Improved charge transfer and morphology on Ti-modified Cu/γ-Al2O3/Al catalyst enhance the activity for methanol steam reforming

The metal-oxide interaction has been considered as an effective factor for catalytic performance in methanol steam reforming. In this work, Ti modified Cu/γ-Al₂O₃/Al catalyst was prepared by anodization technology. It is found that the addition of Ti can largely increase the surface area of the carrier and thus improve the dispersion of copper. The co-existence of Ti⁴⁺ and Ti³⁺ makes the charge transfer between Cu and Ti easier, which improves the redox performance of copper. The DFT calculations reveal that Ti also enhance the adsorption capacity of water and methanol on the surface of the catalysts. Besides, Ti also reduce the acid density on the carrier, inhibit methanol dehydration reaction and thereby reduce the selectivity of the DME. The optimal catalyst CuTi_1.9/γ-Al₂O₃/Al achieves nearly 100% conversion at 275 °C, while the methanol conversion of Cu/γ-Al₂O₃/Al is 82%. And the H₂ output of CuTi_1.9/γ-Al₂O₃/Al reached 69.17 mol/(kg_cat·h) at 300 °C.     

Cu supported on ZnAl-LDHs precursor prepared by in-situ synthesis method on γ-Al2O3 as catalytic material with high catalytic activity for methanol steam reforming

A novel catalyst precursor ZnAl-LDHs/γ-Al₂O₃ was prepared by in-situ synthesis method, and the copper was supported on calcined hydrotalcite catalyst precursor by wet impregnation. The correlation between the structure and the catalytic activity for methanol steam reforming was studied by XRD, SEM, TPR, chemisorption N₂O, IR and N₂ adsorption techniques. The results showed that the ZnAl-LDHs was successfully synthesized by in-situ synthesis method on γ-Al₂O₃ and the copper mass fraction had a great effect on the interactions between support and copper species. Furthermore, the catalyst reducibility and copper surface area evidently influenced catalytic activity for methanol steam reforming. The 10% Cu/γ-Al@MMO exhibited the best catalytic activity, that was, the methanol conversion was 99.98% and the CO concentration was only 0.92% at 300 °C in hydrogen production by methanol steam reforming.     

Hydrogen production from dimethyl ether over Cu/γ-Al2O3 catalyst with zeolites and its effects in the lean NOx trap performance

The purpose of this study is to investigate the effects of mixing three kinds of zeolites (MFI, MOR, and BEA) with the dimethyl ether steam reforming(DME-SR) Cu/γ-Al₂O₃ catalyst to improve H₂ yield at low temperatures, and to identify the de-NOx performance of a combined system of SR catalyst and Lean NOx Trap(LNT). The SR catalyst was prepared by the impregnation method, and a commercialized LNT catalyst was used. The SR reaction experiment was conducted to investigate the effect of the coexistence of CO₂, O₂, NO, and NO₂ among the exhaust gases of the DME engine on the H₂ yield. The study found that the proper mixing of Cu/γ-Al₂O₃ and zeolite increased the H₂ yield at low temperature improving DME hydrolysis. The variation in the H₂ yield according to the kinds of zeolite in the SR catalyst was due to the characteristics of zeolite. The Cu10/γ-Al₂O₃ catalyst mixed with 10% MOR showed the highest H₂ yield. A combined system of SR and LNT uses the H₂ generated mainly from the Cu-based catalyst using the DME-SR reaction for the LNT. When H₂ generated from the SR (Cu10/γ-Al₂O₃ + MOR10) catalyst was used as the reductant of LNT, the NOx conversion at 350 °C or below was improved up to 15% compared to when DME was used. This demonstrates that H₂ as the reductant of LNT is more beneficial than DME. The H₂ generated from the SR catalyst can be used as the reductant of LNT in an after-treatment system. Meanwhile, the SR catalyst that was mixed with zeolite caused the carbon deposition, but the combined system of SR + LNT caused no carbon deposition because the carbon deposited on the SR catalyst reacted with O₂ during the lean-operating period.     

