Claims:WE CLAIM
1. A process for reducing the total acid number (TAN) of acidic crude oil comprising naphthenic acid, said process comprising the following steps:
a) complexing at least one alkali salt with at least one hydrogen bond donor, at a temperature in the range of 20 °C to 100 °C, to obtain a deep eutectic solvent having pH in the range of 8 to 14;
b) mixing acidic crude oil comprising naphthenic acid with said deep eutectic solvent to obtain a first reaction mixture, followed by stirring the first reaction mixture at a temperature in the range of 20 °C to 80 °C, to obtain a first product mixture comprising crude oil with reduced total acid number, alkali metal salts of said naphthenic acids, and unreacted deep eutectic solvent;
c) allowing said first product mixture to settle to obtain a first biphasic mixture comprising an upper layer of crude oil with reduced total acid number and a lower layer comprising alkali metal salts of said naphthenic acids, and unreacted deep eutectic solvent; and
d) obtaining crude oil with reduced total acid number by separating said upper layer from said lower layer of the first biphasic mixture.
2. The process as claimed in claim 1, wherein in step (a), complexation is carried out under an inert atmosphere.
3. The process as claimed in claim 1, wherein in step (a), complexation is carried out at a stirring speed in the range of 200 rpm to 600 rpm.
4. The process as claimed in claim 1, wherein in step (b), mixing is carried out at a stirring speed in the range of 100 rpm to 1000 rpm.
5. The process as claimed in claim 1, wherein the weight ratio of said at least one alkali salt to said at least one hydrogen bond donor is in the range of 1:1 to 1:10.
6. The process as claimed in claim 1, wherein said at least one alkali salt is selected from the group consisting of potassium carbonate (K2CO3), sodium carbonate (Na2CO3), and ammonium carbonate ((NH4)2CO3).
7. The process as claimed in claim 1, wherein said at least one hydrogen bond donor is selected from the group consisting of poly-hydroxy alcohol, an acid, an amine, and a halide; wherein said poly-hydroxy alcohol is at least one alcohol selected from the group consisting of glycerol, and mono ethylene glycol; preferably said poly-hydroxy alcohol is mono ethylene glycol.
8. The process as claimed in claim 1, wherein the weight ratio of said acidic crude oil to said deep eutectic solvent is in the range of 5:1 to 50:1.
9. The process as claimed in claim 1, further comprises a step of recovering hydrogen bond donor and naphthenic acids from said separated lower layer; said step comprises following sub-steps:
i. mixing said separated lower layer with dilute mineral acid to obtain a second reaction mixture having a pH in the range of 1 to 3, followed by stirring the second reaction mixture to decompose said unreacted deep eutectic solvent, and to convert the alkali metal salt of naphthenic acids into naphthenic acids, to obtain a second product mixture comprising naphthenic acids, and said hydrogen bond donor;
ii. mixing said second product mixture with an organic solvent to obtain a second biphasic mixture comprising organic phase comprising said naphthenic acids and aqueous phase comprising said hydrogen bond donor;
iii. separating said organic phase from said second biphasic mixture to obtain a separated organic phase and a separated aqueous phase;
iv. subjecting said separated organic phase to distillation to obtain crude naphthenic acids; wherein the distilled organic solvent is recovered and recycled to step (ii); and
v. isolating said hydrogen bond donor from said separated first aqueous phase and recycling said hydrogen bond donor to step (a).
10. The process as claimed in claim 9, wherein said mineral acid is selected from the group consisting of HCl, and H2SO4; and said organic solvent is selected from the group consisting of dichloromethane, chloroform, and carbon tetrachloride.
, Description: FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. Title of the Invention
A PROCESS FOR REDUCING TOTAL ACID NUMBER OF ACIDIC CRUDE OIL
2. Applicant(s)
Name Nationality Address
RELIANCE INDUSTRIES LIMITED Indian 3RD FLOOR, MAKER CHAMBER-IV, 222, NARIMAN POINT, MUMBAI-400021, MAHARASHTRA INDIA
3. Preamble to the description

The following specification particularly describes the invention and the manner in which it is to be
performed

The present disclosure relates to a process for reducing the total acid number of acidic crude oil.
