Identification of products

Abstract

A marking method which is a method of marking a product having a distillation range is disclosed. The method comprises the step of adding to said product a first marker, a second marker and optionally one or more further markers. Each marker has a distillation range including a minimum boiling point (Min BP), a maximum boiling point (Max BP) and a maximum distillation boiling point (Max DBP) which is the temperature at which the maximum volume of the marker distils. Each marker has a different distillation range from each other marker and at least one marker has a Max DBP which is within the distillation range of the product. The first marker has a distillation range in the marked product which extends over the whole of the product distillation range.

Claims

1. A method of marking a product having a distillation range and identifying the marked product in an unknown sample, comprising adding to said product a first marker, a second marker and optionally one or more further markers, each marker having a distillation range including a minimum boiling point (Min BP), a maximum boiling point (Max BP) and a maximum distillation boiling point (Max DBP) which is the temperature at which the maximum volume of the marker distils, each marker having a different distillation range from each other marker, and at least one marker having a Max DBP which is within the distillation range of the product, wherein the first marker has a distillation range in the marked product which extends over the whole of the product distillation range; analysing said unknown sample by an analytical method capable of providing a response which is proportional to the quantity of marker found in the unknown sample to identify whether said first marker, said second marker or a said further marker is present in said unknown sample; calculating a response ratio of the first and second markers in the unknown sample, to each other; and comparing the response ratio of the first and second markers in the unknown sample with a response ratio of the same markers in a reference sample to determine whether the unknown sample contains the known marked product or a distilled fraction or a residue fraction thereof.

2. The method as claimed in claim 1, wherein the marker distillation ranges of at least two markers overlap each other, and the respective Max DBPs of said at least two markers are different.

3. The method as claimed in claim 1, wherein the second marker has a distillation range in the marked product which extends over a portion of the distillation range over which at least 50% of the distillate fraction volume distils.

4. The method as claimed in claim 1, wherein the second marker has a distillation range in the marked product which extends over a portion of the distillation range over which at least 50% of the distillation residue fraction volume remains.

5. The method as claimed in claim 1, wherein the second marker has a marker distillation range which overlaps the initial boiling point (IBP} of the product.

6. The method as claimed in claim 1, wherein the second marker has a marker distillation range which overlaps the final boiling point (FBP} of the product.

7. The method as claimed in claim 1, wherein said first marker has a lower maximum distillation boiling point (Max DBP) than the max DBP of said second marker and wherein the response ratio of the first marker to the second marker in said unknown sample is greater than the response ratio of the first marker to the second marker in said reference sample, and further comprising determining that the unknown sample contains a distillate fraction of the marked product.

8. The method as claimed in claim 1, wherein said first marker has a lower maximum distillation boiling point (Max DBP) than the max DBP of said second marker and wherein the response ratio of the first marker to the second marker in said unknown sample is less than the response ratio of the first marker to the second marker in said reference sample, and further comprising determining that the unknown sample contains a residue fraction of the marked product.

9. The method as claimed in claim 1, further comprising calculating a correction factor for said first marker by a method comprising: a. distilling a reference sample representing the known marked product containing a known concentration of said first marker to obtain at least two reference distillate fractions each of known distillation volume % and at least two reference residue fractions each of known residue volume %; b. each of said distillate and residue fractions to determine the response of said first marker in each fraction; c. determining the correction factor (CF) for said first marker in each fraction from: $CF=\frac{\mathrm{response}\mathrm{of}\mathrm{first}\mathrm{marker}\mathrm{in}\mathrm{fraction}}{\mathrm{response}\mathrm{of}\mathrm{first}\mathrm{marker}\mathrm{in}\mathrm{reference}\mathrm{sample}}.$

10. The method as claimed in claim 9, further comprising calculating a correction factor for said second marker by a method comprising: a. distilling a reference sample representing the known marked product containing a known concentration of said second marker to obtain at least two reference distillate fractions each of known distillation volume % and at least two reference residue fractions each of known residue volume %; b. each of said distillate and residue fractions to determine the response of said second marker in each fraction; c. determining the correction factor (CF) for said second marker in each fraction from: $CF=\frac{\mathrm{response}\mathrm{of}\mathrm{second}\mathrm{marker}\mathrm{in}\mathrm{fraction}}{\mathrm{response}\mathrm{of}\mathrm{second}\mathrm{marker}\mathrm{in}\mathrm{reference}\mathrm{sample}}.$

11. The method as claimed in claim 9, further comprising interpolating said calculated correction factors over the range of said distillate volume fractions.

12. The method as claimed in claim 9, further comprising interpolating said calculated correction factors over the range of said residue volume fractions.

13. The method as claimed in claim 9, further comprising correlating said correction factor for the first and/or the second marker with the response ratio of said first marker to said second marker at each distillate or residue volume fraction.

