Method for producing dihydroxy compounds

Abstract

The disclosure is directed to the use of an upflow reactor for producing a dihydroxy compound, to a method for producing a dihydroxy compound, and to a method for manufacturing polycarbonate. The upflow reactor for producing a dihydroxy compound of the disclosure comprises: a vessel; a catalyst bed disposed in said vessel; a distributor in fluid communication with an inlet through which reactants are introduced to said distributor, said distributor being disposed at a lower end of said vessel and comprising distributor perforation(s) disposed in said distributor, at least part of which distributor perforations are in a direction facing away from said catalyst bed; and a collector through which said product dihydroxy compound is removed, said collector being disposed at an upper end of said vessel.

Claims

1. An upflow reactor, comprising: a vessel; a catalyst bed disposed in said vessel; a distributor in fluid communication with an inlet through which reactants for producing a dihydroxy compound are introduced to said distributor, said distributor being disposed at a lower end of said vessel and comprising a distributor perforation disposed in said distributor, at least part of which distributor perforation is in a direction facing away from said catalyst bed; and a collector through which the dihydroxy compound is removed, said collector being disposed at an upper end of said vessel.

2. The reactor according to claim 1, wherein said reactor further comprises a distributor screen disposed between said distributor and said catalyst bed.

3. The reactor according to claim 2, further comprising a further distributor screen between said distributor screen and said collector.

4. The reactor according to claim 2, wherein said distributor screen comprises openings with a diameter of 50 to 300 m and has a porosity of 10 to 50% open area.

5. The reactor according to claim 1, wherein said reactor comprises a second screen disposed at said collector.

6. The reactor according to claim 5, wherein said second screen comprises openings with a diameter of 50 to 300 m and has a porosity of 10 to 50% open area.

7. The reactor according to claim 1, wherein the distributor perforation dimensions are such that the mass flow through each perforation is substantially the same.

8. The reactor according to claim 1, wherein an amount of distributor perforations in the distributor is 50 perforations per m.sup.2 or more.

9. The reactor according to claim 8, wherein the amount of distributor perforations is 80 perforations per m.sup.2 or more.

10. The reactor according to claim 8, wherein the amount of distributor perforations is 100 to 200 perforations per m.sup.2.

11. The reactor according to claim 1, wherein said collector comprises a collector perforation disposed in said collector.

12. The reactor according to claim 1, wherein said vessel has a structural geometry that is substantially cylindrical, substantially parallelepiped, substantial spherical, or a combination thereof.

13. The reactor according to claim 1, wherein said distributor comprises a manifold in fluid communication with said inlet into which a reactant is received, and wherein a plurality of arms extend laterally from said manifold, wherein said distributor perforation is disposed in said plurality of arms.

14. The reactor according to claim 1, wherein said collector comprises a manifold, wherein a plurality of arms extend laterally from said manifold, wherein said collector perforation is disposed in said plurality of arms.

15. The reactor according to claim 14, wherein said plurality of arms comprises arms disposed at opposing ends of said manifold and arms disposed intermediate said opposing ends of said manifold, wherein said arms disposed at said opposing ends of said manifold are shorter than said arms disposed intermediate said opposing ends of said manifold.

16. The reactor according to claim 1, wherein said dihydroxy compound is a bisphenol.

17. A method for producing a dihydroxy compound in an upflow reactor as defined in claim 1, said method comprising: introducing a reactant through said inlet to said distributor; flowing said reactant through said catalyst bed; and recovering said dihydroxy compound from said collector.

18. A method for manufacturing polycarbonate, said method comprising: producing a dihydroxy compound according to a method according to claim 17, and reacting said dihydroxy compound with carbonate source to form polycarbonate.

19. The method of claim 18, wherein the carbonate source is phosgene.

20. The method of claim 18, wherein the carbonate source is diphenyl carbonate.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1: Schematic view of one exemplary embodiment of an upflow chemical reactor.

(2) FIG. 2: Schematic view of reactant distributors, where FIG. 2A is a snapshot of distributor 20 and FIG. 2B is a snapshot of a distributor 20 in a reactor.

(3) FIG. 3: Schematic view of a product collector.

(4) FIG. 4: Snapshot of a single stage drawing in upflow reactor.

(5) FIG. 5: Snapshot of upflow reactor drawing.

(6) FIG. 6: Snapshot of side feed pipes below the distributor screen.

(7) FIG. 7: Isometric view snap shots of 3D modelled geometry with bottom distributor screen (left) and top distributor screen (right).

(8) FIG. 8: Snapshot of velocity contours at a sectional centre plane (left) and the velocity contours at a mid-cross sectional plane (right) for base case design.

(9) FIG. 9: Snap shot of velocity contours on a cross sectional plane located 10 mm above the distributor screen.

