Coking-delayed composite defoaming agent and preparation method thereof

Abstract

The invention discloses a coking-delayed composite defoaming agent and a preparation method thereof, and belongs to the technical field of defoaming agent processing. In order to solve the technical problem that the defoaming performance and the foam inhibition performance of a defoaming agent in the prior art need to be further improved, the coking-delayed composite defoaming agent comprises the following raw materials in parts by mass: 10-15 parts of modified capsules, 30-40 parts of silicone oil, 1-3 parts of an emulsifier and 5-10 parts of a thickening liquid. The modified capsule, the silicone oil, the emulsifier and the thickening liquid are prepared into the composite defoaming agent through an emulsion blending method, so that the defoaming performance and the foam inhibition performance of the defoaming agent are improved, and the high-temperature defoaming performance and the high-temperature foam inhibition performance of the defoaming agent in delayed coking are also improved.

Description

Technical Field

[0001] The present invention relates to the technical field of defoamer processing, and particularly relates to a composite defoamer for delayed coking and a preparation method thereof. Background Art

[0002] Delayed coking is a heavy oil processing process with an operating temperature as high as over 480°C. A large amount of foam often occurs in the coking reactor. If not eliminated in time, it will cause liquid flooding in the coke tower, a decrease in heat exchange efficiency, and even abnormal operation of equipment. To inhibit foam, defoamers containing polysiloxane, mineral oil, silicone paste or hydrophobic particles are widely used in the industry.

[0003] In recent years, composite defoamers have gradually become a research hotspot due to their dual functions of "rapid foam breaking + long-lasting foam inhibition". Such products usually use organosilicon, non-silicon systems in combination with carrier particles or emulsifying matrices. By regulating the interfacial tension, inhibiting the stability of the foam film and prolonging the foam inhibition time, they have been initially applied industrially in high-temperature scenarios such as delayed coking and gas purification. However, there are still some problems with composite defoamers for delayed coking.

[0004] In the prior art, in a high-temperature environment, conventional silicone oil-based or emulsion-based defoaming components are prone to volatilization, decomposition or failure, resulting in a sudden drop in defoaming activity. Secondly, the foam formation mechanism is complex, involving multiple factors such as tar and suspended solids, and it is difficult for ordinary surfactants to accurately break the film or maintain long-term foam inhibition effects. To improve the thermal stability, foam inhibition persistence and dispersion stability of defoamers, nano-particles are often added as reinforcing materials, but nano-materials have poor dispersibility in defoamers and are prone to agglomeration, making it difficult to play the role of enhancing defoaming performance. Summary of the Invention

[0005] The purpose of the present invention is to provide a composite defoamer for delayed coking and a preparation method thereof, which are used to solve the technical problem that the defoaming performance and foam inhibition performance of defoamers in the prior art need to be further improved.

[0006] The purpose of the present invention can be achieved by the following technical solutions: A composite defoamer for delayed coking, comprising the following raw materials by mass parts: 10 - 15 parts of modified capsules, 30 - 40 parts of silicone oil, 1 - 3 parts of emulsifier, and 5 - 10 parts of thickening liquid; The modified capsules are prepared by the following steps: A1. Place the modified polysiloxane and modified silicone paste in a reaction kettle, heat up to 40 - 50°C, and keep stirring for 15 - 20 min to obtain a mixed oil phase; A2. Place chitosan and deionized water in a reaction kettle, add acetic acid solution to adjust the pH to 4 ± 0.5, add the mixed oil phase, carry out ultrasonic emulsification for 1 - 5 min, add sodium tripolyphosphate solution, stir for 5 - 10 min, and perform post-treatment to obtain the modified capsules.

[0007] The reaction principle for the preparation of the modified capsules is as follows: During the reaction process, the modified polysiloxane and the modified silicone paste form a homogeneous mixed oil phase under the condition of 40 - 50 °C. Under the condition of pH = 4 ± 0.5, the amino group in the chitosan molecule is protonated to , add the mixed oil phase to form small water-in-oil droplets. Chitosan is positively charged and is evenly distributed on the surface of the oil droplets. Sodium tripolyphosphate is a multi-anionic cross-linking agent, which can undergo electrostatic complexation with protonated chitosan to form a capsule shell layer, and after curing, the modified capsules are obtained.

[0008] The modified polysiloxane is prepared by the following steps: B1. Place polyethylene glycol, acrylic acid, p-toluenesulfonic acid, and catechol in a reaction kettle protected by a nitrogen atmosphere, heat up to 140 - 160 °C, and keep the temperature for reaction for 2 - 4 h, and perform post-treatment to obtain the modified polyether ester; The reaction formula for the preparation of the modified polyether ester is:

[0009] The reaction principle for the preparation of the modified polyether ester is as follows: During the reaction process, under the action of p-toluenesulfonic acid and high temperature, polyethylene glycol and acrylic acid undergo an esterification reaction to obtain the modified polyether ester, where catechol is a polymerization inhibitor to prevent the self-polymerization of acrylic acid during the reaction.

[0010] B2. Place the modified polyether ester, fluorinated polysiloxane, and platinum dichloride in a reaction kettle, heat up to 140 - 160 °C, and keep the temperature for reaction for 4 - 6 h, and perform post-treatment to obtain the modified polysiloxane.

