Eutectic solvent for oil-containing solid waste treatment and inorganic base and CO2 double-circulation oil-solid separation method based on eutectic solvent

Abstract

The invention discloses a deep-eutectic solvent for oil-containing solid waste treatment, an inorganic base and CO2 double-circulation oil-solid separation method based on the deep-eutectic solvent and the deep-eutectic solvent for oil-containing solid waste treatment. The deep-eutectic solvent for oil-containing solid waste treatment is characterized in that branched or cyclic short-chain fatty acid with pKa being 4-6 is used as a hydrogen bond donor; a phenol derivative with pKa being 9-11 or C6-C8 straight-chain alcohol is used as a hydrogen bond acceptor; the ratio of the hydrogen bond donor to the hydrogen bond acceptor is (5: 1)-(1: 5) according to the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor; the regulation and control method based on the deep-eutectic solvent comprises the following steps: (1) reacting inorganic alkali with the deep-eutectic solvent to form a hydrophilic carboxylate and phenate solution; (2) after CO2 is introduced, fatty acid / phenols are collected to form a hydrophobic deep-eutectic solvent again, and meanwhile, a bicarbonate aqueous solution is obtained; and (3) heating the bicarbonate aqueous solution or introducing N2, removing CO2, and forming hydrophilic carboxylate and phenolate again by the eutectic solvent in the formed alkaline carbonate solution. According to the inorganic base and CO2 double-circulation oil-solid separation method based on the eutectic solvent, the eutectic solvent can be recycled.

Description

Technical Field

[0001] The present invention relates to the technical field of oil-containing solid waste treatment, and in particular to a low eutectic solvent for oil-containing solid waste treatment, an inorganic base based on the low eutectic solvent, and a CO2 double-circulation oil-solid separation method. Background Art

[0002] Oily solid waste, such as oily sludge and waste drilling mud, is commonly found in all links of the oil and gas production industry and has been classified as hazardous waste (HW08 category). Taking Fuling shale gas extraction as an example, in the current shale gas extraction process, the amount of ordinary rock cuttings generated by a typical single well drilling is about 1085m 2 , producing oil-based cuttings of about 215m 2 , producing about 48m3 of waste drilling mud and sludge 2 . Taking the oil-containing solid waste generated by the exploitation of Fuling Shale Gas Company as a microcosm, this only reflects the "tip of the iceberg" of solid waste from shale gas exploitation in China. In the "National List of Hazardous Wastes (2021 Edition)", drilling cuttings, oil-based mud, etc. generated in oil and gas exploitation are also listed as highly toxic substances. With the accelerated exploitation of oil and gas resources in my country, higher requirements are also placed on related supporting technologies for the treatment of oil-containing solid waste. The current main oil-containing solid waste treatment technologies include incineration, landfill, cleaning, pyrolysis, etc. The incineration treatment method is characterized by high energy consumption and high pollution; the landfill method of oil-containing solid waste will cause serious pollution to the soil and water bodies; the pyrolysis method has high requirements for equipment, which increases operating costs, and such technologies cannot achieve oil recovery. Summary of the invention

[0003] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a low eutectic solvent for oil-containing solid waste treatment, an inorganic base based on the low eutectic solvent and a CO2 double-circulation oil-solid separation method, and an inorganic base based on the low eutectic solvent and a CO2 double-circulation oil-solid separation method, using an inorganic base / CO2 to form a double cycle. First, the inorganic base reacts with the low eutectic solvent to form a hydrophilic carboxylate and phenolate solution, and after CO2 is introduced, the recovered fatty acids / phenols form a hydrophobic low eutectic solvent again, and a bicarbonate aqueous solution is obtained at the same time; second, heating or introducing N2, bicarbonate decomposition, and after excluding CO2, in the formed alkaline carbonate solution, the low eutectic solvent forms a hydrophilic carboxylate and phenolate again, and after CO2 is introduced, the recovered fatty acids / phenols form a hydrophobic low eutectic solvent again, and a bicarbonate aqueous solution is obtained at the same time, thereby achieving multiple cycles. Based on this control method, the low eutectic solvent can be realized and recycled.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A low eutectic solvent for treating oily solid waste, comprising:

