NISCAIR Online Periodicals Repository Community: IJC-A Vol.51A [2012]

Alkaline hydrolysis of isatin in the presence of mixed CTAB and Triton X-100 micellar systems: Micellisation and kinetic investigations

Wed, 28 Nov 2012 22:58:59 GMT

Title: Alkaline hydrolysis of isatin in the presence of mixed CTAB and Triton X-100 micellar systems: Micellisation and kinetic investigations

Authors: Srikanth, V; Shyamala, P; Satyanarayana, A; Rao, P V Subba

Abstract: Micellisation behaviour of mixed surfactants of CTAB and Triton X-100 in the presence of isatin has been studied by surface tension measurements over a wide range of Triton X-100 mole fractions and total surfactant concentrations. The average interaction parameter has been evaluated using Rubingh theory and found to be -0.396 indicating synergistic behaviour in the mixed micelles. Kinetic studies showed that the pseudo first order rate constant increases with increase in mole fraction of Triton X-100 at constant total surfactant concentration and decreases with increase in total surfactant concentration at constant mole fraction of Triton X-100. Kinetic analysis has been carried out using a Berezin pseudophase model and binding constants determined to explain the micellar effect.

Page(s): 1701-1705

Effect on thermal behaviour of polyamide 66/clay nanocomposites with inorganic flame retardant additives

Wed, 28 Nov 2012 22:58:59 GMT

Title: Effect on thermal behaviour of polyamide 66/clay nanocomposites with inorganic flame retardant additives

Authors: Rathi, Sudesh; Dahiya, J B

Abstract: Polyamide 66 (PA66)/clay nanocomposites have been prepared with inorganic additives by melt blending method using an extruder. Inorganic additives such as potassium nitrate, zinc borate and magnesium hydroxide along with organic phosphinate have been used to study their effect on thermal behaviour of PA66/clay nanocomposites. The nanocomposites have been characterized by XRD which confirms the formation of intercalated and/or exfoliated nanocomposites. The thermal degradation behaviour of nanocomposites has been studied by TG, DTA, DSC and FTIR. PA66/30B nanocomposite is thermally stable in the higher temperature range beyond 450 °C with increase in char yield due to formation of nanocomposite and hindered diffusion of volatile products. DSC curve of PA66/30B shows an endothermic peak at 452 °C with higher heat of absorption (378 J/g) during the decomposition stage due to intercalation of PA66 between the 30B interlayers. The presence of a band in the FTIR spectrum in the range 2224−2245 cm^-1 in all PA66 nanocomposites char residue samples at 400 °C indicates the presence of nitrile group in the degradation products of PA66. The addition of zinc borate along with organic phosphinate induces a change in path of decomposition of polymer, leading to higher char formation which may protect the polymer from burning.

Page(s): 1677-1685

Accelerated polymorphous transformations of alumina induced by copper ions impede spinel formation

Wed, 28 Nov 2012 22:58:59 GMT

Title: Accelerated polymorphous transformations of alumina induced by copper ions impede spinel formation

Authors: Kiss, E; Ratković, S; Vujičić, Dj; Boskovic, G

Abstract: Slower copper spinel formation on alumina type supports relative to zinc and magnesium spinel formation has been investigated. Spinel formation occurs at high temperatures and is usually accompanied by polymorphous transformations of alumina support and sintering. In samples containing zinc and magnesium ions, decelerated polymorphous transformations of alumina occur relative to the transformation of pure aluminum sample. The impeded phase transformation of alumina coincides with decreased degree of sintering. In contrast, copper ions accelerate polymorphous transformations of alumina, and consequently the corresponding copper-aluminaspinel formation is slower. Accelerated sintering may be explained by accelerated phase transformation of alumina, which itself is caused by copper ions slowing down spinel formation.

Page(s): 1669-1676

Catalytic activity of liquid phase prepared Cu-Zn-Al catalyst for CO hydrogenation in a fixed bed reactor

Sat, 08 Dec 2012 16:04:59 GMT

Title: Catalytic activity of liquid phase prepared Cu-Zn-Al catalyst for CO hydrogenation in a fixed bed reactor

Authors: Luan, Chunhui; Zhang, Anrong; Wang, Xiaodong; Huang, Wei; Yin, Lihua

Abstract: Cu-Zn-Al catalyst prepared by a complete liquid phase technology for CO hydrogenation has been investigated in a fixed bed reactor in terms of catalytic performance and compared with catalysts prepared by a traditional method such as co-precipitation. The catalysts are characterized by XRD, NH₃-TPD, H₂-TPR and XPS. Results show that the activity of the liquid phase prepared catalyst is much lower in fixed bed reactor than in a slurry reactor. It was also much lower than that of the catalyst prepared by co-precipitation, although its stability is higher. XPS and XRD characterization reveal that there are obvious differences in the structure, morphology and surface state of the catalysts prepared by the two methods. In the catalyst prepared by liquid phase technology, Cu exists in the form of metallic Cu even though the catalyst is unreduced and there are more acid sites and more carbon on its surface than on the surface of the co-precipitation catalyst. It is concluded that there is a surface carbon film covering the liquid phase catalyst, and the carbon film is an important reason for the low activity when the catalyst is applied to fixed bed reactor. Coke burning off, an effective way for removing the surface carbon, improves the catalyst activity in a fixed reactor.

Page(s): 1663-1668