Showing papers on "Partial oxidation published in 2004"

Renewable hydrogen from ethanol by autothermal reforming.

Abstract: Ethanol and ethanol-water mixtures were converted directly into H2 with approximately 100% selectivity and >95% conversion by catalytic partial oxidation, with a residence time on rhodium-ceria catalysts of <10 milliseconds. Rapid vaporization and mixing with air with an automotive fuel injector were performed at temperatures sufficiently low and times sufficiently fast that homogeneous reactions producing carbon, acetaldehyde, ethylene, and total combustion products can be minimized. This process has great potential for low-cost H2 generation in fuel cells for small portable applications where liquid fuel storage is essential and where systems must be small, simple, and robust.

Catalytic Conversion of Methane to Synthesis Gas by Partial Oxidation and CO2 Reforming

Abstract: The preparation of synthesis gas from natural gas, which is the most important step in the gas-to-liquid transformation, has attracted increasing attention in the last decade. Steam reforming, partial oxidation, and CO 2 reforming are the three major processes that can be employed to prepare synthesis gas. Because steam reforming was reviewed recently in this series [Adv. Catal. 47 (2002) 65], this chapter deals only with the latter two processes. The history of the development of methane conversion to synthesis gas is summarized as an introduction to the partial oxidation of methane, which is reviewed with emphasis on hot spots in reactors, major developments in the reduction of O 2 separation costs, and reaction mechanisms. The various catalysts employed in CO 2 reforming are examined, with emphasis on inhibition of carbon deposition.

Synthesis and characterization of mesoporous alumina with nickel incorporated for use in the partial oxidation of methane into synthesis gas

Abstract: Mesoporous alumina catalysts that incorporate nickel (Ni-Alumina) with different Ni/Al molar ratios of 1:2, 1:5 and 1:10 were synthesized by a one-step sol–gel method using lauric acid as a template The prepared Ni-Alumina catalysts showed a relatively high surface area with a narrow pore size distribution after calcination at 700 °C; these effects were independent of the Ni/Al molar ratio Although weak interactions between nickel oxide and alumina were observed in the Ni-Alumina catalysts with increasing the amounts of nickel precursor, nickel catalysts finely dispersed on an alumina support were obtained in all cases The Ni-Alumina catalysts were found to be highly active in the partial oxidation of methane For the purposes of comparison, a nickel catalyst impregnated on a commercially available alumina support was prepared (Ni-IMP) Various characterization results showed that the 1:10 Ni-Alumina catalyst had stronger metal-support interactions and a more favorable catalyst structure for obtaining finely dispersed nickel particles, compared to the Ni-IMP catalyst The deactivation of catalysts examined in this work was not due to catalyst sintering, but mainly to the carbon deposition The Ni-Alumina catalyst having smaller nickel particles and lower levels of carbon deposition had a more stable catalytic activity than the Ni-IMP catalyst

Modeling of a catalytic autothermal methane reformer for fuel cell applications

Abstract: This paper presents a mathematical modeling of catalytic autothermal reforming (ATR) of methane (CH4) for hydrogen (H2) production. ATR is essentially an oxidative steam reforming, which combines the exothermic partial oxidation (PO) with the endothermic steam reforming (SR) under thermally neutral conditions. A two-dimensional reformer model is developed to simulate the conversion behavior of the reformer. The model covers all aspects of major chemical kinetics and heat and mass transfer phenomena in the reformer. Results show that the performance of the reformer is dependent on the molar air-to-fuel ratio (A/F), molar water-to-fuel ratio (W/F), and the space velocity of the feedstock mixture. The optimal conditions for high CH4 conversion and high H2 yield are at A/F of 3.5, W/F of 1, and space velocity of 20 000/h. Under this condition, CH4 conversion of 98% and H2 yield of 42% on dry basis can be achieved and 1 mol of CH4 can produce 1.9 mol of H2 at an equilibrium reformer temperature of around 1000 K.

Inductively coupled plasma/partial oxidation reformation of carbonaceous compounds to produce fuel for energy production

Abstract: Inductively coupled plasma (ICP) reforming converts carbonaceous compounds into a fuel for use in generating electrical power. Energy rich hydrocarbon fuels, such as coal, marine diesel, oils, and hydrocarbon wastes are employed as a feedstock for the ICP, which transforms the feedstock into a fuel that can be used by fuel cells and gas turbines for the production of electricity. The overall efficiency of an ICP-based electrical power system can be increased by providing partial oxidation within the reaction vessel. The partial oxidation conditions consume a small amount of the reformed fuel gas, thereby liberating sufficient thermal energy to reduce the electrical power requirements of the ICP to maintain desired reactor temperatures, and providing an increase in the overall net electrical power production. The integrated power production system can also adjust to meet an increased requirement for process heat and steam by balancing the effect of partial oxidation.

Zeolite-encapsulated Co(II), Ni(II) and Cu(II) complexes as catalysts for partial oxidation of benzyl alcohol and ethylbenzene

Abstract: Co(II), Ni(II) and Cu(II) complexes of dimethylglyoxime and N,N � -ethylenebis(7-methylsalicylideneamine) have been synthesized in situ in Y zeolite by the reaction of ion-exchanged metal ions with the flexible ligand molecules that had diffused into the cavities. The hybrid materials obtained have been characterized by elemental analysis, SEM, XRD, surface area, pore volume, magnetic moment, FTIR, UV-Vis and EPR techniques. Analysis of data indicates the formation of complexes in the pores without affecting the zeolite framework structure, the absence of any extraneous species and the geometry of encapsulated complexes. The catalytic activities for hydrogen peroxide decomposition and oxidation of benzyl alcohol and ethylbenzene of zeolite complexes are reported. Zeolite Cu(II) complexes were found to be more active than the corresponding Co(II) and Ni(II) complexes for oxidation reactions. The catalytic properties of the complexes are influenced by their geometry and by the steric environment of the active sites. Zeolite complexes are stable enough to be reused and are suitable to be utilized as partial oxidation catalysts. © 2003 Published by Elsevier B.V.

