FR2671104A1 - Process for antipollution treatment of a deactivated catalyst containing at least one noble metal and total recovery of the said metal and of the support alumina - Google Patents

Abstract

Process for antipollution treatment and recovery of the metals in a deactivated catalyst containing at least one metal chosen from the group formed by rhenium and the noble metals of group VIII of the Periodic Classification of the elements. The process is characterised especially in that: a) the catalyst discharged from the industrial unit is optionally subjected to calcination in critical conditions; b) the calcined catalyst undergoes a heat treatment in the presence of an alkaline base in the molten state; c) the solid mass resulting from stage b) is treated with water. The process applies to an antipollution treatment and to the recovery of metals from deactivated catalysts, especially reforming, hydrogenation and hydroformylation catalysts.

Description

 The present invention describes a process for the antipollution treatment and the recovery of noble metals of a deactivated catalyst, in which process the catalyst is virtually completely destroyed and at the same time a virtually total recovery of all the metallic constituents is obtained. of said catalyst and a release aqueous phase for the protection of the environment.

 The starting catalysts generally consist of a mineral support and at least one metal selected from the group consisting of rhenium and the noble metals of group VIII of the periodic table of elements.

 Group VIII noble metal is understood to mean metals such as platinum, palladium, rhodium, ruthenium and iridium in particular.

 The term "inorganic support" means refractory oxides of the aluminum and / or silicon group, such as, for example, aluminum trioxide or silicon dioxide, or mixtures thereof.

 In the reforming, hydrogenation and hydroformylation operations, the deactivation of the catalyst used is essentially due to the accumulation of carbon in the inorganic support, which causes decreases in the pore volume and in the specific surface area, which in turn of limited consequence or even prevents the diffusion of the hydrocarbon molecules to the catalytic sites inside the grains of the catalyst.

 The deactivated catalyst is regenerated by burning carbon with air.

 However, after each operation of said regeneration, the catalyst becomes less stable which gradually requires a regeneration frequency closer and closer until the use of a new new catalyst load becomes inevitable.

Recently the United Nations Environmental Protection Administration under the high authority of its director Mr Mostafa
TOLBA has ruled that a deactivated refining catalyst must now be classified as a highly toxic and hazardous solid waste (The
UNEP document C (88) 90 Final released june 1988, included Spent Catalyst
Source: C & E News pp 21-22, 4/3/1989). It follows that the landfill discharge of such a deactivated catalyst is therefore formally prohibited for the protection of groundwater in particular. On the other hand, its destruction could in the near future become mandatory.

 The noble metals of group VIII of the Periodic Table of Elements are of excessively high cost. An efficient treatment of the recovery of these metals from a deactivated catalyst is therefore a profitable operation.

 The process developed according to the present invention is characterized in that two objectives are achieved which are on the one hand an almost total recovery of all metals selected from the group formed by rhenium and noble metals, said metals being present initially in the deactivated catalyst, and the almost total recovery of the alumina, after a total destruction treatment of the deactivated catalyst, in other words which makes it possible to completely get rid of the constraints relating to the standards of environmental protection whatever they are to date or in the future concerning a solid release containing toxic metals even in small quantities; on the other hand, a neutral aqueous final phase is obtained which is free of any traces of toxic metals and is therefore perfectly rejectable without any sign of pollution. Moreover, the treatment is particularly economical and easy to implement.

 According to the present invention, after a possible calcination with an oxygen-containing gas to eliminate carbon deposition (for example air), a heat treatment of an intimate mixture of a deactivated catalyst with a heat treatment is carried out. alkaline base, for example solid caustic soda, at a temperature equal to or greater than that of the melting of said alkaline base.

 This alkaline melting operation which we call alkaline cooking (that is to say sodium cooking or potassium cooking) can be carried out in an autoclave-type pressure apparatus for example in the presence of an inert gas or a gas containing oxygen (for example air), but an easier technique is preferred simply by using a stainless steel tank open at atmospheric pressure.

 Under these conditions, after said alkaline firing, we obtain a solid mass that we call alkaline cake, which dissolves easily with water despite its very high hardness (comparable to cement).

 On the other hand, a true so-called alkaline paste is prepared before the actual alkaline cooking operation, which is easily obtained by a solid mixture moistened with water, said mixture consisting of the catalyst optionally calcined beforehand and reduced in fine particle size (for example a fraction less than or equal to 500 microns) and the alkaline base in the solid state.

 For example, for a solid mixture consisting of 100 grams of calcined catalyst powder (for example a fraction collected after sieving at 500 microns) and 117.5 grams of caustic soda in pellets, a volume of water of about 30 to 35 milliliters. is sufficient for the formation of a good alkaline paste.

 Then the conditions are very favorable for complete and complete chemical conversion of the alumina with the alkaline base in the molten state to fully soluble alkali aluminate in the next step of dissolving the alkaline cake.

