Low Temperature Steam Reforming Research Articles

Co–Fe/Al2O3 catalyst for low-temperature steam reforming of phenol for hydrogen production

In this study, a series of high-efficient catalyst, Co–Fe/Al2O3, were synthesized via the sol-gel method for low-temperature phenol steam reforming (PSR). The optimized catalyst, 15Co–2Fe/Al2O3, exhibited a remarkable phenol conversion of 95.3%, a H2 yield of 92.1% at 450 °C, GHSV = 7500 h−1 and a steam-to-carbon (S/C) ratio of 10. Furthermore, the catalyst activity was maintained for 660 min before a gradual decline was observed. The NH3-TPD analysis revealed that the addition of Fe enhanced the surface acidity of the catalyst, providing more active sites for phenol adsorption and activation. This study aims to address the challenges associated with high reaction temperatures and poor catalyst stability in PSR. Various characterization techniques have been employed to investigate the reaction mechanisms of bimetallic catalysts in low-temperature PSR.

Novel Ni–Ru/CeO2 catalysts for low-temperature steam reforming of methane

Upgrading of biogas and biomethane into H2-rich streams by steam reforming is regarded as an effective strategy to reduce fossil fuel consumption contributing to the transition towards a green energy system. In this context, novel reactor configurations such as membrane reactors appear a promising route for process intensification, but they require novel catalysts more active at low temperatures, stable, and resistant to coke formation. In this work, we prepared and tested structured catalysts characterized by a low Ni content (7 wt%) and a very low Ru content (≤1 wt%) supported on ceria and deposed onto SiC monoliths. Catalysts were tested at low temperatures (<600 °C), i.e. at temperatures suitable for applications in Pd-based membrane reactors. Fresh and used catalysts were characterized by ICP-MS, N2 physisorption, XRD, TEM, SEM-EDS, XPS and H2-TPR to identify the physicochemical properties affecting the catalytic activity. The catalysts showed good activity towards methane reforming, stable performance, and good resistance to coke formation. Ruthenium affects both the intrinsic catalytic activity and the resistance to the inhibiting effect of steam on the reaction rate. This is related to improved redox properties due to the intimacy between the active metals and their strong-metal-support-interaction with the ceria. Finally, our catalysts show self-activation under reaction conditions, which is an interesting property for applications.

Small iridium clusters supported on TiO2 as catalysts for intensifying low-temperature methane activation and reforming

Hydrogen production via low-temperature (<550 °C) steam reforming of methane (SRM) has attracted increasing research attention due to its importance as an alternative, efficient, and environmentally benign energy carrier. The thermodynamic limitation of low-temperature SRM can be eased by process design such as using a membrane reactor or an adsorption-enhanced reforming process, and an active low-temperature SRM catalyst with high stability would be indispensable. Herein, we report a 2 wt% Ir/TiO2 catalyst that exhibits high methane conversion activity in low-temperature SRM with a relatively high turnover frequency (TOF) and a low activation energy in comparison with the literature. Long-term catalyst stability test demonstrates a good resistance to coking and sintering during low-temperature SRM reactions. In situ spectroscopy analyses and density functional theory (DFT) calculations reveal that the small Ir clusters and Ir single atoms (SAs) are both active for methane conversion, while the clusters exhibit higher activity than SAs for low-temperature SRM reaction. Microkinetic simulation based on DFT calculations shows consistent product formation temperatures and the simulation nicely reproduces the product distribution observed in experimental analysis, which confirms the superior SRM activity of the TiO2-supported Ir clusters in this work.

Tin and lanthanum modified Ni/CeO2 catalyst systems for low temperature steam reforming of ethanol

This work examines the Ni–Sn/Ce–La–O catalyst systems for low-temperature stream reforming of ethanol. Catalysts of 5 and 20 wt% metal loading, and different Ce:La ratios are prepared by ultra-sonication assisted solution combustion synthesis method. Catalysts at total metal loading 5 wt% with 33 and 67 at. % La and optimum Sn (Ni:Sn = 14:1) demonstrate better efficiency compared to the Ni/CeO2 catalysts. At 20 wt% metal loading and Ni:Sn = 1:1 atomic ratio, catalytic activity degrades. The best activity and stability are revealed for the N14S1(5)/CL21 catalyst with 5 wt.% total metal loading, Ni:Sn = 14:1, and Ce:La = 2:1 mol ratio. Physico-chemical characterizations (XRD, H2 -TPR, NH3-TPD, Raman, FESEM, TEM, XPS, N2 adsorption-desorption, DTA/TGA, etc.) are performed to understand the role of the metal loading, Sn, and La in the catalytic activity and coke deposition behavior.

