CN108865225B - Chitosan crude oil demulsifier and preparation method thereof - Google Patents

Abstract

The invention relates to a chitosan crude oil demulsifier and a preparation method thereof. The structural general formula of the demulsifier is shown as formula I, and the preparation method comprises the following steps: 1) performing acylation modification on chitosan to obtain N-acylated chitosan; 2) epoxidizing and modifying the terminal hydroxyl of the polyethylene glycol monomethyl ether to obtain epoxidized polyethylene glycol monomethyl ether; 3) reacting modified polyethylene glycol monomethyl ether with N-acylated chitosan; obtaining polyethylene glycol monomethyl ether grafted N-acylated chitosan; 4) carboxyl alkylation modification is carried out on the polyethylene glycol monomethyl ether grafted N-acylated chitosan to obtain the target product polyethylene glycol monomethyl ether grafted N-acylated carboxyalkyl chitosan. The invention takes chitosan natural high molecular compound as raw material, and has the advantages of wide source, naturalness, no toxicity, good biocompatibility, degradability and the like. The carboxyalkyl, acyl and polyether side chain are introduced into a chitosan molecular chain, and a series of high-efficiency demulsifiers suitable for oil-in-water (O/W) type emulsion are obtained by controlling the position and the substitution degree of each substituent.

Description

Chitosan crude oil demulsifier and preparation method thereof

Technical Field

The invention relates to a chitosan crude oil demulsifier and a preparation method thereof, belonging to the field of petrochemical industry.

Background

In the process of oil field exploitation, along with the implementation of oil extraction process technologies such as steam flooding, surfactant, polymer and ternary complex flooding, the water content of the crude oil emulsion is increased, the stability is enhanced, and the demulsification difficulty of the crude oil is increased. The formation of emulsions can pose a serious hazard to the recovery, transportation and processing of petroleum. The crude oil is emulsified with water, so that the difficulty in extracting the crude oil is increased; transporting the crude oil containing water by pipeline or tank car increases the load of the pump and the transportation cost. Therefore, it is essential to desalt and dewater crude oil emulsions prior to crude oil transportation and processing.

The emulsion is a very complex dispersion system, mainly water-in-oil (W/O) type, and oil-in-water (O/W) type emulsion gradually appears in produced liquid along with the application of new oil extraction technology. The common demulsification methods include flotation, chemical coagulation, chemical and electrochemical technologies, chemical demulsification, membrane separation, biotechnology and the like, and the most widely applied demulsification methods are chemical demulsification methods. The demulsifier required by the chemical demulsification method has been updated for one generation in the past hundred years, and the demulsifier has better and better effect and less dosage. However, as the emulsion becomes more complex, the specificity of the demulsifier becomes stronger. At present, the crude oil demulsifier used in oil fields in China is mainly based on block polymers and tends to develop in the direction of ultrahigh molecular weight. The polysaccharide natural polymer has wide sources, excellent biocompatibility and environmental friendliness, large molecular weight, more active hydrogen, a branch structure and unique rheological property, occupies a large area at an oil-water interface, has good temperature resistance, high interfacial activity and no pollution to the environment, and is an excellent candidate for the demulsifier initiator. Guo Dong hong, etc. uses xanthan gum or guar gum as initiator, and adds with epoxyethane and epoxypropane to synthesize polysaccharide natural high-molecular demulsifier with polyether branch structure, and makes simple evaluation on its demulsification performance. Xu et al found that ethyl cellulose can effectively remove 90% of water in asphalt emulsion and systematically studied its demulsification mechanism. Wangli and the like take polysaccharide and the like as initiators to synthesize five polysaccharide crude oil demulsifiers, and the demulsification performance of the five polysaccharide crude oil demulsifiers is evaluated to a certain extent. Fan and the like synthesize a series of chitosan crude oil demulsifiers, have certain demulsification and dehydration effects on water-in-oil (W/O) crude oil emulsion under the condition that the demulsification temperature is 60 ℃, and discuss the demulsification mechanism.

