Improvements in or relating to catalyst carriers for tubular reactors

Abstract

A catalyst carrier 1 for insertion into a reactor tube of a tubular reactor, with an outer container 10 comprising a side wall 11, and base 12; defining a receptacle 14 which can be closed and opened by attachment and detachment of removable lid 13; for a removable basket 30 insertable and removable when the lid is detached, which may have one or more perforated walls. The basket may comprise an inner wall, an outer wall, a base and a cover defining an annular chamber for holding catalyst and a central channel. The outer wall of the removable basket and the side wall of the outer container may be spaced apart by co-operating formations, retaining an annular gap. The lid of the outer container may comprise a fluid inlet aperture, and a seal for sealing between the outer container and an inner surface of the reactor tube. In this invention the removable basket can be changed for onward processing, recycling and increasing the amount of recoverable catalyst, without replacing the rest of the catalyst carrier.

Description

The present disclosure relates to improvements in or relating to catalyst carriers for tubular reactors. In particular, the present disclosure relates to catalyst carriers and methods that allow for improvements in the recycling, re-use and / or regeneration of catalyst. Background to the Disclosure Conventional, so-called fixed-bed tubular, reactors comprise a reactor shell containing a plurality of tubes, which are usually cylindrical, and which are usually directly filled with catalyst particles. In use, a heat-transfer medium flows through the shell of the reactor outside these tubes and thereby adjusts the temperature of the catalyst in the tubes by heat exchange across the tube wall. Thus, where the reaction is an exothermic reaction, the heat-transfer medium will allow heat to be removed from the catalyst and where the reaction is an endothermic reaction, the heat-transfer medium will provide heat to the catalyst. For some reactions, the heat effects of the reaction are moderate such that they are either not problematic or they can be readily managed. In some cases, the heat effects are sufficiently small that large-diameter tubes may be used. This has the benefit that there is a large volume of catalyst within the tube. However, for more exothermic or endothermic reactions it is necessary that there is efficient heat transfer via the tube wall to the heat transfer medium to enable the conditions within the reactor to be controlled, in order to maintain a stable operating temperature to avoid detrimental effects occurring. Such effects, for exothermic reactions, may include side reactions taking place, damage to the catalyst such as by sintering of the catalytic active sites, and, in a worst case, thermal runaway. Detrimental effects for endothermic reactions may include quenching of the reaction. To achieve the desired efficiency, the surface area of the tube wall per unit length has to be maximised. This has in the past been achieved by installing a greater number of smaller-diameter tubes. In some reactions, the size restriction means that the tubes are only of the order of about 15 to 40 mm internal diameter. However, the use of this multiplicity of tubes increases the cost and complexity of the reactor. Thus, in an attempt to mitigate these problems, an alternative approach has been developed, in particular for more exothermic or endothermic reactions, in which the catalyst is not directly packed into the reactor tubes but is instead contained in a plurality of catalyst carriers that are configured to sit within the reactor tube. WO2011 / 048361A1, WO2012 / 136971A1, WO2016 / 050520A1 and WO2022 / 064212A1 describe some examples of catalyst carriers configured for use in tubular reactors. Catalyst carriers may usefully be used for a wide range of processes. Examples of suitable uses include processes and reactors for exothermic reactions such as reactions for the production of methanol, reactions for the production of ammonia, methanation reactions, shift reactions, oxidation reactions such as the formation of maleic anhydride and ethylene oxide reactions and the like. A particular example where catalyst carriers may be used is in processes and reactors for performing the Fischer-Tropsch reaction. Catalyst carriers may also be used for endothermic reactions such as pre-reforming, dehydrogenation and the like. During operation of a tubular reactor, one or more reactants are flowed through the reactor tubes so as to pass into and through the catalyst carriers and thereby contact the catalyst contained therein. The catalyst(s) and reactant(s) chosen will be dependent on the desired process taking place in the tubular reactor, and these can vary widely. In one example, a tubular reactor may be configured for a Fischer-Tropsch process. In this example the catalyst will be a Fischer-Tropsch catalyst, for example a transition metal catalyst, for example a cobalt-containing Fischer-Tropsch catalyst. The