Epoxidation reaction system and process for preparing propylene oxide

Abstract

The present application relates to a kind of epoxidation reaction system and the preparation method of propylene oxide.The epoxidation reaction system includes N+1 epoxidation reactor and N-1 intercooler of epoxidation reactor: wherein, the N+1 epoxidation reactor is sequentially connected and receives reaction raw material or reaction material from previous epoxidation reactor, to occur epoxidation reaction;The N+1 epoxidation reactor is respectively logic 1~N+1 epoxidation reactor, and logic N+1 epoxidation reactor is filled with fresh inactivated epoxidation catalyst;The N-1 intercooler of epoxidation reactor is respectively the 1~N-1 intercooler of epoxidation reactor, and sequentially connected to logic 1~N epoxidation reactor between, to respectively from logic 1~N-1 epoxidation reactor reaction material is withdrawn heat;Wherein, N≥3.The epoxidation reaction system of the present application can effectively control the temperature of epoxidation reactor, avoid the reaction runaway caused by the rise of reaction temperature.

Description

Technical Field

[0001] This invention relates to an epoxidation reaction system and a method for preparing propylene oxide. Background Technology

[0002] Epoxidation, similar to oxidation, is a highly exothermic reaction. For example, the liquid-phase catalytic reaction of cumene hydroperoxide (CHP) and propylene to prepare propylene oxide is a highly exothermic reaction. In highly exothermic reactions, if the reactants and / or products are highly temperature-sensitive (i.e., thermosensitive substances), additional heat removal methods or temperature control schemes are required in the reaction system to maintain the reactor within a reasonable reaction temperature range. Inadequate temperature control can lead to decreased product selectivity and, in severe cases, runaway reactions, resulting in safety accidents.

[0003] The effect of reactor inlet temperature on peroxide conversion rate in an adiabatic fixed-bed epoxidation reactor can be found in patent CN1692106. For adiabatic fixed-bed reactors, to prevent overheating, the peroxide conversion rate can only be stably controlled below 20% under normal conditions. Furthermore, patent CN1692106 discloses a method for conducting a highly exothermic reaction, employing multiple independent reaction zones connected in series. Through single-stage propylene feeding and multi-stage parallel feeding of organic peroxides, the peroxide concentration in the feed of each reaction zone is kept below 8 wt%, thereby stabilizing the reaction temperature. CN105294606 discloses a method for producing propylene oxide from ethylbenzene peroxide and propylene. The reaction system consists of at least two adiabatic fixed-bed catalytic reactors connected in series. Propylene and ethylbenzene peroxide-containing feedstock are mixed and fed into the primary reactor. The concentration of ethylbenzene peroxide at the inlet of the secondary reactor and the temperature of the inlet material are adjusted by the circulating material at the outlet of the secondary reactor.

[0004] Because organic peroxides are easily decomposed by heat, complete conversion of organic peroxides in the epoxidation reaction zone is important and necessary to ensure the safety and economy of subsequent product separation processes. Patent CN1325484 discloses an epoxidation reaction system using a fixed-bed reactor containing a solid epoxidation catalyst. This system employs multiple fixed-bed reactors connected in series, each containing fresh and partially deactivated catalysts. Olefins are sequentially fed into the reactor containing fresh catalysts, while organic peroxides are fed in parallel into the reactor containing fresh catalysts. The effluent from the reactor containing fresh catalysts must be passed into at least one fixed-bed reactor containing partially deactivated catalysts to ensure complete conversion of the organic peroxides. Patent CN105272947 discloses a method for continuous production of epichlorohydrin. The reaction zone consists of multiple reactors connected in series. Propylene is sequentially fed into the reactors, while organic peroxides are fed into each reactor in parallel. The temperature of the last reactor needs to be higher than that of the penultimate reactor to ensure a 100% conversion rate of the organic peroxides in the last reactor.

[0005] Patent CN104230855 discloses a method for the epoxidation of cumene hydroperoxide and propylene, mainly addressing the issues of high reaction temperature and high propylene / cumene hydroperoxide molar ratio during the epoxidation process. By recycling a portion of the epoxidation product containing PO to the reactor inlet, these problems are effectively solved. In the examples, the CHP conversion rate is 99.4–99.5%, and the PO selectivity is 96.0–96.2%. However, this method, by recycling a portion of the epoxidation product containing PO to the reactor inlet, increases the energy consumption of the recycled material. Patent CN104907009 discloses a reactor and a method for preparing propylene oxide using this reactor. The reactor is filled with an epoxidation catalyst in the middle, has a stripping port at the top, and multiple sets of injectors at the bottom to enhance the mixing effect between the reactants and improve the CHP conversion rate and selectivity. In the examples, the CHP conversion rate is 90.1–99.5%, and the PO selectivity is 91.6–98.2%. This method uses an epoxidation reactor with multiple sets of injectors, making the reaction system more complex and difficult to control.

[0006] Therefore, it is essential to develop a process that is easy to operate and control, has fewer side reactions, high conversion rate of cumene hydroperoxide, and high selectivity for propylene oxide. Summary of the Invention

[0007] In view of the above background, the present invention provides an epoxidation reaction system and a method for preparing propylene oxide. For example, one objective of the present invention is to provide an epoxidation reaction system that can effectively control the temperature of the epoxidation reactor and avoid reaction runaway caused by an increase in reaction temperature. Another objective of the present invention is to provide a method for preparing propylene oxide using an epoxidation reaction system.

