Monolithic Catalysts Research Articles

Comparative full-field velocimetry of liquid flow within monolithic catalyst carriers via CFD simulations and MRV measurements

In reaction engineering, reactor performance can be improved in many cases by overcoming transport limitations. This requires detailed analyses of transport phenomena in the catalytic beds. Nuclear magnetic resonance (NMR) velocimetry measurements have been utilized for analyzing mass transport of gas flows within opaque monoliths. Comparisons to full-field computational fluid dynamics (CFD) simulations, however, show significant deviations. In this study, polyethylene glycol (PEG) and 3D-printed monoliths including one open-cell foam (OCF) and one honeycomb were used to demonstrate that both operating fluid and monolith morphology influence the achievable signal-to-noise ratio and resolution of NMR data. The velocity profiles measured by NMR in OCF agreed well with full-field CFD simulations with ± 5% deviation. In addition, the similarity between the simulated and experimental velocity fields was quantified by the similarity index, which is 1 for identical images. A mean value of 0.83 was determined for a 10 PPI OCF. Thus, using PEG as the operating fluid and a 10 PPI OCF allows to improve both spatial resolution by 34% and the quality of agreement by 13 percentage points compared to the published results of gas velocimetry within 20 PPI OCF. We further identified and quantified possible sources of deviation between CFD and MRV velocity fields. By limiting our analysis to velocities higher than 45% of the maximum velocity, we could achieve similarity indices of 0.95–0.99.

A Joule-heated carbon nanofiber aerogel-supported catalyst for hydrogen production via methanol steam reforming

Copper (Cu)-containing catalysts are preferable in the methanol steam reforming (MSR) process because of their abundant sources, low cost, and high low-temperature activities. During operation, Cu-containing catalysts are typically heated by an external heat source and are most commonly used in their macroscopic powdered form, leading to uneven temperature distributions, nonuniform mass/heat transfer, slow heating rates, and difficult replacement. These issues must therefore be addressed in the design of specific catalysts for the MSR reaction. Herein, a three-dimensional Joule-heated carbon nanofiber aerogel (CNFA)-supported catalyst (Cu/CNFA-op10) was prepared by a facile one-pot method and followed by the catalytic evaluation. It was found that the even temperature distribution, effective heat/mass/electron transfer, and uniform distribution of the Cu nanoparticles, were responsible for the excellent catalytic activities. In addition, the deactivation of the CNFA-supported catalyst was also found and caused by the aggregation and sintering of Cu0/+ nanoparticles, the deposition of amorphous carbon on the surface of active sites, and the chemical state transition of the active particles. In this proof-of-concept demonstration, the high catalytic activity of the Joule-heating-driven catalyst provides a novel strategy for further designing and fabricating 3D monolithic catalysts related to the MSR reaction.

Mass transfer enhancement and drying mechanism of high adhesion saturated impregnated Co-Al2O3 monolithic catalyst

The drying process significantly influences the dispersion of metals, physical properties, and performance of monolithic catalysts. In this research, a cordierite-based monolithic catalyst with Co/γ-Al2O3 was prepared using the slurry and impregnation method. The impact of ambient humidity on metal dispersion, mass transfer performance, and catalytic performance was investigated. The findings revealed distinct crystallization-deliquescence curves in the saturated impregnated monolithic catalysts, with alternating crystallization and deliquescence phenomena occurring as the ambient humidity changed. When the coating adhesion was high, the simultaneous occurrence of internal crystallization and surface dissolution resulted in concentrated internal stress, which facilitated the micro-stripping of the coating, leading to the formation of a cobweb-like microstructure. This process affected the distribution of pore sizes and enhanced mass transfer performance. The Co-based catalysts prepared in this study demonstrated a high selectivity for C5+ products (73.93%) when employed in the Fischer-Tropsch synthesis reaction. This research offers an optimization strategy for catalyst preparation, aiming to develop monolithic catalysts with low melting points, high crystallinity, and supersaturated supported transition metals.

One-Pot Three-Dimensional Printing of a Hierarchical NiMo/Al2O3 Monolithic Catalyst for 4,6-Dimethyldibenzothiophene Hydrodesulfurization.

