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Authors: Naheed, Rafia
Keywords: Natural Sciences
Analytical chemistry
Issue Date: 2012
Publisher: Quaid-i-Azam University Islamabad
Abstract: In present study, the polymerization of butadiene and ethylene were carried out using heterogeneous monometallic, bi-and tri-metallic catalysts. Five types of catalysts, nickel, cobalt monometallic, Ni-Co bi-metallic, and Ni-Co-Pd, Ni-Co-Pt tri-metallic were synthesized by using sol-gel, impregnation and hydrometallurgical methods. The synthesized nano composites were subjected to calcinations at 200, 400, 600 and 900 oC, to study their effects on catalyst morphology, activity and product selectivity. These were characterized by X-ray diffraction (XRD), helium adsorption Brunaur, Emmett and Teller (BET), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectrometer (EDX), transmission electron microscopy (TEM), FT-IR Spectroscopy, temperature programmed reduction (TPR), temperature programmed oxidation (TPO) and X-ray Photoelectron spectroscopic (XPS) studies. The synthesized catalysts were tested for the polymerization of butadiene and ethylene in ethanol, n-hexane and toluene solvents at various temperature and pressure conditions in Parr reactor. The products obtained were characterized by Fourier transform infrared spectroscopy FT-IR, 1H and 13 C Nuclear magnetic resonance spectroscopy (NMR), Gel permeation chromatography (GPC), Thermogravimetric analysis (TGA), Static laser light scattering (SLLS) and Mass spectrometric analysis (MS). The results showed that in ethanol solvent at 130 °C and 1.0 barr pressure, the product obtained consists of aliphatic and aromatic carbonyl compounds and polybutadiene terminated by -OH group. The selectivity of product was obtained in n-hexane and toluene solvent. In order to synthesize hydroxyl group terminated polybutadiene HTPB, the termination of polybutadiene was carried out by acidic solution of ethanol or hydrogen peroxide, whereas the termination of polyethylene was carried out by the acidic solution of ethanol. The significant product was achieved with the catalyst prepared by hydrometallurgical method as compared to other techniques. The best results were achieved with the Ni-Co- Pt catalyst calcined at 900 oC with molecular weight average of 12414 and a polydispersity Mw/Mn value of 1.404 under controlled conditions of temperature 130 oC and pressure 1.0 barr. The microstructure distribution of polybutadiene was studied by carrying out catalytic activity test at different temperature and pressure conditions. 100% stereoregular product of cis-1,4 polybutadiene have been achieved at low temperature 30 oC and pressure 0.5 barr with the catalyst Ni-Co calcined at 900 oC.
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