Hydrogen production by biomass gasification in supercritical water with bimetallic Ni-M/γAl2O3 catalysts (M = Cu, Co and Sn)

Supercritical water gasification (SCWG) of wet biomass is a very promising technology for hydrogen energy and the utilization of biomass resources. Ni-based catalysts are effective in catalyzing SCWG of original biomass and organic compounds for hydrogen production. In this paper, hydrogen production by SCWG of glucose over alumina-supported nickel catalysts modified with Cu, Co and Sn was studied. The bimetallic Ni-M (M = Cu, Co and Sn) catalysts were prepared by a co-impregnation method and tested in an autoclave reactor at 673 K with a feedstock concentration of 9.09 wt.%. XRD, XRF, N₂ adsorption/desorption, SEM and TGA were adopted to investigate the changes of chemical properties between Ni and Ni-M catalysts and the deactivation mechanism of catalysts. According to the experimental results, the hydrogen yield followed this order: Ni-Cu/γAl₂O₃ > Ni/γAl₂O₃ > Ni-Co/γAl₂O₃ > Ni-Sn/γAl₂O₃. The results show that Cu could improve the catalytic activity of Ni catalyst in reforming reaction of methane to produce hydrogen in SCWG. In addition, Cu can mitigate the sintering of alumina detected by SEM. Co was found to be an excellent promoter of Ni-based catalyst in relation to hydrogen selectivity.     

Comparison of hydrogen consumption behavior of chromium and manganese promoted copper-based catalysts

CuO/ZnO/Al₂O₃/MgO–Cr and -Mn catalysts are synthesized using nitrate route via co-precipitation method. The precursors are characterized by XRD. The decomposition behavior of the precursors is analyzed by Air-TGA. The catalysts calcined at 250, 300, 350 and 450 °C are characterized by XRD and BET. CuO particle size reduction and surface area of the catalysts are investigated. Increasing the calcination temperature from 350 °C to 450 °C crystallite size increases about 3 nm, and BET surface area decreases about 30 m²/g. The reduction characteristics of the catalysts are analyzed via TPR and H₂-TGA, and H₂ consumption values of Cr and Mn containing catalysts is found as 40% and 60%, respectively. Peak temperatures of Mn containing catalysts (290–325 °C) are lower than peak temperatures of Cr containing catalysts (300–360 °C) as confirmed by H₂-TGA and H₂-DTG. The optimum H₂ consumption value of 52% is obtained with CuO/ZnO/Al₂O₃/MgO–Mn catalyst calcined at 350 °C.     

Hydrogen-rich syngas production by catalytic cracking of tar in wastewater under supercritical condition

This paper presents the results from experimental study of syngas production by catalytic cracking of tar in wastewater under supercritical condition. Ni/Al₂O₃ catalysts were prepared via the ultrasonic assisted incipient wetness impregnation on activated alumina, and calcined at 600 °C for 4 h. All catalysts showed mesoporous structure with specific surface area in a range of 146.6–215.3 m²/g. The effect of Ni loading (5–30 wt%), reaction temperature (400–500 °C), and tar concentration (0.5–7 wt%) were systematically investigated. The overall reaction efficiency and the gas yields, especially for H₂, were significantly enhanced with an addition of Ni/Al₂O₃ catalysts. With 20%Ni/Al₂O₃, the H₂ yield increased by 146% compared to the non-catalytic experiment. It is noteworthy that the reaction at 450 °C with the addition of 20%Ni/Al₂O₃ had a comparable efficiency to the reaction without catalyst at 500 °C. The maximum H₂ yield of 46.8 mol/kg_tar was achieved with 20%Ni/Al₂O₃ at 500 °C and 0.5 wt% tar concentration. The catalytic performance of the catalysts gradually decreased as the reuse cycle increased, and could be recovered to 88% of the fresh catalyst after regeneration. 20%Ni/Al₂O₃ has a potential to improve H₂ production, as well as a good reusability. Thus, it is considered a promising catalyst for energy conversion of tar in wastewater.     

