Chromatographic analysis of hydrocarbon mixtures

Claim 2

A process for the gas-liquid chromatographic analysis of a hydrocarbon mixture containing paraffins, olefins and aromatics which comprises: (a) passing a first vaporized sample comprising a hydrocarbon mixture containing paraffins, olefins and aromatics and a mobile gas phase in contact with an amount of N,N-bis(2-cyanoethyl)formamide effective to reversibly absorb the aromatics from said first vaporized sample producing a second vaporized sample comprising paraffins, olefins and the mobile gas phase, (b) chromotographically separating a portion of the second vaporized sample by passing said portion through a first gas-liquid chromatographic column, said column effective for chromatographically separating paraffins and olefins, (c) passing said chromatographically separated portion of the second vaporized sample in contact with a flame ionization detector to produce a chromatogram of said paraffins and olefins, (d) desorbing the aromatics from said formamide by contacting said formamide with a mobile gas phase to provide a third vaporized sample comprising aromatics and the mobile gas phase, (e) chromatographically separating the third vaporized sample by passing said third sample through a second gas-liquid chromatographic column, said column effective for chromatographically separating aromatics, (f) passing said chromatographically separated third vaporized sample in contact with the flame ionization detector to produce a chromatogram of said aromatics, (g) passing a second portion of said second vaporized sample in contact with an amount of sulfuric acid effective to irreversibly absorb the olefins from said second vaporized sample producing a fourth vaporized sample comprising paraffins and the mobile gas phase, (h) chromatographically separating the fourth vaporized sample by passing said fourth sample through a third gas-liquid chromatographic column effective for chromatographically separating paraffins, and (i) passing said chromatographically separated fourth vaporized sample in contact with the flame ionization detector to produce a chromatogram of said paraffins.

Claim 3

A process according to claim 1 wherein the mobile gas phase is helium.

Claim 4

A process according to claim 1 wherein the first, second, and third gas-liquid chromatographic columns are wall coated open tubular columns, said coating comprising squalane.

Claim 5

A process according to claim 3 wherein the first chromatographic column also serves as the third chromatographic column.

Claim 6

A process according to claim 1 wherein the N,N-bis(2-cyanoethyl)formamide is dispersed on an inert support.

Claim 7

A process according to claim 1 wherein the sulfuric acid is dispersed on an inert support.

Claim 8

A process according to claim 1 wherein the hydrocarbon mixture is a gasoline containing up to at least C 13 hydrocarbons.

Claim 9

A process according to claim 1 wherein steps (a) and (d) are each conducted at a temperature of 95°-115° C., steps (b), (e) and (h) are each conducted at a programmed temperature in the range of -20° to +100° C., and step (g) is conducted at a temperature of 100° C.±5° C.

Claim 10

A process according to claim 1 wherein the desorption of step (d) is effected with a reverse flow of the mobile gas phase.

Claim 11

In the analysis of a hydrocarbon mixture containing paraffins, olefins and aromatics by gas-liquid chromatographic analysis of the type wherein the several types of hydrocarbons are separated by reversible or irreversible absorption, adsorption or chemical reaction and the effluent therefrom is chromatographically separated in a gas-liquid chromatographic column and analyzed, the improvement which comprises: (a) passing a vaporized sample of a hydrocarbon mixture comprising paraffins, olefins and aromatics in contact with an amount of N,N-bis-(2-cyanoethyl)formamide effective to reversibly absorb the aromatics from said mixture to product a first effluent comprising paraffins and olefins, and (b) passing a portion of the first effluent in contact with an amount of sulfuric acid effective to irreversibly absorb the olefins from the first effluent to produce a second effluent comprising paraffins.

Claim 12

In the analysis of a hydrocarbon mixture containing paraffins, olefins and aromatics by gas-liquid chromatographic analysis of the type wherein the several types of hydrocarbons are separated by reversible or irreversible absorption, adsorption or chemical reaction and the effluent therefrom is chromatographically separated in a gas-liquid chromatographic column and analyzed, the improvement which comprises: (a) passing a vaporized sample of a hydrocarbon mixture comprising paraffins, olefins and aromatics in contact with an amount of N,N-bis-(2-cyanoethyl)formamide effective to reversibly absorb the aromatics from said mixture to product a first effluent comprising paraffins and olefins, and (b) passing a portion of the first effluent in contact with an amount of sulfuric acid effective to irreversibly absorb the olefins from the first effluent to produce a second effluent comprising paraffins.

Claim 13

The improvement according to claim 10 including the following additional step: (c) desorbing the aromatics from the formamide by contacting said formamide with a reverse flow of an inert gas to produce a third effluent comprising aromatics.

Claim 14

The improvement according to claim 10 wherein step (a) is conducted at a temperature of 95°-115° C. and step (b) is conducted at a temperature of 100°±5° C.

Claim 15

The improvement according to claim 11 wherein step (c) is conducted at a temperature of 95°-115° C.

