Method for reactivating a precious metal-iron catalyst and carrying out a chemical reaction

Abstract

The catalytic activity of a spent precious metal-iron catalyst is restored by combining the spent catalyst with an iron(III) compound. This can be accomplished by adding an iron(III) compound to a chemical reaction involving the spent precious metal-iron catalyst. There is no need to add more precious metal. This process is particularly useful in a continuous process for converting nitrogen compounds, such as nitrobenzene, into corresponding amines.

Description

Technology Field

[0001] The present invention relates to a method for reactivating a precious metal-iron catalyst and a chemical reaction using a precious metal-iron catalyst.

[0002] Precious metal catalysts are used industrially in various types of chemical manufacturing processes. They are used, for example, to add hydrogen to organic nitrogen compounds, such as nitrobenzene, to form the corresponding amine; to add hydrogen to organic aldehydes to form the corresponding alcohol; and to produce hydrogen peroxide through the anthraquinone process, as well as in many other applications.

[0003] Precious metal catalysts sometimes contain iron, which improves the performance of the catalyst in some cases. For example, U.S. Patent No. 2,823,235, literature [Underhill et al. , JohnsonMathey Technol. Rev. , 2018, 62, (4) 417], literature[Chin et al. , Applied Catalyst A: General 302 (1) 2006 22-31], literature[Kuroki et al. , ACS Appl. Energy Mater. 2018, 1,2, 324-330], and literature[He et al. , J. Hazardous Materials See , 164(1), 2009, 126-132.

[0004] These catalysts tend to become inactive over time, reducing reaction rates, particularly in continuous processes. In such cases, it is necessary to replace the catalyst periodically. Replacing catalysts is costly.

[0005] An alternative to catalyst replacement is to reactivate the catalyst. Various methods to achieve this have been mentioned. U.S. Patent No. 3,959,382 describes a process for reactivating a palladium hydration catalyst by treating it with an alkali metal or alkaline earth metal compound in a liquid medium. The process described in U.S. Patent No. 4,999,326 relates to the step of contacting a deactivated catalyst with a polar solvent for a naphthalene compound. U.S. Patent No. 5,143,872 and European Patent EP 1853292 describe contacting a spent catalyst with an alkaline aqueous solution. These methods have little to no effect when applied to precious metal-iron catalysts. Literature [Taninouchi et al. , Metallurgical and Materials Transaction B [49(4) 2918 1781-1793] describes a method for recovering platinum group metals from spent automobile catalytic converters by treating with FeCl2 vapor at a temperature of about 927°C. This forms an iron-precious metal alloy that can be recovered using magnetic means.

[0006] In one embodiment, the present invention is a method for reactivating a waste precious metal-iron catalyst. The method comprises the step of combining a waste precious metal-iron catalyst with an iron (III) compound, wherein 10 weight percent or less of precious metal is added to the waste precious metal-iron catalyst based on the weight of iron in the added iron (III) compound.

[0007] The applicant has unexpectedly discovered that combining a spent precious metal-iron catalyst with an iron(III) compound can restore the activity of the spent precious metal-iron catalyst, at least partially. The iron(III) compound is not an additional amount of the precious metal-iron catalyst. On the contrary, in this method, the precious metal is not combined with the spent catalyst, or is combined with very little; the addition of the iron compound alone is sufficient to restore catalytic activity. Therefore, there is no need to add more precious metal in this process, whether in the initial form of the precious metal-iron catalyst or in any other form.

[0008] Another unexpected advantage is that no special processing steps are required to increase catalytic activity to the desired level. It is sufficient to simply form a physical mixture of the spent precious metal-iron catalyst and the iron(III) compound. Therefore, in some embodiments, the iron(III) compound can be added directly to the chemical manufacturing process where the spent precious metal-iron catalyst is present, thereby increasing catalytic activity without the need to treat the spent catalyst separately or change process conditions in any way (other than the addition of the iron(III) compound).