DEFINITION
Total Acid Number (TAN): TAN is considered as a measure of corrosion caused by acidic crude oils and is defined as the number of milligrams of potassium hydroxide required to neutralize the acid content of one gram of crude oil.
Naphthenic acid: Naphthenic acid is a generic name used for all organic acids in crude oil, which includes carboxylic acids, including aliphatic, naphthenic and aromatic acids.
Deep Eutectic Solvent (DES): A DES is generally composed of two or more components such as an inorganic compound (Lewis or Brønsted acids and bases) and a hydrogen bond donor (HBD), which are capable of associating with each other, through hydrogen bond interactions, to form a liquid having composition close to an eutectic mixture. The DES is characterized by a melting point lower than that of each individual component.
Eutectic Mixture: An eutectic mixture is a complex of two or more components formed by hydrogen bonding between these components and which at certain ratios, inhibit the crystallization process of one another resulting in a system having a lower melting point than either of the components.
Hydrogen Bond Donor: The hydrogen bond donor is a molecule or a molecular fragment X–H, in which X is more electronegative than H, and the hydrogen atom H forms an attractive interaction with an atom or a group of atoms in the same or a different molecule, in which there is evidence of bond formation.
Alkali Salts: Alkali salts are products of the neutralization of strong bases and weak acids. Alkali salts are bases, as the conjugate bases from the weak acids hydrolyze to form basic solutions.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Corrosion of the equipment is a major problem in the oil refineries. The corrosion of the refinery equipment is caused due to acidity of the crude oil being refined. The high acidic crude oils (i.e., having high TAN value) typically contain high amount of sulfur (>1 wt. %), metals, acids such as mono carboxylic acids, including aliphatic, naphthenic and aromatic acids. The term naphthenic acid is used for all organic acids contained in the crude oil.
The term “total acid number” (TAN) is considered as a measure of corrosion caused by acidic crude oils. It is desired to have crude oils with low TAN, which reduces the corrosion of the refinery equipment to an extent thereby increasing its life. However, the low TAN value crude oil is costly as compared to the high TAN value crude oil.
In order to increase the refinery margins, the present practice is to mix the highly acidic crudes with nonacidic crudes. However, this approach limits the processing of high acidic crudes. Since, the market value of such acidic crude oil is low and hence to get more economic benefit it is important to process these acidic naphthenic crudes to high value crudes.
Attempts have been made to tackle this problem of acid corrosion by remedies such as coating, addition of corrosion inhibitors in crude oil, or to mix the high acid crude with low acid crude by blending.
However, the above-mentioned methods are not feasible and cost effective due to limited supply of low acid crude and non-uniformity in coating of the processing unit. To reduce the corrosion in processing units, most of the refineries use corrosion inhibitors, and the dosage of the same depends on the TAN value which is a cost to refinery.
Another method to reduce the TAN value is neutralization of acidic crudes with bases. But this method suffers from drawbacks such as emulsion formation, increase in concentration of inorganic salts and additional processing steps.
There is, therefore, felt a need to provide a simple and efficient process for reducing the total acid number of acidic crude oil which uses low cost green solvent on industrial scale.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide a process for reducing total acid number (TAN) of acidic crude oil.
Still another object of the present disclosure is to provide a process for reducing total acid number (TAN) of acidic crude oil that is simple, efficient and inexpensive.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.

SUMMARY
The present disclosure relates to a process for reducing the total acid number of acidic crude oil.
In accordance with the present disclosure, the process for reducing the total acid number (TAN) of acidic crude oil comprising naphthenic acids, comprises the step of complexing at least one alkali salt with at least one hydrogen bond donor, and at a temperature in the range of 20 °C to 100 °C, to obtain a deep eutectic solvent having pH in the range of 8 to 14. The acidic crude oil is mixed with the deep eutectic solvent to obtain a first reaction mixture, followed by stirring the first reaction mixture at a temperature in the range of 20 °C to 80 °C, to obtain a first product mixture comprising crude oil with reduced total acid number, alkali metal salts of said naphthenic acids, and unreacted deep eutectic solvent. The first product mixture is allowed to settle to obtain a first biphasic mixture comprising an upper layer of crude oil with reduced total acid number and a lower layer comprising alkali metal salts of said naphthenic acids, and unreacted deep eutectic solvent. The crude oil with reduced total acid number is obtained by separating the upper layer from the lower layer of the first biphasic mixture.
