Process for preparing alkylene oxide addition products

Abstract

Disclosed is a method for preparing an alkylene oxide addition product, the method comprising: (i) purging a tank reactor with an inert gas to displace any oxygen; (ii) charging the tank reactor with a starting compound capable of undergoing an alkylene oxide addition or insertion reaction; (iii) feeding an alkylene oxide into the tank reactor; (iv) determining: a flow-limited feed rate r1 that is a function of the total amount of alkylene oxide that has been fed; a cooling-rate-limited feed rate r2 that is a function of the utilization of the cooling capacity; and a feed rate r3 limited by the accumulation of unreacted alkylene oxide that is a function of whether an out-of-control pressure is approaching or exceeds a maximum allowable operating pressure of the reactor and / or whether an out-of-control temperature is approaching or exceeds a maximum allowable operating temperature of the reactor or a start temperature of a secondary decomposition reaction, whichever is lower; (v) determining the minimum of r1, r2, and r3, r min ; and (vi) controlling the feed rate of the alkylene oxide to be r min .

Description

[0001] Addition products of epoxides to alcohols, amines, acids or esters are important industrial products with a variety of uses, especially as nonionic surfactants.

[0002] Alkoxylation is typically carried out semi-batch at temperatures between 80°C and 200°C in, for example, a stirred autoclave or a circulating reactor. Alternatively, the liquid reaction mixture can be dispersed into a gas phase containing the alkylene oxide. Typically, a compound with a nucleophilic site (e.g., an alcohol, carboxylic acid, ester, or amine) is first charged with a catalyst, and then the desired amount of alkylene oxide is added, which typically establishes a pressure up to 20 bar (depending on temperature). Suitable catalysts are basic compounds, such as alkali metal alkoxides or Lewis acids.

[0003] For safety reasons, due to the flammability of alkyl oxidants, this method is typically carried out in an inert atmosphere (such as nitrogen or another inert gas). Preferably, the partial pressure of the alkyl oxidant reactants is limited by dilution with an inert gas, ensuring that the gaseous concentration is below the lower limit of the alkyl oxidant's decomposition. This ensures safety and prevents explosive polyaddition of highly reactive alkyl oxidants (such as ethylene oxide).

[0004] Similarly, the rate of addition of alkyl epoxides is limited so that even in the event of a runaway reaction, the reactor pressure and temperature remain within the reactor's design limits and below the initiation temperature of the secondary decomposition reaction. This means that a large safety margin must be employed when the reaction progress within the reactor is unknown.

[0005] However, diluting the alkyl oxidant reactants with an inert gas and using a slow feed rate will reduce the partial pressure of alkyl oxidants in the gas phase, thus lowering the equilibrium concentration of alkyl oxidants in the liquid phase. The low concentration of alkyl oxidants in the liquid phase further slows down the reaction rate.

[0006] US 2009 / 326283 discloses a method for producing an alkylene oxide addition product, the method comprising: (i) charging a stirred reactor with a starting compound and a dilution gas, wherein a portion of the alkylene oxide reacts with the starting compound in a liquid phase and the remaining alkylene oxide forms a gas phase together with the dilution gas; (ii) continuously extracting the liquid phase from the bottom of the reactor and recirculating it to the top of the reactor via a Venturi nozzle; and (iii) metering the gas phase containing the alkylene oxide into the Venturi nozzle via a vacuum line.

[0007] US 2012 / 0035381 discloses a method for preparing polyether alcohols, wherein an epoxide is introduced into a reactor in such a way that the concentration of unreacted epoxide in the liquid reaction mixture in the reactor is increased as much as possible with increasing degree of addition of the epoxide to the initiator, provided that the temperature at which the runaway reaction ends is at least 100 K lower than the initiation temperature of the decomposition reaction of the liquid reaction mixture at any time point.

[0008] This invention relates to a method for controlling the addition reaction of alkyl oxidoxides. The invention seeks to provide a method for preparing alkyl oxidoxide addition products that can be safely carried out at a high reaction rate within a short timeframe.

[0009] This invention relates to a method for preparing alkylene oxide addition products, the method comprising:

[0010] (i) Purge the batch reactor with an inert gas to replace any oxygen;

[0011] (ii) Introduce a starting compound capable of undergoing alkylene oxide addition or insertion reaction into a batch reactor;

[0012] (iii) Feeding the epoxide into a batch reactor;

[0013] (iv) Determine:

[0014] - The feed rate r1 is limited by the flow rate and is a function of the total amount of epoxides fed.

[0015] - The feed rate r2 is limited by the cooling rate and is a function of the utilization rate of the cooling capacity; and

[0016] - The feed rate r3 is limited by the accumulation of unreacted epoxides, which is a function of: whether the runaway pressure is close to or exceeds the reactor’s maximum permissible operating pressure, and / or whether the runaway temperature is close to or exceeds the reactor’s maximum permissible operating temperature or the initiation temperature of the secondary decomposition reaction (whichever is lower), wherein the runaway temperature and runaway pressure are the temperature and pressure generated under the condition that the accumulated amount of unreacted epoxides undergoes a spontaneous adiabatic runaway reaction;

[0017] (v) Determine the minimum value of r1, r2, and r3. min ;as well as

[0018] (vi) Control the feed rate of the epoxide to r min .

[0019] This invention is based on the insight that several constraints typically need to be considered to ensure the success of alkylene oxide addition reactions. These constraints are embodied in feed rates r1, r2, and r3. The calculated feed rates are input into a minimum selector, and the minimum feed rate r is selected.min (It determines the current maximum permissible alkylene oxide feed rate) and is fed as a setpoint to the flow controller. Feed rates r1, r2, and r3 can be reported as mass flow rate or as a percentage of the maximum flow rate. A minimum percentage value specifies the limit. This minimum percentage is used to set the flow rate in the central flow controller, or the valve opening can be specified directly.