[0006] Branched or cyclic short-chain fatty acids with a pKa of 4-6 are hydrogen bond donors;

[0007] Phenol derivatives with a pKa of 9-11 or C6-C8 straight-chain alcohols are hydrogen bond acceptors;

[0008] According to the molar ratio, the ratio of the hydrogen bond donor to the hydrogen bond acceptor is in the range of 5:1-1:5;

[0009] The regulation method based on deep eutectic solvent is:

[0010] (1) using an inorganic base to react with a deep eutectic solvent to form a hydrophilic carboxylate and phenolate solution;

[0011] (2) After CO2 is introduced, fatty acids / phenols are recovered to form a hydrophobic low eutectic solvent again, and a bicarbonate aqueous solution is obtained at the same time;

[0012] (3) After heating the bicarbonate aqueous solution or passing N2 to remove CO2, the low eutectic solvent re-forms hydrophilic carboxylates and phenolates in the formed alkaline carbonate solution.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. The low eutectic solvent is formed by compounding branched or cyclic short-chain fatty acids with a pKa of 4-6 and phenol derivatives with a pKa of 9-11 or C6-C8 straight-chain alcohols. It has properties similar to ionic liquids, with lower saturated vapor pressure, low toxicity, and good biodegradability. It is a new type of green solvent and an ideal alternative to traditional solvents.

[0015] 2. In the regulation method based on the low eutectic solvent of this scheme, inorganic base / CO2 is used to form a double cycle. First, the inorganic base reacts with the low eutectic solvent to form a hydrophilic carboxylate and phenolate solution. After the introduction of CO2, the recovered fatty acids / phenols form a hydrophobic low eutectic solvent again, and a bicarbonate aqueous solution is obtained at the same time; second, heating or introduction of N2, bicarbonate decomposition, and after the removal of CO2, in the formed alkaline carbonate solution, the low eutectic solvent forms hydrophilic carboxylates and phenolates again. After the introduction of CO2, the recovered fatty acids / phenols form a hydrophobic low eutectic solvent again, and a bicarbonate aqueous solution is obtained at the same time, thereby achieving multiple cycles. Based on this regulation method, the low eutectic solvent can be realized and recycled.

[0016] As a preferred embodiment of the present invention, the short-chain fatty acid is one or more of valproic acid (pKa=4.6), 2-ethylhexanoic acid (pKa=4.895), and 3-cyclopentylpropionic acid (pKa=4.81). In this embodiment, valproic acid is further preferred, which has the smallest pKa value and serves as a hydrogen bond donor.

[0017] As a preferred embodiment of the present invention, the phenol derivative is one or more of paeonol (pKa=9.79), 2-methoxyphenol (pKa=9.98), thymol (pKa=10.59), etc. In this embodiment, thymol is further preferred, which has the largest pKa value and serves as a hydrogen bond acceptor.

[0018] As a preferred embodiment of the present invention, the molar ratio of hydrogen bond donor: hydrogen bond acceptor is 1.2:1-1:1.2. In this solution, the hydrogen bond network of the solvent can be optimized, the solubility of various substrates is stronger, and the thermal stability of the solvent is better.

[0019] The embodiment of the present invention also provides an inorganic alkali and CO2 dual circulation oil-solid separation method based on a low eutectic solvent, comprising the following steps:

[0020] S1: The deep eutectic solvent is fully mixed with the oil-containing solid waste, and after stirring and extraction, the solid waste residue is separated by centrifugation;

[0021] S2: adding an inorganic base to the obtained liquid phase, separating the oil phase to obtain a carboxylate / phenolate solution;

[0022] S3: After CO2 is introduced into the carboxylate / phenolate solution, a low eutectic solvent is separated and recycled for cleaning of oily solid waste;

