FIELD OF THE INVENTION

[0001] The present invention relates to an improved process for manufacturing and recovering butynediol from a reaction mixture comprising an aqueous solution containing formaldehyde, acetylene, and suspended catalyst solids. More particularly, the invention relates to an improved process for manufacturing and recovering butynediol from a reaction mixture comprising an aqueous solution containing formaldehyde, acetylene, and suspended catalyst solids in a particular reaction zone, whereby a product slurry stream comprising butynediol, formaldehyde, and suspended catalyst solids is removed from the reaction zone and fed to a filter zone external from the reaction zone, the product slurry stream being moved to and through the external filter zone by injection of a composition comprising acetylene at a point between the reaction zone and the filter zone.

BACKGROUND OF THE INVENTION

[0002] In current processes for manufacturing butynediol from a reaction mixture comprising an aqueous solution containing formaldehyde, acetylene, and suspended catalyst solids in reaction vessels, the vessels contain internal filters, such as candle filters, for separation of suspended catalyst solids from reaction product. In such current reaction vessels, catalyst solids build up on the filters as cake which is removed by back flushing each filter regularly to avoid totally plugging the reactor vessel. Even with this complicated internal filter flushing system, periodic maintenance of the reaction vessel and internal filters is required. This results in costly loss of acetylene and butynediol product since the reactor must be taken off-line.

[0003] U. S. Patent No. 5,444, 169A discloses a process for synthesizing butynediol from an aqueous solution containing formaldehyde by reaction of said formaldehyde with acetylene in the presence of a suspended catalyst solids, wherein the solution is conveyed in a cascade by several reactors, the solution drawn off from the first through the penultimate reactor of the cascade being fed to the next reactor in the cascade, acetylene being introduced into each of the reactors, and a butynediol-rich solution being drawn off only from the last reactor in the cascade. The catalyst is separated from the solution in each individual reactor of the cascade above the last reactor to prevent the catalyst from escaping the reactor.

[0004] U. S. Patent No. 5,407,644A discloses an apparatus for conducting a continuous multi-phase catalytic reaction in a slurry bubble column comprising: (a) a reaction vessel defining a reaction zone therein, the reaction zone being arranged to receive a slurry; (b) a filter member in contact with the reaction zone defining a filtrate zone separated from said reaction zone but within the reactor; (c) means for maintaining a predetermined mean pressure differential across the filter member; and (d) a gas distribution device in the reaction zone.

[0005] U. S. Patent No. 2012/0070356A1 discloses a process for separating liquid from a multiphase mixture contained in a vessel and comprising solid particles and at least one liquid phase forming together at least one suspension, and a gas phase flowing upwards through the suspension such that a gas-lift effect occurs inside the vessel, in which at least part of the multiphase mixture, optionally at least partially degassed, is circulated through at least one cross-flow filter located outside the vessel, but using overflow from the top of the vessel rather than circulation from the base as required in the present invention process.

[0006] WO Patent No. 2009/035974A1 discloses a Fischer-Tropsch reaction system comprising a catalytic reactor fluidly connected with at least two slurry loops, wherein the reactor comprises at least as many reactor product outlets and at least as many slurry return inlets as slurry loops, wherein each slurry loop comprises a separation system comprising at least one separation device for separating concentrated catalyst slurry from liquid product; an inlet of the at least one separator fluidly connected to one of the reactor product outlets via a slurry off take, an outlet of the at least one separator fluidly connected to one of the slurry return inlets via a slurry return, and a product outlet of the at least one separator for removal of liquid product therefrom. This patent discloses more than one external loop with two separate outlets and inlets to the reactor.

