Oxidative Reforming Research Articles

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 H2, 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.

Influence of Nozzle Shape on Partial Oxidation Reforming of Biogas Using Microwave Plasma

Biogas, composed of ∼60% CH4 and ∼40% CO2, is a carbon-neutral fuel but suffers from low flame stability. Thus, for effective utilization, the combustion reaction must be enhanced or biogas must be upgraded. Herein, microwave plasma-assisted combustion was utilized for partial oxidation reforming of biogas to enhance the reforming reaction and to upgrade biogas. The characteristics of the biogas reforming process and effects of the nozzle shape were investigated using four different nozzles. The small thin nozzle suppressed microwave attenuation to the greatest extent and thus most effectively promoted the reforming reaction. Microwave plasma not only reformed CH4 into H2 and CO but also decomposed CO2 (which does not have any calorific value) into CO (which has calorific value); thus, the maximum cold gas efficiency achieved with the small thin nozzle was 112.7%, and the biogas was upgraded. Biogas reforming using O2 as an oxidizer was also evaluated to improve the cold gas efficiency, but the cold gas efficiency undesirably decreased in this reaction relative to that using air with N2 as the oxidizer because the reforming reactions are enhanced by increasing the active radicals like H and OH in the latter.

Scenario assessment for producing methanol through carbon capture and utilization technologies considering regional characteristics

Carbon capture and utilization (CCU) technology can be used to reduce carbon dioxide (CO2) emissions and mitigate climate change. CCU technology efficiencies and regional characteristics were evaluated by integrating process simulation and carbon footprint estimation to determine the optimal social implementation scenarios from the CO2 emissions reduction perspective. Methanol (MeOH) was chosen as the CCU product, and the energy efficiency of MeOH synthesis under various conditions was assessed. For social implementation scenarios, location of each technology, capacity of renewable energy and H2 manufacturing method, process configuration, CO2 source, and separation/recovery technology were used as conditions for the evaluation. Based on 11 cases with varying conditions, the partial oxidation and dry reforming of CH4 was determined to exhibit the greatest CO2 emission reduction potential. However, when considering renewable energy expansion, direct MeOH synthesis exhibited a greater CO2 reduction potential. Based on the results, CCU optimal social implementation scenarios evaluation guidelines were determined. These guidelines can be implemented at a large scale to determine the viability and effectiveness of CCU technologies.

Response surface methodology for optimization of dry oxidative reforming for hydrogen enrichment of biogas

The exploration of domestically available clean and renewable fuel is essential for the attainment of sustainable development goals. The hydrogen (H2)-enriched biogas being renewable and clean can be a highly favorable fuel. In this study, the response surface optimization of dry oxidative reforming using a three-level, three-factor experimental design for hydrogen enrichment of biogas over the nickel-cobalt bimetallic catalyst was investigated. The Box-Behnken design of experimentation was employed to assess the interaction and discrete effect of reforming temperature and ratios of CH4/CO2 and O2/CH4. The effects of CH4/CO2 ratio (1–2) and O2/CH4 ratio (0.3–0.5) on catalytic activity were assessed in the temperature range of 700–800 °C. The conversion of both reactants (CH4 and CO2), yield of products (H2 and CO), and ratio of products (H2/CO ratio) were selected as responses for statistical study. The analysis of variance demonstrated that reforming temperature and O2/CH4 ratio have a statistically considerable impact on the H2 enrichment of biogas by the virtue of higher endothermic nature of the reaction. Experimentally, the maximum H2 enrichment of 44.04% was obtained at 800 °C with 1.5 and 0.5 CH4/CO2 and O2/CH4 ratio, respectively. However, from the statistical model, the optimum H2 enrichment of 36.9% was obtained at 725.68 °C with CH4/CO2 and O2/CH4 ratios of 1.32 and 0.42, respectively. The close agreement between predicted and experimental data shows that the combination of response surface methodology and dry oxidative reforming could be an efficient approach for optimizing the H2 enrichment of biogas and the generation of environment friendly fuel.