 It has been found that the metals selected from the group consisting of rhenium and the noble metals of group VIII of the Periodic Table of Elements, and present in the deactivated catalyst, such as platinum, palladium, rhodium, ruthenium iridium and iron (contaminating metal may come from the reactor) are converted during this alkaline fusion treatment according to the invention into oxides and / or mixed salts of sodium or potassium, which are completely insoluble in the step next aqueous dissolution of the alkali cake, which allows a virtually total and economic recovery of all metals in this group by a conventional separation (eg filtration or centrifugation) and consequently obtaining a liquor d alkali aluminate suitable for a dealumination treatment of the total or second stage total dealumination according to the invention.

 The alkaline fusion of such a solid mixture consisting of a deactivated catalyst, after a possible preliminary calcination with an oxygen-containing gas to remove carbon deposition, and a mineral base (such as, for example, caustic soda ), is a treatment not yet used up to now in any existing process developed for the recovery of noble metals and thus is one of the features of the present invention.

 The Applicant has also used this alkaline fusion technique in the process previously developed for the anti-pollution treatment and metal recovery of a deactivated hydrotreating catalyst and containing at least one metal selected from the group consisting of molybdenum, cobalt, nickel and present in the starting catalyst, and at least one contaminating metal from the group consisting of vanadium, nickel, iron from the treated petroleum feedstock, and has shown the advantages of such treatment of destruction of a deactivated catalyst with caustic soda in the molten state. (FR-A-90-14.129 of 12.11.90).

 With regard to the treatment of the alkaline aluminate liquor, the applicant has also shown in said prior patent that the use of gaseous carbon dioxide makes it possible to obtain, under the optimized operating conditions, substantially total dealumination and that the precipitate of Aluminum is pure aluminum trihydroxide.

STATE OF THE PRIOR ART
Extensive research has shown that virtually all the processes claimed so far relate essentially to the noble metal recovery treatments in the solutions, said metals being used initially in the form of metal carbonyls or coordination complexes in homogeneous catalysis. For example, the following patents may be consulted
For rhodium: US-A-4,275,252; US Patent 4,312,779; US Patent 4,363,765;
US Patent 4,374,287; US Patent 4,388,217; US Patent 4,504,588;
US Patent 4,629,711; US Patent 4,795,538.

For palladium: US-A-4,319,923; US Patent 4,382,845; US Patent 4,435,258;
US A4.623.522.

For ruthenium: US-A-3,904,547; US Patent 4,133,966; US Patent 4,429,057.

 The treatments described for the recovery of noble metals in such solutions generally require a succession of numerous and diversified operations. However, we note that recovery rates are generally not very high and that consequently the solution after treatment still contains a significant metal concentration, which can not meet the strict standards of rejection for the protection of the environment. , and more particularly groundwater.

 However, US Pat. No. 3,469,971 to Oil Products Company indicates that all the noble metals of Group VIII of the Periodic Table of Elements can be recovered in general, but the method described in said patent is more particularly applicable to the recovery of platinum or palladium from a conventional solid supported catalyst based on alumina.

 The unique example presented in said patent to illustrate the invention relates to the recovery of platinum from a conventional platinum / alumina support catalyst, contaminated with an iron deposit.

 According to this US Pat. No. 3,469,971, such a catalyst containing 12.5% by weight of carbon (platinum and iron contents are not indicated) is first treated with a concentrated aqueous solution of acid. sulfuric acid of between 35% and 70% by weight at the boiling point for about 90 minutes, for a partial dissolution of the alumina in soluble aluminum sulphate. The remaining solid containing platinum, contaminating iron and carbon is then calcined with air at a temperature of about 5500C to remove the carbon to a residual content of at least 0.5% by weight. The calcined solid is then successively heated with activated charcoal at a high temperature of 77 ° C. under an inert atmosphere for 3 hours and finally again calcined with air at a temperature of 66 ° C. for 1 hour. The contaminating iron is then selectively extracted from the treated solid by reaction with a concentrated aqueous solution of sulfuric acid at a boiling temperature for 1 hour. The solid residue separated from the acid solution of soluble iron is reacted with a aqua regia solution, consisting of one volume of nitric acid for three volumes of hydrochloric acid, at a temperature between 75 and 800C for a period of duration between 1 and 4 hours to extract platinum. The resulting filtrate is evaporated and finally a concentrated solution of chloroplatinic acid is obtained.

 This application of the invention is not encrypted and in particular the recovery rate of platinum is not indicated. Thus it is not known if the final residue is rejectable according to the standards of environmental protection.

The anti-pollution treatment and recovery of noble metals of a catalyst in the deactivated state according to the present invention is characterized by all of the following advantages
Chemical treatment technique and implementation of the process simplified and economical.

 Selective and nearly complete recovery of metals selected from the group consisting of rhenium and noble metals of group VIII as separate precipitates.

 Separation and recovery of aluminum from the alkali aluminate liquor to pure aluminum trihydroxide precipitate.

 Final production of a neutral aqueous phase free of toxic metals and perfectly dischargeable without risk of environmental pollution.

 The invention relates to a method for the antipollution treatment and the recovery of metals selected from the group consisting of rhenium and noble metals of a catalyst, which catalyst, based on at least one alumina, has been deactivated and contains carbon, at least one active metal selected from the group consisting of rhenium, platinum, palladium, rhodium, ruthenium, and iridium and optionally contaminating iron (in trace amounts); the process being characterized in that: 1. The catalyst is optionally calcined in a first step in the presence of a molecular oxygen gas at a temperature of not more than 700 ° C, preferably 500 ° C or more. 550 "C.

