Process for hydroformylating olefins

Abstract

1. A process for hydroformylating olefins having 6 to 20 carbon atoms in the presence of a cobalt catalyst and in the presence of an aqueous phase with intimate mixing in a reactor, wherein a first stream comprising the hydroformylation product is removed at the top of the reactor and a second stream comprising the aqueous phase is removed from the bottom of the reactor through at least one line leading out of the bottom of the reactor, the process comprising controlling one or more mass flow parameters of the second stream in response to the density of the second stream.

Description

[Technical field]

[0001] The present invention relates to a process for hydroformylating olefins having from 6 to 20 carbon atoms. [Background technology]

[0002] Hydroformylation, also known as the Oxo process, is an important large-scale industrial process for the preparation of aldehydes from olefins, carbon monoxide, and hydrogen. Such aldehydes can be optionally hydrogenated with hydrogen to produce the corresponding alcohols, either in the same operation or in a separate hydrogenation step following the hydroformylation. The hydroformylation is carried out in the presence of a catalyst, which is homogeneously dissolved in the reaction medium. The catalysts used are generally carbonyl complexes of Group VIII transition metals, in particular Co, Rh, Ir, Pd, Pt, or Ru, which may be unmodified or modified, for example, with amine- or phosphine-containing ligands. A summary description of the process carried out on an industrial scale can be found in J. Falbe, "New Syntheses with Carbon Monoxide", Springer Verlag 1980, p. 162 ff.

[0003] Currently, short-chain olefins having up to 5 carbon atoms are mainly hydroformylated using ligand-modified rhodium carbonyl as catalyst, while cobalt is still the central atom with the dominant catalytic activity for long-chain olefins.The reason for this is, firstly, that the cobalt carbonyl catalyst has high catalytic activity regardless of the position of the olefin double bond, the branching structure, and the purity of the olefin to be reacted.Secondly, the cobalt catalyst can be separated from the hydroformylation product and recycled to the hydroformylation reaction relatively easily.Furthermore, since cobalt is cheaper, the loss of catalyst during post-treatment can be more easily tolerated.

[0004] In one conventional method for separating and recycling the cobalt catalyst, the organic phase of the reactor effluent is separated from the cobalt carbonyl complex by treatment with oxygen or air in the presence of weakly acidic water (see DE-AS 24 04 855). In that treatment, the cobalt catalyst is deactivated by oxidation, its central atom is formally converted from oxidation state -1 to +2, and can then be removed by extraction with an aqueous solution (decobaltization). The catalyst complex required for hydroformylation can be reformed from a cobalt(II) salt solution by reaction with carbon monoxide and hydrogen (carbonyl formation). The reformed cobalt catalyst is then extracted from the aqueous phase using the organic phase, preferably using the olefin to be hydroformylated (catalyst extraction). Besides the olefin, the reaction products and by-products of the hydroformylation can also be used for the extraction of the catalyst. The olefin is then hydroformylated in a reactor at high temperature and pressure over the action of the cobalt catalyst (hydroformylation of olefins).

[0005] The reaction products are usually removed at the top of the reactor, especially when vertical tube reactors are used. In particular in the case of higher olefins having 8 or more carbon atoms, the aqueous phase which is fed to the reaction zone and which is necessary to reach a sufficient catalyst concentration in the reaction zone is not completely flushed out, in dissolved or suspended form, with the reaction mixture removed from the top. Therefore, it is preferred that the reaction products are removed not only at the top but also from the bottom space.

[0006] Uncontrolled or poorly controlled withdrawal of the aqueous phase from the bottom space can lead to operational problems: too much aqueous phase can lead to reduced conversion, while not enough aqueous phase can lead to localized temperature spikes, which can cause decomposition of the cobalt catalyst.

[0007] In the prior art, the amount of reaction product removed from the bottom space is determined by the level of the bottom aqueous phase in the reactor.

[0008] EP 1 204 624 B1 discloses a continuous process for the hydroformylation of olefins having 6 to 20 carbon atoms, in which an aqueous phase containing a cobalt catalyst is intimately contacted with the olefin, hydrogen and carbon monoxide in at least one reaction zone (for example in a vertical tubular reactor). The reaction products can be removed not only at the top of the reactor but also from the bottom space of the reactor. The removal of the reaction products from the bottom space of the reactor is preferably phase-controlled.

[0009] EP 1 279 658 B1 discloses a process for the hydroformylation of olefins having 5 to 24 carbon atoms to produce the corresponding aldehydes and / or alcohols having 6 to 25 carbon atoms in a single-step process in the presence of an unmodified cobalt catalyst, in which the bottom aqueous phase is thoroughly mixed with the organic phase in the reactor, the concentration of cobalt compounds in the bottom aqueous phase is in the range of 0.4 to 1.7% by weight, and the level of the bottom aqueous phase is kept constant at steady state.

[0010] EP 3 071 524 B1 discloses a process for the hydroformylation of olefins having 6 to 20 carbon atoms in the presence of a cobalt catalyst and in the presence of an aqueous phase with intimate mixing in a reactor to produce the corresponding hydroformylation products, in which a stream comprising the aqueous phase is removed from the bottom of the reactor and the flow rate of this stream comprising the aqueous phase is controlled as a function of the temperature measured at a point in the bottom of the reactor or in a line leading out from the bottom of the reactor.

[0011] However, the level of the bottom aqueous phase often cannot be measured accurately under the conditions prevailing in the reactor.

[0012] This has been particularly observed in larger reactors when the withdrawal of the aqueous phase is controlled as a function of the temperature measured at a point in the bottom of the reactor or in a line leading out from the bottom of the reactor, as disclosed in EP 3 071 524 B1.

[0013] Radiometric measurements of the bottom aqueous phase level are inaccurate: gamma radiation is attenuated by passing through 30 cm thick steel walls, and the level of the bottom aqueous phase in the reactor is usually not known exactly, even at the time of calibration, making radiometric calibration difficult.

