Low Temperature Steam Reforming Of Ethanol Research Articles

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.

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.

Role of Fe Species of Ni-Based Catalysts for Efficient Low-Temperature Ethanol Steam Reforming.

The suppression of methane and coke formation over Ni-based catalysts for low temperature ethanol steam reforming remains challenging. This paper describes the structural evolution of Fe-modified Ni/MgAl2O4 catalysts and the influence of iron species on methane and coke suppression for low temperature ethanol steam reforming. Ni–Fe alloy catalysts are gradually oxidized by water to generate Ni-rich alloy and γ-Fe2O3 species at steam-to-carbon ratio of 4. The electron transfer from iron to nickel within Ni–Fe alloy weakens the CO adsorption and effectively alleviates the CO/CO2 methanation. The oxidation capacity of γ-Fe2O3 species promotes the transformation of ethoxy to acetate groups to avoid methane formation and the elimination of carbon deposits for anticoking. Ni10Fe10/MgAl2O4 shows a superior performance with a highest H2 yield of 4.6 mol/mol ethanol at 400 °C for 15 h. This research could potentially provide instructions for the design of Ni-based catalysts for low-temperature ethanol steam reforming.

Effect of the Structural and Electronic Properties of Rh/CeXZr1-XO2 Catalysts on the Low-temperature Ethanol Steam-reforming

Abstract. Rh catalysts supported on CexZr1–xO2 (with x= 0-1) materials were synthesized by precipitation method. The influence of the two different cerium salt precursors, ammonium cerium(IV) nitrate and cerium(III) nitrate hexahydrate, over the structure and catalytic activity in steam reforming reaction was investigated. The synthesized catalysts were characterized by various techniques, such as N2 adsorption-desorption, temperature-programmed desorption, X-ray diffraction, Raman spectroscopy, diffuse reflectance UV-Vis, and X-ray photoelectron spectroscopy. The use of ammonium cerium (IV) nitrate as a cerium precursor resulted in solid CexZr1-xO2 solutions with improved oxygen mobility and specific surface area. The catalytic evaluation exhibited the support composition and structure impact on its activity and product yield. The Rh supported on Ce0.5Zr0.5O2 solid solution rendered the higher activity and H2 and CO2 yields among both series, related to improved oxygen mobility and greater Rh0 dispersion. The formation of surface defects adjacent to Rh clusters by strong metal-support interaction effect was suggested by Raman analysis. The close contact between the Rh0 site and oxygen vacancy could be favoring cyclic-like ethanol adsorption and favored the breaking of the C–C bond and further oxidation of adsorbed CO and CHX species.
 
 Resumen. Los catalizadores de Rh soportados en materiales CexZr1 – xO2 (x= 0-1) se sintetizaron mediante el método de precipitación. En este trabajo se investiga la influencia de dos precursores de sal de cerio diferentes, nitrato de amonio cerio (IV) y nitrato de cerio (III) hexahidrato, sobre la estructura y la actividad catalítica en la reacción de reformado con vapor. Los catalizadores sintetizados se caracterizaron mediante diversas técnicas, tal como fisisorción de N2, reducción a temperatura programada, difracción de rayos X, espectroscopía Raman, reflectancia difusa UV-Vis y espectroscopía de fotoelectrones de rayos X. El uso de nitrato de amonio cerio (IV) como precursor de cerio dio como resultado la obtención de soluciones sólidas de CexZr1-xO2 con una movilidad del oxígeno y área específica mejorada. La evaluación catalítica mostró el impacto de la composición y estructura del soporte sobre la conversión y rendimiento de productos. El catalizador Rh soportado en la solución sólida Ce0.5Zr0.5O2 proporcionó la mayor actividad y rendimientos de H2 y CO2 entre ambas series, relacionados con la movilidad del oxígeno mejorada y mayor dispersión de Rh0. El análisis Raman sugirió la formación de defectos superficiales adyacentes a los grupos de Rh debido a fuertes interacciones metal-soporte. El contacto estrecho entre el sitio Rh0 y la vacante de oxígeno estaría favoreciendo la adsorción del etanol en configuración cíclica y favoreciendo la ruptura del enlace C-C y la oxidación de las especies de CO y CHX adsorbidas.

