CN108865228B - Modified crude oil demulsifier and preparation method thereof - Google Patents

Modified crude oil demulsifier and preparation method thereof Download PDF

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CN108865228B
CN108865228B CN201810805687.4A CN201810805687A CN108865228B CN 108865228 B CN108865228 B CN 108865228B CN 201810805687 A CN201810805687 A CN 201810805687A CN 108865228 B CN108865228 B CN 108865228B
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polyethylene glycol
monomethyl ether
glycol monomethyl
chitosan
grafted
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CN108865228A (en
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吕仁亮
张�成
梁成
王存文
徐彩丽
覃远航
王为国
冯魏良
徐汶
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Wuhan Institute of Technology
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G33/00—Dewatering or demulsification of hydrocarbon oils
    • C10G33/04—Dewatering or demulsification of hydrocarbon oils with chemical means
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G81/00—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
    • C10G2300/10—Feedstock materials
    • C10G2300/1033—Oil well production fluids

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Abstract

The invention relates to a modified 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) epoxidizing and modifying the terminal hydroxyl of the polyethylene glycol monomethyl ether; 2) reacting the modified polyethylene glycol monomethyl ether with chitosan to obtain polyethylene glycol monomethyl ether grafted chitosan; 3) carrying out alkylation modification on the polyethylene glycol monomethyl ether grafted chitosan to obtain polyethylene glycol monomethyl ether grafted alkylated chitosan; 4) and (3) carrying out carboxyl alkylation modification on the alkylated chitosan grafted by the polyethylene glycol monomethyl ether to obtain the alkylated carboxyalkyl chitosan grafted by the polyethylene glycol monomethyl ether. 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, alkyl and polyether side chain are introduced into the chitosan molecular chain, and a series of high-efficiency demulsifiers suitable for oil-in-water (O/W) type emulsion can be obtained by controlling the position and the substitution degree of each substituent.

Description

Modified crude oil demulsifier and preparation method thereof
Technical Field
The invention relates to a modified crude oil desalting 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 epoxy 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 aims to provide a modified 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, alkyl 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 of the product, degradability and the like.
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
the modified crude oil demulsifier is characterized by having a general structural formula shown in the following formula (I):
Figure BDA0001738128540000031
R＝H or COCH3
R0，R1R2＝R2＝H or MPEG-CH2-CHOH-CH2-or R6orMMPEG-CH2-CHOR6-CH2-or R10COOHor MPEG-CH2-CH(OR10COOH)-CH2-
R6＝CH3(CH2)aCH2(a＝2，3，4，5...14)R10＝(CH2)b(b＝1，2，3，4，5，6...17)
(I)
the invention also provides a preparation method of the modified crude oil demulsifier, which comprises the following steps:
the preparation method of the modified crude oil demulsifier is characterized by comprising the following steps:
1) epoxidizing and modifying terminal hydroxyl of polyethylene glycol monomethyl ether to obtain 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 D 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.
2) The method comprises the following steps of reacting epoxidized polyethylene glycol monomethyl ether with chitosan:
dissolving the epoxidized polyethylene glycol monomethyl ether prepared in the step 1) in a solvent A, adding an alkali liquor to adjust the pH value of the solution within a certain range, dissolving or swelling chitosan in a solvent B, then dropwise adding the solvent B into a reaction system, stirring and heating the solution at the temperature of 80-120 ℃, reacting at a constant temperature for 2-24 hours, separating and purifying the reaction solution, and freeze-drying the reaction solution to obtain the modified polyethylene glycol monomethyl ether grafted chitosan.
3) The method comprises the following steps of carrying out alkylation modification on active hydrogen on the polyethylene glycol monomethyl ether grafted chitosan to obtain the polyethylene glycol monomethyl ether grafted alkylated chitosan, and specifically comprises the following steps:
adding the polyethylene glycol monomethyl ether grafted chitosan prepared in the step 2) and alkali liquor into a solvent C serving as a reaction medium, stirring, stably heating to 40-60 ℃, and reacting at a constant temperature for 0.5-2 h to alkalize the chitosan; after the alkalization is finished, slowly dropwise adding a certain amount of alkyl halide at the same reaction temperature, and reacting for 4-10 h at constant temperature; washing out the product and adjusting the pH value to be neutral; and then adding a precipitator to fully separate out the product, fully standing for precipitation, filtering, washing a filter cake, drying, dialyzing, and freeze-drying to obtain the polyethylene glycol monomethyl ether grafted alkylated chitosan.
