Numerical and experimental study on hydrogen production via dimethyl ether steam reforming

This work presents the characteristics of catalytic dimethyl ether (DME)/steam reforming based on a Cu–Zn/γ-Al₂O₃ catalyst for hydrogen production. A kinetic model for a reformer that operates at low temperature (200 °C–500 °C) is simulated using COMSOL 5.2 software. Experimental verification is performed to examine the critical parameters for the reforming process. During the experiment, superior Cu–Zn/γ-Al₂O₃catalysts are manufactured using the sol-gel method, and ceramic honeycombs coated with this catalyst (1.77 g on each honeycomb, five honeycombs in the reactor) are utilized as catalyst bed in the reformer to enhance performance. The steam, DME mass ratio is stabilized at 3:1 using a mass flow controller (MFC) and a generator. The hydrogen production rate can be significantly affected depending on the reactant's mass flow rate and temperature. And the maximum hydrogen yield can reach 90% at 400 °C. Maximum 8% error for the hydrogen yield is achieved between modeling and experimental results. These experiments can be further explored for directly feeding hydrogen to proton exchange membrane fuel cell (PEMFC) under the load variations.     

Numerical simulation and experimental study of hydrogen production from dimethyl ether steam reforming in a micro-reactor

To enhance the heat and mass transfer during dimethyl ether (DME) steam reforming, a micro-reactor with catalyst coated on nickel foam support was designed and fabricated. A two-dimensional numerical model with SIMPLE algorithm and finite volume method was used to investigate 1) the fluid flow, 2) the heat transfer and 3) chemical reactions consist of DME hydrolysis, methanol steam reforming, methanol decomposition and water gas shift reactions. Both the numerical and the experimental results showed that the DME conversion in the micro-reactor is higher than that in the fixed bed reactor. The numerical study also showed that the velocity and the temperature distribution were more uniform in the micro-reactor. Wall temperature, porosity and steam/DME ratio have been investigated in order to optimize the process in the micro-reactor. The wall temperature of 270 °C and the steam/DME feed ratio of 5 were recommended. Meanwhile the results indicate that a larger porosity will give a higher DME conversion and CO concentration.     

A review on reforming bio-ethanol for hydrogen production

Bio-ethanol is a prosperous renewable energy carrier mainly produced from biomass fermentation. Reforming of bio-ethanol provides a promising method for hydrogen production from renewable resources. Besides operating conditions, the use of catalysts plays a crucial role in hydrogen production through ethanol reforming. Rh and Ni are so far the best and the most commonly used catalysts for ethanol steam reforming towards hydrogen production. The selection of proper support for catalyst and the methods of catalyst preparation significantly affect the activity of catalysts. In terms of hydrogen production and long-term stability, MgO, ZnO, _CeO2${\mathrm{CeO}}_2$, and _La2O3${\mathrm{La}}_2{\mathrm{O}}_3$ are suitable supports for Rh and Ni due to their basic characteristics, which favor ethanol dehydrogenation but inhibit dehydration. As Rh and Ni are inactive for water gas shift reaction (WGSR), the development of bimetallic catalysts, alloy catalysts, and double-bed reactors is promising to enhance hydrogen production and long-term catalyst stability. Autothermal reforming of bio-ethanol has the advantages of lesser external heat input and long-term stability. Its overall efficiency needs to be further enhanced, as part of the ethanol feedstock is used to provide low-grade thermal energy. Development of millisecond-contact time reactor provides a low-cost and effective way to reform bio-ethanol and hydrocarbons for fuel upgrading. Despite its early R&D stage, bio-ethanol reforming for hydrogen production shows promises for its future fuel cell applications.     

Sustainable hydrogen production for fuel cells by steam reforming of ethylene glycol: A consideration of reaction thermodynamics

The use of renewable biomass, such as ethylene glycol (EG), for hydrogen production offers a more sustainable system compared to natural gas and petroleum reforming. For the first time, the reaction thermodynamics of steam reforming and sorption enhanced steam reforming of EG have been investigated. Gibbs free energy minimization method was used to study the effect of pressure (1-5 atm), temperature (500-1100 K) and water to EG ratio (WER 0-8) on the production of hydrogen and the formation of associated by-products (CH₄, CO₂, CO, C). The results suggest that hydrogen production is optimum when steam reforming occurs at atmospheric pressure, 925 K and with a WER of 8. Moreover, working at high temperature (>900 K) and with a WER above 6 inhibits almost entirely the production of methane and carbon. The main source of hydrogen in the system is found to be steam reforming of methane and water gas shift reaction by the analysis of the response reactions (RERs). Hydrogen production is governed by the former reaction at low temperatures while the latter one comes into prominence as temperature increases. By coupling with in situ CO₂ capture using CaO, the formation of CO₂ and CO can be avoided and high purity of hydrogen (>99%) can be achieved.     

