Method for preparing a β-hydroxycarboxylic acid ester

A method for preparing a β-hydroxycarboxylic acid ester, comprising the steps of:

• mixing an alkylene oxide, a monohydric alcohol, and a composite catalyst, and
• performing a carbonylation esterification reaction in a carbon monoxide atmosphere to obtain the β-hydroxycarboxylic acid ester;
• wherein the composite catalyst comprises a main catalyst, a cocatalyst, and a reducing agent;
• the main catalyst comprises at least one of a cobalt salt and a cobalt hydroxide;
• the cocatalyst is a nitrogen-containing heterocyclic compound;
• and
• the reducing agent is a base metal wherein the cobalt salt is selected from the group consisting of cobalt fluoride, cobalt chloride, cobalt bromide, cobalt iodide, cobalt acetate, cobalt carbonate, cobalt nitrate, cobalt sulfate, and combinations thereof;
• wherein the nitrogen-containing heterocyclic compound is selected from the group consisting of a pyrazole compound, an imidazole compound, a pyridine compound, and a quinolone compound;
• and wherein the base metal is selected from the group consisting of iron, zinc, manganese, nickel copper, and aluminum.