KR100451614B1 - Pyrolysis method of naphthenic acid - Google Patents

Abstract

The present invention relates to a method for removing petroleum acid, for example, naphthenic acid from crude oil or crude oil fraction by heat treatment of crude oil or crude oil fraction.

Description

Pyrolysis method of naphthenic acid

The present invention relates to a process for decomposing naphthenic acid present in crude oil. More specifically, the present invention relates to a method of decomposing naphthenic acid by heat treatment without using a catalyst.

Relatively large amounts of petroleum acids, such as naphthenic acid, in crude oil or its fractions, are harmful to petroleum refineries and more recently to gas generators. In essence, these acids, which are found to be somewhat present in almost all crude oil, are corrosive and can cause equipment failures, so they are more expensive to maintain, require more frequent repairs than necessary, reduce the quality of the product, . ≪ / RTI >

Many documents, including patents and publications, describe the removal of naphthenic acid by a conversion or absorption process. For example, a large amount of water may be added to crude oil or crude oil fraction to remove naphthenic acid, or to some other less corrosive material such as salts. Other methods of removing naphthenic acid are also known, including absorption on, for example, zeolites. In addition, one of the common ways of solving the problems associated with naphthenic acid is to use expensive alloying materials in refineries or gas generators that will use relatively high concentrations of naphthenic acid. Another common method involves blending crude oil of high total acid value (TAN) with crude oil of low TAN, but the latter is much more expensive than the former. U.S. Patent No. 1,953,353 (Lazar et al.), Which is incorporated by reference, teaches the decomposition of naphthenic acid in atmospheric distilled crude oil or distillate at temperatures and ambient pressures of 600 ° F to 750 ° F. However, in the above document, CO ₂ is recognized as the only gaseous non-hydrocarbon naphthenic acid decomposition product, and nothing is mentioned about performing the reaction while continuously sweeping the inert gas to prevent accumulation of the reaction decomposition.

Crude oils or fractions thereof which are inexpensive and suitable for purification, especially those which have a total acid value (TAN) of greater than about 2 mg KOH / gm oil as measured by ASTM Method D-664, It is necessary to reduce it to a small extent.

1 shows the rate of reduction of the total acid number (TAN) with respect to the amount of water added in Example 4. FIG.

According to the present invention, the feedstock containing petroleum acid is heat treated to decompose the petroleum acid to substantially reduce the petroleum acid concentration of the feedstock, or at least to a level where these feedstocks can be treated in a normal carbon steel vessel . As a result, the TAN can be significantly reduced. In the present invention, the heat treatment means, in addition to its ordinary meaning, that there is no catalyst for promoting the conversion of naphthenic acid and an absorber for naphthenic acid is added without adding any substance for reacting with or complexing with naphthenic acid It means that it does not exist. That is, it means that there is no substance used for the purpose of removing naphthenic acid.

The heat treatment corresponds to heating the feedstock to about 400 ° F or more, preferably about 600 ° F or more, for a time sufficient to substantially reduce the TAN of the feedstock while continuously sweeping the slurry produced during the cracking. The seawater is mainly water vapor and is increased by the addition of CO ₂ and / or CO.

Of course, the heat treatment has a time-temperature dependence once the critical temperature is reached. Therefore, as the residence time is correspondingly reduced at higher temperatures, the higher the temperature, the better. However, due to the nature of the feedstock, hydrocarbons can be prevented or minimized too quickly, for example less than about 0.5% by weight, based on the feedstock, of gaseous hydrocarbon products and preferably less than 0.2% Gaseous hydrocarbon products should be generated. The gases produced are mainly water vapor, CO ₂ and CO due to decomposition of naphthenic acid. Other gases that can be generated by very low levels of decomposition include light hydrocarbon gases, such as C ₁ -C ₄ alkyl or iso-alkyl, and small amounts of hydrogen.

According to the method of the present invention, the TAN is preferably less than about 1.5 mg KOH / gm oil, more preferably less than about 1 mg KOH / gm oil, even more preferably less than about 0.5 mg KOH / gm oil, gm < / RTI > oil.