2. The catalyst is subjected, in a second step, to a heat treatment in the presence of an alkaline base at a temperature at least equal to that of the melting of said base, which treatment allows an almost complete conversion of the alumina. alkali aluminate support and almost complete conversion of the oxides of the metals (selected from the group consisting of rhenium, platinum, palladium, rhodium, ruthenium, iridium, iron and initially present in the deactivated catalyst) in alkaline salts or insoluble corresponding oxides thereof.

3. The solid solid mass resulting from the preceding treatment is then optionally dissolved by water allowing complete dissolution of the alkali aluminate, the metals chosen from the group consisting of rhenium, platinum, palladium, rhodium, ruthenium, iridium and iron initially present in the deactivated catalyst being in the form of a precipitate of alkali metal salts or metal oxides easily separable by filtration or by centrifugation.

 As regards the heat treatment with the alkaline base in the molten state, the weight ratio mineral base / mass of catalyst to be treated is preferably at least equal to 1: 1.

 Around the first two steps (1) and 2)) of the method described above are grafted preferred procedures as explained below.

 According to the present invention, the method for the antipollution treatment and the recovery of the metals of a deactivated catalyst, selected from the group consisting of rhenium, noble metals of group VIII and iron, comprises mainly a heat treatment of the catalyst in the presence an alkaline base in the molten state followed by an aqueous treatment and filtration or centrifugation, and finally a possible additional process of successive treatment of the filtrates for recoveries.

elements of the group formed by aluminum and the alkali metal (sodium or potassium) of the alkali aluminate liquor from step 3) of the invention.

First process Destruction of the deactivated catalyst.

 The destruction treatment of the deactivated catalyst is carried out according to the following steps. A preferred mode of processing is shown in the summary scheme of Table 4.

a) optionally the deactivated catalyst, discharged from an industrial unit via line (1), is first subjected to calcination in the presence of a gas containing molecular oxygen (for example by air) in an area (2) for removing the carbon. The calcining temperature should not exceed 7000 C, and is preferably between 500 and 550 ° C, to minimize (at best: avoid) strong interaction of the metal oxides with the alumina of the catalyst support ( and thus a transformation into metal aluminates) and likewise an allotropic transformation of gamma alumina into higher beta and / or alpha aluminas, in other words to promote a maximum transformation of alumina into water-soluble alkali aluminate at a later stage (step d)) and to obtain a concentrated precipitate of metals selected from the group consisting of rhenium, platinum, palladium, rhodium, ruthenium, iridium, iron and initially present in the deactivated catalyst (precipitate 1). ).

b) the calcined catalyst originating from step a) or the deactivated catalyst discharged from the industrial unit is preferably in a zone (3) first subjected to grinding in fine granulometry, preferably with an upper limit of equal particle size; at 2000 micrometers, which allows for easier and more complete chemical interaction of the alumina of the alkali aluminate catalyst support with the alkaline base in the molten state in the next step (step c)) c) the solid mixture constituted by the catalyst powder, calcined or not, and by the alkaline base (for example caustic soda) is treated in an area (4), for example in a stainless steel tank open at atmospheric pressure, at a temperature of temperature at least equal to the melting temperature of said base (melting temperature of caustic soda: 3210C).

However, it has been found that a prior moistening of said solid mixture before the alkaline fusion (in said zone (4)) makes it possible to obtain a weight ratio mineral base / catalyst mass advantageously lower (for example only between 1: 1 and 1.2: 1 in the case of caustic soda), said ratio being necessary for a complete conversion of the alumina of the catalyst support to alkali aluminate and an almost complete conversion of the metals, selected from the group consisting of rhenium, platinum, palladium, rhodium, ruthenium, iridium, iron and initially present in the deactivated catalyst, corresponding alkali salts.

The minimum amount of water required for good wetting of said solid mixture to obtain an intimate mixture in the form of a true so-called alkaline dough is generally between 300 and 350 milliliters per kilogram of calcined catalyst.

The other most favorable operating conditions are: a temperature of between 350 and 4000 ° C., preferably a temperature of between 360 ° and 370 ° C., and a duration of between a few minutes and about sixty minutes, preferably between 30 and 45 minutes.

At the end of the alkaline melting treatment, a compact and very hard solid mass is obtained, comparable to cement, referred to as an alkaline cake.

d) The alkaline cake from step c) is contacted in a zone (5) with deionized water at a temperature between room temperature (generally between 18 and 25 ° C) and the temperature of boiling (generally between 100 and 1050C), preferably at a temperature of between 80 and 90 OC for rapid dissolution of all of the alkali aluminate formed in the previous step (step c)).

It is found that the apparent density of the aqueous solution resulting from the dissolution of the alkaline cake (sodium aluminate liquor) is a critical parameter, which must be between 1 and 1.5, preferably between 1.20 and 1, 25, so that the alkali aluminate liquor remains perfectly stable, that is to say to obtain a precipitate of metals (precipitate 1) as concentrated as possible.

