Catalysts For Steam Reforming Research Articles

Optimization of Rh-containing Catalysts for Low-temperature Steam Reforming of Light Hydrocarbons

Rhodium-containing catalysts on various carriers (Ce0.75Zr0.25O2, Ce0.5Zr0.5O2, Ce0.4Zr0.5Y0.05La0.05O2, γ-Al2O3, TiO2) produced by various methods (sorption-hydrolytic precipitation and incipient wetness impregnation) and differing by mass content of rhodium (from 0.5 to 4 % by mass) were studied. The dependence of the catalytical efficiency of rhodium catalysts on composition, texture, and redox properties of the carrier was studied. The prospect of using associated petroleum gas at Russian deposits was confirmed.

Bimetallic NiFe Nanoparticles Supported on CeO2 as Catalysts for Methane Steam Reforming.

Ni-Fe nanocatalysts supported on CeO2 have been prepared for the catalysis of methane steam reforming (MSR) aiming for coke-resistant noble metal-free catalysts. The catalysts have been synthesized by traditional incipient wetness impregnation as well as dry ball milling, a green and more sustainable preparation method. The impact of the synthesis method on the catalytic performance and the catalysts' nanostructure has been investigated. The influence of Fe addition has been addressed as well. The reducibility and the electronic and crystalline structure of Ni and Ni-Fe mono- and bimetallic catalysts have been characterized by temperature programmed reduction (H2-TPR), in situ synchrotron X-ray diffraction (SXRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Their catalytic activity was tested between 700 and 950 °C at 108 L gcat-1 h-1 and with the reactant flow varying between 54 and 415 L gcat-1 h-1 at 700 °C. Hydrogen production rates of 67 mol gmet-1 h-1 have been achieved. The performance of the ball-milled Fe0.1Ni0.9/CeO2 catalyst was similar to that of Ni/CeO2 at high temperatures, but Raman spectroscopy revealed a higher amount of highly defective carbon on the surface of Ni-Fe nanocatalysts. The reorganization of the surface under MSR of the ball-milled NiFe/CeO2 has been monitored by in situ near-ambient pressure XPS experiments, where a strong reorganization of the Ni-Fe nanoparticles with segregation of Fe toward the surface has been observed. Despite the catalytic activity being lower in the low-temperature regime, Fe addition for the milled nanocatalyst increased the coke resistance and could be an efficient alternative to industrial Ni/Al2O3 catalysts.

Hydrogen generation from glycerol steam gasification over cobalt loaded MgO–Al2O3 hydrotalcite supports

The objective of this research was to determine the effect of the composition of MgO–Al2O3 in hydrotalcite (HT) on the performance of cobalt catalysts in glycerol steam reforming (GSR) for hydrogen. The co-precipitation method was used to prepare five hydrotalcite supports with varying MgO:Al2O3 compositions (1:1, 1:3, 3:1, 1:5, and 5:1), which were then loaded with a 20 wt% Co using the incipient wetness impregnation method. All the catalysts were systematically characterized by X-ray diffraction and temperature-programmed studies (H2 reduction, both CO2 and NH3 desorption). The impregnation of cobalt oxide on hydrotalcite produced different types of cobalt oxides depending on the hydrotalcite composition. HT with high MgO to Al2O3 (3:1, 5:1) ratios favored the formation of a Co-(Mg)–O solid solution, while HT with low MgO to Al2O3 (1:3 and 1:5) ratios favored the formation of Co2AlO4 and CoAl2O4. On the other hand, HT with a 1:1 mol ratio of MgO to Al2O3 minimized the formation of Co-(Mg)–O solid solution and cobalt aluminates while encouraging the formation of mixed phases (Co3O4, Co2AlO4, and CoAl2O4). Interlinked mesopores (N2-physisorption) were observed in the 20 wt% Co/(1:1) MgO:Al2O3 catalyst, and its surface was discovered to be amphoteric (from NH3 and CO2 TPD). Each catalyst was investigated for hydrogen production from glycerol in the range of 400–700 °C. The best hydrogen yield and glycerol conversion to vapor-phase achieved at 600 °C on the 20 wt% Co/(1:1) MgO–Al2O3 catalyst are due to high reducibility and an adequate amount of cobalt available on the surface. The amphoteric behavior of the catalyst prevented hydrogen consumption in the methanation reaction. It is also speeding up the WGS reaction and enhancing the hydrogen yield.

