Description:Field of the invention

[0001] The present invention in general relates to the field of additives for improving the flow properties of crude oil. More particularly, the present invention relates to a pour point depressant composition for improving flow properties of waxy crude oil.

Background of the invention

[0002] Crude oils are mixtures comprising complex hydrocarbons, aqueous phases, and solids of various types. The hydrocarbon in crude oil comprises different compounds that may be grouped into saturates, aromatics, resins and asphaltenes. Hydrocarbons also comprise considerable amounts of wax, primarily paraffins. Paraffins are saturated hydrocarbons with linear chains, branched chains or cyclic structures and have at least 18 carbons which can form waxy solids. Paraffin deposition is a well-known phenomenon that plagues the oil industry all over the world. These waxy solids are normally dissolved in crude oil under high temperatures and high-pressure conditions in subterranean reservoirs. However, the waxy particles may precipitate as wax crystals at atmospheric pressure and temperature. Also, crystallization and solidification of the wax particles result in the crude oil being no longer of pourable consistency at the pour point. This is undesirable because, below the pour point temperature, crude oil would no longer be pumpable.

[0003] Various techniques exist to mitigate wax-induced flow impairment of crude oils. For example, maintaining the crude oil at a desirable high temperature by either insulation or heating of pipelines carrying crude oil. Other methods include mechanically scraping the inside of the pipelines or containers to remove wax deposits. However, such methods are less efficient and not viable economically. Other known methods include the dewaxing of crude oil to improve the flow characteristics of crude oil. However, this method is time-consuming and not economically feasible.

[0004] It is known that the pour point of crude oils can be lowered by suitable additives, which prevent the crystallization of paraffins at a lower temperature. Extensive research led to the development of pour point depressants that deter solidification of wax particles at lower temperatures. Typically, pour point depressants comprise high molecular weight organic molecules containing linear segments of saturated hydrocarbon and optionally one or more additives. Being similar in structure to wax molecules, the linear hydrocarbon segments interact with wax particles and modify the shape, size and size distribution of wax particles. This obstructs the nucleation and growth of wax particles, eventually rendering the wax to lack the property to crystallize and solidify. Commonly used pour point depressants comprise linear, branched or comb polymers. It is known that the efficiency of a pour point depressant stems from molecular architecture of its organic molecules. The number of long hydrocarbon chain segments per unit volume of organic molecules can be an indicator of the efficiency of a pour point depressant in reducing the pour point of crude oil and inhibiting the growth of wax crystals. However, accommodation of a large number of hydrocarbon chains on a base polymer is not favorable due to steric repulsion between long carbon chains.

[0005] In light of the above-mentioned drawbacks, there is a need for a pour point depressant composition that mitigates the problem of steric repulsion between the hydrocarbon chains. There is a need for a pour point depressant composition that improves the flow property of crude oil.

Summary of the Invention

[0006] In various embodiments of the present invention, there is provided a composition of a pour-point depressant. In an embodiment of the present invention, the pour point depressant composition comprises of a compound of formula I, a solvent and at least one additive. The compound of formula I comprises an amine-terminated hyperbranched polyethylenimine core (PEI core) and at least one branch comprising C8-C34 long alkyl chains emanates from the PEI core which includes both amide and amine functional groups, as represented in formula I, wherein the C8-C34 long alkyl chains are attached to the PEI core via smaller linear (C4) carbon chains.

Formula I
where R2 is C8-C34 alkyl chains.

[0007] In an embodiment of the present invention, “n” is an integer between 1 and 200. Integer “n” represents a number of monomers present in amine-terminated hyperbranched polyethylenimine core which is used as a base polymer for the compound of Formula I.

[0008] In an embodiment of the present invention, the mass ratio of formula I and at least one additive is in a range between 1:10 to 10:1.

[0009] In an embodiment of the present invention, the additive is selected from a group comprising of 1) nanoparticles with or without surface coating 2) nanoparticles with grafted polymer chains 3) high molecular weight polymers with different architectures such as a comb or bottle brush and 4) copolymers.

[0010] In an embodiment of the present invention, the solvent is selected from a group comprising of toluene, xylene and mineral oil.

[0011] In an embodiment of the present invention, there is provided a method for preparing the pour point depressant composition of the present invention comprising the steps of preparing a polymeric solution by mixing a predetermined amount of compound of formula I in a solvent; preparing an additive solution by mixing at least one additive in a solvent; and mixing the polymeric solution and additive solution to obtain the pour point depressant composition of the present invention.

