Reactor

Abstract

A liquid / gas reactor is disclosed, which includes a primary catalyst bed having an inlet end and an outlet end, a means for feeding a primary feed stream to the inlet end of the primary catalyst bed, the primary feed stream including fresh feed and recycled at least partially converted liquid product, a secondary catalyst bed having an inlet end and an outlet end, the secondary catalyst bed extending substantially vertically through the primary catalyst bed, a means for feeding a secondary feed stream to the inlet end of the secondary catalyst bed, the secondary feed stream including recycled at least partially converted liquid product, a means for collecting the at least partially converted liquid product from the outlet end of the primary catalyst bed and recycling at least a portion of the at least partially converted liquid product to the inlet ends of the primary catalyst bed and the secondary catalyst bed, a separating wall between the primary and secondary catalyst beds, a means for feeding a primary gas stream only to the inlet end of the primary catalyst bed, and a means for feeding a secondary gas stream only to the inlet end of the secondary catalyst bed. A method for carrying out a gas-liquid reaction using the reactor is also disclosed.

Description

[Technical field]

[0001] The present disclosure relates to a liquid / gas reactor and a process for carrying out a gas / gas reaction using the same. In particular, the present disclosure relates to a liquid / gas reactor for carrying out a liquid recycle process, comprising a primary and a secondary catalyst bed. [Background technology]

[0002] Chemical reactions between liquids and gases are often carried out on solid catalyst beds. The reaction may be exothermic, i.e., generate heat, or endothermic, i.e., use heat to cool the surrounding atmosphere. In some reactions, the heat effect of the reaction is moderate. However, even in these, loss of selectivity can occur if the temperature is not controlled. For very exothermic or endothermic reactions, it is necessary to be more rigorous in controlling the heat effect. In extreme cases, the heat generated by a strong exothermic reaction can cause thermal runaway. Similarly, the cooling effect of a strong endothermic reaction can result in the quenching of the reaction.

[0003] A commonly used method for controlling temperature in liquid / gas reactors in which exothermic or endothermic reactions occur is to recycle the heated or cooled products back to the reactor. This recycle has the effect of limiting the temperature rise by diluting the reactants and reducing the conversion per pass. These so-called "liquid recycle" reactors are widely used commercially, for example, in the hydrogenation of benzene, the selective hydrogenation of olefins to remove alkynes and / or dienes, and the hydrogenation of aldehydes to alcohols.

[0004] A schematic diagram of a typical reactor for the selective hydrogenation of alkynes and dienes in C2 and C3 streams is shown in Figure 1. The hydrogenation unit includes a primary reactor 1 and a finishing reactor 2. The C3 feedstock is fed in line 3 to the primary reactor 1 where it reacts with hydrogen fed in line 4 over a catalyst. The products are extracted in line 5 and cooled in cooler 6 before being sent in line 7 to a liquid / gas separator 8. A portion of the liquid is removed in line 9 and recycled to the primary reactor 1. In the illustrated configuration, the recycle stream 9 is mixed with the feed stream 3 before being fed to the primary reactor 1. Excess gas from the separator is removed in line 10.

[0005] The remaining liquid from the gas / liquid separator is removed in line 11 and fed to finishing reactor 2, which is a plug flow reactor. Product is removed in line 12. It will be appreciated that liquid recycle reactors are partially backmixed since the feed is diluted with the recycle product stream.

[0006] For 100% alkenes hydrogenation to alkanes or aldehydes hydrogenation to alcohols, typical recycle rates of 10-20 times the feed rate are required to avoid a total reactor temperature rise of more than 20 °C. The recycled product significantly dilutes the reactants, thus slowing the reaction rate, and the heat of reaction is at least partially absorbed by the recycled product, both of which serve to reduce the total reactor temperature rise.

[0007] The finishing reactor 2, also known as the polishing reactor, is necessary to produce a high quality product with low levels of unreacted feed components. In order to obtain suitable liquid velocities for good distribution, the cross-sectional area of ​​the finishing stage must be much smaller than in the liquid recirculation reactor, and therefore, to achieve sufficient catalyst volume, a long finishing reactor must be used.