[0014] Furthermore, if the equipment for determining the bottom aqueous phase level is installed inside the reactor and can therefore only be accessed by interrupting the process, with great expense and inconvenience, maintenance of such equipment is very costly and inconvenient.

[0015] Due to inaccurate measurement of the bottom aqueous phase level, the removal of the aqueous phase from the bottom space cannot be controlled accurately enough, which leads to operational disruptions and ultimately to a reduced yield of the crude hydroformylation product. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] DE-AS 24 04 855 [Patent Document 2] EP 1 204 624 B1 [Patent Document 3] EP 1 279 658 B1 [Patent Document 4] EP 3 071 524 B1 [Patent Document 5] DE-OS 21 39 630 [Patent Document 6] DE-AS 12 05 514 [Patent Document 7] DE-AS 19 38 102 [Non-patent literature]

[0017] [Non-Patent Document 1] J. Falbe, "New Syntheses with Carbon Monoxide", Springer Verlag 1980, pp. 162 et seq. [Non-Patent Document 2] Ullmann's Encyclopedia of Industrial Chemistry, Liquid-Liquid Extraction, DOI: 10.1002 / 14356007.b03_06.pub2 Summary of the Invention [Problem to be solved by the invention]

[0018] It was therefore an object of the present invention to provide an improved process for the hydroformylation of olefins having 6 to 20 carbon atoms which results in a stable and sustained operation and, as a result, an increased yield of crude hydroformylation product.

[0019] It has been found that as the volume of the reactor increases, the specific heat loss from the reactor surface decreases, so that the temperature difference between the temperature measured in the highly mixed region of the reactor and the temperature measured at the bottom of the reactor or in a line leading out from the bottom of the reactor becomes small and can no longer be accurately controlled by means of the temperature difference.

[0020] The improved method should therefore make it possible to precisely control the withdrawal of the stream containing the aqueous phase, independent of the temperature difference between the temperature in the highly mixed region of the reactor and the temperature measured at the bottom of the reactor or in a line leading out from the bottom of the reactor. [Means for solving the problem]

[0021] The objects of the present invention are achieved by a process for the hydroformylation of olefins having from 6 to 20 carbon atoms in the presence of a cobalt catalyst and in the presence of an aqueous phase with intimate mixing in a reactor, wherein a first stream comprising the hydroformylation product is removed at the top of the reactor and a second stream comprising the aqueous phase is removed from the bottom of the reactor through at least one line leading out of the bottom of the reactor, the process comprising a step of controlling one or more mass flow parameters of the second stream as a function of the density of the second stream, preferably measured in the line leading out of the bottom of the reactor. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 shows a schematic diagram of a plant for carrying out the method of the invention. [Diagram 2] Figure 2 shows the measured density and density setting values ​​based on Table 1. [Diagram 3] Figure 3 shows the composition ratio of the organic phase in the discharged mixture based on Table 1. [Figure 4] Figure 4 shows the temperature of the discharged mixture based on Table 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The process of the present invention may be continuous, semi-continuous or batchwise, with continuous or semi-continuous processes being preferred.

[0024] A mass flow parameter is a mass flow rate, a mass flow rate, or any other parameter determined based on the mass flow rate and / or the mass flow rate. Preferably, the at least one mass flow parameter is a mass flow rate or a mass flow rate.

[0025] The aqueous phase separates from the organic phase and splits off in the bottom space of the reactor, so that it is no longer mixed with the olefins that are the subject of hydroformylation. The reaction rate in the bottom space of the reactor decreases, and the separated aqueous phase cools slowly. As mentioned above, this cooling can be quite limited when the reactor volume to surface area ratio and any insulation reduces the dissipation of heat generated in the reactor, and therefore the temperature difference in the reactor. Thus, controlling the withdrawal of the bottom stream from a large reactor based on the temperature difference between the reactor bottom and the reaction zone requires a large enough amount of unreacted aqueous phase at the bottom to be cooled enough to create a temperature difference over the reaction zone that is large enough to be meaningful to use as an input for the control loop. However, the presence of a large amount of unreacted aqueous phase in the reactor reduces the volume utilization and productivity of the reactor, thus negating economies of scale.

[0026] It has been found that a stream containing an aqueous phase can be removed from the bottom space of the reactor under density control.

[0027] The basis for this finding is that if the stream withdrawn from the bottom of the reactor is greater than the current settling of water, the organic phase will also be withdrawn from the bottom of the reactor, so that the aqueous stream withdrawn from the bottom of the reactor will also contain an amount of dispersed organic phase. The density of this stream depends on the ratio of the two phases. The exact dependence may be more complicated than linear, but it can be easily measured, and the desired set point for controlling the withdrawal can be determined depending on the specific conditions of the reactor and plant. In contrast to controlling the withdrawal based on the temperature difference in the reactor, the method of the present invention allows water to be removed from the reactor to any desired extent. In very basic terms, if the withdrawn liquid has the density of the pure aqueous phase, it is possible to withdraw more liquid and increase the productivity of the reactor, and if the withdrawn liquid has the density of the pure organic phase, too much liquid is being withdrawn. In the actual operation of such a stirred tank reactor, the density of the stream withdrawn from the bottom will be between the extremes of pure aqueous phase or pure organic phase, depending on the relative amounts of aqueous and organic phases in the stream. One advantage of the present invention is that a desired amount of aqueous phase can be removed while avoiding removing too much of the organic phase. The amount of organic phase withdrawn at the bottom of the reactor is insignificant compared to the organic phase including all of the reactor outlets. In a preferred embodiment, any continuous aqueous phase is removed from the reactor, and only the dispersed aqueous phase remains.

[0028] The process of the present invention allows for the exact removal of the desired amount of aqueous phase, which prevents the aqueous phase level from rising too high. As a result, unintended termination of the hydroformylation reaction can be avoided and continuous operation can be achieved. In other words, the reaction can be stabilized. Furthermore, since the aqueous phase is not continuously present in the reactor, the process of the present invention also minimizes the amount of water in the reactor. This maximizes the available reaction volume and therefore the conversion rate in the reactor.