Oxygen Vacancy Induced Strong Metal-Support Interactions on Ni/Ce0.8Zr0.2O2 Nanorod Catalysts for Promoting Steam Reforming of Toluene: Experimental and Computational Studies.

To develop an efficient Ni-based steam reforming catalyst for tar removal from the products of biomass gasification, Ni/Ce0.8Zr0.2O2 nanorods were designed. The Ni/Ce0.8Zr0.2O2 nanorod was used as a catalyst in steam reforming of toluene, which was regarded as a model compound of biomass gasification tar. At gas hourly space velocity (GHSV) of 24,000 h-1 and Ni loading of 5 wt %, the 5Ni/Ce0.8Zr0.2O2 nanorod catalyst achieved 100% of toluene conversion at 600 °C. After 10 h of operation, toluene conversion still reached 87.6%, and the carbon deposition rate was only 1.9 mg/gcat h-1. The experimental results demonstrated that the 5Ni/Ce0.8Zr0.2O2 nanorod catalyst showed much higher catalytic activity and coking resistance than other Ni-based catalysts reported in the literature. Through different characterization technologies and density functional theory calculations, it was confirmed that the excellent catalytic performance was attributed to the strong metal-support interaction (SMSI) between Ni and the {100} facet of Ce0.8Zr0.2O2. The special surface structure of {100} allowed Ni atoms to anchor to the surface oxygen vacancies and maintained its reduced state by electron transport between surface atoms. The anchored Ni facilitated oxygen vacancies formation and H2O dissociation on the support, while the support modulated the electronic structure of Ni, which promoted its ability to toluene activation.

Synergistic effect of transition metals substitution on the catalytic activity of LaNi0.5M0.5O3 (M = Co, Cu, and Fe) perovskite catalyst for steam reforming of simulated bio-oil for green hydrogen production

Hydrogen is considered an excellent source of renewable and sustainable energy which can be produced from inexpensive starting materials such as biomass. The present study aims at developing a stable catalytic system for bio-oil steam reforming process to produce green hydrogen. The perovskite catalysts LaNi0.5M0.5O3 (M = Co, Cu, and Fe) were synthesized using sol-gel method and their catalytic performance towards hydrogen production and bio-oil conversion was evaluated in a fixed bed tubular reactor. A wide array of techniques such as XRD, BET, NH3 and CO2 -TPD, FE-SEM, XPS, TGA and pyridine-FTIR were used to analyze the material properties of the synthesized catalysts. The results of these analyses verified the successful formation of the highly sought-after perovskite structure with good amount of surface oxygen vacancies as well as medium-strength acidic and basic sites. To establish an efficient catalytic system, process parameter (space-time and reaction temperature) optimization and time on stream (TOS) studies were conducted. The TOS results displayed that LaNi0.5Co0.5O3 perovskite catalyst is stable up to 12 h at 700 °C for space-time of 17.4 kgcat. h/kgmolbio-oil. In-depth characterizations (FE-SEM, TGA, RAMAN spectroscopy and XRD) of spent catalyst after the reaction not only gave further insights about the excellent activity exhibited by the chosen catalyst but also revealed information about the nature of the coke deposited on the surface.

