Method for prolonging service life of phenethyl alcohol gas phase fixed bed dehydration catalyst and increasing yield of dehydration reaction product
By controlling the mass ratio of ethylbenzene to phenethyl alcohol and adding ethylbenzene as an extractant and polymerization inhibitor during the vapor-phase dehydration of phenethyl alcohol, the problem of catalyst coking was solved, the catalyst life was extended, the yield of styrene was improved, and the economic cost was reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHANGZHOU RUIHUA CHEMICAL ENGINEERING TECHNOLOGY CO LTD
- Filing Date
- 2026-02-12
- Publication Date
- 2026-05-19
AI Technical Summary
In the existing technology, the gas-phase dehydration method of phenylethanol has the problem that the active center of the catalyst is covered by coke, which requires frequent regeneration and switching of the catalyst, and the yield of olefin products is not high, resulting in high economic costs.
By controlling the mass ratio of ethylbenzene to phenylethanol and adding ethylbenzene as an extractant and polymerization inhibitor, excessive residence of styrene at active sites is reduced, the self-polymerization reaction is inhibited, the catalyst lifetime is extended, and the product yield is increased.
It effectively extended the catalyst's lifespan, reduced carbon buildup, improved styrene selectivity and yield, and reduced energy consumption and wastewater treatment costs in subsequent processes.
Smart Images
Figure CN122059784A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a dehydration reaction process, specifically a method for producing styrene from phenylethanol via gas-phase dehydration during the combined production of propylene oxide and styrene. Background Technology
[0002] There are already industrialized plants with different process routes for the co-production of propylene oxide and styrene.
[0003] A typical propylene oxide / styrene co-production process includes the following steps: Ethylbenzene reacts with oxygen in oxygen-containing gas to produce ethylbenzene hydrogen peroxide; Ethylbenzene hydrogen peroxide reacts with propylene to produce propylene oxide and phenylethanol; Phenylacetyl alcohol dehydrates to produce styrene; The byproduct acetophenone generated from oxidation and epoxidation reactions is hydrogenated to produce phenylethanol.
[0004] The dehydration reaction of the co-product phenylethanol is endothermic and can be carried out in both the gas and liquid phases. Taking propylene oxide / styrene co-production technology as an example, Halcon's patent US3526674 reports a liquid-phase dehydration method for aromatic alcohols, using alumina microparticle catalysts in a stirred reactor for high-temperature liquid-phase dehydration. Subsequently, Lyondell's patent CN201080013775 discloses a method for producing styrene from 1-phenylethanol, using a mixture of p-toluenesulfonic acid and o-toluenesulfonic acid as a catalyst in the liquid phase. Shell Research International's patents (US6504038, CN200880120037) disclose a method for co-producing propylene oxide and styrene using a gas-phase dehydration method, employing alumina microparticles with a multi-peaked pore size distribution as a catalyst in a fixed-bed reactor for the dehydration reaction. Changzhou Ruihua Chemical Engineering Technology Co., Ltd.'s patent (CN111620759 B) discloses a method for reducing the formation of styrene polymers and extending the operation cycle of the phenylethanol gas-phase dehydration reaction by introducing water vapor during the adiabatic dehydration of phenylethanol.
[0005] Currently, both liquid-phase and gas-phase dehydration methods for organic alcohols have operational industrial applications (e.g., liquid-phase dehydration of 1-phenylethanol at Zhenhai Refining & Chemical and gas-phase dehydration of 1-phenylethanol at CNOOC Shell). Comparatively, liquid-phase dehydration offers the advantage of long-term stable operation and the use of organic strong acid catalysts miscible with the reactants, eliminating catalyst regeneration and switching issues. However, the use of organic strong acid catalysts exposes the liquid-phase reactants and olefin products to an acidic environment for extended periods, leading to increased olefin polymerization and the formation of heavy tar, resulting in increased olefin product loss and significantly higher tar production, thus increasing the economic cost of tar treatment. Gas-phase dehydration avoids the problem of acidic olefin polymerization and offers higher olefin yields. However, gas-phase dehydration typically uses titanium dioxide or alumina as catalysts, and as the reaction proceeds, the active sites of the catalyst are gradually covered by coke, requiring regeneration and catalyst switching. Since the significant material loss in the liquid-phase dehydration process for phenylethanol is economically unacceptable, gas-phase dehydration is more cost-effective.
