Synthesis And Catalysis Properties Of Several Polyoxometalate Catalysts By Low-heating Solid-state Chemical Reaction

Polyoxometalates, one type of well-known polynuclear metal-oxo clusters, have attracted considerable interest for their application in many materials of catalysis, magnetic materials, non-linear optical and antiviral activity owning to their unique structure. The use of room temperature ionic liquids (ILs) as solvent, catalysts, and extractive solvent for chemical reactions offers several advantages from this environmental perspective. They are non-flammable, thermally stable, exhibit negligible vapor pressure (non-volatile), and offer the potential for recyclability. We synthesize a series ionic liquid polyoxometalates (IL-polyoxometalates) for combining the advantages of polyoxometalates with ionic liquids by low-heating solid-state chemical reaction. We study the catalysis properties of the products in the esterification reaction of unitary, binary, tenary and unsaturated carboxylic acid and butanol using polyoxometalates as catalysts. The results demonstrate that IL-polyoxometalates are good catalysts for esterification reaction.Organic esters are important intermediates in chemical and pharmaceutical industries, and they are mostly produced by acid-catalyzed esterification reactions. Various mineral acids, solid super acid and ionic liquids, have been used as catalysts for esterification. However, these acids are extremely corrosive and contaminative and need to be neutralized at the end of the reaction. Furthermore, it is very difficult to separate and reuse the catalysts.The use of propane sulfonate (PS) functionalized IL-polyoxometalates for the esterification reaction is considered to be an effective approach. They could be used as homogeneous catalysts for many esterification reactions because of their good solubility in reaction media, and moreover, at the end of the reaction, the catalysts precipitated and could be recycled without any regeneration being required, just like a heterogeneous system. Thus, these catalysts combine the advantages of homogeneous with heterogeneous catalysis.