A method for removing thiophene sulfur from styrene by catalytic alkylation

Abstract

The present invention provides a method for removing thiophene sulfur from styrene by catalytic alkylation. The method uses concentrated phosphoric acid or dilute sulfuric acid as a catalyst, and catalyzes styrene itself to undergo an alkylation reaction with thiophene-type sulfur-containing compounds in a kettle reactor under a reaction condition of 50 to 70°C to generate high-boiling-point components such as benzylthiophene. These high-boiling-point components are separated from styrene by subsequent distillation, thereby achieving the purpose of desulfurization. Compared with solid acid, liquid acid is easy to separate from the reaction product of the oil phase, and the acidity is milder. The reaction can be carried out under conditions higher than the ambient temperature and is easy to control. In addition, liquid acid has fewer single side reactions of the acid center type, so even at a high temperature (greater than 45°C), the oligomerization of styrene is not serious.

Description

Technical Field

[0001] The invention belongs to the field of chemical process and catalytic technology, and in particular relates to a method for catalyzing alkylation reaction between styrene itself and thiophene sulfur-containing compounds therein. Background Art

[0002] As an important chemical raw material, styrene is widely used due to its excellent physical and chemical properties. It is the fourth largest product of ethylene derivatives. It can be used to produce polystyrene resin, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene terpolymer resin, unsaturated polyester, styrene-butadiene rubber, styrene-butadiene latex and thermoplastic styrene-butadiene rubber and other products. The main production technologies of styrene include ethylbenzene dehydrogenation method, styrene-propylene oxide co-production method, butadiene synthesis method and pyrolysis gasoline extraction distillation recovery method. Ethylbenzene dehydrogenation method, that is, raw materials ethylene and benzene undergo alkylation reaction, ethylbenzene is purified from the reaction product, and then dehydrogenated and refined to obtain styrene products. In 1937, Dow Chemical Company of the United States and BASF of Germany realized the industrialization of ethylbenzene dehydrogenation method, which is currently the mainstream production process of styrene. In order to reduce energy consumption, pyrolysis gasoline extraction distillation recovery method and styrene-propylene oxide co-production method have been developed successively. With the large-scale development of ethylene production facilities, the output of pyrolysis gasoline has increased significantly, and the amount of styrene in pyrolysis gasoline has increased significantly. If styrene is separated before hydrogenation of pyrolysis gasoline, considerable economic benefits can be achieved. There is a small amount of sulfur in the styrene obtained by extraction and distillation, which affects its chemical utilization.

[0003] The current desulfurization methods mainly include hydrodesulfurization, oxidative desulfurization, extractive desulfurization, adsorption desulfurization and alkylation desulfurization. Hydrodesulfurization is the main desulfurization method for fuel oils such as gasoline and diesel. The required reaction temperature (200-400°C) and hydrogen pressure (generally greater than 2MPa) are relatively high. Under high temperature and high pressure, styrene will hydrogenate to produce ethylbenzene or undergo severe polymerization reactions, so hydrodesulfurization technology is not suitable for styrene desulfurization. Oxidative desulfurization is the use of oxidants to oxidize thiophene sulfur-containing compounds into sulfoxides or sulfones, increase the polarity of the sulfur-containing compounds, and then remove the sulfones and sulfoxides by extraction or adsorption. The oxidation reaction activity of sulfur-containing compounds increases with the increase of the electron density of sulfur atoms, but the sulfur-containing compounds in styrene are mainly thiophenes and thiols with low electron density and low oxidation reaction activity, and unsaturated hydrocarbons such as styrene are also easily oxidized. In addition, oxidative desulfurization generally uses H 2 O 2 Or organic peroxide as oxidant, there are great safety hazards, and styrene is easily oxidized, so hydrodesulfurization and oxidative desulfurization are not suitable for removing thiophene sulfur compounds in styrene. Adsorption desulfurization is suitable for substances with high polarity such as mercaptans and sulfides, while thiophene has low polarity. Extraction desulfurization has low efficiency, it is difficult to achieve deep desulfurization, and the extractant is highly dependent on sulfur species, making it difficult to adapt to situations where the raw material composition changes greatly.