4) The method comprises the following steps of (1) carrying out carboxyl alkylation modification on the alkylated chitosan grafted by polyethylene glycol monomethyl ether to obtain the alkylated carboxyalkyl chitosan grafted by polyethylene glycol monomethyl ether, and specifically comprising the following steps:
adding isopropanol into the polyethylene glycol monomethyl ether grafted alkylated chitosan prepared in the step 3), swelling at room temperature, and adding alkali liquor for alkalization for 1-4 h; after alkalization is finished, adding a carboxylation reagent sodium chloroalkyl ate into the reaction liquid, heating to 50-70 ℃, reacting for 3-7 h, and adjusting the pH of the reaction liquid to be neutral; carrying out suction filtration on a reaction product, washing and dialyzing a filter cake, and carrying out freeze drying to obtain alkylated carboxyalkyl chitosan; wherein, preferably, the carbon chain length of the sodium chloroalkylate is C2-C18。
According to the scheme, in the step 1), preferably, the alkalizing agent is sodium hydride; the epoxidation reagent is epichlorohydrin.
According to the scheme, preferably, in the step 2), the mass part ratio of the chitosan to the epoxidized polyethylene glycol monomethyl ether is (1-1.61): (0.816-10.116).
According to the scheme, preferably, in the step 2), the pH value of the solution is 9-14.
According to the scheme, in the step 3), the dosage ratio of the polyethylene glycol monomethyl ether grafted chitosan to the alkyl halide is (0.408-11.61) g, (1.5-3) mL.
According to the scheme, preferably, the solvent C in the step 3) is one or a mixture of two of distilled water and organic alcohol, wherein the organic alcohol is one or more of aliphatic alcohols with 1-10 carbon atoms, such as methanol, ethanol, n-propanol, isobutanol and the like; the alkali liquor is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate; the alkyl halide is alkyl halide corresponding to alkane with 4-16 carbon atoms; the precipitant is acetone.
According to the scheme, in the step 4), the mass part ratio of the polyethylene glycol monomethyl ether grafted alkylated chitosan to the sodium chloroalkyl ate is (1.88-14.77) to (2.9-8.5).
According to the scheme, preferably, in the step 4), 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 a mixture of 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 more of tetrahydrofuran, ethanol, dimethyl sulfoxide, dichloromethane, N-dimethylformamide and N, N-dimethylacetamide.
The synthetic route of the invention is as follows:
1. and (3) performing epoxidation modification on polyethylene glycol monomethyl ether, wherein the modified polyethylene glycol monomethyl ether is recorded as MPEG-M:
Figure BDA0001738128540000051
2. preparing alkylated carboxyalkyl chitosan, synthesizing the polyethylene glycol monomethyl ether grafted alkylated carboxyalkyl chitosan:
Figure BDA0001738128540000061
R＝H or COCH3 R3，R4，R5＝H or MPEG-CH2-CHOH-CH2-
R6＝CH3(CH2)aCH2(a＝2，3，4，5...14) R7＝R3or R6or MPEG-CH2-CH(OR6)-CH2-
R8＝R4orR6or MPEG-CH2-CH(OR6)-CH2- R9R5or R6or MPEG-CH2-CH(OR6)-CH2-
R10＝(CH2)b(b＝1，2，3，4，5，6...17)
R0＝R7or R10COOH or MPEG-CH2-CH(OR10COOH)-CH2-
R1＝R8or R10COOH or MPEG-CH2-CH(OR10COOH)-CH2-
R2＝R9or R10COOH or MPEG-CH2-CH(OR10COOH)-CH2-
aiming at the problems in 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 carboxyalkylated 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) 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 polyether 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 oil 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.
All the starting materials mentioned in the examples below are, unless otherwise specified, commercially available.
