A method for preparing energy-saving composite desulfurizer

Abstract

The present invention belongs to the technical field of desulfurization, and specifically relates to a method for preparing an energy-saving composite desulfurizer. The present invention uses N-methyldiethanolamine as a main desulfurizer, oxazolidine compounds as a synergistic desulfurizer, 5-amino-2-benzimidazolinone and 1-(2-aminoethyl)-2-imidazolinone as desulfurization aids, and compounding corrosion inhibitors, antioxidants and other additives, so that the composite desulfurizer prepared in this way has stable performance, synergistic effects between the components, high selectivity for sulfides, increased sulfur capacity and organic sulfur removal ability, reduced energy consumption, and good corrosion inhibition.

Description

Technical Field

[0001] The invention belongs to the technical field of desulfurization, and in particular relates to a method for preparing an energy-saving composite desulfurizer. Background Art

[0002] The sulfides contained in crude oil will be transferred to the produced natural gas after the catalytic cracking processing unit. The combustion of sulfides such as hydrogen sulfide, mercaptan and sulfide will cause great harm to the environment. Therefore, the processing and use of raw materials such as crude oil and its distillates, natural gas, and refinery gas require desulfurization.

[0003] The industrial gas desulfurization process mainly adopts the wet desulfurization process. Wet desulfurization refers to the use of physical absorbent, chemical absorbent, chemical / physical absorbent or oxidizing absorbent as liquid absorbent, through gas-liquid contact, to transfer acidic gas to liquid phase and purify gas. At present, factories mainly use alcoholamine wet desulfurization. The alcoholamine desulfurizers currently used are mainly monoethanolamine (MEA), diethanolamine (DEA), N-methyldiethanolamine (MDEA) and other alcoholamine substances as desulfurizers. This desulfurizer has a fast desulfurization speed and high efficiency.

[0004] A Chinese patent application document with publication number CN101322900A discloses a composite desulfurization solvent, which contains 93.5wt%-96wt% of N-methyldiethanolamine, and the rest are added with defoaming agent, corrosion inhibitor, antioxidant and enhancer; the composite desulfurization solvent solves the problem that single use of N-methyldiethanolamine has poor selectivity for hydrogen sulfide removal, and removes a large amount of carbon dioxide while removing hydrogen sulfide; however, the composite desulfurization solvent only removes hydrogen sulfide, and does not remove organic sulfur or the removal rate is low, which will cause the subsequent device to increase the processing volume and increase the production energy consumption. Summary of the invention

[0005] The existing desulfurizer has the problem of low organic sulfur removal rate. In order to solve this problem, the present invention provides a method for preparing an energy-saving composite desulfurizer.

[0006] In order to achieve the purpose of the present invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing an energy-saving composite desulfurizer, comprising the following steps:

[0008] (1) 2-(n-pentylamino)ethanol and a solvent are uniformly mixed, 2-ethoxypyridine-3-carboxaldehyde is slowly added dropwise, and p-toluenesulfonic acid is finally added. The temperature is raised to react, water is removed, and the mixture is cooled to room temperature. The fractions are collected by vacuum distillation to obtain an oxazolidine compound.

[0009] (2) Mix the dispersant and water evenly to obtain a mixed solution A;

[0010] (3) Evenly mixing N-methyldiethanolamine, oxazolidine compounds, desulfurization aids and the mixed solution to obtain a mixed solution B;

[0011] (4) The corrosion inhibitor, antioxidant and mixed solution B are mixed evenly, and then the defoaming agent is added and mixed evenly to obtain an energy-saving composite desulfurizer.

[0012] Preferably, the amounts of N-methyldiethanolamine, oxazolidine compound, desulfurization aid, defoamer, corrosion inhibitor, antioxidant, dispersant and water are calculated by weight and are composed of:

[0013] 60-75 parts of N-methyldiethanolamine, 15-22 parts of oxazolidine compounds, 5-8 parts of desulfurization aids, 0.5-1.5 parts of defoaming agents, 0.02-0.05 parts of corrosion inhibitors, 0.5-2 parts of antioxidants, 4-8 parts of dispersants, and 2-5 parts of water.

[0014] Preferably, in step (3), the desulfurization aid is composed of 5-amino-2-benzimidazolidinone and 1-(2-aminoethyl)-2-imidazolidinone in a mass ratio of (1-3):1.

