N-Butanol, dehydration

The relative rates of olefin production and etherification have been shown to vary with reaction conditions (99-101), including temperature and contact time, and with the geometry of the catalyst pore system (99). Bryant (99) has demonstrated kinetic effects in ethanol and n-butanol dehydration that greatly favor olefin formation using a series... 

Figure PI2.8-1 contains plots of the data obtained in n-butanol dehydration trials conducted with each of these batches of catalyst at 600°F and 1 atm. Figure PI2.8-2 contains cross plots of the smoothed data in Figure P12.8-1 that indicate the dependence of the observed rate on the diameter of the catalyst beads at conversions of 7, 14, and 21%. The experimental conditions are such that the catalyst beads are at the same temperature throughout and that there are no significant temperature gradients within the fixed bed.

Since carbocations with different carbon skeleton differ strongly in their stability, they are prone to isomerization due to which the most stable of all possible carbocation is formed. The charge on the carbon atom facilitates this isomerization. The isomerization of carbocations results in the appearance of products, whose structure differs from that which is seemingly pre-determined by the structure of the reactant. For example, for n-butanol dehydration, one can expect the formation of butene-1 but butene-2 is formed. The reason is the isomerization of an intermediate species, carbocation... 

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