Heavy Oils Having Reduced Total Acid Number and Olefin Content

Abstract

A process for treating a heavy oil by heating a feedstock comprising a heavy oil in order to separate from the heavy oil a first fraction. The first fraction contains no more than 25% of the total number of acid groups of the heavy oil. A second fraction contains at least 75% of the total number of acid groups of the heavy oil. The second fraction then is treated under conditions that provide a heavy oil that has a total acid number, or TAN, that does not exceed 1.0 mg KOH/g, or is at least 50% lower than the total acid number prior to treatment, an olefin content that does not exceed 1.0 wt. %, and a p-value of at least 50% of the p-value of the heavy oil prior to treatment, or a p-value that is at least 1.5.

Claims

1-24. (canceled)

25. A process for treating a heavy oil, comprising: (a) heating a feedstock comprising a heavy oil, said heavy oil having acid groups, to remove from said heavy oil a first fraction, wherein said first fraction contains no more than 25% of the total number of acid groups of the heavy oil, and thereby providing a second fraction, wherein said second fraction contains at least 75% of the total number of acid groups of the heavy oil; and (b) treating said second fraction under conditions that provide a treated heavy oil that has a total acid number (TAN) that does not exceed 1.0 mg KOH/g, or a total acid number that is at least 50% lower than the total acid number (TAN) of said heavy oil prior to step (a), an olefin content that does not exceed 1.0 wt. %, and a p-value which is at least 50% of the p-value of said heavy oil prior to step (a), or a p-value of at least 1.5, wherein, in step (b), hydrogen is not added to said second fraction.

26. The process of claim 25 wherein step (a) comprises heating said feedstock comprising a heavy oil to a temperature that does not exceed 350 C. atmospheric equivalent temperature and subjecting said feedstock comprising a heavy oil to a pressure that does not exceed 3 atm.

27. The process of claim 25 wherein step (b) comprises heating said second fraction to a temperature that does not exceed 400 C. atmospheric equivalent temperature and subjecting said second fraction to a pressure that does not exceed 1 atm.

28. The process of claim 27 wherein step (b) comprises heating said second fraction to a temperature that does not exceed 385 C. atmospheric equivalent temperature and subjecting said second fraction to a pressure that does not exceed 1 atm.

29. The process of claim 28 where step (b) comprises heating said second fraction to a temperature that does not exceed 380 C. atmospheric equivalent temperature and subjecting said second fraction to a pressure that does not exceed 1 atm.

30. The process of claim 25 wherein, prior to step (a), said feedstock comprising a heavy oil is heated to a temperature that does not exceed 100 C. atmospheric equivalent temperature, thereby removing components having a boiling point of 100 C. atmospheric equivalent temperature or less from said heavy oil.

31. The process of claim 25 wherein, in step (a), said feedstock comprising a heavy oil is subjected to a pressure that does not exceed 0.66 atm.

32. The process of claim 27 wherein, in step (b), said second fraction is subjected to a pressure of about 0.66 atm.

33. The process of claim 27 wherein, in step (b), said second fraction is heated to a temperature of from about 350 C. atmospheric equivalent temperature to a temperature that does not exceed 400 C. atmospheric equivalent temperature.

34. The process of claim 27 wherein, in step (b), said second fraction is heated to a temperature that does not exceed 400 C. atmospheric equivalent temperature and subjected to a pressure that does not exceed 1 atm for a period of time of from about 1 minute to about 60 minutes.

35. The process of claim 25 wherein, in step (b), said second fraction is heated to a temperature that does not exceed 490 C. atmospheric equivalent temperature and subjected to a pressure that does not exceed 1 atm for a period of time of from about 20 minutes to about 35 minutes.

36. The process of claim 25 wherein said treated heavy oil has a p-value that is at least 75% of the p-value of the heavy oil prior to step (a), or has a p-value of at least 2.0.

37. The process of claim 25 wherein said first fraction contains no more than 10% of the total number of acid groups of the heavy oil, and said second fraction contains at least 90% of the total number of acid groups of the heavy oil.