[0009] Accordingly, in a second aspect, the present invention is a catalytic process for producing one or more chemical products, which is

[0010] a) a step of carrying out a chemical reaction by subjecting one or more starting compounds to reaction conditions in the presence of a precious metal-iron catalyst, wherein under said reaction conditions the one or more starting compounds react to form one or more chemical products, and said reaction continues for a certain period of time so that said precious metal-iron catalyst is at least partially consumed;

[0011] b) then adding an iron (III) compound to the reaction vessel one or more times, adding a precious metal of 10% by weight or less based on the weight of iron in the added iron (III) compound, and then continuing to perform a chemical reaction in the presence of at least partially the waste precious metal-iron catalyst and the added iron (III) compound.

[0012] The present invention is particularly significant in a continuously operated hydrogenation process for the production of aromatic amines. In a third aspect, the present invention

[0013] a) a step of continuously or intermittently introducing a starting nitrogen aromatic compound and hydrogen into a reaction vessel in the presence of a precious metal-iron catalyst, and continuously or intermittently removing an aromatic amine and water produced by the reaction of the starting nitrogen aromatic compound and hydrogen from the reaction vessel to perform a continuous reduction reaction, wherein the reduction reaction continues for a certain period of time so that the precious metal-iron catalyst is at least partially consumed;

[0014] b) a step comprising adding an iron (III) compound to a reaction vessel at least once, adding a precious metal of 10% by weight or less based on the weight of iron in the added iron (III) compound, and then continuing to perform a continuous reduction reaction in the presence of at least partially spent precious metal-iron catalyst and an iron (III) compound.

[0015] The precious metal-iron catalyst is a composition containing at least one precious metal and iron. "Precious metal" means gold, silver, ruthenium, rhodium, palladium, osmium, iridium, and platinum. Among these, palladium and / or platinum are preferred.

[0016] The precious metals and iron within the catalyst may exist as alloys of each other in metallic form, or in the form of salts, oxides, or other compounds. The precious metals and iron may be deposited together on a support. Such a support may be a fixed-bed type support or a particulate support. The support may be any material that is inert under reaction conditions. Examples of useful support materials include zeolites, molecular sieves, titanium dioxide, alumina, silica, other metal oxides and / or nitrides, and various forms of carbon including carbon black, activated carbon (including activated carbon and activated coke), graphite, activated carbon, etc. Activated carbon has a porosity of at least 3000 m² when measured by a gas deposition method. 2 It is microporous carbon with a g.

[0017] The supported new catalyst may contain 1% to 25% by weight of precious metal and 1% to 25% by weight of iron based on the total weight of the supported catalyst on a dry basis. In some embodiments, the weight of the precious metal and iron constitutes at least 2%, at least 3%, or at least 4%, and up to 20%, up to 15%, up to 10%, or up to 7.5% of the total dry weight of the supported new catalyst, respectively. "New" catalyst means a catalyst that has never been used before.

[0018] In certain embodiments, the catalyst is a carbon-supported palladium-iron or palladium-platinum-iron catalyst containing 2% to 10% by weight, particularly 3% to 7.5% by weight of palladium and / or platinum and an equal amount of iron, based on the total dry weight of the new catalyst supported in each case in a new state.

[0019] A method for manufacturing a precious metal-iron catalyst is, for example, U.S. Patent No. 2,823,235, literature [Berry et al. , Applied Catalysis A: General 204(2) 2000 191-201], literature[Underhill et al. , JohnsonMathey Technol. Rev. , 2018, 62, (4) 417], literature[He et al. , J. Hazardous Materials , 164(1), 2009, 126-132], literature[Chin et al. , Applied catalyst A: General 302 (1) 2006 22-31], literature[Kuroki et al. , ACS Appl. Energy Mater. It is described in [2018, 1, 2, 324-330]. A catalyst prepared according to any one of these methods is suitable for use in the present invention.

[0020] Noble metal-iron catalysts are used to carry out chemical reactions. In a chemical reaction, one or more starting compounds undergo reaction conditions including the presence of a catalyst, under which the one or more starting compounds react to form one or more chemical products.

[0021] The chemical reaction may be an oxidation reaction, such as the oxidation of phenol to form hydrogen peroxide, or the oxidation of carbon monoxide; a dechlorination or dehydrochlorination reaction; a deoxygenation reaction; a reduction reaction; a hydrogenation reaction; or any other reaction where a noble metal-iron catalyst is useful.