The development of a competitive-cost and high-efficiency NiMo/Al2O3 hydrodesulfurization (HDS) catalyst remains challenging in the field of petrochemical industry. Herein, a highly efficient NiMo/Al2O3 monolithic HDS catalyst was elaborately designed and successfully fabricated via a one-pot three-dimensional (3D) printing strategy, and its HDS activity was examined for 4,6-dimethyldibenzothiophene conversion. The results unveil that the NiMo/Al2O3 monolithic catalyst prepared by the 3D printing strategy (3D-NiMo/Al2O3) exhibits hierarchical structure due to the combustion of hydroxymethyl cellulose serving as adhesive, which endows the weaker metal-support-interaction between Mo oxides and Al2O3, remarkably promoting sulfidation of both Mo and Ni species and the formation of "Type II" NiMoS active phase, thereby reducing the apparent activation energy (Ea = 109.2 kJ·mol-1) and increasing the catalytic activity (TOF = 4.0 h-1) and thereafter dramatically boosting the HDS performance of 3D-NiMo/Al2O3 compared with that of NiMo/Al2O3 (Ea = 150.6 kJ·mol-1 and TOF = 2.1 h-1) counterpart synthesized by conventional method with P123 serving as the mesoporous template. Therefore, this study offers a facile and straightforward strategy to fabricate an efficient HDS catalyst with hierarchical structures.

Coaxial 3D Printing of Zeolite-based Core-shell Monolithic Cu-SSZ-13@SiO2 Catalysts for Diesel Exhaust Treatment.

Core-shell catalysts with functional shells could increase the activity and stability of the catalysts in selective catalytic reduction with ammonia (NH3 -SCR) for diesel exhaust NOx treatment. However, the conventional approaches based on the multistep fabrication for core-shell structures encounter persistent restrictions regarding the strict synthesis condition and limited design flexibility. Herein, a facile coaxial 3D printing strategy has been for the first time developed to construct zeolite-based core-shell monolithic catalysts with interconnected honeycomb structures, in which the hydrophilic non-compact silica serves as shell and Cu-SSZ-13 zeolite acts as core. Compared to Cu-SSZ-13 monolith suffered from the interfacial diffusion, the SiO2 shell layer can increase the accessibility of active sites over Cu-SSZ-13@SiO2 , resulting in a 10-20% higher NO conversion at the 200-550 °C under 300,000 cm3 g-1 h-1 . Meanwhile, a thicker SiO2 shell enhances the hydrothermal stability of the aged catalyst by inhibiting the dealumination and the formation of CuOx . Other representative monolithic catalysts with different topological zeolites as shell and diverse metal oxides as core can be also realized by this coaxial 3D printing. This strategy allows multiple porous materials to be directly integrated, which allows for flexible design and fabrication of various core-shell monolithic catalysts with customized functionalities. This article is protected by copyright. All rights reserved.

Heat management of Fischer-Tropsch synthesis by designing the catalyst activity and thermal conductivity

3D printing AlSiMg monolith catalysts are more suitable for Fischer-Tropsch synthesis due to their high thermal conductivity and thermally connected nature compared to the rolling FeCrAl monolith catalysts. In this paper, the effects of the catalyst activity and thermal conductivity on the reaction and thermal performance were studied by experiment and simulation. Two catalysts were prepared based on the rolling FeCrAl and 3D printing AlSiMg substrate and were designated as ROL-FeCrAl-MC and 3DP-AlSiMg-MC, respectively. The C5+ yield of 3DP-AlSiMg-MC reached 0.98 g/(gcat•h), 4.44 times that of ROL-FeCrAl-MC. The simulation results indicated that the catalyst activity should be improved synchronously with thermal conductivity to keep the balance between the reaction heat and the heat transfer capacity. The catalyst activity of 3DP-AlSiMg-MC was 67% higher than that of ROL-FeCrAl-MC. It was suited to the high thermal conductivity of 3DP-AlSiMg-MC while that of ROL-FeCrAl-MC was well below expectations.

Kinetics-Based Prediction for Sintering of Pd/CeO2–ZrO2–Al2O3 Three-Way Catalysts during Engine-Bench Aging