Feedstocks that can be effectively treated by this heat treatment process include feedstocks containing naphthenic acid, such as crude oil or crude oil fraction. The crude oil fraction that can be treated is atmospheric distilled crude oil (because naphthenic acid is scarcely present in 400 ° F-naphtha), atmospheric residues and reduced pressure light oil (eg, 650 to 1050 ° F). Preferred feedstocks include crude oil, atmospheric distillated crude oil and reduced pressure light oil, especially crude oil and atmospheric distilled crude oil.

The feed is preferably atmospherically pressurized, at atmospheric pressure or under atmospheric pressure, for example at a pressure of from 0.1 to 100 atm, preferably at a pressure of at most about 15 atm, more preferably from 1 to 10 atm, Nitrogen or other non-oxidizing gas). Since the thermal decomposition may cause acid decomposition, facilities for evacuating gas-phase decomposition products such as water vapor, CO ₂ and CO as well as a minimum decomposition product are required. In particular, to minimize the inhibition of the acid decomposition process, the water vapor generated in the feed or generated during the acid decomposition must be continuously swept. Any hard final material or cracked light hydrocarbon product may be recovered by condensation and optionally re-mixed with the treated feed. In practice, an immersion drum may be used with the exhaust to perform the heat treatment method. In a preferred embodiment, CO ₂ and CO will also be swept. The sweeping gas may be a natural gas or other light hydrocarbon gas which can generally be used in a purifier or gas generating plant. The purging velocity of the sweeping gas is 1 to 2000 SCF / BbI (standard cubic feet per barrel of feed, ft ³ / barrel of feed). Preferably, the gaseous product is removed from the reaction zone such that the sum of the partial pressure of CO _{2 and} the partial pressure of CO is less than 0.5 psia and the partial pressure of H ₂ O is less than about 0.2 psia.

Although the heat treatment is time-temperature dependent, the temperature is preferably 600 to 900 DEG F, more preferably 700 to 800 DEG F. The treatment time (residence time at a certain temperature) may vary widely in inverse proportion to the temperature, for example, 30 seconds to about 10 hours, preferably 1 to 90 minutes, more preferably 30 to 90 minutes to be. Of course, the longer the treatment time at any given temperature, the smaller the TAN value in general, but care must be taken not to exceed the already mentioned degradation level.

As noted, an immersion drum may be used to perform a batch or continuous based process. One of skill in the art can consider tubular reactions to perform the process.

The following examples further illustrate the invention and are not intended to be limiting in any way.

Example 1

Experiments performed on open reactors (all open reactors unless otherwise indicated) included distillation equipment similar to those described in ASTM D-2892 or ASTM D-5236. A sample of about 300 g obtained from a 650 ° F + fraction of crude oil was placed in a distillation flask (crude oil could be used easily, but crude oil was not used to prevent physical loss of the 650 ° F- ). The sample was quickly heated to the desired temperature and left at that temperature for less than 6 hours under an inert atmosphere (e.g. nitrogen). Stirring was carried out by generating nitrogen bubbles through the sample, preferably by stirring with a magnetic stir bar. The aliquots were periodically withdrawn for TAN measurements.

In a series of experiments, a 650 ° F + stock solution of African crude oil (Bolobo) was heat immersed for 6 hours in a temperature range of 400 ° F to 650 ° F for three consecutive days and cooled to room temperature overnight . Experiments were performed at atmospheric pressure under a nitrogen atmosphere. Heat immersion is 400 ° F for the first hour, 450 ° F for the second hour, 500 ° F for the third hour, 550 ° F for the fourth hour, 600 ° F for the fifth hour, 650 Lt; 0 > F. The sample was cooled to room temperature and allowed to stand overnight before taking an aliquot. The content of naphthenic acid was monitored by the initial TAN and the TAN after each experimental day. The results are shown in Table 1 below.

[Table 1]

(1) Obtained from crude oil analysis

(2) Two aliquots were taken after each test day and tested independently

The TAN decreased almost linearly during these experiments.

Example 2

In a series of experiments, heat-treated naphthenic acid decomposition was performed in open and closed reactors. In the open type reactor, the generated gas was allowed to slowly escape, while in the closed type reactor, the produced gas was detained. TAN reduction and gas production were measured and the results are shown in Table 2.

[Table 2]

The closed reactor consists of a tubular bomb (25 gm of oil at a reactor volume of 65 cc) or a small bomb (5 gm of oil at a reactor volume of 12 cc).

