Method for inhibiting polymerization during the recovery and purification of unsaturated mononitriles
View Patent ↗Economical processes are disclosed for recovery and refining of valuable nitrogen-containing organic compounds formed by catalytic oxidation of least one feed compound selected from the group consisting of propane, propylene, isobutane and isobutylene in the presence of ammonia to produce a gaseous. Processes of the invention include quenching the gaseous reactor effluent with an aqueous quench liquid; forming an aqueous solution comprising the corresponding unsaturated mononitrile, hydrogen cyanide and other organic co-products; and using an integrated sequence of distillations and phase separations to recover for recycle of a useful aqueous liquid, and obtain the desired nitrogen-containing products. According to the invention aqueous solutions are fractionated in an integrated system of multi-stage columns while an effective polymerization inhibiting amount of at least one member of a preselected class of p-phenylenediamine compounds is maintained therein.
1. A process for recovery of at least one of acrylonitrile, methacrylonitrile, acetonitrile, and hydrogen cyanide, formed by catalytic ammoxidation of propane, propylene or isobutylene with ammonia and a gaseous source of dioxygen which process comprises:
providing an aqueous solution comprising acrylonitrile or methacrylonitrile, hydrogen cyanide and other organic co-products;
fractionating the aqueous solution as by distillation in at least a first multi-stage column and a second multi-stage column; and
maintaining within the columns an effective polymerization inhibiting amount consisting of at least one compound represented by the formula:
wherein Ph is a phenylene group, and R 1 and R 2 are the same or different and are hydroxyl free organic alkyl moieties having about 2 to about 10 carbon atoms with the proviso that neither R nor R 2 is a phenyl group.
2. The process according to claim 1 wherein the effective polymerization inhibiting amount is in a range upward from about 50 to about 1000 parts per million parts of unsaturated mononitrile present in the aqueous solution.
3. The process according to claim 2 wherein the organic moieties R 1 and R 2 are members of a group consisting of ethyl, propyl, butyl, hexyl, heptyl, octyl, nonyl and decyl straight and branched-chain hydrocarbon groups.
4. The process according to claim 1 wherein the phenylenediamine compounds are members of a group consisting of N,N′-dialkyl-p-phenylenediamine compounds.
5. The process according to claim 4 wherein the unsaturated mononitrile is acrylonitrile, and the feed compounds are members of a group consisting of propane and propylene.
6. The process according to claim 5 wherein the phenylenediamine compounds are members of a group consisting of N,N′-di-sec-propyl-p-phenylenediamine, N,N′-di-sec-butyl-p-phenylenediamine, N,N′-di-isobutyl-p-phenylenediamine, and N,N′-di-tert-butyl-p-phenylenediamine.
7. The process according to claim 5 wherein the compound is N,N′-di-sec-butyl-p-phenylenediamine.
8. A process for recovery of at least one of acrylonitrile, methacrylonitrile, acetonitrile, and hydrogen cyanide, formed by catalytic ammoxidation of propylene and/or propane with ammonia and a gaseous source of dioxygen which process comprises:
providing an aqueous solution comprising acrylonitrile, hydrogen cyanide and other organic co-products of an ammoxidation reaction of propylene and/or propane with ammonia and a gaseous source of dioxygen;
fractionating the aqueous solution as by distillation in a multi-stage column to obtain a high boiling fraction comprising a major amount of the acrylonitrile in the aqueous solution and a low boiling fraction comprising a major amount of the hydrogen cyanide in the aqueous solution; and
maintaining within the column an effective polymerization inhibiting amount consisting of at least one phenylenediamine compound represented by the formula:
wherein Ph is a phenylene group, and R 1 and R 2 are the same or different and are hydroxyl free and nitroso free organic moieties having about 2 to about 10 carbon atoms with the proviso that neither R 1 nor R 2 is a phenyl group.
9. The process according to claim 8 wherein the organic moieties R 1 and R 2 are members of a group consisting of ethyl, propyl, butyl, hexyl, heptyl, octyl, nonyl and decyl straight and branched chain hydrocarbon groups.
10. The process according to claim 8 wherein the phenylenediamine compounds are members of group consisting of N,N′-di-sec-propyl-p-phenylenediamine, N,N′-di-sec-butyl-p-phenylenediamine, N,N′-di-isobutyl-p-phenylenediamine, and N,N′-di-tert-butyl-p-phenylenediamine.