Chitosan is a natural macromolecule which is produced second to cellulose in nature, widely exists in wings and shells of arthropods (arachnids, crustaceans), and also exists in cell walls of fungi and algae, and has excellent biocompatibility and environmental friendliness. Compared with polysaccharide such as xanthan gum and cellulose, the chitosan contains more active amino groups and is easier to graft and modify. Carboxymethyl chitosan can be obtained by carboxymethylation of chitosan, and the solubility of chitosan is greatly changed due to the introduction of hydrophilic group carboxyl; the carboxymethyl chitosan is modified by quaternization, so that the amphoteric polyelectrolyte with both carboxyl and quaternary ammonium salt groups in the molecule can be obtained. Chinese patent CN 201310289037.6 describes a polysaccharide modified crude oil demulsifier. Polysaccharide is used as an initiator, and quaternary amination modification and polyether grafting modification are carried out on the polysaccharide to obtain the polysaccharide modified crude oil demulsifier. Chinese patent CN 201610644945.6 describes a preparation method of polyelectrolyte type crude oil desalting demulsifier. Glycidyl dimethyl alkyl ammonium chloride and amination modified polyether are grafted to carboxymethyl chitosan to obtain the polyelectrolyte type crude oil desalting demulsifier. In Chinese patent CN201610644992.0, glycidyl dimethyl alkyl ammonium chloride and isocyanate modified polyether are grafted to carboxymethyl chitosan to obtain a novel efficient crude oil desalting demulsifier. In the Chinese patent CN201610644943.7, glycidyl dimethyl alkyl ammonium chloride and polyether modified by acrylic acid esterification are grafted to carboxymethyl chitosan to obtain the comb-shaped polymer crude oil desalting demulsifier. In Chinese patent CN201610644993.5, glycidyl dimethyl alkyl ammonium chloride and aldehyde modified polyether are grafted to carboxymethyl chitosan to obtain a polyether grafted chitosan derivative crude oil desalting demulsifier. In the Chinese patent CN201610645442.0, glycidyl dimethyl alkyl ammonium chloride and polyether modified by nitrophenyl ester are grafted to carboxymethyl chitosan to obtain the efficient crude oil desalting demulsifier. China patent CN201610645444.X glycidyl dimethyl alkyl ammonium chloride and epoxy modified polyether are grafted onto carboxymethyl chitosan to obtain the chitosan crude oil desalting demulsifier. In the Chinese patent CN201610645497.1, glycidyl dimethyl alkyl ammonium chloride and polyether after halogenation modification are grafted to carboxymethyl chitosan to obtain a chitosan natural polymer modified crude oil desalting demulsifier. In Chinese patent CN201610648933.0, glycidyl dimethyl alkyl ammonium chloride and esterified and modified polyether are grafted to carboxymethyl chitosan to obtain a double-ion type crude oil desalting demulsifier. The demulsifier has the advantages of wide source of the polysaccharide demulsifier, naturalness, innocuity, sustainability, good use safety and the like, and can remove oil-soluble salts in crude oil emulsion while demulsifying. However, these chitin demulsifiers are mainly aimed at water-in-oil (W/O) crude oil emulsions.

With the heavy use of new oil recovery technology, the oil-in-water (O/W) emulsion has larger proportion and stronger stability while improving the recovery ratio of crude oil. Oil-in-water (O/W) emulsions are complex in composition and generally include dirty oil, scale, organic matter, corrosive gases, sludge and clays, surfactants and co-surfactants, and the like. Due to the presence of these substances, the oil-water interfacial tension and the zeta potential of the oil droplet surface can be greatly reduced, and the high polymer contained in the emulsion can increase the viscosity of water, so that a very stable oil-in-water (O/W) emulsion is formed, and the emulsion breaking and separation of the emulsion are very difficult.

At present, the domestic demulsifiers aiming at oil-in-water (O/W) type emulsions are only CW-01, PDM-1, BH-1, RD-1 and the like. The demulsifiers are poor in environmental friendliness and easy to cause irreversible secondary pollution; in addition, each oil field crude oil production fluid has more or less different compositions and properties, and a demulsifier capable of treating all types of crude oil production fluids does not exist. Therefore, the development of a novel and environmentally friendly oil-in-water (O/W) demulsifier to solve the problems caused by the new technology of oil recovery has become an important and urgent problem to be solved in the later development of oil fields.

Disclosure of Invention

The invention provides a chitosan crude oil demulsifier and a preparation method thereof aiming at the problems in the prior art. The demulsifier takes chitosan natural high molecular compounds as raw materials, and introduces carboxyalkyl, acyl and polyether side chains on a chitosan molecular chain, so that the obtained demulsifier can realize high-efficiency demulsification on oil-in-water (O/W) crude oil emulsion. The preparation method of the demulsifier has the advantages of wide raw material source, naturalness, no toxicity, good biocompatibility, degradability and the like.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

the chitosan crude oil demulsifier is characterized by having a structural general formula shown in the following formula (I):

the invention also provides a preparation method of the chitosan crude oil demulsifier, which comprises the following steps:

a preparation method of a chitosan crude oil demulsifier is characterized by comprising the following steps:

1) performing acylation modification on amino on chitosan to obtain N-acylated chitosan, which comprises the following specific steps:

dissolving chitosan in an organic acid aqueous solution, adding organic alcohol for dilution, adding acid anhydride according to 0.5 time of the amount of substances of amino groups on the chitosan under the condition of stirring, standing at room temperature for 24-48 h, adding a precipitator, washing the precipitate, and freeze-drying to obtain N-acylated chitosan; preferably, the organic alcohol is used in an amount of 80% by volume or more of the whole system. (acylation reaction is carried out in a homogeneous system consisting of organic alcohol, organic acid and water, the content of the organic alcohol in the system is as high as 80%. the acylation reaction is preferentially carried out on amino groups of sugar rings due to the competition effect of hydroxyl groups of the organic alcohol, so that the system has excellent selectivity, and the acylation reaction is carried out on the amino group at the C2 position only.)