[0022] In some embodiments, the chemical reaction is the reduction (hydrogenation) of a nitrogen compound to a corresponding amine. The nitrogen compound may be a nitrogen aromatic compound in which nitrogen groups are directly bonded to carbon atoms of an aromatic ring. In certain embodiments, the nitrogen compound is nitrobenzene, and the resulting amine is aniline.

[0023] A chemical reaction is carried out for a certain period of time in the presence of a noble metal-iron catalyst, so that the noble metal-iron catalyst is at least partially consumed. The catalyst is considered to be at least partially consumed during or after use in the chemical reaction, and the catalyst exhibits a decrease in activity when a decrease in the rate of the chemical reaction occurs in the presence of the noble metal-iron catalyst itself (i.e., without adding an iron(III) compound). The decrease in activity can be measured in situ by periodically measuring the reaction rate or by recovering all or part of the catalyst and measuring its activity through appropriate tests.

[0024] The applicants have discovered that metals, particularly iron, within a catalyst can be depleted during use. Consequently, the metal content of the catalyst, particularly the iron content, differs from that of a new catalyst during use. Changes in metal content, particularly the depletion of iron, are believed to reduce the reaction rate by lowering catalytic activity, at least partially. Therefore, a catalyst is considered to be at least partially consumed when all or part of the iron content at the start (i.e., the iron content within the catalyst prior to use) is lost.

[0025] In the present invention, iron is replenished by combining at least partially consumed precious metal-iron catalyst and an iron (III) compound. This is carried out while adding 10 weight percent or less of precious metal to the waste precious metal-iron catalyst based on the weight of iron in the added iron (III) compound. Preferably, any precious metal added during this combination step is added to the iron (III) compound at a maximum impurity level, e.g., 500 weight ppm or less, 100 weight ppm or less, or 10 weight ppm or less based on the weight of iron. In some embodiments, the precious metal is not added together with the iron (III) compound, so the entire amount of precious metal in the combination is provided by the waste precious metal-iron compound.

[0026] Even if additional precious metals are added, they can be added in the form of new precious metal-iron catalysts.

[0027] The above iron(III) compounds may be, for example, iron halides (III), such as iron fluoride (III), iron chloride (III), iron bromide (III), etc.; iron nitrate (III), iron phosphate (III); iron pyrophosphate (III), iron oxide (Fe2O3); basic iron carbonate (III), iron carbonate (III), ferric hydroxide, iron alkoxylide (III); iron(III) aryl oxides, such as iron phenoxide; iron(III) carboxylates; iron(III) salicylates; iron(III) 3,5-di-t-butyl salicylates; iron(III) acetylacetonates; and iron(III) t-butylacetylacetonates. In some cases where external organic species are to be avoided in the reaction, inorganic iron(III) compounds are preferred.

[0028] In some embodiments, the iron(III) compound may be solid, insoluble, and non-reactive in the reaction mixture except for catalytic activity under the conditions of the chemical reaction used. The solid and / or supported iron(III) compound may be in a physical form, such as a catalyst layer or catalyst particles, for example. In the case of a particulate form, the longest dimension of the solid and / or supported iron(III) compound (including the support, if any) may be 10 nm to 10 mm, or 25 nm to 100 μm.

[0029] Iron(III) compounds can be transported on a support as described above in relation to a noble metal-iron catalyst.

[0030] Iron (III) compounds particularly suitable for reduction and / or hydrogenation reactions, such as the reduction of an organic nitrogen compound to a corresponding amine (in particular, hydrogenation of a nitrogen aromatic compound, such as nitrobenzene, to an aromatic amine, such as aniline), are ferric hydroxide or iron oxide, which can be carried on an inorganic support, in particular on the carbon support described above (e.g., activated carbon support).

[0031] Waste precious metal-iron catalysts and iron(III) compounds can be combined by simply mixing the materials to form a physical mixture. Generally, there is no need to treat the physical mixture in any specific way, such as promoting or inducing chemical reactions, fusion, or alloying, or otherwise marrying the starting materials. Such physical mixtures have often been found to possess catalytic activity comparable to that of new precious metal-iron catalysts.

