Improvement of steam methane reforming via in-situ CO2 sorption over a nickel-calcium composite catalyst

Optimization of steam methane reforming (SMR) reaction by CO₂ sorption enhancement was investigated. In this study, the sorption-enhanced steam methane reforming reaction (SESMR) was conducted to maximize hydrogen production via suitable adjustments in the operating conditions of the reaction, which include the molar ratio of steam to CH₄, space velocity, and temperature. The reforming catalysts were prepared by a physical mixture of 20 wt% Ni/Al₂O₃ and CaO. The results reveal that there are significant differences in CH₄ conversion between the SMR and the SESMR from 18% to 108%; this conversion strongly depended on the reaction conditions. High-purity H₂ products (98.9%) with <0.1 ppmv CO were obtained by SESMR under the suitable conditions of 2600 cm³/g/h, steam/CH₄ molar ratio of 4 and 823 K. This implies that the high-quality H₂ produced through the SESMR process could be directly used for the proton-exchange membrane fuel cell.     

Ni-hydrocalumite derived catalysts for ethanol steam reforming on hydrogen production

Hydrocalumite derived catalysts prepared by co-precipitation with non-noble metal Nickel(Ni) as main active site were tested in ethanol steam reforming, and the influences of Ni (5,10,15 wt%) content were mainly tested in this research. Meanwhile, the physicochemical properties of the prepared catalysts were analyzed through different characterizations including BET, X-ray diffraction (XRD), H₂-temperature programmed reduction (H₂-TPR) and CO₂-temperature programmed desorption (TPD). As the Ni increased, the specific surface area, crystallite size of Ni, reducibility and basicity of catalysts were changed, which further affected their activities. On this basis, the best performance in this catalytic system was presented when Ni in the catalysts was 15 wt%, the ethanol conversion and hydrogen yield could reach almost 100% and 85% at 650 °C respectively. Thus, this kind of catalyst is effective for ethanol steam reforming.     

Simulation of sorption enhanced staged gasification of biomass for hydrogen production in the presence of calcium oxide

A novel two-step sorption enhanced staged gasification of biomass for H₂ production was proposed and studied using Aspen Plus software. An equilibrium model based on Gibbs free energy minimization was developed and validated. The results showed that the two-step process was more advantageous for H₂ production compared with the conventional steam gasification and the one-step process. The independent control of each stage could realize a high temperature steam gasification in the first stage and a subsequent lower temperature steam reforming in the second stage, which thus promoted the gasification of biomass and benefited the water gas shift (WGS) reaction to produce more H₂. Meanwhile, the in situ CO₂ absorption of CaO in the second stage could enrich the H₂ concentration in the product gas, and also further shifted the WGS reaction equilibrium to convert more CO to H₂. With further introduction of catalyst for steam methane reforming (SMR), high-purity H₂ with the concentration of 99.7 vol% and yield of 142.8 g/kg daf biomass could be achieved.     

Hydrogen production from methane and solar energy – Process evaluations and comparison studies

Three conventional and novel hydrogen and liquid fuel production schemes, i.e. steam methane reforming (SMR), solar SMR, and hybrid solar-redox processes are investigated in the current study. H₂ (and liquid fuel) productivity, energy conversion efficiency, and associated CO₂ emissions are evaluated based on a consistent set of process conditions and assumptions. The conventional SMR is estimated to be 68.7% efficient (HHV) with 90% CO₂ capture. Integration of solar energy with methane in solar SMR and hybrid solar-redox processes is estimated to result in up to 85% reduction in life-cycle CO₂ emission for hydrogen production as well as 99–122% methane to fuel conversion efficiency. Compared to the reforming-based schemes, the hybrid solar-redox process offers flexibility and 6.5–8% higher equivalent efficiency for liquid fuel and hydrogen co-production. While a number of operational parameters such as solar absorption efficiency, steam to methane ratio, operating pressure, and steam conversion can affect the process performances, solar energy integrated methane conversion processes have the potential to be efficient and environmentally friendly for hydrogen (and liquid fuel) production.     