[0020] Runaway reactions can occur for various reasons. If insufficient or complete cooling failure occurs during alkylene oxide addition, the heat released by the unreacted alkylene oxide in the reactor through the exothermic reaction will cause an increase in reactor pressure and temperature. The increased temperature will lead to a faster reaction rate, which in turn will generate more heat and even higher temperatures. The resulting runaway reaction is almost entirely adiabatic because the increase in temperature and pressure can no longer be limited by cooling.

[0021] While the concentration of unreacted epoxides constitutes the driving force for the addition of epoxides to the continuously growing epoxide chains in the addition product, excessive accumulation of unreacted epoxides must be avoided. The spontaneous polyaddition reaction of unreacted epoxides can lead to runaway reactions that can no longer be controlled by existing cooling capabilities.

[0022] During a runaway reaction, a critical condition will not occur as long as the reactor's design conditions or the initiation temperature of any secondary reactions are not reached. However, if these conditions are exceeded, the reactor may be damaged or even destroyed. In the worst-case scenario, secondary reactions may occur when sufficiently high temperatures are reached, reaching levels that could cause a thermal explosion that could break the reactor apart. Due to the significant potential hazards to personnel, the plant, and the environment, these situations must be reliably prevented.

[0023] Flow-limited feed rate r1

[0024] In this method, starting materials (primarily starting compounds capable of undergoing epoxide addition or insertion reactions) are introduced into a batch reactor in a pre-defined stoichiometric amount, feeding the batch reactor with epoxides. A flow-limited feed rate r1 is a function of the total amount of epoxides fed. It constitutes a feed rate limitation specific to the formulation and / or reactor.

[0025] The relationship between the maximum permissible feed rate and the total amount of epoxide fed is typically based on experience collected from previous batches. The flow-limited feed rate r1 can also account for limitations imposed by reactor design or the reactor periphery, such as maximum permissible flow rates and other safety limits. The first set of flow rate profiles can be calculated in advance using simulation tools.

[0026] This relationship can be depicted as an alkylene oxide feed curve, which is a function of the maximum permissible feed rate relative to the total amount of alkylene oxide fed, from which the feed rate r1 can be obtained. This flow curve will be implemented with separate coordinates (x, y), where the x-value represents the total amount of alkylene oxide added and the y-value represents the maximum permissible feed rate.

[0027] In one embodiment, the flow-limited feed rate r1 is based on a computer memory that stores the alkylene oxide feed profiles as discussed above.

[0028] The feed rate r1 is conceived as a limiting factor, particularly during start-up and in the early stages of the reaction when conversion is low. This is due to the fact that only a small amount of enthalpy is released at this stage of the process, resulting in low utilization of cooling capacity. Furthermore, the low amount of alkylene oxide poses no hazard even under the assumption of spontaneous adiabatic runaway. This initial limitation on the maximum alkylene oxide feed rate prevents excessively rapid addition in the early stages of the alkylene oxide addition step, which could lead to instability in process conditions, for example, due to a small heat exchange area in the reactor due to a low liquid level. At the end of the batch, the maximum feed rate is typically determined by r2 or r3. By using this method, the alkylene oxide feed rate can be maximized while operating within safe limits.

[0029] In one embodiment, the feed rate r1 is determined according to the following equation:

[0030]

[0031] Where a1 [kg / h] is the feed rate, b1 [1 / h] is the slope, and m oxide This refers to the amount of epoxide already fed [kg]. Once the intended total amount of epoxide has been fed, the feed rate r1 is reduced to 0 kg / h. The feed rate a1 is not particularly limited and depends on the intended reactor size and process. The feed rate a1 can range from 1 to 20,000 kg / h, such as 10 to 15,000 kg / h, or for example, 500 to 5,000 kg / h. The slope b1 can range from 0.0 to 2.0 / h (h -1 ), more preferably 0.3 to 0.7 h -1 Within the range, such as 0.5 h -1 .

[0032] The feed rate r1 can be adjusted based on the amount of epoxide already fed, m. oxide However, this can change. For example, assuming the total amount of epoxide is 3,000 kg, the feed rate can be gradually increased according to the above equation until m... oxideThis corresponds to 1,000 kg, and then remains constant. Therefore, in another embodiment, for 0 kg < m oxide ≤ (y m oxide_total The range of feed rate r1 is determined by the following equation:

[0033]

[0034] Where y m oxide_total [kg] represents the total amount of epoxide to be fed into the reactor. oxide_total A portion of the equation, where y has values ​​of 0 < y < 1, such as 0.1 < y < 0.7, a1 [kg / h] is the feed rate, b1 [1 / h] is the slope, and m oxide This refers to the amount of epoxide already fed in [kg]. This portion y m oxide_total Typically, the total amount of epoxide to be fed into the reactor is m oxide_total The feed rate is between 10 wt.% and 70 wt.% or between 25 wt.% and 50 wt.%. The feed rate a1 and slope b1 are as defined above.

[0035] In (y m oxide_total ) < m oxide ≤ m oxide_total Within the specified range, the feed rate r1 is determined according to the following equation:

[0036] r1 = c1

[0037] Where c1 [kg / h] is the constant feed rate. The feed rate c1 is not particularly limited, but appropriately corresponds to when m oxide = (y m oxide_total The value of r1 obtained from the above equation is given.

[0038] Once the envisioned total amount of epoxide has been fed... oxide_total The feed rate r1 then drops to 0 kg / h.

[0039] In one embodiment, the feed rate r1 is determined by one or more analytical equations according to any one of the two embodiments described above, and the minimum value r of r1, r2, and r3 is taken as the minimum value r. min Used as a setting value for the flow controller.

[0040] In another embodiment, the feed rate r1 constitutes the setpoint of the flow controller, particularly the PID controller. This controller attempts to maximize the flow rate of the epoxide. In this case, the setpoint SP... r1 This corresponds to r1 in the equation above.

[0041] Feed rate r2 limited by cooling rate

[0042] Alkoxylation is an exothermic reaction, thus generating heat during the reaction. Therefore, alkoxylation reactors are equipped with cooling devices such as half-jacketed structures, internal coils, and / or external heat exchangers. Continuous cooling is necessary to maintain the desired reaction temperature during the alkylene oxide addition process. Cooling capacity is particularly important for the addition of ethylene oxide and propylene oxide due to their high enthalpy of reaction.

