Method for realizing efficient directional synthesis based on programmable temperature control dynamic electric heating mode and application thereof

Abstract

The invention discloses a method for realizing efficient directional synthesis based on a programmable temperature control dynamic electric heating mode and application of the method in synthesis of cyclopentadiene tripolymer. The method comprises the following steps: firstly, building a programmable temperature control dynamic heating platform, and controlling heating / cooling by controlling on / off of a direct-current power supply; rapid switching between high temperature and low temperature is realized by changing voltage, current and other conditions, and a reaction network is effectively adjusted by optimizing a'temperature-time 'curve, so that production of a target product cyclopentadiene tripolymer is promoted. Furthermore, according to the method for optimizing the reaction conditions, the working conditions of dynamic heating are determined, so that the target reaction network is accurately matched, and the highest reactant conversion rate, target product selectivity and target product space-time yield are achieved. In addition, the reactor disclosed by the invention can be used for reaction in different modes: intermittent reaction and continuous flow reaction can be realized, and the reactor is flexible and adjustable.

Description

Technical Field

[0001] The present invention relates to the field of aerospace fuel technology, and more specifically to a method for realizing efficient directional synthesis based on programmable temperature control dynamic electric heating and its use. More specifically, it relates to a method for realizing efficient directional synthesis based on programmable temperature control dynamic electric heating and its use in synthesizing cyclopentadiene trimer. Background Art

[0002] Improving the energy density of hydrocarbon fuels is a key way to increase the operating range, speed and payload capacity of aerospace vehicles. Cyclopentadiene trimer (TCPD) with multiple bridged rings has good physical and chemical properties and energy characteristics, and can be used as a precursor, fuel component, etc., and has broad application prospects in the fields of high-density hydrocarbon fuels.

[0003] The synthesis of TCPD is usually obtained by Diels-Alder reaction with dicyclopentadiene (DCPD) as raw material. The process of synthesizing TCPD from DCPD involves many typical thermochemical reactions. The depolymerization of DCPD to generate CPD is an endothermic process, while the polymerization reaction of CPD and DCPD is an exothermic reaction. Due to the conflicting temperature requirements between DCPD depolymerization and CPD-DCPD copolymerization, the traditional continuous heating technology cannot meet the optimal reaction conditions for improving the yield of TCPD. Under high-temperature continuous heating, the highly active CPD will inevitably polymerize with other substances in the system to form low-value polymers. In addition, the temperature-time curve has a significant impact on the series reaction network of DCPD depolymerization and CPD-DCPD polymerization. The above reaction process is often carried out in a reactor or fixed bed with constant temperature continuous heating. It is difficult to achieve time control of the reaction temperature and it is impossible to further improve the yield of the target product.

[0004] US3701812A discloses a method for synthesizing cyclopentadiene trimer, wherein the cyclopentadiene trimer is continuously generated at 260-310°C and 3.2-3.8 MPa for 5-25 minutes, and the conversion rate is 40-50%. The above-mentioned synthesis process requires high temperature and high pressure, and has high requirements for equipment. At the same time, high reaction temperature will lead to increased energy consumption and an increase in low-value by-products, thereby reducing the product yield.

[0005] Patent CN109867584A uses dicyclopentadiene as raw material, adds antioxidant to prepare dicyclopentadiene solution, and mixes with inert solvent in a mass ratio of 3:7 or 2:8 in a reactor for reaction. The reaction temperature is 140℃~180℃ and the absolute pressure is 140~180kpa for 20~24h. After the reaction, cyclopentadiene trimer with a purity of more than 95% is obtained by distillation separation. Although the invention is carried out at a relatively low temperature and low pressure, the reaction time is long and the intermittent production efficiency is low, which is not suitable for large-scale industrial production.