The step of complexation is carried out under an inert atmosphere.
The step of complexation is carried out at a stirring speed in the range of 200 rpm to 600 rpm.
The step of mixing is carried out at a stirring speed in the range of 100 rpm to 1000 rpm.
In accordance with the present disclosure, the weight ratio of the at least one alkali salt to the at least one hydrogen bond donor is in the range of 1:1 to 1:10.
In accordance with the present disclosure, the at least one alkali salt is selected from the group consisting of potassium carbonate (K2CO3), sodium carbonate (Na2CO3), and ammonium carbonate ((NH4)2CO3).
In accordance with the present disclosure, the at least one hydrogen bond donor is selected from the group consisting of poly-hydroxy alcohol, an acid, an amine, and a halide.
In accordance with the present disclosure, the poly-hydroxy alcohol is at least one alcohol selected from the group consisting of glycerol, and ethylene glycol, preferably the poly-hydroxy alcohol is ethylene glycol.
In accordance with the present disclosure, the weight ratio of the acidic crude oil to the deep eutectic solvent is in the range of 5:1 to 50:1.
In accordance with the present disclosure, the process for reducing the total acid number of acidic crude oil further comprises a step of recovering hydrogen bond donor and naphthenic acids from the separated lower layer comprising unreacted deep eutectic solvent and alkali metal salts of the naphthenic acids. The step comprises the sub-step of mixing the separated lower layer with dilute mineral acid to obtain a second reaction mixture having a pH in the range of 1 to 3, followed by stirring the second reaction mixture to decompose the unreacted deep eutectic solvent, and to convert the alkali metal salt of naphthenic acids into naphthenic acids, to obtain a second product mixture comprising naphthenic acids, hydrogen bond donor, and precipitated solids. The second product mixture is mixed with an organic solvent to obtain a second biphasic mixture comprising organic phase comprising the naphthenic acids and aqueous phase comprising the hydrogen bond donor. The organic phase is separated from the second biphasic mixture to obtain a separated organic phase and a separated aqueous phase. The separated organic phase is subjected to distillation to obtain crude naphthenic acids. The distilled organic solvent is recovered and recycled for mixing with the second product mixture. The hydrogen bond donor is isolated from the separated first aqueous phase and recycled for complexing with at least one alkali salt.
In accordance with the present disclosure, the mineral acid is selected from the group consisting of HCl, and H2SO4, and the organic solvent is selected from the group consisting of dichloromethane, chloroform, and carbon tetrachloride.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates a schematic of process flow diagram for reducing the total acid number of acidic crude oil in accordance with the present disclosure.
Reference number Elements
102 First mixer
104 Second mixer
106 Separator
108 Acidic crude oil storage
110 Storage tank for crude oil having reduced TAN
112 Recovery unit
114 Naphthenic acid stream
116 Ethylene glycol stream

DETAILED DESCRIPTION
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details, are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
When an element is referred to as being "mounted on," “engaged to,” "connected to," or "coupled to" another element, it may be directly on, engaged, connected or coupled to the other element. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
Terms such as “inner,” “outer,” "beneath," "below," "lower," "above," "upper," and the like, may be used in the present disclosure to describe relationships between different elements as depicted from the figures.
The present disclosure provides a process to overcome the drawbacks of the conventional processes. Particularly, the present disclosure provides a process for reducing the TAN value of acidic crude oil.
The process for reducing TAN value of the acidic crude oil of the present disclosure is described with reference to Figure 1, which depicts a schematic flow diagram (100) of the process.
In accordance with the present disclosure, at least one alkali salt is complexed with at least one hydrogen bond donor in a first mixer (102), at a predetermined pressure, at a first predetermined temperature, while stirring under inert atmosphere at a first predetermined speed for a first predetermined time period to obtain a deep eutectic solvent having pH in the range of 8 to 14.
