Motionless mixers are used as internals to improve the behavior of tubular reactors (diam. 40 mm) for homogeneous liq. phase reactions at low Reynolds no. (Re = 0.005-100). Small gradients in temp. or d. normally lead to large stochastic backmixing of the fluid. Such flow perturbations can effectively be suppressed in addn. to a flattening of the flow profile if regularly assembled internals are used. The motionless mixers used are SMX and SMV, CH, the ratios of the effective fluid velocity to the axial dispersion coeff. are .apprx.80 and 70 m-1, resp. [on SciFinder (R)]