reactant(s) for the Fischer-Tropsch process may comprise hydrogen and carbon monoxide gases which may be derived from syngas. The catalysts used in catalyst carriers may be ‘poisoned’ if exposed to substances that damage the catalyst. In the example of the Fischer-Tropsch catalyst, when syngas is formed it may contain poisons, such as sulphur, which can permanently damage the catalyst. Typically, the syngas will be subjected to a purification pre-treatment to remove the sulphur before it reaches the tubular reactor. However, there remains a risk that the purification pre-treatment may not fully remove all of the poisonous substances in the syngas, for example due to the use of out-of-specification syngas or a malfunction in the purification pre-treatment. The catalysts used in catalyst carriers may also degrade over time even where not subjected to an acute poisoning event. As such, intermittently it may be necessary to replace the catalyst carriers in the tubular reactor with ones containing fresh catalyst. Summary of the Disclosure The present disclosure provides in a first aspect a catalyst carrier for insertion into a reactor tube of a tubular reactor, the catalyst carrier comprising an outer container and a removable basket for holding catalyst; the outer container comprising a side wall, a base and a removable lid, the side wall and the base defining a receptacle that can be closed and opened by attachment and detachment of the removable lid; the removable basket being insertable into and removable from the receptacle when the removable lid is detached. Beneficially, the configuration of the catalyst carrier may increase the sustainability of the product by allowing an easy means for separating the catalyst from other parts of the catalyst carrier which may typically be metal. Use of the removable basket may ease the segregation of the catalyst for onward processing or recycling and may also increase the amount of the catalyst that can be recovered. It may also speed up the process of catalyst removal or recovery compared to the use of prior art catalyst carriers that typically require cutting or grinding of the catalyst carrier to permit access to the catalyst. Further, the use of the removable basket may permit easier re-use of components of the catalyst carrier. For example, the outer container may be re-used with a fresh removable basket containing catalyst. The old removable basket may be emptied and later re-used or may be recycled, e.g. if damaged or at the end of its useful life. For example, catalyst may over time fuse to metal parts of the catalyst carrier. With prior art catalyst carriers this would result in the whole carrier having to be discarded as it could not easily be recycled, re-used or regenerated. Beneficially, the configuration of the catalyst carrier with the removable basket allows for partial or full re-use of the components with only those components that are damaged needing to be replaced. In some embodiments the removable basket comprises one or more perforated walls. It will be understood that the perforation of the walls may be of any suitable configuration. Indeed, in the present specification where a wall or tube is described as perforated all that is required is that there is means to allow reactants and products to pass through the walls or tubes. Possible configurations include, but are not limited to, the use of a mesh, or the puncturing of an otherwise solid wall with a plurality of apertures that may be arranged regularly or stochastically, or the use of apertures that are overlaid by a mesh. In some embodiments the removable basket defines an annular chamber for holding catalyst. In some embodiments the removable basket comprises an inner wall, an outer wall, a base and a cover defining an annular chamber for holding catalyst and a central channel. In some embodiments the inner wall and the outer wall are perforated. The annular arrangement of the chamber holding the catalyst beneficially permits a flow of reactants through the catalyst in the radial direction, typically outwardly from the central channel. In some embodiments the inner wall and the outer wall are attached to or integrally formed with the base of the removable basket. This may beneficially assist with manual handling of the removable basket. In some embodiments the base of the portion of the removable basket that borders the annular chamber is unperforated. In some embodiments a central portion of the base of the removable basket bordering the central channel comprises a drain hole. In some embodiments the cover of the removable basket is separate from or removable from the inner wall and the outer wall. This may assist with loading and unloading of catalyst from the annular chamber. In particular, the use of a separate cover may greatly speed up processing by avoiding the need for any unscrewing or other detachment of the cover from the rest of the removable basket. Instead the cover may be simply lifted off. In some embodiments the cover of the removable basket comprises a