Preparation And Properties Of New Composite Metal Oxide Solid Base Catalyst

The solid base catalyst have been widely used in the transesterification reaction, aldol condensation, oxidation, reduction and other organic reactions due to its high reactivity, easy separation and good reproducibility. With the needs for world's sustainable development and green chemistry, environmentally friendly solid base catalyst has become a hot research.LDHs is a kind of two-dimensional layered nanomaterials, and widely applied in the field of catalysis because of their controllable compositions and lattice orientation effect. It was shown that LDHs and its derivatives are good solid base catalysts due to their surface structures containing rich hydroxyls and basicity. In this paper, novel metal oxide composite catalysts were prepared by thermal decomposition of composite precursors combined LDHs with cyanamid or CNTs, showing that their morphologies, structures and properties are related to precursor composition and organic support content.1. The MgFe-CH2N2-LDH precursors were prepared by a very rapid mixing and nucleation process in a colloid mill, after calcination a series of magnetic nanorod catalysts were obtained and applied to transesterification of tributyrin with methanol. The relationship between the structures and catalytic performances of the as-prepared samples has been investigated by means of XRD, CO2-TPD, in situ FTIR, XPS and HRTEM. The results are as follows:(1) MgFe2O4/MgO composite catalysts exhibit stronger basic and better catalytic performances compared with single MgFe2O4 or MgO species because there is a strong interaction between appropriate amount of MgFe2O4 and MgO species. (2) Their properties and crystal morphologies are relative to the amount of cyanamid, in which moderate cyanamid is favorable to formation of rod-like crystals of MgFe2O4 and increases strong base sites and catalytic performance. The as-prepared catalysts have good stability, which catalytic performances did not significantly change after five times recycle.2. Calcium-based solid base catalysts were prepared by ultrasound-assisted method through combination of CaAl-LDHs with the covalent modification CNTs, and used to the self-condensation reaction of 2,5-hexanedione. The relationship between the structures and catalytic performances of the as-prepared samples has been investigated by means of XRD, CO2-TPD, in situ FTIR, XPS and TEM. The results show that the covalent modification CNTs have more acidic groups and easily interact with the basic site of oxide, which led to the formation of some Bronsted base, so as to enhance catalytic performance for self-condensation reaction of 2,5-hexanedione. The catalyst has good stability, which catalytic performances did not obviously alter after five times recycle.