[0011] The reaction formula for the preparation of the modified polysiloxane is:

[0012] In the formula: ; .

[0013] The reaction principle for the preparation of the modified polysiloxane is as follows: During the reaction process, under the catalysis of platinum dichloride, the olefinic unsaturated double bond in the modified polyether ester and the silicon hydride of the fluorinated polysiloxane undergo an addition reaction to obtain the modified polysiloxane.

[0014] Further, in step A1, the dosage ratio of the modified polysiloxane to the modified silicone paste is 1 - 2 g: 20 - 30 g; in step A2, the dosage ratio of chitosan, deionized water, the mixed oil phase, and the sodium tripolyphosphate solution is 0.5 - 1 g: 1000 - 1500 mL: 35 - 40 mL: 3 - 5 mL. The acetic acid solution consists of an acetic acid aqueous solution with a concentration of 1 - 5 wt%, and the sodium tripolyphosphate solution consists of a sodium tripolyphosphate aqueous solution with a concentration of 30 - 50 wt%. The post-treatment step includes: after the reaction is completed, when the reaction solution cools down to room temperature, perform suction filtration. Wash the filter cake with deionized water 2 - 3 times, transfer it to an oven at a temperature of 60 - 70 °C, and dry it to a constant weight to obtain the modified capsules.

[0015] Further, in step B1, the dosage ratio of polyethylene glycol, acrylic acid, p-toluenesulfonic acid, and catechol is 2 - 4 g: 1 - 3 g: 0.1 - 0.3 g: 0.01 - 0.02 g. The post-treatment step includes: after the reaction is completed, when the reaction solution cools down to room temperature, slowly add sodium bicarbonate to the reaction solution until no more bubbles emerge. Perform suction filtration, and transfer the filtrate to a rotary evaporator at a temperature of 50 - 70 °C and rotate until no liquid is collected to obtain the modified polyether ester; in step B2, the dosage ratio of the modified polyether ester, fluorinated polysiloxane, and cumene hydroperoxide is 2 - 4 g: 2 - 4 g: 0.1 - 0.3 g. The post-treatment step includes: after the reaction is completed, when the reaction solution cools down to room temperature, perform suction filtration, and transfer the filtrate to a rotary evaporator at a temperature of 60 - 70 °C and rotate until no liquid is collected to obtain the fluorinated polysiloxane.

[0016] Further, the preparation method of the fluorinated polysiloxane is as follows: Place toluene, octamethylcyclotetrasiloxane, 2,4,6,8-tetramethylcyclotetrasiloxane, 1,1,3,3-tetramethyldisiloxane, and 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane in a reaction kettle protected by a nitrogen atmosphere. Heat it to 30 - 40 °C, add a catalyst, and keep the reaction at a constant temperature for 20 - 24 h. Then perform post-treatment to obtain the fluorinated polysiloxane.

[0017] The preparation reaction formula of the fluorinated polysiloxane is:

[0018] The preparation reaction principle of the fluorinated polysiloxane is: During the reaction process, octamethylcyclotetrasiloxane, 2,4,6,8-tetramethylcyclotetrasiloxane, and 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane undergo ring-opening polymerization under the action of a catalyst to obtain block polysiloxane. Using 1,1,3,3-tetramethyldisiloxane as the end-capping agent, the fluorinated polysiloxane is obtained.

[0019] Further, the dosage ratio of toluene, octamethylcyclotetrasiloxane, 2,4,6,8 - tetramethylcyclotetrasiloxane, 1,1,3,3 - tetramethyldisiloxane, 1,3,5 - trimethyl - 1,3,5 - tris(3,3,3 - trifluoropropyl)cyclotrisiloxane and the catalyst is 300 - 350 mL:5 - 7 g:30 - 35 g:1 - 2 g:2 - 4 g:0.1 - 0.2 g. The catalyst is trifluoromethanesulfonic acid. The post - treatment steps include: after the reaction is completed, when the reaction solution cools to room temperature, add 0.5 - 1 g of anhydrous sodium bicarbonate and 5 - 10 g of anhydrous sodium sulfate, stir for 3 - 5 min, perform suction filtration, transfer the filtrate to a rotary evaporator at 80 - 90 °C, and rotate until no liquid is collected to obtain fluorinated polysiloxane.

[0020] Further, the modified silica paste is prepared by the following method: C1. Place silica white and n - octanol in a reaction kettle, heat up to 25 - 35 °C, keep warm and stir for 25 - 35 min, then heat up to 100 - 110 °C, keep warm and react for 2 - 3 h, and perform post - treatment to obtain modified silica white. The reaction principle for the preparation of modified silica white is: During the reaction process, under high - temperature conditions, the silanol groups on the surface of silica white and n - octanol undergo a condensation reaction to form silicon ether bonds, thus obtaining modified silica white.

[0021] C2. Place the modified silica white and dimethyl silicone oil in a reaction kettle, heat up to 160 - 190 °C, keep warm and react for 0.5 - 1 h, and perform post - treatment to obtain modified silica paste.

[0022] The reaction principle for the preparation of modified silica paste is: During the reaction process, the viscosity of dimethyl silicone oil decreases at 160 - 190 °C high temperature, and a close - coated adsorption layer is formed on the surface of silica white, forming a gel - like modified silica paste similar to "oil - in - solid".

