Steam Reforming Of Hydrocarbons Research Articles

Perovskite-Derivative Ni-Based Catalysts for Hydrogen Production via Steam Reforming of Long-Chain Hydrocarbon Fuel

Large-scale hydrogen production by the steam reforming of long-chain hydrocarbon fuel is highly desirable for fuel-cell application. In this work, LaNiO3 perovskite materials doped with different rare earth elements (Ce, Pr, Tb and Sm) were prepared by a sol-gel method, and the derivatives supported Ni-based catalysts which were successfully synthesized by hydrogen reduction. The physicochemical properties of the as-prepared catalysts were characterized by powder X-ray diffraction, high-resolution transmission electron microscopy, N2 adsorption–desorption isotherms, H2 temperature-programmed reduction, and X-ray photoelectron spectroscopy. The catalytic performance of the as-prepared catalysts for hydrogen production was investigated via the steam reforming of n-dodecane. The results showed that the catalyst forms perovskite oxides after calcination with abundant mesopores and macropores. After reduction, Ni particles were uniformly distributed on perovskite derivatives, and can effectively reduce the particles’ sizes by doping with rare earth elements (Ce, Pr, Tb and Sm). Compared with the un-doped catalyst, the activity and hydrogen-production rate of the catalysts are greatly improved with rare earth element (Ce, Pr, Tb and Sm)-doped catalysts, as well as the anti-carbon deposition performance. This is due to the strong interaction between the uniformly distributed Ni particles and the support, as well as the abundant oxygen defects on the catalyst surface.

Boosting oxygen vacancy formation and Ni dispersion by Ce0.9Y0.1O2 nanorod: Efficient water and hydrocarbon activation

Ni-based higher hydrocarbon steam reforming (SR) catalyst usually encounters low water dissociation rate and carbon deposition-induced inactivity and instability. Herein, we report a Ni–Ce0.9Y0.1O2-nanorod (Ni–CYO–NR) with a MgSiO3 postcoating that exhibits a TOF and conversion of 0.18·s−1 and 95% at 700 ℃ and carbon deposition amount and deactivation rate constant 2 orders of magnitude lower than those of Ni–Ce0.9Y0.1O2-nanoparticle (Ni–CYO–NP). Characterization results suggested that Ni–CYO–NR has a higher oxygen vacancy concentration and Ni dispersion than Ni–Ce0.9Zr0.1O2–NR and Ni–CYO–NP because of its CYO(110) nature. DFT calculations revealed that CYO(110) has the lowest formation energy of oxygen vacancies and energy barrier for H2O dissociation relative to CZO(110) and CYO(111). Additionally, MgSiO3 postcoating inhibited the deep sintering of Ni, which in turn suppressed carbon formation. This demonstrates that the superior n-dodecane SR performance of MgSi–Ni–CYO–NR can be attributed to the enhanced and stabilized O–H, C–C, and C–H bond dissociation and carbon formation resistance and removal.

Catalytic Biomass Gasification in Supercritical Water and Product Gas Upgrading

AbstractThe gasification of biomass with supercritical water, also known as SCWG, is a sustainable method of hydrogen production. The process produces a mixture of hydrogen, carbon oxides, and hydrocarbons. Upgrading this mixture through steam or dry reforming of hydrocarbons to create synthesis gas and then extra hydrogen is a viable way to increase hydrogen production from biomass. This literature review discusses combining these two processes and recent experimental work on catalytic SCWG of biomass and its model compounds and steam/dry reforming of produced hydrocarbons. It focuses on catalysts used in these processes and their key criteria, such as activity, selectivity towards hydrogen and methane, and ability to inhibit carbon formation and deposition. A new criterion is proposed to evaluate catalyst performance in biomass SCWG and the need for further upgrading via reforming, based on the ratio of hydrogen bound in hydrocarbons to total hydrogen produced during SCWG. The review concludes that most catalysts used in biomass SCWG trap a large proportion of hydrogen in hydrocarbons, necessitating further processing of the product stream.

