Reformer experimental results

Experimental results concerning the development of a small-scale 1 kW autothermal reformer of propane were reported by Rampe et al. [76]. In the proposed reactor, two reactions occur on a metal honeycomb structure coated with platinum. Air and water are mixed before they are fed to the reactor in counterflow to the product gas outside the reactor wall, where the water is vaporized and the steam and air are heated up. Then, they are mixed with propane at the bottom of the reactor. It was verified that the preheating operation mode led to about a 4% higher efficiency, since the higher inlet air temperature causes a higher temperature level in the reaction zone, resulting in improved kinetics of the reforming reaction. 

Lenz and Aicher reported the experimental results obtained with an autothermal reformer fed with desulfurized kerosene employing a metallic monolith coated with alumina washcoat supporting precious metal catalysts (Pt and Rh) [78]. The experiments were performed at steam-to-carbon ratios S/C = 1.5-2.5 and... 

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. 

All these derivations assume that radical R is converted to oxidation products and that it does not reform the hydrocarbon. The relations are summarized in Table II, which also includes the experimental results for methane and ethane. 

Figure 4.49 Experimental results of the reformer plant (source IMM).

The development of MEMS technology during the 80s induced a strong research effort focused on fluid and heat flow studies in microchannels. Since then, various silicon-based systems such as microbiochips, MOEMS, etc... have contributed to reinforce this trend and a lot of experimental results were published. In parallel to these studies, very compact heat exchangers for air conditioning purposes were developed and have lead to research programs on minichannels. In the same manner, the possible use of such minichannels in other systems such as reformers, fuel cells,... has also produced considerable interest in this field. 

Although the deactivation of Industrial catalysts is often due to two or more different causes, the modeling of simultaneous deactivation phenomena has not been widely studied (refs. 1, 2). The occurrence of two different deactivation processes not only adds another level of complexity to the determination of the intrinsic kinetic behavior but also complicates the interpretation of the experimental results. In our previous studies regarding the thloresistance of naphtha reforming catalysts (refs. 3, 4) we have shown that the activity decay caused by the presence of sulfur compounds in the feed is often accompanied by coking. In this situation, the thioresistance cannot be obtained in a simple way from the deactivation curves. The characteristics of the sulfur poisoning have to be deduced from the overall deactivation rate. 

Surfactant molecules are in dynamic equilibrium among three possible states (monomers adsorbed at the interface of the aqueous solution with a non-polar phase, monomers molecularly dispersed in the solution, and micellar aggregates formed when the CMC is reached). From various theoretical considerations, as well as experimental results, it can be said that micelles are dynamic structures whose stability is in the range of milliseconds to seconds.2223 Thus, in an aqueous surfactant solution, micelles break and reform at a fairly rapid rate, in the range of milliseconds.24 26... 

In complete contrast with these developments, Kobosev approached the problem of supported metal catalysts from the viewpoint of atomic dispersion and from the viewpoint of the theory of active ensembles which bears his name. Over a period of years, Kobosev and co-workers investigated the behavior of catalysts containing very small amounts of supported metal. Many of their observations have been reviewed recently (2) and they inspired Poltorak to investigate very carefully dilute platinum catalysts on silica gel (3, 4). The studies from Poltorak s laboratory, originating from the desire to check the theoretical and experimental results of Kobosev, have led independently to many of the same conclusions reached by ourselves starting from the commercially available platinum catalysts for reforming (5). 

In principle, it should be possible to use experimental results on pure compounds coupled with mechanistic considerations to predict the product distribution in a catalytic reformate. In practice the situation is considerably more complex since the final product mix depends not only on the relative rates at which different compounds are converted to aromatics but also on isomerization that may precede aromatization, on... 

During the first year, most gasification trials were performed with the gasifier operated in conventional, air-blown mode. Experimental results included characterization of the gas obtained from gasification of switchgrass, preliminary evaluation of the performance of the steam reformer, and preliminary evaluation of the catalytic water-gas shift reactors. 

Furthermore impurities in the helium coolant, mainly the air constituents, can cause corrosion effects on the outside reformer tube walls which eventually change its properties. Measurements of impurity contents in Dragon and AVR revealed a large scattering of the data. Experimental results obtained within the Dragon project indicate a strong corrosion of aluminum and titanium, i.e., the formation of Cr-, Mn-, Si-, and Ti-oxide layers, and an increased corrosion rate in moist helium compared with a dry atmosphere [26]. 

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