TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The carbonyl-containing component is selected from one or several of carboxylic acid species, aldehyde species, and/or ketone species. The carboxylic acid is 1-20C carboxylic acid, optionally having branched or cyclic structure; selected from formic acid, acetic acid, propionic acid, butyric acid, pentanoic acid, hexanoic acid, heptanoic acid, and octanoic acid, and/or their branched chain, aromatic, or cyclic derivative. The alcohol is selected from aliphatic alcohol, unsaturated alcohol, aryl-substituted aliphatic alcohol, amino-alcohol, diol, triol, and/or polyol; or a phenolic compound. The aliphatic alcohol is 1-20C aliphatic alcohol, which is primary alcohol, secondary alcohol, tertiary alcohol, or may contain branched or cyclic structure; selected from methanol, ethanol, 1-propanol, 2-propanol, 2-chloro-1-propanol, 1-chloro-2-propanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, 1-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2,2-dimethyl-1-propanol, cyclopentanol, 1-hexanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 4-methyl-1-pentanol, 2,2-dimethyl-1-butanol, 2,3-dimethyl-1- butanol, 3,3-dimethyl-1-butanol, 2-ethyl-1-butanol, 3-ethyl-1-butanol, cyclohexanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, 1-decanol, 2-decanol, 1-dodecanol, 2-dodecanol, 1- tetradecanol, 2-tetradecanol, 1-hexadecanol, 2-hexadecanol, 1-octadecanol, and/or 2-octadecanol. The alcohol comprising the phenolic compound has 1-5 condensed aromatic rings, and is selected from phenol, napthol, 1-hydroxyanthracene, 2-hydroxyanthracene, 1,4-dihydroxyanthracene, 1-hydroxyphenanthrene, 1-hydroxypyrene, hydroxybenzopyrene, hydroxypentacene, hydroxynaphtacene, and/or hydroxychrysene. The amine is selected from alkyl amino, dialkyl amino, arylamino, diarylamino, alkylarylamino, alkylaminoaryl, arylaminoalkyl, and/or alkaminoalkyl. Preferred Process: In the process (P1), when the pyrolysis oil vapor is treated with atomized alcohol, the condensation reaction is an esterification, and the reaction product is an ester; or when the pyrolysis oil vapor is treated with atomized amine, the reaction product is an amide. The condensation reaction proceeds in the absence of a catalyst, or the process further involves delivering a homogeneous acid catalyst to the reactive condensation unit. The conditions allowing the esterification reaction between the carbonyl-containing component and the alcohol in the absence of a catalyst comprise reaction time of 40-70 seconds and 110-130 degrees C. The process involves generating pyrolysis oil product by: pyrolyzing a biomass to generate a heated pyrolysis oil vapor comprising at least one carbonyl-containing component; delivering the pyrolysis oil vapor to a reactive condensation unit, delivering the atomized alcohol or amine to the reactive condensation unit to form a reaction mix comprising the pyrolysis oil vapor and the atomized alcohol or amine; maintaining the reaction mix under conditions suitable for generating at least one condensation reaction product in the absence of a catalyst; and condensing the pyrolysis oil vapor and the at least one condensation reaction product to form a pyrolysis oil product having an increased ester or amide content and increased stability when compared to a condensed pyrolysis oil product not treated with the atomized alcohol or amine. The reactive condensation unit further comprises a heterogeneous acid catalyst bed. The pyrolysis unit further comprises a conveyor system disposed within the pyrolysis unit for continual passage of biomass through the pyrolysis unit. EXAMPLE - No suitable example given.