Low-energy-consumption, high-selectivity composite desulfurization solvent and preparation method thereof

Abstract

The invention discloses a low-energy-consumption and high-selectivity composite desulfurization solvent and a preparation method thereof, belonging to the technical field of petrochemical gas desulfurization, comprising a desulfurizer and a solvent. The desulfurizer is prepared by first using 4-aminopyridine as a raw material, sequentially through a diazotization reaction and a hydrolysis reaction to obtain a hydroxy-modified dipyridine, then using the hydroxy-modified dipyridine as a ligand to obtain a dipyridine complex based on ruthenium metal, and then using the hydroxyl groups on the ligand to esterify with p-diethylamine benzoate under the condition of 2-(2-pyridyl)pyrrolidine to form a desulfurization auxiliary agent structure with dipyridine as an acceptor, diethylaniline as a donor and an ester group as a bridge, combining the desulfurizer effect of the hindered amine with the promoting effect of the desulfurizer, and further improving the removal selectivity of the desulfurization solvent.

Description

Technical Field

[0001] The invention relates to the technical field of petrochemical gas desulfurization, and in particular to a low-energy-consumption and high-selectivity composite desulfurization solvent and a preparation method thereof. Background Art

[0002] Mixed gases include natural gas, refinery gas, synthesis gas and liquefied petroleum gas. Industrial gases such as natural gas, synthesis gas and refinery gas usually contain hydrogen sulfide (H2S) and organic sulfides. Organic sulfides mainly include carbonyl sulfide, carbon disulfide, and mercaptans and sulfides with different carbon numbers. These various organic / inorganic sulfide components are not only easy to cause corrosion of equipment and pipelines during mining, processing, transportation and use, but also cause environmental pollution when used as fuel, and cause serious harm to human health. Therefore, before the mixed gas is further processed and utilized, it must be purified to meet the requirements of subsequent utilization.

[0003] At present, there are many methods for desulfurization of mixed gas at home and abroad. Desulfurization can be divided into dry desulfurization and wet desulfurization according to its weak acidity and strong reducibility. Dry desulfurization uses the reducibility and flammability of hydrogen sulfide to desulfurize or directly burn with solid oxidants and adsorbents. Wet desulfurization is a liquid desulfurizer that first absorbs and desulfurizes and then analyzes and recovers through physical and chemical principles. The organic amine liquid (alcoholamine) mainly used in wet desulfurization is mainly monoethanolamine (MEA), diethanolamine (DEA), diglycolamine (DGA), diisopropanolamine (DlPA), triethanolamine (TEA) and N-methyldiethanolamine (MDEA) as the main agent of desulfurization. Alcoholamine wet desulfurization is a common method for removing hydrogen sulfide from natural gas and refinery gas. Most of the alcohol amines currently used are N-methyldiethanolamine (MDEA) or its mixture with steric hindrance effect. This type of desulfurizer has a certain selectivity for the removal of H2S / CO2, but the removal selectivity is poor. While removing hydrogen sulfide, a large amount of carbon dioxide is also removed. For mixed gases with a higher CO2 / H2S ratio, its removal selectivity still needs to be improved. The low removal selectivity will cause the subsequent processing capacity of the device to increase, requiring a large amount of amine liquid circulation, increasing production energy consumption, and causing high energy consumption of the device.

[0004] The prior art has a technical solution that adds a desulfurization aid with electron transfer promotion function to the hindered amine to improve the removal selectivity, but the desulfurization agent component is still mainly concentrated in the hindered amine. The selectivity of the desulfurization solvent composed of the desulfurization agent and the desulfurization aid obtained by direct mixing may be further improved. Summary of the invention

[0005] In view of the above problems, the present invention provides a composite desulfurization solvent with low energy consumption and high selectivity and a preparation method thereof.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] A low-energy-consumption and high-selectivity composite desulfurization solvent comprises a desulfurization agent and a solvent. The preparation method of the desulfurization agent comprises the following steps:

[0008] (1) Preparation of modified bipyridine

[0009] Weigh 4-aminopyridine and dissolve it in a dilute sulfuric acid solution, slowly add a sodium nitrite solution under stirring, stir and react at 30-50° C. for 2-3 hours until no bubbles are generated, add sodium hydroxide while hot until the pH is above 10, continue to keep warm and stir and react for 0.5-1 hour, add hydrochloric acid to adjust the pH to 7-8, continue to drop an organic acid until the pH stabilizes at 5-6, concentrate under reduced pressure, add isopropanol to extract the product, and obtain modified bipyridine;