2) Epoxidizing and modifying the terminal hydroxyl of the polyethylene glycol monomethyl ether to obtain the epoxidized polyethylene glycol monomethyl ether, which comprises the following steps:

dissolving 1 mol part of polyethylene glycol monomethyl ether in a solvent A at room temperature, adding a proper amount of a solvent B and 1-5 mol parts of an alkalizing agent, heating to 20-40 ℃, reacting for 3-8 h, slowly dropwise adding 2.5-10 mol parts of an epoxidation agent into a reaction solution, heating to 20-40 ℃, reacting for 3-20 h, separating, purifying and freeze-drying the reaction solution to obtain epoxidized polyethylene glycol monomethyl ether; wherein the number average molecular mass of the polyethylene glycol monomethyl ether is 350-5000.

3) The method comprises the following steps of reacting epoxidized polyethylene glycol monomethyl ether with N-acylated chitosan:

dissolving or swelling the N-acylated chitosan prepared in the step 1) in a solvent C, adding an alkali liquor to adjust the pH value of the solution within a certain range, dissolving the prepared epoxidized polyethylene glycol monomethyl ether in the solvent A, then dropwise adding the solution into a reaction system, stirring and heating the solution at the temperature of 80-120 ℃, reacting at a constant temperature for 12-24 hours, separating and purifying the reaction solution, and freeze-drying the reaction solution to obtain the target product modified polyethylene glycol monomethyl ether grafted N-acylated chitosan.

4) The carboxyl alkylation modification is carried out on the modified polyethylene glycol monomethyl ether grafted N-acylated chitosan to obtain the modified polyethylene glycol monomethyl ether grafted N-acylated carboxyalkyl chitosan, and the specific steps are as follows:

dissolving or swelling the modified polyethylene glycol monomethyl ether grafted N-acylated chitosan prepared in the step 3) in a solvent D, and adding alkali liquor for alkalization for 1-2 h; after alkalization is finished, adding a carboxylation reagent sodium chloroalkyl ate into the reaction liquid, heating to 50-70 ℃ after the carboxylation reagent sodium chloroalkyl ate is added, reacting for 2-7 hours, and adding an acid solution to adjust the pH of the reaction liquid to be neutral; carrying out suction filtration on the reaction product, washing and dialyzing a filter cake, and freeze-drying to obtain the modified polyethylene glycol monomethyl ether grafted N-acylated carboxyalkyl chitosan; wherein, preferably, the carbon chain length of the sodium chloroalkylate is C₂-C₁₈。

According to the scheme, the organic alcohol in the step 1) is preferably one or more of aliphatic alcohols with 1-10 carbon atoms, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol and the like; the acid anhydride is one or more of acetic anhydride, propionic anhydride, n-butyric anhydride, isobutyric anhydride, n-valeric anhydride, n-hexanoic anhydride, n-octanoic anhydride and other anhydrides corresponding to fatty acid with 2-10 carbon atoms; the precipitant is acetone.

According to the scheme, preferably, in the step 2), the alkalizing agent is sodium hydride or sodium hydroxide; the epoxidation reagent is epichlorohydrin.

According to the scheme, preferably, in the step 3), the mass part ratio of the N-acylated chitosan to the epoxidized polyethylene glycol monomethyl ether is (0.872-1.384): (0.7-10).

According to the scheme, preferably, in the step 3), the pH value of the solution is 9-14.

According to the scheme, preferably, in the step 4), the mass part ratio of the modified polyethylene glycol monomethyl ether grafted N-acylated chitosan to the sodium chloroalkyl ate is (3.055-15.96): (4.6-15.48).

According to the scheme, preferably, in the step 4), in the process of dissolving the N-acylated chitosan by using the solvent D and adding alkali liquor for alkalization, the alkali liquor is added in a small amount for multiple times; after the alkalization is finished, the carboxylation reagent sodium chloroalkyl ate is added in a small amount for multiple times.

According to the scheme, the solvent A is preferably anhydrous toluene.

According to the scheme, preferably, the solvent B is one or more of tetrahydrofuran, ethanol, dimethyl sulfoxide, dichloromethane, N-dimethylformamide and N, N-dimethylacetamide.

