Partial Oxidation and Autothermal Reforming

Ke Liu,1 Gregg D. Deluga,1 Anders Bitsch-Larsen,2 Lanny D. Schmidt,2 and Lingzhi Zhang1 

2Department of Chemical Engineering Materials Science, University of Minnesota 

The alternating blasts of steam and air maintained the bed temperature at -1000 °C. Thus when steam was added, thermodynamic equilibrium favored the production of CO and H2, not C02. Although natural gas has been widely used in most of Europe and America with the discovery of reliable supplies and construction 

Hydrogen and Syngas Production and Purification Technologies, Edited by Ke Liu, Chunshan Song and Velu Subramani 

In recent years, H2 and CO have become important starting materials for the chemical industry. The mixture has come to be known as synthesis gas, or syngas. Currently, production of syngas is dominated by steam reforming 3 

As an alternative to steam reforming, methane and other hydrocarbons may be converted to hydrogen for fnel cells via partial oxidation  

8 Hydrogen generation by pyrolysis or thermal cracking of hydrocarbons 

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Hydrogen production from carbonaceous feedstocks requires multiple catalytic reaction steps For the production of high-purity hydrogen, the reforming of fuels is followed by two water-gas shift reaction steps, a final carbon monoxide purification and carbon dioxide removal. Steam reforming, partial oxidation and autothermal reforming of methane are well-developed processes for the production of hydro-... 

Chapter 3 Catalytic Partial Oxidation and Autothermal Reforming... 

Two reaction mechanisms do exist in literature for partial oxidation. One of them proposes that the reaction starts with catalytic combustion followed by reactions of lower rate, namely, steam reforming, CO2 reforming, and WGS. This mechanism is supported by the fact that water is found as primary product of partial oxidation and autothermal reforming in many cases. The other mechanism proposes direct partial oxidation at very short residence times. The reaction is significantly faster than steam reforming and usually performed in the difiiusion-limited regime. 

Compared with other hydrocarbon fuels such as ethanol, methane, and gasohne, SR of methanol exhibits a relatively high theoretical conversion efficiency, low conversion temperature, and low by-product formation [117]. Partial oxidation and autothermal reforming (ATR) of methanol are also possible, but play a minor role. 

A certain portion of the hydrogen produced by the fuel processor is frequently fed back to it, because it is not completely consumed by the fuel cell (see Section 2.3). The curious situation may then arise where the fuel processor efficiency exceeds 100%. In particular, this is the situation for steam reforming, where substantially more heat is required to run the process compared with partial oxidation and autothermal reforming (see Section 3). A fuel processor running on steam reforming may reach up to 120% efficiency according to the Eqs. (2.2) and (2.3). 

Murcia-Mascaros et al. performed partial oxidation and autothermal reforming over self-developed and commercial copper/zinc oxide catalysts [172]. The temperature was limited to 300 °C to prevent degradation of the catalyst. At this temperature about 80% conversion was achieved at a low weight hourly space velocity of 36 L (h gcat) over the commercial catalyst. This was the case both for partial oxidation conditions (O/C ratios of 0.6 and 0.8) and autothermal conditions (0/C ratio 0.6 and S/C ratio 1.1). The lowest selectivity towards carbon monoxide was achieved under autothermal conditions. 

Methane or natural gas steam reforming performed on an industrial scale over nickel catalysts is described above. Nickel catalysts are also used in large scale productions for the partial oxidation and autothermal reforming of natural gas [216]. They contain between 7 and 80 wt.% nickel on various carriers such as a-alumina, magnesia, zirconia and spinels. Calcium aluminate, 10-13 wt.%, frequently serves as a binder and a combination of up to 7 wt.% potassium and up to 16 wt.% silica is added to suppress coke formation, which is a major issue for nickel catalysts under conditions of partial oxidation [216]. Novel formulations contain 10 wt.% nickel and 5 wt.% sulfur on an alumina carrier [217]. The reaction is usually performed at temperatures exceeding 700 °C. Perovskite catalysts based upon nickel and lanthanide allow high nickel dispersion, which reduces coke formation. In addition, the perovskite structure is temperature resistant. 

In the production of synthesis gases from hydrocarbons, the components hydrogen and carbon monoxide usually appear as complementary products, carbon dioxide can be obtained as a by-product as well. Apart from hydrocarbons and steam (steam reforming), some processes require carbon dioxide (CO2 reforming) as well as oxygen or air (partial oxidation and autothermal reforming) as feedstock. Usually, the process selection depends on two factors ... 

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