WO2014122505A1

WO2014122505A1 - Apparatus for the synthesis on a catalytic bed and for the separation of liquid-liquid-gas phases

Info

Publication number: WO2014122505A1
Application number: PCT/IB2013/051056
Authority: WO
Inventors: Alberto BRUCATO; Franco GRISAFI; Giorgio MICALE; Francesca SCARGIALI; Antonio BUSCIGLIO; Francesco ROCCAFORTE; Elio DI LELLA
Original assignee: Universita' Degli Studi Di Palermo; Ecoil S.R.L.; C.M.S. S.R.L.
Priority date: 2013-02-08
Filing date: 2013-02-08
Publication date: 2014-08-14

Abstract

Synthesis apparatus on catalytic bed and separation of synthetic products comprising a gaseous phase and two liquid phases, a heavier liquid phase and the other liquid phase lighter, the apparatus comprising - a synthesis module (M1 ) comprising a first tube (1) provided with an opening at one end and closed at a second end by a mesh (7), the first tube (1) being adapted to contain a catalytic bed (6) therein; - and a separation module (M2) for separating the two liquid phases and the gaseous phase originating from the synthesis module (M1), comprising a second tube (V) arranged adjacent to the second end of the first tube (1), communicating therewith at a first end thereof, and having, at a second end thereof, a first closure element (13) that is provided with a through hole.

Description

APPARATUS FOR THE SYNTHESIS ON A CATALYTIC BED AND FOR THE SEPARATION OF LIQUID-LIQUID-GAS PHASES

APPARATUS FOR THE SYNTHESIS, ON A CATALYTIC BED, AND SEPARATION OF LIQUID-GASEOUS PHASES

Field of the invention

The present invention relates to an apparatus for the synthesis, on a catalytic bed, and separation of liquid-gaseous phases that can be used for example as a reactor/separator in the production of biodiesel by means of the transesterification of vegetable oils.

State of the art

Various reactors are known for the synthesis on a catalytic bed and separation of liquid-gaseous phases that are used for example in the production of biodiesel. The transesterification reaction of vegetable oils for the production of biodiesel takes place, in the presence of a suitable catalyst, between the triglycerides contained in the oils and a simple alcohol, such as methanol or ethanol, from which there are obtained the alkyl esters of interest (i.e. biodiesel) and glycerine, as illustrated hereunder while considering methanol as the simple alcohol:

o

H 0 H

CH₃— 0— C— R

H— C— 0— C— R H— C— OH

0 0

H— C— 0— C— R' + 3 CH,0H H— C— OH + CH 3,—~ 0— C— R'

0

H— C— 0— C— R " H— C—OH II

I I CH,— 0— C— R"

H H

triglyceride 3 methanol glycerol 3 methyl esters of fatty acids

The industrial process also requires various separation stages and successive purification steps.

The catalytic systems most currently used in the industrial field are the homogeneous systems. In the last decade, however, solid catalysis, the advantages of which include the ease of separation of the products from the catalyst due to the solid nature thereof, and operating conditions of the entire process that are milder than those of the non-catalytic processes with supercritical alcohol, has been increasingly subject of study. The first heterogeneous catalysts to be investigated for the synthesis of biodiesel were Amberlyst®-15 (ion- exchange polymer resin), Nafion® (perfluorinated polymer with ionic properties), Envirocat® EPZG (catalyst based on montmorillonnite doped with potassium), natural kaolinite, zeolites, BO/ZrO, sulphated SnO, utilised

• in the transesterification of β-ketoesters for the production of pheromone precursors and of other natural products;

• in the esterification of carboxylic acids, category of organic compounds into which free fatty acids fall.

The capacity of solid acid catalysts to also promote the transesterification of the triglycerides and the esterification of the free fatty acids makes them particularly suitable in the event of feedstock for the production of biodiesel having a high FFA content.

An example of reactor/separator for synthesis on catalytic bed and separation of liquid-gas and the relative process are described in document WO2009145954A1. The process continuously includes the contact of a component containing triglycerides with an alcohol and a catalyst at a high temperature in a reactor/centrifugal separator. A less dense phase that includes the biodiesel product is continuously separated from a denser phase containing glycerine in said reactor/separator by means of the application of a centrifugal force. Disadvantageously this reactor/separator has a complex construction, with consequent high installation costs, and management difficulties linked to wear, the need to maintain and the reliability of the mechanical members, which also have high operating costs, and uncertainties on operational continuity.

