[DESCRIPTION] [Invention Title]

METHOD OF REMOVING THE CALCIUM FROM HYDROCARBONACEOUS OIL USING MALEIC ACID OR ITS DERIVATIVES [Technical Field]

The present invention relates to a method of removing calcium from hydrocarbonaceous oil using maleic acid or its derivatives, and more particularly, to a method of removing calcium from hydrocarbonaceous oil using maleic acid or its derivatives, comprising mixing maleic acid (hereinafter, referred to as "MA") or derivatives thereof, which are hydrophilic, with hydrocarbonaceous oil, including calcium-containing crude oil or hydrocarbon residue, to thus prepare a homogeneous mixture, from which calcium can then be efficiently removed. [Background Art]

Calcium in crude oil is mainly present in the form of calcium naphthenate. Further, crude oil having a high calcium content is crude oil (Heidrum, Captain) native to the North Sea, crude oil (Bohai, Shangri) native to China, crude oil (Shering) native to Indonesia, and crude oil

(San Joaquin Valley) native to North America, as well as crude oil (Doba, Quito) native to West

Africa, including Chad and Sudan, where new oil wells are being drilled these days.

In the high-calcium crude oils, since calcium naphthenate functions as an emulsion stabilizer, problems related to the separation of an aqueous layer during a desalting process are caused, and thereby an excessive amount of water flows into a refining device, or an excessive amount of organic material is fed into a wastewater disposal plant, undesirably resulting in low efficiency of the overall process of treating crude oil. Further, calcium present in the residue of the crude oil passed through the refining device causes problems since it functions to inactivate the catalyst within a short time period in a catalytic cracking process using an FCCU (Fluid

Catalytic Cracking Unit) or an RFCCU (Residue Fluidized Catalytic Cracking Unit). Moreover, when the residue is combusted in a boiler, a large amount of calcium sulfate is produced in the boiler, drastically reducing boiler efficiency. Therefore, high-calcium crude oil requires an additional calcium treatment process before a typical refining process is conducted. Furthermore, the demand for efficient calcium removal methods, capable of assuring economic benefits with respect to general crude oil, is increasing.

US Patent No. 4,778,589 discloses a method of removing calcium from hydrocarbonaceous oil using an aqueous solution of hydroxocarboxylic acid, in particular, citric acid. When calcium is removed, calcium citrate is produced. Calcium citrate has low solubility in water, and thus a large amount of precipitate remains in a desalting device, remarkably decreasing calcium removal efficiency. Further, upon the removal of calcium from hydrocarbonaceous oil containing high concentrations of calcium, the pH of the aqueous solution that is used becomes too high, leading to device corrosion problems.

In addition, US Patent No. 4,778,590 discloses a method of removing calcium using amino-carboxylic acid or salts thereof, in particular, EDTA (Ethylene Diamino Tetra Acetic Acid). However, since the EDTA, having low solubility in water, requires the use of an excessive amount of water to prepare it into a calcium removal agent in the form of an aqueous solution, it is disadvantageous in terms of transport and use, resulting in economic and industrial inefficiency. hi addition, US Patent No. 4,778,591 discloses a method of removing calcium from hydrocarbonaceous oil using aqueous carbonic acid and salts thereof, in particular, ammonium carbonate. However, the above method has been reported to be economically disadvantageous because ammonium carbonate should be used in an amount about 5 times as much as the amount of calcium in order to achieve calcium removal efficiency of 90% or higher.

In addition, US Patent Nos. 4,778,592 and 4,789,463 disclose a method of removing iron from hydrocarbonaceous oil using EDTA and citric acid, respectively. Further, US Patent No. 4,853,109 discloses a method of removing calcium using dicarboxylic acid, in particular, oxalic acid. However, since the solubility of oxalic acid in water is typically low, it is difficult to prepare the acid in the form of a high-concentration aqueous solution. Thus, when the acid is formed into a calcium removal agent, it requires the use of an excessive amount of water, and therefore it is disadvantageous in terms of transport and use, incurring economic and industrial problems. Furthermore, the above patent discloses the use of 50% aqueous solution in a desalting extraction process, and is consequently difficult to use industrially. US Patent No. 4,988,433 discloses the use of monocarboxylic acid and salts thereof for calcium removal. In particular, ammonium carboxylic acid is used, hi order to achieve calcium removal efficiency of 80% or higher, acetic acid should be used in an amount about 30 times as much as the amount of calcium. Also, in a continuous process, acetic acid is used in an amount 3.3 times as much as the amount of calcium, but the removal efficiency is low, around 46%, and thus the above technique is not industrially important. Further, due to the thorough dissolution of acetic acid in hydrocarbonaceous oil, the upper portion of a distillation device may undesirably corrode in processes subsequent to a desalting process.

