Oxidative Steam Reforming Of Methane Research Articles

Comprehensive Study of Steam Reforming of Methane in Membrane Reactors

A 2D model and heat transfer mechanism are proposed to analyze and study oxidative steam reforming of methane (OSRM) in a membrane reactor. The model describes mass and thermal dispersions for gas and solid phases. It also accounts for transport through the membrane. The effects of operating parameters on methane conversion and H2 yield are analyzed. The parameters considered are the bed temperature (800–1100 K), molar oxygen-to-carbon ratio (0.0–0.5), and steam-to-carbon ratio (1–4). The results show that our model prevents overestimation and provides valuable additional information about temperature and concentration gradients in membrane reactor which is not available in a simple one-dimensional approach. Simulation results show that large temperature and concentration gradients cannot be avoided. The particle properties and the bed diameter have a considerable effect on the extent of gas mixing. Effective gas mixing coefficient also increases with increasing gas and solid velocity. In membrane reactor, simulation results show that mixing which depends on operational and design parameters has a strong effect on the hydrogen conversion. Also, the removal of hydrogen with membranes breaks equilibrium barrier leading to efficient production of hydrogen, reduced reactor size, and tube lengths. The model can be used in real-time simulation of industrial reactors for control and optimization purposes.

Oxidative steam reforming of methane over nickel catalysts supported on Al2O3–CeO2–La2O3

Nickel supported on Al2O3–CeO2–La2O3 provided excellent catalytic features and high coking resistance in oxidative steam reforming of methane.

Hydrogen production from oxidative reforming of methane on Ni/γ-Al2O3 catalysts: Effect of support promotion with La, La–Ce and La–Zr

Ni/Al2O3 catalysts promoted by adding La2O3, La2O3–CeO2 and La2O3–ZrO2 were investigated on oxidative and steam reforming aiming the hydrogen production. The samples were characterized by surface area estimation (BET), XRD, TPR, TPD-H2 and XANES. Analysis of TEM and TPO was performed as complementary characterization for catalysts after reaction. The oxidative steam reforming of methane at temperatures above 500°C reveals that all the promoted catalysts presented better activities than the unpromoted. Below 500°C, the catalysts presented deactivation due to metallic nickel species oxidation and the TEM analysis of Ni/Al and Ni/La–Al catalysts revealed that the lanthanum addition led to a decrease in the Ni species particle size and also to a better active phase dispersion. The results suggest that below 500°C the activity may be related to differences in the metallic area values, although the Ni/La2O3–Al2O3 catalysts have shown a different behavior.

Stable hydrogen production by methane steam reforming in a two zone fluidized bed reactor: Experimental assessment

The Two Zone Fluidized Bed Reactor concept is proposed for hydrogen production via the steam reforming of methane (SRM) including integrated catalyst regeneration. In order to study the effect of the contact mode, the oxidative SRM has been carried out over a Ni/Al2O3 catalyst using a fixed bed reactor (fBR), a conventional fluidized-bed reactor (FBR) and the proposed two-zone fluidized bed reactor (TZFBR). The technical feasibility of these reactors has been studied experimentally, investigating their performance (CH4 conversion, CO and H2 selectivity, and H2 global yield) and stability under different operating conditions.Coke generation in the process has been verified by several techniques. A stable performance was obtained in the TZFBR, where coke formation was counteracted with continuous catalyst regeneration. The viability of the TZFBR for carrying out this process with a valuable global yield to hydrogen is demonstrated.