According to the scheme, preferably, the solvent C is one or more of distilled water, isopropanol, sodium hydroxide solution, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide, acetic acid and methanol.

According to the scheme, preferably, the solvent D is one or a mixture of more of distilled water, isopropanol, sodium hydroxide solution, hydrochloric acid solution, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, acetic acid and methanol.

The synthetic route of the invention is as follows:

1. epoxidizing and modifying the terminal hydroxyl of the polyethylene glycol monomethyl ether, wherein the modified polyethylene glycol monomethyl ether is recorded as MPEG-M:

2. preparing N-acylated carboxyalkyl chitosan, synthesizing polyethylene glycol monomethyl ether grafted N-acylated carboxyalkyl chitosan:

compared with the prior art, the invention has the following beneficial effects:

1) the invention takes chitosan natural high molecular compound as raw material, and has the advantages of wide source, naturalness, no toxicity, biodegradability, compatibility, sustainability, good use safety and the like.

2) The modified polyethylene glycol monomethyl ether grafted N-acylated carboxyalkyl chitosan prepared by the invention is a high-efficiency crude oil demulsifier. The demulsifier has a comb-shaped structure, has large molecular weight and more branched chains, occupies a large area at an oil-water interface, and has high interfacial activity. The demulsifier has strong competitive adsorption capacity on an oil-water interface, is easy to adsorb and replace natural emulsifiers such as asphalt, paraffin, resin and the like adsorbed on the interface on the oil-water interface, and can realize high-efficiency demulsification on oil-in-water (O/W) type crude oil emulsion. The emulsion breaker is added to enable emulsion droplets to be aggregated to form larger oil droplets and destroy an oil-water interface film, so that the emulsion breaking and deoiling effects are achieved, a water phase after emulsion breaking is clear, an oil-water interface is neat, and the deoiling efficiency is high.

3) According to the method for preparing the chitosan natural polymer modified crude oil demulsifier, the molecular structure of the demulsifier, such as molecular weight, substitution degree, hydrophobic chain segment length aggregation structure and the like, can be changed by selecting sodium carboxylate and alkyl chains with different carbon chain lengths, or changing the using amount ratio of reaction raw materials, or changing the conditions of reaction temperature, reaction time and the like of a reaction system, so that the deoiling effect of the synthesized high-efficiency demulsifier is regulated and controlled, and the method is suitable for crude oils with different properties (different producing areas and different oil-containing water contents).

Detailed Description

For a better understanding of the present invention, the following examples are given to further illustrate the present invention, but the present invention is not limited to the following examples.

Example 1

The preparation method of the N-N-butyrylated carboxymethyl chitosan grafted by polyethylene glycol monomethyl ether comprises the following specific steps:

(1) synthesis of N-acylated chitosan: mixing 2g Chitosan (CS) (M)_w179.17kDa, degree of deacetylation>95 percent and 100-200 mPas) is dissolved in 40mL 10 percent acetic acid water solution, 160mL methanol is added for dilution, 5.9mmol of N-butyric anhydride is added under the stirring condition, the mixture is placed for 24 hours at room temperature, 260mL acetone is added as a precipitator, the precipitate is washed three times by methanol and ether respectively, and freeze drying is carried out, thus obtaining white water-soluble solid N-N-butyrylated chitosan (A)₄CS)。

Wherein the dosage of the n-butyric anhydride is 0.5 times of the dosage of amino substances contained in the chitosan, and the specific calculation method is as follows:

the saccharide units of chitosan are glucosamine residues, the molecular weight of this residue (saccharide units of chitosan) is 161, 2g of chitosan (degree of deacetylation > 95%) contains the amount of amino groups: 2 g/161 g/mol × 95% ═ 0.0118mol, i.e. 11.8 mmol; the mass of n-butyric anhydride is then: 0.5 × 11.8mmol ═ 5.9 mmol.

(2) Synthesis of epoxidized polyethylene glycol monomethyl ether: taking polyethylene glycol monomethyl ether (M)_n5000)5g (1mmol) was dissolved in 50mL of anhydrous toluene, 50mL of tetrahydrofuran and 0.036g (1.5mmol) of sodium hydride reagent were added, and the temperature was raised to 25 ℃ to react for 4 hours. 0.37mL (4mmol) of epichlorohydrin was slowly added dropwise to the reaction mixture, and the reaction was carried out at 40 ℃ for 6 hours. Adding the reaction solution into 200mL of diethyl ether, carrying out suction filtration, washing with diethyl ether for 3 times, carrying out vacuum drying, dissolving the product into 200mL of dichloromethane, washing with distilled water for three times, carrying out liquid separation, drying with anhydrous magnesium sulfate, carrying out reduced pressure distillation on the filtrate after suction filtration, and carrying out freeze drying to obtain the epoxidized polyethylene glycol monomethyl ether.