[0006] Patent CN101215217A discloses a method for catalytically synthesizing cyclopentadiene trimer, triphenylphosphine nickel chloride (Ni(PPh 3 ) 2 Cl 2 ) is used as the main catalyst and the co-catalyst zinc powder to catalyze the batch intermittent synthesis of cyclopentadiene trimer from cyclopentadiene. The reaction temperature is 50-70°C and the reaction time is 3-5h under normal pressure, and the reaction yield is increased to 83.2%. The cost of nickel catalyst is low, but the subsequent separation of the catalyst is difficult, and catalyst solid waste will be generated and the treatment cost is high, which increases the production cost.

[0007] It can be seen that many polymerization reaction systems have reactions with both endothermic and exothermic thermal effects, and the control of temperature over time is crucial to the regulation of the reaction network. Due to continuous heating, the traditional thermal synthesis method lacks time control of the reaction temperature and time, and the reaction is in a state close to equilibrium, which faces severe challenges in improving conversion rate, selectivity, space-time yield and energy efficiency. For example, in the thermochemical reaction of dicyclopentadiene depolymerization-copolymerization, the traditional constant temperature heating method is used. In addition to the target product cyclopentadiene trimer, by-products such as tetramers and pentamers are also produced in the reaction product. There are reactions with both endothermic and exothermic thermal effects in this reaction system. The depolymerization reaction of dicyclopentadiene needs to increase the temperature, and the copolymerization reaction of cyclopentadiene-dicyclopentadiene needs to reduce the temperature. The thermodynamic requirements of the two reactions are contradictory. Under constant temperature continuous heating, the reaction is easy to get out of control, and low-value polymers are inevitably generated, which is not conducive to efficient production.

[0008] In order to solve the above problems, the present invention is proposed. Summary of the invention

[0009] The present invention aims at the shortcomings of the prior art mentioned in the background technology, and adopts a programmable temperature-controlled dynamic electric heating method to dynamically control the reaction temperature, thereby achieving higher reaction conversion rate, selectivity and target product space-time yield. The method controls the heating / cooling of the reaction by controlling the on / off of a DC power supply; by adjusting the voltage and current, rapid heating and cooling are achieved, the time scale of rapid generation and consumption of cyclopentadiene is accurately matched, and the reaction conditions are improved by condition optimization, thereby achieving efficient production of cyclopentadiene trimer.

[0010] The method adopted by the present invention is: based on an electric heating platform, a programmable temperature-controlled dynamic heating is performed on the reaction to achieve time control of the reaction temperature curve. Specifically, the reactant (dicyclopentadiene) is introduced into the electric heating tube through a micro pump, the reaction heating / cooling is controlled by controlling the on / off of the DC power supply, the maximum / minimum temperature, heating time, and oscillation period of the reaction are changed by adjusting the voltage and current of the power supply, the obtained product is analyzed, and the optimal reaction conditions are determined by condition optimization to achieve the highest reactant conversion rate, target product selectivity, and target product space-time yield.

[0011] The present invention adopts the following technical solutions:

[0012] The present invention aims to propose a programmable temperature-controlled dynamic electric heating method, assisted by Bayesian optimization, to achieve efficient directional synthesis, such as the synthesis of cyclopentadiene trimer.

[0013] The first aspect of the present invention provides a method for realizing efficient directional synthesis based on programmable temperature control dynamic electric heating, which comprises the following steps:

[0014] (1) Construction of a programmable temperature-controlled electric heating platform: including a raw material delivery system, a computer data acquisition and control system, and an electric heating tubular reactor;

[0015] (2) Control the temperature rise / fall of the reaction by controlling the on / off of the DC power supply; adjust the temperature rise rate of the reaction by adjusting the voltage and current output by the DC power supply; collect and monitor data through the data acquisition system.

[0016] (3) Explore the impact of different process conditions on the experimental scheme, use Bayesian optimization to assist the experiment, use the optimized experimental conditions to carry out experimental verification, compare and analyze the experimental results obtained each time, obtain the optimal reaction conditions, and achieve efficient directional synthesis.

