It is known to produce polyketones which are linear alternating polymers of (a) one or more olefins and (b) carbon monoxide, by a liquid phase (slurry) process in which the olefins and carbon monoxide are polymerised together in methanol, ethanol or propanol solvent in the presence of a palladium catalyst. Such a process, which is disclosed in more detail in, for example, EP 121965 and EP 314309, typically employs a catalyst derived from (a) a palladium compound (b) a source of an anion which is either non-coordinating or only weakly coordinating to palladium and (c) a bisphosphine of formula R'R2P-R-PR3R4 (I) where R'to R4 are independently aryl groups which can optionally be polar substituted and R is a divalent organic bridging group such as- (CH2) n- (n = 2-6). A source of the anion is typically its conjugate acid.

EP 0516239 relates to a process for the preparation of polyketones in a system comprising at least one reactor and at least one mechanical contact zone wherein the volume of suspension present in the mechanical contact zone is substantially less than the volume of the suspension present in the reactor, the suspension is passed through the mechanical contact zone and high shearing forces of at least 0.25 kW/m3, relative to the total volume of the polymer suspension present in the reactor are exerted on the polymer particles dispersed in the suspension present in the mechanical contact zone. In particular EP 0516239 relates to a loop system where the polymer suspension is recycled from the bottom of the reactor by means of a pump to the top of an injector-mixing

nozzle.

However, a problem with carrying out the process of the prior art, particularly in alcohol based slurry phase, is that fouling of the reactor occurs and, in particular, fouling of the loop. Without wishing to be bound by any theory, it is believed that fouling takes the form of a thin layer of paper-like material upon which particulate product is subsequently deposited. This fouling would severely restrict the operation of the process particularly if the process was operated in continuous mode. Fouling of mechanical parts such as the pump and the eductor of the nozzle is particularly serious since this may lead to the process being shut-down. The polyketone polymerisation reaction is exothermic and for large scale operations it is necessary to provide a heat exchanger for removal of heat of reaction. Fouling of the heat exchanger will reduce its efficiency and will also necessitate the process being shut-down for cleaning.

A number of approaches to overcoming the fouling problem have been tried.

Soluble additives can be used. However, these are not very successful at reducing the fouling and in addition increase the complexity of the catalyst system or even deactivate it. Seeding the reactor at the start of the process has the effect of decreasing the level of fouling. In particular, the seed material can itself be a polyketone. However, the fouling is decreased, but not eliminated by such an approach. Further approaches have included polishing the reactor surfaces or applying Nylon or Teflon coatings to them, in order to reduce or prevent adhesion of the fouling layer. However, these also have not proved totally effective, and add to the cost of the procedure. It would therefore be desirable to operate a polyketone process without having to circulate the polymer suspension through a loop conduit and without having to remove heat through a heat transfer surface which is in direct contact with the polymer suspension.

It has also been found that the stability of the catalyst used in a polyketone polymerisation process may be dependent upon the concentration of the gaseous reagents in the liquid reagents (such as the diluent) and, in particular, the concentration of carbon monoxide in the diluent. It is therefore desirable to ensure that there is a high surface area for mass transfer between the gaseous reagents and the liquid reagents.

Thus, according to a first embodiment of the present invention there is provided a process for the preparation of a linear alternating polymer of (a) one or more olefins and (b) carbon monoxide which process comprises :

A) contacting a mixture of carbon monoxide and one or more olefins in a reactor vessel at an elevated temperature and pressure with a catalyst in a liquid diluent in which diluent the catalyst is dissolved and the polymer forms a suspension; B) withdrawing a gaseous stream either directly or indirectly from the reactor vessel; C) at least in part recycling the gaseous stream to the lower part of the reactor vessel.