Typically, the predetermined pressure is atmospheric pressure; the first predetermined temperature is in the range of 20 °C to 100 °C, the first predetermined speed is in the range of 200 rpm to 600 rpm, and the first predetermined time period is in the range of 0.1 hour to 10 hours.
The deep eutectic solvent so obtained is thereafter mixed with acidic crude oil comprising naphthenic acids, from acidic crude oil storage (108), to obtain a first reaction mixture in a second mixer (104), followed by stirring the first reaction mixture at a second stirring speed, at a second predetermined temperature for a second predetermined time period, to obtain a product mixture comprising crude oil with reduced total acid number, alkali metal salts of said naphthenic acids, and unreacted deep eutectic solvent. On mixing with the deep eutectic solvent, the naphthenic acids present in the acidic crude oil form alkali metal salts of the naphthenic acids, which are not acidic thereby resulting in reduced TAN value of crude oil. The alkali metal salts of naphthenic acids are insoluble in crude oil but readily dissolve in the unreacted deep eutectic solvent. The acidic crude oil also comprises dissolved solids, which are readily soluble in the unreacted deep eutectic solvent.
Typically, the second predetermined speed is in the range of 100 rpm to 1000 rpm, preferably the second predetermined speed is 400 rpm; the second predetermined temperature is in the range of 20 °C to 80 °C and the second predetermined time period is in the range of 0.5 hour to 5 hours. In one embodiment, the second predetermined temperature is 45 ?C.
The product mixture comprising crude oil with reduced total acid number and the unreacted deep eutectic solvent is then transferred to a separator (106), wherein the product mixture is allowed to settle to obtain a first biphasic mixture comprising an upper layer of crude oil with reduced total acid number and a lower layer comprising alkali metal salts of the naphthenic acids, and unreacted deep eutectic solvent.
The step of separation of the upper layer comprising crude oil with reduced total acid number from the mixture is carried out in the separator (106), wherein the upper layer is separated from the first biphasic mixture to obtain crude oil with reduced total acid number, which is received in a storage tank (110).
Typically, the crude oil having reduced total acid number can be separated from the lower layer comprising alkali metal salts of the naphthenic acids, and unreacted deep eutectic solvent by using at least one separation technique selected from the group consisting of centrifugation, pressure nutsche filtration, agitated nutsche filtration, vacuum filtration, and belt filtration. The separated crude oil having reduced TAN can be subjected to further processing and the lower layer comprising alkali metal salts of the naphthenic acids, and the unreacted deep eutectic solvent can be subjected to further processing.
Further, the lower layer comprising alkali metal salts of the naphthenic acids and the unreacted deep eutectic solvent that is received from the separator (106) is sent to a recovery unit (112). In the recovery unit, the lower layer is mixed with dilute mineral acid to obtain a second reaction mixture having a pH in the range of 1 to 3, followed by stirring the second reaction mixture to decompose the unreacted deep eutectic solvent, to convert the alkali metal salts of the naphthenic acids into naphthenic acids, and to precipitate the dissolved solids, to obtain a second product mixture comprising naphthenic acids, and the hydrogen bond donor, wherein the second product mixture is mixed with an organic solvent to obtain a second biphasic mixture comprising organic phase comprising the naphthenic acids and aqueous phase comprising the hydrogen bond donor, wherein the organic phase is separated from the second biphasic mixture to obtain a separated organic phase and a separated aqueous phase, wherein the separated organic phase is subjected to distillation to obtain the pure naphthenic acids stream (114), wherein the distilled organic solvent is recovered and recycled for mixing with the second product mixture. The separated first aqueous phase is further processed in the recovery unit (112) to isolate the hydrogen bond donor and the isolated hydrogen bond donor stream (116) is then recycled back to the first mixer (102).
