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WO1999061186A1 - Procede de reconstruction d'un catalyseur a base de cobalt/manganese/brome a partir d'un residu contenant un catalyseur epuise - Google Patents

Procede de reconstruction d'un catalyseur a base de cobalt/manganese/brome a partir d'un residu contenant un catalyseur epuise Download PDF

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WO1999061186A1
WO1999061186A1 PCT/US1999/011447 US9911447W WO9961186A1 WO 1999061186 A1 WO1999061186 A1 WO 1999061186A1 US 9911447 W US9911447 W US 9911447W WO 9961186 A1 WO9961186 A1 WO 9961186A1
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residue
alloy
catalyst
range
powder
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David Feitler
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Priority claimed from US09/086,169 external-priority patent/US6001763A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/90—Regeneration or reactivation
    • B01J23/94—Regeneration or reactivation of catalysts comprising metals, oxides or hydroxides of the iron group metals or copper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J38/00—Regeneration or reactivation of catalysts, in general
    • B01J38/48—Liquid treating or treating in liquid phase, e.g. dissolved or suspended
    • B01J38/60—Liquid treating or treating in liquid phase, e.g. dissolved or suspended using acids
    • B01J38/62—Liquid treating or treating in liquid phase, e.g. dissolved or suspended using acids organic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J38/00—Regeneration or reactivation of catalysts, in general
    • B01J38/48—Liquid treating or treating in liquid phase, e.g. dissolved or suspended
    • B01J38/68—Liquid treating or treating in liquid phase, e.g. dissolved or suspended including substantial dissolution or chemical precipitation of a catalyst component in the ultimate reconstitution of the catalyst
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B47/00—Obtaining manganese
    • C22B47/0009—Obtaining manganese from spent catalysts
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
    • C22B7/009—General processes for recovering metals or metallic compounds from spent catalysts
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • This invention relates to a process for producing a cobalt/manganese catalyst for the oxidation of alkyl-aromatic compounds.
  • the parent application related to the recovery of cobalt (Co), manganese (Mn) and bromine (Br) from a residue of used catalyst in a catalytic process and the reconstitution of catalyst from the recovered materials.
  • Co cobalt
  • Mn manganese
  • Br bromine
  • IP A isophthalic acid
  • TA terephthalic acid
  • TMLA trimellitic acid
  • 2,6-naphthalenedicarboxylic acid (2,6-NDA) is produced and recovered from the product stream of a large-scale facility for the liquid-phase, homogeneously catalyzed oxidation of the appropriate precursor alkylaromatic compounds under pressure (referred to in the art as the "Amoco ® Mid-Century ® process", or "Mid- Century” process, for brevity).
  • the catalytic reaction is carried out with air in the presence of an acetic acid/water mixture which functions as a solvent for the reactants.
  • the process produces a stream of undesired materials as a residue which entrains components of the catalyst.
  • This residue comprises a mixture of oxygen-containing derivatives of the reactants and reaction products including partially oxidized and dealkylated oxidized mixtures of aromatic compounds, tars, and ring-brominated aromatic compounds, much of which residue is complexed with components of the catalyst used, namely Co-Mn-Br, or, Co-Mn-Br-Ce (cerium), or, Co-Mn-Br-Zr (zirconium).
  • the compounds include acetates, bromides and bromoacetates of Co and Mn; a wide array of aromatic and polynuclear carboxylic acids, aromatic and polynuclear aldehydes; aromatic and polynuclear mixed carboxylic acid aldehydes, including ring-brominated aromatic compounds; and, unidentified Co and/or Mn complexes and salts of the anions of acetic acid, hydrobromic acid and any of the aforementioned aromatic carboxylic acids.
  • the amount of this residue is relatively small, typically in the range from 0.1 to 25 weight percent of the polycarboxylic acid produced, though usually less than about 10%, the net amount of such residue produced annually in a commercial plant is so large that it is desirable to recover the metal components, specifically the Co and Mn, and the halogen component, namely Br and compounds of Br.
  • the term "Br value” refers to either molecular Br, or bromine compounds such as HBr and MnBr 2 , or the bromine content or value of the stream.
  • this residue has been treated in the following main ways: (i) incineration to provide flyash for further processing, namely, to recover its metal content; or, (ii) discharging to a residue pond notwithstanding the loss of the value of the Co, Mn and Br content in the resulting earthy residue, or the adverse environmental impact of doing so; or, (iii) precipitating the metal values as carbonates, treating the remaining organic components and halides by dilution followed by anaerobic digestion and reconstituting catalyst by dissolving metal carbonates in acetic acid; or, (iv) calcining the residue to oxides and utilizing the oxides for other applications.
  • Fig 1 there is schematically illustrated the main steps of a currently used commercial process for recovering catalyst from the residue.
  • the organic matter in the residue is destroyed by incineration while the catalyst components are converted to an ash.
  • This ash is difficult and/or expensive to convert to reusable forms of catalyst for the oxidation of methyl-substituted benzenes.
  • the residue stream is incinerated in step 2 to produce a mixed metal oxide flyash which is collected in step 3.
  • step 6 Since not all the Co and Mn from the residue is transferred into the flyash collected, the remainder is lost in the incinerator's residue discharged to step 6. Collected flyash (from the incinerator in step 2) is washed with water in step 4 to remove the soluble salts and sodium bromide which are discarded (step 5). In the next step 7, the washed ash containing a major proportion ( > 50%) by weight of Co and Mn is converted to acetates and bromides of Co and Mn by digestion and extraction before being returned to catalyst inventory (step 9). Material not extracted from the washed ash is discarded (step 6). Catalyst is fed from storage (9) to the process (step 10).