US Patent No. 5,593,573 discloses the use of sulfonic acid or its salts, in particular, ammonium sulfate, as a calcium removal agent. According to the above patent, for the optimal use of ammonium sulfate, the pH of the aqueous solution layer is controlled to be 6-8, and also, a 10% precipitation inhibitor is used therewith so as to prevent the production of a great amount of calcium sulfate in the desalting process. Thus, the above patent suffers because the use of the agent is complicated and economic benefits are negated. Further, to maintain the calcium removal efficiency at 70% or higher, ammonium sulfate should be used in an amount at least 6 times the amount of calcium, leading to negation of economic and

industrial benefits. Furthermore, since sulfonic acid, which is a strong acid, remains in the hydrocarbonaceous oil, it causes problems of corrosion of the distillation device in processes subsequent to the desalting process.

US Patent Application Publication Nos. 2004-45875 and 2005-241997 disclose a method of removing metal and amine from hydrocarbonaceous oil using aqueous hydroxy acid. Examples of the hydroxy acid used include glycolic cid, glucolic acid, C2-C4 alpha-hydroxy acid, and polyhydroxy acid. Among these, the glycolic acid is problematic because it remains in the hydrocarbonaceous oil and consequently corrodes the upper portion of a distillation column at high temperatures in processes subsequent to the desalting process. US Patent No. 6,905,593 discloses a method of removing calcium from hydrocarbonaceous oil by maintaining the pH of an aqueous layer in the range of 3.0-5.0 using acetic acid and aqueous ammonia. However, the control of the pH requires an excessive amount of water, and acetic acid should be used in an amount 9 times the amount of calcium so as to assure calcium removal efficiency of 98% or higher, and the industrial usefulness of the above method is thus limited. Further, in the case where a great amount of acetic acid is used, secondary corrosion of the distillation device is caused by the acetic acid dissolved in hydrocarbonaceous oil.

Japanese Unexamined Patent Publication No. Sho. 52-30284 discloses a method of removing various metals from crude oil using inorganic acid, alkyl phosphate ester and an oxidant. Japanese Unexamined Patent Publication No. Sho. 47-22947 discloses a method of removing metal using alkyl phosphate ester and alkyl carboxylic acid in the absence of inorganic acid, but it results in low metal removal efficiency.

In the above patents, with the goal of removing calcium from hydrocarbonaceous oil including crude oil, inorganic acid or organic acid, in particular, monoacid, diacid, or hydroxy acid is used in such a manner that it is dissolved in water to thus prepare a high concentrate for a

calcium removal agent, which is then diluted with a great amount of water in the desalting process. However, these acids require the use of great amount of water so as to mitigate the problem of low solubility thereof. In the case of monoacid, since excess calcium removal agent should be used, there are problems related to the control of the pH of the aqueous layer and corrosion. Further, the use of hydroxy acid undesirably results in economic and industrial disadvantages concerning secondary corrosion and problems analogous thereto. [Disclosure] [Technical Problem]

As a result of conducting research to avoid the problems encountered in the related art, the present inventors have found that, when MA or its derivatives, which are a hydrophilic compound, are used, the compound can be reacted with a calcium compound using only the water present in hydrocarbonaceous oil or a small additional amount of water, thanks to the high water-solubility thereof, thus making it possible to easily and efficiently remove the calcium from hydrocarbonaceous oil, including high-calcium crude oil or hydrocarbon residue. Accordingly, an object of the present invention is to provide a method of efficiently removing calcium from hydrocarbonaceous oil, including crude oil or hydrocarbon residue, using MA or its derivatives. [Technical Solution]

In order to accomplish the above object, the present invention provides a method of removing calcium from hydrocarbonaceous oil using MA or its derivatives, comprising steps of:

1) adding MA or its derivatives to a hydrocarbon source containing calcium, to thus prepare a homogeneous mixture; 2) subjecting the maleic acid or its derivatives in the homogeneous mixture, along with calcium naphthenate present in the homogeneous mixture to metal substitution, to thus produce calcium dicarboxylate; and 3) desalting the calcium

dicarboxylate to remove it. [Advantageous Effects]

Unlike conventional calcium removal methods, in the method of removing calcium according to the present invention, a hydrophilic compound is mixed with a calcium-containing oil, such as crude oil, to thus prepare a homogeneous mixture, which is then reacted with calcium so that the calcium is deposited as an insoluble material to remove it, thereby effectively removing calcium while solving problems related to the limited mixing ratio of crude oil having high concentrations of calcium, to pH control, and to the transport and use thereof due to the use of excessive amount of water. Thus, the method of the present invention can be advantageously applied to the extraction of high-calcium crude oil from an oil well, the pretreatment of crude oil before distillation, the removal of calcium from hydrocarbon mixtures, or the efficient removal of calcium from other oils containing calcium, and is therefore expected to be industrially useful.