Study of LPG steam reform using Ni/Mg/Al hydrotalcite-type precursors

Liquefied petroleum gas (LPG) is a mixture of hydrocarbons that has a broad distribution network in several countries. In this context, the objective of this study was to evaluate the steam reforming of LPG using catalysts derived from hydrotalcites. The precursors were characterized by X-ray fluorescence analysis, BET surface area, temperature programmed reduction, thermogravimetric analysis, in situ X-ray diffraction spectroscopy and X-ray absorption spectroscopy. Catalysts were synthesized with 47.5% Ni content without increasing the particle diameter. All catalysts showed the formation of the same gas phase products: H₂, CO, CH₄ and CO₂. Ni_1.64Mg_1.36Al catalyst showed the highest conversion (about 70%) and lower deactivation by coke deposition after 24 h reaction. The use of higher reaction temperatures (1073 and 1173 K), for steam reforming process, resulted in higher conversions of LPG, increased formation of H₂ and lowered the formation of carbon deposits.     

Bimetallic catalysts performance during ethanol steam reforming: Influence of support materials

Ni–Cu catalysts supported on different materials were tested in ethanol steam reforming reaction for hydrogen production. These catalysts were evaluated at reaction temperature of 400 °C under atmospheric pressure. The reagents, with a water/ethanol molar ratio equal to 10, were fed at 70 dm³/(h g_cat) (after vaporization). Analysis of the ethanol conversion, as well as evaluation and quantification of the reaction products, indicated the catalyst 10% Ni–1% Cu/Ce_0.6Zr_0.4O₂ as the most appropriate for the ethanol steam reforming under investigated reaction conditions, among the studied catalysts. During 8 h of reaction this catalyst presented an average ethanol conversion of 43%, producing a high amount of H₂ by steam reforming and by ethanol decomposition and dehydrogenation parallel reactions. Steam reforming, among the observed reactions, was quantified by the presence of carbon dioxide. About 60% of the hydrogen was produced from ethanol steam reforming and 40% from parallel reactions.     

Hydrogen production by coupled catalytic partial oxidation and steam methane reforming at elevated pressure and temperature

Hydrogen production by coupled catalytic partial oxidation (CPO) and steam methane reforming of methane (OSMR) at industrial conditions (high temperatures and pressures) have been studied over supported 1 wt.% NiB catalysts. Mixture of air/CH₄/H₂O was applied as the feed. The effects of O₂:CH₄ ratio, H₂O:CH₄ ratio and the gas hourly space velocity (GHSV) on oxy-steam reforming (OSRM) were also studied. Results indicate that CH₄ conversion increases significantly with increasing O₂:CH₄ or H₂O:CH₄ ratio. However, the hydrogen mole fraction goes through a maximum, depending on reaction conditions, e.g., pressure, temperature and the feed gases ratios. Carbon deposition on the catalysts has been greatly decreased after steam addition. The supported 1 wt.% NiB catalysts exhibit high stability with 85% methane conversion at 15 bar and 800 °C during 70 h time-on-stream reaction (CH₄:O₂:H₂O:N₂ = 1:0.5:1:1.887). The thermal efficiency was increased from 35.8% by CPO (without steam) to 55.6%. The presented data would be useful references for further design of enlarged scale hydrogen production system.     

Perovskite-based catalysts for tar removal by steam reforming: Effect of the presence of hydrogen sulfide

One of the greatest problems in biomass gasification processes is the conditioning of the produced synthesis gas, which contains various contaminants, including tar and hydrogen sulfide. Nickel catalysts, designed for steam reforming of aliphatic hydrocarbons (natural gas and nafta), are usually deactivated by coke deposition and sulfur poisoning. In this work, nickel and/or manganese catalysts derived from perovskites were prepared by the citrate method and characterized by X-ray diffraction, N₂ physisorption and temperature programmed reduction. The catalysts were evaluated in the steam reforming of toluene, used as tar model compound, in the absence of H₂S at 700 °C and in the presence of 50 ppm H₂S at 800 °C. LaNi_0.5Mn_0.5O₃ catalyst showed higher activity and stability in the absence of H₂S. LaMnO₃ catalyst, although less active in the absence of H₂S, showed increased stability in the presence of H₂S, with conversion of about 60%. H₂ production was only observed in the absence of H₂S.     

Thermodynamic analysis of hydrogen production via glycerol steam reforming with CO2 adsorption

Thermodynamic equilibrium for glycerol steam reforming to hydrogen with carbon dioxide capture was investigated using Gibbs free energy minimization method. Potential advantage of using CaO as CO₂ adsorbent is to generate hydrogen-rich gas without a water gas shift (WGS) reactor for proton exchange membrane fuel cell (PEMFC) application. The optimal operation conditions are at 900 K, the water-to-glycerol molar ratio of 4, the CaO-to-glycerol molar ratio of 10 and atmospheric pressure. Under the optimal conditions, complete glycerol conversion and 96.80% H₂ and 0.73% CO concentration could be achieved with no coke. In addition, reaction conditions for coke-free and coke-formed regions are also discussed in glycerol steam reforming with or without CO₂ separation. Glycerol steam reforming with CO₂ adsorption has the higher energy efficiency than that without adsorption under the same reaction conditions.     