  • a portion of the catalyst from step 10 is recycled internally in step 11, being returned to storage of catalyst in step 9 for re-use in the liquid-phase oxidation reactor in step 10 or directly returned to the process, while the desired products of the reaction are separated and sent elsewhere for further processing.
  • a purge stream from step 11 generates the residue stream 1. This residue is then incinerated to start the recovery and re-use process anew.
  • some portion of the metal content of the catalyst typically from 30% to 40%, and depending upon the quality of the flyash and conditions for processing it, as much as 90% of the residue's metal content, is lost from this system, and inevitably all the Br.
  • an appropriate pyrometallurgical treatment system I refer to a pyrometallurgical system in which the metal components are rendered into a reduced molten state.
  • Such systems include those in which: (i) organic residue is directly introduced into a molten metal bath as described in detail in the parent application; or, (ii) an electric or plasma arc or torch, either directly or indirectly heats the organic residue, resulting in a pool of molten metal; or, (iii) an induction heating means heats the organic residue, resulting in a pool of molten metal; or, (iv) the organic residue is charged to a pool of molten salt or molten glass and the molten metal separated and collected from the bottom of the system.
  • the parent '194 application specifically teaches how a molten metal bath may be used to treat the residue from a Mid-Century plant and capture the Co and Mn metal values in a molten bath of essentially the same metals. Similar results may be acheived by the use of electric and plasma arc systems, of which numerous examples are known.
  • U.S. Patent No. 4,431,612 to Bell et al describes the use of a high current DC electric arc, which includes a sump containing a molten bath, which can be a molten metal, and the accumulation of metallic elements from mixed chlorinated wastes (PCB's and PCB contaminated materials) charged to the system in the molten metal bath.
  • PCB's and PCB contaminated materials mixed chlorinated wastes
  • U.S. Patent No. 5,534,659 to Springer et al describes the use of a plasma arc for treating organic and inorganic wastes and isolating molten metal and slag therefrom, and adding steam to the system to ensure the conversion of all carbon containing components to carbon monoxide and carbon dioxide.
  • a plasma arc for treating organic and inorganic wastes and isolating molten metal and slag therefrom, and adding steam to the system to ensure the conversion of all carbon containing components to carbon monoxide and carbon dioxide.
  • Retech, Inc. describes an apparatus for the treatment of wastes using a plasma torch in a centrifugal chamber, with the discharge of molten metal through a center hole, and subsequent use of atomization to render the metal in powder form.
  • U.S. Patent No. 5,085,738 to Harris describes the destruction of organic wastes by thermal conversion in a pool of molten lead in the absence of oxygen.
  • U.S. Patent No. 3,890,908 to von Klenck et al describes pyrolytic destruction of waste by passage through a bath of molten metal or glass in the absence of air.
  • a feed stream of the organic residue under appropriate process conditions to one of the aforementioned pyrometallurgical processes will result in two product streams and a slag: (i) a gas phase comprising carbon monoxide, hydrogen and bromine values; (ii) molten metal containing cobalt, manganese and carbon; and, depending on the composition of the feed, the slag composition consisting essentially of metal oxides other than those of Co and Mn, although a substantial amount of Mn may be directed to the slag, as specifically described in the parent '194 application.
  • Co and Mn metals are separately digested in glacial acetic acid, or concentrated aqueous acetic acid, and added to the reactor separately to allow precise control of the ratio of the Co and Mn acetates.
  • cobalt or manganese acetate can be prepared by digestion of the respective metal hydroxides. These hydroxides are often prepared by digesting the metal in a strong acid such as nitric acid, precipitating by treatment with caustic, washing, and collecting the insoluble hydroxide (see U.S. Patent No. 1,637,281 to Schatz).
  • the alloy obtained in the pyrometallurgical system of this invention has as its main components: cobalt, manganese and carbon, the amount of carbon remaining depending upon treatment of molten alloy.
  • substantially complete digestion I refer to the digestion of at least 90% of the Co/Mn metals. Partial digestion, unless proportional, is un- suited for the reconstitution of this catalyst because changing the Co/Mn ratio from that received in the waste, would require readjusting the ratio. The problem of disposing of, or otherwise treating or re-processing the undigested material would remain.
  • the prior art does not teach the digestion of a Co/Mn/C alloy in acetic acid. There is no suggestion in the prior art that an alloy of Co/Mn/C be deliberately converted to a powder for the purpose of digestion in non-alcoholic glacial acetic acid, non-alcoholic solutions of acetic acid, or a mixture of non-alcoholic acetic acid and the quench stream; and, no suggestion that the powder be in a size range smaller than 5000 ⁇ m, preferably in the range from about 5 ⁇ m to 1000 ⁇ m, most preferably in the range from 45 ⁇ m to 500 ⁇ m, so that it will lend itself to substantially complete digestion of the metals in the aforesaid digesting liquids even at ambient pressure, making superatmospheric digestion in the aforesaid solutions unnecessary.
  • Mn powder is readily digested in hot acetic acid; and powdered Co is partially digested in 80% acetic acid (20% water) but leaves a heel even at reflux at ambient pressure.
  • the alloy herein contains carbon present in an amount smaller than either the Co or Mn but greater than 0.5%. The amount of carbon held in the alloy is limited by the saturation limit. This hrnit may be as much as 7% based on the total weight of the alloy, and depends on the composition of the alloy (see C.R Acad. Sc. Paris, vol 264 pg 281-284, January 16 1967).