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.

Effects of metal loading and support modification on the low-temperature steam reforming of ethanol (LTSRE) over the Ni–Sn/CeO2 catalysts

This article presents the effect of metal loading and support modification with MgO on low-temperature steam reforming of ethanol (LTSRE) over Ni–Sn/CeO2 catalysts prepare by a single-pot solution combustion synthesis (SCS) method. Atmospheric pressure activity study of these catalysts (0.5 g) is performed at different temperatures (200–400 °C), H2O:EtOH = 12: 1 mol ratio, and feed flow rate 0.1 ml/min. After 10 h TOS at 400 °C, NiSn(5)/CM12 catalyst with 5 wt.% total metal loading, optimal Sn (Ni:Sn = 14:1), and Ce:Mg = 1:2 mol ratio shows EtOH conversion 100% and H2 selectivity 70% with low coke deposition. Physicochemical characterizations (XRD, Raman, FESEM, TEM, and N2 adsorption-desorption) reveal that addition of MgO in CeO2 and an optimal amount of Sn decrease both Ni and support particle sizes while oxygen storage capacity (OSC) of the support increases (by XPS). Alkaline characteristics of MgO reduces support's acidity and improves active metal-support interaction, as evaluated by NH3-TPD and H2-TPR.

Facile synthesis of low-cost Co-Cu/C alloy catalysts for hydrogen-rich syngas production from low-temperature steam reforming of biomass tar

Recovering beneficial metal ions from industrial effluents by suitable support can be an efficient and environment-friendly way to prepare specific catalysts directly. Herein, modified lignite was developed as an ion exchange material and used to prepare Co-Cu bimetallic catalysts for hydrogen-rich syngas production from steam reforming reactions. For all the catalysts studied, Co75Cu15/600 (carbonization temperature at 600 °C) exhibits the optimal catalytic activity and stability in both steam reforming of toluene and biomass tar under low temperatures. Fresh and spent catalysts were detailedly characterized to investigate the metal interactions and catalyst deactivation. The introduction of Cu contributes to the formation of Co-Cu alloy and the lower particle size of Co (4.17 nm), thereby suppressing the carbon deposition, the oxidation of metals and the change of catalyst structure after reaction. Therefore, the inexpensive and readily-available Co-Cu/C has the potential to serve as a promising catalyst for large-scale biomass gasification technology.

Steam reforming of ethanol for hydrogen production by low-temperature steam reforming using modified Ni-Sn/CeO2 catalyst

This study focuses on the development of Ni-Sn bimetallic catalysts supported on ZrO2 modified CeO2 and their application for low temperature steam reforming of ethanol (LTSRE) at different temperature 200–400 °C. The catalyst powders are prepared by an ultrasonic-assisted solution combustion synthesis method. The ethanol conversion and selectivity of H2, CO2, CO, and CH4 has been studied with feed composition H2O:EtOH = 12: 1 mol ratio, feed flow rate 0.1 cc/min, and reaction time 20 hrs. Fresh and spent catalysts are characterized using XRD, FTIR, Raman, FESEM, XPS, and TGA-DTA. ZrO2 changes the support chemistry and enhances the activity and stability of the catalyst. At 400 °C, 100 % ethanol (EtOH) conversion, 69 % H2 selectivity with least coke deposition is observed for the catalyst with 5 wt% metal (Ni:Sn = 14:1) loading on Ce:Zr 1:2 mol ratio (NiSn5/CZ12) support.