[0023] Further, in step C1, the dosage ratio of silica white and n - octanol is 1 - 2 g:25 - 35 g. The post - treatment steps include: after the reaction is completed, when the reaction cools to room temperature, perform suction filtration, wash the filter cake with deionized water 2 - 3 times, transfer it to an oven at 50 - 60 °C, and dry to constant weight to obtain modified silica white. In step C2, the dosage ratio of modified silica white and dimethyl silicone oil is 1 - 2 g:10 - 15 g. The post - treatment steps include: after the reaction is completed, let it stand for 0.5 - 1 h, remove the upper liquid, and seal to obtain modified silica paste.

[0024] The present invention also provides a preparation method for a composite defoamer for delayed coking, which includes the following steps: S1. Place the thickening liquid in a reaction kettle, heat up to 65 - 75 °C, keep warm and stir for 10 - 15 min to obtain a mixed aqueous phase; S2. Place silicone oil, modified capsules and emulsifier in a reaction kettle, heat up to 40 - 50 °C, keep warm and stir for 15 - 20 min, slowly add the mixed aqueous phase, and let it stand for 10 - 12 h to obtain a composite defoamer.

[0025] Furthermore, in step S1, the thickening liquid is composed of sodium carboxymethyl cellulose and deionized water in a mass ratio of 1:10; in step S2, the emulsifier is composed of Tween - 60 and Span - 60 in a mass ratio of 1:1.

[0026] The present invention has the following beneficial effects: 1. The present invention prepares fluorinated polysiloxane through telomerization, further obtains modified polysiloxane by hydrosilylation of fluorinated polysiloxane and modified polyether ester, modifies fumed silica with long - chain alkyl groups, and prepares modified silicone paste with dimethyl silicone oil. The modified polysiloxane and modified silicone paste are encapsulated with chitosan and sodium tripolyphosphate to obtain modified capsules, and the silicone oil, modified capsules, emulsifier and thickening liquid are prepared into a composite defoamer by emulsion blending method. The present invention prepares fluorinated polysiloxane with fluorosilane segments through telomerization reaction. During the defoaming process, the fluorosilane segments are extremely easy to migrate to the foam interface, and its surface tension is extremely low, which can quickly destroy the stability of the foam film. At the same time, the modified polyether ester segments can improve the dispersibility and wettability of the composite defoamer in water and oil systems, enabling it to accelerate the spread to the foam film surface, significantly shortening the natural rupture time of the foam, and improving the defoaming rate of the composite defoamer. The fluorosilane segments in the modified polysiloxane contain carbon - fluorine bonds with relatively high bond energy, which can improve the high - temperature resistance of the composite defoamer, making its structure not easily pyrolyzed, oxidized or broken during the coking process, ensuring long - term defoaming activity. At the same time, the grafted polyether ester segments in the modified polysiloxane form a spatial three - dimensional obstacle structure, forming a protective layer at the interface to inhibit the formation of new bubbles. When used in combination with the modified silicone paste, it has a good synergistic and stable release effect.

[0027] 2. The present invention modifies fumed silica with n - octanol with a long chain segment, and further blends it with dimethyl silicone oil to obtain modified silicone paste. The surface of fumed silica is rich in silanol groups, which causes it to be prone to moisture absorption, agglomeration and difficult to disperse in the oil phase in the defoamer. After modification with n - octanol, the silanol on the surface of fumed silica decreases, improving the dispersibility of the modified silicone paste in the defoamer, enabling it to quickly enter the foam film layer, destroy the stable structure of the liquid film, improve the defoaming performance and foam - suppressing performance of the composite defoamer, and the fumed silica skeleton has good thermal stability, and dimethyl silicone oil has strong heat resistance, making the composite defoamer still maintain activity during the delayed coking stage.

[0028] 3. The present invention utilizes chitosan and sodium tripolyphosphate to crosslink and form a shell layer, encapsulating modified polysiloxane and modified silicone paste to obtain modified capsules. The modified silicone paste itself has excellent interfacial activity and permeability. After being encapsulated by the capsules formed by the crosslinking of chitosan - sodium tripolyphosphate, it can be rapidly ruptured and instantaneously released under the contact of the foam interface, achieving highly efficient defoaming in the "burst release - membrane rupture" mode. Dimethyl silicone oil and hydrophobic fumed silica have high thermal stability, and the capsule structure of the modified capsules further delays their high - temperature inactivation, thereby enhancing the effective time of the composite defoamer under the high - temperature conditions of delayed coking. In addition, the intact capsules can continuously release slowly, and the released silicone paste and modified polysiloxane can form an interfacial barrier and cooperate with fumed silica to construct a physical foam - inhibiting layer to achieve long - term foam inhibition. Detailed implementation manners

[0029] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0030] Tween - 60 used in the present invention is purchased from Hai'an Petrochemical Factory in Jiangsu Province. The product name is polyoxyethylene sorbitan monostearate, and the model is emulsifier Tween series T - 60. Span - 60 used in the present invention is purchased from Hai'an Petrochemical Factory in Jiangsu Province. The product name is sorbitan monostearate, and the model is S - 60. Fumed silica used in the present invention is purchased from LingShou KaiQi Mineral Products Processing Factory, with the brand of KaiQi and a content of 98%. Dimethyl silicone oil used in the present invention is purchased from Shandong ChuangLi New Materials Co., Ltd. The product name is dimethyl silicone oil, with the brand of ChuangLi and the product grade of premium product. Polyethylene glycol used in the present invention is purchased from Shanghai Kaisheng New Materials Co., Ltd., with a molecular weight of 600, the brand of Saudi Sabic, and the product name of polyethylene glycol 600. Silicone oil used in the present invention is purchased from Shandong Qimin Chemical Technology Co., Ltd. The product name is methyl silicone oil, with a molecular weight of 300 - 1000.