Example 1
The preparation method of the butyl carboxymethyl chitosan grafted by the polyethylene glycol monomethyl ether comprises the following specific steps:
(1) 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, filtering, and weighing with diethyl etherAnd (3) newly washing for several times, carrying out vacuum drying, dissolving the product into 200mL dichloromethane, washing with distilled water for three times, separating liquid, drying with anhydrous magnesium sulfate, carrying out vacuum filtration, carrying out reduced pressure distillation on the filtrate, and carrying out freeze drying to obtain the epoxidized polyethylene glycol monomethyl ether.
(2) Synthesis of polyethylene glycol monomethyl ether grafted chitosan: accurately weigh 1g of Chitosan (CS) (M)w179.17kDa, degree of deacetylation>95% and 100-200 mPas) into a three-neck flask containing 50mL of dimethyl sulfoxide, adding a sodium hydroxide solution to adjust the pH of the solution to 6, dissolving 10.116g of the epoxidized polyethylene glycol monomethyl ether prepared in the step (1) into 10mL of an anhydrous toluene solution, dropwise adding the solution into a reaction system by using a constant-pressure dropping funnel within 10min, heating to 120 ℃, 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 chitosan.
(3) Preparing the butyl chitosan grafted by the polyethylene glycol monomethyl ether: 6.058g of polyethylene glycol monomethyl ether grafted chitosan prepared in the step (2) is put into a 250mL three-neck flask, 12mL of isopropanol and 2g of potassium hydroxide are added, the temperature is raised to 40 ℃ smoothly under the stirring condition, and the temperature is kept constant for 2h so as to alkalize the chitosan. After the alkalization is finished, slowly dropwise adding 3mL of n-butyl bromide at the same reaction temperature, and reacting for 6h at constant temperature. After the reaction was completed, 20mL of methanol was added to the three-necked flask to wash out the product. And (2) adjusting the pH value of the system to 7 by using 10% dilute hydrochloric acid by mass fraction, adding 10mL of acetone as a precipitator, fully standing for precipitation, filtering, washing a filter cake by using methanol and ether for three times respectively, drying in an oven at 80 ℃ overnight, dialyzing, and freeze-drying to obtain the methyl polyethylene glycol monomethyl ether grafted butyl chitosan.
(4) Preparing the butyl carboxymethyl chitosan grafted by the polyethylene glycol monomethyl ether: 13.615g of the methyl polyethylene glycol ether grafted butyl chitosan prepared in the step (3) is put into a 250mL three-neck flask, 50mL of isopropanol is added, swelling is carried out for 30min at room temperature, 10mL of 10% sodium hydroxide solution is added into the reaction solution for 5 times at intervals of 5min, and alkalization is carried out for 2 h. After the alkalization is finished, dividing 2.9g of sodium chloroacetate into 5 parts, adding one part into the reaction solution every 1min, heating to 60 ℃ after the addition is finished, reacting for 4h, and adjusting the pH of the reaction solution to be neutral by using 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 methyl polyethylene glycol grafted butyl carboxymethyl chitosan serving as the demulsifier 1.
Example 2
The preparation method of the polyethylene glycol monomethyl ether grafted hexyl carboxymethyl chitosan comprises the following specific steps:
(1) synthesis of epoxidized polyethylene glycol monomethyl ether: taking polyethylene glycol monomethyl ether (M)n1900)1.9g (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 the reaction solution for several times by using the diethyl ether, carrying out vacuum drying, dissolving the product into 200mL of dichloromethane, washing the obtained product for three times by using distilled water, carrying out liquid separation, drying the obtained product by using anhydrous magnesium sulfate, carrying out reduced pressure distillation on the filtered solution after suction filtration, and carrying out freeze drying to obtain the epoxidized polyethylene glycol monomethyl ether.
(2) Synthesis of polyethylene glycol monomethyl ether grafted chitosan: accurately weigh 1g of Chitosan (CS) (M)w179.17kDa, degree of deacetylation>95% and 100-200 mPas) into a three-neck flask containing 50mL of dimethyl sulfoxide, adding a sodium hydroxide solution to adjust the pH of the solution to 6, taking 3.916g of the epoxidized polyethylene glycol monomethyl ether prepared in the step (1) into 10mL of anhydrous toluene solution, dropwise adding the solution into a reaction system by using a constant-pressure dropping funnel within 10min, heating to 120 ℃, and reacting at 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 chitosan.
