US3394582A - Chromatographic analysis - Google Patents

Description

July 30, 1968 5.1.. MUNRO ETAL 3,394,582

CHROMATOGRAPHIC ANALYSIS Filed Oct. Z50. 1964 m E @v E m mY. w. mokomo TRLv o NNI-R T WUEM T WMS .f A LJR BNG. Y B jm@ s MEQ v l Nm 1mOZ U W O mw @v D v W dv? LH m vm @N SE o w mmotwz Y United States Patent O 3,394,582 CHROMATOGRAPHIC ANALYSIS Bradley L. Munro, Newton J. Sellars, and George R. Harvey, Jr., Bartlesville, Okla., assignors to Phillips Petroleum Company, a corporation of Delaware Filed Oct. 30, 1964, Ser. No. 407,805 7 Claims. (Cl. 73-23.1)

ABSTRACT or THE DISCLOSURE Normally vaporous components in a pressurized liquid stream containing normally vaporous and normally liquid components are analyzed by obtaining a liquid sample in a sample loop, passing a carrier gas through the sample loop to iiush the sample components therefrom and vapor- .fizing only the normally vaporous components, removing the liquid components from the stream by sorption, and then passing the vaporous components to a chromatographic analysis zone.

This invention relates to an improved method and apparatus for the chromatographic analysis of fluids. In another aspect, this inventon relates to a method and apparatus for the chromatographic analysis of a relatively light, or more volatile, fluid fraction in the presence of a relatively heavy, or less volatile, fluid fraction.

A conventional method for the determination of theV concentration of constituents in a fluid mixture involves the use of a chromatographic analyzer. In chromatography, a sample of material to be analyzed is introduced into a column containing the selective sorbent of partitioning material. A carrier gas is directed into the column so as to force the sample material therethrough. The selective sorbent, or partitioning material, tends to hold the constituents of the material. This results in the several constituents of the tluid mixture flowing through the column at diiierent rates of speed, depending upon their a'linities for the packing or partitioning material. The column eliiuent thus consists initially of the carrier gas alone, the individual constituents of the fluid mixture appearing later at spaced time intervals. A conventional method for detecting the presence and concentration of these constituents is to compare the thermal conductivity of the column eiiiuent gas with the thermal conductivity of the carrier gas directed to the column.

Conventionally, in the operation of a chromatographic analyzer, the sample iiuid mixture is introduced into a chromatographic column as a vapor representative of the iiuid mixture. The conventional vaporous chromatographic method of analysis cannot be applied effectively to the analysis of relatively light constituents contained in relatively heavy liquids as heating the sample mixture to the analysis temperature, preparatory to the introduction of the sample into the column, results in the premature separation of the light constituents for the heavier liquid in the sample valve. Particular difficulty is encountered when attempting to analyze vapors present in liquids maintained under high pressure.

Conventionally, in the analysis of vapors contained in liquids under high pressure, the liquid mixture is flashed to atmospheric pressure. The rate or volume of both ashed vapors and remaining liquid is determined and the vaporized portion and remaining liquid both separately analyzed. From these determinations, the original composition of the sample fluid mixture is determined.

Accordingly, an object of our invention is to provide an 3,394,582 Patented July 30, 1968 ice improved chromatographic method of analysis and apparatus therefor.

Another object of our invention is to provide an irnproved chromatographic method and apparatus for the analysis of a relatively light, or more volatile, uid fraction in the presence of a relatively heavy, or less volatile, liquid fraction.

Another object of our invention is to provide a chromatographic method and apparatus for the analysis of vapors maintained in a liquid under pressure.

Other objects, advantages and features of our invention will be readily apparent to those skilled in the art from the following description, the drawing and appended claims.

By our invention, we have provided a chromatographic method and apparatus wherein the pressure of a sample liquid is :increased and the sample liquid is introduced into a iirst chromatographic zone maintained at an elevated temperature; the vaporous eliiuent comprising a portion of the sample liquid is passed from the first chromatographic zone to a second chromatographic zone; the presence and concentration of the constituents of the eiiiuent passed from the rst chromatographic zone to the second chromatographic zone is determined by analysis of the eiiiuent from the second chromatographic zone; the .rst chromatographic zone is backflushed with a liquid; and then both the iirst and second chromatographic zones are backiiushed 'with a gaseous stream.

