RU2607914C1 - Method of forming and composition of anti-turbulent additive - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: present invention relates to an anti-turbulent additive of suspension type based on higher α-olefins, characterised by that it is a colloidal solution, which additionally contains technical carbon, potassium palmitate and octanol in following ratio of components, wt%: poly-α-olefin 30–35; technical carbon 1–2; potassium palmitate 1-2; octanol – balance. Present invention relates to a method of producing anti-turbulence additive of suspension type.

EFFECT: technical result of present invention is a method of producing and composition of anti-turbulent additive, making it possible to improve quality and quantity of fine-dispersed polymer component in additive of suspension shape, reduced number of steps of producing anti-turbulent additive and increased efficiency of process equipment.

2 cl, 1 dwg, 1 tbl, 2 ex

Description

The invention relates to the oil industry, and in particular to the pipeline transport of oil and oil products with anti-turbulent additives (PTP), which reduce the hydrodynamic resistance of turbulent flow and thereby intensify the pumping of hydrocarbon liquids.

Compared with gel-type additives based on concentrated solutions of poly-α-olefins in heptane (for example, RF patent No. 2230074), suspension PTP has an order of magnitude lower viscosity and contains three to four times more useful substance (polymer) in its composition.

The industrial polymerization of α-olefins in a reactor is usually carried out in a non-polar solvent (e.g., heptane) in the presence of Ziegler-Natta catalysts and a highly viscous solution of poly-α-olefins called polymerizate is obtained, which contains less than 10% polymer and more than 90% heptane. Heptane does not reduce resistance, and therefore is an expensive ballast. Such a concentrate (polymerizate), called the “gel” (solution) type anti-turbulent additive, is dosed in small quantities (10 g / m ³ -100 g / m ³ ) into the oil flow of the main pipeline [G.V. Nesyn, V.N. Manzhay, A.V. Ilyushnikov. Industrial synthesis and assessment of the hydrodynamic efficiency of potential SGDS agents in oil pipelines // Engineering Physics Journal. 2003.V. 76. No. 3. C. 142-146]. But the delivery of an additive in the form of a concentrated solution with a low content of a hydrodynamically active substance (polymer) in it and with an overwhelming proportion of expensive ballast (heptane) to metering sites, often remote and difficult to access, is an economically costly undertaking. An attempt to increase the polymer content in the concentrate above 10% leads to an exponential increase in the viscosity of the solution and its transformation into a non-fluid jelly, which cannot be pumped into the oil pipeline due to the high back pressure in it. Therefore, in the last decade, anti-turbulent suspension form additives have been widely used. Such additives of a new generation in their structure and consistency are similar to hevea juice, which is colloidal in nature and is an emulsion of polyisoprene (natural rubber) in water stabilized by natural surfactants.

A large number of patents related to a method for producing suspension-type anti-TB drugs are described for cryogenic grinding of polymers [US Pat. U.S. Patent 4,826,728. U.S. 4,720,397, Pat. US 4340076]. Since polymers and copolymers of higher α-olefins are highly elastic rubber-like materials with a low glass transition temperature (polyhexene and polyoctene, for example, have a glass transition temperature below minus 70 ° C), they are mechanically milled in liquid nitrogen, i.e. below their glass transition temperature. In this case, the dispersion of polymer bodies is accompanied by partial destruction of macromolecules. The obtained fine polymer powder with various additive ingredients is then placed in a dispersion medium in which the polymer does not dissolve.

Another approach to the formation of suspension PTP, fundamentally different from the above method, is to obtain a fine dispersion even at the stage of polymerization of alpha-olefins. In patents [Pat. U.S. 6126872, Pat. US 6160036, Pat. USA 4693321] describes a very original solution, the meaning of which is that PTP obtained by encapsulation and subsequent microblock polymerization of higher alpha-olefins. Using a special nozzle, droplets of the monomer containing the catalyst are placed in a shell to prevent poisoning of the catalyst. Inside the nozzle there is a cylindrical channel of small diameter surrounded by a cylindrical channel of a larger diameter. A monomer with a catalyst enters through a small-diameter channel, and shell material enters through the annulus between the two channels. The flow rates are selected so that the shell material uniformly covers the droplets of the monomer with the catalyst, resulting in capsules in which the microblock polymerization of higher alpha-olefins proceeds for a conversion of 95% within 24-72 hours.

Another method for the preparation of PTP described in RF patent No. 2443720 is based on the suspension polymerisation of alpha-olefins in perfluorinated alkanes (PFA). On the one hand, PFAs are an inert medium and therefore do not deactivate the active sites of the Ziegler-Natta catalytic system. On the other hand, PFAs are not a solvent both for higher alpha olefins and for their polymers, which allows for suspension polymerization. The suspension polymerization product of higher alpha-olefins is a finely dispersed suspension, which, after replacing the expensive PFA with a dispersion medium of a different chemical nature, is a commercial form of the suspension type PTP.

