Tadashi Asanuma

Methanol to olefins using ZSM-5 zeolite catalyst membrane reactor

A ZSM-5 zeolite catalyst membrane without pinholes was successfully prepared by synthesizing ZSM-5 zeolite layer on the outer surface of a cylindrical alumina ceramic filter. In the preparation of the membrane, to enhance the smoothness of the outer surface of the filter, a filter with pores of 0.1 μm in diameter was employed. Furthermore, the hydrothermal synthesis was repeated using the same samples. The obtained zeolite membrane showed a molecular sieving effect for the permeation of gaseous xylene and diethylbenzene isomers. The ratio of the permeability of the para-isomer to the meta-isomer was about 2.7 for xylene and 6.0 for diethylbenzene, respectively. The membrane was used as a catalytic membrane reactor to recover olefins from methanol. By adjusting the diffusion rate to the chemical reaction rate for producing olefins within the ZSM-5 zeolite layer, olefins were successfully produced at a high selectivity (about 80-90%) from methanol at high conversions of 60-98%.

Preparation of syndiotactic polyolefins by using metallocene catalysts

SummaryPolyolefins having syndiotactic structure were obtained by using 1-methyl-1-ethylidene-(cyclopentadienyl-1′-fluorenyl) zirconium dichloride and methylaluminoxane as a catalyst. 1-Butene and 4-methyl-1-pentene gave crystalline polymers having syndiotactic structure, while 1-pentene, 1-hexene and 1-octene gave noncrystalline polymers having syndiotactic structure.The identification of syndiotactic and isotactic polyolefins was made by 13C-NMR, X-ray diffraction, and differential scanning calorimetry.

Photodimerization of styrene, p-methylstyrene, and α-methylstyrene in the presence of 1,2,4,5,-tetracyanobenzene

U.v. excitation of styrene, p-methylstyrene, and α-methylstyrene in the presence of the electron acceptor tetracyanobenzene produces 1,2,3,4-tetrahydronaphthalene derivatives as the main products in addition to 1,2-cis and 1,2-trans-disubstituted cyclobutanes.

Radiation-induced reactions of syndiotactic polypropylene

SummaryThe radiation-induced reaction of highly syndiotactic polypropylene was examined by following the changes in limiting viscosity, molecular weight distribution, and stereoregularity. The degree of syndiotacticity clearly decreased even when there was no apparent change in molecular weight. Irradiation at an elevated temperature caused a marked decrease in molecular weight and formation of unsaturated residues.

Photosensitized dimerization of styrene derivatives by a cation radical transfer mechanism

Selective photoexcitation of phenanthrene in a mixture of phenanthrene, α-methylstyrene, and m-dicyanobenzene in MeCN and in MeCN–MeOH (1 : 1) gave 1,4-dimethyl-1-phenyl-1,2,3,4-tetrahydronaphthalene and 1,4-dimethyl-1-methoxy-1,4-diphenylbutane, respectively, products which are formed from the α-methylstyrene cation radical which is formed by cation radical transfer from phenanthrene cation radical to α-methylstyrene.

Photocyclodimerization of p-methoxystyrene in the presence of 1,4-dicyanobenzene

Irradiation of p-methoxystyrene in the presence of electron acceptors in polar solvents gives a trans-head-to-head cyclodimer of the olefin via its cation radical.

Photocyclodimerization of p-(NN-dimethylamino)styrene

U.v. excitation of p-(NN-dimethylamino)styrene produces the 1,2-cis-cyclodimer in non-polar solvents, whereas the 1,2-trans-cyclodimer is obtained in polar solvents.