[0029] Advantageously, the density of the second stream (second stream is used as a synonym for the stream containing the aqueous phase) can be accurately measured, independent of any temperature difference between any points in the reactor. Thus, by controlling at least one mass flow parameter of the second stream depending on the density of the second stream, it is possible to efficiently remove the aqueous phase in the reactor, independent of the volume of the reactor. Furthermore, this approach allows the proportion of the aqueous phase in the reactor to be minimized, thus realizing a longer residence time of the organic phase, which may increase the conversion in the reactor.

[0030] Preferably, controlling one or more mass flow parameters of the second stream in response to the density of the second stream comprises measuring the density of the second stream and determining one or more control variables based on the measured density, comparing the one or more control variables to one or more reference values ​​to determine one or more control quantities, and using the one or more control quantities to determine one or more actuation signals to control the one or more mass flow parameters of the second stream. It is further preferred that controlling one or more mass flow parameters of the second stream in response to the density of the second stream is performed using a closed loop control system comprising the above control steps.

[0031] The density of the second stream may be measured by any means and at any point suitable for measuring density. Preferably, the density of the second stream is measured in a line leading out from the bottom of the reactor.

[0032] When the density of the second stream is measured in a line leading out from the bottom of the reactor, the density is preferably measured with one or more Coriolis mass flowmeters.

[0033] Coriolis mass flowmeters are commercially available and their operation is known to those skilled in the art. If one or more Coriolis mass flowmeters are used in the line leading out of the bottom of the reactor to measure the density of the second stream, a person skilled in the art would use common sense to determine how many Coriolis mass flowmeters to use and how to install them in relation to the line leading out of the bottom of the reactor.

[0034] Of course, the density of the individual phases, and therefore the density of the two-phase stream, also depends on the temperature. The determination of the temperature dependence of the density of the individual phases can be easily performed by determining the density at various temperatures. The density of the mixture at various temperatures can be easily calculated as the mass average of the densities of the two phases. This allows the density sensor at the reactor outlet to be calibrated to the temperature measured at the reactor outlet. Also, as in other cases of controlling valves or the like based on a temperature-dependent value, it may be preferable to use a temperature-compensated value as the basis for control. Thus, in order to keep the ratio of the two phases in the stream removed from the reactor constant, it may be preferable to use a temperature-compensated density instead of the density at the actual temperature of the stream as the basis for controlling the total amount of that stream. The reference point for temperature compensation may be chosen arbitrarily, but it is preferable to choose a temperature close to the operating temperature of the reactor. Temperature-compensated density sensors, in particular temperature-compensated Coriolis density sensors, are commercially available. Alternatively, the temperature dependence of the density of the two-phase mixture may be stored in the process control system. In other words, the density measured at the reactor outlet may be presented to the operator as "density at x°C" (where x is the selected reference temperature in°C), and the control logic will keep that value, and thus the ratio of the two phases, constant.

[0035] Based on the measured density of the second flow, one or more control variables can be determined by mathematically transforming the measured density. Mathematical models and / or algorithms to be applied to this transformation are known to those skilled in the art. In the simplest case, one control variable is the measured density of the second flow.

[0036] The one or more reference values ​​may be static and / or dynamic. In the case of static values, the one or more reference values ​​are predefined values ​​that may be changed from time to time. In the case of dynamic values, the one or more reference values ​​are controlled and / or optimized to increase the yield of the crude hydroformylation product depending on one or more variables determined from the respective reaction plant and / or other reaction plants associated with the respective reaction plant, such as reaction temperature, yield of the crude hydroformylation product, feed composition and / or catalyst loading. The control and / or optimization of the one or more reference values ​​is performed in a control device. Preferably, the control device, for example a control device implemented in a central processing unit / distributed control system or a control device comprising a cloud computing means, is configured to execute an analytical algorithm based on the results of the machine learning algorithm. The machine learning algorithm preferably comprises a decision tree, a naive Bayes classification, a nearest neighbor, a neural network, a convolutional neural network, a generative adversarial network, a support vector machine, a linear regression, a logistic regression, a random forest, and / or a gradient boosting algorithm. Preferably, the machine learning algorithm is organized to process high-dimensional inputs into much lower-dimensional outputs. Such machine learning algorithms are called "intelligent" because they can be "trained". The algorithm can be trained using records of training data. The records of training data include input training data and corresponding output training data. The output training data of a record of training data is the expected result generated by the machine learning algorithm when the input training data of the same record of training data is given as input. The deviation between this expected result and the result actually generated by the algorithm is observed and evaluated using a "loss function". This loss function is used as feedback to adjust the parameters of the internal processing chain of the machine learning algorithm. For example, the parameters may be adjusted with an optimization goal of minimizing the value of the loss function that results when all input training data is given to the machine learning algorithm and the result is compared to the corresponding output training data.The result of this training is that, given a relatively small number of training data records as the "ground truth", a machine learning algorithm can perform well on an order of magnitude larger number of input data records. The machine learning algorithm is preferably trained on the input data.

[0037] In the simplest case, one reference value is a predefined reference value for the density of the second flow.

[0038] Preferably, the reference value(s) and the control variable(s) are input parameters to the control device(s), and the control variable(s) are determined by applying a mathematical model and / or algorithm based on the input parameters. The mathematical model and / or algorithm to be applied to the control device(s) to determine the control variable(s) are known to those skilled in the art or can be derived based on simple tests and common sense. Suitable control devices are, for example, PID controllers, model predictive controllers, adaptive controllers, nonlinear controllers, fuzzy controllers, or state space controllers, etc.

[0039] Based on the one or more control variables, one or more actuation signals for controlling one or more mass flow parameters of the second stream are determined. The one or more control variables are input parameters to one or more actuators. The actuators are, for example, valves with actuators. The actuators can be operated pneumatically, hydraulically, electronically, electromagnetically, manually, or in any mixed form of the above. If the actuators are valves with actuators, the actuation signal is a state in which the valve is open.