The disadvantages of all of the above methods for the formation of SST suspension form are the use of expensive components, multi-stage process, the use of specific equipment and increased requirements for observing the nuances of the technological regulations.

An alternative method of obtaining fine dispersions is the conversion of the polymer into a suspension antiturbulent additive by thermal reprecipitation [US Pat. RF No. 2481357]. This method is the closest to the present invention and was taken by us as a prototype.

In the prototype, to obtain a fine suspension, it is proposed to use thermal reprecipitation of (co) polymers of higher alpha-olefins in a liquid, which forms a system with a polymer with an upper critical mixing temperature, the value of which lies in the vicinity of + 50 ° C. Such a liquid is a non-solvent for the (co) polymer at a temperature close to room temperature and becomes a solvent at a temperature above the critical mixing temperature.

The sequence of technological stages of obtaining the suspension described in the aforementioned patent (prototype), is as follows (quote):

1. Homo- or copolymerization of higher α-olefins (C ₆ -C ₁₂ ) in the monomer mass under the action of a Ziegler-Natta catalyst to a deep conversion of the monomer (comonomers). The catalyst system preferably consists of titanium trichloride and diethylaluminium chloride.

2. Mechanical grinding of the synthesized polymer block at room temperature into sufficiently large particles larger than 1-10 mm.

3. Mixing at room temperature the crushed polymer and a liquid in which the polymer does not dissolve at room temperature and in which it dissolves at elevated temperature. If necessary, add an anti-agglomerator and a breakdown inhibitor in a ratio corresponding to the final additive formulation.

4. Dissolution of the polymer in a liquid at elevated temperature and stirring.

5. Slow cooling of the mixture to room temperature and obtaining a commodity form of a suspension additive.

The disadvantages of the prototype include the following:

- Firstly, the preparatory stage of grinding the polymer, which is an elastomer, requires additional costs for equipment and electricity. In addition, mechanical degradation of polymer chains is possible at this stage.

- Secondly, due to the inertia of the process of dissolving macromolecular compounds when the system is heated above the critical mixing temperature, a sufficiently long time is required until the solution is completely homogenized, which reduces the overall productivity of the process equipment. Prolonged heating also leads to thermal degradation of the polymer and, as a consequence, to a decrease in the quality of PTP.

- Thirdly, during cooling of the heated system, delamination often occurs, which leads to the formation of rather than a suspension, but of a flocculent polymer swollen in a non-solvent (for example, in a mixture of hexanol-1 and dipropylene glycol monomethyl ether in a 2: 1 ratio). It is noted that at high polymer concentrations this system is very unstable and can easily coagulate into a single massive jelly.

The objective of the present invention is to provide a method for the preparation and selection of the composition of an anti-turbulent additive, which allows to increase the quality and quantity of the finely dispersed polymer component in the additive of the suspension form, reducing the number of stages for the preparation of anti-turbulent additives and increasing the productivity of the technological equipment used.

The technical solution of the proposed method is the conversion of a true polymer solution into a suspension by precipitation. The present invention, in contrast to the prototype, solves the technological problem of combining the stage of synthesis of poly-α-olefin and the process of transferring the polymer into a suspension without the stage of its mechanical dispersion with subsequent dissolution.

The proposed suspension composition of anti-turbulent additives contains: 30-35 mass. % poly-α-olefin with a very high MM ~ (5-10) ⋅ 10 ⁶ , 60-65 mass. % octanol, ~ 1-2 mass. % potassium palmitate, ~ 1-2 mass. % finely divided carbon black (soot).

The developed method for converting a true solution of ultra-high molecular weight polymer into a colloidal form does not affect the quality of the synthesized product (there is no degradation of polymer chains and MM does not change) and allows to increase the content of the polymer component in PTP to 35%. When forming a colloidal composition, affordable and cheap components are used.

As described in our patent No. 2230074, the synthesis of poly-α-olefins on Ziegler-Natta catalysts is carried out in a reactor containing a good solvent (heptane) for the monomer and polymer.

The methodology of the proposed method for the formation of suspension PTP consists of four stages.

At the initial stage, a 10% solution of ultrahigh molecular weight polyhexene in heptane, obtained immediately after synthesis in the reactor, was used to form the PTP of the suspension form. The dynamic viscosity of this solution (non-Newtonian fluid) is extremely high and, depending on the shear rate specified during the measurements, is in the range η = 10-20 Pa s. With a further increase in polymer concentration, the solution practically loses fluidity.