Low-temperature steam reforming of phenol for hydrogen production over Co/Al2O3–ash catalysts

A low-cost, high-performance catalyst for phenol steam reforming (PSR) at low temperature was prepared by introducing waste coal ash into Co/Al2O3. The optimized content of coal ash in the catalyst were ranged from 50 to 65 wt%, presenting over 97% phenol conversion and 92% H2 yield at low temperature of 450 °C. The stability for the best catalyst with an ash content of 50 wt% exceeded 85 h. Two-step reduction of Co3O4 to Co0 via CoO was identified by in-situ XRD. DFT calculations showed that phenol adsorption and decomposition were preferred on the FeCo bimetal surface rather than the single Co surface. H2O adsorption and dissociation fascinated on the CaO incorporated Al2O3 surface. Both Fe and Ca in the coal ash improved the catalyst performance in PSR at low temperature. This work gives an opportunity to solve the drawbacks of high reaction-temperature and low catalyst-stability in PSR, and furthermore benefits to get a deep insight into the reaction mechanism of PSR over the catalyst.

Ethane formation via catalytic low-temperature steam reforming of C3+-alkanes

The present work aims at studying low-temperature steam reforming (LTSR) of model mixtures of flare gases containing C2H6-C4H10 in methane excess over a highly dispersed Rh-based catalyst. 1 wt% Rh/Ce0.75Zr0.25O2 catalyst was prepared by sorption-hydrolytic deposition. Catalytic properties were studied in the LTSR of model fuel gas mixtures at 200–350 °C. The catalysts provided complete conversion of C2+-hydrocarbons into CH4, CO2 and H2 at 320–350 °C. The conversion of propane and heavier alkanes over Rh at low temperature (200–300 °C) allows obtaining high ethane concentrations in the products, which is not observed in the case of nickel catalysts. The influence of hydrogenolysis reaction to ethane formation is discussed. Ethane has a higher calorific value than methane and can compensate the negative effect of the product gas dilution by carbon dioxide and hydrogen that are formed in the reaction. This can be useful for adjusting the fuel properties (calorific value, Wobbe index, methane number) of the resulting gas mixtures.

Nanoarchitectonics of Ni/CeO2 Catalysts: The Effect of Pretreatment on the Low-Temperature Steam Reforming of Glycerol.

CeO2 nanosphere-supported nickel catalysts were prepared by the wetness impregnation method and employed for hydrogen production from glycerol steam reforming. The dried catalyst precursors were either reduced by H2 after thermal calcination or reduced by H2 directly without calcination. The catalysts that were reduced by H2 without calcination achieved a 95% glycerol conversion at a reaction temperature of only 475 °C, and the catalytic stability was up to 35 h. However, the reaction temperature required of catalysts reduced by H2 with calcination was 500 °C, and the catalysts was rapidly inactivated after 25 h of reaction. A series of physicochemical characterization revealed that direct H2 reduction without calcination enhanced the concentration of oxygen vacancies. Thus, the nickel dispersion was improved, the nickel nanoparticle size was reduced, and the reduction of nickel was increased. Moreover, the high concentration of oxygen vacancy not only contributed to the increase of H2 yield, but also effectively reduced the amount of carbon deposition. The increased active nickel surface area and oxygen vacancies synergistically resulted in the superior catalytic performance for the catalyst that was directly reduced by H2 without calcination. The simple, direct hydrogen reduction method remarkably boosts catalytic performance. This strategy can be extended to other supports with redox properties and applied to heterogeneous catalytic reactions involving resistance to sintering and carbon deposition.

Modification of CuO–ZrO2–ZnO Mixed Oxide Catalyst with Mn, Ga, Ni: Impact on Physicochemical Properties and Hydrogen Production via Low Temperature Steam Reforming of Ethanol

