Autothermal catalyst

Kolb, G, Baier, T, Schurer, J, Tiemann, D, Ziogas, A, Ehwald, H, Alphonse, P. A micro-structured 5 kW complete fuel processor for iso-octane as hydrogen supply system for mobile auxiliary power units. Part I—Development of the autothermal catalyst and reactor. Chem. Eng. J. 2008 137(l-3) 653-663. 

Steam Reforming. When relatively light feedstocks, eg, naphthas having ca 180°C end boiling point and limited aromatic content, are available, high nickel content catalysts can be used to simultaneously conduct a variety of near-autothermic reactions. This results in the essentiaHy complete conversions of the feedstocks to methane ... 

MPa (300—400 psig), using a Ni-based catalyst. Temperatures up to 1000°C and pressures up to 3.79 MPa (550 psia) are used in an autothermal-type reformer, or secondary reformer, when the hydrogen is used for ammonia, or in some cases methanol, production. 

Flow reversal performance is controlled weakly by the period r. Flow reversal is an autothermal operation and as such exhibits parametric sensitivity. Greater stability can be ensured by the conventional expedient of providing cooling in the catalyst bed. It can also be done through bypassing part of the reactor effluent gas around the recuperator section. 

Schematic diagram of the reactor for ATR of hydrocarbons. 1 = Autothermal reformer, 2 = burner section, 3 = combustion chamber, 4 = catalyst, and 5 = heater.

The catalysts for low-temperature and high-temperature reforming of ethanol under OSR/autothermal conditions are listed in Tables 8 and 9, respectively. In the absence of added 02, each mole of ethanol converted should produce 6 moles of H2 and 2 moles of C02, which corresponds to an exit H2 composition of 75%. Depending upon the 02/EtOH ratio used in the OSRE reaction, the composition of H2 will vary between 50% for 02/EtOH ratio of 1.5 and H20/EtOH ratio of 0, and 75% for 02/EtOH ratio of 0 and H20/EtOH ratio of 3. 

Table 9 Selected catalysts for the high-temperature oxidative steam reforming/autothermal reforming of ethanol...

This review analyzed the chemistry involved, thermodynamics, catalysts used, reaction pathways and mechanisms of various reforming techniques reported for the conversion of ethanol into H2-rich gas. The known reforming processes are broadly classified into three categories, namely steam reforming of ethanol (SRE), partial oxidation of ethanol (POE) and oxidative steam reforming (OSR)/autothermal reforming of ethanol. All these reactions are thermodynamically favorable even at lower temperatures, above 200 °C. 

CO = 25 vol.%, C02 = 12 vol.%) not containing any hydrocarbons and a low tar (200 mg Nm 3) content at 800 °C and S/C (steam over carbon ratio) = 1.5. Problems associated with pyrolysis oil gasification are similar to those of biomass gasification. Gasification of the tar fraction and conversion of methane formed are important challenges. Both require highly active and stable steam/autothermal reforming catalysts. 

The transformation of straw and agrofood residues with high sulfur and ash content requires the development of materials for sulfur abatement at high temperature, tar cracking and as monolith for syngas production by exothermic or autothermal processes thanks to catalysts supported on materials with a high thermal conductivity. 

There are three major gas reformate requirements imposed by the various fuel cells that need addressing. These are sulfur tolerance, carbon monoxide tolerance, and carbon deposition. The activity of catalysts for steam reforming and autothermal reforming can also be affected by sulfur poisoning and coke formation. These requirements are applicable to most fuels used in fuel cell power units of present interest. There are other fuel constituents that can prove detrimental to various fuel cells. However, these appear in specific fuels and are considered beyond the scope of this general review. Examples of these are halides, hydrogen chloride, and ammonia. Finally, fuel cell power unit size is a characteristic that impacts fuel processor selection. 

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