(3) Preparing polyethylene glycol monomethyl ether grafted hexyl chitosan: and (3) putting 2.958g of the polyethylene glycol monomethyl ether grafted chitosan prepared in the step (2) into a 250mL three-neck flask, adding 12mL of distilled water and 2g of potassium hydroxide, smoothly heating to 40 ℃ under the stirring condition, and keeping the temperature for 2 hours to alkalize the chitosan. After the alkalization is finished, slowly dropwise adding 3mL of bromo-n-hexane at the same reaction temperature, and reacting for 6h at constant temperature. After the reaction was completed, 20mL of methanol was added to the three-necked flask to wash out the product. Adjusting the pH value of the system to 7 by using dilute hydrochloric acid with the mass fraction of 10%, adding 10mL of acetone as a precipitator, fully standing for precipitation, filtering, washing a filter cake by using methanol and ether for three times respectively, drying in an oven at 80 ℃ overnight, dialyzing, and freeze-drying to obtain the polyethylene glycol monomethyl ether grafted hexyl chitosan.
4) Preparation of polyethylene glycol monomethyl ether grafted hexyl carboxymethyl chitosan: 5.895g of polyethylene glycol monomethyl ether grafted hexyl chitosan prepared in the step (3) is put into a 250mL three-neck flask, 50mL of isopropanol is added, swelling is carried out for 30min at room temperature, 10mL of 10% sodium hydroxide solution is taken and added into the reaction solution for 5 times at intervals of 5min, and alkalization is carried out for 2 h. After the alkalization is finished, dividing 2.9g of sodium chloroacetate into 5 parts, adding one part into the reaction solution every 1min, heating to 60 ℃ after the addition is finished, reacting for 4h, and adjusting the pH of the reaction solution to be neutral by using 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 hexyl carboxymethyl chitosan serving as the demulsifier 2.
Example 3
The preparation method of the methoxy polyethylene glycol grafted octyl carboxymethyl chitosan comprises the following specific steps:
(1) 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 the reaction solution for several times by using the diethyl ether, carrying out vacuum drying, dissolving the product into 200mL of dichloromethane, washing the obtained product for three times by using distilled water, carrying out liquid separation, drying the obtained product by using anhydrous magnesium sulfate, carrying out reduced pressure distillation on the filtered solution after suction filtration, and carrying out freeze drying to obtain the epoxidized polyethylene glycol monomethyl ether.
(2) Synthesis of polyethylene glycol monomethyl ether grafted chitosan: accurately weigh 1g of Chitosan (CS) (M)w179.17kDa, degree of deacetylation>95% and 100-200 mPas) into a three-neck flask containing 50mL of dimethyl sulfoxide, adding a sodium hydroxide solution to adjust the pH of the solution to 6, taking 1.616g of the epoxidized polyethylene glycol monomethyl ether prepared in the step (1) to dissolve in 10mL of anhydrous toluene solution, and using constant pressure dropping to leakThe bucket is dripped into the reaction system within 10min, the temperature is raised to 120 ℃, and the reaction is carried out for 24h at constant temperature. And dialyzing the reaction solution for 3 days after the reaction is finished, and freeze-drying to obtain the polyethylene glycol monomethyl ether grafted chitosan.
(3) Preparation of methoxy polyethylene glycol grafted octyl chitosan: and (3) putting 1.808g of the polyethylene glycol monomethyl ether grafted chitosan prepared in the step (2) into a 250mL three-neck flask, adding 6mL of distilled water, 12mL of isopropanol and 2g of potassium hydroxide, smoothly heating to 40 ℃ under the stirring condition, and keeping the temperature for 2 hours to alkalize the chitosan. After the alkalization is finished, slowly dropwise adding 3mL of bromo-n-octane at the same reaction temperature, and reacting for 6h at constant temperature. After the reaction was completed, 20mL of methanol was added to the three-necked flask to wash out the product. And (2) adjusting the pH value of the system to 7 by using 10% dilute hydrochloric acid by mass fraction, adding 10mL of acetone as a precipitator, fully standing for precipitation, filtering, washing a filter cake by using methanol and ether for three times respectively, drying in an oven at 80 ℃ overnight, dialyzing, and freeze-drying to obtain the methoxy polyethylene glycol grafted octyl chitosan.
