Nalco/exxon Energy Chemicals,l.p.

C Tom Rowe

Michael K Poindexter

Youdong Tong

Aromatic compounds in small amounts function as antifoulant additives in pyrolysis furnaces which are subjected to elevated temperatures from about 500.degree. C. to about 1200.degree. C. when thermally convening hydrocarbons to ethylene as well as other useful products. These furnaces produce material that deposits and accumulates upon furnace surfaces including furnace radiant coils and transfer line exchangers. The present antifoulant additives inhibit and suppress the formation and deposition of material on furnace surfaces. The present invention is a method for inhibiting the formation of coke on the surfaces of a radiant heating section of a pyrolysis furnace and the surfaces immediately downstream of such section in contact with a hydrocarbon feedstock which comprises decoking the pyrolysis furnace, and prior to processing the hydrocarbon feedstock, adding an inhibiting compound to the pyrolysis furnace. The inhibiting compound is selected from the group consisting of substituted benzenes, substituted naphthalenes, substituted anthracenes, substituted phenanthrenes, and mixtures thereof wherein the inhibiting compound contains at least one substitutent having at least 2 carbon atoms. A thin catalytically inactive coke layer is formed on the surfaces of the pyrolysis furnace. The hydrocarbon feedstock is then fed into the furnace, whereby the surfaces of the furnace are inhibited against the formation of a catalytically active coke during the processing of the hydrocarbon feedstock.

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Missouri City, TX, United States of America

C Tom Rowe