[0008] Another type of liquid recirculation reactor developed by the inventors of the present invention and disclosed in EP 2516050(B1) is shown in Figure 2. The reactor disclosed in EP 2516050(B1) is a modification of a packed bed liquid / gas reactor 21 which improves the effectiveness of the catalyst and eliminates the need for a finishing reactor by providing a minor (or secondary) catalyst bed 23 extending through a major (or primary) catalyst bed 22. Separate feed streams 24, 25 are provided to the primary and secondary catalyst beds 22, 23, and a mixture of fresh feed stream 26 and recycled product 27 is fed to the primary bed 22 while only the recycled product 27 is fed to the secondary bed 23, allowing improved overall conversion to be achieved. A gas stream 28 is fed to both the primary and secondary catalyst beds through a shared vapor space at the top of the reactor.

[0009] As the liquid and gaseous reactants pass through the catalyst beds, the pressure drops from a maximum at the inlet end of the catalyst bed (where the reactants enter) to a minimum at the outlet end (where the products and excess reactants exit). The present inventors have surprisingly found that in the primary / secondary catalyst bed configuration of the EP 2516050(B1) reactor, the pressure drop through the primary and secondary catalyst beds should ideally be identical to achieve optimal overall conversion. The pressure drop can be calculated by the Ergun equation and depends on factors such as the particle size of each catalyst bed, bed voidage and liquid flow rate. Consistently achieving the same pressure drop through both catalyst beds has proven surprisingly difficult in practice. For example, the particle size of the catalyst in each bed may be different if loaded from different batches, or the voidage in each bed may be different due to differences in catalyst loading or catalyst settling after loading.

[0010] Accordingly, the present invention aims to solve one or more problems associated with prior art liquid / gas reactors and to provide a liquid / gas reactor capable of achieving consistent and improved conversion rates. Summary of the Invention

[0011] According to a first aspect of the present invention there is provided a liquid / gas reactor comprising: (a) a primary catalyst bed having an inlet end and an outlet end; (b) means for supplying a primary feed stream to an inlet end of the primary catalyst bed, the primary feed stream comprising fresh feed and recycled at least partially converted liquid product; and (c) a secondary catalyst bed having an inlet end and an outlet end, the secondary catalyst bed extending substantially vertically through the primary catalyst bed; (d) means for supplying a secondary feed stream to an inlet end of the secondary catalyst bed, the secondary feed stream comprising recycled at least partially converted liquid product; and (e) means for collecting the at least partially converted liquid product from the outlet end of the primary catalyst bed and for recycling at least a portion of the at least partially converted liquid product to the inlet ends of the primary catalyst bed and the secondary catalyst bed; (f) a separation wall between the primary catalyst bed and the secondary catalyst bed; (g) means for supplying a primary gas flow only to the inlet end of the primary catalyst bed; (h) means for supplying a secondary gas stream only to the inlet end of the secondary catalyst bed.

[0012] By providing a means to supply separate gas flows to the primary and secondary catalyst beds, the gas flows to the primary and secondary catalyst beds are independent of one another and can optionally be individually controlled. The inventors have surprisingly found that this can mitigate the effects of unequal pressure drops across the catalyst beds, resulting in more consistent and improved overall conversion.

[0013] Thus, in some embodiments, the reactor includes a means for separately controlling the flow rate of the primary gas stream and the flow rate of the secondary gas stream. The flow rates of the gas streams can be controlled by any suitable means, such as flow control valves. In one configuration, the primary and secondary gas streams may be supplied to the reactor from separate sources at separately controlled flow rates. Alternatively, the primary and secondary gas streams may be supplied from a single source through a conduit that is branched to provide separate primary and secondary gas streams. In such an embodiment, a flow control valve may be provided in each branch to separately control the flow rates of the primary and secondary gas streams.

[0014] The gas flow rate should be sufficient to maintain the liquid feed saturated with the gas reactant throughout the entire area of ​​both catalyst beds. Saturation can be determined, for example, by the formation of excess gas reactant bubbles. Alternatively or additionally, the hydrogen level in the vent stream can be analyzed. If the hydrogen level is high enough, it can be inferred that the liquid feed is saturated with the gas reactant. If it is determined that either bed is not saturated with the gas reactant, the flow rate of gas to that bed can be increased.

[0015] The secondary catalyst bed is fed only with feed that has already been reacted and therefore at least partially converted, such that the product stream exiting the secondary catalyst bed provides a more fully converted end product compared to a reactor without a secondary catalyst bed.

