Commercial reforming

These catalysts presented difficult experimental problems for the GSCA examination. Even so, the results do provide additional data in the search to define the structure of this important commercial reforming catalyst. 

The data collected to date for Pt-Re or Rh-Re are similar to those obtained with Pt-Sn. Thus, these preliminary Pt-Re data are consistent with a model for Pt-Re that resembles that shown in figure 1 for Pt-Sn in Which Re would replace tin. However, instrument sensitivity to Re(0), proof of complete reduction, and other problems do not permit us to eliminate the presence of any Re(0) in these catalysts, and certainly not for catalysts under commercial reforming conditions. Even if we could confirm the absence of Re(0) in these catalysts, the ESCA data alone could not be used to define the location of Re... 

N2. Sulfur containing odorants (mercaptans, disulfides, or commercial odorants) are added for leak detection. Because neither fuel cells nor commercial reformer catalysts are sulfur tolerant, the sulfur must be removed. This is usually accomplished with a zinc oxide sulfur polisher and the possible use of a hydrodesulfurizer, if required. The zinc oxide polisher is able to remove the mercaptans and disulfides. However, some commercial odorants, such as Pennwalf s Pennodorant 1013 or 1063, contain THT (tetrahydrothiophene), more commonly known as thiophane, and require the addition of a hydrodesulfurizer before the zinc oxide catalyst bed. 

The validity of these assumptions will be demonstrated by KINPTR s ability to predict the wide range of commercial reformer performance and feedstock with no additional parameters. 

The accuracy of KINPTR over a wide spectrum of conditions and feedstocks will be demonstrated in this section. KINPTR predictions will be compared to a variety of R16H start-of-cycle and aging data from pilot plant and commercial reformers. Pilot plant data were obtained in both adiabatic and isothermal reactors. These predictions required complete reforming... 

KINPTR simulations of commercial reforming (Table XVIII) will be used in this section to demonstrate process sensitivity. In the base case, a full-range Mid-Continent naphtha (55 wt. % paraffins) is reformed to a constant octane of 90 R + 0 over the entire cycle. With a reactor pressure of 1695 kPa and a 7.2 H2 recycle ratio, the start-of-cycle reactor inlet temperature to achieve target octane is predicted to be 759 K. The deactivation simulation shows that it would take about 1 year to reach the end-of-cycle temperature of about 798 K. The start-of-cycle C5+ yield for this case is 86 vol %. The model predicts that the yield would decline by 4.8 vol % over the cycle. 

KINPTR is used several thousand times a year for both research and commercial reformer estimates. The model has four principal uses commercial monitoring, reformer diagnostics, optimization, and research and development guidance. 

The model provides a performance reference to evaluate commercial reformer operation by taking into account the wide variation in operating conditions, feedstocks, and product octane typically experienced commercially. Such variations in reformate yield have already been discussed in Fig. 29, where the model effectively predicts the yield variations. As a monitoring tool, the model is routinely used to assess reformer yield and activity losses due to catalyst deactivation relative to fresh catalyst model estimates. When commercial yield and/or activity losses relative to the model are uneconomical, a decision to regenerate the catalyst is made. A typical monitoring trend (Fig. 36) illustrates the use of the model as a performance reference. 

Fig. 36. Commercial reforming monitoring using KINPTR Shifts in temperature and yields relative to start of cycle KINPTR.

Properties and Aging Rates for Commercial Reforming Catalysts... 

This review is concerned with a discussion of the reactions of hydrocarbons over bifunctional catalysts, primarily from the viewpoint of mechanism and kinetics. Some discussion will also be given of the structure and properties of typical bifunctional reforming catalysts, since this is somewhat helpful in understanding how the catalyst functions in promoting the various reactions. In addition, at appropriate places in the article, the practical application of the principles of bifunctional catalysis in commercial reforming processes will be considered. 

