IE83667B1 - A process for removing pyrophoric catalyst - Google Patents

Description

A process for removing pyrophoric catalyst Introduction The invention relates to a factory scale process for carrying out a hydrogenation reaction.

Hydrogenation reactions are frequently carried out in the presence of a pyrophoric catalyst such as Raney Nickel. This presents a serious difficulty because flammable liquids such as methanol or ethanol are often used as hydrogenation solvents. The removal of the catalyst from the reaction mixture after the hydrogenation reaction is complete, presents serious difficulties. Generally the reaction mixture is passed through a filter, the catalyst is filtered out and removed in a closed circuit.

Handling of the resultant catalyst presents difficulties and the commonly used multiplate filters, which necessitate generation of hazardous dry material, require extensive safety precautions and extended operation times to facilitate safe removal of the catalyst.

DE—A-4325682 (= US5,690,836) describes a method for removing a catalyst such as Raney Nickel from hydrogenation reaction product. The reaction product is passed through a hollow tubular filter medium which is back—washable. The process is described on a laboratory scale and is not suitable for large factory scale use.

There is therefore a need for an improved process for carrying out a hydrogenation reaction which will overcome these problems.

Statements of Invention According to the invention there is provided a batch process for carrying out a hydrogenation reaction comprising the steps of:— mixing a pyrophoric catalyst with reactants and solvents to form a reaction mixture in a reaction vessel; adding hydrogen to the reaction vessel; after hydrogenation, removing the desired hydrogenation product from the reaction vessel; delivering the pyrophoric catalyst-rich material from the reaction vessel to a pressure filter comprising a container having an upper rim closable by a removable lid, the container having a removable filter bag and the pyrophoric-rich material being retained in the bag; adding water to the pyrophoric catalyst—rich material in the filter to saturate the pyrophoric catalyst—rich material on the filter; opening the lid; and removing the filter bag containing the spent pyrophoric material from the pressure filter in a water wet form.

In a preferred embodiment of the invention the pressure filter is a single platc pressure filter, the catalyst being held in the filter in a wet form.

In one embodiment the catalyst is Raney Nickel.

Preferably the contents of the reaction vessel are decanted after hydrogenation, the desired hydrogenation product being substantially removed while allowing the catalyst—rich material to settle at the bottom of the vessel.

Preferably the reaction vessel is an agitated vessel, the agitator being stopped to allow the catalyst to settle at the bottom of the vessel.

In one embodiment of the invention the process includes the step of washing the catalyst—rich material in the filter with a solvent to recover residual desired hydrogenation product.

Detailed Description of the Drawings The invention will be more clearly understood from the following description given by way of example only with reference to the accompanying drawings in which:— Fig.1 is a perspective view from the front of a filter apparatus used in the process of the invention; Fig.2 is a perspective view from the side of the filter apparatus of Fig. l; Fig.3A is an exploded perspective view of a removable filter bag and associated clamping band; Fig. 3B is a perspective view of the filter bag in position; Fig. 4 is a top view of a clam—shell lid of the filter apparatus of Fig. 1; and Fig. 5 is a cross—sectional view of the filter apparatus of the invention.

Detailed Description The invention will be more clearly understood from the following description given by way of example only.

We have found a new method of removing a spent pyrophoric reaction catalyst from a reaction mixture, safely, cheaply and rapidly using a single plate pressure filter.

In the process, after hydrogenation, the reaction mixture is decanted, the desired hydrogenation product is substantially removed and catalyst rich material which settles at the bottom of the vessel is delivered to a single plate pressure filter. The spent catalyst is retained in the filter bag on the filter plate while the product rich solvent is led away from the bottom outlet of the pressure filter to a receiving vessel.

The retained catalyst material is washed with a solvent to recover residual product and then washed with water to saturate the catalyst material which is then safely and easily transferred to drums and stored under water awaiting recovery.

Referring to Figs. 1 to 5 there is illustrated a filter apparatus 1 of the invention. The filter apparatus 1 comprises a container having a domed base 2, a generally cylindrical sidewall 3 terminating in an upper rim 4 closed by a removable lid 5 having lifting lugs 6. The lid 5 is fixed in pressure—tight engagement with the sidewall 3 by flange engaging screw clamps 7 and an embedded polytetrafluoroethene gasket 8.

The filter container has a single removable, perforated filter plate 9 which is supported in spaced-apart relation from the base 2 by supports 12. The base 2 has an outlet 10 below the filter plate 9. The outlet 10 is fitted with an outlet valve 13 for discharge of product—rich solvent.

