Jayaraj Christopher

Chemical structure of bitumen-derived asphaltenes by nuclear magnetic resonance spectroscopy and X-ray diffractometry

Abstract Asphaltene samples obtained from bitumen processed at three Indian refineries were characterized for chemical composition and structure by nuclear magnetic resonance (n.m.r.) spectroscopy and X-ray diffractometry (XRD). The average structural parameters were obtained by combined 1H, 13C and DEPT spectral editing techniques. New equations were used for the estimation of n.m.r. average structure parameters. The macrostructure and crystalline parameters of these samples were obtained by XRD. A combined n.m.r. and XRD procedure was used to estimate the size of the average aromatic structural unit. Asphaltenes from one of the bitumens (ASP-D) was found to have different structural parameters from those of the asphaltenes from the other two bitumens. The number of aromatic rings per unit sheet in ASP-D was eight, compared with 13 for both ASP-M and ASP-H. XRD data indicated that the aromatic sheets are randomly oriented in ASP-D. The structural parameters allowed a model structure of the asphaltenes to be constructed.

Progress on layered hydrotalcite (HT) materials as potential support and catalytic materials

Mixed metal oxides derived from layered hydrotalcite (HT) materials are extensively used as a potential catalyst and catalytic support in various organic transformations. Numerous such materials have been developed by varying framework divalent and trivalent metal ions, and interlayer anions. The intercalation of anions present in HT facilitates the design of high surface area materials possessing exposed active sites, which enhances the catalytic and adsorption properties. These HT materials have also been used as drug carriers, and in enzyme encapsulation owing to their flexible accommodation of organic anions in the interlayer of the HT structure. The present review is focused on a recent development in the preparation of various HT materials using different metals and intercalating ions and their importance in the various catalytic processes, such as base catalyzed alkylation, isomerization, condensation and esterification. Effectiveness of transition metals containing HT for redox catalytic processes, viz. oxidation of alcohol, alkyl aromatics, phenol and reduction of nitro compounds have been discussed. Further, the importance of the introduction of a hard anion like silicate into the interlayer space of the HT and its applications in various organic reactions has also been covered in this review.

Silicate anion intercalated cobalt-aluminium hydrotalcite (CoAl-HT-Si): a potential catalyst for alcohol oxidation

Silicate intercalated CoAl hydrotalcite materials were synthesized (CoAl-HT-Si) and systematically characterized. The intercalated hydrotalcite materials lead to the formation of solid solutions of cobalt silicate and cobalt spinel structures, which have higher surface area and pore volume than pure CoAl-HT. The XPS studies revealed the presence of cobalt in divalent and trivalent oxidation states on the surface. The resultant materials were found to be promising catalysts for oxidation of various alcohols.

Silicate anion-stabilized layered magnesium–aluminium hydrotalcite

Layered magnesium–aluminum hydrotalcite (HT) were completely intercalated and stabilized with silicate anions. The silicate anion-stabilized HT retained the layered structure and possessed a high surface area of 530–540 m2 g−1 with needle-like particles 60 nm × 4 nm in dimension. The findings of FT-IR, powder XRD, TGA, DSC and 29Si MAS-NMR revealed that silicate anions were intercalated and coated on the surface of layered HTs with the formation of a solid solution of magnesium silicate and HT. The resultant silicate-anion-intercalated materials are found to be promising catalysts for the synthesis of 1-phenoxy-2-propanol using phenol with propylene oxide.

An environmentally friendly route for grafting of molybdenum carbonyl onto a diaminosilane-modified SBA-15 molecular sieve and its catalytic behaviour in olefin epoxidation

A simple route has been established for grafting molybdenum carbonyl onto the surface of a diaminosilane-modified SBA-15 molecular sieve. The successful grafting of the molybdenum carbonyl species onto diamine-functionalized SBA-15 was evident from FT-IR studies. The resultant molybdenum-carbonyl-complex-grafted SBA-15 (SBA-DA-Mo) materials show promising activity for the epoxidation of various olefins with good conversion (90–95%) and the formation of epoxide as the major product. The catalytic activity remains constant over several runs.

