Presence Of Steam Research Articles

Pilot-Scale Study of CO2 Capture by CaO-Based Sorbents in the Presence of Steam and SO2

Calcium looping cycles require an oxy-fired calciner burning coal for sorbent regeneration. Thus, in addition to O2 and CO2, the flue gases will include both steam and SO2, and similarly, carbonation of real flue gases will occur in the presence of steam. However, to date, most research has been done without either of these two gaseous components present. Here, batch combustion experiments were performed in a pilot-scale fluidized-bed reactor to study the effects of steam and SO2 addition on CO2 capture by limestone-based sorbents calcined under oxygen-enriched air and oxy-fuel conditions. The initial fast kinetically controlled CO2 capture stage was dramatically reduced when the sorbent was calcined at realistic temperatures in the presence of SO2. This is attributed to both greater sintering due to higher local calcination temperatures required by high CO2 concentrations and CaSO4 formation. By contrast, steam in the synthetic flue gas during carbonation extended the initial, high-efficiency CO2 capture...

Alkaline Steam Foam: Concepts and Experimental Results

Summary Experimental studies have shown that the steam-foam process can be enhanced significantly by injecting a suitably formulated alkali/surfactant mixture in the aqueous phase of steam. Emulsionscreening tests, corefloods, and flow-visualization experiments using an alpha olefin sulfonate (AOS) surfactant with 16–18 carbon, Na2CO3, and a heavy Californian crude have shown that alkaline steam foam offers significant advantages over regular steam foam by combining the benefits of thermal and chemical enhanced-oil-recovery (EOR) processes. First, Na2CO3 reduces surfactant consumption by adsorption by rendering the clay surface more negatively charged. Second, by precipitating divalent ions that get ion exchanged off the clays, Na2CO3 reduces surfactant consumption by precipitation. Third, a suitably formulated alkali/surfactant system reduces the oil/water interfacial tension (IFT) sufficiently to enable the heavy oil to be emulsified into the aqueous phase in the presence of steam. This oil-in-water emulsion is less viscous than the oil alone and can be readily transported. Consequently, the residual-oil saturation (ROS) is reduced to a value less than that of steam. Fourth, this lower ROS reduces the destabilizing effect of oil on foam, resulting in stronger steam foam that provides better mobility control than regular steam foam. Therefore, it has the potential to further reduce steam gravity override. Fifth, the reduction in gravity override also reduces loss of heat to the cap rock, thereby improving steam utilization. When applied to steamdrive, alkaline steam foam has the benefit of increasing foam-propagation rate, improving mobility control, improving steam use, and reducing the ROS. Potential applications of alkaline steam foam to steam soaks and steam-assisted gravity drainage (SAGD) are also discussed.

Understanding of the operation behaviour of a Passive Autocatalytic Recombiner (PAR) for hydrogen mitigation in realistic containment conditions during a severe Light Water nuclear Reactor (LWR) accident

In the context of hydrogen risk mitigation in nuclear power plants (NPPs), experimental studies of a possible poisoning of Passive Autocatalytic Recombiners (PARs) by fission products (FPs) and aerosols released during a core meltdown accident were mainly conducted in the past with non-radioactive fission product surrogates (e.g., in the H2PAR facility at Cadarache, France). The decision was taken in 1997 to complete these studies by a test in the Phébus facility, a research nuclear reactor also at Cadarache: it was a rare opportunity to expose catalyst samples to an atmosphere as representative as possible of a core meltdown accident, containing gaseous fission products and aerosols released during the degradation of an actual irradiated nuclear fuel bundle. Before testing in Phébus during the FPT3 experiment, reference and qualification tests were performed in the H2PAR facility using the same samples — the so-called “coupons” — and coupons holder to check that the apparatus was functional and correctly designed for avoiding to tamper with the thermal-hydraulics and chemical conditions in the Phébus containment. The correct operation of catalysts was checked by measuring the surface temperature increase of the coupons due to the exothermic reaction between hydrogen and oxygen. After the Phébus FPT3 test (November 2004), REKO-1 tests were initiated at Jülich, Germany, to confirm the discrepancy in coupons temperature observed in Phébus FPT3 and H2PAR PHEB-03 tests, and to study the operation behaviour of PARs. Besides, before REKO-1 tests, a first interpretation of H2PAR and Phébus experiments was led to the conclusion that their difference during the operation was due to the different experimental conditions. Samples of catalysts (IRSN/IRCELYON coupon) similar to those used in Phébus and H2PAR facilities were exposed in REKO-1 facility to an atmosphere similar to that of the Phébus model containment. During the REKO-1 experiments, the temperatures of the coupon surface, together with the oxygen and hydrogen recombination kinetics, were measured as a function of the oxygen fraction in the feed. In these conditions, the inlet oxygen fraction was shown to be the main parameter affecting the recombination rate. The presence of steam was also taken into account during the IRSN/IRCELYON coupon operation in REKO-1. Finally, the PAR surface temperatures during the REKO-1 tests (both optical and thermocouple measurements) are compared with those obtained during the FPT3 and PHEB-03 tests. Then, the experimental observations (from the Phébus FPT3, H2PAR PHEB03 and REKO-1 tests) were corroborated by numerical calculations using the SPARK code developed at IRSN for catalytic reactors and recombiners applications. Despite the loss of performance experienced by the coupons in the FPT3 test, as compared with the PHEB-03 test, this study does not challenge the qualification of PARs for risk mitigation in Pressurized Water Reactor (PWR) NPPs, and suggests that they could still be efficient in the rich burn conditions of partially inerted (oxygen depleted) Boiling Water Reactor (BWR) containments.