Millisecond methane steam reforming for hydrogen production: A computational fluid dynamics study

The potential of methane steam reforming to produce hydrogen in thermally integrated micro-chemical systems at short contact times was theoretically explored. Methane steam reforming coupled with methane catalytic combustion in microchannel reactors for hydrogen production was studied numerically. A two-dimensional computational fluid dynamics model with detailed chemistry and transport was developed. To provide guidelines for optimal design, reactor behavior was studied, and the effect of design parameters such as catalyst loading, channel height, and flow arrangement was evaluated. To understand how steam reforming can happen at millisecond contact times, the relevant process time scales were analyzed, and a heat and mass transfer analysis was performed. The importance of energy management was also discussed in order to obtain a better understanding of the mechanism responsible for efficient heat exchange between highly exothermic and endothermic reactions. The results demonstrated the feasibility of the design of millisecond reforming systems, but only under certain conditions. To achieve this goal, process intensification through miniaturization and the improvement in catalyst performance is very important, but not sufficient; very careful design and implementation of the system is also necessary to enable high thermal integration. The channel height plays an important role in determining the efficiency of heat exchange. A proper balance of the flow rates of the combustible and reforming streams is an important design criterion. Reactor performance is significantly affected by flow arrangement, and co-current operation is recommended to achieve a good energy balance within the system. The catalyst loading must be carefully designed to avoid insufficient reactant conversion or hot spots. Finally, operating windows were identified, and engineering maps for designing devices with desired power were constructed.     

Parametric study on electrochemical reforming of glycerol for hydrogen production

Hydrogen production by electrochemical reforming of glycerol was investigated in this study. Within this scope, the performance of the system under different operating conditions was evaluated by parametric studies and optimum operating conditions were determined. The effects of membrane type, membrane pre-treatment procedure and temperature were investigated. System performance was examined also with long-term tests. The formation of hydrogen at the cathode was determined by analyzing the product gases by gas chromatography. Optimum condition for maximum hydrogen production was obtained with the Zn/Zn electrode pair in the presence of 0.4 M glycerol and 0.04 M H₂SO₄ at the anode side, 0.04 M H₂SO₄ at the cathode side and with pre-treated Nafion XL membrane. As the result of performance tests, room temperature and 2 V potential were found to be the most suitable operating conditions.     

Overview of hydrogen production from biogas reforming: Technological advancement

In this article, possibilities of biogas reforming techniques for hydrogen production are discussed. The consideration of biogas reforming to produce H₂ and fuel cell application from membrane technology is presented. In steam reforming process, methane requires a high temperature for reaction, but a suitable catalyst can manage a higher temperature. The ratio of H₂/CO is close to 3, which means higher H₂ yield (above 70%). The ratio of H₂/CO to nearly 2 and H₂ yield almost 67% and also reduces the soot formation for partial oxidation process. In Auto thermal reforming, higher yield of H₂ is around 74% with the ratio of H₂/CO close to 2.8. The dry reforming process leads to a molar ratio H₂/CO of nearly one and H₂ yield of approximately 50%. The ratio of H₂/CO correspondingly improves and generates H₂ yield of approximately 60% for dry oxidation reforming process. For sustainable decentralized power generation in remote and rural areas, large-scale development of H₂ energy technology is required. Biogas reforming is an auspicious process for the production of green hydrogen gas as well as for reducing overburden on natural gas. The main benefit of using biogas for H₂ production as a renewable energy source is reducing excessive burden on natural gas and greenhouse gas emissions. Nowadays, the importance of renewable H₂ production has increased due to many reasons such as depletion of fossil fuel reserves, global environmental issues, energy issues, and demand for pure H₂.     