[0015] By adopting the above technical solution, the nitrogen atom and carbonyl group in the structure of 5-amino-2-benzimidazolinone and 1-(2-aminoethyl)-2-imidazolidinone can attract each other with the organic sulfur compound through hydrogen bonds, so that the sulfide is close to the amino active site to react and complete the desulfurization. The synergistic effect of the two can further improve the desulfurization efficiency; under this ratio, the synergistic effect of the two reaches the optimal level.

[0016] Preferably, in step (1), the molar ratio of 2-(n-pentylamino)ethanol to 2-ethoxypyridine-3-carboxaldehyde is (1.3-1.7):1.

[0017] By adopting the above technical solution, under this ratio, when 2-(n-pentylamino)ethanol is slightly excessive, the reaction rate can be increased.

[0018] Preferably, in step (1), the amount of p-toluenesulfonic acid used is 0.5%-1.5% of the total mass of 2-(n-pentylamino)ethanol and 2-ethoxypyridine-3-carboxaldehyde.

[0019] By adopting the above technical scheme, excessive use of p-toluenesulfonic acid may destroy the structure of the generated oxazolidine compounds, affecting the yield and quality of the oxazolidine compounds; if too little p-toluenesulfonic acid is used, 2-(n-pentylamino)ethanol and 2-ethoxypyridine-3-carboxaldehyde cannot react fully, resulting in incomplete reaction and low conversion rate.

[0020] Preferably, in step (1), the solvent is selected from toluene, cyclohexane and n-hexane.

[0021] Preferably, in step (1), the reaction temperature is 60-80° C. and the reaction time is 5-8 h.

[0022] By adopting the above technical scheme, there are few side reactions within the reaction time and temperature range; too high temperature and reaction time will make the energy of the reaction system too high, the molecular motion will be intensified, and the side reactions will increase; too low temperature and time will easily lead to slow reaction rate, incomplete reaction, and reduced yield.

[0023] Preferably, in step (2), the dispersant is selected from one of methanol, ethanol, ethylene glycol, propylene glycol and glycerol.

[0024] By adopting the above technical scheme, methanol and other alcohol substances have good solubility for other components, and the hydroxyl groups in their structure can form hydrogen bonds with components such as N-methyldiethanolamine and oxazolidine compounds to maintain the stability of the system. At the same time, the addition of dispersant can improve the viscosity of the composite desulfurizer and increase the desulfurization rate of the composite desulfurizer.

[0025] Preferably, in step (2), the mixing temperature is 20-30° C. and the mixing time is 20-30 min.

[0026] Preferably, in step (3), the mixing temperature is 35-45° C. and the mixing time is 1-3 h.

[0027] By adopting the above technical solution, the components are mixed more fully within the temperature and time range.

[0028] In summary, the beneficial effects of the present invention are:

[0029] (1) The present invention introduces oxazolidine compounds into the composite desulfurizer, and the organic sulfide can be well embedded between the pyridine ring and the active site of the oxazolidine compound, and adsorbed or reacted through interactions such as van der Waals force, so that it has good selectivity for sulfide; during the desulfurization process, the nitrogen atoms on the pyridine ring of the oxazolidine compound and the nitrogen atoms in the oxazolidine ring can react with the sulfide molecules, fixing the sulfide in the composite desulfurizer to achieve desulfurization;

[0030] (2) In the composite desulfurizer of the present invention, 5-amino-2-benzimidazolinone and 1-(2-aminoethyl)-2-imidazolidinone can improve the sulfur capacity of the composite desulfurizer; the different structures of the two make their adsorption sites complementary; after the two are compounded, the complementary adsorption sites enable the two to adsorb different sulfides, thereby increasing the sulfur capacity of the composite desulfurizer;

[0031] (3) The present invention uses N-methyldiethanolamine as the main desulfurizer, oxazolidine compounds as synergistic desulfurizers, 5-amino-2-benzimidazolone and 1-(2-aminoethyl)-2-imidazolidinone as desulfurization aids, and compounded with corrosion inhibitors, antioxidants and other additives. The composite desulfurizer prepared in this way has stable performance, synergistic effects among the components, high selectivity for sulfides, increased sulfur capacity and removal capacity for organic sulfur, reduced energy consumption, and good corrosion inhibition. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the removal rate of hydrogen sulfide, carbon dioxide and organic sulfur by the composite desulfurizer prepared in Examples 1-4 and Comparative Examples 1-5 of the present invention. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is explained in detail below with reference to several representative embodiments of the present invention.