  • the absorbent stream may be aqueous acetic acid, or a mixture of acetic acid and HBr, and/or MnB ⁇ , and such other products of reaction which are absorbed during recirculation of the stream through the absorption zone. Since the composition of the stream varies in both acetic acid and HBr, as well as other components, it's effect on the alloy in powder form, is not predictable.
  • the process of this invention is uniquely well suited to recover essentially all of the Co, Mn and Br values in both of these residue streams.
  • essential- tially all is meant that in excess of 90%, typically in excess of 95%, and preferably in excess of 99% of the components may be recovered.
  • the process is operated to re-manufacture a catalyst at the same ratio as the incoming residue.
  • incoming residue is meant a single stream from a given Mid- Century plant, or the combination of multiple streams from plants producing the same or different product, or streams of earthy residues, or streams of earthy residues and plant residue streams.
  • a further advantage of this invention is that much equipment already existing in a facility for the recovery of Co and Mn values from flyash may be used to remanufacture catalyst from the recovered Co/Mn/C alloy thus decreasing costs.
  • the Co and Mn components of an organic waste residue of used catalyst from a facility for the oxidation of an alkylaromatic compound may be recovered by feeding the waste into a pyrometallurgical reaction zone to produce an alloy of Mn/Co/C, with the ratio of Mn/Co being in the range from about 5:1 to 1:5, and carbon being present in an amount in the range from 0 to 7% by weight of the alloy; concurrently liberating off-gases with bromine values; forming a metal powder of the alloy having a primary particle size smaller than 5000 ⁇ m; and substantially completely digesting the powder with a non-alcoholic digesting liquid to produce a salt solution of the Co and Mn acetates.
  • the digesting liquid is glacial acetic acid, or, aqueous acetic acid, or, a mixture of acetic acid and a quench stream obtained by absorbing evolved gases from the reaction zone.
  • a solubilizing agent such as oxygen gas, reducing agent, activator, promoter or accelerator.
  • Bromine is also recovered from the earthy residue (if on hand) which may be processed while plant residue is being processed. Since the Co, Mn and Br compounds recovered from added earthy residue will be in excess over that required to replenish depleted catalyst from a process generating plant residue, the excess Co, Mn and Br compounds may be used for other purposes.
  • Figure 1 is a flowsheet schematically illustrating the steps in a currently used commercial process for the recovery of Co and Mn values from flyash collected by incinerating residue obtained from the Mid-Century process.
  • Figure 2 is a flowsheet schematically illustrating the steps in the process claimed herein for the recovery of Co, Mn and Br substantially quantitatively from the residue obtained in the same Mid-Century process, and reformulating, recombining and reconstituting the effluent streams to regenerate the Co/Mn/Br catalyst.
  • This same flowsheet also illustrates the steps in the process claimed herein to handle multiple plant waste streams, and to produce a desired ratio of Co/Mn in the melt, or even pure cobalt.
  • Figure 3 is a flowsheet schematically illustrating the steps in the process illustrated in Fig 2, when the process depicted therein is carried out in con- junction with converting earthy residue. A portion of the Co, Mn and Br produced is exported because it is in excess of that required for re-manufacture of the depleted catalyst.
  • Figure 4 diagrammatically illustrates a reactor of known design and construction to provide a bath of substantially pure molten Co.
  • Figure 5 is a flowsheet schematically illustrating the steps in the process illustrated in Fig 2, detailing unit operations for the reclamation of desired catalyst.
  • Figure 6 is a flowsheet analogous to one shown in Fig 5, except that provision is made for processing a residue when metal digestion proceeds in a proportionate fashion, that is the ratio of Co to Mn in solution is the same as that found in the alloy allowing a heel of metal to be maintained and reused.
  • Fig 2 schematically illustrates the main steps of a preferred embodiment of the novel process in which residue is collected and de-watered in step 1, then fed, along with a molecular oxygen-containing gas, preferably oxygen, from a source of oxygen 2, or water in the form of steam, to a thermochemical reaction zone in which a reactor contains molten Co/Mn alloy (step 3). Residue is added to the melt and converted in the presence of the oxygen, to molten alloy and a slag layer which floats on the surface of the melt (step 8). Vapors leaving the reactor as effluent gas include CO, H2, and bromine-containing matter, mainly HBr and MnB ⁇ .
  • a molecular oxygen-containing gas preferably oxygen
  • a source of oxygen 2 preferably water in the form of steam
  • the bromine containing components are collected in a scrubber or other liquid-gas-contacting device in step 4.
  • Effluent from the scrubber consists essentially of CO and H2 which are ducted away to step 5 where they are used for their fuel value, or for some other economically desirable purpose.
  • Molten alloy is withdrawn from the bath 3 and atomized to form a powder of the alloy which is collected as a fine alloy powder in step 6.
  • the alloy powder is then reacted with aqueous acetic acid, or hydrobromic acid, separately or combined, or optionally combined with the products of bromine value recovery (step 4).
  • the desired composition of re-manufactured Co/Mn catalyst may also be adjusted by addition of MnO from the slag, or Mn(OAc) 2 or MnBr 2 solution prepared from the MnO slag in step 8.
  • Re-manufactured catalyst is stored in step 9, preferably after filtering to remove insoluble materials including particles of unreacted alloy or carbon, and after conventional treatment to remove corrosion metals.
  • Stored catalyst is fed, as required, to the reactor in the Mid-Century process in step 10 to synthesize the desired reaction product.
  • the product is then obtained by conventional means, returning a portion of the catalyst to the process with an internal recycle in step 11, and purging a portion to a residue stream.
  • a portion of the internally recycled catalyst may be returned to storage in step 9, and the residue is discharged to step 1 where the process is started anew.