(10) FIG. 10: Snapshot of modified geometry with perforations at the bottom face of feed pipes.

(11) FIG. 11: Snapshot of velocity contours at a sectional centre plane (left) and the velocity contours at a cross sectional plane 10 mm above the bottom distributor screen (right).

(12) FIG. 12: Snapshot comparison of velocity contours on a cross sectional plane located 10 mm above the distributor screen; with perforations facing upwards (left) and with apertures facing downward (right).

(13) FIG. 13: Snapshot comparison of velocity contours on a centre sectional plan; with two distributor screens (left) and with one distributor screen (right).

(14) FIG. 14: Geometry model of pipe network model.

(15) FIG. 15: Velocity contours on surface (left) and the velocity contours on a sectional plane (right) of pipe network model.

EXAMPLES

(16) Reactor Geometry

(17) An upflow test kit reactor was designed to have three catalyst bed sections. The total height of the reactor is about 4.4 metres and the diameter is about 0.74 metres. There are two solid partitions dividing the whole reactor into three sections. The schematics of one such section is shown in FIG. 4 (showing distributor 20, distributor screen 27, catalyst bed 12, collector screen 47, and collector 40) and the full schematic of the drawing is shown in FIG. 5 (showing a reactor with three reaction sections: a first stage reaction zone, a second stage reaction zone, and a third stage reaction zone, each having a catalyst bed 12). a distributor system with distributor 20 and distributor screen 27, a first stage reaction zone with catalyst bed 12, a collector system with collector 40 and collector screen 47, a second stage reaction zone with catalyst bed 12, and a third stage collector zone with catalyst bed 12). Each section of the reactor is provided with a distributor system comprising a distributor 20 and a distributor screen 27 and a collector system comprising a collector 40 and a collector screen 47. The distributor system is provided at the bottom of the section and the collector system is provided in the top of the section. Below distributor screen 27, a distributor 20 is provided in the form of a series of side feed pipes to distribute the liquid feed. These side feed pipes are arranged as shown in FIG. 6. Alternatively to the embodiment shown in FIG. 6, each of the side feed pipes may be distribution arms 32 that are attached to a single manifold 28 which enters the reactor, rather than separately entering the reactor (as in the embodiment of FIG. 2B). Each side feed pipe is provided with a set of perforations to distribute the feed across the cross-section. The isometric views of the modelled geometry is shown in FIG. 7.

(18) Process Conditions

(19) The raw materials for bisphenol A manufacture are phenol and acetone. The premixed feed of phenol and acetone are sent to the reactor as per the conditions given in table 1.

(20) TABLE-US-00001 TABLE 1 Process conditions at the inlet and outlet Value Condition Units Inlet Outlet Mass flow kg/h 700 700 Temperature C. 55-65 80-85 Density kg/m.sup.3 1025 1033 Viscosity Pa .Math. s 4.4 4.4 Surface Tension N/m 0.03 0.03

(21) The most important information needed in the current problem is the flow distribution. The deviation from the uniform flow distribution which is referred to as mal-distribution is defined as expressed below.

(22) $\mathrm{maldistribution}=\frac{\max \mathrm{Velocity}-\min \mathrm{Velocity}}{\mathrm{Average}\mathrm{Velocity}\mathrm{at}a\mathrm{defined}\mathrm{cross}\mathrm{section}}$

(23) At a distance of 10 mm above the bottom distributor plate, the mal-distribution is calculated and used as metric to compare across various design alternatives. The mal-distribution numbers at these cross sections are compared across different designs/scenarios to understand the flow behaviour (or reactor behaviour).

Example 1: Base Case Reactor with Two Distributors (Comparative)

(24) A base case design, comprises four side feed pipes and two distributors. The four feed pipes were modelled with 46 perforations with a perforation diameter of 10 mm. The longer pipe was modelled with 13 perforations at 5 cm spacing and the shorter one was with 10 perforations with same spacing. Initially, perforations were made on the upper side of the tube (facing upwards). The distributor plate was modelled with 3825 number of smaller perforations with 5 mm diameter. The distributor screen is 7 mm thick.

(25) The cold flow simulations were done to the geometry with a design as explained in the previous paragraph and the results are shown in FIGS. 8 and 9. FIG. 8 shows the velocity contours of the base case design on a mid-axial sectional plane (left) and also at a mid-cross sectional plane (right). The velocity contours on the axial sectional plane indicated a developing flow and the velocity contours at the cross-sectional plane indicated a parabolic type of flow pattern. These results are as expected in a typical flow through pipe situation. The mal-distribution at the mid cross sectional plane was found to be 151% and it is due to the developing flow pattern with parabolic flow profile. The plane of interest for uniform flow distribution is just above the lower distributor screen. The velocity contours at a plane which is 10 mm above the lower distributor screen are as shown in FIG. 9. The mal-distribution is 189% and this high non-uniformity was attributed to the high velocity patches as highlighted in FIG. 9. The high velocity patches are believed to be due to the fact that more amount of fluid was trying to travel through the first perforation it encounters. These high velocity patches may lead to channeling in the catalyst bed as well.