[0043] At the start of the reaction, due to the low liquid level in the reactor, heat exchange in reactors without external circulation is often affected by the small heat exchange area. During the reaction, although the effective heat exchange area increases, the product viscosity may also gradually increase, negatively impacting the heat transfer coefficient. Since all these factors affecting heat balance occur simultaneously and are product- and reactor-specific, an automated controller is needed to adapt the alkyl oxidoxide feed rate (heat generation) to the reactor's actual heat removal capacity. This automated control ensures that the reactor's full cooling capacity is always utilized, even taking into account changing climatic conditions (e.g., the contrast between winter and summer). This allows for minimizing the alkyl oxidoxide feed time during phases when cooling capacity is not fully utilized.

[0044] When the heat generation exceeds the cooling capacity, even if the coolant flow rate is maximized and the coolant inlet temperature is kept as low as possible, the target reactor temperature cannot be maintained and the temperature will rise.

[0045] The purpose of the feed rate r2 is to reduce the alkylene oxide feed rate once the full cooling capacity is reached or exceeded, in order to maintain stable temperature control in the reactor. As long as the cooling capacity is not fully utilized, the feed rate r2 does not limit the alkylene oxide feed rate.

[0046] Remaining cooling capacity can be determined in various ways, for example, by at least one of the following parameters:

[0047] - Coolant inlet flow temperature;

[0048] - The difference between the current reactor temperature and the predetermined reactor temperature;

[0049] - Coolant flow rate;

[0050] - The opening degree of the coolant flow valve;

[0051] - The difference between the current reactor temperature and the coolant inlet temperature;

[0052] - The temperature difference between the coolant inlet flow and the coolant return flow; and

[0053] - Thermal balance between coolant inlet flow and coolant return flow.

[0054] Logical combinations of two or more of the above parameters are also envisioned, such as the opening degree of the coolant flow valve and the difference between the current reactor temperature and the predetermined reactor temperature; or the coolant flow rate and the difference between the current reactor temperature and the predetermined reactor temperature.

[0055] In one embodiment, the feed rate r2 is determined according to the following equation:

[0056]

[0057] Where a R It is the specific heat transfer area per unit volume of liquid reactor [m²] 2 / m 3 F is a measure of the reactor's heat transfer capacity [kg (epoxide) / (m³)]. 2 s)], and V R (m oxide ) is the volume of the liquid reaction component [m 3 The equation applies under the assumption that the specific cooling surface area inside the reactor is approximately constant and the heat transfer resistance does not change significantly.

[0058] For example, F can be calculated as follows:

[0059]

[0060] Where T R The desired reactor temperature [°C], T cool,min α is the lowest temperature of the cooling device [°C], and α is the heat transfer coefficient [kW / m]. 2 K], and ΔH R, AO It is the specific heat of reaction [kJ / kg].

[0061] Specifically, the feed rate r2 can be determined by the above analytical equation, and the minimum value r of r1, r2, and r3 can be obtained. min Used as a setting value for the flow controller.

[0062] In another embodiment, the feed rate r2 constitutes the setpoint for the flow controller, particularly the PID controller. This controller attempts to exceed the setpoint SP for the reactor's internal temperature. TRThe excess amount is the allowable amount ΔT, such as 3K. In one embodiment, the set value SP is... r2 (That is, the feed rate r2 at a specific time point during this process) is calculated as follows:

[0063]

[0064] If the cooling limit is active, i.e., r2 = r min The offsets of r1 and r2 ensure that cooling control is maximized (cooling valves are fully open), and the oxide flow rate is so high that the reactor internal temperature is maximized within the permissible operating window. The oxide flow rate effectively regulates the reactor internal temperature while the cooling valves are fully open.

[0065] Feed rate r3 limited by the accumulation of unreacted epoxides

[0066] The purpose of the feed rate r3 is to identify potential conditions that could lead to exceeding permissible operating pressures or temperatures before risks occur. The feed rate r3, limited by the accumulation of unreacted epoxides, is a function of whether the runaway pressure is close to or exceeds the reactor's maximum permissible operating pressure, and / or whether the runaway temperature is close to or exceeds the reactor's maximum permissible operating temperature or the initiation temperature of the secondary decomposition reaction (whichever is lower). Runaway pressure and runaway temperature are the temperatures and pressures resulting from a spontaneous adiabatic runaway reaction of accumulated unreacted epoxides.

[0067] In one embodiment, the maximum permissible accumulation of unreacted epoxides throughout the process can be pre-calculated by setting specific boundary conditions. These boundary conditions include a minimum reaction temperature and a minimum initial dosage, and may include inertization conditions for the batch reactor. During the reaction, control parameters related to the amount of unreacted epoxides are measured. A preferred control parameter is the current reactor pressure. The vapor pressure of the epoxides contributes to the total pressure in the batch reactor (provided the minimum temperature is sufficiently high). Therefore, the current reactor pressure is considered a representative indicator of epoxide accumulation.

[0068] Therefore, determining the feed rate r3, which is limited by the accumulation of unreacted alkylene oxides, may include establishing a predetermined cut-off pressure and comparing the current reactor pressure with that predetermined cut-off pressure. When the current reactor pressure approaches or exceeds the predetermined cut-off pressure, r3 is reduced or set to zero.

[0069] The predetermined cutoff pressure can be a fixed cutoff pressure independent of the reaction process. However, the predetermined cutoff pressure is preferably a function of the total amount of alkylene oxide fed. As alkylene oxide is fed into the reactor, the volume of the liquid phase increases, thereby compressing the gas phase and causing an increase in the partial pressure of the inert gas. With the same permissible partial pressure of unreacted alkylene oxide, the reactor pressure is higher. Therefore, the predetermined cutoff pressure will increase with the total amount of alkylene oxide fed.