(3) Polyethylene glycol monomethyl ether grafted N-N-butyrylated chitosanAnd (3) sugar synthesis: fetch 1g A₄Adding 50mL of distilled water into a 250mL three-neck flask, adding sodium hydroxide to adjust the pH value of the solution to 9, dissolving 10g of epoxidized polyethylene glycol monomethyl ether into 10mL of anhydrous toluene, dropwise adding the solution into a reaction system within 10min through a constant-pressure dropping funnel, stirring, heating to 110 ℃, and reacting at a constant temperature for 24 h. And dialyzing the reaction solution for 3 days after the reaction is finished, and freeze-drying to obtain the polyethylene glycol monomethyl ether grafted N-N-butyrylated chitosan.

(4) Carboxymethylation of polyethylene glycol monomethyl ether grafted N-butyrylated chitosan: 5.014g of polyethylene glycol monomethyl ether grafted N-N-butyrylated chitosan is put into a 250mL three-neck flask, 100mL of distilled water is added until the chitosan is completely dissolved at room temperature, 10mL of 10% sodium hydroxide solution is evenly divided into 5 parts, the 5 parts are added into the reaction solution at intervals of 5min for 5 times, and the mixture is alkalized for 1 h. After the alkalization is finished, 4.6g of sodium chloroacetate is divided into 5 parts, one part is added into the reaction liquid every 1min, the temperature is raised to 60 ℃ after the addition is finished, the reaction is carried out for 2h, and the pH value of the reaction liquid is adjusted to be neutral by acetic acid. And after the reaction is finished, performing suction filtration, washing a filter cake for three times by using acetone, dialyzing for three days after washing, and performing freeze drying to obtain the polyethylene glycol monomethyl ether grafted N-N-butyrylated carboxymethyl chitosan serving as the demulsifier 1.

Example 2

The preparation method of the N-N-butyrylated carboxymethyl chitosan grafted by polyethylene glycol monomethyl ether comprises the following specific steps:

(1) synthesis of N-acylated chitosan: mixing 2g Chitosan (CS) (M)_w179.17kDa, degree of deacetylation>95 percent and 100-200 mPas) is dissolved in 40mL of 10 percent acetic acid water solution, 160mL of methanol is added for dilution, 5.9mmol of N-hexyl anhydride is added according to 0.5 time of the amount of amino substances under the condition of stirring, 260mL of acetone is added as a precipitator after the mixture is placed for 24 hours at room temperature, and the precipitate is washed three times by methanol and ether respectively and is frozen and dried to obtain white water-soluble solid N-N-hexanoylated chitosan (A)₆CS). The calculation of the amount of n-hexanoic anhydride used was as described in step (1) of example 1.

(2) Synthesis of epoxidized polyethylene glycol monomethyl ether: taking polyethylene glycol monomethyl ether (M)_n1900)1.9g (1mmol) dissolved in 50mL of anhydrous nailTo benzene was added 50mL of tetrahydrofuran and 0.036g (1.5mmol) of sodium hydride reagent, and the mixture was heated to 25 ℃ for 4 hours. 0.37mL (4mmol) of epichlorohydrin was slowly added dropwise to the reaction mixture, and the reaction was carried out at 40 ℃ for 6 hours. Adding the reaction solution into 200mL of diethyl ether, carrying out suction filtration, washing with diethyl ether for 3 times, carrying out vacuum drying, dissolving the product into 200mL of dichloromethane, washing with distilled water for three times, carrying out liquid separation, drying with anhydrous magnesium sulfate, carrying out reduced pressure distillation on the filtrate after suction filtration, and carrying out freeze drying to obtain the epoxidized polyethylene glycol monomethyl ether.

(3) Synthesizing polyethylene glycol monomethyl ether grafted N-N-hexanoyl chitosan: take 1.128g A₆Adding 50mL of distilled water into a 250mL three-neck flask, adding sodium hydroxide to adjust the pH value of the solution to 9, dissolving 3.8g of epoxidized polyethylene glycol monomethyl ether into 10mL of anhydrous toluene, dropwise adding the solution into a reaction system within 10min through a constant-pressure dropping funnel, stirring, heating to 110 ℃, and reacting at a constant temperature for 24 h. And dialyzing the reaction solution for 3 days after the reaction is finished, and freeze-drying to obtain the polyethylene glycol monomethyl ether grafted N-N-hexanoyl chitosan.

