HYDROTHERMALLY ACTIVATED SILICA-ALUMINA. II. VARIATIONS IN CATALYTIC ACTIVITIES FOR 1-BUTEN ISOMERIZATION AND POLIMERIZATION, AND IN THE AMOUNT OF ACID WITH PRETREATMENT TEMPERATURE

Article abstract of DOI:10.1246/bcsj.55.965

The technique of hydrothermal activation was used to prepare well-mixed and fully hydroxylated silica-alumina catalyst, SA-nMHT (n=13, 25, or 50 denotes the alumina content (wt percent)).Their catalytic activities and cis/trans selectivities for the 1-butene isomerization (k₁ and c/t), the catalytic activities for the 1-butene polymerization (k_p), the amount of acid (A), and the number of the surface hydroxyl group (N_OH) were measured as a function of the degassing temperature (T_d) over the 25-700 deg C range; the following results were obtained: (1) k₁ changed prominently with T_d and reached its maximum around 300 deg C. (2) c/t was about 0.9 below 500 deg C, but exceeded 1.2 at 700 deg C. (3) k_p increased till 300 deg C and became constant above that temperature. (4) A was almost independent of T_d above 100 deg C. (5) N_OH decreased from 11-15 (at 100 deg C) to 0.5 group nm^-2 (at 700 deg C).An analysis of these data led to the conclusion that the SA-nMHT sample underwent the surface structural changes three times during the thermal dehydroxylation between 25 and 700 deg C.The sequence of structural change was sketched, and the different dependecies upon T_d of k₁, k_p and A were explained.