KR20000016464A - Molybdenum epoxidation catalyst recovery - Google Patents

Abstract

PURPOSE: A process for recovery of molybdenum catalyst from a process is provided which can reduce the molybdenum content of more than 1,000 wt.% ppm in a stream to below 50 ppm. CONSTITUTION: An aqueous epoxidation process stream containing molybdenum and sodium values and organic is treated for organic removal as by incineration and an aqueous solution containing molybdenum and sodium is recovered, cooled, acidified and contacted with activated carbon and an aqueous stream reduced molybdenum is recovered, further molybdenum reduction can be achieved by treatment with basic ion exchange resin. An aqueous blowdown stream is poured in a cooling zone(1) through a line(2) in which the temperature of aqueous blowdown stream falls down from about 90°C to below 40°C. The cooled stream is transferred to the zone(4) in which the stream is acidified to below pH 5(preferably pH 1-3) by adding sulfuric acid through the line(5) to transfer carbonate to carbon dioxide. To reduce further molybdenum if necessary, the stream is passed though the zone(9) through the line(10), the zone(11) through the zone(16) and the zone(13) through the line(14).

Description

Molybdenum Epoxidation Catalyst Recovery

Very successful processes for the co-production of polyethylene oxide and styrene monomers include molecular oxygen oxidation of ethyl benzene to form ethyl benzene hydroperoxide, reaction of propylene oxide with propylene to form 1-phenyl ethanol, and Dehydration of 1-phenyl ethanol to styrene monomers. The basic patent describing such a process is US Pat. No. 3,351,635.

In carrying out the process, the epoxidation reaction mixture is usually reacted with the molybdenum material contained after separation of the unreacted propylene by distillation to form sodium molybdate and with the acid and phenol also contained in the epoxide. It is treated with an aqueous solution of caustic in excess of the amount necessary to react with the same organic impurities. See, for example, US Pat. Nos. 4,405,572, 5,210,354, 5,276,235, and 5,171,868.

One problem that exists in this conventional practice has been the disposal of relatively large amounts of aqueous process streams containing molybdenum, sodium and organic materials and such streams. The presence of molybdenum was particularly troublesome because molybdenum had to be removed to meet environmental regulations prior to spillage.

U.S. Patent No. 5,439,657 and co-pending US Patent Application No. 08 / 510,727, filed August 30, 1995, relate to such molybdenum containing streams and the separation of molybdenum from these streams.

Despite the actual conventional efforts, there is still room for improvement in the treatment of the process stream in view of the increasingly stringent environmental concerns, especially in the removal of molybdenum.

An aqueous epoxidation process stream containing molybdenum and sodium materials as well as organic materials is treated by known methods such as incineration to separate organic materials prior to carbon layer treatment. During the incineration process, particulate ash made of molybdenum and sodium material passes down the incinerator together with the incineration gas. This ash-containing gas is quenched by mixing water to form an incinerator blowdown stream. The blowdown stream is an aqueous solution of molybdenum material, such as sodium molybdate, and sodium material, such as sodium carbonate, that remains from the epoxidation process stream. Such blowdown solutions should not be released directly due to environmental hazards associated with the molybdenum heavy metals contained. According to the invention, the aqueous blowdown stream which is practically free of organic matter is preferably cooled and then acidified as H ₂ SO ₄ so that the carbonate is converted to CO ₂ which can be easily removed. The essentially carbonate free stream is then contacted with the solid activated carbon sorbent to remove the contained molybdenum material. Subsequently, the resulting aqueous solution in which the molybdenum content is significantly reduced can be disposed of properly, or, if the maximum molybdenum criterion is very stringent, the aqueous effluent resulting from the carbon treatment is substantially basic ion exchange material such that complete molybdenum removal is achieved. Is further processed by contact with.

Instead of incineration, other known processes such as wet air oxidation or biological treatment can be used prior to carbon treatment to remove organic matter. In such a case, acidification as described above to separate the CO ₂ is unnecessary. Incineration, however, represents a preferred method for separating organic matter.

The preparation of oxirane compounds such as propylene oxide by the catalytic reaction of olefins with organic hydroperoxides is a process of great commercial importance. Generally homogeneous molybdenum catalysts are used. An oxirane process for co-producing propylene oxide and styrene monomer is an example of such a technique.

The process of the present invention relates to the recovery of molybdenum epoxidation catalyst material from a process stream in such epoxidation process techniques.

1 schematically illustrates an embodiment of the invention.

According to a preferred embodiment of the present invention, an aqueous epoxidation stream containing molybdenum catalyst material, sodium material and organic material remaining after caustic solution treatment is incinerated according to known procedures. Intrinsically complete combustion of organic material is achieved. Molybdenum and sodium material, mainly in the form of sodium molybdate and sodium carbonate, are recovered as an aqueous incinerator blowdown stream.