In a second embodiment of our invention, a sample uid mixture comprised at least in part of a liquid is introduced into a irst chromatographic zone maintained at an elevated temperature; the varporous eii'luent comprising a portion of the sample mixture is passed from the first chromatographic zone to a second chromatographic zone; the presence and concentration of constituents present in the eliiuent passed from the iirst chromatographic zone to the second chromatographic zone is determined by analysis of the second chromatographic zone eiil-uent; the first chromatographic zone is backilushed with a liquid; and then both the irst and second chromatographic zones are backiiushed with a gaseous stream.

The invention is applicable to the analysis of a light vaporizable fraction of a liquid mixture wherein the entire liquid mixture cannot readily be vaporized and maintained in the vaporous state while subjecting the vaporized liquid to chromatographic analysis. The invention is particularly applicable to the analysis of normally vaporous hydrocarbons contained within normally liquid hydrocarbons under elevated pressures. The invention will hereinafter be described as applied to the analysis of relatively light readily-vaporizable hydrocarbons present in mineral seal oil at an elevated pressure. It will be understood by those skilled in the art that the invention is not limited thereto, but is generally applicable to the analysis of vaporizable fractions of a liquid mixture.

FIGURE 1 is a schematic representation of one embodiment of the invention with valves 31 and 32 maintained in a first position.

FIGURE 2 is a schematic representation of the said irst embodiment 0f our invention with 31 and 32 maintained in a second position.

FIGURE 3 is a schematic representation of said iirst embodiment of our invention with valves 31 and 32 maintained in a third position.

Referring to FIGURE l of the drawings, a sample mixture comprising C1C6 hydrocarbons and mineral seal oil is passed via conduit means 10 to a conventional densitometer 11 and from densitometer 11 via conduit means 12, and valve means 13 to a Jerguson gauge 14. Initially during the introduction of the sample mixture into Jerguson gauge 14, valves 17 and 25 are maintained in the closed position. It is understood by those skilled in the art that the positioning of valves ,17, and other valve means hereinafter described can be controlled by conventional timing mechanisms known and generally used in the art of chromatographic analysis.

A sample mixture is introduced into Ierguson gauge 14, passed from Jertguson gauge 14 via conduit means 21, and llashed across valve 22. The sample inlet -conduit means and the Jerguson gauge 14 are cooled to prevent premature ashing of the sample mixture. After a sufficient period of time to insure the attainment of a representative sample within Ierguson gauge 14, the sample mixture within Ierguson gauge :14 is blocked in by closing valves 13 anid 22. The presence of a uniform sample mixture in Ierguson gauge 14 is indicated by a constant reading on the in line densitometer 11.

The Ipressure on the sample mixture in Jerguson gauge 14 is raised so that the sample mixture will not prematurely flash, when in a subsequent step it is sent through a heated sample valve as hereinafter described. The pressure on the sample mixture is raised by pressuring the top of Jerguson gauge 18 with a pressure regulated gas passed via conduit means 24, 19 and valve means 26 lfrom gas cylinder 23 at the elevated pressure to Jerguson gauge 18. Jerguson gauge 18 and interconnecting conduit 16 is filled with mercury. Valves 17 and 25 are then opened, thus sending a sample mixture at an increased pressure through conduit 27 to a sample valve 28.

Chromatographic columns 36, 40, valves 25, 28, 30, 31, 32, detector 44 and attendant conduit means are positioned within zone 55 hereinafter referred to as the analysis zone. The pressurized sample mixture is introduced via conduit means 27 and valve means 25 to sample valve 28. Sample valve 28 can comprise a conventional chromatographic analyzer sample valve, such as the slide valve described in U.S. Patent No. 2,846,121. The sample mixture is vented from valve 28 via conduit means 29 and valve means 30.