Brief description of the drawings

[0012] The present invention is described by way of embodiments illustrated in the accompanying drawings herein:

[0013] Fig. 1 illustrates FTIR data of the compound of formula I, in accordance with an embodiment of the present invention;

[0014] Fig. 2 illustrates 1H-NMR spectroscopy of the compound of formula I, in accordance with an embodiment of the present invention;

[0015] Fig. 3 illustrates microscopy images of model waxy crude oil added with the pour point depressant composition having different concentrations (a) 100 ppm (b) 200 ppm and (c) 500 ppm of compound of formula I, in accordance with an embodiment of the present invention;

[0016] Fig. 4 illustrates temperature-dependent elastic modulus G’ (solid symbol) and viscous modulus G” (hollow symbol) of 10wt% model waxy crude oil with different concentrations of compound of formula I, in accordance with an embodiment of the present invention;

[0017] Fig. 5 illustrates temperature-dependent elastic modulus G’ (solid symbol) and viscous modulus G” (hollow symbol) of non-asphaltenic crude oil with different concentrations of the compound of formula I, in accordance with an embodiment of the present invention;

[0018] Fig. 6 illustrates temperature-dependent elastic modulus G’ (solid symbol) and viscous modulus G” (hollow symbol) of waxy crude oil-1 with different concentrations of compound of formula I, in accordance with an embodiment of the present invention;

[0019] Fig. 7 illustrates temperature-dependent elastic modulus G’ (solid symbol) and viscous modulus G” (hollow symbol) of waxy crude oil-2 with different concentrations of compound of formula I, in accordance with an embodiment of the present invention;

[0020] Fig. 8 illustrates temperature-dependent elastic modulus G’ (solid symbol) and viscous modulus G” (hollow symbol) of waxy crude oil-2 with different concentrations of pour point depressant composition containing 1:1 ratio of compound of formula I and silicon dioxide nanoparticle, in accordance with an embodiment of the present invention; and

[0021] Fig. 9 illustrates temperature-dependent elastic modulus G’ (solid symbol) and viscous modulus G” (hollow symbol) of waxy crude oil-3 with different concentrations of pour point depressant composition containing 1:1 ratio of compound of formula I and silicon dioxide nanoparticle, in accordance with an embodiment of the present invention.

Detailed description of the invention

[0022] The present invention discloses a pour point depressant composition comprising a compound of formula I, a solvent and at least one additive for reducing the pour point of waxy crude oil and thereby improving its flow properties, in accordance with an embodiment of the present invention. The invention further provides a method of preparation of pour point depressant composition, in accordance with an embodiment of the present invention.

[0023] The disclosure is provided to enable a person having ordinary skill in the art to practice the invention. Exemplary embodiments herein are provided only for illustrative purposes and various modifications will be readily apparent to persons skilled in the art. The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. The terminology and phraseology used herein are for the purpose of describing exemplary embodiments and should not be considered limiting. Thus, the present invention is to be accorded the widest scope encompassing numerous alternatives, modifications, and equivalents consistent with the principles and features disclosed herein. For purposes of clarity, details relating to technical material that is known in the technical fields related to the invention have been briefly described or omitted so as not to unnecessarily obscure the present invention.

[0024] In an embodiment of the present invention a pour point depressant composition comprising a compound of formula I, a solvent and at least one additive is provided. The compound of formula I comprises of a dendrimeric amine-terminated hyperbranched polyethylenimine (also referred as PEI) core and emanating from the core is at least one branch comprising C8-C34 long alkyl chains containing both amide and amine functional groups, wherein said C8-C34 long alkyl chains are attached to the hyperbranched polyethylenimine core via smaller linear (C2-C5) carbon chains.

where R2 is C8 -C34 alkyl chains.

[0025] In an embodiment of the present invention, “n” is an integer between 1 and 200, preferably between 1 and 60.

[0026] In an embodiment of the present invention, the regions of terminal amine groups of the dendrimeric hyperbranched polyethylenimine core of formula I produce more branches for hyperbranched polyethylenimine core by attaching repeated smaller carbon chain units containing amide and amine functional groups to the terminal amine groups of branched polyethylenimine. This enables the hyperbranched PEI core to accommodate a large number of long alkyl chains.

[0027] In an embodiment of the present invention, the branched polyethylenimine (PEI) core is represented in formula II.

Formula II
where, R is C2H4 or C3H6 or C4H8.

[0028] In an embodiment of the present invention, the hyperbranched polyethylenimine (PEI) core is represented in formula III.

Formula III
where, R is C2H4 or C3H6 or C4H8.

[0029] In an embodiment of the present invention, the compound of formula I comprise at least two long-side alkyl chains per ethylenimine monomer. The number of branches emanating from the amine-terminated hyperbranched polyethylenimine core is increased by attaching a linear carbon chain of acrylic esters such as octyl acrylate, lauryl acrylate, stearyl acrylate, palmityl acrylate and behenyl acrylate, etc., by nucleophilic addition reaction. In an exemplary embodiment of the present invention, the nucleophilic addition reaction is Michael’s addition reaction. Increasing the number of branches emanating from the core enables the incorporation of a large number of long hydrocarbon chain segments per hyperbranched polyethylenimine core. In an exemplary embodiment of the present invention, the ratio of the number of long side chains to branched PEI core is 40:1 to 320:1. In various embodiments of the present invention, the branching by Michael’s addition reaction is bifurcated into at least four branches at the end, resulting in a large number of linear hydrocarbon chain to the branched polyethylenimine core as represented in formula I.

