Steam supported partial oxidation

Lenz et al. [73] described the development of a 3 kW monolithic steam-supported partial oxidation reactor for jet fuel, which was developed to supply a solid oxide fuel cell (SOFC). The prototype reactor was composed of a ceramic honeycomb monolith (400 cpsi) operated between 950 C at the reactor inlet and 700°C at the reactor outlet [74]. The radial temperature gradient amoimted to 50 K which was attributed to inhomogeneous mixing at the reactor inlet. The feed composition corresponded to S/C ratio of 1.75 and O/C ratio of 1.0 at 50 000 h GHSV. Under these conditions, about 12 vol.% of each carbon monoxide and carbon dioxide were detected in the reformate, while methane was below the detection limit. Later, Lenz et al. [74] described a combination of three monolithic reactors coated with platinum/rhodium catalyst switched in series for jet fuel autothermal reforming. An optimum S/C ratio of 1.5 and an optimum O/C ratio of 0.83 were determined. Under these conditions 78.5% efficiency at 50 000 h GHSV was achieved. The conversion did not exceed 92.5%. In the product of these... 

Running a fuel processor at an O/C ratio of 1.0 or higher in the presence of steam feed should be termed steam supported partial oxidation. 

Figure 4.4 Temperature profile as determined by Aicher et al. in a steam supported partial oxidation reactor S/C= 1.4 ...

Pino et al. reported significant activity and favourable selectivity patterns for their platinum/ceria catalyst. However, the experiments were performed at a very high S/C ratio of 3.6 and a high O/C ratio of 1.3, which shifts the conditions into the field of steam supported partial oxidation [233]. 

Villegas et cd. performed autothermal reforming of isooctane over a 2wt.% platinum catalyst on a ceria/zirconia mixed support (Ceo.67Zro.33O2) [71]. The tests were performed at a gas hourly space velocity of 150000h. Full conversion of isooctane was achieved at 710 °C under conditions of steam supported partial oxidation (O/C = 1 S/C = 2). The optimum hydrogen content in the reformate was achieved at a lower O/C ratio of 0.75 and S/C ratio of 1.5. The carbon dioxide content in the reformate was always higher than the carbon monoxide content, which contradicted the thermodynamic calculations performed by the same workers [71], see Section 3.3. This supports the assumption that platinum preferably catalyses catalytic combustion. 

Liu and Krumpelt reported 100 h of stable operation for their perovskite catalyst LaCro.95Ruo.05O3 at 800 °C reaction temperature, low S/C 1.5 and O/C 1.0 for steam supported partial oxidation of dodecane [253]. 

Table 5.7 Equilibrium reformate composition as achieved by steam supported partial oxidation (0/C= 1.2) and autothermal reforming (O/C = 0.88) of methane gas compositions are provided after the reformer and after water addition plus water-gas shift equilibrium at 250°C.

Aicher et al. [72] developed an autothermal reformer for diesel fuel dedicated to supplying a molten carbonate fuel cell system from Ansaldo Fuel Cells S.p.A., Italy. The diesel fuel (which contained less than 10 ppm sulfur for the pilot plant application) was injected into the steam and air flows, which were pre-heated by a diesel burner to 3 50 °C. The reactor itself was operated at 4 bar, a S/C ratio of 1.5 and high O/C ratio of 0.98, which makes the reactor into a steam supported partial oxidation device. Consequently, the dry hydrogen content of the reformate was rather low with less than 35 vol.%. The operating temperature of the honeycomb had to be kept well above 800 °C to prevent coke formation and the presence of light hydrocarbons such as ethylene and propylene in the reformate. The reactor was operated for 300 h, which led to a slight deterioration in the catalyst performance. 

A breadboard gasoline fuel processor was assembled by Moon et d. [67]. Fixed bed reactors served for reforming by steam supported partial oxidation (see Section 7.1.1), followed by high and low temperature water-gas shift Commercial iron oxide/ chromium oxide catalyst was applied for high temperature shift at a 4200 h gas hourly space velocity and 450 °C reaction temperature, while the copper/zinc oxide low temperature water-gas shift catalyst was operated at 250 °C and 5600 h gas hourly space velocity. 

