Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
319 words
In the process for recovery of butadiene from a hydrocarbon mixture made up predominantly of C 4 hydrocarbons and containing a minor amount of C 5 saturated and unsaturated hydrocarbons, said mixture being obtained as overhead product from an initial fractionation step employed to separate larger quantities of C 5 and higher hydrocarbons from the C 4 hydrocarbon fraction, wherein the hydrocarbon mixture is subject to extractive distillation in the presence of a selective polar solvent and butadiene is separated from the fat solvent bottoms of extractive distillation by sequential flashing and stripping of the fat solvent in low pressure flashing and stripping zones operated at pressures lower than that employed in the extractive distillation to afford vapor products containing predominantly butadiene, a relatively high concentration of C 5 hydrocarbons and a minor amount of polar solvent, followed by compression of the combined overhead vapor products of low pressure flashing and stripping and passage of a portion of the compressed vapor product to a second stripping zone operated at a higher pressure for recovery of butadiene as an overhead product with the remainder of the compressed vapor overhead being recycled as reboiled vapor to the extractive distillation step; the improvement which comprises, a. condensing a portion of the combined vapor overhead product of compression into a liquid stream, b. water washing the condensed liquid stream obtained in step (a) to remove polar solvent therefrom leaving a condensed liquid product containing butadiene and a relatively high concentration of C 5 saturated and unsaturated hydrocarbons which is substantially free of polar solvent, c. returning the condensed liquid product from step (b) substantially free of polar solvent to the initial fractionation step employed to separate larger quantities of C 5 and higher hydrocarbons from the C 4 hydrocarbon fraction whereby C 5 saturated and unsaturated hydrocarbons contained in the condensed liquid are substantially removed from the hydrocarbon mixture passed to extractive distillation.
Claim 2
Dependent Claim
319 words
In the process for recovery of butadiene from a hydrocarbon mixture made up predominantly of C 4 hydrocarbons and containing a minor amount of C 5 saturated and unsaturated hydrocarbons, said mixture being obtained as overhead product from an initial fractionation step employed to separate larger quantities of C 5 and higher hydrocarbons from the C 4 hydrocarbon fraction, wherein the hydrocarbon mixture is subject to extractive distillation in the presence of a selective polar solvent and butadiene is separated from the fat solvent bottoms of extractive distillation by sequential flashing and stripping of the fat solvent in low pressure flashing and stripping zones operated at pressures lower than that employed in the extractive distillation to afford vapor products containing predominantly butadiene, a relatively high concentration of C 5 hydrocarbons and a minor amount of polar solvent, followed by compression of the combined overhead vapor products of low pressure flashing and stripping and passage of a portion of the compressed vapor product to a second stripping zone operated at a higher pressure for recovery of butadiene as an overhead product with the remainder of the compressed vapor overhead being recycled as reboiled vapor to the extractive distillation step; the improvement which comprises, a. condensing a portion of the combined vapor overhead product of compression into a liquid stream, b. water washing the condensed liquid stream obtained in step (a) to remove polar solvent therefrom leaving a condensed liquid product containing butadiene and a relatively high concentration of C 5 saturated and unsaturated hydrocarbons which is substantially free of polar solvent, c. returning the condensed liquid product from step (b) substantially free of polar solvent to the initial fractionation step employed to separate larger quantities of C 5 and higher hydrocarbons from the C 4 hydrocarbon fraction whereby C 5 saturated and unsaturated hydrocarbons contained in the condensed liquid are substantially removed from the hydrocarbon mixture passed to extractive distillation.
Claim 3
Dependent Claim
28 words
The process according to claim 1 wherein the hydrocarbon mixture is obtained as overhead product from an initial fractionation of a butadiene-containing by-product stream from petroleum hydrocarbon pyrolysis.
Claim 4
Dependent Claim
20 words
The process according to claim 2, wherein the hydrocarbon mixture contains up to about 0.5% by weight C 5 hydrocarbons.
Claim 5
Dependent Claim
37 words
The process according to claim 1, wherein the polar solvent is recovered as lean solvent, substantially free of hydrocarbons at the bottom of the low pressure stripping zone and the lean solvent is recycled to extractive distillation.
Claim 6
Dependent Claim
109 words
The process according to claim 4, wherein further solvent recovery is facilitated by passing the overhead product of extractive distillation and a minor portion of the lean solvent recovered at the bottom of the low pressure stripping zone to a solvent recovery system comprising a water washing zone and a distillation zone in which solvent is recovered in admixture with water as a washing zone bottoms product and the washing zone bottoms product is passed to the distillation zone wherein the polar solvent contained therein is concentrated for recycle to extractive distillation, said concentrated polar solvent being removed as an overhead product of distillation and recycled to extractive distillation.
Claim 7
Dependent Claim
39 words
The process according to claim 5, wherein the polar solvent removed by water washing of the condensed liquid product in step (b) is recovered by passing the water washed solvent to the distillation zone of the solvent recovery system.
Claim 8
Dependent Claim
12 words
The process according to claim 1 wherein the polar solvent is acetonitrile.
Claim 9
Dependent Claim
12 words
The process according to claim 6, wherein the polar solvent is acetonitrile.