Organophosphorous antifoulants in hydrodesulfurization

Claim 1

In a method for reducing fouling of surfaces contacted with hydrodesulfurization feedstocks during hydrodesulfurization thereof without adversely affecting hydrodesulfurization catalysts, said hydrodesulfurization comprising a successive series of continuously practiced steps including: A. heating a hydrodesulfurization feedstock to a temperature in the range from about 200° to 700° F, B. admixing with said feedstock a source of hydrogen gas so as to produce a product mixture initially comprised of from about 0.1 to 1.0 parts by weight of hydrogen per 100 parts by weight of said feedstock, C. subjecting said mixture simultaneously to a pressure of from about 400 to 500 psig and a temperature in the range from about 650° to 700° F, while contacting said mixture with a hydrodesulfurization catalyst, D. exposing the product system to a least one flashing zone such that the pressure thereof is reduced to a value ranging from about 10 to 50 psig and separating the resulting gas phase from the resulting liquid phase, and E. fractionally distilling said resulting liquid phase using an initial liquid phase temperature from about 200° to 350° F and maintaining during such distillation pressure in the range from about 10 to 50 psig, thereby to remove from said resulting liquid phase lower boiling fractions developed during step (C) above, the improvement which comprises the steps of: a. admixing at least one material selected from the group consisting of said hydrodesulfurization feedstock, said mixture, said product system, and said liquid phase, a small amount of at least one additive preceding at least one of the respective said processing steps in said series designated above as (A) through (E) and thereafter b. subjecting said resulting mixture to the remaining successive process steps in said series, said additive being at least one compound selected from the group consisting of phosphate esters, thiophosphate esters, phosphite esters, and thiophosphite esters, said phosphate esters and said thiophosphate esters being characterized by the general formula ##STR8## where: X is sulfur or oxygen R 1 , r 2 , and R 3 are each independently selected from the group consisting of hydrogen, and addition complex of hydrogen with an amine, alkyl, aryl, alkaryl, cycloalkyl, alkenyl, and aralkyl provided that in any given such phosphate ester at least one and not more than two of each of R 1 , R 2 and R 3 are hydrogen or an addition complex of hydrogen with an amine, and said phosphite esters and said thiophosphite esters being characterized by the general formula ##STR9## where: X is sulfur or oxygen R 4 , r 5 , and R 6 are each independently selected from the group consisting of hydrogen, an addition complex of hydrogen with an amine, alkyl, aryl, alkaryl, cycloalkyl, alkenyl, and aralkyl, provided that in any given such phosphite ester at least one and not more than two of each of R 4 , R 5 , and R 6 are each hydrogen or an addition complex of hydrogen with an amine.