Optimization of Rh-containing Catalysts for Low-temperature Steam Reforming of Light Hydrocarbons

Rhodium-containing catalysts on various carriers (Ce0.75Zr0.25O2, Ce0.5Zr0.5O2, Ce0.4Zr0.5Y0.05La0.05O2, γ-Al2O3, TiO2) produced by various methods (sorption-hydrolytic precipitation and incipient wetness impregnation) and differing by mass content of rhodium (from 0.5 to 4 % by mass) were studied. The dependence of the catalytical efficiency of rhodium catalysts on composition, texture, and redox properties of the carrier was studied. The prospect of using associated petroleum gas at Russian deposits was confirmed.

Steam reforming of ethanol for hydrogen production: Efficacy of ceria promoted Cu–Co on mesoporous cellular foam silica

Mesoporous silica-supported metals are often used as catalysts in the steam reforming of hydrocarbons to produce hydrogen or syngas. In the current study, the steam reforming of ethanol was undertaken using mesoporous cellular foam silica (MCF) and SBA-15 as supports with bimetals Cu and Co in different proportions. Among these 20% Cu–Co (1:1)/MCF was found to be superior exhibiting good activity and stability for hydrogen production. Thereafter, Ce was introduced to reduce coke deposition on the said catalyst. Amongst all synthesized catalysts 5%Ce–10%Cu–10%Co/MCF led to higher hydrogen yield (82.1%) with 97.4% conversion of ethanol at a lower temperature (673 K) using steam to carbon (S/C) ratio of 6. The effect of temperature, GHSV, and S/C ratio on H2 production was systematically examined. Ce-promoted Cu–Co/MCF provided high stability for three cycles, indicating its multi-cycle durability and selectivity. 5%Ce–10%Cu–10%Co/MCF produces hydrogen from ethanol in a sustainable way.

Distinct coking depth in steam reforming of oxygen-containing organics and hydrocarbons

In steam reforming of organics in a fixed-bed reactor, catalyst particles in varied location of catalyst bed will experience different history of contacting with reactants/products. This may affect accumulation of coke in varied section of catalyst bed, which are investigated in steam reforming of some typical oxygen-containing organics (acetic acid, acetone and ethanol) and hydrocarbons (n-hexane and toluene) in a fixed-bed reactor with double layers of catalyst bed for investigating coking depth at 650 °C over Ni/KIT-6 catalyst in this study. The results indicated that the intermediates derived from the oxygen-containing organics in steam reforming could hardly penetrate the upper-layer catalyst to form coke in the lower-layer catalyst. In converse, they reacted quickly over the upper-layer catalyst via gasification or coking, forming coke almost exclusively in the upper-layer catalyst. The hydrocarbon intermediates from the dissociation of hexane or toluene could easily penetrate and reach the lower-layer catalyst to form even more coke therein than the upper-layer catalyst. The characterization showed that the insufficient gasification of *CxHy species led to their aggregation/integration to form more aromatic coke, especially from n-hexane. The aromatic-ring containing intermediates from toluene tended to integrate with *OH species to form ketones that further involved in coking, forming coke of less aromatic nature than that from n-hexane. Steam reforming of oxygen-containing organics also produced oxygen-containing intermediates and coke of higher aliphatic nature, lower carbon to hydrogen (C/H) ratio, lower crystallinity and thermal stability.

Ni-Infiltrated Spherical Porcelain Support as Potential Steam Reforming Microchannel Reactor

This paper describes the fabrication of kaolinite (Al2O3-2SiO2-2H2O) spherical bulbs by slip casting. The bisque-fired parts present a porosity of about 30% with submicron porosity confirmed by scanning electron microscopy. In addition, plate-like grains with channels were observed. After nickel infiltration of the specimens, nanosized Ni particles covered the surfaces of the channels of these grains. Permeation tests in 5% H2 at 400 and 600 °C resulted in fluxes between 0.05 and 0.06 mol·m-2·s-1 at a pressure gradient of 200 MPa·m-1. Potential applications of these specimens include supports for hydrocarbon (namely ethanol) steam reforming.

