Shape-selective isopropylation of biphenyl over a highly dealuminated mordenite: effect of propylene pressure

A highly dealuminated H-mordenite (H-M) catalyzed the selective isopropylation of biphenyl to 4,4-diisopropylbiphenyl (4,4-DIPB). The high selectivity is ascribed to the shape-selective catalysis in mordenite pores. The selectivity of 4,4-DIPB decreased during the isopropylation of biphenyl due to isomerization of 4,4-DIPB under low propylene pressure. The increase of propylene pressure suppressed the isomerization in the isopropylation. 4,4-DIPB itself was isomerized over highly dealuminated H-M under low propylene pressure.     

The vinylation of bromobiphenyls using homogeneous nickel catalysts

The vinylation of 4-bromo-4-hydroxybiphenyl and ethyl acrylate was studied using the catalyst NiCl₂-H₂O/PPh₃ in the presence of inorganic base. Ethyl 4-(4-hydroxyphenyl)cinnamate was formed as vinylation product with a selectivity as high as 98%. The effect of solvent, ligand and base for some halides was examined to show the applicability of the catalyst system.     

Development of salmon milt DNA/salmon collagen composite for wound dressing

This study aims to develop a novel wound dressing comprising salmon milt DNA (sDNA) and salmon collagen (SC). The sDNA/SC composites were prepared by incubating a mixture of an acidic SC solution, an sDNA solution, and a collagen fibrillogenesis inducing buffer (pH 6.8) containing a crosslinking agent (water-soluble carbodiimide) for gelation, and a subsequent ventilation-drying process to give sDNA/SC films. The conjugation between sDNA and SC were confirmed by sDNA-elution assay and fluorescence microscopy. The sDNA/SC films with various doses of sDNA (sDNA/SC weight ratios of 1:5, 1:10, and 1:20) were used for in vitro cell cultures to evaluate their growth potentials of normal human dermal fibroblasts (NHDF) and normal human epidermal keratinocytes (NHEK). It was found that NHDF proliferation was increased by sDNA conjugation, whereas NHEK proliferation was dose-dependently inhibited. In light of the in vitro results, the appropriate dose of sDNA for in vivo study was determined to be the ratio of 1:10. For the implantation in full-thickness skin defects in rat dorsal region, the sDNA/SC films were reinforced by incorporating them on a porous SC sponge, because the sDNA/SC films exhibited early contraction and inadequate morphologic stability when implanted in vivo. The regenerated tissue in the sDNA/SC sponge group showed similar morphology to native dermis, while the SC sponge group without sDNA showed epithelial overgrowth, indicating that additional sDNA could reduce epidermal overgrowth. Furthermore, blood capillary formation was significantly enhanced in the sDNA/SC sponge group when compared to the SC sponge group. In conclusion, the results suggest that the sDNA/SC composite could be a potential wound dressing for clinical applications.     

Fe(III) containing MCM-48 type mesoporous molecular sieves with framework zeolite secondary building units

Fe(III) containing mesoporous materials (FeMMSH) with zeolite building units were first time synthesized. XRD and N2 adsorption/desorption analysis confirm the mesoporous characters similar to MCM-48. FT-IR analysis of FeMMSH showed an additional band at about 530-550 cm(-1), characteristic of double five-membered ring of zeolite (ZSM-5) secondary building unit. The Fe(III) in FeMMSH materials is present in tetrahedral, and distorted tetrahedral framework are evident from EPR and DRUV-VIS spectra.     

Shape-selective alkylation of isopropylnaphthalene on MCM-22 zeolite

An MCM-22 zeolite with an Si/Al ratio 13 was found to exhibit higher selectivity to β,β-diisopropylnaphthalene in the alkylation of isopropylnaphthalene with isopropylalcohol, as compared with other zeolites such as mordenite, Y and beta having similar Si/Al ratios. This high selectivity is ascribed to the specific pore shape of MCM-22 zeolite. The gradual increase in the selectivity with reaction time is due to its pore modification by coke deposit.     