Claim 16

A gas-liquid chromatographic apparatus for analyzing the paraffinic, olefinic and aromatic composition of hydrocarbon mixtures comprising: (a) means for transporting a first vaporized sample comprising a hydrocarbon mixture comprising paraffins, olefins, and aromatics and a mobile gas phase to a first absorbing means, (b) a first absorbing means for reversibly absorbing aromatic compounds from said first vaporized sample to produce a second vaporized sample comprising paraffins and olefins, said first absorbing means comprising an amount of N,N-bis(2-cyanoethyl)formamide effective to reversibly absorb aromatic compounds, (c) means for transporting a portion of said second vaporized sample to a first chromatographic separation means, (d) a first gas-liquid chromatographic separation means for chromatographically separating paraffins and olefins, (e) detection means for detecting chromatographically separated paraffins, olefins and/or aromatics, and producing a chromatogram, (f) means for transporting chromatographically separated paraffins and olefins from said first chromatographic separation means to said detection means, (g) means for desorbing aromatic compounds from said first absorbing means to produce a third vaporized sample comprising aromatics and transporting said third vaporized sample to a second chromatographic separation means, (h) a second gas-liquid chromatographic separation means for chromatographically separating aromatics, (i) means for transporting chromatographically separated aromatics from said second chromatographic separation means to said detection means, (j) means for transporting a second portion of said second vaporized sample to a second absorbing means, (k) a second absorbing means for irreversibly absorbing olefins from a portion of the second vaporized sample to produce a fourth vaporized sample comprising paraffins, said second absorbing means comprising an amount of sulfuric acid effective to irreversibly absorb olefins, (l) means for transporting said fourth vaporized sample from said second absorbing means to a third chromatographic separation means, (m) a third gas-liquid chromatographic separation means for chromatographically separating paraffins, and (n) means for transporting chromatographically separated paraffins from said third chromatographic separation means to said detection means.

Claim 17

A gas-liquid chromatographic apparatus for analyzing the paraffinic, olefinic and aromatic composition of hydrocarbon mixtures comprising: (a) means for transporting a first vaporized sample comprising a hydrocarbon mixture comprising paraffins, olefins, and aromatics and a mobile gas phase to a first absorbing means, (b) a first absorbing means for reversibly absorbing aromatic compounds from said first vaporized sample to produce a second vaporized sample comprising paraffins and olefins, said first absorbing means comprising an amount of N,N-bis(2-cyanoethyl)formamide effective to reversibly absorb aromatic compounds, (c) means for transporting a portion of said second vaporized sample to a first chromatographic separation means, (d) a first gas-liquid chromatographic separation means for chromatographically separating paraffins and olefins, (e) detection means for detecting chromatographically separated paraffins, olefins and/or aromatics, and producing a chromatogram, (f) means for transporting chromatographically separated paraffins and olefins from said first chromatographic separation means to said detection means, (g) means for desorbing aromatic compounds from said first absorbing means to produce a third vaporized sample comprising aromatics and transporting said third vaporized sample to a second chromatographic separation means, (h) a second gas-liquid chromatographic separation means for chromatographically separating aromatics, (i) means for transporting chromatographically separated aromatics from said second chromatographic separation means to said detection means, (j) means for transporting a second portion of said second vaporized sample to a second absorbing means, (k) a second absorbing means for irreversibly absorbing olefins from a portion of the second vaporized sample to produce a fourth vaporized sample comprising paraffins, said second absorbing means comprising an amount of sulfuric acid effective to irreversibly absorb olefins, (l) means for transporting said fourth vaporized sample from said second absorbing means to a third chromatographic separation means, (m) a third gas-liquid chromatographic separation means for chromatographically separating paraffins, and (n) means for transporting chromatographically separated paraffins from said third chromatographic separation means to said detection means.

Claim 18

An apparatus according to claim 14 wherein the first, second and third gas-liquid chromatographic separation means each comprises a wall coated open tubular column, said coating comprising squalane.

Claim 19

An apparatus according to claim 15 wherein the first chromatographic means also serves as the third chromatographic means and the transporting means of element (f) also serves as the transporting means of element (n).

Claim 20

An apparatus according to claim 14 wherein the detection means comprises a flame ionization detector.

Claim 21

An apparatus according to claim 14 wherein the N,N-bis(2-cyanoethyl)formamide of the first absorbing means is dispersed on an inert support of diatomaceous earth.

Claim 22

An apparatus according to claim 14 wherein the sulfuric acid of the second absorbing means is dispersed on an inert support of diatomaceous earth and comprises about 40% of the combined weight of said acid and said support.

Claim 23

An apparatus according to claim 14 including the following: (o) means to maintain the first absorbing means at a temperature of 95°-115° C., (p) means to provide a programmed temperature in the range of -20 to +100° C. for the first, second and third chromatographic separation means, and (g) means to maintain the second absorbing means at a temperature of 100° C.±5° C.