[0006] To extend the operation cycle of phenylethanol gas-phase dehydration, researchers have made corresponding efforts in catalysts and reactors. For example, Shell Research Ltd.'s patent (CN200880120037) uses a catalyst with alumina particles having a multi-peaked pore size distribution. In the reaction of phenylethanol dehydration to styrene at 1.0 bara pressure and 300°C, the conversion rate of phenylethanol is 99.8%, while the selectivity for styrene is 94.9-95.4%, and the activity decrease rate is 0.48% / 100h. Changzhou Ruihua Chemical Engineering Technology Co., Ltd.'s patent (CN201711349721) discloses a method for preparing a catalyst suitable for α-phenylethanol dehydration. When this catalyst is used for the dehydration of α-phenylethanol to styrene, the content of heavy components in the dehydration product is lower, approximately between 0.1% and 0.2%, far lower than the 2%-4% heavy component content in the dehydration product using existing γ-alumina catalysts.
[0007] Therefore, existing methods need to be improved. Summary of the Invention
[0008] The main objective of this application is to provide a method for extending the service life of a phenylethanol gas-phase fixed-bed dehydration catalyst and increasing the yield of dehydration reaction products. By adding ethylbenzene and controlling its mass ratio with phenylethanol, ethylbenzene, an organic compound with a boiling point close to that of the dehydration product styrene, is more effective than water vapor, an inorganic compound with a lower boiling point than styrene, in reducing the self-polymerization reaction caused by excessive residence of styrene at active sites. This inhibits the formation of carbon precursors, thereby extending the catalyst's service life. Ethylbenzene also acts as a chain transfer agent in styrene polymerization, "interrupting" the growing polymer chains. Short-chain styrene polymers are more easily freed from the constraints of the catalyst channels and carried to the next process by the reaction products.
[0009] To achieve the above objectives, in a first aspect, this application provides a method for extending the service life of a phenylethanol gas-phase fixed-bed dehydration catalyst and increasing the yield of dehydration reaction products, comprising the following steps: S1. The raw material entering the fixed-bed dehydration reaction system is vaporized, wherein the raw material contains water, phenethyl alcohol and ethylbenzene, and the mass ratio of ethylbenzene to phenethyl alcohol is controlled to be 0.01-0.4:1; S2. The gas after the dehydration reaction is cooled and condensed, and then oil and water are separated. The resulting oil phase material is used as the raw material for the styrene separation unit. S3. The aqueous phase material after oil-water separation is sent to the aqueous phase extraction system to extract the phenylethanol, acetophenone, and styrene dissolved in the aqueous phase; S4. The extracted ethylbenzene containing phenylethanol, acetophenone, and styrene is used, in part or in whole, as the feed for the dehydration reaction of the fixed-bed dehydration reaction system.
[0010] Optionally, the mass ratio of ethylbenzene to phenethyl alcohol is controlled to be 0.05-0.075:1, meaning the optimal value for the addition ratio of ethylbenzene to phenethyl alcohol is preferably found within this range. An ethylbenzene addition ratio greater than 7.5% prevents the catalyst from coking and reduces its effectiveness, but also increases the energy consumption for subsequent ethylbenzene separation processes. An ethylbenzene addition ratio less than 5% does not achieve the desired effect in preventing catalyst coking. Optionally, in step S3, ethylbenzene is used as the extractant in the aqueous phase extraction system.
[0011] Optionally, in step S3, the aqueous phase extraction system first uses ethylbenzene extraction to pre-recover phenylethanol and acetophenone in the aqueous phase, and then uses steam stripping to remove organic matter from the aqueous phase.