11. The process according to claim 10 wherein the compound is N,N′-di-sec-butyl-p-phenylenediamine.
12. A process for recovery of at least one of acrylonitrile, methacrylonitrile, acetonitrile, and hydrogen cyanide, formed by catalytic ammoxidation of propylene or propane with ammonia and a gaseous source of dioxygen which process comprises:
providing an aqueous solution comprising acrylonitrile and high boiling organic compounds;
fractionating the aqueous solution as by distillation in a multi-stage column to obtain a high boiling fraction comprising a high boiling fraction comprising essentially all the organic compounds boiling above about 100° C., a sidedraw product stream comprising at least 99 percent by weight of acrylonitrile, and a low boiling fraction substantially free of the high boiling organic compounds; and
maintaining within the column an effective polymerization inhibiting amount consisting of at least one compound represented by the formula:
wherein Ph is a phenylene group, and R 1 and R 2 are the same or different and are hydroxyl free and nitroso free organic moieties having about 2 to about 10 carbon atoms with the proviso that neither R 1 nor R 2 is a phenyl group.
13. The process according to claim 12 wherein the organic moieties R 1 and R 2 are members of a group consisting of ethyl, propyl, butyl, hexyl, heptyl, octyl, nonyl and decyl straight and branched-chain hydrocarbon groups.
14. The process according to claim 12 wherein the phenylenediamine compounds are members of a group consisting of N,N′-di-sec-propyl-p-phenylenediamine, N,N′-di-sec-butyl-p-phenylenediamine, N,N′-di-isobutyl-p-phenylenediamine, and N,N′-di-tert-butyl-p-phenylenediamine.
15. The process according to claim 14 wherein the compound is N,N′-di-sec-butyl-p-phenylenediamine.
16. A process for recovery of at least one of acrylonitrile, methacrylonitrile, acetonitrile, and hydrogen cyanide, formed by catalytic ammoxidation of isobutylene or isobutane with ammonia and a gaseous source of dioxygen which process comprises:
providing an aqueous solution comprising methacrylonitrile, hydrogen cyanide and other organic co-products of an ammoxidation reaction of isobutylene and/or isobutane with ammonia and a gaseous source of dioxygen;
fractionating the aqueous solution as by distillation m a multi-stage column to obtain a high boiling fraction comprising a major amount of the methacrylonitrile in the aqueous solution and a low boiling fraction comprising a major amount of the hydrogen cyanide in the aqueous solution; and
maintaining within the column an effective polymerization inhibiting amount consisting of at least one compound represented by the formula:
wherein Ph is a phenylene group, and R 1 and R 2 are the same or different and are hydroxyl free organic alkyl moieties having about 2 to about 10 carbon atoms with the proviso that neither R 1 nor R 2 is a phenyl group.
17. The process according to claim 16 wherein the phenylenediamine compounds are members of a group consisting of N,N′-di-sec-propyl-p-phenylenediamine, N,N′-di-sec-butyl-p-phenylenediamine, N,N′-di-isobutyl-p-phenylenediamine, and N,N′-di-tert-butyl-p-phenylenediamine.
18. The process according to claim 17 wherein the compound is N,N′-di-sec-butyl-p-phenylenediamine.
19. A process for recovery of at least one of acrylonitrile, methacrylonitrile, acetonitrile, and hydrogen cyanide, which process comprises:
forming a gaseous reaction effluent by ammoxidation of propylene with ammonia and a gaseous source of dioxygen in the presence of a heterogeneous catalyst comprising cobalt;
contacting the gaseous reaction effluent with an aqueous liquid to obtain an aqueous solution comprising acrylonitrile, hydrogen cyanide and other organic co-products;
fractionating the aqueous solution as by distillation in a multi-stage column to obtain a high boiling fraction comprising a major amount of the acrylonitrile in the aqueous solution and a low boiling fraction comprising a major amount of the hydrogen cyanide in the aqueous solution; and
maintaining within the column an effective polymerization inhibiting amount consisting of at least one compound represented by the formula:
wherein Ph is a phenylene group, and R 1 and R 2 are the same or different and are hydroxyl free organic alkyl moieties having about 2 to about 10 carbon atoms with the proviso that neither R 1 nor R 2 is a phenyl group.
20. The process according to claim 19 wherein the phenylenediamine compounds are members of a group consisting of N,N′-di-sec-propyl-p-phenylenediamine, N,N′-di-sec-butyl-p-phenylenediamine, N,N′-di-isobutyl-p-phenylenediamine, and N,N′-di-tert-butyl-p-phenylenediamine.
21. The process according to claim 20 wherein the compound is N,N′-di-sec-butyl-p-phenylenediamine.