In practice, it is found that a suitable volume of water to obtain an apparent density of the alkali cake dissolution solution from the treatment of one kilogram of calcined catalyst equal for example to 1.21 is 5 liters per kilogram. catalyst to be treated.

e) The heterogeneous solution of the aqueous solution of the alkaline cake from step d) is filtered or centrifuged in a zone (6).

A precipitate 1 is thus recovered in zone (7) consisting essentially of all the insoluble metals selected from the group consisting of rhenium, platinum, palladium, rhodium, ruthenium, iridium, iron and present initially in the deactivated catalyst, and a filtrate 1 in zone (8) containing only aluminum, dissolved in the alumina support of the catalyst
The precipitate 1, highly concentrated in noble metal (whose content is much higher than that of natural ores), can be advantageously sold for example to a mining company specialized in the treatment of the recovery of noble metals or if it is desired can dissolve very easily said precipitate in an aqueous solution of mineral acid, which can be used for a new catalyst preparation. For example, the precipitate 1 from the treatment of a conventional reforming catalyst (Pt on alumina support) dissolves very slowly. easily in an aqueous solution of hydrochloric acid or aqua regia solution, and is transformed into chloroplatinic acid.

Similarly, if desired, the filtrate 1 of the zone (8) (alkaline aluminate liquor) generally containing a very low soluble noble metal residual concentration (less than or equal to at most 5 ppm) can be easily recovered from of an aluminum production company. It is known to those skilled in the art that the sodium aluminate liquor obtained from the metallurgical treatment of bauxite by a concentrated aqueous solution of sodium hydroxide (for example in the Bayer process) is the main source of production of sodium hydroxide. aluminum on an industrial scale, thanks to an igneous electrolysis treatment in the presence of cryolite and fluorite.

Second Process possible treatments for the recovery of aluminum from the alkali aluminate liquor and the removal of residual traces of the soluble metals in said liquor.

 The steps described above in the first deactivated catalyst destruction process, namely steps a) b) c) d) e) are optionally supplemented by the following sequence of steps: f) g) h) i) as shows the summary scheme of Table 4 in the case of a preferred mode of treatment.

f) the filtrate 1 of the zone (8) from step e) is treated in zone (9) by a stream of gaseous carbon dioxide to precipitate the soluble aluminum from the alkaline aluminate liquor. The dealumination treatment temperature in step f) is between ambient temperature (generally between 18 and 250 ° C.) and the boiling temperature (generally between 100 and 105 ° C.), and is preferably between 500 ° C. and 1000C, and even more preferably between 800C and 1000C.

The rate of bubbling of the carbon dioxide gas and the reaction time must correspond at least to the stoichiometric amount necessary for a complete conversion of the amount of alkali aluminate in the solution to be treated to precipitated aluminum trihydroxide. In practice, it can be seen, for example, that an hourly flow rate of said gas of 80 liters and a duration of 3 hours allow a practically total dealumination for the treatment of one kilogram of the calcined starting catalyst.

Said dealumination treatment is practically completed when the pH of the solution reaches a stable value, generally between 9.1 and 9.2.

Under these operating conditions, the concentration of the remaining soluble aluminum reaches a limit detection value by the plasma method, less than or equal to 3 milligrams per liter.

The white aluminum precipitate (precipitate 2 recovered in zone (10)), of excellent filterability, is identified by the X-ray diffraction method as being Al (OH) 3 aluminum trihydoxide containing only extremely small proportions of the mono aluminum oxyhydroxide (A1OOH) and Dowsonite (NaAlCO3 (OH) 2), in the case where the alkaline base is caustic soda). On the other hand, the analysis of the precipitate by the X-ray fluorescence method shows that c is a pure aluminum precipitate, free from any detectable trace of noble metal.

The pure aluminum trihydroxide thus recovered (precipitate 2) is a perfectly recoverable product in the same way as the Bayer hydrate from the metallurgical treatment of bauxite, for example for the manufacture of pure alumina which can be used, for example, as a carrier for refining catalyst.

g) le filtrat 2 de la zone (11) provenant de l'étape f) et contenant du carbonate alcalin soluble est traité en zone (12) de nouveau par un bullage de dioxyde de carbone gazeux à une température comprise entre la température correspondant à la limite supérieure de congélation et la température ambiante, de préférence entre OOC et 10 C et de manière encore plus préférée à une température voisine de OOC (0 C + 2"C) permettant de récupérer en zone (13) du bicarbonate alcalin peu soluble (précipité 3) par la réaction de bicarbonatation bien connue dans le cas où la base alcaline est la soude caustique

During this treatment of the dealumination in zone (9) of the filtrate 1 recovered in zone (8), the alkali carbonate soluble in the filtrate 2 recovered in zone (11) is formed at the same time, according to the following reactions in the case where the alkaline base is caustic soda

g) the filtrate 2 of the zone (11) originating from stage f) and containing soluble alkali carbonate is treated in zone (12) again by bubbling carbon dioxide gas at a temperature between the temperature corresponding to the upper freezing limit and the ambient temperature, preferably between OOC and 10 C and even more preferably at a temperature of 0 ° C (0 ° C + 2 ° C) for recovering in zone (13) poorly soluble alkaline bicarbonate (precipitate 3) by the well known bicarbonation reaction in the case where the alkaline base is caustic soda

Its recovery is very easily in zone (13) by conventional filtration type Buchner filter for example.

