No abstract

A process model based on the thermodynamic models of Sanchez−Lacombe and PC-SAFT EoS is developed to simulate and analyze the impact of vaporized n-hexane as an induced condensing agent on the rate of gas phase ethylene polymerization on supported catalyst. The simulation results of the process model indicate that the cosolubility phenomenon (i.e., the enhancement in the equilibrium concentration of ethylene in the amorphous phase of polyethylene in the presence of n-hexane) cannot be the sole reason for the experimentally observed increase in the polymerization rate seen over the entire duration of reaction. At the beginning, the rate of ethylene polymerization is enhanced much more strongly than would be expected simply from the cosolubility effect alone. However, as the reaction proceeds, the enhancement magnitude gradually decreases and reaches a steady-state value corresponding to the promotion magnitude in the equilibrium concentration of ethylene predicted by the two thermodynamic models.

No abstract

We prepared poly(vinyl alcohol) (PVA)/SiO 2 and PVA/SiO 2 /glutaraldehyde (GA) nanocomposite membranes in a single step using the solution casting method. The structure, morphology, and properties of these nanocomposite membranes were characterized by Raman spectroscopy, atomic force microscopy, small-and wideangle X-ray scattering, thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis (DMA). The influence of silica and GA loading on the meso-scale characteristics of the composite membranes was investigated. The results showed that silica deposited in the form of small nanoparticles (*1 nm) in the PVA/ SiO 2 membranes, while bigger submicron particles ([25 nm) were formed in the PVA/SiO 2 /GA membranes. The water uptake of the PVA/SiO 2 membranes increased with temperature, but the PVA/SiO 2 /GA membranes were completely dissolved above 50°C. We can therefore conclude that the addition of GA deteriorated the properties of PVA/SiO 2 membranes. The thermal stability of the PVA/ SiO 2 membranes increased with the increasing silica loading with a maximum char yield of 46 % for PVA/SiO 2 / 4T. Even DMA profiles indicated a promising increase in E R (rubbery modulus) from 6 MPa (PVA membrane) to 1015 MPa (PVA/SiO 2 /4T) at 250°C, showing high mechanical strength of these membranes.