High catalytic performance of Fe-rich palygorskite clay-supported Ni catalysts for steam reforming of toluene

AbstractThe development and application of Fe-rich palygorskite clay has been restricted significantly by its red colour and low grade. Moreover, the nano-structured properties of palygorskite and the relatively large Fe content of Fe-rich palygorskite clay have received insufficient attention. The present study involved the synthesis of Ni-based catalysts via a coprecipitation method using Fe-rich palygorskite clay as the support. The catalysts were then evaluated for their performance for catalytic steam reforming of toluene (CSRT). The experimental findings revealed that the Fe in Fe-rich palygorskite clay interacted strongly with Ni and formed Fe-Ni alloys. The catalyst with a Ni/Fe mass ratio of 14 (Ni14/FePal) calcined in air at 600°C exhibited superior performance for CSRT under the reaction temperature 700°C and S/C molar ratio of 1.0. According to the kinetics study, Ni14/FePal exhibited the lowest apparent activation energy (33.99 kJ mol−1) among the catalysts, which further confirmed the superior catalytic activity in CSRT. The characterizations of the catalysts used demonstrated that the excellent stability and resistance to coke formation of Ni14/FePal were attributable to the presence of a sufficient amount of highly dispersed Fe-Ni alloys on its surface.

Probing crystalline phase effect of rare earth metal oxides (REO) on Cu/REO (RE=Gd, Eu, Sm) catalysts for methanol steam reforming (MSR) to produce H2

In this work, to study the phase structure effect, three groups of Cu/REO catalysts were prepared with cubic and monoclinic Gd2O3, Eu2O3 and Sm2O3 supports for MSR reaction to produce H2. Based on CH3OH conversion and H2 yield, the reaction performance of the catalysts ranks as Cu/Sm2O3-M > Cu/Sm2O3–C > Cu/Gd2O3-M > Cu/Gd2O3–C > Cu/Eu2O3-M > Cu/Eu2O3–C. For the same kind of REO, Cu supported on the monoclinic support shows better performance than on the cubic one. Despite the phase structure difference, Sm2O3 is the best support among all the three kinds of REOs. Compared with Cu/REO catalysts prepared with cubic supports, the corresponding catalysts prepared with monoclinic supports generally possess more surface oxygen vacancies, which can generate more surface active oxygen (O2–) and moderate basic sites. Moreover, the contents of Cu + on the catalysts follow the same sequence. The reaction performance is positively related to the amount of these three types of surface sites. But metallic Cu0 species is necessary to maintain the Cu+ ↔ Cu0 redox cycle. Furthermore, on a catalyst with good performance, those vital surface reaction intermediates can be stabilized during the reaction. Cu/Sm2O3-M possesses the largest quantities of these surface sites, and has the appropriate amount of Cu+ and Cu0 after reduction, thereby displaying the optimal performance in all the catalysts. In conclusion, evident support crystal structure effect is observed for Cu/REO catalysts, and a monoclinic phase REO is a better support than the respective cubic phase one.

High H2 selective performance of Ni-Fe-Ca/H-Al catalysts for steam reforming of biomass and plastic

The development of a selective catalyst for the conversion of biomass and plastics into H2 by steam reforming can combat the energy crisis and global warming. In this work, support Ni-Fe-Ca/H-Al bifunctional catalysts were prepared by loading Ni and Fe into pretreatment CaO/Al2O3 (Ca/H-Al) carriers and showed high catalytic activity for the steam reforming of biomass and plastic. Moreover, the idea of bidirectional degradation was exploited to strengthen the pyrolysis of plastic with a high H/C and biomass with a high O/C. Interestingly, the products presented high H2 selective (1302.10 mL/g) and low CO2 yield (120.23 mL/g) in 7Ni-5Fe-Ca/H-Al(2:4) catalyst compared with current reports. Here, the abundant oxygen vacancies (Ov) in the H-Al carrier exhibited an electron-deficient nature, providing active sites for anchoring NiO. Meanwhile, NiO interacted with Ca2Fe2O5 to produce more defective Ov sites, which stabilized the NiO particles in the 7Ni-5Fe-Ca/H-Al (2:4) catalyst, and the interaction between the catalyst and the carrier was enhanced, leading to the reduction of weakly basic sites, this property promoted the strong adsorption of CO2 and H2O by the catalyst, contributing to the enhancement of efficient steam conversion and the promotion of conversion of by-products to H2. Notably, 7Ni-5Fe-Ca/H-Al(2:4) catalysts maintained structural integrity after regeneration and exhibited excellent regenerability in H2 selection and CO2 adsorption. The work provides a new idea for the study of efficient H2 production from steam reforming of biomass and plastics.

