Method for promoting thioetherification of mercaptan in C8 and C9 fractions in nitrogen atmosphere

Abstract

The invention provides a method for promoting thioetherification of mercaptan in C8 and C9 fractions in a nitrogen atmosphere, which comprises the following steps: adding aldehydes into the cracked C8 and C9 fractions in industrial production, and catalyzing styrene and mercaptan in a solution to generate an addition reaction by using modified activated clay as a catalyst in the nitrogen atmosphere, thereby obtaining the mercaptan in the C8 and C9 fractions. An added aldehyde substance and mercaptan are subjected to a condensation reaction, and mercaptan is further subjected to thioetherification. And during catalysis, activated clay is utilized to adsorb part of sulfide, so that the quality of the product is improved. The reaction can be completed at normal temperature and normal pressure, and hydrogen is not added, so that unsaturated hydrocarbon hydrogenation can be avoided; the solid catalyst is easy to recover, equipment investment is low, and operation is safer.

Description

Technical Field

[0001] The invention belongs to the technical field of desulfurization of C8 and C9 fractions, and in particular relates to a method for promoting thioetherification of mercaptans in C8 and C9 fractions under a nitrogen atmosphere. Background Art

[0002] Today, ethylene production capacity continues to be released, and the resulting by-product cracking gasoline output has increased significantly. Among them, C8 and C9 fractions account for about 10% to 20% of the ethylene content. Reasonable use of these resources will produce great economic benefits.

[0003] The C8 fraction can be extracted and distilled using a sulfolane mixed solvent to recover crude styrene. After decolorization and refining, crude styrene is widely used in the production of polystyrene resins, acrylonitrile-butadiene-styrene terpolymer resins, etc. This not only allows high-value-added styrene to be obtained at a low cost, but also greatly reduces the hydrogen consumption of cracked gasoline hydrogenation. The C9 fraction has a complex composition, including a large number of active components and inactive components. C9 petroleum resin has excellent plasticity, adhesion and good compatibility with other polymers, and is widely used in paints and coatings, inks, adhesives, hot melt adhesives, rubber processing and other fields and industries. The active components such as indene, styrene, and methyl styrene rich in the cracked C9 fraction are high-quality raw materials for the production of C9 petroleum resin. However, due to the presence of a certain amount of S in ethylene cracking crude oil, the cracked C8 and C9 fractions contain about 200ppm of S, which seriously affects the quality, odor and color of downstream products such as C8 extracted styrene and C9 petroleum resin. Therefore, desulfurization of C8 and C9 fractions is very necessary.

[0004] Mercaptan has a foul odor and is a typical representative of sulfides. It not only affects product quality, but also causes sulfur poisoning of catalysts and affects reaction production. Common desulfurization processes in industry include hydrodesulfurization, oxidative desulfurization, and extractive desulfurization. However, hydrodesulfurization is not suitable for the removal of mercaptans in C8 and C9 fractions, because hydrogen will cause a large loss of unsaturated hydrocarbons in the fraction, and the reaction is mostly completed under high temperature and high pressure, which is easy to cause polymerization of unsaturated hydrocarbons; oxidative desulfurization usually refers to the use of strong oxidants to convert mercaptans into sulfone substances, which are subsequently removed from the system by extraction methods, but unsaturated hydrocarbons in C8 and C9 fractions are easily oxidized to form aldehydes and acids, which is not conducive to the recovery of hydrocarbon substances; although the solvent extraction desulfurization method is simple to operate and has a certain desulfurization effect, it is limited by the choice of solvents. It is difficult to find a suitable extraction solvent, and most organic solvents are expensive and toxic, difficult to handle after desulfurization, and easy to cause damage to the environment. Therefore, this method has not been widely used in the field of desulfurization. In order to achieve the removal of mercaptan compounds in products, many new technologies have been developed and applied in industry. At present, the main method for removing mercaptan is to convert mercaptan into sulfide substances and then remove them by distillation process. Chinese patent CN102125846A discloses a mercaptan etherification catalyst, which is used to remove mercaptan and diolefins in light fractions such as catalytic cracking gasoline, catalytic cracking gasoline and coking gasoline after using one of the metal oxides such as Mg, Ca, Ba to modify alumina. The catalyst has high efficiency in removing mercaptan and diolefins, and no alkali slag is discharged. Chinese patent CN110860285A discloses a preparation method for low-temperature thioetherification and diolefin selective hydrogenation catalyst, which involves removing mercaptan in gasoline and liquefied petroleum gas, and selectively hydrogenating diolefins and alkynes therein to monoolefins, and the reaction conditions are moderate, and the reaction activity is high. Although the above method can efficiently realize the thioetherification of mercaptan, the reaction process will cause the selective hydrogenation of olefins, and high temperature is also easy to cause the polymerization of olefins. Chinese patent CN117964451A discloses a method for using a modified clay adsorbent in the desulfurization of a styrene system. The treated activated clay has an improved removal effect on small molecular mercaptans in styrene. However, further research has found that the desulfurization effect on industrial cracking C8 and C9 fractions is significantly reduced under a nitrogen atmosphere. Summary of the invention