According to a second embodiment of the present invention, there is provided a process for the preparation of a linear alternating polymer of (a) one or more olefins and (b) carbon monoxide which process comprises: A) contacting a mixture of carbon monoxide and one or more olefins in a reactor vessel at an elevated temperature and pressure with a catalyst in a liquid diluent in which diluent the catalyst is dissolved and the polymer forms a suspension, which contacting takes place in a reactor vessel which is partially filled with suspension so that the reactor vessel has a gaseous headspace above the level of the polymer suspension; B) withdrawing a gaseous stream either directly or indirectly from the headspace of the reactor vessel; C) at least in part recycling the gaseous stream to the reactor vessel at a position below the level of polymer suspension in the reactor vessel; and D) withdrawing polymer suspension from the reactor vessel with the proviso that the polymer suspension is not recycled to the reactor vessel.

It is preferred to recycle the gaseous stream to the lower part of the reactor vessel, preferably to the bottom of the reactor vessel.

The polymer suspension may be withdrawn from the reactor vessel either continuously or intermittently. The polymer is then separated from the diluent.

Suitably, the gaseous stream is at least in part recycled to the reactor vessel via a gas loop conduit. Preferably, substantially the whole of the gaseous stream is recycled to the reactor vessel via a gas loop conduit. However, a small purge stream may be removed (either from the headspace of the reactor vessel or from the gaseous stream) in order to prevent the accumulation of gaseous by-products (such as methane or hydrogen) in the reactor system (reactor vessel and gas loop conduit).

Preferably, the gaseous recycle stream is introduced to the reactor vessel using a facility for the introduction of gaseous reagents. Preferably, the facility is positioned in the lower part of the reactor vessel. The gaseous recycle stream may be introduced to

the reactor vessel through more than one such facility. Preferably, the facility sparges the gaseous recycle stream into the reactor vessel thereby distributing gas bubbles widely through the liquid diluent. Suitably, the facility may extend across substantially the whole cross-sectional area of the reactor vessel. Preferably, the facility covers only part of the reactor vessel cross-sectional area so as to induce circulation of the polymer suspension in the reactor vessel, for example, the facility may be offset from the centre of the reaction vessel. The facility may be a gas nozzle, a perforated pipe or ring (a sparger), or a perforated grid. The gaseous stream passes out of the holes of the sparger or grid. The outlet holes of the sparger may be on the upper or lower side of the pipe or ring. It is preferred to have the outlet holes on the lower side of the sparger since this reduces the risk of polymer particles entering the outlet holes, particularly, when the gaseous stream is being sparged into the reactor vessel at low volumetric flow rates.

Spargers are described in"Chemical Engineers'Handbook", Robert H Perry and Cecil H Chilton, Fifth Edition at pages 5-47 to 5-48. Preferably, the sparger is positioned horizontally within the reactor vessel.

In a further aspect of the present invention there is provided a reactor system for the preparation of a linear alternating polymer of (a) one or more olefins and (b) carbon monoxide which reactor system comprises: A) a reactor vessel having an outlet for withdrawing a gaseous recycle stream; B) a facility for introducing at least a portion of the gaseous recycle stream to the reactor vessel; and C) a gas loop conduit having a first end which is in communication with the outlet and a second end which is in communication with the facility ; wherein the outlet is in the upper part of the reactor vessel and the facility is in the lower part of the reactor vessel.

Suitably, the reactor vessel may be fitted with baffles or a draught tube which will assist in circulating the polymer suspension within the reactor vessel.

Optionally, the reactor vessel may be fitted with a mechanical agitator such as a stirring device (for example, a paddle, propeller or turbine) so as to provide an additional means of mixing the contents of the reactor vessel. Preferably, the power transmitted by the optional mechanical agitator to the polymer suspension is at least 1.5 kW/m3, more preferably in the range 2 to 15 kW/m3, based on the volume of polymer suspension

present in the reactor vessel. The mechanical agitator may be positioned either above or below the facility for introducing the gaseous stream, preferably, above the facility.

