No abstract

Hierarchical Y zeolite-containing mesoporous silica _ aluminas were prepared by the one pot sol-gel method using malic acid. Properties for the catalytic cracking of vacuum gas oil (VGO) were estimated using a Curie point pyrolyzer, to establish a novel and very simple estimation method for the catalytic cracking of VGO. Prepared catalysts showed higher conversions and selectivities for gasoline than zeolite single, indicating that yields of gasoline for zeolite-containing catalysts increased compared with that of zeolite single. Higher content of aluminum species in the catalysts resulted in decreased olefin/paraffin ratios and increased iso-/n-ratios (ratio of branched products to straight-chained ones), indicating that hydrogen transfer and isomerization were promoted by the addition of acid sites into the matrix. Catalysts with mesopores tended to form larger amounts of multibranched products, which are very important in modern petroleum refining. When the yields of gasoline, singlebranched products and multi-branched products were plotted against the conversion of VGO, the linear relationships were observed and the effect of kinds of zeolite was rather small, indicating that the activity and the selectivity were largely affected by the presence of matrices. Comparison of the yields of gasoline, single-branched products and multi-branched products at the same conversions showed that Y zeolite-containing catalysts always showed the highest yields and ZSM-5-containing catalysts showed the lowest yields although the differences were small. Pore size of the zeolite probably also affected the yields in the treatment of large molecules such as VGO. The present findings suggest that the appropriate combination of zeolite and matrix is the most important factor to obtain high catalytic activity and high yields of gasoline and branched products.

The structure of hexanuclear 6-methyl-2-pyridinethiolato copper(I) [Cu6(6-mpyt)(6)] crystals has been studied by the X-ray diffraction analysis. These crystals show highly efficient luminescence whose color changes drastically from red to green-blue with lowering temperature from room temperature (RT) to liquid nitrogen temperature (LNT). This is a new example of luminescence thermochromism for hexanuclear copper(I) cluster compounds. Two relaxed luminescence bands appear predominantly: one (CC-band), red luminescence appearing in the lower-energy region around 1.8 eV at higher temperature, is assigned to the transition between intramolecular orbitals (MO) of a Cu cluster center (CC), and the other (CT-band), green-blue luminescence appearing at the higher energy side of 2.6 eV than the CC-band at lower temperature, is assigned to a charge transfer (CT) transition from the CC-MO to a ligand MO. Additionally, the CT band can be deconvoluted to two subbands CT(L) and CT(H). The intensities of the CC- and the CT-bands change complementarily with temperature via a thermal activation process, giving the thermochromism. All of these band shapes can be fitted by a Gaussian function, and their widths are fairly large obeying the hyperbolic cotangent law. These features reflect our system to be a strong electron-lattice coupling one. The relaxation process of the photoexcited states is discussed in terms of a configuration coordinate model.

The thermal polymerization of macrocyclic S‐aryl thioesters, trimer (m‐CTE‐3), tetramer (m‐CTE‐4), and pentamer (m‐CTE‐5) was investigated. The polymerization of m‐CTE‐3 without a catalyst proceeded efficiently at 280 °C for 10 min in the solid phase to provide poly(S‐aryl thioester) with a weight‐average molecular weight of 1,100,000. Moreover, the solid‐phase polymerization of m‐CTE‐3 proceeded with increasing crystallinity and molecular weight.

Thermal polymerizations of macrocyclic S-aryl thioester trimer with a 5-tbutylisophtaloyl skeleton (m-CTE-3) were investigated. The polymerization of m-CTE-3 without catalysts occurred at over 260 • C in the solid state and heating at 280 • C for 10 min produced a polymer with a M w of 370 000. Quaternary onium salts or crown ether complexes enhanced the solid-phase thermal polymerization of m-CTE-3. In the case of the polymerization using 18-crown-6 ether (18-C-6)/potassium halide complexes, the polymerization occurred at around 200 • C. It was proved that 18-C-6/KBr was the most effective catalyst to produce high molecular weight polymers with M w as much as 850 000. It was also suggested that the solid-phase polymerization proceeded in a chain-growth reaction mode.