N- Butane isomerization

Activity in n-butane isomerization reaction of various alkaline salts of H3PW12O40 and H4SiWi2O40 was shown to be strongly dependent on the strength and number of accessible protons whereas the stability with time on stream was correlated to the presence of mesoporosity. For the liquid iC4/C4 continuous alkylation reaction, the strength and the number of acid sites appeared less important than the existence of mesoporosity indicating that the diffusion of the reactants and of the products plays an important role in this reaction. 

The activity and decay behaviour of the different porous heteropolycompounds were compared in two reactions requiring strong acid sites the n-butane isomerization and the isobutane/2-butene alkylation. Although these two reactions are important in the petroleum refining industry, n-butane isomerization is often used as a "test reaction" since it is known that this reaction requires very strong acid sites and only a limited number of oxides are active in this reaction, under mild conditions (T = 473 K). 

Catalytic activity in n-butane isomerization at 473 K after 4 min of time on stream. 

It is striking to observe that the most initially active samples were the most stable with time on stream in the n-butane isomerization. 

K. Tomishige, A. Okabe, and K. Fujumoto, Effect of hydrogen on n-butane isomerization over Pt/SOa -Zr02 and Pt/Si02 + S04 -Zr02, Appl. Catal. A 194, 383-393 (2000). 

Asuquo, R.A., Eder-Mirth, G., and Lercher, J.A. (1995) n-butane isomerization over acidic mordenite. J. Catal,... 

Fig. 6 FT-IR spectra of catalytic surface during n-butane isomerization at 323 K taken every 16 minutes. This shows the difference in IR spectra from before activation to during reaction. The black lines show the spectra first at the start of the reaction, and the next is at the maximum reaction rate. ...

Isomerization Today. Present isomerization capacity in the Western Hemisphere and Western Europe is estimated to be about 50,000 BPD basis information provided in Refs. 26 and 34. It is not known how many World War II plants may still be operating or are capable of being returned to service, but the number is believed to be very small. Near the end of World War II isomerization capacity peaked out at 45,000- 50,000 BPD of which slightly over 40,000 BPD consisted of n-butane isomerization. All of these installations used one of five processes employing aluminum chloride complexes (25). 

C. Y. Hsu, C. R. Heimbuch, C. T. Armes, and B. C. Gates, A highly active solid superacid catalyst for n - butane isomerization a sulfated oxide containing iron, manganese and zirconium, J. Chem. Soc. Chem. Commun. 1645-1646 (1992). 

Over SbFs/metal oxides, it was proposed that n-butane isomerization proceeded via carbenium ion intermediates formed by hydride ion transfer from n-butane to the Lewis acid sites [55]. The details of sul-fated zirconia as a hydrocarbon conversion catalyst have been summarized by Davis et al. [56],... 

Solid superacids of the sulfated zirconia type were found active for n-butane isomerization at low reaction temperatures (50). These catalysts, however, were rapidly deactivated with time on stream. The isomerization selectivity and the stability of sulfated zirconia catalysts can be incerased by the introduction of Pt and by carrying out the reaction in the presence of H2. Higher catalytic activities were obtained when Pt was impregnated after the impregnation of zirconia gel with 0.5 M H2SO4 (51). Sulfated zirconia promoted with Fe or Mn showed an even higher activity than unpromoted SZ for the low temperature isomerization of n-butane (52). 

Estimate the composition of the liquid and vapor phases when n-butane isomerizes at 311 K (100°F). Assume that the reaction occurs in the vapor phase. 

In this context, additional isobutane availabilities could be derived from n-butane isomerization, an operation which offers two variants, one of them induding the recyding of unconverted n-butane after separation. As a rule, isomerization takes place in the gas phase, around 150 to 200"C, under hydrogen pressure (13 to 15.10 Pa absolute), in the presence of a fixed catalyst bed of the reforming type, based on platinum (0.35 per cent weight) deposited on alumina promoted by traces of organic chlorides. Ooce-through... 

Structure of ZrOa-SO/ samples prepared by various methods and their catalytic properties in n-butane isomerization... 

Iso-butane is a highly demanded chemical in the refinery industry for the production of alkylates (by alkylation with butenes), and methyl tert-butyl ether (MTBE) (from isobutene and methanol), both important additives for reformulated gasolines. n-Butane isomerization is performed over platinum supported on chlorinated alumina. The chlorine compound which is continuously supplied to the feed in order to maintain the activity [1] is harmful to the environment. 

The economic data concerning the production of isobutane by vapor phase n-butane isomerization, with and without recycling of unconverted n-butane, and concerning the production of isobutene by dehydrogenation, by the three main current industrial processes, are given in Table 6.5 a. The corresponding feed and product compositions are given in Table 6.5 b. 

Coke deposited on sulfated zirconia catalyst during n-butane isomerization was studied using TPHe, using the methanator/FID configuration The treatment in helium up to 650°C removed all the coke from the catalyst. This... 

TABLE 7.29. Kinetic Parameters for n-Butane Isomerization Over Metal Catalysts... 

Metal halide supported on sulfonic acid resin AlClj - sulfonic acid resin Catalysis of n-butane isomerization 2 X 10 ... 

Promoted sultated zirconia I e-, Mn-proinoted S(V -ZKh Catalysis of n-butane isomerization 7 X lO" ... 

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