Effect of Sr Substitution on the Novel La1-xSrxCo0.5Ni0.5O3-δ Perovskite-Type Catalysts for Hydrogen Production in Ethanol Steam Reforming

La1-xSrxCo0.5Ni0.5O3-δ perovskites with different substitution of La by Sr have been firstly synthesized and applied as catalysts for ethanol steam reforming (ESR). The effect of partial Sr substitution on the performance and stability of La1-xSrxCo0.5Ni0.5O3-δ for ESR was investigated. The synthesized samples were characterized by XRD, SEM, BET, and EDS techniques. The results show that with the increase of substitution of La by Sr, the pore size and surface area of La1-xSrxCo0.5Ni0.5O3-δ perovskite increase. The doping of Sr causes changes in the specific surface area, pore volume, and pore size of the catalyst, which in turn causes changes in its catalytic activity. Meanwhile, La0.1Sr0.9Co0.5Ni0.5O3-δ with a highest SBET presents the highest ethanol conversion rate among all the samples. The modifications of catalyst characteristics caused by the Sr substitution in La1-xSrxCo0.5Ni0.5O3-δ directly affect its catalytic performance in the ESR. What is more, the influences of operating parameters on the catalytic activity of La0.1Sr0.9Co0.5Ni0.5O3-δ were studied in detail, and the optimum conditions were determined and applied for stability experiments. When the temperature is lower than 500°C, the selectivity of gas products is most likely affected by the dehydrogenation of ethanol and the decomposition of acetaldehyde. Meanwhile, the improving hydrogen selectivity and reducing the formation of by-products can be achieved by increasing the reaction temperature. The best catalytic performance for hydrogen production was achieved with La0.1Sr0.9Co0.5Ni0.5O3-δ which presented the highest ethanol conversion (98.7%) under the optimal reaction conditions. La0.1Sr0.9Co0.5Ni0.5O3-δ perovskites with higher strontium degree of substitution exhibited an excellent activity and stability of the catalysts derived.

Inhibitory effect of trace impurities on methanol reforming by Cu/ZnO/Al2O3 catalyst: Steam reforming and autothermal reforming of model bio-methanol

Model bio-methanol was prepared by adding a trace quantity of lower alcohols (ethanol, 1-propanol, and 1-butanol) as model impurities to methanol. The catalytic performance of the Cu/ZnO/Al2O3 catalyst for steam reforming (SR) and autothermal reforming (ATR) of model bio-methanol was investigated to evaluate the inhibitory effect of lower alcohols. In SR, the activity (methanol conversion and H2 production rate) markedly decreased from the initial stage of the reaction. In ATR, the initial activity decreased slightly, and the activity decreased gradually with reaction time. In SR, the lower alcohol adsorbed strongly on the catalyst, resulting in the inhibition of methanol adsorption on Cu. In ATR, although the conversion of lower alcohol was promoted, the quantity of carbonaceous species derived from the lower alcohols increased with the reaction time. These inhibitory effects of lower alcohols were due to the inability of the Cu-based catalyst to cleave C-C bonds in lower alcohols.

HYDROGEN PRODUCTION FROM ETHANOL BY STEAM REFORMING OVER NICKEL AND COBALT GEOTHERMAL WASTE SUPPORTED CATALYST

Hydrogen production was studied over nickel and cobalt geothermal waste-supported catalysts. Due to their good catalytic activity, nickel, and cobalt are widely used as catalysts in ethanol steam reforming. The geothermal waste catalyst (GWC) was synthesized by hydrothermal process, then prepared using wet-impregnation with nickel nitrate and cobalt nitrate as the precursors. SEM analysis shows that nickel and cobalt successfully adhered to the GWC, which decreased the surface area. Using nickel and cobalt in ethanol steam reforming produces a higher hydrogen yield than a GWC. The best hydrogen yield was 43.04% over Ni/GWC at 550oC. Nickel can actively break C-C, OH, and C-H bonds to produce hydrogen and reduces the brønsted acid site as the carbon formation active site.