Synthesis and Heterogenization of Siloxane Functionalized Cobalt Complex: Potential Catalyst for Oxidation of Alcohols

Cobalticinium complex containing siloxane moiety on ligand center was first time synthesized, characterized and heterogenized on the surface of SBA-15 molecular sieves. FT-IR and 29Si-MAS-NMR spectrum evidence the successful grafting of the cobalt complex on the surface of SBA-15. N2 sorption isotherm of cobalticinium complex grafted sample showed the decrease in surface area, pore volume, further confirms the presence of complex inside the channel of mesoporous SBA-15. The heterogenized complex exhibited promising activity for oxidation of alcohols with good selectivity of ketone. Further the catalytic activity remains intact after two recycles.Graphical AbstractCobalticinium complex possessing siloxane functionality was prepared first time and heterogenized on SBA-15 surface. The resultant materials showed as promising recyclable heterogeneous catalyst for oxidation of alcohols.

Use of HPLC to monitor olefins, dienes, and aromatics in the dehydrogenated products of higher n-paraffins

ABSTRACT The linear higher olefins are generated through catalytic dehydrogenation of long-chain linear paraffins. During the catalytic dehydrogenation, a variety of dienes and aromatics are also formed. These side products not only cause coking of the catalyst, but also hamper in the reaction course of olefins with other substrate. A method has been developed based on the High-Performance Liquid Chromatography with Refractive Index detection for simultaneous estimation of olefins, dienes, and aromatics in the catalytic dehydrogenated product of model compound decane. The application of method for monitoring of the dehydrogenated stream from C10-C14 n-paraffins has also been discussed.

Elemental analysis of FCC catalysts by XRF & ICP techniques - A statistical comparison

Abstract FCC catalysts obtained from different refineries were analysed by ICP and XRF techniques for the elements Al, Ni, V, Ti & Fe and the results were compared statistically by Paired t-test, Regression analysis and F-test. It was observed that both the techniques are equivalent and there is no significant difference between the results for the analysis of Al, Ni, V, Ti & Fe in FCC catalysts. However, statistical analysis indicates that XRF is more precise compared to ICP. Therefore, XRF technique can be used routinely for the analysis of Al, Ni, V, Ti and Fe in FCC catalysts in place of ICP with advantage.

Novel HPLC-RI-UV based method for simultaneous estimation of saturates, olefins, conjugated dienes and aromatics in full range cracked gasoline

Abstract A fast method based on High performance liquid chromatography technique for the estimation of Saturates, Olefins, Conjugated dienes and Aromatics in Cracked gasoline samples has been developed. In this work, the focus was on choosing the right reference standard against which olefin could be estimated. The olefin reference standard was first shortlisted using Nuclear Magnetic Resonance spectroscopy and Gas chromatography based Simulated Distillation analysis as per ASTM D2887. The values estimated against shortlisted standards using HPLC were compared with values obtained using standard Flourescent Indicator Adsorption(FIA) based ASTM D1319 method to select one. The aromatics were estimated against o-Xylene.

Rapid method for determination of dehydro abietic acid in gum rosin and disproportionate rosin by proton nuclear magnetic resonance spectroscopy

In present work a simple, direct and rapid method developed based on proton nuclear magnetic resonance spectroscopy for the quantitative determination of dehydroabietic acid in gum rosin and disproportionated rosins and validated. This method can also be applied to the determination of other acids of gum rosins like abietic acid, pimaric acid isopimaric acid, palustric acid, neo abietic acid, levopimaric acid, tetrahydro abietic acid, dihydro abietic acid. Dehydroabietic acid has been estimated using aromatic proton while vinyl propton was used for estimation of other acids in gum rosins. Analysis of rosin acid methyl ester derivative in disproportionated rosins was also carried out by gas chromatography-mass spectroscopy to identify peak of dehydro abeitic acid along with abeitic acid based on their mass fragmentation pattern and quantified using gas chromatography with flame ionization detector. Good correlation was observed between the results of gas chromatography with flame ionization detector with newly developed nuclear magnetic resonance method.