The invention provides a process and a reactor for the preparation of an alkylene glycol from an alkylene oxide. Alkylene oxide, water, a homogeneous carboxylation catalyst and a homogenous hydrolysis catalyst are supplied to a reactor comprising a carboxylation zone and a hydrolysis zone. One or more ejectors are used to mix carbon dioxide and the liquid reagents in the carboxylation zone so that alkylene oxide reacts with carbon dioxide in the presence of water in the carboxylation zone to form a reaction solution comprising alkylene carbonate, water, the homogeneous carboxylation catalyst and the homogeneous hydrolysis catalyst. The reaction solution is supplied from the carboxylation zone to a hydrolysis zone, wherein alkylene carbonate and water react to form a product solution comprising alkylene glycol, the homogeneous carboxylation catalyst and the homogeneous hydrolysis catalyst. Carbon dioxide released by the reaction of alkylene carbonate and water in the hydrolysis zone is supplied to the carboxylation zone. Product solution is withdrawn from the hydrolysis zone.