Screening of steam-reforming catalysts using unsupervised machine learning

In this article, a bidirectional clustering model proposed for methanol-reforming catalysts demonstrates excellent mathematical performance and is of significance for the discovery of methanol-reforming catalysts.

Effect of support on the performance of PtRu-based catalysts in oxidative steam reforming of ethanol to produce hydrogen.

Oxidative steam reforming of ethanol (OSRE) to produce hydrogen has been investigated over a series of supported PtRu catalysts, with different supports. Bimetallic PtRu-based catalysts were prepared by the impregnation method using H2PtCl6 and RuCl3 as precursors. Six supports (reducible oxides of ZrO2, CeO2, and Co3O4, and irreducible oxides of ZnO, Al2O3, and NiO) were chosen to fabricate bimetallic catalysts. The catalytic performance of the OSRE reaction in the series of PtRu-based samples was evaluated using a fixed-bed flow reactor under atmospheric pressure. In front reaction, the catalyst was pre-activated by reduction under 200°C for 3h. The gas hourly space velocity was adjusted at 66,000 h-1, and the optimal molar ratios of the H2O/EtOH and O2/EtOH feeds were 4.9 and 0.44, respectively. The results indicated that the PtRu supported on the ZrO2 and CeO2 exhibited superior catalytic performance in the OSRE reaction under a low temperature (a TR of approximately 320°C) for producing the main products of H2 and CO2 with lower CO and CH4 by-products. Also, it was quite stable during a long time evaluation; the maximum YH2 maintained at 4.5-4.2, and the CO distribution approached 3.3-3.5mol% around 84h test at 340°C over the PtRu/ZrO2 catalyst.

Synthesis, application, and characteristics of mesoporous alumina as a support of promoted Ni-Co bimetallic catalysts in steam reforming of methane

In this research, mesoporous alumina synthesized from sol-gel self-assembly (EISA) procedure has been used as an efficient supporting material for bimetallic Ni-Co active sites to be applied in the steam reforming of methane (SRM) reaction for the first time. For this purpose, after confirming the formation of porous alumina structure via N2 adsorption/desorption, transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and field emission scanning electron microscopy (FESEM), and fourier-transform infrared spectroscopy (FT-IR) techniques, we have loaded this support with various Ni/Co mass ratios (0/1, 1/2, 1/1/, 2/1/, 1/0), characterized their structural properties with various techniques, and tested their performance in the SRM process. Overall, presence of Co particles depicted efficient performance in not only catalyst morphology, but also in reaction activity. Among bimetallic synthesized catalysts, 10Ni-10Co exhibited the highest CH4 conversion of 95.7 % and H2 yield of 96.2 % with the lowest carbon deposition of 3.6 wt%, owing to improved active site dispersion and higher BET surface area. After loading this catalyst with cerium, promotion effect of only 1 wt% CeO2 particles caused the best performance with an average CH4 conversion of 97.0 %, H2 yield of 98.8 %, H2/CO molar ratio of 4.0, and CO2/CH4 molar ratio of 0.3 at 700 °C.

