Isospecific polymerization of styrene with supported nickel acetylacetonate/methylaluminoxane catalysts

Summary The polymerization of styrene with catalysts based on Ni(acac)₂ supported on SiO₂ and Al₂O₃ was investigated. Using catalysts based on MAO supported on silica, a highly isotactic polystyrene was obtained. Nevertheless, the Al₂O₃-supported catalyst can promote isospecific polymerization activated by common. alkyl aluminum compounds even by any prior support treatment with MAO. Received: 3 March 1998/Revised version: 14 April 1998/Accepted: 14 April 1998     

Polymerization of ethylene by chromium acetylacetonate/methylaluminoxane catalyst system

Summary The present paper deals with polymerization of ethylene by chromium acetylacetonate - Cr(acac)₃ - activated by alkylaluminium, e.g. Al(C₂H₅)₃ or Al(i-C₅H₉)₃, or methylaluminoxane (MAO). The influence of polymerization parameters on catalyst performance, such as Al/Cr mole ratio, temperature, aging time, type of cocatalyst, was investigated. High activities were obtained only when MAO was the cocatalyst. The polymers were characterized by size exclusion chromatography (SEC) and differential scanning calorimetry (DSC) analyses. Received: 11 September 1997/Revised version: 5 January 1998/Accepted: 20 March 1998     

Geochemical effects of electro-osmosis in clays

Geochemical effects of electro-osmosis in bentonite clay are studied in the laboratory, where a 6 mm thick bentonite layer is subjected to direct current. Acidification and alkalization near anode and cathode are expected, possibly causing mineral deterioration, ion mobilization and precipitation of new solids. Afterwards the clay is analysed by XRF and anolyte and catholyte are analysed by ICP-MS. In addition, as a preliminary experiment treated bentonite is analysed by high resolution μ-XRF. Electro-osmotic flow is observed. Due to its carbonate content the bentonite is pH-buffering. Alkalization in the catholyte is substantial. Ca, Na and Sr are significantly removed from the clay and accumulate in the catholyte. Recovery in the catholyte accounts for a small fraction of the element-loss from the clay. The rest will have precipitated in undetected solid phases. μ-XRF indicates the loss of Ca-content throughout the bentonite layer.     

Hydrophobically modified poly(ethylene glycol) as reactive clays inhibitor additive in water‐based drilling fluids

Adsorption measurements and inhibition tests were used to investigate the mechanisms of shale stabilization by hydrophobically modified poly(ethylene glycol) (PEG). Commercially available PEG with a large range of molar masses and PEG diesters were adsorbed on smectite‐rich clay from saline solutions and the clay/polymer complexes obtained were characterized by thermogravimetric analysis and x‐ray diffraction. The adsorption isotherms obtained for all unmodified PEG showed low affinity for the clay surface, however they all accessed the interlamellar spaces of the clay and reduced the clay water content of the complexes obtained. The PEG macromolecules had their affinity for the clay strongly enhanced by the hydrophobic modification especially with dodecanoic acid and were intercalated into the clay matrix, reducing, in a more efficient way, the water uptake by the clay. Conventional rolling tests were performed to evaluate the effect of polymers on the clay cuttings integrity. Results show that under conditions promoting the adsorption of polymers on both external and interlayer clay surfaces, displacement of the water from the clay was obtained and dispersion and disintegration of clay cuttings were inhibited. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Simulation and cost estimate for biodiesel production using castor oil

Brazilian government has established a regulation that imposes the commercialization of diesel blended with 3% of biodiesel by volume. Castor oil has being considered an option to guarantee the supply of biodiesel needed. For this reason, in this work, a continuous biodiesel plant was designed and simulated in HYSYS simulator using castor oil as feedstock. The developed process was capable of producing biodiesel at high purity using an alkali catalyst. Material and energy flows, as well as sized unit operations were used to conduct an economic assessment of the process. Total capital investment, total manufacturing cost and after annual equivalent cost were also calculated. A study of production costs was performed considering the fluctuations of the raw material prices and the glycerin purification step.     

Distribution of fungi and aflatoxins in a stored peanut variety

The objective of the present study was to evaluate the mycoflora and occurrence of aflatoxins in stored peanut samples (hulls and kernels) from Tupã, State of São Paulo, Brazil. The samples were analyzed monthly over a period of one year. The results showed a predominance of Fusarium spp. (67.7% in hulls and 25.8% in kernels) and Aspergillus spp. (10.3% in hulls and 21.8% in kernels), and the presence of five other genera. The growth of Aspergillus flavus was mainly influenced by temperature and relative humidity. Analysis of hulls showed that 6.7% of the samples were contaminated with AFB₁ (mean levels = 15–23.9 μg/kg) and AFB₂ (mean levels = 3.3–5.6 μg/kg); in kernels, 33.3% of the samples were contaminated with AFB₁ (mean levels = 7.0–116 μg/kg) and 28.3% were contaminated with AFB₂ (mean levels = 3.3–45.5 μg/kg). Analysis of the toxigenic potential revealed that 93.8% of the A. flavus strains isolated were producers of AFB₁ and AFB₂.     

Ozone Application in Recirculating Aquaculture System: An Overview

In recirculating aquaculture systems (RAS), particulates (including feces, uneaten feed, bacteria, and algae) can cause several problems, in that they may harbor pathogens, can physically irritate the fish, and upon decomposition, release ammonia and consume oxygen. Mechanical filters, foam fractionators, and other engineered devices are used to remove particles quickly from aquaculture systems, in order to improve fish health and decrease the load on biofilters and oxygenators. Ozone is used in RAS as a disinfectant, to remove organic carbon, and also to remove turbidity, algae, color, odor and taste. Ozone can effectively inactivate a range of bacterial, viral, fungal and protozoan fish pathogens. But the effectiveness of ozone treatment depends on ozone concentration, length of ozone exposure (contact time), pathogen loads and levels of organic matter. In spite of ozone is a very effective oxidizing agent, higher ozone concentrations are a risk to cultured fish stocks causing gross tissue damage and stock mortalities, and also are a risk to bacterial films on the biofilter.