Economic analysis of hydrogen production from steam reforming process: A literature review

The interest in steam reforming process as an efficient method for hydrogen production has been greatly increasing, due to its efficiency during hydrogen production and low environmental problems compared to other techniques. The main objective of this review was to present a comprehensive study of environmental, economic aspects of hydrogen production from steam reforming of raw materials such as biomass, bio-gas, ethanol, and natural gas. From literature review, it was found that among methods for hydrogen production, steam reforming of natural gas has lower installed capital due to the precence of high amounts of unconverted hydrocarbons in the produced gas (so-called tar) during other methods such as steam reforming of bio-gas.     

A comparative assessment on hydrogen production from low- and high-temperature electrolysis

In this work a comparative analysis between low- and high-temperature electrolysis for hydrogen generation is assessed. A hydrogen production system based on Solid Oxide Electrolysis Cells (SOEC) is designed and modeled and compared to the performance of a more mature system based on PEM technology. The SOEC system mainly consists of an SOEC stack, a heat recovery system and a hydrogen compression section. Experimental data measured in steam electrolysis tests performed on single solid oxide cells were utilized into the model to characterize the stack performance. The model carries out a thermodynamic analysis in order to calculate the energy efficiency and the exergetic consumption of the system; these performances are subsequently compared with those of a low-temperature hydrogen generation system evaluated from experimental data measured in test sessions performed on a complete BoP integrating a pressurized Proton Exchange Membrane (PEM) electrolyser. The comparison is carried out with the two electrolysis systems generating hydrogen at the same production rate and pressure. The results of this study show that the modeled SOEC hydrogen generation system can compete with the PEM electrolyser, achieving better performance than the low-temperature system at hydrogen production rate higher than 18.3 g h⁻¹ (corresponding to 0.25 A cm⁻²) and showing an energy efficiency up to 14% higher than the PEM system at 1 A cm⁻².     

Underwater vehicle hydrogen production from methanol steam reforming using hydrogen peroxide

Methanol steam reforming (MSR) can supply hydrogen (H₂) to underwater vehicles equipped with a fuel cell. Low reaction temperatures ensure the composition of the reformed gas suitable for the H₂ purification unit and increase the design freedom of a reforming plant. However, such temperatures decrease the catalyst activity and thereby the methanol (MeOH) conversion and H₂ production. Herein, hydrogen peroxide (H₂O₂) was supplied with MeOH and water (H₂O) to ensure sufficient MeOH conversion and H₂ production at low temperatures. A tube reactor loaded with a commercial Cu/Zn catalyst was installed in an electric furnace maintained at 200–250 °C, and MeOH and 0 wt%, 11.88 wt%, 22.51 wt%, and 32.07 wt% H₂O₂ were supplied. When the furnace temperature was 200 °C, the MeOH conversion was 49.3% at 0 wt% H₂O₂ but 93.5% at 32.07 wt% H₂O₂. The effect of adding H₂O₂ was greater under the temperature conditions where the MeOH conversion was 100% or less. To analyze the effect of H₂O₂ addition on catalyst durability, the furnace was maintained at 200 °C, and the reactor was continuously operated for 110 h with 0 wt% and 32.07 wt% H₂O₂. The addition of H₂O₂ did not significantly decrease the Cu/Zn catalyst durability.     

Carbon nanotubes and hydrogen production from the reforming of toluene

Catalytic steam reforming of liquid hydrocarbons is one of the promising alternatives for hydrogen production. However, coke deposition on the reacted catalyst results in catalyst deactivation and also CO₂ emission during reforming are among the main challenges in the process. In this work, the production of high-value carbon nanotubes (CNTs) during hydrogen production from catalytic reforming of toluene has been investigated. Thus, less carbon emission and higher product values can be expected from the process. A two-stage fixed bed pyrolysis-reforming reactor was used in this work. The results showed that the addition of a Ni–Mg–Al catalyst, with an additional downstream stainless steel mesh, increased hydrogen production from 24.8 to 54.8 (mmol H₂ g⁻¹ toluene), when water (steam) was injected at a rate of 0.01 g min⁻¹. CNTs were also produced in the process in the presence of the Ni–Mg–Al catalyst and with a water injection rate of 0.01 g min⁻¹ had the highest band ratio of G′/G when analyzed by Raman spectrometry, indicating the highest purity of CNTs. In addition, Raman spectra of the generated CNTs showed that the purity of CNTs was reduced with the addition of water for reforming without the Ni–Mg–Al catalyst. The presence of the Ni–Mg–Al catalyst significantly increased the yield of CNTs formed on the surface of the stainless steel mesh and also improved the quality of the CNTs in relation to the distribution of diameters and their length.     