Microkinetic and sensitivity analysis of oxidative dry reforming of methane on Ni–Co catalyst using a reaction mechanism based on Ni

Microkinetic modelling performed for ODRM reaction. Effects of temperature and space–time variations match well with experimental data. Sensitivity analysis was performed to provide a reduced mechanism.

К 125-летию со дня рождения лауреата Нобелевской премии академика Николая Николаевича Семенова Матричная конверсия природного газа в синтез-газ и водород как перспективное направление газохимии и энергетики

The basic principles of a new technology of non-catalytic oxidative reforming of hydrocarbon gases into syngas and hydrogen, based on the combustion of rich hydrocarbon-air or hydrocarbon-oxygen mixtures stabilized by the surface of a permeable matrix, are presented. The kinetics of the process, the prospects for its technological implementation and the most interesting applications are discussed.

Development of Microwave-Matrix Partial Oxidation Reformer

This study proposes a novel microwave-matrix reformer (MMR) to convert biogas, a greenhouse gas that causes climate change, into high-quality fuel energy. To show its performance potential, it has identified the characteristics of biogas conversion and product gas for O 2 /C ratio, steam supply, reformed gas recirculation, and recirculated water supply, which affect CH 4 and CO 2 conversions. The reforming characteristics for different variables were achieved as follows. The optimal conditions of the MMR were 100% recirculation rate and 10 mL/min water supply when O 2 /C ratio and total gas supply were 1 and 30L/min, respectively. Under these conditions, CH 4 conversion was 68.6%, CO 2 conversion was 37.9%, H 2 selectivity was 88.1%, and H 2 /CO was 1.54, which were resonable for applying to stack for Solid Oxide Fuel Cell.

Hydrogen production from partial oxidation and autothermal reforming of methanol from a cold start in sprays

Hydrogen is a noticeable clean fuel that can be applied in power generation and transport. Hydrogen production from methanol via thermochemical methods has been widely studied and used. In these methods, autothermal reforming (ATR) simultaneously contains endothermic steam reforming and exothermic partial oxidation of methanol (POM), The latter can help start the experiment and provide heat for the former. This study aims to perform methanol ATR by sprays via an h-BN-Pt catalyst without preheating, mainly focusing on the effects of operating conditions on hydrogen production and methanol conversion. Meanwhile, the comparison between ATR and POM of methanol is also carried out. The results of POM indicate that the highest H2 and CO concentrations are obtained at the air-to-methanol molar ratio (O2/C) of 0.7, and the CH3OH conversion can reach 100%. However, through the ATR process, the methanol conversion reaches 60% at O2/C = 0.7 with steam-to-methanol molar ratio (S/C) of 1.5. At S/C = 0.5, it is observed that the CH3OH conversion is up to 100% with increasing the O2/C ratio, and the H2 yield is higher than that of POM. The effects of S/C and O2/C ratios on ATR indicate that the CH3OH conversion and reaction temperature are significantly increased with decreasing the S/C ratio and increasing the O2/C ratio. Overall, the H2 yield from ATR at S/C of 0.5 and O2/C of 0.7 is highest with 1.697 mol (mol CH3OH)−1.

Hydrogen Production via Partial Oxidation Reforming of Methane with Gliding Arc Discharge Plasma

AbstractHydrogen production from partial oxidation reforming of methane in a gliding arc discharge (GAD) reactor is investigated. The effects of input power, the oxygen‐carbon molar ratio (O/C), and residence time are studied, respectively. Products such as H2, CO, CO2, and C2‐C4 hydrocarbons can be detected in the outlet gas. The experimental result shows that the input power of 36.4 W, the relitively low O/C of 0.705 and the 13.8 s residence time in this system will bring the highest H2 energy yield. Compared to the decomposition of methane, partial oxidation of methane with air can maintain a stable discharge state and no carbon deposition on electrodes is observed during the reaction process. Optical emission spectroscopy (OES) is also employed to characterize this methane‐air plasma. Based on the results of the experiment and OES, a possible mechanism of methane partial oxidation process was proposed, which points out that collisions of high‐energy electrons and excited N2 species (mainly N2(A)) with other species (such as O2, CH4) in the plasma region are two main ways for the activation of this reforming system. Hydrogen is generated principally through the H‐abstraction reaction and the H‐coupling reaction.

