Conceptual design of a Ca–Cu chemical looping process for hydrogen production in integrated steelworks

A novel configuration of the Ca–Cu looping process is proposed for the production of a H₂-enriched fuel gas by means of the sorption enhanced water gas shift (SEWGS) of blast furnace gas (BFG) in steel mills. CO₂ is simultaneously removed from the gas using a CaO-based sorbent. A Cu/CuO chemical loop supplies the energy required for the regeneration of the sorbent via the exothermic reduction of CuO with coke oven gas (GOG). The process is carried out in an arrangement of interconnected fluidized-bed reactors operating at atmospheric pressure, which allows for a solids' segregation step to be introduced that will reduce significantly the solid circulation between reactors A reference case study is presented, where the SEWGS is operated at 600 °C and the regeneration of the sorbent at 870 °C. About 27% of the BFG can be decarbonized in the SEWGS reactor producing 110 Nm³ of H₂ per tonne of steel. A CO₂ capture ratio of 31% with respect to the total carbon emissions in the steel mill can be achieved. More than 60% of the thermal input can be recovered as high-temperature heat, which could be efficiently recovered for producing electricity.     

An evaluation of hydrogen production from the perspective of using blast furnace gas and coke oven gas as feedstocks

Blast furnace (BF) is a large-scale reactor for producing hot metal where coke and coal are consumed as reducing agent and fuel, respectively. As a result, a large amount of CO₂ is liberated into the atmosphere. The blast furnace gas (BFG) and coke oven gas (COG) from the ironmaking process can be used for H₂ production in association with carbon capture and storage (CCS), thereby reducing CO₂ emissions. In this study thermodynamic analyses are performed to evaluate the feasibility of H₂ production from BFG and COG. Through the water gas shift reaction (WGSR) of BFG, almost all CO contained in BFG can be converted for H₂ production if the steam/CO (S/C) ratio is no less than unity and the temperature is at 200 °C, regardless of whether CO₂ is captured or not. The maximum H₂ production from WGSR is around 0.21 Nm³ (Nm³ BFG)⁻¹. Regarding H₂ production from COG, a two-stage reaction of partial oxidation (POX) followed by WGSR is carried out. It is found the proper conditions for syngas formation from the POX of COG is at the oxygen/fuel (O/F) ratio of 0.5 and the temperature range of 1000-1750 °C where the maximum syngas yield is 2.83 mol (mol hydrocarbons)⁻¹. When WGSR is subsequently applied, the maximum H₂ production from the two-stage reaction can reach 0.83 Nm³ (Nm³ COG)⁻¹.     

Hydrogen generation from the hydrolysis of aluminum promoted by Ni–Li–B catalyst

In this study, the high activity Ni–Li–B catalysts were fabricated through wet chemical reduction method. Their morphological structures, crystallinity, surface area and composition were examined by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) method and energy-dispersive X-ray spectroscopy (EDS). The aluminum-water reaction tests were explored in the range of temperatures from 35–75 °C. It was found that water could react with aluminum to generate hydrogen gas. The yield and hydrogen generation rate were significantly increased when all prepared catalysts were added into the reaction. The Ni–Li–B (X_LiCl = 0.1 g) catalyst exhibited the highest cumulative hydrogen volume of 201.3 ml with an average hydrogen production rate of 0.50 ml min⁻¹ at 55 °C. This phenomenon could be pointed to the emergence of the micro galvanic cell formed by the Ni–Li–B, Li/Ni–Li–B, Li and Al, which accelerated aluminum to rapidly react with water.     