central aperture providing a fluid inlet to the central channel. In some embodiments the cover of the removable basket is annular. In some embodiments the portion of the cover of the removable basket that borders the annular chamber is unperforated. Beneficially, the configuration of the cover may act to channel incoming fluid into the central channel and avoid leakage of fluid directly into the annular chamber. In some embodiments, with the removable lid of the outer container attached the removable basket is compressed between the removable lid and the base of the outer container. Beneficially this may assist in holding the removable basket stationary with respect to the outer container. Also, this may be of particular benefit where a separate cover for the removable basket is used that is not otherwise attached to the inner and outer walls. Instead the compressing action squeezes the removable basket between the removable lid and base of the outer container holding the cover in position. In some embodiments the outer container and the removable basket comprise co-operating formations for securing the removable basket relative to the side wall of the outer container. Beneficially, this may help to define the relative location of the removable basket to the outer container and to define and maintain the required gaps there between. In some embodiments the outer container and the removable basket comprise co-operating formations for spacing apart the removable basket from the side wall of the outer container and the co-operating formations hold the removable basket such that an annular gap is retained between the side wall of the outer container and the outer wall of the removable basket. Beneficially, this may assist to define and maintain the required gaps there between. In some embodiments the co-operating formations are provided on: - the removable lid of the outer container and the cover of the removable basket; and / or on the bases of the outer container and the removable basket. In some embodiments the co-operating formations comprise one or more co-operating projections and recesses. In some embodiments the co-operating formations comprise one or more annular projections and recesses. In some embodiments the annular projections and recesses are continuous or discontinuous around their annular path. In some embodiments the annular projections and recesses consist of circular projections and recesses. In some embodiments a lower face of the removable lid of the outer container comprises two concentrically-arranged annular recesses. In some embodiments the cover of the removable basket comprises two concentrically-arranged annular deformities producing two annular projections for engaging the removable lid of the outer container and two annular recesses for engaging against the inner wall and outer wall of the removable basket. In some embodiments a sealing member, such as an O-ring, may be provided between the cover of the removable basket and the lower face of the removable lid of the outer container. For example, the sealing member may be provided in one or both of the concentrically-arranged annular recesses, or at a location between the concentrically-arranged annular recesses. In some embodiments an upper face of the base of the outer container comprises two concentrically-arranged annular recesses. In some embodiments the base of the removable basket comprises two concentrically-arranged annular deformities producing two annular projections for engaging the base of the outer container and two annular recesses for engaging against or being attached to the inner wall and outer wall of the removable basket. In some embodiments a sealing member, such as an O-ring, may be provided between the upper face of the base of the outer container and the base of the removable basket. For example, the sealing member may be provided in one or both of the concentrically-arranged annular recesses, or at a location between the concentrically-arranged annular recesses. Beneficially, the co-operating formations may help to maintain axial alignment of the components of the catalyst carrier. In some embodiments the co-operating formations may help to keep the central axes of the removable basket and outer container coincident. In some embodiments a lower face of the base of the outer container comprises an annular projection for engaging against a lid of a neighbouring catalyst carrier when the catalyst carriers are installed as a stack in a reactor tube. Beneficially, this may help to maintain alignment of the stack within the reactor tube. In some embodiments with the removable lid of the outer container attached, a fluid-tight seal is formed between the removable lid and the cover such that fluid passing through the removable lid is directed into the central channel. In some embodiments the removable lid of the outer container comprises an inlet aperture providing a fluid inlet to the receptacle of the outer container. In some embodiments the inlet aperture is arranged centrally on the removable lid. In some