A carrier gas such as helium is transmitted via conduit means 47 to a multi-port, multi-conduit valve 32. A suitable multi-port valve means is described in U.S. Patent No. 3,111,849. The carrier gas is transmitted through valve means 32 via conduit 4S and from valve means 32 via conduit means 49 to a multi-port, multi-conduit valve 31. Valve 31 can be a valve means such as valve means 32. The carrier gas is transmitted from valve means 31 via conduit means 53 and conduit means 33 to sample valve 28.

Sample valve 28 is maintained at an elevated temperature, said elevated temperature the temperature of hereinafter described chromatographic column 36. As illustrate-d in FIGURE 1, the pressurized sample mixture at an elevated temperature is injected into the carrier gas stream flowing through sample valve 28 via conduit means 33 and 34.

The carrier gas containing the sample mixture is passed via conduit means '34 to a chromatographic column 36 containing a suitable packing material such as ire brick. Column 36 is maintained at a constant elevated temperature. The mineral seal oil liquid contained in the carrier gas passed to column 36 is retained by the re brick packing within column 36.

A vaporous eluent comprising carrier gas and C1-C6 hydrocarbons is passed via conduit means 37 to valve means 31 and from valve means 31 to chromatographic column via conduit means 38 and 39. Column 40 contains a suitable packing material capable of selectively retarding the flow of Cl-C hydrocarbons therethrough. A suitable packing material comprises 10 Weight percent bis(2methoxyethyl) phthalate on Chromosorb, a packing material distributed by Johns-Manville Products Corp., Celite Division, 22 E. 40th St., New York, N.Y.

' The vaporous effluent from chromatographic column 40 is passed via conduit means 41, conduit means 42 within valve means 32, and conduit means 43 to a conventional `detector adapted to measure a property of the fluid mixture directed thereto, which property is representative of the composition of the uid mixture. Detector 44 can advantageously comprise a thermal conductivity analyzer which includes a temperature sensitive resistance element disposed in the path of fluid flow. A reference element, not shown, can be disclosed in the carrier gas llow. Suc-h a detector provides signals representative of the difference in thermal conductivity between the column eluent and the carrier gas. The temperature differences between the resistance elements can =be measured by an electrical bridge circuit, such as a Wheatstone bridge, for example. However, detector 44 lcan also be any other type of apparatus known in the art for measuring a property of a gaseous stream. Refractometers, radiation absorption analyzers and conductivity cells are examples of such apparatus. The effluent from detector 44 is vented via conduit means 46.

As illustrated in FIGURE 1, the pressure of the sample mixture was increased to prevent premature flashing of a portion of the sample `mixture in sample valve 28 prior to injection of sample into the carrier gas stream. Thus, it can readily be seen that should sample valve 28 be maintained at a temperature that would not cause flash vaporization of a portion of the sample mixture within the valve, it would not be necessary to increase the pressure of the sample mixture and the sample mixture could thus be introduced directly into the carrier gas stream.

After completion of the analysis steps described in the description of FIGURE 1, valves 31 and 32 are positioned as illustrated in FIGURE 2 and columns 36 and 40 are backushe-d as hereinafter described. Referring to FIG- URE 2, a liquid solvent capable of removing the mineral seal oil from the packing material within column 36 is passed via conduit means 50 and valve means 51 to valve means 31. The particular solvent employed is one that is capable of removing that portion of the sample mixture retained in column 36 and one that can in turn be separated from the packing material in column 36 by a 'gaseous stream in a subsequent drying step. Suitable solvents include the light hydrocarbons containing C-Cm carbon atoms per molecule. The liquid solvent s passed from valve 31 via conduit means 37 to a downstream region of chromatographic column 36 and through chromatographic column 36 in a backushing step. The solvent containing the mineral seal oil is removed from chromatographic column 36 via conduit means 34 and vented via sample valve means 28, conduit means 33, conduit means 57 in valve means 31, and conduit means 56.

