Ship-in-a-bottle synthesis of 2,4,6-triphenylthiapyrylium cations encapsulated in zeolites Y and beta: a novel robust photocatalyst

The 2,4,6-triphenylthiapyrylium ion has been obtained imprisoned inside the supercages of the tridirectional, large pore zeolites Y and beta via ship-in-a-bottle synthesis from chalcone and acetophenone in the presence of hydrogen sulfide. The resulting solids are efficient and robust photocatalysts that are able to degrade phenol and aniline in water with a higher efficiency than the P-25 TiO2 standard. Preliminary tests have shown that these encapsulated dye materials are also efficient photocatalysts for the oxidative degradation of malodorous sulfurcontaining molecules.

Structure Absorption Spectra Correlation in a Series of 2,6-Dimethyl-4-arylpyrylium Salts

A combined experimental and theoretical study of the absorption spectra of a group of closely related pyrylium perchlorates 1-11 are presented. Minor changes in the position of the substituents lead to drastic changes in the absorption spectra in this series of compounds. We have attempted to explain the observed changes using the x,y-band notation developed by Balaban and co-workers. Absorption spectra of all compounds are compared with results from time-dependent density functional theory (TDDFT) and Zerner’s intermediate neglect of differential overlap (ZINDO/S) level calculations. Results of the calculations are in good agreement with experimental observations and an interesting correlation between Balaban’s notations and the MO transitions are obtained for simple derivatives. It is suggested that for more complex systems such as R- and â-naphthyl substituted systems, the empirical method is not appropriate.

Model Compound Studies on the Devulcanization of Natural Rubber Using 2, 3-Dimethyl-2-Butene

The mechanism of devulcanization of sulfur-vulcanized natural rubber with aromatic disulfides and aliphatic amines has been studied using 23-dimethyl-2-butene (C5H1,) as a low-molecular weight model compound. First C6H12 was vulcanized with a mixture of sulfur, zinc stearate and N-cyclohexyl-2-benzothiazylsulfenamide (CBS) as accelerator at 140 °C, resulting in a mixture of addition products (C(,H 1 i-S,-C5H 1 i ). The compounds were isolated and identified by High Performance Liquid Chromatography (HPLC) with respect to their various sulfur ranks. In it second stage, the vulcanized products were devulcanized using the agents mentioned above at 200 °C. The kinetics and chemistry of the breakdown of the sulfur-hridges were monitored. Both devulcanization agents decompose sulfidic vulcanization products with sulfur ranks equal or higher than 3 quite effectively and with comparable speed. Di phenyldisulfide as devulcanization agent gives rise to a high amount of mono- and disulfidic compounds formed during the devulcanization, hexadecylamine, as devulcanization agent, prevents these lower sulfur ranks from being formed.

Propionylation of anisole to 4-methoxypropiophenone over zeolite H-beta

The results of a detailed study of the propionylation of anisole over various medium and large pore zeolites such as H-ZSM-5, H-beta, H-Na-beta. H-mordenite. H-Y and H-RE- Y are presented and discussed. In addition, homogenous catalysts and amorphous Si02-Al2O3 are also included for comparison, The catalyst and process parameters are optimised to enhance the conversion of propionyl chloride(PC) and selectivity to 4-methoxypropiophenone(4-MOPP).

A comparative study on aniline alkylation activity using methanol and dimethyl carbonate as the alkylating agents over Zn–Co–Fe ternary spinel systems

The catalyst compositions of the Zn1−xCOxFe2O4 (x= 0, 0.2, 0.5, 0.8 and 1.0) spiel series possessing ‘x’ values, x less than or equal to 0.5, are unique for selective N-monomethylation of aniline using methanol as the alkylating agent. Since dimethyl carbonate (DMC) is another potential non-toxic alkylating agent, alkylation of aniline was investigated over various Zn–Co ferrites using DMC as the alkylating agent. The merits and demerits of the two alkylating agents are compared. Catalytic activity followed a similar trend with respect to the composition of the ferrospinel systems. DMC is active at comparatively low temperature, where methanol shows only mild activity. However, on the selectivity basis, DMC as an alkylating agent could not compete with methanol, since the former gave appreciable amounts of N,N-dimethylaniline (NNDMA) even at low temperature where methanol gave nearly 99% N-methylaniline (NMA) selectivity. As in the case of methanol, DMC also did not give any C-alkylated products.

Synthesis of dimethyl acetal of ketones: design of solid acid catalysts for one-pot acetalization reaction

The synthesis of dimethyl acetals of carbonyl compounds such as cyclohexanone, acetophenone, and benzophenone has successfully been carried out by the reaction between ketones and methanol using different solid acid catalysts. The strong influence of the textural properties of the catalysts such as acid amount and adsorption properties (surface area and pore volume) determine the catalytic activity. The molecular size of the reactants and products determine the acetalization ability of a particular ketone. The hydrophobicity of the various rare earth exchanged Mg–Y zeolites, K-10 montmorillonite clay, and cerium exchanged montmorillonite (which shows maximum activity) is more determinant than the number of active sites present on the catalyst. The optimum number of acidic sites as well as dehydrating ability of Ce3+-montmorillonite and K-10 montmorillonite clays and various rare earth exchanged Mg–Y zeolites seem to work well in shifting the equilibrium to the product side.

On Finite Mixture of Pareto and Beta Distnbutions

Department of Statistics, Cochin University of Science and Technology

Extracellular beta-Glucosidase production by marine Aspergillus sydowii BTMFS 55

The beta-glucosidase enzyme purified from the marine fungus, Aspergillus sydowii BTMFS 55 showed a good yield of enzyme production under solid state fermentation. The statistical optimization of the media components revealed that moisture content, concentration of peptone and inoculum are the major parameters which supported the maximal enzyme production. The purified enzyme showed low pH activity and stability, glucose tolerance and activation by ethanol. It could produce ethanol from wheat bran and rice straw by simultaneous saccharification and fermentation with yeast.The glucosidase purified from Aspergillus sydowii BTMFS 55 shows great potential for several biotechnological applications such as the production of bio-ethanol from agricultural biomass and improvement in the aromatic character of wines and fruit juices through the hydrolysis of flavour glucosidic precursors. There is immense scope for the application of this marine fungus in the biofuel production besides in other industries provided further studies are pursued in exploiting this enzyme and the organism particularly scale up studies with respect to application. There is also ample scope for cloning of the gene encoding beta-glucosidase in domesticated hosts such as Pichia pastoris or S. cerevisiae that can produce ethanol directly from cellulosic biomass.