Comparative Study on Steam and Oxidative Steam Reforming of Methane with Noble Metal Catalysts

Methane steam reforming (SR) and oxidative steam reforming (OSR) are two catalytic processes for generating syngas. Catalysts based on Ru, Rh, and Pt noble metals deposited over CeO2 and Al2O3 carriers were prepared by solution combustion synthesis and tested toward the methane SR reaction. The best catalysts were further tested toward the methane OSR reaction, to see any benefit coming from the presence of a slight amount of oxygen. These catalysts were then characterized using Brunauer-Emmet-Teller (BET), CO chemisorption, transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques. The highest conversion of methane was reached by the 1.5% Rh/CeO2 catalyst for the methane SR reaction and by the 1.5% Ru/Al2O3 for the methane OSR reaction. These two best catalysts were then further compared in terms of hydrogen concentration, yield, H2-to-CO molar ratio, and CO2-to-CO selectivity ratio. The 1.5% Rh/CeO2 catalyst for SR performed better than the 1.5% Ru/Al2O3 catalyst for OSR reaction, a...

Stable hydrogen production by methane steam reforming in a two-zone fluidized-bed reactor: Effect of the operating variables

The oxidative steam reforming of methane in a two-zone fluidized-bed reactor (TZFBR) was investigated over a Ni/Al2O3 catalyst. The effects of the main operating variables (temperature, steam/oxygen ratio, steam/methane ratio and relative velocity with respect to the minimum fluidization velocity) have been studied. A comparison has been made with results given in the literature in terms of hydrogen yield. Despite working with very low steam/methane ratios, high values of hydrogen yield at both high methane conversion and at steady state were obtained in the TZFBR.

Oxidative steam reforming of methane to synthesis gas in microchannel reactors

Oxidative steam reforming of methane to synthesis gas (syngas) over an alumina supported bimetallic Pt–Rh catalyst was comparatively investigated in coated and packed microchannel reactors. In the first configuration, thin layers of catalysts are coated on opposite walls of a single microchannel, while the second one is described by particulate catalysts packed into an empty microchannel of dimensions identical with the first one. Both geometries are compared on the basis of methane conversion and CO selectivity measured at different values of parameters, namely reaction temperature (773–923 K), molar steam-to-carbon (S/C = 0–3.0) and oxygen-to-carbon (O2/C = 0.47–0.63) ratios in the feed, and contact time (0.36–0.71 mg min cm−3). Although methane conversions are found to be comparable, the coated catalyst gave significantly higher CO selectivities than the packed counterpart in the whole parameter range. Increase in all of the parameter values led to improvement in methane conversion, while CO selectivity increased only with temperature and contact time. Molar H2/CO ratios obtained in the coated microchannel reactor are found to vary between 1.0 and 3.0 which are at least three times smaller than those produced in the packed microchannel reactor. Catalyst deactivation is not detected in both configurations. Stable operation up to 72 h over coated microchannel verified mechanical and chemical stability of the Pt–Rh coating that produced syngas with H2/CO ratio of 2.12 at temperatures lower than employed in industrial reformers. Different flow distribution properties of coated and packed microchannels seem to play roles in affecting the product distribution.

Oxidative steam reforming of methane over Ni/α-Al 2O 3 modified with trace noble metals

Ni catalysts supported on α-Al 2O 3 modified with small amounts of noble metals (Pd, Pt, Au, Ir, Rh and Ru) were prepared by a co-impregnation method to investigate catalytic performance and catalyst bed temperature profile in oxidative steam reforming of methane. Modification of the Ni catalyst with noble metals was effective to decreasing the bed temperature near the catalyst bed inlet, and it is found that Pd is the most effective modifier among the noble metals. Additive effect of Pd has some aspects: the increase of the metal dispersion, suppression of oxidation and enhancement of reducibility judging from characterization results of H 2 adsorption and evaluation by pulse reaction technique using O 2 and H 2. The extended X-ray absorption fine structure (EXAFS) analysis suggests that the excellent properties can be due to small Pd metallic cluster interacted with Ni particles.

Oxidative steam reforming of methane over Ni/α-Al2O3 modified with trace Pd

Ni catalysts supported on α-Al2O3 modified with small amounts of Pd were prepared by different impregnation methods to investigate catalytic performance and catalyst bed temperature profile in oxidative steam reforming of methane. The Pd + Ni bimetallic catalysts prepared by the co-impregnation method showed higher resistance to hot-spot formation than monometallic Ni and bimetallic Pd/Ni catalysts prepared by two sequential impregnations, in particular, Pt + Ni catalysts prepared by the co-impregnation method. The additive effect of Pd on the Pd/Ni catalysts was discussed on the bases of metal particle size and structural analysis by Pd K-edge extended X-ray absorption fine structure (EXAFS).