[0034] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples are all commercially available unless otherwise specified.

[0035] In the present invention, the corrosion inhibitor can be selected from commonly used corrosion inhibitors without special restrictions. In the following embodiments, the corrosion inhibitor is sodium hexametaphosphate; in the present invention, the antioxidant can be selected from commonly used antioxidants without special restrictions. In the following embodiments, the antioxidant is 2,6-di-tert-butylphenol; in the present invention, the defoamer can be selected from commonly used defoamers without special restrictions. In the following embodiments, the defoamer is tertiary amino silicone oil.

[0036] Example 1

[0037] A method for preparing an energy-saving composite desulfurizer, the specific steps are as follows:

[0038] (1) Add 31.5 g of 2-(n-pentylamino)ethanol and 80 mL of toluene to a four-necked flask and stir for 20 min, slowly dropwise add 22.67 g of 2-ethoxypyridine-3-carboxaldehyde, and finally add 0.54 g of p-toluenesulfonic acid. Heat to 65 °C and react for 7 h. Use a water separator to reflux and separate water. After the separation is completed, cool to room temperature and collect the fractions by vacuum distillation to obtain oxazolidine compounds.

[0039] (2) Add 5 g of ethylene glycol and 3 g of water into a reactor, heat to 20 °C and stir for 25 min to obtain a mixed solution A;

[0040] (3) Add 70 g of N-methyldiethanolamine, 17 g of oxazolidine compound, 6 g of 5-amino-2-benzimidazolidinone and 2 g of 1-(2-aminoethyl)-2-imidazolidinone to mixed solution A, heat to 35 °C and stir for 2 h to obtain mixed solution B;

[0041] (4) Add 0.03 g of corrosion inhibitor and 0.5 g of antioxidant to the mixed solution B and stir for 1 h, then add 1.5 g of defoaming agent and stir for 1 h to obtain an energy-saving composite desulfurizer.

[0042] Example 2

[0043] A method for preparing an energy-saving composite desulfurizer, the specific steps are as follows:

[0044] (1) Add 25.59 g of 2-(n-pentylamino)ethanol and 80 mL of toluene to a four-necked flask and stir for 20 min, slowly dropwise add 22.67 g of 2-ethoxypyridine-3-carboxaldehyde, and finally add 0.25 g of p-toluenesulfonic acid. Heat to 70 °C and react for 8 h. Use a water separator to reflux and separate water. After the separation is completed, cool to room temperature and collect the fractions by vacuum distillation to obtain oxazolidine compounds.

[0045] (2) Add 6 g methanol and 4 g water into a reactor, heat to 20 °C and stir for 25 min to obtain a mixed solution A;

[0046] (3) Add 65 g of N-methyldiethanolamine, 20 g of oxazolidine compound, 4 g of 5-amino-2-benzimidazolidinone and 2 g of 1-(2-aminoethyl)-2-imidazolidinone to mixed solution A, heat to 35 °C and stir for 2 h to obtain mixed solution B;

[0047] (4) Add 0.05 g of corrosion inhibitor and 1 g of antioxidant to the mixed solution B and stir for 1 h, then add 0.5 g of defoaming agent and stir for 1 h to obtain an energy-saving composite desulfurizer.

[0048] Example 3

[0049] A method for preparing an energy-saving composite desulfurizer, the specific steps are as follows:

[0050] (1) 33.46 g of 2-(n-pentylamino)ethanol and 80 mL of cyclohexane were added to a four-necked flask and stirred for 20 min. 22.67 g of 2-ethoxypyridine-3-carboxaldehyde was slowly added dropwise, and finally 0.84 g of p-toluenesulfonic acid was added. The temperature was raised to 60 °C and reacted for 5 h. At the same time, a water separator was used to reflux and separate water. After the separation of water was completed, the mixture was cooled to room temperature and the fraction was collected by vacuum distillation to obtain an oxazolidine compound.

[0051] (2) Add 4 g propylene glycol and 2-5 g water into a reaction kettle, heat to 30 °C and stir for 25 min to obtain a mixed solution A;

[0052] (3) Add 75 g of N-methyldiethanolamine, 15 g of oxazolidine compound, 2.5 g of 5-amino-2-benzimidazolidinone and 2.5 g of 1-(2-aminoethyl)-2-imidazolidinone to mixed solution A, heat to 45 °C and stir for 1 h to obtain mixed solution B;

[0053] (4) Add 0.02 g of corrosion inhibitor and 2 g of antioxidant to the mixed solution B and stir for 1 h, then add 1 g of defoaming agent and stir for 1 h to obtain an energy-saving composite desulfurizer.

