PROTOLYTIC CRACKING OF LOW-MOLECULAR-WEIGHT ALKANES IN THE PRESENCE OF IRON-PROMOTED AND MANGANESE-PROMOTED SULFATED ZIRCONIA - EVIDENCE OFA COMPENSATION EFFECT

Low conversions of propane, n-butane, and 2,2-dimethylpropane were mea sured with each reactant in the presence of iron-and manganese-promote d sulfated zirconia in a once-through plug-flow reactor at 101 kPa, 47 3-723 K, and reactant partial pressures of 25, 250, and 1000 Pa. Rates of the reactions (overall conversion of propane, of n-butane, and of 2,2-dimethylpropane; formation of methane from each of the three react ants; formation of ethene from propane and from n-butane; and formatio n of ethane from n-butane) were determined by extrapolating the declin ing conversions to zero time on stream. The apparent activation energi es and apparent pre-exponential factors characterizing these reactions , which are inferred to proceed via carbonium-ion transition states, f all near a straight line on a compensation effect plot. The plot is su ggested to represent the family of reactions proceeding via protolytic cracking and dehydrogenation and carbonium-ion transition states. (C) 1997 Published by Elsevier Science Ltd.