[0007] The above described methods can add complexity, processing limitations, and/or cost to a process for manufacturing butynediol from a reaction mixture comprising an aqueous solution containing formaldehyde, acetylene and suspended catalyst solids. A simple economical process for manufacturing butynediol from such a reaction mixture is needed. SUMMARY OF THE INVENTION

[0008] The present invention provides an economical improved process for manufacturing and recovering butynediol from a reaction mixture comprising an aqueous solution containing formaldehyde, acetylene, and suspended catalyst solids in a particular reaction zone, whereby a product slurry stream comprising butynediol, formaldehyde, and suspended catalyst solids is removed from the reaction zone and fed to a filter zone external from the reaction zone, the product slurry stream being moved to and through the external filter zone by injection of a gaseous composition comprising acetylene at a point between the reaction zone and the filter zone. An embodiment of the invention process involves the steps of: a) removing from the reaction zone a product slurry stream comprising butynediol, formaldehyde and suspended catalyst solids; b) feeding the product slurry stream of step a) comprising butynediol, formaldehyde, and suspended catalyst solids to a filter zone, said filter zone being external from the reaction zone, said product slurry stream of step a) being moved to and through the filter zone by injection of a gaseous composition comprising acetylene at a point between the reaction zone and the filter zone; c) recovering from the filter zone of step b) filtered slurry comprising, for example, suspended catalyst solids, butynediol, formaldehyde, acetylene, and water; d) recovering from the filter zone of step b) product filtrate liquor comprising, for example, butynediol, water, and unreacted formaldehyde; e) feeding the recovered filtered slurry stream of step d) comprising, for example, suspended catalyst solids, butynediol, formaldehyde, acetylene, and water to the reaction zone as recycle. The reaction zone of the present invention comprises a reactor vessel devoid of internal filter assemblies.

[0009] Another embodiment of the invention involves the steps of: a) removing from the reaction zone a product slurry stream comprising butynediol, formaldehyde, and suspended catalyst solids; b) feeding the product slurry stream of step a) comprising butynediol, formaldehyde, and suspended catalyst solids to a filter zone, said filter zone being external from the reaction zone, said product slurry stream of step a) being moved to and through the filter zone by injection of a gaseous composition comprising acetylene at a point between the reaction zone and the filter zone; c) recovering from the filter zone of step b) filtered slurry comprising, for example, suspended catalyst solids, butynediol, formaldehyde, acetylene, and water; d) recovering from the filter zone of step b) product filtrate liquor comprising, for example, butynediol, water, and unreacted formaldehyde; e) optionally i) splitting the recovered filtered slurry of step c) into a liquid stream comprising formaldehyde, suspended catalyst solids, and butynediol, and a vapor stream comprising acetylene, wherein either the liquid stream of step e) is fed to the reaction zone as recycle, and the vapor stream of step e) is fed to an overhead vapor stream from the reaction zone, or ii) the recovered filtered slurry of step c) comprising butynediol, formaldehyde, acetylene, and suspended catalyst solids is fed to the reaction zone as recycle. The reaction zone of this embodiment, again, comprises a reactor vessel devoid of internal filter assemblies.

[00010] Another embodiment of the invention process involves the filter zone comprising one or a plurality of filter assemblies in parallel such that the product slurry stream comprising butynediol, water, formaldehyde and suspended catalyst solids can be selectively fed to one or more of the filters. Another embodiment involves the product slurry stream comprising butynediol, water, formaldehyde and suspended catalyst solids being alternately fed to one or more of the filter assemblies. The filter assembly comprises a filtration surface across which the filtered slurry is passed prior to being recycled to the reactor and through which the product filtrate stream is filtered to give a product stream containing essentially no solids. The filtration surface can consist of a membrane, or fine mesh gauze type interface of suitable pore size to retain the solids in the slurry while allowing the filtrate to pass at a suitable rate. Cross flow filtration devices available include tubular modules, pleated cartridge modules and plate and frame modules as described in "Handbook of Industrial Membrane Technology," p61-135, Editor Mark C Porter, Noyes Publications, Westwood, New Jersey, (1990).

[00011] Another embodiment of the invention process comprises the above steps and wherein a portion of the product slurry stream of step a) comprising butynediol, formaldehyde, and suspended catalyst solids is fed through a pump zone prior to injection of the composition comprising acetylene at a point between the reaction zone and the filter zone.