[0016] The secondary catalyst bed may be located at any suitable location within the primary catalyst bed, but it will be understood that the secondary catalyst bed extends vertically through the primary catalyst bed such that the inlet and outlet ends of the secondary catalyst bed are not blocked by the primary catalyst bed. In some embodiments, the secondary catalyst bed is located at the center of the primary catalyst bed, such that the primary catalyst bed forms an annulus around the secondary catalyst bed. Alternatively, the secondary catalyst bed may be offset to the side of the primary catalyst bed or placed against the wall of the reactor.

[0017] The reactor is a liquid / gas reactor in that the fluid passing through the reactor is in both the liquid and gas phases. The fluid passes over a solid, i.e., a heterogeneous catalyst, within the reactor.

[0018] The reactor and its components may be constructed of any suitable material. In some embodiments, the separation wall is formed from an insulating material. This may be particularly useful when the primary and secondary catalyst beds are operated at different temperatures.

[0019] The separation wall may be of any suitable structure. For example, the separation wall may be formed by an internal pipe, in which the secondary catalyst bed is placed. The separation wall may be of any suitable cross-sectional shape, such as circular. Alternatively, the separation wall may be formed, for example, by a half-pipe fixed to the wall of the reactor.

[0020] In some embodiments, the secondary catalyst bed includes a cover for isolating the inlet end of the secondary catalyst bed from the inlet end of the primary catalyst bed, and the secondary gas and feed stream are supplied to the inlet end of the secondary catalyst bed inside the cover. It will be understood that the cover defines a closed cavity above the inlet end of the secondary catalyst bed into which the secondary gas and feed stream are supplied. Thus, the cover may be in the form of a convexly curved plate or dome, or may comprise either side walls and a roof, or a single continuous side wall and a roof. In some embodiments, the cover includes at least partially an extension of the separation wall above the primary and secondary catalyst beds, such that the extension of the separation wall forms the side walls of the cover.

[0021] In some embodiments, the cover includes a removable cap. Providing a removable cap allows convenient access to the secondary catalyst bed when necessary, for example, to replace the catalyst. In some embodiments, the cover further includes a gasket for forming an airtight seal with the removable cap.

[0022] The reactor may include a means for collecting the product stream from the outlet end of the secondary catalyst bed. In some embodiments, the means for collecting the product stream from the outlet end of the secondary catalyst bed includes a conduit for diverting the product stream from the secondary catalyst bed to a receiving section of the reactor, the receiving section being isolated from the outlet end of the primary catalyst bed, at least in terms of liquid flow. The receiving section may be a vessel or part of the reactor suitable for receiving the product stream exiting the secondary catalyst bed and keeping it separate from the product stream exiting the primary catalyst bed. For example, the receiving section may include a baffle offset to one side of the bottom of the reactor, the baffle acting as a weir overflowed with the product from the secondary catalyst bed. Alternatively, the baffle may be combined with a roof through which a conduit passes to form a closed vessel for receiving the product from the secondary catalyst bed. In such a case, provision may be made for equalizing the vapor pressure between the respective sides of the baffle and for an overflow of the product from the secondary catalyst bed to the outlet end of the primary catalyst bed.

[0023] In some embodiments, all of the at least partially converted product from the outlet end of the primary catalyst bed is recycled, a portion is recycled to the inlet end of the primary catalyst bed, and a portion is recycled to the inlet end of the secondary catalyst bed.

[0024] In some embodiments, the reactor includes means for regulating the temperature of the recirculated product stream, such as a heater and / or a cooler.

[0025] In some embodiments, the reactor includes means for separately controlling the flow rate of the primary feed stream and the flow rate of the secondary feed stream. For example, the primary feed stream and the secondary feed stream may each be controlled by a flow control valve in the respective line. The flow rate of the secondary feed stream fed to the secondary catalyst bed may be equal to the final product rate. However, for ease of control, it is preferred to feed an excess of up to 100%. The excess may be combined, for example, with a recycle stream from the primary catalyst bed. In a particularly preferred embodiment, the excess overflows the weir and is thus combined with the outflow from the primary reactor bed. Preferably, the final product rate is then controlled by the overflow of the excess across the weir to maintain a desired liquid level on the primary catalyst bed side of the weir.

[0026] The feed flow ratio can be defined as the ratio of the flow rate of the secondary feed stream to the flow rate of the primary feed stream. Similarly, the bed cross-sectional area ratio can be defined as the ratio of the cross-sectional area of ​​the secondary catalyst bed to the cross-sectional area of ​​the primary catalyst bed.

