Temperature Profile Of Catalyst Bed Research Articles

Temperature profile in a two-stage fixed bed reactor for catalytic partial oxidation of methane to syngas

Detailed axial temperature distribution has been studied in a two-stage process for catalytic partial oxidation of methane to syngas, which consists of two consecutive fixed bed reactors with oxygen or air separately introduced. The first stage of the reactor, packed with a combustion catalyst, is used for catalytic combustion of methane at low initial temperature. While the second stage, filled with a partial oxidation catalyst, is used for the partial oxidation of methane to syngas. A pilot-scale reactor packed with up to 80 g combustion catalyst and 80 g partial oxidation catalyst was employed. The effects of oxygen distribution in the two sections, and gas hourly space velocity ( GHSV) on the catalyst bed temperature profile, as well as conversion of methane and selectivities to syngas were investigated under atmospheric pressure. It is found that both oxygen splitting ratio and GHSV have significant influence on the temperature profile in the reactor, which can be explained by the synergetic effects of the fast exothermic oxidation reactions and the slow endothermic (steam and CO 2) reforming reactions. Almost no change in activity and selectivity was observed after a stability experiment for 300 h.

Effect of Support on the Suppression of Hot Spot Formation in the Partial Oxidation of Methane

Abstract Ni-based catalysts supported on perovskite oxides and α-Al2O3 were prepared to investigate catalytic performance and catalyst bed temperature profile in the partial oxidation of methane. Ni/LaAlO3 showed high activity and remarkably suppressed hot spot formation in the catalyst bed even at high space velocity. The effect of support is discussed on the basis of the state of Ni.

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).

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.

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.

Temperature profile of catalyst bed during oxidative steam reforming of methane over Pt-Ni bimetallic catalysts

The catalyst bed temperature during oxidative reforming of methane (CH 4/H 2O/O 2/Ar = 40/30/20/10) at 1123 K and atmospheric pressure was investigated by infrared thermography over γ-Al 2O 3 supported bimetallic Pt-Ni catalysts prepared by different impregnation methods: co-impregnation and sequential impregnation. The thermographical results 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. Temperature programmed reduction (TPR) with H 2 revealed that the addition of Pt by a sequential impregnation method greatly promoted the reduction of Ni species; furthermore, infrared spectra of CO adsorption suggests that the surface composition of Pt on the catalyst prepared by the sequential method is much higher than that for the catalyst prepared by the co-impregnation method. The surface enrichment of Pt is responsible for the effective overlap between the combustion and reforming zones, and this can enhance the inhibition of hot spot formation.

Steady-state simulation of an ammonia synthesis converter

A simple one-dimensional model of a T.V.A. ammonia synthesis converter approximates closely the ammonia production rate and the catalyst bed temperature profile of an industrial reactor. Using this simulation, the effects of space velocity, feed gas ammonia and inert contents, reactor heat conductance, and catalyst activity upon reactor stability, ammonia production rate, and catalyst bed temperature profile have been determined.