Abstract: A process for producing hyperbranched, dendritic polyglycerol from glycerol comprising the steps of adding in a vessel glycerol and a CaO-based catalyst, flushing an inert gas to the resulting mixture and hermetically closing the reaction vessel, allowing pressure to build up from 1 to 10 bar above atmospheric, and heating the reaction mixture at a reaction temperature of at least 100° C. and below its boiling point. The process further comprising the steps of maintaining the reaction conditions until at least 40 wt. % of glycerol is polycondensed and converted into hyperbranched polyglycerol, with concomitant water formation, and separating the dendritic polyglycerol from other components in the mixture. The calcium based catalyst is nanostructured calcium oxide in the form of a powder of mean particle size smaller than 100 nm measured according to ASTM D4464.