A model for studying the catalyst fragmentation in the early stages of olefin polymerization is presented. The model is based on measurable and observable parameters of the catalyst and on the energy balance for the fragmentation phenomenon. The model allows the fragmentation behaviors to be discriminated regarding the influence of particle size, polymerization rate, and active site distribution. The results are supported by experimental studies available in the literature indicating the deterministic nature of the model and its capabilities of prediction. The performance of the model allows the optimization of the catalyst synthesis in terms of the nature of the support as well as particle and pore morphology.

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The presence of pharmaceuticals in aqueous environmental matrices often requires efficient and selective preconcentration procedures. Thus, silicas (SILs) were synthesized by a molecular imprinting technique using an acid-catalyzed sol-gel process and the following drugs as templates: fluoxetine, gentamicin, lidocaine, morphine, nifedipine, paracetamol, and tetracycline. The materials were subjected to sorbent extraction assisted by ultrasonic treatment to remove the drugs and the consequent formation of molecular imprinted cavities. The surface area of the resulting materials ranged from 290 to 960 m(2)/g. Adsorption tests were performed with the molecular imprinting phases. In terms of the potential selectivity, the SILs were subjected to the adsorption of drugs from samples such as potable and surface water. The adsorption capacity remained in the range between 55 and 65% for both matrices, while for the nonimprinted SIL it remained between 15 and 20%.

The removal of azo‐dyes, recalcitrant compounds found in several industrial effluents, was investigated by an environmentally friendly hybrid adsorbent material based on grape stalk encapsulated by the sol–gel method. The winemaking process produces a large amount of grape stalk. This solid waste represents an environmental problem for wineries. The hybrid adsorbent based on grape stalk was synthetized by the acid catalyzed sol–gel route and characterized by different techniques. According to the zeta potential values, the resulting hybrid material is negatively charged at a wide pH range (2.0–12.0). The adsorption of the cationic azo‐dye Basic Blue 41 onto the hybrid material was evaluated in aqueous solution. The studies of pH (3.0–12.0), adsorbent concentration (0.5–5.0 g L−1), kinetic and adsorption equilibrium were investigated at 303 K. The kinetic data were best fitted to the pseudo‐second order kinetic model. Equilibrium studies showed that the hybrid material achieved a maximum adsorption capacity of 205.3 mg g−1. The large amount of solid waste generated from wine production represents a serious impasse for wineries regarding its storage and disposal, from both ecological and economical points of view. Alternatively, this agricultural solid waste may represent a source of raw material to create new products, increasing the life cycle and adding value to the previously discarded material. In this work, grape stalk was employed as adsorbent for dye removal, promoting the reduction of environmental contamination. The results showed that it is a promising material to use as efficient eco‐friendly adsorbent for the treatment of wastewater.

Slurry polymerization processes are used to produce high-density polyethylene of tailor-made properties. The formation of fouling in slurry reactors as well as in its peripheral equipment, such as external heat exchangers, is attributed either to the deposition of oligomers (wax) or to the buildup of electrical charge in small polymer particles. In order to understand the causes of fouling formation, samples were gathered from polymerization processes and they were characterized by microscopy in this research. The results show the existence of an aluminum-based layer as a common element in the samples analyzed. It is supposed that such a layer is formed by the reaction of trialkyl aluminum and water residues during the start-up procedure of the plant.

Summary: Concomitant immobilization of zirconocene (Cp 2 ZrCl 2 ) into a silica matrix was performed during the SiO 2 synthesis through non-hydrolytic sol-gel method. Two different routes, varying the SiCl 4 :Si(OEt) 4 ratio were evaluated in terms of zirconocene content and catalyst activity in ethylene polymerization, using methylaluminoxane (MAO) as cocatalyst. The catalysts were characterized by Rutherford backscattering spectrometry, Fourier transform infrared spectroscopy, diffuse reflectance spectroscopy, scanning electron microscopy and X-ray dispersive spectroscopy. The zirconocene content laid between 0.60 and 1.02 wt.% Zr/SiO 2 , depending upon the components ratio employed in the sol-gel synthesis. Catalyst grains presented of irregular shape (20-100 mm size) and zirconocene distribution was not uniform. Both routes led to supported catalysts active in ethylene polymerization. Catalyst activity was intermediate between that exhibited by the homogeneous and the grafted zirconocene on silica. Resulting polyethylenes presented narrow molecular weight distribution and molecular weight slightly higher than that observed in the case of polymer produced with the homogeneous system.