A further example, described in document US4235847, relates to a redistributor of a liquid-gas mixture (only two phases) on a reaction chamber with a fixed-bed catalyst. This system is exclusively designed for the re-mixing and uniform redistribution on a catalytic bed of a gas-liquid mixture originating from a preceding catalytic bed. The teachings of this document do not envisage the separation of two liquid phases, indeed it envisages the mixing of a second quench liquid with the first liquid originating from the overlying catalytic bed and subsequently the formation of froth obtained by mixing the steam, separated by means of a complex structure and which determines significant overall dimensions of the entire system, with the liquid obtained by mixing said first liquid and said second quench liquid. This system does not therefore envisage the recovery and removal from the reactor of one of two liquid phases and the subsequent re-introduction of the lighter, liquid phase alone in a successive catalytic section together with a gaseous phase that is as yet distinct from said second liquid phase. In this system there is indeed neither a zone present that is adapted to the sedimentation- separation of two liquid phases nor would it be possible to in any way retrieve one of the two liquid phases, once separation has occurred, due to the absence of exit routes for the heavier liquid phase.

There is therefore a need to provide an innovative apparatus that allows the aforementioned drawbacks to be overcome.

Summary of the invention

The main aim of the present invention is to provide an apparatus for the synthesis, on a catalytic bed, and separation of liquid-gaseous phases that is simpler from the point of view of construction and operation and less bulky than the known solutions, thus allowing the efficacy and use of the catalyst to be maximised.

A further aim of the invention is to produce an apparatus suitable for being used in all fine chemicals sectors wherein the process to be developed provides a catalytic fixed-bed (reactor) synthesis stage, followed by a separation of immiscible liquid phases (separator), such as for example in a biodiesel production process by means of transesterification of vegetable oils.

The present invention therefore proposes to achieve the above discussed aims by providing an apparatus for synthesising, on a catalytic bed, and separating at least three synthesis products comprising a gaseous phase, a first liquid phase and a second liquid phase that is lighter than the first liquid phase, the apparatus comprising a synthesis module comprising a first tube provided with an opening at one end and closed at a second end by a mesh, the first tube being adapted to contain a catalytic bed therein; a separation module for separating the first and the second liquid phases and the gaseous phase originating from the synthesis module, comprising a second tube arranged adjacent to the second end of the first tube, which communicates therewith at a first end thereof, and having, at a second end thereof, a first closure element that is provided with a through hole for the sole passage of the second liquid and of the gaseous phase; wherein said second tube comprises therein a third tube that is affixed at a first end thereof to the first closure element, so as to define a first meatus between the second tube and the third tube, and a single fourth tube inside the third tube so as to define a second meatus between the third tube and the fourth tube, said fourth tube being affixed at a first end thereof in proximity of the through hole of the first closure element so as to communicate directly with said through hole or cross said through hole, wherein, in proximity of the first closure element, there are envisaged within the first meatus, a separation zone between the first liquid phase and the second liquid phase and at least one first side collection hole in the second tube to collect the first, heavier liquid phase, wherein the third tube is provided with first side openings at the first end that are arranged along its side surface for the passage of the second liquid phase from the first meatus to the second meatus ,

wherein the third tube is closed at the second end and is provided with a header for collecting the first and second liquid phases originating from the synthesis module, said header being configured to make the first and the second liquid phases flow along the outer side surface of the third tube as far as the first closure element, wherein the third tube is provided, between the first end and the second end, with second side openings for directly connecting the first meatus and an inner zone of the third tube and above the second meatus, said second side openings being arranged along the side surface of the third tube for the passage of the gaseous phase alone, originating from the synthesis module, from the first meatus directly into the third tube and subsequently into the fourth tube, whereby the first liquid phase, which is heavier than the second liquid phase, is maintained in the lower part of the first meatus and the second, lighter liquid phase passes from the first meatus to the second meatus until it falls into the fourth tube, said first liquid phase being collectible through the first side hole .