Rare earth oxides are useful for partial oxidation of natural gas to ethane and ethylene. Samarium oxide doped with alkali metal halides is the most effective catalyst for producing predominantly ethylene. In syngas chemistry, addition of rare earths has proven to be useful to catalyst activity and selectivity. Formerly thorium oxide was used in the Fisher-Tropsch process. Recently ruthenium supported on rare earth oxides was found selective for lower olefin production. Also praseodymium-iron/alumina catalysts produce hydrocarbons in the middle distillate range. Further unusual catalytic properties have been found for lanthanide intermetallics like CeCo2, CeNi2, ThNis- Rare earth compounds (Ce, La) are effective promoters in alcohol synthesis, steam reforming of hydrocarbons, alcohol carbonylation and selective oxidation of olefins. 

Partial oxidation runs at 700-1000 °C, typically on a platinum or rhodium catalyst supported on alumina or other oxides and c) Autothermal Reforming (ATR) which combines steam reforming and partial oxidation reactions to produce a roughly thermo-neutral reaction ... 

Zhang J, Wang Y, Ma R, Wu D (2003) Characterization of alumina-supported Ni and Ni-Pd catalysts for partial oxidation and steam reforming of hydrocarbons. Appl Catal A-Gen 243(2) 251-259... 

There is growing interest in the partial oxidation of the C5 fraction of the hydrocarbon stream from naphtha steam crackers since there is no real market for them at the present time. Furthermore, the partial oxidation of lower alkanes and alkenes continues to pose challenging problems for catalysis researchers. In the case of C5 hydrocarbon oxidation to form phthalic anhydride, the challenge is even greater since the catalyst needs not only to insert oxygen selectively, but also promote the formation of C-C bonds in an oxidative medium. In recent years, several studies have been reported in the literature, focusing on Cg oxidation using catalysts such as supported vanadia, VPO catalysts, and molybdates [1-11]. ... 

The major advantages of this route over the steam reforming are the H /CO ratio of ca. 2 suitable for downstream processes and the exothermicity of the reaction which eliminates the need for a fuel gas [2]. Many catalysts for the partial oxidation of methane to synthesis gas, consisting of supported metals such as Ni, Co and Fe and noble metals Pd, Ir, Rh, Ru, Pt, etc have been described in the literature [2-9],... 

Porous carbon materials are used for many applications in various industrial or domestic domains adsorption (air and water purification, filters manufacture, solvents recovery), electrochemistry (electrodes for batteries, supercapacitors, fuel cells), catalyst support (industrial chemistry, organic synthesis, pollutants elimination),. .. Porous carbons used at the present time are generally activated carbons, i.e. materials prepared by pyrolysis of natural sources, like fhiit pits, wood or charcoal. Pyrolysis is followed by a partial oxidation, under steam or CO2 for instance, leading to the development of the inner porosity. 

One of the most attractive alternatives to steam reforming for syngas production appears to be the catalytic partial oxidation (CPO) catalysed by supported noble metal [9]. Perovskites incorporating the noble metal in the structure represent a valid alternative to reduce the catalyst unit mass cost. 

Nickel is the most widely used electro-catalyst in SOEC anodes and therefore, steam reforming of CH4 on Ni supported catalysts have been widely studied [59,58]. The major reactions that CH4 can undergo during reforming or partial oxidation can be summarized as [58]... 

Solid Waste - The steam-reforming process contains up to 8-9 catalytic steps catalysts are replaced after 2-6 years of service. Partial oxidation and coal gasification use 3-4 catalysts. The catalysts contain " hexavalent chromium, nickel, zinc, iron, and mineral supports therefore these materials could not be disposed into landfills, Companies that specialize in producing catalysts or metal-processing companies customarily recycle catalysts. 

An exception in terms of catalysts is the catalytic partial oxidation or OSR of methanol due to the low reaction temperature required. Copper [25, 32-36] and palladium-zinc ahoy [36-38] have been proven to give high selectivities and space-time yields. For the latter system, the palladium forms an alloy with the zinc oxide support under reducing conditions above 300 °C and is stable under the reaction conditions of methanol steam reforming [39]. However, the stability of the ahoy under CPO has not been proven so far by X-ray diflraction after exposure to reaction conditions. 

Major issues in steam reforming and catalytic partial oxidation or catalytic oxidative steam reforming are oxygen storage and the acidity of the catalyst support, which could be relevant in terms of soot or alkene formation. 

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