Simulation of steam reforming of biogas in an industrial reformer for hydrogen production

The paper aims to investigate the steam reforming of biogas in an industrial-scale reformer for hydrogen production. A non-isothermal one dimensional reactor model has been constituted by using mass, momentum and energy balances. The model equations have been solved using MATLAB software. The developed model has been validated with the available modeling studies on industrial steam reforming of methane as well as with the those on lab-scale steam reforming of biogas. It demonstrates excellent agreement with them. Effect of change in biogas compositions on the performance of industrial steam reformer has been investigated in terms of methane conversion, yields of hydrogen and carbon monoxide, product gas compositions, reactor temperature and total pressure. For this, compositions of biogas (CH₄/CO₂ = 40/60 to 80/20), S/C ratio, reformer feed temperature and heat flux have been varied. Preferable feed conditions to the reformer are total molar feed rate of 21 kmol/h, steam to methane ratio of 4.0, temperature of 973 K and pressure of 25 bar. Under these conditions, industrial reformer fed with biogas, provides methane conversion (93.08–85.65%) and hydrogen yield (1.02–2.28), that are close to thermodynamic equilibrium condition.     

Modelling of H2 production via sorption enhanced steam methane reforming at reduced pressures for small scale applications

The production of H₂ via sorption enhanced steam reforming (SE-SMR) of CH₄ using 18 wt % Ni/Al₂O₃ catalyst and CaO as a CO₂-sorbent was simulated for an adiabatic packed bed reactor at the reduced pressures typical of small and medium scale gas producers and H₂ end users. To investigate the behaviour of reactor model along the axial direction, the mass, energy and momentum balance equations were incorporated in the gPROMS modelbuilder^®. The effect of operating conditions such as temperature, pressure, steam to carbon ration (S/C) and gas mass flow velocity (G_s) was studied under the low-pressure conditions (2–7 bar). Independent equilibrium based software, chemical equilibrium with application (CEA), was used to compare the simulation results with the equilibrium data. A good agreement was obtained in terms of CH₄ conversion, H₂ yield (wt. % of CH₄ feed), purity of H₂ and CO₂ capture for the lowest (G_s) representing conditions close to equilibrium under a range of operating temperatures pressures, feed steam to carbon ratio. At G_s of 3.5 kg m⁻²s⁻¹, 3 bar, 923 K and S/C of 3, CH₄ conversion and H₂ purity were up to 89% and 86% respectively compared to 44% and 63% in the conventional reforming process.     

Hydrogen production by radio frequency plasma stimulation in methane hydrate at atmospheric pressure

Methane hydrate, formed by injecting methane into 100 g of shaved ice at a pressure of 7 MPa and reactor temperature of 0 °C, was decomposed by applying 27.12 MHz radio frequency plasma in order to produce hydrogen. The process involved the stimulation of plasma in the methane hydrate with a variable input power at atmospheric pressure. It was observed that production of CH₄ is optimal at a slow rate of CH₄ release from the methane hydrate, as analyzed by in light of the steam methane reforming (SMR) and the methane cracking reaction (MCR) processes in accordance with the content of gas production. In comparison with the steam methane reforming (SMR), it was found that methane-cracking reaction (MCR) was dominant in conversion of CH₄ into hydrogen. An H₂ content of 55% in gas production was obtained from conversion of 40% of CH₄ at an input power of 150 W. The results clearly show that hydrogen can be directly produced from methane hydrate by the in-liquid plasma method.     

Hydrogen production by reforming of liquid hydrocarbons in a membrane reactor for portable power generation—Experimental studies