Preferential CO oxidation over nanosized gold catalysts supported on ceria and amorphous ceria–alumina

1wt.% Au supported on CeO2–Al2O3 (Ce/Ce+Al: 0, 2, 5, 10, 15, and 20mol%) was prepared by impregnation in organic medium of high-surface area supports prepared by Evaporation Induced Self Assembly (EISA) route. For comparison, a 1wt.% Au/CeO2 was also prepared using a commercial support. All the prepared catalysts present a BET surface area roughly between 200 and 340m2g−1. The reducibility, the oxygen storage capacity (OSC) and the oxygen mobility determined by oxygen isotopic exchange (OIE) of the 1wt.% Au/CeO2–Al2O3 are enhanced by the presence of gold and increases with the cerium content in the support. The values of the OSC and the oxygen mobility in the Au/CeO2–Al2O3 catalysts with high cerium loading are higher than those determined on their Au/CeO2 counterpart. The activity in CO oxidation of the Au/CeO2–Al2O3 catalysts increases with the cerium content in the support, which could be linked to the better oxygen mobility of these systems, whereas in CO-PrOx the Au/CeO2–Al2O3 catalysts with medium cerium loading (Ce/Ce+Al=5 and 10mol%) present the highest CO conversion at 50–60°C. The catalysts are stable at 100°C in CO+O2+H2 mixtures. The addition of CO2 in the stream strongly deactivates Au/CeO2, whereas Au/CeO2–Al2O3 is less affected. Whatever the catalyst, the presence of steam has no significant effect on the catalytic performances.

Thermodynamic characteristics of surface densified solid Scots pine wood

Wetting phenomena of surface densified solid wood and its surface energetic behavior were investigated. The specimens of three different initial thicknesses (22 mm, 20 mm, and 18 mm) were surface densified to a target thickness of 15 mm in order to obtain three different degrees of surface densification. After surface densification one third of the specimens was heat treated at 200 °C in the presence of steam, and one third of the specimens was oil treated with linseed oil. The sessile drop technique was used to estimate the apparent contact angle of water, diiodomethane, and formamide on control and surface densified wood. The contact angle data were used to determine the surface free energies of the control and surface densified wood by the Owens Wendt Rabel and Kaelble (OWRK) method. The results of contact angle measurements revealed that surface densification process affects surface wettability. The apparent contact angles of test liquids were higher in the case of surface densified wood compared to the control undensified wood. Heat treatment and oil treatment of the surface densified wood additionally increased the contact angle of tested liquids. Furthermore, a larger reduction in the void spaces of the wood due to higher degree of densification did not affect the apparent contact angles of tested liquids and consequently the surface free energy. The surface densification process lowered the surface energetics and the polarity of wood. Furthermore, heat treatment and oil treatment additionally increased the hydrophobic character of the examined surfaces and lowered the dispersive and polar components of surface free energy.