(4) Carboxymethylation of polyethylene glycol monomethyl ether grafted N-hexanoylated chitosan: adding 7.57g of polyethylene glycol monomethyl ether grafted N-N-hexyl acylation chitosan into a 250mL three-neck flask, adding 100mL of distilled water, completely dissolving at room temperature, taking 10mL of 10% sodium hydroxide solution, equally dividing into 5 parts, adding the 5 parts into the reaction solution at intervals of 5min for 5 times, and alkalizing for 1 h. After the alkalization is finished, 4.6g of sodium chloroacetate is divided into 5 parts, one part is added into the reaction liquid every 1min, the temperature is raised to 60 ℃ after the addition is finished, the reaction is carried out for 2h, and the pH value of the reaction liquid is adjusted to be neutral by acetic acid. And after the reaction is finished, performing suction filtration, washing a filter cake for three times by using acetone, dialyzing for three days after washing, and performing freeze drying to obtain the polyethylene glycol monomethyl ether grafted N-N-butyrylated carboxymethyl chitosan serving as the demulsifier 2.

Example 3

The preparation method of the N-N-butyrylated carboxymethyl chitosan grafted by polyethylene glycol monomethyl ether comprises the following specific steps:

(1) synthesis of N-acylated chitosan: 2g Chitosan (CS) (M)_w179.17kDa, degree of deacetylation>95% and a viscosity of 100 to 200 mPas) in 40mLAdding 160mL of methanol into 10% acetic acid aqueous solution for dilution, adding 5.9mmol of N-caprylic anhydride according to 0.5 time of the amount of amino substances under the condition of stirring, standing at room temperature for 24h, adding 260mL of acetone as a precipitator, washing the precipitate with methanol and ether respectively for three times, and freeze-drying to obtain white water-soluble solid N-N-octanoylated chitosan (A)₈CS). The method for calculating the amount of n-octanoic anhydride used is described in reference to step (1) in example 1.

(2) Synthesis of epoxidized polyethylene glycol monomethyl ether: taking polyethylene glycol monomethyl ether (M)_n750)0.75g (1mmol) was dissolved in 50mL of anhydrous toluene, 50mL of tetrahydrofuran and 0.036g (1.5mmol) of sodium hydride reagent were added, and the temperature was raised to 25 ℃ to react for 4 h. 0.37mL (4mmol) of epichlorohydrin was slowly added dropwise to the reaction mixture, and the reaction was carried out at 40 ℃ for 6 hours. Adding the reaction solution into 200mL of diethyl ether, carrying out suction filtration, washing with diethyl ether for 3 times again, carrying out vacuum drying, dissolving the product into 200mL of dichloromethane, washing with distilled water for three times, carrying out liquid separation, drying with anhydrous magnesium sulfate, carrying out reduced pressure distillation on the filtrate after suction filtration, and carrying out freeze drying to obtain epoxidized polyethylene glycol monomethyl ether;

(3) synthesizing polyethylene glycol monomethyl ether grafted N-N-octanoyl chitosan: get 1.256g A₈Adding 50mL of distilled water into a 250mL three-neck flask, adding sodium hydroxide to adjust the pH value of the solution to 9, dissolving 1.5g of epoxidized polyethylene glycol monomethyl ether into 10mL of anhydrous toluene, dropwise adding the solution into a reaction system within 10min through a constant-pressure dropping funnel, stirring, heating to 110 ℃, and reacting at a constant temperature for 24 h. And dialyzing the reaction solution for 3 days after the reaction is finished, and freeze-drying to obtain the polyethylene glycol monomethyl ether grafted N-N-octanoyl chitosan.

(4) Carboxymethylation of polyethylene glycol monomethyl ether grafted N-octanoylated chitosan: 5.015g of polyethylene glycol monomethyl ether grafted N-N-octanoylated chitosan is put into a 250mL three-neck flask, 100mL of distilled water is added until the chitosan is completely dissolved at room temperature, 10mL of 10% sodium hydroxide solution is evenly divided into 5 parts, the 5 parts are added into the reaction solution at intervals of 5min for 5 times, and the mixture is alkalized for 1 h. After the alkalization is finished, 4.6g of sodium chloroacetate is divided into 5 parts, one part is added into the reaction liquid every 1min, and the temperature is raised to 60 ℃ after the addition is finished, and the reaction is carried out for 2 h. And after the reaction is finished, performing suction filtration, washing a filter cake for three times by using acetone, dialyzing for three days after washing, and freeze-drying to obtain the polyethylene glycol monomethyl ether grafted N-N-octanoylated carboxymethyl chitosan serving as the demulsifier 3.

