Oxidative Steam Reforming Research Articles

Energy and exergy optimization of oxidative steam reforming of acetone–butanol–ethanol–water mixture as a renewable source for H2 production via thermodynamic modeling

Abstract Acetone–butanol–ethanol–water mixture is obtained by fermentation of biomass namely, corncob, wheat straw, sugarbeets, sugarcane, etc. For using the individual components, one alternative is to separate the mixture by distillation, which is costly and energy intensive operation. This paper proposes its other use in available conditions to produce hydrogen fuel by oxidative steam reforming process. For the proposed process, thermodynamic equilibrium modeling has been performed by using non-stoichiometric approach of Gibbs free energy minimization. The compositions of acetone, butanol and ethanol in mixture are 0.33:0.52:0.15 on molar basis. The influence of pressure (1–10 atm), temperature (573–1473 K), steam to ABE mixture molar feed ratio (F ABE = 5.5–8.5), and oxygen to ABE mixture molar feed ratio (F OABE = 0.25–1) have been tested by simulations on the yield of products (at equilibrium) namely, H2, CH4, CO2, CO, and carbon as solid. The optimum conditions for maximum production of desired H2, minimization of undesired CH4, and elimination of carbon (solid) formation are T = 973 K, P = 1 atm, F ABE = 8.5, and F OABE = 0.25. Under same operating conditions, the maximum generation of H2 is 7.51 on molar basis with negligible carbon formation. The total energy requirement for the process (295.73 kJ/mol), the energy required/mol of hydrogen (39.37 kJ), and thermal efficiency (68.09%) of the reformer have been obtained at same operating conditions. The exergy analysis has also been investigated to measure the work potential of the energy implied in the reforming process.

Global vision from the thermodynamics of the effect of the bio-oil composition and the reforming strategies in the H2 production and the energy requirement

The yield of H2 and by-products and the heat duties in the reforming of different oxygenates in bio-oil (acids, ketones, aldehydes, phenols and saccharides) have been compared by means of thermodynamic analysis, focusing on steam reforming (SR), oxidative steam reforming (OSR) and autothermal reforming (ATR) as alternatives. The study is performed by minimization of Gibb's energy method with ProII-Simsci® 10.1 software and has been extended for a wide range of conditions (temperature, steam/carbon (S/C) and O2/C ratios, and inert gas addition). The results of products yield and heat duties of SR are slightly different with oxygenates of different nature, and S/C = 5 and 610–644 °C range are the most suitable conditions for attaining high equilibrium H2 yield (90–92%) without excessive penalty in energy requirements. At S/C = 1.5, the inert addition increases slightly hydrogen yield and decreases coke formation, but this effect is not significant for S/C ratios above 5. Original correlations are proposed to predict the maximum yield of H2 and byproducts and the optimum temperature for the SR of oxygenates, from the values of the C/S ratio in the feed and the H/C, O/C and O/H ratios characteristic of the oxygenates composition. At 630 °C, ATR regime is achieved with a different O2/C ratio for the oxygenates, in the 0.12–0.22 range (aldehydes < acids ≈ phenols < ketones), and with H2 yield of 83–77%.

Detailed kinetic mechanism for the hydrogen production via the oxidative reforming of ethanol

Ethanol is increasingly growing as feedstock for syngas production. In this work, a detailed kinetic mechanism for the oxidative steam reforming (OSR) of ethanol over a Pt-Ni/CeO2-SiO2 catalyst has been compared against experimental data and apparent kinetics. The rate of production and sensitivity analyses were performed to identify reaction paths, species, and reactions having a significant impact on the distribution of the products. The results have demonstrated that the formation of CH3CHO, which leads to the CH3 and CO, is due to the hydrogen abstraction forming the CH3CHOH, whereas the formation of C2H4, which leads to HCO, CH3, and coke precursors, is related to the pathways forming CH2CH2OH. The production of CH2CH2OH is successfully hindered by the presence of catalysts, giving a phenomenological reason for the suppression in coke formation. This analysis provides theoretical insights into the kinetic aspects of OSR, aiming at the development of optimized catalysts.