In practice, it is found, for example, that the maximum formation of the crystallized precipitate of alkaline bicarbonate in step g) in zone (12) is obtained with a hourly flow rate of gaseous carbon dioxide bubbling equal to 80 liters in the filtrate (2 ) recovered in zone (11) and from the treatment of one kilogram of calcined catalyst obtained in step a) in zone (2), and at a temperature kept constant and equal to 0 C for a period of 3 hours.

In the case where the alkaline base is caustic soda, analyzes by X-ray fluorescence and X-ray diffraction methods show that the precipitate (3) obtained in zone (13) is pure sodium bicarbonate. It is therefore a commercially valuable product, but it can be optionally converted into caustic soda economically according to the caustic reaction well known in metallurgy

According to the new treaty of mineral chemistry of Paul Pascal Volume II p.908, the
decomposition of sodium bicarbonate according to reaction 4) in carbonate
sodium is important from 60 ° C, it is almost total at 1000C
from the work of Dyer and Grantier.

Gaseous carbon dioxide recovered from reactions) and 6 can be
optionally used for the treatment of dealumination in step f)
in zone (9) and / or in step g) in zone (12) for the treatment of
bicarbonatation.

The aqueous and concentrated solution of caustic soda obtained in the reaction
t 53 may possibly be evaporated to obtain a solid mass
moistened, which can be used for the preparation of the sodium paste before
treatment of the alkaline fusion described above in step d) and
performed in zone (5).

In the case where the alkaline base is caustic soda, it has been discovered that the caustification can also be done quantitatively from the sodium bicarbonate obtained in step g) in zone (12) (precipitate 3) according to US Pat. invention, if the reaction between said sodium bicarbonate and lime is carried out in the presence of water at a temperature above room temperature and below the boiling temperature, generally at a temperature between 500C and the boiling point ; for example for a temperature equal to 100 ° C the caustification becomes total after one hour.

h) the filtrate 3 obtained in zone (14) and coming from step g) is treated in zone (15) then in zone (16) as described below for complete and complete elimination of the soluble residual metals, selected from the group consisting of rhenium, platinum, palladium, rhodium, ruthenium, iridium, iron and initially present in the deactivated catalyst, in order to obtain an aqueous phase free of said metals; said filtrate 3 after readjustment in zone (15) at an acid pH, preferably between 2.5 and 3.5, is passed in zone (16) on a suitably chosen complexing resin. It is found that the most effective polymer-grafted chemical chelating groups are the following: an oxime, a quinoline, or their derivatives.A virtually complete and complete retention of the residual metals, selected from the group formed by rhenium, platinum , palladium, rhodium, ruthenium, iridium, iron and initially present in the deactivated catalyst, can thus be obtained by choosing at least one of the preceding groups grafted on a polymeric support.

i) the acidic aqueous phase from the zone (16) (step h)) is finally optionally neutralized in zone (17) at a pH equal to 7 by a concentrated aqueous solution of caustic soda. It therefore only contains neutral sodium chloride in the case where the alkaline base is caustic soda. An adequate method is to reject at sea this aqueous solution.

EXEMPT FS
The following examples serve to illustrate and show the advantages of practicing the process of the present invention but they should not be construed as limiting.

EXAMPLE 1
Two catalysts deactivated, platinum on gamma alumina support, are processed from the industrial reforming units of gasolines.

 Catalyst A recovered from a fixed bed of an industrial unit is subjected before calcination by air with a flow rate equal to 60 liters, at a temperature of 5000C for 3 hours to eliminate carbon deposition, before treatment with caustic soda in the molten state according to the invention.

The compositions of the metals and metalloids in weight percent of this catalyst A are as follows

<tb>% <SEP> Weight <SEP> P <SEP> Fe <SEP> Al <SEP> C <SE> S <SEP> Cl
<tb><SEP> Before <SEP> calcination <SEP> air <SEP> 0.27 <SEP> 0.30 <SEP> 46.06 <SEP> 10.0 <SEP> 0.02 <SEP> 0, 91
<tb><SEP> After <SEP> calcination <SEP> air <SEP> 0.31 <SEP> 0.34 <SEP> 51.29 <SEP><0.1<SEP><0.1<SEP> 1.05
<Tb>
Catalyst B recovered at the outlet of the regenerative reactor of the circulating bed of an industrial unit has the following composition, in weight percent
C <0.1%, S <0.1%, C1 = 0.98%, Fe = 0.32%, Pt = 0.29%,
Al = 51.89%. This deactivated catalyst B containing no carbon deposit is therefore treated directly with the caustic soda in the molten state.

Operating conditions of the successive operations according to the invention 1. Alkaline fusion 1.1 Prior formation of an alkaline paste
100 grams of powder (particle size less than 500 micrometers)
collected after grinding and sieving catalyst A or catalyst B.