Progress in the synthesis and applications of hexaaluminate-based catalysts

ABSTRACT The development of materials that can exhibit thermal resistance at very high temperatures, thus allowing them to be applied as catalysts and thermal insulators, amongst other possible uses, is a research subject of great interest. This is the case for hexaaluminates, a class of hexagonal aluminate compounds with a unique structure that are stable at very high temperatures up to 1600°C and exhibit exceptional resistance to sintering and thermal shock, thus making them attractive catalysts for high-temperature applications. In this review, the structure of hexaaluminates is presented first. The most recent advances in synthetic methods (sol-gel, reverse microemulsion, hydrothermal synthesis, carbon-templating, solution combustion synthesis, and freeze-drying methods) are discussed subsequently, with the aim of maximizing textural properties and including in their structure metals known to be active in catalytic applications, such as combustion of CH4, partial oxidation, and dry reforming of CH4 to produce synthetic gas, and the decomposition of N2O. Finally, other applications, such as their function as a thermal barrier, are also addressed.

Numerical Investigation of the Effects of Coke on Transport Properties in an Oxidative Fuel Cell Reformer.

Experimental investigations on the technical viability of solid oxide fuel cells to replace internal combustion engines in automobiles have increased in recent years. However, the performance and stability of catalysts in the presence of carbon is key for the commercial success of fuel cell reformers. In this paper, finite element method was used to study the effect of coke deposition on heat and mass transfer during the catalytic partial oxidation of ethanol in a packed bed reactor. The properties of Ni/Al2O3 catalyst bed were investigated after being subjected to several hours of carbon buildup. Bed permeability, porosity, and temperature distribution were significantly affected after just 1500 s of reaction time. It was observed that void fraction and permeability became nonuniform across the bed. These two parameters decreased with axial position, and the difference became more pronounced with time. A decrease in bed porosity reduced the bed temperature due to an increase in effective thermal conductivity and ethanol conversion and hydrogen selectivity decreased as a result. Thus, it was concluded that heat transfer becomes a limiting factor in reforming reactions in the presence of carbon. Production distribution before deactivation was also studied, and it was observed that a maximum ethanol conversion of 100% was achieved at 600 °C and a C/O ratio of 1.0. Finally, results from the reactions were compared to that of a different study to validate the reaction mechanism and similar results were found in the literature.

Development of partial oxidation reformer in gliding arc plasma-matrix burner

In this study, a new type of plasma-burner reformer was proposed to convert methane or biogas into high-quality energy. The novel reformer is a combined technology as a plasma combustor and a matrix burner. The sequential mechanism of in-line plasma-burner reformer can improve POX reforming in the higher hydrogen-rich gas production.In order to present the performance potential for the novel PBR, the characteristics of conversion and product gases were identified according to the O2/C ratio, total feed gas, CO2: CH4 ratio, and recirculation of reformed gas, and the results are as follows:The reforming characteristics for each variable were identified, and the optimal operating condition of the PMBR was O2/C ratio of 1.0 and total feed gas of 20 L/min. At this time, CH4 conversion was 64%, H2 selectivity was 39%, and H2/CO ratio was 1.13, which were the results applicable to the SOFC fuel cell stack for RPG (Residential Power Generator).Recirculation of reformed gas increased the amount of hydrogen and carbon monoxide, which are combustible gases, especially the amount of hydrogen. As a result, the hydrogen selectivity is improved, and high-quality gas can be produced.