[0008] To achieve the above objectives, a first aspect of the present invention provides an epoxidation reaction system, comprising N+1 epoxidation reactors and N-1 inter-reactor coolers: wherein,

[0009] The N+1 epoxidation reactors are connected in sequence and receive reaction raw materials or reaction materials from the previous epoxidation reactor to carry out the epoxidation reaction; the N+1 epoxidation reactors are logic 1 to N+1 epoxidation reactors respectively, and the logic N+1 epoxidation reactor is filled with fresh and non-deactivated epoxidation catalyst.

[0010] The N-1 inter-epoxidation reactor coolers are the first to N-1 inter-epoxidation reactor coolers, and are connected in sequence between logic 1 to N epoxidation reactors to remove heat from the reactants from logic 1 to N-1 epoxidation reactors respectively.

[0011] Where N≥3.

[0012] The epoxidation reaction of this invention is a strongly exothermic reaction. Excessive temperature not only leads to reduced product selectivity but also poses a risk of runaway reactions. This invention uses coolers between each epoxidation reactor to control the reaction temperature. The more epoxidation reactors there are, the smaller the adiabatic temperature rise in each reactor, and the more uniform the reaction temperature control. However, increasing the number of reactors increases the corresponding equipment investment. Therefore, this invention does not strictly limit the upper limit of the value of N, but it must be not less than 3.

[0013] The N+1 epoxidation reactors in this invention are adiabatic fixed-bed reactors known in the art, where materials can flow from top to bottom; these will not be described in detail here. The coolers between the N-1 epoxidation reactors in this invention are coolers known or commonly used in the art capable of heat removal; the heat removal method is not limited to air cooling, water cooling, or thermal integration.

[0014] In some embodiments of the present invention, the logic 1 to N epoxidation reactors are filled with fresh, undeactivated, or partially deactivated epoxidation catalysts. Preferably, the logic 1 epoxidation reactor is filled with a partially deactivated epoxidation catalyst. In the present invention, the number of active sites in the epoxidation catalyst gradually decreases with increasing reaction time, i.e., the activity gradually decreases.

[0015] In this invention, a fresh, undeactivated epoxidation catalyst means that the epoxidation catalyst has not been used in a reaction and the active sites on the epoxidation catalyst are completely undamaged; in this invention, a partially deactivated epoxidation catalyst means that the catalyst has been in contact with the reactants for a certain period of time under reaction conditions, and the active sites have been lost, but have not reached a completely deactivated state.

[0016] In this invention, the degree of deactivation of the partially deactivated epoxidation catalyst is defined as follows: with the number of active sites in the fresh, undeactivated epoxidation catalyst being 100%, an active site count of 30% to 70% is sufficient to qualify as a partially deactivated epoxidation catalyst for use in this invention. However, the partially deactivated epoxidation catalyst of this invention should not be limited to the above-mentioned limitations.

[0017] In this invention, due to the series operation of multiple reactors, the reactant concentration is highest in the logic 1 epoxidation reactor (also known as the logic first epoxidation reactor). If the catalyst activity in this reactor is too high, it will lead to excessively high reactant conversion, excessive adiabatic temperature rise, and excessively low product selectivity, and is also prone to runaway temperature risks. In addition, as the reactants flow down the cascade reactor, the catalyst deactivation rate also gradually decreases, with the fastest catalyst deactivation rate in the logic first epoxidation reactor. Therefore, when high-concentration materials enter a reactor with lower epoxidation catalyst activity, the reaction temperature is easier to control.

[0018] In this invention, a non-deactivated catalyst is selected in the logic N+1 epoxidation reactor (also known as the logic end-stage epoxidation reactor) to ensure that the reaction product at the outlet of the logic end-stage epoxidation reactor does not contain cumene peroxide, thus preventing cumene peroxide from penetrating the reactor and mixing into the reaction product.

[0019] In this invention, propylene and a solution containing cumene hydroperoxide can be used as reaction raw materials to prepare propylene oxide using the reaction system.

[0020] In some embodiments of the present invention, the reaction raw materials include propylene and a solution containing cumene hydroperoxide; wherein,

[0021] The molar ratio of alkylbenzene to cumene peroxide in the solution containing cumene peroxide is b1, and the molar ratio of propylene to cumene peroxide in the solution containing cumene peroxide is a1, wherein a1 and b1 satisfy a1+1.40b1≥6.20.

[0022] In some embodiments of the present invention, the value of a1+1.40b1 is not greater than 50.

[0023] In this invention, the higher the value of a1+1.40b1, the slower the reaction rate and the more stable the reaction temperature control during the epoxidation reaction. However, if the value of a1+1.40b1 is too high, it will lead to an excessive amount of circulating propylene and circulating hydrogen peroxide isopropylbenzene, and an increase in the energy consumption of the distillation system. From an economic point of view, the value of a1+1.40b1 should not be too high.

[0024] In some embodiments of the present invention, the epoxidation reaction system may further include a propylene feed preheater to preheat the propylene to above 50°C before it is fed into the logic 1 epoxidation reactor.

[0025] In some embodiments of the present invention, in the logic N+1 epoxidation reactor (also known as the logic end-position epoxidation reactor), the reaction temperature rise is no more than 10°C; the outlet temperature is 100°C to 140°C.