Amount of solid caustic soda used = 117.5 grams
Volume of permuted water used: 35 milliliters.

1.2 Operational conditions of the alkaline fusion operation
Reaction temperature = 370 ° C
Reaction time = 1 hour 2. Dissolution of the resulting alkaline cake and separation of the metal
noble insoluble.

Quantity of permuted water used = 500 milliliters
Temperature for dissolving the alkaline cake = 900C
Buchner filtration with a 1 micrometer porosity paper filter
Wash the insoluble product with deionized water until neutral pH.

3. Dealumination of the aqueous sodium aluminate filtrate from
the previous operation.

CO2 bubbling rate: 60 liters / hour
CO2 bubbling time: hours
Reaction temperature: 90 ° C
After reaction, filtration on büchner and aqueous washing of the precipitate of
Al (OH) 3 until neutral pH.

4. Bicarbonation of the filtrate from the dealumination operation:
Reaction temperature 0 C
CO2 bubbling flow: 60 liters
CO2 bubbling time: 3 hours
After reaction, filtration on büchner and aqueous washing of the precipitate of
sodium bicarbonate up to pH = 7.5 5. Conversion of residual sodium carbonate remaining soluble in the filtrate
from bicarbonation sodium chloride
Addition of hydrochloric acid until complete cessation of release
gaseous at pH = 3.5.

Readjustment of acidic pH up to neutral pH with caustic soda, for
finally obtain an aqueous solution of neutral sodium chloride
discharged at sea without any risk of pollution.

The results are given in Table 1
Table 1

Pt <SEP> Al <SEP> Fe
<tb> (mg / l) <SEP> (g / 1) <SEP> (mg / l)
<tb> Fusion <SEP> Filtrats <SEP> cata <SEP> A <SEP><<SEP> 1 <SEP> 102.4 <SEP> 0 <SEP> Rate <SEP> of <SEP> precialcaline <SEP> pitation <SEP> (% <SEP> wt)
<tb> + <SEP> cata <SEP> B <SEP><<SEP> 1 <SEP> 113.9 <SEP> 0 <SEP> Pt <SEP>#<SEP> 100
<tb> dissolution <SEP> (plasma) <SEP> Fe <SEP>#
<tb> aqueous <SEP> FX <SEP> cata <SEP> A <SEP> 17.94 <SEP> 15.21 <SEP> 0.083 <SEP> Na <SEP> = <SEP> 3.85
<tb> cake <SEP> (% <SEP> wt) <SEP> cata <SEP> B <SEP> 16.79 <SEP> 15.34 <SEP> 0.084 <SEP> Na <SEP> = <SEP> 3 88
<tb> alkaline <SEP> and <SEP> DRX <SEP> - <SEP> cata <SEP> A <SEP> Na2Pt (OH) 6 + Fe2O3 + Al (OH) 3
<tb> filtration
<tb> Disalination <SEP> Before <SEP> Treatment <SEP> CO2 <SEP> Al <SEP> = <SEP> 102.4 <SEP> g / 1 <SEP><SEP> Rate <SEP> Precipitation <SEP > (% <SEP> wt)
<tb> Filtrate <SEP> After <SEP> Treatment <SEP> CO2 <SEP> Al <SEP>#<SEP> 5 <SEP> mg / 1 <SEP>#<SEP> 99.99
<tb> cata <SEP> A <SEP> DRX <SEP> Al (OH) 3 <SEP> + <SEP> Amount <SEP> Very <SEP> Low <SEP> NaAlCO3 (OH) 2
<tb> Bicarbonation <SEP> Before <SEP> treatment <SEP> CO2 <SEP> Na <SEP> = <SEQ> 134.92 <SEP> g / 1 <SEP><SEP> rate <SEP> precipitation <SEP > (% <SEP> wt)
<tb> Filtrate <SEP> After <SEP> treatment <SEP> CO2 <SEP> Na <SEP> = <SEP> 24.61 <SEP> g / 1 <SEP> 81.76
<tb> cata <SEP> A <SEP> DRX <SEP> HNa <SEP> CO3 <SEP> (predominantly <SEP> species) <SEP> + <SEP> HNa3 (CO3) 2,2H2O
<Tb>
The platinum recovery of the catalyst is almost complete, the residual platinum content in the filtrate if there is any is not measurable by the plasma method (limit of detection).

 The treatment of the sodium aluminate filtrate with gaseous carbon dioxide at a high temperature is an extremely efficient dealumination method: the precipitation rate is at least 99.99% by weight.

 The soluble sodium carbonate produced during the previous operation of the dealumination can therefore be recovered in the form of sodium bicarbonate which can be recovered in a high yield.

 For the antipollution treatment and platinum recovery of a deactivated gasoline reforming catalyst, the results of the platinum and contaminating iron assays show that both metals are completely and completely precipitated. As a result, the step of passing the filtrate over a complexing resin according to the invention is not necessary in this case.