[0023] S4: heating the bicarbonate aqueous solution separated in S3 or introducing N2 to eliminate CO2, thereby forming an alkaline carbonate solution and separating the oil phase; after introducing CO2 into the obtained carboxylate / phenolate solution, the low eutectic solvent is recovered again and recycled.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This scheme is based on the inorganic alkali and CO2 double-circulation oil-solid separation method of low eutectic solvent. It adopts a new type of green solvent low eutectic solvent, which is an amine-free switch solvent system, safe and environmentally friendly, and suitable for industrial promotion and application; inorganic alkali / CO2 is used to form a double cycle to form a circulation cleaning of oil-containing solid waste. First, in "Switch-I", the low eutectic solvent and the oil-containing solid waste are mixed, extracted by stirring, and the solid waste residue is separated by centrifugation. Then, inorganic alkali is added to the obtained liquid phase to separate the oil phase; the obtained carboxylate / phenolate solution is used in "Switch-II", and after CO2 is introduced, a low eutectic solvent is obtained, and it is used to clean the oil-containing solid waste and separate the solid waste residue; heating or N2 is introduced, bicarbonate is decomposed, and after CO2 is eliminated, the oil phase is separated in the formed alkaline carbonate solution; after CO2 is introduced into the obtained carboxylate / phenolate solution, the low eutectic solvent is recovered again and recycled.

[0026] As a preferred embodiment of the present invention, the agent-solid ratio of the deep eutectic solvent to the oil-containing solid waste is 1:2-3:1. The above agent-solid ratio range can ensure that the solvent fully penetrates into the oil-containing solid waste, thereby improving the oil extraction efficiency and processing speed.

[0027] As a preferred embodiment of the present invention, the inorganic base is one or more of Na2CO3, CaCO3, NaOH, and Ca(OH)2. In this embodiment, the inorganic base NaOH is further preferred, as the stronger alkalinity at the same concentration can promote the formation of carboxylate / phenolate solution and improve the "on-off" cycle efficiency.

[0028] As a preferred embodiment of the present invention, in step S3, CO2 is introduced at a rate of 50-60 mL / min until the volume of the upper oil phase remains unchanged. In this scheme, CO2 is introduced at a rate of 50-60 mL / min to achieve rapid recovery of fatty acids / phenols to form a hydrophobic low eutectic solvent again. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic diagram of regulation based on a deep eutectic solvent in Example 1 of the present invention;

[0030] Figure 2 This is a schematic diagram of the double-circulation oil-solid separation of inorganic alkali and CO2 based on a low eutectic solvent in Example 4 of the present invention;

[0031] Figure 3 This is a phase transition experimental diagram of the deep eutectic solvent before and after the introduction of CO2 in Example 1 of the present invention;

[0032] Figure 4 This is a phase transition experimental diagram of the low eutectic solvent before and after the introduction of CO2 in Example 2 of the present invention;

[0033] Figure 5 This is a phase transition experimental diagram of the low eutectic solvent before and after the introduction of CO2 in Example 3 of the present invention. DETAILED DESCRIPTION

[0034] Typical embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments without departing from the scope of the present invention, and the descriptions and illustrations therein are essentially used for illustration purposes rather than for limiting the present invention.

[0035] Example 1

[0036] This embodiment discloses a low eutectic solvent for treating oil-containing solid waste, comprising:

[0037] 2-Ethylhexanoic acid is a hydrogen bond donor;

[0038] 2-Methoxyphenol is a hydrogen bond acceptor;

[0039] According to the molar ratio, the ratio of 2-ethylhexanoic acid to 2-methoxyphenol is 1:1.

[0040] The regulation method based on the deep eutectic solvent is:

[0041] (1) Mix 4.5 ml of a deep eutectic solvent and add an inorganic base NaOH solution to make 9 ml, and react to form a hydrophilic carboxylate and phenolate solution;

[0042] (2) introducing CO2 at 50 ml / min for 2 h in an ice-water bath, and then standing for 10 min, the solution was separated into layers, and fatty acids / phenols were recovered to form a hydrophobic low eutectic solvent again. The upper oil phase was 4.5 ml, and the recovery rate of the low eutectic solvent was 100%. At the same time, a bicarbonate aqueous solution was obtained;

[0043] (3) After heating the bicarbonate aqueous solution or passing N2 to remove CO2, the low eutectic solvent re-forms hydrophilic carboxylates and phenolates in the formed alkaline carbonate solution.

[0044] like Figure 1 Shown is a phase transition experimental diagram of the low eutectic solvent before and after the introduction of CO2 in this embodiment.