38. The process of claim 37 wherein said first fraction contains no more than 5% of the total number of acid groups of the heavy oil, and said second fraction contains at least 95% of the total number of acid groups of the heavy oil.

39. The process of claim 38 wherein said first fraction contains no more than 3% of the total number of acid groups of the heavy oil, and said second fraction contains at least 97% of the total number of acid groups of the heavy oil.

40. The process of claim 25 wherein said treated heavy oil has an API gravity which is no more than 0.5 greater than that of said heavy oil prior to step (a).

41. The process of claim 40 wherein said treated heavy oil has an API gravity which is no more than 0.2 greater than that of said heavy oil prior to step (a).

42. The process of claim 41 wherein said treated heavy oil has an API gravity which is no more than 0.1 greater than that of said heavy oil prior to step (a).

43. The process of claim 25 wherein step (b) is performed in the absence of a stripping gas.

44. The process of claim 25, and further comprising: recombining at least a portion of said first fraction with said treated heavy oil of step (b).

45. The process of claim 25, and further comprising: subjecting said treated heavy oil to cavitation.

46. The process of claim 45 wherein said cavitation is hydrodynamic cavitation.

47. The process of claim 25, and further comprising: subjecting said treated heavy oil to visbreaking.

48. The process of claim 25, and further comprising: subjecting said treated heavy oil to a hydrogen addition process.

49. The process of claim 25 wherein, in step (a), hydrogen is not added to said feedstock.

Description

[0032] The invention now will be described with respect to the drawing, wherein.

[0033] The FIGURE is a schematic of an embodiment of the method for treating a heavy oil in accordance with the present invention.

[0034] Referring now to the drawing, as shown in the FIGURE, a heavy oil in line 10 is pumped and heated and sent to fractionator 11. In general, fractionator 11 is operated at a temperature of about 300 C. in the bottom, and in any event, the temperature does not exceed 350 C., and a pressure that does not exceed 3 atm, whereby a fraction, comprised of diluents, water vapor, naphtha, and lighter ends in the form of gases, which have a boiling point less than 250 C. (AET), i.e., a 250 C. fraction, are withdrawn from fractionator 11 through line 12 and passed to knock-out drum 17. The 250 C. fraction contains no more than 25% of the naphthenic acids of the heavy oil. Off gases are withdrawn from knock-out drum 17 through line 19, while the remainder of the 250 C. fraction is withdrawn from knock-out drum 17 through line 18. Thus, a fraction that has a boiling point of less than 250 C. at atmospheric pressure (i.e., a 250 C. fraction) is separated from the heavy oil, whereby the resulting heavy oil contains a minimal amount of components that decrease the stability of the heavy oil, and further treatment to reduce the total acid number (TAN) of the heavy oil facilitates the maintenance of acceptable olefin levels.

[0035] A heavier heavy oil fraction is withdrawn from fractionator 11 through line 13 and passed to decarboxylation column 14. In general, decarboxylation column 14 is operated at a temperature that does not exceed 380 C. and a pressure that does not exceed 1 atm. The heavy oil is treated in decarboxylation column 14 for a period of time such that the naphthenic acids and other acidic components that may be present in the heavy oil are reacted, whereby the total acid number (TAN) is reduced to an acceptable level, i.e., not exceeding 1.0 mg KOH/g, or is at least 50% below the total acid number prior to the treatment of the heavy oil. In decarboxylation column 14, through the combination of heat and residence time, weak chemical bonds are broken, and acid gases such as CO.sub.2, NO.sub.x, and sulfur species such as H.sub.2S and COS are liberated. In general, the heavy oil is treated in decarboxylation column 14 for a period of time of from about 1 minute to about 60 minutes. Incondensable gases or off gases, such as CO.sub.2, NO.sub.2, and CO, as well as steam, are withdrawn from decarboxylation column 14 through line 15. A decarboxylated heavy oil is withdrawn from decarboxylation column 14 through line 16.