[0032] Mixing may be carried out, for example, by recovering all or part of the precious metal-iron catalyst that has been at least partially consumed from a chemical reaction, and by combining said recovered precious metal-iron catalyst with said iron(III) compound to form a physical mixture. The physical mixture thus obtained may be reintroduced into the chemical reaction of interest. "Recovering" means that the catalyst is separated at least partially from the reactants of the chemical reaction. This may be carried out, for example, by removing the spent catalyst from the reaction vessel, by removing the reactants from the reaction vessel and leaving the spent catalyst in the reaction vessel, or by withdrawing a recycling stream containing all or part of the catalyst from the reaction vessel. Recycling the spent catalyst, for example, by forming a mixture of the spent catalyst and the iron(III) compound recovered from the reaction vessel and reintroducing the resulting mixture into the reaction vessel, is not considered, for the purposes of the present invention, as the addition of precious metal.

[0033] An unexpected advantage of the present invention is that the spent catalyst does not need to be recovered from the chemical reaction. By combining it with an iron (III) compound in the presence of the reactants, a mixture of the spent catalyst and the iron (III) compound can be formed in situ even if the chemical reaction proceeds. In such an embodiment, the iron (III) compound can be simply introduced into the reaction vessel when the reaction proceeds in the presence of the spent catalyst, and the chemical reaction is then carried out when both the spent catalyst and the iron (III) compound are present.

[0034] Generally, a mixture of at least partially consumed noble metal-iron catalyst and iron(III) compounds is introduced into the chemical reaction when the starting noble metal-iron catalyst is at least partially consumed. If desired, any analytical method suitable for the specific chemical reaction can be used to monitor the decrease in catalytic activity and the consequent decrease in reaction rate. For example, the conversion rate of one or more starting materials can be determined, and a lower conversion rate indicates a greater loss of catalytic activity and a decrease in reaction rate. Similarly, the consumption rate of one or more starting materials can be measured, and a decrease in consumption rate again indicates a decrease in catalytic activity and reaction rate. The concentration and / or rate of one or more products of the chemical reaction can be measured as an indicator of the decrease in catalytic activity and reaction rate. If desired, a sample of the noble metal-iron catalyst can be recovered from the chemical reaction to analyze the iron content or evaluate the catalytic activity.

[0035] Instead of monitoring the chemical reaction, or in addition to it, a general rate of decline of catalytic activity for any specific chemical reaction under a specific set of operating conditions can be empirically established. Then, using the empirical data, the time when the catalytic activity and reaction rate will decline should be estimated at least once, and an iron (III) compound should be supplied to the reaction vessel. In this way, using the empirical data, a schedule for supplying the iron (III) compound to the reaction can be established. In this case, the iron (III) compound can be added intermittently or continuously to maintain the desired catalytic activity and reaction rate.

[0036] After that, the chemical reaction continues in the presence of both the spent precious metal-iron catalyst and the iron(III) compound.

[0037] The present invention is useful in a continuous process. In such a continuous process, one or more starting materials are introduced into a reaction vessel continuously or intermittently in the presence of a noble metal-iron catalyst, and one or more reaction products are removed from the reaction vessel continuously or intermittently. When the noble metal-iron catalyst is partially or wholly consumed, the catalytic activity and the chemical reaction rate are increased by adding an iron(III) compound to the reaction vessel continuously or intermittently during continuous operation. The chemical reaction is then continued in the presence of the partially or wholly consumed noble metal-iron catalyst and the iron(III) compound.

[0038] In certain embodiments, the chemical reaction produces a corresponding aromatic amine by reacting a starting nitrogen aromatic compound with hydrogen. If the nitrogen aromatic compound is nitrobenzene, the amine product will be aniline.

[0039] In a useful continuous process for producing aniline according to the present invention, nitrobenzene and hydrogen are introduced intermittently or continuously into the lower part of a reaction vessel operating at a temperature exceeding the boiling point of aniline (at 1 atm), e.g., 200 to 260°C. The internal pressure of the reaction vessel may be, e.g., a gauge of 10 to 30 atm (1013 to 3040 kPa). Nitrobenzene and hydrogen react within the reaction vessel in the presence of a noble metal-iron catalyst to produce aniline and water. Aniline and water are removed in the gaseous phase continuously or intermittently from the upper part of the reaction vessel, thereby purifying the aniline. The reaction continues for a certain period until the noble metal-iron catalyst is at least partially consumed. During the continuous process, an iron (III) compound is added intermittently or periodically to the reaction vessel, and the reaction continues in the reaction vessel after the addition of the iron (III) compound in the presence of the noble metal-iron catalyst and the iron (III) compound, at least partially consumed.