The pressure of the gaseous stream which is recycled to the reactor vessel should be sufficiently high to overcome the static head in the reactor vessel. It is known how to calculate the pressure of the gaseous stream which is required to overcome the static head in a reactor vessel. Where the facility for the introduction of the gaseous stream is a sparger, it is preferred that the pressure of the gaseous stream is sufficiently high to ensure uniform distribution of said stream through the holes in the sparger and no back flow of the polymer suspension. It is known how to create appropriate pressure drops in the sparger to ensure good distribution of the gaseous stream and no backflow of the polymer suspension.

An advantage of the process of the present invention is that it provides a high surface area for mass transfer between the gaseous reagents and the liquid reagents.

In order to reduce fouling of the reactor system, at least one liquid reagent (which is free of catalyst) is sprayed into the headspace of the reactor vessel, for example, via a nozzle. The spray knocks down foam or entrained liquid and thereby reduces catalyst and polymer carry over into the gaseous stream which is withdrawn from the reactor vessel.

At least one liquid reagent (which is free of catalyst) may also be sprayed onto the walls of the reactor vessel, at or immediately above the gas-liquid interface, at a sufficiently high velocity for the spray to scour the walls of the reactor vessel thereby reducing fouling at the gas-liquid interface (hereinafter referred to as jet cleaning). A coating may be applied to the part or all of the walls of the reactor vessel to reduce adhesion of the fouling layer and to ease jet cleaning. The coating may be of a polyamide (for example a homopolymer of an aminomonocarboxylic acid or a copolymer of a primary diamine and a dicarboxylic acid) or of a polytetrafluoroethylene (PTFE).

The liquid reagent which is sprayed into the headspace or onto the walls of the reactor vessel may be make-up liquid reagent, liquid reagent which has been recovered from downstream polymer recovery and drying operations, or liquid reagent which has been condensed from and separated from the gaseous stream which is withdrawn from the reactor vessel. Preferably, the liquid reagent is liquid diluent.

The reactor vessel may be fitted with an overhead condenser or cooler for

removal of heat from the gases in the headspace of the reactor vessel. Where the reactor vessel is fitted with an overhead condenser, the gaseous stream which is recycled to the reactor vessel may be withdrawn from the overhead condenser or cooler (i. e. is withdrawn indirectly from the reactor vessel). Thus, in yet a further aspect of the present invention there is provided a reactor system for the preparation of a linear alternating polymer of (a) one or more olefins and (b) carbon monoxide, which reactor system comprises: A) a reactor vessel fitted with an overhead condenser or cooler which overhead condenser or cooler has an outlet for a gaseous recycle stream; B) a facility for introducing at least a portion of the gaseous recycle stream to the reactor vessel which facility is positioned in the lower part of the reactor vessel; and C) a gas loop conduit having a first end which is in communication with the outlet of the overhead condenser or cooler and a second end which is in communication with the facility.

Where the reactor vessel is fitted with an overhead condenser, any liquid separated in the overhead condenser may be returned to the reactor vessel. Preferably, the separated liquid is sprayed into the headspace or onto the walls of the reactor vessel as described above.

There will usually be associated with the reactor vessel other ancillary equipment; for example, where the process is operated in a continuous mode, a means for discharging polymer suspension continuously from the reactor vessel will typically be fitted.

Generally, the gaseous recycle stream is circulated through the gas loop conduit with the aid of a gas circulation device such as a blower or compressor. Preferably, the gas loop conduit is provided with a further condenser or cooler downstream of the blower or compressor for removal of heat of compression. Makeup gases (for example, carbon monoxide and gaseous olefins) may be conveniently introduced to the gas loop conduit either upstream or downstream of the blower or compressor. Thus, an advantage of a gas loop conduit is that this provides flexibility with respect to the rate of addition of gaseous reagents to the reactor system.