In addition, a second aspect of the invention relates to a process for synthesising, on a catalytic bed, and separating at least three synthesis products comprising a gaseous phase and two liquid phases, of which a first liquid phase and a second liquid phase lighter than the first liquid phase, the process being executable by means of the aforementioned apparatus, the process comprising the following steps: - synthesising on a catalytic bed in the synthesis module (M1 ) and producing the synthesis products;

- separating the two liquid phases and the gaseous phase in the separation module (M2), wherein the separating step, when the apparatus is fully operational, provides that the heavier, first liquid phase accumulates, due to gravity, in the lower part of the first meatus and the second, lighter liquid phase is maintained on the surface within the first meatus, above the second, heavier liquid phase, passing from the first meatus to the second meatus through the first side openings until it falls along the inner surface of the fourth tube, said first liquid phase being collected through the first side hole, and wherein, when the apparatus is fully operational, the gaseous phase passes from the first meatus directly into the third tube through the second side openings and then into the fourth tube, descending along a central zone of said fourth tube. The constructive and management simplicity of the reactor/separator of the present invention allows multiplication, without increasing costs, of the number of reaction stages with intermediate separation of products, thus maximizing the efficacy of use of the catalyst, the purchase and periodic replacement of which typically have a marked impact on the total cost of the operation.

The reactor/separator of the invention is preferably a modular apparatus suitable for continuous processes that involve the coexistence of two liquid phases (reagents and/or products) and a solid catalyst and that benefit from the articulation of the process over multiple reaction stages spaced out by a phase separation. The apparatus of the invention is also capable of effectively managing the presence of an additional gaseous phase, thus reaching a total of four interacting stages (the solid catalyst, the two liquid phases and the gaseous phase), an event that occurs for example in certain transesterifications with solid catalysis.

The invention relates in particular to a trickle-bed reactor completed by functional elements for the distribution of the liquid phase on the top of the catalyst bed and functional elements for the separation, downstream of the bed, of the two immiscible liquid phases, to allow the removal of one of them. The practical embodiment of the apparatus provides the articulation in three distinct modules, specifically tailored to process needs, and the set of three modules constitutes a reaction stage. It is possible to multiply the number of reaction stages, in order to push the reaction towards completion, thanks to the removal of one or more reaction products after each stage.

Regardless of the fact that the practical embodiment is articulated in one or more modules, the other constructive details are designed so as to eliminate the need for outer tubular connections between different reaction stages, thus simplifying the management and maintenance thereof and minimizing the footprint and energy consumption. In practice, the multiplication of the reaction stages is simply obtained by placing into vertical columns the required number of reaction/separation stages, without any increase of the footprint.

The reactor/separator, object of the present invention, may be advantageously used to produce bio-fuels that allow a minimum 50% reduction of greenhouse gases compared to fossil diesel, such as for example envisaged by Directive

2009/98/EC. It can be used both in new biodiesel plant installations and in the progressive replacement due to obsolescence of existing installations.

A further advantage of the invention is the decrease in unit production cost thanks to the use of waste such as feedstock from the biodiesel production process.

This reactor/separator can also be used for the recovery of used cooking oils and fats. With reference to the production of biodiesel from used cooking oils and fats, the invention allows the waste cycle in relation to the EWC codes 20 01 25 and 20

01 26 to be closed, thus also guaranteeing in the computerised European system,

"SISTRI" in Italy, the total management flow from the manufacturer, on the recovery, on the total reuse of the aforementioned recovered waste.

The application potential of the the reactor-separator of the invention can also be extended to other reactive systems characterised by the coexistence of a solid catalyst, by two immiscible liquid phases and by the usefulness of proceeding with the on-site separation of one of the liquid phases.

The dependent claims describe preferred embodiments of the invention.

Brief description of the drawings

Further characteristics and advantages of the invention will become more evident in the light of the detailed description of preferred, but non-exclusive, embodiments of an apparatus illustrated by way of a non-limiting example, with the assistance of the accompanying drawings, in which:

Figure 1a shows a flow chart of a reference process;

Figure 1b shows a flow chart of a process that can be performed with an apparatus according to the present invention;

Figure 2 shows a perspective view of an apparatus of the invention;

Figure 3 shows a cross-sectional view of the apparatus of figure 2,

Figures 4a-4d show top views of certain components of the apparatus of Figure 3;

Figure 5 shows an enlarged view of one part of the cross-sectional view of Figure

3;

Figure 6 shows a cross-section along the A-A plane of the view of Figure 5;

Figure 7 shows a perspective, partially cross-sectional view of the part of the apparatus shown in Figure 5;

Figure 8 shows a perspective view of a component of the apparatus shown in Figure 5.

The same reference numbers in the drawings iindicate the same elements or components.

