Reforming butane steam

Subsequently, 1000-h durability for butane steam reforming could be achieved at a S/C 3.2 over an improved catalyst formulation, as shown in Figure 4.9. 

Figure4.9 1000-h durability ofa catalyst coating for butane steam reforming at an S/C 3.2 weight hourly space velocity 300 L (hgcat) (source IMM).

Rings Hydrocarbon steam reforming. Butane oxidation. 

Figure 8.7 confirms that this is correct A single nickel catalyst used for steam reforming of n-butane deactivates steadily and gains weight due to the accumulation of carbon, but a Ni-Au catalyst maintains its reforming activity at a constant level [F. Besenbacher, I. ChorkendorfF, B.S. Clausen, B. Hammer, A.M. Molenbroek, J.K. Norskov and I. Stensgaard, Science 279 (1998) 1913]. 

Figure 8.7. Steam reforming of n-butane as a function of time for a conventional Ni catalyst and a novel Ni-Au alloy catalyst, showing the superior stability ofthe latter. [Adapted from...

Hydrocarbon feedstocks for steam reformers include natural gas, refinery gas, propane, LPG and butane. Naphtha feedstocks with boiling points up to about 430°F can also be used. The ideal fuels for steam reformers are light hydrocarbons such as natural gas and refinery gas, although distillate fuels are also used. Residual fuels are not used since they contain metals that can damage reformer tubes. 

In addition to natural gas, steam reformers can be used on light hydrocarbons such as butane and propane and on naphtha with a special catalyst. Steam reforming reactions are highly endothermic and need a significant heat source. Often the residual fuel exiting the fuel cell is burned to supply this requirement. Fuels are typically reformed at temperatures of 760 to 980°C (1,400 to 1,800°F). 

Fig. 5. Conversion of n-butane as a function of time-on-stream during steam reforming in a flow reactor. The gray curve shows the conversion of the pure nickel catalyst, and the black curve represents the gold/nickel catalyst. From Reference (79).

Hydrocarbons react with steam in an endothermic reaction to form carbon monoxide and hydrogen. The most important feedstock for the catalytic steam reforming process is natural gas. Other feedstocks are associated gas, propane, butane, liquefied petroleum gas, and some naphtha fractions (q.v.). The choice is usually made on the availability and the price of the raw material. 

Figure 2 Influence of MgO content in the support of catalysts of senes B on the rate of coking and the length of the induction period in the steam reforming of n-butane (H2OC=0 5 1)...

Thiagarajan, N., U. Ranke and F. Ennenbach, "Propane/butane dehydrogenation by steam active reforming," Achema 2000, Frankfurt, Germany, May 2000. 

Ethane, propane, and butane, usually present in smaller concentrations in addition to methane in most natural gases, react in the steam reforming in similar way, with the overall reaction corresponding to Equation (35). With higher hydrocarbons, as contained in naphtha, the reaction is more complex. Higher paraffins in naphtha feed will be first completely cracked down in a methane-forming reaction, which proceeds between 400 and 600 °C and could be described, for example, as follows (Eq. 56) ... 

The industrially most important and currently cheapest hydrogen production process is the catalytic steam reforming process in which steam is reacted with natural gas (methane) or light crude oil fractions (propane, butane, naphtha with b.p. s < 200°C). The hydrogen produced comes partly from the steam utilized and partly from the hydrocarbons, in the case of methane 1/3 from water and 2/3 from the methane ... 

Steam reforming reaction of ethane, propane, and n-butane are represented by Equations 2.21-2.23, while the thermodynamic data for these reactions are summarized in Tables 2.1-2.9, respectively ... 

Table 2.9. Thermodynamic Data for the Steam Reforming of ra-Butane C4H10(g) + 4H20(g) 9H2(g) + 4CO(g)...

Figure 2.12. Arrhenius plots for the steam reforming of methane, ethane, n-butane, /t-hexane, and benzene over Pd/Ce02 catalyst. Water partial pressure is lOOtorr. Adapted from Wang and Gorte.144...

Figure 2.33. TGA data showing the effect of alloying of nickel with gold on the amount of carbon deposited on the catalyst surface during steam reforming of n-butane.10...

Igarashi, A., Ohtaka, T., and Motoki, S. Low-temperature steam reforming of n-butane over Rh and Ru catalysts supported on Zr02. Catalysis Letters, 1992, 13 (3), 189. 

Mori et al. concluded that n-butane reformed over a Ni/Al203 catalyst at 450 °C by a single-site mechanism with the hydrocarbon and the steam competing for the nickel surface when the amount of H2O adsorbed was not... 

Another cyclical process is the Phillips STAR pro-cess.t ] It uses a fixed-bed fired-tube reactor operating at a positive superatmospheric pressure. In many respeets, it is similar in design to a steam reforming furnaee with the heat of reaction provided by firing outside the tubes, thus operating at near-isothermal conditions. Steam is used as a diluent to lower the partial pressure of the reactants and, thus, to achieve reasonable conversion levels of about 30-40% for propane and 45-55% for butanes. It also helps slow down the deposition of carbon (coke) on the eatalyst, thereby extending cycle time from minutes to hours. 

In all cases, it is the composition of the gas in terms of hydrocarbon type that is more important in the context of the application. For example, in petrochemical appUcations, the presence of propylene and butylene above 10% v/v can have an adverse effect on hydrodesulfurization before steam reforming. On the other hand, petrochemical processes, such as in the production of iso-octane from iso-butane and butylene, can require the exclusion of the saturated hydrocarbons. 

Natural gas constituents heavier than methane are also excellent petrochemical feedstocks [1]. Ethane is the most desirable starting material for producing ethylene whenever a minimum amount of byproducts is desired. Propane and butane can also be dehydrogenated to olefins, propylene, and butene, and butene can be further dehydrogenated to butadiene. The naphtha fraction, which is also known as natural gasoline, has a low octane number, but is an excellent feedstock for cracking to olefins and/or steam reforming. 

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