Towards the low temperature growth of uniform diameter multi walled carbon nanotubes by catalytic chemical vapour deposition technique

Mesoporous MCM-41 molecular sieves containing f-block transition elements（gadolinium） with various Si/Gd ratios（50,75 and 100） were synthesised by a hydrothermal method.Their mesoporous structure was confirmed by X-ray diffraction,nitrogen sorption studies,thermogravimetric analysis,scanning and transmission electron microscopy.The local environment of Gd in the material was studied by electron paramagnetic resonance.The compatibility of the catalyst for the synthesis of uniform diameter CNTs by varying the temperature from 400 to 650°C with fixed flow rates of N2 and C2H2（140 ml/min and 40 ml/min,respectively）.The product is mostly metal containing thin MWCNTs with diameter of 1020 nm.Characterisation shows that a combination of Gd-MCM-41（100） catalyst gives a high yield of high quality MWCNTs under optimum growth conditions.

A novel manganese tungstate nanorod catalyst for the oxidation of styrene with tert-butyl hydroperoxide as oxidant

Catalyst,solvent and process parameters are the keys for the selective oxidation of styrene and other olefins to value added intermediates.Hence MnWO_(4)was synthesized by the one-pot hydrothermal method using Pluronic F127 as a surfactant,characterized and evaluated for the oxidation of styrene and different olefins,using tert-butyl hydroperoxide(TBHP)as oxidant.X-ray diffractogram confirmed the phase purity of MnWO_(4)which became further evident from the near surface equimolar proposition of Mn and W in+2 and+6 oxidation states,respectively,as inferred from X-ray photoelectron spectra.N_(2)sorption followed typeⅣa isotherm with H_(3)hysteresis loop,starting at the relative pressure(P/P_(o))of 0.9,typically of mesoporous materials containing macropores as further confirmed by pore-size distribution.Transmission electron microscope images of MnWO_(4)revealed its nanorod morphology.In the absence of catalyst,styrene conversion was 35%with benzaldehyde as the sole product and addition of 75 g of MnWO_(4)increased the styrene conversion to 97.3%,and the styrene oxide selectivity from 0%to 85%demonstrated its activity and selectivity.For the maximum conversion and styrene oxide selectivity optimum temperature,styrene:TBHP molar ratio,catalyst amount and solvent were found to be 70℃,1:2,75 mg,and acetonitrile,respectively.MnWO_(4)catalyst retained its activity and selectivity for five recycles,confirming its recoverability and reusability.From the kinetic studies,pre-exponential factor and apparent activation energy were found to be 0.206 s^(-1)and 31.5 kJ·mol^(-1),respectively,and a reaction mechanism was proposed.MnWO_(4)catalyst was active for oxidation of alkenes,cycloolefins and alkenyl aromatics with high selectivity for epoxides.