[Description of Drawings]

FIG. 1 is a graph illustrating the Ca removal efficiency depending on the reaction time of solid MA in Example 1 of the present invention; and

FIG. 2 is a graph illustrating the Ca removal efficiency depending on the amount of MA in Example 3 of the present invention. [Best Mode]

Hereinafter, a detailed description will be given of the present invention. According to the present invention, the method of efficiently removing calcium from hydrocarbonaceous oil including calcium-containing crude oil or hydrocarbon residue is provided. In the present invention, the selective use of MA or derivatives thereof, which are a hydrophilic compound, is characteristic.

More particularly, in the present invention, MA or its derivatives are reacted with the calcium in the oil to thus produce an insoluble compound that is able to be deposited, whereby

the calcium can be effectively removed through the simple and easy process of the invention.

The method of removing the calcium according to the present invention comprises 1) adding MA or derivatives thereof, which are a hydrophilic compound, to a hydrocarbon source containing calcium, thus preparing a homogeneous mixture; 2) subjecting the MA or derivatives thereof and the calcium naphthenate present in the homogeneous phase to metal substitution, thus producing calcium dicarboxylate; and 3) desalting the calcium dicarboxylate to thus remove it.

Individual steps are described in detail below.

The present invention is intended to remove calcium from a hydrocarbon source, not limited to high-calcium crude oil and hydrocarbon residue, including atmospheric residue or vacuum residue, which is a semi-finished product obtained in a crude oil refining process, but also including other hydrocarbon oils, such as oil shale, oil sands, liquefied coal oil, and tar sands. Accordingly, the method of the present invention enables the effective removal of calcium from a hydrocarbon source containing 10 to 3,000 ppm calcium. First, MA or derivatives thereof, which are a compound containing a carboxylic group, are selected, and are then added to a hydrocarbon source including calcium-containing crude oil or hydrocarbon reside from which the calcium should be removed. Upon the addition thereof, the compound (MA or its derivatives) may be directly added in a solid phase or in a liquid phase. The compound is used in a molar ratio of 0.5 to 20, and preferably, 1.0 to 10 relative to the amount of calcium contained in the crude oil. When the molar ratio is less than 0.5, the removal efficiency is decreased in terms of the equivalent reaction. On the other hand, when the ratio exceeds 20, the disposal cost is increased, and furthermore, the cost of post-treatment in a wastewater disposal plant after the desalting process is greatly increased. In the case where the compound is added to the crude oil or hydrocarbon oil to thus

prepare a homogeneous mixture, any method which is known to those skilled in the art may be applied. For example, the added compound is stirred at a predetermined temperature from -10 to 200 ⁰ C, and preferably from 20 to 140 ⁰ C, for a time period ranging from 1 sec to 2 hours, and preferably from 0.2 min to 30 min, so as to realize complete dispersion and sufficient dissolution thereof. Thereby, a homogeneous mixture, in which the compound is completely dissolved, may be obtained.

Thereafter, the compound is dissolved in water which is already present in the crude oil. In the crude oil, since water is typically present in an amount of 0.1 to 0.5%, the compound may be dissolved therein even without the use of additional water. However, in the case of vacuum residue having no water, the compound may be added in a liquid phase, that is, in a state of being diluted with water or an organic solvent. In this case, the compound is diluted to a concentration of 5 to 80 wt% with water or an organic solvent. Such a compound is present in a homogeneously mixed state.

In the homogeneous mixture, the compound and the calcium naphthenate are subjected to metal substitution, thus producing calcium dicarboxylate. As such, in order to efficiently realize metal substitution between calcium metal, which is present in a very small amount, and viscous crude oil or hydrocarbon residue, it is very important that the stirring speed of the reactor be controlled. For example, a stirring speed on the order of 100-4,000 rpm or a Reynolds number of 4,000 or more should be preferably maintained to assure a desired mixing state, and, more preferably a stirring speed of 200-3,000 rpm is maintained. In particular, in the case of a continuous process, the stirring speed of an impeller is increased when a mixing pump and a centrifugal pump have the same mixing capability.

For efficient metal substitution, it is preferred that a reaction temperature ranging from 10 to 200°C, and preferably from 50 to 140°C, and a reaction time ranging from 1 sec to 4 hours, and preferably from 1 min to 60 min, be maintained.