Process for CO2 Capture from High-Pressure and Moderate-Temperature Gas Streams

A novel CO2 capture process was developed using a Mg(OH)2-based sorbent suitable for warm gas CO2 removal from high-pressure coal gasification gas streams. The purpose of this study is to perform a preliminary energy study and develop a method to implement this sorbent in a power plant. The proposed CO2 removal process involves sorption of CO2 at 200–300 °C and regeneration at 385 °C. The operational temperature is ideal for CO2 capture downstream to the water–gas shift reactor in an integrated gasification combined cycle (IGCC) power plant but is applicable to other warm gas cleanup processes as well. This technology offers the ability to fully utilize the potential efficiency increases associated with warm gas clean up. Additionally, the sorbent is able to operate in the presence of steam, which distinguishes it from other technologies that require an energy-intensive drying step prior to CO2 separation. Regeneration is carried out at 280 psi and 400 °C, resulting in a high-pressure CO2 product stream, ...

Structure of silica-supported molybdenum oxide studied by in situ spectroscopy under reactive and non-reactive conditions

In this communication, new results on the structure of silica-supported molybdenum oxide catalysts using operando and in situ Raman spectroscopy are presented. The detailed structure, that is, the ratio of dioxo to monooxo surface molybdenum oxide, strongly depends on temperature and gas-phase composition. Whereas increasing the catalyst temperature to 500°C results in an increase in the monooxo/dioxo intensity ratio, the ratio is reduced by the presence of steam. The observed behavior is attributed to shifts in the equilibrium between monooxo and dioxo species resulting from hydration/dehydration of the catalyst in agreement with theoretical predictions.

Stabilization of ZSM-5 zeolite catalysts for steam catalytic cracking of naphtha for production of propene and ethene

In order to increase ethene and propene, naphtha steam catalytic cracking has been considered. The cracking of C5–C12n-alkanes with ZSM-5 has been studied in absence and in presence of steam and the influence of the operation variables was studied. Irreversible catalyst deactivation by dealumination also occurs in the reactor when the cracking is carried out in the presence of steam. To diminish steam deactivation, the influence of zeolite Si/Al framework and a postsynthesis treatment by phosphorous have been studied and optimized. Much more stable catalyst can be achieved that result in an increase in activity without penalty for production of ethene and propene.

Influence of High-Temperature Steam on the Reactivity of CaO Sorbent for CO2 Capture

Calcium looping is a high-temperature CO(2) capture technology applicable to the postcombustion capture of CO(2) from power station flue gas, or integrated with fuel conversion in precombustion CO(2) capture schemes. The capture technology uses solid CaO sorbent derived from natural limestone and takes advantage of the reversible reaction between CaO and CO(2) to form CaCO(3); that is, to achieve the separation of CO(2) from flue or fuel gas, and produce a pure stream of CO(2) suitable for geological storage. An important characteristic of the sorbent, affecting the cost-efficiency of this technology, is the decay in reactivity of the sorbent over multiple CO(2) capture-and-release cycles. This work reports on the influence of high-temperature steam, which will be present in flue (about 5-10%) and fuel (∼20%) gases, on the reactivity of CaO sorbent derived from four natural limestones. A significant increase in the reactivity of these sorbents was found for 30 cycles in the presence of steam (from 1-20%). Steam influences the sorbent reactivity in two ways. Steam present during calcination promotes sintering that produces a sorbent morphology with most of the pore volume associated with larger pores of ∼50 nm in diameter, and which appears to be relatively more stable than the pore structure that evolves when no steam is present. The presence of steam during carbonation reduces the diffusion resistance during carbonation. We observed a synergistic effect, i.e., the highest reactivity was observed when steam was present for both calcination and carbonation.

In situ X-ray diffraction of CaO based CO2 sorbents

In situ X-ray diffraction coupled with Rietveld refinement has been used to study CO2 capture by CaO, Ca(OH)2 and partially hydrated CaO, as a function of temperature. Phase quantification by Rietveld refinement was performed to monitor the conversion to CaCO3 and the results were compared to those derived using thermogravimetric analysis (TGA). It was found that Ca(OH)2 converted directly to 100% CaCO3 without the formation of a CaO intermediate, at ca. 600 °C. Both pure CaO and partially hydrated CaO (33.6 wt% Ca(OH)2) reached the same capture capacity, containing approximately 65 wt% CaCO3 at 800 °C. It was possible to provide direct evidence of the capture mechanism. The stresses in the Ca(OH)2 phase of the partially hydrated CaO were found to be more than 20 times higher than its strength, leading to disintegration and the generation of nano-sized crystallites. The crystallite size determined using diffraction (75 × 16 nm) was in good agreement with the average crystallite size observed using TEM (of 83 × 16 nm). Electron diffraction patterns confirmed coexistence of CaO and Ca(OH)2. The analysis provides an explanation of the enhanced capture/disintegration observed in CaO in the presence of steam.