The thermal deactivation of Pd/CeO2–ZrO2–Al2O3 (Pd/CZA) three-way catalysts (TWCs) was studied using a full-sized washcoated monolithic honeycomb after engine-bench aging at 600–1000 °C under a stoichiometric-lean-rich cycling gas condition. This was followed by chassis dynamometer driving tests. The nanoscale structure of these aged catalysts was characterized by gas adsorption, X-ray diffraction, and electron microscopy imaging to elucidate the thermal deactivation mechanism. Aging at high temperatures and for long periods facilitated the Pd particle growth via surface migration and coalescence, which caused a drop in the number of active sites and thus the catalytic activity. The detailed particle growth kinetics was analyzed using simulated laboratory-scale aging of Pd/CZA powder samples at different temperatures (700–1000 °C) and periods of time (0–40 h). The as-obtained Pd particle size vs time data were successfully fitted by applying the Finke–Watzky model with two-step agglomeration, which provided the rate constants for the initial slow growth and the subsequent faster growth. The temperature dependence of the as-obtained rate constants showed simple Arrhenius-type behavior, which was expressed using the optimized frequency factor and activation energy for the Pd particle growth. Furthermore, these results were roughly consistent with the data obtained by the engine-bench aging test for the monolithic honeycomb catalysts. The sintering kinetic model developed in the present study will be useful for the prediction of TWC deactivation and lifetime.

Preparation and characterization of Na4Mn9O18 whiskers on channel surface of cordierite honeycomb ceramics for soot catalytic combustion

Na4Mn9O18 whiskers were prepared on the wall of cordierite honeycomb ceramics using the molten salt synthesis, and Na4Mn9O18 whiskers were grew on channel surface of cordierite honeycomb ceramics to form hierarchical microstructure for catalytic combustion of soot. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were used to characterize the structural morphology and phase compositions. Na4Mn9O18 whiskers with aspect ratio of 24.4 measured by statistics. It was found that the loading rate of the monolithic catalyst reaches 3.588% while the binding rate after sonication almost no change. Whiskers are tightly combined with the cordierite ceramic substrate by the binding strength experiments and EDS analysis. The oxygen temperature-programmed desorption (O2-TPD) measurements were performed to investigate the O2 adsorption property. The catalytic performance of the samples were examined by semi-quantitative thermal gravimetric analysis (TG-DTG) and temperature-programmed oxidation (TPO). The catalyst performance study demonstrates that Na4Mn9O18 whiskers decrease the soot combustion temperature apparently. Experiments show the characteristic temperature could be reduced by increasing the catalyst loading. The Na4Mn9O18 decreased the ignition temperature of soot particles oxidation, and the cycle stability experiment confirmed that the sample (0h-m-k) has good structural stability and stable catalytic performance. The coarseness of the interface increased because Na4Mn9O18 whiskers grew on the cordierite substrate, and the trapping ability improved. Na4Mn9O18 is an important type of catalyst which is rarely studied in catalytic oxidation of soot. This catalyst displays good activity and stability in the soot catalytic oxidation. This unique microstructure has potential application in the DPF field.

Biomimetic porphyrin-modified 3D porous composite material adsorption enhances photocatalytic CO2 reduction and tetracycline oxidative degradation

Facing energy waste caused by carbon emissions and environmental pollution brought by the overuse of antibiotics, this work successfully synthesized a series of biomimetic porphyrin-modified three-dimensional (3D) porous composites as catalysts and used photocatalysis to recycle CO2 greenhouse gas and degrade tetracycline (TC) into harmless small molecules. The integration of adsorption and catalysis is an important way to achieve efficient photocatalysis. A prepared composite material (x-TA/C-ZCF) featured a porous structure, high content of pyridine nitrogen, and modified surface amino groups with strong adsorption capacity for CO2, as well as excellent light absorption performance derived from the incorporation of the TCPP porphyrin component. This material showed outstanding pollutant adsorption and degradation capacity for the photocatalytic reduction of CO2 and degradation of TC. Notably, 1-TA/C-ZCF catalyst achieved high yields of CO (392.23 μmol g−1) and CH4 (34.55 μmol g−1) and excellent TC adsorption degradation effect. In terms of practical application, the sponge monolithic material is designed to facilitate recycling and reuse, and showed excellent reusability and stability. This work, combined with the design of dual degradation functional monolithic catalysts with the advantages of adsorption and catalysis, will provide valuable reference for the preparation of efficient photocatalysts for resource and environmental applications.

Redox-Induced In Situ Growth of MnO2 with Rich Oxygen Vacancies over Monolithic Copper Foam for Boosting Toluene Combustion.