EXAMPLE 2
A deactivated palladium catalyst supported on gamma alumina from an industrial gasoline hydrogenation unit is treated. This catalyst has the following composition in weight percentage

<tb><SEP>%<SEP> Weight <SEP> P <SEP> Fe <SEP> C <SEP> S
<tb> After <SEP> calcination <SEP> air <SEP> 0.3 <SEP> 0.055 <SEP> 6.5 <SEP> 0.9
<tb><SEP> calcination <SEP> air <SEP><SEP> 0.32 <SEP> 0.058 <SEP><<SEP> 0.1 <SEP>
<Tb>
The operating conditions of the successive operations of the catalyst treatment are identical to those indicated for the catalyst A of Example I, except that the filtrate from the bicarbonation operation is further treated by passage over a complexing resin.

 The results are given in Table 2.

Table 2

Pd <SEP> Al <SEP> Fe <SEP> rate <SEP> of <SEP> precipitation
<tb> (mg / l) <SEP> (g / 1) <SEP> (mg / l) <SEP> (% <SEP> weight)
<tb> Filtrate <SEP>#<SEP> 5 <SEP> 104.9 <SEP> 0 <SEP> Pd # 99.99 <SEE> Fe <SEP> = <SEP> 100
<tb> Fusion <SEP> alkaline <SEP> + <SEP> dissolving <SEP> aqueous <SEP> (plasma)
<tb><SEP> C <SEP> Alkaline <SEP> and <SEP> Filtration
<tb> D <SEP> R <SEP> X <SEP> Nax <SEP> Pd3O4 <SEP> + <SEP> Al (OH) 3 <SEP> Small <SEP> Quantity
<tb> (insoluble) <SEP> + <SEP> Fe2O3
<tb> Disalination <SEP><SEP><SEP> Precipitation <SEP><SEP> Al (OH) 3 <SEP> (% <SEP> Weight) <SEP>: <SEP>#<SEP> 99 99
<tb> Bicarbonation <SEP><SEP><SEP><SEP><SEP> Bicarbonate <SEP><SEP> Sodium <SEP> (% <SEP> Weight) <SEP>: <SEP> 82 45
<tb> - <SEP> adjustment <SEP> to <SEP> a <SEP> pH <SEP> equal <SEP> to <SEP> 3 <SEP> by <SEP> HCl / H2O <SEP> concentrated.
<Tb>

Total <SEP> total <SEP> and <SEP> complete <SEP> of <SEP> - <SEP> Passage <SEP> on <SEP> 100 <SEP> grams <SEP> of <SEP> resin <SEP> DUOLITE <SEP> ES <SEP> 346 <SEP> (SEP function> amidoxime <SEP> grafted
<tb> residual palladium <SEP> residual <SEP> remaining <SEP> soluble <SEP> on <SEP> a <SEP> macroporous <SEP> polystyrene <SEP> backbone.
<Tb>

in <SEP> filtrate <SEP> - <SEP> temperature <SEP>: <SEP> 25 <SEP> C <SEP> - <SEP> Duration <SEP> of <SEP> pumping <SEP> liquid <SEP>: <SEP> 2 <SEP> h
<tb>(<SEP>) and <SEP> recycle <SEP> in <SEP> continuous <SEP> of <SEP> filtrate <SEP> on <SEP> said <SEP> resin, <SEP> in <SEP> reads <SEP> fixed).
<Tb>

Result <SEP> of <SEP> assay <SEP> of <SEP> palladium <SEP> in <SEP><SEP> solution <SEP> after <SEP> pass <SEP> on <SEP> said <SEP> resin
<tb>(<SEP> plasma method) <SEP>: <SEP><<SEP> 1 <SEP> mg / 1 <SEP>(<SEP> limit of <SEP> detection).
<Tb>

 The treatment of a deactivated palladium catalyst on gamma alumina support according to the invention also makes it possible to recover said noble metal with a very high yield.

 The final aqueous phase completely free of traces of toxic metals and containing only sodium chloride after neutralization with an aqueous solution of concentrated caustic soda can be rejected at sea without any risk of pollution.

EXAMPLE 3
This example is intended to show that the antipollution treatment and recovery of metals according to the invention is also applicable to the recovery of rhenium and noble metals of group VIII of the periodic table of elements other than platinum and palladium.

 The catalysts to be treated are conventionally synthesized by impregnating a cubic gamma alumina with an aqueous solution of metal salt followed by calcination with air.

 The operating conditions of the alkaline melting and the aqueous dissolution of the resulting alkaline cake are identical to those of catalyst A of Example I.

 The results are given in Table 3.

Table 3

<tb><SEP> Metal <SEP> Residual <SEP> Rate <SEP> of <SEP> Precipitated
<tb><SEP> Catalyst <SEP> in <SEP> filtrate <SEP> tation <SEP> (% <SEP> wt) <SEP> Diffraction <SEP> X
<tb><SEP> (mg / 1)
<tb> Rh / Al2O3 <SEP> gamma: <SEP># 1 <SEP># 100 <SEP><SEP> Rh2O3 * + Al (OH) 3 + Fe2O3
<tb> 0.3% <SEP> wt
<tb> Ru / Al2O3 <SEP> gamma: <SEP># 5 <SEP><SEP># 99.99 <SEP><SEP> Ru2O3 * + Al (OH) 3 + Fe2O3
<tb> 0.3% <SEP> wt
<tb> Re / Al2O3 <SEP> gamma: <SEP> 41 <SEP><SEP>#<SEP> 100 <SEP> Na2Re207 * + Al (OH) 3
<tb> 0.3% <SEP> wt <SEP> + Fe2O3
<tb> Ir / Al2O3 <SEP> gamma: <SEP># 5 <SEP><SEP># 99.99 <SEP><SEP> IrO2 * + Al (OH) 3 + Fe2O3
<tb> 0.3% <SEP> wt
<Tb>
* predominant species.