By the term polyketone is meant a linear polymer comprised of alternating-CO- and-X-units derived from one or more olefins. Typically X is either-CH2CH2-, in the

case where carbon monoxide and ethylene are copolymerised, or a statistical mixture of- CH2CH2-and-CH2CH (R)- (R = Cl-C8 alkyl, phenyl or methyl or ethyl substituted phenyl), in the case where carbon monoxide, ethylene and at least one C3-CI0 alpha olefin are polymerised. It is preferred that the process of the present invention is used to prepare polyketones of the latter composition and in particular that the polyketones are those prepared from carbon monoxide and mixtures of ethylene and C3-C6 alpha olefins.

Most preferred of all are those materials prepared from carbon monoxide and mixtures of ethylene and propylene or ethylene and butylene. For the preferred polyketones, it is preferred that at least 70 mol% of the-X-units are-CH2CH2-, most preferably at least 80 mol%. The exact composition of the polyketone can be adjusted by making appropriate changes to the relative proportions of the reactants employed.

The polyketone prepared using the method of the present invention may have a number average molecular weight of between 20,000 and 1,000,000 preferably between 40,000 and 500,000, more preferably between 50,000 and 250,000, for example 60,000 to 150,000.

The polyketone prepared using the method of the present invention will suitably have a particle size in the range 1 tm to 2000 p. m, preferably 10 zip to 1000, and most preferably 50 ßm to 750 Rm As regards the catalyst, any catalyst which is suitable for the polymerisation of carbon monoxide and one or more olefins to give polyketones can be used. In particular, Group VIII metal catalysts are preferred and in particular those based on palladium. A typical catalyst composition would be that described in EP 121965 and EP 314309, as set out herein above.

Alternatively, a catalyst composition which is based on: (a) a Group VIII metal compound, (b) a Lewis acid of the general formula MF,,, in which M represents an element that can form a Lewis acid with fluorine, F represents fluorine and n has the value 3 or 5 and (c) a dentate ligand containing at least two phosphorus-, nitrogen-or sulphur-containing dentate groups through which the dentate ligand can complex with the Group VIII metal.

These catalyst compositions are set out in EP 508502.

Also suitable are catalyst compositions as detailed in EP 619335 which comprise (a) a Group VIII metal compound, containing at least one ligand capable of coordinating to the Group VIII metal and (b) a boron hydrocarbyl compound preferably a Lewis acid of the formula BXYZ where at least one of X Y and Z is a monovalent hydrocarbyl group.

Typically the boron hydrocarbyl compound is a compound of the formula BR3 where R is a Cl-C6 alkyl, or an aryl group for example, a substituted or unsubstituted phenyl group, for example C6H5, CIC6H4, or C6F5.

The ligand capable of coordinating to the Group VIII metal may be a bidentate phosphine ligand having at least two phosphorus atoms joined by a bridging group of the formula-(N) x-(P) y~N~ where(N) x-(P) y~N~ where x is 0 or 1 and y is 0 or 1, in particular, a bridging group of the formula- (NR2) X-(PR3) y~NR2~ where each R2 is the same or different and R2 and R3 represent a monovalent organic group. A preferred ligand has the formula (II) R12P- (nez) X (PR3) y NR2-PR'2 where each R'is independently an aryl, alkyl, alkoxy, amido or substituted derivative thereof, R2 is a hydrogen, a hydrocarbyl or hetero group, R3 is a hydrocarbyl or hetero group. For any of the catalyst systems described herein above preferred bidentate ligands are (o-anisyl) 2P-X-P (o-anisyl) 2 or Ph2P-X-PPh2 where Ph = phenyl, X =- (CH2) n-and n = 2-4, or X = N (R) R = Cl-C6 alkyl or aryl.

Suitable solvents for the process include alcohols, (e. g. methanol or ethanol), ketones (e. g. acetone), ethers, halogenated solvents (e. g. chloroform or dichloromethane), saturated or unsaturated hydrocarbons (e. g. toluene, pentane, hexane, heptane, or cyclohexane) and mixtures thereof. Alternatively, the process can be solvent-free if one of the reactant olefins is a liquid under reaction conditions.