At the second stage, in order to increase the fluidity of the concentrated polymer solution, an equal volume of butanol is added in small portions with a working stirrer, i.e. form a system with a ratio of a polymer solution in heptane: butanol = 1: 1. At the same time, finely dispersed carbon black is added in an amount of 3% of the polymer content in the system. As a result of the procedure, the viscosity of the system decreases sharply and, therefore, the fluidity of the polymer solution increases due to the loss of “spinnability”, which makes it easy and without loss to move it from the synthesis reactor.

At the third stage, to form an aggregatively and kinetically stable colloidal PTP system, a dispersion medium of the following composition is prepared: 95 mass. % octanol and 5% of the mass. potassium palmitate. A dispersion medium of the above composition is prepared in an amount of 20% of the mass of the system obtained in the previous step. Then, with thorough and intensive stirring, the solution obtained in the second stage is portioned into the prepared dispersion medium.

At the final stage, by decanting the upper layer of the system obtained in the third stage, the excess of the dispersion medium is separated from the precipitated phase precipitated in the form of a powder. Then, octanol is added to the remaining dispersed phase in an amount equal to twice the mass of the polymer contained in the initial 10% concentrated solution taken in the first stage for the preparation of suspension PTP. Subsequent vacuum distillation (P _abs ~ 10 kPa) with slight heating (~ 60 ° C) and stirring remove boiling residues of heptane (T _boil = 98 ° C) and butanol (T _boil = 117 ° C). As a result, the high-boiling octanol (T _boiling point = 195 ° C) becomes a dispersion medium. The final composition of the PTP is shown in table 1.

The dynamic viscosity of the PTP obtained by the described method is 0.5-1.0 Pa · s, i.e. it is an order of magnitude smaller than that of a polymer solution after synthesis containing a significantly smaller fraction of the polymer (~ 10%) per unit volume of the solution.

We carried out the deposition of the polymer from the solution and its dispersion have several advantages compared with the thermal reprecipitation described in the prototype:

- Firstly, the present invention claims a method that allows, without reducing the molecular weight, to isolate the polymer synthesized in the reactor from a concentrated solution in the form of a finely dispersed suspension and eliminates the additional stage of mechanical grinding described in the prototype.

- Secondly, when precipitating from a solution, it is possible to obtain PTP with an ultrahigh molecular weight polymer content of up to 35%, which has not undergone mechanical and thermal degradation.

- Thirdly, the proposed method can be easily implemented in practice on an industrial scale.

.To confirm the absence of polymer chain degradation during the preparation of the colloidal consistency of PTP, accompanied by a loss in the quality of the active component due to a decrease in the molecular mass of the polymer, the formed additive is examined on a capillary viscometer in a laminar flow regime and subjected to hydrodynamic testing on a turbulent rheometer to determine its anti-turbulent properties. A turbulent rheometer is structurally simple and similar to a capillary viscometer, but allows hydrodynamic studies in both the laminar and turbulent regions of the fluid flow [M.M. Gareev, Yu.V. Lisin, V.N. Manzhay, A.M. Shammazov / Anti-turbulent additives to reduce the hydraulic resistance of pipelines. SPb .: Subsoil. 2013. 228 p.]. The measured value of the effect of reducing hydrodynamic resistance (DR,%), which characterizes the reduction in energy costs for moving a unit volume of liquid, is calculated by the formula

.

The formula characterizes the ratio of the difference between the resistance coefficients of the solvent and the polymer solution (Δλ = λ _S -λp) to the value of the resistance coefficient of the solvent (λ _S ). The relative value of DR is a measure of reducing the energy cost of pumping a polymer solution compared to the original solvent. The effectiveness of the polymer sample is judged by the value of the "optimal" concentration (C _OPT. , Kg / m ³ ), i.e. concentration at which the maximum value of the effect (DR _MAX ,%) is observed at a given shear stress (τ, Pa) on the wall of the cylindrical channel. The smaller the numerical value of C _OPT , the more effective the additive is considered.

To prove the absence of polymer chain degradation during the formation of colloidal consistency PTP by the claimed method, comparative measurements of the intrinsic viscosity [η] of two polyisoprene solutions (MM = 2.1⋅10 ⁶ ) with different backgrounds are carried out. The first series of dilute solutions of polyisoprene (natural rubber) in heptane to determine [η] is prepared according to the generally accepted (reference - ET) scheme from a polymer sample that has not been dispersed to a suspension state. A second series of dilute solutions is prepared from the same polymer sample, but which was previously dispersed by the method described above during the formation of a suspension composition (PTP) and then isolated from it. The characteristic viscosities of solutions determined by capillary viscometry with different histories practically coincided ([η] _ET = 0.42 m ³ / kg and [η] _PTP = 0.41 m ³ / kg). After conducting turbo-geometric testing, it was found that the “optimal” concentrations of these solutions (C _ET = 2.0 kg / m ³ and C _PTP = 2.1 kg / m ³ ) were also close in magnitude, at which the maximum effects of a decrease in hydrodynamic resistance constitute DR _MAX = 28% for these samples at the same shear stress of 10 Pa in a turbulent rheometer. The results obtained by viscometric and turbo-geometric methods indicate the absence of destruction of macromolecules during the formation of anti-turbulent additives of the colloidal type according to the proposed method.