Finally, the produced calcium dicarboxylate is removed through a desalting process. To this end, a general production process may be applied. In the present invention, the process was performed using PED (Portable Electronic Desalter, available from Inter Av.). For example, at a DC voltage of 3,000 Volts, the desalting process was performed for a time period ranging from 10 min to 2 hours, and preferably 1 hour, and at 50-100°C, and preferably 9O ⁰ C. hi such a case, water may be used in an amount of 5-50%, and preferably 10%. Further, an additive is used to increase oil-water separation efficiency, and any additive typically known in the art may be used. For example, a commercially available demulsifier (Prochem 2X24, Petrolite) may be used in an amount of 1-100 ppm, and preferably 2-10 ppm. In the present invention, the method of removing the calcium is preferably conducted at a reaction pressure ranging from atmospheric pressure to 20 ami. hi this way, according to the present invention, the hydrophilic compound having high solubility in water is added to hydrocarbonaceous oil, such as crude oil or hydrocarbon residue, and thus, conventional problems related to the use of excessive amounts of water, pH control, corrosion, and the limited mixing ratio of crude oil containing high concentrations of calcium can be solved, and calcium can be easily and economically removed at high efficiency.

Therefore, the method of the present invention is expected to be variously applicable to diverse fields requiring the removal of calcium, in particular, the extraction of high-calcium crude oil from an oil well, the pretreatment of crude oil before distillation, and the removal of calcium from hydrocarbon mixtures and other oils. [Mode for Invention]

Below, the present invention is more specifically described through the following examples, but the scope of the present invention is not limited thereto.

Example 1 Doba crude oil, native to West Africa (Chad), was blended with general crude oil, to

thus prepare crude oil for a test having a concentration of 20%, which is referred to as 20% Doba blend. As a result of analysis through ICP, the concentration of calcium was measured to be an average of 56 ppm.

Into a 500 ml round bottom flask, 95 ml of 20% Doba blend was added, and thereafter 22 mg (1 equivalent) of MA was added in a solid phase, after which the flask was fitted into a 500 ml heating mantle and was then stirred at 1 ,000 rpm using a mechanical stirrer.

Using a heating mantle controller, the reaction temperature was increased from room temperature to 140°C, and the reaction time was set to be 0.5-10 min, as shown in Table 1 below.

After the completion of the reaction, the reaction temperature was decreased to 90°C within 30 sec using ice water, after which 5 ml of deionized water was added and 1 mg of a demulsifier (Prochem 2x24, Petrolite) was then added, followed by performing a stirring process at 90°C for l5 min.

After the stirring process, the reaction solution was transferred into the glass tube of a

PED (Portable Electric Desalter) in order to conduct a desalting process. As the PED, EDPT (Electrostatic Dehydration & Precipitation Tester)-228, made by Inter Av Inc (San Antonio,

Texas, USA), was used. The glass tube containing the sample was placed in the PED, and then the PED was operated at 90°C for 30 min at 3,000 Volts to realize good oil-water separation.

After the completion of the oil- water separation, 20 g of the sample was removed from the middle layer of the separated oil and then subjected to an ICP test. In an actual distillation process, the period of time required to transfer the crude oil to the desalter was about 10 min. As such, during the first 3 min, the temperature was increased from room temperature to 14O ⁰ C, and, for the next 7 min, the reaction temperature was maintained at 140°C.

In Example 1, the amount of solid MA was unchanged, and the reaction temperature and time were changed. In such a case, the results of Ca removal efficiency are shown in Table 1 below and in FIG. 1.

TABLE l

As is apparent from Table 1 and FIG. 1, the Ca removal efficiency was gradually increased with the increase in reaction time and reaction temperature. Thus, in the case where MA was added in the distillation process, the Ca removal effect was confirmed. Example 2

Using an aqueous MA solution, the reaction time and the reaction temperature were adjusted to be suitable for an actual distillation process. The test method was the same as in Example 1 , with the exception that an aqueous solution in which 4 g of MA was dissolved in 10 g of deionized water was used to easily add the MA.

As a result of a test simulating the transfer of the sample to the desalter using CRA (Calcium Removal Agent), the Ca removal efficiency was determined to gradually increase with the increase in time and temperature, and the Ca removal efficiency was increased more than when using the solid MA. The results are shown in Table 2 below.

TABLE 2

Accordingly, in the case where liquid MA is applied to a distillation process, it is expected that the process can be more efficiently performed using an aqueous MA solution and that the Ca removal effect is higher than when using the solid MA.

Example 3

The Ca removal efficiency was measured depending on the amount of liquid MA. The test method was the same as in Example 2, with the exception that the reaction temperature was set at 140°C, the reaction time was set at 10 min and the amount of the aqueous MA solution was changed. The results are shown in Table 3 below and in FIG. 2.

TABLE 3

As is apparent from Table 3 and FIG. 2, when the amount of MA was increased from 0.5 equivalents to 1.0 equivalent, the Ca removal efficiency was gradually increased. Consequently, it was confirmed that the amount of MA was controlled to thus realize desired Ca removal performance.