International Journal of Scientific and Research Publications, Volume 4, Issue 11, November 2014 1 ISSN 2250-3153 www.ijsrp.org Catalytic oxidation of polyphenol trihydroxybenzene by Pd-containing poly (vinyl alcohol) Ahmed I. Hanafy Chemistry department, Faculty of Science, Taif University, Taif, Saudi Arabia. Permanent address: Chemistry department, Faculty of Science, Al-Azhar University, Cairo, Egypt Abstract- Simple and environment friendly Pd-containing poly (vinyl alcohol) PVA catalysts were prepared by casting from their aqueous solutions. A series of PVA containing different ratios of Pd was characterized by IR, electronic spectroscopy, thermal analysis, XRD, Field-emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). The binding of Pd to the polymer matrix and its effect on the polymer structure was studied by means of XRD, XPS and thermal analysis. The catalytic activity of the Pd-based catalysts towards the oxidation of polyphenol trihydroxy benzene was investigated and showed a significant catalytic activity in case of the polymer sample containing the lowest Pd concentration ( A 1 ). The oxidation mechanism was proposed. Kojic acid was used to inhibit the oxidation reaction and it has been observed to be a non competitive inhibitor. Index Terms- polymer; inorganic compound; XRD; XPS; DTA; oxidation. I. INTRODUCTION oly (vinyl alcohol) PVA is a polymer with exceptional properties such as water solubility, biodegradability, biocompatibility, non-toxicity and non-carcinogenity that possesses the capability to form hydrogels by chemical or physical methods [1–4]. PVA, as semicrystalline material, exhibits certain physical properties resulting from the crystal- amorphous interfacial effect [5]. Moreover, it contains a carbon backbone with hydroxyl groups attached to methane carbons. These hydroxyl groups can be a source of hydrogen bonding, hence they assist in the formation of polymer blends [6]. PVA is well known for its wide range of potential applications in industrial, pharmaceutical, medical fields and continues to draw much attention of the researchers [7–9] due to the role of OH group and hydrogen bonds [10]. Its fields of applicability were widely broadened during the latest years due to the development of medicine, biomaterials, controlled drug release systems, environmental protection systems, new ecological systems for water purification and conductive systems for renewable energy sources, etc. [11–13]. During the latest years many research groups focused their attention on the study of PVA films or gels obtained by the simple addition of salts to the aqueous PVA solution. Very interesting properties have been obtained. Different additives are usually added to polymer in order to modify and improve its properties. Inorganic additives such as transition metal salts have a considerable effect on the optical and electrical properties of PVA polymer [14]. Palladium is one of the most catalytically versatile transition metals, its complexes being efficient catalysts for a wide range of C C coupling, C H functionalization, and hydrocarbon oxidation reactions [15–17]. The vast majority of Pd-catalyzed reactions involve Pd 0 and Pd 2+ oxidation states and these transformations have been extensively investigated for the past several decades [16,18–21]. Pd-catalysts are widely employed both in academia and in industry, making Pd the most extensively used metal catalyst for the synthesis of a wide variety of organic compounds [22–24], including pharmaceuticals [25,26], heteroarenes [27] and natural products[28]. Palladium compounds are interesting catalysts in the field of catalytic oxidation which is widely used in a pollution control technology for removing organic compounds. Palladium has been used in the hydroxylation of benzene [29] and oxidation of alcohols [30], ketones [31] and phenol[32]. In this study, synthesis and characterization of simply prepared and environment friendly catalysts using the easily degradable PVA and a small amount of Pd ion were presented. These catalysts were used in the catalytic oxidation of polyphenol trihydroxy benzene with and without H 2 O 2 at room temperature. II. EXPERIMENTAL SECTION 2.1. Preparation of PVA-Pd samples 1.0 gm of poly vinyl alcohol (PVA) was dissolved in about 50 ml dist. water with heating and continuous stirring. To the above solution the required amount of PdCl 2 was added dropwise with vigorous steering and heating at ~100 °C. The solution was poured to the Petri dish and put in the oven at 80 °C for ~ 8h to get the plastic sheet. The Petri dish was put over the water bath, so the plastic sheet was easily removed and it will be ready for usage. Four samples were prepared by this simple method; the pure polymer PVA (A 0 ), polymer containing 0.005 wt.% Pd ( A 1 ), polymer containing 0.01 wt.% Pd (A 2 ), polymer containing 0.05 wt.% (A 3 ). 2.2.Physico-chemical characterizations IR spectra for PVA and PVA-Pd samples were recorded in the solid state as KBr pellet on JASCOFTIR-600 Plus with a spectral resolution of 2 cm −1 and accumula-tion of 100 scans at room temperature. X-ray diffraction (XRD) data of the samples were measured at room temperature by using a Philips diffractometer (type PW 3710). The patterns were run with Ni- filtered copper radiation (λ = 1.5404Å) at 30 kV and 10 mA with a scanning speed of 2θ = 2.5º/min. All electronic spectra and kinetic studies measurement were performed using Varian Cary 4 Bio UV/vis spectrophotometer. X-ray photoelectron spectroscopy (XPS) measurements were obtained on a P