(4) Preparing the butyl carboxymethyl chitosan grafted by the polyethylene glycol monomethyl ether: and (3.09 g) of the methoxy polyethylene glycol grafted octyl chitosan prepared in the step (3) is placed in a 250mL three-neck flask, 50mL of isopropanol is added, swelling is carried out for 30min at room temperature, 10mL of 10% sodium hydroxide solution is added into the reaction solution for 5 times at intervals of 5min, and alkalization is carried out for 2 h. After the alkalization is finished, dividing 2.9g of sodium chloroacetate into 5 parts, adding one part into the reaction solution every 1min, heating to 60 ℃ after the addition is finished, and reacting for 4 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 methoxy polyethylene glycol grafted octyl carboxymethyl chitosan serving as the demulsifier 3.
Example 4
The preparation method of the methoxy polyethylene glycol grafted octyl carboxypropyl chitosan comprises the following specific steps:
(1) 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 is slowly dropped into the reaction solution at the temperature of 40 DEG CAnd reacting for 6 hours. Adding the reaction solution into 200mL of diethyl ether, carrying out suction filtration, washing the reaction solution for several times by using the diethyl ether, carrying out vacuum drying, dissolving the product into 200mL of dichloromethane, washing the obtained product for three times by using distilled water, carrying out liquid separation, drying the obtained product by using anhydrous magnesium sulfate, carrying out reduced pressure distillation on the filtered solution after suction filtration, and carrying out freeze drying to obtain the epoxidized polyethylene glycol monomethyl ether.
(2) Synthesis of polyethylene glycol monomethyl ether grafted chitosan: 1.61g of Chitosan (CS) (M) was accurately weighedw179.17kDa, degree of deacetylation>95% and 100-200 mPas) into a three-neck flask containing 50mL of dimethyl sulfoxide, adding a sodium hydroxide solution to adjust the pH of the solution to 6, taking 0.816g of the epoxidized polyethylene glycol monomethyl ether prepared in the step (1) to dissolve in 10mL of anhydrous toluene solution, dropwise adding the solution into a reaction system by using a constant-pressure dropping funnel within 10min, heating to 120 ℃, and reacting at 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 chitosan.
(3) Preparation of methoxy polyethylene glycol grafted octyl chitosan: 1.408g of polyethylene glycol monomethyl ether grafted chitosan prepared in the step (2) is put into a 250mL three-neck flask, 12mL of isopropanol and 2g of potassium hydroxide are added, the temperature is raised to 40 ℃ smoothly under the stirring condition, and the temperature is kept constant for 2h so as to alkalize the chitosan. After the alkalization is finished, slowly dropwise adding 3mL of bromo-n-octane at the same reaction temperature, and reacting for 6h at constant temperature. After the reaction was completed, 20mL of methanol was added to the three-necked flask to wash out the product. And (2) adjusting the pH value of the system to 7 by using 10% dilute hydrochloric acid by mass fraction, adding 10mL of acetone as a precipitator, fully standing for precipitation, filtering, washing a filter cake by using methanol and ether for three times respectively, drying in an oven at 80 ℃ overnight, dialyzing, and freeze-drying to obtain the methoxy polyethylene glycol grafted octyl chitosan.