Supercritical water gasification of fuel gas production from waste lignin: The effect mechanism of different oxidized iron-based catalysts

Iron and iron oxides have been employed to catalyze supercritical water gasification (SCWG) of lignin, a typical component of pulp and paper mill wastewater. To investigate the effects of different oxidation sates of Fe-based catalysts during SCWG process, all simulations were carried out through ReaxFF molecular dynamics method. During the catalytic SCWG process, the degradation rate of guaiacyl dimer lignin (GDL) molecule was inversely proportional to the valence state of iron, the higher oxidation state of Fe in iron-based catalyst was, the lower the catalytic degradation ability would be, and then GDL molecule underwent a series of reactions, accompanying with the generation of small molecules, among most of them were fuel gas products. In terms of gas products, Fe catalyst had a unique advantage in catalytic hydrogen production. Moreover, it is found that iron with low oxidation state was beneficial to the formation of CO, while iron with high oxidation state was CO₂. Our simulation results further revealed the formation mechanisms of CO, CO₂ and CH₄. Migration of lattice oxygen in iron oxides was also visualized through figure, and spent catalyst showed different sources in the final, demonstrating that SCW participates in the entire reaction providing not only H but also O free radicals.     

Hydrogen production from the pyrolysis–gasification of waste tyres with a nickel/cerium catalyst

Hydrogen production from the pyrolysis-gasification of waste tyres has been investigated with a Ni/CeO₂/Al₂O₃ catalyst using a two-stage fixed bed reaction system. The conditions of catalyst preparation such as Ni and CeO₂ content and calcination temperature were investigated in relation to product yield and composition. The fresh and reacted catalysts were analysed using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The results showed that there were small changes in the gas and hydrogen yield by adding 5 wt.% of CeO₂ into the Ni/CeO₂/Al₂O₃ catalyst. The gas yield related to the mass of waste tyre and the amount of reacted water were increased with the increase of CeO₂ content from 5 to 15 wt.%. However, with the further increase of CeO₂ content to 30 wt.%, the gas yield related to the mass of tyre and the amount of reacted water was reduced. Increasing the Ni content of the catalyst showed a positive influence on the gas yield and hydrogen production. The investigation of the calcination temperature of the Ni/CeO₂/Al₂O₃ catalyst showed that the oil yield related to the mass of tyre and reacted water decreased from 28.4 to 23.4 wt.% for the catalyst calcined at 500 °C, and decreased from 24.2 to 17.7 wt.% for the catalyst calcined at 750 °C. When the Ni content of the catalyst was increased from 5 to 20 wt.%. there were only small changes in total gas and hydrogen production from the pyrolysis-gasification of waste tyre. Lower coke deposition on the reacted catalyst was obtained for the Ni/CeO₂/Al₂O₃ catalyst prepared at the calcination temperature of 750 °C compared with the 500 °C calcination temperature.     

Development of highly efficient and reusable Ruthenium complex catalyst for hydrogen evolution

Herein, we report an efficient, environmentally friendly and stable catalyst development to hydrogen evolution from sodium borohydride hydrolysis. For this purpose, Ruthenium complex catalyst successfully fabricated via 5-Amino-2,4-dichlorophenol-3,5-ditertbutylsalisylaldimine ligand and RuCl₃·H₂O salt. Ru complex catalyst was identified with X-Ray Diffraction Analysis, Infrared Spectroscopy, Elemental Analysis, Transmission electron microscopy, Scanning Electron Microscope and Brunauer-Emmett-Teller Surface Area Analysis. According to the analysis results, it was confirmed that Ru complex catalyst was successfully synthesized. Ru complex was used as a catalyst in NaBH₄ hydrolysis. The kinetic performance of Ru complex catalyst was evaluated at various reaction temperatures, various sodium borohydride concentration, catalyst concentration and sodium hydroxide concentration in hydrogen evolution. The apparent activation energy for the hydrolysis of sodium borohydride was determined as 25.8 kJ mol^?1. With fully conversion, the promised well durability of Ru complex was achieved by the five consecutive cycles for hydrogen evolution in sodium borohydride hydrolysis The hydrogen evolution rates were 299,220 and 160,832 mL H₂ g_cat^?1 min^?1 in order of at 50 °C and 30 °C. Furthermore, the proposed mechanism of Ru complex catalyzed sodium borohydride hydrolysis was defined step by step. This study provides different insight into the rational design and utilization and catalytic effects of ruthenium complex in hydrogen evolution performance.     