[0027] Generally, the bed cross-sectional area ratio is selected to maintain the necessary vapor / liquid mixing and achieve the necessary wetting of the catalyst. The bed cross-sectional area ratio may be 0.1 to 5 times, 0.2 to 3 times, or 0.5 to 2 times the feed flow ratio. In some embodiments, the bed cross-sectional area ratio is 1:1. This allows the secondary catalyst bed to maintain a liquid velocity that provides good vapor / liquid mixing and good wetting, which is generally at the same level as is achieved in the primary catalyst bed.

[0028] The recycle rate may be controlled to target a temperature rise of 10-15°C or less across the primary catalyst bed. The exact recycle rate required to achieve this depends on the heat generated by the reaction, which in turn depends on the reactants used. For example, lighter alcohols may generate more heat of reaction than heavier alcohols and therefore require a higher recycle rate to increase the dilution factor. In general, the ratio of recycle stream to fresh feed fed to the primary catalyst bed may be 1-100, 5-50, 10-40, 15-35, or 20-30. A ratio of 20-30 is particularly preferred for reactions such as butanal hydrogenation. For octanal hydrogenation, lower ratios can be used since the heat of reaction is lower and the heavier alcohols are less sensitive to temperature and therefore a higher temperature rise can be tolerated. For example, a ratio of 1-10 can be used. The ratio of recycle product fed to the secondary catalyst bed to fresh feed fed to the primary catalyst bed may be 1-2. The ratio of recycle product to final product fed to the secondary catalyst bed is preferably greater than 1, for example 1-2.

[0029] Any suitable catalyst may be used in the primary and secondary catalyst beds. In general, the choice of catalyst will depend on the reaction being carried out, but may include nickel, copper, chromium, palladium, or any mixture thereof. The catalyst may also be in any suitable form, such as pellets, extrudates, resins, or impregnated packings. Suitable catalyst supports may include, for example, alumina, silica, vanadia, zirconia, or carbon. The catalysts used in the primary and secondary catalyst beds may be the same or different.

[0030] The reactor may be suitable for use in any exothermic or endothermic reaction that can be carried out on a solid catalyst bed. Examples of exothermic reactions include hydrogenation of aldehydes, ketones, alkynes, dienes, or aromatic compounds, and oxidation reactions. Examples of endothermic reactions include dehydrogenation reactions. In particular, the reactor of the present invention may be suitable for liquid-phase hydrogenation reactions (i.e., hydrogenation of liquid reactants with hydrogen vapor), such as the selective hydrogenation of butadiene to butene, the production of cyclohexane from benzene, the hydrogenation of butanal to butanol, or the hydrogenation of octanal to octanol, the hydrogenation of dimethyl succinate to 1,4-butanediol, or the production of 2-ethylhexanol from 2-ethyl-hex-2-enal.

[0031] According to a second embodiment of the present invention there is provided a method for carrying out a gas-liquid reaction using a reactor of the first aspect, the method comprising: (a) feeding a primary feed stream to an inlet end of a primary catalyst bed of a reactor, the primary feed stream comprising fresh feed and recycled at least partially converted liquid product; (b) providing a primary gas stream to an inlet end of the primary catalyst bed; (c) causing a reaction in a primary catalyst bed; (d) collecting an at least partially converted liquid product stream from the outlet end of the primary catalyst bed; (f) recycling at least a portion of the at least partially converted liquid product stream to the inlet end of the secondary catalyst bed; (f) recycling at least a portion of the at least partially converted liquid product stream to the inlet end of the secondary catalyst bed of the reactor; (g) providing a secondary gas stream to an inlet end of the secondary catalyst bed; (h) causing reaction in a second catalyst bed; (i) collecting a product stream from the secondary catalyst bed separately from an at least partially converted liquid product stream from an outlet end of the primary catalyst bed.

[0032] It will be appreciated that the reaction in the primary catalyst bed occurs between the primary gas stream and the primary feed stream, and the reaction in the secondary catalyst bed occurs between the secondary gas stream and the secondary feed stream.

[0033] In some embodiments, all of the at least partially converted liquid product from the primary catalyst bed is recycled, or alternatively, a portion of the at least partially converted liquid product may be collected and recovered from the reactor.