In the above results, the TAN was not reduced at all in the closed system, suggesting that acid decomposition was prevented due to automatic pressure rise. Direct comparison of the open system with the closed system shows that the TAN is reduced by more than 50% as compared to the closed system in the open system, as shown in Experiments 4 and 5.

Example 3

In another series of experiments, the heat treated naphthenic acid was decomposed in an autoclave to demonstrate the advantage of sweeping the gaseous product from the reaction zone. In Test 1, the resulting gas was continuously swept into helium at a rate of 1275 SCF / BbI, while in Test 2, the resulting gas was held at a maximum pressure of 100 psig. The TAN was measured and the results are shown in Table 3.

[Table 3]

From the above results, it can be seen that sweeping the gas from the reaction zone significantly reduced the TAN and 82% relative to the initial TAN (5.3). In contrast, without sweeping the gas at all, the TAN decreased by only 45.5%.

Example 4

In another series of experiments conducted in an autoclave, the inhibitory effect of water vapor in the presence or absence of CO ₂ and / or CO was studied in relation to TAN reduction by heat treatment. The results are shown in Table 4. In each test, the estimated water partial pressure (H ₂ O, psia) due to TAN conversion was less than 2 (distinct from added water).

[Table 4]

In Test 1, the TAN was the greatest reduction (86.2%) in these series of tests when there was carbon dioxide produced by the decomposition of naphthenic acid without the addition of steam. Test 2, Test 3 and Test 4 showed a gradual decrease in the TAN compared to the case of adding water to the sweeping gas without increasing the amount of water. In Tests 5, 6 and 7, a similar amount of water was added together with a mixture of CO, CO ₂ and CO ₂ and CO, respectively. The TAN reduction rate was lower in all three experiments than in the reference test 2.

These effects can be more easily seen in FIG. 1, plotting% TAN reduction rate versus added water (g / min) using the results obtained in Table 4.

Claims (19)

(a) heat treating the crude oil or crude oil fraction feedstock at a temperature of at least 400F and a treatment zone of 0.1 to 100 atmospheres pressure for a time sufficient to reduce its total acid number (TAN); (b) A method of reducing the TAN of crude oil or crude oil fraction feedstock comprising using sweeping gas of 1 to 2,000 ft ³ per barrel to remove water vapor which simultaneously impedes reduction of TAN in the treatment zone during said heat treatment. The method according to claim 1, Wherein the gaseous reaction products of CO ₂ , CO and water vapor to be simultaneously removed in the treatment zone are produced. 3. The method of claim 2, To this the gaseous reaction product and a CO partial pressure of the sum of the CO ₂ partial pressure is lower than the partial pressure of water vapor 0.5psia removed to less than 0.2 psia. 3. The method of claim 2, Wherein the gaseous reaction product of CO, CO ₂ , water vapor and light hydrocarbons is removed from the treatment zone. 3. The method of claim 2, Wherein all of the gaseous reaction products are removed from the treatment zone. The method according to claim 1, Wherein the feedstock is dehydrated crude oil. 3. The method of claim 2, Wherein the TAN of the feedstock is greater than 2 mg KOH / gm feedstock. 8. The method of claim 7, Wherein the heat treated feedstock has a TAN less than 1.5 mg KOH / gm feedstock. 8. The method of claim 7, RTI ID = 0.0 > 600 F. < / RTI > 8. The method of claim 7, RTI ID = 0.0 > 900 F. < / RTI > 10. The method of claim 9, Wherein the treatment time range is from 1 minute to 10 hours. 10. The method of claim 9, Wherein the heat treated feedstock has a TAN less than 1.0 mg KOH / gm feedstock. 10. The method of claim 9, Wherein the feedstock is crude oil. 10. The method of claim 9, Wherein the feed is crude oil distilled from atmospheric distillation. 10. The method of claim 9, Wherein the feed is atmospheric residues. 10. The method of claim 9, Wherein the feedstock is dewaxed at 650 to 1050F. 10. The method of claim 9, Wherein less than 0.5% by weight of gaseous hydrocarbon product is present on the gas based on the feedstock. 10. The method of claim 9, Wherein the process pressure is between 1 and 10 atmospheres. 5. The method of claim 4, Wherein the light hydrocarbon is a C ₁ -C ₄ hydrocarbon.