The changes in morphology due to the formation of polyethylene in the pores of three silica-supported, chromium oxide catalysts were followed by using mercury porosimetry and electron microscopy.Ethylene polymerization from 0.1 to 20 g of polymer/g of catalyst was carried out from the gas phase in a fluid bed reactor at 1-atm total pressure with a nitrogen diluent. A catalyst with 1.7 cm3/g pore volume fragmented due to the formation of polymer in the pores and thereby maintained an open structure. Catalysts containing 1.1 and 2.3 cm3/g pore volume did not fragment extensively, and the product polymer congested the pores and impeded the continued polymerization. Total pore volume and pore size are not the only controlling factors in the fracturing process. Mercury porosimetry showed that fracture of the 1.7 cm3/g catalyst started after a polymer yield of just 0.4 gPE/g^, maintaining monomer access to the active sites. The 0.1-1-^m catalyst fragments contained a pore microstructure much like that of the starting material, thus demonstrating how the pore structure of the original catalyst particles may influence the polymerization process after fragmentation is complete.

The high-temperature treatments in the activation of Phillips polymerization catalysts cause dramatic changes in the morphology of the silica support. The void structure of three commercial catalysts supplied by Phillips with pore volumes of 1.1,1.7, and 2.3 cm3/g were studied by using mercury porosimetry. It was found that the higher pore volume systems were similar in many ways but were different from the 1.1 cm3/g catalyst after the various activation treatments. The similarities included similar pore volume inside pores with diameter larger than 20 nm, bimodal pore-size distribution, and almost the same ethylene polymerization activity. IntroductionIn the polymerization of ethylene using supported chromium catalysts, the structure of the support may influence both the polymerization activity and the resulting polymer. A support that has a high pore volume and fractures easily generally exhibits greater activity. Chromium deposited on a support with large pores produces a lower molecular weight polymer.' Since these discoveries, there has been a need to examine more closely how the catalyst morphology affects the polymerization process. In a recent review article, Karol stated, "Catalyst characterization studies and use of model reactions appear necessary in studies relating catalyst structure to polymer molecular weight distribution".2Earlier studies have shown that the total pore volume, the average pore size, and the surface area of the catalyst have significant influence on polymerization activity. Carrick et al. impregnated a variety of silica supports with average pore diameters ranging from 2.2 to 20 nm with bis(triphenylsily1) chromate3 The results indicate that the average pore diameter of the support should be at least 6.7 nm for adequate polymerization activity. McDaniel found that the activity of 2% titanium on a silica support of 1.6 cm3/g pore volume was an order of magnitude higher than that of 2% titanium on a silica support of 0.43 cm3/g pore vo1ume.l However, the activity of 2% titanium on a 3.2 cm3/g pore volume support was only slightly higher than that for the 1.6 cm3/g pore volume support. Similar results were found for chromium-silica catalysts. Munoz-Escalona et al. also found greater activity when titanium was deposited on a support with a pore volume of 1.6 cm3/g compared to 0.9 ~m~/ g .~ Little research has been conducted to understand how the void structure of the support influences the polymerization. McDaniel studied the fracturing of supported chromium and titanium catalysts by removing the polymer from the fragmented catalyst after reaction.' The catalysts were characterized by nitrogen sorption before and after polymerization. The polymerization did not change the surface area, but increased the pore volume in the macropores (defined by McDaniel as >60-nm diameter). From this observation he concluded that fracturing occurred along pores greater than 60 nm in diameter, and, therefore, a greater amount of macropores results in a higher polymerization activity due to the fracture ...

A B S T R A C TThe potential use of dried anaerobic granular sludge (DAGS) as a substitute for granular activated carbon (GAC) for removing phenol and lead from aqueous solution was examined in a batch system. To make the comparison between adsorption/biosorption process fair, the working sorption pH, temperature, mixing speed and contact time were fixed at 4, 30˚C, 250 rpm and 24 h, respectively for both the sorbents. Adsorption/biosorption isotherms were developed for both the single and binary component systems and expressed by four models. Model parameters were estimated by the nonlinear regression method using STATISTICA version 6 and EXCEL 2007 software. The maximum loading capacity (q m ) of the phenol was 66.8234 and 37.0370 mg/g for lead onto GAC, while it was 70.0183 mg/g for phenol and 89.8783 mg/g for lead onto DAGS in single system. However, in binary system, the loading capacity decreased because of competition between compounds to binding sites of adsorbent/biosorbent.

Atorvastatin have problem of very slightly aqueous solubility (0.1-1 mg/ml). Nano-suspension is used to enhance it’s of solubility and dissolution profile. The aim of this study is to formulate Atorvastatin as a nano-suspension to enhance its solubility due to increased surface area of exposed for dissolution medium, according to Noyes-Whitney equation.         Thirty one formulae were prepared to evaluate the effect of ; Type of polymer, polymer: drug ratio, speed of homogenization, temperature of preparation and inclusion of co-stabilizer in addition to the primary one; using solvent-anti-solvent precipitation method under high power of ultra-sonication. In this study five types of stabilizers (TPGS, PVP K30, HPMC E5, HPMC E15, and Tween80) were used in three different concentrations 1:1, 1:0.75 and 1:0.5 for preparing of formulations. At the same time, tween80 and sodium lauryl sulphate have been added as a co-stabilizer.          Atorvastatin nano-suspensions were evaluated for particle size, PDI, zeta potential, crystal form and surface morphology. Finally, results of particle size analysis revealed reduced nano-particulate size to 81nm for optimized formula F18 with the enhancement of in-vitro dissolution profile up to 90% compared to 44% percentage cumulative release for the reference Atorvastatin calcium powder in 6.8 phosphate buffer media. Furthermore, saturation solubility of freeze dried Nano suspension showed 3.3, 3.8, and 3.7 folds increments in distilled water, 0.1N Hcl and 6.8 phosphate buffers, respectively. Later, freeze dried powder formulated as hard gelatin capsules and evaluated according to the USP specifications of the drug content and the disintegration time.        As a conclusion; formulation of poorly water soluble Atorvastatin calcium as nano suspension significantly improved the dissolution of the drug and enhances its solubility.

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