[0030] In an embodiment of the present invention, the molecular weight of the branched polyethylenimine core and hyperbranched polyethylenimine core are respectively greater than 400 g/mol and 1,400 g/mol. The compound of formula I of the pour point depressant composition exhibits a lower molecular weight in a range from 6,700 g/mol to 2,600,000 g/mol, while having a higher number of long-side alkyl chains. Low molecular weight molecules with long side alkyl chains surprisingly exhibit efficiency as pour point depressants for crude oil at very low dosages. For a fixed ppm value of the pour point depressant composition of the present invention added in crude oil, the number of the molecules of compound of formula I per unit volume of waxy oil is more for lower molecular weight molecules than those of higher molecular weight ones. As a result, a large number of molecules of pour point depressant composition are adsorbed on the surface of the wax crystals, and thereby efficiently preventing the growth of wax crystals and the formation of a three-dimensional network structure. Also, the lower molecular weight molecules of pour point depressant composition can diffuse easily in a waxy oil medium and, therefore, increases the rate of adsorption or nucleation with the wax crystallite.

[0031] In an embodiment of the present invention, the hyperbranched polyethylenimine core comprises 20 branches, each having an amine (-NH2) functional group. During Michael’s addition reaction for adding branches emanating from the core, long carbon chain acrylic ester reacts with the core, where each amine functional group from the core substitutes two long carbon chain segments. This results in the formation of the hyperbranched polyethylenimine core comprising 40 long carbon chain (C18) segments. In an embodiment, the hyperbranched polyethylenimine core comprises 40 branches which can accommodate 80 long carbon chain segments.

[0032] In dendrimeric polymer, steric repulsion between long carbon chains increases with the increase in length of the carbon chain i.e., the longer carbon chain remains separated at a greater distance when compared with the shorter ones. Therefore, the accommodation of a large number of long hydrocarbon chains on the hyperbranched polyethylenimine core is not favorable in a pour point depressant due to the steric repulsion between long carbon chains, which negatively affects the reactivity of a compound. Since the steric repulsion between the smaller carbon chain segments is less than those of large ones. The smaller carbon chains are attached to the branched polyethylenimine core thereby forming branches, in accordance with various embodiments of the present invention. Subsequently, each branch is further bifurcated to increase the surface area of the hyperbranched polyethylenimine core for the attachment of a larger number of long carbon chain segments.

[0033] In an embodiment of the present invention, a method for synthesis of compound of formula I is provided.

[0034] Step 1: In an embodiment of the present invention, the method comprises the steps of reacting a branched polyethylenimine with alkyl acrylate in the presence of methanol solution to obtain ester-terminated hyperbranched polyethylenimine, as shown below. The reaction is carried out at a temperature in a range from 25oC to 50oC for a duration in a range from 36-96 hours under stirring conditions. Excess methanol solution and methyl acrylate from the reaction mixture is removed by rotary evaporation at a temperature of 40oC.

Where R1 is an alkyl chain with C1-C8

[0035] Step 2: The ester-terminated hyperbranched polyethylenimine, is reacted with ethylenediamine in the presence of methanol solution to obtain amine-terminated hyperbranched polyethylenimine, as shown below. The reaction between ester-terminated hyperbranched polyethylenimine and ethylenediamine is carried out at a temperature in a range from 25oC to 50oC for a duration of 48-120 hours under stirring conditions. Excess methanol solution and ethylenediamine from the reaction mixture are removed by rotary evaporation at a temperature of 40oC. In an exemplary embodiment, the rotary evaporation is carried out at least twice with methanol, twice with Isopropyl alcohol and twice with butanol.

[0036] Step 3: Subsequently, amine-terminated hyperbranched polyethylenimine is reacted with alkyl acrylate in the presence of methanol solution. In an embodiment of the present invention, the reaction between amine-terminated hyperbranched polyethylenimine and alkyl acrylate is carried out by dropwise addition of alkyl acrylate into amine-terminated hyperbranched polyethylenimine as shown below. This results in the attachment of a large number of linear hydrocarbon chain segments to the hyperbranched polyethylenimine core. The reaction between amine-terminated hyperbranched polyethylenimine and stearyl acrylate is carried out at a temperature in a range from 25oC to 50oC for a duration of 36-96 hours.

where R2 is an alkyl chain with C8-C34

[0037] The reaction mixture of amine-terminated hyperbranched polyethylenimine and alkyl acrylate is left undisturbed for a duration of 24 hours at a temperature of 25oC, resulting in the formation of a precipitation layer. The precipitation layer is washed with methanol solution and rinsed with water. Subsequently, the precipitation layer is washed with acetone and dried in vacuum for a duration of 48 hours at a temperature of 30oC to obtain the multi-arm star polymer having a hyperbranched polyethylenimine core and long alkyl side chains of formula I.

[0038] In various embodiments of the present invention, the method overcomes the challenge of high attachment density of long hydrocarbon chains, by bifurcating each branch of the smaller hydrocarbon chain from the branched polyethylenimine core to increase the surface area. This helps in minimizing the steric repulsion between long carbon chains and thereby accommodating a higher number of long hydrocarbon chain segments on the hyperbranched polyethylenimine core. This is implemented by attaching smaller linear carbon chain segments (C6) containing both amide and amine functional groups to the branched PEI (base polymer). Long carbon chain segments (C18) are attached to the base polymer via smaller ones (C6). In this manner, each branch of the base polymer is bifurcated into four branches which enables high attachment density of long hydrocarbon chain segments on the base polymer, since the steric repulsion between the smaller carbon chain segments is less than those of large ones. Attaching smaller carbon chain segments to the base polymer and thereby bifurcating each branch to increase the surface area of the base polymer for the attachment of a larger number of long carbon chain segments is an alternative to the direct attachment of a large number of long carbon chain segments to the base polymer.

