ON THE SPATIAL DEMAND OF COKE DEPOSITS IN ZEOLITES

In samples of HY with different degree of dealumination about 9 % per weight of coke has been produced with butadiene at 530 K. The H/C-ratio has been determined by NMR to be less than 0.5. The sorption capacities and the nuclear relaxation times of n-butane and benzene in the coked and the uncoked samples have been compared. The sorption capacity for butane remains almost unchanged, that for benzene decreases to about 65 to 80 % a depending on the degree of dealumination. In the relaxation times for both sorbates, an influence of the paramagnetic moment of the coke deposits is observed. The relaxation times indicate a change in the packing of the molecules for n-butane and a restriction of the motion in the case of benzene. The number of C-atoms per cavity, the H/C-ratio and the influence on the motion of the two molecules suggest that the coke consists of entities of more than 20 C-atoms like e.g. coronen, leaving at least one half of the cavities free.