Rb. Gore et Wj. Thomson, PULSED GAS-PHASE ALKYLATION OF ISOBUTANE 2-BUTENE OVER SULFATED ZIRCONIA/, Applied catalysis. A, General, 168(1), 1998, pp. 23-32
A pulsed-feed alkylation study of gas-phase 2-butene with isobutane wa
s conducted over sulfated zirconia (SZ) to determine the effect of tem
perature and feed composition on the dominant reactions and deactivati
on mechanisms. For all conditions, high initial conversion of 2-butene
to C-5 was observed, which is attributed to alkylation followed by ra
pid cracking on the strongest acid sites. These sites deactivated quic
kly, and then the steady-state catalyst behavior was observed to be di
fferent at different temperatures. During alkylation at 50 degrees C,
the catalyst deactivated after 40 pulses, which is attributed to the b
uild-up of trimethylpentane (TMP) products that do not readily desorb
from the catalyst surface at this temperature, and was verified when p
ulses of pure 2,3,4-TMP over SZ produced similar cracking results. At
100 degrees C, the adsorbed alkylation and/or oligomerization products
were very selectively cracked to form 2-butene, resulting in a net de
hydrogenation of isobutane to 2-butene. At temperatures in the 150-250
degrees C range, the product selection was dominated by high cracking
rates, but the catalytic activity remained stable with nearly complet
e conversion of 2-butene at the highest temperatures. It was also foun
d that the deactivated catalyst at 50 degrees C could be regenerated b
y simply heating to 150 degrees C, which apparently removed the adsorb
ed hydrocarbons by either volatilization or cracking. (C) 1998 Elsevie
r Science B.V.