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.

Hydrogen production on Pd0.01Zn0.29Mg0.7Al2O4 spinel catalyst by low temperature ethanol steam reforming reaction

This study investigated the low-temperature ethanol steam reforming (LTESR) performance of a Pd0.01Zn0.29Mg0.7Al2O4 catalyst. Although it was present in a very small amount, the Pd component was the key to the partial CO-water gas shift and CO-methanation that, eventually, helped to increase the yield of H2 during LTESR. An 80% yield of H2 was maintained even after 30 h at 450 °C on the Pd0.01Zn0.29Mg0.7Al2O4 catalyst with 100% ethanol conversion. Furthermore, the spinel structure of the catalyst remained unchanged after the reaction, and there was no increase in size owing to particle-to-particle aggregation. This study demonstrated that the Pd and Zn components could be stably located in the spinel structure of the MgAl2O4 with no sintering of the particles. Moreover, the oxygen transfer capacity of the MgAl2O4 spinel structure helped maintain the catalytic performance for long time periods by transferring oxygen to the reduced catalytic metal species (Zn or Pd) during the reaction, even though this induced oxygen defects in the spinel crystal. Overall, improved catalyst activity and an extended catalyst lifespan were observed.

Pt nanoparticles encapsulated in a hollow zeolite microreactor as a highly active and stable catalyst for low-temperature ethanol steam reforming

High dispersion of Pt nanoparticles encapsulated in hollow Pt@HBZ microreactor has been successfully fabricated through the function of resorcinol-formaldehyde layer during the synthesis process. The low-temperature ethanol steam reforming (LT-ESR) on the Pt@HBZ was studied using various techniques with a focus on the structural characterization of the catalysts, reaction mechanism, and understanding of the structure-activity relationship. The results of steady-state-activity testing, comparisons with those from Pt-beta and Pt-SiO2 catalysts showed that the Pt@HBZ exhibited superior activity, stability and low by-products with negligible deactivation phenomena for 15 h during LT-ESR. The hindering effect of zeolite shell could effectively improve the concentration of relatively large molecules (i.e., ethanol and acetaldehyde) in the hollow micro-environment and promote the molecules reacted with Pt active sites to achieve a complete catalytic conversion. Moreover, due to the “purification effect” for the undesired products (CO, CH4, acetaldehyde and unreacted ethanol), the existence of a large number of microreactors in the reaction system can obtain high-purity hydrogen production.

Low temperature ethanol steam reforming for process intensification: New Ni/MxO–ZrO2 active and stable catalysts prepared by flame spray pyrolysis

Steam reforming of hydrocarbons is a mature technology and its implementation on other substrates such as bio-ethanol appears as a ready opportunity to produce H2 from renewable sources. The Low Temperature Ethanol Steam Reforming (LT-ESR, 300–500 °C) could be a really efficient technology from the energetic point of view. However, deactivation by coke deposition remains the biggest issue, due to inefficient carbon gasification by steam in such low temperature range. We demonstrated the feasibility of the process at low temperature taking into account both activity and deactivation issues. The attention was focused on the addition of basic promoters and on the development of an unconventional preparation procedure, in comparison with a traditional precipitation/impregnation route, to improve stability and activity.Therefore, in this work several catalysts were studied, differently promoted by alkali and alkali earth oxides (CaO, MgO, K2O) using a non conventional doping method. H2 yield and selectivity to CO demonstrated tightly related to the promoter adopted. Flame Spray Pyrolysis synthesis of nickel nanoparticles stabilized in a zirconia matrix (Ni/MxO-ZrO2) was performed, obtaining more stable catalysts toward deactivation by coking with respect to the analogous prepared by traditional precipitation/impregnation. The effect of the doping using a scalable one-pot technique was investigated by means of characterization of fresh catalysts and activity testing. Catalyst resistance toward deactivation was studied by SEM-EDX, TEM, Raman spectroscopy and temperature programmed analysis. Among the promoters, CaO and K2O showed the best performance, producing a reformate with low CO/CO2 ratio and, thus, leading to higher H2 yield with consequent lower impact on H2 purification in an integrated process. K2O deeply modified the chemical behaviour of the catalyst allowing to achieve a significant H2 production also at very low temperature (300 °C).