Chromatographic column 40 is backushed with a gaseous stream, preferably the carrier gas, passed via conduit means 47, conduit means 60 within valve means 32, and conduit means 41 to the downstream region of chromatographic column 40. The gaseous stream is withdrawn from chromatographic column 40 via conduit means 39 and passed to detector 44 via conduit means 59 in valve means 31, conduit means 49, conduit means 62 within valve means 32, conduit means 54, conduit means 61 within valve means 32, and conduit means 43. By backushing column 40 in the 4described manner, column 40 is flushed of any Cq-ifraction retained in column 40.

Valves 31 and 32 are then positioned as illustrated in FIGURE 3 and columns 36 and 40 backflushed with a gaseous stream passed to the said columns as hereinafter described. A gaseous stream, preferably the carrier gas employed, is passed |via conduit means 47 to valve means 32 and to the downstream region of chromatographic column 40 via conduit means 60 within valve means 32, and conduit means 41. The gaseous stream is passed from column 40 via conduit means 39, conduit means 38 within valve means 31 and conduit means 37 to the downstream region of chromatographic column 36.

The gaseous stream is passed from chromatographic column 36 via conduit means 34, Ivalve means 28, conduit means 33, con-duit means 53 within valve means 31, conduit means 49, conduit means 62 within valve means 32, conduit means 54, conduit means 61 within valve means 32 and conduit means 43 to detector 44. The gaseuos stream is withdrawn from detector 44 via conduit means 46.

In the backilushed position, as illustrated in FIGURES 2 and 3, columns 36 and 40 are backflushed with a gaseous stream until a stable base line is achieved as noted by detector 44.

In a specific embodiment of the invention, chromatographic column 36 is 10 inches in length and contains fire brick as a packing material and chromatographic column 40 is a 40-foot long column containing a packing material comprising weight percent bis(2-methoxy ethyl) phthalate on Chromosorb. Columns 36 and 40 are maintained at 104 F. A sample mixture comprising mineral seal oil and Cl--C` hydrocarbons is introduced via conduit means 10 to densitometer 11 at 950 p.s.i.g. The pressure of the sample mixture is elevated to 1100 p.s.i.g. by the passage of gas from gas cylinder 23 in the previously described manner. A 2-microliter liquid sample of the sample mixture is injected by valve 28 into the carrier gas stream. Helium is employed as the carrier gas and the backilushing gas. n-Heptane is employed as the solvent passed to column 36 in the backilushing step.

By our invention, we have provided a chromatographic method of analysis wherein a relatively light vaporizable fraction can be analyzed in the presence of a relatively heavy involatile fraction. We have further by our invention provided an improved method for backflushing a chromatographic column comprising the steps of (l) backilushing the column initially with a liquid solvent, and (2) subsequently backflushing the column with a gaseous stream to dry the column and prepare the chromatographic column for the next analysis.

As will be evident to those skilled in the art, various modifications of this invention can be made, or followed, in the light of the foregoing disclosure, without departing from the spirit or scope thereof.

We claim:

1. A method of analyzing normally vaporous components within a liquid stream maintained at a first pressure containing normally vaporous and normally liquid components comprising:

(a) isolating a portion of said liquid stream at said first pressure;

(b) increasng the pressure of said portion to a second pressure higher than said first pressure and sufiicient to prevent the normally vaporous components therein from flashing at an increased analysis temperature;

(c) passing said portion at said second pressure to a sample zone within an analysis zone which is maintained at an increased analysis temperature;

(d) isolating a sample of said portion at said second pressure in said sample zone;

(e) passing a carrier gas through said sample zone at a third pressure which is lower than said second pressure;

(f) vaporizing said normally vaporous components in said carrier gas;

(g) removing said normally liquid components from said carrier gas;

(h) passing said carrier gas containing said vaporous components to a chromatographic analysis zone.

2. The method of claim 1 wherein steps (g) and (h) comprise in sequence, passing the carrier-gas stream from step (f) through a sorption zone wherein said normally liquid components are sorbed; passing the effluent from said sorption zone which contains said normally vaporous components in the vaporous state to a chromatographic column wherein said vaporized components are sorbed; and measuring a property of the effluent from said chromatographic column which is representative of the composition of said vaporized components.