[0026] In this invention, the reaction temperature rise refers to the reactor outlet material temperature minus the reactor inlet material temperature.

[0027] The epoxidation reaction system of this invention can effectively control the temperature of the epoxidation reactor when used to prepare propylene oxide, avoiding reaction runaway caused by temperature rise. Furthermore, by using specific molar ratios of alkylbenzene to cumene hydroperoxide and propylene to cumene hydroperoxide to control the epoxidation reaction system, the generation of side reactions in the epoxidation reaction can be effectively avoided, improving the selectivity of the target product, propylene oxide. Reasonable control of the reaction temperature rise and outlet reaction temperature of the logic N+1 epoxidation reactor in the epoxidation reaction system can effectively prevent cumene hydroperoxide from penetrating the reaction bed, reducing the generation of side reactions of cumene hydroperoxide in the subsequent distillation system.

[0028] The second aspect of the present invention provides a method for preparing propylene oxide, comprising the steps of: continuously passing reactants through the epoxidation reaction system described in the first aspect above to undergo an epoxidation reaction to generate propylene oxide;

[0029] The reaction raw materials include propylene and a solution containing cumene hydroperoxide; the molar ratio of alkylbenzene to cumene hydroperoxide in the solution containing cumene hydroperoxide is b1, and the molar ratio of propylene to cumene hydroperoxide in the solution containing cumene hydroperoxide is a1, wherein a1 and b1 satisfy a1+1.40b1≥6.20.

[0030] In some embodiments of the present invention, the value of a1 ranges from 2 to 12.

[0031] In some embodiments of the present invention, the solution containing cumene hydroperoxide contains 40 wt% to 90 wt% alkylbenzene; wherein the alkylbenzene is selected from at least one of ethylbenzene, cumene, and butylbenzene.

[0032] In this invention, the solution containing cumene hydroperoxide includes alkylbenzene as a solvent, and the solution containing cumene hydroperoxide can be prepared by reacting air or oxygen with cumene gas and liquid.

[0033] In some embodiments of the present invention, the conditions for the epoxidation reaction include: a temperature of 40 to 140°C, preferably 60 to 120°C; and a pressure of 3 MPag to 12 MPag, preferably 4.0 MPag to 8.0 MPag.

[0034] The epoxidation reaction in the preparation method of this invention is a pure liquid phase reaction, and the reaction pressure needs to be higher than the bubble point pressure of the material under the reaction temperature conditions.

[0035] In some embodiments of the present invention, based on the amount of catalyst loaded in the logic N+1 epoxidation reactor, the mass hourly space velocity (MSV) of the cumene hydroperoxide is 0.2–2 h⁻¹. -1 The cumene hydroperoxide mentioned here refers to the cumene hydroperoxide contained in the solution.

[0036] In some embodiments of the present invention, the reaction temperature rise in the logic N+1 epoxidation reactor is less than 10°C; the outlet temperature is 100°C to 140°C.

[0037] In some embodiments of the present invention, the epoxidation catalyst packed in the logic 1 to N+1 epoxidation reactor is a titanium-containing catalyst; preferably a titanium-silicon molecular sieve catalyst or a titanium dioxide catalyst.

[0038] Compared with the prior art, the beneficial effects of the present invention include:

[0039] (1) The epoxidation reaction system provided by the present invention can effectively control the temperature of the epoxidation reactor and avoid reaction runaway caused by the rise in reaction temperature;

[0040] (2) The epoxidation reaction system and the method for preparing propylene oxide provided by the present invention control the epoxidation reaction system by using a specific molar ratio of alkylbenzene to cumene hydroperoxide and a molar ratio of propylene to cumene hydroperoxide, which can effectively avoid the generation of side reactions in the epoxidation reaction and improve the selectivity of the target product propylene oxide.

[0041] (3) The epoxidation reaction system and the method for preparing propylene oxide provided by the present invention can effectively prevent cumene hydroperoxide from penetrating the reaction bed and mixing into the reaction products by reasonably controlling the reaction temperature rise and outlet reaction temperature of the logic N+1 epoxidation reactor in the epoxidation reaction system, and reduce the generation of cumene hydroperoxide in the subsequent distillation system side reactions; if the reaction temperature in the epoxidation reactor is too high, it may lead to increased oxygen generation and cause safety risks. Attached Figure Description

[0042] The present invention will now be described in further detail with reference to the accompanying drawings.

[0043] Figure 1 This is a schematic diagram of the epoxidation reaction system and material flow used in the embodiments of the present invention;

[0044] Figure 2 This is a schematic diagram of the epoxidation reaction system and material flow used in the embodiments of the present invention;

[0045] Figure 3 This is a schematic diagram of the epoxidation reaction system and material flow used in the embodiments of the present invention;

[0046] Figure 4 This is a schematic diagram of the epoxidation reaction system and material flow used in the embodiments of the present invention.

[0047] Figures 1-4 In the diagram, 1 represents the raw material propylene; 2 represents a cumene hydroperoxide solution containing alkylbenzenes; 3 represents the product of the epoxidation reaction; and C1 represents the propylene feed preheater.

