I. Synthesis and Testing of a Supported Shilov Oxidation Catalyst and II. Influence of Structural Features on Zeolite Characterization by Constraint Index Testing

Citation

Carpenter, John Reeves, III (2010) I. Synthesis and Testing of a Supported Shilov Oxidation Catalyst and II. Influence of Structural Features on Zeolite Characterization by Constraint Index Testing. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/WGZA-R541. https://resolver.caltech.edu/CaltechTHESIS:09292009-141737581

Abstract

This thesis is composed of two separate projects invoking the use of heterogeneous catalyst, one focused on catalyst development and another on characterization.

The first project concentrates on the development of a heterogeneous catalyst for alkane oxidation utilizing Shilov chemistry. Three techniques for creating heterogeneous catalyst are compared using Wacker oxidation: supported molten salts, supported aqueous phases (SAP), and ion-exchanged zeolites. From the Wacker oxidation study the supported aqueous phase catalyst was identified as the best potential method for developing a Shilov oxidation catalyst.

Initial work focused on oxidation of ethanesulfonate loaded onto the SAP catalyst. Similar turnovers were achieved on the SAP catalyst as have been seen in the homogeneous system. The reaction parameters of liquid loading, oxygen pressure, reactant concentration, copper (II) chloride concentration, and acid addition were investigated. While the SAP catalyst was successful in the oxidation of ethanesulfonate, attempts to perform ethane oxidation in a flow system were not. The loss of chloride ions is believed to lead to the deactivation.

The second project investigates anomalous Constraint Index (CI) results for zeolites containing cages that are relatively larger than their pore opening. The CI test utilizes the competitive cracking of 3-methylpentane and n-hexane to classify structures as having small, medium, or large pores. However, structures like SSZ-23, SSZ-25, SSZ-28 and SSZ-35 with these large cages have CI results consistent with a larger pore classification than the pores in them.

Incomplete hemi-cages on the external surface may provide a nonselective active site that would result in lower CI results. This work looks at this possibility by comparing SSZ-25 and SSZ-35 with ZSM-5 and BEA* that are normally behaving medium- and large-pore structures respectively. The surface is passivated by a dealumination treatment and the CI test is compared on the parent and treated samples. No evidence of activity on the external surface having an influence on the CI test is observed. Several techniques are also used to further investigate accessibility. Finally we observed that for structures with multiple distinct features, different fouling rates in each feature may result in observable changes in the CI value over time.

Thesis Files