The influence of CuO/ZrO2/ZnO (Cu/Zr/Zn) catalyst modification with Mn, Ni, Ga on the physicochemical properties and activity toward hydrogen production in steam reforming of ethanol (SRE) reaction has been evaluated. The increase in hydrogen yield and the lowest selectivity to acetaldehyde were observed upon Cu/Zr/Zn modification with Mn and Ga. The physicochemical characterisation of spent catalysts revealed changes in catalysts phase compositions and reducibility. In the case of Cu/Zr/Zn, Cu/Zr/Zn/Ni and Cu/Zr/Zn/Ga catalysts, the CuO phase was reduced to metallic phase and Cu2O. Therefore, these spent catalysts exhibited lower reduction degree (Rd) in comparison with fresh catalysts. On the other hand, the addition of Mn preserved the copper on + 2 oxidation state during SRE reaction as indicated by XRD and XPS. The µRaman experiments showed that carbon deposit is formed only on the surface of Cu/Zr/Zn/Ni catalyst, which is the reason for the vast deactivation and the lower total activity of this catalyst in SRE. This was also supported by XPS which additionally showed interaction of carbon containing by-products with the surface active sites. In the case of other synthesised catalysts, no carbon formation was stated.Graphical

Evaluating the effects of OH-groups on the Ni surface on low-temperature steam reforming in an electric field.

The effect of OH-groups on the surface of a Ni catalyst for low-temperature (473 K) steam reforming of methane in an electric field (EF) was investigated. Ni-doped YSZ (Zr0.65Y0.05Ni0.3O2) was chosen as a highly active catalyst for this purpose. The effects on catalyst activity of adding hydrogen and steam in the pre-treatment were assessed with and without EF. When an EF was applied, activity increased irrespective of the electronic state of Ni, whereas the metallic Ni state was necessary for activity without EF. Furthermore, the highest activity with EF was observed for the pre-treatment with a mixture of H2 and H2O. Investigation of the superiority using XPS measurements showed an increase in the amount of Ni(OH)2, OH groups and H2O near the surface after the activity test, which are regarded as the reaction sites with EF. This finding suggests that a pre-treatment with steam increases the surface OH groups and Ni(OH)2 on the Ni catalyst, and enhances surface proton conduction, thereby improving the activity.

Experimental verification of kinetics and internal diffusion impact on low temperature steam reforming of a propane-methane mixture over Ni-based catalyst

Experiments were made on three fractions (0.5–1, 2–2.5 and 3–5 mm) of a Ni/Cr2O3/Al2O3 catalyst in order to verify the kinetics and influence of internal diffusion transport on the apparent reaction rate of low-temperature steam reforming of a propane-methane mixture. Feed gas composition was: C3H8 = 22.6%, CH4 = 77.4%, H2O/C = 0.51, GHSV = 11600 h−1, temperature 300–370 °C. To analyze the experimental data, a plug-flow reactor model with fixed temperature profiles was used; the profiles were obtained by interpolating the measurements of a moving thermocouple placed along the axis of the catalyst bed. The global kinetic scheme included the parallel reactions of propane steam reforming and propane hydrogenolysis. The catalyst effectiveness factor was calculated with the effective diffusion coefficient based on the Wilke formula, Thiele modulus and experimental pore size distribution. Experimental data for all catalyst fractions are described well by the proposed model at a porous catalyst tortuosity factor 1.53 and permeability coefficient 0.26.

Comparative evaluation of tar steam reforming over graphitic carbon supported Ni and Co catalysts at low temperature

The development of cheap and highly dispersed nano-catalyst is one of the key technologies for low temperature steam reforming (SR) of biomass tar. This work used acid-washed and oxidized Shengli lignite char (OXAWSL) as carbon precursor to load Co (Co/OXAWSL) and Ni (Ni/OXAWSL) via ion exchange method to SR of toluene and biomass tar. The Co/OXAWSL was more active and stable than Ni/OXAWSL during the 30 h test with a final toluene conversion of 85% at a relatively low temperature of 450 °C and steam to carbon ratio (S/C) of 3.4, which resulted from its small particle size (5.6 nm) and high dispersion (12.3%) of Co. The relatively high H2 production (42.59 mmol/g-biomass) over Co0.1/OXAWSL (450 °C, S/C = 3.4) in SR of tar was also obtained. A low Ea (22.0 kJ/mol) value of Co/OXAWSL and good affinity to oxygen for Co explained its excellent performance. The low-temperature tar cracking process can provide theoretical and technical support for the large-scale industrial utilization of biomass pyrolysis and gasification.