[0031] Example 1 This example provides a preparation method of modified polysiloxane used for modified capsules of a composite defoamer for delayed coking, including the following steps: Step Ⅰ. Prepare fluorinated polysiloxane Weigh: 3000 mL of toluene, 50 g of octamethylcyclotetrasiloxane, 300 g of 2,4,6,8 - tetramethylcyclotetrasiloxane, 10 g of 1,1,3,3 - tetramethyldisiloxane and 20 g of 1,3,5 - trimethyl - 1,3,5 - tris(3,3,3 - trifluoropropyl)cyclotrisiloxane and place them in a reaction kettle protected by a nitrogen atmosphere. Heat up to 30 °C, add 1 g of trifluoromethanesulfonic acid, and keep the temperature for reaction for 20 h. After the reaction is completed, wait for the reaction solution to cool to room temperature, add 5 g of anhydrous sodium bicarbonate and 50 g of anhydrous sodium sulfate, stir for 3 min, filter by suction, transfer the filtrate to a rotary evaporator at 80 °C, and rotate until no liquid is collected to obtain fluorinated polysiloxane.

[0032] Step II: Prepare modified polyether ester Weigh: 20 g of polyethylene glycol, 10 g of acrylic acid, 1 g of p - toluenesulfonic acid and 0.1 g of catechol and place them in a reaction kettle protected by a nitrogen atmosphere. Heat up to 140 °C, keep the temperature for reaction for 2 h. After the reaction is completed, wait for the reaction solution to cool to room temperature, slowly add sodium bicarbonate to the reaction solution until no bubbles emerge, filter by suction, transfer the filtrate to a rotary evaporator at 50 °C, and rotate until no liquid is collected to obtain modified polyether ester.

[0033] Step III: Prepare modified polysiloxane Weigh: 20 g of modified polyether ester, 20 g of fluorinated polysiloxane and 1 g of platinum dichloride and place them in a reaction kettle. Heat up to 140 °C, keep the temperature for reaction for 4 h. After the reaction is completed, wait for the reaction solution to cool to room temperature, filter by suction, transfer the filtrate to a rotary evaporator at 60 °C, and rotate until no liquid is collected to obtain modified polysiloxane.

[0034] Example 2 This example provides a preparation method of modified polysiloxane used in modified capsules for a delayed coking composite defoamer, including the following steps: Step I: Prepare fluorinated polysiloxane Weigh: 3250 mL of toluene, 60 g of octamethylcyclotetrasiloxane, 325 g of 2,4,6,8 - tetramethylcyclotetrasiloxane, 15 g of 1,1,3,3 - tetramethyldisiloxane and 30 g of 1,3,5 - trimethyl - 1,3,5 - tris(3,3,3 - trifluoropropyl)cyclotrisiloxane and place them in a reaction kettle protected by a nitrogen atmosphere. Heat up to 35 °C, add 1.5 g of trifluoromethanesulfonic acid, and keep the temperature for reaction for 22 h. After the reaction is completed, wait for the reaction solution to cool to room temperature, add 7 g of anhydrous sodium bicarbonate and 70 g of anhydrous sodium sulfate, stir for 4 min, filter by suction, transfer the filtrate to a rotary evaporator at 85 °C, and rotate until no liquid is collected to obtain fluorinated polysiloxane.

[0035] Step II: Prepare modified polyether ester Weigh: 30 g of polyethylene glycol, 15 g of acrylic acid, 2 g of p-toluenesulfonic acid and 0.15 g of catechol and place them in a reaction kettle protected by a nitrogen atmosphere. Heat up to 150 °C and keep the reaction for 3 h. After the reaction is completed, wait for the reaction solution to cool to room temperature. Slowly add sodium bicarbonate to the reaction solution until no more bubbles emerge. Filter by suction. Transfer the filtrate to a rotary evaporator at 60 °C and rotate until no liquid is collected to obtain the modified polyether ester.

[0036] Step III: Prepare the modified polysiloxane Weigh: 30 g of the modified polyether ester, 30 g of the fluorinated polysiloxane and 1.5 g of platinum dichloride and place them in a reaction kettle. Heat up to 150 °C and keep the reaction for 5 h. After the reaction is completed, wait for the reaction solution to cool to room temperature. Filter by suction. Transfer the filtrate to a rotary evaporator at 65 °C and rotate until no liquid is collected to obtain the modified polysiloxane.