[0070] Comparing the calculated runaway pressure and temperature with the reactor's design limits provides information about remaining safety margins. These margins can be used to optimize operation, such as increasing the feed rate or raising the reaction temperature. Continuously calculating the runaway pressure and temperature throughout the reaction process allows for timely and safe termination of the reaction, especially before the actual runaway becomes detectable.

[0071] The feed rate r3 depends on the concentration of unreacted alkylene oxide in the reactor determined during the reaction process. The amount of unreacted alkylene oxide in the reactor is a critical quantity when modeling the alkoxylation reaction. The amount of unreacted alkylene oxide is related to the reaction rate and therefore to process optimization. At the same time, it is a critical quantity from a process safety perspective and should be limited.

[0072] The concentration of epoxides can be determined directly or indirectly.

[0073] In one embodiment, the amount of unreacted epoxides in the reactor is determined by online spectrometry or online calorimetry.

[0074] An indirect method for determining the concentration of unreacted alkyl oxides has been found to be simple and widely applicable: measuring the pressure in the reactor. If the alkyl oxide is fed at a rate faster than its reaction rate, the accumulated unreacted oxides lead to an increase in the partial pressure of the alkyl oxide, resulting in an increase in the total reactor pressure. Therefore, the concentration of unreacted alkyl oxides can be calculated when the solubility coefficient of the alkyl oxide in the reaction mixture is known and the compressive pressure of the inert gas (such as nitrogen) has been calculated. As alkyl oxides are fed into the reactor, the volume of the liquid phase increases, thereby compressing the gas phase and causing an increase in the partial pressure of the inert gas. As a result, some of the inert gas in the gas phase dissolves into the liquid phase.

[0075] Therefore, in the embodiments, the amount of unreacted epoxide in the reactor was determined by a thermodynamic model based on the following...

[0076] - The total amount of epoxy alkyl already fed in,

[0077] - Current reactor pressure and current reactor temperature, and

[0078] - Amount of starting compound.

[0079] Knowing the amount of accumulated unreacted oxides, the temperature and pressure resulting from a spontaneous adiabatic runaway reaction can be calculated based on a thermodynamic model. The calculated runaway temperature and pressure can then be compared with the reactor's design limits and / or with the onset temperature of the secondary decomposition reaction. The reactor's design limits for temperature and pressure should be understood as the highest permissible operating temperature and maximum permissible operating pressure for a batch reactor. The highest permissible operating temperature and maximum permissible operating pressure should be understood as the highest temperature and maximum pressure that may occur without damaging the batch reactor.

[0080] In some cases, at a given point, the initial temperature of the secondary decomposition reaction of the liquid mixture in a batch reactor may be below the vessel's maximum permissible operating temperature. Exceeding this initial temperature results in an exothermic decomposition reaction that cannot be stopped by the vessel's remaining cooling capacity in the event of a loss of energy supply. In such cases, the temperature following the adiabatic runaway of the alkoxylation reaction is limited to below this initial temperature.

[0081] The secondary decomposition reaction occurs because the starting compound or its alkoxylated product may undergo a highly exothermic decomposition reaction upon reaching the initiation temperature. The initiation temperature of the decomposition reaction of the alkoxylated product depends on the degree of addition of the alkyl oxide to the starting compound.

[0082] Similarly, when sufficient pressure cannot be released during and after a runaway reaction, the pressure generated during or after the runaway reaction can be limited to below the maximum permissible operating pressure of the batch reactor or the safety valve protecting the batch reactor. Insufficient pressure release may occur because the volume of gas generated during the runaway reaction is too large to be discharged through a reasonably sized safety valve, or because of the risk of releasing toxic or other hazardous substances from the reactor during pressure release.

[0083] In the thermodynamic model, the amount of unreacted, accumulated epoxide, n A This defines the energy potential that might be released under runaway conditions. During this runaway, the process temperature increases with the oxide conversion ξ and can be described as...

[0084]

[0085] in

[0086] Δh R Indicates enthalpy of reaction

[0087] c p Indicates the heat capacity of the reactor contents

[0088] alkoxylation degree θ

[0089] Here, θ is also a function of the conversion rate ξ, θ = θ(ξ).

[0090] Due to its high reactivity, runaway occurs on a short timescale and is modeled as adiabatic. The highest temperature occurs at the end of the runaway (when the free oxide is completely converted, ξ = 1), therefore

[0091]

[0092] Not only does the temperature increase during the runaway, but the pressure also increases. In the early stages of the runaway, the pressure increases due to the rise in temperature. As the consumption (conversion) of free epoxides increases during the runaway, the pressure decreases again. Therefore, the maximum pressure does not occur at the end of the runaway, but rather during the runaway at the conversion rate ξ. + When, it can be calculated as

[0093]

[0094] To limit the computational workload, runaway temperature and pressure can be calculated by simulating the alkyl oxidase present in the reactor as a stepwise reaction over k steps. After each step, the temperature rise ΔT in the reactor originates from the heat generated (enthalpy of reaction), resulting in a new intermediate temperature. After each virtual reaction that removes a portion Δn, the amount of alkyl oxidase remaining in the reactor and the amount of products formed through that reaction are recalculated.

[0095] A suitable equation for determining the feed rate r3 should describe the safe acceleration rate of the alkyl oxidoxide during the reaction. This can be reliably determined experimentally using reaction calorimetry and scaled up to production conditions. Therefore, the equation for r3 can be obtained from experimental data. For typical systems, a constant accumulation of alkyl oxidoxide is acceptable. Therefore, the permissible acceleration rate increases proportionally with increasing reaction volume. This yields a linear equation. In one embodiment, the feed rate r3 can be determined according to the following equation:

[0096]

[0097] Where R Cal It is the slope of the straight line (corresponding to the increase in the rate of acceleration relative to the amount of alkyl epoxide added), m oxide C is the amount of epoxide added, and C is the permissible rate of addition of epoxide to the starting compound.

[0098] Specifically, the feed rate r3 can be determined by the above analytical equation, and the minimum value r of r1, r2, and r3 can be obtained. min Used as a setting value for the flow controller.