Fatigue behavior of a Hi-Nicalon™/SiC–B4C composite at 1200°C in air and in steam

Effects of steam environment on fatigue behavior of a non-oxide ceramic composite with a multilayered matrix were investigated at 1200 °C. The composite was produced via chemical vapor infiltration (CVI). The composite had an oxidation inhibited matrix, which consisted of alternating layers of silicon carbide and boron carbide and was reinforced with laminated woven Hi-Nicalon™ fibers. Fiber preforms had pyrolytic carbon fiber coating with boron carbon overlay applied. Tensile stress–strain behavior and tensile properties were evaluated at 1200 °C. Tension-tension fatigue tests were conducted at 0.1 Hz and at 1.0 Hz for fatigue stresses ranging from 100 to 140 MPa in air and in steam. Fatigue run-out was defined as 105 cycles at 0.1 Hz and as 2 × 105 cycles at 1.0 Hz. Presence of steam had little influence on fatigue performance at 1.0 Hz, but noticeably degraded the fatigue lifetimes at 0.1 Hz. Specimens that achieved run-out were subjected to tensile tests to failure to characterize the retained tensile properties. Prior fatigue in air and in steam caused significant reduction in tensile strength and modulus. Composite microstructure, as well as damage and failure mechanisms were investigated.

Selection of modifying additives for improving the steam tolerance of methane afterburning palladium catalysts

In this work, we discuss the problem of the afterburning of methane from the exhaust gases of automobile engines fueled by natural gas. In exhaust neutralizers, the PdO/Al2O3 catalyst, the main drawback of which is the reduction of its activity under the action of steam that always present in exhaust gases, is commonly used. To improve the tolerance to steam, a series of PdO-MexOy/Al2O3 binary catalysts (Me is Co, Cu, Fe, Ni, Mn, or Sn) was prepared and studied. Comparative tests under conditions modeling the methane afterburning process in automobile neutralizers show that Pd catalysts promoted with nickel, cobalt, and tin oxides are more resistant to the inhibiting action of steam. The high crystallinity of supported PdO and its uniform distribution over the surface of modified Al2O3 are indicated as criteria for the stability of catalysts in the presence of steam. Optimization of the concentration of promotors and the preparation method used for their introduction allows the deactivation of Pd catalysts under the action of steam to be almost completely eliminated.

Surface chemistry of phase-pure M1 MoVTeNb oxide during operation in selective oxidation of propane to acrylic acid

The surface of a highly crystalline MoVTeNb oxide catalyst for selective oxidation of propane to acrylic acid composed of the M1 phase has been studied by infrared spectroscopy, microcalorimetry, and in situ photoelectron spectroscopy. The acid–base properties of the catalyst have been probed by NH3 adsorption showing mainly Brønsted acidity that is weak with respect to concentration and strength of sites. Adsorption of propane on the activated catalyst reveals the presence of a high number of energetically homogeneous propane adsorption sites, which is evidenced by constant differential heat of propane adsorption qdiff,initial=57kJmol−1 until the monolayer coverage is reached that corresponds to a surface density of approximately 3 propane molecules per nm2 at 313K. The decrease of the heat to qdiff,initial=40kJmol−1 after catalysis implies that the surface is restructured under reaction conditions. The changes have been analyzed with high-pressure in situ XPS while the catalyst was working applying reaction temperatures between 323 and 693K, different feed compositions containing 0mol.% and 40mol.% steam and prolonged reaction times. The catalytic performance during the XPS experiments measured by mass spectrometry is in good agreement with studies in fixed-bed reactors at atmospheric pressure demonstrating that the XPS results taken under operation show the relevant active surface state. The experiments confirm that the surface composition of the M1 phase differs significantly from the bulk implying that the catalytically active sites are no part of the M1 crystal structure and occur on all terminating planes. Acrylic acid formation correlates with surface depletion in Mo6+ and enrichment in V5+ sites. In the presence of steam in the feed, the active ensemble for acrylic acid formation appears to consist of V5+ oxo-species in close vicinity to Te4+ sites in a Te/V ratio of 1.4. The active sites are formed under propane oxidation conditions and are embedded in a thin layer enriched in V, Te, and Nb on the surface of the structural stable self-supporting M1 phase.