[0039] The bifurcations of each branch of the long hydrocarbon chain take place in step 1 and 3. In step 1 and 3, bifurcation takes place by Michael’s addition reaction between the terminal -NH2 (amine) group of the molecules with the alkyl acrylic esters. In these reactions, the nitrogen atom of the terminal -NH2 group forms a bond with the two alkyl acrylate molecules i.e., the two hydrogen atoms of the -NH2 group is replaced with the two alkyl acrylate molecules, resulting in each branch of the core molecule is bifurcated into two branches.

[0040] Advantageously, the method of the present invention comprises minimal steps for the synthesis of the compound of Formula I which is capable of scaling up for large-scale production. In addition, the impurities generated during the method of synthesis of the present invention can be easily separated, thereby enhancing the purity of the synthesized compound of Formula I. It is known that the synthesis of higher generations of various dendrimers having a large number of branches takes more than a month. Advantageously, the duration of the method of synthesis of the present invention is in a range of 5-6 days. The method of the present invention achieves a reduction in synthesis time by starting the synthesis process with branched PEI as a core material. As branched PEI has an adequate number of branches, more branches can be achieved at the beginning of the synthesis process. This enables the method to synthesize the compound of Formula I with a higher number of branches in less time.

[0041] In various embodiments of the present invention, the additives of the pour point depressant composition are selected from a group comprising of 1) nanoparticles with or without surface coating, 2) nanoparticle-polymer composite, 3) high molecular weight polymers with comb and 4) copolymers such as ethyl vinyl acetate copolymer, ethylene–butene copolymer, alkyl esters of styrene–maleic anhydride co-polymers, etc. In an embodiment of the present invention, the additive is silicon dioxide (SiO2) nanoparticles.

[0042] In an embodiment of the present invention, there is provided a method for preparing the pour point depressant composition of the present invention comprising the steps of preparing a polymeric solution by mixing a predetermined amount of the compound of Formula I in a solvent; preparing an additive solution by mixing an additive in a solvent; and mixing the polymeric solution and additive solution to obtain the pour point depressant composition.

[0043] In an embodiment of the present invention, the polymeric solution is prepared by mixing the compound of Formula I in an amount of up to 10 % w/w in a solvent in various hydrocarbons such as toluene, paraffin oil, mineral oil and xylene, and also in other solvents such as chloroform, N-methyl pyrrolidone, dimethyl formamide, etc.

[0044] In an embodiment of the present invention, the additive solution is prepared by mixing at least one additive in an amount up to 10 % w/w in a solvent in various hydrocarbons such as toluene, paraffin oil, mineral oil and xylene, and also in other solvents such as chloroform, N-methyl pyrrolidone, dimethyl formamide, etc.

[0045] In an embodiment, the polymeric solution and additive solution are mixed in certain proportions to obtain the pour point depressant composition. In the compositions, the mass ratios of polymeric and additive solution vary between 1:10 to 10:1.

[0046] In an embodiment of the present invention, additive and the compound of Formula I synergistically exhibit multiple functions such as wax inhibitors and flow improvers for waxy crude oil. The composition of the present invention, when added to crude oils, SiO2 nanoparticles enhance the adsorption of asphaltenes and resins from crude oils on their surface, since SiO2 nanoparticles have a high adsorption affinity and large surface area to volume ratio. The adsorbed asphaltenes and resins on the surface of SiO2 nanoparticles are thereby dispersed and stabilized in oils and thus the aggregation of asphaltenes and resins in the crude oil is prevented. The addition of a composition containing formula I and SiO2 nanoparticles in the crude oil, therefore, reduces the number of nucleation sites for wax crystals and the number of wax crystals and also increases the size of wax crystals when compared with adding only formula I in crude oil. The decrease in the number of wax crystals inhibits the formation of the wax crystal network. Thus, the additives and formula I synergistically enhance the flow property i.e., decrease the viscosity and viscoelastic moduli of crude oil.

[0047] Further, advantageously, the pour point depressant composition comprising the compound of Formula I comprising a amine-terminated hyperbranched PEI core having long (C8-C34) alkyl side chains and at least one additive of the present invention acts as an efficient flow improver and wax inhibitor for crude oil. It is observed that the flow behavior of waxy oil gels is significantly improved with the addition of a very small amount of 100-500 ppm of the composition. Further, the composition of the present invention decreases the viscosity and viscoelastic moduli of crude oil, thereby improving the flow behavior. The long side alkyl chains of the compound of formula I interact with the wax crystals in the crude oil and intervene during the processes of nucleation and growth of waxes, and thereby viscosity and viscoelastic moduli of waxy oil gels are reduced. Advantageously, the viscosity and viscoelastic moduli of waxy crude oil are reduced by more than ten­fold. Surprisingly, the composition of the present invention alters the shape and size of wax crystals in crude oil by the addition of a very small amount of the composition comprising the compound of Formula I and at least one additive.