The process is suitably carried out under super-atmospheric pressure e. g. 1-300 barg, preferably 1-150 barg, more preferably 10-100 barg, most preferably 20-70 barg, for example, 40-70 barg. Suitably, the process is carried out at a temperature in the range 25-130°C for example 50-95°C.

The molar ratio of olefinic compounds to carbon monoxide is preferably 10: 1- 1: 10 in particular 5: 1-1: 5.

The process of the invention may of course be carried out in conjunction with other known methods for reducing fouling, such as the use of polished or coated reactor surfaces, additives and seeding as previously mentioned.

Preferred embodiments of the reactor system for operating the process of the invention are shown in the accompanying drawings (Fig. l and 2).

Figure 1 shows a reactor system comprising a reactor vessel 1 and a gas loop conduit 2. The gas loop conduit 2 is provided with a gas circulation device 3 (for example, a compressor or blower). Make-up gaseous reagents are introduced to the gas loop conduit 2 via line 4. A sparger 5 is positioned in the reactor vessel 1. Optionally a draught tube (not shown) may be positioned in the reactor vessel 1 to enhance circulation of the polymer suspension in the reactor vessel 1. The reactor vessel 1 is fitted with a set of actuated dump valves (not shown). A portion of the polymer suspension (hereinafter referred to a reactor slurry) is transferred from the reactor vessel 1 to one or more flash vessels (not shown) through the dump valves, to give a slurry (hereinafter referred to as flashed slurry) having a higher polymer concentration than the reactor slurry. The flashed slurry is then transferred to polymer washing and drying sections (not shown) optionally via a stripper (not shown). Liquid diluent recovered from the polymer washing and/or drying sections may be recycled to the reactor vessel.

Optionally a portion of the liquid diluent recovered from the polymer washing and/or drying sections is vaporised and fed to the stripper. In the stripper, residual olefin monomers are stripped from the flashed slurry before the flashed slurry is passed to the washing and drying sections. The gas which is separated from the polymer suspension in the flash vessel (s) may be recycled to the gas loop conduit 2. Optionally this gas is recycled to the gas loop conduit 2 using a multistage compressor (not shown).

Preferably, the multistage compressor has a pre-cooler and an inter-cooler for condensing condensable vapours. It is preferred that a portion of the liquid (for example, liquid diluent) that condenses in these coolers is used to dilute the flashed slurry so that the solids concentration is reduced to a value which allows the slurry to flow readily.

Liquid that condenses in the pre-cooler or inter-cooler which is not required for diluting the flashed slurry may be returned to the reactor vessel 1. The reactor vessel 1 is also provided with an overhead condenser 6. Condensed liquid is returned to the reactor vessel via line 7 while a gaseous stream is recycled to the reactor vessel via gas loop conduit 2 and the gas circulation device 3. Optionally the condensed liquid from line 7 (and optionally any recycled liquid from the downstream sections) is sprayed into the headspace of the reactor vessel I via one or more nozzles (not shown) Optionally a heat

exchanger (not shown) is positioned on the gas loop conduit downstream of the gas circulation device 3.

Figure 2 shows a typical process flow diagram. The process was simulated using an ASPEN PLUS (release 9.3) package. Table 1 shows process parameters for Streams 11 to 22 as modelled using the ASPEN PLUS (release 9.3) package. The flow-rates correspond to a polymer production rate of 6,314 kg/hr.

Stream 11 is a purge taken to control the accumulation of methane, hydrogen and any other gaseous by-products in the gas recycle loop. Stream 15 is the gas recycle to the reactor vessel 25. Heat of reaction is removed in the condenser/cooler 23 from the reactor head vapour stream 13. Stream 22 (a compressed gaseous recycle from flash stage 24, is also sent to the condenser/cooler 23. Stream 14 is liquid that condenses in the condenser/cooler 23. Stream 12 is uncondensed vapour and gas from the condenser/cooler 23 which is recycled to the reactor vessel 25 via a recycle blower 26.