[0005] In order to solve the above-mentioned deficiencies of the prior art, the present invention discloses a method for promoting the thioetherification of mercaptans in C8 and C9 fractions under a nitrogen atmosphere. Under a nitrogen atmosphere, aldehyde substances are added to the C8 and C9 fractions, and modified activated clay is used as a catalyst to catalyze the addition reaction of styrene and mercaptan in the solution. At the same time, the added aldehyde substances are used to undergo a condensation reaction with mercaptan to further thioetherify the mercaptan.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A method for promoting thioetherification of mercaptans in C8 and C9 fractions under a nitrogen atmosphere, comprising:

[0008] (1) Place the reactor in a water bath at 25-35°C and purge the reactor with nitrogen. Keep the nitrogen purge throughout the experiment.

[0009] (2) taking C8 and C9 fractions, adding aldehyde substances to the C8 and C9 fractions and mixing them evenly, wherein the molar ratio of the aldehyde substances to the mercaptan in the C8 and C9 fractions is 1:1-3, adding the mixed solution to the reactor, and introducing nitrogen into the mixed solution, keeping nitrogen blowing, and continuously stirring;

[0010] (3) adding ion exchange modified activated clay to the reactor, maintaining nitrogen purge during the reaction, continuously stirring the reaction, calculating the desulfurization rate of the filtrate using a sulfur analyzer, calculating the mercaptan conversion rate using a gas chromatograph, and analyzing the sulfur species using a gas chromatography-mass spectrometer, wherein the solid-liquid ratio of the ion exchange modified activated clay to the mixed solution is 1 g:10-20 mL.

[0011] Furthermore, the C8 and C9 fractions are replaced by a styrene-hexanethiol mixed solution.

[0012] Furthermore, in step (1), nitrogen is blown for 5 to 15 minutes, in step (2), nitrogen is blown for 20 to 50 minutes, and in step (3), nitrogen is blown for 2 to 6 hours to ensure that the reaction is completely completed under a nitrogen atmosphere.

[0013] Furthermore, the aldehyde substance is one of benzaldehyde, formaldehyde and acetaldehyde.

[0014] Furthermore, the activated clay is one or more of bentonite, diatomaceous earth and kaolin.

[0015] Furthermore, the preparation method of the ion exchange modified activated clay is as follows: the ion solution and the activated clay are mixed according to a solid-liquid ratio of 1g:15-25mL, the ion exchange temperature is 70-90°C, the time is 5-8 hours, and after the exchange, the modified clay is filtered and washed to neutrality to obtain the modified clay; the modified clay is placed in an oven at 90-110°C and dried for 10-20 hours, and then calcined at 140-200°C under an inert atmosphere for 6 hours. The calcined modified clay is tableted and ground, and sieved with a standard sieve to obtain 20-40 mesh ion exchange modified activated clay.

[0016] Furthermore, the concentration of the ion solution is 0.10-0.20 mol / L, and the ion precursor is one or more of Cu(NO3)2, Fe(NO3)3, Co(NO3)2, and HCl.

