Provided herein are molecular sieve membranes for separating hydrocarbons of a lube feed stock into a permeate and a retentate based on molecular shape. The molecular sieve membranes comprise one or more layers of size-selective catalyst and a porous support comprising a plurality of diffusing gaps. Each layer of size-selective catalyst has a plurality of perpendicular membrane channels and a plurality of opening pores. The porous support is in fluidic communication with the plurality of opening pores to provide a fluidic pathway between the perpendicular membrane channels and the diffusing gaps. Also provided are processes for separating n-paraffins from other hydrocarbons in a lube feed stock using the present molecular sieve membranes.