Preparation, Structure And Property Of Layered Surface Supported Zirconium Base Solid Acid Catalyst

Esterification of acetic acid with glycol mono alkyl ethers is an important route to obtain glycol mono alkyl ether acetates. The present industrial process for glycol mono alkyl ether acetate production suffers from problems such as corrosion of equipment, separation difficulty and environmental pollution. To eliminate these problems caused by the use of concentrated sulfuric acid as the catalyst, much attention has been paid to the development of solid catalysts. Previous work has indicated that solid acid catalysts show promise as a substitute for the corrosive liquid acid catalysts. In present work, a new kind of layered surface supported zirconium base solid acid catalyst has been prepared. The catalyst shows high catalytic activities, good selectivity and long lifetime for esterification of acetic acid with glycol mono alkyl ethers. The catalyst has been fully characterized, and its structural features has been discussed. This work presents new principles for using solid catalysts as a replacement for H₂SO₄ in esterification, and it has important significance for catalyst theory and application;On the basis of screening catalysts in view of activity, lifetime and selectivity for glycol mono alkyl ether acetate synthesis, the more effective catalytically active component-zirconium sulfate tetrahydrate has been selected, and the optimum reaction conditions were determined. In addition, it was found that the zirconium sulfate tetrahydrate is equally effective for the synthesis of other glycol mono alkyl ether acetates.The zirconium sulfate tetrahydrate has been characterized by XRD, TPDE, TPD and TG-DTA. Results show that it is a layered compound with moderate strength B-acid sites. Its acidic properties are connected with the water of crystallization situated in the interlayers, because the hydrogens of the water of crystallization may be farther from layer than expected due to the strong induction of Zr⁴⁺ and hydrogen bonding with the oxygen of SO₄^2-The intercalation behavior of layered zirconium sulfate tetrahydrate with organic polar molecules has been studied by means of XRD and IR. It was shown that amines with strong basicity such as n-alkylamines (butylamine and propylamine) and pyridine possess high intercalation ability, and can be intercalated directly into the interlayer. With the increase in basicity, the intercalation ability becomes higher, but higher basicities lead to some decomposition of the layers. The XRD results together with estimates of molecular dimensions suggest that a bilayer orientation of amine molecules may be formed. Some small alcohols such as methanol and ethanol possess limited intercalation ability. It was found however that acetic acid and glycol mono ethyl ethers did not readily intercalate with the interlayer region, so that B-acid sites in the interlayer cannot be utilized fully in their esterification reaction.In the synthesis of glycol mono ethyl ether acetate catalyzed by layered zirconium sulfate tetrahydrate, it was found that the water of crystallization was stable and its structure does not change with use, so that the catalyst has a long lifetime. High temperature may however cause loss of the water of crystallization...