[0048] Figure 1 The epoxidation reaction system in the diagram has N = 4, and has 5 epoxidation reactors and 3 inter-reactor coolers; C2, C3, and C4 are the inter-reactor coolers for epoxidation reactors 1-3, respectively; R1, R2, R3, and R4 are logic 1-4 epoxidation reactors filled with partially deactivated epoxidation catalysts, respectively; R5 is the logic last epoxidation reactor filled with fresh, non-deactivated epoxidation catalysts.

[0049] Figure 2 The epoxidation reaction system in the diagram has N = 5, and has 6 epoxidation reactors and 4 inter-reactor coolers; C2, C3, C4, and C5 are the inter-reactor coolers for epoxidation reactors 1-4, respectively; R1, R2, R3, R4, and R5 are logic 1-5 epoxidation reactors filled with partially deactivated epoxidation catalysts; R6 is the logic last epoxidation reactor filled with fresh, non-deactivated epoxidation catalysts.

[0050] Figure 3 The epoxidation reaction system in the diagram has N = 3, and has 4 epoxidation reactors and 2 inter-reactor coolers; C2 and C3 are the inter-reactor coolers for epoxidation reactors 1-4, respectively; R1, R2, and R3 are logic 1-3 epoxidation reactors filled with partially deactivated epoxidation catalysts; R4 is the logic last epoxidation reactor filled with fresh, non-deactivated epoxidation catalysts.

[0051] Figure 4 The epoxidation reaction system in the diagram has N = 2, with 3 epoxidation reactors and 1 inter-reactor cooler; C2 is the inter-reactor cooler for the 1st and 2nd epoxidation reactors; R1 and R2 are the logic 1st and 2nd epoxidation reactors filled with partially deactivated epoxidation catalysts; R3 is the logic last epoxidation reactor filled with fresh, non-deactivated epoxidation catalysts. Detailed Implementation

[0052] To make the present invention easier to understand, the present invention will be described in detail below with reference to embodiments and accompanying drawings. These embodiments are for illustrative purposes only and are not limited to the scope of application of the present invention.

[0053] In the following examples, the epoxidation catalysts packed in each epoxidation reactor are hydrophobic titanium-silicon catalysts, sourced from the Shanghai Research Institute of Petrochemical Technology.

[0054] In the following examples, the epoxidation reactors at the end of the logic are all filled with fresh, non-deactivated hydrophobic titanium-silicon catalysts; with the number of active sites of the fresh, non-deactivated hydrophobic titanium-silicon catalysts being 100%, the other epoxidation reactors are all filled with partially deactivated hydrophobic titanium-silicon catalysts with 30% to 70% of the active sites.

[0055] In the following examples, a1 represents the molar ratio of propylene to cumene hydroperoxide in the solution containing cumene hydroperoxide; b1 represents the molar ratio of alkylbenzene to cumene hydroperoxide in the solution containing cumene hydroperoxide.

[0056] In the following embodiments, the product selectivity and feed conversion rate are calculated using the following methods:

[0057] (1) Conversion rate of cumene hydroperoxide:

[0058]

[0059] In the formula, x CHP The conversion rate of cumene hydroperoxide is expressed as a percentage (%). The first logical step is the mass fraction of cumene peroxide at the inlet of the epoxidation reactor, in wt%. The mass fraction of hydrogen peroxide and cumene at the outlet of the epoxidation reactor at the end of the logic is expressed in wt%.

[0060] (2) propylene oxide selectivity:

[0061]

[0062] In the formula, S PO Selectivity for propylene oxide, in %; The molar flow rate of propylene oxide at the outlet of the epoxidation reactor at the end of the logic is expressed in kmol / h. The molar flow rate of propylene oxide at the inlet of the first-order epoxidation reactor is expressed in kmol / h. The first logic step is the molar flow rate of cumene hydroperoxide at the inlet of the epoxidation reactor, in kmol / h. The molar flow rate of cumene peroxide at the outlet of the epoxidation reactor at the end of the logic is expressed in kmol / h.

[0063] Example 1

[0064] like Figure 1 As shown, Example 1 provides an epoxidation reaction system including a propylene feed preheater C1, logic 1-5 epoxidation reactors (N value is 4) R1-R5, and intercoolers C2-C4 between the first and third epoxidation reactors.

[0065] R1, R2, R3, and R4 are logic 1 to 4 epoxidation reactors, respectively, filled with partially deactivated epoxidation catalyst; R5 is the logic last epoxidation reactor, filled with fresh, undeactivated epoxidation catalyst. Coolers C2-C4 between the 1st and 3rd epoxidation reactors are sequentially connected between logic 1 to 4 epoxidation reactors.

[0066] Example 2

[0067] like Figure 2 As shown, Example 2 provides an epoxidation reaction system including a propylene feed preheater C1, logic 1-6 epoxidation reactors (N value is 5) R1-R6, and inter-epoxidation reactor coolers C2-C5 between the first and fourth epoxidation reactors.

[0068] R1, R2, R3, R4, and R5 are logic 1 to 4 epoxidation reactors, respectively, filled with partially deactivated epoxidation catalyst; R6 is the logic last epoxidation reactor, filled with fresh, undeactivated epoxidation catalyst. Coolers C2-C5 between the 1st and 4th epoxidation reactors are sequentially connected between logic 1 to 5 epoxidation reactors.

