Use of zeolites for stabilizing oils

Abstract

The present invention relates to the use of zeolites or of agglomerates based on zeolites in order to improve the thermal stability of oils and the invention is targeted in particular at the use of these zeolitic compounds for stabilizing the oils or the formulations based on oils participating in the composition of refrigerants.

Claims

1. A method for improving the thermal stability of a composition, said composition containing an oil, subjected to variations in temperature, which comprises adding at least one zeolitic adsorbent, in the form of a powder formed of zeolite(s) or of agglomerate(s) formed of zeolite(s) to the composition, wherein the at least one zeolitic adsorbent is free of metal impregnation and the at least one zeolitic adsorbent is based on zeolite(s) A exchanged with potassium, the degree of exchange of which is between 50% and 70% (reported as molar equivalents) of all of the exchangeable cationic sites, wherein the at least one zeolitic adsorbent is present in an effective amount to limit or reduce the total acid number of the oil and the effective amount is about 40 mg to about 1000 mg per 5 g of oil.

2. The method as claimed in claim 1, wherein the at least one zeolitic adsorbent is chosen from a mixture of zeolite A type and one or both of zeolites of faujasite type and zeolites Y.

3. The method as claimed in claim 2, wherein the at least one zeolitic adsorbent is chosen from a mixture of zeolites of zeolite A type and zeolites of faujasite type.

4. The method as claimed in claim 1, wherein the oil is chosen from mineral, organic or silicone oils and fats used, alone or as mixtures, as automotive lubricants and industrial lubricants but also used as motor oils, hydraulic fluids, gear oils, brake fluids, oils for compressors, oils for turbines, oils for refrigeration and air conditioning systems, corrosion inhibitors, cooling lubricants, insulating oils, white oils, greases and the like.

5. The method as claimed in claim 1, wherein the oil is an oil used in dynamic or static refrigeration systems.

6. The method as claimed in claim 1, wherein the oil is an oil based on polyalkylene glycols (PAGs), on polyol esters (POEs) and/or on polyvinyl ethers (PVEs).

7. The method as claimed in claim 1, wherein the oil is an oil used in refrigeration systems and comprises at least one refrigerant.

8. The method as claimed in claim 1, wherein the oil is an oil used in refrigeration systems and comprises at least one refrigerant selected from the group consisting of hydrofluoroolefins (HFOs), hydrofluorocarbons (HFCs), and mixtures thereof in all proportions.

9. The method as claimed in claim 1, wherein the oil is a mixture of an oil and of a refrigerant, said mixture being chosen from PAG oil and 1,1,1,2-tetrafluoroethane, PAG oil and 2,3,3,3-tetrafluoropropene, POE oil and 1,1,1,2-tetrafluoroethane, POE oil and 2,3,3,3-tetrafluoropropene, PVE oil and 1,1,1,2-tetrafluoroethane, and PVE oil and 2,3,3,3-tetrafluoropropene.

10. The method as claimed in claim 1, wherein the oil is employed in refrigeration systems, motor vehicle or domestic air conditioning systems, heat pumps, electric transformers or metal cutting and milling instruments.

11. A refrigerating fluid comprising at least one oil selected from the group consisting of PAGs, POEs and PVEs, and at least one zeolite, wherein the at least one zeolite is free of metal impregnation and the at least one zeolite is based on zeolite(s) A exchanged with potassium, the degree of exchange of which is between 50% and 70% (reported as molar equivalents) of all of the exchangeable cationic sites, wherein the at least one zeolite is present in an effective amount to limit or reduce the total acid number of the oil and the effective amount is about 40 mg to about 1000 mg per 5 g of oil.

12. The method of claim 1, wherein the at least one zeolitic adsorbent is selected from the group consisting of zeolite 3A powder and agglomerates based on zeolite A powder, wherein the potassium exchange is carried out on the powder, the agglomerate, or both.

13. The method of claim 8, wherein the refrigerant is selected from the group consisting of tetrafluoroethanes, tetrafluoropropenes, and mixtures thereof in all proportions.

14. The method of claim 13, wherein the refrigerant is selected from the group consisting of 1,1,1,2-tetrafluoroethane, 2,3,3,3-tetrafluoropropene, and mixtures thereof in all proportions.