The lid 5 has several fittings including a main catalyst inlet line 15, a decant inlet valve 16 and a water wash inlet line 17. A light port 18, a sight glass 19, pressure relief line 20 and a nitrogen purge line 21 are also provided. An earth clip 22 is located on the lid 5.

The filter container has two jacketed coils 30 with inlet and outlets 31, 32. The jackets may be heated or cooled, as required, to heat or cool the contents of the filter container. A hot water pressure release device 23 and a hot water overflow 27 are also provided.

Referring especially to Fig. 3 there is illustrated a removable filter bag 40 of water/solvent permeable material, typically of acid resistant polypropylene monofilament or multifilament weave (about 10 micron pores), with a top rim 41 held in position against the side wall 3 of the filter container by a band 11. A releasable ring clamp 42 is provided on the band 11. The clamp 42 is adjustable to maximise the diameter of band 11 and thus tighten the filter bag rim 41 against the filter sidewall 3. The bottom of the filter bag 40 rests on a perforated filter plate 9 which is supported by a filter plate support 12. The filter is inerted by first applying a vacuum and then breaking the vacuum with nitrogen. Most of the contents of a reaction vessel after settling are pressure decanted from the reaction vessel and fed into the closed single plate pressure filter apparatus 1 through an inlet line 16.

Liquid free of catalyst is discharged through the bottom outlet valve 13 and transferred to a receiving vessel. The residual catalyst in the reaction vessel is fed to the filter through the larger inlet line 15 followed by a solvent wash to recover residual product. The spent catalyst is retained in a filter bag 40 while the desired product is drained off and removed, by applying pressure to the apparatus 1, through to a receiving vessel via the outlet valve 13. Water is then added through the wash inlet line 17 to wash out residual solvent to waste and to saturate the retained catalyst material. The pressure in the filter apparatus 1 is released and the lid 5 is removed by passing a chain through the lugs 6 and hoisting the lid 5 off. Water saturated catalyst is scooped directly to drums and stored under water. Alternatively the filter bag 40 is lifted out and the water wet catalyst is removed and stored for disposal.

The filter bag 40 may be reused. Alternatively the filter bag 40 is lifted out of the pressure filter and the bag containing catalyst charged to a drum where it is stored under water and sent for catalyst recovery.

The filter container is mounted on a wheeled chassis 50 so that the filter apparatus may be easily moved from one location to another.

The invention provides a simple, cheap and rapid method for removing spent pyrophoric catalyst from hydrogenation catalyst-rich material. The filter apparatus is cheap to set up and maintain. By keeping the pyrophoric catalyst water wet the catalyst does not pose a safety hazard and may be easily taken from the filter apparatus 1 directly or in removable filter bags 40 and safely and easily transferred to drums containing water for storage and recovery.

The invention is not limited to the embodiments hereinbefore described which may be varied in detail.

Claims (2)

Claims

1. A batch process for carrying out a hydrogenation reaction comprising the steps of :- mixing a pyrophoric catalyst with reactants and solvents to form a reaction mixture in a reaction vessel; adding hydrogen to the reaction vessel; after hydrogenation, removing the desired hydrogenation product from the reaction vessel; delivering the pyrophoric catalyst—rich material from the reaction vessel to a pressure filter comprising a container having an upper rim closable by a removable lid, the container having a removable filter bag and the pyrophoric—rich material being retained in the bag; adding water to the pyrophoric catalyst—rich material in the filter to saturate the pyrophoric catalyst—rich material on the filter; opening the lid; and removing the filter bag containing the spent pyrophoric material from the pressure filter in a water wet form.

2. A process as claimed in claim 1 including the step of washing the catalyst- rich material in the filter with a solvent to recover residual desired hydrogenation product. A process as claimed in claim 1 or 2 wherein the pressure filter is a single plate pressure filter, the catalyst being held in the filter in a wet form. A process as claimed in any preceding claim wherein the catalyst is Raney Nickel. A process as claimed in any preceding claim wherein the contents of the reaction vessel are decanted after hydrogenation, desired hydrogenation product being substantially removed while allowing the catalyst-rich material to settle in the bottom of the reaction Vessel. A process as claimed in any preceding claim wherein the reaction vessel is an agitated vessel, the agitator being stopped to allow the catalyst to settle at the bottom of the vessel.