Behavior of nickel catalysts in supercritical water gasification of glucose: Influence of support

The catalytic performance of Ni-based supercritical water gasification (SCWG) catalysts may be influenced strongly by the nature of support. In this paper, Ni catalysts with the different supports (CeO₂/Al₂O₃, La₂O₃/Al₂O₃, MgO/Al₂O₃, ZrO₂/Al₂O₃) were prepared by two-step impregnation method. The fresh and used catalysts were characterized by X-ray diffraction patterns (XRD), scanning electron microscopy with an Energy Dispersive X-ray (SEM-EDX), Brunauer–Emmett–Teller (BET) specific surface area measurements, X-ray photoelectron spectroscopy (XPS) and Thermo-gravimetric analyses (TGA). The catalyst performance testing was conducted by SCWG of glucose at 673 K and 23.5 MPa with an autoclave reactor, to evaluate the influence of support on the hydrogen production. The results showed that H₂ yield for different supports decreased in order: CeO₂/Al₂O₃ > La₂O₃/Al₂O₃ > MgO/Al₂O₃ > Al₂O₃ > ZrO₂/Al₂O₃, and H₂ selectivity decreased in order: CeO₂/Al₂O₃ > La₂O₃/Al₂O₃ > ZrO₂/Al₂O₃ > Al₂O₃ > MgO/Al₂O₃. Ni catalysts were deactivated in SCWG reaction because of sintering and coke deposition. Compared with other supports, CeO₂ can be used as the promoter of carbon removal from catalyst surfaces.     

Copper promoted Co/MgO: A stable and efficient catalyst for glycerol steam reforming

Different types of cobalt-based mixed oxide catalysts (20 wt%Co/MgO, 5 wt%Cu-20 wt% Co/MgO, 20 wt%Co/50%MgO–50%Al₂O₃) were synthesized by the co-precipitation method and applied for hydrogen production from glycerol steam reforming. The catalysts were characterized using X-ray diffraction (XRD), H₂-Temperature-programmed reduction (H₂-TPR), CO₂-Temperature Programmed desorption, CO-Chemisorption, and CHN techniques. The H₂-TPR analysis showed the reducibility of cobalt-oxide (5Cu20CM; 5 wt%Cu-20 wt% Co/MgO) was enhanced by the copper, and reduction profiles of cobalt oxide shifted to a lower temperature (<450 °C). Among the catalysts, 5Cu20CM showed a maximum yield of hydrogen (74.6%) with 100% conversion of glycerol to the gaseous phase. The superior catalytic performance of 5Cu20CM for glycerol conversion was attributed to the smaller particle size (7 nm), higher dispersion of cobalt (35.0%), and the higher surface area (56 m²/g) of cobalt metal. Furthermore, Raman spectroscopy of the spent catalysts confirmed that the copper promoted cobalt-magnesium catalyst suppressed the carbon formation, consequently, 5Cu20CM catalyst showed a stable performance up to 30 h.     

Hydrogen production from glycerol dry reforming over Ag-promoted Ni/Al2O3

In recent times, glycerol has been employed as feedstock for the production of syngas (H₂ and CO) with H₂ as its main constituent. This study centers on dry reforming of glycerol over Ag-promoted Ni/Al₂O₃ catalysts. Prior to characterization, the catalysts were synthesized using the wet impregnation method. The reforming process was carried out using a fixed bed reactor at reactor operating conditions; 873–1173 K, carbon dioxide to glycerol ratio of 0.5 and gas hourly space velocity (WHSV) in the range of 14.4 ≤ 72 L g_cat⁻¹ h⁻¹). Ag (3)-Ni/Al₂O₃ gave highest glycerol conversion and hydrogen yield of 40.7% and 32%, respectively. The optimum conditions which gave highest H₂ production, minimized methane production and carbon deposition were reaction temperature of 1073 K and carbon dioxide to glycerol ratio of 1:1. This result can attributed to the small metal crystallite size characteristics possessed by Ag (3)–Ni/Al₂O₃, which enhanced metal dispersion in the catalyst matrix. Characterization of the spent catalyst revealed the formation of two types of carbon species; encapsulating and filamentous carbon which can be oxidized by O₂.     