[0017] The advantages and positive effects of the present invention are:

[0018] (1) Due to the easy oxidation and polymerization of unsaturated hydrocarbons in the cracked C8 and C9 fractions, the thioetherification method of mercaptan in a nitrogen atmosphere is more suitable for the conversion of mercaptans in the cracked C8 and C9 fractions, and the nitrogen atmosphere is more in line with industrial production conditions. Ion-modified activated clay is used as a catalyst to catalyze the addition reaction of styrene and mercaptan in the solution. At the same time, the added aldehyde substance is used to react with mercaptan to further thioetherify the mercaptan, thereby improving the quality of the product.

[0019] (2) The reaction of the present invention can be completed at room temperature and pressure, and no hydrogen is added, which can avoid hydrogenation of unsaturated hydrocarbons; the solid catalyst is easy to recover, the equipment investment is small, and the operation is safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a gas chromatographic detection diagram before and after the reaction of Example 1 of the present invention;

[0021] Figure 2 The results of gas chromatography-mass spectrometry before the reaction in Example 1 of the present invention are as follows;

[0022] Figure 3 The results of gas chromatography-mass spectrometry after the reaction in Example 1 of the present invention are as follows;

[0023] Figure 4 Examples 1 to 5 of the present invention: different metal ion-modified activated clay and unmodified activated clay were added to a styrene-thiol solution, and the corresponding desulfurization rate and thiol conversion rate;

[0024] Figure 5 For Examples 6 to 9 of the present invention: Under nitrogen atmosphere, Cu 2+ The modified activated clay was added to styrene-thiol solutions containing different aldehydes, and the corresponding thiol conversion rates;

[0025] Figure 6 This is a gas chromatographic detection diagram before and after the reaction of Example 7 of the present invention;

[0026] Figure 7 For Example 10 to Example 12 of the present invention: Cu 2+ The desulfurization rate and conversion rate of sulfur substances after adding modified activated clay to the cracked C8 fraction and adding benzaldehyde under different atmospheres;

[0027] Figure 8 For Examples 13 to 15 of the present invention: Cu 2+ The desulfurization rate and conversion rate of sulfur substances after adding modified activated clay to the cracked C9 fraction and adding benzaldehyde under different atmospheres; DETAILED DESCRIPTION

[0028] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0029] Example 1

[0030] The activated clay was modified by ion exchange method using Cu(NO3)2. 2+ The concentration is 0.15 mol / L, the solid-liquid ratio is 1 (g): 20 (mL), the modification temperature is 80°C, the modification is carried out for 6 hours, the modified clay is filtered and washed to neutrality, and then placed in an oven at 100°C for drying for 12 hours. After treatment, it is calcined in an inert atmosphere for 6 hours at a calcination temperature of 150°C. The calcined modified clay is tableted and ground, and sieved using a standard sieve to obtain 20-40 mesh Cu 2+ Ion exchange modified activated clay;

[0031] Prepare a styrene-hexanethiol solution with a sulfur content of 2000ppm, mix it evenly, take a certain amount of the styrene-hexanethiol solution and add it to the reactor, place the reactor in a water bath at 30°C, add the dried modified activated clay, the solid-liquid ratio is 1 (g): 15 (mL), the reaction time is 3 hours, after the reaction is completed, filter and take out about 0.75mL of the solution, use a sulfur analyzer to calculate the desulfurization rate, and the desulfurization rate is 21%. Use a gas chromatograph to analyze the solution before and after the reaction, calculate the mercaptan conversion rate, and the analysis shows that the mercaptan conversion rate is about 100%. Example 1 Gas chromatographic detection diagram before and after the reaction is as follows Figure 1 The sulfur species were analyzed by gas chromatography-mass spectrometry, and the products were mainly dihexyl disulfide, the addition product of styrene and hexanethiol, and the condensation product of a trace amount of styrene oxidized to benzaldehyde and hexanethiol. Figure 2 , Figure 3 They are respectively the detection results of gas chromatography-mass spectrometry before and after the reaction of Example 1 of the present invention), the main chemical reaction equation is as follows, and the other products are side reactions caused by impurities in styrene.