[00012] Another embodiment of the invention process involves removing from the reaction zone the product slurry stream comprising butynediol, formaldehyde, and suspended catalyst solids via a gas-liquid disengagement zone. This gas-liquid disengagement zone may be either within or outside of the reaction zone. BRIEF DESCRIPTION OF THE DRAWING

[00013] Fig. 1 shows a diagrammatic view of an embodiment of the present process involving a reaction zone and a filter zone external from the reaction zone.

[00014] Fig. 2 shows a diagrammatic view of another embodiment of the present process involving a reaction zone and a filter zone external from the reaction zone.

[00015] Fig. 3 shows a diagrammatic view of another embodiment of the present process involving a reaction zone, gas-liquid disengagement zone and a filter zone external from the reaction zone.

[00016] Fig. 4 shows a diagrammatic view of another embodiment of the present process involving a reaction zone, a circulation pump and a filter zone external from the reaction zone.

DETAILED DESCRIPTION OF THE INVENTION

[00017] As a result of intense research in view of the above, we have found that we can - economically and effectively manufacture butynediol from a reaction mixture comprising an aqueous solution containing formaldehyde, acetylene and suspended catalyst solids. The process avoids the problems associated with having filters within the reaction zone, such as within a reactor vessel. The process involves manufacturing butynediol from a reaction mixture comprising an aqueous solution containing formaldehyde, acetylene, and suspended catalyst solids in a particular reaction zone, such as a reactor vessel devoid of internal filter assemblies, whereby a product slurry stream comprising butynediol, formaldehyde, and suspended catalyst solids is removed from the reaction zone at an appropriate point, such as at the bottom of a reactor vessel, and fed to a filter zone external from the reaction zone, the product slurry stream being moved to and through the external filter zone by injection of a composition comprising acetylene at a point between the reaction zone and the filter zone.

[00018] The term butynediol ("BYD") represents the compound structure HOCH ₂ C≡CCH ₂ OH. Percentages are in volume % unless otherwise indicated. Flow rates of gaseous streams are presented in SCF per minute. Flow rates of liquid streams are presented in gallons (US) per minute.

[00019] The reactor vessel for use as the reaction zone in the present invention may comprise one of current use in such a process, except being devoid of internal filter assemblies. Such a reactor vessel may be a bubble column wherein acetylene and other gases are injected at the base of the reactor both to conduct the reaction and to maintain the catalyst solids in suspension, or a stirred tank reactor which uses an agitator to maintain catalyst solids in suspension and to assist in gas dispersion, or some combination thereof.

[00020] Reaction conditions in the reaction zone include a temperature of from 40 to 110°C, for example, from 60 to 110°C, pressure from 0 to 20 psig, for example from 1.5 to 16 psig, and pH from 3-9. Contents of the reaction zone are agitated by either or both of mechanical means, for example a stirrer, or gaseous injection.

[00021] Catalyst for use in the reaction zone of the present process and suspended as solids in the product slurry stream comprising butynediol and formaldehyde may be added to the reaction zone or produced in the reaction zone. The catalyst precursor comprises a compound of copper, such as, for example, copper carbonate. As a non-limiting example of producing the catalyst in situ, the following procedure may be followed:

(1) A batch of formaldehyde solution, water, and sodium bicarbonate is charged to the reactor.

(2) Continuously, a mixture of acetylene and nitrogen are fed to the compressor which is circulating gas through the reactor. The same mixture exits the system to flare.

(3) A batch of copper carbonate slurry in water is fed to the reactor.

(4) Carbon dioxide is evolved from the copper carbonate as it converts to catalyst. The carbon dioxide exits the system to flare. Nearly all acetylene feed is consumed with very little venting to flare.

(5) Formic acid is produced continually during this procedure requiring addition of sodium bicarbonate slurry to control pH. [00022] After copper carbonate is converted to catalyst (e.g., 12 to 20 hours), the process reaction conditions are transitioned to normal and continuous butynediol production begins. Fresh continuous formaldehyde feed is started.

[00023] In situ production of catalyst may be conducted when a previous catalyst batch in the reaction zone is spent and needs to be replaced.