More particularly, the lower layer (obtained from the separator (106)) is sent to the recovery unit (112). Typically, in the recovery unit (112) the lower layer comprising the unreacted deep eutectic solvent and alkali metal salts of the naphthenic acids are mixed with an acid (such as dilute HCl) at a predetermined temperature (typically at 25 °C) to obtain a second reaction mixture having a pH value in the range of 1 to 3. On mixing with the mineral acid, the unreacted deep eutectic solvent in the lower layer decomposes to provide a second product mixture comprising the hydrogen bond donor, whereas the alkali metal salt of naphthenic acids in the lower layer are converted to the naphthenic acids. The second product mixture comprises precipitated solids, hydrogen bond donor, water, and naphthenic acids. The second product mixture is mixed with dichloromethane (DCM) to obtain a second biphasic mixture comprising dichloromethane phase (organic phase) comprising the naphthenic acids and aqueous phase comprising the hydrogen bond donor. The dichloromethane phase is separated from the second biphasic mixture to obtain a separated dichloromethane phase comprising the naphthenic acids and a separated aqueous phase comprising the hydrogen bond donor. The dichloromethane phase containing naphthenic acids can be distilled to obtain crude naphthenic acids and the dichloromethane collected after the distillation can be recycled back for the extraction of naphthenic acids. Further, the at least one hydrogen bond donor and water in the separated aqueous phase can be separated by distillation or membrane separation of water to recover the at least one hydrogen bond donor, which can be recycled back to the first mixer (102).
In accordance with the embodiments of the present disclosure, the predetermined weight ratio of the at least one alkali salt to the at least one hydrogen bond donor can be in the range of 1:1 to 1:10, typically the molar ratio is 1:6.
The at least one alkali salt can be selected from the group consisting of potassium carbonate (K2CO3), sodium carbonate (Na2CO3), and ammonium carbonate ((NH4)2CO3). Typically, the at least one alkali salt is potassium carbonate (K2CO3).
The at least one hydrogen bond donor can be selected from the group consisting of poly-hydroxy alcohol, an acid, an amine, and a halide.
Particularly, the poly-hydroxy alcohol can be selected from the group consisting of glycerol, and ethylene glycol. Preferably, poly-hydroxy alcohol is ethylene glycol.
As in case of ionic liquids, the combination of the strength of the cation and the anion determines the acidity or basicity of the ionic liquid. The same is true for the deep eutectic solvent’s nature. However, the acidity or basicity of deep eutectic solvent is determined by the nature of the alkali salt and the hydrogen bond donor. In the present disclosure, alkali/basic salt potassium carbonate (K2CO3), when mixed with hydrogen bond donor ethylene glycol, provides basic deep eutectic solvent (DES).
Further, the deep eutectic solvent obtained, on combining the at least one alkali salt and the at least one hydrogen bond donor compound, has a melting point that is much lower than either of the individual constituents. For example, when potassium carbonate having a melting point of 891 °C is mixed with ethylene glycol having a melting point of 17 °C, the deep eutectic solvent obtained has a melting point below 0 °C. Additionally, the deep eutectic solvent (potassium carbonate and ethylene glycol) is homogenous and transparent colourless liquid.
It is observed that the deep eutectic solvent of the present disclosure is prone to structural changes in the presence of moisture. Therefore, the deep eutectic solvent is prepared under inert atmosphere. Also, for the same reason, the deep eutectic solvent is stored in sealed vials to eliminate contamination with moisture.
Typically, the process of the present disclosure can be operated in a mode selected from the group consisting of a batch mode, semi-continuous mode and continuous mode.
The process of the present disclosure can be used to reduce the TAN value of acidic crude oil, wherein the acidic crude oil can have total acid number (TAN) in the range of 0.5 to 5, but is not limited to this range.
The weight ratio of the acidic crude oil to the deep eutectic solvent can be in the range of 5:1 to 50:1. Typically, the weight ratio of the acidic crude oil to the deep eutectic solvent can be 25:1; preferably the weight ratio can be 10:1.
Typically, the first mixer (102) and the second mixer (104) can be at least one selected from the group consisting of a stirrer, static mixer, jet mixer, and pump mixer.
In the step of neutralizing, the total acid number (TAN) of acidic crude oil is reduced to a value in the range of 0.01 to 0.04 and the percentage of TAN value reduction is in the range of 95% to 99.5%.
In the present disclosure, the proposed process is capable of reducing TAN of acidic oil by removing greater than 90% of the naphthenic acid.