Solar hydrogen production: A comparative performance assessment

Hydrogen is a sustainable fuel option and one of the potential solutions for current energy and environmental problems. Its eco-friendly production is really crucial for better environment and sustainable development. In this paper, various solar hydrogen production methods are discussed. A comparative performance assessment study of solar thermal and photovoltaic (PV) hydrogen production methods is carried out. It is found that the solar thermal hydrogen production via electricity production is an environmentally benign method and possesses higher exergy efficiency than PV hydrogen production. However, the latter is better in a way that it does not involve any moving parts. PV hydrogen production suffers lower exergy efficiency because of low PV efficiency.     

Thermodynamic analysis of hydrogen production from glycerol autothermal reforming

In this work, thermodynamics was applied to investigate the glycerol autothermal reforming to generate hydrogen for fuel cell application. Equilibrium calculations employing the Gibbs free energy minimization were performed in a wide range of temperature (700–1000 K), steam to glycerol ratio (1–12) and oxygen to glycerol ratio (0.0–3.0). Results show that the most favorable conditions for hydrogen production are achieved with the temperatures, steam to glycerol ratios and oxygen to glycerol ratios of 900–1000 K, 9–12 and 0.0–0.4, respectively. Further, it is demonstrated that thermoneutral conditions (steam to glycerol ratio 9–12) can be obtained at oxygen to glycerol ratios of around 0.36 (at 900 K) and 0.38–0.39 (at 1000 K). Under these thermoneutral conditions, the maximum number of moles of hydrogen produced are 5.62 (900 K) and 5.43 (1000 K) with a steam to glycerol ratio of 12. Also, it should be noted that methane and carbon formation can be effectively eliminated.     

A thermodynamic study of propanol reforming in presence of hydrazine for hydrogen production

Thermodynamic analysis of hydrogen production from propanol reforming reactions, by decomposition and steam reforming, in presence of hydrazine was evaluated as a function of temperature (300–900 K) at a constant pressure of 1 atm. The molar ratio of reactants were varied to identify the conditions leading to hydrogen rich product stream with low carbon formation. Steam reforming of propanol displayed higher hydrogen production and a gradual decrease in carbon content with an increase in the steam/propanol ratio. Addition of hydrazine leads to a further enhancement in hydrogen amount along with a suppression in coking. A similar trend was observed in case of propanol decomposition reaction. Addition of hydrazine leads to a favorable condition for hydrogen production along with a decrease in carbon formation. In both, steam reforming and decomposition, methane and water seem to be the stable products at low temperature, which react together at elevated temperatures following steam reforming of methane to generate CO and hydrogen. Hydrazine, on the other hand diminishes carbon at low temperature and produces ammonia, which decomposes at higher temperature to generate hydrogen and nitrogen. It is clear that steam assists in eliminating carbon at higher temperature whereas hydrazine is helpful in removing carbon formation at lower temperature. Also, a considerably high ratio of H₂/CO can be maintained in both the reactions, propanol steam reforming and propanol decomposition, by introducing a hydrazine stream in the feed.     

Impact of bioethanol impurities on steam reforming for hydrogen production: A review

Hydrogen fuel cells (H₂–FCs) are promising devices for pollution-free and efficient power production. Renewable H₂ from biomass is often produced through catalytic ethanol steam reforming (ESR), which requires a steam/ethanol molar ratio of at least three. The bioethanol obtained by biomass fermentation contains large amounts of water and can be directly subjected to ESR without complex purification steps. However, a wide spectrum of impurities is present in such bioethanol samples, thus complicating the ESR process. Acetic acid, fusel alcohols, ethyl acetate, and sulfur components have been reported as important bioethanol impurities, and also as the main precursors of carbon deposits on the ESR catalyst. On the other hand, amines, methanol, and aldehydes, which are minor bioethanol impurities, have been reported to enhance the H₂ production. This review seeks to define alternatives to reduce the above negative impurities and increase the positive ones during biomass pretreatment and fermentation. Additionally, ESR catalysts are reviewed to identify the features that make them more resistant to deactivation. The combination of strategies to control the impurities during biomass pretreatment, fermentation, purification and the development of highly resistant catalysts may allow processes to produce H₂ from biomass with a low carbon footprint, rendering H₂–FCs an environmentally friendly technology for power production.     