[0040] In a simple case, if the measured density of the second stream exceeds a predefined reference value for the density of the second stream, the mass flow rate and / or mass flow rate of the second stream is increased, if the measured density of the second stream is below a predefined reference value for the density of the second stream, the mass flow rate and / or mass flow rate of the second stream is decreased.

[0041] Suitable pressure reactors for carrying out the process according to the invention are known to those skilled in the art. Pressure reactors include, for example, tubular reactors, stirred tanks, gas circulation reactors, bubble columns, loop reactors, and other reactors commonly used for gas-liquid reactions, which may optionally be further subdivided by internal structure. Examples of suitable reactors are loop reactors, vertical high-pressure bubble column reactors, optionally equipped with coaxial tubular internal structures, or vertical tube reactors. Preferably, the reactor is a vertical bubble column reactor or a vertical tube reactor.

[0042] The temperature in the reactor is usually from 100 to 250° C., in particular from 145 to 200° C. The prevailing pressure in the reactor is preferably from 100 to 400 bar abs, in particular from 200 to 300 bar abs.

[0043] A portion of the reaction mixture contained in the reactor may be discharged at an upper region of the reactor and returned to a lower region of the reactor to achieve sufficient mixing. As an example, the discharged reaction mixture may be passed through a pump and then mixed with the starting material, and the starting material mixed with the discharged reaction mixture may be fed to the reactor.

[0044] In the present specification, the term "olefin" refers not only to one olefin but also to a mixture of various olefins, for example isomeric olefins. Olefins having 6 to 20 carbon atoms can be hydroformylated by the process according to the invention. The process according to the invention is particularly suitable for the hydroformylation of isomeric olefin mixtures produced by oligomerization of lower olefins, such as propene and butene. Typical oligomers useful as olefins for the process according to the invention include, inter alia, dipropene, tripropene, and tetrapropene, dibutene, tributene, and tetrabutene, as well as propene and butene cooligomers. Butene oligomers can be obtained on a large industrial scale by known oligomerization processes, for example the Octol process of Huls and the Dimersol process of IFP. It is preferable to use oligomers based on the so-called raffinate 2, a stream essentially comprising linear butenes, n-butane, and isobutane, with up to 5% by mass, preferably up to 3% by mass, of isobutene. Linear long-chain terminal olefins, obtainable, for example, by the SHOP process or the Ziegler process, or also linear long-chain internal olefins, can be hydroformylated according to the process according to the invention.

[0045] The hydroformylation is carried out in the presence of hydrogen and carbon monoxide. The two gases are customarily used in the form of a mixture, the so-called synthesis gas. The composition of the synthesis gas used in the process according to the invention can vary between wide limits. The molar ratio of carbon monoxide to hydrogen is usually about 10:1 to 1:10, in particular 2.5:1 to 1:2.5. A preferred ratio is about 40:60 (CO:H2).

[0046] In the process according to the invention, the extraction of the catalyst and the hydroformylation of the olefins are carried out in one step in the reactor. The carbonyl formation can be carried out simultaneously or optionally in an upstream catalyst formation step (precarbonylation).

[0047] In the optional catalyst formation step (precarbonylation), an aqueous cobalt(II) salt solution is brought into intimate contact with carbon monoxide and hydrogen to form the cobalt catalyst. This catalyst formation step is carried out in the presence or absence of the olefin to be hydroformylated, preferably at temperatures between 50 and 200° C., in particular at temperatures between 60 and 140° C., and under pressures between 100 and 400 bar abs, in particular at pressures between 200 and 300 bar abs. The catalyst formation is preferably carried out in apparatuses customary for gas-liquid reactions, such as, for example, stirred tanks equipped with a sparging stirrer, bubble columns or trickle-bed columns. Advantageously, activated carbon, zeolites or basic ion exchangers on which cobalt carbonyl is supported, as described in DE-OS 21 39 630, are used in the catalyst formation step. The cobalt (II) salt-containing aqueous solution and the cobalt catalyst-containing aqueous solution obtained in the catalyst formation step are then fed to a reactor together with the olefin to be hydroformylated, and any organic solvent optionally used, as well as hydrogen and carbon monoxide.

[0048] Carbonyl formation is particularly favored in an upstream catalyst formation step when linear, relatively long chain terminal olefins are hydroformylated to form primarily linear aldehydes / alcohols. Lower reaction temperatures are then typically employed in the reactor to minimize the formation of undesirable branched hydroformylation products. However, under the conditions employed in the reactor, active cobalt catalysts are not formed at a sufficient rate.

[0049] In many cases, it is preferred that carbonyl formation, catalyst extraction, and olefin hydroformylation are carried out in tandem in the same reactor, due to the lower technical requirements. In a preferred embodiment of the process of the present invention, cobalt catalyst formation, cobalt catalyst extraction into the organic phase, and olefin hydroformylation are carried out in tandem in the same reactor, by intimately contacting an aqueous cobalt(II) salt solution, an olefin, and optionally an organic solvent in a reaction zone under hydroformylation conditions.

[0050] Regardless of whether the carbonyl formation is carried out in an upstream catalyst formation step, it is preferred that the starting materials are introduced into the reactor in such a way that good mixing of the two phases occurs and the exchange area between the two phases is as large as possible. For this purpose, metering devices known to the skilled artisan can be used, such as, for example, turbulent tubes filled with packings or mixing nozzles for multiphase systems. It is particularly preferred that sufficient mixing is carried out using a mixing nozzle in order to maintain turbulence in the reactor. Thus, in a suitable embodiment, sufficient mixing is achieved by simultaneously introducing the aqueous cobalt(II) salt solution, the olefin, the carbon monoxide and the hydrogen into the reactor in a circulation system using a mixing nozzle, as described in DE-AS 12 05 514 and DE-AS 19 38 102. The organic solvent optionally used is either present in the reactor or is introduced into the reactor simultaneously with the other starting materials, in particular using a mixing nozzle.

