A highly hydrophilic A-type zeolite membrane was prepared by a hydrothermal synthesis on the outer surface of a porous α-alumina tube. Increasing and decreasing the permeation temperature between 308 and 473 K over 40 cycles in a period of 4 months did not damage the membrane. Permeation tests with a variety of permeates showed that the membrane possessed two types of pores:  zeolitic pores of 0.4−0.43 nm diameter and nonzeolitic pores. Molecules larger than C2H6 were not able to permeate through the zeolitic pores. The separation factors of the membrane were dependent on molecular size, affinity to the pore walls, and hydrophobicity of the permeating molecules. The combination of permeants also affected the permeation rates. H2O molecules could be concentrated in the zeolitic and nonzeolitic pores, thus reducing the permeation of the hydrophobic permeants. The H2O/H2 separation factor was larger than 160 at permeation temperatures of 303−473 K.

Skeletal isomerization of 4,6-dimethyldibenzothiophene (4,6-DMDBT) was performed at 270 °C for 1 h at a hydrogen pressure of 2.5 MPa using a Ni-supported Y-type zeolite catalyst. Alkyldibenzothiophenes (alkyl-DBTs), which were produced by methylmigration and transalkylation, were further desulfurized at 255−300 °C for 2−120 min at a hydrogen pressure of 2.5 MPa using a CoMo/Al2O3 catalyst. The produced alkyl-DBTs, which carried 1−3 methyl groups, could be classified into three groups on the basis of activation energy for desulfurization. Group I included 2,8-DMDBT and C1-DBT, which carried no methyl groups at either the 4- or 6-position. Group III included unreacted 4,6-DMDBT, and group II contained other alkyl-DBTs with 1−3 methyl groups. No alkyl-DBTs with 4 methyl groups were found in the products of 4,6-DMDBT. The steric hindrance of the methyl groups on 4,6-DMDBT was relieved by methylmigration and transalkylation, and, as a result, the desulfurization activation energy, 37.2 kcal/mol, for 4,6-DMDBT was decreased to 24−33 kcal/mol for alkyl-DBTs in group II and to 23 kcal/mol for alkyl-DBTs in group I. Desulfurization reactivity of the alkyl-DBTs was also examined on the basis of molecular orbital calculation using the WinMOPAC program. The cross sectional area of the Sσn orbital on the sulfur atom, which was in contact with the catalyst surface, was 0.12 nm2 for 4,6-DMDBT, 0.70 nm2 for 4-MDBT, and 1.27 nm2 for DBT. Thus the desulfurization reactivity increases with increasing overlapping area of the Sσn orbital with the catalyst active site. A wider cross sectional area was achieved by migration of methyl groups using the zeolite catalyst.