Frictional Diffusion (FricDiff) is a separation technology based on differences of diffusivities in a mass-separating sweep gas. Previously, Frictional Diffusion has been applied to the separation of azeotropic mixtures and gas mixtures where the product is on feed side. In this work, the application range is extended by studying hydrogen–hydrocarbon separations. In this case, the target product is obtained on the sweep-side. In contrast to the feed-side product case, it is shown that the purity of a sweep-side product is inherently limited by the ratio of the diffusion coefficients. This limitation can, however, be overcome with a small pressure difference which induces a convective flow superimposing diffusion. Thereby, the purity of product increases from 65% to more than 95%. On the other hand increasing pressure difference decreases the recovery to lower than 40% for the sweep-side product. The positive effect of pressure difference is confirmed by using a single-tube FricDiff unit. A good agreement between experimental and modeling data is observed which suggests the potential of FricDiff for higher purity separations for both feed-side and sweep-side products.