The process of the present disclosure can be carried out without use of water, without use of expensive corrosion inhibitors. The process avoids the formation of stable emulsions and surfactants, and trims down the usage of de-emulsifiers and Calcium Releasing Agent (CRA) in desalting. Further, the components of the deep eutectic solvent, namely the hydrogen bond donor can be recovered and recycled in the process, thereby lowering the cost of operation.
The crude naphthenic acids, recovered in the process of the present disclosure have various industrial applications and provide economic benefits, thereby reducing the operating cost of the operation.
As can be gathered from the preceding description, the process of the present disclosure, for reducing the total acidic number of the crude oil by neutralizing and thereafter removing the naphthenic acids therein by treating the acidic crude oil with the deep eutectic acid, can be carried out at mild operating conditions as compared to the conventional processes.
Further, the process of the present disclosure can be used for reducing total acid number of highly acidic crude oil/VGO/diesel/kerosene, wherein the total acid number can be greater than 2.
The removal of the naphthenic acids prevents catalyst deactivation and protects the refinery equipment such as crude distillation unit (CDU) and vacuum distillation unit (VDU) from high temperature corrosion.
Thus, using the process as described herein above, the low value acidic crude oil can be converted into high value non-acidic crudes oil, thereby resulting in improved refining margins.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
EXPERIMENTAL DETAILS:
Experiment 1: Preparation of Deep Eutectic Solvent (DES)
Example 1: Preparation of Deep Eutectic Solvent (DES) using potassium carbonate and ethylene glycol.
Potassium carbonate (10 g, 0.178 mol) and mono ethylene glycol (77.41 g, 1.247 mol) were mixed in a round bottom flask at 353.15 K, at atmospheric pressure, at a stirring speed of 400 rpm for 2 hours to obtain a homogenous, transparent, and colorless liquid of Deep Eutectic Solvent.
Experiment 2: Treatment of acidic crude oil with DES for reducing TAN
Example 1: Treatment of acidic Model oil with DES for reducing TAN
Model oil (50 g) having an initial TAN of 0.92, was mixed with DES (2 g), prepared in Example 1, in a 3 neck round bottom flask at 45 °C and stirred at 400 rpm for 60 min to obtain a mixture comprising the model oil with reduced TAN. The mixture was transferred to a separating funnel and allowed to separate into biphasic layers containing an upper layer of the model oil and a lower layer of unreacted DES, followed by separating the model oil layer from the unreacted DES layer by decanting. The TAN of the separated oil was found to be 0.02. The % reduction of TAN was found to be 97.8%.
Example 2: Treatment of acidic crude oil with DES for reducing TAN and Sulfur
Crude oil (50 g), having an initial TAN of 2.45 mg KOH/g of oil and Sulfur having 1.99% (from CHNS analysis), was mixed with DES (2 g) obtained in Example 1, in a 3 neck round bottom flask at 45°C and stirred at 400 rpm for 30-60 min. The mixture was transferred to a separating funnel and allowed to separate into biphasic layers containing an upper layer of the crude oil and a lower layer of unreacted DES, followed by separating the crude oil layer from the unreacted DES layer by decanting. The TAN and Sulfur analysis of the separated crude oil was found to be 0.02 mg KOH/g and 1.37% respectively. The % reduction of TAN and Sulfur was found to be 99.18 % and 20-30% respectively.
Example 3: Treatment of acidic vacuum gas oil with DES for reducing TAN
Vacuum gas oil (VGO) (50 g), having an initial TAN of 2.74, was mixed with DES (5 g) obtained in Example 1, in a 3 neck round bottom flask at 45 °C and stirred at 400 rpm for 60 min. Since, VGO is highly viscous and solid at room temperature; the separation of the mixture was done at a temperature of 45 °C, by adding 1:1 mole of hydrocarbon (various crudes) to methanol. The mixture was transferred to a separating funnel and allowed to separate into biphasic layers containing an upper layer of oil and a lower layer of unreacted DES, followed by separating the oil layer from the unreacted DES layer. The TAN of the separated oil was found to be 0.03. The % reduction of TAN was found to be 98.9%.