Detailed description of preferred embodiments of the invention

With reference to the figures there is represented a preferred embodiment of the apparatus of the present invention, suitable for continuous processes that involve the coexistence of two liquid phases and a gaseous phase, in the quality of reagents and/or products, in contact with a solid catalyst.

The reference process, outlined in the flow chart of Figure 1a, implies the presence of two reactant phases, one gaseous GAS and one liquid LIQ, which react in contact with the solid catalyst, forming products which are, in turn, divided into a gaseous phase GAS, and into two immiscible liquid phases, a light liquid phase LIQ1 and a heavy liquid phase LIQ2. The synthesis stage is then followed by a separation stage of the two immiscible liquid phases, in which the gaseous phase GAS is distanced together with the light liquid phase.

This reference process can benefit from articulation of the process itself over multiple reaction stages, spaced out out by the intermediate removal of the heavy liquid phase LIQ2 containing the undesired products, thereby promoting the thermodynamics of the reaction. The transesterification of vegetable oils into biodiesel is one practical example of an industrial process with these characteristics.

The apparatus of the invention, acting as reactor/separator, allows the adoption of a better process, that is schematically illustrated in Figure 1 b, by virtue of the advantages arising from articulation of the entire process over multiple reaction stages, each reaction stage comprising a catalytic bed synthesis step, an intermediate separation step of the two immiscible liquid phases, and a redistribution step of the light liquid phase LIQ1 and of the gaseous phase GAS, preferably distinct from each other and not mixed in the form of froth, in a subsequent reaction stage. It is possible to multiply the number of reaction stages in order to push the reaction toward completion.

This apparatus includes at least two blocks, each block consisting of:

- a synthesis or reaction module M1 , designed as a fixed trickle-bed catalytic reactor.

- a separation module M2 to divide the effluent discharged from the synthesis module M1 in three fluid phases, two liquid phases and a gaseous phase, and remove the heavier liquid phase;

- a collection and redistribution module M3 for the non-converted reagents, present in the lighter liquid phase and in the gaseous phase, towards a further synthesis module envisaged in the successive block.

Modules M1 , M2 and M3 are arranged vertically one on top of the other, as shown in Figures 2 and 3. Each block, therefore, allows performance of a reaction stage as defined above.

In the event that, on the other hand, the design of the reaction is such that all the reagents are converted until almost completion of the reaction in a single synthesis step, the apparatus of the invention only comprises:

- the synthesis or reaction module M1 , designed as a fixed, trickle-bed catalytic reactor. - and the separation module M2 to divide the effluent discharged from the synthesis module M1 in three fluid phases, two liquid phases and a gaseous phase, and remove the heavier liquid phase.

In most cases, however, the reactor/separator of the invention comprises a plurality of blocks, each comprising the three modules M , M2 and M3, stacked vertically on top of each other so as to produce a structure in the form of a column consisting of the superpositioning of multiple modules, as illustrated in Figure 2. Each module appears externally as a tube with flanged ends.

The flanged tubes 1 , ', 1 ", representing the outer shell of each module, are arranged one on top of the other and coupled by means of bolts passing through suitable non-threaded holes 3. Each flange is equipped with at least one annular groove, for example a double annular groove 2 that is preferably concentric to the central hole of the respective tube 1 , 1 ', 1", in which to allocate the o-rings that serve to seal with the flange of the adjacent module. In each module there is also envisaged the presence of a hole 4 for connection to a rupture disc, i.e. a safety device, such as for example a membrane designed to break if a predetermined pressure within the modules is exceeded.

The three modules M1 , M2 and M3 are substantially identical from the outside at less than the length of the respective flanged tubes 1 , 1', and 1". However, each module is distinguished by a particular internal geometry that is specifically designed to produce a predetermined route for the various fluid phases that cross it.

The synthesis or reaction module M1 is provided, downstream of the flanged tube 1 thereof, with a support mesh 7 of the catalytic bed 6. In particular, the support mesh 7 is positioned between two flanges, an end flange of the module M1 and an end flange of the module M2. The solid catalyst is lowered from the upper part into the central hole 16 of the flanged tube 1 , coming to rest on top of the above- mentioned mesh 7, which acts both as mechanical support for the entire catalytic bed 6 and as distribution plate of the reactive mixture comprising the two liquid phases and the gaseous phase. The support mesh 7, illustrated in Figure 4b, is in fact provided with a reduced passage area 23 from the module M1 to the module M2. This passage area 23 consists of a fine mesh net of dimensions such that the solid catalyst particles cannot through cross it.