[0004] Alkylation desulfurization technology can remove thiophene sulfur compounds in gasoline while maintaining the octane number unchanged. It is one of the non-hydrogenation desulfurization technologies with better desulfurization effect. However, the gasoline alkylation desulfurization reaction process and catalyst are not suitable for the alkylation desulfurization of thiophene sulfur compounds in styrene. The gasoline alkylation desulfurization reaction is generally carried out in a fixed bed reactor using a solid acid catalyst, and the temperature is generally between 55 and 400°C. Compared with gasoline, styrene is more active and easier to polymerize. When using solid acid catalysts such as zeolite molecular sieves, styrene can form free radicals when heated. At 120°C, the free radical generation rate increases significantly, initiating polymerization, so a lower reaction temperature is required. More importantly, the solid acid catalyst has a complex composition and contains There are different types of acid centers such as Lewis acid and Lewis acid (e.g., Journal of Petroleum (Petroleum Processing), 2022, 38(2): 234-244). The alkylation reaction of gasoline does not specifically limit the type of acid in the solid acid catalyst. For example, in a gasoline alkylation desulfurization method disclosed in a U.S. invention patent (Patent No. 6048451), it is proposed Both solid acid and Lewis acid can be used for alkylation desulfurization of gasoline. However, Lewis acid can catalyze olefin polymerization. Therefore, when solid acid is used as a catalyst to catalyze the alkylation reaction to remove thiophene sulfur compounds in styrene, there are many side reactions and olefin oligomerization is more serious. In addition, it is difficult to separate solid acid from the liquid product. Therefore, in a tank reactor, there are many problems in using solid acid as a catalyst to catalyze the alkylation reaction of thiophene sulfur compounds in styrene with styrene itself.

[0005] There are few reports on the alkylation desulfurization of styrene, especially the alkylation reaction of catalytic styrene itself with thiophene sulfur-containing compounds therein. A Chinese invention patent (CN101514137A) discloses a method for removing trace sulfur from styrene by catalytic distillation, characterized in that sulfur-containing styrene and isobutylene with a sulfur content of no more than 500ppm enter from the stripping section and the bottom of the catalytic distillation tower respectively, and the sulfur-containing components in styrene and isobutylene undergo a alkylation reaction in the reaction section (the catalyst is an acidic ion exchange resin or a solid acid catalyst) to generate heavy components, and at the same time, styrene and the generated heavy components are separated in the catalytic distillation tower, and a partial condenser is set at the top of the tower, and unreacted isobutylene is extracted in the gas phase, and desulfurized styrene is extracted in the liquid phase, and the sulfur content is ≤10ppm. However, this method requires the additional addition of isobutylene as an alkylating agent, which increases the cost. In addition, the boiling points of isobutylene (101.4°C) and styrene (145°C) are both greater than 100°C, the temperature is high, the energy consumption is large, and the operation is complicated, the catalyst is not easy to regenerate, and the operating cost is high. Summary of the invention

[0006] The present invention aims to overcome the disadvantages of solid acid catalysts in autoclave reactors and provide a liquid acid catalyst and method suitable for catalyzing the alkylation reaction of styrene itself with thiophene sulfur-containing compounds under mild conditions in autoclave reactors.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] The liquid acid catalyst provided by the present invention is concentrated phosphoric acid or dilute sulfuric acid. The method is as follows: in a kettle reactor, using the concentrated phosphoric acid or dilute sulfuric acid as a catalyst, under mild reaction conditions, catalyzes alkylation reaction of styrene itself with thiophene sulfur-containing compounds to generate high-boiling point components such as benzylthiophene

[0009] Furthermore, the mild reaction conditions are a temperature of 50 to 70° C. and a reaction pressure of normal pressure to 10 MPa. The reaction can be carried out in an air atmosphere or in an inert atmosphere.

[0010] Furthermore, the concentration of phosphoric acid in the concentrated phosphoric acid ranges from 2 mol / L to 4 mol / L. Preferably, the concentration of phosphoric acid in the concentrated phosphoric acid is 4 mol / L.

[0011] Furthermore, the concentration of sulfuric acid in the dilute sulfuric acid ranges from 8 mol / L to 16 mol / L. Preferably, the concentration of sulfuric acid in the dilute sulfuric acid is 10 mol / L.

[0012] In one of the preferred embodiments of the present invention, when concentrated phosphoric acid with a concentration of 4 mol / L is used as a catalyst, the reaction temperature is 60°C.