[0017] Preferably, in step (1), a K-type thermocouple is placed at the outlet of the reaction tube of the electrically heated tubular reactor to measure the temperature of the solution, which is set as the reaction temperature;

[0018] 3-10 thermocouples were welded on the outer wall of the reaction tube to monitor the wall temperature of the reactor;

[0019] The system pressure was regulated by a back pressure valve. The programmed temperature control process was implemented in a custom-made electrically heated tubular reactor.

[0020] Preferably, in step (3), the different process conditions include reaction pressure, maximum reaction temperature, heating rate, and residence time.

[0021] The second aspect of the present invention provides a use of the method described in the first aspect of the present invention for synthesizing cyclopentadiene trimer.

[0022] The reaction of synthesizing cyclopentadiene trimer by heating with dicyclopentadiene as raw material is a typical tandem reaction, which involves the depolymerization of dicyclopentadiene and the polymerization of cyclopentadiene and dicyclopentadiene. To improve the yield of the target product cyclopentadiene trimer, due to the contradiction between the depolymerization of dicyclopentadiene and the copolymerization of cyclopentadiene-dicyclopentadiene in terms of temperature, the traditional constant temperature continuous heating method will cause the reaction to be out of control, and side reactions will inevitably occur, generating low-value polymers. The technology of the present invention can effectively achieve rapid alternating heating and cooling, control the temperature change curve, thereby effectively suppressing the occurrence of side reactions, and can also reduce the average temperature to reduce energy consumption, and can improve reaction efficiency and product selectivity. By changing the reaction conditions and assisting with Bayesian optimization, the best process conditions can be quickly found. Under the best process conditions, TCPD can be efficiently synthesized under batch and continuous conditions.

[0023] For programmable dynamic heating technology, a direct electric heating test experimental platform is used, which includes a raw material delivery system, a computer data acquisition system and a tubular reaction system. The operation method is simple and can be used for both batch production for exploratory experiments and continuous production for large-scale preparation. Its application prospects in industry are becoming more and more extensive.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention aims to propose a programmable temperature-controlled dynamic electric heating method and a corresponding device, assisted by Bayesian optimization, to achieve efficient directional continuous synthesis, such as the synthesis of cyclopentadiene trimer. The present invention first builds a programmable temperature-controlled dynamic heating platform, and controls the heating / cooling by controlling the on / off of a DC power supply; the rapid switching between high temperature and low temperature is achieved by changing the voltage, current size and other conditions, and the reaction network is effectively adjusted by optimizing the "temperature-time" curve, thereby promoting the production of the target product cyclopentadiene trimer. Further, the method for optimizing the reaction conditions of the present invention determines the working conditions of dynamic heating (reaction temperature amplitude, reaction pressure, heating rate, etc.) to accurately match the target reaction network (matching the time scale of rapid generation and directional consumption of cyclopentadiene), and achieves the highest reactant conversion rate, target product selectivity and target product space-time yield. At the same time, the optimization method can achieve global optimization based on as little experimental data as possible, greatly reducing the workload of the experiment. In addition, the reactor of the present invention can react in different ways: it can react intermittently or continuously, and it is flexible and adjustable.

[0026] Specific:

[0027] (1) A method for controlling the reaction temperature over time by programmable dynamic electric heating. A programmed temperature timing control process is implemented in an electric heating tubular reactor. By adjusting the current of the DC power supply, the reaction system can be heated or cooled in a timely and rapid manner, and can also be switched between high and low temperatures appropriately. The heating and cooling rates of the programmable temperature control dynamic heating method are both adjustable.

[0028] (2) A method for regulating the DCPD depolymerization-polymerization reaction network by a programmable temperature-time mode. The present invention applies programmable temperature-controlled dynamic electric heating technology to the DCPD synthesis TCPD reaction. By controlling the heating rate, constant temperature time and cooling rate, the change of the reaction system temperature over time is programmable to match the time scale of the generation and appropriate consumption of key intermediates, thereby effectively regulating the kinetic and thermodynamic state of the reaction network.

