The retention of copper ions by AlPO4-5/VAPO-5 and their effect on reactant access

The reaction of copper salts with AlPO₄-5 or V^v-VAPO-5 under acidic (CuCl₂, pH adjusted to 2) but especially basic conditions (Cu(NH₃) ₄ ²⁺ , pH adjusted to 9) gives ion incorporations greater than expected by a simple ion exchange mechanism (both AlPO₄-5 and V^v-VAPO-5 could be expected to have no cation exchange capacity). Ion incorporation is proposed to occur initially at defect sites, and examination of the ESR spectrum of a dehydrated, evacuated CuCl₂-exchanged AlPO₄-5 shows that these defect sites give rise to a number of unique environments upon Cu^II incorporation. The CuCl₂-exchanged VAPO-5 retains a significant toluene accessibility to the V^v sites in the VAPO-5. However, the toluene accessibility in the Cu(NH₃) ₄ ²⁺ -exchanged VAPO-5 is significantly reduced and we propose this is due to a combination of the presence of crystalline CuO and structural collapse from reaction with base (NH₄OH). The ability of treatment with base (NH₄OH, pH 13) to restrict access of toluene to the V^v sites of the original VAPO-5 was verified in a separate experiment.     

Characterization and reactivity of MoO3 supported on AlPO4

A series of MoO₃/AlPO₄ catalysts with molybdena content varying from 2 to 16 wt% were prepared and characterized by low temperature oxygen chemisorption (LTOC), ammonia chemisorption, X-ray diffraction (XRD) and electron spin resonance (ESR). Maximum O₂ uptake was observed at 6 wt% MoO₃ loading indicating the completion of monolayer. The ESR results are in conformity with LTOC and XRD data. The activities of the catalysts were tested in methanol partial oxidation and are correlated with their surface characteristics wherever possible.IICT Communication No. 3188.     

Modifications of carbon for polymer composites and nanocomposites

The various forms of carbon used in composite preparation include mainly carbon-black, carbon nanotubes and nanofibers, graphite and fullerenes. This review presents a detailed literature survey on the various modifications of the carbon nanostructures for nanocomposite preparation focusing upon the works published in the last decade. The modifications of each form of carbon are considered, with a compilation of structure-property relationships of carbon-based polymer nanocomposites. Modifications in both bulk and surface modifications have been reviewed, with comparison of their mechanical, thermal, electrical and barrier properties. A synopsis of the applications of these advanced materials is presented, pointing out gaps to motivate potential research in this field.