[0051] Optionally usable organic solvents are inert hydrocarbons, such as paraffin fractions, aromatic hydrocarbons, such as benzene, toluene or xylene, or aldehydes and / or alcohols, but in particular the hydroformylation products of the olefins used. High-boiling hydroformylation by-products can further be used as solvents. The use of a solvent can be advantageous, for example to reduce the viscosity, during the hydroformylation of long-chain olefins to form long-chain aldehydes.

[0052] The first stream is withdrawn at the top of the reactor and contains, in addition to the hydroformylation product, unreacted olefins and a significant amount of aqueous phase. The second stream is withdrawn from the bottom of the reactor and, in addition to the aqueous phase, may contain a significant amount of partially reacted organic phase. Preferably, the second stream withdrawn from the bottom of the reactor contains 10-80% by volume of aqueous phase.

[0053] The reactor described has the characteristics of a so-called stirred tank; it is a very well mixed reactor. In such a reactor, the reactor volume is limited and only partial conversion is possible. Therefore, preferably, the hydroformylation is continued in a post-reactor, ideally to complete the hydroformylation, in order to obtain the desired product yield as much as possible. In a preferred embodiment, the first and second streams are fed to the post-reactor.

[0054] The temperature in the latter reactor is usually 100-250° C., in particular 145-200° C. The prevailing pressure in the latter reactor is preferably in the range of 100-400 bar abs, in particular 200-300 bar abs. A uniform transport of the material from the reactor to the latter reactor is preferably achieved by maintaining a constant differential pressure of a few bars between the reactor and the latter reactor, the latter reactor being at a lower pressure. The differential pressure is preferably 2-5 bar. The differential pressure allows for a simple control of the discharge from the first reactor. The differential pressure can be maintained by means of an adjustable valve or a diaphragm.

[0055] Preferably, in the latter reactor too, a first stream comprising the hydroformylation product is withdrawn at the top and a second stream comprising the aqueous phase is withdrawn at the bottom. Preferably, the second stream withdrawn from the bottom of the latter reactor is also withdrawn under density control. Thus, in a preferred embodiment, one or more mass flow parameters of the second stream withdrawn from the latter reactor are controlled as a function of the density of the second stream, preferably measured in a line leading out from the bottom of the latter reactor.

[0056] The mass flow parameter(s) of the second stream withdrawn from the subsequent reactor are preferably correspondingly controlled by the same means as the mass flow parameter(s) of the second stream withdrawn from the first reactor. Preferred embodiments of the control of the mass flow parameter(s) of the second stream withdrawn from a reactor are also preferred embodiments of the control of the mass flow parameter(s) of the second stream withdrawn from a subsequent reactor.

[0057] Advantageously, the pressure difference between the downstream reactor and the discharge line or lines is set so that the discharge can be well controlled. This can be done by means of a pressure regulator such as an adjustable valve or a diaphragm. This pressure difference is also preferably between 2 and 5 bar.

[0058] For work-up, the streams withdrawn from the reactor and, if a subsequent reactor is employed, the subsequent reactor are depressurized to an intermediate pressure of between 10 and 80 bar abs, preferably between 10 and 50 bar abs. Preferably, the streams are combined either before, during or after depressurization.

[0059] The depressurized stream is oxygenated in the presence of an aqueous cobalt(II) solution, where the cobalt catalyst decomposes to form cobalt(II) salts, which are then extracted into the aqueous phase and the two phases are then separated (decobaltization step).

[0060] Preferably, the oxygen is provided by supplying air. The treatment is preferably carried out at a temperature of 90 to 130°C.

[0061] The aqueous cobalt(II) solution is preferably weakly acidic with a pH of 3 to 5, preferably 3.5 to 4.5. The aqueous cobalt(II) solution may be a fresh aqueous cobalt(II) solution to replenish lost cobalt(II) and / or a portion of the aqueous cobalt(II) solution before separation may be recycled.

[0062] The treatment can be carried out in a pressure vessel which is filled so that the exchange area between the two phases is as large as possible (eg with Raschig rings) or by reducing the pressure in an empty pressure vessel.

[0063] The separation of the aqueous phase from the organic phase is preferably carried out in a phase separation vessel. Suitable vessels or devices for phase separation are disclosed, for example, in Ullmann's Encyclopedia of Industrial Chemistry, Liquid-Liquid Extraction, DOI: 10.1002 / 14356007.b03_06.pub2. As a phase separation vessel, a mixer-settler apparatus is preferred.

[0064] The organic phase remaining after separation of the aqueous phase may then be suitably worked up, for example by distillation and / or hydrogenation.

[0065] The aqueous phase (cobalt(II) salt solution) is fed to a reactor, or to a catalyst formation step, or to a decobaltization step.

[0066] The water content in the reactor, in the subsequent reactor if one is used, and in the separation of the organic and aqueous phases are preferably controlled by means of dynamic decoupling in order to avoid fluctuations in the operating conditions. The principles of dynamic decoupling, for example by full dynamic decoupling with feedback of the dynamic conditions, are well known to those skilled in the art, in particular to those skilled in the art of automation technology.

[0067] Preferably, a distributed control system with PID controllers is used to control one or more mass flow parameters of the second stream taken from the reactor and one or more mass flow parameters of the aqueous phase taken from the phase separation, and if a later reactor is used, one or more mass flow parameters of the second stream taken from the later reactor. In such a case, one set of controllers is adjusted to run slower compared to the other controllers, using dynamic decoupling, to avoid fluctuations in operating conditions. This corresponds to a longer time to reach steady state after changing the setpoint of the controller more than usual. A set of controllers refers to the controllers used to control either a) one or more mass flow parameters of the second stream taken from the reactor, b) if a later reactor is used, one or more mass flow parameters of the second stream taken from the later reactor, or c) one or more mass flow parameters of the aqueous phase taken from the phase separation, for example the mass flow rate and / or mass flow rate of the aqueous phase taken from the phase separation vessel.

[0068] Avoiding fluctuating operating conditions has advantages, for example, due to less cumulative valve stem travel commanded by the control action (lower valve travel index), which may result in longer valve life, less fresh water addition, and / or less catalyst loss.

[0069] The method according to the invention is explained in more detail by means of the attached drawings.

