Isomerization light paraffins

Mobil s High Temperature Isomerization (MHTI) process, which was introduced in 1981, uses Pt on an acidic ZSM-5 zeoHte catalyst to isomerize the xylenes and hydrodealkylate EB to benzene and ethane (126). This process is particularly suited for unextracted feeds containing Cg aHphatics, because this catalyst is capable of cracking them to light paraffins. Reaction occurs in the vapor phase to produce a PX concentration slightly higher than equiHbrium, ie, 102—104% of equiHbrium. EB conversion is about 40—65%, with xylene losses of about 2%. Reaction conditions ate temperature of 427—460°C, pressure of 1480—1825 kPa, WHSV of 10—12, and a H2/hydtocatbon molar ratio of 1.5—2 1. Compared to the MVPI process, the MHTI process has lower xylene losses and lower formation of heavy aromatics. 

Serra, J.M., Chica, A. and Corma, A. (2003) Development of a low temperature light paraffin isomerization catalysts with improved resistance to water and sulphur by combinatorial methods. Appl. Catal. A Gen., 239, 35. 

Par-Isom [Paraffin isomerization] A process for isomerizing light naphtha in order to improve the octane number. The proprietary catalyst was developed by Cosmo Oil Company and Mitsubishi Heavy Industries, and the process was developed by UOP. The oxide catalyst is claimed to be more efficient than zeolite catalysts currently used for this process. 

Total Isomerization Also called TIP. An integrated process which combines light paraffin isomerization, using a zeolite catalyst, with the IsoSiv process, which separates the unconverted normal paraffins so that they can be returned to the reactor. Developed by Union Carbide Corporation and now licensed by UOP. The first plant was operated in Japan in 1975 by 1992, more than 25 units had been licensed. 

Metal-Zeolite Catalyzed Light Paraffin Isomerization... 

The isomerization process is utilized to convert light paraffins such as butane, pentane, and hexane into higher-octane isoparaffins. Isoparaffins have higher octane numbers than normal paraffins of the same carbon number. For example, n-pentane has a research octane number of about 61, and isopentane has an octane number of approximately 92. 

Tn commercial petroleum refining, isomerization of light paraffins has been A applied for many years. Until recently the scope of the process was limited, however, and its main application was isomerization of butane as feed preparation for alkylation processes. Generally, except for a few specific cases, no commercial justification could be found for isomerization of pentane and hexane fractions since in most cases the quality requirements for motor gasoline could be met by alternative processing routes and by addition of various additives, such as lead tetraalkyls, to improve fuel burning characteristics. 

The following examples illustrate the application of high-throughput screening tools together with heuristic search algorithms in the development of new enhanced catalyst for two fields of industrial interest, olefin epoxidation and the isomerization of light paraffins. 

Search for New Catalytic Materials for isomerization of Light Paraffin 1137... 

The hydroisomerization of light paraffins (C5-C6-C7) to produce their branched isomers is an important industrial process aimed at improving the octane number of the light straight mm stream (LSR). Reformulated gasolines with their impact on olefins and aromatics reduction [26, 27] have increased the number of LSR isomerization units. Table 5.1 gives the octane number of the different C5-C7 linear and branched paraffins. 

Search for New Catalytic Materials for Isomerization of Light Paraffin 1143 Tab. 5.2 Composition of the seven best-ranked catalytic materials of the three generations. 

Catalytic Reforming A catalytic reaction of heavy naphtha(1) used to produce high-octane gasoline. The byproducts are hydrogen and light hydrocarbons the primary reaction is dehydrogenation of naphthenes to produce aromatics. Some reshaping of paraffins to produce aromatics and some isomerization of paraffins to produce isoparaffins also occur. 

Bullen P.J. et al, Light Paraffin Isomerization Using Sulfated Metal Oxide Catalysts (AIChE Spring National Meeting, Houston, 1999). 

Application To selectively isomerize a paraxylene depleted-C8 aromatics mixture to greater than equilibrium paraxylene concentration using ExxonMobil Chemical s XyMax and Advanced MHAI processes. Simultaneously, ethylbenzene (EB) and nonaromatics in the feed are converted to benzene and light paraffins, respectively. Conversion of EB is typically 60-80%. 

In order to confirm the acidity results measured using the indicators shown in Table 17.1, we have investigated as many acid-catalyzed reactions as possible. The reactions are summarized in Table 17.4 [43, 48, 118, 119]. Among them, the skeletal isomerization of light paraffins, in particular butane and pentane, has been the most widely applied. The isomerization of butane at room temperature was a well known test reaction for superacidity at the beginning of this work [43, 48, 118]. The activity for many of the reactions tested correspond to the acidities as determined by use of the Hammett indicators. 

Diffiisional restrictions increase the effectiveness of olefin interception sites placed within catalyst pellets. Very high olefin hydrogenation turnover rates or site densities within pellets prevent olefin readsorption and lead to Flory distributions of lighter and more paraffinic hydrocarbons. Identical results can be obtained by introducing a double-bond isomerization function into FT catalyst pellets because internal olefins, like paraffins, are much less reactive than a-olefins in chain initiation reactions. However, light paraffins and internal olefins are not particularly useful end-products in many applications of FT synthesis. Yet, similar concepts can be used to intercept reactive olefins and convert them into more useful products (e.g., alcohols) and to shift the carbon number distribution into a more useful range. In the next section, olefin readsorption model simulations are used to explore these options in the control of FT synthesis selectivity. 

Thus for light paraffin isomerization, the selectivity depends importantly on the ratio of rate constants involved in steps Yi and Xt i.e., kyjkxt 1 is desired. This implies that relative activities of the two independent catalyst components are involved, and may be controllable in the manner discussed in Section II,E,2. One may reduce fcx, by decreasing X-com-ponent strength to increase said ratio. This reduction of strength should... 

Realizations of such microcompartments are obtained in normal heterogeneous catalysis by using zeolite crystals as support material, e. g., in the formation of are-nes from cycloparaffins by use of Y-zeolite crystals as catalysts [15] or the hydro-isomerization of light paraffins by Pt-doped Y-zeolite [16]. Concentration effects, resembling channeling in enzyme-catalyzed reactions, are caused by the hindrance of the transport of larger molecules through the apertures between the cavities which form the three-dimensional pore texture of zeolite crystals. 

Isomerization of light paraffins Methane oxidative coupling. 

The isomerization of light paraffin using superacid solid catalysts is a clean way to increase the octane number of hydrocarbons. On this basis, sulfated metal oxides have attracted the attention of many research groups owing to their high activity in acid catalyzed reactions [1]. Sulfated zirconia was found to be a promising catalyst in this field and at the industrial level [2],... 

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