[0012] Optionally, in step S2, a polymerization inhibitor and a pH adjuster are added during the cooling and condensation of the gas after the dehydration reaction. These agents are also added to the cooling and condensation system of the dehydration reaction product to delay the polymerization of styrene in the reaction product and prevent corrosion of subsequent process equipment and pipelines. The phenylethanol in the feed originates from the oxidation and epoxidation reaction processes. Although the phenylethanol feed stream undergoes alkali washing and water washing in these processes, it still contains a small amount of unwashed acidic substances. Furthermore, since the dehydration reaction is usually carried out under negative pressure, a small amount of air enters the phenylethanol vaporization system, the dehydration reaction system, and the dehydration reaction product cooling and condensation oil-water separation system. This air then reacts with the reaction product or undergoes an oxidation reaction to generate acidic substances or hydrogen peroxide-like substances that promote styrene polymerization. Therefore, a pH adjuster and a polymerization inhibitor are needed.
[0013] Optionally, in step S1, the ethylbenzene contained in the raw material comes from at least one of the following: fresh ethylbenzene from the propylene oxide / styrene co-production process, recyclable ethylbenzene separated from the propylene oxide / styrene co-production process, and ethylbenzene extracted by the aqueous phase extraction system.
[0014] Optionally, in step S1, when ethylbenzene is added in the liquid phase, ethylbenzene, phenylethanol, and water enter the phenylethanol vaporization system together for vaporization; when ethylbenzene is added in the gas phase, it is uniformly mixed with the phenylethanol vaporized by the phenylethanol vaporization system and water.
[0015] Optionally, the fixed-bed dehydration reaction system in step S1 is a single-stage or multi-stage fixed-bed dehydration reactor.
[0016] Optionally, in step S1, the raw material is heated to 200-380°C to carry out a dehydration reaction in the fixed-bed dehydration reaction system.
[0017] Optionally, the aqueous phase extraction system can be an extraction tower or an extraction tank with multi-stage mixing and separation. That is, the aqueous phase extraction function after condensation of the dehydration reaction products can be achieved using either an extraction tower structure or an extraction tank structure with multi-stage mixing and separation. At 20°C, the solubility of phenylethanol in water is 2.3% wt, and the solubility of acetophenone in water is 0.55% wt. Since the phenylethanol concentration in the feed for the dehydration reaction is typically 90%, with the remainder mainly being acetophenone, and the phenylethanol conversion rate in the dehydration reaction is usually controlled above 89%, the aqueous phase after cooling of the dehydration reaction products contains a high concentration of phenylethanol and acetophenone. Therefore, it is more economical and reasonable to pre-recover phenylethanol and acetophenone from the aqueous phase using ethylbenzene extraction, and then further remove organic matter from the aqueous phase using steam stripping. This achieves both the goal of recovering the dehydration reaction feedstock and increasing the dehydration reaction yield, while also reducing the COD concentration of the wastewater.
[0018] This invention provides a method for extending the service life of a phenylethanol gas-phase fixed-bed dehydration catalyst and increasing the yield of dehydration reaction products. Compared with existing technologies, its advantages are as follows: catalyst deactivation is mainly affected by catalyst coking. By adding ethylbenzene and controlling its mass ratio with phenylethanol, ethylbenzene, an organic compound with a boiling point close to that of the dehydration product styrene, is more effective than water vapor, an inorganic compound with a lower boiling point than styrene, in reducing the self-polymerization reaction caused by excessive residence of styrene at active sites. This inhibits the formation of carbon deposit precursors. In addition, ethylbenzene is also a chain transfer agent for styrene polymerization, interrupting the growing polymer chains. Short-chain styrene polymers are more likely to escape the constraints of the catalyst channels and be carried to the next process by the reaction products. Therefore, the lower the degree of coking, the longer the catalyst life. Taking the addition of 7.5% ethylbenzene as an example, the carbon deposit content decreased from 16.27% to 9.84%, a reduction of 39.52%. Attached Figure Description
[0019] Appendix Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation
[0020] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.
[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.