Streams 19,20 and 21 are fresh monomer feeds of propylene, ethylene and carbon monoxide respectively. Stream 17 is take-off of polymer suspension. Stream 16 comprises recovered liquid from the downstream flash, washing and drying sections (not shown). A portion of Streams 16 and/or 14 is sprayed into the headspace of the reactor vessel to knock down any entrained catalyst and polymer into the reactor vessel 25. A portion of Streams 16 and/or 14 may also be used to intermittently spray the walls of the reactor vessel at high pressure to remove any fouling polymer (jet cleaning) before the fouling polymer has a chance to build up significantly. The flow rates provided in the Table are averaged over time.

Table 1-Simulated Process Data STREAM 11 12 13 14 15 16 17 18 19 20 21 22 Temp (°C) 44. 6 40. 0 63. 3 40. 0 44. 6 40. 0 66. 0 44. 6 27. 7 20. 0 35. 0 150.5 Pressure (bar) 52.00 50. 00 50. 00 50. 00 52. 00 70. 00 50. 00 52. 00 52. 00 52. 00 52. 00 50.00 VapourFrac 1. 000 1. 000 1. 000 0. 000 1. 000 0. 000 0. 000 1. 000 0. 000 1. 000 1. 000 1. 000 Mole Flow 20.767 10980.084 10980.084 9. 617 101. 482 129. 476 51.625 (kmol/hr) Mass Flow 600. 000 317237. 594 348550.813 58967.230 2846.952 3608.321 1590.132 (kg/hr) I I Volume Flow 10.276 5559.616 5433.088 0. 795 26. 663 62. 871 34. 655 (CUM/hr) Enthalpy-1.962-1038.927-1063.902-44.005-1035.520-78.994-78.5 98-1037.482 0. 042 4.693-13.496-1.043 (MMBTU/hr) Mass Flow (kg/hr): DCM 54.192 28652.813 59717.934 31299.010 28598.619 57683.000 57862.770 28652.813 0.000 0.000 0.000 233.944 C2 22.808 12059.318 11928.580 602.481 12036.511 212.800 946.807 12059.318 0.000 2846.952 0.000 733.222 C3 0.922 487.752 991.653 511.751 486.829 1061.276 1069.123 487.752 404.690 0.000 0.000 7.845 CO 7.156 600. 218 274485.969 0.000 0.000 3605.387 593.062 hydrogen 1.330 703.465 703.465 0.000 702.135 0.000 0.000 703.465 0.000 0.000 1.330 0.000 methane 1.604 848.254 848.135 21.940 846.649 3.000 25.175 848.254 0.000 0.000 1.604 22.059 Table (cont.) Mass Flow 32903.297 316637. 594 58967.230 404.690 2846.952 3608.321 1590.132 (kg/hr) 496-1.043 (MMBTU/hr) Temp (°C) 0.000 0. 000 0. 000 0. 000 0. 000 0. 000 66. 000 0. 000 0. 000 0. 000 0. 000 0. 000 Pressure (bar) 52.00 50. 00 50. 00 0. 00 52. 00 70. 00 50. 00 52. 00 52. 00 52. 00 52. 00 50. 00 MoleFlow 0. 000 0. 000 0. 000 0. 000 0. 000 0. 000 0. 064 0. 000 0. 000 0. 000 0. 000 0.000 (kmol/hr) Mass Flow (). 00 () 0. 000 0.000 0.0000. 0000. 000 6314. 0200. 0000. 0000. 0000. 0000.000 (kg/hr) VolumeFlow 0. 000 0. 000 0. 000 0. 000 0. 000 0. 000 6. 764 0. 000 0. 000 0. 000 0. 000 0.000 (CUM/hr) Enthalpy 0. 000 0. 000 0. 000 0. 000 0. 000 0.000-24.794 0. 000 0. 000 0. 000 0. 000 0.000 (MMBTU/hr) Mass Flow (kg/hr): Polymer 0.000 0.000 0.000 0.000 0.000 0.000 6314. 020 0.000 0.000 0.000 0.000 0.000