Deactivation study of the BICOVOX catalysts used in low temperature steam reforming of ethanol for H2 production

The γ-BICOVOX, having high O2- mobility at low temperature (≤300 °C), might be a good catalyst for hydrogen production by low temperature steam reforming (LTSR) of ethanol. LTSR (at atmospheric pressure) of ethanol over Bi4(V0.90Co0.10)2O11-δ (BICOVOX) catalysts (synthesized by a solution combustion method and calcined at 400, 600 and 800 °C) has been investigated at the reaction conditions of 400 °C, H2O: EtOH molar ratio 23:1 and 0.35 ml min−1 feed flow rate. Catalysts remain active for the time period of ~30 h and after that start to deactivate. According to the XRD analysis γ- BICOVOX decomposes to BiVO4, Bi2O3, and Bi phases due to a reducing environment present inside the reactor. According to the XPS analysis, decrease in γ- BICOVOX amount diminishes the oxygen vacancy in the lattice. This probably causes significant decline in O2- mobility through the lattice and consequently carbon deposition occurs (derived from XPS, FESEM & DTGA) leading to an almost complete deactivation of the catalysts within 150 h.

Activation of a nickel-chromium catalyst for low-temperature steam reforming of C2+-alkanes

Activation of a nickel-chromium catalyst for low temperature steam reforming of C2+-alkanes to methane rich gas has been studied by TPR and XRD in situ techniques. The activation procedure has been studied with the following reducing agents: hydrogen, syngas, methanol and the reaction mixture of low-temperature steam reforming. Attempts were made to activate the catalyst at 300, 340 and 420 °C. Activated samples were tested in low-temperature steam reforming of a methane-propane mixture. A passivation process has been proposed and tested for compatibility with following activation in the LTSR reaction mixture.

The effects of support morphology on the performance of Pt/CeO2 catalysts for the low temperature steam reforming of ethanol

A series of Pt/CeO2 catalysts with different support morphologies was studied for the low temperature ethanol steam reforming. Different ceria nanostructures (nanocube_NC, nanorod_NR and flower-like_FL) were prepared by the hydrothermal method and are compared with CeO2 obtained by precipitation. Support morphology was found to influence certain reaction routes, even though the reaction scheme was the same regardless of the support. Concerning catalyst stability at 573 K, Pt/CeO2- PPT exhibited rapid deactivation, whereas Pt/CeO2- NR remained rather stable. XPS surface analysis before and after reaction at 573 K revealed significant degree of Pt reduction on CeO2 nanorods, directly related to the reduction of Ce4+ into Ce3+. DRIFTS experiments under reaction conditions for 5 h, revealed an accumulation of acetates on the Pt/CeO2- PPT catalyst, likely due to the imbalance between the rate of acetate species decomposition to CHx (not facilitated over Ptδ+ of the catalyst with the lower Pt dispersion), and their desorption as CH4.

Low temperature steam reforming of ethanol over cobalt doped bismuth vanadate [Bi4(V0.90Co0.10)2O11-δ (BICOVOX)] catalysts for hydrogen production

The atmospheric pressure low temperature steam reforming of ethanol over Bi4(V0.90Co0.10)2O11-δ (BICOVOX) catalysts, synthesize by a solution combustion synthesis method and calcined at 400, 600 and 800 °C, has been investigated at different reactor temperatures, H2O: EtOH molar ratios and feed flow rates. For fresh catalysts amount, crystallinity and particle size of pure γ-BICOVOX phase is observed to increase with increasing calcination temperature. Phase purity and crystallinity of the catalysts are almost retained till 30 h of activity study with some amount of carbon formation as derived from XRD, XPS, FESEM and simultaneous DTA-TGA study. Catalyst calcined at 600 °C (BICOVOX-600) exhibits the highest ethanol conversion (100%) with maximum H2 selectivity (80%) under reaction conditions of 400 °C, 23:1H2O: EtOH molar ratio and 0.35 cc min−1 feed flow rate. The maximum O2− vacancy present in lattice and lowest coke deposition could explain the best performance of BICOVOX-600 catalyst.

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 40Pt0.025NiMn2O4/60γ-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.