[0048] In addition to modifying the viscosity and viscoelastic behavior of waxy crude oil, the composition of the present invention also advantageously alters the morphology gel-like network structure of wax crystals. The increase in the number of long alkyl chains per hyperbranched PEI core reduces the rate of deposition of wax. This results in a reduction in the viscosity and viscoelastic moduli of waxy crude oil. The compound of Formula I of the present invention separates the wax crystals of crude oil into an individual domain. This causes a reduction in the width of wax crystals and becomes elongated. This leads to a decrease in the number of connections between the wax crystallite and thereby reduces the elasticity of waxy crude oil. From the flow behavior analysis of waxy oil gels in the presence of the compound of Formula I, it is concluded that the addition of a very small amount of the pour point depressant composition of the present invention is also cost-effective for pipeline transportation of waxy crude oil.

[0049] The disclosure herein provides illustrates exemplary embodiments in accordance with an embodiment of the present invention. The examples used herein for such illustration are intended merely to facilitate an understanding of ways in which the embodiments may be practiced and to further enable those of skill in the art to practice the embodiments. Accordingly, the following examples should not be construed as limiting the scope of the embodiments herein.

Working Examples

Example 1

[0050] The synthesis procedure of the compound of Formula I involves three steps.

Step 1: Synthesis of ester-terminated hyperbranched Polyethylenimine.

[0051] Branched polyethylenimine (PEI) of molecular weight 800 Da was used in this synthesis step. 0.0l mol of PEI (800 Da) was dissolved in 70 ml of methanol and the solution was cooled in an ice bath. 21.87 g (0.0254 mol) of methyl acrylate (MA) was added dropwise into a three-necked round-bottomed (RB) flask containing PEI solution equipped with a magnetic stirrer, a reflux condenser and a heater. The cold mixture was warmed at 25°C for 48 hours. The reaction temperature was then raised to 45°C and allowed to react for another 48 hours. A slight excess of MA was used in this reaction. The excess of MA and methanol were removed by rotary evaporation at 40°C resulting in an amber-colored viscous syrup of ester-terminated hyperbranched PEI.

Step 2: Synthesis of amine-terminated hyperbranched Polyethylenimine.

[0052] Amine-terminated hyperbranched PEI was synthesized by attaching EDA to ester-terminated PEI. 50 g (0.832 mol) of EDA was dissolved in 50 ml of methanol and the solution was cooled in dry ice. ln, another reaction vessel, 22.516 g (0.009 mol) of synthesized ester-terminated PEI was dissolved in 60 ml of methanol and the flask was also cooled in dry ice. The cold ester-terminated PEI solution was gradually added to the EDA solution at a certain rate at a low temperature (keeping the reaction vessel in a dry ice bath). After the addition was completed, the mixture was allowed to warm to 45°C and the reaction continued for 48 hours. The excess EDA and methanol were removed by performing rotary evaporation twice with methanol, twice with isopropyl alcohol, and twice with butanol at 40°C. As a result, a pale, amber-colored viscous syrup was obtained.

Step 3: Synthesis of multi-arm star polymer with hyperbranched PEI core and long alkyl side chains (compound of formula I).

[0053] Amino-terminated hyperbranched PEI was attached with stearyl acrylate to obtain multi-arm star polymer with hyperbranched PEI core and long-chain alkyl esters. Stearyl acrylate 25.96 g (0.08 mol) was mixed in 50 ml of methanol in a beaker under stirring at 40 °C. 6.128 g (0.002 mol) of amino-terminated hyperbranched PEI was dissolved in 40 ml of methanol in a beaker. The PEI solution was transferred into a three-necked RB flask at 40°C. To the PEI solution, stearyl acrylate solution was added dropwise at 40°C for 20 minutes. The mixture was stirred for 48 hours at 40°C. When the reaction was over, the mixture was allowed to stand for 24 hours at 25°C. Two layers with top yellow liquid and bottom white precipitated were seen. The yellow liquid was transferred into a beaker and the white precipitated solution was washed three times with methanol and rinsed with water to remove residues of the washing solution. The mixture was then centrifuged at 15000 RPM for 75 minutes at 25°C to separate the water-methanol mixture from the white precipitate solid. The solid was dissolved in acetone and allowed to stand for 48 hours at 10°C. The white precipitate was again collected by filtration of the above mixture and washed with acetone and then dried under vacuum for 48 hours at 30°C. The sample was crushed and ground in order to prepare powders of multi-arm star polymer with hyperbranched PEI core and long alkyl side chains (Formula I).