Characterization and activity test of commercial Ni/Al2O3, Cu/ZnO/Al2O3 and prepared Ni–Cu/Al2O3 catalysts for hydrogen production from methane and methanol fuels

In this study, methane and methanol steam reforming reactions over commercial Ni/Al₂O₃, commercial Cu/ZnO/Al₂O₃ and prepared Ni–Cu/Al₂O₃ catalysts were investigated. Methane and methanol steam reforming reactions catalysts were characterized using various techniques. The results of characterization showed that Cu particles increase the active particle size of Ni (19.3 nm) in Ni–Cu/Al₂O₃ catalyst with respect to the commercial Ni/Al₂O₃ (17.9). On the other hand, Ni improves Cu dispersion in the same catalyst (1.74%) in comparison with commercial Cu/ZnO/Al₂O₃ (0.21%). A comprehensive comparison between these two fuels is established in terms of reaction conditions, fuel conversion, H₂ selectivity, CO₂ and CO selectivity. The prepared catalyst showed low selectivity for CO in both fuels and it was more selective to H₂, with H₂ selectivities of 99% in methane and 89% in methanol reforming reactions. A significant objective is to develop catalysts which can operate at lower temperatures and resist deactivation. Methanol steam reforming is carried out at a much lower temperature than methane steam reforming in prepared and commercial catalyst (275–325 °C). However, methane steam reforming can be carried out at a relatively low temperature on Ni–Cu catalyst (600–650 °C) and at higher temperature in commercial methane reforming catalyst (700–800 °C). Commercial Ni/Al₂O₃ catalyst resulted in high coke formation (28.3% loss in mass) compared to prepared Ni–Cu/Al₂O₃ (8.9%) and commercial Cu/ZnO/Al₂O₃ catalysts (3.5%).     

Underwater vehicle hydrogen production from methanol steam reforming using hydrogen peroxide

Methanol steam reforming (MSR) can supply hydrogen (H₂) to underwater vehicles equipped with a fuel cell. Low reaction temperatures ensure the composition of the reformed gas suitable for the H₂ purification unit and increase the design freedom of a reforming plant. However, such temperatures decrease the catalyst activity and thereby the methanol (MeOH) conversion and H₂ production. Herein, hydrogen peroxide (H₂O₂) was supplied with MeOH and water (H₂O) to ensure sufficient MeOH conversion and H₂ production at low temperatures. A tube reactor loaded with a commercial Cu/Zn catalyst was installed in an electric furnace maintained at 200–250 °C, and MeOH and 0 wt%, 11.88 wt%, 22.51 wt%, and 32.07 wt% H₂O₂ were supplied. When the furnace temperature was 200 °C, the MeOH conversion was 49.3% at 0 wt% H₂O₂ but 93.5% at 32.07 wt% H₂O₂. The effect of adding H₂O₂ was greater under the temperature conditions where the MeOH conversion was 100% or less. To analyze the effect of H₂O₂ addition on catalyst durability, the furnace was maintained at 200 °C, and the reactor was continuously operated for 110 h with 0 wt% and 32.07 wt% H₂O₂. The addition of H₂O₂ did not significantly decrease the Cu/Zn catalyst durability.     

Experimental optimization analysis on operating conditions of CO removal process from hydrogen-rich reformate

The catalytic effects of CO preferential oxidation and methanation catalysts for deep CO removal under different operating conditions (temperature, space velocity, water content, etc.) are systematically studied from the aspects of CO content, CO selectivity, and hydrogen loss index. Results indicate that the 3 wt% Ru/Al₂O₃ preferential oxidation catalysts reduce CO content to below 10 ppm with a high hydrogen consumption of 11.6–15.7%. And methanation catalysts with 0.7 wt% Ru/Al₂O₃ also exhibit excellent CO removal performance at 220–240 °C without hydrogen loss. Besides, NiCl_x/CeO₂ methanation catalysts possess the characteristics of high space velocity, high activity, and high water-gas resistance, and can maintain the CO content at close to 20 ppm. Based on these experimental results, the coupling scheme of combining NiCl_x/CeO₂ methanation catalysts (low cost and high reaction space velocity) with 0.7 wt% Ru/Al₂O₃ methanation catalysts (high activity) to reduce CO content to below10 ppm is proposed.     