Thermodynamic study of hydrogen production from crude glycerol autothermal reforming for fuel cell applications

This study presents a thermodynamic analysis of hydrogen production from an autothermal reforming of crude glycerol derived from a biodiesel production process. As a composition of crude glycerol depends on feedstock and processes used in biodiesel production, a mixture of glycerol and methanol, major components in crude glycerol, at different ratios was used to investigate its effect on the autothermal reforming process. Equilibrium compositions of reforming gas obtained were determined as a function of temperature, steam to crude glycerol ratio, and oxygen to crude glycerol ratio. The results showed that at isothermal condition, raising operating temperature increases hydrogen yield, whereas increasing steam to crude glycerol and oxygen to crude glycerol ratios causes a reduction of hydrogen concentration. However, high temperature operation also promotes CO formation which would hinder the performance of low-temperature fuel cells. The steam to crude glycerol ratio is a key factor to reduce the extent of CO but a dilution effect of steam should be considered if reforming gas is fed to fuel cells. An increase in the ratio of glycerol to methanol in crude glycerol can increase the amount of hydrogen produced. In addition, an optimal operating condition of glycerol autothermal reforming at a thermoneutral condition that no external heat to sustain the reformer operation is required, was investigated.     

Regenerable and durable catalyst for hydrogen production from ethanol steam reforming

In this work, perovskite-type oxides La_1−xCa_xFe_0.7Ni_0.3O₃ were prepared by using a citrate complex method. The catalysts were employed in the reactions of steam reforming of ethanol (SRE) and oxidative steam reforming of ethanol (OSRE) to produce hydrogen. A reduction-oxidation cycle was proposed to overcome the problems of active component sintering and carbon deposition encountered in SRE reaction. In the ex-situ reactions, highly dispersed surface nickel particles formed during the reduction of La_1−xCa_xFe_0.7Ni_0.3O₃, while during the introduction of an oxidative atmosphere these particles could be oxidized and restored back into the perovskite bulk. Owing to the existence of this segregation-incorporation cycle of nickel species in the perovskite oxides, the sintering of nickel particles under OSRE was found depressed effectively. Besides, this work proved that the oxygen in the feed is helpful to the elimination of deposited carbon. It seems promising for overcoming the problems of the active component sintering and carbon deposition in SRE reaction by regulating the redox ability of the perovskite-type oxides and the feed composition.     

Sustainable and energy efficient hydrogen production via glycerol reforming techniques: A review

Hydrogen-based energy solutions are among the alternative energy choices due to their clean emissions and high efficiency. H₂ is a highly convenient energy source, particularly if derived from sustainable feedstock. With the renewed emphasis on biodiesel production globally, large quantities of glycerol are expected to be produced as a major by-product. Reforming of this glycerol can provide a sustainable and H₂-rich feedstock. The study reveals that 7H₂ molecules were produced/molecule of glycerol in GSR, which is much higher than the commercially available SRM process. This also endorses the concept of circular economy and the 3Rs (Reuse, Reduce, and Recycle) by utilization of a by-product. This review highlights the recent advancements in different types of glycerol reforming technologies for H₂ production. The highly endothermic reaction and the coking of Ni-based catalysts are still the main limitations in its commercialization. It has been found that among different glycerol reforming techniques, the GSR is the finest with the least drawbacks. Hence, corresponding solutions to overcome these obstacles are deliberated.     

Renewable hydrogen production concepts from bioethanol reforming with carbon capture

This paper is assessing the hydrogen production from bioethanol at industrial scale (100000 Nm³/h hydrogen equivalent to 300 MW thermal) with carbon capture. Three carbon capture designs were investigated, one based on pre-combustion capture using chemical gas–liquid absorption and two based on chemical looping (one based on syngas and one using direct bioethanol looping). The carbon capture options were compared with the similar designs without carbon capture. The designs were simulated to produce mass and energy balances for quantification of key performance indicators. A particular accent is put on assessment of reforming technologies (steam and oxygen-blown autothermal reforming) and chemical looping units, process integration issues of carbon capture step within the plant, modelling and simulation of whole plant, thermal and power integration of various plant sub-systems by pinch analysis. The results for chemical looping designs (either syngas-based or direct bioethanol) show promising energy efficiency coupled with total carbon capture rate.