  • the process details and equipment used in the loop formed by steps 9, 10 and 11 which result in the discharge of the residue in step 11 and from distillation of the desired carboxylic acid, are all well known and set forth in one or more patents relating to the Mid-Century process.
  • Some U.S. patent references are Nos. 4,162,991; 4,266,084; 4,311,521; 4,794,195; 4,876,385; 4,876,386; 5,081,290; and 5,181,290; and, the specific disclosures thereof relating to the process operating conditions which generate recoverable residue, are incorporated by reference thereto as if fully set forth herein. Details of processes and equipment used in the removal of corrosion metals are also well known and set forth in one or more patents relating to the Mid-Century process.
  • Fig 3 there is schematically illustrated the processing of earthy residue in conjunction with plant residue.
  • earthy residue is processed along with plant residue as follows: Earthy residue is dredged from a sludge pond, dried in driers at 12, and the dried earthy residue fed to the reactor at 3 with oxygen from 2.
  • earthy residue may be combined with plant residue before drying both in step 1.
  • step 12 dried earthy residue from step 12 is fed to the reaction zone in step 3 and Br compounds recovered by scrubbing with any desired absorbent in step 4.
  • the CO and H2 may be recovered for use in step 5.
  • the build-up of alloy is prevented by withdrawing melt from the bath in step 13.
  • essentially pure Co may be withdrawn at 14 if an essentially pure cobalt melt is used in the reactor and excess oxygen is added to convert all Mn in the residue which is not driven off as MnBr2 vapor, to MnO which is withdrawn as slag.
  • Components such as silica, alumina and magnesium oxide are also withdrawn as slag.
  • Br is recovered in step 4 and excess Br values removed for other uses.
  • step 13 If no more catalyst for storage is required, then excess Co/Mn alloy is withdrawn in step 13 for export, either as ingots of alloy or as powder alloy. If essentially pure Co is to be recovered in 14, then excess oxygen over actual stoichiometric is fed to an essentially pure Co melt in the reactor, thus removing Mn from the melt as MnO. The MnO is rejected to the slag which is removed at 15. Residue is also conventionally obtained in step 1 after the reaction product from step 10 is distilled. This residue, along with residue obtained from the internal catalyst recycle in step 11, is fed in step 3, into the molten alloy bath in a reactor schematically illustrated in Fig 4, and referred to generally by reference numeral 20.
  • the reactor 20 is a cylindrical induction furnace having a steel body 23 with induction coils 21 built into 75% alumina refractory-lined walls 22 of the reactor which is provided with a water-cooled gated slag discharge spout 33 equipped with a tightly fitting gate 38 which is opened periodically to discharge slag 40.
  • mullite fiber insulation is packed between the outer surface of the refractory walls 22 and the inner surface of the steel body 23 of the reactor.
  • Molten alloy 30 is held in the lower portion of the reactor; the level of the melt is preferably maintained below the slag discharge spout 33.
  • the lower portion of the reactor preferably rests on a 95% magnesite ramming mix 27 which is packed between the lower steel outer surface of the reactor and a supporting structure of chromic oxide-alumina bonded 90% super-duty firebrick 28.
  • Hot gases from the reactor are led through an effluent discharge nozzle 24 through a pressure lock to a water scrubber (not shown).
  • a water scrubber (not shown).
  • residue is led into it through the tuyere 25 through which residue mixed with oxygen is introduced into melt 30.
  • oxygen may also be injected into the molten alloy bath through a separate conduit. An over-accumulation of molten alloy is prevented by withdrawing a portion through the molten alloy taphole 29.
  • Residue may contain in the range from about 0.01% to about 45% by weight (wt) of Co and Mn combined, on a water-free basis, typically from about 2% to 10% by wt, and includes small quantities of other metals, particularly Ce and Zr, each typically present in an amount less than 1% by wt of dry residue, and other metals added deliberately as either catalyst promoters or unavoidably present as corrosion products.
  • dry residue is meant that the moisture content is less than 1% by wt.
  • Mn typically predominates in the residue, the weight ratio of Mn/Co being as much as 5:1, though in some instances Co predominates, the Co/Mn ratio being in the range from 1:1 to about 5:1; typically the Mn/Co ratio is 1:2 to 5:1.
  • Plant residue contains a mixture of components.
  • a composition of residue drawn from the patent literature is shown in Table 1. It is understood that the specific residues will vary with the feeds and process conditions and the process of this invention is in no way limited by this particular example of residue composition.
  • this residue is dried to remove water prior to injection into the molten Co/Mn or Co bath.
  • the preference for a dried feed is entirely economic, in that there is a cost penalty attached to heating water.
  • Sludges will vary widely in composition depending on the age of the plant, the time resident in the pond and any treatments added to the pond water or process effluent stream.
  • the sludge will also contain biomass of varying composition and in general fewer of the organic components described in Table 1.
  • clays, binders, flocculants and settling agents may also be present, these being determined by local conditions.
  • recovery of Co and Mn in this invention is largely insensitive to the additional contaminants introduced by clays, binders and floculants.
  • Typical impurities introduced are Si0 2> A1 2 0 3 , MgO, and Fe in the forms they may be present in clays, binders and floculants.
  • the sludge be dried before addition to molten bath. Drying may take place separately from the plant residue stream, or the streams may be consolidated and dried.
  • the reactor is charged with any convenient form of Co and Mn metals in proportions to produce a Co/Mn alloy having approximately the same ratio of Co:Mn as is expected to be formed when the melt reaches equilibrium with a feed of residue from the Mid-Century process.