Application of BICOVOX catalyst for hydrogen production from ethanol

Catalytic activity of cobalt-doped bismuth vanadate [Bi4(V0.90Co0.10)2O11−δ ; BICOVOX] powder, prepared by a solution combustion synthesis and calcined at 800 °C (BICOVOX-800), for hydrogen production using low-temperature steam reforming of ethanol, has been reported in this paper. The effects of reaction temperature (250–400 °C) and feed concentration (H2O/EtOH = 2.5:1 and 23:1 mol ratio) on the steady-state ethanol conversion and selectivity of H2, CO2, CO, and CH4 have been investigated (up to 30 h). It is observed that with an increase in reaction temperature and H2O/EtOH mole ratio, H2 and CO2 selectivity increases and CO and CH4 selectivity decreases. The maximum H2 selectivity and ethanol conversion are observed to be 63 and 88%, respectively, for H2O/EtOH = 23:1 mol ratio at 400 °C. The XRD results show that the fresh BICOVOX-800 has pure γ-phase and is highly crystalline. The used catalyst (more than 150 h total) is detected to have less crystallinity and to partially decompose into Bi2O3 and BiVO4 phases.

Mechanistic Insights into Catalytic Ethanol Steam Reforming Using Isotope‐Labeled Reactants

The low-temperature ethanol steam reforming (ESR) reaction mechanism over a supported Rh/Pt catalyst has been investigated using isotope-labeled EtOH and H2 O. Through strategic isotope labeling, all nonhydrogen atoms were distinct from one another, and allowed an unprecedented level of understanding of the dominant reaction pathways. All combinations of isotope- and non-isotope-labeled atoms were detected in the products, thus there are multiple pathways involved in H2 , CO, CO2 , CH4 , C2 H4 , and C2 H6 product formation. Both the recombination of C species on the surface of the catalyst and preservation of the C-C bond within ethanol are responsible for C2 product formation. Ethylene is not detected until conversion drops below 100 % at t=1.25 h. Also, quantitatively, 57 % of the observed ethylene is formed directly through ethanol dehydration. Finally there is clear evidence to show that oxygen in the SiO2 -ZrO2 support constitutes 10 % of the CO formed during the reaction.

Highly loaded Ni-based catalysts for low temperature ethanol steam reforming.

This paper describes the design of high-loading Ni/Al2O3 catalysts (78 wt% Ni) for low temperature ethanol steam reforming. The catalysts were synthesized via both co-precipitation (COP) and impregnation (IMP) methods. All the catalysts were measured by N2 adsorption-desorption, XRD, H2-TPR, and H2 pulse chemisorption. The characterization results demonstrated that the preparation method and the loading significantly affected the nickel particle size, active nickel surface area and catalytic performance. Over COP catalysts, large nickel particles were presented in nickel aluminum mixed oxides. In comparison, IMP catalysts gained more "free" NiO particles with weak interaction with the aluminum oxide. Consequently, COP catalysts yielded smaller nickel particles and larger active nickel surface areas than those of IMP catalysts. High loading is beneficial for obtaining sufficient active nickel sites when nickel particles are dispersed via COP, whereas excessive nickel content is not desired for catalysts prepared by IMP. Specifically, the 78 wt% nickel loaded catalyst synthesized by COP possessed small nickel particles (∼6.0 nm) and an abundant active nickel area (35.1 m(2) gcat(-1)). Consequently, COP-78 achieved superior stability with 92% ethanol conversion and ∼35% H2 selectivity at 673 K for 30 h despite the presence of a considerable amount of coke.