[0069] Example 3

[0070] like Figure 3 As shown, Example 3 provides an epoxidation reaction system including a propylene feed preheater C1, logic 1-4 epoxidation reactors (N is 3) R1-R4, and a cooler C2-C3 between the first and second epoxidation reactors.

[0071] R1, R2, and R3 are logic 1-4 epoxidation reactors, respectively, filled with partially deactivated epoxidation catalyst; R4 is the logic last epoxidation reactor, filled with fresh, undeactivated epoxidation catalyst. Coolers C2-C3 between the first and second epoxidation reactors are sequentially connected between logic 1-3 epoxidation reactors.

[0072] Example 4

[0073] Example 4 uses the epoxidation reaction system provided in Example 1 to prepare propylene oxide.

[0074] The preparation method of propylene oxide in this embodiment includes the following steps:

[0075] Propylene 1, after being preheated to 65°C by propylene feed preheater C1, is mixed with a solution 2 containing cumene hydroperoxide and fed from the top into the epoxidation reactor R1 of the logic 1 epoxidation reaction system as the reaction feedstock. The mass flow rate of the cumene hydroperoxide solution is 100 kg / h, and the mass flow rate of the propylene feedstock is 69.5 kg / h. The mass concentration of cumene hydroperoxide in the solution is 40 wt%, and the mass concentration of cumene is 60 wt%. The value of a1+1.40b1 in the reaction feedstock is 8.66. The final epoxidation reactors in the logic 1 are each loaded with 16.67 kg of catalyst, while the other epoxidation reactors are loaded with 8.33 kg of catalyst, resulting in a total mass hourly space velocity (MHSV) of 0.8 h⁻¹ for cumene hydroperoxide. -1 .

[0076] To ensure that the reactions in each epoxidation reactor are purely liquid-phase, the pressure of each reactor is controlled at 6.0 MPa, and the inlet temperature of each reactor is controlled between 40℃ and 140℃. All inlet temperatures are adjusted based on the outlet temperature to maintain the outlet temperature of each reactor below 140℃, thus regulating the inlet temperature range. To prevent overheating, the flow rate of cooling water used in the inter-reactor coolers C2-C4 is adjusted to ensure that the outlet temperature of each reactor does not exceed 140℃. In the final epoxidation reactor R5, the reaction outlet temperature is controlled at 120℃, and the reaction temperature rise is controlled below 10℃.

[0077] The effluent from the reaction zone was tested and found to have a cumene hydrogen peroxide conversion rate of 98.3% and a propylene oxide selectivity of 96.1%.

[0078] Example 5

[0079] Example 5 uses the epoxidation reaction system provided in Example 2 to prepare propylene oxide.

[0080] The preparation method of propylene oxide in this embodiment includes the following steps:

[0081] Propylene 1, after being preheated to 65°C by propylene feed preheater C1, is mixed with a solution 2 containing cumene hydroperoxide and fed from the top into epoxidation reactor R1 of logic 1 in the epoxidation reaction system. The mass flow rate of the cumene hydroperoxide-containing solution is 100 kg / h, and the mass flow rate of the propylene is 60 kg / h. The mass concentration of cumene hydroperoxide in the solution is 40 wt%, and the mass concentration of cumene is 60 wt%. The value of a1+1.40b1 in the reaction feed is 8.66. The final epoxidation reactor in logic 1 is loaded with 14.29 kg of catalyst, while other epoxidation reactors are loaded with 7.14 kg of catalyst, resulting in a total mass hourly space velocity (MHSV) of 0.8 h⁻¹ for cumene hydroperoxide. -1 .

[0082] To ensure that the reactions in each epoxidation reactor are purely liquid-phase, the pressure of each reactor is controlled at 6.0 MPa, and the inlet temperature of each reactor is controlled between 40℃ and 140℃. All inlet temperatures are adjusted based on the outlet temperature to ensure that the outlet temperature of each reactor does not exceed 140℃, thus regulating the range of inlet temperatures. To prevent overheating, the flow rate of cooling water used in the inter-reactor coolers C2-C5 is adjusted to ensure that the outlet temperature of each reactor does not exceed 140℃. In the final epoxidation reactor R5, the reaction outlet temperature is controlled at 120℃, and the reaction temperature rise is controlled below 10℃.

[0083] The material 3 at the outlet of the reaction zone was tested and found to have a cumene hydrogen peroxide conversion rate of 99.5% and a propylene oxide selectivity of 98.7%.

[0084] Example 6

[0085] Example 6 uses the epoxidation reaction system provided in Example 3 to prepare propylene oxide.

[0086] The preparation method of propylene oxide in this embodiment includes the following steps:

[0087] Propylene 1, after being preheated to 65°C by propylene feed preheater C1, is mixed with a solution 2 containing cumene hydroperoxide and fed from the top into epoxidation reactor R1 of logic 1 in the epoxidation reaction system. The mass flow rate of the cumene hydroperoxide solution is 100 kg / h, and the mass flow rate of the propylene is 69.5 kg / h. The mass concentration of cumene hydroperoxide in the solution is 40 wt%, and the mass concentration of cumene is 60 wt%. The value of a1+1.40b1 in the reaction feed is 8.66. The final epoxidation reactor in logic 1 is loaded with 20 kg of catalyst, while other epoxidation reactors are loaded with 10 kg of catalyst, resulting in a total mass hourly space velocity (MHSV) of 0.8 h⁻¹ for cumene hydroperoxide. -1 .