Preparation of nanocrystalline metal (Cr,Al, Mn,Ce, Ni,Co and Cu) modified ferrite catalysts for the high temperature water gas shift reaction

Water gas shift reaction is an essential process of hydrogen production and carbon monoxide removal from syngas. Fe–Cr–Cu catalysts are typical industrial catalysts for high temperature water gas shift reaction but have environmental and safety concerns related to chromium content. In this work nanocrystalline metal (M)-modified ferrite catalysts (M = Cr, Al, Mn, Ce, Ni, Co and Cu) for replacement of chromium were prepared by coprecipitation method and the effects of promoters on the structural and catalytic properties of the iron based catalysts were studied. Prepared catalysts were characterized using X-ray diffraction (XRD), N₂ adsorption (BET), temperature-programmed reduction (TPR) and transmission electron microscopies (TEM) techniques. Temperature-programmed reduction measurements inferred that copper favors the active phase formation and significantly decreased the reduction temperature of hematite to magnetite. In addition, water gas shift activity results revealed that Fe–Al–Cu catalyst with Fe/Al = 10 and Fe/Cu = 5 weight ratios showed the highest catalytic activity among the prepared catalysts. Moreover, the effect of calcination temperature, GHSV and steam/gas ratio on the catalytic performance of this catalyst was investigated.     

Performance of a water gas shift pilot plant processing product gas from an industrial scale biomass steam gasification plant

In this paper, the performance of a commercial Fe/Cr based catalyst for the water gas shift reaction was investigated. The catalyst was used in a water gas shift pilot plant which processed real product gas from a commercial biomass steam gasification plant with two different qualities: extracted before and extracted after scrubbing with a rapeseed methyl ester gas scrubber. The performance of the WGS pilot plant regarding these two different gas qualities was investigated. For this reason, extensive chemical analyses were carried out. CO, CO₂, CH₄, N₂, O₂, C₂H₆, C₂H₄, and C₂H₂ and H₂S, COS, and C₄H₄ S were measured. In addition, GCMS tar and NH₃ analyses were performed. Furthermore, the catalyst's activity was observed by measuring the temperature profiles along the reactors of the water gas shift pilot plant. During the 200 h of operation with both product gas qualities, no catalyst deactivation could be observed. A CO conversion up to 93% as well as a GCMS tar reduction (about 28%) along the water gas shift pilot plant was obtained. Furthermore, a specific H₂ production of 63 g H₂ per kg biomass (dry and ash free) was reached with both product gas qualities. No significant performance difference could be observed.     

Longevity test for a Water–Gas Shift catalyst

Catalyst poisoning is one of the most significant problems associated with the commercial application of water gas shift catalysts. Conventional site blocking poisoning with sulphur compounds, and particularly by H₂S, is common. This work reports the effect of H₂S exposure on a Pt-based Water–Gas Shift catalyst. A 100 h continuous experiment was made to study the catalyst viability in the presence of 1 ppm H₂S. As well as different experimental conditions, temperature, gas hourly space velocity, steam carbon ratio and a concentration of 300 ppm H₂S. Gas chromatography (GC) was used in this study to analyse the outlet gas composition through time, and thereby the catalyst performance.     