[0034] In some embodiments, the method includes the additional step of heating or cooling the at least partially converted liquid product stream prior to recycling to the primary and / or secondary catalyst beds. It will be appreciated that the step of heating or cooling the at least partially converted liquid product stream occurs between steps (d) and (e) / (f) of the method.

[0035] In some embodiments, the method includes separately controlling the flow rates of the primary and secondary gas streams. The flow rates of the primary and secondary gas streams may be controlled by any suitable means, for example, by separate flow control valves on each line.

[0036] The method can be used to carry out any suitable reaction. In some embodiments, the reaction is the hydrogenation of an aldehyde to an alcohol. Alternatively, the reaction may be the selective hydrogenation of a diene or alkyne to an olefin. In other embodiments, the reaction is the hydrogenation of an aromatic ring in an aromatic compound.

[0037] The catalyst and reaction conditions used in the process depend on the reaction being carried out. For example, if the reaction is hydrogenation of an aldehyde, a copper / carbon or copper / chromium catalyst can be used and the reaction can be carried out at a temperature of about 140° C. to about 200° C. and at a pressure of at least 1 MPa above ambient pressure. For selective hydrogenation of dienes, a palladium or alumina catalyst can be used and the reaction can be carried out at a temperature of about 20° C. to about 130° C. and at a pressure of about 0.5 MPa to about 2 MPa above ambient pressure. [Brief description of the drawings]

[0038] [Figure 1] FIG. 1 shows an example of a liquid / gas reactor known from the prior art. [Diagram 2] FIG. 1 shows another example of a liquid / gas reactor known from the prior art. [Diagram 3] FIG. 1 illustrates a liquid / gas reactor according to one embodiment of the present invention. [Figure 4] FIG. 2 illustrates a liquid / gas reactor according to another embodiment of the present invention. [Diagram 5] FIG. 2 shows a close-up view of a liquid / gas reactor according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] A liquid / gas reactor according to an embodiment of the first aspect of the invention is shown diagrammatically in Figure 3. The reactor 31 comprises a primary catalyst bed 32 and a secondary catalyst bed 33 separated from each other by a separating wall 43. The secondary catalyst bed 33 is centrally arranged such that the primary catalyst bed 32 forms an annulus around the secondary catalyst bed 33. Gas is fed to the reactor via a line 34 which branches to feed a primary gas stream 34a to the primary catalyst bed 32 and a separate secondary gas stream 34b to the secondary catalyst bed 33. Each branch 34a, 34b may have respective means (not shown) for individually controlling the flow rate of gas to the primary and secondary catalyst beds 32, 33.

[0040] Fresh feed is provided via line 35 and mixed with a portion 52 of the recycled product stream 36 to provide a primary feed stream 41. The primary feed stream 41 is fed to the primary catalyst bed 32 where reaction occurs between the primary feed stream 41 and the primary gas stream 34a. Another portion of the recycled product stream 36 is provided to a secondary feed stream 42. The secondary feed stream 42 is fed to the secondary catalyst bed 33 where further reaction occurs between the secondary feed stream 42 and the secondary gas stream 34b.

[0041] Off-gas is removed from the bottom of reactor 31 via line 37. The at least partially converted product from the primary catalyst bed 32 is recovered via line 38 using pump 39. The temperature of the at least partially converted product stream is regulated by heater / cooler 40 before being recycled via line 36 to the primary and secondary feed streams 41, 42. The more fully converted product from the secondary catalyst bed 33 is collected via line 44.

[0042] The primary and secondary catalyst beds 32, 33 have an inlet end (generally indicated at 45) through which reactants enter, and an outlet end (generally indicated at 46) through which products and excess reactants exit. The secondary catalyst bed 33 includes a cover 47 (shown in more detail in FIG. 5) for isolating the inlet end of the secondary catalyst bed 33 from the inlet end of the primary catalyst bed 32. The secondary feed stream 42 and the secondary gas stream 34b are supplied to the secondary catalyst bed 33 in a cavity defined by the cover 47, allowing separate flow rates of gas to be supplied to the primary and secondary catalyst beds 32, 33. Without wishing to be bound by theory, it is believed that by separately controlling the flow rates of gas to the primary and secondary catalyst beds, the effects of different pressure drops through the primary and secondary catalyst beds can be mitigated, ensuring consistent reaction rates and therefore consistent improved overall conversion despite pressure drop differences.