(4) Preparation of methoxy polyethylene glycol grafted octyl carboxypropyl chitosan: and (3) putting 2.09g of the methoxy polyethylene glycol grafted octyl chitosan prepared in the step (3) into a 250mL three-neck flask, adding 50mL of isopropanol, swelling at room temperature for 30min, adding 10mL of 10% sodium hydroxide solution into the reaction solution for 5 times at intervals of 5min every time, and alkalizing for 2 h. After the alkalization is finished, 3.6g of sodium chlorobutyrate 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, so that the reaction is carried out for 4 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 methoxy polyethylene glycol grafted octyl carboxypropyl 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 1-2, the demulsifier 1-4 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
Figure BDA0001738128540000121

Claims (11)

1. The modified crude oil demulsifier is characterized by having a general structural formula shown in the following formula (I):
Figure FDA0002827611520000011
2. the preparation method of the modified crude oil demulsifier is characterized by comprising the following steps:
1) epoxidizing and modifying the terminal hydroxyl of the polyethylene glycol monomethyl ether to obtain epoxidized polyethylene glycol monomethyl ether;
2) reacting epoxidized polyethylene glycol monomethyl ether with chitosan:
dissolving the epoxidized polyethylene glycol monomethyl ether prepared in the step 1) in a solvent A, adding an alkali liquor to adjust the pH value of the solution, dissolving or swelling chitosan in a solvent B, then dropwise adding the chitosan into a reaction system, heating to 80-120 ℃, reacting at a constant temperature for 2-24 hours, separating and purifying the reaction solution, and freeze-drying to obtain modified polyethylene glycol monomethyl ether grafted chitosan;
3) carrying out alkylation modification on active hydrogen on the polyethylene glycol monomethyl ether grafted chitosan:
adding the polyethylene glycol monomethyl ether grafted chitosan prepared in the step 2) and alkali liquor by taking a solvent C as a reaction medium, heating to 40-60 ℃, and reacting for 0.5-2 h; after the alkalization is finished, adding alkyl halide dropwise at the same reaction temperature, and reacting for 4-10 h; washing out the product and adjusting the pH value to be neutral; then adding a precipitator, precipitating, filtering, purifying a filter cake, and freeze-drying to obtain the polyethylene glycol monomethyl ether grafted alkylated chitosan;
4) performing carboxyl alkylation modification on the alkylated chitosan grafted by polyethylene glycol monomethyl ether:
adding isopropanol into the polyethylene glycol monomethyl ether grafted alkylated chitosan prepared in the step 3), swelling at room temperature, and adding alkali liquor for alkalization for 1-4 h; after alkalization is completed, adding sodium chloroalkyl acid into the reaction liquid, heating to 50-70 ℃, and reacting for 3-7 hours; separating and purifying the reaction product, and freeze-drying to obtain alkylated carboxyalkyl chitosan; wherein the length of the carbon chain of the sodium chloroalkyl acid is C2-C18。
3. The preparation method of the modified crude oil demulsifier according to claim 2, wherein in step 2), the mass part ratio of the chitosan to the epoxidized polyethylene glycol monomethyl ether is (1-1.61): 0.816-10.116.
4. The preparation method of the modified crude oil demulsifier according to claim 2, wherein in step 2), the pH value of the solution is in the range of 9 to 14.
5. The preparation method of the modified crude oil demulsifier according to claim 2, wherein in step 3), the amount ratio of the polyethylene glycol monomethyl ether-grafted chitosan to the alkyl halide is (0.408-11.61) g (1.5-3) mL.
6. The method for preparing the modified crude oil demulsifier according to claim 2, wherein the solvent C in step 3) is one or a mixture of two of distilled water and an organic alcohol, wherein the organic alcohol is one or more of fatty alcohols having 1 to 10 carbon atoms; the alkyl halide is alkyl halide corresponding to alkane with 4-16 carbon atoms; the precipitant is acetone.
7. The preparation method of the modified crude oil demulsifier according to claim 2, wherein in step 4), the mass part ratio of the polyethylene glycol monomethyl ether-grafted alkylated chitosan to the sodium chloroalkyl ate is (1.88-14.77) to (2.9-8.5).
8. The method for preparing the modified crude oil demulsifier according to claim 2, wherein in step 4), the lye is added in small amounts and multiple times; the addition mode of the sodium chloroalkyl is small-amount multiple addition.
9. The method for preparing the modified crude oil demulsifier according to any one of claims 2 to 8, wherein the solvent A is anhydrous toluene; the solvent B is one or a mixture of more of distilled water, isopropanol, sodium hydroxide solution, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide, acetic acid and methanol.
10. The method for preparing the modified crude oil demulsifier according to claim 9, wherein the step 1) 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 D and 1-5 mol parts of an alkalizing agent, heating to 20-40 ℃, reacting for 3-8 h, 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.
11. The method for preparing the modified crude oil demulsifier according to claim 10, wherein in step 1), the alkalizing agent is sodium hydride; the epoxidation reagent is epichlorohydrin; the solvent D is one or more of tetrahydrofuran, ethanol, dimethyl sulfoxide, dichloromethane, N-dimethylformamide and N, N-dimethylacetamide.
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