[0037] Example 3 This example provides a preparation method of a modified polysiloxane used for a modified capsule of a compound defoamer for delayed coking, including the following steps: Step I: Prepare the fluorinated polysiloxane Weigh: 3500 mL of toluene, 70 g of octamethylcyclotetrasiloxane, 350 g of 2,4,6,8-tetramethylcyclotetrasiloxane, 20 g of 1,1,3,3-tetramethyldisiloxane and 40 g of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane and place them in a reaction kettle protected by a nitrogen atmosphere. Heat up to 40 °C, add 2 g of trifluoromethanesulfonic acid, and keep the reaction for 24 h. After the reaction is completed, wait for the reaction solution to cool to room temperature. Add 10 g of anhydrous sodium bicarbonate and 100 g of anhydrous sodium sulfate and stir for 5 min. Filter by suction. Transfer the filtrate to a rotary evaporator at 90 °C and rotate until no liquid is collected to obtain the fluorinated polysiloxane.

[0038] Step II: Prepare the modified polyether ester Weigh: 40 g of polyethylene glycol, 30 g of acrylic acid, 3 g of p-toluenesulfonic acid and 0.2 g of catechol and place them in a reaction kettle protected by a nitrogen atmosphere. Heat up to 160 °C and keep the reaction for 4 h. After the reaction is completed, wait for the reaction solution to cool to room temperature. Slowly add sodium bicarbonate to the reaction solution until no more bubbles emerge. Filter by suction. Transfer the filtrate to a rotary evaporator at 70 °C and rotate until no liquid is collected to obtain the modified polyether ester.

[0039] Step III: Prepare the modified polysiloxane Weigh: 40 g of the modified polyether ester, 40 g of the fluorinated polysiloxane and 3 g of platinum dichloride and place them in a reaction kettle. Heat up to 160 °C and keep the reaction for 6 h. After the reaction is completed, wait for the reaction solution to cool to room temperature. Filter by suction. Transfer the filtrate to a rotary evaporator at 70 °C and rotate until no liquid is collected to obtain the modified polysiloxane.

[0040] Example 4 This example provides a preparation method of modified silicone paste used for modified capsules of a composite defoamer for delayed coking, including the following steps: Step (1), preparing modified silica Weigh: 10 g of silica and 250 g of n-octanol and place them in a reaction kettle. Heat up to 25°C, keep warm and stir for 25 min, then heat up to 100°C and keep warm for reaction for 2 h. After the reaction is completed, wait for the reaction to cool down to room temperature, carry out suction filtration, wash the filter cake with deionized water twice, transfer it to an oven at 50°C, and dry it to constant weight to obtain modified silica.

[0041] Step (2), preparing modified silicone paste Weigh: 10 g of modified silica and 100 g of dimethyl silicone oil and place them in a reaction kettle. Heat up to 160°C and keep warm for reaction for 0.5 h. After the reaction is completed, let it stand for 0.5 h, remove the upper liquid, and seal it to obtain modified silicone paste.

[0042] Example 5 This example provides a preparation method of modified silicone paste used for modified capsules of a composite defoamer for delayed coking, including the following steps: Step (1), preparing modified silica Weigh: 15 g of silica and 300 g of n-octanol and place them in a reaction kettle. Heat up to 30°C, keep warm and stir for 30 min, then heat up to 105°C and keep warm for reaction for 2.5 h. After the reaction is completed, wait for the reaction to cool down to room temperature, carry out suction filtration, wash the filter cake with deionized water twice, transfer it to an oven at 55°C, and dry it to constant weight to obtain modified silica.

[0043] Step (2), preparing modified silicone paste Weigh: 15 g of modified silica and 125 g of dimethyl silicone oil and place them in a reaction kettle. Heat up to 170°C and keep warm for reaction for 1 h. After the reaction is completed, let it stand for 1 h, remove the upper liquid, and seal it to obtain modified silicone paste.

[0044] Example 6 This example provides a preparation method of modified silicone paste used for modified capsules of a composite defoamer for delayed coking, including the following steps: Step (1), preparing modified silica Weigh: 20 g of silica and 350 g of n-octanol and place them in a reaction kettle. Heat up to 35°C, keep warm and stir for 35 min, then heat up to 110°C and keep warm for reaction for 3 h. After the reaction is completed, wait for the reaction to cool down to room temperature, carry out suction filtration, wash the filter cake with deionized water three times, transfer it to an oven at 60°C, and dry it to constant weight to obtain modified silica.

[0045] Step (2), preparing modified silicone paste Weigh: 20 g of modified silica white and 150 g of dimethyl silicone oil, place them in a reaction kettle, heat up to 190 °C, keep the temperature for reaction for 1 h. After the reaction is completed, let it stand for 1 h, remove the upper liquid, seal it, and obtain modified silicone paste.

[0046] Example 7 This example provides a preparation method of modified capsules for a compound defoamer in delayed coking, including the following steps: Step ①, prepare a mixed oil phase Weigh: 10 g of the modified polysiloxane prepared in Example 1 and 200 g of the modified silicone paste prepared in Example 4, place them in a reaction kettle, heat up to 40 °C, keep the temperature and stir for 15 min to obtain a mixed oil phase.

[0047] Step ②, prepare modified capsules Weigh: 5 g of chitosan and 10000 mL of deionized water, place them in a reaction kettle, add 1 wt% acetic acid aqueous solution to adjust the pH to 3.9, add 350 mL of the mixed oil phase, carry out ultrasonic emulsification for 1 min, add 3 mL of 30 wt% sodium tripolyphosphate aqueous solution, stir for 5 min. After the reaction is completed, wait for the reaction solution to cool to room temperature, carry out suction filtration, wash the filter cake with deionized water twice, transfer it to an oven at 60 °C, and dry it to constant weight to obtain modified capsules.