Efficient hydrogen production by low-temperature steam reforming of propane using catalysts with very small amounts of Pt loaded on NiMn2O4 particles

The purpose of the present work is to unveil the effect of very small amounts of Pt loaded onto a NiMn₂O₄ spinel catalyst on the chemical characteristics and catalytic activity for low-temperature steam reforming (LTSR) of propane. In the H₂-TPR curves of the Pt-loaded catalysts, the reduction corresponding to Pt²⁺ → Pt⁰ occurred largely at approximately 200–350 °C. It is due to the high accumulation of hydrogen on the PtNi alloy. X-ray photoelectron spectroscopy measurements proved that the PtNi component acted as the active species. The catalysts with Pt loaded on 40NiMn₂O₄/60γ-Al₂O₃ show higher propane conversion due to the larger metal interface area created between Pt, Ni, and MnO. In particular, the 40Pt_0.025NiMn₂O₄/60γ-Al₂O₃ catalyst maintained a very low amount of carbon deposition, a stable propane conversion of 100% and a hydrogen production capacity of 60% at 450 °C, even after 100 h of LTSR.     

Thermochemical hydrogen production using Rh/CeO2/γ-Al2O3 catalyst by steam reforming of ethanol and water splitting in a packed bed reactor

This study is focused on investigating the dual performance of Rh/CeO₂/γ-Al₂O₃ catalyst for steam reforming of ethanol (SRE) and thermochemical water splitting (TCWS) using a packed bed reactor. The catalyst is designed to be thermally stable containing an active phase of Rh and the redox component of CeO₂ for oxygen exchange, supported on γ-Al₂O₃. The catalyst has been characterised by SEM, XRD, BET, TPR, TPD, XPS and TGA before testing in the reactor. The optimal temperature for SRE reaction over this catalyst is between 700 °C and 800 °C to produce high concentrations of hydrogen (~60%), and low CO and CH₄. The selectivity towards CO and CH₄ is higher at low temperatures and drops with rise in reaction temperature. Further, Rh/CeO₂/γ-Al₂O₃ is found to be active for TCWS at relatively low temperatures (≤1200 °C). At temperatures as low as 800 °C, this catalyst is especially found suitable for multiple redox cycles, producing a total of 48.9 mmol/g_cat in four redox cycles. The catalyst can be employed for large number of redox cycles when the reactor is operated at lower temperatures. Finally, the reaction pathways have been proposed for both SRE and TCWS on Rh/CeO₂/γ-Al₂O₃ catalyst.     

Hydrogen generation characteristics of reduced DME steam reforming catalysts according to heating methods

The purpose of this study is to investigate the hydrogen generation characteristics of H₂-reduced dimethyl ether (DME) steam reforming (SR) catalysts using different heating processes. The effects of the H₂ reduction temperature and space velocity were investigated to identify an optimal reaction environment. Both the resistive and induction heating methods were used. The catalysts were prepared by impregnating copper over a γ-Al₂O₃ support. The Cu/Al₂O₃ catalysts with different loading amounts of 5–15 wt% Cu exhibited different characteristics when subjected to hydrogen reduction. The variation in acidity had a dominant effect on the DME-SR activity, and 15Cu/Al₂O₃ that underwent hydrogen reduction treatment at 500 °C attained improved performance at low temperatures and low formation of by-products, allowing for the achievement of its highest H₂ concentration of 74.08% at 375 °C. The induction heating reactor had an energy consumption that was about 25% lower than that of the resistive heating reactor.     

Steam reforming of dimethyl ether over a novel anodic γ-Al2O3 supported copper bi-functional catalyst

A novel porous alumina monolithic material was prepared through the anodization technology, and its catalytic performance for hydrolysis of dimethyl ether (DME) was investigated. The anodic γ-Al₂O₃ exhibited higher catalytic activity due to its stronger acidity, better hydrophilicity and lower activation energy than the commercial γ-Al₂O₃ and also showed good stability in a 110 h test. Meanwhile, a series of Cu/anodic γ-Al₂O₃ catalysts were prepared by impregnation method, and the mechanism of Cu loading was studied. Furthermore, the effect of Cu loading and CuO crystallite size on the activity of catalyst for DME steam reforming was investigated. The experimental results show that the conversion of DME was related to both of the Cu loading and the CuO crystallite size, while the selectivity of CO was very sensitive to the latter. In addition, the synergetic effects of different catalysts on DME steam reforming reaction system were also discussed.     