Gold nanoparticles-assisted sodium borohydride supported on titania as a catalyst for the oxidative steam reforming of methanol and CO oxidation

Gold nanoparticles-assisted sodium borohydride supported on titania as a catalyst for the oxidative steam reforming of methanol and CO oxidation

The role of promoters in Cu/Acid‐MMT catalysts for production of hydrogen via steam reforming of dimethyl ether

AbstractBackgroundThe steam reforming of dimethyl ether (DME) is one of the promising technologies for high‐efficiency hydrogen production. The key issue for the steam reforming of DME is the development of catalysts with higher performance. In this study, a series of X‐Cu/Acid‐MMT (X = Co, Ni, Zr, Ce) catalysts were prepared via the impregnation method using Acid‐MMT obtained by montmorillonite activated with nitric acid (20 wt%) at 80 °C for 12 h as the support and metallic nitrate as precursor. The catalysts were characterized by XRD, H2‐TPR, XPS, N2O titration and N2 adsorption–desorption at low temperature.ResultsThe introduction of promoter X could reduce the interaction between Cu and the support, and more CuO was reduced to Cu0; meanwhile, it was beneficial for improving the dispersion of Cu. This would enhance the reaction rate of steam reforming of DME. Therefore, the introduction of promoter X significantly increased DME conversion, especially Ni‐Cu/Acid‐MMT presented the maximum DME conversion. However, Ni‐Cu/Acid‐MMT exhibited low H2 yield, high selectivity of CO and CH4 due to reverse water gas shift reaction and methanation reaction. Co‐Cu/Acid‐MMT catalyst presented the maximum H2 yield, high conversion of DME, relatively low selectivity of CH4 and better stability.ConclusionsThe introduction of promoters to Cu/Acid‐MMT catalyst improved the catalyst performance for the steam reforming of DME. Among these catalysts, Co‐Cu/Acid‐MMT exhibited remarkable catalytic performance, which is expected to be a potential catalyst for steam reforming of DME. © 2022 Society of Chemical Industry (SCI).

Influence of drying technique on Pt/In2O3 aerogels for methanol steam reforming

In this paper we present a comparison of aerogels which are dried under different conditions. Of those, most important are the solvent, temperature, and pressure. Criteria of comparison rely mostly on results from analysis of nitrogen adsorption experiments, as well as transmission electron microscopy imaging. Platinum loaded indium oxide aerogels were picked as a model system for this study as they can be used as highly effective heterogeneous catalysts in methanol steam reforming. The compared drying methods include supercritical drying from CO2, supercritical CO2 - ethanol mixture, freeze drying from tert-butanol and ambient conditions drying from acetone and 1-Methoxyheptafluoropropane. High porosities and large specific surface areas can be achieved via supercritical, freeze- and ambient conditions drying, while retaining the original gel morphology in this system for most methods except freeze drying and ambient conditions drying from acetone.Schematic of a phase diagram (left) describing drying methods for solvogels by sublimation, evaporation or supercritical drying of the solvent. The results of those methods on the final aerogels are compared for the system of indium oxide aerogels loaded with platinum nanoparticles.

Steam reforming of bio-alcohols over Ni-M (Cu, Co, Pt)/MCF-S (MgO, La2O3, CeO2) for renewable and selective hydrogen production: Synergistic effect of MCF silica and basic oxides on activity and stability profiles

In the current investigation, highly active, and stable catalyst-support systems were developed by employing the benefits of the 3D mesoporous arrangement of MCF silica and O2− Lewis basic sites of MgO, La2O3, and CeO2 in a single system for renewable and selective H2 production via steam reforming (SR) of bio-alcohols, viz., ethanol (SRE), glycerol (SRG), n-butanol (SRB), and ethylene glycol (SREG). The impact of aging time [24, 48, and 72 h ] on structural and surface features of MCF silica was also investigated to develop novel type of mesoporous materials with the best textural properties, viz., Cu-Ni-Co/MCF-MgO for SRE, Ni-Cu/MCF-La2O3 for SRG, Pt-Ni-Cu/MCF-La2O3 for SRB and Ni-Cu/MCF-CeO2 for SREG which were characterized by several physio-chemical techniques; for instance, BET, H2-TPD, H2-TPR, TGA, XRD, TEM, SEM, EDX as well as high-resolution XPS analysis. The efficacy of the combination of MCF silica with basic metal oxides was evident from the results showing nearly complete reactant conversion, no coke formation, high selectivity (>84 % H2 yield), and long-term stability beyond 680 h (> 68 h time on stream (TOS) for one cycle over > 10 cycles) for all bio-alcohols whereas MCF silica without any basic metal oxides, i.e. Ni-Cu/MCF was stable only up to ≤ 64 h (≤ 16 h TOS for one cycle up to ≤ 4 cycles) due to the absence of O2− Lewis basic sites leading to coking. Such a huge difference in catalytic stability between MCF-S (MgO, La2O3, CeO2) and Ni-Cu/MCF catalysts clearly justifies the synergistic effect of the 3D mesoporous structure of MCF silica and O2− Lewis basic sites on high metal dispersion, strong metal-support interaction (SMSI), coke inhibition. It proved their efficacy as potential commercial SR catalysts for sustainable H2 production from bio-alcohols. Finally, catalytic reaction mechanisms were developed for SRE, SRG, SRB, SREG and intrinsic reaction kinetics were studied over their corresponding catalyst-support systems in the absence of external mass transfer and intra-particle diffusion resistancs. The apparent activation energies for SRE, SRG, SRB, and SREG were calculated as 7.2, 11.2, 10.5, and 12.1 kcal/mol, respectively.