[0088] To ensure that the reactions in each epoxidation reactor are purely liquid-phase, the pressure of each reactor is controlled at 6.0 MPa, and the inlet temperature of each reactor is controlled between 40℃ and 140℃. All inlet temperatures are adjusted based on the outlet temperature to ensure that the outlet temperature of each reactor does not exceed 140℃, thus regulating the inlet temperature range. To prevent overheating, the flow rate of cooling water used in the inter-reactor coolers C2-C3 is adjusted to ensure that the outlet temperature of each reactor does not exceed 140℃. In the final epoxidation reactor R5, the reaction outlet temperature is controlled at 120℃, and the reaction temperature rise is controlled below 10℃.

[0089] The material 3 at the outlet of the reaction zone was tested and found to have a cumene hydrogen peroxide conversion rate of 97.9% and a propylene oxide selectivity of 95.7%.

[0090] Example 7

[0091] Example 4 uses the epoxidation reaction system provided in Example 1 to prepare propylene oxide.

[0092] The preparation method of propylene oxide in this embodiment includes the following steps:

[0093] Propylene 1, after being preheated to 65°C by propylene feed preheater C1, is mixed with a solution 2 containing cumene hydroperoxide and fed from the top into epoxidation reactor R1 of logic 1 in the epoxidation reaction system. The mass flow rate of the cumene hydroperoxide solution is 100 kg / h, and the mass flow rate of the propylene feed is 81 kg / h. The mass concentration of cumene hydroperoxide in the solution is 40 wt%, and the mass concentration of cumene is 60 wt%. The value of a1+1.40b1 in the reaction feed is 9.66. The final epoxidation reactor in logic 1 is loaded with 16.67 kg of catalyst, while other epoxidation reactors are loaded with 8.33 kg of catalyst, resulting in a total mass hourly space velocity (MHSV) of 0.8 h⁻¹ for cumene hydroperoxide. -1 .

[0094] To ensure that the reactions in each epoxidation reactor are purely liquid-phase, the pressure of each reactor is controlled at 6.0 MPa, and the inlet temperature of each reactor is controlled between 40℃ and 140℃. All inlet temperatures are adjusted based on the outlet temperature to maintain the outlet temperature of each reactor below 140℃, thus regulating the inlet temperature range. To prevent overheating, the flow rate of cooling water used in the inter-reactor coolers C2-C4 is adjusted to ensure that the outlet temperature of each reactor does not exceed 140℃. In the final epoxidation reactor R5, the reaction outlet temperature is controlled at 120℃, and the reaction temperature rise is controlled below 10℃.

[0095] The material 3 at the outlet of the reaction zone was tested and found to have a cumene hydrogen peroxide conversion rate of 98.8% and a propylene oxide selectivity of 96.7%.

[0096] Example 8

[0097] Example 8 uses the epoxidation reaction system provided in Example 1 to prepare propylene oxide.

[0098] The preparation method of propylene oxide in this embodiment includes the following steps:

[0099] Propylene 1, after being preheated to 65°C by propylene feed preheater C1, is mixed with a solution 2 containing cumene hydroperoxide and fed from the top into epoxidation reactor R1 of logic 1 in the epoxidation reaction system. The mass flow rate of the cumene hydroperoxide-containing solution is 100 kg / h, and the mass flow rate of the propylene is 52 kg / h. The mass concentration of cumene hydroperoxide in the solution is 40 wt%, and the mass concentration of cumene is 60 wt%. The value of a1+1.40b1 in the reaction feed is 7.16. The final epoxidation reactor in logic 1 is loaded with 16.67 kg of catalyst, while the other epoxidation reactors are loaded with 8.33 kg of catalyst, resulting in a total mass hourly space velocity (MHSV) of 0.8 h⁻¹ for cumene hydroperoxide. -1 .

[0100] To ensure that the reactions in each epoxidation reactor are purely liquid-phase, the pressure of each reactor is controlled at 6.0 MPa, and the inlet temperature of each reactor is controlled between 40℃ and 140℃. All inlet temperatures are adjusted based on the outlet temperature to maintain the outlet temperature of each reactor below 140℃, thus regulating the inlet temperature range. To prevent overheating, the flow rate of cooling water used in the inter-reactor coolers C2-C4 is adjusted to ensure that the outlet temperature of each reactor does not exceed 140℃. In the final epoxidation reactor R5, the reaction outlet temperature is controlled at 120℃, and the reaction temperature rise is controlled below 10℃.

[0101] The material 3 at the outlet of the reaction zone was tested and found to have a cumene hydrogen peroxide conversion rate of 98.0% and a propylene oxide selectivity of 95.3%.

[0102] Comparative Example 1

[0103] like Figure 4 As shown, Comparative Example 4 provides an epoxidation reaction system including a propylene feed preheater C1, logic 1-2 epoxidation reactors (N is 2) R1-R2, and a first epoxidation reactor intercooler C2.

[0104] R1 and R2 are logic 1 and 2 epoxidation reactors respectively, which are filled with partially deactivated epoxidation catalyst; R3 is the logic final epoxidation reactor filled with fresh, undeactivated epoxidation catalyst. The first epoxidation reactor intercooler C2 is connected between logic 1 and 2 epoxidation reactors.

