system for the Knoevenagel condensation reaction. For the first time, a mixed oxide catalyst derived from hydrotalcite-like Sr0.5Ca2.5Al precursor was synthesized by co-precipitation method and subsequently calcined for 5 h at 850 °C. The catalysts were characterized by various techniques. The Sr0.5Ca2.5Al mixed oxide was also compared with the usual Ca3Al sample in terms of structural characteristics and catalytic activity in the Knoevenagel reaction between active methylene compounds and benzaldehyde. The findings revealed that the Sr0.5Ca2.5Al mixed oxide sample is considerably active in this reaction compared to the Ca3Al sample due to its stronger basicity. The kinetics of the Knoevenagel condensation reaction over the Sr0.5Ca2.5Al catalyst was investigated and indicated that it follows from the second-order model. The stability and reusability of the catalyst sample were studied and it was found that the Sr0.5Ca2.5Al catalyst has high stability and a good lifetime. The effects of reaction time, amount of catalyst, and reaction temperature on benzaldehyde conversion (%) and product selectivity (%) were assessed in this study using the Box-Behnken design. The appropriateness of the quadratic regression model was evaluated through the ANOVA method. Under optimal conditions, the conversion percentage of benzaldehyde and product selectivity reached 97% and 84%, respectively.

High chemical stability poly(oxindole biphenylene)/ZrO2 porous separator for alkaline water electrolysis

Porous separators are essential for alkaline electrochemical energy technologies, such as alkaline water electrolyzers (AWEs). These separators are promising alternatives to dense membranes because they offer the potential for low cost and high ionic conductivity. However, two significant challenges in developing efficient and durable alkaline energy systems are the suppression of hydroxide ions-induced degradation and the reduction of gas permeation in porous separators. Compared to hydrophobic polysulfone (PSF), KOH-doped poly (oxindole biphenylene) (POBP) is a highly stable ion-solvating polymer that can conduct both potassium and hydroxide ions. Building upon this, a series of porous separators based on POBP polymer with different zirconia loads were designed using NIPS to investigate the chemical stability and water electrolysis performance where the Z60 separator exhibits remarkable characteristics, including low area resistance (0.227 Ω cm2), high bubble point pressure (0.813 MPa), low H2 permeability (0.5 L min−1·cm−2) and exceptional 5040 h of ex-situ durability in 6 M KOH at 80 °C. Furthermore, the Z60 diaphragm showed a higher breaking time and lower weight loss after 261 h at 80 °C in the Fenton reagent, with the remaining mass being Z60 was 38 %. Notably, the Z60 diaphragm, when equipped with Ni–Al catalysts, achieved a current density of 0.5 A/cm2 at 1.7 V, which surpasses that of Zirfon (0.5 A/cm2 at 1.8 V). More importantly, when using Ni foam catalysts, the Z60 diaphragm demonstrated stable operation under 0.125 and 0.5 A/cm2 current densities at 80 °C for more than 900 h and 1200 h, significantly improving the durability of the porous separators. The results of this study showed that the blending of POBP can lead to the development of highly chemically stable porous diaphragms, thereby opening up a new avenue for advanced AWEs.

Role of oxophilic metal ions (Mo, Zr, Ti) impregnated Ni/γ-Al2O3 catalysts for hydrothermal liquefaction of kraft lignin

In this study, the effect of oxophilic metal ions (Mo, Zr, and Ti) loaded Ni/γ-Al2O3 (Al) catalysts was explored for the first time for the hydrothermal liquefaction of kraft lignin using IPA for 30 min/280 °C. The liquefaction of lignin was noticed to be 65.4 wt% with 10 wt% loaded Ni/Al with an 81.3% total conversion. The performance of Ni/Al was enhanced remarkably by using the oxophilic metal ions as promoters owing to an increase in the Lewis character of the catalyst's surface. The bio-oil yield was a maximum of 72 wt% with a 91.5% conversion using 3 wt% loaded Ti–10Ni/Al. The different alcoholic solvents such as methanol, ethanol, and IPA were also examined for the same. However, the best liquefaction was noticed with IPA owing to better H-donor tendency. Additionally, a series of IPA-water co-solvent examinations attributed to a significant improvement in the liquefaction to 74.8 wt% (50:50) IPA-water system. The optimum catalyst 10Ni–3Ti/Al was tested for four catalytic cycles, which indicated a slight loss in the catalytic activity because of blockage of the catalytic active site by char deposition. The GC-MS investigation of optimum catalytic bio-oil showed the highest selectivity of acetosyringone (68.5%) and 2-methoxy-phenol (22.8%), which was observed to be only 30.1 and 5.1% for non-catalytic bio-oil. The 1H NMR and FT-IR investigation of raw lignin and bio-oil proved the breakage of lignin's 3D structure into respective G-and S-type monomeric compounds. Additionally, catalysts were characterized using the XRD, BET, and XPS analysis.