[0043] The reactor of the present invention is a process for the synthesis of aliphatic C2-C olefins over a Cu / Cr or Cu / C catalyst. 20It can be used for the hydrogenation of aldehydes to the corresponding alcohols. For this reaction, the same catalyst is generally used in both catalyst beds. The residence time is about 0.1 to about 10 hours, based on the feed. The temperature of the catalyst bed ranges from about 100°C to about 200°C, and the absolute pressure is about 0.1 to about 5 MPa. Alternatively, the reaction may be carried out over a nickel catalyst, in which case the residence time is about 0.1 to about 10 hours, based on the feed. The reaction is carried out at a temperature of about 70°C to about 150°C and an absolute pressure of about 0.1 to about 5 MPa.

[0044] The recycle of the at least partially converted product stream is believed to advantageously limit the temperature rise across the reactor. By limiting the temperature rise, the outlet temperature can be limited. This has the advantage of limiting or avoiding by-product formation and can provide improved selectivity. Furthermore, low inlet temperatures are avoided. This is beneficial since low inlet temperatures require a large induction zone in the reactor inlet before the reaction can start. However, the recycle rate is preferably not greater than necessary, as this would dilute the reactants too much with the product, reducing the effectiveness of the catalyst.

[0045] Whatever catalyst system is used, the recycle rate is preferably about 1 to about 50 times the fresh feed rate. The catalyst bed may be sized such that the liquid superficial velocity ranges from about 0.2 to about 20 cm / s. Hydrogen is generally fed in an amount about equal to or up to about twice the stoichiometric requirement. Aliphatic C2-C 20 Because the hydrogenation of aldehydes is an exothermic reaction, a cooler 40 is used to remove the heat of reaction from the recycled product stream.

[0046] Another embodiment of the invention is shown diagrammatically in Figure 4. The reactor shown in Figure 4 is substantially the same as the reactor shown in Figure 3, but with the addition of a conduit 48 to direct the product from the outlet end of the secondary catalyst bed 33 to a weir formed by a baffle 49 offset to one side of the bottom of the reactor 31. The weir is filled with product from the secondary catalyst bed 33, so that any overflow mixes with the partially converted product from the primary catalyst bed 32 and is recycled via line 38. Flooding of the weir with product from the secondary catalyst bed 33 can prevent the entry of product from the primary catalyst bed 32. There may be a roof over the weir, so that the partially converted product from the primary catalyst bed 32 is deflected by the roof and does not enter the product recovered via line 44. The product from the weir is recovered via line 44.

[0047] A more detailed enlarged view of the top of the reactor 31 is shown in Figure 5. The secondary catalyst bed 33 includes a cover 47, which includes a continuous side wall 50 formed by an extension of the separating wall 43. The cover 47 further includes a removable cap 51, which allows access to the secondary catalyst bed 33 when necessary, such as for changing the catalyst. The cover 47 also includes a gasket 52 for forming an airtight seal between the side wall 50 and the cap 51. The cover defines a cavity above the inlet end of the secondary catalyst bed 33 into which the secondary gas stream 34b and the secondary feed stream 42 are fed. This keeps the secondary gas stream 34b separate from the primary gas stream 34a fed to the inlet end of the primary catalyst bed 32, and allows the flow rates of the primary and secondary gas streams 34a, 34b to be controlled separately. EXAMPLES

[0048] Effect of different pressure drops on reactor performance The performance of the reactor shown in Figure 2 was investigated at different secondary catalyst bed conditions resulting in different pressure drops. The reactor was used for the hydrogenation of butyraldehyde to butanol.

[0049] The primary and secondary catalyst beds each had the same bed length of 10,000 mm. The primary catalyst bed had a diameter of 1000 mm. The pressure at the top of the reactor was 3 MPa, while the pressure at the bottom of the reactor was primarily a function of the pressure drop through the primary catalyst bed, which is calculated by Ergun's equation. The assumed constant temperature was set at 150° C. The hydrogen flow rate through the secondary catalyst bed was measured under different bed conditions (Examples 1-3).

[0050] Comparative Example 1 Comparative Example 1 is a reference example. The particle size and packing in the secondary catalyst bed were the same as in the primary catalyst bed, and the pressure drop through the primary and secondary catalyst beds was the same. The hydraulic diameter of the particles was 1.6755 mm, and the void fraction was 0.38.