Optimized Ni/Al2O3–SiO2 Catalyst for Steam Reforming of Phenol with Enhanced Hydrogen Production and Stability

Abstract Well-designed Ni/Al2O3–SiO2 catalysts synthesized with nickel as the active metal and alumina–silica as the catalyst mixture support were investigated for steam reforming of phenol with enhanced hydrogen production and stability. The prepared catalysts were characterized using x-ray diffraction, field emission scanning electron microscopy, Brunauer–Emmett–Teller (BET), Fourier transform infrared, hydrogen temperature-programmed reduction, pyridine diffuse reflectance infrared Fourier transform spectroscopy (Py-IR), and thermal gravimetric-differential scanning calorimetry (TG-DSC) techniques in detail. The BET results show that their specific surface areas ranged from 29.832 to 220.330 m2·g–1. The Py-IR results indicate the existence of large Lewis acid regions in the pure C-Ni (“C-Nix-Siy” means the Ni/Al2O3-to-SiO2 catalyst prepared with Ni(CH3COO)2 · 4H2O with SiO2 support mass ratios of y/(x + y).) and C-Ni4-Si1. The effects of the Ni/Al2O3-to-SiO2 mass ratio, reaction temperature, and active metal salt anion species on catalytic activity were studied. The results show that the C-Ni4-Si1 catalyst using nickel acetate tetrahydrate as the active metal salt with an SiO2 mass ratio of 20 wt% achieves a maximum phenol conversion of 97.3 % and hydrogen production of 92.7 % at 550°C. The stability of C-Ni4-Si1 was further investigated, and it was shown to react continuously and stably for more than 800 min at 550°C with excellent catalytic reaction stability. A final weight loss of only 9.31 % shown in the TG-DSC result of the spent C-Ni4-Si1 catalyst confirmed the excellent thermal stability and low coking rate of C-Ni4-Si1.

Sustained release catalysis: Dynamic copper releasing from stoichiometric spinel CuAl2O4 during methanol steam reforming

Dynamic copper releasing from a stoichiometric CuAl2O4 catalyst in methanol steam reforming (MSR) is investigated via detailed characterizations of six samples that are collected after testing for different time (TOS). It reveals that Cu can be liberated from spinel structure under the MSR conditions, serving as the active species. The Cu releasing rate increases first and then decreases with TOS, and the released Cu atoms agglomerate into nano entities. Consequently, the number of these Cu nanoparticles increases quasi-linearly with TOS, suggesting at least part of newly released Cu do not coalesce with the former nanoparticles but form new entities anchored on the surfaces of remnant defective Cu-Al spinel, which retains a small portion of Cu2+ (5.8%) in spinel lattice even at a prolonged TOS of 300 h. The findings evidence the dynamic changes of both active Cu metal and local surface structures, which are essentially different from conventional catalysis.