Example 4: Treatment of acidic crude oil (Doba) with DES for reducing TAN
Crude oil (Doba) (50 g), having an initial TAN of 2.4 mg of KOH/g of oil, was mixed with DES (7 g) &water (1 g) was mixed in a 3 neck round bottom flask at 50 °C and stirred at 350 rpm for 60 min. The objective of the present experiment is to find the effect of water dilution. The mixture was transferred to a separating funnel and allowed to separate into biphasic layers containing an upper layer of oil and a lower layer of unreacted DES, followed by separating the oil layer from the unreacted DES layer. The TAN of the separated oil was found to be 1.2 mg of KOH/g of oil. The % reduction of TAN was found to be 50%.
Example 5: Treatment of acidic crude oil (Doba) with DES for reducing TAN
Crude oil (Doba) (100 g), having an initial TAN of 2.08 mg of KOH/g of oil, was mixed with DES (10 g) &water (7 g) was mixed in a 3 neck round bottom flask at a temperature of 115-120 °C and stirred at 180 rpm for 10 min. The objective of the present experiment is to find the effect of water dilution. Samples were collected at every five minutes, it was observed that TAN was reduced from 2.05 to 0.01 mg of KOH/g of oil within 5 min. water is collected as distillate. Water addition does not have any effect on the TAN reduction.
Example 6: Treatment of acidic crude oil (Doba) having an initial TAN of 2.08 mg of KOH/g of oil.
Crude oil (Doba) (100 g), having an initial TAN of 2.08 mg of KOH/g of oil, was mixed with DES (3 g) was mixed in a 3 neck round bottom flask at a temperature of 130-135 °C and stirred at 180 rpm for 10 min. Samples were collected at every 2 minutes, it was observed that TAN was reduced from 2.05 to 0.01 mg of KOH/g of oil within 5 min. water addition does not have any effect on the TAN reduction.
Example 7: TAN reduction (especially naphthenic acid removal) from a crude blend
The blend was prepared in such a way that Mangala crude 200 g, Rancodar crude 200g, Doba crude 300g and Merry-16 300g of different crudes having different properties are blended by weight basis. After blending the crude blend having an initial TAN of 0.9894 mg of KOH/g of oil. The blended crude is considered as initial feed for our TAN reduction. The experiment was conducted at 600C in a continuous capillary reactor. The temperature of the reactor is mentioned by a jacket having continuous water circulation by thermostat. The flow rates of crude and DES is controlled by two peristaltic pumps having a flow rate of 0.933 L/h and 0.4368 respectively. The samples were collected at subsequent intervals and TAN was measured. We found that the TAN was reduced from 0.933 to almost zero. There is a complete reduction of naphthenic acid content in the crude blend .the unreacted DES is recovered and recirculated continuously until it gets saturated. The overflow will contains the treated crude free of acidity.

Experiment 3: Recovery of naphthenic acid from spent DES
The unreacted DES layer, recovered in Example 2, was mixed with a dilute HCl at 25 °C until the pH of the reaction mixture was equal to 2, and then the reaction mixture was stirred to obtain a product mixture. Under the acidic conditions, the product mixture contained naphthenic acids, ethylene glycol, water and precipitated solids. The solids were separated from the product mixture to obtain a first resultant mixture containing ethylene glycol, water and naphthenic acids. The naphthenic acids in the first resultant mixture were extracted with dichloromethane (DCM) and the second resultant mixture containing ethylene glycol and water was recovered. Separated dichloromethane layer containing extracted naphthenic acids was distilled to obtain crude naphthenic acids and the distilled dichloromethane was recycled back for extraction of naphthenic acids. The ethylene glycol and water in the second resultant mixture were separated by distilling out water to obtain pure ethylene glycol, which was recycled back to prepare DES in the first mixer (102).
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, a process for reducing TAN of acidic crude oil, that;
? facilitates reduction of total acid number of highly acidic crude oil (having TAN greater than 2) by 90% or greater;
? reduces the corrosion of refinery equipment such as the crude distillation unit (CDU) and vacuum distillation unit (VDU) from high temperature corrosion;
? is simple, economic and inexpensive;
? does not involve use of water;
? minimizes use of corrosion inhibitors;
? evades the formation of emulsions and surfactants; and
? reduces the use of de-emulsifiers and CRA agents.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.