Characterization

[0054] The FTIR spectra of the compound of formula I are illustrated in Fig. 1. From Fig. 1, an N-H stretching vibration absorption peak is broad and observed at 3500-3200 cm-1 (marked as (1)), and an N-H bending vibration absorption peak was observed at 1630 cm-1 (marked as (4)). This confirms the presence of the -NH group (secondary amine). Further, a saturated C-H stretching vibration absorption peak was observed at 3000-2800 cm-1 (marked as (2)), a C-H bending vibration absorption peak appeared at 1470 cm-1 (marked as (5)), and the C-H rocking vibration absorption peak appeared at 720 cm-1 (marked as (7)). This confirms the presence of -CH2 and -CH3 groups. The FTIR data also confirmed the presence of amide groups from the C=O stretching vibration absorption peak that appeared at 1735 cm-1 (marked as (3)). The FTIR data also confirmed the formation of the bond between the amine and acrylic ester group from the C-N stretching vibration absorption peak appeared at 1180 cm-1 (marked as (6)). The result of 1H-NMR spectroscopy is shown in figure 2. 1H NMR (CDCl3, d): (1) 0.85 (t, 120H, -CH3), (2) 1.25 (m, 1200H, -O-C-(CH2)15-), (3) 1.65 (m, 80H, -(C)15-CH2-C), (4) 4.05 (t, 80H, -COO-CH2-C-), (5) 2.75 (t, 80H, N-C-CH2-CO-), (6) 2.50 (t, 80H, N-CH2-C-CO-), (7) 2.40 (t, 40H, -CON-C-CH2-N-), (8) 3.25 (t, 40H, -C-CON-CH2-), (9) 2.55 (t, 40H, N-C-CH2-CO-), (10) 2.15 (t, 40H, N-CH2-C-CO-), (11) 3.45 (t, 12H, N-C-CH2-NH-C), (12) 3.85 (t, 16H, -C-N-CH2-C-NH), (13) 3.65 (t, 48H, N-CH2-CH2-N), (14) 4.55 (t, 40H, -C-C-CONH-).

[0055] The presence of all those absorbance peaks in the FTIR spectra along with various splitting of the peaks at various chemical shifts of the NMR data of the compound of formula I confirms the formation of expected architecture and the presence of various functional groups of the molecule (Fig.1 and 2).

Flow Property

[0056] The compound of formula I as prepared by Example 1 was tested for improvement in the flow property of crude oils.

[0057] The flow behavior of waxy oil gels is significantly improved with the addition of a very small amount (100-500 ppm) of the compound of formula I. From the flow behavior measurements, it is seen that viscosity and viscoelastic moduli decrease ten-fold with the addition of smaller dosages of the compound of formula I. The long side alkyl chains of the compound of formula I interact with the wax crystals by Van der Waals or hydrophobic interaction and adsorb on its surface. This intervenes in the growth of wax crystals to form a three-dimensional network structure, thereby reducing the viscosity and viscoelastic moduli of waxy oil gels. Moreover, the structure of waxy oil gels and the shape and size of wax crystals are also altered by the addition of a very small amount of the compound of formula I. The wax crystals are seen to separate into the individual domain with the addition of the compound of formula I (Fig. 3). The width of the crystal domain reduces and becomes more elongated with the increase in the concentration of the compound of formula I (Fig. 3). This leads to a decrease in the number of connections between the wax crystallite and thereby reduces the elasticity of waxy oil gels.

[0058] Tables 1-4 exhibit the rheological property of Model oil, non-asphaltenic crude oil, and waxy crude oil in the presence of the compound of formula I at different concentrations. Temperature sweep rheological experiments were performed with a stress-controlled Anton Paar MCR 702 rheometer. For these measurements, a required amount of the compound of formula I dissolved in a solvent was added to the crude oil at 60oC and stirred for an hour. A cone-plate geometry (CP-25) of cone radius 12.5 mm, cone angle 2o and measuring gap 0.105 mm were used. The inner surface of the measuring system was smooth stainless steel while the bottom plate was sandblasted. A sample volume of 0.5 ml was loaded in the cone-plate geometry. The temperature of the sample was controlled by a Peltier unit and a water circulation system for counter-cooling. Temperature sweep experiments were performed at a fixed oscillatory strain amplitude of 0.01% and angular frequency of 6.28 rads-1. Viscoelastic moduli (G’ and G”) of waxy crude oil at several different concentrations of the compound of formula I were measured as a function of temperature while cooling at a rate of 1°C/min are illustrated in figures 4 to 7. The range of temperature explored in these experiments was 60oC to 20-30oC.

Table 1: Flow property improvement for Model waxy crude oil (Mixture of Wax and Mineral oil)
Amount at which maximum reduction of G’ and G” is achieved.
(ppm) Temperature (oC) Elastic modulus (G’)
reduction Viscous modulus reduction (G”)
500 20 10-fold 24-fold
25 144-fold 147-fold

Table 2: Flow property improvement for non-asphaltenic crude oil
Amount at which maximum reduction of G’ and G” is achieved.
(ppm) Temperature (oC) Elastic modulus (G’)
Reduction Viscous modulus reduction (G”)
1000 30 6-fold 7-fold
35 6-fold 7 fold

Table 3: Flow property improvement for a waxy crude oil-1
Amount at which maximum reduction of G’ and G” is achieved.
(ppm) Temperature (oC) Elastic modulus (G’)
Reduction Viscous modulus reduction (G”)
1000 30 4-fold 3-fold
35 5-fold 5-fold

Table 4: Flow property improvement for a waxy crude oil-2
Amount at which maximum reduction of G’ and G” is achieved.
(ppm) Temperature (oC) Elastic modulus (G’)
Reduction Viscous modulus reduction (G”)
1000 25 7-fold 7-fold
30 9-fold 10-fold

[0059] Table 5 exhibits comparative data on the flow improvement of crude oil by the compound of formula I as compared to existing additives.