Numerical Simulation of Methane and Propane Reforming Over a Porous Rh/Al2O3 Catalyst in Stagnation-Flows: Impact of Internal and External Mass Transfer Limitations on Species Profiles

Hydrogen production by catalytic partial oxidation and steam reforming of methane and propane towards synthesis gas are numerically investigated in stagnation-flow over a disc coated with a porous Rh/Al2O3 layer. A one-dimensional flow field is coupled with three models for internal diffusion and with a 62-step surface reaction mechanism. Numerical simulations are conducted with the recently developed computer code DETCHEMSTAG. Dusty-Gas model, a reaction-diffusion model and a simple effectiveness factor model, are alternatively used in simulations to study the internal mass transfer inside the 100 µm thick washcoat layer. Numerically predicted species profiles in the external boundary layer agree well with the recently published experimental data. All three models for internal diffusion exhibit strong species concentration gradients in the catalyst layer. In partial oxidation conditions, a thin total oxidation zone occurs close to the gas-washcoat interface, followed by a zone of steam and dry reforming of methane. Increasing the reactor pressure and decreasing the inlet flow velocity increases/decreases the external/internal mass transfer limitations. The comparison of reaction-diffusion and Dusty-Gas model results reveal the insignificance of convective flow on species transport inside the washcoat. Simulations, which additionally solve a heat transport equation, do not show any temperature gradients inside the washcoat.

Experimental Study of the Effect of Start of Injection and Blend Ratio on Single Fuel Reformate RCCI

Abstract A new concept of single fuel reactivity-controlled compression ignition (RCCI) has been proposed through the catalytic partial oxidation (CPOX) reformation of diesel fuel. The reformed fuel mixture is then used as the low reactivity fuel and diesel itself is used as the high reactivity fuel. In this paper, two reformate mixtures from the reformation of diesel were selected for further analysis. Each reformate fuel mixture contained a significant fraction of inert gases (89% and 81%). The effects of the difference in the molar concentrations of the reformate mixtures were studied by experimenting with diesel as the direct injected fuel in RCCI over a varying start of injection timings and different blend ratios (i.e., the fraction of low and high reactivity fuels). The reformate mixture with the lower inert gas concentration had earlier combustion phasing and shorter combustion duration at any given diesel start of injection timing. The higher reactivity separation between reformate mixture and diesel, compared with gasoline and diesel, causes the combustion phasing of reformate-diesel RCCI to be more sensitive to the start of injection timing. The maximum combustion efficiency was found at a CA50 before top dead center (TDC), whereas the maximum thermal efficiency occurs at a CA50 after TDC. The range of energy-based blend ratios in which reformate-diesel RCCI is possible is between 25% and 45%, limited by ringing intensity (RI) at the low limit of blend ratios, and coefficient of variance (COV) of net indicated mean effective pressure (IMEPn) and combustion efficiency at the high limit. Intake boosting becomes necessary due to the oxygen deficiency caused by the low energy density of the reformate mixtures as it displaces intake air.

Process evaluation and optimization of methanol production from shale gas based on kinetics modeling

The downstream production from shale gas to methanol has attracted attention in recent years. However, the traditional thermodynamic modeling method cannot precisely predict process performances. To this end, kinetics-based reaction models of methane reforming and methanol synthesis are developed for a rigorous simulation of this route. The evaluation of process performance is addressed from the perspectives of economics and environment. Then, the effects of reacting temperature and pressure on production cost and pollutant emissions are investigated in the interest of process optimization. The results demonstrate that an increased temperature enhances the conversion of methane in partial oxidation reforming, leading to superior performance in both economics and environment. It is also found that the reforming pressure for lower production cost and emissions tends to increase as temperature elevates. The results shows that the lowest production cost is 58.13 $/t methanol, while the lowest emissions of CO2, SO2, NOx and soot are 124.7 kg/t, 0.181 kg/t, 0.226 kg/t and 0.054 kg/t. Ultimately, a trade-off between the contradictory economic and environmental targets is conducted to acquire the optimal operating condition. The method developed in this study provides guidance to the design and optimization for downstream process of shale gas.

Bioalcohol Reforming: An Overview of the Recent Advances for the Enhancement of Catalyst Stability

The growing demand for energy production highlights the shortage of traditional resources and the related environmental issues. The adoption of bioalcohols (i.e., alcohols produced from biomass or biological routes) is progressively becoming an interesting approach that is used to restrict the consumption of fossil fuels. Bioethanol, biomethanol, bioglycerol, and other bioalcohols (propanol and butanol) represent attractive feedstocks for catalytic reforming and production of hydrogen, which is considered the fuel of the future. Different processes are already available, including steam reforming, oxidative reforming, dry reforming, and aqueous-phase reforming. Achieving the desired hydrogen selectivity is one of the main challenges, due to the occurrence of side reactions that cause coke formation and catalyst deactivation. The aims of this review are related to the critical identification of the formation of carbon roots and the deactivation of catalysts in bioalcohol reforming reactions. Furthermore, attention is focused on the strategies used to improve the durability and stability of the catalysts, with particular attention paid to the innovative formulations developed over the last 5 years.