The separation module M2 has an innovative internal configuration that allows separation of the two immiscible liquid phases LIQ1 and LIQ2 to be separated thanks to the difference in density thereof.

The separation module M2 is provided, within the central hole 16 of the flanged tube 1 ' thereof, with two inner tubes that are concentric to each other and also with respect to the outer tube 1 '. These inner tubes are:

- a draft tube 8, with the function of differentiating the path followed by the various liquid and gaseous phases;

- and a connecting tube 9 between the separation module M2 and the collection and redistribution module M3, inside said draft tube 8, with the function of gaseous phase and light liquid phase downpipe.

In the case in which the apparatus consists only of a module M1 and a module M2, this tube 9 acts as exhaust tube of the gaseous and light liquid phase.

The diameter of the draft tube 8 is intermediate between the diameter of the outer tube 1 ' and the diameter of the connecting tube 9. A first meatus 7 is defined between the tube V and the draft tube 8, while a second meatus 18 is defined between the draft tube 8 and the connecting tube 9.

The draft tube 8 is preferably affixed at a first end thereof to the bottom or closure element 13 of the tube V which constitutes a dividing element between the separation module M2 and the redistribution module M3.

The connecting tube 9 is also affixed at a first end thereof in proximity of the bottom 13 so as to communicate with a through hole envisaged in said bottom 13 or so as to at least partially cross said bottom 13. In both modes, therefore, the module M2 communicates with the module M3. In the example of Figure 5, the connecting tube 9 totally crosses the through hole in the bottom 3.

At its first end, the draft tube 8 is preferably closed by the bottom 13 but is advantageously provided with side openings 22, preferably in the form of an arch, arranged along its cylindrical side surface for the passage, when the apparatus is fully operational, of the lighter liquid phase from the first meatus17 to the second meatus 18. At a second end thereof, the draft tube 8 is closed by a closure element 8' and is provided with a header 19 of the two liquid phases, entering the separation module M2 through the mesh 7. The header 19 is configured to slide said liquid phases along the outer side surface of the draft tube 8. Said header 19 is formed, in a preferred embodiment illustrated in Figures 5 to 8, by the closure element 8' of the draft tube 8, defining a base of the cylinder of the tube 8, and by protrusions 30 that are integral to said closure element 8' and arranged along the cylindrical side surface of said draft tube 8 and spaced out by spaces or openings 24 for the passage of the liquid phases from the header 19 to the first meatus 7. Closure surface 8' and protrusions 30 therefore define a substantially ashtray-shaped header.

In addition, between the first end and the second end of the draft tube 8, there are envisaged further side openings or holes 20 arranged along the side surface of the tube 8 to the passage of the gaseous phase from the first meatus 17 within the draft tube 8 and, therefore, in the passage channel 21 inside the connecting tube 9.

Advantageously, the side openings 20 are positioned at the protrusions 30 so that the liquid phases, which cross the spaces 24 and slide along the cylindrical side surface of the draft tube 8, do not encounter said side openings 20, which will be intended for the passage of the gaseous phase.

The side openings 20 are preferably arranged in proximity of the second end , of the draft tube 8, i.e. in proximity of the closure element 8'.

Advantageously, the connecting tube 9, inside the tube 8, has a length such that its upper end is always arranged beneath the side openings 20 of the draft tube 8. Preferably, but not necessarily, the length of tube 9 is equal to about half of tube 8. With this configuration of the separation module M2, the two liquid phases originating from module M1 reach the header 19 and then slide along the outer side surface of the draft tube 8 until they reach the bottom 13 and, when fully operational, the heavier liquid phase precipitates and is maintained in the lower part of the second tube 1 ', separating from the lighter liquid phase due to gravity, and said lighter liquid phase passes from the first meatus 17 to the second meatus 18 until it falls into the connecting tube 9. The gaseous phase originating from module M1 passes, on the other hand, into the first meatus 17 and, being when fully operational, the lower part of the tube 1 ' occupied by the two liquid phases up to in proximity of the upper end of the connecting tube 9, said gaseous phase tends to cross the side openings 20 and to enter the connecting tube 9.