Table 5: Data on flow improvement in comparison with existing additives
Dosage of pour point depressants Reduction in viscosity/viscous modulus/elastic modulus
Present Invention 100-1000 ppm Elastic and viscous modulus reduces by 150-fold
US6140276 100-10,000 ppm -
US8481632B2 250-1000 ppm -
L. Cuiqin, S. Peng and S. Weiguang and W. Jun, “Synthesis and Properties of Dendritic Long-Chain Esters as Crude Oil Flow Improver Additives”
200-1200 ppm Viscosity reduces by two-fold
US2021/0017466A1 500-1000 ppm Viscosity reduces less than two-fold
F. Yang, B. Yao, C. Li, G. Sun and X. Ma, “Oil dispersible polymethylsilsesquioxane (PMSQ) microspheres improve the flow behaviour of waxy crude oil through spacial hindrance effect”, 50-1600 ppm Elastic modulus reduces by 3-fold and viscous modulus reduces by 2-fold

Duration of Synthesis

[0060] Advantageously, the method in accordance with an embodiment of the present invention comprises only minimal steps. This enables the synthesis of the compound of formula I present invention within a week. Table 6 provides a comparison of the duration of preparation of dendrimeric polymers of the present invention and the method of preparation of other dendrimeric polymers disclosed in the prior art. As seen from table 6, the method of the present invention is completed in 120 hours (5 days) while synthesizing a large number of branches.
Table 6: Comparison of duration of synthesis
Number of branches Duration of Synthesis (hours)
Method of the present invention 40 120
J. Peterson et. al, “Synthesis and CZE analysis of PAMAM dendrimer with an ethylenediamine core”, 32 1128
O. Yemul and T. Imae, “Synthesis and characterization of poly(ethyleneimine) dendrimers”) 32 240
L. Cuiqin, “Synthesis and properties of dendritic long-chain esters as crude oil flow improver additives”, China Petroleum Processing and Petrochemical Technology” 8 192
US4507466 32 212

Working Example 2

Preparation of Pour Point Depressant Composition

[0061] The pour point depressant compositions were prepared by mixing the compound of formula I prepared by example 1 with silicon dioxide nanoparticles in various proportions. The mass ratio of mixing the compound of formula I and silicon dioxide nanoparticles in the compositions vary between 1:10 to 10:1. Flow property improvement of waxy crude oils and waxy model oils with different concentrations of pour point depressant composition as prepared was tested.

Flow Property

[0062] A waxy crude oil-2 was heated to 70oC with continuous stirring for at least 1 hour before using it for any experiment. 5% w/w of Formula I solution was prepared by dissolving Formula I in toluene at 25oC. SiO2 nanoparticles were used as additives for the composition. 5% w/w of additives dispersion was prepared by sonicating additives dispersed in toluene for 1 hour. In a typical example, a composition (50% w/w) of Formula I and additives were added to the crude oil. 40 mg of prepared 5% w/w Formula I solution and 40 mg of prepared 5% w/w of additives dispersion were added to the waxy crude oil-2 one after another under continuous stirring for 30 minutes at 60oC. The concentration of the composition in the crude oil was observed to be 2000 ppm.

[0063] A waxy crude oil-2 was heated to 70oC with continuous stirring for at least 1 hour before using it for any experiment. 5% w/w of Formula I solution was prepared by dissolving Formula I in toluene at 25oC. SiO2 nanoparticles were used as additives for the composition. 5% w/w of additives dispersion was prepared by sonicating additives dispersed in toluene for 1 hour. In a typical example, a composition (50% w/w) of Formula I and additives were added to the waxy crude oil. 100 mg of prepared 5% w/w Formula I solution and 100 mg of prepared 5% w/w of additives dispersion were added to the 2 g of the crude oil one after another under continuous stirring for 30 minutes at 60oC. The concentration of the composition in the crude oil-2 was observed to be 5000 ppm. Tables 7 and figure 8, show the flow property improvement of waxy crude oil 2 with different concentrations of pour point depressant composition.

Table 7: Flow property improvement for a waxy crude oil-2
Amount of the composition at which maximum reduction of G’ and G” is achieved.
(ppm) Amount of Formula I
(ppm) Amount
of additives
(ppm) Temperature (oC) Reduction in Elastic modulus
(G’) Reduction in Viscous modulus
(G”)
2000 1000 1000 25 7-fold 7-fold
30 8-fold 10-fold
35 5-fold 6-fold
5000 2500 2500 25 14-fold 13-fold
30 22-fold 22-fold
35 9-fold 9-fold

[0064] A waxy crude oil-3 of a certain concentration was prepared by mixing wax in mineral oil at 70oC. 50% w/w of wax was dissolved in mineral oil (D-130) at 70oC and the solution was filtered. The filtrate collected is termed a stock solution. The stock solution was heated and stirred for homogenization and then an aliquot was diluted with mineral oil (D-130) to get a waxy model oil with 10% w/w of wax. The WMO with 10% w/w of wax was heated to 70oC with continuous stirring for at least 30 min before using it for any experiment. 5% w/w of Formula I solution was prepared by dissolving Formula I in mineral oil (D-130) at 60oC. SiO2 nanoparticles were used as additives for the composition. 5% w/w of additives solution was prepared by dissolving additives in mineral oil (D-130). In a typical example, a composition (50% w/w) of Formula I and additives were added to the WMO. 40 mg of prepared 5% w/w Formula I solution and 40 mg of prepared 5% w/w of additives solution were added to the waxy crude oil-3 one after another under continuous stirring for 30 minutes at 60oC. The concentration of the composition in the waxy crude oil-3 was observed to be 2000 ppm.