Partial oxidation of methane on co-precipitated Ni–Mg/Al catalysts modified with copper or iron

Methane transformation to hydrogen and synthesis gas (CO + H₂) by heterogenous catalysts can play an important role to secure the supply of energy, chemicals and fuels in the future. Methane is the main constituent of natural gas and biogas and it is also found in crystalline hydrates at the continental slopes of many oceans. In view of this vast reserves and resources, the use of methane as chemical feedstock has to be intensified. In this present work, (NiMg)Al catalysts doped with Fe or Cu, prepared by co-precipitation method and characterized by different techniques, were studied in the partial oxidation of methane (T_reaction = 750 °C, CH₄/O₂ ratio = 2). The effect of catalyst composition and pre-treatment conditions of these catalysts were investigated. Also, these catalysts show a very high activity and selectivity in the partial oxidation reaction, which depends on the conditions of catalysts preparation. The obtained results indicated increasing of activity and selectivity with decreasing calcination temperature and increasing nickel and aluminium contents in the catalysts composition. The solid doped with iron constituted the best catalyst for the total oxidation of methane and for the water–gas shift reaction. On the other hand, the addition of copper was remarkably improved the catalytic performances of the (NiMg)Al solid. So, the presence of this element supported the partial oxidation of methane with production of syngas (CO + H₂). With the addition of iron or copper for the catalyst composition, we were observed (in our previous work) the possibility of formation of NiM (M = Fe or Cu) alloy which increased nickel particles dispersion. In the case of copper, the reducibility of NiO was also assisted (TPR results) which increased catalytic activity in partial oxidation of methane.     

A coordinatively saturated cobalt complex as a new kind catalyst for efficient electro- and photo-catalytic hydrogen production in purely aqueous media

It has been shown that coordinatively unsaturated complexes can catalyze hydrogen production via an unstable hydride intermediate. Herein we present a new kind of water soluble catalyst based on a coordinatively saturated cobalt complex, [(phen)₂Co(CN)₂]?ClO₄1 that is formed by the reaction of 1,10-phenanthroline (phen), Co(ClO₄)₂·6H₂O and tetracyanoethylene (TCNE). Under photoirradiation with blue light (λ_max = 469 nm) in air, together with [Ru(bpy)₃]Cl₂ and ascorbic acid in a pH 5.5 aqueous solution, 1 possesses photocatalytic activity for water reduction to hydrogen with an initial turnover number (TON) of 1232H₂ per mol of catalyst at first 10 h, and this activity is sustained for at least 70 h. This can be attributed to that oxidative quenching by 1 (k_q = 1.69 × 10¹⁰ M^?1 s^?1) dominates over reductive quenching to [Ru(bpy)₃]Cl₂ by ascorbic acid (k_q = 1.55 × 10¹⁰ M^?1 s^?1). Additionally, 1 electrocatalyze hydrogen generation from a neutral water with a turnover frequency (TOF) of 1113.1 mol of hydrogen per mole of catalyst per hour (mol H₂/mol catalysts/h) at an overpotential (OP) of 838 mV. We hope this can afford a new method in proton or water reduction catalysis using coordinatively saturated complexes in purely aqueous media.     

Electrochemical evaluation of molybdenum disulfide as a catalyst for hydrogen evolution in microbial electrolysis cells

There is great interest in hydrogen evolution in bioelectrochemical systems, such as microbial electrolysis cells (MECs), but these systems require non-optimal near-neutral pH conditions and the use of low-cost, non-precious metal catalysts. Here we show that molybdenum disulfide (MoS₂) composite cathodes have electrochemical performance superior to stainless steel (SS) (currently the most promising low-cost, non-precious metal MEC catalyst) or Pt-based cathodes in phosphate or perchlorate electrolytes, yet they cost ∼4.5 times less than Pt-based composite cathodes. At current densities typical of many MECs (2-5 A/m²), the optimal surface density with MoS₂ particles on carbon cloth was 25 g/m², achieving 31 mV less hydrogen evolution overpotential than similarly constructed Pt cathodes in galvanostatic tests with a phosphate buffer. At higher current densities (8-10 A/m²) the MoS₂ catalyst had 82 mV less hydrogen evolution overpotential than the Pt-based catalyst. MoS₂ composite cathodes performed similarly to Pt cathodes in terms of current densities, hydrogen production rates and COD removal over several batch cycles in MEC reactors. These results show that MoS₂ can be used to substantially reduce the cost of cathodes used in MECs for hydrogen gas production.     

