Preparation and characterization of intercalated bentonites as catalysts and supports

This dissertation concerns research that involves synthetic, catalytic, and spectroscopic studies of pillared clay materials. The surface modification of pillared clays as supports for enzyme immobilization is also involved in this research.; (A) Three pillared clays have been prepared by intercalating bentonite with Ga{dollar}{bsol}sb{lcub}13{rcub}{dollar}, GaAl{dollar}{bsol}sb{lcub}12{rcub}{dollar}, and Al{dollar}{bsol}sb{lcub}13{rcub}{dollar} polyoxycations respectively. The textural properties are studied by XRD, surface area and pore size measurements, SEM, and TGA. The results show that two dimensional channel structures have been created in all three pillared clays. The thermal stabilities of the three pillared clays decrease as GaAl{dollar}{bsol}sb{lcub}12{rcub}{dollar}/B-H {dollar}>{dollar} Ga{dollar}{bsol}sb{lcub}13{rcub}{dollar}/B-H {dollar}>{dollar} Al{dollar}{bsol}sb{lcub}13{rcub}{dollar}/B-H. Of the pillared clays, GaAl{dollar}{bsol}sb{lcub}12{rcub}{dollar}/B-H and Ga{dollar}{bsol}sb{lcub}13{rcub}{dollar}/B-H are thermally stable above 700{dollar}{bsol}sp{bsol}circ{dollar}C. Acidic properties are studied with pyridine adsorption, FT-IR, and ammonia TPD. It is found that acid sites have been doubled on such clay after pillaring. Both Bronsted and Lewis sites are detected on three pillared clays. However, the strengths of Bronsted acid sites on Ga{dollar}{bsol}sb{lcub}13{rcub}{dollar}/B-H are found to be higher than those on the other two pillared clays. A different Lewis acid site is observed on Ga{dollar}{bsol}sb{lcub}13{rcub}{dollar}/B-H. Catalytic testing, by a pulse technique, reveals that the conversion of butane at 550{dollar}{bsol}sp{bsol}circ{dollar}C is about 45%, and the selectivity to aromatics is 50% on Ga{dollar}{bsol}sb{lcub}13{rcub}{dollar}/B-H.; The cation exchange capacity (CEC) of GaAl{dollar}{bsol}sb{lcub}12{rcub}{dollar} pillared clay is restored by heat treatment in an ammonia atmosphere. This pillared clay is then re-intercalated with Ga{dollar}{bsol}sb{lcub}13{rcub}{dollar}, GaAl{dollar}{bsol}sb{lcub}12{rcub}{dollar}, and Al{dollar}{bsol}sb{lcub}13{rcub}{dollar} polyoxycations. XRD, and surface area, and pore size measurement data show that additional pillars are introduced into the pillared clay. The data for thermal stability of re-pillared samples indicates improvements in desired properties after re-intercalation, especially for GaAl{dollar}{bsol}sb{lcub}12{rcub}{dollar} re-pillared material. Acidic studies show that the additional pillars introduced by re-pillaring produce more acid sites on pillared clays.; (B) Protamine cations are intercalated into a bentolite-L clay at pH 10.4 by ion-exchange, giving a protamine-pillared clay with a d-spacing of 51 A and producing hydrophobic surfaces. Alkaline phosphatase, which is negatively charged at this pH, is immobilized on both the interlamellar and external surfaces of the pillared clay via electrostatic and hydrophobic mechanisms. The amount of protamine for pretreating the clay is very important for activity retention of the immobilized enzyme. More protamine can attach more enzyme on the surface of the clay, however, too much protamine causes denaturation of the enzyme due to entrapment and uncoiling. The pH profile for the immobilized enzyme is similar to that of free enzyme, except for a little broad region on the acidic side.