[0065] A waxy crude oil-3 of a certain concentration was prepared by mixing wax in mineral oil at 70oC. 50% w/w of wax was dissolved in mineral oil (D-130) at 70oC and the solution was filtered. The filtrate collected is termed a stock solution. The stock solution was heated and stirred for homogenization and then an aliquot was diluted with mineral oil (D-130) to get a waxy model oil with 10% w/w of wax. The WMO with 10% w/w of wax was heated to 70oC with continuous stirring for at least 30 min before using it for any experiment. 5% w/w of Formula I solution was prepared by dissolving Formula I in mineral oil (D-130) at 60oC. SiO2 nanoparticles were used as additives for the composition. 5% w/w of additives solution was prepared by dissolving additives in mineral oil (D-130). In a typical example, a composition (50% w/w) of Formula I and additives were added to the WMO. 100 mg of prepared 5% w/w Formula I solution and 100 mg of prepared 5% w/w of additives solution were added to the waxy crude oil-3 one after another under continuous stirring for 30 minutes at 60oC. The concentration of the composition in the waxy crude oil-3 was observed to be 5000 ppm. Tables 8 and figure 9, show the flow property improvement of waxy crude oil 3 with different concentrations of pour point depressant composition.

Table 8: Flow property improvement for a waxy crude oil-3
Amount of the composition at which maximum reduction of G’ and G” is achieved.
(ppm) Amount of Formula I
(ppm) Amount
of additives
(ppm) Temperature (oC) Reduction in Elastic modulus (G’) Reduction in Viscous modulus (G”)
2000 1000 1000 30 2-fold 1.2-fold
35 1.5-fold 1.3-fold
5000 2500 2500 30 4.3-fold 3-fold
35 5.5-fold 5-fold

[0066] While the exemplary embodiments of the present invention are described and illustrated herein, it will be appreciated that they are merely illustrative. It will be understood by those skilled in the art that various modifications in form and detail may be made therein without departing from the scope of the invention.
, C , Claims:1) A pour point depressant composition comprising: a compound of formula I, a solvent and at least one additive,

Formula I

where R2 is an alkyl chain with C8-C34, n is an integer between 1 and 200,
wherein the compound of formula I comprises a dendrimeric amine terminated hyperbranched polyethylenimine core, with at least one branch emanating from the hyperbranched polyethylenimine core comprising C8-C34 long alkyl chains including both amide and amine functional groups as represented in formula I, and wherein the C8-C34 long alkyl chains are attached to the hyperbranched polyethylenimine core by attaching one or more smaller linear (C5) carbon chains comprising both amide and amine functional groups.

2) The composition as claimed in claim 1, wherein the solvents are selected from a group comprising of toluene, xylene, mineral oil.

3) The composition as claimed in claim 1, wherein the additive is selected from a group comprising of nanoparticles with or without surface coating, nanoparticle-polymer composite, high molecular polymers with comb, and copolymers.

4) The composition as claimed in claim 1, wherein the mass ratio of a compound of formula I and at least one additive varies between 1:10 to 10:1.

5) The composition as claimed in claim 1, wherein the molecular weight of the compound of formula I is in a range from 6,700 g/mol to 2,600,000 g/mol.

6) The composition as claimed in claim 1, wherein ratio of long alkyl chains to the core in formula I is in a range from 40:1 to 320:1.

7) The composition as claimed in claim 1, wherein the molecular weight of the polyethylenimine core of formula I is in a range from 400 g/mol to 80,000 g/mol.

8) The composition as claimed in claim 1, wherein the concentration of the compound of formula I is in a range from 5000 ppm, preferably in the range of 250-2500 ppm.

9) A method of preparation of the pour point depressant composition comprising the steps of:

a) preparing a polymeric solution by mixing a predetermined amount of compound of formula I in a solvent;
b) preparing an additive solution by mixing an additive in a solvent; and
c) mixing the polymeric solution and the additive solution to obtain the pour point depressant composition.

10) The method as claimed in claim 9, wherein the solvent is selected from a group comprising of toluene, paraffin oil, mineral oil and xylene, chloroform, N-methyl pyrrolidone and dimethyl formamide.

11) The method as claimed in claim 9, wherein the additive is selected from a group comprising of nanoparticles with or without surface coating, nanoparticle-polymer composite, high molecular polymers with comb, and copolymers.

12) The method as claimed in claim 9, wherein the concentration of the polymeric solution is up to 10% w/w.

13) The method as claimed in claim 9, wherein the concentration of the additive solution is up to 10% w/w.