Methane thermocatalytic decomposition to COx-free hydrogen and carbon nanomaterials over Ni–Mn–Ru/Al2O3 catalysts

Thermocatalytic decomposition of methane is proposed to be an economical and green method to produce CO_x-free hydrogen and carbon nanomaterials. In this work, the catalytic performance of Ni–Mn–Ru/Al₂O₃ catalyst under different reaction parameters (such as, pre-reduction temperature, reaction temperature, space velocity, etc.) were investigated to obtain optimum reaction conditions. The catalysts were characterized by N₂ adsorption/desorption, X-ray diffraction, inductively coupled plasma optical emission spectrometer and hydrogen temperature programmed reduction. For the 60 wt% Ni-5 wt% Mn-10 wt% Ru/Al₂O₃ catalyst using Ru(NO)(NO₃)_x(OH)_y(x + y = 3) as Ru precursor, the methane conversion rate obtained is high as 93.76% under optimum reaction conditions (reduction at 700 °C for 1 h, reaction at 750 °C, GSHV = 36,000 mL/g_cat h). Carbon nanomaterials formed during the process of methane thermocatalytic decomposition were characterized by scanning electron microscopy, thermal gravimetric analyzer and Raman spectroscopy. Carbon nanofibers were formed over all the Ni–Mn–Ru/Al₂O₃ catalysts.     

Hydrogen production through autothermal reforming of CH4: Efficiency and action mode of noble (M = Pt,Pd) and non-noble (M = Re,Mo, Sn) metal additives in the composition of Ni-M/Ce0.5Zr0.5O2/Al2O3 catalysts

Hydrogen production through autothermal reforming of methane (ATR of CH₄) over promoted Ni catalysts was studied. The control of the ability to self-activation and activity of Ni-M/Ce_0.5Zr_0.5O₂/Al₂O₃ catalysts was achieved by tuning their reducibility through the application of different types (M = Pt, Pd, Re, Mo or Sn) and content (molar ratio M/Ni = 0.003, 0.01 or 0.03) of additive. The comparison of the efficiency and action mode of noble (M = Pt, Pd) and non-noble (M = Re, Mo, Sn) metal additives in the composition of Ni-M/Ce_0.5Zr_0.5O₂/Al₂O₃ catalysts was performed using X-ray fluorescence analysis, N₂ adsorption, X-ray diffraction, high-resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction with hydrogen, and thermal analysis. The composition-characteristics-activity correlations were determined. It was shown that the introduction of a promoter does not affect the textural and structural properties of catalysts but influences their reducibility and performance in ATR of CH₄. At the similar dispersion of NiO active component (11 ± 2 nm), the Ni²⁺ reduction is intensified in the following order of additives: Mo < Sn < Re ≤ Pd < Pt. It was found that for the activation of Ni and Ni–Sn catalysts before ATR of CH₄ tests, the pre-reduction is required. On the contrary, the introduction of Pt, Pd and Re additives leads to the self-activation of catalysts under the reaction conditions and an increase of the H₂ yield due to the enhanced reducibility of Ni²⁺. The efficient and stable catalyst for hydrogen production has been developed: in ATR of CH₄ at 850 °C over an optimum 10Ni-0.9Re/Ce_0.5Zr_0.5O₂/Al₂O₃ catalyst the H₂ yield of 70% is attained. The designed catalyst has enhanced stability against oxidation and sintering of Ni active component as well as high resistance to coking.     

Hydrogen production by autothermal reforming of methane over NiPd catalysts: Effect of support composition and preparation mode

NiPd/Ce_0.5Zr_0.5O₂/Al₂O₃ and NiPd/La₂O₃/Ce_0.5Zr_0.5O₂/Al₂O₃ catalysts were prepared by incipient wetness co-impregnation method or sequential impregnation method for autothermal reforming of methane (ATR of CH₄). The influence of the preparation mode, Ce_0.5Zr_0.5O₂ and La₂O₃ additives on the physicochemical properties of NiPd supported catalysts and the effect on their activity to produce hydrogen by ATR of CH₄ were investigated. Characterization of fresh and spent Ni-based catalysts by X-ray fluorescence spectroscopy, N₂ adsorption, X-ray diffraction, H₂ temperature-programmed reduction, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were performed. It was demonstrated that support composition determines NiO dispersion as well as reducibility of Ni species through different strength of Ni-support interaction. The preparation method modifies the phase composition and catalyst ability for reduction. The catalyst evolution under reaction conditions was studied. The NiO (∼15 nm) and NiPd alloy (∼18 nm) phases were observed in the spent catalysts. It was found that the Ni^o/NiO ratio can be regulated by support composition and preparation mode of catalysts. It is demonstrated that studied catalysts provide high methane conversion of 90–100%, CO yield of 55–85% and H₂ yield of 55–75% in ATR of CH₄ at 750–950 °C. The optimal composition and preparation method of catalyst were selected. The best ATR of CH₄ performance is provided by 10 Ni_0.5Pd/10Ce_0.5Zr_0.5O₂/Al₂O₃ catalyst prepared by Pd/Ni sequential impregnation method that can be associated with peculiarity of NiPd particles structure and the optimal ratio between NiO species with different ability for reduction.     