Example 2: Change in Perforation Facing Direction to Dissipate Momentum

(26) Based on the simulation results discussed for example 1, it was concluded that the high velocity patches are due to the fact that more fluid is trying to pass through the first perforation as it is the lower resistant path. This has resulted in high local velocities at the first aperture. It is possible to minimise the impact of high velocity patches on the catalyst bed by dissipating the momentum with an impingement plate. It was decided to dissipate the momentum using the bottom wall of the section as an impingement plate. This requires the placement of perforations at the bottom face of the side tubes such that fluid travels downward from these pipes and impinges on the bottom wall and dissipates the momentum. Modifications were done to the geometry model to pursue this and taken forward for the Computational Fluid Dynamics (CFD) simulations. A snap shot of modified geometry with perforations at the bottom face of the feed pipes is as shown in FIG. 10.

(27) CFD simulation results are shown in FIGS. 11 and 12. It was observed that when perforations are facing downwards, the fluid enters the reactor downward with higher velocities and the momentum of these smaller jets got dissipated in the zone below the feed pipes due to their impingement on the bottom wall of the section. The fluid after losing its momentum travels upward without disturbing the reaction section (where catalyst bed will be placed). Due to this, the mal-distribution has decreased significantly and the higher velocity patches were found to disappear in the velocity contours just above the lower distributor screen. This is evident as shown in FIGS. 11 and 12. The mal-distribution has come down significantly as shown in FIG. 12.

Example 3: Effect of Number of Distributor Screens

(28) Geometry model was developed with one and two distributor screens and CFD simulations were done to understand the role of the additional distributor screen. The simulation results are shown in FIG. 13. It is clear that the distributor screen at the bottom is mainly to support the catalyst bed and also to help redistribute the fluid. But the role/need of the top distributor screen is in question without the support from CFD modelling. Based on the simulation results, it was found that the top distributor screen is playing a role in maintaining uniform flow even after the reaction section. As a result, the dead space in the reactor was minimised significantly. This is very critical for a good residence time distribution. In FIG. 13, the simulation results with a single distributor screen are compared with the results of two distributor screens and the smaller dead space is clearly evident when the top distributor screen was added.

Example 4: Pipe Network Model

(29) In a feed distribution system, it is ideal to have uniform flow throughout the reactor cross section. In order to achieve good flow distribution across the cross section, it is needed to introduce the feed uniformly across the cross section. In order to distribute the feed effectively four feed pipes have been chosen with 50 perforations (46 in previous simulations). When the distribution system was modelled in this way, it was found that the amount of the feed that flows through these apertures varied significantly. It was understood that different lengths of flow paths were responsible for this behaviour. It is later thought that even though flow path lengths are different for different perforations, same flow can be achieved by playing with the perforation diameters. Here, CFD simulation work to achieve uniform flow through these perforations is discussed in detail.

(30) To be computationally efficient, a pipe network model is modelled as the geometry so that the perforation diameters can be manipulated to assure the same liquid flow through every perforation. The visualised pipe network model geometry is shown in FIG. 14.

(31) Simulations were done on the meshed geometry and the flow rates through every perforation of two pipes (M1 and S1) were monitored. The remaining two pipes (M2 and S2) were assumed to be identical as the first two (M1 and S1). The perforation diameters were changed by trial and error in order to maintain more or less uniform flow through these perforations. The velocity contours of the pipe network model as shown in FIG. 15. The velocity magnitude in the four pipes is very identical based on the colour legend. However, the numerical results are tabulated in Table 2. The total flow rate of 0.2 kg/s was equally distributed to all the feed pipes approximately. Since the number of perforations was different for longer pipe (M1) and shorter pipe (S1), the feed flow rate per perforation is different for these different pipes. The average feed flow rate for M1 pipe perforation is 0.00362 kg/s and for S1 pipe is 0.00438 kg/s. Another point to be noted is the variation along each pipe is minimised by trial and error simulation approach. For example, all the perforations in M1 pipe deliver pretty much the same flow rate and the same is true for S1 pipe as well. The standard deviation numbers were also computed and tabulated to highlight this conclusion. The remaining two pipes were assumed to be identical to reduce the computational intensity.