[0048] Example 8 This example provides a preparation method of modified capsules for a compound defoamer in delayed coking, including the following steps: Step ①, prepare a mixed oil phase Weigh: 15 g of the modified polysiloxane prepared in Example 2 and 250 g of the modified silicone paste prepared in Example 5, place them in a reaction kettle, heat up to 45 °C, keep the temperature and stir for 17 min to obtain a mixed oil phase.

[0049] Step ②, prepare modified capsules Weigh: 7 g of chitosan and 12500 mL of deionized water, place them in a reaction kettle, add 3 wt% acetic acid aqueous solution to adjust the pH to 4.2, add 370 mL of the mixed oil phase, carry out ultrasonic emulsification for 3 min, add 40 mL of 40 wt% sodium tripolyphosphate aqueous solution, stir for 7 min. After the reaction is completed, wait for the reaction solution to cool to room temperature, carry out suction filtration, wash the filter cake with deionized water twice, transfer it to an oven at 65 °C, and dry it to constant weight to obtain modified capsules.

[0050] Example 9 This example provides a preparation method of modified capsules for a compound defoamer in delayed coking, including the following steps: Step ①, prepare a mixed oil phase Weigh: 20 g of the modified polysiloxane prepared in Example 3 and 300 g of the modified silicone paste prepared in Example 6, place them in a reaction kettle, heat up to 50 °C, keep warm and stir for 20 min to obtain a mixed oil phase.

[0051] Step ②, prepare the modified capsules Weigh: 10 g of chitosan and 15000 mL of deionized water, place them in a reaction kettle, add a 5 wt% acetic acid aqueous solution to adjust the pH to 4.5, add 400 mL of the mixed oil phase, carry out ultrasonic emulsification for 5 min, add 50 mL of a 50 wt% sodium tripolyphosphate aqueous solution, stir for 10 min. After the reaction is completed, wait for the reaction solution to cool to room temperature, carry out suction filtration, wash the filter cake with deionized water 3 times, transfer it to an oven at 70 °C, and dry it to constant weight to obtain the modified capsules.

[0052] Example 10 This example provides a preparation method of a compound defoamer for delayed coking, including the following steps: Step 1, prepare the mixed aqueous phase Mix sodium carboxymethyl cellulose and deionized water evenly according to a mass ratio of 1:10 to obtain a thickening solution for standby; Weigh by mass parts: 5 parts of the thickening solution, place it in a reaction kettle, heat up to 65 °C, keep warm and stir for 10 min to obtain the mixed aqueous phase.

[0053] Step 2, prepare the compound defoamer Mix Tween-60 and Span-60 evenly according to a mass ratio of 1:1 to obtain an emulsifier for standby; Weigh by mass parts: 10 parts of the modified capsules prepared in Example 7, 30 parts of silicone oil and 1 part of the emulsifier, place them in a reaction kettle, heat up to 40 °C, keep warm and stir for 15 min, slowly add the mixed aqueous phase, and let it stand for 10 h to obtain the compound defoamer.

[0054] Example 11 This example provides a preparation method of a compound defoamer for delayed coking, including the following steps: Step 1, prepare the mixed aqueous phase Mix sodium carboxymethyl cellulose and deionized water evenly according to a mass ratio of 1:10 to obtain a thickening solution for standby; Weigh by mass parts: 7 parts of the thickening solution, place it in a reaction kettle, heat up to 70 °C, keep warm and stir for 13 min to obtain the mixed aqueous phase.

[0055] Step 2, prepare the compound defoamer Mix Tween-60 and Span-60 evenly according to a mass ratio of 1:1 to obtain an emulsifier for standby; Weigh by mass parts: 13 parts of the modified capsules prepared in Example 8, 35 parts of silicone oil, and 2 parts of emulsifier, put them into a reaction kettle, heat up to 45 °C, keep warm and stir for 17 min, slowly add the mixed aqueous phase, and let it stand for 11 h to obtain a composite defoamer.

[0056] Example 12 This example provides a preparation method of a composite defoamer for delayed coking, which includes the following steps: Step 1: Prepare the mixed aqueous phase Mix sodium carboxymethylcellulose and deionized water evenly according to a mass ratio of 1:10 to obtain a thickening liquid for standby; Weigh by mass parts: 10 parts of the thickening liquid, put it into a reaction kettle, heat up to 75 °C, keep warm and stir for 15 min to obtain the mixed aqueous phase.

[0057] Step 2: Prepare the composite defoamer Mix Tween-60 and Span-60 evenly according to a mass ratio of 1:1 to obtain an emulsifier for standby; Weigh by mass parts: 15 parts of the modified capsules prepared in Example 8, 40 parts of silicone oil, and 3 parts of emulsifier, put them into a reaction kettle, heat up to 50 °C, keep warm and stir for 20 min, slowly add the mixed aqueous phase, and let it stand for 12 h to obtain the composite defoamer.

[0058] Comparative Example 1 The difference between this comparative example and Example 12 is that when preparing the mixed oil phase in step ①, 1,1,3,3-tetramethyldisiloxane is used to replace the modified polysiloxane in equal amount.