Microwave-assisted catalytic decomposition of N2O over hexaferrites

A series of Al substituted hexaferrites (Ba(2)Mg(2)Fe(12-x)Al(x)O(22), x = 0-6) were synthesized by sol-gel method and used as new catalysts for high concentration N(2)O decomposition. Substitution of Fe with Al increased the redox behavior and surface area and thus led to the enhancement of activity under conventional heating mode. On the other hand, the pure hexaferrite (x = 0) showed the highest activity for N(2)O decomposition under microwave discharge mode: the complete conversion of N(2)O was obtained at about 583 K. The presence of steam in the inlet gas further enhanced the activity, irrespective of the Al content in the materials. (C) 2011 Elsevier B.V. All rights reserved.

Steam reforming of glycerol over Ni/Al 2O 3 catalyst

Glycerol steam reforming has been investigated in a 10-mm ID fixed-bed reactor containing Ni/Al 2O 3 catalyst using a wide range of the steam-to-carbon ratio (1.1 ≤ STCR ≤ 4.0) at temperatures between 723 K and 823 K. Physicochemical characterization revealed that the catalyst surface was populated by both weak and strong acid and basic sites although the catalyst appeared to have a net surface acidity. H 2, CO 2 and CO were the main gaseous products with H 2:CO 2 ratio at approximately 2.15 while H 2:CO ratio varied between 6.0 and 16.0 depending on the reactant feed composition. The specific glycerol consumption rate exhibited fractional reaction orders with respect to both glycerol (0.48) and steam (0.34) and activation energy of about 60 kJ mol −1. Mechanistic considerations indicated that glycerol and steam underwent associative and dissociative adsorption, respectively on two different sites with the surface reaction being the rate-determining step. Additionally, carbon deposition has a positive dependency on the glycerol partial pressure, but it was inhibited in the presence of steam.

Role of Cr and V on the stability of potassium-promoted iron oxides used as catalysts in ethylbenzene dehydrogenation

Potassium-promoted iron oxides are the most widely used catalysts for catalytic dehydrogenation of ethylbenzene to styrene. Besides potassium, other minor promoters are also added into the catalyst for different purposes, either enhancing catalyst stability or activity/selectivity. Chromium (Cr) and vanadium (V) are two historically used promoters. Cr is widely accepted to be a structure stabilizer and V can increase the selectivity to styrene but with detrimental effect on stability and activity of the catalysts. Since the effects of these two promoters are known and opposite, the effects of Cr and V on the solid state phase behavior of K-promoted iron oxide were investigated. Gas environments consisting of H 2, CO 2, ethylbenzene and steam were used to explore the interaction between the gas composition and the phase behavior of the doped iron oxides. The experiments were performed in a thermogravimetric analyzer under various gas environments and X-ray powder diffraction was used to quantitatively characterize the phase changes. The Cr and V promoted K–promoted iron oxide had very different responses to the different gas phase environments, but in the presence of steam and ethylbenzene Cr stabilized the iron oxide against reduction whereas V destabilized the iron oxide. These data support the idea that the promoters influence K-promoted iron oxide stability under low steam-to-ethylbenzene operation via modifying the phase behavior of the iron oxide.

Influence of Catalyst and Temperature on Gasification Performance

In the present study the catalytic steam gasification of biomass to produce hydrogen-rich gas with calcined dolomite and Nano-NiO/γ-Al2O3 as catalyst in an externally heated fixed bed reactor was investigated. The influence of the catalyst and reactor temperature on gasification performance was studied at the temperature range of 700°C-900°C. Over the ranges of experimental conditions examined, Nano-NiO/γ-Al2O3 and calcined dolomite both revealed better catalytic performance, at the presence of steam, tar was completely decomposed as temperature increases from 800°C to 900°C. Higher temperature resulted in more H2 and CO2 production, and dry gas yield. The highest H2 content of 58.27V% and the highest H2 yield of 2.23 Nm3/ kg biomass were observed at the highest temperature level of 900°C.