High-performance Rh/CeO2 catalysts prepared by l-lysine-assisted deposition precipitation method for steam reforming of toluene

Catalytic steam reforming of aromatic hydrocarbons is important for the hydrogen production from jet/diesel fuels and tar elimination during biomass gasification. In this work, a series of Rh/CeO2 catalysts were prepared by different methods, including impregnation, deposition precipitation (DP) and l-lysine assisted DP (LDP) methods and were used for steam reforming of toluene. The Rh/CeO2(LDP-1) catalyst prepared by LDP method with optimal l-lysine addition (nL-lysine/Rh = 1), showed the superior catalytic activity and stability, as well as the excellent resistance to carbon deposition under severe reaction conditions, mainly because the significant enhancement in Rh dispersion, surface Rh0 content and the concentration of surface oxygen vacancy. The highly dispersed Rh particles with great surface Rh0 content enabled the excellent ability for CC and CH bonds scissions. Meanwhile, the high content of oxygen vacancy on the support facilitated H2O activation, providing available reactive oxygen species for reacting with CHx intermediates and eliminating carbon deposition. Furthermore, the mechanism for the steam reforming of toluene based on a dual-site functional catalyst was proposed, wherein CHO group was identified as a key intermediate for CO, CO2 and H2 gaseous products generation. This study shows that l-lysine-assisted deposition precipitation method provides great advantages in preparing highly active and stable metal-based catalysts for steam reforming reactions.

Experimental Study on the Ethanol-Assisted Catalytic Steam Reforming of Endothermic Hydrocarbon Fuel.

Thermal protection is a critical problem in the development of hypersonic aircraft. To enhance the thermal protection capability of hydrocarbon fuel, the ethanol-assisted catalytic steam reforming of endothermic hydrocarbon fuel was proposed. The result shows that the total heat sink can be significantly improved by the endothermic reactions of ethanol. A higher water/ethanol ratio can promote the steam reforming of ethanol and further increase the chemical heat sink. The addition of 10 wt % ethanol at 30 wt % water content can improve the total heat sink by 8-17% at 300-550 °C, which is caused by the heat absorption by phase transition and chemical reactions of ethanol. The reaction region of thermal cracking moves backward, resulting in the suppression of thermal cracking. Meanwhile, the addition of ethanol can inhibit the coke deposition and increase the working temperature upper limit of the active thermal protection.

ОБЗОР ПЕРСПЕКТИВ ПРИМЕНЕНИЯ МЯГКОГО ПАРОВОГО РИФОРМИНГА ЛЕГКИХ УГЛЕВОДОРОДОВ НА НЕФТЯНЫХ И ГАЗОКОНДЕНСАТНЫХ МЕСТОРОЖДЕНИЯХ

Soft steam reforming (SSR) of hydrocarbons to produce methane can be used to process associated petroleum gas and condensate stabilization gas into 90% methane. The article provides a review of scientific and technical literature devoted to various aspects of the SSR technology development: reactor design, process modes and general technological design, catalysts and mathematical modeling. Catalysts and process modes to provide 100 % conversion of raw materials are determined. A review of ways to inhibit coke formation by promoting metal oxides and optimizing of size of nickel metal centers is carried out. Mathematical models for accurate calculation of the SSR process with two- and three-stage kinetic scheme are described. The problems of conducting the process in an industrial reactor are characterized. Directions of improvement of the SSR technology in order to implement it at hydrocarbon fields are proposed

Reactive molecular dynamics study on catalytic pyrolysis and steam reforming of hydrocarbon fuel

The strong endothermic capability of catalytic steam reforming highlights its potential for improving the heat sink of hydrocarbon fuels. To explore the complex interaction between catalytic pyrolysis and steam reforming reactions, as well as their contributions to the heat sink of fuels, the reactive force-field molecular dynamics (ReaxFF-MD) simulation is employed in this work to investigate the palladium-catalyzed pyrolysis and steam reforming of n-dodecane (n-C12H26). The results show that pyrolysis reaction supplies C1 and C2 components, and then participates in the steam reforming generating more than 90% of aldehyde groups. Meanwhile, compared to catalytic pyrolysis reaction, the catalytic steam reforming containing 25 n-C12H26 and 300 H2O reduces 40.54% of carbon atoms deposited inside the palladium lattice, and improves the heat sink from 254.18 kcal/mol to 386.03 kcal/mol. Furthermore, our simulated results quantitatively describe the detailed contributions of catalytic pyrolysis and steam reforming to the simulation process. With more H2O added, the proportion of steam reforming gradually increases, which reaches 35.08% in the system containing 25 n-dodecane and 300 H2O. Moreover, the contribution of H atoms in the formation of H2 also indicates the variation in the proportion of steam reforming.