[0013] In another preferred embodiment of the present invention, when dilute sulfuric acid with a concentration of 10 mol / L is used as a catalyst, the reaction temperature is 60°C.

[0014] In a specific implementation, the method of removing thiophene aromatic heterocyclic sulfur-containing compounds in styrene by alkylation using liquid acid as a catalyst according to the present invention mainly comprises the following steps:

[0015] (1) placing a styrene solution containing a thiophene-based sulfur-containing compound and a liquid acid in a tank reactor, wherein the volume ratio of the styrene solution to the liquid acid catalyst is 2 to 5;

[0016] (2) While stirring at a speed of 1500 to 2000 rpm, the temperature of the reactor is slowly adjusted to 50 to 70°C, and the pressure is from normal pressure to 10 MPa under air or inert gas atmosphere. After reacting for 10 to 12 hours, the temperature is lowered to room temperature, and after standing, the lower aqueous phase liquid acid is separated by a separatory funnel to obtain the upper oil phase product.

[0017] The preferred reaction conditions are: the catalyst is 4 mol / L concentrated phosphoric acid, the temperature is 60°C, the air atmosphere is at normal pressure, the volume ratio of styrene to liquid acid catalyst is 5, and the reaction time is 720 minutes. Or the catalyst is 10 mol / L dilute sulfuric acid, the temperature is 60°C, the air atmosphere is at normal pressure, the volume ratio of styrene to liquid acid catalyst is 5, and the reaction time is 720 minutes.

[0018] This type of reaction is applicable to the removal of thiophene-type aromatic heterocyclic sulfur-containing compounds from other chemical products mainly composed of styrene or containing styrene.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are:

[0020] (1) Compared with the use of solid acids such as MCM-22 and MCM-49 as catalysts in a kettle reactor, the liquid acid and styrene are liquid-liquid two-phases and can be easily separated by liquid separation, thus overcoming the disadvantage that solid acid and liquid are difficult to separate.

[0021] (2) Compared with solid acids such as MCM-22 and MCM-49, liquid acids such as concentrated phosphoric acid and dilute sulfuric acid are milder in acidity and can react at temperatures above ambient, making the reaction easier to control.

[0022] (3) Liquid acids have a single acid center type. Concentrated phosphoric acid and dilute sulfuric acid only contain B acid. Therefore, even at high temperatures (greater than 45°C), the oligomerization of styrene is not serious.

[0023] In general, compared with solid acids, liquid acids such as concentrated phosphoric acid and dilute sulfuric acid are more suitable for catalyzing the alkylation reaction of styrene and thiophene sulfur-containing compounds in a kettle reactor. This method is relatively safe, the catalyst is easier to separate from the reactants, it has wide applicability and good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a graph showing the conversion rates of thiophene and styrene after the alkylation reaction in Example 1.

[0025] FIG. 2( a ) is a graph showing the thiophene conversion rate after alkylation reaction catalyzed by 4 mol / L concentrated phosphoric acid at different temperatures in Examples 1, 2, and 3.

[0026] FIG. 2( b ) is a graph showing the conversion of styrene after alkylation reaction catalyzed by 4 mol / L concentrated phosphoric acid at different temperatures in Examples 1, 2, and 3.

[0027] Figure 3 This is a graph showing the conversion rates of thiophene and styrene after the alkylation reaction catalyzed by dilute sulfuric acid with a concentration of 10 mol / L at 60°C in Example 3.

[0028] Figure 4This is a graph showing the conversion rates of thiophene and styrene after the alkylation reaction catalyzed by HY zeolite molecular sieve in Comparative Example 1.

[0029] Figure 5 This is a graph showing the conversion rates of thiophene and styrene after the alkylation reaction catalyzed by mordenite molecular sieve in Comparative Example 2.

[0030] Figure 6 This is a graph showing the conversion rates of thiophene and styrene after the alkylation reaction catalyzed by MCM-22 zeolite molecular sieve in Comparative Example 3.

[0031] Figure 7 This is a graph showing the conversion rates of thiophene and styrene after the alkylation reaction catalyzed by MCM-49 zeolite molecular sieve in Comparative Example 4.

[0032] Figure 8 This is a graph showing the conversion of thiophene and styrene after the alkylation reaction catalyzed by macroporous sulfonic acid resin A36 in Comparative Example 5.