Synchrotron-Based XANES Speciation of Chromium in the Oxy-Fuel Fly Ash Collected from Lab-Scale Drop-Tube Furnace

Speciation of chromium (Cr) in the fly ash collected from oxy-firing of Victorian brown coal has been reported for the first time to address the potential formation of toxic Cr(VI) and the variation of the quantities of Cr(III)-bearing species with flue gas composition. Synchrotron-based X-ray absorption near-edge structure (XANES) was employed for Cr speciation. Apart from a pure O(2)/CO(2) mixture (27/73, v/v) versus air, the O(2)/CO(2) mixtures doped with SO(2), HCl, and steam individually or together to simulate real flue gas have also been tested. Under all of the conditions tested here, the fractions of Cr(VI) in the fly ashes are insignificant, constituting no more than 5% of the total Cr. The test of Cr-doped brown coal in pyrolysis further confirmed that the Cr(VI) formation preferentially occurred through a local oxidation of Cr(III) at the oxygen-containing functions sites within coal matrix, rather than through an oxidation by external bulk O(2). This reaction is also highly temperature-dependent and slower than the interaction between Cr(III) and other metals such as iron oxide. Increasing temperature to 1000 °C inhibited the oxidation of Cr(IIII) to Cr(VI). Shifting the combustion gas from air to O(2)/CO(2) exerted little effect on the Cr(VI) formation. Instead, the formation of iron chromite (FeCr(2)O(4)) was facilitated in O(2)/CO(2), probably due to a strong reducing microenvironment formed by the CO(2) gasification reaction within the char matrix. The accumulation of HCl in flue gas favored the vaporization of chromium as gaseous chloride/oxychloride, as expected. The coexistence of SO(2) inhibited this phenomenon by promoting the formation of sulfate. The presence of steam was even beneficial for the inhibition of water-soluble Cr sulfate through stabilizing the majority of Cr into alumino-silicate which is in the slagging phase.

Evaluation of thermodynamic properties of H4SiO4 in the ideal gas state from experimental data

Thermodynamic properties of gaseous silicon hydroxides are necessary for analyzing the silicate condensation phenomena in the primordial solar nebula [Hashimoto, 1992], the silica precipitation in steam-rich geothermal systems and recent concerns with the corrosion or deposition of SiO2-containing alloys and ceramics in high-temperature moist environments. Experimental transpiration studies (i.e. studies of the partial pressures of Si over solid phases in the presence of steam) of the reaction of water vapor with cristobalite [Hashimoto, 1992; Jacobson, et al., 2005] agree that at 1100-1650 K and water pressures close to 0.1 MPa the vapor phase concentration of Si is determined by the reaction SiO2(s) + 2H2O(g) = H4SiO4(g). (1) Mass spectrometric data on the volatile species formed from SiO2(s) and water at 1473–1773 K and water vapor pressure between 0.018 and 0.094 MPa [Opila, et al., 1997] also confirm that H4SiO4 is the primary reaction product. However, the literature data on the thermodynamic properties of gaseous H4SiO4 [Allendorf, et al., 1995; Jacobson, et al., 2005; Rutz and Bockhorn, 2005] differ up to 18 kJmol and 9 JKmol in the value of enthalpy of formation and the entropy at Tr=298.15 K and the standard pressure   P 0.1 MPa. Therefore, it was decided employ all available data for the reaction (1) to determine the optimal values of ΔfG and S of H4SiO4(g) at 298.15 K and 0.1 MPa. Selection of experimental data In addition to the transpiration data we accepted data on the solubility of quartz and amorphous silica in water vapor of density below 15 kg·m. The accepted data set of data to calculate the values of equilibrium constant of reaction (1) is given in Table.

Interactions of supported nickel and nickel oxide catalysts with methane and steam at high temperatures

The catalytic performance of cermets made of 10% nickel or nickel oxide supported on YSZ (yttria-stabilized zirconia) for chemical looping combustion (CLC) and steam reforming (SR) of methane at 700 °C is investigated. Steam reforming of methane over the reduced catalyst resulted in a syngas containing more than 70% hydrogen and about 15% carbon monoxide. Chemical looping combustion of methane with insufficient lattice oxygen could potentially lead to 40–65% hydrogen rich gas products. Prolonged induction period (e.g. 30–80 min) in reduction of nickel oxide by methane has been observed in the presence of steam. The span of induction period increases by increasing steam partial pressure. It is hypothesized that the delayed reduction of nickel oxide is related to the retarding effect of steam on autocatalytic reactions of methane and hydrogen with lattice oxygen of nickel oxide and the subsequent reforming reactions.