 The results show that the treatment according to the invention is also applicable to various catalysts for recovering noble metals of group VIII or rhenium.

Table 4

<tb><SEP> TISON <SEP> CATALYST
<tb><SEP> has <SEP> CALCINA <SEP> 1 <SEP> OFF
<tb><SEP> 3
<tb><SEP> GRINDING
<tb><SEP> b
<tb><SEP> 4
<tb><SEP> FUSION <SEP> ALKALINE
<tb><SEP> (cooking <SEP> alkaline)
<tb><SEP> C <SEP>.
<Tb>

<SEP> l = 55
<tb><SEP> | <SEP> AQUEOUS <SEP> l
<tb><SEP> U
<tb><SEP> d
<tb><SEP>&verbar;<SEP>&verbar;<SEP> uh <SEP> c) u <SEP> Rt <SEP> or <SEP> PId <SEP> Ful
<tb><SEP> e
<tb><SEP> 14 <SEP> | <SEP> 1 <SEP> 12 <SEP> 13
<tb><SEP> FILTRAT <SEP> 2
<tb><SEP> I
<tb><SEP> 14 \ <SEP> 12
<tb>t5>
<tb><SEP> f6
<tb><SEP> | <SEP> + <SEP> Hcl <SEP> pH <SEP> acid <SEP> | <SEP> COMPLEXING
<tb><SEP> i <SEP> 17
<tb><SEP> II <SEP> LI:
<tb><SEP> (Aqueous <SEP> Phase
<tb><SEP> Final)
<Tb>

Claims (4)

CLAIMS 1. A process for the antipollution treatment of a catalyst, which catalyst, based on at least one alumina, is deactivated and contains carbon and at least one metal selected from the group consisting of rhenium, noble metals of group VIII and iron , the method being characterized in that it comprises the following alkaline melting step  (c) after forming a solid mixture of the catalyst and a  alkaline base, said solid mixture is subjected to a heat treatment at  a temperature at least equal to that of the melting of said base. 2. Process according to claim 1 wherein the basic weight ratio  alkaline / mass of catalyst to be treated is at least 1: 1 3. Process according to one of Claims 1 and 2, in which the alkaline base  is caustic soda. 4. Process according to one of Claims 1 to 3, comprising the steps  following successive  a) The deactivated catalyst is subjected to calcination in the presence of a  gas containing molecular oxygen at a temperature not exceeding  not 700 "C,  c) The alkaline melting step is carried out. 5. Process according to one of Claims 1 to 3, comprising the steps  following successive  b) The catalyst is subjected to grinding in fine granulometry with a  upper limit of particle size equal to 2000 micrometers;  c) The alkaline melting step is carried out. 6. Process according to one of Claims 1 to 3, comprising the steps  following successive  a) The deactivated catalyst is subjected to calcination in the presence of a  gas containing molecular oxygen at a temperature not exceeding  not 700 "C;  b) The catalyst is subjected to grinding in fine granulometry with a  upper limit of particle size equal to 2000 micrometers;  c) The alkaline melting step is carried out. 7. Method according to one of Claims 1 to 6, then comprising the steps  following successive  d) The solid mass obtained in step c) is brought into contact with water  permuted at a temperature between room temperature and  boiling point, the density of the resulting aqueous solution being  between 1 and 1.5  e) The heterogeneous solution obtained in step d) is subjected to separation,  recovering a precipitate consisting essentially of metals,  chosen from the group formed by rhenium, the noble metals of the group  VIII and iron, said metals being initially present in the catalyst  deactivated, and a filtrate containing only the soluble salt of aluminum  from the alumina of the support. 8. The method of claim 7 further comprising the steps  following successive  f) The filtrate from step e) is subjected to dealumination by the  gaseous carbon dioxide, at a temperature between  room temperature and boiling temperature.  g) The filtrate from step f) is subjected to bicarbonation by  gaseous carbon dioxide, at a temperature between  temperature corresponding to the upper limit of freezing and the  ambient temperature. 9. The method of claim 8 wherein the solution obtained at step  g) is passed on a complexing resin after acidification. The process according to claim 9 wherein the complexing resin  has at least one function chosen from the group formed by the oxime,  quinoline, oxime derivatives and quinoline derivatives. 11. Method according to one of claims 9 and 10 wherein the solution  obtained after passing over a complexing resin is rejected at sea  after neutralization. 12. Method according to one of claims 1 to 11 wherein it is carried out in  step c), a humidification of the solid mixture constituted by the  catalyst and the alkaline base prior to said heat treatment.