[0070] Figure 1 shows a schematic diagram of a plant for carrying out the process of the invention. The plant comprises a reactor 1 and a subsequent reactor 13, in which both the flow rate of the stream withdrawn from the bottom of the reactor and the flow rate of the stream withdrawn from the bottom of the subsequent reactor are controlled according to the invention.

[0071] As shown in FIG. 1, oxo gas 4, olefin 5, and aqueous cobalt (II) salt solution 6 are introduced into reactor 1 through nozzle 3 by means of pump 2. The density of the stream taken out through line 12 leading out from the bottom of the reactor is measured by means of a Coriolis mass flowmeter and used for control 7. The controller output of the density controller is fed as a setpoint to mass flow controller 8. The measured density is compared with a predetermined reference value for density. As soon as the measured density exceeds the predetermined reference value, a signal is sent to controller 8 to increase the mass flow rate, which in turn opens valve 9. Similarly, as soon as the measured density is below the predetermined reference value for density, a signal is sent from controller 8 to close valve 9.

[0072] A first stream comprising the hydroformylation product is removed at the top of reactor 1 by means of line 10 and passes through differential pressure regulator 11. Provided that valve 9 is partially open, a second stream comprising the aqueous phase is removed from the bottom of the reactor and sent by means of line 12 to join line 10.

[0073] The combined streams withdrawn at the top and at the bottom of the reactor are introduced into the subsequent reactor 13. The density of the stream withdrawn through line 19 leading out from the bottom of the subsequent reactor is measured using a Coriolis mass flowmeter and used in the control device 14. The controller output of the density control device is derived by comparing the measured density with a predetermined reference value for density. The controller output of the density control device is used as a setpoint for the mass flow control device 15. As soon as the measured density exceeds the predetermined reference value, a signal is sent to the control device 15 to increase the mass flow rate, which in turn opens the valve 16. Similarly, as soon as the measured density falls below the predetermined reference value for density, a signal is issued from the control device 15 to close the valve 16. A first stream comprising the hydroformylation product is withdrawn at the top of the subsequent reactor 13 using line 17 and passes through a control valve 18. Provided that valve 16 is partially open, a second stream containing the aqueous phase is removed from the bottom of the subsequent reactor and combined with the stream from line 17 .

[0074] The combined streams removed at the top of the subsequent reactor by line 17 and from the bottom of the subsequent reactor by line 19 are introduced into a high temperature, reduced pressure vessel 20, where the prevailing pressure is lower than that of the reactor or subsequent reactors, and where they are treated with air supplied by line 23 and compressor 24 in the presence of a cobalt(II) salt solution supplied by line 21 and pump 22.

[0075] The mixture obtained in the hot vacuum vessel 20 is sent to a phase separator 26 using line 25, and the aqueous phase is discharged from the phase separator using line 27. The crude hydroformylation product is discharged from the phase separator using line 28. The off-gas is discharged from the phase separator using line 29. The height of the liquid-liquid interface in the phase separator 26 is measured and controlled by a level controller 31. The controller output is used to manipulate the setpoint of the water mass flow controller 33. The water mass flow is manipulated by changing the axial position of valve 32 in the water line 30. The height of the gas-liquid interface in the phase separator 26 is measured and controlled by a level controller 36. The controller output is used to manipulate the setpoint of the organic mass flow controller 35. The organic mass flow is manipulated by changing the axial position of valve 34 in the product line 28. The off-gas mass flow is measured and controlled by flow controller 38 by manipulating the axial position of valve 37 in the off-gas line 29.

[0076] The preferred embodiments of the present invention are as follows: These embodiments do not limit the scope of the present invention.

[0077] 1. A process for the hydroformylation of olefins having from 6 to 20 carbon atoms in the presence of a cobalt catalyst and in the presence of an aqueous phase with thorough mixing in a reactor, wherein a first stream comprising the hydroformylation product is removed at the top of the reactor and a second stream comprising the aqueous phase is removed from the bottom of the reactor through at least one line leading out of the bottom of the reactor, the process comprising controlling one or more mass flow parameters of the second stream in response to the density of the second stream, preferably measured in the line leading out of the bottom of the reactor.

[0078] 2. The method of embodiment 1, wherein the method is continuous or semi-continuous.

[0079] 3. The method of embodiment 1 or 2, wherein the one or more mass flow parameters are mass flow rate, mass flow rate, or any other parameter determined based on mass flow rate and / or mass flow rate.

[0080] 4. A method according to any one of embodiments 1 to 3, comprising measuring the density of the second stream and determining one or more control variables based on the measured density, comparing the one or more control variables to one or more reference values ​​to determine one or more control quantities, and using the one or more control quantities to determine one or more actuation signals to control one or more mass flow parameters of the second stream, preferably using a closed loop control system.

[0081] 5. The method of any one of the preceding claims, wherein the density is measured with one or more Coriolis mass flowmeters.

[0082] 6. The method according to any one of the preceding claims, wherein the measured density of the second stream is compared to a predetermined reference value for the density of the second stream, and if the measured density of the second stream exceeds the predetermined reference value for the density of the second stream, the mass flow rate and / or mass flow velocity of the second stream is increased.

[0083] 7. The method according to any one of the preceding claims, wherein the measured density of the second stream is compared to a predetermined reference value for the density of the second stream, and if the measured density of the second stream is less than the predetermined reference value for the density of the second stream, the mass flow rate and / or mass flow rate of the second stream is reduced.

[0084] 8. The method of any one of the preceding embodiments, wherein the density of the second stream is measured at at least one point in a line leading out from the bottom of the reactor.

[0085] 9. The method of any one of the preceding claims, wherein the thorough mixing is performed using a mixing nozzle.

[0086] 10. The method of any one of the preceding embodiments, wherein the first stream and the second stream are sent to a subsequent reactor.

[0087] 11. The process of embodiment 10, wherein a first stream comprising the hydroformylation product is removed at the top of the subsequent reactor and a second stream comprising the aqueous phase is removed from the bottom of the subsequent reactor.