One of the most promising technologies for lightweight, compact, portable power generation is proton exchange membrane (PEM) fuel cells. PEM fuel cells, however, require a source of pure hydrogen. Steam reforming of hydrocarbons in an integrated membrane reactor has potential to provide pure hydrogen in a compact system. Continuous separation of product hydrogen from the reforming gas mixture is expected to increase the yield of hydrogen significantly as predicted by model simulations. In the laboratory-scale experimental studies reported here steam reforming of liquid hydrocarbon fuels, butane, methanol and Clearlite^® was conducted to produce pure hydrogen in a single step membrane reformer using commercially available Pd–Ag foil membranes and reforming/WGS catalysts. All of the experimental results demonstrated increase in hydrocarbon conversion due to hydrogen separation when compared with the hydrocarbon conversion without any hydrogen separation. Increase in hydrogen recovery was also shown to result in corresponding increase in hydrocarbon conversion in these studies demonstrating the basic concept. The experiments also provided insight into the effect of individual variables such as pressure, temperature, gas space velocity, and steam to carbon ratio. Steam reforming of butane was found to be limited by reaction kinetics for the experimental conditions used: catalysts used, average gas space velocity, and the reactor characteristics of surface area to volume ratio. Steam reforming of methanol in the presence of only WGS catalyst on the other hand indicated that the membrane reactor performance was limited by membrane permeation, especially at lower temperatures and lower feed pressures due to slower reconstitution of CO and H₂ into methane thus maintaining high hydrogen partial pressures in the reacting gas mixture. The limited amount of data collected with steam reforming of Clearlite^® indicated very good match between theoretical predictions and experimental results indicating that the underlying assumption of the simple model of conversion of hydrocarbons to CO and H₂ followed by equilibrium reconstitution to methane appears to be reasonable one.     

A review on bi/polymetallic catalysts for steam methane reforming

Blue hydrogen production by steam methane reforming (SMR) with carbon capture is by far the most commercialised production method, and with the addition of a simultaneous in-situ CO₂ adsorption process, sorption-enhanced steam methane reforming (SESMR) can further decrease the cost of H₂ production. Ni-based catalysts have been extensively used for SMR because of their excellent activity and relatively low price, but carbon deposition, sulphation, and sintering can lead to catalyst deactivation. One effective solution is to introduce additional metal element(s) to improve the overall performance. This review summarizes recent developments on bi/polymetallic catalysts for SMR, including promoted nickel-based catalysts and other transition metal-based bi/polymetallic materials. The review mainly focuses on experimental studies, but also includes results from simulations to evaluate the synergistic effects of selected metals from an atomic point of view. An outlook is provided for the future development of bi/polymetallic SMR catalysts.     

Synergistic catalysis of bi-metals in the reforming of biomass-derived hydrocarbons: A review

Biomass such as ethanol and glycerol has emerged as an alternative feedstock for hydrogen (H₂) production in recent years. Ethanol, which is high in H_2, can easily be derived from renewable biomass sources, whereas; glycerol is a by-product of biodiesel expected to be surplus in the coming years. Several catalytic reforming routes involving biomass such as steam, CO₂, auto thermal, partial oxidation and aqueous-phase reforming can produce syngas or H₂. Bimetallic catalysis is one of the potential solutions to reduce carbon formation and catalysts deactivation in reforming processes since it can produce more stable catalysts from the synergistic effect of the combined metals. There are many reviews on catalyst designs and reaction pathways reported in the literature; nevertheless, comparative literature is lacking on the metal configuration of bimetallic catalyst in biomass reforming particularly for ethanol and glycerol reforming reactions. Therefore, studies linked with the synergistic effects of various bi-metal combinations of catalysts used in biomass reforming processes have been reviewed in the paper. Moreover, the study provides data for the application of bimetallic catalyst for industrial biomass processes.     

Hydrogen production from methane and natural gas steam reforming in conventional and microreactor reaction systems

Ni-based (over MgO and Al₂O₃) and noble metal-based (Pd and Pt over Al₂O₃) catalysts were prepared by wet impregnation method and thereafter impregnated in microreactors. The catalytic activity was measured at several temperatures, atmospheric pressure and different steam to carbon, S/C, ratios. These conditions were the same for conventional, fixed bed reactor system, and microreactors. Weight hourly space velocity, WHSV, was maintained equal in order to compare the activity results from both reaction systems. For microreactor systems, similar activities of Ni-based catalyst were measured in the steam methane reforming (SMR) activity tests, but not in the case of natural gas steam reforming tests. When noble metal-based catalysts were used in the conventional reaction system no significant activity was measured but all catalysts showed some activity when they were tested in the microreactor systems. The analysis by SEM and TEM revealed a carbon-free surface for Ni-based catalyst as well as carbon filaments growth in case of noble metal-based catalysts.     