[0105] Comparative Example 2

[0106] Comparative Example 2 uses the epoxidation reaction system provided in Example 1 to prepare propylene oxide.

[0107] The preparation method of propylene oxide in this embodiment includes the following steps:

[0108] Propylene 1, after being preheated to 65°C by propylene feed preheater C1, is mixed with a solution 2 containing cumene hydroperoxide and fed from the top into epoxidation reactor R1 of logic 1 in the epoxidation reaction system. The mass flow rate of the cumene hydroperoxide solution is 100 kg / h, and the mass flow rate of the propylene is 34.7 kg / h. The mass concentration of cumene hydroperoxide in the solution is 40 wt%, and the mass concentration of cumene is 60 wt%. The value of a1 + 1.40b1 ≥ in the reaction feed is 5.66. The final epoxidation reactor in logic 1 is loaded with 16.67 kg of catalyst, while other epoxidation reactors are loaded with 8.33 kg of catalyst, resulting in a total mass hourly space velocity (MHSV) of 0.8 h⁻¹ for cumene hydroperoxide. -1 .

[0109] To ensure that the reactions in each epoxidation reactor are purely liquid-phase, the pressure of each reactor is controlled at 6.0 MPa, and the inlet temperature of each reactor is controlled between 40℃ and 140℃. All inlet temperatures are adjusted based on the outlet temperature to ensure that the outlet temperature of each reactor does not exceed 140℃, thus regulating the inlet temperature range. To prevent overheating, the flow rate of cooling water used in the inter-reactor coolers C2-C4 is adjusted to ensure that the outlet temperature of each reactor does not exceed 140℃. In the final epoxidation reactor R5, the reaction outlet temperature is controlled at 120℃, and the reaction temperature rise is controlled below 10℃.

[0110] The material 3 at the outlet of the reaction zone was tested and found to have a cumene hydrogen peroxide conversion rate of 97.8% and a propylene oxide selectivity of 85.3%.

[0111] Comparative Example 3

[0112] Comparative Example 3 uses the epoxidation reaction system provided in Comparative Example 1 to prepare propylene oxide.

[0113] The preparation method of propylene oxide in this embodiment includes the following steps:

[0114] Propylene 1, after being preheated to 65°C by propylene feed preheater C1, is mixed with a solution 2 containing cumene hydroperoxide and fed from the top into epoxidation reactor R1 of logic 1 in the epoxidation reaction system. The mass flow rate of the cumene hydroperoxide solution is 100 kg / h, and the mass flow rate of the propylene feed is 69.5 kg / h. The mass concentration of cumene hydroperoxide in the solution is 40 wt%, and the mass concentration of cumene is 60 wt%. The value of a1+1.40b1 in the reaction feed is 8.66. The final epoxidation reactor in logic 1 is loaded with 25 kg of catalyst, while other epoxidation reactors are loaded with 12.5 kg of catalyst, resulting in a total mass hourly space velocity (MHSV) of 0.8 h⁻¹ for cumene hydroperoxide. -1 .

[0115] To ensure that the reactions in each epoxidation reactor are purely liquid-phase, the pressure of each reactor is controlled at 6.0 MPa, and the inlet temperature of each reactor is controlled between 40℃ and 140℃. All inlet temperatures are adjusted based on the outlet temperature to ensure that the outlet temperature of each reactor does not exceed 140℃, thus regulating the inlet temperature range. To prevent overheating, the flow rate of cooling water used in the inter-reactor cooler C2 is adjusted to ensure that the outlet temperature of each reactor does not exceed 140℃. In the final epoxidation reactor R5, the reaction outlet temperature is controlled at 120℃, and the reaction temperature rise is controlled below 10℃.

[0116] The material 3 at the outlet of the reaction zone was tested and found to have a cumene hydrogen peroxide conversion rate of 95.3% and a propylene oxide selectivity of 90.5%.

[0117] Comparative Example 4

[0118] Comparative Example 4 uses the epoxidation reaction system provided in Example 1 to prepare propylene oxide.

[0119] The preparation method of propylene oxide in this embodiment includes the following steps:

[0120] Propylene 1, after being preheated to 65°C by propylene feed preheater C1, is mixed with a solution 2 containing cumene hydroperoxide and fed from the top into epoxidation reactor R1 of logic 1 in the epoxidation reaction system. The mass flow rate of the cumene hydroperoxide solution is 100 kg / h, and the mass flow rate of the propylene feed is 46.3 kg / h. The mass concentration of cumene hydroperoxide in the solution is 40 wt%, and the mass concentration of cumene is 60 wt%. The value of a1 + 1.40b1 ≥ 6.66 in the reaction feed is given. The final epoxidation reactor in logic 1 is loaded with 16.67 kg of catalyst, while other epoxidation reactors are loaded with 8.33 kg of catalyst, resulting in a total mass hourly space velocity (MHSV) of 0.8 h⁻¹ for cumene hydroperoxide. -1 .

[0121] To ensure that the reactions in each epoxidation reactor are purely liquid-phase, the pressure of each reactor is controlled at 6.0 MPa, and the inlet temperature of each reactor is controlled between 40℃ and 140℃. All inlet temperatures are adjusted based on the outlet temperature to ensure that the outlet temperature of each reactor does not exceed 140℃, thus regulating the inlet temperature range. To prevent overheating, the flow rate of cooling water used in the inter-reactor coolers C2-C4 is adjusted to ensure that the outlet temperature of each reactor does not exceed 140℃. In the final epoxidation reactor R5, the reaction outlet temperature is controlled at 145℃, and the reaction temperature rise is controlled below 20℃.