Effect of potassium addition on a long term performance of Co–ZnO–Al2O3 catalysts in the low-temperature steam reforming of ethanol: Co-precipitation vs citrate method of catalysts synthesis

The promotion effect of potassium on Co–ZnO–Al2O3 catalysts in the steam reforming of ethanol has been studied with samples prepared by co-precipitation and citrate methods. Experimental results of catalytic activity, selectivity and coke deposition phenomena are reported. Potassium addition (1 and 2wt.%) had a significant influence on catalytic efficiency at various ethanol+water vapours streams (H2O:EtOH=21:1, 15:1, 12:1 molar ratios). It acts as a promoter improving catalyst stability, activity as well as marginalizing coke deposition on the catalyst surface. Catalysts prepared by the co-precipitation method, with smaller cobalt active phase crystallites and with potassium deposited on the catalyst surface are more stable in the steam reforming of ethanol than those with large crystallites prepared by citrate method, into which potassium was introduced together with all others components. The efficiency of the potassium promotion is higher when it is deposited on the catalyst surface with smaller cobalt active phase crystallites. The water excess equivalent to the H2O:EtOH molar ratio higher than 15:1 has been necessary for the stable SRE. Even potassium-promoted K–Co–ZnO–Al2O3 catalyst needs the ethanol–water feed with a large excess of water.

Bimetallic Ni–Cu Catalysts for the Low-Temperature Ethanol Steam Reforming: Importance of Metal–Support Interactions

The activity of bimetallic Ni–Cu catalysts in ethanol steam reforming was evaluated and compared to the activity of the corresponding monometallic Ni catalyst. Copper addition positively affected the catalytic activity only if the proper metal–support interactions, as well as the proper ratio between the different reducible species, were maintained. This target can be pursued by tuning the synthesis conditions. .

Rh–Fe/Ca–Al2O3: A Unique Catalyst for CO-Free Hydrogen Production in Low Temperature Ethanol Steam Reforming

Low temperature ethanol steam reforming (ESR) was studied over a series of 1 wt% Rh–x % Fe catalysts with various Fe loading (x = 0–10 wt%) and on different supports (Ca–Al2O3, SiO2 and ZrO2). The results show that close interaction between Rh and Fe is required to reduce the CO selectivity to almost negligible values. In addition, Rh–Fe supported on Ca–Al2O3 exhibits the best performance in terms of CO selectivity and hydrogen yield as compared to other supports. Characterization by XPS and XANES indicates the presence of FexOy species upon reduction, resulting in the formation of coordinatively unsaturated ferrous (CUF) active sites along the Rh–FexOy interface. These CUF sites promote water–gas shift reaction during low temperature ESR. Temperature programmed oxidation and Raman spectroscopy of spent catalysts also indicate that the addition of iron oxide reduces coke deposition and forms more reactive coke. Hence, the catalyst lifespan is significantly extended.

On the activity of bimetallic catalysts for ethanol steam reforming

The performance of CeO2-supported Pt–Ni and Pt–Co catalysts in the low temperature-Ethanol Steam Reforming (ESR) reaction has been evaluated studying the effect of the preparation method (impregnation/coprecipitation) and parameters such as dilution ratio, temperature, water-to-ethanol feed ratio and Gas Hourly Space Velocity (GHSV). The results show that impregnated samples perform better. In particular, the Pt/Ni/CeO2 catalyst starting from 350 °C leads to a products distribution very close to the equilibrium calculations, with a low CO content that is ideal for fuel cells devices. In addition, the Co-based catalysts appear attractive in terms of hydrogen yield and coking tendency.For the Pt/Ni sample at 370 °C, the analysis of products distributions vs contact time suggests a surface reaction path involving ethanol dissociative adsorption, dehydrogenation to acetaldehyde at short contact time (5–40 ms), followed by decomposition, reforming and CO-WGS reactions, to obtain H2, CH4, CO2 and CO. The last step is the methanation reaction, occurring at contact times higher than 100 ms, which drives the system to the equilibrium.