embodiments the removable lid of the outer container comprises an upstanding outer rim comprising one or more inlet ports providing a fluid path towards the inlet aperture. In some embodiments the removable lid of the outer container comprises a screw thread for attachment. In some embodiments the outer container further comprises a threaded ring attached to or integrally formed with an upper end of the side wall, the threaded ring comprising a screw thread for engaging with the screw thread of the removable lid. In some embodiments the threaded ring is welded to the side wall. In some embodiments the outer container further comprises a seal for sealing between the outer container and an inner surface of the reactor tube. In some embodiments the seal is retained by being compressed between the removable lid and side wall of the outer container or between the removable lid and a threaded ring of the outer container. In some embodiments the outer container further comprises one or more hold-down pads within the annular chamber. The present disclosure provides in a second aspect a method comprising the steps of: i) installing catalyst into a plurality of catalyst carriers as claimed in any preceding claim by filling catalyst into the removable baskets, inserting the removable baskets into the open receptacles of the outer containers and attaching the removable lids to close the receptables; ii) installing the plurality of catalyst carriers into a reactor tube of a tubular reactor; iii) operating the tubular reactor for a period of time; iv) subsequently removing the plurality of catalyst carriers from the reactor tube; v) detaching the removable lids and removing the removable baskets from the outer containers; and vi) emptying the catalyst from the removable baskets. In some embodiments the method further comprising: vii) recycling or re-using the outer containers and / or the removable baskets. In some embodiments the method further comprising: viii) re-using or regenerating the catalyst. The catalyst carrier and method of the present disclosure may usefully be used in a wide range of processes. Examples of suitable uses include processes and reactors for exothermic reactions such as reactions for the production of methanol, reactions for the production of ammonia, methanation reactions, shift reactions, oxidation reactions such as the formation of maleic anhydride and ethylene oxide reactions and the like. A particularly preferred use is in processes and reactors for performing the Fischer-Tropsch reaction. Endothermic reactions such as pre-reforming, dehydrogenation and the like may also be carried out in conjunction with the present methods and linked sets. The removable baskets of the catalyst carriers of the present disclosure may be filled or partially filled with any catalyst suitable for the intended reaction. For example, a Fischer-Tropsch catalyst may be used for the Fischer-Tropsch reaction. Cobalt-containing Fischer-Tropsch catalysts are preferred. The catalyst may be provided as catalyst particles or a catalyst monolith. The catalyst may be provided as a single bed of catalyst or multiple beds of catalyst. The catalyst carrier may be configured to promote axial and / or radial flow through the catalyst. In some embodiments the catalyst carrier may be configured to preferentially promote radial flow through the catalyst. The catalyst carriers of the present disclosure, in particular the outer containers and removable baskets thereof, may be formed of any suitable material. Such material will generally be selected to withstand the operating conditions of the tubular reactor. The catalyst carrier may be fabricated from carbon steel, aluminium, stainless steel, other alloys or any material able to withstand the reaction conditions. Brief Description of the Drawings Embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a catalyst carrier according to the present disclosure; Figure 2 is an enlarged view of a portion of Figure 1; Figure 3 is an enlarged view of another portion of Figure 1; Figure 4 is a perspective view of the removable lid of the catalyst carrier of Figure 1; and Figure 5 is a schematic view of a plurality of catalyst carriers installed in a reactor tube. Detailed Description In the following, aspects and embodiments of the present disclosure will be described, by way of example only, with reference to a vertically orientated tubular reactor having a plurality of vertical reactor tubes extending between an upper tube sheet and a lower tube sheet. However, it will be understood that the present disclosure may also be applied to other configurations of tubular reactor that may adopt other orientations. Additionally, in this specification any reference to orientation; for example, terms such as top, bottom, upper, lower, above, below and the like is used with regard to the orientation of the parts as illustrated in the drawings being referenced but is not to be seen as restrictive on the potential orientation of such parts in actual use. For example, a part described as