  • the initial heating of the charge is effected by the induction coils.
  • a hot charge may be generated by any other suitable means such as in an electric arc furnace from which molten alloy is transferred to the reactor.
  • oxygenated residue is injected into the melt.
  • the temperature of the melt is allowed to increase until the desired temperature of the melt in the operating range from about 1150°C to about 2500 °C, is reached. No additional carbonaceous matter is required to be added to the residue to satisfy the chemical needs of the thermochemical reaction.
  • the heat energy in the molten alloy incites disproportionation of the organic moieties in the residue, converting them to CO and H 2 while the Br is liberated mainly as HBr and MnBr2 gases.
  • thermochemical reaction may be either exothermic, endothermic, or neutral, depending upon the amount and composition of the carbonaceous matter in the residue, when a typical water-free residue is fed to the reactor, and the amount of oxygen.
  • additional heat required to maintain the temperature of the bath may be supplied by electricity in the induction coils, or by introducing a fuel directly in the bath for the sole purpose of maintaining its temperature.
  • fuel may be provided with natural gas, propane or any other sources of heat energy from other plant vent or waste streams (such as brominated organic compounds derived from vent streams) which are less expensive than electricity, and are unrelated to and independent of the chemical conversion of residue into Co, Mn and Br.
  • the melt in which the residue is to be converted be Co or a Co/Mn alloy particularly where an alloy is to be recovered.
  • the ratio of Co:Mn in the melt is not critical.
  • both Co and Mn are replenished in the bath when residue is fed to the bath in the presence of oxygen, and whatever amounts of carbon monoxide, hydrogen, hydrogen bromide, and metal bromides which are generated in the vapor phase.
  • a Co/Mn alloy containing essentially no bromine compounds, is recovered for reuse.
  • the alloy most typically formed is from residue in which the ratio of Mn/Co is in the range from about 1:1 to about 3:1.
  • the reactor may be operated under either atmospheric, subatmospheric or superatmospheric pressure, typically in the range from more than 1, up to about 20 bar (atmospheres), preferably in the range from 1 to 10 bar, the reactor being designed and constructed to operate under the conditions chosen.
  • the reaction is run under conditions whereby the reactants are exposed to process conditions for a sufficient length of time as to ensure complete reaction.
  • I define a numerical criterion for such time as the rate at which cobalt is added divided by the total mass of the metal phase of melt. This measure is similar to the standard definition of Weight Hourly Space Velocity and is hereafter referred to as WHSV.
  • Suitable ranges of operating conditions are between 0.1 hr “1 and lxlO "5 hr “1 , preferably between 10 "2 hr “1 and 10 "4 hr “1 .
  • the upper limit of residence time will be that required to recover the lowest concentration of Co in a residue having the highest concentration of carbonaceous matter which is to be destroyed.
  • Temperature and oxygen feed rates may be used to control the chemical constitution of the system. If, as is generally desired, low carbon levels in the melt are to be obtained, higher temperatures are clearly preferred, as are higher oxygen feed rates. If all the manganese fed is to be retained in either the melt or as vapor phase MnBr 2 then some carbon must be allowed to build up in the metal alloy phase. If all manganese is to be removed from the molten phase, then the reaction must be driven with sufficient oxygen to achieve 95 + % purity. Since all desired materials can be recovered no matter what combination of the three phases they are distributed in, the choice of operating conditions and subsequent product distribution becomes a matter of local economic preference and convenience.
  • the stoichiometric level of oxygen is the amount of oxygen that is required to convert all carbon present to carbon monoxide without conversion to carbon dioxide, or converting metals to metal oxides, or hydrogen to water.
  • the amount of oxygen added to meet this stoichiometry must take into consideration oxygen or oxygen equivalents in the incoming feed.
  • the amount of divalent metals entering the system except those which leave the system in the vapor phase as bromide compounds count as oxygen equivalents.
  • the organic residues of the Mid-Century process typically contain large amount of oxygen, having carbon to oxygen ratios of 7/2 or higher.
  • oxygen levels must be raised sufficiently to react with the desired amount of MnO.
  • Moles 0 2 gas to be added ⁇ 0*- O ⁇ + Mndon x -Co +2 - Mn +2 ⁇ /2 wherein, Q is the total moles of carbon fed including any carbon in added fuel,
  • O t ⁇ t is the total atom equivalents of oxygen in the feed
  • Mi is the Moles of Mn to be rejected as oxide
  • Co +2 is divalent cobalt in the feed, and,
  • Mn +2 is divalent cobalt in the feed to be retained in the bath and not rejected as either MnO or MnBr 2 in the vapor phase.
  • Reactor Design and Construction Design of suitable reactors to perform this reaction are disclosed in U.S.
  • Fig 5 there is shown a flowsheet schematically illustrating the steps and processing units to digest powder alloy, and to recover values from gases evolved after those values are absorbed in a liquid quench or scrubber stream.
  • Molten Co/Mn alloy from a reservoir 3 of a furnace such as a molten metal or electric arc furnace, is periodically discharged and led to an atomiser 6 in which the melt is quenched with a high velocity stream of fluid, typically water at ambient temperature under pressure in the range from 1 to about 20 bar, producing a powder.
  • a high velocity stream of fluid typically water at ambient temperature under pressure in the range from 1 to about 20 bar
  • Effluent from the furnace is led to a liquid quenching tower or scrubber 4 into which aqueous acetic, aqueous HBr acid, and preferably recycled scrubber stream from scrubber reservoir 4a is introduced.