Commercial reforming catalysts have both metal and acid sites. Both could contribute to cyclization. If there are four or more carbon atoms in the side chain of a mono-alkylaromatic or ortho-substituted dialkylaromatic hydrocarbon, cyclization can yield either five- or six-membered rings. This multiplicity of reaction pathways helps to clarify the roles of the metal and acid components in dehydrocyclization and other reactions. 

For the most part, the data for alkane and cycloalkane conversion with Pt-Sn catalysts have been at atmospheric pressure. For commercial reforming operations, a much higher pressure is utilized. 

ETfect of Hydrocarbons in N2 on the Platinum Functions. In a commercial reforming unit some hydrocarbons are always present in the system. In order to examine their effects, the individual hydrocarbons, — CH4, C2H6, and n-C6H,4—in N2 were used to treat catalysts under simulating conditions of dehydration which was 482°C in N2 or air, 3600 h for 4 hrs. The results are listed in Table IV. 

The study was carried out in relatively small isothermal reactors without recycle, constructed fortesting and comparison of different catalysts and feedstocks. Detailed information about catalyst performance under different conditions can be efficiently obtained under very controlled conditions in such equipment (/). However, exact predictions of the performance of a commercial reformer unit consisting of 3-4 adiabatic reactors will need detailed kinetic and reactor modeling, which is not included in this paper. 

Steam reforming (SR), partial oxidation (POX), and ATR are three major commercial reforming processes. In this work, ATR syngas was chosen as the feed gas, and the feed inlet molar flow rate, nt0, was 1 mol/s. With the composition given in Table 9.1, this flow rate was chosen because a sufficient H2 molar flow rate would hence be provided to generate a power of 50 kW via the fuel cell for a five-passenger car.4 Heated air was used as the sweep gas. 

The relationship between nickel size, surface area, and catalyst activity has been accepted for many years in regard to commercial reforming catalysts, and... 

Several commercial reforming processes are available for license worldwide. A list of reforming processes with a summary of key process features is presented in Table 3. Several commercial processes are available, dominated by UOP and Axens Technologies for semiregenerative and continuous reforming. Other licensors included Houdry Division, Chevron, Engelhard, ExxonMobil, and Amoco, but none of them is currently... 

Parera, J. Figoli, N. Reactions in the commercial reformer. In Catalytic Naphtha Reforming ... 

The alloy catalysts used in these early studies were low surface area materials, commonly metal powders or films. The surface areas, for example, were two orders of magnitude lower than that of platinum in a commercial reforming catalyst. Hence these alloys were not of interest as practical catalysts. The systems emphasized in these studies were combinations of metallic elements that formed continuous series of solid solutions, such as nickel-copper and palladium-gold. The use of such systems presumably made it possible to vary the electronic structure of a metal crystal in a known and convenient manner, and thereby to determine its influence on catalytic activity. Bimetallic combinations of elements exhibiting limited miscibility in the bulk were not of interest. Aspects of bimetallic catalysts other than questions related to the influence of bulk electronic structure received little attention in these studies. 

Isomerization reactions of alkanes and cycloalkanes occur very readily on bifunctional catalysts containing both metal and acidic sites (3,4), the latter being associated with the carrier employed for the metal. This mode of reaction is very important for the catalysts used in commercial reforming, which will be discussed in Chapter 5. In such bifunctional catalysts, the metal and acidic sites catalyze different steps in the reaction sequence. 

Investigations of the isomerization of alkanes in recent years have provided evidence that the reaction can occur on certain metals, notably platinum, in the absence of a separate acidic component in the catalyst (20-22). While it has been shown that a purely metal-catalyzed isomerization process can occur, the findings do not challenge the commonly accepted mode of action of bifunctional reforming catalysts in which separate metal and acidic sites participate in the reaction. The available data at conditions commonly employed with commercial reforming catalysts indicate that a purely metal-catalyzed process does not contribute appreciably to the overall isomerization reaction on a bifunctional catalyst. 

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