being orientated vertically may also be orientated horizontally. A catalyst carrier 1 according to the present disclosure is shown in Figure 1. The catalyst carrier is suitable for insertion into a reactor tube of a tubular reactor. The catalyst carrier 1 comprises an outer container 10 and a removable basket 30 for holding catalyst 50. The outer container 10 comprises a side wall 11, a base 12 and a removable lid 13. The side wall 11 and the base 12 define a receptacle 14 that can be closed and opened by attachment and detachment of the removable lid 13. The removable basket 30 is insertable into and removable from the receptacle 14 when the removable lid 13 is detached. The outer container 10 is shown in Figure 1 and comprises the side wall 11, the base 12 and the removable lid 13. The side wall 11 may be tubular, and optionally circular in cross-section. The side wall 11 may be smooth or it may be shaped. Suitable shapes include pleats, corrugations, and the like. The side wall 11 may have a plurality of apertures 38 towards the upper end of the side wall 11. The apertures 38 may be of any configuration. In some embodiments, the apertures 38 may be holes or slots. Means for attachment of the removable lid 13 may be provided at or towards the upper end of the side wall 11. In some embodiments, and as shown in the example of Figures 1 and 2, a screw thread connection may be provided. For example, a threaded ring 61 may be joined to the upper end of the side wall 11 by a suitable means, e.g. a weld 62. The base 12 may be circular in external shape. The side wall 11 and base 12 may be formed from sheet material. The side wall 11 and base 12 may be formed in one piece or may be attached to each other, for example by one or more welds. The base 12 closes off the bottom end of the side wall 11 leaving the upper end open. One or more drain apertures (not shown) may be provided in the base 12, optionally at or towards its centre. As shown in Figures 1,2 and 4, the removable lid 13 of the outer container 10 may comprise a plug portion 64 and an annular ring 65 that upstands from the plug portion 64. The plug portion 64 may have an external screw thread connection 63 matching that of the threaded ring 61 and an inlet aperture 27 providing a fluid inlet to the receptacle 14 of the outer container 10. The annular ring 65 may have an inwardly-facing chamfered face 68. The annular ring 65 may comprise a plurality of apertures 66 that extend through the wall thickness to permit fluid flow through the annular ring 65 to reach the inlet aperture 27. In some embodiments the outer container further comprises a seal 60 for sealing between the outer container 10 and an inner surface of the reactor tube. In some embodiments the seal 60 is retained by being compressed between the removable lid 13 and the side wall 11 of the outer container 10 or between the removable lid 13 and the threaded ring 61 of the outer container 10. The apertures 38 of the side wall 11 may be located below the seal 60. The side wall 11 may continue above the seal 60. Thus the seal 60 may be located at the top of the catalyst carrier 1, optionally near the top surface, or it may be located at a suitable point on the side wall 11 provided that it is located above the apertures 38. The seal 60 may be sufficiently compressible to accommodate the smallest diameter of the reactor tube. The seal 60 may generally be a flexible, sliding seal. The seal 60 may engage against an inner surface of the reactor tube such that liquids and gases passing along the reactor tube are preferentially directed to flow through an interior of the catalyst carrier 1. The seal 60 may, for example, be configured to form a sliding seal against the inner surface of the reactor tube. The seal 60 may comprise a deformable flange, optionally an annular flange, extending from the side wall 11 of the catalyst carrier 1. The flange may be sized to be larger than the internal diameter of the reactor tube such that as the catalyst carrier is inserted into the reactor tube it is deformed to fit inside and interact with the reactor tube. An inner portion 60a of the seal 60 may define a clamping surface that is sandwiched and retained between the removable lid 13 and the threaded ring 61. The deformable flange may be angled relative to the inner portion. The deformable flange may be angled towards the upper end of the catalyst carrier 1. The seal 60 may, for example, comprise a single layer of material. Alternatively, the seal 60 may comprise at least a first seal layer and a second seal layer. The seal 60 may comprise more than two seal layers. For example, it may comprise four, five or six seal layers. Suitable seals are described, for example, in WO2022064212. The removable basket 30 may comprise one or more perforated walls. The removable basket 30 may define an annular chamber 33 for holding the catalyst 50. In some embodiments the removable basket 30 comprises an inner wall 31, an outer wall 32, a base 34 and a cover 35 that define the annular chamber 33 as well as a central channel 