Example 4

The preparation method of the N-N-octanoylated carboxypropyl chitosan grafted by the polyethylene glycol monomethyl ether comprises the following specific steps:

(1) the same procedure as in step (1) of example 3 gave N-N-octanoylated chitosan (A)₈CS)。

(2) Synthesis of epoxidized polyethylene glycol monomethyl ether: taking polyethylene glycol monomethyl ether (M)_n350) was dissolved in 50mL of anhydrous toluene, 50mL of tetrahydrofuran and 0.036g (1.5mmol) of sodium hydride reagent were added, and the mixture was heated to 25 ℃ and reacted for 4 hours. 0.37mL (4mmol) of epichlorohydrin was slowly added dropwise to the reaction mixture, and the reaction was carried out at 40 ℃ for 6 hours. Adding the reaction solution into 200mL of diethyl ether, carrying out suction filtration, washing with diethyl ether for 3 times again, carrying out vacuum drying, dissolving the product into 200mL of dichloromethane, washing with distilled water for three times, carrying out liquid separation, drying with anhydrous magnesium sulfate, carrying out reduced pressure distillation on the filtrate after suction filtration, and carrying out freeze drying to obtain epoxidized polyethylene glycol monomethyl ether;

(3) synthesizing polyethylene glycol monomethyl ether grafted N-N-octanoyl chitosan: get 1.256g A₈Adding 50mL of distilled water into a 250mL three-neck flask, adding sodium hydroxide to adjust the pH value of the solution to 9, dissolving 0.7g of epoxidized polyethylene glycol monomethyl ether into 10mL of anhydrous toluene, dropwise adding the solution into a reaction system within 10min through a constant-pressure dropping funnel, stirring, heating to 110 ℃, and reacting at a constant temperature for 24 h. And dialyzing the reaction solution for 3 days after the reaction is finished, and freeze-drying to obtain the polyethylene glycol monomethyl ether grafted N-N-octanoyl chitosan.

(4) Carboxypropylation of polyethylene glycol monomethyl ether grafted N-N-octanoylated chitosan: 4.015g of polyethylene glycol monomethyl ether grafted N-N-octanoylated chitosan is put into a 250mL three-neck flask, 100mL of distilled water is added until the chitosan is completely dissolved at room temperature, 10mL of 10% sodium hydroxide solution is evenly divided into 5 parts, the 5 parts are added into the reaction solution at intervals of 5min for 5 times, and the mixture is alkalized for 1 h. And after the alkalization is finished, dividing 9.5g of sodium chlorobutyrate into 5 parts, adding one part of sodium chlorobutyrate into the reaction solution every 1min, heating to 60 ℃ after the addition is finished, and reacting for 2 h. And after the reaction is finished, performing suction filtration, washing a filter cake for three times by using acetone, dialyzing for three days after washing, and freeze-drying to obtain the polyethylene glycol monomethyl ether grafted N-N-octanoylated carboxymethyl chitosan serving as the demulsifier 4.

Comparative example 1

And a commercial product number SP series demulsifier is used as a demulsifier comparative example 1.

Comparative example 2

And a commercial product number JL series demulsifier is used as the demulsifier comparative example 2.

Demulsification effect experiment of demulsifier

Crude oil provided by Wuhan division of China petrochemical company Limited is used as the oil for demulsification experiments to carry out experiments, and the water content in the crude oil is measured to be 50 percent according to GB/T8929-88 (distillation method).

The dehydration temperature is set to be 40-80 ℃, and the concentration of a demulsifier in the crude oil is 70-220 ppm. The demulsification performances of the demulsifiers 1-4 prepared in examples 1-4 and the demulsifier comparative examples 1-2 prepared in comparative examples were tested with reference to "crude oil demulsifier usability detection method (bottle test method)" of the national petroleum and gas industry standard SY/T5281-2000, and a mechanical oscillation method was used as an oscillation method for a dehydration test bottle in the test.

The method comprises the following specific steps: pouring the crude oil emulsion sample into a 100mL measuring cylinder with a plug, and heating in a constant-temperature water bath for 30 min; adding a certain amount of crude oil demulsifier solution into the measuring cylinder with the plug by using a pipette; adopting a mechanical oscillation method, enabling the amplitude to be larger than 20cm, enabling the oscillation time to be 5min, fully mixing uniformly, and then placing the measuring cylinder with the plug in a constant-temperature water bath again for standing and settling; timing, recording the dehydration amount at different times (20min, 40min, 60min, 80min, 100min and 120min), and observing and recording the color of the sewage when the sedimentation is stopped.

The experimental result shows that compared with the comparative demulsifier 1-3, the demulsifier 1-3 obtained by the method has better dehydration and desalination effects within the ranges of the dehydration temperature of 40-80 ℃ and the demulsifier concentration of 70-220 ppm, and the effect is optimal particularly when the concentration is 200ppm and the dehydration temperature is 50 ℃.

The demulsifiers 1-4 prepared in examples 1-4 and the demulsifiers provided in comparative examples 1-2, the effect of the demulsification and dehydration experiments under the above-mentioned optimum concentration and temperature conditions, are shown in Table 1.