3. The method of claim 2 further comprising flushing said sorption zone with a liquid solvent for said normally liquid components to thereby remove said normally liquid components therefrom, and backllushing said chromatographic column with a gaseous stream.

4. The method of claim 3 further comprising backflushing said sorption zone with a gaseous stream.

5. A chromatographic sampling apparatus comprising:

(a) a first pressure vessel means having a first end and a second end;

(b) first conduit means for introducing a pressurized liquid sample into said first pressure vessel means, said first conduit means communicating with the first end of said first pressure vessel and having a first valve means positioned therein;

(c) second conduit means communicating with the second end of said first pressure vessel;

(d) sample valve means adapted to obtain a liquid sample from a liquid passed thereto;

(e) third conduit means communicating between said rst end of said first pressure vessel means and said sample valve means for passing yliquid sample therethrough, said third conduit means having a second valve means operatively positioned therein;

(f) fourth conduit means communicating with said third conduit means at a point 4between said second valve means and said first end of said first pressure vessel means, said fourth conduit means having a third valve means operatively positioned therein;

(g) second pressure vessel means having a first end and a second end, said second pressure vessel means having mercury therein;

(h) fifth conduit means communicating with said first end of said second pressure means;

(i) fourth valve means connecting said fifth conduit means with said second conduit means;

(j) sixth conduit means communicating with said second end of said second pressure vessel and having a fifth valve means operatively positioned therein;

(k) a pressure inducing means for increasing the fluid pressure in said second pressure vessel means;

(l) seventh conduit means communicating with said pressure reducing means and said sixth conduit means at a point between said second end of said second pressure vessel and said fifth valve means for passing pressurizing iluid therethrough;

(m) sixth valve means operatively positioned in said seventh conduit means.

6. The apparatus of claim 5 further comprising a liquid density measuring means operatively positioned in said first conduit means, and an eighth conduit means operatively connected to said sample valve means with a seventh valve means operatively positioned therein.

7. The apparatus of claim 5 further comprising a first sorption column having a first end and a second end containing a packing material that selectively retards the constituents of a fluid mixture directed therethrough, a second sorption column having a first end and a second end containing a packing material that selectively retards the constituents of the fluid mixture directed therethrough, means for measuring a property of a fluid representative of the composition thereof, a first multi-port valve means, a second multi-port valve means, ninth conduit means communicating between said first multi-port valve means and the rst end of said first sorption column, said sample valve means connected to said ninth cond-uit means and adapted to introduce a fluid therein, tenth conduit means communicating between said first multi-port valve means and the second end of said first sorption column, eleventh conduit means communicating between said first multi-port valve means and the first end of said second column, twelfth conduit means communicating between the second end of said second column and said second multi-port valve means, thirteenth conduit means connecting between said second multi-port valve means and said means for measuring, fourteenth conduit means comunicating between said rst and said second multi-port valve means, fteenth conduit means communicating with said second multi-port valve means for introducing a carrier gas thereto, sixteenth conduit means communicating with said first multiport valve means for introducing a liquid solvent thereto, and seventeenth conduit means communicating with said first multi-port valve means to vent luids therefrom.

References Cited Lichtenfels et al.: Analytical Chemistry, vol. 28, No. 9, September 1956, pp. 1376-1379; copy in 73-23.1.

Porter et al.: Analytical Chemistry, vol. 31, No. 5, May 1969, pp. 866-870, copy in 73-23.1.

RICHARD C. QUEISSER, Primary Examiner.

0 CHARLES A. RUEHL, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF 'CORRECTION Patent N0. 3,394,582 July 30, 1968 Bradley L. Munro et al.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 4S, "reducing" should read inducing Column 7, line l, "Connecting" should read -e communicating signed e'h'd sealed this 30th dey ef December 1969.

(SEAL) Attest:

Edwardv M. Fletcher, Jr. WILLIAM E. SCHUYLER,

Attesting Officer Commissioner of Patents

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