Improved hydrogen production performance of Ni–Al2O3/CaO–CaZrO3 composite catalyst for CO2 sorption enhanced CH4/H2O reforming

Bifunctional composite catalysts are very intrigued to produce hydrogen via CO₂ sorption enhanced CH₄/H₂O reforming. However, their hydrogen production performance declined over multiple cycles, owing to the structure collapse and the sintering of active component under high-temperature regeneration. This work reported the facile synthesis of long-lasting Ni–Al₂O₃/CaO–CaZrO₃ composite catalysts with less inert components (36 wt%) for stable hydrogen production over the multiple cycles of CO₂ sorption enhanced CH₄/H₂O reforming. The effects of reaction and regeneration temperature on the hydrogen production performance of Ni–Al₂O₃/CaO–CaZrO₃ were explored. Ni–Al₂O₃/CaO–CaZrO₃ demonstrated high activity and stability while fixing reaction temperature as 600 °C and regeneration temperature as 750 °C. Of particular importance, H₂ concentration was 98 vol% even after 10 hydrogen production cycles due to the inert component CaZrO₃ having a cross-linked structure. The distribution of CaZrO₃ in the composite as a coral-like structure inhibited the sintering of CaO through high Taman temperature and physical separation. Moreover, it provided the skeleton support and pore volume for the repeated expansion and contraction process of CaO to CaCO₃ during the cycling process. Finally, the sintering of Ni slowed down in appropriate regeneration temperature to maintain the structure of the composite catalyst, which further improved the catalyst's stability over multiple cycles.     

Hydrogen production by biomass gasification in supercritical water over Ni/γAl2O3 and Ni/CeO2-γAl2O3 catalysts

Hydrogen production by supercritical water gasification (SCWG) is a promising technology for wet biomass utilization. Ni catalyst can realize the high gasification efficiency of biomass near the critical temperature of water. In this paper, Ni/γAl₂O₃ and Ni/CeO₂-γAl₂O₃ catalysts were prepared by an impregnation method. The catalyst performance for glucose gasification in supercritical water was tested in autoclave reactor. All experiments were carried out in the autoclave at 673 K, 24.5 MPa, and the concentration of glucose was 9.09 wt.%. The catalysts before and after reaction were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET specific surface area measurements, X-ray fluorescence spectrum (XRF) and Thermo-gravimetric analyses (TGA) in order to investigate on the chemical property and catalytic mechanism. The experimental results showed that hydrogen yield and hydrogen selectivity increased sharply with addition of Ni/γAl₂O₃ and Ni/CeO₂-γAl₂O₃ catalysts. The catalytic activity and H₂ selectivity of Ni/CeO₂-γAl₂O₃ was higher than that of Ni/γ-Al₂O₃ catalyst. The results revealed that carbon deposition and coking led to the deactivation of the catalysts. Ce in the Ni/CeO₂-γAl₂O₃ catalyst had a certain role in the inhibition of carbon deposition and coking.     