[0029] (3) The efficient synthesis of cyclopentadiene trimer by programmable temperature-controlled electric heating can be performed both intermittently and continuously. Cyclopentadiene trimer can be efficiently synthesized by programmable temperature-controlled dynamic electric heating in intermittent and continuous flow reactors. The optimal time-temperature pattern of the efficient DCPD depolymerization-polymerization reaction network is determined by Bayesian optimization to achieve efficient and continuous production of cyclopentadiene trimer. By controlling the heating rate, constant temperature time and cooling rate, the change of the reaction system temperature over time is programmable to match the time scale of the generation and appropriate consumption of the key intermediate CPD, thereby effectively regulating the kinetic and thermodynamic state of the reaction network. This process can achieve high DCPD conversion, high selectivity for cyclopentadiene trimer and high space-time yield without the use of any catalyst.

[0030] 2. The present invention is different from the patents US3701812A, CN109867584A and CN101215217A mentioned in the background technology in that:

[0031] (1) Different heating methods. Patents US3701812A, CN109867584A and CN101215217A all use a constant heating method, while this article uses programmable temperature control dynamic heating, and the reaction is carried out in a variable temperature manner.

[0032] (2) Different reaction times. Patents CN109867584A and CN101215217A both use a long-term heating method, and the reaction time is longer than 4 hours. The dynamic continuous flow reaction used in this article can control the reaction time to about 10 minutes, greatly reducing time costs and energy consumption, and also significantly improving the reactant conversion rate and product selectivity.

[0033] (3) No need to add catalyst. Patent CN101215217A requires the addition of catalyst to promote the formation of cyclopentadiene trimer. However, the programmable temperature-controlled dynamic electric heating method used in this paper can reduce the average temperature of the reaction without using a catalyst, thereby reducing energy consumption.

[0034] The present invention aims to provide an experimental device, experimental method and optimization method of programmable temperature-controlled dynamic electric heating, which can improve the efficiency and reduce the energy consumption by improving the reaction conditions, and can be used in the efficient synthesis of cyclopentadiene trimer.

[0035] 3. The present invention has developed a programmable temperature-controlled dynamic electric heating technology to achieve dynamic adjustment of the reaction temperature curve to improve the synthesis efficiency of TCPD. Compared with the conventional constant temperature continuous heating steady-state method, the programmable temperature-controlled dynamic heating method achieves instantaneous control of temperature. By adjusting the current and voltage in the electric heating system, the reaction system can be quickly switched between low temperature and high temperature. The experimental method of programmable temperature-controlled dynamic heating of the present invention can accurately control the "temperature-time" curve, thereby controllably adjusting the complex reaction network of "depolymerization-polymerization", thereby achieving the synthesis of the target product with low energy consumption and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the structure of the electrically heated tubular reactor device customized for the present invention.

[0037] Figure 2 This is the reaction temperature curve of Comparative Example 2.

[0038] Figure 3 This is the reaction temperature curve of Example 3. DETAILED DESCRIPTION

[0039] The present invention is further described below by way of examples, which are not limited to the examples. Experimental methods without specific conditions specified in the examples are generally carried out under conventional conditions and conditions described in the manual, or under conditions recommended by the manufacturer. The general equipment, materials, reagents, etc. used are all commercially available unless otherwise specified.

[0040] In this embodiment, a K-type thermocouple is placed at the outlet of the reaction tube of the electrically heated tubular reactor to measure the temperature of the solution, which is set as the reaction temperature; 5 thermocouples are welded on the outer wall of the reaction tube to monitor the wall temperature of the reactor; and the system pressure is regulated by a back pressure valve.

[0041] Comparative Example 1: (Constant Temperature Electric Heating Reaction)

[0042] a. Before the experiment, a DCPD solution with a concentration of 75 wt% was prepared using toluene as the solution. The raw material was pumped into the reaction tube (SUS316, When the tube is filled with liquid, adjust the system pressure through the back pressure valve. When the system pressure is stable at 2MPa, close the needle valves on both sides to make the liquid in the tubular reactor static.