Advantageously, there is envisaged at least a first side hole 12 in the side surface of the tube 1 ', in proximity of the bottom 13, to collect the heavier liquid phase that accumulates between the upper end of the side openings 22 and the bottom 13, and there is envisaged a control system of the interface between the two liquid phases in the lower part of the tube V to check that the interface level is maintained below the upper end of the arch-shaped side openings 22. Underneath said upper end the drops of the lighter liquid phase LIQ1 descending from the outer meatus 17 separate from those of the heavier liquid phase LIQ2, which, due to gravity, continue to precipitate onto the bottom. The drops of the lighter liquid phase LIQ1 then reascend along the inner meatus 18.

This control system of the interface between the two liquid phases in the lower part of the tube 1' comprises a level indicator of the LIQ1/LIQ2 interface, placed externally of the module M2 and connected to said tube 1 ' by means of second side holes 5 produced in the side surface of said tube 1 '.

Preferably, the second holes 5 are positioned one in proximity of the bottom 13 of the tube V and the other in a position having a quota or height that is greater than the upper end of the side openings 22.

Preferably, but not necessarily, the second 5 holes are positioned diametrically opposite the first side hole 12 and additional holes, such as, for example, a third side hole 10 for the optional collection of a sample of the lighter liquid phase and a fourth side hole 11 for the connection of a refractive index meter for the two liquid phases, as a further or alternative automatic indicator of the LIQ1/LIQ 2 interface level.

Preferably, the third side hole 10 is positioned at the upper end of the connecting tube 9 and the fourth side hole 11 is positioned just below the upper end of the side openings 22. The redistribution module M3 allows the collection of the light liquid phase LIQ1 and of the gaseous phase and their subsequent homogeneous redistribution in a new successive synthesis module M1 , arranged in series.

The module M3 comprises the tube 1" that is flanged at two ends. This tube 1 " is closed at the upper end by the bottom or closure element 13 of the tube 1' and is closed at the lower end by a distribution plate 15 of the light liquid phase.

The module M3 is also provided, within the central hole of the flanged tube 1 " thereof, with at least two tubes 14 for the descent and release of the gaseous phase. In an alternative variation it is possible to envisage just one one tube 14. The two tubes 14 are affixed to a first end thereof in proximity of the distribution plate 15 so as to communicate with respective through holes envisaged in said distribution plate 15 or so as to at least partially cross said plate 15. In both modes, therefore, the module M3 communicates with an underlying synthesis module M1. In the example of Figure 3, the tubes 14, which are two in number, totally cross the respective through holes of the distribution plate 15.

Preferably the tubes 14 are arranged diametrically opposite each other and so as to be in proximity of the inner wall of the tube 1". This allows minimisation of distribution plate 15 by passing by the light liquid phase originating from the tube 9.

The distribution plate 15, illustrated in Figure 4d together with the tubes 14, has a central area 25 that is provided with a plurality of small holes for a homogeneous distribution of the light liquid phase within an underlying synthesis module M1. As regards the fluid dynamics of the whole reactive mixture within the apparatus, it is convenient to deal with the matter by single module and by single phase.

Within the synthesis module M1 , the fresh reagents (liquid phase and gaseous phase) or not converted reagents (the two immiscible liquid phases and the gaseous phase), depending on whether the module M1 is part of the first reaction stage or of an intermediate stage, enter in parallel flow from the upper part of the central hole 16, possibly downstream of a distribution plate that is analogous to plate 15 of the module M3. The fresh or non-converted reagents trickle through the whole catalytic bed 6 where they react and, crossing the holes in the support mesh 7, flow into module M2. A typical example of application of the invention relates to the management of transesterification reactions of vegetable oils. In this case, a gas ethanol stream (GAS) and an unreacted (or partially reacted) triglyceride stream (LIQ) are inlet into module M1. There are therefore outlet from the module M1 a gaseous phase consisting of the part of the gas not involved in the reaction and two liquid phases consisting of: LIQ1 , a relatively light mixture of alcohol ethers of unreacted fatty acids and triglycerides; LIQ2, a heavy glycerolic phase obtained as a byproduct of the transesterification reaction. Thanks to the separation module M2, the liquid phase LIQ2 can be extracted, while the gaseous phase GAS and the partially reacted LIQ1 mixture can be directed to the redistribution module M3, which will arrange to direct said phases to any M1 module arranged in cascade.

The way in which the gaseous phase GAS and the liquid phase LIQ flow, in contact with the solid catalytic particles, is typical of trickle reactors; reference should therefore be made to the relevant scientific literature for any further clarification in this regard.