[0010] (2) Preparation of complex

[0011] Weigh ruthenium trichloride and dissolve it in dimethylformamide solvent, add lithium chloride and the modified dipyridine, stir and reflux for reaction for 4-6 hours under protective atmosphere, stand overnight to cool after the reaction is completed, add ether to dilute the reaction system, separate the precipitate, wash and dry to obtain;

[0012] (3) Preparation of desulfurizer

[0013] The complex is weighed and dissolved in a dichloromethane solvent, p-diethylaminobenzoic acid and 2-(2-pyridyl)pyrrolidine are added, and the mixture is stirred for reaction for 12-24 hours under a protective atmosphere. After the reaction is completed, the mixture is separated and purified by a silica gel column to obtain the product.

[0014] In some preferred embodiments, the molar ratio of the 4-aminopyridine to the sulfuric acid and the sodium nitrite in step (1) is 1:(2-2.5):(1.1-1.2).

[0015] In some preferred embodiments, the mass ratio of the ruthenium trichloride to the lithium chloride and the modified bipyridine in step (2) is 1:(0.5-1):(2.6-2.8).

[0016] In some preferred embodiments, the mass ratio of the complex to the p-diethylaminobenzoic acid and the 2-(2-pyridyl)pyrrolidine in step (3) is 1:(0.3-0.34):(0.23-0.25).

[0017] In some preferred embodiments, the solvent is a mixed solvent of deionized water and diol in a volume ratio of 1:(9-10), and the diol is one or more of 1,3-propylene glycol, 1,4-butanediol, and 1,5-pentanediol.

[0018] In some preferred embodiments, the mass ratio of the desulfurizing agent to the solvent is 1:(2-5).

[0019] In some preferred embodiments, the low-energy consumption and high-selectivity composite desulfurization solvent further comprises a hindered amine, and the mass ratio of the hindered amine to the desulfurization agent is (1-2): 10;

[0020] As an optional technical solution of the present invention, the addition of hindered amines in the desulfurization solvent can purify organic sulfur compounds that are difficult to be completely removed by the desulfurizer of the present invention.

[0021] In some preferred embodiments, the hindered amine is one or more of N-dibenzylazetidine-3-ol, tert-butylaminoethoxyethanol, 1,3-di-tert-butylamino-2-propanol, and 1-cyclohexyl-3-azetidinol.

[0022] In some preferred embodiments, the low-energy consumption and high-selectivity composite desulfurization solvent also includes additives, and the additives are one or more of corrosion inhibitors, defoamers, stabilizers, and antioxidants; the corrosion inhibitor is one or more of imidazolyl dithiourea, 2-amino-imidazolinone, di(propynyloxymethyl)isopropylbenzyl ammonium chloride, and di(propynyloxymethyl)butylbenzyl ammonium chloride; the defoamer is one or more of dimethyl silicone oil, ethyl silicone oil, methylphenyl silicone oil, and polyether-modified silicone oil; the stabilizer is one or more of N-(tert-butyloxycarbonyl)ethanolamine, morpholine, and piperazine; the antioxidant is one or more of hydroquinone, naphthalene polyphenol, p-hydroxyanisole, thiodipropionic acid, and diethylhydroxylamine.

[0023] Another aspect of the present invention is to provide a method for preparing the low-energy-consumption and high-selectivity composite desulfurization solvent, comprising the following steps:

[0024] S1, prepare the desulfurizing agent for standby use;

[0025] S2, dispersing and dissolving the desulfurizing agent in the solvent, adding the hindered amine and the additive, and circulating with stirring and refluxing for 20-40 minutes to obtain.