Case Studies

Example 1. 150 ml of heptane and 60 ml of hexene-1 are loaded into a 1 liter reactor, then 5 ml of a solution of triisobutylaluminum in heptane with a concentration of 0.29 mmol / ml and 1.2 mmol of propyltrimethoxysilane. The polymerization is carried out at a temperature of 20 ° C for an hour. At the end of the synthesis, 20 ml of isopropanol is added to deactivate the catalyst. A portion of the polymerizate is taken from the reactor and the polymer content in it is determined by the dry residue. Using gel permeation chromatography it was found that as a result of the synthesis obtained ultrahigh molecular weight polyhexene (MM = 7⋅10 ⁶ )

Example 2. For the preparation of the PTP suspension form, a concentrated solution of polyhexene (10% wt.) In heptane obtained after synthesis in a reactor is used (Example 1). After the formation of PTP according to the method described above, a colloidal system containing 33% of the polymer is obtained.

For comparative rheological tests of the created PTP, 1.2 grams of suspension PTP and 0.4 grams of pure polymer (previously precipitated from the polymerizate) are dissolved in 100 ml of heptane, respectively, and two solutions with a polyhexene concentration of 4 kg / m ³ are obtained for further hydrodynamic studies. Then, from these solutions two series of more dilute solutions are prepared (2.0 kg / m ³ ; 1.0 kg / m ³ ; 0.05 kg / m ³ ; 0.025 kg / m ³ ) and viscometric measurements are carried out. Values of the intrinsic viscosity of solutions prepared from suspension PTP and from pure polymer are approximately the same and equal to [η] _PTP = 1.31 m ³ / kg and [η] _ET = 1.33 m ³ / kg, respectively. The results obtained indicate the stability of the polymer during the preparation of colloidal PTP.

To conduct a comparative turbo-geometric test, from solutions of the created PTP and pure polymer with a concentration of 4 kg / m ³ described in Example 3, extremely dilute solutions are prepared with concentrations: C = 0.05 kg / m ³ ; 0.025 kg / m ³ ; 0.0125 kg / m ³ ; 0.0062 kg / m ³ ; 0.0031 kg / m ³ . Freshly prepared solutions of each concentration are passed through a turbo-meter at a shear stress of τ = 10 Pa, providing a turbulent flow regime (Re = 8000). The results of the hydrodynamic tests are shown in FIG. 1. The figure 1 shows the dependence of the magnitude of the effect of DR,% at τ = 10 Pa on the concentration of the polymer in heptane. The solutions are prepared from polyhexene isolated from the polymerizate obtained in the reactor. Solutions are prepared from colloidal PTP containing 33% of the active component (polyhexene). It can be seen that the proposed anti-turbulent additive, the optimum concentration of which is With _OPT ≈ 0.005 g / m ³ , is an extremely effective agent for reducing hydraulic resistance. The practical coincidence of curves 1 and 2 indicates that the conversion of a concentrated polymer solution into a colloidal form by the proposed method does not affect the quality of the active component (polymer), which indicates the absence of destruction in the process of formation of PTP.

Claims (3)

1. The anti-turbulent additive of the suspension type based on higher α-olefins, characterized in that it is a colloidal solution, which additionally contains carbon black, potassium palmitate and octanol in the following ratio of components,% mass .: Poly-α-olefin 30-35 Carbon black 1-2 Potassium palmitate 1-2 Octanol rest 2. A method of producing a suspension-type anti-turbulent additive according to claim 1, which reduces the hydrodynamic resistance of hydrocarbon liquids, comprising producing a highly dispersed polymer soluble in hydrocarbon liquids, having a high molecular weight, synthesized by (co) polymerization in heptane of higher α-olefins under the action of a Ziegler catalyst Natta, characterized in that the fluidity of the viscous poly-α-olefin solution obtained in the synthesis reactor is increased by adding butanol and octanol, isolated from poly polar solution fine powder of poly-α-olefin as a new phase of the dispersion, concentrated and the resulting stabilized colloidal composition soot and potassium palmitate.

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