Influence of nitric acid-assisted hydrothermal conditions on the characteristics of TiO2 catalysts and their activity in the oxidative steam reforming of methanol

Titania (TiO2) nanoparticles (NPs) with different morphologies (spherical, rod-shaped, and mixed) were prepared by hydrothermal treatment of different nitric acid (HNO3)/titanium (IV) isopropoxide (TTIP) molar ratios (0.25, 0.5, 1.0, and 1.7) at different hydrothermal temperatures (90, 150, 200, and 250 °C), hydrothermal times (6, 12, and 24 h), and calcination temperatures (500, 625, and 750 °C). The crystalline structure, morphology, and surface texture of the obtained TiO2 NPs were characterized by X-ray diffraction, nitrogen adsorption–desorption isotherm, field emission-scanning electron microscopy, and high resolution-transmission electron microscopy analyses. Under a larger HNO3: TTIP molar ratio, higher hydrothermal temperature, and higher hydrothermal time, the spherical mixed anatase–rutile phase TiO2 NPs were converted to a nanorod (NR)-shaped rutile phase (TiO2-R). The TiO2-R NRs gave the highest methanol conversion level (65%) and hydrogen yield (45%) in the oxidative steam reforming of methanol at 400 °C.

Ceria nanorod supported gold nanoparticles as structured catalysts for the oxidative steam reforming of methanol: Effect of CTAB concentration on physiochemical properties and catalyst performance

Ceria (CeO2) supports were synthesized by hydrothermal treatment with different Cetyltrimethylammonium bromide (CTAB) concentrations (CeO2-X: 0.135, 0.270, 0.540 and 1.080, where X is the CTAB concentration in mmol). The micro-structures of bundle-like ceria nanorods (NR) were produced by thermal treatment of the crystalline Ce(OH)CO3 precursor. The exposed crystal planes of (200) and (111), corresponding to the d-spacing of 0.27 and 0.31 nm, were confirmed by high resolution-transmission electron microscopy (HR-TEM). The fundamental characteristics of CeO2-0.135 led to the highest surface area, surface area normalized reducibility and oxidized gold species (Aun+/Au0) on the surface, relatively higher oxygen vacancies and a smaller average gold particle size (7.9 nm). The activity results show that the Au/CeO2-0.135 has the highest methanol conversion and H2 production rate for oxidative steam reforming of methanol (OSRM). The reducibility and gold particle size played a crucial role in determining the H2/CO2 ratio at the temperature of 200 °C.

Reforming of methanol to produce hydrogen over the Au/ZnO catalyst

Gold particle with an average size of dAu ~ 4 nm was dispersed on ZnO by the deposition precipitation method. The fabricated Au/ZnO catalyst was used to produce hydrogen from reforming of methanol. Four reforming reactions, i.e., decomposition of methanol (DM), steam reforming of methanol (SRM), partial oxidation of methanol (POM) and oxidative steam reforming of methanol (OSRM), were evaluated in a fixed bed reactor. A reaction temperature of TR > 623 K was required for catalyzing reactions of DM and SRM. Interestingly, high methanol conversion (CMeOH > 90%) was found from reforming reactions of POM and OSRM at an amazing low temperature of TR < 473 K. Besides, a presentable hydrogen yield (RH2 ~ 2.4) and a low selectivity of CO (SCO ~ 1%) were simultaneously attained from the reaction of OSRM. Therefore, the low temperature OSRM reaction over the Au/ZnO catalyst is suggested as a friendly reforming process for on-board production of hydrogen.

The Interfacial Effect on H2 Production from Oxidative Steam Reforming of Ethanol Over Rh/Ce1-xLaxO2-δ Nanocatalysts

Background: The production of hydrogen from catalytic reforming ethanol has attracted wide attention, which provides a promising way to replace fossil fuels with sustainable energy carriers. Methods: In this work, the Ce1-xLaxO2-δ solid solution (CL) supported Rh catalysts (nRh/CL, n = 0.5, 1 and 2 wt.%) were prepared by a traditional impregnation method with a variation of Rh loading. The different interface structure of nRh/CL catalysts and their catalytic performance in oxidative steam reforming (OSR) reaction were investigated. Results: Rh was loaded by the traditional impregnation method, and ethanol conversion and H2 yield declined in the order of 1%Rh/CL &gt; 2%Rh/CL &gt; 0.5%Rh/CL. Conclusion: The supports of the nRh/CL catalysts were confirmed to be Ce1-xLaxO2-δ solid solution, but only for the 1%Rh/CL catalyst, the Rh species were well-dispersed on the support and formed a Rh2O3//Ce1-xLaxO2-δ interface structure. The super-cell structure of Rh3+-O-RE3/4+ (RE = Ce, La) on the surface of 0.5%Rh/CL catalyst and the formation of interfacial Ce1-x-yLaxRhyO2-δ solid solution for 2%Rh/CL catalyst had effects on the self-activation of the nRh/CL catalysts. The typical lattice expansion of Ce1-xLaxO2-δ solid solution lowered the energy for migration. And the excellent hydrogen and oxygen mobility at the Rh//Ce1-xLaxO2-δ interface for 1%Rh/CL catalyst guaranteed the good catalytic performance for OSR at low temperature.