Efficient one-pot synthesis of CO2-based functional polycarbonates combining ROCOP and ROMP

The incorporation of diverse macromolecular blocks into CO2-based polycarbonates offers a promising approach for tailoring the properties of polycarbonates for special needs. In this work, we report for the first time the synthesis and characterization of an ABA triblock copolymer polycarbonate-b-polyalkenamer-b-polycarbonate in combination of ROCOP and ROMP via a one-pot route from CO2, epoxides and cycloalkenes. Cis-2-butene-1,4-diol as the bifunctional chain transfer agent was used as a “bridge” for the combination of different blocks as well as an effective regulator for the molecular weight of the polymers. In the one-pot reaction, the conversion of cycloalkenes reached 99.9% within 0.5 h, while the conversion of CHO was initially marginal at 0.5% but gradually increased to 99.7% after 24 h. The significant discrepancy in reaction rates between the two processes enables efficient synergistic reactions within the one-pot system. Specifically, hydroxyl-telechelic polyalkenamer is initially formed via ROMP and subsequently acts as an active species for ROCOP when coordinated with the porphyrin Al catalyst. This one-pot strategy provides a unique and simple method for controllably constructing functional polycarbonates with single-modal molecular weight distributions. By integrating the advantages of polyalkenamers and polycarbonates, this approach proves to be a viable solution for addressing the unsatisfactory thermal properties of aliphatic polycarbonates.

Copper nanoparticles encapsulated in zeolitic imidazolate framework-8 as a stable and selective CO2 hydrogenation catalyst

Metal–organic frameworks have drawn attention as potential catalysts owing to their unique tunable surface chemistry and accessibility. However, their application in thermal catalysis has been limited because of their instability under harsh temperatures and pressures, such as the hydrogenation of CO2 to methanol. Herein, we use a controlled two-step method to synthesize finely dispersed Cu on a zeolitic imidazolate framework-8 (ZIF-8). This catalyst suffers a series of transformations during the CO2 hydrogenation to methanol, leading to ~14 nm Cu nanoparticles encapsulated on the Zn-based MOF that are highly active (2-fold higher methanol productivity than the commercial Cu–Zn–Al catalyst), very selective (>90%), and remarkably stable for over 150 h. In situ spectroscopy, density functional theory calculations, and kinetic results reveal the preferential adsorption sites, the preferential reaction pathways, and the reverse water gas shift reaction suppression over this catalyst. The developed material is robust, easy to synthesize, and active for CO2 utilization.

Copper and zinc-impregnated mesoporous gamma-alumina catalyst for hydrothermal liquefaction of alkali lignin

The complete utilization of lignocellulose is a sustainable key for bio-refineries, where the utilization of evitable lignin is a great challenge owing to its structural complexity. Here, the effect of Cu and Zn-loaded mesoporous γ-Al2O3 catalysts was examined for the first time for the hydrothermal liquefaction of alkali lignin in an ethanol/water solvent system. It showed excellent performance towards the liquefaction as compared to that of (commercial) com-5Cu/γ-Al2O3 catalyst. Here, the bio-oil yield was observed to be 47.7 wt% for com-5Cu/Al catalyst which was increased to 59.1% for syn-5Cu/Al. It was increased substantially to 65.4 wt% for syn-10Cu/Al. However, only a 40 wt% bio-oil yield was found for the non-catalytic (NC) reaction. Additionally, a further significant improvement to 74.7 wt% was noticed for Zn (5 wt%) modified syn-10Cu/Al catalyst. Here, the screening of the water-ethanol mixture, and reaction parameters were also evaluated which showed a small increase in bio-oil yield to 77.4 wt% for ethanol/water (75/25, v/v). The GC-MS analysis of bio-oil exhibited the high specificity of vanillin (69.3%) for syn-10Cu-5Zn/Al. The 1H NMR and FT-IR investigation also validate the diverse functionality of bio-oils. The reusability of the optimum catalyst (syn-10Cu-5Zn/Al) was also tested for three successive catalytic cycles that exhibited the good performance of the catalyst up to the second cycle.

Low-cost Co–Al spinel and M–Co–Al (M = Fe and Ce) catalysts for selective catalytic reduction of NOx with NH3

Low-cost Co–Al spinel and M–Co–Al (M = Fe and Ce) catalysts for selective catalytic reduction of NOx with NH3

Regulation of Pt Loading on Co/Al2O3 Catalysts for Selective Hydrogenation and Hydrogenolysis of 5‐Hydroxymethylfurfural to 2,5‐Bis(hydroxymethyl)furan and 2,5‐Dimethylfuran

AbstractSelective hydrogenation and hydrogenolysis of 5‐hydroxymethylfurfural (HMF) to 2,5‐bis(hydroxymethyl)furan (BHMF) and 2,5‐dimethylfuran (DMF) were explored by regulating the nanosized Pt on Co/Al2O3 catalysts. Characterization results revealed that the catalyst acidity was influenced by adjusting the Co/Pt composition, while the addition of more Pt loading on Co/Al2O3 catalysts resulted in a facilitation of H2 reduction process. Lower size of catalyst particles was obtained for the Co−Pt system in comparison to the monometallic Co/Al2O3 catalyst. Additionally, the structural characterizations by XRD, XANES, and XPS established the co‐existences between metallic Pt0/Co0 and oxophilic PtO2/CoOx, acting as the active components for the reactions. Operated under a full HMF conversion, the Co1Pt0.050Al catalyst with high Pt loading gave >99.9 % BHMF selectivity at 40 °C; whereas, an 86.7 % of DMF selectivity was noticeable over low Pt loading of the Co1Pt0.013Al catalyst at 160 °C. This investigation evidenced that the selective production of BHMF or DMF towards hydro‐conversion of HMF was relied on the amount of Pt contents on Co/Al2O3 catalyst, in which the metal sizes and acidity had meaningful effects on the hydrogenation and hydrogenolysis processes.