(32) TABLE-US-00002 TABLE 2 Optimised perforation diameters and the flow rates M1 S1 Perfora- flow rate Perfora- flow rate tion Diameter (kg/s) tion Diameter (kg/s) D1 0.01 0.003798 D15 0.009 0.004284 D2 0.01 0.003721 D16 0.009 0.004232 D3 0.01 0.003617 D17 0.009 0.004133 D4 0.01 0.003521 D18 0.095 0.004501 D5 0.0105 0.003767 D19 0.0095 0.004348 D6 0.0105 0.003654 D20 0.0095 0.004189 D7 0.0105 0.003537 D21 0.0098 0.004274 D8 0.011 0.003742 D22 0.0105 0.004674 D9 0.011 0.003618 D23 0.0105 0.004498 D10 0.011 0.003595 D24 0.011 0.004734 D11 0.011 0.003565 D25 0.0105 0.004338 D12 0.011 0.003529 D13 0.0108 0.003470 D14 0.0105 0.003519 Mean 0.003618 Mean 0.004382 SD 0.000104 SD 0.000196

(33) Set forth below are some examples of an upflow reactor as disclosed herein.

(34) Embodiment 1: Use of an upflow reactor for producing a dihydroxy compound, said upflow reactor comprising: a vessel; a catalyst bed disposed in said vessel; a distributor in fluid communication with an inlet through which reactants are introduced to said distributor, said distributor being disposed at a lower end of said vessel and comprising a distributor perforation (preferably distributor perforations, e.g., a plurality of distributor perforations) disposed in said distributor, at least part of which distributor perforations are in a direction facing away from said catalyst bed; and a collector through which said product dihydroxy compound is removed, said collector being disposed at an upper end of said vessel.

(35) Embodiment 2: The use according to Embodiment 1, wherein said reactor further comprises a distributor screen disposed between said distributor and said catalyst bed, wherein said distributor screen preferably comprises openings with a diameter of 50-300 m and has a porosity of 10-50% open area.

(36) Embodiment 3: The use according to any of the preceding embodiments, wherein said reactor comprises a second screen disposed at said collector, preferably wherein said second screen has a porosity of 10-50% open area.

(37) Embodiment 4: The use according to embodiment 3, wherein said second screen comprises openings with a diameter of 50-300 m.

(38) Embodiment 5: The use according to any of the preceding embodiments, wherein said collector comprises one or more collector perforations disposed in said collector.

(39) Embodiment 6: The use according to any of the preceding embodiments, wherein at least part of said collector perforations are in a direction facing away from the said catalyst bed.

(40) Embodiment 7: The use according to any of the preceding embodiments, wherein the distributor perforation dimensions are such that the mass flow through each perforation is substantially the same.

(41) Embodiment 8: The use according to any of the preceding embodiments, comprising 50 perforations per m.sup.2 or more, such as 80 perforations per m.sup.2 or more, preferably 100-200 perforations per m.sup.2.

(42) Embodiment 9: The use according to any of the preceding embodiments, further comprising at least one further distributor screen between said first distributor screen and said collector, wherein said further distributor screen preferably comprises openings with a diameter of 50-300 m.

(43) Embodiment 10: The use according to embodiment 9, wherein said further distributor screen has a porosity of 10-50% open area.

(44) Embodiment 11: The use according to any of the preceding embodiments, wherein said vessel has a structural geometry that is substantially cylindrical, substantially parallelepiped, substantial spherical, or a combination thereof.

(45) Embodiment 12: The use according to any of the preceding embodiments, wherein said distributor comprises a manifold in fluid communication with said inlet into which a reactant is received, and wherein a plurality of arms extend laterally from said manifold, wherein said one or more distributor perforations are disposed in said plurality of arms.

(46) Embodiment 13: The use according to any of the preceding embodiments, wherein said collector comprises a manifold, wherein a plurality of arms extend laterally from said manifold, wherein said one or more collector perforations are disposed in said plurality of arms.

(47) Embodiment 14: The use according to Embodiment 12 or 13, wherein said plurality of arms comprises arms disposed at opposing ends of said manifold and arms disposed intermediate said opposing ends of said manifold, wherein said arms disposed at said opposing ends of said manifold are shorter than said arms disposed intermediate said opposing ends of said manifold.

(48) Embodiment 15: A method for producing a dihydroxy compound in an upflow reactor as defined in any one of Embodiments 1-13, said method comprising: introducing a reactant through said inlet to said distributor; flowing said reactant through said catalyst bed; and recovering said dihydroxy compound from said collector.

(49) Embodiment 16: A method for manufacturing polycarbonate, said method comprising: producing a dihydroxy compound according to a method according to Embodiment 15, and reacting said dihydroxy compound with carbonate source, such as phosgene or diphenyl carbonate.

(50) Embodiment 17: The use according to any one of Embodiments 1-14, or the method according to Embodiment 15 or 16, wherein said dihydroxy compound is a bisphenol, preferably bisphenol A.