15. The refrigerating fluid of claim 11, wherein the oil is selected from the group consisting of PAGs and PVEs.

16. The refrigerating fluid of claim 11, wherein the zeolite is selected from a mixture of zeolites A and one or both of zeolites of the faujasite type and zeolites Y.

17. The method of claim 1, wherein the at least one zeolitic adsorbent is based on zeolite(s) 3A.

18. The method of claim 1, wherein the at least one zeolitic adsorbent is based on zeolite(s) 4A.

19. The method of claim 1, wherein the at least one zeolitic adsorbent is based on zeolite(s) 5A.

20. The method of claim 1, wherein the at least one zeolitic adsorbent is added in the form of a powder formed of zeolite(s).

21. The method of claim 1, wherein the at least one zeolitic adsorbent is added in the form of agglomerate(s) formed of zeolite(s).

22. The method of claim 1, wherein the at least one zeolitic adsorbent is present in the effective amount to limit or reduce the total acid number (TAN 14 day) of the oil such that the total acid number is maintained at or below 2.7 mg KOH/g.

23. The refrigerating fluid of claim 11, wherein the at least one zeolite is present in the effective amount to limit or reduce the total acid number (TAN-14 day) of the oil such that the total acid number is maintained at or below 2.7 mg KOH/g.

24. A method for improving the thermal stability of a composition, said composition containing an oil, subjected to variations in temperature, which comprises adding at least one zeolitic adsorbent, in the form of a powder formed of zeolite(s) or of agglomerate(s) formed of zeolite(s) to the composition, wherein the at least one zeolitic adsorbent is free of metal impregnation and the at least one zeolitic adsorbent is based on zeolite(s) A exchanged with potassium, the degree of exchange of which is between 50% and 70% (reported as molar equivalents) of all of the exchangeable cationic sites, wherein the at least one zeolitic adsorbent is present in an effective amount to limit or reduce the total acid number of the oil such that the total acid number (TAN-14 day) is maintained at or below 2.7 mg KOH/g.

25. A refrigerating fluid comprising at least one oil selected from the group consisting of PAGs, POEs and PVEs, and at least one zeolite, wherein the at least one zeolite is free of metal impregnation and the at least one zeolite is based on zeolite(s) A exchanged with potassium, the degree of exchange of which is between 50% and 70% (reported as molar equivalents) of all of the exchangeable cationic sites, and at least one other alkali or alkaline earth metal, the degree of exchange of which is between 30% and 50% (reported as molar equivalents) of all of the exchangeable cationic sites.

26. The refrigerating fluid of claim 25, wherein the at least one other alkali or alkaline earth metal is sodium.

27. The refrigerating fluid of claim 25, wherein the at least one zeolite is present in an effective amount to limit or reduce the total acid number of the oil such that the total acid number (TAN-14 day) is maintained at or below 2.7 mg KOH/g.

28. The refrigerating fluid of claim 25, wherein the at least one zeolite is present in an effective amount to limit or reduce the total acid number of the oil and the effective amount is about 40 mg to about 1000 mg per 5 g of oil.

Description

EXAMPLE 1

Thermal Stability Tests on an Oil without Refrigerant

(1) The thermal stability tests are carried out on oil compositions for refrigerating systems, without refrigerant, according to the standard ASHRAE 97-2007: Sealed glass tube method to test the chemical stability of materials for use within refrigerant systems.

(2) The test conditions are as follows: weight of lubricant: 5 g weight of zeolitic adsorbent: 40 to 1000 mg temperature: 200 C. duration: 14 days

(3) The zeolitic adsorbent and the lubricant are introduced into a glass tube with a volume of 42.2 ml. The tube is subsequently placed under vacuum, then sealed in order to hermetically close it and placed in an oven at 200 C. for 14 days.