[0059] Comparative Example 2 The difference between this comparative example and Example 12 is that when preparing the mixed oil phase in step ①, adding the modified silicone paste is cancelled.

[0060] Comparative Example 3 The difference between this comparative example and Example 12 is that when preparing the mixed aqueous phase in step one, adding the modified capsules is cancelled.

[0061] Performance test: Refer to the standard HG / T 4028-2008 "High-temperature silicone defoamer" to measure the defoaming power of the composite defoamers prepared in Examples 10 - 12 and Comparative Examples 1 - 3; Refer to the standard GB / T 26527-2024 "Silicone defoamer" to measure the foam suppression performance of the composite defoamers prepared in Examples 10 - 12 and Comparative Examples 1 - 3. The specific data is the total volume of the foam and the liquid at 30 min of the air drum; Paraffin oil, oleic acid, and coking residue were placed in a reaction kettle at a mass ratio of 60:3:10, and the temperature was raised to 250 - 300 °C. Nitrogen was introduced through a glass bulb tube inserted at the bottom to simulate the high-temperature environment of delayed coking. Referring to the standards HG / T 4028 - 2008 "High-temperature silicone defoamer" and GB / T 26527 - 2024 "Silicone defoamer", the high-temperature defoaming power and high-temperature foam suppression performance of the composite defoamers prepared in Examples 10 - 12 and Comparative Examples 1 - 3 were measured. The specific data are shown in Table 1.

[0062] Table 1 - Performance test data table of each sample

[0063] Data analysis: Comparative analysis of the data in Table 1 shows that the defoaming power of the composite defoamer prepared in the present invention is 29 s, the foam suppression performance is 98 mL, the high-temperature defoaming power is 37 s, and the high-temperature foam suppression performance is 115 mL. All the data are better than those of the comparative examples; Comparative analysis of the data of Comparative Example 1 and Example 12 shows that the defoaming power, foam suppression performance, high-temperature defoaming power, and high-temperature foam suppression performance of Comparative Example 1 decreased significantly. It shows that the present invention prepares fluorinated polysiloxane with fluorosilane segments through telomerization reaction. During the defoaming process, the fluorosilane segments are extremely easy to migrate to the foam interface, and its surface tension is extremely low, which can quickly destroy the stability of the foam film. At the same time, the modified polyether ester segments can improve the dispersibility and wettability of the composite defoamer in water and oil systems, enabling it to accelerate the spread to the foam film surface, significantly shortening the natural rupture time of the foam, and improving the defoaming rate of the composite defoamer. The fluorosilane segments in the modified polysiloxane contain carbon-fluorine bonds with relatively high bond energy, which can improve the high-temperature resistance of the composite defoamer, making its structure not easily pyrolyzed, oxidized, or broken during the coking process, ensuring long-term defoaming activity. At the same time, the grafted polyether ester segments in the modified polysiloxane form a three-dimensional steric hindrance structure, forming a protective layer at the interface to inhibit the formation of new bubbles. When used in combination with the modified silicone paste, it has a good synergistic and stable release effect; Comparative analysis of the data of Comparative Example 2 and Example 12 shows that the defoaming power, foam suppression performance, high-temperature defoaming power, and high-temperature foam suppression performance of Comparative Example 2 decreased significantly. It shows that the present invention modifies fumed silica with long-chain n-octanol and further compounds it with dimethyl silicone oil to obtain a modified silicone paste. The surface of fumed silica is rich in silanol groups, resulting in its easy moisture absorption, agglomeration, and difficult dispersion in the oil phase in the defoamer. After being modified with n-octanol, the silanol on the surface of fumed silica decreases, improving the dispersibility of the modified silicone paste in the defoamer, enabling it to quickly enter the foam film layer, destroy the stable structure of the liquid film, and improve the defoaming performance and foam suppression performance of the composite defoamer. Moreover, the fumed silica skeleton has good thermal stability, and dimethyl silicone oil has strong heat resistance, making the composite defoamer still maintain its activity during the delayed coking stage; By comparing and analyzing the data of Comparative Example 3 and Example 12, it can be found that the defoaming power, foam suppression performance, high-temperature defoaming power, and high-temperature foam suppression performance of Comparative Example 3 have decreased significantly. This shows that in the present invention, by using chitosan and sodium tripolyphosphate to crosslink and form a shell layer, encapsulating the modified polysiloxane and modified silicone paste to obtain modified capsules, the modified silicone paste itself has excellent interfacial activity and permeability. After being wrapped by the capsules formed by the crosslinking of chitosan-sodium tripolyphosphate, it can be rapidly ruptured and instantaneously released under the contact of the foam interface, achieving efficient defoaming in the form of "burst release - membrane rupture". Dimethyl silicone oil and hydrophobic silica have high thermal stability, and the capsule structure of the modified capsules further delays their high-temperature inactivation, thereby enhancing the sustained effect time of the composite defoamer under the high-temperature conditions of delayed coking. In addition, the unbroken capsules can be continuously slowly released, and the released silicone paste and modified polysiloxane can form an interfacial barrier and cooperate with silica to construct a physical foam suppression layer to achieve long-term foam suppression.

