Method for inhibiting polymerization during the recovery and purification of unsaturated mononitriles

A process for recovery of valuable nitrogen-containing organic compounds 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 of at least one compound represented by the formula:
• 3
• wherein Ph is a phenylene group, and R1 and R2 are the same or different and are hydroxyl free organic moieties having about 2 to about 10 carbon atoms with the proviso that neither R1 nor R2 is a phenyl group.

A process for recovery of valuable nitrogen-containing organic compounds 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 of at least one phenylenediamine compound represented by the formula:
• 4
• wherein Ph is a phenylene group, and R1 and R2 are the same or different and are hydroxyl free organic moieties having about 2 to about 10 carbon atoms with the proviso that neither R1 nor R2 is a phenyl group.

A process for recovery of valuable nitrogen-containing organic compounds 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 of at least one compound represented by the formula:
• 5
• wherein Ph is a phenylene group, and R1 and R2 are the same or different and are hydroxyl free organic moieties having about 2 to about 10 carbon atoms with the proviso that neither R1 nor R2 is a phenyl group.

A process for recovery of valuable nitrogen-containing organic compounds 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 in 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 of at least one compound represented by the formula:
• 6
• wherein Ph is a phenylene group, and R1 and R2 are the same or different and are hydroxyl free organic moieties having about 2 to about 10 carbon atoms with the proviso that neither R1 nor R2 is a phenyl group.

A process for recovery of valuable nitrogen-containing organic compounds 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 of at least one compound represented by the formula:
• 7
• wherein Ph is a phenylene group, and R1 and R2 are the same or different and are hydroxyl free organic moieties having about 2 to about 10 carbon atoms with the proviso that neither R1 nor R2 is a phenyl group.