[0054] Example 4

[0055] A method for preparing an energy-saving composite desulfurizer, the specific steps are as follows:

[0056] (1) Add 29.52 g of 2-(n-pentylamino)ethanol and 80 mL of n-hexane to a four-necked flask and stir for 20 min, slowly dropwise add 22.67 g of 2-ethoxypyridine-3-carboxaldehyde, and finally add 0.63 g of p-toluenesulfonic acid. Heat to 80 °C and react for 6 h. Use a water separator to reflux and separate water. After the separation is completed, cool to room temperature and collect the fractions by vacuum distillation to obtain oxazolidine compounds.

[0057] (2) Add 8 g of propylene glycol and 5 g of water into a reactor, heat to 25 °C and stir for 20 min to obtain a mixed solution A;

[0058] (3) Add 60 g of N-methyldiethanolamine, 22 g of oxazolidine compound, 4.5 g of 5-amino-2-benzimidazolidinone and 1.5 g of 1-(2-aminoethyl)-2-imidazolidinone to mixed solution A, heat to 45 °C and stir for 3 h to obtain mixed solution B;

[0059] (4) Add 0.04 g of corrosion inhibitor and 1 g of antioxidant to the mixed solution B and stir for 1 h, then add 1 g of defoaming agent and stir for 1 h to obtain an energy-saving composite desulfurizer.

[0060] Comparative Example 1

[0061] The difference from Example 1 is that this comparative example uses an equal amount of formaldehyde instead of 2-ethoxypyridine-3-carboxaldehyde to prepare oxazolidine compounds, and the rest is the same as Example 1.

[0062] Comparative Example 2

[0063] The difference from Example 1 is that this comparative example uses an equal amount of ethanolamine instead of 2-(n-pentylamino)ethanol, and the rest is the same as Example 1.

[0064] Comparative Example 3

[0065] The difference from Example 1 is that no oxazolidine compound is added in this comparative example, and the rest is the same as Example 1.

[0066] Comparative Example 4

[0067] The difference from Example 1 is that the ratio of 5-amino-2-benzimidazolidinone to 1-(2-aminoethyl)-2-imidazolidinone is adjusted in this comparative example, and the rest is the same as Example 1, as shown in Table 1.

[0068] Table 1 Addition amount of 5-amino-2-benzimidazolidinone and 1-(2-aminoethyl)-2-imidazolidinone

[0069]

[0070] Comparative Example 5

[0071] The difference from Example 1 is that the components in the composite desulfurizer are adjusted in this comparative example, and the rest are the same as Example 1, as shown in Table 2 for details.

[0072] Table 2 Addition amount of each component

[0073]

[0074] Related tests and analysis

[0075] The composite desulfurizers prepared in Examples 1-4 and Comparative Examples 1-5 were put into a low-pressure desulfurization system with a pressure of 4KPAG for a cyclic use period of more than 5500 hours, and samples were taken every eight hours. The test results are shown in Table 1. Figure 1 .

[0076] Combination Figure 1 By comparing Comparative Example 1 with Example 1, it can be seen that the pyridine ring in the structure of the oxazolidine compound has a strong polarity. During the desulfurization process, the pyridine ring can form hydrogen bonds and other forces with the sulfide, attracting the sulfide to approach the composite desulfurizer, thereby improving the rate and efficiency of the desulfurization reaction. The presence of the pyridine ring can enhance the nucleophilicity of the oxazolidine ring, and the synergistic effect of the pyridine ring and the oxazolidine ring makes it have better desulfurization performance.

[0077] Combination Figure 1 By comparing Comparative Example 2 with Example 1, it can be seen that the carbon chain in the structure of the oxazolidine compound can interact with the long-chain part of the long-chain sulfide molecule through non-polar action, which helps to increase the solubility of the sulfide molecule in the composite desulfurizer and improve the desulfurization rate.

[0078] Combination Figure 1 By comparing Comparative Example 3 with Example 1, it can be seen that the oxazolidine compounds have a fast sulfur substitution rate, a large sulfur capacity, and a high selectivity; using oxazolidine compounds as synergistic desulfurization agents not only maintains good selectivity and removal rate for hydrogen sulfide, but also has a high removal rate for organic sulfur, and a high total sulfur removal rate.