TABLE 1

Claims (10)

1. A preparation method of a chitosan crude oil demulsifier is disclosed, wherein the chitosan crude oil demulsifier has a structural general formula shown in the following formula (I):

the method is characterized by comprising the following steps:

1) carrying out acylation modification on amino on chitosan:

dissolving chitosan in an organic acid aqueous solution, adding organic alcohol for dilution, adding acid anhydride according to 0.5 time of the amount of amino substances on the chitosan, standing for 24-48 h, adding a precipitator, washing the precipitate, and freeze-drying to obtain N-acylated chitosan;

2) epoxidizing and modifying the terminal hydroxyl of the polyethylene glycol monomethyl ether to obtain epoxidized polyethylene glycol monomethyl ether;

3) the method comprises the following steps of reacting epoxidized polyethylene glycol monomethyl ether with N-acylated chitosan:

dissolving or swelling the N-acylated chitosan prepared in the step 1) in a solvent C, adjusting the pH value of the solution, dissolving the epoxidized polyethylene glycol monomethyl ether prepared in the step 2) in the solvent A, then dropwise adding the solution into a reaction system, heating to 80-120 ℃, reacting for 12-24 hours, separating and purifying reaction liquid, and freeze-drying to obtain the modified polyethylene glycol monomethyl ether grafted N-acylated chitosan;

4) carrying out carboxyl alkylation modification on the modified polyethylene glycol monomethyl ether grafted N-acylated chitosan:

dissolving or swelling the modified polyethylene glycol monomethyl ether grafted N-acylated chitosan prepared in the step 3) in a solvent D, and adding alkali liquor for alkalization; after alkalization is completed, adding sodium chloroalkyl acid into the reaction liquid, heating to 50-70 ℃, and reacting for 2-7 hours; separating and purifying the reaction liquid, and freeze-drying to obtain the modified polyethylene glycol monomethyl ether grafted N-acylated carboxyalkyl chitosan; wherein the carbon chain length of the sodium chloroalkyl is C2-C18.

2. The method for preparing the chitosan-based crude oil demulsifier according to claim 1, wherein the volume consumption of the organic alcohol in step 1) is more than 80% of the total system.

3. The method for preparing the chitosan-based crude oil demulsifier according to claim 1, wherein the organic alcohol in step 1) is one or more of fatty alcohols having 1 to 10 carbon atoms; the acid anhydride is one or more of acid anhydrides corresponding to fatty acid with 2-10 carbon atoms; the precipitant is acetone.

4. The preparation method of the chitosan-based crude oil demulsifier according to claim 1, wherein in step 3), the mass part ratio of the N-acylated chitosan to the epoxidized polyethylene glycol monomethyl ether is (0.872-1.384) - (0.7-10).

5. The preparation method of the chitosan-based crude oil demulsifier according to claim 1, wherein in step 3), the pH value of the solution is in the range of 9-14.

6. The preparation method of the chitosan crude oil demulsifier according to claim 1, wherein in step 4), the mass part ratio of the modified polyethylene glycol monomethyl ether-grafted N-acylated chitosan to sodium chloroalkyl ate is (3.055-15.96): (4.6-15.48).

7. The method for preparing the chitosan-based crude oil demulsifier according to claim 1, wherein in step 4), the alkali liquor is added in small amount for multiple times; the addition mode of the sodium chloroalkyl is small-amount multiple addition.

8. The method for preparing the chitosan-based crude oil demulsifier according to any one of claims 1 to 7, wherein the solvent A is anhydrous toluene; the solvent C is one or more of distilled water, isopropanol, sodium hydroxide solution, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide, acetic acid and methanol; the solvent D is one or a mixture of more of distilled water, isopropanol, sodium hydroxide solution, hydrochloric acid solution, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide, acetic acid and methanol.

9. The method for preparing the chitosan-based crude oil demulsifier according to claim 8, wherein the step 2) is as follows:

dissolving 1 mol part of polyethylene glycol monomethyl ether in a solvent A at room temperature, adding a proper amount of a solvent B and 1-5 mol parts of an alkalizing agent, heating to 20-40 ℃, reacting for 3-8 h, slowly dropwise adding 2.5-10 mol parts of an epoxidation agent into a reaction solution, heating to 20-40 ℃, reacting for 3-20 h, separating, purifying and freeze-drying the reaction solution to obtain epoxidized polyethylene glycol monomethyl ether; wherein the number average molecular mass of the polyethylene glycol monomethyl ether is 350-5000.

10. The method for preparing the chitosan-based crude oil demulsifier according to claim 9, wherein in step 2), the alkalizing agent is sodium hydride or sodium hydroxide; the epoxidation reagent is epichlorohydrin; the solvent B is one or more of tetrahydrofuran, ethanol, dimethyl sulfoxide, dichloromethane, N-dimethylformamide and N, N-dimethylacetamide.