The two immiscible liquid phases LIQ1 and LIQ2, outlet from the module M1 , are obliged to flow into the header 19 due to the reduced passage area 23 of the support mesh 7. Indeed, advantageously, the diameter of the above-mentioned passage area 23 is smaller than the diameter of the underlying header 19. From the latter, both the liquid phases flow into outer meatus 17, crossing the spaces 24 characteristic of the header 19, while adhering along the outer surface of the draft tube 8. The function of the header 19 is to prevent the liquid drops from dripping inside the openings or side holes 20 for the passage of the gaseous phase, which were especially produced under the areas of the header 19 without spaces 24. In the start-up phase of the apparatus of the invention, the two liquid phases accumulate on the bottom 13 of the module M2, between the arches of ascent of the side openings 22 and said bottom 13, which acts as divider plate of the modules M2 and M3. In this zone of the module M2 there will commence the segregation of the two liquid phases, with the accumulation on the bottom 13 of the heavy liquid phase LIQ2 and the accumulation on the surface of the light liquid phase LIQ1 on account of the difference in densities thereof (see the example of Figure 5). The level of the light liquid phase will increase until it reaches, when fully operational, the upper edge of the connecting tube 9. At that point, the light liquid phase LIQ1 will fall into the passage channel 21 , preferably a single channel, to flow into module M3 together with the gaseous phase GAS that advances within the draft tube 8. The heavy liquid phase LIQ2 will, on the other hand, be collected, when fully operational, from the bottom of the outer meatus 17 by means of the relevant side hole 12.

The gaseous phase GAS arriving from module M1 into module M2 follows, on the other hand, a path that is facilitated by the load losses, passing through the side openings 20 that are present on the outer wall of the draft tube 8, to then cross the passage channel 21 inside the connecting tube 9 and arriving inside the module M3. By effect of the arrangement of the loads (LIQ and GAS) from the top and with outlet from the bottom of the set of modules, the gas tends to go spontaneously downwards being subject to models lad losses between module M1 and module M2 and between module M2 and module M3. The pressure in module M1 thus settles at slightly higher values than the current value in module M2, which is in turn slightly higher than the value in module M3. The pressures in the different modules are not imposed, but spontaneously settle at the values necessary for the orderly outflow of the vapour phase.

In module M3, the gaseous phase GAS and the light liquid phase LIQ1 are redistributed in the underlying module M1. The gaseous phase easily passes from special down tubes 14. The light liquid phase LIQ1 , which accumulates on the distribution plate 15, passes through the holes in the central area 25 to then evenly distribute itself over the surface of a catalytic bed contained in the synthesis module M1 of the successive reaction stage.

Claims

1 . An apparatus for synthesing, on a catalytic bed, and separating at least three synthesis products comprising a gaseous phase, a first liquid phase and a second liquid phase that is lighter than the first liquid phase, the apparatus comprising

- a synthesis module (M1 ) comprising a first tube (1 ) provided with an opening at one end and closed at a second end by a mesh (7), the first tube (1 ) being adapted to contain a catalytic bed (6) therein;

- a separation module (M2) for separating the first and the second liquid phases and the gaseous phase originating from the synthesis module (M1 ), comprising a second tube (V) arranged adjacent to the second end of the first tube (1 ), which communicates therewith at a first end thereof, and having, at a second end thereof, a first closure element (13) that is provided with a through hole for the sole passage of the second liquid and of the gaseous phase;

wherein said second tube (1 ') comprises therein

a third tube (8) that is affixed at a first end thereof to the first closure element (13), so as to define a first meatus (17) between the second tube (1 ') and the third tube (8),

and a single fourth tube (9) inside the third tube (8) so as to define a second meatus (18) between the third tube (8) and the fourth tube (9), said fourth tube (9) being affixed at a first end thereof in proximity of the through hole of the first closure element (13) so as to communicate directly with said through hole or cross said through hole,

wherein, in proximity of the first closure element (13), there are envisaged within the first meatus (17), a separation zone between the first liquid phase and the second liquid phase and at least one first side collection hole (12) in the second tube (V) to collect the first, heavier liquid phase,

wherein the third tube (8) is provided with first side openings (22) at the first end that are arranged along its side surface for the passage of the second liquid phase from the first meatus (17) to the second meatus (18),

wherein the third tube (8) is closed at the second end and is provided with a header (19) for collecting the first and second liquid phases originating from the synthesis module (M1 ), said header ( 9) being configured to make the first and the second liquid phases flow along the outer side surface of the third tube (8) as far as the first closure element (13),