Catalytic performance and QXAFS analysis of Ni catalysts modified with Pd for oxidative steam reforming of methane

Pd–Ni bimetallic catalysts prepared by co-impregnation and sequential impregnation methods were compared in the catalytic performance in oxidative steam reforming of methane. The sequential impregnation was more effective to the suppression of hot spot formation. According to the structural analysis by in situ quick-scanning X-ray absorption fine structure (QXAFS) during the temperature programmed reduction, the sequential impregnation method gave the bimetallic particles with higher Pd surface composition because of the low possibility of the Pd–Ni bond formation. Higher surface composition of Pd with higher reducibility than Ni is connected to the enhancement of the catalyst reducibility and the suppression of the hot spot formation.

Catalytic performance and characterization of Pt–Ni bimetallic catalysts for oxidative steam reforming of methane

Effects of methane oxygen mixture addition to steam reforming of methane and subsequent removal of the methane oxygen mixture from the oxidative steam reforming of methane on catalytic performance were investigated using monometallic Ni and Pt catalysts and two Pt–Ni bimetallic catalysts. Hysteresis with respect to the addition and removal of the methane oxygen mixture was observed clearly on a Pt–Ni bimetallic catalyst prepared by co-impregnation method and the Ni catalyst. In contrast, no hysteresis was observed for a Pt–Ni catalyst that was prepared by sequential impregnation method. Combined with characterization results obtained using EXAFS analysis and FTIR of CO adsorption, Pt–Ni catalyst was prepared by sequential impregnation is formed Pt–Ni alloy particles, where Pt atoms are segregated on the surface, enhances the reducibility of Ni drastically and this is related to the behavior without hysteresis.

Catalytic performance and characterization of Pd/Ni0.2Mg0.8Al2O4 in oxidative steam reforming of methane under atmospheric and pressurized conditions

Abstract Catalytic performance and characterization of Pd/Ni 0.2 Mg 0.8 Al 2 O 4 were investigated in oxidative steam reforming of methane under atmospheric and pressurized conditions. Pd/Ni 0.2 Mg 0.8 Al 2 O 4 showed much higher methane conversion under high partial pressure of steam, where Ni 0.2 Mg 0.8 Al 2 O 4 lost the reforming activity because the Ni species was oxidized under atmospheric pressure. In addition, the addition of Pd on Ni 0.2 Mg 0.8 Al 2 O 4 was effective to improve the stability and resistance to coke formation in oxidative steam reforming of methane under pressurized conditions. On the other hand, the formation of Pd–Ni alloy over Pd/Ni 0.2 Mg 0.8 Al 2 O 4 was confirmed from the characterization results of TPR, TEM, EXAFS and FTIR, and this can contribute to high catalytic performance of Pd/Ni 0.2 Mg 0.8 Al 2 O 4 .

Oxidative Steam Reforming of Methane over Ni Catalysts Modified with Noble Metals

The effects of addition of small amounts of noble metals such as Pt, Pd, and Rh to Ni/γ-Al2O3 and NiO-MgO solid solutions were investigated on the catalyst activation, catalyst bed temperature profile, and carbon formation behavior in oxidative steam reforming of methane. Addition of Pt and Pd by a sequential impregnation method to Ni/γ-Al2O3 had a much more remarkable effect than by a co-impregnation method on the resistance to deactivation by oxidation of Ni and suppression of hot-spot formation. Temperature-programmed reduction, extended X-ray absorption fine structure, and Fourier transform infrared spectroscopy suggested that the noble metal atoms introduced by the sequential impregnation method were preferably located on the surface to form an alloy. Addition of noble metals (Pt, Pd, and Rh) to Ni0.2Mg0.8O solid solution catalysts inhibited carbon formation in the oxidative steam reforming of methane under pressurized conditions.