Oxidative steam reforming of ethanol over Rh based catalysts in a micro-channel reactor

Oxidative steam reforming of ethanol (OSRE) was studied over Rh/CeO₂/Al₂O₃ catalysts in a micro-channel reactor. First, the catalyst support, Al₂O₃, was deposited on to the metallic substrate by washcoating and then the CeO₂ and active metal were sequentially impregnated. The effect of support composition as well as active metal composition on oxidative steam reforming of ethanol in a micro-channel reactor was studied at atmospheric pressure, with water to ethanol molar ratio of 6 and oxygen to ethanol molar ratio ranging from 0.5 to 1.5, over a temperature range of 350-550 °C. Ceria added to 1%Rh/Al₂O₃ showed higher activity and selectivity than 1%Rh/Al₂O₃ alone. Out of the various catalysts tested, 2%Rh/20%CeO₂/Al₂O₃ performed well in terms of activity, selectivity and stability. The OSRE performance was compared with that of SRE over 2%Rh/20%CeO₂/Al₂O₃ catalyst at identical operating conditions. Compared to SRE, the activity in OSRE was higher; however the selectivity to desired products was slightly lower. The H₂ yield obtained in OSRE was ∼112 m³ kg⁻¹ h⁻¹, as compared to ∼128 m³ kg⁻¹ h⁻¹ in SRE. The stability test performed on 2%Rh/20%CeO₂/Al₂O₃ at 500 °C for OSRE showed that the catalyst was stable for ∼40 h and then started to deactivate slowly. The comparison between packed bed reactor and micro-channel reactor showed that the micro-channel reactor can be used for OSRE to produce hydrogen without any diffusional effects in the catalyst layer.     

Synthesis and regeneration of mesoporous Ni–Cu/Al2O4 catalyst in sub-kilogram-scale for methanol steam reforming reaction

A green template-free method is proposed for the synthesis of mesoporous Ni–Cu/Al₂O₄ catalyst in sub-kilogram scale. In the convenient synthetic method, an intermediate is formed via electrostatic forces and hydrogen bonding interactions between the aluminate ions and the metal ions and/or metal hydroxides under suitable pH conditions. The desired Ni–Cu/Al₂O₄ composites, with Ni/Cu molar ratios of 10%, 20% and 30% of Cu at Cu/Al molar ratio of 10.0%, respectively, are then obtained from calcination. The nitrogen adsorption-desorption isotherms show that the Ni–Cu/Al₂O₄ composites have specific surface areas of 136–170 m²g^-1. The Ni–Cu/Al₂O₄ products are used as catalyst materials in the methanol steam reforming (MSR) of hydrogen and are shown to have a high conversion efficiency (>99%), a low methane concentration, good stability, and a high hydrogen yield (H₂/methanol molar ratio ≈ 3.0) at low reaction temperatures in the range of 200–300 °C. In addition, the coke formation on the catalyst surface is less than 1.0 wt% even after a reaction time of 30 h. Notably, the Ni–Cu/Al₂O₄ catalyst can be regenerated by calcination at 800 °C and retains a high methanol conversion efficiency of close to >99% when reused in MSR.     

Optimization for hydrogen production from methanol partial oxidation over Ni–Cu/Al2O3 catalyst under sprays

In this work, a novel Ni–Cu/Al₂O₃ catalyst is used to trigger the partial oxidation of methanol (POM) for hydrogen production. This reaction system also employed ultrasonic sprays to aid in dispersing methanol fuel. The prepared catalyst is analyzed by scanning electron microscope (SEM), energy-dispersive X-ray (EDX) spectroscopy, and X-ray diffraction (XRD) to explore the catalyst's surface structure, elemental composition, and physical structure, respectively. The Box-Behnken design (BBD) of response surface methodology (RSM) is utilized for experimental design to achieve process optimization. The operating parameters comprise the O₂/C molar ratio (0.5–0.7), preheating temperature (150–250 °C), and weight percent (wt%) of Ni (10–30%) in the catalyst. The results show that methanol conversion is 100% in all the operating conditions, while the reaction temperature for H₂ production ranges from 160 to 750 °C, stemming from heat released by POM. The significance and suitability of operating conditions are also analyzed by analysis of variance (ANOVA). It indicates that the highest H₂ yield is 2 mol (mol CH₃OH)^?1, occurring at O₂/C = 0.5, preheating temperature = 150 °C, and Ni wt% = 10. Compared with the commercial h-BN-Pt/Al₂O₃ catalyst, the prepared Ni–Cu/Al₂O₃ catalysts have higher activity for H₂ production. The O₂/C ratio is the most influential factor in the H₂ yield. Moreover, the interaction of the O₂/C ratio and Ni content is sound, reflecting that changing Ni content in the catalyst will affect the trend of H₂ yield under each O₂/C.     