  • the scrubber stream is typically a mixture of aqueous acetic acid, HBr acid, MnBr2, NaBr and such other products of reaction as are absorbed during recirculation of the stream through the reaction zone.
  • the scrubbed gases may be conventionally demisted and polished to remove traces of acid materials before recovering the heat values in 5.
  • the scrubber liquid is periodically or con- tinuously purged from scrubber reservoir 4a and makeup liquid continuously or periodically added as required. Bromine values from 4a may be conventionally recovered and returned to the Mid Century process directly, or incorporated in the metal acetate stream before or after digestion of metals.
  • Gaseous effluent from the scrubber 4, including mainly CO and H2 may be conventionally demisted and polished to remove traces of acid materials before storing in 5 to recover their heat values, or as synthesis gas.
  • a scrubber stream from 4a is led into a corrosion resistant digester 7 into which powder metal from atomiser 6 is fed.
  • the digester 7, is typically a glass fiber-reinforced resin, glass-lined, or stainless steel tank which is vented to allow the safe release of hydrogen gas, and fitted with a means of supplying heat, such as steam coils.
  • the metals are digested in a mixture of acetic acid and water chosen to meet the requirements of further processing and catalyst utilization.
  • Recycle scrubber liquors from 4a may be used as all or part of the digestion liquids depending upon the desired composition of the catalyst with respect to bromine components.
  • the digestion is preferably carried out at about atmospheric pressure at a temperature in the range from about 120 °C to 150 °C, either continuously or batch-wise until substantially all Co and Mn is in solution as salts. If batch-wise the digestion is typically complete in less than 72 hr. If Mn is to be recovered from oxides of Mn in slag, the slag is also digested in the digesting liquid.
  • a stream of salt solution is withdrawn from digester 7, and conventionally filtered to remove suspended carbon particles; it is then treated in vessel 16 with conventional procedures to remove unwanted metals introduced by corrosion of equipment, usually iron, chromium and nickel, but others may be present. Typically the treatment removes these corrosion metals from solution as precipitates which are filtered off.
  • the resulting Co/Mn salt solution may be adjusted in concentration by evaporation, addition of small amounts of conventionally prepared cobalt and/or manganese acetates, mixed with solution from the scrubber reservoir 4a, or by any combination of the preceding before storing in 9 for reuse in a Mid Century process.
  • Fig 6 there is shown an embodiment analogous to that described in Fig 5 above, except that the rate of digestion of the Co and Mn components is controlled so as to provide the desired ratio of salts in the salt solution removed from the digester 7. Under such circumstances, unreacted metal may be either left in the reactor, or, removed from the reactor and stored in storage vessel 7a, for digestion in a latter batch. Integration
  • This process offers numerous opportunities for integration into plant operations, both supplying and consuming waste heat through heat exchange, and offering CO/H 2 as either fuel for heat recovery or as a feed for chemical reactions.
  • This invention may be conventionally integrated into the general operation of a plant for oxidation of an alkylaromatic, and means for integration therein forms no part of this invention.
  • Catalyst is re-manufactured by first atomizing the molten metal to produce a powder metal then reacting the powder metal with aqueous acetic acid or aqueous acetic acid/hydrobromic acid mixtures or acidic streams containing manganese bromide or any combinations thereof at temperatures in the range from 80° to 150 °C to produce the metal acetates.
  • HBr may be added in the amount desired.
  • a slag comprises a major proportionby weight of MnO
  • Recovery of Mn and Br values from the Vapor Phase The Br and Mn values transported in the vapor phase are preferably recovered by any conventional unit operations for removing materials from the vapor phase. Such unit operations include condensation, desublimation, quenching and scrubbing the effluent gas with water, or, concentrated or dilute acetic acid, or aqueous hydrobromic acid.
  • a scrubber will typically be operated in a recirculating mode resulting in a scrubbing solution approaching equilibrium concentrations of MnBr2 and HBr. These operations may be carried out under atmospheric or superatmospheric conditions up to 20 bar, and elevated temperature up to 250°C, such as are optimum for such processes.
  • the thermal energy (BTU content) of the effluent gases after the bromine content is removed may be recovered by employing a conventional gas-fed boiler.
  • the energy content may also be converted directly to electricity by a device such as a fuel cell.
  • the primary source of material to reconstitute catalyst is the molten metal withdrawn from the bath. It is preferred to reduce the size of solid metal particles by a size reduction technique such as atomization in order to facilitate the digestion to metal salt at reduced temperatures and pressures by virtue of a higher surface area. In general recombination of at least one of the two other streams collects, slag and vapor phase scrubbing solution will be required to reconstitute catalyst. While the active catalyst is generally considered mixture of Co/Mn and HBr or bromide salts, in some cases bromine content of the aromatic oxidation reaction is managed separately. In these cases the bromine compound containing scrubber stream may be recycled separately from the reconstitution of a catalyst which is solely Co and Mn acetates. Excess Recovery
  • the average molecular composition corresponds approximately to benzoic acid
  • the residue herein consists essentially of acetates of Co and Mn, and HBr, the remaining organics being expressed as benzoic acid.
  • Designations of "moles” refers to kilogram-moles (KgMoles).
  • the percent by weight of Br and Co in the residue fed to the reactor is maintained the same in each of the examples below, as is the reactor pressure of 10 atm. In each case, the recovered melt of metal is atomized and converted to re-manufactured catalyst.
  • the amount of oxygen injected is about 157.9 Kg/hr (4.93 KgMoles) and effluent from the reactor is led to a water scrubber.
  • about 70.4 Kg of molten alloy are withdrawn every 8 hr, and atomized to yield a powder having an average particle diameter of 100 ⁇ m, using a high pressure water stream.