[0099] In another embodiment, the feed rate r3 constitutes the setpoint for the flow controller, particularly the PID controller. This controller adjusts the oxide flow rate towards a specific safety limit. This limit is defined by the maximum concentration of unreacted alkylene oxide. This concentration can be determined indirectly through process variables (e.g., reactor pressure) or via thermal balance calculations of the reaction system.

[0100] The permissible concentration of alkyl oxide (known from system safety-related data) can be converted into a partial pressure by, for example, the gas solubility at reactor temperature, and this partial pressure is superimposed on the compression behavior of the inert gas. This produces a curve that can typically be described by a simple equation, such as one derived from the ideal gas law.

[0101] The compression of an inert gas phase can be described as follows

[0102]

[0103] in

[0104]

[0105]

[0106] Where V0 is the volume of the gas phase at the start of the reaction [m]. 3 ], V m(oxide) It is the volume of the gas phase when a predetermined amount of alkyl epoxide has been fed [m]. 3 ], ρ L It is the density of the liquid phase [kg / m³] 3 ], and m oxide This refers to the amount of epoxide already fed [kg], p i,m(oxide) It is the pressure in the compressed inert gas phase, and p i,0 It is the gas phase pressure at the start of the reaction.

[0107] In the function term describing compression in the reactor, the partial pressure of oxides (p) can now be added to take into account safety and process technology. AO Typically, this can be described using a constant value. This yields a setpoint of 3 (SP). r3 That is, the feed rate r3:

[0108]

[0109] Where p AO This is the permissible partial pressure [bar] of the epoxide, for example, a constant. Therefore, the setpoint of the third controller can be described as a function of the start-up pressure and the reaction process.

[0110] In one embodiment, each of r1, r2, and r3 is determined according to the analytical equations described herein, and the minimum value of r1, r2, and r3 is r. min Used as a setting value for flow controllers.

[0111] In another embodiment, each of r1, r2, and r3 constitutes the setpoint of the flow controller, particularly the PID controller. The minimum output of these three controllers is selected to determine r. min .

[0112] In a preferred embodiment, the method includes

[0113] - Obtain process data, including reactor temperature, reactor pressure, total amount of starting compound before alkyl epoxide addition, and total amount of alkyl epoxide already fed;

[0114] - Based on the embedded model and acquired process data, the prediction method responds to future changes in the feed rate of alkyl epoxides; and

[0115] - When determining r3, consider the predicted future response.

[0116] The acquired process data may further include variables indicating the utilization rate of the cooling capacity.

[0117] The acquired process data can be current process data, data obtained from previous batches, or assumed typical process conditions.

[0118] Appropriately, the feed rate of the alkyl epoxide is controlled to r via a distributed control system (DCS). min The distributed control system includes a controller selected from proportional-integral-derivative (PID) controllers and model predictive controllers, particularly nonlinear model predictive controllers, or combinations thereof.

[0119] The model-based predictive controller must include an appropriate model to allow for predictions about the behavior of the reaction system, reactor, and its peripheral equipment. The following systems should be modeled:

[0120] -Reaction system (kinetics and thermodynamics of the reaction);

[0121] - Thermal balance between reactor and peripheral systems (heat that can be dissipated and dynamic behavior of the system).

[0122] - Safety system (calculation of safety limits for operating conditions);

[0123] - Epoxide supply (considering maximum flow rate, formulation quantity, and possible dependencies on other consumption units).

[0124] The distributed control system includes a host computer coupled to one or more controllers via communication links. The host computer enables end users to configure, monitor, initiate, and terminate control operations of the controlled process by interacting with the controllers. The controllers execute control applications and provide outputs to actuate valves that control the alkylene oxide feed rate.

[0125] The method according to the present invention includes the following steps:

[0126] (i) Purge the batch reactor with an inert gas to replace any oxygen;

[0127] (ii) Introduce a starting compound capable of undergoing alkylene oxide addition or insertion reactions into a batch reactor.

[0128] (iii) Feed the epoxide into the batch reactor.

[0129] Generally, it is essential to ensure thorough mixing of the reactor contents in all reaction phases. This can be achieved using a stirrer, an external circulation system, or a combination of both.

[0130] The reactor preferably includes an agitator, which is preferably suspended freely within the reactor. As another means of increasing mixing intensity, a combination of a batch reactor and an external circulation system can be employed. The liquid reaction mixture is drawn from the bottom of the reactor and reintroduced at the top or below the liquid level via the external circulation system. The external circulation system typically includes a pump and preferably may contain at least one heat exchanger.

[0131] Once the minimum liquid fill level is reached, properly activate the external circulation loop. To do this, open the drain valve at the bottom of the reactor and pump the liquid phase into the circulation loop, then reintroduce it at the top of the reactor.

[0132] The alkyl epoxide addition reaction is highly exothermic. The temperature within the reactor must be maintained at a desired level or regulated to a desired level by cooling. Cooling typically occurs via the reactor wall and / or by means of heat exchanger surfaces built into the reactor and / or external to the pumped circulation, such as cooling coils, cooling cylinders, plate, tube bundle, or mixed heat exchangers. These should be configured so that cooling can also occur effectively at the start of the metering addition phase (i.e., at low fill levels). Internal cooling devices, especially cooling coils, are appropriately positioned close to the reactor wall, particularly to avoid interfering with the movement of the agitator (if present).

[0133] There are no particular limitations on the suitable coolant used for the cooling device, and it includes water, mixtures of water and glycol, and / or oil. Preferably, the coolant is water.

[0134] Heat exchanger devices can also be used to heat the contents of the reactor to the reaction temperature at the start of the reaction.

[0135] The batch reactor is inertized, i.e., purged with an inert gas to replace any oxygen and other gases that may be detrimental to the addition reaction. Preferably, the batch reactor is purged and evacuated several times with an inert gas. This is accomplished by means of devices known to those skilled in the art for this purpose, such as vacuum pumps. Alternating pressure reduction and purging with an inert gas removes air and trace amounts of water. Nitrogen, argon, or carbon dioxide can be used as the inert gas. Nitrogen is preferred because it is readily available and therefore inexpensive. Preferably, oxygen is replaced to less than 3 vol.%, particularly less than 0.3 vol.%.

