US2449585A - Suppression of corrosion in ferrous alloy vessels in the treatment of hydrocarbons - Google Patents

Description

Patented Sept. 21, 1948 ALLOY VESSELS IN HYDROCARBON THE TREATMENT OF Elza Q. Camp, Goose Creek; Ten, assignor; by mcsne assignments,- to Standard Oil Development Company, Elizabeth, N. J a corporation of Delaware, v No Drawing.

The present invention is directed {to a method 1 Application-August 19, 1946, Serial No. 691,655

8 c aims. (01. ne 50') V optionally may be separatel introduced therein whereby hydrocarbons in contact with ayferrous alloy reaction vessel are thermally reacted under non-catalytic conditions and corrosion of the vessel and the deposition. of carbon thereon is stock through ferrous alloy tubes arranged in a turnace so that they would be maintained at high temperatures and the carbon deposition and the corrosion heretofore mentioned take place in the tubes of the furnace; this corrosion and carbon deposition may be so rapid that the process is inoperable or at least not commercially attractive. This rapid corrosion may be encountered even though the tubes are constructed of ferrous alloy, such as the nickel and chromium alloyed with iron commonly known as 18-8 alloy which, under many conditions, is very resistant to corresion.

It is an object of the present invention to react thermally a hydrocarbon feed stock under noncatalytic conditions While suppressing corrosion of the reaction vessel and carbon deposition on the walls thereof.

Other objects and advantages of the present invention will be seen from the following detailed description.

In accordance with the present invention, a hydrocarbon feed stock is thermally reacted in the vapor phase under non-catalytic conditions in a reaction vessel with the hydrocarbon in contact with the ferrous alloy forming the interior wall of the vessel and corrosion of the reaction vessel and formation and deposition of carbon on the walls of the reaction vessel is suppressed by maintaining within the reaction zone a small amount of an organic acid. In conducting the operation, it is preferred to employ a petroleum fraction boiling within the range of 200 to 400 F. as the feed stock and maintain the thermal reaction at a temperature within the range of 900 to1650 F. The organic acid is preferably introduced into the feed stock passed into the reaction vessel but and may be maintained in the reaction zon in amounts extending" over a substantial range but usually 5% is the maximum amount employed. Usually itwill be found that greatei eoncentra tion's donotproduce improved results" over the use or a 4% concentration of said acid.

Th organic acidemployed for inhibiting the corrosion of the ferrous alloy vessel and the product and deposition of carbon Within the reaction mm preferably shouldhave a low. boiling range to insure that it remains in the vapor phase with the hydrocarbon i-eed stock. Preferred examples of low molecular weight organic acid suitable for use in the; practice of the. present invention' are formic. acid,- acetic acid andpropionic acid; however, itmay at times befound desirable to employ other acids or greater molecular weight, such as butyricand. valeric acids. 7 .Theadvantages in the practice of the present invention will be further shown by the following examples. In the first example conditions simulating the prior art were employed and in the subsequent examples the method of the present invention was carried out.

Example I A petroleum fraction boiling within the range of 200 to 400 F. was heated to a temperature of 1450 F. and passed into vapor phase through a reaction vessel constructed of l88 chromiumnickel alloy steel for an interval of 20 hours. The reaction was then terminated and the interior of the reaction vessel examined. It was found that the 18-7-8 alloy had been corroded at a rate of the order of 1 to 2 inches penetration per year and was coated with a. copious quantity of carbon.

Example II A portion of the same feed stock used in Example I was employed and to the feed stock 3% by weight of formic acid was added and the mix- 4 boxylic acid in the feed stock in the reaction zone to suppress corrosion of said vessel.

4. A method in accordance with claim 3 in which the concentration of carboxylic acid in the feed stock is no greater. than 5%.

5. A method for conducting a vapor phase reaction including the steps of contacting a hydro- The advantage of the practice'of the present invention will be obvious. It will be seen that reactions heretofore impossible or commercially unattractive due to the rapid corrosion of the equipment and deposition of the carbon thereon may be conducted in accordance with the'present invention and the corrosion of the reaction vessel suppressed and fouling of the vessel'by the depocarbon feed stock boiling within the range of 200 to 400. F. in the vapor phase and in contact with a ferrous alloy reaction vessel to a temperature within the range of 900 to 1650 F. to cause non=catalytic reaction of the feed stock and maintaining a carboxylic acid in the hydrosition of carbon thereon suppressed or eliminated.

I-Iaving fully described and illustrated the prac tice of the present invention, what I desire to claim as new and useful and to secure by Letters Patent is: a i v 1., A method for treating a hydrocarbon'feed stock comprising the steps of subjecting the feed stock in a vapor phase in contact with a ferrous alloy reaction vessel to a high temperature to cause non-catalytic reaction thereof and maintaining a carboxylic acid in the feed stock while it is in the reaction zoneto suppress corrosion of saidvessel. v

v 2. A method in accordance with claim 1 in which the concentration of the carboxylic acid in the feed stock is no greater than 5%.

3. A method for conducting a vapor phase reaction at elevated temperatures including the steps of subjecting a hydrocarbon feed stock to a temperature within the range of 900 to 1650 F. while it is in contact with a ferrous alloy reaction vessel to cause non-catalytic reaction thereof and maintaining a small amount of carcarbon feed stock in the reaction zone in aconcentration no greater than 5% to suppress corrosion of said vessel.

6. A method in accordance with claim 5 in which the carboxylic acid is acetic acid.

'7. A method in accordance with claim 5 in which the carboxylic acid is formic acid.

8. A method in accordance with claim 5 in which the carboxylic acid is propionic acid] ELZA Q. CAMP.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS