PROCESS TO PREPARE PARAFFIN WAX

Abstract

The present invention provides a paraffin wax having a congealing point according to ASTM D938 of at least 75° C. and a Saybolt colour according to ASTM D156 of at least 25 cm.

Claims

1. A paraffin wax having a congealing point according to ASTM D938 of at least 75° C. and a Saybolt colour according to ASTM D156 of at least 25 cm.

2. A paraffin wax according to claim 1, having a congealing point according to ASTM D938 in the range of from 75 to 85° C.

3. A paraffin wax according to claim 1, having a congealing point according to ASTM D938 of at least 80° C.

4. A paraffin wax according to claim 1, having a Saybolt colour according to ASTM D156 of at least 30 cm.

5. A paraffin wax according to claim 1, having an oil content according to ASTM D721 of less than 0.5 wt. %.

6. A paraffin wax according to claim 1, wherein the paraffin wax is a Fischer-Tropsch derived paraffin wax.

7. A process to prepare a Fischer-Tropsch derived paraffin wax, the process at least comprising the following steps: (a) providing a Fischer-Tropsch product stream comprising paraffins having from 10 to 300 carbon atoms; (b) separating the Fischer-Tropsch product stream of step (a), thereby obtaining at least a fraction comprising 10 to 17 carbon atoms and a fraction comprising 18 to 300 carbon atoms; (c) subjecting the fraction comprising 18 to 300 carbon atoms of step (b) to a hydrogenation step, thereby obtaining a hydrogenated fraction comprising 18 to 300 carbon atoms; (d) separating the hydrogenated fraction comprising 18 to 300 carbon atoms of step (c), thereby obtaining one or more first light waxes having a congealing point in the range of 30 to 75° C. and a second heavy wax having a congealing point according to ASTM D938 in the range of 75 to 120° C.; (e) separating the heavy wax of step (d) to obtain a distillate wax fraction having a congealing point of at least 75° C.; (f) hydrofinishing the distillate wax fraction of step (e) thereby obtaining a hydrofinished wax fraction having a congealing point according to ASTM D938 of at least 75° C. and a Saybolt colour according to ASTM D156 of at least 25 cm.

8. A process according to claim 7, wherein the heavy wax of step is separated in step (e) by short path distillation at a pressure between 0.05 mbar and 0.5 mbar.

9. A process according to claim 7, wherein the heavy wax of step is separated in step (e) by short path distillation at a pressure between 0.1 and 0.3 mbar.

10. A process according to claim 7, wherein the hydrofinished wax fraction has a congealing point according to ASTM D938 in the range of from 75 to 85° C.

11. A process according to claim 7, wherein the hydrofinished wax fraction has a congealing point according to ASTM D938 of at least 80° C.

12. A process according to claim 7, wherein the hydrofinished wax fraction has a Saybolt colour according to ASTM D156 of at least 30 cm.

13. A process according to claim 7, wherein the hydrofinished wax fraction has an oil content according to ASTM D721 of less than 0.5 wt. %.

14. A process according to claim 7, wherein the hydrofinished wax fraction has an oil content according to ASTM D721 of less than 0.45 wt. %.

15. A paraffin wax according to claim 1, having an oil content according to ASTM D721 of less than 0.45 wt. %.

Description

[0058] FIG. 1 schematically shows a process scheme of the process scheme of a preferred embodiment of the process according to the present invention.

[0059] For the purpose of this description, a single reference number will be assigned to a line as well as a stream carried in that line.

[0060] The process scheme is generally referred to with reference numeral 1.

[0061] In a Fischer-Tropsch process reactor a Fischer-Tropsch product stream is obtained (not shown). This product is separated in a distillation column 2 into a fraction 10 comprising 10 to 17 carbon atoms and a fraction 20 comprising 18 to 300 carbon atoms. Fraction 20 is fed to a hydrogenation reactor 3 wherein fraction 20 is converted to a hydrogenated fraction 30. Fraction 30 is distilled in a vacuum distillation column 4 to recover one or more wax fractions 40 having a congealing point in the range of from 30 to 75° C. and a heavy fraction 50. Fractions 40 is fed to a hydrofinishing reactor 5 wherein fractions 40 is converted to hydrofinished fractions 60 having a congealing point in the range of from 30 to 75° C.

[0062] Heavy wax 50 is distilled in a short path distillation column 6 to recover a distillate wax fraction 70 having a congealing point of at least 80° C.

[0063] Fraction 70 is fed to a hydrofinishing reactor 7 wherein fraction 70 is converted to a hydrofinished fraction 80 having a congealing point of at least 80° C.

[0064] The fraction 10 is fed to a hydrogenation reactor 8 wherein fraction 10 is converted to a hydrogenated fraction 90 comprising 10 to 17 carbon atoms.

[0065] The present invention is described below with reference to the following Examples, which are not intended to limit the scope of the present invention in any way.

EXAMPLES

Example

Preparation of Fischer-Tropsch Derived Paraffin Wax Fractions Having a Congealing Point of at Least 80° C.

[0066] A Fischer-Tropsch derived paraffin wax having a congealing point of at least 80° C. was obtained using a Fischer-Tropsch process. To this end a Fischer-Tropsch effluent was prepared according to the method described in U.S. Pat. No. 6,858,127. Based on C1+ hydrocarbons the effluent had a C30+ content of 51.1% m and a C60+ content of 28.5% m.

[0067] The effluent was separated in a fraction A which is in the gas phase at ambient conditions and a fraction B which is in the liquid or solid phase at ambient conditions. For all distillations described below care was taken to avoid temperatures above 370° C. for any part of the distillation equipment in contact with hydrocarbons and to avoid contact of hydrocarbons with oxygen. All distillations described below were carried out in a continuous mode.

[0068] Fraction B was subjected to a distillation at atmospheric pressure yielding a top stream comprising a fraction containing molecules with 9 or less carbon atoms, a side cut C containing molecules with 10 to 17 carbons atoms and a bottom stream D containing molecules with 18 to 300 carbon atoms. The effective cutpoint for the separation between streams C and D was 310° C.

[0069] Fraction C was hydrogenated over a nickel catalyst as described in WO 2007/082589 (Catalyst G). Process conditions were: a weight hourly space velocity (WHSV) of 1.0 kg/l/h, 30 bar of pure hydrogen at reactor inlet, a hydrogen over feedstock ratio of 1000 Nl/kg and a temperature of 220° C.

[0070] The hydrogenated product was separated in a fraction E which is in the gas phase at ambient conditions and a fraction F which is in the liquid phase at ambient conditions. Fraction F consists of hydrogenated normal paraffins in the C10 to C17 range.

[0071] The residue of the atmospheric distillation (fraction D) was subjected hydrogenated over a nickel catalyst as described in WO 2007/082589 (Catalyst G). Process conditions were: a weight hourly space velocity (WHSV) of 1.0 kg/l/h, 30 bar of pure hydrogen at reactor inlet, a hydrogen over feedstock ratio of 1000 Nl/kg and a temperature of 220° C.

[0072] The hydrogenated product was separated in a fraction G which is in the gas phase at ambient conditions and a fraction H which is in the solid phase at ambient conditions. Fraction H consists of hydrogenated normal paraffins in the C18 to C300 range.

[0073] Fraction H is subjected to a vacuum distillation. The distillation was run at a bottom temperature of 320° C. and a pressure of 15 mbar. The effective cutpoint between bottom stream and heaviest distillate was 490° C. Several refined waxes were obtained as distillates of which the heaviest was subjected to a hydrofinishing operation over a nickel catalyst as described in WO 2007/082589 (Catalyst G). Process conditions were: a weight hourly space velocity (WHSV) of 1.0 kg/l/h, 60 bar of pure hydrogen at reactor inlet, a hydrogen over feedstock ratio of 1000 Nl/kg and a temperature of 240° C.

[0074] The residue of this vacuum distillation (fraction J) is subjected to a short path distillation with an effective cut point of 540° C. The distillation was run at 0.2 mbar and 260° C.

[0075] The distillate of the short path distillation (fraction K) is subjected to a hydrofinishing operation over a nickel catalyst as described in WO 2007/082589 (Catalyst G). Process conditions were: a weight hourly space velocity (WHSV) of 1.0 kg/l/h, 60 bar of pure hydrogen at reactor inlet, a hydrogen over feedstock ratio of 1000 Nl/kg and a temperature of 240° C.

[0076] The product was separated in a fraction L which is in the gas phase at ambient conditions and a fraction M which is in the solid phase at ambient conditions. Fraction M is obtained as a refined wax with a congealing point of about 80° C. The yield of fraction M was 6.8% m of the Fischer-Tropsch effluent on a hydrocarbon basis.

[0077] Fraction M is the desired heavy Fischer-Tropsch based distillate hard wax. Properties of fraction M can be found in Table 1.

TABLE-US-00001 TABLE 1 Paraffin wax product (fraction L) Congealing point, ° C. 81.1  According to ASTM D938 Oil content, % w, 0.33 According to ASTM D721 Saybolt colour.sup.a, cm 30+   According to ASTM D156 Cloud point, ° C. 88    According to ASTM D5773 Kinematic viscosity at 3.95 120° C., mm2/s According to ASTM D445 .sup.aThe Saybolt colour scale is used to quantify colour intensity for mildly coloured substances in liquid state. For this objective waxes are molten for measurement. The scale runs from <−16 cm to >30 cm. >30 cm means water white. The higher the number the better (i.e. the lesser) the colour.

Discussion

[0078] The results in Table 1 show that starting from a hydrogenated Fischer-Tropsch effluent having C30+ content of 51.1% m and a C60+ content of 28.5% m a Fischer-Tropsch derived paraffin wax having a congealing point of about 80° C. was obtained. Furthermore, the paraffin wax has a low oil content and a high Saybolt colour.

[0079] These observations indicate that the obtained refined Fischer-Tropsch paraffin wax can be advantageously used in applications such as candles, hot melt adhesives, crayons, packaging, and PVC extrusion lubricants.