Effect of ruthenium addition on molybdenum catalysts for syngas production via catalytic partial oxidation of methane in a monolithic reactor

Hydrogen is mainly produced from hydrocarbon resources. Natural gas, mostly composed of methane, is widely used for hydrogen production. As a valuable feedstock for ‘Fischer–Tropsch’ (FT) process and ‘Gas to Liquids’ (GTL) technology, syngas production from catalytic partial oxidation of methane (CPOM) is gaining prominence especially owing to its more desirable H₂/CO ratio; relatively less energy consumption, and lower investment, compared to steam reforming processes (SMR), the leading technology.In the present study, effect of ruthenium (Ru) addition on molybdenum (Mo) catalysts for syngas production from methane (CH₄) via partial oxidation in a monolithic reactor was investigated. Mo based catalysts supported on Nickel (Ni) and Cobalt (Co) metal oxides and Ni-Co bimetallic oxides and their Ru added versions were developed, characterized, and tested for performance in a monolithic type reactor system. Catalyst activity was investigated in terms of H₂ and CO selectivity, CH₄ conversion; and CO₂ emission and it is concluded that addition of Ru over the structure led to increase in catalytic activity and reduction in carbon deposition over the catalyst surface.     

Ni/Ru–Mn/Al2O3 catalysts for steam reforming of toluene as model biomass tar

The catalytic steam reforming of the major biomass tar component, toluene, was studied over two commercial Ni-based catalysts and two prepared Ru–Mn-promoted Ni-base catalysts, in the temperatures range 673–1073 K. Generally, the conversion of toluene and the H₂ content in the product gas increased with temperature. A H₂-rich gas was generated by the steam reforming of toluene, and the CO and CO₂ contents in the product gas were reduced by the reverse Boudouard reaction. A naphtha-reforming catalyst (46-5Q) exhibited better performance in the steam reforming of toluene at temperatures over 873 K than a methane-reforming catalyst (Reformax 330). Ni/Ru–Mn/Al₂O₃ catalysts showed high toluene reforming performance at temperatures over 873 K. The results indicate that the observed high stability and coking resistance may be attributed to the promotional effects of Mn on the Ni/Ru–Mn/Al₂O₃ catalyst.     

Optimization of hydrogen production from steam reforming of biomass tar over Ni/dolomite/La2O3 catalysts

Industrially, the endothermic process of steam reforming is carried out at the lowest temperature, steam to carbon (S/C) ratio, and gas hourly space velocity (GHSV) for maximum hydrogen (H₂) production. In this study, a three-level three factorial Box-Behnken Design (BBD) of Response Surface Methodology (RSM) was applied to investigate the optimization of H₂ production from steam reforming of gasified biomass tar over Ni/dolomite/La₂O₃ (NiDLa) catalysts. Consequently, reduced quadratic regression models were developed to fit the experimental data adequately. The effects of the independent variables (temperature, S/C ratio, and GHSV) on the responses (carbon conversion to gas and H₂ yield) were examined. The results indicated that reaction temperature was the most significant factor affecting both responses. Ultimately, the optimum conditions predicted by RSM were 775 °C, S/C molar ratio of 1.02, and GHSV of 14,648 h⁻¹, resulting in 99 mol% of carbon conversion to gas and 82 mol% of H₂ yield.     

Bioethanol/glycerol mixture steam reforming over Pt and PtNi supported on lanthana or ceria doped alumina catalysts

The catalytic activity of Pt and PtNi catalysts supported on γ-Al₂O₃ modified by La and Ce oxides was investigated in the steam reforming of ethanol/glycerol mixtures. In general, all the catalysts fully converted the glycerol at the temperatures tested. However, the conversion of ethanol depended on the reaction temperature and catalyst type. The conversion into gaseous products operating at 500 °C and 450 °C was 100% using the most active catalysts (PtNiAl6La and PtNiAl10Ce). These two bimetallic catalysts gave H₂ yields close to those predicted by thermodynamic equilibrium at these temperatures. However, when the reaction temperature was lowered to 400 °C, these catalytic systems and the PtNiAl one recorded a significant decrease in ethanol conversion and H₂ yield, which moved away from the thermodynamic equilibrium value. This deviation was due to intermediate liquid products (acetaldehyde, acrolein, etc.) not being further reformed and the formation of other gaseous ones (light alkanes and ethylene). PtNiAl10Ce catalyst presented the highest conversion into gas at 400 °C, resulting in the largest H₂ yield, followed by PtNiAl6La and PtNiAl catalysts. This order is in agreement with the Ni/Al surface atomic ratio measured by XPS technique in reduced samples. However, filamentous carbon nanotubes were detected but this carbon type maintained the active sites accessible for reactants, since TEM and TGA results showed that the density of this carbon was lower for PtNiAl₁₀Ce catalyst. Pt catalysts presented lower activity than PtNi catalysts possibly due to the formation of carbon nanotubes, which covered some metallic active sites.