[00024] Referring more particularly to the drawings, where compositions are presented as non-limiting examples, Fig.l shows an embodiment of the present invention involving a reaction zone and a filter zone external from the reaction zone. The reaction zone contains copper carbonate-based catalyst prepared in-situ as shown above. In this particular embodiment, 90 % of the vapor feedstock comprising, for example, 70 % acetylene, 3 % methanol, 4 % water, 5 % nitrogen and 8 % carbon dioxide, enters the bottom of reaction zone VI via stream LI at a flow rate of 5300 SCF /minute; while liquid feedstock comprising, for example, 40 % formaldehyde, 7 % methanol and 53 % water enters the top of reaction zone VI via stream L2 at a flow rate of 55 gallons/minute. Reaction zone VI is maintained at a pressure of aboutlO psig, a temperature of about 90°C, and is agitated e.g. stirred. Liquid product stream L3 comprising, for example, 10 % formaldehyde, 4 % methanol, 36 % butynediol and 50 % water on a solids-free basis, and from 15 to 40 volume % solids, is removed from the bottom of reaction zone VI at a flow rate of 500 gallons/minute. Stream L3 is fed to the bottom of filter zone V2. The remaining 10 % of the vapor feedstock is fed via stream L8 at 530 SCF/minute to aid moving stream L3 to and through the filter zone V2. Filtrate product liquor comprising, for example, 10 % formaldehyde, 4 % methanol, 36 % butynediol, 50 % water and essentially no solids is removed from filter zone V2 via stream L9 at 55 gallons/minute and sent to a butynediol recovery. From the top of filter zone V2 a stream L4 can be treated in either of two optional ways, as follows: (1) stream L4 can be fed to reaction zone VI as recycle, or (2) stream L4 can be split into liquid recycle stream L5 comprising, for example, 10 % formaldehyde, 4 % methanol, 36 % butynediol and 50 % water; and vapor stream L6 comprising, for example, 70 % acetylene, 4 % methanol, 4 % water, 4 % nitrogen and 8 % carbon dioxide. Stream L5 is fed to reactor VI as recycle. Vapor stream L6 is combined with an overhead vapor stream from reaction zone VI to form stream L7 comprising, for example, 26 % acetylene, 14 % formaldehyde, 13 % methanol, 29 % water, 13 % nitrogen and 7 % carbon dioxide. [00025] In the non-limiting example embodiment shown in Fig.l, compositions of the various streams, on a solids-free basis, are shown in Table 1. Percentages are in weight percent.

Table 1

[00026] Solids may be present in stream L3 of Fig. 1 at from 5 to 40 % by volume, such as from 15 to 40 %, for example, from 25 to 40 % by volume, and are essentially entirely separated in filter zone V2 to provide an essentially solids free stream L9.

[00027] The product slurry stream L3 of Fig. 1 comprising butynediol, formaldehyde and suspended catalyst solids, optionally, may be fed at least partially through a pump zone prior to injection of the composition comprising acetylene at a point between the reaction zone and the filter zone in order to support, e.g., maintain or increase, the flow rate of the product slurry stream. An example of a useful pump scheme for this purpose is one or more lobe or gear pumps.

[00028] Referring now to Fig. 2, rather than being split into gas and liquid phases, stream L4 is fed directly to the reaction zone VI as recycle. All other flows are identical to those of Fig. 1.

[00029] Referring now to Fig. 3, stream L3 is drawn from a gas liquid disengagement zone located within or optionally outside of and fed from the reaction zone VI. All other flows are identical to those of Fig. 1. [00030] Referring now to Fig. 4, the flow of stream L3 is supported, e.g. maintained or increased, from the reaction zone VI to and through the filter zone V2 using a pump, e.g. a lobe or gear pump. All other flows are identical to those of Fig. 1.

[00031] All patents, patent applications, test procedures, priority documents, articles, publications, manuals, and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this invention and for all jurisdictions in which such incorporation is permitted.

[00032] When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.

[00033] While the illustrative embodiments of the invention have been described with particularity, it will be understood that various other modifications will be apparent to and may be readily made by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is not intended that the scope of the claims hereof be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present invention, including all features which would be treated as equivalents thereof by those skilled in the art to which the invention pertains.