[0032]

[0033] Example 2

[0034] Same as Example 1, except that Cu 2+ Replaced with Fe 3+ The analysis showed that the desulfurization rate was 12% and the mercaptan conversion rate was about 48%.

[0035] Example 3

[0036] Same as Example 1, except that Cu 2+ Replace with H+ The analysis showed that the desulfurization rate was 10% and the mercaptan conversion rate was about 32%.

[0037] Example 4

[0038] Same as Example 1, except that Cu 2+ Replaced with Co 2+ , the desulfurization rate is 6% and the mercaptan conversion rate is about 20%.

[0039] Example 5

[0040] The same as Example 1, except that unmodified activated clay was added. The desulfurization rate was 4% and the mercaptan conversion rate was about 14%.

[0041] Example 6

[0042] Prepare a styrene-hexanethiol solution with a sulfur content of 2000 ppm. After mixing evenly, take a certain amount of the styrene-hexanethiol solution and add it to a reactor that has been purged with nitrogen for 10 minutes. The reactor is placed in a water bath at 30°C. After the solution has been purged with nitrogen for 30 minutes, add the dried Cu 2+ The modified activated clay had a solid-liquid ratio of 1 (g): 15 (mL), and the nitrogen purge reaction time was 3 hours. After the reaction was completed, about 0.75 mL of the solution was filtered out, and the desulfurization rate was calculated using a sulfur analyzer, and the desulfurization rate was 21%. The solution before and after the reaction was analyzed using a gas chromatograph to calculate the thiol conversion rate, and the analysis showed that the thiol conversion rate was about 60%.

[0043] Example 7

[0044] The same as Example 6, except that benzaldehyde was added to the styrene-thiol solution at a molar ratio of 1:2 to thiol. Analysis showed that the desulfurization rate was 20% and the thiol conversion rate was about 84%.

[0045] Example 8

[0046] Same as Example 7, except that benzaldehyde was replaced by formaldehyde. The desulfurization rate was 21% and the mercaptan conversion rate was about 82%.

[0047] Example 9

[0048] Same as Example 7, except that benzaldehyde was replaced by acetaldehyde. The desulfurization rate was 20% and the mercaptan conversion rate was about 80%.

[0049] Example 10

[0050] The same as Example 1, except that the solution was replaced with an industrial cracking C8 fraction with a sulfur content of 186 ppm. The desulfurization rate was 28% and the sulfide conversion rate was about 46%.

[0051] Embodiment 11

[0052] The same as Example 10, except that the reaction was completely carried out under a nitrogen atmosphere. The desulfurization rate was 26% and the sulfide conversion rate was about 37%.

[0053] Example 12

[0054] The same as Example 11, except that benzaldehyde was added to the solution in a molar ratio of 1:2 to mercaptan. Analysis showed that the desulfurization rate was 28% and the sulfide conversion rate was about 54%.

[0055] Example 13

[0056] The same as Example 1, except that the solution was replaced with an industrial cracking C9 fraction with a sulfur content of 115 ppm. The desulfurization rate was 32% and the sulfide conversion rate was about 70%.

[0057] Embodiment 14

[0058] Same as Example 13, except that the reaction was carried out under a nitrogen atmosphere. Analysis showed that the desulfurization rate was 30% and the sulfide conversion rate was about 56%.

[0059] Embodiment 15

[0060] The same as Example 14, except that benzaldehyde was added to the solution in a molar ratio of 1:2 to mercaptan. Analysis showed that the desulfurization rate was 32% and the sulfide conversion rate was about 79%.