[0051] Comparative Example 2 Comparative Example 2 was used to measure the effect of varying the particle size of the secondary catalyst bed while keeping the porosity the same. The particles in the secondary catalyst bed were smaller in diameter (1.4904 mm) than the particles in the primary catalyst bed (1.6755 mm). The porosity of both beds was the same as in Comparative Example 1 (i.e., 0.38). The smaller particles may result, for example, from undesired attrition of the particles during loading of the catalyst into the reactor. Each loading of catalyst particles is somewhat different, and therefore the level of undesired attrition may vary from loading to loading.

[0052] Comparative Example 3 Comparative Example 3 was used to measure the effect of varying the porosity in the secondary catalyst bed while keeping the particle size the same. The secondary catalyst bed had a larger porosity (0.40) than the primary catalyst bed (0.38). The particle size of both beds was the same as in Comparative Example 1 (i.e., 1.6755 mm). The different porosities could result, for example, from different compression of the catalyst particles as they are loaded into the reactor. Each loading of catalyst particles is somewhat different, and therefore the compression could be different for each loading.

[0053] Table 1 shows the fluxes achieved through the secondary catalyst bed in each of Comparative Examples 1-3.

[0054] [Table 1]

[0055] In Comparative Example 2, the flow of hydrogen through the secondary catalyst bed was reduced, which slowed the reaction rate, resulting in lower conversion, less efficient use of the secondary catalyst, and reduced reactor performance.

[0056] In Comparative Example 3, the hydrogen flow through the secondary catalyst bed was increased, which may lead to lower selectivity, shorter residence time and / or lower conversion, and may provide a path for hydrogen to bypass the primary catalyst bed, resulting in lower hydrogen flow rate through the primary catalyst bed and lower conversion in the primary reactor bed and reduced reactor performance.

[0057] The benefits of providing separate primary and secondary gas flows In contrast to the above examples, in the reactor according to the invention, the pressure drop on the primary and secondary sides can be controlled independently, as shown in Figure 3. Again, the primary and secondary catalyst beds each had the same bed length of 10,000 mm. The primary catalyst bed had a diameter of 1000 mm. The pressure at the top of the primary catalyst bed was 3 MPa, while the pressure at the bottom of the reactor was mainly a function of the pressure drop through the primary catalyst bed, which was calculated by Ergun's equation. The pressure at the top of the secondary catalyst bed was controlled to keep a constant flow rate through the secondary catalyst bed. The assumed constant temperature was set at 150°C.

[0058] Example 4 Example 4 was a repeat of Comparative Example 1, except that the reactor was as shown in Figure 3 and the pressure at the top of the secondary catalyst bed was controlled to maintain a constant flow rate through the secondary catalyst bed.

[0059] Example 5 Example 5 was a repeat of Comparative Example 2, except that the reactor was as shown in Figure 3 and the pressure at the top of the secondary catalyst bed was controlled to maintain a constant flow rate through the secondary catalyst bed.

[0060] Example 6 Example 6 was a repeat of Comparative Example 3, except that the reactor was as shown in Figure 3 and the pressure at the top of the secondary catalyst bed was controlled to maintain a constant flow rate through the secondary catalyst bed.

[0061] Table 2 shows the fluxes achieved through the secondary catalyst bed in each of Examples 4-6.

[0062] [Table 2]

[0063] Because the present invention allows for independent control of the pressure at the top of the secondary catalyst bed so as to keep the flow rate through the secondary catalyst bed constant, the problems identified above with respect to the comparative examples do not occur and optimal reactor performance is maintained across all examples.

Claims

1. 1. A liquid / gas reactor comprising: (a) a primary catalyst bed having an inlet end and an outlet end; (b) means for supplying a primary feed stream to the inlet end of the primary catalyst bed, the primary feed stream comprising fresh feed and recycled at least partially converted liquid product; and (c) a secondary catalyst bed having an inlet end and an outlet end, the secondary catalyst bed extending substantially vertically through the primary catalyst bed; (d) means for supplying a secondary feed stream to the inlet end of the secondary catalyst bed, the secondary feed stream comprising recycled at least partially converted liquid product; and (e) means for collecting the at least partially converted liquid product from the outlet end of the primary catalyst bed and recycling at least a portion of the at least partially converted liquid product to the inlet ends of the primary catalyst bed and the secondary catalyst bed; (f) a separation wall between the primary catalyst bed and the secondary catalyst bed; (g) means for supplying a primary gas stream only to the inlet end of the primary catalyst bed; (h) means for supplying a secondary gas stream only to said inlet end of said secondary catalyst bed.