Sorption-enhanced chemical looping oxidative steam reforming of methanol for on-board hydrogen supply

Hydrogen is an indispensable energy carrier for the sustainable development of human society. Nevertheless, its storage, transportation, and in situ generation still face significant challenges. Methanol can be used as an intermediate carrier for hydrogen supplies, providing hydrogen energy through instant methanol conversion. In this study, a sorption-enhanced, chemical-looping, oxidative steam methanol-reforming (SECL-OSRM) process is proposed using CuO–MgO for the on-board hydrogen supply, which could be a promising method for safe and efficient hydrogen production. Aspen Plus software was used for feasibility verification and parameter optimization of the SECL-OSRM process. The effects of CuO/CH3OH, MgO/CH3OH, and H2O/CH3OH mole ratios and of temperature on H2 production rate, H utilization efficiency, CH3OH conversion, CO concentration, and system heat balance are discussed thoroughly. The results indicate that the system can be operated in auto-thermal conditions with high-purity hydrogen (99.50 vol%) and ultra-low-concentration CO (< 50 ppm) generation, which confirms the possibility of integrating low-temperature proton-exchange membrane fuel cells (LT-PEFMCs) with the SECL-OSRM process. The simulation results indicate that the CO can be modulated in a lower concentration by reducing the temperature and by improving the H2O/CH3OH and MgO/CH3OH mole ratios.

Chemical looping induced CH3OH–H2-PEMFC scheme for fuel cell vehicle: Parameter optimization and feasibility analysis

In this work, a hybrid system combined with chemical looping methanol reformer (CL-reformer) and high-temperature proton exchange membrane fuel cell (HT-PEMFC) is proposed for the vehicle power supply. The Cu-based chemical looping induced methanol reforming is introduced to optimize the energy supply scheme of fuel cell vehicles. The start-up and working stages of the integrated system are comprehensively considered and simulated via the ASPEN Plus software. In start-up stage, the lattice oxygen participates the oxidative steam reforming of methanol, achieving auto-thermal hydrogen generation and Cu-based oxygen carrier (OC) reduction (Cu2+→Cu0), and the reduced OC can be regenerated by the air oxidation (Cu0→Cu2+); In working stage, the reduced OC (Cu0) plays the role of catalyzing methanol conversion, and the heat generated from HT-PEMFC stack can be recovered by the methanol reforming module. The effects of CL-reformer conditions on the methanol reformate quality and the performance of HT-PEMFC stack are investigated. Furthermore, the feasibility of maintaining thermally neutral of the integrated system is discussed. Simulation results indicate that the CL-reformer-HT-PEMFC system can achieve auto-thermal operation, in which the system electrical efficiencies of 21.6%–26.7% and 47.7% can be obtained at start-up and working stages, respectively.

Production of Hydrogen-Rich Gas by Oxidative Steam Reforming of Dimethoxymethane over CuO-CeO2/γ-Al2O3 Catalyst

The catalytic properties of CuO-CeO2 supported on alumina for the oxidative steam reforming (OSR) of dimethoxymethane (DMM) to hydrogen-rich gas in a tubular fixed bed reactor were studied. The CuO-CeO2/γ-Al2O3 catalyst provided complete DMM conversion and hydrogen productivity &gt; 10 L h−1 gcat−1 at 280 °C, GHSV (gas hourly space velocity) = 15,000 h−1 and DMM:O2:H2O:N2 = 10:2.5:40:47.5 vol.%. Comparative studies showed that DMM OSR exceeded DMM steam reforming (SR) and DMM partial oxidation (PO) in terms of hydrogen productivity. Thus, the outcomes of lab-scale catalytic experiments show high promise of DMM oxidative steam reforming to produce hydrogen-rich gas for fuel cell feeding.