Catalytic and FT-IR study on the reaction pathway for oxidation of propane and propylene on V- or Mo–V-based catalysts

Abstract: A series of V- and Mo–V-based catalysts, i.e. undoped and K-doped VO x /Al 2 O 3 , MoVNbO, MoVSbO and MoVTeNbO mixed metal oxides, have been tested in the oxidation of propane and propylene. All the catalysts are active and relatively selective in the partial oxidation of propane and propylene, although the nature of reaction products changes depending on the characteristics of the catalysts. Thus, acrylic acid (MoVTeNbO), acetic and acrylic acid (MoVSbO), acetic acid (MoVNbO) and propylene and CO x (supported catalysts) were the most important products obtained from both propane and propylene. FT-IR spectroscopy of NH 3 indicates the presence of Bronsted and Lewis acid sites, although the acidity decreases in the order: MoVNbO > VO x /Al 2 O 3 > MoVSbO > MoVTeNbO > K-doped VO x /Al 2 O 3. FT-IR studies of propylene adsorbed and desorbed at different temperatures allowed us to propose three different intermediates: (i) a π-allylic compound, intermediate in the selective oxidation of propylene to acrylic acid; (ii) an enolic-type compound, intermediate in the hydration/oxidation of the olefin to form acetone and acetic acid; (iii) a π-bonded propylene species interacting with Lewis acid sites, precursor in the deep oxidation of propylene. Accordingly, the key factors in the achievement of an active and selective catalyst for the oxidation of propane to acrylic acid as MoVTeNbO mixed oxides is tentatively proposed. The role of acid sites in selective and non-selective pathways are also discussed.

Activity and Selectivity of a Nanostructured CuO/ZrO2 Catalyst in the Steam Reforming of Methanol

Abstract: Steam reforming of methanol for production of hydrogen can be carried out over copper based catalyst. In the work presented here, the catalytic properties of a CuO/ZrO2 catalyst (8.5wt%) synthesised by a templating technique were investigated with respect to activity, long term stability, CO formation, and response to oxygen addition to the feed. The results were obtained using a fixed bed reactor and compared to a commercial methanol synthesis catalyst CuO/ZnO/Al2O3. It is shown that, depending on the time on stream, the temporary addition of oxygen to the feed has a beneficial effect on the activity of the CuO/ZrO2 catalyst. After activation, the CuO/ZrO2 catalyst is found to be more active (per copper mass) than the CuO/ZnO/Al2O3 system, more stable during time on stream (measured up to 250h), and to produce less CO. Structural characterisation by means of X-ray powder diffraction (XRD) and X-ray absorption spectroscopy (XAS) reveals that the catalyst (as prepared) consists of crystalline, tetragonal zirconia with small domain sizes (about 60A) and small/disordered crystallites of CuO.

Ag/alumina catalysts for the selective catalytic reduction of NOx using various reductants

Abstract: A series of Ag-based catalysts supported on unpromoted or Ce-promoted γ-alumina were prepared and studied for the selective catalytic reduction (SCR) of NOx with various reductants. The activity for NO reduction increased as the oxygen-content in the reaction mixture increased from 2% to 10%. The influence of Ag loading, the catalytic support used and the type of the reductant on NO reduction was examined. Moderate silver loadings (3%) exhibit the most efficient deNOx activity, while increasing the metal loading or using a Ce-promoted alumina support inhibits the catalytic activity. Among C3H6, CH4 and CO used as reducing agents, C3H6 has the higher reducing activity. C2H4, C2H6, C3H8, C4H10, 1-C4H8 and 1,3-C4H6 were also tested as reducing agents, suggesting that use of higher and less saturated hydrocarbons results in an enhanced deNOx performance. Higher concentrations of the optimum reductant (1-C4H8) significantly improved the deNOx performance, achieving over 80% NOx reduction and an interestingly broad active temperature window (300–550 °C). NOx is reduced by reacting with intermediates generated from partial oxidation of hydrocarbons used as reductants. Increased availability of these species either by more C atoms in higher hydrocarbons, their easier formation from less saturated hydrocarbons or higher reductant concentration explains the improvement of NOx reduction. The performance of Ag catalysts was linked with the formation of different crystal phases, which are stabilized through a strong interaction with the alumina support. Existence of Ag in oxidation state +1 seems to be the active phase that favors most the NO reduction.

Combined partial oxidation and dry reforming of methane to synthesis gas over noble metals supported on Mg–Al mixed oxide

Abstract: Combined partial oxidation and dry reforming of methane (PO–DRM) to synthesis gas at 850 °C over noble metals, supported on Mg–Al mixed oxide, has been studied. Ruthenium, rhodium, and platinum catalysts were prepared from layered double hydroxide (LDH) precursors, synthesized by a reconstruction reaction of Mg–Al mixed oxide. Due to a “memory effect” of a calcined hydrotalcite, a layered structure of catalyst precursors was recreated upon exposure of the mixed oxide to an aqueous solution of noble metals, which were pre-chelated with ethylenediaminetetraacetate (EDTA) to anionic species. Among the three metals tested, ruthenium revealed the most attractive catalytic performance toward PO–DRM reaction. It was shown that amount of metal could be lowered from 2.0 to 0.1% of the weight of support without any decrease in catalytic activity or in selectivity to syngas product.