Steam reforming of dimethyl ether over Cu–Ni/γ-Al2O3 bi-functional catalyst prepared by deposition–precipitation method

Cu–Ni/γ-Al₂O₃ catalysts with different metal contents for dimethyl ether steam reforming (DME SR) were prepared by the method of deposition–precipitation. Characterization of specific surface area measurement (BET), X-ray diffraction (XRD) and hydrogen temperature-programmed reduction (H₂-TPR) revealed that nickel improved the dispersion of copper, increased the interaction between copper and γ-Al₂O₃, and therefore, inhibited the sintering of copper. Ammonia temperature-programmed desorption (NH₃-TPD) showed that metal particles could occupy the acid sites, leading to the decrease in acid amount and acid strength of Cu–Ni/γ-Al₂O₃ catalyst. Kinetic measurements indicated that γ-Al₂O₃ is vital for DME SR and a higher content of γ-Al₂O₃ in catalyst was needed. The addition of nickel suppressed the water gas shift (WGS) reaction. Initial durability testing showed that the conversion of DME over Cu–Ni/γ-Al₂O₃ catalyst was always almost complete during the 30 h experimental reaction time. Therefore, Cu–Ni/γ-Al₂O₃ could be a potential DME SR catalyst for the production of hydrogen.     

Methanol steam reforming over PdZn/ZnAl2O4/Al2O3 in a catalytic membrane reactor: An experimental and modelling study

A catalytic membrane reactor equipped with Pd–Ag metallic membranes and loaded with PdZn/ZnAl₂O₄/Al₂O₃ catalytic pellets was tested for the methanol steam reforming reaction (S/C = 1) aimed at producing a pure hydrogen stream for PEM fuel cell feeding. The catalyst was prepared in two steps. First, commercial γ-Al₂O₃ pellets were impregnated with ZnCl₂ and calcined at 700 °C to obtain a ZnAl₂O₄ shell, and subsequently impregnated with PdCl₂ and reduced at 600 °C to obtain PdZn alloy nanoparticles. The catalyst was tested both in a conventional packed bed reactor and in a catalytic membrane reactor. A 3D CFD non-isothermal model with mass transfer limitations was developed and validated with experimental data. The reactions of methanol steam reforming, reverse water-gas shift and methanation were modeled under different pressure, temperature and feed load values. The model was used to study and simulate the CMR under different operation conditions.     

Hydrogen production from steam reforming of bioethanol using Cu/Ni/K/γ-Al2O3 catalysts. Effect of Ni

Hydrogen to be used as a raw material in fuel cells or even as a direct fuel can be obtained from steam reforming of bioethanol. The key aim of this process is to maximize hydrogen production, discouraging at the same time those reactions leading to undesirable products, such as methane, acetaldehyde, diethyl ether or acetic acid, that compete with H₂ for the hydrogen atoms. Cu–Ni–K/γ-Al₂O₃ catalysts are suitable for this reaction since they are able to produce acceptable amounts of hydrogen working at atmospheric pressure and a temperature of 300°C. The effect of nickel content in the catalyst on the steam-reforming reaction was analyzed. Nickel addition enhances ethanol gasification, increasing the gas yield and reducing acetaldehyde and acetic acid production.     

Catalytic steam reforming of biomass-derived acetic acid over modified Ni/γ-Al2O3 for sustainable hydrogen production

In order to obtain sustainable H₂, the catalytic steam reforming of acetic acid derived from biomass was performed by using the catalysts modified with basic promoters (Mg, La, Cu, and K). La and K increased the total basicity of Ni/γ-Al₂O₃ by 30.6% and 93.4%, respectively, which could induce ketonization, producing acetone. In contrast, Mg reduced the number of middle and strong basic sites by 17.2% and improved the number of weak basic sites by 5% for Ni/γ-Al₂O₃, which promoted the steam reforming of acetic acid (ca. 100% of H₂ and carbon selectivity at even 450 °C) without ketonization. Moreover, the amount of carbon deposited on Ni/Mg/γ-Al₂O₃ was 55.1% less than that deposited on Ni/γ-Al₂O₃. When Cu was employed, the conversion was ca. 60% with less than 70% of H₂ selectivity, at all temperatures considered herein.     

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.     

