In situ synthesis of nanoclay filled polyethylene using polymer supported metallocene catalyst system

In situ ethylene polymerizations were performed using bis(cyclopentadiene)titanium dichloride supported on polyethersulfone as catalyst. The bis(cyclopentadiene)titanium dichloride supported on polyethersulfone catalyst activity estimated by ethylene polymerization was 360 kgPE/molTi/h. During polymerization the fillers used were montmorillionite nanoclays having surface modifications with 35-45 wt% dimethyl dialkyl(14-18)amine (FA) and 25-30 wt% trimethyl stearyl ammonium (FB). These fillers were pretreated with methylaluminoxine (MAO; cocatalyst) for better dispersion onto the polymer matrix. The formation of polyethylene within the whole matrix was confirmed by FTIR studies. It was found that the nature of nanofiller did not have any remarkable effect on the melting characteristics of the polymer. TGA study indicates that nanoclay FB filled polyethylene has higher thermal stability than nanoclay FA filled polyethylene. The melting temperature of the obtained polyethylenes was 142 ºC, which corresponds to that synthesized by the polyether sulfone supported catalyst

Counter-intuitive comparable diffusivity of xylene isomers in zeolitic mesopores: Confirmation from adsorption and catalysis studies

The reaction of commercial interest, toluene methylation to selectively obtain para-xylene has been studied. For this purpose, zeolite Beta is modified to impart mesoporosity in the crystals such that formation of kinetically favour para-isomer (as advocated by some schools earlier) facilitates and diffuse out easily. However, when this modification did not meet the expectation, pore openings on crystal surface have been narrowed using tetraethyl ortho-silicate (TEOS). Albeit, TEOS is found to enter the pores of modified zeolite and no para-selectivity could be attained and proportion of meta-isomer higher than thermodynamically determined is obtained. Catalytic- and xylene adsorption kinetic- results led to conclude (1) diffusivity of para-xylene is only 1.33 times higher than that of the meta-isomers in parent and hierarchical zeolite Beta samples and (2) extent of increase in diffusivity of para- and meta-xylene due to mesoporosity generation is comparable (about 1.14 times) unlike increase by 2 order of magnitude reported in case of ZSM-5. These observations dispel the early reckoning: large pore zeolites affording para-xylene selectivity in the reaction of toluene methylation

Counter-intuitive comparable diffusivity of xylene isomers in zeolitic mesopores: Confirmation from adsorption and catalysis studies

517-524The reaction of commercial interest, toluene methylation to selectively obtain para-xylene has been studied. For this purpose, zeolite Beta is modified to impart mesoporosity in the crystals such that formation of kinetically favour para-isomer (as advocated by some schools earlier) facilitates and diffuse out easily. However, when this modification did not meet the expectation, pore openings on crystal surface have been narrowed using tetraethyl ortho-silicate (TEOS). Albeit, TEOS is found to enter the pores of modified zeolite and no para-selectivity could be attained and proportion of meta-isomer higher than thermodynamically determined is obtained. Catalytic- and xylene adsorption kinetic- results led to conclude (1) diffusivity of para-xylene is only 1.33 times higher than that of the meta-isomers in parent and hierarchical zeolite Beta samples and (2) extent of increase in diffusivity of para- and meta-xylene due to mesoporosity generation is comparable (about 1.14 times) unlike increase by 2 order of magnitude reported in case of ZSM-5. These observations dispel the early reckoning: large pore zeolites affording para-xylene selectivity in the reaction of toluene methylation

Application of monolithic stirred reactor in hydrogenation reaction

572-575Hydrogenation of 1-octene was carried out in a monolithic stirred reactor. A cordierite monolith with HZSM-5 washcoat, impregnated with Pd was used as catalyst. The reactions were conducted between 50-65ºC and 250-400 psi hydrogen pressure. The effects of temperature and pressure on conversion and selectivity were measured. Major part of 1-octene was converted to n-octane and some isomers of octene were formed. However, at higher operating condition they were converted to n-octane. The experiments proved that the monolithic reactor is an attractive alternative reactor

Bioethanol selective oxidation to acetaldehyde over Ag–CeO₂: role of metal–support interactions

Inserted Ag creates oxygen vacancy on the surface of CeO2, leading to enhanced catalytic activity.</p