Comparative analysis of biomass and coal based co-gasification processes with and without CO2 capture for HT-PEMFCs

With the seasonal availability and low energy density of biomass and the high environmental impact of coal, the co-gasification of biomass and coal is an alternative approach facilitating a trade-off between renewable and non-renewable resources. The aim of this study was to investigate hydrogen production from the co-gasification of biomass and coal integrated by means of the sorption-enhanced water gas shift reactor (G-SEWGS) for a high temperature proton exchange membrane fuel cell (HT-PEMFC). The effects of the gasifier temperature, the steam to fuel ratio (S/F ratio), and the equivalence ratio (ER) on the hydrogen production performance and environmental impact of the G-SEWGS were theoretically analysed and compared with the conventional gasifier integrated with the water gas shift reactor (G-WGS) and the sorption-enhanced gasifier integrated with the water gas shift reactor (SEG-WGS). As compared to the conventional water gas shift reactor, the addition of a CaO sorbent in the modified water gas shift reactor not only reduces the amount of the CO₂ emission but also leads to an increase in the hydrogen concentration and hydrogen content. The G-SEWGS provides better performance in terms of its fuel processor efficiency and CO₂ emission than the G-WGS and the SEG-WGS. Also, the problem of sulphur compound in the hydrogen-rich gas can be reduced by using of the sorption-enhanced water gas shift reactor (SEWGS). The best system exergy efficiency, which was around 22% for the power generation, was determined from the HT-PEMFC integrated with the G-SEWGS. The main exergy destruction of around 70% of the total loss was caused by hydrogen production processes.     

Water enhanced methanol decomposition for simultaneous heat recovery and ready-to-use synthesis gas production over CO2 capture enhanced Ni/zeolite 4A catalyst

Methanol decomposition is considered as a “one stone two birds” approach for simultaneously recovering waste heat and affording synthesis gas. However, this approach requires efficient catalysts with high CO selectivity and low selectivity to byproducts. Herein, a rational design of CO₂ capture enhanced Ni/zeolite 4 A catalyst for synthesis gas production by water enhanced methanol decomposition is reported. 5%-Ni/NaA-500 catalyst achieves the Y_H2 of 80.6%, Y_CO of 76.2%, H₂/CO molar ratio of 2.11, high stability, low selectivity to CO₂ and CH₄, and no coke at 325 °C. Ni atoms highly disperse on the surface and microporous of zeolite 4 A, and the strong interaction between Ni atoms and zeolite 4 A inhibits the reduction of Ni atoms. Consequently, Ni³⁺, Ni²⁺ and Ni⁰ coexist in 5%-Ni/NaA-500, and the redox couples of Ni³⁺↔Ni²⁺, Ni²⁺↔Ni⁰, and Ni³⁺↔Ni⁰ will enhance the redox processes during methanol decomposition. CO₂ capture capacity of x%-Ni/NaA-Y below 350 °C promotes the reverse water gas shift reaction by concentrating CO₂ molecules, which hence increases CO selectivity and declines the selectivity to byproducts. The reaction path follows CH₃OH→CH₃O→CH₂O→CHO→CO. This work will pave the way to industrial applications that combine ready-to-use synthesis gas production and heat recovery.     

Hydrogen production by steam reforming of liquefied natural gas (LNG) over mesoporous Ni-Al2O3 aerogel catalyst prepared by a single-step epoxide-driven sol-gel method