[0043] b. The heating power supply used is a DC regulated power supply, which can effectively provide heat to the reaction tube through resistance heating and computer control. The upper and lower ends of the reaction tube are clamped by copper blocks (5cm×5cm×2cm) on the outer wall respectively. The temperature of the liquid in the tube is measured by a K-type thermocouple wire. The specific device is as follows: Figure 1 As shown, turn on the DC power supply, when the reaction temperature rises to 250°C and maintains for 2 hours, wrap the reaction tube with insulation cotton to prevent heat loss. After 2 hours, stop heating, remove the insulation cotton for rapid cooling, and take out the product for chromatographic analysis, which is recorded as Scheme A.

[0044] Comparative Example 2:

[0045] Compared with Comparative Example 1, when the system pressure is stable, the needle valves on both sides of the reaction tube are not closed, and the cyclopentadiene trimer is continuously synthesized. The flow rate of the pump is adjusted to 0.8 ml / min, that is, the residence time is 10.6 min, and the other conditions remain unchanged, which is recorded as Scheme B. The reaction temperature curve of Comparative Example 2 is shown in FIG. Figure 2 shown.

[0046] Example 1: (Batch synthesis of cyclopentadiene trimer by programmable temperature control dynamic electric heating)

[0047] By adjusting the voltage and current, the conditions in step a were changed to a maximum temperature of 250°C, a minimum temperature of 135°C, a heating time of 31s, and a cooling time of 30s. The process was repeated and the reaction lasted for 2h. The other preparation processes were the same as those in comparative example 1, and were recorded as scheme C.

[0048] Embodiment 2:

[0049] Except that the reaction time was changed to 1.5 h, the other processes were the same as those in Example 1, which is recorded as Scheme D.

[0050] Example 3: (Continuous Synthesis of Cyclopentadiene Trimer by Programmable Temperature Control Dynamic Electric Heating)

[0051] The reaction pressure was stabilized at 2MPa, the maximum temperature was 250°C, the minimum temperature was set to 135°C, the heating time was 31s, the cooling time was 30s, and the residence time was set to 10.6min, which was recorded as Scheme E. Compared with Example 1, the reactor was changed from intermittent to continuous. The reaction temperature curve of Example 3 is shown in FIG. Figure 3 shown.

[0052] Embodiment 4:

[0053] The maximum temperature of dynamic heating was adjusted to 200° C., and the flow rate of the pump was adjusted to 5 ml / min, that is, the residence time was 1.6 min. The remaining steps were consistent with Example 3, which is recorded as Scheme F.

[0054] Embodiment 5:

[0055] The flow rate of the pump was adjusted to 4 ml / min, i.e. the residence time was 2.2 min. The remaining steps were the same as those in Example 4. Remember Scheme G.

[0056] Embodiment 6:

[0057] The flow rate of the pump was adjusted to 2 ml / min, that is, the residence time was 4.2 min, and the remaining steps were consistent with Example 4, recorded as Scheme H.

[0058] Embodiment 7:

[0059] Except that the flow rate of the pump is adjusted to 1 ml / min, that is, the residence time is 8.5 min, the remaining steps are consistent with Example 4, which is recorded as Scheme I.

[0060] Embodiment 8:

[0061] Compared with Example 4, the flow rate of the pump is adjusted to 0.7 ml / min, that is, the residence time is 12.1 min, and the other steps remain unchanged, which is recorded as Scheme J.

[0062] Embodiment 9:

[0063] Compared with Example 4, the flow rate of the pump is adjusted to 0.5 ml / min, that is, the residence time is 17.0 min, and the other steps remain unchanged, which is recorded as Scheme K.

[0064] Embodiment 10:

[0065] Compared with Example 3, the minimum temperature is adjusted to 100°C, the maximum temperature is adjusted to 300°C, and the other conditions remain unchanged, which is recorded as Scheme M.

[0066] Embodiment 11:

[0067] Except that the minimum temperature is adjusted to 140°C and the maximum temperature is adjusted to 180°C, the other conditions are the same as those in Example 3, which is recorded as Scheme N.