Co-Fe-Si Aerogel Catalytic Honeycombs for Low Temperature Ethanol Steam Reforming

Cobalt talc doped with iron (Fe/Co~0.1) and dispersed in SiO2 aerogel was prepared from silica alcogel impregnated with metal nitrates by supercritical drying. Catalytic honeycombs were prepared following the same procedure, with the alcogel synthesized directly over cordierite honeycomb pieces. The composite aerogel catalyst was characterized by X-ray diffraction, scanning electron microscopy, focus ion beam, specific surface area and X-ray photoelectron spectroscopy. The catalytic layer is about 8 µm thick and adheres well to the cordierite support. It is constituted of talc layers of about 1.5 µm × 300 nm × 50 nm which are well dispersed and anchored in a SiO2 aerogel matrix with excellent mass-transfer properties. The catalyst was tested in the ethanol steam reforming reaction, aimed at producing hydrogen for on-board, on-demand applications at moderate temperature (573–673 K) and pressure (1–7 bar). Compared to non-promoted cobalt talc, the catalyst doped with iron produces less methane as byproduct, which can only be reformed at high temperature, thereby resulting in higher hydrogen yields. At 673 K and 2 bar, 1.04 NLH2·mLEtOH(l)−1·min−1 are obtained at S/C = 3 and W/F = 390 g·min·molEtOH−1.

Hydrogen from bioethanol: Catalytic honeycombs loaded with Co-Fe/ZnOfor small-scale energy applications

ABSTRACTCatalytic monoliths loaded with ZnO-supported Co-Fe catalysts were prepared in one step by the in situ urea method and tested in the ethanol steam reforming reaction to produce hydrogen. The most active and selective formulation was attained with a Fe/Co molar ratio between 0.05 and 0.1, which showed negligible amounts of methane among the reaction products, thus offering an active and selective material for the low-temperature steam reforming of ethanol for small-scale energy applications.

Carbon monoxide-free hydrogen production via low-temperature steam reforming of ethanol over iron-promoted Rh catalyst

For the first time, a novel iron-promoted Rh catalyst is developed to produce CO-free H 2 through steam reforming of ethanol at low temperatures, between 623 and 673 K. The iron oxides in the vicinity of Rh sites reduce the CO adsorption on Rh sites and transfer the adsorbed CO from Rh to COO-formate species on Fe x O y for the subsequent water–gas shift reaction, resulting in a high H 2 yield, extremely low CO selectivity, and a long Rh life span.

H 2 production from stable ethanol steam reforming over catalyst of NiO based on flowerlike CeO 2 microspheres

Catalyst of nickle oxide based on flowerlike cerium microspheres with high dispersion was made to achieve simultaneous dehydrogenation of ethanol and water molecules on multi-active sites. XRD, 77 K N 2 adsorption and FESEM were applied to analyse and observe the catalyst's structure, porosity and morphology. This special morphology catalyst represented novel stability more than 600 h for hydrogen production at low temperature ethanol steam reforming. Ethanol-water mixtures could be converted into H 2 with average selectivity value of 61.5 mol.% and average ethanol conversion 95.0 mol.% at 350 °C, with GHSV∼1.0 × 10 5 h −1, low CO selectivity about average value of 2.1 mol.%, during 550 h reforming stability test. Catalytic parameters with respect to yield of H 2, activity, selectivity towards hydrogen production and stability with time on stream were determined.

Deactivation Studies of Rh/Ce0.8Zr0.2O2 Catalysts in Low Temperature Ethanol Steam Reforming

Rapid deactivation of Rh/Ce0.8Zr0.2O2 catalysts during low temperature ethanol steam reforming was studied. A significant build-up of reaction intermediates, instead of carbon deposit, was observed at low reaction temperatures. This appears to be the cause of rapid catalyst deactivation. Co-feed experiments indicated that possible intermediate products acetone and ethylene caused more severe catalyst deactivation than other oxygenates such as acetic acid and acetaldehyde.