Source: Dissertation Abstracts International, Volume: 76-11(E), Section: B.

Adviser: Gary L. Haller.

Employing a combination of TPD, XPS, NEXAFS, titration and PCA, the functional group distribution of oxygen functionalized MWCNT has been clarified. Different oxidation reagents, oxidation time and annealing temperature effects on the different functional group distributions, as well as the total acidity, have been determined. Stronger oxidation reagents, as for example acids, induces more carboxyl groups than hydroxyl groups. However, weaker oxidation reagents behave just the opposite. Nitric acid treatment induces bond cleavage in the C-C network via electrophilic attack. The resultant vacancy sites are then oxidized in a sequential reaction. Alcohol is first oxidized into aldehyde, and aldehyde is further oxidized into acid. A longer oxidation time gives a greater ratio of carboxyl groups to hydroxyl groups. Annealing temperature plays a significant role in functional groups concentration. At 400°C, several of the groups begin to dissociate. Most of the carboxyl groups disappear after 500°C. The hydroxyl groups are stable at temperatures below 800°C.

Two methods, wet impregnation and ion exchange, were used to prepare Pt supported on MWCNT catalysts. For wet impregnation methods, the Pt particles size is mostly affected by the defects on the MWCNT, which is the site for anchoring the metal particles. The catalytic hydrogenation rate of benzene is mostly affected by the carboxylic group that affects the polarity of the catalyst. The oxygen concentration of the MWCNT matrix determines the Pt electronegativity which is demonstrated by competitive hydrogenation of benzene and toluene reaction catalyzed by Pt. Using the strong electrostatic adsorption method, two precursors (CPA and PTA) uptake curve on two hours nitric acid MWCNT (with a PZC about 4) were investigated. The results were compared with a model from the literature. It was demonstrated that this method can be a scientific way to prepare desirable catalysts with good Pt metal particle dispersion.