[0026] The beneficial effects of the present invention are:

[0027] In view of the problem that in the prior art, a desulfurizer and a desulfurization aid can only be directly mixed for desulfurization, which hinders further improvement of the desulfurization selectivity, the present invention provides a composite desulfurization solvent comprising a desulfurizer and a solvent, wherein the desulfurizer has both the function of hindered amine desulfurization and the function of desulfurization aid in enhancing ion conduction. Specifically, the present invention first uses 4-aminopyridine as a raw material, sequentially obtains hydroxy-modified dipyridine through diazotization reaction and hydrolysis reaction, and then uses the hydroxy-modified dipyridine as a ligand to obtain a dipyridine complex based on ruthenium metal, which has large steric hindrance and alkalinity similar to those of hindered amines. At the same time, the hydroxyl groups on the ligand are used to generate an esterification product with p-diethylaminobenzoic acid under the conditions of 2-(2-pyridyl)pyrrolidine, forming a desulfurization aid structure with dipyridine as an acceptor, diethylaniline as a donor, and an ester group as a bridge, thereby combining the desulfurization agent function of the hindered amine with the promotion function of the desulfurizer, and further improving the desulfurization selectivity of the desulfurization solvent. The desulfurizer of the present invention has a high adsorption and removal effect on hydrogen sulfide, but has a relatively limited removal effect on organic sulfur compounds. To improve applicability, an appropriate amount of conventional hindered amines can be added to the composite desulfurization solvent to adsorb organic sulfur compounds. DETAILED DESCRIPTION

[0028] The present invention is further described in conjunction with the following examples. Example 1

[0029] A low-energy-consumption and high-selectivity composite desulfurization solvent comprises a desulfurizer and a solvent, wherein the mass ratio of the desulfurizer to the solvent is 1:4, and the preparation method of the desulfurizer comprises the following steps:

[0030] (1) Preparation of modified bipyridine

[0031] Weigh 4-aminopyridine and dissolve it in a 0.2 mol / L dilute sulfuric acid solution, slowly add a sodium nitrite solution under stirring, stir and react at 40°C for 2 hours after the addition is completed until no bubbles are generated, add sodium hydroxide while hot until the pH is above 10, continue to keep warm and stir and react for 0.5 hours, add hydrochloric acid to adjust the pH to 7-8, continue to drop an organic acid until the pH stabilizes at 5-6, concentrate under reduced pressure, add isopropanol to extract the product, and obtain modified dipyridine; the molar ratio of the 4-aminopyridine to the sulfuric acid and the sodium nitrite is 1:2.2:1.1;

[0032] (2) Preparation of complex

[0033] Weigh ruthenium trichloride and dissolve it in dimethylformamide solvent, add lithium chloride and the modified dipyridine, stir and reflux for reaction for 5 hours under protective atmosphere, let stand overnight to cool after the reaction is completed, add ether to dilute the reaction system, separate the precipitate, wash and dry to obtain; the mass ratio of the ruthenium trichloride to the lithium chloride and the modified dipyridine is 1:0.72:2.68;

[0034] (3) Preparation of desulfurizer

[0035] The complex is weighed and dissolved in a dichloromethane solvent, p-diethylaminobenzoic acid and 2-(2-pyridyl)pyrrolidine are added, and the reaction is stirred for 12-24 hours under a protective atmosphere. After the reaction is completed, the reaction system is concentrated under reduced pressure, and is placed into a silica gel column (500 meshes), and acetonitrile / deionized water (v / v=12:1) is used as a mobile phase to elute and remove unreacted reactants, collect the product, and evaporate the solvent to obtain the product; the mass ratio of the complex to p-diethylaminobenzoic acid and the 2-(2-pyridyl)pyrrolidine is 1:0.32:0.24;

[0036] The solvent is a mixed solvent of deionized water and 1,4-butanediol, with a volume ratio of 1:10;

[0037] The method for preparing the composite desulfurization solvent with low energy consumption and high selectivity comprises the following steps:

[0038] S1, prepare the desulfurizing agent for standby use;

[0039] S2, dispersing and dissolving the desulfurizing agent in the solvent, circulating with stirring and refluxing for 30 minutes to obtain. Example 2

[0040] A composite desulfurization solvent comprises a desulfurizer and a solvent, wherein the mass ratio of the desulfurizer to the solvent is 1:4, and the preparation method of the desulfurizer comprises the following steps:

[0041] (1) Preparation of modified bipyridine

[0042] Weigh 4-aminopyridine and dissolve it in a 0.2 mol / L dilute sulfuric acid solution, slowly add a sodium nitrite solution under stirring, stir and react at 40°C for 2 hours after the addition is completed until no bubbles are generated, add sodium hydroxide while hot until the pH is above 10, continue to keep warm and stir and react for 0.5 hours, add hydrochloric acid to adjust the pH to 7-8, continue to drop an organic acid until the pH stabilizes at 5-6, concentrate under reduced pressure, add isopropanol to extract the product, and obtain modified dipyridine; the molar ratio of the 4-aminopyridine to the sulfuric acid and the sodium nitrite is 1:2.2:1.1;

[0043] (2) Preparation of complex

[0044] Weigh ruthenium trichloride and dissolve it in dimethylformamide solvent, add lithium chloride and the modified dipyridine, stir and reflux for reaction for 5 hours under protective atmosphere, let stand overnight to cool after the reaction is completed, add ether to dilute the reaction system, separate the precipitate, wash and dry to obtain the complex, and use the complex as a desulfurization agent; the mass ratio of the ruthenium trichloride to the lithium chloride and the modified dipyridine is 1:0.72:2.68;

[0045] The solvent is a mixed solvent of deionized water and 1,4-butanediol, with a volume ratio of 1:10;

[0046] The method for preparing the composite desulfurization solvent with low energy consumption and high selectivity comprises the following steps:

[0047] S1, prepare the desulfurizing agent for standby use;

[0048] S2, dispersing and dissolving the desulfurizing agent in the solvent, circulating with stirring and refluxing for 30 minutes to obtain. Example 3

[0049] A low-energy-consumption and high-selectivity composite desulfurization solvent comprises a desulfurizer, a hindered amine and a solvent, wherein the mass ratio of the desulfurizer to the hindered amine and the solvent is 1:0.1:4, and the preparation method of the desulfurizer comprises the following steps:

[0050] (1) Preparation of modified bipyridine

[0051] Weigh 4-aminopyridine and dissolve it in a 0.2 mol / L dilute sulfuric acid solution, slowly add a sodium nitrite solution under stirring, stir and react at 40°C for 2 hours after the addition is completed until no bubbles are generated, add sodium hydroxide while hot until the pH is above 10, continue to keep warm and stir and react for 0.5 hours, add hydrochloric acid to adjust the pH to 7-8, continue to drop an organic acid until the pH stabilizes at 5-6, concentrate under reduced pressure, add isopropanol to extract the product, and obtain modified dipyridine; the molar ratio of the 4-aminopyridine to the sulfuric acid and the sodium nitrite is 1:2.2:1.1;

[0052] (2) Preparation of complex

[0053] Weigh ruthenium trichloride and dissolve it in dimethylformamide solvent, add lithium chloride and the modified dipyridine, stir and reflux for reaction for 5 hours under protective atmosphere, let stand overnight to cool after the reaction is completed, add ether to dilute the reaction system, separate the precipitate, wash and dry to obtain; the mass ratio of the ruthenium trichloride to the lithium chloride and the modified dipyridine is 1:0.72:2.68;

[0054] (3) Preparation of desulfurizer

[0055] The complex is weighed and dissolved in a dichloromethane solvent, p-diethylaminobenzoic acid and 2-(2-pyridyl)pyrrolidine are added, and the reaction is stirred for 12-24 hours under a protective atmosphere. After the reaction is completed, the reaction system is concentrated under reduced pressure, and is placed into a silica gel column (500 meshes), and acetonitrile / deionized water (v / v=12:1) is used as a mobile phase to elute and remove unreacted reactants, collect the product, and evaporate the solvent to obtain the product; the mass ratio of the complex to p-diethylaminobenzoic acid and the 2-(2-pyridyl)pyrrolidine is 1:0.32:0.24;

[0056] The hindered amine is a mixture of tert-butylaminoethoxyethanol and 1,3-di-tert-butylamino-2-propanol in a mass ratio of 1:1;

[0057] The solvent is a mixed solvent of deionized water and 1,4-butanediol, with a volume ratio of 1:10;

[0058] The method for preparing the composite desulfurization solvent with low energy consumption and high selectivity comprises the following steps:

[0059] S1, prepare the desulfurizing agent for standby use;

[0060] S2, dispersing and dissolving the desulfurizing agent in the solvent, adding the hindered amine, and circulating with stirring and refluxing for 30 minutes to obtain. Example 4

[0061] A composite desulfurization solvent comprises a hindered amine and a solvent, wherein the mass ratio of the hindered amine to the solvent is 1:4, and the hindered amine is a mixture of tert-butylaminoethoxyethanol and 1,3-di-tert-butylamino-2-propanol in a mass ratio of 1:1.