14. The method as claimed in claim 13, comprising comparing the response ratio of the first marker to the second marker in the unknown sample to the correlation of the correction factor for the first and/or the second marker with the response ratio of said first marker to said second marker in the reference sample to determine the correction factor to use to calculate the proportion of a distillate or a residue fraction of said marked product present in said unknown sample.

15. The method as claimed in claim 14, comprising calculating the proportion of a distillate or a residue fraction of said marked product present in said unknown sample.

Description

(1) The invention is described herein with reference to the accompanying drawings, which are:

(2) FIG. 1: A schematic distillation profile of a distillable product containing markers D and R.

(3) FIG. 2: distillation profile of diesel fuel containing markers A and B used in Example 1.

(4) FIG. 3: marker concentration vs distillate volume for markers A and B from Example 1.

(5) FIG. 4: plot of marker ratio vs correction factor for markers A and B in distillate from Example 1.

(6) FIG. 5: marker concentration vs residue volume for markers A and B from Example 1.

(7) FIG. 6: plot of marker ratio vs correction factor for markers A and B in residue from Example 1.

(8) FIG. 7: Process diagram for calibration method

(9) FIG. 8: Process diagram for sample analysis method

(10) The method of the invention will be further described in the following examples.

EXAMPLE 1

(11) A diesel fuel was marked with two markers (Tag A and Tag B) at a marker concentration of each marker of 1 ppm to form a marked mixed hydrocarbon product. The ratio of Tag A to Tag B was 1:1. The marked mixed hydrocarbon was then used to calibrate the measurement device so that identification and quantification of the markers can be made in any mixed hydrocarbon matrix.

(12) Distillation profiles of Tag A and Tag B within the mixed hydrocarbon were determined using a modified ASTM D-86 protocol. 10% by volume fractions were collected and measured for marker content. The analytical method used for the markers was gas chromatographymass spectrometry using single ion monitoring. Deuterated versions of Tag A and Tag B were used as internal standards. Distillation curves were created from the values in Table 1 and these are shown in FIG. 2 for each marker.

(13) TABLE-US-00001 TABLE 1 Distillation Equivalent Distillate Temp ( C.) % Tag A % Tag B Volume Point (%) 197.8 64.94 12.74 10 212.2 79.05 20.04 20 228.0 97.32 31.35 30 244.6 124.3 47.32 40 261.4 162.72 77.14 50 278.5 191.03 130.29 60 296.2 162.4 189.59 70 315.8 94.07 205.6 80 339.9 22.73 193.29 90 369.6 1.41 96.59 100

(14) It may be advantageous to have a larger number of data points and so distillation volumes smaller than 10% by volume may be preferred. The distillate fractions where there is only a single marker can be determined from these curves and so a quantification range QR may be established, as shown in FIG. 2 between the vertical dotted lines.

(15) The volume of marker measured in each known total volume of distillate was measured and tabulated in Table 2. The volume of marker measured in each known total volume of distillation residue, was measured and tabulated in Table 3. A table for each of the Distillate and the distillation Residue was created separately because they may be deemed as separate products for future quantification. In Tables 2 and 3, the percent marker was calculated relative to the originally marked diesel. Once fully distilled the distillation curves for each marker were produced and are shown in FIG. 3. Note, these curves detail the marker content in the bulk distillate volume, and not the marker content at each distillate fraction as shown in FIG. 2.

(16) TABLE-US-00002 TABLE 2 Distillate Total Marker A Marker B Distilled % Marker Marker % Marker Marker Correction Correction Volume % A A ppm B B ppm Ratio A/B Factor Factor 0 0 0.00 0 0.00 0 0 0 10 64.94 0.65 12.74 0.13 5.0973 1.5399 7.8493 20 72.00 0.72 16.39 0.16 4.3926 1.3890 6.1013 30 80.44 0.80 21.38 0.21 3.7628 1.2432 4.6780 40 91.40 0.91 27.86 0.28 3.2805 1.0941 3.5891 50 105.67 1.06 37.72 0.38 2.8015 0.9464 2.6513 60 119.89 1.20 53.15 0.53 2.2559 0.8341 1.8816 70 125.97 1.26 72.64 0.73 1.7341 0.7939 1.3767 80 121.98 1.22 89.26 0.89 1.3666 0.8198 1.1203 90 110.95 1.11 100.82 1.01 1.1005 0.9013 0.9919 100 100.00 1.00 100.40 1.00 0.9961 1.0000 0.9961

(17) TABLE-US-00003 TABLE 3 Residue Total Remaining Marker A Marker B Residue % Marker Marker % Marker Marker Correction Correction Volume % A A ppm B B ppm Ratio A/B Factor Factor 100 100.00 1.00 100.00 1.00 1.0000 1.0000 1.0000 90 103.89 1.04 110.13 1.10 0.9433 0.9625 0.9080 80 107.00 1.07 121.40 1.21 0.8814 0.9346 0.8237 70 108.38 1.08 134.26 1.34 0.8072 0.9227 0.7448 60 105.73 1.06 148.75 1.49 0.7108 0.9458 0.6723 50 94.33 0.94 163.07 1.63 0.5784 1.0601 0.6132 40 70.15 0.70 171.27 1.71 0.4096 1.4255 0.5839 30 39.40 0.39 165.16 1.65 0.2386 2.5379 0.6055 20 12.07 0.12 144.94 1.45 0.0833 8.2850 0.6899 10 1.41 0.01 96.59 0.97 0.0146 70.9220 1.0353 0 0.00 0.00 0.00 0.00 0.0000 0.0000 0.0000