[0136] Starting compounds capable of undergoing alkyl alkylation addition or insertion reactions are appropriately loaded into the reactor along with a catalyst to form a liquid phase.

[0137] Typical examples of starting compounds capable of undergoing alkylene oxide addition or insertion reactions are alcohols, acids (such as carboxylic acids), esters (such as alkyl carboxylic acid esters or polyol carboxylic acid esters), amines, hydrogen sulfide, and thiols.

[0138] The preferred alcohol is a compound having formula (I).

[0139] R 1 -OH(I)

[0140] Where R 1 It is a straight-chain or branched hydrocarbon group having 1 to 22 carbon atoms, preferably 8 to 18 carbon atoms and 0 or 1 to 3 double bonds. Typical examples include, in addition to lower aliphatic alcohols (methanol, ethanol, and isobutanol and pentanol), fatty alcohols, specifically hexanol, octanol, 2-ethylhexanol, decanol, lauryl alcohol, isotearyl alcohol, myristol, cetyl alcohol, palm oil alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol, transoleyl alcohol, petroselinyl alcohol, linolyl alcohol, linolenyl alcohol, elaeostearyl alcohol, arachidyl alcohol, gadoleyl alcohol, benzyl alcohol, erucyl alcohol, and brassidyl alcohol, as well as their industrial-grade mixtures, which are obtained, for example, by high-pressure hydrogenation of industrial-grade methyl esters based on fats and oils, or aldehydes from the Roelen carbonyl oxidation process, and as monomer fractions in the dimerization reaction of unsaturated fatty alcohols.

[0141] Industrial-grade fatty alcohols with 12 to 18 carbon atoms can be used, such as coconut fatty alcohol, palm fatty alcohol, palm kernel fatty alcohol, or tallow fatty alcohol.

[0142] The preferred acid is a carboxylic acid having formula (II).

[0143] R 2 -COOH(II)

[0144] Where R 2 It is a straight-chain or branched acyl group having 1 to 22 carbon atoms and 0 or 1 to 3 double bonds. Typical examples are, in particular, fatty acids, specifically hexanoic acid, octanoic acid, 2-ethylhexanoic acid, decanoic acid, lauric acid, isotriadecanoic acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, isostearic acid, oleic acid, transoleic acid, petroselic acid, linoleic acid, linolenic acid, elaeostearic acid, arachidic acid, gadooleic acid, benzyl acid, and erucic acid, as well as their industrial-grade mixtures, which are obtained, for example, by pressure cracking of natural fats and oils, reduction of aldehydes from the Roelen carbonyl oxidation process, or dimerization of unsaturated fatty acids.

[0145] Industrial-grade fatty acids with 12 to 18 carbon atoms, such as coconut fatty acids, palm fatty acids, palm kernel fatty acids, or tallow fatty acids, can be used. It should be understood that it is also possible to ethoxylate functionalized carboxylic acids, such as hydroxycarboxylic acids (e.g., ricinoleic acid or citric acid) or dicarboxylic acids (e.g., adipic acid).

[0146] Suitable esters include those obtained using carboxylic acids and alcohols or polyols (especially glycerol, trimethylolpropane, or pentaerythritol) having 1 to 22, and preferably 1 to 4, carbon atoms. When they are full esters, the alkylene oxide group is inserted into the carbonyl ester bond.

[0147] Suitable amines include compounds having formula (III).

[0148] R 3 -NH-R 4 (III)

[0149] Where R 3 and R 4 Each of these is independently hydrogen, an alkyl group having 1 to 18 carbon atoms, a hydroxyalkyl group having 1 to 4 carbon atoms, or an aminoalkyl group having 1 to 6 carbon atoms. Typical examples are methylamine, dimethylamine, ethylamine, diethylamine, methylethylamine, and various propylamines, butylamine, pentamine, and aliphatic amines with similar structures.

[0150] Furthermore, suitable amines include compounds having formula (IV).

[0151] (IV)

[0152] Each R is independently a C2-C6 straight-chain alkylene or a C3-C6 branched alkylene; m is in the range of 0 to 70; n is in the range of 0 to 35; and B indicates the continuation of the structure by branching.

[0153] Typical examples of amines having formula (IV) include (poly)alkylene polyamines (such as hexamethylenediamine, diethylenetriamine and triethylenetetramine) and polyalkylene imides (such as polyethyleneimine).

[0154] Suitable thiols include alkyl thiols (such as ethanethiol, propanethiol, or butanethiol) and alkyl polythiols (such as ethane-1,2-dithiol and propane-1,3-dithiol).

[0155] Typically, the molar ratio between the epoxide and the starting compound can be from 1:1 to 200:1, preferably from 1:1 to 50:1, and especially from 1:1 to 20:1.

[0156] If the starting compound is a liquid, the reaction can proceed in the absence of an external solvent. However, if an external solvent is required or desired, suitable external solvents include aprotic solvents (such as ethers), which are not readily added to alkyl epoxides, as well as protic solvents such as water and lower alcohols (including methanol, ethanol, n-propanol, isopropanol, and tert-butanol) and glycols (including ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol).

[0157] Epoxide addition reactions can be carried out appropriately in the presence of catalysts that can have homogeneous or heterogeneous properties. Suitable homogeneous catalysts include phosphine, such as triarylphosphine, like triphenylphosphine; alkali metals, such as sodium and potassium metals; and alkali metal hydroxides and alkali metal alkoxides, especially sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium tert-butoxide, potassium tert-butoxide, cesium hydroxide, cesium methoxide, and cesium tert-butoxide.

[0158] Suitable heterogeneous catalysts include bimetallic cyanide (DMC) catalysts and layered double hydroxide (LDH) catalysts, such as hydrotalcite, known in the art. DMC and LDH catalysts exhibit very high activity in alkyl epoxide addition reactions and make it possible to prepare, for example, polyether polyols at very low catalyst concentrations (100 ppm or less) under optimal conditions, thus typically eliminating the need to separate the catalyst from the finished product.

