Disclosed is a method and reactor system for converting oxygenate and/or olefin contaminants in a methanol to olefin reactor system product effluent to hydrocarbons, including paraffin compounds, preferably over a sulphided catalyst of the type Nickel or Cobalt combined with Molybdenum or Tungsten. In one embodiment, the oxygenate-containing stream to be hydrogenated comprises one or more of the following streams, alone or in combination: a quench tower bottoms stream, a water absorption unit bottoms stream, a C₄+ stream, and/or a C₅+ stream.