The present disclosure relates, according to some embodiments, to compositions, apparatus, methods, and systems that may be used to produce polyols, for example, polyether polyols with a narrow range of molecular weights, with little if any unsaturated byproducts, in a sustained and/or continuous reaction, with efficient heat transfer, and/or at high production rates. For example, in some embodiments, teachings of the disclosure may be used to produce polyether polyols in a continuous loop flow process. A continuous loop flow process may be practiced such that heat is effectively transferred and/or product properties (e.g., range of molecular weights) are controllable. For example, a continuous loop flow process may use one or more continuous flow loops comprising a heat exchanger, a means to move material around each loop, inlets for catalyst, monomer, initiator or starter, and an outlet for polyol product.