[0022] like Figure 1 As shown in the attached figure, 01 represents the phenylethanol vaporization system; 02 represents the fixed-bed dehydration reaction system; 03 represents the dehydration reaction product cooling and condensation and oil-water separation system; and 04 represents the aqueous phase extraction system after condensation of the dehydration reaction product. S01 represents the phenylethanol feed; S02 represents the steam feed; S03 represents the ethylbenzene feed; S04 represents the gaseous phase phenylethanol, steam, and ethylbenzene mixture reaction feed; S05 represents the reaction system discharge; S06 represents the oil phase discharge after condensation of the dehydration reaction product; S07 represents the aqueous phase discharge after condensation of the dehydration reaction product; S08 represents the polymerization inhibitor and pH adjuster feed; S09 represents the extracted ethylbenzene; S10 represents the extracted ethylbenzene; and S11 represents the extracted aqueous phase.
[0023] like Figure 1 As shown, three feed streams—phenylethanol SO1, water vapor SO2, and ethylbenzene SO3—are introduced into the phenylethanol vaporization system O1 and vaporized by the heat source into a gaseous mixture SO4.
[0024] The gaseous mixture SO4 is heated to a reaction temperature of 200-380°C in a fixed-bed dehydration reaction system O2 and then undergoes a dehydration reaction in a single-stage or multi-stage fixed-bed dehydration reactor. In the fixed-bed dehydration reaction system O2, more than 90% of phenylethanol is converted into styrene, acetophenone, and heavy components, with a styrene selectivity of more than 97%.
[0025] The output S05 from the fixed-bed dehydration reaction system 02 enters the dehydration reaction product cooling, condensation and oil-water separation system 03. The resulting oil phase S06 is sent to the subsequent styrene separation unit to separate the product styrene, recycled ethylbenzene and heavy component tar.
[0026] To delay the polymerization of styrene in the reaction products and prevent corrosion of subsequent process equipment and pipelines, a polymerization inhibitor and a pH adjuster, SO8, are added to the cooling and condensation system of the dehydration reaction products.
[0027] The aqueous phase S07 separated by the dehydration reaction product cooling, condensation, and oil-water separation system 03 is sent to the aqueous phase extraction system 04 after the dehydration reaction product has been condensed. In this extraction system, ethylbenzene S09 is used as the extractant to extract phenethyl alcohol, acetophenone, and styrene dissolved in the water. The extracted ethylbenzene S10 is preferentially used as the feedstock ethylbenzene S03 for the phenethyl alcohol vaporization system, and the extracted aqueous phase S11 is further sent to the subsequent stripping tower to recover the remaining phenethyl alcohol, acetophenone, ethylbenzene, and styrene.
[0028] Example 1 Dehydration catalyst coking test: Experimental conditions: reaction temperature: 300℃, catalyst mass: 5.0024g, catalyst: industrial dehydration catalyst from Changzhou Ruihua Chemical Engineering Technology Co., Ltd., space velocity: 2.0h-1, water-to-phenyl-ethanol ratio: 0.25:1, absolute pressure: 40Kpa, isothermal reactor.
[0029] The weight gain of the catalyst before and after the experiment was obtained by TG-DTG (thermogravimetric analysis-differential thermogravimetric analysis). Characterization method: Under air atmosphere, the test temperature was increased from an initial temperature of 30℃ to 800℃ at a heating rate of 10℃ / min. The test results are as follows: Catalyst deactivation is mainly affected by catalyst coking. The weight gain in the table above represents the degree of coking; therefore, the lower the degree of coking, the longer the catalyst life. Taking the addition of 7.5% ethylbenzene as an example, the carbon deposit content decreased from 16.27% to 9.84%, a reduction of 39.52%.
[0030] Example 2: A combined 600,000-ton / year styrene / 270,000-ton / year propylene oxide plant, constructed using the process of Changzhou Ruihua Chemical Engineering Technology Co., Ltd., after adding the aforementioned two-stage extraction tanks, reduced the average COD concentration of the dehydrated aqueous phase from 12,000 mg / L to 3,000 mg / L. Approximately 72 kg / h of phenylethanol, acetophenone, and styrene can be recovered.
[0031] Example 3: Another combined unit, with a capacity of 600,000 tons / year of styrene and 270,000 tons / year of propylene oxide, built based on the process of Changzhou Ruihua Chemical Engineering Technology Co., Ltd., saw its average COD concentration in the dehydrated aqueous phase decrease from 17,000 mg / L to 5,000 mg / L after the addition of the aforementioned extraction tower system. Approximately 96 kg / h of phenylethanol, acetophenone, and styrene can be recovered.