[0159] In addition, suitable heterogeneous catalysts include cyanide-free metal salts such as zinc chloride, zinc bromide, zinc iodide, zinc acetate, zinc acetylacetone, zinc benzoate, zinc nitrate, ferric sulfate (II), ferric bromide (II), ferric chloride (II), cobalt chloride (II), cobalt thiocyanate (II), nickel chloride (II), and nickel nitrate (II).

[0160] A mixture of various metal salts can also be used.

[0161] Epoxides can be metered into the reactor via a feed device (particularly a nozzle at the bottom of a batch reactor), through a distribution ring immersed in the liquid, or metered into the reactor's recirculation stream (if present). The feed device can be a liquid feed device or a gas feed device. Typically, the epoxide is liquid before being metered into the reactor and evaporates upon introduction. Stirring energy is introduced into the liquid phase to induce mixing, during which a small amount of the epoxide dissolves in the liquid phase; the remainder forms a gas phase above the liquid with a gas used for inertization.

[0162] The method of the present invention is typically carried out discontinuously. Once sufficient alkyl epoxide addition has been achieved, the reaction product is removed from the reactor.

[0163] The present invention is further illustrated by the following working examples.

[0164] Example 1

[0165] A method for preparing alkyl oxidase addition products is carried out by: purging a batch reactor with an inert gas to replace any oxygen; charging the batch reactor with a starting compound capable of performing alkyl oxidase addition or insertion reactions; and charging the reactor with alkyl oxidase.

[0166] The reactor has a 5 m 3 The free volume. The introduced amount is 1,000 kg, and the density is 1,000 kg / m³. 3 The starting compound (the gas volume in the reactor at the start of the reaction is V0 = 4 m³). 3 3000 kg of alkyl epoxide was added, and the density of the liquid system was constant at ρ. L =1,000 kg / m 3 The final liquid volume was 4,000 kg / 1,000 kg / m³. 3 = 4 m 3 (The gas volume of the reactor is 1 m³) 3 ).

[0167] This batch reactor includes three PID controllers. The feed rates r1, r2, and r3 each constitute the setpoint for one of the flow controllers. The minimum value of r1, r2, and r3 is rmin It is determined from these three settings.

[0168] PID controller 1 is configured to set the maximum allowable flow rate. For 0 kg < m³ / s oxide The range is ≤ 1,000 kg, that is, the initial 1,000 kg of epoxide added, with a set value SP. r1 (Feed rate r1) is calculated as follows:

[0169]

[0170] Where m oxide This is the amount of alkyl epoxide that has been fed. After 1,000 kg / h of alkyl epoxide has been fed, the setpoint SPr1 (i.e., feed rate r1) corresponds to 1,500 kg / h.

[0171] For 1,000 kg < m oxide The range is ≤ 3,000 kg, that is, the remaining 2,000 kg of epoxide is added, with a set value SP. r1 (Feed rate r1) is set as follows:

[0172]

[0173] Therefore, for the remaining 2,000 kg of epoxide, the feed rate r1 remains constant at 1,500 kg / h. Once a total of 3,000 kg of epoxide has been fed, SP r1 The feed rate (r1) then drops to 0 kg / h.

[0174] PID controller 2 is configured to use the reactor's maximum cooling capacity. The controller attempts to exceed the setpoint SP for the reactor's internal temperature. TR The excess is the allowable amount ΔT, which in this case is 3 K. The setpoint SP r2 (That is, the feed rate r2 at a specific time point during this process) is calculated as follows:

[0175]

[0176] The PID controller 3 adjusts the oxide flow rate towards the safety limits. The permissible alkylene oxide concentration (known from the system's safety-related data) can be converted into a partial pressure by, for example, the gas solubility at reactor temperature, and this partial pressure is superimposed on the compression behavior of the inert gas. This produces a curve that can generally be described by a simple equation, such as that derived from the ideal gas law. The compression of the inert gas phase can be described as follows:

[0177]

[0178] in

[0179]

[0180]

[0181] Where V0 is the volume of the gas phase at the start of the reaction [m]. 3 ], V m(oxide) It is the volume of the gas phase when a predetermined amount of alkyl epoxide has been fed [m]. 3 ], ρ L It is the density of the liquid phase [kg / m³] 3 ], and m oxide This refers to the amount of epoxide already fed [kg], p i,m(oxide) It is the pressure in the compressed inert gas phase, and p i,0 It is the gas phase pressure at the start of the reaction.

[0182] In the function term describing compression in the reactor, the partial pressure of oxides (p) can now be added to take into account safety and process technology. AO Here, p AO This can be described by a constant value. This yields the setpoint 3 (SP). r3 That is, the feed rate r3:

[0183]

[0184] Where p AO It is the permissible partial pressure [bar] of the epoxide, which is a constant in this case.

[0185] The minimum value r of r1, r2, and r3 is determined by comparing the units. min Furthermore, the feed rate of the alkyl epoxide is controlled to r via a PID controller. min .

[0186] Example 2

[0187] Perform the same method as described in Example 1, except that each of r1, r2, and r3 is determined according to the following analytical equation, and the minimum value of r1, r2, and r3 is r. min Used as a setting value for the alkylene oxide flow controller.

[0188] For 0 kg < m oxide For the range ≤ 1,000 kg, i.e., the first 1,000 kg of epoxide added, the feed rate r1 is determined according to the following equation:

[0189]

[0190] Where m oxideThis refers to the amount of epoxide already fed. After 1,000 kg / h of epoxide has been fed, the setpoint SPr1 (i.e., feed rate r1) corresponds to 1,500 kg / h. For 1,000 kg < m oxide For the range of ≤ 3,000 kg, i.e., the remaining 2,000 kg of epoxide is added, the feed rate r1 remains constant at 1,500 kg / h. Once the intended total amount of epoxide (i.e., 3,000 kg) has been fed, the feed rate r1 is reduced to 0 kg / h.

