A method for producing a hydrocarbon material having a reduced nitrogen content involves contacting a nitrogen-containing hydrocarbon feedstock, e.g., crude shale oil, shale oil derived gas oil, mixtures thereof and the like, in at least one reaction zone with a catalyst to polymerize at least a portion of the contained nitrogen compounds, e.g., refractory high boiling nitrogen-containing compounds, and, thereafter, separating, e.g., flashing, the resulting reactor effluent to produce a hydrocarbon material having a reduced nitrogen content relative to the feedstock and effluent. This hydrocarbon material may be advantageously used in hydrocarbon hydrotreating. Also provided is a novel apparatus which can be used to carry out the method of the present invention.