Inhibition of sintering and coking by post-coating group IIA metal oxides on trace-Rh-promoted Ni-based catalysts for high-temperature steam reforming

Liquid hydrocarbon steam reforming (SR) faces the challenges of sintering and carbon deposition induced deactivation of catalysts. Herein, the strategy for stabilizing trace Rh-promoted Ni-based catalysts by post-coating group IIA metal oxide is proposed. The stabilities for catalytic n-dodecane SR are as followed: Mg–Rh–Ni–CZO > Sr–Rh–Ni–CZO > Ba–Rh–Ni–CZO ∼ Ca–Rh–Ni–CZO ∼ Rh–Ni–CZO. The reduction suppression of Rh–Ni by alkaline-earth metal oxide and the formation of Mg–O–Ni bonds in Mg–Rh–Ni–CZO are demonstrated by TPR and EXAFS techniques. The TEM and TGA characterization results confirm that IIA metal oxide inhibit Ni sintering, in turn decreasing the carbon deposition amount and graphitic carbon proportion. Negligible Ni sintering and low carbon deposition (0.7 mg/g-cat.·mmol-C12H26) occurs in Mg–Rh–Ni–CZO after SR at 700 °C for 50 h. Contrarily, the MgO-precoated Rh–Ni–Mg–CZO do not exhibit improved catalytic performance owing to the correlation between sintering and coking behaviors with interfacial structures.

Natural Hydrogen: A New Source of Carbon-Free and Renewable Energy That Can Compete With Hydrocarbons

Natural Hydrogen: A New Source of Carbon-Free and Renewable Energy That Can Compete With Hydrocarbons

Equilibrium Composition of Products Formed by Non-catalytic Conversion of Hydrocarbons

The kinetic patterns of the attainment of the equilibrium product composition in non-catalytic processes of partial oxidation and of steam and carbon dioxide reforming of hydrocarbons in the temperature range 1400–1800 K, characteristic of these processes, were analyzed. The need for such analysis is caused by the rapidly increasing consumption of natural gas as a chemical feedstock and by growing attention to environmental problems, in particular, to a decrease in СО2 emissions or to partial CO2 utilization. The forward and reverse water gas shift reactions (WGSRs) play an important role in approach to the equilibrium product composition in these processes. Analysis has shown that the elementary reactions characteristic of forward and reverse WGSRs start to play a significant role long before the equilibrium in the system is attained. Already in the intermediate steps of the process, the distribution of the major reaction products, Н2, СО, Н2О, and СО2, almost corresponds to the equilibrium value of Kt = ([H2][CO2])/([CO][H2O]), close to the WGSR equilibrium constant Keq, and further conversion of the products occurs at Kt values close to Keq.

Complex Processing of Adsorbent Used in the Purification of Hydrogen-Containing Gas

The problems of processing spent adsorbents with a high concentration of chemisorbed chlorine-containing compounds for their reuse are studied in this article. The genesis of the phase composition and morphology at all technological stages of thermochemical regeneration of the spent adsorbent - Axstrap-860 by means of alkaline modification with a combined solution of sodium and potassium hydroxides has been tested by diffractometry and elemental analysis. The results show that the formation of a layer with an increased concentration of alkali metals in the form of the corresponding carbonates and NaOH on the surface of the granules and in the volume of sodium and potassium aluminates provides adsorption of HCl, which are slightly inferior to the fresh adsorbent. The conditions for the removal of halogen-containing substances from technogenic raw materials with the subsequent isolation of useful products have been optimized: (1) crystalline NaCl intended for the preparation of electrolyte for electrode boilers and steam generators; (2) a mixture of chlorides and hydroxochlorides of aluminum tested in the process of coagulation purification of turbid natural and waste waters; (3) pseudoboehmite for the production of an adsorbent-desiccant and the synthesis of magnesium-aluminum spinel using the technology of destruction-epitaxial transformation, and a promising carrier for catalysts for steam reforming of hydrocarbons. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Enhancing reactant selectivity for Ni/Mg reforming catalysts using silicalite-1 shells: A modeling study