wherein the third tube (8) is provided, between the first end and the second end, with second side openings (20) for directly connecting the first meatus ( 7) and an inner zone of the third tube (8) and above the second meatus (18), said second side openings (20) being arranged along the side surface of the third tube (8) for the passage of the gaseous phase alone, originating from the synthesis module (M1 ), from the first meatus (17) directly into the third tube (8) and subsequently into the fourth tube (9),

whereby the first liquid phase, which is heavier than the second liquid phase, is maintained in the lower part of the first meatus (17) and the second, lighter liquid phase passes from the first meatus (17) to the second meatus (18) until it falls into the fourth tube (9), said first liquid phase being collectible through the first side hole (12).

2. The apparatus according to claim 1 , wherein there is envisaged a control system of the interface between the first and second liquid phases in the lower part of the meatus (17) to check that the interface level is maintained below an upper end of the first side openings (22).

3. The apparatus according to claim 2, wherein said control system comprises an interface level indicator that is connected to said second tube (1') by means of second side holes (5) envisaged in the side surface of said second tube (1');

4. The apparatus according to claim 3, wherein there are envisaged two second side holes (5), one arranged in proximity of the first closure element (13) and the other in a position above said upper end of the first side openings (22).

5. An apparatus according to any one of the preceding claims, wherein the header (19) is formed by a second closure element (8') of the third tube (8) provided with protrusions (30) arranged along the cylindrical side surface of the third tube (8) and separated by spaces (24) for the passage of the first and second liquid phases from the header (19) to the first meatus (17).

6. The apparatus according to claim 5, wherein the second side openings (20) are positioned at the protrusions (30) so that the first and second liquid phases crossing the spaces (24) flow along the cylindrical side surface without encountering said second side openings.

7. An apparatus according to any one of the preceding claims, wherein there is envisaged a redistribution module (M3) for redistributing the second liquid phase and the gaseous phase originating from the fourth tube (9), said redistribution module (M3) comprising a fifth tube (1") that is arranged adjacent to the second end of the second tube (1'), communicating therewith at a first end thereof via the through hole of the first closure element (13), and having at a second end thereof a further closure element ( 5) provided with a central perforated area.

8. The apparatus according to claim 7, wherein the fifth tube (1") comprises therein at least one sixth tube (14) for the descent and release of the gaseous phase and said central perforated area is provided with a plurality of holes for a homogeneous distribution of the second liquid phase downstream of the redistribution module (M3), and wherein said at least one sixth tube (14) is preferably affixed to a first end thereof, in proximity of the further closure element (15) so as to communicate directly with the respective through holes envisaged in said further closure element (15) or so as to at least partially cross said further closure element (15).

9. An apparatus according to any one of the preceding claims, wherein the support mesh (7) is provided with an passage area (23) from the first tube (1) to the second tube (1') having a lesser diameter than the diameter of the underlying header (19).

10. The apparatus according to claim 7, wherein there are envisaged at least two vertically-stacked blocks, each block comprising from the top downwards a synthesis module (M1 ), a separation module (M2) and a redistribution module (M3).

11. Process for synthesising, on a catalytic bed, and separating at least three synthesis products comprising a gaseous phase and two liquid phases, of which a first liquid phase and a second liquid phase lighter than the first liquid phase, the process being executable by means of the apparatus according to claim 1 and comprising the following steps: - synthesising on a catalytic bed (6) in the synthesis module (M1 ) and producing the synthesis products;

- separating the two liquid phases and the gaseous phase in the separation module (M2),

wherein said separating step, when the apparatus is fully operational, provides that the heavier, first liquid phase accumulates, due to gravity, in the lower part of the first meatus (17) and the second, lighter liquid phase is maintained on the surface within the first meatus (17), above the second, heavier liquid phase, passing from the first meatus (17) to the second meatus (18) through the first side openings (22) until it falls along the inner surface of the fourth tube (9), said first liquid phase being collected through the first side hole (12),

and wherein, when the apparatus is fully operational, the gaseous phase passes from the first meatus (17) directly into the third tube (8) through the second side openings (20) and then into the fourth tube (9), descending along a central zone of said fourth tube (9).

12. The process according to claim 10, wherein following separation there is provided, by means of a redistribution model (M3), a redistribution of the second liquid phase and of the gaseous phase, originating from said fourth tube (9), within a further synthesis module (M1 ) provided under said redistribution module (M3) and communicating therewith.