[0061] Example 1 to Example 5: Different metal ion modified activated clay and unmodified activated clay were added to styrene-hexanethiol solution, and the corresponding desulfurization rate and mercaptan conversion rate were as follows: Figure 4 As shown in the figure, by comparison, it can be seen that the conversion effects of different ion-modified clay on hexanethiol are as follows: Cu 2+ >Fe 3+ >H + >Co 2+ >Unmodified; addition products of disulfide, thiol and styrene, and condensation products of benzaldehyde and thiol were observed by gas chromatography-mass spectrometry; Example 6 Under nitrogen atmosphere, Cu 2+ When modified activated clay was added to styrene-hexyl mercaptan solution, the mercaptan conversion rate was lower than that under air. Example 7 to Example 9 In a nitrogen atmosphere, different aldehydes were added to styrene-hexyl mercaptan solution, and the corresponding mercaptan conversion rates were as follows: Figure 5 As shown, the mercaptan conversion rate is significantly improved, and the type of aldehydes has little effect; the gas chromatography detection diagram before and after the reaction of Example 7 is as shown Figure 6 As shown, it was observed using a gas chromatograph that after adding benzaldehyde, the yield of the condensation product of benzaldehyde and mercaptan was significantly increased.

[0062] The desulfurization rate and conversion rate of sulfur substances corresponding to the C8 fraction of Examples 10 and 11 are as follows: Figure 7 As shown; the desulfurization rate and conversion rate of sulfur substances corresponding to the C9 fraction of Examples 13 to 15 are as follows Figure 8 shown; from Figure 7 and Figure 8 It can be seen that under different atmospheres, the adsorption removal rates of sulfides in C8 and C9 fractions are slightly different, but the sulfide conversion rate under nitrogen atmosphere is significantly lower than that under air atmosphere. When a certain amount of benzaldehyde is added under nitrogen, the sulfide conversion rate in C8 fraction increases from 37% to 54%, and the sulfide conversion rate in C9 fraction increases from 56% to 79%. It can be seen that the addition of aldehydes promotes the further thioetherification of sulfides under nitrogen atmosphere.

[0063] The above embodiments and descriptions are only for illustrating the principles and best embodiments of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, all of which fall within the scope of the present invention to be protected.

Claims

1. A method for promoting the thioetherification of mercaptans in C8 and C9 fractions under a nitrogen atmosphere, characterized in that: include: (1) Place the reactor in a water bath at 25-35°C and purge the reactor with nitrogen. Keep the nitrogen purge throughout the experiment. (2) taking C8 and C9 fractions, adding aldehyde substances to the C8 and C9 fractions and mixing them evenly, wherein the molar ratio of the aldehyde substances to the mercaptan in the C8 and C9 fractions is 1:1-3, adding the mixed solution to the reactor, and introducing nitrogen into the mixed solution, keeping nitrogen blowing, and continuously stirring; (3) Adding ion-exchange modified activated clay into the reactor, maintaining nitrogen purge during the reaction, and continuously stirring the reaction, wherein the solid-liquid ratio of the ion-exchange modified activated clay to the mixed solution is 1 g: 10-20 mL.

2. The method according to claim 1, characterized in that The C8 and C9 fractions are replaced by a styrene-hexyl mercaptan mixed solution.

3. The method according to claim 1, characterized in that In step (1), nitrogen is blown for 5 to 15 minutes, in step (2), nitrogen is blown for 20 to 50 minutes, and in step (3), nitrogen is blown for 2 to 6 hours to ensure that the reaction is completely completed under a nitrogen atmosphere.

4. The method according to claim 1, characterized in that: The aldehyde substance is one of benzaldehyde, formaldehyde and acetaldehyde.

5. The method according to claim 1, characterized in that The activated clay is one or more of bentonite, diatomaceous earth and kaolin.

6. The method according to claim 1, characterized in that The preparation method of the activated clay modified by ion exchange is as follows: the ion solution and the activated clay are mixed according to a solid-liquid ratio of 1g:15-25mL, the ion exchange temperature is 70-90°C, the time is 5-8 hours, and after the exchange, the modified clay is filtered and washed to neutrality; The modified clay is placed in an oven at 90-110°C and dried for 10-20 hours, and then calcined at 140-200°C for 6 hours under an inert atmosphere. The calcined modified clay is tableted and ground, and sieved using a standard sieve to obtain 20-40 mesh ion exchange modified activated clay.

7. The method according to claim 6, characterized in that The concentration of the ion solution is 0.10-0.20 mol / L, and the ion precursor is selected from one or more of Cu(NO3)2, Fe(NO3)3, Co(NO3)2, and HCl.

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