(18) At each measured volume the ratio of marker A to marker B was also determined and recorded. It can be seen from the data above, in Table 2, that the ratio of the two markers can be used to determine the final distillation temperature achieved and total distillate volume obtained in any fraction of the original marked diesel. An ideal tracer would measure 100% marker relative to the original marked diesel since it is derived from the same marked product and so is a portion of the marked product. However, it can be seen that the marker content is either deficient in relative content or in excess of the relative content, therefore a correction factor may be made to account for this. Correction factors for each marker were calculated and tabulated as seen in Table 2 above. It can now be seen that we can assign a correction factor, for each marker, across the distillation range of the marked diesel. The correction factors for each of marker A and marker B were plotted in FIG. 4 and interpolated using a polynomial fit to produce a curve for each marker in the distillate. Using the marker ratio we can determine, from the relevant curve, the position of the final distillation point and thus the distillate volume, and thus we can determine the correction factors to be made to the marker content at this distillation volume. Thus by creating a marker ratio to correction factor curve as shown in FIGS. 4 and 6 we can now determine the correction factor at any distillation point by use of either a curve fit or curve spline.

(19) Similar marker concentration curves and correction factor curves were made for the distillation residue and these are shown in FIGS. 5 and 6.

(20) It can be seen from Tables 2 and 3 above and plots in FIGS. 3 and 5, that there is always an excess of marker A in the distillate and there is always an excess of marker B in the residue. Therefore, if a sample is measured and it contains a significant increase in Marker A above normal analytical precision, we can deem this sample to have been distilled and the resultant product being measured is the resulting distillate from the distillation. Conversely, if the sample contains a significant increase in marker B then sample has been distilled and the resulting product being measured is the remaining distillation residue.

EXAMPLE 2

(21) 50 ml of the marked diesel fuel used in Example 1 (containing Marker A and Marker B, each at 1 ppmv) was mixed with 50 ml of used lubricating oil (ULO) which had an initial boiling temperature of 283 C. The resulting mixture was then subjected to atmospheric distillation to a temperature of 270 C. using a modified ASTM D-86 protocol. The volume of distillate recovered was 27 ml. Samples of un-distilled mixture, distillate, and Residue were analysed for the presence of marker. Results are tabulated in Table 4 below.

(22) The concentration is shown as measured %, representing the volume of the marked diesel calculated to be in the sample using the measured concentration of the marker. This is calculated from the relationship (measured concentration of marker in sample/concentration of marker in marked diesel)*100%. Using the marker ratio NB found by analysis, the correction factor is obtained using the interpolated curves in FIG. 4 (for the distillate) and FIG. 6 (for the residue). The correction factor was then multiplied by the measured % to provide a corrected concentration of each marker in the sample. The Reported % diesel in sample column in Table 4 is the content of the marked diesel that is calculated to be present in the sample, calculated using an average of the corrected ppm of marker A and marker B. The reported value is calculated from: (corrected measured concentration of marker/concentration of marker in original marked product)*100) %.

(23) TABLE-US-00004 TABLE 4 Correction Reported Theoretical Measured % Ratio Factor Corrected % % diesel % diesel Sample A B A/B A B A B in sample in sample Un-distilled 49.7 51.3 0.9688 1.000 1.000 49.7 51.3 50.5 50 Distillate 97.9 38.2 2.5628 1.035 2.677 101.3 102.3 101.8 100 Residue 114 53.8 0.2119 2.749 0.638 31.3 34.3 32.8 31.5

(24) The theoretical % diesel in sample column in Table 4 is the content of the marked diesel that would be present in the sample, calculated from knowledge of the amount of distillate distilled. For example, based on the IBP of the ULO, no ULO should distil over at 270 C. so the distillate (diesel lights) derives 100% from the original marked diesel. Since 27 ml was distilled from the original 50 mls marked diesel, 23 ml diesel (diesel heavies) remains in the residue fraction together with the 50 ml ULO. Therefore, the composition of original diesel remaining in the final product is (23/(23+50)*100)%.

(25) Although the dilution of the product could be obtained only from measuring one of the markers, using the corrected concentration from both of the markers, for example as an average concentration may provide a means of compensating for measurement errors. It can be seen from Table 4 that the calculation of corrected concentration gives different values for marker A and marker B, when they were added to the diesel at the same concentration (1 ppm of each). An average of the corrected concentrations for A and B were used to calculate the reported values in Table 4.