Dow Chemical (United Kingdom)

Abstract Multiphase particle in a cell simulation of fluidized beds for different Geldart group particles (A, B and D) were investigated. The minimum fluidization velocities predicted by the Barracuda Virtual Reactor® were compared and contrasted by theoretical predictions with the Wen‐Yu model. The optimal drag force coefficients based on the Wen‐Yu model for MP‐PIC simulations was further evaluated for different particle sizes and densities for Group A catalysts. A neural network model was constructed for the optimal model constants as a function of the explanatory variables for group A catalysts. This work illustrates the importance of choosing the correct value for the drag force coefficients to obtain realistic simulation results for fluidized beds. This work clearly demonstrates that the Barracuda simulation results are very sensitive to the value of the Wen‐Yu parameter. Using multiphase particle in cell simulations in conjunction with a neural network model can be directly used in further studies as a rapid tool to get the correct values for realistic drag force coefficients based on the Wen‐Yu model.

A practical and user‐friendly strategy for the chain‐end reduction of halogen terminated polymers that employs hydrogen gas and heterogeneous catalysis (palladium on carbon) is reported. Quantitative dehalogenation of a wide variety of monomer families (polystyrenes, polyacrylates, and polymethacrylates) with either chlorine or bromine chain‐ends is observed. The utility of this chain‐end reduction is further highlighted by mild reaction conditions, simple purification, and compatibility with a wide range of solvents. image

Abstract Extrusion of polymeric materials can be made more efficient by modelling with computational techniques. Material‐dependent data obtained through a constitutive equation is required to close the fluid dynamic equations. The paper outlines constitutive equations developed for non‐Newtonian behaviour and details the choice that is required to obtain a constitutive equation that encapsulates actual material behaviour. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.

The reliability of newly installed cables is expected to be as high as possible from commissioning to replacement. The cable oversheath (jacket) provides the first line of defence for the cable during transportation, installation and throughout its life in the laying environment. As such choosing the most appropriate oversheath material is essential to protect the cable at all stage of its life.

The asymmetric hydrogenation of 1-aryl-2-imidazol-1-yl-ethanones offers a concise route to homochiral 1-aryl-2-imidazol-1-yl-ethanols. Catalytic asymmetric transfer hydrogenation with formic acid using [(R,R)-TsDPEN]Ru(Cymene)Cl as precatalyst was shown to be effective in this transformation. Preliminary process development showed that the hydrogenation could be carried out under mild conditions at a molar substrate-to-catalyst (S/C) ratio of 1000−2000.

The application of asymmetric hydrogenation to the manufacture of pharmaceutical intermediates has become increasingly prevalent in the past three to five years. This review focuses on the hydrogenation substrates and their use, rather than comparing the specific catalysts employed. The literature published between 2002 and 2003 is covered, with some pertinent examples from 2001, all of which demonstrate the increasing number of applications for this technology.

Phosphazene bases such as {(NMe2)3P=N–)3P=NBut} have been reported in the literature to be strongly basic materials with basicities up to 1×1018 times stronger than that of diazabicycloundecene (DBU) a strong hindered amine base used in organic reactions. A study of these phosphazene bases as catalysts revealed that they can be activated by small amounts of water, which all silicone feed stocks contain, to form an active ionic base catalyst [(NMe2)3P=N–)3P–NHBut]+[OH]−. This paper discusses the use of these types of base catalysts, and their analogues, as ring-opening polymerization catalysts for cyclosiloxanes. Phosphazene base catalysts can be used at low concentrations to make high molecular weight polydimethylsiloxanes with short reaction times over a wide temperature range. Molecular weight can easily be controlled in the presence of suitably functionalized endblockers. Water and carbon dioxide have been shown to have a significant impact on the polymerization rates. Polymers prepared show excellent thermal stability by thermogravimetric analysis (TGA), following neutralization of the catalyst, with decomposition onset temperatures >500°C in some cases. As a result of the extremely low levels of catalyst used, the polymers often do not require filtration.