CA1205768A - Use of morpholine neutralized phosphate and thiophosphate esters as ethylene furnace anti-coking antifoulants - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

An improved method of reducing fouling and corrosion in ethylene cracking furnaces using petroleum feedstocks, comprising treating the petroleum feedstock with at least 10 ppm of a compound chosen from the group consisting of phosphite esters, phosphate esters, thiophosphite esters, thiophosphate esters and mixtures thereof, said esters being characterized by the formulae:

Description

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Weinland, in United States 4,105,540~ describes the use of phosphorus containing compounds as anti-foulants in ethylene cracking furnaces.
Specifically, this Weinland patent, discloses that phosphate and phosphite mono and dlesters in small amounts function as anti-foulant additives in ethylene cracking furnaces which are subjected to elevated temperatures from about 500 - l700F. These furnaces produce material that deposits and accumu-lates upon furnace surfaces including furnace coils and transfer lina exchangers and fouls these surfaces leading inevitably to plant shutdown and expensive maintenance. The anti-foulants of the Weinland patent inhibit and suppress this fouling and also help to clean up previously fouled furnace surfaces.
The invention disclosed in United States 4,1~5,540 is generally described in the following way: -"This invention entails an improved process for reducing the foulingtendencies experienced in ethylene cracking furnaces including the formation of coking and polymer deposition on furnace coils and transfer line exchangers.
The treatm~nt is effective over the temperature range 500 ~ 1700F. which are found in ethylene cracking furnaces.
"The method involves treatment of feed stock with at least 10 ppm and, preferably 25 - 100 ppm of the phosphorus esteranti-foulants described below. In addition, it is preferred that plant equipment surfaces be pretreated with these compounds in the absence of the feed stock. The phosphate ester compounds employed in this invention are characterized by the general formula:

ORl = P -- OR2 \ OR3 3~

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where Rl, R2, and R3 are each individually selected from the gr~up consisting of hydrogen, addition complexes of hydrogen with amines, alkyl, aryl, alkaryl and cycloalkylyl, alkenyl, and aralkyl, and provided that in any given such phosphate ester at least one and not more than two of each of Rl, R2, and R3 are hydrogen or an addition complex of hydrogen with an amine.
"The phosphite ester compounds employed in this invention are characterized by the general formula:

~ OR6 where: R4, R5, andR6 are each individually selected from the group consisting of hydrogen, addition complexes of hydrogen with amines, alkyl~ aryl, alkary] and cycloalkyl, alkenyl, and provided that in any given such phosphite ester at least one and not more than two of each of Rl, R2, and R3 are hydrogen or an addition complex of hydrogen with an amine."
The preferred amine neutralized phosphate and phosphite mono and di esters are neutralized with fatty amines with a preferred amine being the material Primene 81-R, which is described in United States ~,105,5~0 as follows:

"The primary constituent of 'Primene 81-R' is reported to be`:
CH3 CH3 CH~

H3C - Cl CH2 -- C - NH2 CH3 CH3 C~13 "The primary constituent of 'Primene JM-T' is reported to be essen-tially the same structure as 'Primene 81-R,' but with 22 carbons. 'Primena' is a trademark of the Rohm ~ Haas Company for its brand of tertiary alkyl primary amines."

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Experience has shown that the phosphate and phosphite esters des-cribed above which have been neutrali~ed with fat~y ami.nes such as Primene 81-R
when used over prolonged periods of time in ethylene furnaces while providing an~i-.fouling protection do not provide corrosion protection.
It would be a benefit i.f it were possible to provide anti-foulant composi~ions having effectiveness of those described iTI United States 4,105,540 yet would also provide corrosi.on protection when used over prolonged periods of time.
This invention provides an improved method of reducing fouling and corrosion in ethylene cracking furnaces using petroleum feedstocks, which com-prises treating the petroleum feedstock with at least 10 ppm, and preferably 25 - 200 ppm, of a compound chosen from the group consisting of phosphite esters, phosphate esters, thiophosphite esters, thiophosphate esters and mixtures thereof, said esters being represented by Formulae I and II below:
Formula I

/ XRl X = P --XR2 Formula II

RlX --P
\

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In the above formulae, X equals S or O, and Rl, R2, and R3 are each independently selected from the group consisting of hydrogen, moTpholine, alkyl, aryl, alkaryl, cycloalkyl J alkenyl, and aralkyl, provided that at least one, ancl not more than two, of each Rl> R2, and R3 are morpholine. When the term morpholine is used herein and in the claims, it means the morpholine salt group.
Specific examples of compounds falling under the above formulas and which represent preferred species of the invention are the morpholine salts of:
(l) a blend of the mono and di isooctylthiophosphate ester;

(2) a blend of the mono and di isooctylphosphate ester; and

(3) di n-butylphosphite.
A more detailed description of these phosphite, phosphate and thio-phosphate compounds and their methods of manufacture are disclosed in United States 4,105,540~
To illustrate the advantages of the invention, the following are presented by way of Examples.
. .~ .
Pxample ~
A commercial ethylene plant was treated with an organo phosphorus Primene 81~R anti-foulant of United S~ates 4,105,540. The treatment success-fully prevented fouling of the furnace coils and transfer line exchangers.
After several months had passed, evidence of corrosion was observed.
~xample 2 A morpholine neutralized phosphate ester was developed to overcome the potential corrosion problem.
The experimental procedure consisted of placing the compound to be tested along with water and a hea~y aromatic naphtha into a laborato:ry autoclave.

The mixture was heated to 160C and held at that temperature for 6 hours.
Using the above experimental technique, the following morpholine salts were compared against a commercial product of the Weinland patent:
~ 1) a blend of the mono and di isooctylthiophosphate ester;
(2~ a blend of the mono and di isooctylphosphate ester; and (3) di n-butylphosphite.
In all instances, the compositions of the invention substantially reduced corrosion, which corrosion was evidenced when the Weinland products were run.

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Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An improved method of reducing fouling and corrosion in ethylene cracking furnaces using petroleum feedstocks, comprising treating the petroleum feedstock with at least 10 ppm of a compound chosen from the group consisting of phosphite esters, phosphate esters, thiophosphite esters, thiophosphate esters and mixtures thereof, said esters being characterized by the formulas:

and where X equals S or 0, and R1, R2, and R3, are each independently selected from the group consisting of hydrogen, morpholine, alkyl, aryl, alkaryl, cycloaklyl, alkenyl, and aralkyl, provided that in at least one, and not more than two, of each R1, R2, and R3 are morpholine.

2. The method of Claim 1 where the ester is a blend of the mono and di isooctylthiophosphate ester.

3. The method of Claim 1 where the ester is a blend of the mono and di isooctylphosphate ester.

4, The method of Claim 1 where the ester is di n-butylphosphite.

5. The method of Claim 1 where from 25 to 200 ppm of the ester is used.