Spectroscopic and kinetic insights into the methane reforming over Ce-pyrochlores

High thermal stability and oxygen conductivity of pyrochlores makes them a potential catalyst for the dry reforming of methane (DRM). In this study, noble metal (Pt, Ru) substituted Ce2Zr2O7 and Ce2Ti2O7 pyrochlores have been synthesized by modified Pechini method. The effect of variation of dopant concentration and position was examined to achieve strong metal-support interaction. Ce2Zr1.96Pt0.04O7-δ exhibited the best catalytic activity towards DRM and hence, been studied for partial oxidation (POM) and autothermal reforming of methane (ATR). Syngas ratio (H2/CO) was tuned by varying the O2 concentration in the feed. Insights obtained from both ex-situ and in situ characterization were exploited to discern the reaction mechanism. The surface intermediates were examined by DRIFTS on Ce2Zr1.96Pt0.04O7-δ for DRM, POM and ATR. Besides adsorbed CH4 and CO on Pt, the presence of carbonate and formate species were also identified. Thus, a dual-site mechanism via carbonate and formate formation was proposed for DRM over Ce2Zr1.96Pt0.04O7-δ.

80 Hours operation of a tubular solid oxide fuel cell using propane/air

High power density and simple design are vital for these fuel cell-based portable power generation devices. This study provides an 8.6 g tubular SOFC with embedded a catalytic partial oxidation reformer, which is fabricated and operated for more than 100 h using propane/air. Nickel-iron nanosheets, as catalysts for reforming, supported on α-Al2O3 foam ceramic are synthesized by hydrothermal treatment. Testing for 80 h gives a power degradation of about 20% compared with the initial value. It is mainly attributed to sulfur-poisoning of nickel near anode/electrolyte interface according to transmission electron microscope (TEM) analysis. From TEM/energy dispersive spectroscopy line-scan results across the anode/electrolyte interface, sulfur as either aggregate at the nickel/yttria-stabilized zirconia grain boundaries or on the nickel grain surface, and no obvious carbon phase is founded. The maximum power density is 0.67 W cm−2 at 700 °C using propane/air (12 vol% propane), about 5% higher than the same cell using 20 vol% hydrogen.

Oxidative Catalytic Cracking and Reforming of Coal Pyrolysis Volatiles over NiO

Catalytic cracking of Pingshuo (PS) coal pyrolysis volatiles was investigated over NiO on a two-stage fixed bed reactor. The effect of the NiO loading amount and catalytic upgrading temperature on ...

Hydrogen Production by Partial Oxidation Reforming of Methane over Ni Catalysts Supported on High and Low Surface Area Alumina and Zirconia

The catalytic activity of the partial oxidation reforming reaction for hydrogen production over 10% Ni supported on high and low surface area alumina and zirconia was investigated. The reforming reactions, under atmospheric pressure, were performed with a feed molar ratio of CH4/O2 = 2.0. The reaction temperature was set to 450–650 °C. The catalytic activity, stability, and carbon formation were determined via TGA, TPO, Raman, and H2 yield. The catalysts were calcined at 600 and 800 °C. The catalysts were prepared via the wet-impregnation method. Various characterizations were conducted using BET, XRD, TPR, TGA, TPD, TPO, and Raman. The highest methane conversion (90%) and hydrogen yield (72%) were obtained at a 650 °C reaction temperature using Ni-Al-H-600, which also showed the highest stability for the ranges of the reaction temperatures investigated. Indeed, the time-on-stream for 7 h of the Ni-Al-H-600 catalyst displayed high activity and a stable profile when the reaction temperature was set to 650 °C.