Hydrogen production from acetic acid steam reforming over nickel-based catalyst synthesized via MOF process

In our earlier work, we have reported that Ni supported on γ-Al₂O₃–La₂O₃–CeO₂ (ALC) catalyst prepared via metal organic framework (MOF) was more active for acetic acid steam reforming (AASR) [1]. Here we report detailed study on the performance of this catalyst for AASR. Effects of operating conditions such as temperatures (400–650 °C), steam to carbon molar ratio (S/C) and feed flow rate (1.5–5.5 mL/h) were evaluated and optimized. Results showed an excellent activity for AASR at the molar ratio S/C = 6.5, feed flow rate = 2.5 mL/h and, at 600 °C with almost total conversion and more than 90% of H₂ yield. The ordered porous structure of embedded nickel supported catalyst promotes excellent steam reforming activity and water gas shift reaction even at low temperatures, which leads to the good stable behaviour up to 36 h of TOS. The coke formation was also significantly suppressed by ALC support. Catalyst regenerated by passing oxygen at 500 °C and followed by reduction in hydrogen also show a good activity. Catalysts were characterized by DT-TGA, XRD, TEM, H₂-TPR and N₂-adsorption-desorption to understand the micro structure and coke deposition behaviour.     

Hydrogen production by steam reforming of dimethyl ether and CO-PrOx in a metal foam micro-reactor

A bi-function catalyst containing CuZnAlCr and HZSM-5 was used to generate hydrogen by stream reforming of dimethyl ether (SRD) in a metal foam micro-reactor and a fix-bed reactor. Dimethyl ether conversion of 99% and hydrogen yield of >95% was reached with HZSM-5/CuZnAlCr (mass ratio of 1:1) in the micro-reactor. A suitable balance between the dimethyl ether hydrolysis and methanol reforming steps requires the proper acidity and the metal sites. The CuZnAlCr/HZSM-5 properties, effect of CuZnAlCr to HZSM-5 mass ratio were investigated in the metal foam micro-reactor. Moreover, CO was removed from hydrogen-rich gas by preferential oxidation reaction (CO-PrOx) with PtFe/γ-Al₂O₃ catalyst in a similar metal foam micro-reactor follows the SRD stage. With the optimized O₂/CO ratio and reaction temperature, the CO concentration dropped to <10 ppm and hydrogen yield of ∼90% were achieved in the new-type SRD-COPrOx system. The SRD-COPrOx system provide a constant hydrogen production with CO concentration lower than 10 ppm during 20 h. The results indicate that metal foam micro-reactor has the great potential in the DME steam reforming to supply hydrogen for low-temperature fuel cells.     

Production of hydrogen from steam reforming of methanol carried out by self-combusted CuCr1-xFexO2 (x = 0–1) nanopowders catalyst

In this present work, the delafossite type CuCr_1-xFe_xO₂ (x = 0–1) nanopowder was prepared by a self-combusted glycine nitrate process used for the steam reforming of methanol (SRM). The effectiveness of hydrogen production was upgraded by the preparation of CuCr_1-xFe_xO₂ (x = 0–1). The prepared Cu based materials were characterized by field emission scanning electron microscope studies, X-ray diffraction studies, energy dispersive X-ray studies, and Brunauer-Emmett-Teller studies. The CuCr_1-xFe_xO₂ (x = 0–1) nanopowders were studies by the hydrogen production by methanol steam reforming reaction. The Cu based catalyst exhibited high catalytic activity and hydrogen production rate as 1740 ml/min g-cat at 360 °C. Furthermore, the catalyst nanopowder was stable up to 1200 min without any considerable changes in steam reforming methanol and product selectivity in the SRM process. The production rate of CuCr_1-xFe_xO₂ was improved by the adequate amount of iron incorporation (60%) and adjusted the feeding rate of methanol. These conditions obtain the best performance could reach the hydrogen production of 301.45 (μmol (min g-cat)⁻¹) at 350° over CuCr_0.4Fe_0.6O₂ with a flow rate of 60 sccm.     

Catalysts for hydrogen production in a multifuel processor by methanol,dimethyl ether and bioethanol steam reforming for fuel cell applications

Methanol, dimethyl ether and bioethanol steam reforming to hydrogen-rich gas were studied over CuO/CeO₂ and CuO–CeO₂/γ-Al₂O₃ catalysts. Both catalysts were found to provide complete conversion of methanol to hydrogen-rich gas at 300–350 °C. Complete conversion of dimethyl ether to hydrogen-rich gas occurred over CuO–CeO₂/γ-Al₂O₃ at 350–370 °C. Complete conversion of ethanol to hydrogen-rich gas occurred over CuO/CeO₂ at 350 °C. In both cases, the CO content in the obtained gas mixture was low (<2 vol.%). This hydrogen-rich gas can be used directly for fuelling high-temperature PEM FC. For fuelling low-temperature PEM FC, it is needed only to clean up the hydrogen-rich gas from CO to the level of 10 ppm. CuO/CeO₂ catalyst can be used for this purpose as well. Since no individual WGS stage, that is necessary in most other hydrogen production processes, is involved here, the miniaturization of the multifuel processor for hydrogen production by methanol, ethanol or DME SR is quite feasible.     