貴金属修飾Ni/α-Al2O3触媒のメタンの酸化リフォーミング反応

貴金属修飾Ni/α-Al2O3触媒のメタンの酸化リフォーミング反応

Surface modification of Ni catalysts with trace Pd and Rh for oxidative steam reforming of methane

Abstract Bimetallic catalysts (Pd–Ni and Rh–Ni) were prepared by co-impregnation and sequential impregnation methods to investigate catalytic performance in oxidative steam reforming of methane. These bimetallic catalysts gave high methane conversion even at low W / F such as 0.07 g h/mol. The thermographical observation clearly demonstrated that the catalyst bed temperature was strongly dependent on the preparation method. The bimetallic catalyst prepared from the sequential impregnation method exhibited much higher resistance to hot-spot formation in oxidative reforming of methane. In particular, Pd–Ni catalysts prepared by the sequential impregnation method showed higher resistance to hot-spot formation than monometallic Pd and Ni catalysts, and this can be a synergetic effect of Pd and Ni. Temperature-programmed reduction (TPR) with H 2 revealed that the addition of Pd or Rh by a sequential impregnation method greatly promoted the reduction of Ni species. Extended X-ray absorption fine structure (EXAFS) analysis confirmed the formation of Pd–Ni alloy and the preferential location of Pd atoms on the surface of the bimetallic particles over the Pd/Ni catalysts. Surface modification of Ni with Pd by sequential impregnation is effective for promotion of the activity and suppression of hot-spot formation.

Surface modification of Ni catalysts with trace Pt for oxidative steam reforming of methane

Hysteresis of catalytic performance with respect to temperature increasing and decreasing in oxidative steam reforming of methane (CH 4/H 2O/O 2/Ar = 40/30/20/10) over the monometallic Ni catalysts disappeared by the modification with Pt, and the additive effect of Pt by the sequential impregnation method (Pt/Ni) was much more significant than that by the co-impregnation method (Pt + Ni) in terms of catalytic performance and catalyst bed temperature profile. Characterization results by means of TEM, TPR, EXAFS, and FTIR suggest that the Pt atoms on the Pt/Ni catalysts were located more preferably on the surface to form a Pt Ni alloy than those on the Pt + Ni catalysts. The modification of Ni with Pt suppressed the oxidation of Ni species near the bed inlet in the oxidative steam reforming of methane at 1123 K, although the species on the monometallic Ni catalysts were oxidized under similar conditions. This can be due to the decreased oxidation rate of the species and the increased reduction rate caused by the surface modification of Ni with Pt. Consequently, the Pt Ni species can be maintained in the metallic state near the bed inlet, and the species can be the active site for the reforming reaction as well as the combustion reaction, which this leads to a lower bed temperature and smaller temperature gradient than those seen for the monometallic Ni catalysts.

Promoting Effect of Pd Addition to Ni0.2Mg0.8Al2O4 in Oxidative Steam Reforming of Methane

Abstract Addition of Pd to Ni0.2Mg0.8Al2O4 promoted oxidative steam reforming of methane, and it gave high activity under high partial pressure of steam and low W/F, where Ni0.2Mg0.8Al2O4 showed very low activity. The Ni0.2Mg0.8Al2O4 requires the H2 reduction pretreatment; however, Pd/Ni0.2Mg0.8Al2O4 can be activated automatically by the reactant gases of oxidative reforming of methane.