Catalytic combustion has been known to be an effective technique in volatile organic compound (VOC) abatement. Developing monolithic catalysts with high activity at low temperatures is vital yet challenging in industrial applications. Herein, monolithic MnO2-Ov/CF catalysts were fabricated via the in situ growth of K2CuFe(CN)6 (CuFePBA, a family of metal-organic frames) over copper foam (CF) followed by a redox-etching route. The as-synthesized monolith MnO2-Ov-0.04/CF catalyst displays a superior low-temperature activity (T90% = 215 °C) and robust durability for toluene elimination even in the presence of 5 vol % water. Experimental results reveal that the CuFePBA template not only guides the in situ growth of δ-MnO2 with high loading over CF but also acts as a source of dopant to create more oxygen vacancies and weaken the strength of the Mn-O bond, which considerably improves the oxygen activation ability of δ-MnO2 and consequently boosts the low-temperature catalytic activity of the monolith MnO2-Ov-0.04/CF toward toluene oxidation. In addition, the reaction intermediate and proposed mechanism in the MnO2-Ov-0.04/CF mediated catalytic oxidation process were investigated. This study provides new insights into the development of highly active monolithic catalysts for the low-temperature oxidation of VOCs.

Sol-gel mediated synthesis and characterization of hierarchically porous Fe2O3/SiO2 monolithic catalyst for high temperature sulfuric acid decomposition

To address the issues faced by microparticulate catalysts in fixed bed reactors for high temperature sulfuric acid decomposition viz. channeling and mass transfer, we report the preparation, characterization of Fe2O3/SiO2 hierarchical porous monoliths and testing of its catalytic properties. Monoliths with varying Fe2O3 amounts (5–30 wt%) are synthesized by a modified sol-gel approach and characterized by powder XRD, Mössbauer spectroscopy, SAXS, SEM-EDS and XPS. The Fe2O3(15 wt%)/SiO2 monolith exhibited a SO2 yield of ∼62% at 800 °C. The spent catalyst investigation established the dynamic nature of catalyst surface to accomplish the reaction mechanistic demands.

Rational 3D Structure of Monolithic Catalysts for Enhanced Hydrolytic Dehydrogenation of Ammonia Borane

Monolithic catalysts have irreplaceable advantages in hydrogen (H2) production through catalytic dehydrogenation from liquid-phase hydrogen storage materials. However, monolithic catalysts suffer from an inevitable reduction in accessible active sites due to the reduced specific surface area and hindered mass transfer. Therefore, a rational three-dimensional (3D) structure of monolithic catalysts is needed to adjust the structural factors for maximizing performance. Herein, a series of efficient and low-cost 3D catalysts with designed periodic structures were successfully fabricated. Due to the optimized specific surface area and bubble transport of the elaborate 3D structure, compared to the disordered foam structure, the new series of monolithic catalysts showed 2.3- and 1.6-fold improvement in overall catalytic performance at 298 and 318 K without any change in physiochemical characteristics, with hydrogen generation rates of 2548 and 3885 mL gcat–1 min–1, respectively. In addition, a three-period structural design philosophy for 3D catalysts was summarized, and the concept of surface activity was introduced to provide quantifiable criteria for guidance of structural optimization. The outcomes in this paper may open up new insights for building high-efficiency monolithic catalysts.

Preparation of Monolithic LaFeO3 and Catalytic Oxidation of Toluene.

Porous LaFeO3 powders were produced by high-temperature calcination of LaFeO3 precursors obtained by hydrothermal treatment of corresponding nitrates in the presence of citric acid. Four LaFeO3 powders calcinated at different temperatures were mixed with appropriate amounts of kaolinite, carboxymethyl cellulose, glycerol and active carbon for the preparation of monolithic LaFeO3 by extrusion. Porous LaFeO3 powders were characterized using powder X-ray diffraction, scanning electron microscopy, nitrogen absorption/desorption and X-ray photoelectron spectroscopy. Among the four monolithic LaFeO3 catalysts, the catalyst calcinated at 700 °C showed the best catalytic activity for the catalytic oxidation of toluene at 36,000 mL/(g∙h), and the corresponding T10%, T50% and T90% was 76 °C, 253 °C and 420 °C, respectively. The catalytic performance is attributed to the larger specific surface area (23.41 m2/g), higher surface adsorption of oxygen concentration and larger Fe2+/Fe3+ ratio associated with LaFeO3 calcined at 700 °C.