[0064] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can understand and utilize the present invention well. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A composite defoamer for delayed coking, characterized in that, It includes the following raw materials by mass parts: 10 - 15 parts of modified capsules, 30 - 40 parts of silicone oil, 1 - 3 parts of emulsifier, and 5 - 10 parts of thickening liquid; The modified capsules are prepared by the following steps: A1. Put the modified polysiloxane and modified silica paste into a reaction kettle, heat up to 40 - 50 °C, keep warm and stir for 15 - 20 min to obtain a mixed oil phase; A2. Put chitosan and deionized water into a reaction kettle, add acetic acid solution to adjust the pH = 4 ± 0.5, add the mixed oil phase, carry out ultrasonic emulsification for 1 - 5 min, add sodium tripolyphosphate solution, stir for 5 - 10 min, and perform post - treatment to obtain modified capsules; The modified polysiloxane is prepared by the following steps: B1. Put polyethylene glycol, acrylic acid, p - toluenesulfonic acid, and catechol into a reaction kettle protected by a nitrogen atmosphere, heat up to 140 - 160 °C, keep warm and react for 2 - 4 h, and perform post - treatment to obtain modified polyether ester; B2. Put the modified polyether ester, fluorinated polysiloxane, and platinum dichloride into a reaction kettle, heat up to 140 - 160 °C, keep warm and react for 4 - 6 h, and perform post - treatment to obtain modified polysiloxane.

2. The composite defoamer for delayed coking according to claim 1, characterized in that, In step A1, the dosage ratio of the modified polysiloxane to the modified silica paste is 1 - 2 g:20 - 30 g; in step A2, the dosage ratio of chitosan, deionized water, the mixed oil phase, and the sodium tripolyphosphate solution is 0.5 - 1 g:1000 - 1500 mL:35 - 40 mL:3 - 5 mL, the acetic acid solution consists of 1 - 5 wt% acetic acid aqueous solution, and the sodium tripolyphosphate solution consists of 30 - 50 wt% sodium tripolyphosphate aqueous solution.

3. The composite defoamer for delayed coking according to claim 1, wherein In step B1, the dosage ratio of polyethylene glycol, acrylic acid, p - toluenesulfonic acid, and catechol is 2 - 4 g:1 - 3 g:0.1 - 0.3 g:0.01 - 0.02 g; in step B2, the dosage ratio of the modified polyether ester, fluorinated polysiloxane, and cumyl hydroperoxide is 2 - 4 g:2 - 4 g:0.1 - 0.3 g.

4. A composite defoamer for delayed coking according to claim 1, characterized in that, The preparation method of the fluorinated polysiloxane is: Put toluene, octamethylcyclotetrasiloxane, 2,4,6,8 - tetramethylcyclotetrasiloxane, 1,1,3,3 - tetramethyldisiloxane, and 1,3,5 - trimethyl - 1,3,5 - tris(3,3,3 - trifluoropropyl)cyclotrisiloxane into a reaction kettle protected by a nitrogen atmosphere, heat up to 30 - 40 °C, add a catalyst, keep warm and react for 20 - 24 h, and perform post - treatment to obtain fluorinated polysiloxane.

5. A composite defoamer for delayed coking according to claim 4, characterized in that, The dosage ratio of toluene, octamethylcyclotetrasiloxane, 2,4,6,8 - tetramethylcyclotetrasiloxane, 1,1,3,3 - tetramethyldisiloxane, 1,3,5 - trimethyl - 1,3,5 - tris(3,3,3 - trifluoropropyl)cyclotrisiloxane, and the catalyst is 300 - 350 mL:5 - 7 g:30 - 35 g:1 - 2 g:2 - 4 g:0.1 - 0.2 g, and the catalyst is trifluoromethanesulfonic acid.

6. The composite defoamer for delayed coking according to claim 1, characterized in that, The modified silica paste is prepared by the following method: C1. Put fumed silica and n - octanol into a reaction kettle, heat up to 25 - 35 °C, keep warm and stir for 25 - 35 min, then heat up to 100 - 110 °C, keep warm and react for 2 - 3 h, and perform post - treatment to obtain modified fumed silica; C2. Place the modified silica white and dimethyl silicone oil in a reaction kettle, heat up to 160 - 190 °C, keep the temperature for reaction for 0.5 - 1 h, and obtain the modified silicone paste after post-treatment.

7. A composite defoamer for delayed coking according to claim 6, characterized in that, In step C1, the dosage ratio of the silica white and n-octanol is 1 - 2 g: 25 - 35 g; in step C2, the dosage ratio of the modified silica white and dimethyl silicone oil is 1 - 2 g: 10 - 15 g.

8. A preparation method of a composite defoamer for delayed coking according to any one of claims 1-7, characterized in that, It includes the following steps: S1. Place the thickening liquid in a reaction kettle, heat up to 65 - 75 °C, keep the temperature and stir for 10 - 15 min to obtain a mixed aqueous phase; S2. Place the silicone oil, modified capsules and emulsifier in a reaction kettle, heat up to 40 - 50 °C, keep the temperature and stir for 15 - 20 min, slowly add the mixed aqueous phase, and let it stand for 10 - 12 h to obtain a composite defoamer.

9. The preparation method of a composite defoamer for delayed coking according to claim 8, characterized in that, In step S1, the thickening liquid is composed of sodium carboxymethyl cellulose and deionized water in a mass ratio of 1:10; in step S2, the emulsifier is composed of Tween-60 and Span-60 in a mass ratio of 1:1.

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