[0033] Fig. 9 This is a graph showing the conversion rates of thiophene and styrene after the alkylation reaction catalyzed by 10 mol / L hydrochloric acid in Comparative Example 6.

[0034] Fig.10 This is a graph showing the conversion rates of thiophene and styrene after the alkylation reaction catalyzed by 10 mol / L nitric acid in Comparative Example 7.

[0035] FIG. 11( a ) is a graph showing the thiophene conversion rate after the alkylation reaction catalyzed by using phosphoric acid at concentrations of 0.5 mol / L and 1.5 mol / L in Comparative Example 8.

[0036] Figure 11(b) is a graph showing the styrene conversion rate after the alkylation reaction was catalyzed by using phosphoric acid concentrations of 0.5 mol / L and 1.5 mol / L in Comparative Example 8.

[0037] FIG. 12( a ) is a graph showing the thiophene conversion rate after the alkylation reaction using sulfuric acid at concentrations of 1 mol / L and 5 mol / L in Comparative Example 9.

[0038] Figure 12(b) is a graph showing the styrene conversion rate after the alkylation reaction using sulfuric acid at concentrations of 1 mol / L and 5 mol / L in Comparative Example 9. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and through specific embodiments. The following embodiments are merely illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0040] Example 1

[0041] First, prepare a 1% thiophene / styrene solution. Then weigh 50mL of 1% thiophene / styrene solution and 10mL of 4mol / L concentrated phosphoric acid into a 100mL three-necked flask, and then place the flask in a water bath. After the addition is complete, slowly heat the water bath to 60°C, react for 12 hours under strong stirring (speed of 2000 rpm), and take samples every hour. The mixture is filtered and centrifuged to obtain the product. Styrene does not polymerize.

[0042] The product composition was analyzed using a Thermo-Fisher Trace300-Isq7000 chromatography-mass spectrometer. Figure 1 It can be seen that the conversion rate of thiophene is 84%, and the conversion rate of styrene is 28%.

[0043] Example 2

[0044] The difference from Example 1 is that the reaction temperature is 50°C.

[0045] Example 3

[0046] The difference from Example 1 is that the reaction temperature is 70°C.

[0047] As shown in Figure 2(a), the conversion rate of thiophene increases with the increase of temperature, but the increase is lower when the temperature changes from 60°C to 70°C. After 720 minutes of reaction, the conversion rate of thiophene is 84% ​​at 60°C and 89% at 70°C. As shown in Figure 2(b), the conversion rate of styrene also increases with the increase of temperature, but the conversion rate is basically the same after 720 minutes of reaction from 50°C to 60°C. In order to obtain a higher thiophene conversion rate and recover more styrene, 60°C is the appropriate temperature.

[0048] Example 4

[0049] The difference from Example 1 is that dilute sulfuric acid with a concentration of 10 mol / L is used as a catalyst. Figure 3 It can be seen that the conversion rate of thiophene reaches 96%, and the conversion rate of styrene is 51%. It can be seen that dilute sulfuric acid can also be used for the alkylation reaction of styrene and thiophene, but compared with the reaction effect of concentrated phosphoric acid under the same conditions, its styrene recovery rate is lower.

[0050] Comparative Example 1

[0051] The difference from Example 1 is that SiO 2 / Al 2 O 3 Hydrogen-type Y zeolite molecular sieve (HY) with a molar ratio of 25 was used as a catalyst. 1 g of HY molecular sieve was added to 50 ml of 1% thiophene / styrene solution. The reaction temperature was 60°C. Figure 4As shown, the conversion rates of thiophene and styrene are both low, both at around 20%.

[0052] Comparative Example 2

[0053] The difference from Example 1 is that SiO 2 / Al 2 O 3 Hydrogen-type mordenite molecular sieve (H-MOR) with a molar ratio of 25 was used as a catalyst. 1 g of H-MOR molecular sieve was added to 50 ml of 1% thiophene / styrene solution, and the reaction temperature was 60°C. Figure 5 As shown, thiophene and styrene are substantially unreactive.

[0054] Comparative Example 3

[0055] The difference from Example 1 is that MCM-22 is used as the catalyst, 1 g of MCM-22 molecular sieve is added to 50 ml of 1% thiophene / styrene solution, and the reaction temperature is 60°C. Figure 6 As shown, thiophene was almost completely converted after 480 minutes of reaction, but styrene loss was relatively large, and the styrene loss was higher than 88% after 640 minutes.