  • the composition of the particles is essentially the same as that of the melt beneath the slag.
  • a bath of Co/Mn/MnO/C (341/194/463/1.4) containing 1000 Kg of molten metal and slag is maintained at the given equilibrium composition at 2200 °C under 10 atm pressure in the reactor. Essentially all the MnO is present in the slag which forms an immiscible layer above the Co/Mn alloy.
  • Example 3 Mn in which solution Co and Mn are 4.1% and 3.9% by wt, respectively. There is essentially no free acid.
  • slag is digested with HOAc to yield a solution of Mn(OAc) 2 and as much of this solution as necessary is added to provide the desired 1/1 ratio of Co/Mn in the re-manufactured catalyst.
  • re-manufactured catalyst is filtered to remove suspended carbon in the alloy.
  • a bath of Co/Mn/MnO/C (548/11/424/17) containing 1000 Kg of molten metal and slag is maintained at the given equilibrium composition at 1500°C under 10 atm pressure in the reactor. Essentially all the MnO is rejected to slag which forms an immiscible layer above the molten metal. 292 Kg/hr of dry plant residue containing 2% Co, 2% Mn and 4% Br by wt, is injected into the molten alloy with oxygen.
  • the WHSV based on Co is 0.01028 hr "1 .
  • the amount of oxygen injected is about 163.8 Kg/hr (5.12 KgMoles) and effluent from the reactor is led to a water scrubber.
  • about 47.6 Kg of essentially pure Co 95 + %) are withdrawn every 8 hr.
  • the molten metal may be cast as ingots for export from the plant, or the molten metal may be atomized as in Example 1 above to yield a powder.
  • the composition of the metal particles is essentially the same as that of the melt beneath the slag.
  • Example 1 During operation at equilibrium, about 69.6 Kg of molten alloy are withdrawn every 8 hr, and atomized to form a powder metal as in Example 1 above.
  • the composition of the metal powder is essentially the same as that of the melt beneath the slag.
  • 1040 L of scrubber water are collected containing 90.3 Kg of MnBr 2 and 24.2 Kg of HBr. MnO accumulates in the slag at a rate of about 0.08 Kg/hr. Slag levels are adjusted by periodic withdrawals, and the slag withdrawn and atomized as in Example 1 above.
  • Example 1 The 69.6 Kg of powder metal, the scrubber water and 127 Kg of glacial HOAc are combined as in Example 1, to produce a solution of mixed acetates and bromides of Co and Mn in which solution Co and Mn are 4.1% and 4.0% by wt, respectively. There is essentially no free acid.
  • slag is digested with HOAc to yield a solution of Mn(OAc) 2 and as much of this solution as necessary is added to provide the desired 1/1 ratio of Co/Mn in the re-manufactured catalyst.
  • re-manufactured catalyst is filtered to remove suspended carbon in the alloy.
  • Example 5 Ratio of Co/Mn 1/1 in residue fed; conditions for producing essentially pure cobalt (99. + % pure) by rejecting essentially all Mn from molten metal.
  • a bath of Co/Mn/MnO/C (485/4.5/509.3/7) containing 1000 Kg of molten metal and slag is maintained at the given equilibrium composition at 1700 °C under 10 atm pressure in the reactor. Essentially all the MnO is rejected to slag which forms an immiscible layer above the molten metal.
  • 292 Kg/hr of dry plant residue containing 2% Co, 2% Mn and 4% Br by wt, is injected into the molten alloy with oxygen.
  • the WHSV based on Co is 0.0119 hr "1 .
  • the amount of oxygen injected is about 190.4 Kg/hr (5.95 KgMoles) and effluent from the reactor is led to a water scrubber.
  • about 47.1 Kg of essentially pure Co (99 + %) are withdrawn every 8 hr.
  • the molten metal may be cast as ingots for export from the plant, or the molten metal may be atomized as in Example 1 above to yield a powder.
  • the composition of the metal particles is essentially the same as that of the melt beneath the slag.
  • a bath of Co/Mn/MnO/C (285/694/0/21) containing 1000 Kg of molten metal and slag is maintained at the given equilibrium composition at 2000 °C under 10 atm pressure in the reactor.
  • the WHSV based on Co is 5.83 x 10 "3 hr "1 .
  • the amount of oxygen injected is about 131.1 Kg/hr (4.10 KgMoles) and effluent from the reactor is led to a water scrubber.
  • the amount of oxygen injected is about 131.1 Kg/hr (4.10 KgMoles) and effluent from the reactor is led to a water scrubber.
  • about 160 Kg of molten alloy are withdrawn every 8 hr, and atomized to form a powder metal as in Example 1 above.
  • the composition of the metal powder is essentially the same as that of the melt beneath the slag.
  • the bath maintained at the same equilibrium composition and under the same temperature and pressure conditions as in Example 6, is fed with the same amount of dry plant residue (292 Kg/hr) to provide a WHSV based on Co of 5.96 x 10 " 3 hr "1 .
  • the amount of oxygen injected is about 132.8 Kg/hr (4.15 KgMoles) and effluent from the reactor is led to a water scrubber.
  • the bath composition is Co/Mn/MnO/C (288/683/22/6 by wt). About 157 Kg of molten alloy are withdrawn every 8 hr, and atomized to form a powder metal as in Example 1 above. The composition of the metal powder is essentially the same as that of the melt beneath the slag. During the same 8 hour period, 1040 L of scrubber water are collected containing 99 Kg of MnBr 2 and 18.1 Kg of HBr. MnO accumulates in the slag at 0.45 Kg/hr. Slag levels are adjusted by periodic withdrawals.