The blowdown stream containing molybdenum and sodium is cooled and acidified to pH5 or below by addition of sulfuric acid or such as HCl, and with proper agitation the carbonate is converted to CO ₂ where it is vaporized and separated. Temperatures of 10 ° C. to 50 ° C. may be used to minimize corrosion and special materials of the structure while achieving CO ₂ removal.

The acidified blowdown solution after CO ₂ removal, or the corresponding acidic molybdenum-containing aqueous stream, in which other organic material removal processes are used, is then contacted with solid activated carbon so that most of the molybdenum material in the aqueous stream is adsorbed onto the activated carbon. Effectively removed from the stream.

More than one layer of carbon can be used which can be recycled or disposed of by caustic aqueous solution washing when the molybdenum removal capacity is reduced to a certain level.

The above process is effective to reduce the level of molybdenum contained in the aqueous process stream from at least 1,000 ppm by weight up to about 50 ppm.

If it is desired to further lower the level of molybdenum in the plant effluent stream, in a particularly preferred embodiment the aqueous stream after carbon treatment is further contacted with basic or chelate ion exchange resins to achieve complete separation of molybdenum. That is, an aqueous stream with less than about 10 ppm molybdenum is produced.

Activated carbon or charcoal used include those obtained from lignite, gas black, coconut, bagasse, wood, sawdust, peat, pulp-mill waste, blood, bone and the like. Special activated carbons include Calgon Corporation granular carbon such as Calgon F-400, F-200 or React AW, NORIT granular activated carbon such as NORIT C, Cenco activated carbon from Central Scientific Company, West Virginia Pulp and Paper Company Nuchar, and Darco Division, ICI AMERICAS, Inc. Rohm and Hass Ambersorb carbonaceous adsorbents such as X-340 can be used as Rohm and Hass active Amberlite. Representative commercially available activated carbons include type CAL granular coal (Calgon Corporation) and NORIT ROW 0.8 granular activated carbon (NORIT Corporation).

Ion exchange resins that can be used in the practice of the present invention are basic anion exchange resins which are commercially well known products. Both strong base resins and weak base resins can be used.

Strong base resins may be produced by the reaction of chloromethylated styrene-DVB copolymers with tertiary amines such as trimethylamine to yield quaternary ammonium groups.

The main types of weak base anion exchangers are amine derivatives of styrene-DVB copolymers, epichlorohydrin-amine condensation products, and amine derivatives of phenol-formaldehyde products, the primary, secondary or tertiary amine groups, or of these groups It may contain some or all of the mixture.

Weak base styrene-DVB resins, for example, may be used by amination of chloromethylated copolymers in much the same way that strong base styrene-DVB resins are made, except that primary or secondary amines are generally used instead of tertiary amines. Can be prepared.

US patents describing the preparation of basic anionic resins that may be used in the present invention include 4,025,476, 3,791,996, 3,817,878, 3,346,516, 4,082,701, 3,843,566, 3,813,353, 3,812,061, 3,882,053, 3,793,296,3,793,273233 3,108,922, 3,005,786, 3,637,535 and 4,052,343.

Hereinafter, the present invention will be further described with reference to the accompanying drawings. Referring to FIG. 1, an aqueous incinerator blowdown stream is introduced into the cooling zone 1 via line 2. In zone 1, the temperature of the aqueous stream is reduced from about 90 ° C. up to about 40 ° C. by conventional heat exchange processes. The stream thus cooled is passed to line 4 via line 3 so that at low pH, ie below 5, preferably at a pH of about 9.5 by addition of sulfuric acid through line 5 in zone 4 Acidify to a pH of 1-3. Other acids, such as hydrochloric acid, may also be used.

By this acidification, the carbonate material in the aqueous stream is converted to carbon dioxide, which is usually a gas and is removed as steam via line (6). A stripping gas such as nitrogen (not shown) can be introduced into zone 4 to assist in the removal of CO ₂ .

Substantially carbonate free solution exits zone 4 via line 7 and contacts the solid activated carbon layer in zones 8 and 9. While such carbon contact is shown to occur in two layers, it can be appreciated that more or fewer carbon regions may be used as appropriate.

As a result of the above treatment, the content of molybdenum contained can be reduced from 1000 ppm to 50 ppm in the stream leaving the carbon treatment region 9.

It should be noted that acidification before carbon layer contact is essential. If the aqueous stream is not acidified, carbon layer contact is not effective for molybdenum removal.

As shown, carbon layer contact is effective in reducing most molybdenum materials, for example up to 50 ppm. However, in certain areas it is necessary to reduce the molybdenum content to less than 10 ppm because of more stringent requirements.

If it is important to further lower the molybdenum content, in a particularly preferred embodiment of the present invention, after the acidification and carbon layer treatment described above, the aqueous stream exits the zone 9 via line 10 and contacts the zone 11. The aqueous stream in zone 11 effectively removes additional molybdenum such that the aqueous stream exiting zone 11 through line 12 has a molybdenum content of 10 ppm or less, preferably 5 ppm or less. Contact with basic ion exchange resin.

