Preparation of mesoporous alumina films by anodization: Effect of pretreatments on the aluminum surface and MTBE catalytic oxidation

摘要

Mesoporous materials are both scientifically and technologically important because of the presence of voids of controllable dimensions at atomic, molecular, and nanometric scales. Over the last decade, there has been both an increasing interest and research effort in the synthesis and characterization of these types of materials. The purposes of this work are to study the physical and chemical changes in the properties of mesoporous alumina films produced by anodization in sulphuric acid by different pretreatments on the aluminium surface such as mechanical polishing [MP] and electropolishing [EP]; and to compare their properties such as morphology, structure and catalytic activity with those present in commercial alumina. The morphologic and physical characterizations of the alumina film samples were carried out by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The chemical evaluations were performed by the oxidation of methyl-rert-butyl-ether (MTBE) at 400 deg C under O_2/He oxidizing conditions (Praxair, 2.0 percent O_2/He balance). According to the results, the samples that presented higher activities than those in AI2O3/AI [MP] and commercial alumina in the MTBE oxidation (69 percent ), were those prepared by Al_2O_3/Al [EP]. The average mesoporous diameter was 17 nm, and the morphological shape was equiaxial; thus, that pore distribution was the smallest of all with a homogeneous distribution.