Ruthenium substituted pyrochlore metal oxide catalysts Y2Ce2-xRuxO7-δ (x = 0–0.4) for oxidative steam reforming of ethanol

Metal oxides Y2Ce2-xRuxO7-δ (x = 0–0.4) with partial substitution of Run+ cations in the host structure were synthesized to study their catalytic activity on oxidative steam reforming of ethanol (OSRE). The samples were characterized using X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and temperature-programmed reduction (TPR). The performances investigated by varied temperatures, Ru ion content, carbon-to-oxygen ratios and long-term stability. The lowest activation temperature on OSRE is 300 °C, which is significantly lower than that of La2Ce2-xRuxO7-δ (400 °C). The cell dimension of Y2Ce2-xRuxO7-δ was reduced compare to La2Ce2-xRuxO7-δ for the replacement of the Y3+ ion with La3+ ion. The reduced unit cell in the host structure not only increase the surface composition of the Ce4+ ions, but also induce the synergetic effect of Run+/Ru4+ (n > 4) and Ce4+/Ce3+, which lead to the enhanced OSRE activity. The optimized catalyst Y2Ce1.6Ru0.4O7-δ showed selectivity of hydrogen SH2 = 84(4)% (YH2 = 2.5(1) mol/mol EtOH) and carbon monoxide SCO = 48(1)% for long-term stability test at T = 300 °C, C/O = 0.5, and O2/C2H5OH = 1.5.

Deactivation of Ni spinel derived catalyst during the oxidative steam reforming of raw bio-oil

Deactivation of a bulk catalyst derived from NiAl2O4 spinel during the oxidative steam reforming (OSR) of raw bio-oil has been studied. The experiments were performed in a continuous system with two units in series: a thermal treatment unit at 500 °C for the controlled deposition of pyrolytic lignin, and a fluidized bed reactor (700 °C; S/C, 6; O/C, 0.34; space time, 0.15 gcatalysth·gbio-oil−1; time on stream, 1, 2, 4 and 6 h) for the OSR of the remaining oxygenates. The deactivation affects the reforming of bio-oil oxygenates according to their reactivity (from lower to higher), with the reforming of phenols being rapidly affected. The causes of deactivation are: i) coke deposition on the Ni0 sites and on the Al2O3 support (6 wt% of each coke type after 6 h on stream), and; ii) sintering of Ni0 crystals (with an increase in crystal size from 10.8 to 17.7 nm (measured by TEM)). The catalyst deactivation rate increases with time on stream, with the bio-oil oxygenates being the main coke precursors.

Thermodynamic assessment of the oxidative steam reforming of biomass fast pyrolysis volatiles

The joint process of pyrolysis-steam reforming is a novel and promising strategy for hydrogen production from biomass; however, it is conditioned by the endothermicity of the reforming reaction and the fast catalyst deactivation. Oxygen addition may potentially overcome these limitations. A thermodynamic equilibrium approach using Gibbs free energy minimization method has been assumed for the evaluation of suitable conditions for the oxidative steam reforming (OSR) of biomass fast pyrolysis volatiles. The simulation has been carried out contemplating a wide range of reforming operating conditions, i.e., temperature (500–800 °C), steam/biomass (S/B) ratio (0–4) and equivalence ratio (ER) (0–0.2). It is to note that the simulation results under steam reforming (SR) conditions are consistent with those obtained by experiments. Temperatures between 600 and 700 °C, S/B ratios in the 2–3 range and ER values of around 0.12 are the optimum conditions for the OSR under autothermal reforming (ATR) conditions, as they allow attaining high hydrogen yields (10 wt% by mass unit of the biomass in the feed), which are only 12–15% lower than those obtained under SR conditions.

Hydrogen generation from methanol reforming for fuel cell applications: A review

Methanol is regarded as an important liquid fuel for hydrogen storage, transportation, and in-situ generation due to its convenient conveyance, high energy density, and low conversion temperature. In this work, an overview of state-of-the-art investigations on methanol reforming is critically summarized, including the detailed introduction of methanol conversion pathways from the perspective of fuel cell applications, various advanced materials design for catalytic methanol conversion, as well as the development of steam methanol reformers. For the section of utilization pathways, reactions such as steam reforming of methanol, partial oxidation of methanol, oxidative steam reforming of methanol, and sorption-enhanced steam methanol reforming were elaborated; For the catalyst section, the strategies to enhance the catalytic activity and other comprehensive performances were summarized; For the reactor section, the newly designed steam methanol reformers were thoroughly described. This review will benefit researchers from both fundamental research and fuel cell applications in the field of catalyzing methanol to hydrogen.