As shown, the pH of the treated aqueous stream is adjusted to 6 to 8 in zone 13 by addition of caustic solution through line 14 before exiting the effluent through line 15.

In a particularly preferred embodiment, both a plurality of carbon and ion exchange resin layers are used. The ion exchange resin layer can be appropriately regenerated by washing the caustic aqueous solution, and in a particularly preferred embodiment, the washing liquid containing molybdenum removed from the resin layer is sent back to the zone 4, which molybdenum adsorbs activated carbon. Practically eliminated.

As illustrated, caustic aqueous solution is introduced into zone 11 through line 16 during the regeneration cycle, and the aqueous regeneration stream containing molybdenum removed is removed from zone 11 through line 17 through zone 4. Is sent to.

The carbon layer, which has lost its ability to effectively adsorb molybdenum material, is treated by water washing and drying to be used as landfill or fuel.

The following examples illustrate the invention with reference to FIG. 1.

The aqueous blowdown process stream from the propylene oxide / styrene monomer manufacturing process is introduced into the cooling zone 1 via line 2 at a flow rate of 24000 lbs / hr after incineration of organic material. The blowdown stream consists of 86 wt% water, 0.2 wt% sodium molybdate, 14 wt% sodium carbonate and sodium bicarbonate, and 0.01 wt% organic matter.

In zone 1 the temperature of the aqueous stream is reduced from 90 ° C to 40 ° C. This cooled stream is sent via line 3 to the acidification zone 4 to reduce the pH from 9.5 to 3 by addition of 94% sulfuric acid at a flow rate of 2700 lbs / hr.

Carbon dioxide generated by the reaction of carbonate and sulfuric acid is removed as steam through line 6 at a flow rate of 1600 lbs / hr.

The acidified aqueous stream is withdrawn via line 7 to contact the layer of activated carbon in zones 8 and 9. Activated carbon used is Calgon F-400, F-200 or React AW. The liquid construction rate is 2-10 × volume / hour, and the removed aqueous stream removed via line 10 after carbon layer treatment has a molybdenum content of less than 30 ppm.

This aqueous stream is sent to zone 11 via line 10 at a flow rate of 25140 lbs / hr, contacting the weakly basic solid ion exchange resin Rohm and Haas 392 S at 30 ° C. to further reduce the molybdenum content. Other similar resins such as Amberlyst A-21 or NTEC Solutions Inc. Advanced affinity chromatography (AAC) resins may also be used. For best results the ion exchange resin should be adjusted in the form of sulfate. The liquid construction rate is 4X volume / hour (generally 2-12 is preferred) and the aqueous stream exiting zone 11 through line 12 has a molybdenum content of 5 ppm or less.

The aqueous stream thus treated is sent to zone 13 via line 12 to adjust the pH to 6-8 by addition of caustic solution through line 14. The resulting aqueous stream is properly discharged via line 15 to a plant outlet with a quality that meets the most stringent requirements.

After the ion exchange resin layer has exhausted its ability to remove the molybdenum material, the resin layer is contacted with a caustic solution introduced through line 16 to regenerate the stream containing molybdenum removed from line 17 Is sent to the area 4 via.

Claims (7)

A method of epoxidizing propylene to peroxides by reaction of propylene with an organic hydroperoxide using a molybdenum epoxidation catalyst, wherein the epoxidation process yields an aqueous epoxidation process stream containing molybdenum and sodium, wherein A process for epoxidation of propylene to propylene oxide, comprising contacting the stream with solid activated carbon and recovering the aqueous stream with reduced molybdenum. A process for epoxidizing propylene to propylene oxide by reaction with an organic hydroperoxide, wherein the epoxidation process yields an aqueous epoxidation process stream containing molybdenum, sodium and organics, wherein the stream is incinerated and the Isolate an aqueous stream containing molybdenum and sodium from the incinerator, acidify the separated aqueous stream and separate the CO ₂ formed during the acidification, contact the remaining solution with solid activated carbon, and reduce the molybdenum aqueous stream. A process for epoxidation of propylene to propylene oxide, comprising recovering propylene oxide. The method of claim 1, wherein the separated aqueous stream is acidified with PH of 5 or less. The process of claim 1, wherein the separated aqueous stream is acidified as H ₂ SO ₄ . The process of claim 2, wherein the separated aqueous stream is acidified as HCl. The process of claim 1 wherein the recovered aqueous stream with reduced molybdenum is contacted with a basic ion exchange resin and the aqueous stream with further reduced molybdenum is recovered. 3. The process of claim 2 wherein the recovered aqueous stream with reduced molybdenum is contacted with a basic ion exchange resin and the aqueous stream with further reduced molybdenum is recovered.