A mesoporous Ni-Al₂O₃ aerogel catalyst was prepared by a single-step epoxide-driven sol-gel method and a subsequent supercritical CO₂ drying method (NA-ES catalyst). For comparison, a mesoporous Ni-Al₂O₃ aerogel catalyst was also prepared by a single-step alkoxide-based sol-gel method and a subsequent supercritical CO₂ drying method (NA-AS catalyst). Differences in physicochemical properties and catalytic activities of mesoporous Ni-Al₂O₃ aerogel catalysts in the steam reforming of liquefied natural gas (LNG) were investigated. Textural properties of Ni-Al₂O₃ aerogel catalysts were affected by the preparation method. Nickel species were highly dispersed in alumina through the formation of nickel aluminate phase in both NA-ES and NA-AS catalysts. However, chemical states of Al atoms in both catalysts were quite different. In addition, nickel species in the NA-ES catalyst exhibited high reducibility and high dispersion compared to those in the NA-AS catalyst. In the steam reforming of LNG, NA-ES catalyst exhibited a better catalytic performance than NA-AS catalyst in terms of LNG conversion and hydrogen yield, although both catalysts showed a stable catalytic performance during the reaction without deactivation behavior. Furthermore, NA-ES catalyst with small average nickel diameter suppressed water-gas shift reaction. Reducibility and dispersion of nickel species served as important factors determining the catalytic performance of the catalysts.     

Nanofiber structured oxygen defective CoFe2O4-x catalyst for the water-gas shift reaction in waste-to-hydrogen processes

Waste-to-hydrogen processes are a way to produce hydrogen from waste and reduce the amount of landfill/incineration of wastes simultaneously through the gasification of waste. The water-gas shift (WGS) reaction is a key step in this waste-to-hydrogen process by removing the CO and producing additional H₂. A nanofiber-structured CoFe₂O₄ catalyst was synthesized by the electrospinning method, and the catalytic performance in WGS using waste-derived synthesis gas was compared with that of catalysts prepared by sol-gel, hydrothermal, and co-precipitation methods. The CoFe₂O₄ catalyst synthesized by the electrospinning method showed a clear nanofiber structure and revealed a superior redox property. This superior redox property, which has a large relation with the high oxygen storage capacity of the catalyst, induced the formation of an active phase (Co⁰ and Fe₃O₄) in CoFe₂O₄. As a result, the nanofiber structured oxygen defective CoFe₂O_4-x prepared by the electrospinning method showed the best catalytic activity in this study.     

The kinetics of acetic acid steam reforming on Ni/Ca-Al2O3 catalyst

As a significant by-product of many thermochemical and biological waste conversion processes, acetic acid (AcOH) is often investigated as model feedstock in the production of sustainable hydrogen from non-fossil sources. The kinetics of its steam reforming were extracted from packed bed reactor experiments over an industrially produced 14 wt% Ni/Ca-Al₂O₃ catalyst at atmospheric pressure. The model consisting of AcOH steam reforming producing CO₂ and H₂, AcOH decomposition to CO and H₂, and water gas shift, achieved the best fit, reflected in the lowest average relative errors (ARE) with experimental results, with ARE values below 5.4% and 6.4% on AcOH and water conversions respectively, and below 4% on H₂ mol fraction. This model was validated away from equilibrium using additional experimental points, as well as for a wide range of equilibrium conditions with varying temperature (600–700 °C) and feed molar steam to carbon ratios (3–8) at atmospheric pressure using an independent method.     

Options for net zero emissions hydrogen from Victorian lignite. Part 1: Gaseous and liquefied hydrogen

