this invention pertains to an improved process for preparing noncyclic polyalkylene polyamine compounds in high selectivity by reacting an alkanolamine and an alkylene amine in the presence of an inert gas and an acidic catalyst . the improvement resides in effecting the reaction under fixed bed catalytic conditions and maintaining the reaction conditions such that a vapor phase condition exists for the reaction mixture comprising both reactants and products . to accomplish the formation of vapor phase conditions sufficient inert gas is injected into the feedstream along with alkanolamine and alkylene amine so that the dew point temperature of the reaction product mix is below the reaction temperature at reaction pressure .