[0191] The feed rate r2 is determined according to the following equation:

[0192]

[0193] Where a R It is the specific heat transfer area per unit volume of liquid reactor [m²] 2 / m 3 F is a measure of the reactor's heat transfer capacity [kg (epoxide) / (m³)]. 2 s)], and V R (m oxide ) is the volume of the liquid reaction component [m 3 The equation applies under the assumption that the specific cooling surface area inside the reactor is approximately constant and the heat transfer resistance does not change significantly.

[0194] F is calculated as follows:

[0195]

[0196] Where T R The desired reactor temperature [°C], T cool,min α is the lowest temperature of the cooling device [°C], and α is the heat transfer coefficient [kW / m]. 2 K], and ΔH R, AO It is the specific heat of reaction [kJ / kg].

[0197] The feed rate r3 is determined according to the following equation:

[0198]

[0199] Where R Cal It is the slope of the straight line (corresponding to the ratio of the acceleration rate to the amount of alkyl epoxide added) [1 / h], m oxide C is the amount of epoxide already fed [kg], and C is the permissible rate of addition of the starting compound [kg / h].

[0200] The minimum value r of r1, r2, and r3 is determined by comparing the units. min The feed rate of the epoxide is controlled to r via a flow controller (especially a PID controller). min .

Claims

1. A method for preparing alkylene oxide addition products, the method comprising: (i) Purge the batch reactor with an inert gas to replace any oxygen; (ii) The batch reactor is loaded with a starting compound capable of undergoing alkylene oxide addition or insertion reactions; (iii) Feeding the epoxide into the batch reactor; (iv) Determine: - The feed rate r1 is limited by the flow rate and is a function of the total amount of epoxides fed. - The feed rate r2 is limited by the cooling rate and is a function of the utilization rate of the cooling capacity; as well as - The feed rate r3 is limited by the accumulation of unreacted epoxides, which is a function of whether the runaway pressure is close to or exceeds the maximum permissible operating pressure of the reactor, and / or whether the runaway temperature is close to or exceeds the maximum permissible operating temperature of the reactor or the initiation temperature of the secondary decomposition reaction, whichever is lower, wherein the runaway temperature and the runaway pressure are the temperature and pressure generated under the condition of spontaneous adiabatic runaway reaction of the accumulated amount of unreacted epoxides; (v) Determine the minimum value of r1, r2, and r3. min ;as well as (vi) Control the feed rate of the epoxide to r min .

2. The method according to claim 1, wherein, The utilization rate of this cooling capacity is determined by at least one of the following parameters: - The difference between the current reactor temperature and the predetermined reactor temperature; - The location of the coolant valve; - The difference between the current reactor temperature and the coolant inlet temperature; as well as -Balance the heat capacity of the coolant inlet flow and the coolant return flow.

3. The method according to claim 1 or 2, wherein, Determining the feed rate r3, which is limited by the accumulation of unreacted epoxides, includes establishing a predetermined cut-off pressure and comparing the current reactor pressure with the predetermined cut-off pressure.

4. The method according to claim 3, wherein, The predetermined cut-off pressure is a function of the total amount of alkyl epoxide already fed.

5. The method according to claim 1 or 2, wherein, The cumulative amount of unreacted epoxides in the reactor was continuously determined by online spectrometry or online calorimetry.

6. The method according to claim 1 or 2, wherein, The amount of unreacted epoxides accumulated in the reactor was determined using a thermodynamic model based on the following... - The total amount of epoxy alkyl already fed in, - Current reactor pressure and current reactor temperature, and - Amount of starting compound.

7. The method according to any one of the preceding claims, wherein, The flow-limited feed rate r1 is based on a computer memory that stores the alkylene oxide feed profile.

8. The method according to any one of the preceding claims, the method comprising: - Obtain process data, including reactor temperature, reactor pressure, total amount of starting compound, and total amount of epoxide already fed; - Based on the embedded model and the acquired process data, the method is used to predict the future response of the method to changes in the feed rate of the epoxide; as well as - When determining r3, consider the predicted future response.

9. The method according to any one of the preceding claims, wherein, a) The flow-limited feed rate r1 is determined according to the following equation: Where a1 [kg / h] is the feed rate, b1 [1 / h] is the slope, and m oxide This refers to the amount of epoxide already fed in [kg]; or b) For 0 kg < m oxide ≤ (y m oxide_total The range of the flow-limited feed rate r1 is determined by the following equation: Where (y) m oxide_total [kg] is the total amount of epoxide to be fed into the reactor. oxide_total In this part, a1 [kg / h] is the feed rate, b1 [1 / h] is the slope, and m oxide This refers to the amount of epoxide already fed in [kg], and For (y) m oxide_total ) < m oxide ≤ m oxide_total The range of the flow-limited feed rate r1 is determined according to the following equation: r1 = c1 Where c1 [kg / h] is the feed rate, preferably corresponding to when m oxide = (y m oxide_total According to the equation above, r1 = a1 + b1 m oxide The feed rate obtained from the r1 value.

10. The method according to any one of the preceding claims, wherein, The feed rate r2, which is limited by the cooling rate, is determined according to the following equation: Where a R It is the specific heat transfer area per unit volume of liquid reactor [m²] 2 / m 3 F is a measure of the reactor's heat transfer capacity [kg (epoxide) / (m³)]. 2 s)], and V R (m oxide ) is the volume of the liquid reaction component [m 3 ].

11. The method according to any one of the preceding claims, wherein, The feed rate r3, which is limited by the accumulation of unreacted epoxides, is determined according to the following equation: Where R Cal It is the slope of the straight line (corresponding to the ratio of the acceleration rate to the amount of alkyl epoxide added) [1 / h], m oxide C is the amount of epoxide already fed [kg], and C is the permissible rate of addition of the starting compound [kg / h].

12. The method according to any one of the preceding claims, wherein, The feed rate of the alkyl oxide is controlled to r via a distributed control system (DCS). min The distributed control system includes a controller selected from proportional-integral-derivative (PID) controllers and model predictive controllers, particularly nonlinear model predictive controllers, or combinations thereof.

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