[0036] The 250 C..sup. fraction in line 18 is passed to line 16, where it is recombined with the decarboxylated heavy oil.

[0037] The 250 C. fraction in line 18 may be recombined with the decarboxylated heavy oil in line 16 either before or after subjecting the heavy oil to further processing to reduce the density and viscosity of the heavy oil. The decarboxylated heavy oil in line 16 is a treated and stable heavy oil that has a total acid number (TAN) that does not exceed 1.0 mg KOH/g, or is at least 50% below the total acid number prior to the treatment of the heavy oil, and an olefin content that does not exceed 1.0 wt. %, and a p-value that is at least 50% of the p-value of the heavy oil prior to treatment, or a p-value that is at least 1.5.

[0038] The invention now will be described with respect to the following example; however, the scope of the present invention is not intended to be limited thereby.

EXAMPLE

[0039] Four samples of a heavy oil having a TAN of 5.32 mg KOH/g, a bromine number (a measure of olefin content wherein a bromine number of 10 gBr2/100 g generally or approximately corresponds to an olefin content of 1.0%) of 5.72 gBr2/100 g, a p-value of 3.48, and a density of 0.9714 g/cm.sup.3, were treated in a topping step, to remove a fraction containing 3% of the total acid groups of the original oil samples, and having a resulting fraction boiling point (at atmospheric pressure) of less than 250 C. (i.e., a 250 C..sup.1 fraction), and then the samples were treated in a second step to remove napthenic acid components therefrom.

[0040] In the topping step, each of Samples 1 and 2 were heated to 350 C. at a pressure of 252 mmHg. Sample 3 was heated to 257 C. at a pressure of 125 mmHg, and Sample 4 was heated to 276 C. at a pressure of 125 mmHg. In the reaction step, Sample 1 was heated to 367 C. at a pressure of 500 mmHg for 32 minutes, and Sample 2 was heated to 373 C. at 500 mmHg for 20 minutes. Sample 3 was heated to 385 C. at a pressure of 760 mmHg (i.e., atmospheric pressure) for 15 minutes, and Sample 4 was heated to 385 C. at a pressure of 760 mmHg for 2 minutes.

[0041] After the topping step and the second step, each of the 250 C..sup. fractions that were separated previously from the heavy oil samples was recombined with each of the treated residue Samples 1 through 4. After the 250 C..sup. fractions were recombined with each of the treated Samples 1 through 4, the TAN values, bromine numbers, and p-values for each of Samples 1 through 4 were measured. After the above measurements, each of Samples 1 through 4 were subjected to an additional distillation step at 300 C. under vacuum (20 mmHg pressure) to verify whether olefins were produced during the second step. After the distillation under vacuum, the TAN values, bromine numbers, and p-values again were measured. The increases in density, as measured in API gravity, of each of the recombined oil samples, also were measured. It can be seen from the results with respect to Sample 3 that the reaction severity (combination of time and temperature) was too high and thus the bromine number, which is indicative of olefin content, was higher than desired.

[0042] The TAN values, bromine numbers, p-values, and increases in density for each of Samples 1 through 4 are given in Table 1 below.

TABLE-US-00001 TABLE 1 Density Bromine P- Increase Sample Topping Condition Reaction Conditions TAN Number Value ( API) 1 350 C./252 mmHg 367 C./500 mmHg/32 min. 1.0 9.2 3.1 0 2 350 C./252 mmHg 373 C./500 mmHg/20 min 0.89 10.6 3 0 3 257 C./125 mmHg 385 C./760 mmHg/15 min. 0.99 16.69 2.5 0.05 4 276 C./125 mmHg 385 C./760 mmHg/2 min. 1.90 8.72 3.15 0

[0043] The disclosures of all patents and publications, including published patent applications, are herein incorporated by reference to the same extent as if each patent and publication were incorporated individually by reference.

[0044] It is to be understood, however, that the scope of the present invention is not to be limited to the specific embodiments described above. The invention may be practiced other than as particularly described and still be within the scope of the accompanying claims.