| Popis: |
The effect of the structure of particular group of polymeric catalysts of the oxidation process on their catalytic activity, in the model reaction of hydroquinone oxidation to p-benzoquinone with hydrogen peroxide, was investigated. Two series of terpolymers of acrylonitril (AN) and vinyl acetate (VA) crosslinked with either divinylbenzene (DVB) or trihydroxymethylpropane triacrylate (TMPA) or trihydroxymethylpropane trimethacrylate (TMPMA) (Table 2) were obtained in suspension polymerization. Dependently on the type of crosslinking monomer the products showed either the gel structure or porous one. In two-stage process the nitrile groups of terpolymer were subjected to aminolysis with hydrazine and amino groups obtained in this way were modified with thiourea in the presence of alkyl iodide (Scheme A). The supports containing aminoguanidyl, carboxyl or hydroxyl groups were obtained (Table 1 and 3) and their structures were characterized using FT-IR method. The proper catalysts were prepared via sorption of Cu(II) ions on these supports. Some parameters of these catalysts and of the catalysts prepared in one-stage aminolysis of terpolymers with guanidine carbonate or aminoguanidine carbonate were compared. They were: hydroquinone conversion degree (L H2Q ), yield of quinone (YQ) as a main product and selectivity of the catalysts calculated on this basis (Table 4 and 5, Fig. 5 and 6). The catalysts crosslinked with DVB and subjected to one-stage modification showed the highest activity and selectivity (close to 100 %). In all cases the catalysts with amino-guanidyl groups were more active than those with hydrazine groups not subjected further modification. The results obtained show that the conditions encouraging the formation of N202 complexes as well as advantageous microenvironment formed by uncomplexed functional groups determine the activity and selectivity of the catalysts investigated. |
