Abstract: Fouling of equipment used for processing of organic feed streams containing olefinic compounds is controlled by inhibiting polymerization of the olefinic compounds by carrying out the processing in the presence of from about 20 ppb to less than 1000 ppb of a stable free radical, such as a nitroxide.

Abstract: Deposit formation on the interior surfaces of structures confining heated hydrocarbon fluids such as refinery units, particularly preheating stages associated with process units such as distillation units, hydrotreaters and thermal crackers, is inhibited by incorporating in the feed stock a small percentage (usually at least about 0.0005 weight percent) of a macrocyclic polyamine formed by cyclodehydration of reaction products of hydrocarbon substituted succinic anhydrides or carboxylic acids with poly 3-amino propyl compounds or by acylation of macrocyclic polyamine and polycyclic polyamines with hydrocarbon substituted succinic anhydride or carboxylic acids. It is desirable in some instances to dissolve additionally in the hydrocarbon fluid such as a feed stock along with the macrocyclic polyamine an oil-soluble dispersant, antioxidant and mixtures thereof.