Butane isomerization conversion rate

The two rate constants of Equation 19, klt and k21, are, respectively, proportional to the net dehydrogenation rate of step 1 and that of step 2. Thus, if experimental conditions are chosen so that the isomerization reaction rate between 1-butene and 2-butenes is slow compared with the two dehydrogenation rates of n-butane, then the concentration distributions of 1-butene and 2-butenes in the reaction products provide information concerning the relative value of kit and k2t. To fulfill the above experimental conditions, we performed several experimental runs with a very low partial pressure of n-butane at differential conversion levels. Analyses of these experimental data indicated that the value of klt may be approximately 10 times larger than that of k2ty provided that the reaction scheme shown by Equation 23 is correct. From Table III the ratio of kit/k2t can be calculated to be 15. The separation of these reactions will be studied further. 

The combination of Pt or Pd with CS25H0.5PW12O40 (Cs2.5) is also very effective for the isomerization of n-butane to isobutane (381). The reaction rate and selectivity for conversion to isobutane are summarized in Table XXXIV (381, 382). The activity in the presence of H2 changed little with time. Pt- and Pd-Cs2.5 show very high selectivities (94-96%) relative to those of Pt/SO -/ Zr02 (47%) and Pt/HZSM-5 (34%), whereas the activities of Pt- and Pd-Cs2.5 for the formation of isobutane are comparable to those of Pt/HZSM-5 and Pt/S04 /Zr02. Pt-Cs2.5 catalyzes the reaction even at 473 K and 0.05 atm of H2. 

The rate of isomerization is comparable to the rate of conversion of n-butane to isobutane under identical conditions no molecules having more than one atom of C13 were found. Consequently, the reaction must be an intramolecular rearrangement. It is evident that, in the presence of an acid catalyst, the bonds in a saturated hydrocarbon arc not as inert as we might suppose. 

Example 11-7 The rate of isomerization of o-butane with a silica-alumina catalyst is measured at 5 atm and 50°C in a laboratory reactor with high turbulence in the gas phase surrounding the catalyst pellets. Turbulence ensures that external-diffusion resistances are negligible, and so Q = Q. Kinetic studies indicate that the rate is first order and reversible. At 50°C the equilibrium conversion is 85%. The effective diffusivity is 0.08 cm /sec at reaction conditions, and the density of the catalyst pellets is 1.0 g/cm, regardless of size. The measured, global rates when pure n-butane surrounds the pellets are as follows ... 

Anderson considers hydrogenolysis reactions in detail, along with isomerization reactions, on supported metals. The model is illustrated using butane in Figure 1. The parameters used are X, the fractional conversion of reactant the isomerization selectivity, the selectivity, S, to a j-carbon-number product (C ) the ratio, T., of the desorption rate of adsorbed C. (C. ) to the rate... 

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