36. The inner wall 31 and the outer wall 32 may be tubular, and optionally circular in crosssection. The inner wall 31 and / or the outer wall 32 may be formed in one piece with the base 34 or may be attached to the base 34, for example by crimping or one or more welds. In some embodiments both the inner wall 31 and the outer wall 32 are perforated, for example being formed of a mesh material. In some embodiments the portion 34a of the base 34 of the removable basket 30 that borders the annular chamber 33 is unperforated. In some embodiments the cover 35 of the removable basket 30 is separate from or removable from the inner wall 31 and the outer wall 32. The cover 35 may be formed of sheet material. The sheet material may be unperforated. The cover 35 may comprise a central aperture 37 providing a fluid inlet to the central channel 36. The portion 35a of the cover 35 that borders the annular chamber 33 may be unperforated. In some embodiments the outer container 10 and the removable basket 30 comprise cooperating formations for spacing apart the removable basket 30 from the side wall 11 of the outer container 10. In some embodiments the co-operating formations hold the removable basket 30 such that an annular gap 40 is retained between the side wall 11 of the outer container 10 and the outer wall 32 of the removable basket 30. In some embodiments the co-operating formations are provided on the removable lid 13 of the outer container 10 and the cover 35 of the removable basket 30 and / or on the bases 12, 34 of the outer container 10 and the removable basket 30. In some embodiments the co-operating formations comprise one or more co-operating projections and recesses. The co-operating formations may comprise one or more annular projections and recesses. As shown in Figure 1 and the enlarged view of Figure 2, a lower face 20 of the removable lid 13 of the outer container 10 may comprise two concentrically-arranged annular recesses 21. In some embodiments the cover 35 of the removable basket 30 comprises two concentrically-arranged annular deformities producing two annular projections 41 for engaging the removable lid 13 of the outer container 10 and two annular recesses 42 for engaging against the inner wall 31 and outer wall 32 of the removable basket 30. As shown in Figure 1 and the enlarged view of Figure 3, an upper face 22 of the base 12 of the outer container 10 may comprise two concentrically-arranged annular recesses 23. In some embodiments the base 34 of the removable basket 30 comprises two concentrically-arranged annular deformities producing two annular projections 43 for engaging the base 12 of the outer container 10 and two annular recesses 44 for engaging against or being attached to the inner wall 31 and outer wall 32 of the removable basket 30. In some embodiments a lower face 25 of the base 12 of the outer container 10 comprises an annular projection 26 for engaging against a lid, for example against a chamfered face 68 of a lid, of a neighbouring catalyst carrier when the catalyst carriers are installed as a stack in a reactor tube. The components of the catalyst carrier 1 may be formed of any suitable material. Such material will generally be selected to withstand the operating conditions of the reactor. Generally, the catalyst carrier 1 will be fabricated from carbon steel, aluminium, stainless steel, other alloys or any material able to withstand the reaction conditions. Suitable thicknesses for the walls will be of the order of about 0.1 mm to about 1.0 mm, preferably of the order of about 0.3 mm to about 1.0 mm. In use the catalyst carrier 1 may be assembled by first filling catalyst 50 into the removable basket 30 and then inserting the removable basket 30 into the outer container 10. Alternatively, the removable basket 30 can be filled in situ in the outer container 10. To fill the removable basket 30 the cover 35 is simply removed and catalyst 50 may be poured into the annular chamber 33. One or more hold down pads 70 may be inserted on top of the catalyst 50 to assist in applying a compressive load onto the particles of catalyst. The cover 35 is then replaced. Once the removable basket 30 is inserted into the outer container 10 and with the removable lid 13 of the outer container 10 in place, the removable basket 30 may be compressed between the removable lid 13 and the base 12 of the outer container 10. On insertion, the cooperating formations may engage one another to establish and to maintain the desired annular gap 40. For example, at the lower end the two annular projections 43 of the base 34 of the removable basket 30 are engaged into the two annular recesses 23 of the base 12 of the outer container and at the upper end the two annular projections 41 of the cover 35 of the removable basket 30 are engaged into the two annular recesses 21 of the removable lid 13. A sealing member, such as an O-ring, may be provided in one or both of the annular recesses 21, or elsewhere between the removable lid 13 and the cover 35. Each catalyst carrier 1 may generally comprise