Tianxi Cai

Studies of a new alkene oligomerization catalyst derived from nickel sulfate

Abstract NiSO4/γ-Al2O3 shows very high catalytic activity in alkene oligomerization with good selectivity for dimers. Its acidity plays a very important role in the catalytic behavior. However, it is the acid site with an acid strength of H0≤−3.0 that is related to the oligomerization of alkenes. Comparatively strong acidity is produced through the interaction of sulfate anions and γ-Al2O3 during calcination. Ni(II) is partially reduced to Ni(I) by reacting with ethene and propene at ambient temperature or evacuation at high temperatures. Dimerization of ethene can be considered as coordination catalysis at active sites of Ni(I), while oligomerization of propene proceeds via dual catalysis due to both coordination catalysis and acid catalysis. But-1-ene is catalytically oligomerized via mainly acid catalysis. Thus, it can be concluded that as the number of carbon atoms of the alkenes increases, the mechanism of oligomerization of the alkene over the catalyst shifts from coordination catalysis to acid catalysis.

Selective hydrogenation of crotonaldehyde over raney cobalt catalysts modified with heteropolyacid salts

RCo-based catalysts were modified with Keggin type heteropolyacid salts, including alkali, alkaline earth and transition metal salts. The selective hydrogenation of crotonaldehyde was investigated over these catalysts. The selectivities to crotyl alcohol can be improved on all modified catalysts. Among them, the catalyst modified with copper salts of 12-molybdophosphates shows the best performance in improving the selectivity.

A dynamic study of isomerization on MoOx catalyst

The dynamics of n-heptane isomerization on the reduced MoO3 catalyst have been studied in a fixed bed flow reactor. In the reaction temperature ranging from 523 to 673 K, the apparent energy for n-heptane isomerization obtained from the Arrhenius plot was 49.3 kJ/mol. At 573 K, the reaction orders of 0.33 in n-heptane and 0.35 in H2 have been obtained.