The ability of a zeolite shell to enhance the selective conversion of hydrocarbons through diffusional limitations was investigated using a multi-scale model of a fixed-bed reactor. The impact of shell thickness and molecule/pore size on the catalytic performance of silicalite-1 zeolite encapsulated nickel catalyst pellets for steam reforming of C1-C7 hydrocarbons is reported. A reaction–diffusion model using kinetic expressions established in literature was employed. The model was verified through comparison with reported experimental results for steam reforming data over a temperature range of 748 – 1113 K and pressure of 1 – 10 bar. Comparisons are also made against experimental data for steam reforming in the presence of a zeolite shell. Evaluation of the Weisz-Prater criterion for both the core and encapsulated catalyst confirmed mass transfer limitation induced by the utilization of a zeolite shell. The model was used to suggest an optimal thickness that balances diffusional limitations imposed by the zeolite layer on methane versus that of the heavier hydrocarbons. The optimum thickness varied as a function of hydrocarbon size and shape which determined the diffusion rates. For toluene and heptane, a 50 nm thick shell was sufficient to wholly prevent reaction. Hydrocarbons like propane and butane required a shell 7.5 and 5 μm thick. Increasing the gas-hourly-space-velocity from 10,000 to 60,000 h-1 caused a decrease in the optimum shell thickness. This approach can be modified for application to other mixed hydrocarbon systems to predict optimal catalyst design.

Modular reactors with electrical resistance heating for hydrocarbon cracking and other endothermic reactions

AbstractWe propose and demonstrate by calculations novel modular reactor configurations with electrical resistance heating for endothermic reactions such as cracking and steam reforming of hydrocarbons. The basic unit of each module consists of a set of wires, tubes, plates, monolith, or gauze/wire meshes arranged in parallel or series to satisfy the current–voltage constraints. The smaller dimensions such as spacing and diameter are selected to obtain nearly uniform heating temperature within the reaction zone.

Steam Reforming of Hydrocarbons for Synthesis Gas Production

Steam Reforming of Hydrocarbons for Synthesis Gas Production

Multicomponent oxide composites for carriers in catalytic applications

AbstractBinary, ternary, and quaternary composite oxides of rare earths (La and Ce) with one or more of aluminum, magnesium, and zirconium, prepared by coprecipitation are studied. Potential use is carrier in steam or dry reforming of hydrocarbons and ethanol. Individual components influence specific surface area, porosity, acidity, hydrothermal stability, and oxygen storage capacity (OSC) differently. Interaction effects between components further influence these properties resulting in unexpected trends. Alumina and magnesia form solid solutions with zirconia until 650℃. Magnesia imparts better hydrothermal stability to zirconia. Aluminum and magnesium form MgAl2O4 spinel in ternary composites. Specific surface area varies linearly with alumina content. Alumina influences porosity, whereas magnesia influences pore diameter. The composites are mesoporous. Only binary composites present unimodal, pore size distribution. Composites containing alumina present type H2 isotherms while the remaining composites present H3 type isotherms. OSC increases over ZrO2/CeO2 5.7 to 15.3 molar. Magnesia and alumina affect microstructure and hydrothermal stability in contrasting ways. Thermogravimetry indicates that ternary composites of zirconia with alumina or magnesia form through oxolation. Surface hydroxyls with varying acidity are seen by FTIR in as synthesized samples. Magnesia and zirconia influence acidity in opposite ways, which impacts deactivation in the decomposition of 2‐methyl‐3‐butyn‐2‐ol.

Design, synthesis, and characterization of a porous ceramic-supported CeO2 nanocatalyst for COx-free H2 evolution

The use of fossil fuels threatens environmental systems and causes an increase in greenhouse gas emissions, thereby leading to global warming. Such a scenario has spurred research into renewable hydrogen energy production as a strategy to replace fossil fuels. In this regard, thermochemical water splitting using redox reactions with metal oxides, which generates neither CO nor CO2 gas, is a promising approach with advantages over general hydrocarbon steam reforming. However, preventing catalytic deactivation due to nanocatalyst agglomeration or sintering during thermocycling at high temperatures (>800 °C) is a significant challenge. In this work, the design, synthesis, and characterization of a new CeO2-based catalytic model were carried out through a combination of theoretical and experimental approaches. From thermodynamic simulations, an optimal support material was first selected. A CeO2 nanoparticle-dispersed porous support structure was subsequently synthesized. The recyclable CeO2–support structure showed good capability and repeatability for hydrogen generation during consecutive thermocycles with no undesirable side reactions or particle sintering. It is anticipated that the results of this study will facilitate greater efficiency in the development of catalytic materials and allow for more effective materials to be designed so as to accelerate the realization of economical green energy production based on thermochemical cycles.