Product distribution reforming

Fig. 15.2 Cost of hydrogen fuel for five different modes of production, distribution and retail. All options other than electrolysis are NC-based for on-site reforming and electrolysis the cost for hydrogen manufacture is included in the retail-site costs.

The severe working conditions often encountered in an H2 production process, such as high temperature and high space velocity, combined with the necessity for a long catalyst lifetime, impose the development of an appropriate synthetic procedure to stabilize the catalyst. The reforming activity and product distribution over supported metal catalysts depend on the choice of metal and its content, the presence of promoters, the type of support and method of catalyst preparation. 

The selectivity of the reforming process depends on various factors such as the nature of the catalytically active metal, support, solution pH, feed and reaction conditions, as shown in Figure 6.4. By manipulating the process conditions, it is possible to control the product distribution. 

Consequently, in the absence of NEtz, the main catalytic species should be H2RhCl(PPh3)2(solv), whereas, in the presence of NEt3, RhH(PPh3)3 should be formed. We are aware that such a conclusion is somewhat speculative however, it seems the most likely if we look at all the experimental data reported on the subject. Table 1 reports experimental results concerning both activity and product distribution, determined in different conditions. Since the Rh(I) mono hydride complex is a catalytic species, it is reformed in every step of the reaction and its concentration remains constant. Therefore, rate data are calculated by the ratio of slopes of plots of organic substrate concentration, divided by the Rh(I) concentration, versus reaction time. The slope of these curves is obtained at about 70 % conversion of the substrate. 

Thermodynamics. - Thermodynamic calculations on the reformate product distribution and carbon formation characteristics for n-Ci6, a model diesel fuel compound, were examined over the temperature range 500 to 900°C and over an O/C ratio of 1 to 1.5 using HSC Chemistry.The equilibrium amount of each species formed was normalized on the basis of one mole of n-C16 fed to the reactor. 

Distributed hydrogen production via small-scale reforming is less costly than centralized production. Distributed hydrogen production would be attractive especially in the early stages of a hydrogen economy. Hydrogen could be provided where it was needed, allowing supply to match demand. 

Abstract In this paper, we discuss the results of a preliminary systematic process simulation study the effect of operating parameters on the product distribution and conversion efficiency of hydrocarbon fuels in a reforming reactor. The ASPEN One HYSYS-2004 simulation software has been utilized for the simulations and calculations of the fuel-processing reactions. It is desired to produce hydrogen rich reformed gas with as low as possible carbon monoxide (CO) formation, which requires different combinations of reformer, steam to carbon and oxygen to carbon ratios. Fuel properties only slightly affect the general trends. 

Figure 5. Product distribution from partial oxidation reforming of premium gasoline using the ANL catalyst.

Figure 7. Product Distribution from Reforming Synthetic Sulfur-Free Fuel Using the ANL Catalyst.

Although the above-discussed studies have defined sulfur-poisoning tolerances for conventional nickel catalysts used in steam reforming of natural gas and naptha, they have not considered in sufficient detail the kinetics of poisoning at above-threshold concentrations nor the effects of catalyst and/or gas compositions on rate of deactivation and tolerance level. Nor is there any previous report on the effects of sulfur on product distribution (i.e., relative rates of production of H 2, CO, CH4) in steam reforming of hydrocarbons. 

Also at Palm Springs, two papers by the Methanol Fuel Cell Alliance (Ballard/BASF/BPAmoco/Daimler Chrysler/Methanex/Statoil) and the Methanol Institute, respectively, portray the existing substantial methanol production, distribution and trading based on natural gas reform/synthesis gas/methanol, as in the Methanex Canada plant. Methanol from biomass is a future possibility. A methanol pump can be fitted within the footprint of many existing diesel/gasoline filling stations, and an Identic refuelling nozzle has been developed in Sweden, to avoid confusion between methanol and alternative fuels. 

Graf et al.108 performed a comparative study of steam reforming of methane, ethane and ethylene on Pt, Rh, and Pd supported on YSZ. They observed that the reactivity and product distribution depends on the type of noble metal loaded. Over Rh/YSZ catalyst, the reactivity decreased in the order C2H6 > CdE > CH4. On the other hand, over Pt/YSZ, methane reacted much faster than the C2 hydrocarbons and the order of reactivity is CH4 > C2H4 > C2H6 (Fig. 2.8). The higher reactivity of Rh... 

When considering the beneficial effect of the high hydrogenolysis activity of iridium in suppressing formation of carbonaceous residues, it must be remembered that such activity may simultaneously have an adverse effect on the product distribution in reforming. A catalyst containing iridium alone on alumina is limited in this manner. For platinum-iridium catalysts, the interaction between the platinum and iridium moderates the hydrogenolysis activity... 

In the top-fired reformer, the burners are located only on the roof between the rows of reformer tubes. The heating is direct from the combustion products to the tube walls. In this configuration firing occurs only at one level, heating the natural gas as it enters the reformer. The burner to tube ratio is low and the combustion air product distribution is simplified. The unit is compact, using less steel, and has large tube capacities (600—1000) per radiant section. However, the operating environment above the box is uncomfortable and the control of heat input into the reformer is limited. 

While the emphasis in this discussion is on the chemistry of aromatics production from the point of view of product distribution and mechanisms, it is necessary to describe the catalyst used briefly. Until about 20 years ago a number of different catalysts were used for catalytic reforming, including vanadium (126), molybdenum (47), cobalt-molybdenum (159), and chromia (3,41,85,100) catalysts. Since the time when platinum reforming catalysts were introduced to the industry (2, 24, 56,... 

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