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.     

Hydrogen production by steam reforming of liquefied natural gas (LNG) over Ni/Al2O3–ZrO2 xerogel catalysts: Effect of calcination temperature of Al2O3–ZrO2 xerogel supports

Al₂O₃–ZrO₂ (AZ) xerogel supports prepared by a sol-gel method were calcined at various temperatures. Ni/Al₂O₃–ZrO₂ (Ni/AZ) catalysts were then prepared by an impregnation method for use in hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of calcination temperature of AZ supports on the catalytic performance of Ni/AZ catalysts in the steam reforming of LNG was investigated. Crystalline phase of AZ supports was transformed in the sequence of amorphous γ-Al₂O₃ and amorphous ZrO₂ → θ-Al₂O₃ and tetragonal ZrO₂ → (θ + α)-Al₂O₃ and (tetragonal + monoclinic) ZrO₂ → α-Al₂O₃ and (tetragonal + monoclinic) ZrO₂ with increasing calcination temperature from 700 to 1300 °C. Nickel oxide species were strongly bound to γ-Al₂O₃ and θ-Al₂O₃ in the Ni/AZ catalysts through the formation of solid solution. In the steam reforming of LNG, both LNG conversion and hydrogen composition in dry gas showed volcano-shaped curves with respect to calcination temperature of AZ supports. Nickel surface area of Ni/AZ catalysts was well correlated with catalytic performance of the catalysts. Among the catalysts tested, Ni/AZ1000 (nickel catalyst supported on AZ support that had been calcined at 1000 °C) with the highest nickel surface area showed the best catalytic performance. Well-developed and pure tetragonal phase of ZrO₂ in the AZ1000 support played an important role in the adsorption of steam and the subsequent spillover of steam from the support to the active nickel.     

The influence of Ni loading on coke formation in steam reforming of acetic acid

Steam reforming of acetic acid on Ni/γ-Al₂O₃ with different nickel loading for hydrogen production was investigated in a tubular reactor at 600 °C, 1 atm, H2O/HAc = 4, and WHSV = 5.01 g-acetic acid/g-cata.h^?1. The catalysts were characterized by temperature programmed oxidation (TPO) and differential thermal analysis (DTA), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The results showed that the amount of deposited carbidic-like carbon decreased and graphitic-like carbon increased with Ni loading increasing from 9 to 15 wt%. The Ni/γ-Al₂O₃ catalyst with 12 wt% Ni loading had higher catalytic activity and lower coke deposited rate.     

Enhancing hydrogen production by dry reforming process with strontium promoter

Hydrogen is an ideal energy carrier and can play a very important role in the energy system. The present study investigated the enhancement of hydrogen production from catalytic dry reforming process. Two catalysts namely Ni/γ-Al₂O₃ and Co/γ-Al₂O₃ promoted with different amounts of strontium were used to explore selectivity and yield of hydrogen production. Spent and fresh catalysts were characterized using techniques such as BET, XRD, H₂-TPR, CO₂-TPD, TGA and O₂-TPO. The catalyst activity and characterization results displayed stability improvement due to addition of Sr promoter. The least coke formations i.e. 3.8 wt% and 5.1 wt% were obtained using 0.75 wt% Sr doped in Ni/γ-Al₂O₃ and 0.5 wt% Sr doped in Co/γ-Al₂O₃ catalysts respectively. Time on stream tests of promoted catalysts for about six hours at 700 °C showed stable hydrogen selectivity. Moreover, the hydrogen selectivity was significantly improved by the addition of Sr in Ni and Co based catalysts. For instance the hydrogen selectivity increased from 45.9% to 47.8% for Ni/γ-Al₂O₃ and from 48% to 50.9% for Co/γ-Al₂O₃ catalyst by the addition of 0.75 wt% Sr in Ni/γ-Al₂O₃ and 0.5 wt% Sr in Co/γ-Al₂O₃ catalyst respectively.