Rh Nanoparticles Dispersed on ZrO2–CeO2 Migrate to Al2O3 Supports to Mitigate Thermal Deactivation via Encapsulation

Full-scale monolithic three-way catalysts (TWCs) comprising Rh, oxygen-scavenging ZrO2–CeO2 (ZC), and γ-Al2O3 as a binder component were studied after real engine aging. The fatal irreversible deactivation that occurred under stoichiometric-lean-rich perturbation at 1000 °C for 40 h (SLR aging) was attributed to the complete encapsulation of Rh nanoparticles by ZC, leading to the physical blockage of gas adsorption. Preaging the catalyst under a rich condition at 1000 °C for 40 h (R aging) drastically mitigated this deactivation, i.e., the catalyst with R–SLR combined aging sustained its catalytic performance much better than the catalyst with SLR aging at the same temperature (1000 °C) and total time (80 h). X-ray mapping and high-temperature environmental electron microscopic analyses suggested that R aging promoted the migration of Rh nanoparticles across the ZC surface toward the boundary with the Al2O3 binder. Owing to the strong bonding with the Al2O3 surface, Rh nanoparticles were trapped at or near the boundary. Consequently, these Rh nanoparticles were unlikely to be fully covered by ZC even under the SLR aging condition because the encapsulation was induced through repetitive oxygen release/storage cycles at the Rh/ZC interface. Thus, we propose that Rh nanoparticles in contact with ZC and Al2O3 played crucial roles to hinder the encapsulation caused by SLR aging at 1000 °C. Rh nanoparticles supported on the dual-oxide support of ZC and Al2O3 were subjected to engine aging and chassis dynamometer tests. The deterioration extents of the TWC and oxygen storage capacity performances were successfully mitigated using this dual-oxide support formulation.

Pd/oCNT Monolithic Catalysts for Continuous-Flow Selective Hydrogenation of Cinnamaldehyde

Chemical engineering optimization from a batch process to continuous flow in liquid-phase hydrogenation brings a significant improvement in efficiency. However, its further application is limited due to the severe pressure drop and tube blockage problems in a powder-form catalyst fixed-bed reactor, especially for nanocarbon-supported catalysts. In this work, spherical monoliths containing oxygenated carbon nanotube (oCNT)-supported Pd nanoparticles (ca. average size of 2 mm) are fabricated via an in situ gelation method and applied for cinnamaldehyde (CAL) selective hydrogenation in a continuous-flow system. The simulated results by the computational fluid dynamics–discrete element method (CFD–DEM) coupled method show that the pressure drop of the monolith catalyst bed is maintained within 0.4 Pa. The Pd/oCNT monolithic catalyst exhibits excellent CAL conversion of 85.8% and hydrocinnamaldehyde (HCAL) selectivity of 93.5% within a high weight hourly space velocity (WHSV) of 0.012 s–1 at mild reaction conditions (30 °C, 3 bar). The catalyst maintains robust catalytic activity and HCAL selectivity (>93%) under varied reaction temperatures (30/60 °C), H2 partial pressures (3–10 bar), and WHSVs (0.012–0.184 s–1) and a stable reaction activity for more than 60 h time on stream, revealing the possibility in industrial hydrogenation reactions. The catalytic activity of the monolithic catalyst is determined by the surface properties of the carbon nanotubes and the chemical interactions between Pd nanoparticles and supports. The oxygenated functional groups and surface defects on oCNTs are beneficial for strong chemical interaction with Pd species, which forms abundant electron-deficient Pdδ+ species to facilitate C═C hydrogenation. This study puts forward insights into and perspectives for selective hydrogenation reactions in both electronic structure tuning of the active phase at the atomic scale and fabrication of monolithic catalysts at the macroscopic scale.

3D-printed N-doped porous carbon aerogels for efficient flow-through degradation and disinfection of wastewater

Peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) have great potential for water treatment. Herein, a 3D nitrogen-doped porous carbon (3D-NPC) aerogel has been prepared by direct ink writing of a hydrogel containing agarose, urea, sodium chloride and hydroxypropyl methylcellulose, and subsequent freeze-drying and pyrolysis. The obtained 3D-printed aerogel exhibits multiple desirable properties including self-supportability, hierarchical porous structure, and good structural stability, and thus can be used as a monolithic catalytic filter in flow-through experiments. The 3D-NPC catalysts have demonstrated excellent PMS-based performances toward degradation of organic dyes and disinfection of bacterial culture. The degradation efficiency of Rhodamine B by 3D-NPC is as high as 97.2% within 5 min and the high degradation efficiency can be sustained for 5 h. Moreover, 100% inactivation of bacteria by 3D-NPC can also be maintained for at least 5 h, which far exceeds those of traditional catalysts. The key reactive species of the 3D-NPC + PMS system is found to be singlet oxygen in both Rhodamine B degradation and antibacterial disinfection, where the non-radical pathway contributes to the majority of the catalytic activity. Our work has innovatively presented a 3D-printed monolithic catalyst for efficient flow-through degradation and disinfection.