[0122] The material 3 at the outlet of the reaction zone was tested and found to have a cumene hydrogen peroxide conversion rate of 99.1% and a propylene oxide selectivity of 87.3%.

[0123] Comparative Example 5

[0124] Comparative Example 5 uses the epoxidation reaction system provided in Comparative Example 1 to prepare propylene oxide.

[0125] The preparation method of propylene oxide in this embodiment includes the following steps:

[0126] Propylene 1, after being preheated to 65°C by propylene feed preheater C1, is mixed with a solution 2 containing cumene hydroperoxide and fed from the top into epoxidation reactor R1 of logic 1 in the epoxidation reaction system. The mass flow rate of the cumene hydroperoxide solution is 100 kg / h, and the mass flow rate of the propylene feed is 69.5 kg / h. The mass concentration of cumene hydroperoxide in the solution is 40 wt%, and the mass concentration of cumene is 60 wt%. The value of a1+1.40b1 in the reaction feed is 8.66. The final epoxidation reactor in logic 1 is loaded with 25 kg of catalyst, while other epoxidation reactors are loaded with 12.5 kg of catalyst, resulting in a total mass hourly space velocity (MHSV) of 0.8 h⁻¹ for cumene hydroperoxide. -1 .

[0127] To ensure that the reactions in each epoxidation reactor are purely liquid-phase, the pressure of each reactor is controlled at 6.0 MPa, and the inlet temperature of each reactor is controlled between 40℃ and 140℃. All inlet temperatures are adjusted based on the outlet temperature to ensure that the outlet temperature of each reactor does not exceed 140℃, thus regulating the inlet temperature range. To prevent overheating, the flow rate of cooling water used in the inter-reactor cooler C2 is adjusted to ensure that the outlet temperature of each reactor does not exceed 140℃. In the final epoxidation reactor R5, the reaction outlet temperature is controlled at 145℃, and the reaction temperature rise is controlled below 20℃.

[0128] The material 3 at the outlet of the reaction zone was tested and found to have a cumene hydrogen peroxide conversion rate of 97.3% and a propylene oxide selectivity of 88.7%.

[0129] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing propylene oxide, comprising the steps of: continuously passing reactants through an epoxidation reaction system to undergo an epoxidation reaction to generate propylene oxide; the epoxidation reaction system comprising N+1 epoxidation reactors and N-1 inter-reactor coolers; wherein, The N+1 epoxidation reactors are connected in sequence and receive reaction raw materials or reaction materials from the previous epoxidation reactor to carry out the epoxidation reaction; the N+1 epoxidation reactors are logic 1 to N+1 epoxidation reactors respectively, and the logic N+1 epoxidation reactor is filled with fresh and non-deactivated epoxidation catalyst. The N-1 inter-epoxidation reactor coolers are the first to N-1 inter-epoxidation reactor coolers, and are connected in sequence between logic 1 to N epoxidation reactors to remove heat from the reactants from logic 1 to N-1 epoxidation reactors respectively. Where N≥3; The reaction raw materials include propylene and a solution containing cumene hydroperoxide; wherein, The molar ratio of alkylbenzene to cumene peroxide in the solution containing cumene peroxide is b1, and the molar ratio of propylene to cumene peroxide in the solution containing cumene peroxide is a1. a1 and b1 satisfy a1+1.40b1≥6.20; the value of a1 ranges from 2 to 12. The logic 1~N epoxidation reactors are filled with partially deactivated epoxidation catalysts.

2. The preparation method according to claim 1, characterized in that, In the logic N+1 epoxidation reactor, the reaction temperature rise is no more than 10°C, and the outlet temperature is 100°C~140°C; where the reaction temperature rise refers to the reactor outlet material temperature minus the reactor inlet material temperature.

3. The preparation method according to any one of claims 1-2, characterized in that, The solution containing cumene hydroperoxide contains 40 wt% to 90 wt% alkylbenzene; wherein the alkylbenzene is selected from at least one of ethylbenzene, cumene, and butylbenzene.

4. The preparation method according to any one of claims 1-2, characterized in that, The conditions for the epoxidation reaction include: a temperature of 40~140℃ and a pressure of 3Mpag~12Mpag.

5. The preparation method according to claim 4, characterized in that, The conditions for the epoxidation reaction include: a temperature of 60℃ to 120℃ and a pressure of 4.0 MPag to 8.0 MPag.

6. The preparation method according to any one of claims 1-2, characterized in that, Based on the amount of catalyst loaded in the logic N+1 epoxidation reactor, the mass hourly space velocity (MSV) of the cumene hydroperoxide is 0.2~2h. -1 .

7. The preparation method according to any one of claims 1-2, characterized in that, The epoxidation catalysts packed in the logic 1~N+1 epoxidation reactors are titanium-containing catalysts.

8. The preparation method according to claim 7, characterized in that, The epoxidation catalysts packed in the logic 1~N+1 epoxidation reactors are either titanium silica molecular sieve catalysts or titanium dioxide catalysts.

Images