The present invention provides an improved catalytic fast pyrolysis process for increased yield of useful and desirable products, while greatly reducing or eliminating fouling of various critical process lines which are likely to transfer heavy hydrocarbons, aromatics and oxygenates. The process comprises steps including feeding a fluid solvent stream having a Snyder Polarity Index of at least 2.4 to one or more of i) the raw fluid product stream from a catalytic fast pyrolysis process fluidized bed reactor to a first separation system, ii) the fluid product stream from the first separation system to a quench vapor/liquid separation system, iii) the vapor phase stream from the quench vapor/liquid separation system to a product recovery system, and, optionally, to the spent catalyst steam stripping system upstream of the catalyst regeneration system.