[0045] Example 2

[0046] This embodiment discloses a low eutectic solvent for treating oil-containing solid waste, comprising:

[0047] 2-Ethylhexanoic acid is a hydrogen bond donor;

[0048] n-Octanol is a hydrogen bond acceptor;

[0049] According to the molar ratio, the ratio of 2-ethylhexanoic acid to n-octanol is 1:1.

[0050] The regulation method based on the deep eutectic solvent is:

[0051] (1) Mix 5 ml of a deep eutectic solvent and add an inorganic base NaOH solution to form 8.5 ml of the solution to form a hydrophilic carboxylate and phenolate solution;

[0052] (2) After passing CO2 in an ice-water bath at 60 ml / min for 2 h, the solution was allowed to stand for 30 min, and the solution was separated into layers. The fatty acids / phenols were recovered to form a hydrophobic low eutectic solvent again. The upper oil phase was 4.7 ml, and the recovery rate of the low eutectic solvent was 94%. At the same time, a bicarbonate aqueous solution was obtained;

[0053] (3) After heating the bicarbonate aqueous solution or passing N2 to remove CO2, the low eutectic solvent re-forms hydrophilic carboxylates and phenolates in the formed alkaline carbonate solution.

[0054] like Figure 2 Shown is a phase transition experimental diagram of the low eutectic solvent before and after the introduction of CO2 in this embodiment.

[0055] Example 3

[0056] This embodiment discloses a low eutectic solvent for treating oil-containing solid waste, comprising:

[0057] 2-Ethylhexanoic acid is a hydrogen bond donor;

[0058] n-Hexanol is a hydrogen bond acceptor;

[0059] According to the molar ratio, the ratio of 2-ethylhexanoic acid to n-octanol is 1:1.

[0060] The regulation method based on the deep eutectic solvent is:

[0061] (1) 4.5 ml of a deep eutectic solvent was mixed, and 7.5 ml of an inorganic base NaOH solution was added to react to form a hydrophilic carboxylate and phenolate solution;

[0062] (2) After passing CO2 in an ice-water bath at 60 ml / min for 2 h, the solution was allowed to stand for 30 min, and the solution was separated into layers. The fatty acids / phenols were recovered to form a hydrophobic low eutectic solvent again. The upper oil phase was 4.5 ml, and the recovery rate of the low eutectic solvent was 100%. At the same time, a bicarbonate aqueous solution was obtained;

[0063] (3) After heating the bicarbonate aqueous solution or passing N2 to remove CO2, the low eutectic solvent re-forms hydrophilic carboxylates and phenolates in the formed alkaline carbonate solution.

[0064] like Figure 3 Shown is a phase transition experimental diagram of the low eutectic solvent before and after the introduction of CO2 in this embodiment.

[0065] Example 4

[0066] The circulation performance of the low eutectic solvent for oil-containing solid waste treatment of the present invention in the separation of oil-containing solids was investigated using Changcheng Drilling Changning drill cuttings, Shengli Oilfield Xinhaixingda oil sludge, and Xinjiang Oilfield oil sands as the research objects.

[0067] The low eutectic solvent prepared in Example 1 is used in the above oil-containing solid separation test. The inorganic base and CO2 double circulation oil-solid separation method based on the low eutectic solvent includes the following steps:

[0068] S1: The low eutectic solvent and the oil-containing solid waste are fully mixed, the mass ratio of the low eutectic solvent to the oil-containing solid waste is 2:1, and after stirring at 25°C for 20 minutes, a small amount of water is added; then centrifuged at 1000 rpm for 5 minutes to separate the solid residue;

[0069] S2: adding an inorganic base NaOH to the obtained liquid phase, wherein the amount of the inorganic base is an equal molar ratio to the deep eutectic solvent, and separating the oil phase to obtain a carboxylate / phenolate solution;

[0070] S3: introducing CO2 into the carboxylate / phenolate solution at a rate of 10 mL / min until the volume of the upper oil phase remains unchanged, separating and obtaining a low eutectic solvent, and recycling it for cleaning the oil-containing solid waste;

[0071] S4: heating the bicarbonate aqueous solution separated in S3 or introducing N2 to eliminate CO2, thereby forming an alkaline carbonate solution and separating the oil phase; after introducing CO2 into the obtained carboxylate / phenolate solution, the low eutectic solvent is recovered again and recycled.