[0056] Comparative Example 4

[0057] The difference from Example 1 is that MCM-49 is used as a catalyst, 1 g of MCM-49 molecular sieve is added to 50 ml of 1% thiophene / styrene solution, and the reaction temperature is 60°C. Figure 7 As shown, thiophene conversion was 90% after 720 minutes of reaction, and the thiophene conversion rate was very high, but styrene loss was also relatively high, about 70% conversion in 720 minutes. Under equivalent reaction conditions, the styrene recovery rate was not as high as that of liquid acid.

[0058] Comparative Example 5

[0059] The difference from Example 1 is that acidic ion exchange resin A36 is used as a catalyst. 1 g of acidic resin A36 is added to 50 ml of 1% thiophene / styrene solution and reacted at 60° C. for 560 minutes. Figure 8 As shown, although thiophene is almost completely converted, the conversion rate of styrene is relatively high, almost reaching 100%, which fails to achieve the purpose of recovering styrene.

[0060] Comparative Example 6

[0061] The difference from Example 1 is that hydrochloric acid is used as a catalyst, 10 ml of 10 mol / L hydrochloric acid is added to 50 ml of 1% thiophene / styrene solution, and the reaction is carried out at 60° C. for 720 minutes. Fig. 9 As shown, the conversion rates of thiophene and styrene are both about 50%, and the reaction effect is worse than that of phosphoric acid and sulfuric acid.

[0062] Comparative Example 7

[0063] The difference from Example 1 is that nitric acid is used as a catalyst, 10 ml of 10 mol / L nitric acid is added to 50 ml of 1% thiophene / styrene solution, and the reaction is carried out at 60° C. for 720 minutes. Fig.10 As shown, the styrene conversion rate is low, about 35%, but the thiophene conversion rate is also low, only about 40%, and the reaction catalytic effect is poor.

[0064] Comparative Example 8

[0065] The difference from Example 1 is that when the phosphoric acid concentrations are 0.5 mol / L and 1.5 mol / L respectively and the reaction temperature is 60° C., as shown in FIG. 11( a ) and FIG. 11( b ), the conversion rates of thiophene and styrene are both relatively low.

[0066] Comparative Example 9

[0067] The difference from Example 2 is that when the concentration of dilute sulfuric acid is 1 mol / L and 5 mol / L respectively and the reaction temperature is 60°C, as shown in FIG. 12(a) and FIG. 12(b), thiophene and styrene are basically unreacted.

[0068] The present invention has been described above to clearly disclose the catalyst composition and preparation conditions of the present invention. However, it is clear to those skilled in the art that some modifications and improvements may be made to the present invention. Therefore, any modifications and improvements made to the present invention should be within the scope of the present invention as long as they do not depart from the spirit of the present invention. The scope of the present invention is set forth in the appended claims.

Claims

1. A method for removing thiophene sulfur from styrene by catalytic alkylation, characterized in that: The method uses a liquid acid as a catalyst to catalyze the alkylation reaction of styrene itself with a thiophene-type sulfur-containing compound to generate a benzylthiophene high-boiling point component, and the high-boiling point component is separated from styrene by subsequent distillation, and the liquid acid is concentrated phosphoric acid or dilute sulfuric acid; When 4 mol / L concentrated phosphoric acid is used as a catalyst, the reaction temperature is 60°C; the volume ratio of styrene to concentrated phosphoric acid is 2 to 5; When 10 mol / L dilute sulfuric acid is used as a catalyst, the reaction temperature is 60°C, and the volume ratio of styrene to dilute sulfuric acid is 2-5.

2. The method according to claim 1, characterized in that The reaction is carried out in a tank reactor.

3. The method according to claim 2, characterized in that The reaction includes the following steps: (1) placing a styrene solution containing a thiophene-based sulfur-containing compound and a liquid acid in a tank reactor; (2) While stirring at a speed of 1500 to 2000 rpm, the temperature of the reactor is slowly adjusted to the desired temperature, and after reacting for 10 to 12 hours, the temperature is lowered to room temperature, and after standing, the liquid acid and the reaction product are separated by a liquid separation method.

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