[0079] Combination Figure 1 By comparing Comparative Example 4 with Example 1, it can be seen that 5-amino-2-benzimidazolidinone and 1-(2-aminoethyl)-2-imidazolidinone act synergistically, and under the ratio of the present invention, the synergistic effect of the two reaches the best.

[0080] Combination Figure 1 By comparing Comparative Example 5 with Example 1, it can be seen that by adjusting the component ratio of the composite desulfurizer, the desulfurization rates of hydrogen sulfide and organic sulfur are reduced, indicating that the component ratio of the composite desulfurizer in the present invention has been optimized.

[0081] The composite desulfurizer prepared by the present invention finally measures that the sulfur content of the purified gas is less than 8ppm, carbon dioxide is almost not removed, the energy consumption of the device is reduced by 25%-45%, the removal effect is good, and the performance is stable.

[0082] The physical and chemical properties of the composite desulfurizer of the present invention are shown in Table 3.

[0083] Table 3 Physical and chemical properties

[0084]

[0085] The above is an exemplary description of the present invention. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or equivalent replacement that can be done by other technicians in this field without expending creative labor falls within the protection scope of the present invention.

Claims

1. A method for preparing an energy-saving composite desulfurizer, characterized in that: The steps include: (1) 2-(n-pentylamino)ethanol and a solvent are uniformly mixed, 2-ethoxypyridine-3-carboxaldehyde is slowly added dropwise, and p-toluenesulfonic acid is finally added. The temperature is raised to react, water is removed, and the mixture is cooled to room temperature. The fractions are collected by vacuum distillation to obtain an oxazolidine compound. (2) Mix the dispersant and water evenly to obtain a mixed solution A; (3) Evenly mixing N-methyldiethanolamine, oxazolidine compounds, desulfurization aids and mixed solution A to obtain mixed solution B; (4) The corrosion inhibitor, antioxidant and mixed solution B are mixed evenly, and then the defoaming agent is added and mixed evenly to obtain an energy-saving composite desulfurizer; The desulfurization aid is composed of 5-amino-2-benzimidazolidinone and 1-(2-aminoethyl)-2-imidazolidinone in a mass ratio of (1-3):

1.

2. The method for preparing the energy-saving composite desulfurizer according to claim 1, characterized in that: The amounts of the N-methyldiethanolamine, oxazolidine compound, desulfurization aid, defoamer, corrosion inhibitor, antioxidant, dispersant and water are calculated by weight, and the composition is: 60-75 parts of N-methyldiethanolamine, 15-22 parts of oxazolidine compounds, 5-8 parts of desulfurization aids, 0.5-1.5 parts of defoaming agents, 0.02-0.05 parts of corrosion inhibitors, 0.5-2 parts of antioxidants, 4-8 parts of dispersants, and 2-5 parts of water.

3. The method for preparing the energy-saving composite desulfurizer according to claim 1, characterized in that: In step (1), the molar ratio of 2-(n-pentylamino)ethanol to 2-ethoxypyridine-3-carboxaldehyde is (1.3-1.7):

1.

4. The method for preparing the energy-saving composite desulfurizer according to claim 1, characterized in that: In step (1), the amount of p-toluenesulfonic acid used is 0.5%-1.5% of the total mass of 2-(n-pentylamino)ethanol and 2-ethoxypyridine-3-carboxaldehyde.

5. The method for preparing the energy-saving composite desulfurizer according to claim 1, characterized in that: In step (1), the solvent is selected from toluene, cyclohexane and n-hexane.

6. The method for preparing the energy-saving composite desulfurizer according to claim 1, characterized in that: In step (1), the reaction temperature is 60-80°C and the reaction time is 5-8h.

7. The method for preparing the energy-saving composite desulfurizing agent according to claim 1, characterized in that: In step (2), the dispersant is selected from one of methanol, ethanol, ethylene glycol, propylene glycol and glycerol.

8. The method for preparing the energy-saving composite desulfurizer according to claim 1, characterized in that: In step (2), the mixing temperature is 20-30°C and the mixing time is 20-30 minutes.

9. The method for preparing the energy-saving composite desulfurizer according to claim 1, characterized in that: In step (3), the mixing temperature is 35-45° C. and the mixing time is 1-3 h.

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