Methane reforming over a high temperature stable-NiCoMgOx supported on zirconia–hafnia catalyst

Abstract The unusually high temperature stable NiCoMgO x (Ni/Co/Mg:1:0.2:1.2)/zirconia–hafnia catalyst has been investigated for syngas generation via the catalytic partial oxidation of methane (CPOM), oxidative steam reforming of methane (OSRM) and oxidative CO 2 reforming of methane (OCRM) processes. The catalyst, even when calcined at 1400 °C for 4 h, showed excellent activity/selectivity for the CPOM, OSRM and the OCRM reactions. On account of its high thermal stability, hot spots in the catalyst bed and/or high temperatures prevailing at the catalyst surface during the oxy-reforming processes would have little or no effect on the catalytic activity/selectivity of the NiCoMgO x /zirconia–hafnia catalyst, thus making the catalyst suitable even for operating under adiabatic conditions. While the selectivity for CO increased considerably with increasing reaction temperature for the CPOM process, the selectivity for H 2 was affected to a much lesser extent. The selectivity for CO and H 2 in the CPOM reaction was found to decrease with increasing space velocity; the H 2 selectivity was however affected to a greater extent. For the OSRM process, the H 2 O/CH 4 ratio profoundly influenced the H 2 /CO ratio and the heat of the reaction. Depending on the H 2 O/CH 4 ratio, the OSRM process could be operated in a mildly exothermic, thermoneutral or mildly endothermic mode. The CO 2 conversion increased rapidly with increasing OCRM temperature and correspondingly the exothermicity of the OCRM reaction was found to decrease with increasing reaction temperature. At 900 °C, the OCRM reaction was mildly exothermic and provided high methane conversion and syngas selectivity.

Oxidative steam reforming of methane under atmospheric and pressurized conditions over Pd/NiO–MgO solid solution catalysts

The effect of the Pd loading in NiO–MgO solid solution was investigated in oxidative steam reforming of methane under atmospheric and pressurized conditions. The small amounts of Pd addition on Ni 0.2Mg 0.8O can inhibit the oxidation of Ni species and the mixture can maintain the reforming ability at low W/ F conditions under atmospheric pressure, where Ni 0.2Mg 0.8O catalyst deactivated. In addition, Ni 0.2Mg 0.8O catalyst improved remarkably, gaining both high activity and excellent stability by the addition of small amounts of Pd under pressurized conditions. The deactivation rate was closely related to the amount of deposited carbon. Characterization results of TEM, TPR, EXAFS and FTIR suggest that Pd–Ni alloy particles are formed on Pd/Ni 0.2Mg 0.8O catalysts. The Pd–Ni alloy particles with a low ratio of Pd to Ni can play an important role in the high resistance to carbon deposition.

Partial oxidation of methane to syngas with or without simultaneous steam or CO 2 reforming over a high-temperature stable-NiCoMgCeO x supported on zirconia–hafnia catalyst

A NiCoMgCeO x (Ni/Co/Mg/Ce:1:0.2:1.2:1.2)/zirconia–hafnia catalyst with unusually high thermal stability has been investigated for syngas generation via a process that includes the catalytic partial oxidation of methane (CPOM), the oxidative steam reforming of methane (OSRM) and the oxidative CO 2 reforming of methane (OCRM). The catalyst calcined at 1400 °C (for 4 h) showed excellent activity/selectivity for the CPOM, OSRM and the OCRM reactions; furthermore no catalyst deactivation was observed for a period of 20 h. For the CPOM process, the selectivity for H 2 was >95% at reaction temperatures ≥650 °C; however temperatures above 800 °C were required to achieve >95% CO selectivity. While the reaction temperature had a considerable influence on the CPOM product H 2/CO ratio, the space velocity (at 850 °C) did not affect it to any significant extent. For the OSRM process, the H 2O/CH 4 ratio and the reaction temperature had a strong effect on the product H 2/CO ratio and the heat of the reaction; depending on the H 2O/CH 4 ratio and reaction temperature, the OSRM process could be operated in a mildly exothermic, thermoneutral or mildly endothermic mode. The CO 2 conversion was very strongly affected by the reaction temperature in the OCRM process; reasonably high CO 2 conversion (>40%) could only be obtained at high OCRM reaction temperatures (>850 °C). The exothermicity of the OCRM reaction was found to decrease with increasing reaction temperature.