[0088] 12. The method of embodiment 11, wherein one or more mass flow parameters of the second stream removed from the bottom of the subsequent reactor through at least one line leading out from the bottom of the subsequent reactor are controlled as a function of the density of the second stream, preferably measured in a line leading out from the bottom of the subsequent reactor.

[0089] 13. The method of embodiment 12, wherein the one or more mass flow parameters are mass flow rate, mass flow rate, or any other parameter determined based on the mass flow rate and / or mass flow rate.

[0090] 14. The method of embodiment 12 or 13, comprising measuring the density of the second stream and determining one or more control variables based on the measured density, comparing the one or more control variables to one or more reference values ​​to determine one or more control quantities, and using the one or more control quantities to determine one or more actuation signals to control one or more mass flow parameters of the second stream, preferably using a closed loop control system.

[0091] 15. The method of any one of embodiments 12-14, wherein the density is measured with one or more Coriolis mass flowmeters.

[0092] 16. A method according to any one of embodiments 12 to 15, wherein the measured density of the second stream is compared with a predetermined reference value for the density of the second stream, and if the measured density of the second stream exceeds the predetermined reference value for the density of the second stream, the mass flow rate and / or mass flow velocity of the second stream is increased.

[0093] 17. A method according to any one of embodiments 12 to 16, wherein the measured density of the second flow is compared with a predetermined reference value for the density of the second flow, and if the measured density of the second flow is less than the predetermined reference value for the density of the second flow, the mass flow rate and / or mass flow velocity of the second flow is reduced.

[0094] 18. The method of any one of embodiments 12-17, wherein the density of the second stream is measured at at least one point in a line leading out from the bottom of the reactor.

[0095] 19. The method of any one of the preceding embodiments, comprising a catalyst formation step in which an aqueous cobalt (II) salt solution is intimately contacted with carbon monoxide and hydrogen to form a cobalt catalyst.

[0096] 20. The method of any one of the preceding embodiments, wherein the formation of the cobalt catalyst, the extraction of the cobalt catalyst into the organic phase, and the hydroformylation of the olefin are carried out in conjunction with one another in the same reactor by intimately contacting an aqueous cobalt(II) salt solution, carbon monoxide, hydrogen, and the olefin, and optionally an organic solvent, in the reactor under hydroformylation conditions.

[0097] 21. The method of any one of the preceding claims, wherein the first and second streams removed from the reactor, or from a subsequent reactor if one is present, are oxygenated in the presence of an aqueous cobalt(II) salt solution, whereby the cobalt catalyst decomposes to form cobalt(II) salts, which are extracted into an aqueous phase, and the two phases are then separated.

[0098] 22. The method of any one of the preceding embodiments, wherein a portion of the aqueous phase is recycled to the reactor or to the catalyst formation step.

[0099] 23. The method of embodiment 21 or 22, wherein the mass flow rate and / or mass flow rate of the aqueous phase withdrawn from the phase separation is controlled in response to one or more mass flow parameters of the second stream withdrawn from the reactor and, if a subsequent reactor is used, also in response to one or more mass flow parameters of the second stream withdrawn from the subsequent reactor.

[0100] 24. The method of embodiment 23, wherein the mass flow rate and / or mass flow rate of the aqueous phase removed from the phase separation is controlled as a function of one or more mass flow rate parameters of the second stream removed from the reactor and, if a subsequent reactor is used, also as a function of one or more mass flow rate parameters of the second stream removed from the subsequent reactor, is achieved by dynamic decoupling of the different water contents of the reactor and the phase separation.

[0101] 25. The method of any one of the preceding embodiments, wherein a distributed control system, preferably a distributed control system comprising a PID controller, is used to control one or more mass flow parameters of the second stream removed from the reactor and, if a subsequent reactor is used, also to control one or more mass flow parameters of the second stream removed from the subsequent reactor.

[0102] 26. The method of embodiment 25, wherein a distributed control system, preferably a distributed control system comprising a PID controller, is also used to control the mass flow rate and / or mass flow rate of the aqueous phase removed from the phase separation.

[0103] 27. The method of embodiment 26, wherein one set of controllers is adjusted to run slower compared to the other controllers.

[0104] 28. The method of embodiment 21 or 22, wherein the water content in the reactor, the water content in the subsequent reactor if a subsequent reactor is used, and the water content of the phase separation are controlled using dynamic decoupling.

[0105] 29. The method according to any one of the preceding embodiments, wherein the temperature in the reactor is from 100 to 250°C, in particular from 145 to 200°C.

[0106] 30. The method according to any one of the preceding embodiments, wherein the temperature in the subsequent reactor is from 100 to 250°C, in particular from 145 to 200°C.

[0107] 31. The method according to any one of the preceding embodiments, wherein the prevailing pressure in the reactor is between 100 and 400 bar abs, in particular between 200 and 300 bar abs.

[0108] 32. The method according to any one of embodiments 10 to 30, wherein the prevailing pressure in the subsequent reactor is from 100 to 400 bar abs, in particular from 200 to 300 bar abs. EXAMPLES

[0109] The examples do not limit the invention.

[0110] Example 1 In the continuous process carried out in a plant according to FIG. 1, the following parameters were set:

[0111] [Table 1]

[0112] The yield of crude hydroformylation product (28) was 12 400 kg / h.

[0113] Example 2 A laboratory mini-plant system was used to carry out the continuous hydroformylation of octene. Olefins were fed to the first stirred reactor using a high pressure pump. Synthesis gas was taken from a high pressure pipeline. The reactor was operated at a pressure of about 300 bar.

[0114] An aqueous solution containing 1.8% by mass of cobalt formate as a catalyst precursor was fed to the reactor using a high-pressure pump (under such conditions, the carbon monoxide present in the reactor acts as a ligand for the catalyst, which is generated in situ in the reactor and transfers from the aqueous phase to the organic phase).