2. 10. The reactor of claim 1 further comprising means for independently controlling the flow rates of said primary gas stream and said secondary gas stream.

3. 10. The reactor of claim 1, wherein the secondary catalyst bed is located at the center of the primary catalyst bed, such that the primary catalyst bed forms an annulus around the secondary catalyst bed.

4. 10. The reactor of claim 1, wherein the separation wall is made of an insulating material.

5. 10. The reactor of claim 1, wherein the secondary catalyst bed includes a cover for isolating the inlet end of the secondary catalyst bed from the inlet end of the primary catalyst bed, and wherein the secondary gas stream and the secondary feed stream are supplied to the inlet end of the secondary catalyst bed inside the cover.

6. 6. The reactor of claim 5, wherein the cover comprises an extension of the separator wall above the primary catalyst bed and the secondary catalyst bed.

7. 6. The reactor of claim 5, wherein the cover comprises a removable cap.

8. 8. The reactor of claim 7, wherein the cover further comprises a gasket for forming an airtight seal with the removable cap.

9. 10. The reactor of claim 1 further comprising means for collecting a product stream from said outlet end of said secondary catalyst bed.

10. 10. The reactor of claim 9, wherein the means for collecting the product stream from the outlet end of the secondary catalyst bed comprises a conduit for diverting the product stream from the secondary catalyst bed to a receiving portion of the reactor, the receiving portion being isolated from the outlet end of the primary catalyst bed.

11. 2. The reactor of claim 1, wherein all of the at least partially converted product from the outlet end of the primary catalyst bed is recycled, a portion is recycled to the inlet end of the primary catalyst bed, and a portion is recycled to the inlet end of the secondary catalyst bed.

12. 10. The reactor of claim 1 further comprising means for adjusting the temperature of the recycle stream of the at least partially converted liquid product.

13. 10. The reactor of claim 1 further comprising means for independently controlling the flow rates of said primary feed stream and said secondary feed stream.

14. 2. The reactor of claim 1, wherein the feed flow ratio is the ratio of the flow rate of the secondary feed stream to the flow rate of the primary feed stream, and the bed cross-sectional area ratio is the ratio of the cross-sectional area of ​​the secondary catalyst bed to the cross-sectional area of ​​the primary catalyst bed, and the bed cross-sectional area ratio is 0.5 to 2 times the feed flow ratio.

15. 15. The reactor of claim 14, wherein the bed cross-sectional area ratio is 1:

1.

16. A method for carrying out a gas-liquid reaction using a reactor according to any one of claims 1 to 15, comprising the steps of: (a) feeding a primary feed stream to the inlet end of the primary catalyst bed of a reactor, the primary feed stream comprising fresh feed and recycled at least partially converted liquid product; (b) supplying a primary gas stream to the inlet end of the primary catalyst bed; (c) causing reaction in the primary catalyst bed; (d) collecting an at least partially converted liquid product stream from the outlet end of the primary catalyst bed; (e) recycling at least a portion of the at least partially converted liquid product stream to the primary feed stream; (f) recycling at least a portion of the at least partially converted liquid product stream to the inlet end of the secondary catalyst bed of the reactor; (g) supplying a secondary gas stream to the inlet end of the secondary catalyst bed; (h) causing reaction in the secondary catalyst bed; (i) collecting a product stream from said secondary catalyst bed separately from an at least partially converted liquid product stream from said outlet end of said primary catalyst bed.

17. 17. The method of claim 16, wherein all of the at least partially converted liquid product from the primary catalyst bed is recycled.

18. 17. The method of claim 16, comprising the additional step of heating or cooling the at least partially converted liquid product stream prior to recycling.

19. 17. The method of claim 16, wherein the flow rate of the primary gas stream and the flow rate of the secondary gas stream are controlled independently.

20. 17. The method of claim 16, wherein the reaction is the hydrogenation of an aldehyde to an alcohol, the selective hydrogenation of a diene or alkyne to an olefin, or the hydrogenation of an aromatic ring in an aromatic compound.

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