Hydrogen Production on Cu-Ni Catalysts via the Oxy-Steam Reforming of Methanol

In this work, bimetallic Cu-Ni catalysts supported on binary oxides containing ZnO, ZrO2, CeO2 and Al2O3 were investigated in hydrogen production via the oxidative steam reforming of methanol (OSRM). Their physicochemical properties were extensively studied using various methods such as BET, TPR-H2, TPD-NH3, XRD, SEM-EDS, ToF-SIMS and XPS. The reactivity measurements showed that the active phase and support composition played an important role in the activity of the catalyst in the OSRM. The most active system at higher temperatures was 30% Cu–10% Ni/CeO2·Al2O3, with high catalytic activity attributed to the Cu0.8Ni0.2 alloy formation. In addition, the reactivity results showed that the most active catalyst exhibited high acidity and was easily reduced. At low temperatures, the best catalytic properties were exhibited by 30% Cu–10% Ni/ZrO2·Al2O3. The reactivity and physicochemical properties of the studied catalysts confirmed the crucial role of alloy composition on their catalytic properties in the oxy-steam reforming of methanol. The obtained results validate the possibility of using Cu-Ni catalysts for hydrogen production.

Chemical looping oxidative steam reforming of methanol: A new pathway for auto-thermal conversion

Auto-thermal reforming of methanol is an attractive route for low-temperature methanol conversion for hydrogen production. This paper describes utilization the lattice oxygen of Cu2O/Ca2Fe2O5 participates the partial oxidation of methanol to achieve the efficient auto-thermal reforming of methanol. ASPEN Plus software was adopted to verify the feasibility of auto-thermal conversion of methanol via Cu↔Cu2O looping and provided a comprehensive understanding of the associated process via operating parameter optimization. A series of CuO/Ca2Fe2O5 with different contents of copper were prepared as the catalytic oxygen carrier (COC) which goes through the reduction → catalytic methanol conversion →re-oxidation. The surface and bulk properties of COCs were characterized by XRD, XPS, TEM-EDS mapping, Raman, and H2-TPR; the reaction pathways were investigated using CH3OH-pulse and in situ DRIFTS. Results indicate that 40 % Cu-loaded Cu2O-Ca2Fe2O5 shows the highest catalytic activity of the synthesized COCs, and the presence of Ca2Fe2O5 tunes the redox activity and mobility of the lattice oxygen, obtaining a H2 production rate of 37.6 μmol·H2∙g−1·COC·s−1 at 240 °C. The reaction pathways of chemical looping methanol conversion follow the sequence: CH3OH full oxidation → formaldehyde intermediate → methyl-formate intermediate as the amount of lattice oxygen decreases gradually.

A hybrid phosphorus-acid fuel cell system incorporated with oxidative steam reforming of methanol (OSRM) reformer

In this paper, a phosphoric acid fuel cell integrated with reformer and evaporator is demonstrated. Oxidative steam reforming of methanol (OSRM) process is employed in this system in cooperated with a high efficient evaporator, and the reacted gas is sent into a phosphorus-acid fuel cell (PAFC) for direct power generation after surplus methanol/water filtration. The results show that the maximum power density of this hybrid system achieves 277 mW/cm2 without CO2 removal, while it achieves 485 mW/cm2 when employing pure hydrogen as the fuel.

The influence of the size of metal particles on the catalytic activity of Ni and Cu-supported catalysts in methanol reforming reaction

The aim of the work was to investigate how the size of Ni and Cu-supported nanoparticles influence their activity in an oxidative steam reforming of methanol. The size of metal particles was controlled by the initial introduction or elimination of oxygen-containing groups on the surface of carbon nanotubes. The results of the activity tests showed that catalysts with the smallest metal nanoparticles were the least active since they easily underwent oxidation during the process.

Oxidative steam conversion of light alkanes

Oxidative steam reforming of C2-C4 alkanes was studied in an annular catalytic reactor under atmospheric pressure over two catalysts. Concentrations of the products of chemical reactions in the outlet gas mixture were measured at different temperatures of reactor. Effects of temperature have been compared for different residence time for the inlet gas ratio water/air/C2-C4 alcanes of 7: 4.5:1.

Effect of acid on the crystalline phase of TiO2 prepared by hydrothermal treatment and its application in the oxidative steam reforming of methanol

Titania (TiO2) supports with anatase (A), mixed, and rutile (R) crystalline phases were prepared via the hydrothermal treatment of titanium isopropoxide and investigated as a catalyst for the oxidative steam reforming of methanol (OSRM). The different TiO2 phases were synthesized using different types of acid: acetic (HAc), nitric, and a mixture of HAc and hydrochloric acids, and hydrothermal (90 or 200 °C) or calcination (560 or 750 °C) temperatures. X-ray diffraction analysis revealed the crystal structure of successfully synthesized TiO2 with different TiO2-A:TiO2-R ratios. The TiO2-R with (110) and (101) planes showed the highest catalytic activity for OSRM in the temperature range of 200–400 °C.