a container that is sized such that it is of a smaller dimension than the internal dimension of a reactor tube 100 into which it is to be placed in use. A portion of a reactor tube 100 is shown schematically in Figure 5. Typically, the seal 60 is sized such that it interacts with the inner wall of the reactor tube 100 when the catalyst carrier 1 is in position within the reactor tube 100. Parameters such as carrier length and diameter may be selected to accommodate different reactions and configurations of reactor tube 100. The catalyst carriers 1 may be used in a tubular reactor which typically comprises a housing that is divided into a head space, a heat-exchange zone and a footer space by two tube sheets - an upper tube sheet and a lower tube sheet. The upper tube sheet separates the head space from the heat-exchange zone. The lower tube sheet separate the footer space from the heat-exchange zone. A plurality of reactor tubes 100 extend between the upper tube sheet and the lower tube sheet. A large number of reactor tubes may be provided, for example between 20 and 5000 reactor tubes may be present. Each reactor tube may have, for example, an internal diameter of between 20 and 150 mm. In some embodiments the internal diameter may be about 85 mm. Each reactor tube is intended to be filled or substantially filled with a stacked arrangement of catalyst carriers 1. In particular, it is typically desired that the catalyst carriers 1 cover all or substantially all of the length of the reactor tube between the upper tube sheet and the lower tube sheet, i.e. that they cover all or substantially all of the length of the heatexchange zone. The head space may provide access to an upper end of the reactor tubes to allow loading of the catalyst carriers 1 into the reactor tubes. The footer space may provide access to the lower end of the reactor tubes to allow unloading of the catalyst carriers 1 from the reactor tubes. In use, the catalyst carriers 1 may be used as follows: i) installing catalyst 50 into a plurality of the catalyst carriers 1 by filling the catalyst 50 into the removable baskets 30, inserting the removable baskets 30 into the open receptacles 14 of the outer containers 10 and attaching the removable lids 13 to close the receptables 14; ii) installing the plurality of catalyst carriers 1 into the reactor tube 100 of a tubular reactor as shown schematically in Figure 5; iii) operating the tubular reactor for a period of time; iv) subsequently removing the plurality of catalyst carriers 1 from the reactor tube 100; v) detaching the removable lids 13 and removing the removable baskets 30 from the outer containers 10; and vi) emptying the catalyst 50 from the removable baskets 30. Optionally the use may also comprise: vii) recycling or re-using the outer containers 10 and / or the removable baskets 30; and optionally further comprise: viii) re-using or regenerating the catalyst 50. As shown in Figure 5, within the stack of catalyst carriers 1, the annular projection 26 on the base 12 of an upper catalyst carrier 1 may be engaged against the removable lid 13 of an underlying catalyst carrier 1 with the annular projection 26 nested against the chamfered face 68 of the upstanding ring 65. In use the tubular reactor may be operated to pass one or more reactants through the reactor tubes 100 from the inlet end to the outlet end of each. In a tubular reactor with downflow utilising catalyst carriers 1, reactant(s) flow downwardly through each reactor tube 100 and thus first contact the uppermost catalyst carrier 1 of the stack. The seal 60 blocks the passage of the reactant(s) around the side of the catalyst carrier 1. Therefore, the reactants are directed inwardly through the apertures 66 into and through the central inlet 27. The reactants then pass through the central aperture 37 of the cover 35 of the removable basket 30 into the central channel 36. By-pass flow is limited or prevented by the sealing effect of contact between the annular projections 41 and the recesses 21. The reactants then enter the annular chamber 33 through the perforated inner wall 31 and then pass radially through the catalyst 50 towards the outer wall 32. During this passage the reactant(s) contact the catalyst 50 and reaction occurs to form product(s). Unreacted reactant(s) and product(s) then flow through the perforated outer wall 32 of the removable basket 30. The side wall 11 then directs reactant(s) and product(s) upwardly within the annular gap 40 until they reach the apertures 38 in the side wall 11. They are then directed through the apertures 38 and flow downwardly between the outer surface of the side wall 11 and the inner surface of the reactor tube where heat transfer takes place. The unreacted reactant(s) and product(s) may then contact the top of the underlying catalyst carrier 1 in the stacked formation and the process described above may repeat. This pattern may repeat as the reactant(s) and product(s) pass down the stacked formation until they are collected out of the lower end of the reactor tube 100.