(4) The oil used in this test is the PAG ND8 oil sold by Nippon Denso. The adsorbents used originate from CECA. The total acid number of the oil is measured at t=2 hours (t=0 for the control) and then at t=14 days, by quantitative determination with 0.01N methanolic potassium hydroxide solution. The results are shown in the following table 1:

(5) TABLE-US-00001 TABLE 1 Amount of Type of adsorbent TAN (mg KOH/g) Adsorbent adsorbent (mg) t = 2 hours t = 14 days None 0.1 1.6 Siliporite 3A 200 <0.1 0.4 NK30 AP Powder Siliporite 3A 200 <0.1 0.4 NK30 AP Powder overexchanged

(6) These results show that the zeolitic adsorbents make it possible to considerably slow down the rate of increase in the total acid number (TAN) of an oil.

EXAMPLE 2

Thermal Stability Tests on an Oil with Refrigerant

(7) The thermal stability tests are carried out on oil compositions for refrigerating systems, that is to say comprising a refrigerant, according to the standard ASHRAE 97-2007: Sealed glass tube method to test the chemical stability of materials for use within refrigerant systems.

(8) The test conditions are as follows: weight of refrigerant: 2.2 g weight of lubricant: 5 g weight of zeolitic adsorbent: 40 to 1000 mg temperature: 200 C. duration: 14 days

(9) The zeolitic adsorbent and the lubricant are introduced into a glass tube with a volume of 42.2 ml. The tube is subsequently placed under vacuum and then the refrigerant is added. The tube is then sealed in order to hermetically close it and is placed in an oven at 200 C. for 14 days.

(10) Various analyses are carried out at the end of the test: The gas phase is recovered in order to be analyzed by gas chromatography: the main impurities are identified by GC/MS (gas chromatography/mass spectrometry). Impurities coming from the refrigerant and those coming from the lubricant can thus be grouped together. The lubricant is analyzed: color (by spectrocolorimetry, Labomat Dr Lange Lico220 Model MLG131), water content (by Karl Fischer coulometric titration, Mettler DL37) and total acid number (by quantitative determination with 0.01N methanolic potassium hydroxide solution).

(11) The lubricants used in the tests are commercial PAG and POE oils: PAG ND8 and POE Ze-GLES RB68, sold respectively by Nippon Denso and Nippon Oil.

(12) The refrigerants used for these tests are either HFO-1234yf or R-134a.

(13) The results shown in the following table 2 are obtained with HFO-1234yf and, as lubricant, commercial PAG oil PAG ND8 and various zeolitic adsorbents supplied by CECA S.A.

(14) TABLE-US-00002 TABLE 2 Type of Amount of Adsorbent adsorbent adsorbent (mg) TAN (mg KOH/g) None 4.7 Siliporite NK30 3A 200 1.7 AP Powder Siliporite NK30 3A 1000 2.6 AP Powder Siliporite NK30 3A 200 1.5 AP Powder overexchanged Siliporite NK30 3A 1000 2.5 AP Powder overexchanged Siliporite NK30 3A 1000 1.6 Beads (Static) Siliporite NK10 4A 1000 2.7 AP Powder Siliporite NK20 5A 1000 2.4 Siliporite G5 XP 10A 1000 2.7 Powder

(15) These first results show that the presence of zeolitic adsorbents in oils makes it possible to considerably reduce the TAN of said oils.

(16) These results are confirmed, in the following table 3, with the tests carried out with compositions comprising R-134a and, as lubricant, PAG ND8 oil and various zeolitic adsorbents.

(17) TABLE-US-00003 TABLE 3 Siliporite Siliporite NK30 NK30 AP AP Powder Adsorbent None Powder overexchanged Type of adsorbent 3A 3A Amount of 200 200 adsorbent (mg) TAN (mg KOH/g) 2.9 0.5 0.4

(18) It is thus observed that, in the presence of zeolitic adsorbent, the total acid number of an oil at the end of the test is greatly reduced, generally divided by 2 or 3. For the tests in the presence of HFO1234yf, it changes from 4.7 mg KOH/g without adsorbent to values of between 1.5 and 2.7 mg KOH/g with adsorbent. For the tests with R-134a, it changes from 2.9 mg KOH/g without adsorbent to 0.5 mg KOH/g with adsorbent.

(19) In addition, whatever the type of adsorbent (3, 4, 5 or 10 ), the results are identical: the total acid number is divided by a factor of approximately 2 in the tests carried out in the presence of 1 g of adsorbent.