[0068] Embodiment 12:

[0069] Except that the maximum temperature is adjusted to 180°C, the remaining steps are the same as those in Example 3, which is recorded as Scheme O.

[0070] Embodiment 13:

[0071] The maximum temperature was adjusted to 200°C, and the remaining steps were the same as those in Example 3, which is referred to as Scheme P.

[0072] Embodiment 14:

[0073] Compared with Example 3, the maximum temperature of dynamic heating is adjusted to 300° C., and the other conditions remain unchanged, which is recorded as Scheme Q.

[0074] Embodiment 15:

[0075] Except that the heating time is adjusted to 7 s, the other conditions are the same as those in Example 3, which is recorded as Scheme R.

[0076] Embodiment 16:

[0077] Compared with Example 3, the heating time was adjusted to 161 s, and the other conditions remained unchanged, which is recorded as Scheme S.

[0078] Embodiment 17:

[0079] The heating time was adjusted to 255 s, and the other conditions were the same as those in Example 3, which was recorded as Scheme T.

[0080] Example 18: (Dynamic continuous synthesis of cyclopentadiene trimer optimization reaction)

[0081] The heating time was adjusted to 90 s, the maximum temperature of dynamic heating was adjusted to 249° C., and the other processes were the same as those in Example 3, which is recorded as Scheme U.

[0082] Example 19: Compared with Example 10, the heating time is adjusted to 65s, and the other conditions remain unchanged, which is recorded as Scheme V.

[0083] The experimental conditions of the above embodiments and comparative examples were substituted into the actual reaction, and the reaction results were detected by gas chromatography (listed in Tables 1 and 2). The results in Table 1 show that the yield of TCPD obtained by the dynamic heating method in the intermittent reaction is slightly higher than that obtained by the constant temperature heating method. Converting the intermittent reaction to a continuous reaction, the dynamic heating method of programmable temperature-controlled electric heating can efficiently and continuously produce TCPD. This process can achieve high DCPD conversion rate and high selectivity for TCPD without using any catalyst. The yield of TCPD in the continuous flow reaction using programmable temperature-controlled electric heating reached 66.39% (Scheme V), while the traditional continuous heating method was only 32.84% (Scheme B). At the same time, the space-time yield of TCPD obtained by optimizing the programmable temperature-controlled electric heating (Schemes U and V) is also greatly improved compared to the traditional constant temperature heating method (the results are shown in Table 2).

[0084] Table 1 Batch reaction results

[0085]

[0086]

[0087] Table 2 Continuous reaction results

[0088]

[0089]

[0090] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A method for realizing efficient directional synthesis based on programmable temperature control dynamic electric heating, characterized in that: It includes the following steps: (1) Construction of a programmable temperature-controlled electric heating platform: including a raw material delivery system, a computer data acquisition and control system, and an electric heating tubular reactor; (2) Controlling the temperature rise / fall of the reaction by controlling the on / off of the DC power supply; adjusting the temperature rise rate of the reaction by adjusting the voltage and current output by the DC power supply; collecting and monitoring data through a data acquisition system; (3) Explore the impact of different process conditions on the experimental scheme, use Bayesian optimization to assist the experiment, use the optimized experimental conditions to carry out experimental verification, compare and analyze the experimental results obtained each time, obtain the optimal reaction conditions, and achieve efficient directional synthesis.

2. The method according to claim 1, characterized in that In step (1), a K-type thermocouple is placed at the outlet of the reaction tube of the electrically heated tubular reactor to measure the temperature of the solution, which is set as the reaction temperature; 3-10 thermocouples were welded on the outer wall of the reaction tube to monitor the wall temperature of the reactor; The system pressure is regulated by a back pressure valve.

3. The method according to claim 1, characterized in that In step (3), different process conditions include reaction pressure, maximum reaction temperature, heating rate, and residence time.

4. Use of the method according to any one of claims 1 to 3 for synthesizing cyclopentadiene trimer.

Images