[0072] The residual oil content on the oil-containing solid surface after cleaning was determined by Soxhlet extraction, and the oil removal rate was obtained by formula (1).

[0073]

[0074] Where R0——initial oil content of oil-containing solids (wt%);

[0075] R1——Residual oil content on the solid surface after cleaning (wt%).

[0076] Table 1 Cleaning of oil-containing solid waste by a low eutectic solvent system constructed with 2-EHA and 2-methoxyphenol in a molar ratio of 1:1

[0077]

[0078] Taking Changning drill cuttings of Great Wall Drilling, Xinhai Xingda oil mud of Shengli Oilfield, and oil sand of Xinjiang Oilfield as the objects, the low eutectic solvent prepared in Example 1 was used for the above-mentioned oil-containing solid separation test. It was found that the removal rate of the surface oil of the solid waste reached more than 90%, and the recovery rate of the low eutectic solvent was more than 90% on average, and the low eutectic solvent can be recycled.

[0079] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A low eutectic solvent for treating oily solid waste, characterized in that: include: Branched or cyclic short-chain fatty acids with a pKa of 4-6 are hydrogen bond donors; Phenol derivatives with a pKa of 9-11 or C6-C8 straight-chain alcohols are hydrogen bond acceptors; According to the molar ratio, the ratio of the hydrogen bond donor to the hydrogen bond acceptor is in the range of 5:1-1:5; The regulation method based on deep eutectic solvent is: (1) using an inorganic base to react with a deep eutectic solvent to form a hydrophilic carboxylate and phenolate solution; (2) After CO2 is introduced, fatty acids / phenols are recovered to form a hydrophobic low eutectic solvent again, and a bicarbonate aqueous solution is obtained at the same time; (3) After heating the bicarbonate aqueous solution or passing N2 to remove CO2, the low eutectic solvent will once again form hydrophilic carboxylates and phenolates in the formed alkaline carbonate solution.

2. The deep eutectic solvent for treating oil-containing solid waste according to claim 1, characterized in that: The short-chain fatty acid is one or more of 2-ethylhexanoic acid, valproic acid, and 3-cyclopentylpropionic acid.

3. The deep eutectic solvent for treating oil-containing solid waste according to claim 2, characterized in that: The phenol derivative is one or more of 2-methoxyphenol, thymol and paeonol.

4. The deep eutectic solvent for treating oil-containing solid waste according to claim 3, characterized in that: The molar ratio of hydrogen bond donor to hydrogen bond acceptor is 1.2:1-1:1.

2.

5. A method for oil-solid separation based on an inorganic alkali and CO2 double circulation of a low eutectic solvent, characterized in that: The following steps are involved: S1: The deep eutectic solvent is fully mixed with the oil-containing solid waste, and after stirring and extraction, the solid waste residue is separated by centrifugation; S2: adding an inorganic base to the obtained liquid phase, wherein the amount of the inorganic base is an equal molar ratio to the deep eutectic solvent, and separating the oil phase to obtain a carboxylate / phenolate solution; S3: After CO2 is introduced into the carboxylate / phenolate solution, a low eutectic solvent is separated and recycled for cleaning of oily solid waste; S4: heating the bicarbonate aqueous solution separated in S3 or introducing N2 to eliminate CO2, thereby forming an alkaline carbonate solution and separating the oil phase; after introducing CO2 into the obtained carboxylate / phenolate solution, the low eutectic solvent is recovered again and recycled.

6. The method for oil-solid separation based on inorganic alkali and CO2 double circulation of a deep eutectic solvent according to claim 5, characterized in that: The agent-solid ratio of the low eutectic solvent to the oil-containing solid waste is 1:2-3:

1.

7. The method for oil-solid separation based on inorganic alkali and CO2 double circulation of a deep eutectic solvent according to claim 5, characterized in that: The inorganic base is one or more of Na2CO3, CaCO3, NaOH, and Ca(OH)2.

8. The method for oil-solid separation based on inorganic alkali and CO2 double circulation with a deep eutectic solvent according to claim 5, characterized in that: In step S3, CO2 is introduced at a rate of 50-60 mL / min until the volume of the upper oil phase remains unchanged.

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