Claims

1. A catalyst carrier for insertion into a reactor tube of a tubular reactor, the catalyst carrier comprising an outer container and a removable basket for holding catalyst;the outer container comprising a side wall, a base and a removable lid, the side wall and the base defining a receptacle that can be closed and opened by attachment and detachment of the removable lid;the removable basket being insertable into and removable from the receptacle when the removable lid is detached.

2. The catalyst carrier of claim 1, wherein the removable basket comprises one or more perforated walls.

3. The catalyst carrier of claim 1 or claim 2, wherein the removable basket defines an annular chamber for holding catalyst.

4. The catalyst carrier of any preceding claim, wherein the removable basket comprises an inner wall, an outer wall, a base and a cover defining an annular chamber for holding catalyst and a central channel.

5. The catalyst carrier of claim 4, wherein the inner wall and the outer wall are perforated.

6. The catalyst carrier of claim 4 or claim 5, wherein the base of the portion of the removable basket that borders the annular chamber is unperforated.

7. The catalyst carrier of any one of claims 4 to 6, wherein the cover of the removable basket is separate from or removable from the inner wall and the outer wall.

8. The catalyst carrier of any one of claims 4 to 7, wherein the cover of the removable basket comprises a central aperture providing a fluid inlet to the central channel.

9. The catalyst carrier of any one of claims 4 to 8, wherein the portion of the cover of the removable basket that borders the annular chamber is unperforated.

10. The catalyst carrier of any one of claims 4 to 9, wherein with the removable lid of the outer container attached, the removable basket is compressed between the removable lid and the base of the outer container.

11. The catalyst carrier of any preceding claim, wherein the outer container and the removable basket comprise co-operating formations for spacing apart the removable basket from the side wall of the outer container.

12. The catalyst carrier of any one of claims 4 to 10, wherein the outer container and the removable basket comprise co-operating formations for spacing apart the removable basket from the side wall of the outer container and the co-operating formations hold the removable basket such that an annular gap is retained between the side wall of the outer container and the outer wall of the removable basket.

13. The catalyst carrier of claim 12, wherein the co-operating formations are provided on:the removable lid of the outer container and the cover of the removable basket; and / oron the bases of the outer container and the removable basket.

14. The catalyst carrier of claim 12 or claim 13, wherein the co-operating formations comprise one or more co-operating projections and recesses.

15. The catalyst carrier of any one of claims 12 to 14, wherein the co-operating formations comprise one or more annular projections and recesses.

16. The catalyst carrier of any one of claims 12 to 15, wherein a lower face of the removable lid of the outer container comprises two concentrically-arranged annular recesses.

17. The catalyst carrier of any one of claims 12 to 16, wherein the cover of the removable basket comprises two concentrically-arranged annular deformities producing two annular projections for engaging the removable lid of the outer container and two annular recesses for engaging against the inner wall and outer wall of the removable basket.

18. The catalyst carrier of any one of claims 12 to 17, wherein an upper face of the base of the outer container comprises two concentrically-arranged annular recesses.

19. The catalyst carrier of any one of claims 12 to 18, wherein the base of the removable basket comprises two concentrically-arranged annular deformities producing two annular projections for engaging the base of the outer container and two annular recesses for engaging against or being attached to the inner wall and outer wall of the removable basket.

20. The catalyst carrier of any one of claims 12 to 19, wherein a lower face of the base of the outer container comprises an annular projection for engaging against a lid of a neighbouring catalyst carrier when the catalyst carriers are installed as a stack in a reactor tube.

21. The catalyst carrier of any preceding claim, wherein the removable lid of the outer container comprises an inlet aperture providing a fluid inlet to the receptacle of the outer container.

22. The catalyst carrier of any preceding claim, wherein the outer container further comprises a seal for sealing between the outer container and an inner surface of the reactor tube.

23. The catalyst carrier of claim 22, wherein the seal is retained by being compressed between the removable lid and the side wall of the outer container or between the removable lid and a threaded ring of the outer container.

24. A method comprising the steps of:i) installing catalyst into a plurality of catalyst carriers as claimed in any preceding claim by filling catalyst into the removable baskets, inserting the removable baskets into the open receptacles of the outer containers and attaching the removable lids to close the receptables;ii) installing the plurality of catalyst carriers into a reactor tube of a tubular reactor;iii) operating the tubular reactor for a period of time;iv) subsequently removing the plurality of catalyst carriers from the reactor tube;v) detaching the removable lids and removing the removable baskets from the outer containers; andvi) emptying the catalyst from the removable baskets.

25. The method of claim 24, further comprising:vii) recycling or re-using the outer containers and / or the removable baskets;and optionally further comprising:viii) re-using or regenerating the catalyst.21

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