[0062] Experimental example

[0063] The performance of the composite desulfurization solvent described in Examples 1-4 was tested using a simulated absorption device. Specifically, a mixed gas containing a certain proportion of nitrogen, hydrogen sulfide and carbon dioxide was introduced into an absorption container containing the composite desulfurization solvent (1L) described in Examples 1-4 at a certain flow rate (100 mL / min) at room temperature for bubbling absorption. After absorbing for a certain period of time (30 min), the exhaust gas at the outlet of the absorption container was analyzed for components, and the contents of hydrogen sulfide and carbon dioxide were determined by gas chromatography.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A low-energy-consumption and high-selectivity composite desulfurization solvent, characterized in that: The desulfurizing agent comprises a desulfurizing agent and a solvent, and the preparation method of the desulfurizing agent comprises the following steps: (1) Preparation of modified bipyridine Weigh 4-aminopyridine and dissolve it in a dilute sulfuric acid solution, slowly add a sodium nitrite solution under stirring, stir and react at 30-50° C. for 2-3 hours until no bubbles are generated, add sodium hydroxide while hot until the pH is above 10, continue to keep warm and stir and react for 0.5-1 hour, add hydrochloric acid to adjust the pH to 7-8, continue to drop an organic acid until the pH stabilizes at 5-6, concentrate under reduced pressure, add isopropanol to extract the product, and obtain modified bipyridine; (2) Preparation of complex Weigh ruthenium trichloride and dissolve it in dimethylformamide solvent, add lithium chloride and the modified dipyridine, stir and reflux for reaction for 4-6 hours under protective atmosphere, stand overnight to cool after the reaction is completed, add ether to dilute the reaction system, separate the precipitate, wash and dry to obtain; (3) Preparation of desulfurizer The complex is weighed and dissolved in a dichloromethane solvent, p-diethylaminobenzoic acid and 2-(2-pyridyl)pyrrolidine are added, and the mixture is stirred for reaction for 12-24 hours under a protective atmosphere. After the reaction is completed, the mixture is separated and purified by a silica gel column to obtain; The molar ratio of the 4-aminopyridine to the sulfuric acid and the sodium nitrite in step (1) is 1:(2-2.5):(1.1-1.2); The mass ratio of the ruthenium trichloride to the lithium chloride and the modified bipyridine in step (2) is 1:(0.5-1):(2.6-2.8); The mass ratio of the complex to the p-diethylaminobenzoic acid and the 2-(2-pyridyl)pyrrolidine in step (3) is 1:(0.3-0.34):(0.23-0.25); The solvent is a mixed solvent of deionized water and diol, the volume ratio of which is 1:(9-10), and the diol is one or more of 1,3-propylene glycol, 1,4-butanediol, and 1,5-pentanediol; The mass ratio of the desulfurizing agent to the solvent is 1:(2-5).

2. A low-energy-consumption, high-selectivity composite desulfurization solvent according to claim 1, characterized in that: The low-energy-consumption and high-selectivity composite desulfurization solvent also includes a hindered amine, and the mass ratio of the hindered amine to the desulfurization agent is (1-2):

10.

3. A low-energy-consumption, high-selectivity composite desulfurization solvent according to claim 2, characterized in that: The hindered amine is one or more of N-dibenzylazetidine-3-ol, tert-butylaminoethoxyethanol, 1,3-di-tert-butylamino-2-propanol, and 1-cyclohexyl-3-azetidinol.

4. A low-energy-consumption, high-selectivity composite desulfurization solvent according to claim 2, characterized in that: The low-energy-consumption and high-selectivity composite desulfurization solvent also includes additives, and the additives are one or more of corrosion inhibitors, defoamers, stabilizers, and antioxidants.

5. The method for preparing a composite desulfurization solvent with low energy consumption and high selectivity according to claim 4, characterized in that: The following steps are involved: S1, prepare the desulfurizing agent for standby use; S2, dispersing and dissolving the desulfurizing agent in the solvent, adding the hindered amine and the additive, and circulating with stirring and refluxing for 20-40 minutes to obtain.