[0115] The reactor output is fed to a lower pressure vessel where air is added to oxidize and deactivate the catalyst, removing it from the organic phase to the aqueous phase. The oxidation vessel output is fed to a phase separator. The feed rate to the phase separator was 431-451 g / h, of which about 50 g / h was water fed to the reactor together with the catalyst solution. The phase separator was neither heated nor insulated, so its contents were at a uniform temperature. In the phase separator, the aqueous phase settled to the bottom and was discharged. In this mini plant, the aqueous phase was discarded and not recycled to the reactor.

[0116] A Coriolis mass flowmeter that measured and reported the mass flow rate, temperature, and density of the exit stream was installed in the pipe used to discharge the water from the phase separator. The density measurement was used as the process variable input to a density controller to operate a valve installed in the pipe used to discharge the aqueous phase. The density setpoint of the controller was selected such that the density of the exit stream at the given temperature of 40-50°C was in the two-phase region. This effectively ensured that all of the aqueous phase was discharged from the phase separator and no level measurement was required.

[0117] Analytical results were recorded daily. The amounts of organic and aqueous phases were determined by collecting the discharged stream at the bottom of the phase separator and measuring the volume of each phase after settling for a sufficient time to obtain two well-separated, clear phases. Table 1 shows the results of this experiment. Figures 2, 3 and 4 show the measured density and density setpoints, the composition of the organic phase in the discharged mixture and the temperature of the discharged mixture, respectively, based on Table 1.

[0118] This example shows that even when the temperature difference between the relatively hot reaction zone and the relatively cool aqueous phase settling zone cannot be determined, it is possible to remove a mixture of the two phases in a desired ratio by controlling the density to drain the aqueous phase, thereby completely removing the aqueous phase without removing undesirably large amounts of the organic phase. The density of the cobalt salt solution is 1 kg / dm 3 , there is enough room for a larger density setpoint and, since the analysis can be done continuously in the commercial plant, the control feedback can be faster and the amount of organic phase taken from the commercial reactor can be even less compared to the mini-plant.

[0119] [Table 2] [Explanation of symbols]

[0120] 1. Reactor 2. Pump 3 Nozzles 4. Oxoga 5. Olefins 6. Cobalt(II) Salt Aqueous Solution 7 Control 8 Mass flow controller 9 Valve 10 Lines 11 Differential pressure regulator 12 Line 13 Rear reactor 14 Control device 15 Mass flow controller 16 Valve 17 Line 18 Control valve 19 Line 20 High-temperature and reduced-pressure vessel 21 Line 22 Pump 23 Line 24 Compressor 25 Line 26 phase separator 27 Line 28 Product Line 29 Off-gas line 30 Water Line 31 Liquid level regulator 32 Valve 33 Water mass flow controller 34 Valve 35 Mass flow controller for organic matter 36 Liquid level regulator 37 Valve 38 Flow Control Device

Claims

1. 1. A process for hydroformylating olefins having from 6 to 20 carbon atoms in the presence of a cobalt catalyst and in the presence of an aqueous phase with intimate mixing in a reactor, wherein a first stream comprising the hydroformylation product is removed at the top of the reactor and a second stream comprising the aqueous phase is removed from the bottom of the reactor through at least one line leading out of the bottom of the reactor, the process comprising controlling one or more mass flow parameters of the second stream in response to the density of the second stream.

2. 10. The method of claim 1, wherein the density of the second stream is measured in a line leading out from the bottom of the reactor.

3. 3. The method of claim 1 or 2, wherein the one or more mass flow parameters are mass flow rate, mass flow rate, or any other parameter determined based on the mass flow rate and / or mass flow rate.

4. 4. The method of claim 1, further comprising the steps of: measuring a density of the second stream and determining one or more control variables based on the measured density; comparing the one or more control variables to one or more reference values ​​to determine one or more control quantities; and determining one or more actuation signals using the one or more control quantities to control one or more mass flow parameters of the second stream.

5. 5. The method of claim 1, wherein the density is measured with one or more Coriolis mass flowmeters.

6. 6. The method according to claim 1, wherein the measured density of the second stream is compared with a predetermined reference value for the density of the second stream, and the mass flow rate and / or mass flow velocity of the second stream is increased if the measured density of the second stream exceeds the predetermined reference value for the density of the second stream.

7. 7. The method according to claim 1, wherein the measured density of the second stream is compared to a predetermined reference value for the density of the second stream, and if the measured density of the second stream is less than the predetermined reference value for the density of the second stream, the mass flow rate and / or the mass flow rate of the second stream is reduced.

8. 8. The method of claim 1, wherein the density of the second stream is measured at at least one point in a line leading out from the bottom of the reactor.

9. 9. The process of any one of claims 1 to 8, wherein the first stream and the second stream are sent to a subsequent reactor.

10. 10. The process of claim 9, wherein a first stream comprising the hydroformylation product is removed at the top of the subsequent reactor and a second stream comprising the aqueous phase is removed from the bottom of the subsequent reactor.

11. 11. The method of claim 10, wherein one or more mass flow parameters of the second stream removed from the bottom of the subsequent reactor through at least one line leading out from the bottom of the subsequent reactor are controlled in response to the density of the second stream.

12. 12. The process according to any one of claims 1 to 11, wherein the first and second streams withdrawn from the reactor or from the subsequent reactor, if present, are oxygenated in the presence of an aqueous cobalt (II) salt solution, in which the cobalt catalyst decomposes to form cobalt (II) salts, which are extracted into an aqueous phase, and the two phases are then separated.

13. 13. The method of claim 12, wherein the water content in the reactor, the water content in the subsequent reactor if a subsequent reactor is used, and the water content of the phase separation are controlled using dynamic decoupling.

14. 14. The process according to any one of claims 1 to 13, wherein the temperature in the reactor is from 100 to 250°C, and if a subsequent reactor is used, the temperature in the subsequent reactor is from 100 to 250°C.

15. 15. The process according to any one of claims 1 to 14, wherein the prevailing pressure in the reactor is from 100 to 400 bar abs, and if a subsequent reactor is used, the prevailing pressure in the subsequent reactor is from 100 to 400 bar abs.

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