High H2 selectivity with low coke formation for methanol steam reforming over Cu/Y1.5Ce0.84Ru0.04O4 catalyst in a microchannel plate reactor

The synthesized novel metal oxides Y_xCe_yRu_zO₄ (x = 1.5, y = 0.84, z = 0.04) which was produced by the sol-gel method was used as a support for Cu active metal on the surface of a microchannel plate reactor in the methanol steam reforming (MSR) process. The prepared catalysts were characterized by X-ray powder diffraction (XRD), BET surface area analysis (S_BET), energy-dispersive X-ray analysis (EDX), field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), temperature-programmed desorption (NH₃-TPD), and temperature-programmed reduction (H₂-TPR). High methanol conversion (99.5%) and H₂ selectivity (98.7%) and low CO selectivity (1.4%) were achieved for Cu/Y_xCe_yRu_zO₄ coated microchannel reactor at 250 °C. FE-SEM images and TGA curve of the spent catalyst displayed no coke formation on the surface of the catalyst after 32 h on stream at 300 °C. The low reduction temperature of Cu, high BET surface area, and high pore volume of the catalyst are considered imperative factors that cause a better dispersion of copper on the Y_1.5Ce_0.84Ru_0.04O₄ support.     

Cu substituted ZnAl2O4 ex-LDH catalysts for medium-temperature WGS – effect of Cu/Zn ratio and thermal treatment on catalyst efficiency

The effect of Cu/Zn ratio of ex-LDH oxide-based catalysts for medium–temperature water–gas shift reaction (MT–WGS) was investigated. A series of CuZnAl–LDH precursors with different Cu/Zn molar ratio were synthesized by co-precipitation and oxide (Zn,Cu)_xAl₂O₄ catalysts were prepared via subsequent calcinations at 380 °C or 700 °C. The prepared materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), thermogravimetry with evolved gas analysis (TG/DTG/EGA), N₂ adsorption, N₂O chemisorption and temperature-programmed reduction (H₂-TPR). MT-WGS activity evaluation was carried out on the basis of measurements made in a differential reactor in kinetic regime. Catalysts’ properties were investigated and effect of composition (Cu/Zn molar ratio) and the calcination temperature of CuZnAl-LDH precursors on structural transformation, active surface area and MT-WGS rate constant was shown. The highest activity of (Zn,Cu)_xAl₂O₄ catalyst with Cu/Zn molar ratio of 1.5 calcined at mild conditions was attributed to easy reducible and accessible Cu surface.     

Effect of metal additives on the catalytic performance of Ni/Al2O3 catalyst in thermocatalytic decomposition of methane

Thermocatalytic decomposition of methane is proposed to be an economical and green method to produce CO_x-free hydrogen and carbon nanomaterial. In present work, 60 wt% Ni/Al₂O₃ catalysts with different additives (Cu, Mn, Pd, Co, Zn, Fe, Mg) were prepared by co-impregnation method to investigate promotional effects of these metal additives on the activity and stability of 60 wt% Ni/Al₂O₃ and find out a really effective promoter for decomposition of methane. The catalyst was characterized by N₂ adsorption/desorption, X-ray diffraction, scanning electron microscopy, inductively coupled plasma optical emission spectrometer and hydrogen temperature programmed reduction. While metal additives (5 wt%) were added into 60 wt% Ni/Al₂O₃, the activity stability of 60 wt% Ni/Al₂O₃ was improved and the CH₄ conversion of 60 wt% Ni/Al₂O₃ was also improved except Zn addition. Mn addition was found to improve the catalytic activity of 60 wt% Ni/Al₂O₃ significantly and the CH₄ conversion of 5 wt% Mn-60 wt% Ni/Al₂O₃ was ∼80%. Cu addition was found to remarkably improve the catalytic stability of 60 wt% Ni/Al₂O₃ and the CH₄ conversion of 5 wt% Cu-60 wt% Ni/Al₂O₃ decreased from 61% to 45% after 250 min of reaction time. Carbon nanomaterials formed in the thermocatalytic decomposition process were characterized by X-ray diffraction, scanning electron microscopy, thermal gravimetric analyzer and Raman spectroscopy. Carbon deposits consist of amorphous carbon and carbon nanofibers.