  • Example 1 The 157 Kg of atomized metal, the 1040 L of scrubber water and 323 Kg of glacial HOAc are combined as in Example 1, to produce a solution of mixed acetates and bromides of Co and Mn in which solution Co and Mn are 3.6% and 10.5% by wt, respectively. There is essentially no free acid.
  • slag is digested with HOAc to yield a solution of Mn(OAc) 2 and as much of this solution as necessary is added to provide the desired 1/3 ratio of Co/Mn in the re-manufactured catalyst.
  • re- manufactured catalyst is filtered to remove suspended carbon in the alloy.
  • Example 8 Residue fed is a mixture of plant residue and earthy residue from a particular sludge pond in which there was no liner in the bottom of the pond.
  • a bath of Co/Mn/MnO/C (409/244/337/8.8) containing 1000 Kg of molten metal and slag is maintained at the given equilibrium composition at 1900 °C under 10 atm pressure in the reactor. Essentially all the MnO is present in the slag which forms an immiscible layer above the Co/Mn alloy.
  • the WHSV based on Co is 0.017 hr "1 .
  • the Co powder was black, the Mn powder silvery.
  • 1.57 g of the Co and 3.13 g of the Mn were together placed in a 250 ml round-bottomed flask equipped with a heating mantel and a water cooled reflux condenser, and mixed.
  • Glacial acetic acid 133.3 g was added to the flask. Vigorous evolution of gas was observed before the addition of water. The rate of gas formation increased when water (27.7 g) was added. The solution remained clear, pale brown during this period. Heating was initiated and gas evolution increased and then diminished. No visible amount of silver powder remained in the flask, indicating that essentially all the Mn was digested.
  • Example 10 A Co/Mn/C alloy was prepared by melting Co metal, Mn metal together with carbon dust in a graphite-lined induction furnace under an inert (hydrogen) atmosphere blanket. The melt was allowed to equilibrate and then atomized by contacting with a high pressure water spray in the presence of argon. The resultant powder was sieved into two fractions with a U.S. Standard No. 80 Test Sieve, one larger than 180 ⁇ m, the other smaller (i.e. -80 mesh). The powder is representative of one obtained from the output a thermochemical reaction zone, whether a molten metal bath, electric arc furnace, or other pyrometallurgical means having a thermochemical reaction zone into which de-watered residue of used catalyst is received. The material analysis indicated 47.5% Co; 51.3% Mn and 0.9% Carbon.
  • Experiment 11 5.2 g of -80 mesh alloy powder was placed in a 250 ml round-bottomed flask equipped with a heating mantel and a water cooled reflux condenser. Glacial acetic acid (133.3 g) and water (27.7 g) were added to the flask and heating initiated. As in Example 10 above, the liquid rapidly developed a pink color and the solution was purple when it started to reflux. After 19 hours heating was halted, and the sample filtered and washed with water and isopropanol. A small amount (0.55 g) of a non-magnetic, non-pyrophoric black powder was recovered as a solid residue.

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Abstract

L'invention concerne un procédé de récupération d'une solution d'acétates de Co et de Mn ou d'autres composants utiles, à partir d'un résidu de catalyseur épuisé évacué d'une installation, pour réaliser une oxydation de composés alkylaromatiques catalysés de façon homogène en phase liquide destinée à produire des acides aromatiques polycarboxyliques. Le résidu est pyrolysé dans une zone de réaction pour former un métal fondu dans un arc électrique ou dans un four à bain de métal fondu, dans des conditions propres à transformer généralement tout le carbone présent dans le résidu principalement en CO, hydrogène et composés vaporisés dans un effluent à partir de la zone de réaction. L'effluent est passé à travers un moyen de contact liquide-gaz pouvant produire un flux de trempe ou d'épuration. Le résidu peut également être de la boue provenant d'un bassin dans lequel le résidu est stocké. L'alliage récupéré est atomisé pour former une poudre métallique pouvant ensuite être digérée dans de l'acide acétique, et/ou un bromure d'hydrogène aqueux, et/ou des mélanges desdits composés avec le flux de trempe ou d'épuration, pour former les sels correspondants. Outre les valeurs du Mn et du brome (Br) extraites de l'effluent, ces valeurs peuvent, au besoin, également être récupérées à partir de la scorie. Du Co sensiblement pur peut être récupéré et exporté, en particulier si un résidu boueux provenant d'un bassin est traité à des fins écologiques.
PCT/US1999/011447 1998-05-28 1999-05-24 Procede de reconstruction d'un catalyseur a base de cobalt/manganese/brome a partir d'un residu contenant un catalyseur epuise Ceased WO1999061186A1 (fr)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5358549A (en) * 1992-05-05 1994-10-25 Molten Metal Technology, Inc. Method of indirect chemical reduction of metals in waste
US5534659A (en) * 1994-04-18 1996-07-09 Plasma Energy Applied Technology Incorporated Apparatus and method for treating hazardous waste
US5759229A (en) * 1996-07-29 1998-06-02 Feitler; David Method for recovering cobalt/manganese/bromine values from residue containing used catalyst

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5358549A (en) * 1992-05-05 1994-10-25 Molten Metal Technology, Inc. Method of indirect chemical reduction of metals in waste
US5534659A (en) * 1994-04-18 1996-07-09 Plasma Energy Applied Technology Incorporated Apparatus and method for treating hazardous waste
US5759229A (en) * 1996-07-29 1998-06-02 Feitler; David Method for recovering cobalt/manganese/bromine values from residue containing used catalyst

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