Effects of SiO2/Al2O3 ratio of H-mordenite on encapsulated products inside the pores in shape-selective isopropylation of biphenyl

The effects of SiO2/Al2O3 ratio of H-mordenite on the selectivity of encapsulated products in the pores and of bulk products were investigated in the isopropylation of biphenyl. The selectivity of 4,40 -diisopropylbiphenyl (4,40 -DIPB) of bulk products was varied with SiO2/Al2O3 ratio. Highly dealuminated H-mordenite gave a selectivity higher than 80%, whereas the selectivity was low for H-mordenite with SiO2/Al2O3 ratio of 10-20. On the other hand, the selectivity of 4,40 -DIPB in encapsulated DIPB isomers was higher than 85% for all H-mordenites regardless of SiO2/Al2O3 ratio. These results show that all H-mordenites catalyze the isopropylation of biphenyl with high shape-selectivity inside the pore. The low selectivity of 4,40 -DIPB in bulk products for H-mordenites with low SiO2/Al2O3 ratio was not due to a lack of shape-selectivity of the H-mordenites, but to non-regioselective isopropylation at the external acid sites. Non-regioselective catalysis over H-mordenite with low SiO2/Al2O3 ratio could be induced by choking pores by coke deposition. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development of a 24-anode linear-array fine-mesh PMT with 85% photoelectron detection efficiency and 100 ps TTS at B≤1 T

By shortening the distance between the photocathode and the first dynode to 1 mm and using a finer mesh size of 2500 lines/in. with 4 μm^φ, a 24 anode linear-array of fine-mesh photomultiplier tube has produced a clear single-photon peak in its pulse-height distribution under a strong magnetic field of B≤1 T, and provided σ_TTS=100 ps of transit time spread (TTS) and 85% of photoelectron detection efficiency.     

Investigation of micro-phase separation of the additive,cyclotriphosphazene, in lubricant films of hard disk media

The micro-phase separation of the additive, cyclotriphosphazene (X-1P), in perfluoropolyether (PFPE) lubricant films on hard disk media was studied. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) indicated that the small spots appearing on the disk surface consisted predominantly of X-1P. Observation using an atomic force microscope (AFM) revealed the micro-phase separation process to be the sudden, continuous appearance of new spots some time after coating the film. Some spots grew over previous ones, while some spots dissolved. Finally, they stopped growing and the number of spots became saturated. The solubility of X-1P in the lubricant film increased in the order of ZDIAC, ZDOL2000, ZDOL4000 and Z03, and that in bulk lubricant increased in the order of Z03, ZDOL4000, ZDOL2000 and ZDIAC. The order of solubility of X-1P in the film did not correspond to that in the bulk.     

Transalkylation reaction – An alternative route to produce industrially important intermediates such as cymene

Selective formation of cymene by transalkylation reaction of toluene with cumene and 1,4-diisopropylbenzene is described. The effect of various reaction parameters on the activity and selectivity is studied over H-Beta and results are compared with H-Y and H-ZSM-12. The performance and deactivation of the zeolites are attributed to their structural properties.     

Friedel–Crafts benzylation of aromatics with benzyl alcohols catalyzed by heteropoly acids supported on mesoporous silica

Heteropoly acids (HPA), such as tungstophosphoric acid (H₃PW₁₂O₄₀ · xH₂O) (HPW), molybdophosphoric acid (H₃PMo₁₂O₄₀ · xH₂O) (HPMo) and tungstosilicic acid (H₄SiW₁₂O₄₀ · xH₂O) (HSiW) were supported on mesoporous silica such as MCM‐41, FSM‐16 and SBA‐15 by the impregnation method to enhance the catalytic activity of these solid acids by their dispersion on the support with high surface area. These supported solid catalysts were used in the benzylation of benzene and substituted aromatics with benzyl alcohol (BnOH). The immobilization enhanced the catalytic performances and HPW supported on MCM‐41 exhibited the best activity for benzylation among the heteropoly acids, although dibenzyl ether (DBE) formation by the dehydration of BnOH also occurred. The mesoporous architecture of the silica enhances the activity of benzylation because of the high dispersion of HPW on the support with high surface area; however, no steric restriction by the pores of mesoporous silica was observed. The catalysts used in the present study retained their catalytic activity for five reaction cycles. The rate of benzylation of substituted benzenes and benzylating agents was influenced by the electronic nature of the substituent. Electron‐donating groups enhanced the rate of reaction; however, electron‐withdrawing groups retard the benzylation. These results show that the reactivity of benzene and benzyl alcohols was retarded by electron‐withdrawing groups. The formation of polybenzylated products was influenced by the reactivity of diphenylmethane products. The benzylation accompanies the DBE formation by the dehydration of BnOH, particularly in the initial stages, because the benzylation of aromatics with BnOH is not as rapid as the dehydration of BnOH. However, direct benzylation of benzene occurs with DBE and DBE participates in the benzylation of benzene via BnOH after its hydrolysis. This is further supported by the effect of water on the benzylation of benzene by DBE, although there is a possibility of direct benzylation of DBE with benzene. Copyright © 2006 Society of Chemical Industry