NiCoAl-Based Monolithic Catalysts for the N2O Intensified Decomposition: A New Path towards the Microwave-Assisted Catalysis

Nitrous oxide (N2O) is considered the primary source of NOx in the atmosphere, and among several abatement processes, catalytic decomposition is the most promising. The thermal energy necessary for this reaction is generally provided from the external side of the reactor by burning fossil fuels. In the present work, in order to overcome the limits related to greenhouse gas emissions, high heat transfer resistance, and energy losses, a microwave-assisted N2O decomposition was studied, taking advantages of the microwave’s (MW) properties of assuring direct and selective heating. To this end, two microwave-susceptible silicon carbide (SiC) monoliths were layered with different nickel–cobalt–aluminum mixed oxides. Based on the results of several characterization analyses (SEM/EDX, BET, ultrasound washcoat adherence tests, Hg penetration technique, and TPR), the sample showing the most suitable characteristics for this process was reproduced in the appropriate size to perform specific MW-assisted catalytic activity tests. The results demonstrated that, by coupling this catalytic system with an opportunely designed microwave heated reactor, it is possible to reach total N2O conversion and selectivity of a highly concentrated N2O stream (50 vol%) at T = 550 °C, the same required in the conventionally heated process to remove N2O from a less concentrated gas stream (20 vol%).

Wood‐Derived, Monolithic Chainmail Electrocatalyst for Biomass‐Assisted Hydrogen Production

AbstractThe chainmail catalyst by encapsulating an active species within the carbon support is a well‐established concept to endorse extraordinary stability for catalytic reactions under harsh conditions. Conventional chainmail catalysts inevitably suffer from poor accessibility to active sites, leading to extra voltage to compensate the sluggish diffusion kinetics in electrocatalysis. Herein, the naturally abundant wood material is converted into a monolithic chainmail electrocatalyst by encapsulating cobalt nanoparticles within N‐doped carbonized wood. Such a monolithic chainmail catalyst is employed directly as electrode for hydrogen evolution (HER), oxygen evolution (OER), and monosaccharide oxidation reactions (MOR) with benchmark performance. By coupling the HER with MOR, the electrolyzer equipped with the monolithic chainmail catalyst allows hydrogen production at a current density of 100 mA cm−2 with a full cell voltage of only 1.36 V. Such design of wood‐derived chainmail catalyst provides a promising way to fabricate robust electrocatalysts for future production of hydrogen and value‐added chemicals.

Thermal conversion of organic furniture waste to hydrogen fuel via catalytic air gasification over monolithic spinel-type oxide-supported nickel catalysts

Furniture waste sawdust, as a byproduct of the furniture industry, is discharged in huge amounts annually. However, traditional strategies applied for their treatment have resulted in crucial environmental issues. As an eco-friendly alternative option to treat Furniture waste sawdust, this study developed a catalytic gasification technology using spinel-type oxide (AB2O4)-supported Ni catalysts under an air atmosphere to generate H2-rich gas. To this end, different metals are substituted as A cation in the spinel structure, followed by wash-coating on the monolithic reactor and impregnation with Ni to prepare Ni/MAl2O4 (M = Ca, Co, Ba, Zn, Zr, Mg, or Cu) catalysts. The employment of catalysts greatly enhanced the gas yield and H2 and CO selectivities, while significantly reducing the CO2, CH4, and C2-C4 generation, attributable to stimulated dry- and steam-methane reforming reactions. In particular, the highest gas yield (81.67 wt%) and H2 selectivity (32.19 vol%), lowest CO2, and almost zero CH4 and C2-C4 contents are obtained over Ni/CoAl2O4 catalyst, owing to the high oxygen transfer potential, appropriate basicity, and high Ni dispersion. Furthermore, a considerably enhanced gas yield and slightly increased H2 selectivity are observed when the gasification temperature is increased from 700 to 800 °C, reaching the maximum at 87.31 wt% and 32.87 vol%, respectively. Moreover, different catalyst-to-feedstock ratios from 1/5 to 1/20 gently influenced the gas yield and composition. Overall, the emerging potential of monolithic spinel-type oxide-supported Ni catalysts for hydrocarbon cracking, along with the use of waste materials as feedstock, can open new prospects for the economical and eco-friendly generation of H2 via gasification technology.”

Coated monolithic catalysts for better selective catalytic reduction: Concerns about structural integrity, catalytic activity and anti-poisoning performance

Coated monolithic catalysts for better selective catalytic reduction: Concerns about structural integrity, catalytic activity and anti-poisoning performance