[0032] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A method for extending the service life of a phenylethanol gas-phase fixed-bed dehydration catalyst and increasing the yield of dehydration reaction products, characterized in that, Includes the following steps: S1. The raw material entering the fixed-bed dehydration reaction system is vaporized, wherein the raw material contains water, phenethyl alcohol and ethylbenzene, and the mass ratio of ethylbenzene to phenethyl alcohol is controlled to be 0.01-0.4:1; S2. The gas after the dehydration reaction is cooled and condensed, and then oil and water are separated. The resulting oil phase material is used as the raw material for the styrene separation unit. S3. The aqueous phase material after oil-water separation is sent to the aqueous phase extraction system to extract the phenylethanol, acetophenone, and styrene dissolved in the aqueous phase; S4. The extracted ethylbenzene containing phenylethanol, acetophenone, and styrene is used, in part or in whole, as the feed for the dehydration reaction of the fixed-bed dehydration reaction system.
2. The method for extending the service life of a phenylethanol gas-phase fixed-bed dehydration catalyst and increasing the yield of dehydration reaction products as described in claim 1, characterized in that: The mass ratio of ethylbenzene to phenylethanol is controlled to be 0.05-0.075:
1.
3. The method for extending the service life of a phenylethanol gas-phase fixed-bed dehydration catalyst and increasing the yield of dehydration reaction products as described in claim 1, characterized in that: In step S3, ethylbenzene is used as the extractant in the aqueous phase extraction system.
4. The method for extending the service life of a phenylethanol gas-phase fixed-bed dehydration catalyst and increasing the yield of dehydration reaction products as described in claim 3, characterized in that: In step S3, the aqueous phase extraction system first uses ethylbenzene extraction to pre-recover phenylethanol and acetophenone from the aqueous phase, and then removes organic matter from the aqueous phase by steam stripping.
5. The method for extending the service life of a phenylethanol gas-phase fixed-bed dehydration catalyst and increasing the yield of dehydration reaction products as described in claim 1, characterized in that: In step S2, a polymerization inhibitor and a pH adjuster are added when the gas after the dehydration reaction is cooled and condensed.
6. The method for extending the service life of a phenylethanol gas-phase fixed-bed dehydration catalyst and increasing the yield of dehydration reaction products as described in claim 1, characterized in that: In step S1, the ethylbenzene contained in the raw material comes from at least one of the following: fresh ethylbenzene from the propylene oxide / styrene co-production process, recyclable ethylbenzene separated from the propylene oxide / styrene co-production process, and ethylbenzene extracted by the aqueous phase extraction system.
7. The method for extending the service life of a phenylethanol gas-phase fixed-bed dehydration catalyst and increasing the yield of dehydration reaction products as described in claim 6, characterized in that: In step S1, when ethylbenzene is added in the liquid phase, it enters the phenylethanol vaporization system together with phenylethanol and water for vaporization. When ethylbenzene is added in the gas phase, it is uniformly mixed with phenylethanol and water after being vaporized by the phenylethanol vaporization system.
8. The method for extending the service life of a phenylethanol gas-phase fixed-bed dehydration catalyst and increasing the yield of dehydration reaction products as described in claim 1, characterized in that: The fixed-bed dehydration reaction system in step S1 is a single-stage or multi-stage fixed-bed dehydration reactor.
9. The method for extending the service life of a phenylethanol gas-phase fixed-bed dehydration catalyst and increasing the yield of dehydration reaction products as described in claim 1, characterized in that: In step S1, the raw material is heated to 200-380°C to carry out a dehydration reaction in the fixed-bed dehydration reaction system.
10. The method for extending the service life of a phenylethanol gas-phase fixed-bed dehydration catalyst and increasing the yield of dehydration reaction products as described in claim 1, characterized in that: The aqueous phase extraction system is an extraction tower or an extraction tank that involves multi-stage mixing followed by separation.