This two-part paper investigates the feasibility of producing export quantities (770 t/d) of blue hydrogen meeting international standards, by gasification of Victorian lignite plus carbon capture and storage (CCS). The study involves a detailed Aspen Plus simulation analysis of the entire production process, taking into account fugitive methane emissions during lignite mining. Part 1 focusses on the resources, energy requirements and greenhouse gas emissions associated with production of gaseous and liquefied hydrogen, while Part 2 focusses on production of ammonia as a hydrogen carrier.In this study, the proposed process comprises lignite mining, lignite drying and milling, air separation unit (ASU), dry-feed entrained flow gasification, gas cooling and cleaning, sour water-gas shift reaction, acid gas removal, pressure swing adsorption (PSA) for hydrogen purification, elemental sulphur recovery, CO₂ compression for transport and injection, hydrogen liquefaction, steam and gas turbines to generate all process power, plus an optional post-combustion CO₂ capture step. High grade waste heat is utilised for process heat and power generation. Three alternative process scenarios are investigated as options to reduce resource utilisation and greenhouse gas emissions: replacing the gas turbine with renewable energy from off-site wind turbines, and co-gasification of lignite with either biomass or biochar. In each case, the specific net greenhouse gas intensity is estimated and compared to the EU Taxonomy specification for sustainable hydrogen.This is the first time that a coal-to-hydrogen study has quantified the greenhouse gas emissions across the entire production chain, including upstream fugitive methane emissions. It is found that both gaseous and liquefied hydrogen can be produced from Victorian lignite, along with all necessary electricity, with specific emissions intensity (SEI) of 2.70 kg CO₂-e/kg H₂ and 2.73 kg CO₂-e/kg H₂, respectively. These values conform to the EU Taxonomy limit of 3.0 kg CO₂-e/kg H₂. This result is achieved using a Selexol™ plant for CO₂ capture, operating at 89.5%–91.7% overall capture efficiency. Importantly, the very low fugitive methane emissions associated with Victorian lignite mining is crucial to the low SEI of the process, making this is a critical advantage over the alternative natural gas or black coal processes.This study shows that there are technical options available to further reduce the SEI to meet tightening emissions targets. An additional post-combustion MDEA CO₂ capture unit can be added to increase the capture efficiency to 99.0%–99.2% and reduce the SEI to 0.3 kg CO₂-e/kg H₂. Emissions intensity can be further reduced by utilising renewable energy rather than co-production of electricity on site. Net zero emissions can then be achieved by co-gasification with ≤1.4 dry wt.% biomass, while a higher proportion of biomass would achieve net-negative emissions. Thus, options exist for production of blue hydrogen from Victorian lignite consistent with a ‘net zero by 2050’ target.     

Hydrogen production by steam reforming of ethanol over an Ir/CeO2 catalyst: Reaction mechanism and stability of the catalyst

Steam reforming of ethanol over an Ir/CeO₂ catalyst has been studied with regard to the reaction mechanism and the stability of the catalyst. It was found that ethanol dehydrogenation to acetaldehyde was the primary reaction, and acetaldehyde was then decomposed to methane and CO and/or converted to acetone at low temperatures. Methane was further reformed to H₂ and CO, and acetone was directly converted into H₂ and CO₂. Addition of CO, CO₂, and CH₄ to the water/ethanol mixture proved that steam reforming of methane and the water gas shift were the major reactions at high temperatures. The Ir/CeO₂ catalyst displayed rather stable performance in the steam reforming of ethanol at 650 °C even with a stoichiometric feed composition of water/ethanol, and the effluent gas composition remained constant for 300 h on-stream. The CeO₂ in the catalyst prevented the highly dispersed Ir particles from sintering and facilitated coke gasification through strong Ir–CeO₂ interaction.     

Characteristics and performance of the Co–CeO2 catalyst as a function of the promoter (La,Pr, and Zr) used in high temperature water gas shift reaction

The catalysts used to facilitate the water gas shift reaction (WGSR) are generally harmful to the environment. Therefore, catalysts that have high activity and stability in WGSR and do not pollute the environment need to be fabricated. Herein, three promoters (La, Pr, and Zr) are added into Co–CeO₂ (CoCe) catalyst to improve catalytic performance in a high temperature WGSR to produce high-purity hydrogen from waste-derived synthesis gas. Various techniques are employed to confirm the changes in the properties that affect the catalytic performance. The catalytic reaction is performed at a high gas hourly space velocity to screen the performance of the promoted CoCe catalysts. The CoCeZr catalyst shows the highest CO conversion (X_CO = 88% at 450 °C) due to its high Co dispersion and oxygen vacancy resulting from the addition of Zr to the CoCe catalyst; thus, it is most suitable for use in high temperature WGSR.