[0040] In a continuous process, a convenient method for adding an iron(III) compound is to withdraw a recycling stream containing waste precious metal-iron catalyst from the reaction vessel, combine the waste precious metal-iron catalyst with an iron(III) compound in whole or in part of the recycling stream, reintroduce the corresponding part of the recycling stream containing the waste precious metal-iron catalyst, and add the iron(III) compound to the reaction vessel. This can be performed intermittently or continuously. The recycling stream typically contains a liquid phase, which may include, for example, an unreacted starting material, a solvent, and / or a portion of the product. Part or all of the liquid phase may be removed from the recycling stream before the recycling stream is reintroduced into the reaction vessel. For example, the product may be recovered from the recycling stream before the recycling stream is reintroduced into the reaction vessel. In the case of a nitrogen aromatic hydrogenation reaction, the recycling stream may contain a portion of the product aromatic amine (aniline in the case of nitrobenzene hydrogenation). Part or all of the aromatic amine may be recovered from the recycling stream before the recycling stream is reintroduced into the reaction vessel.

[0041] The following examples are provided to demonstrate the invention, but are not intended to limit its scope. All parts and percentages are by weight unless otherwise specified. All molecular weights are number averages unless otherwise specified.

[0042] Examples 1 to 4 and comparative samples A and B

[0043] The reaction time experiment is performed in the following approximate manner: Fill a 300 mL autoclave (Autoclave Engineers Model ABA-300, with a steam jacket and equipped with a stirrer) with 0.027 g to 0.028 g of the palladium-iron catalyst listed below, 17.2 mL of nitrobenzene, 30 mL of methanol, and 50 mL of water. Seal the reactor, purify it with hydrogen, and pressurize it with nitrogen to a gauge pressure of 30 bar (3,040 kPa). Flow steam through the jacket to heat the contents of the reactor to 100°C. Designate the time it takes for the contents of the reactor to reach 100°C as time T0. The pressure in the reactor is continuously measured. At the point when the pressure becomes constant (T c Determines (indicating the termination of the reaction). The reaction time is T c It is calculated as -T0.

[0044] In Comparative Sample A, the palladium-iron catalyst is a novel catalyst sample containing about 4.6 wt% palladium, 0.4 wt% platinum, and 5.15 wt% iron (all determined by dry weight-based inductively coupled plasma-mass spectrometry (ICP-MS)). The metals are transported on carbonaceous support particles. The palladium-iron catalyst is prepared according to the method described in U.S. Patent No. 2,823,235.

[0045] In the case of comparative sample B, the palladium-iron catalyst was obtained from a commercial aniline production plant using a spent sample of the same palladium-iron catalyst.

[0046] The reaction times of comparative samples A and B are 7.1 to 7.2 minutes and 19.3 to 19.7 minutes, respectively. Therefore, in this test, the activity of the spent catalyst is about one-third of the activity of the new catalyst.

[0047] ICP-MS analysis of the spent catalyst revealed that the levels of palladium and platinum in the spent catalyst were almost the same as those in the new catalyst. However, the iron content of the spent catalyst was reduced by about 60%, which is a decrease to about 2.1 wt% of the catalyst.

[0048] Comparative sample B is repeated four more times, and in each case, ferric chloride (FeCl3·6H2O) is added as a physical mixture with the spent catalyst. In Example 1, ferric chloride is added in a manner sufficient to provide 1 part by weight of iron per 100 parts by weight of spent catalyst. In Examples 2 to 4, ferric chloride is added to provide 2, 3, and 4 parts by weight of iron per 100 parts by weight of spent catalyst, respectively. The approximate total amount of iron (including iron derived from the spent catalyst and ferric chloride) and the reaction time are shown in Table 1 along with the results of Comparative samples A and B.

[0049] [Table 1]

[0050]

[0051] As shown in the data in Table 1, adding ferric chloride to the reaction significantly reduces the reaction time compared to the spent catalyst. When the iron content in the reaction mixture increases to approximately the iron content of the new catalyst, the reaction time is essentially the same but is not faster than when the new catalyst is provided. The less the amount of iron(III) compound added, the greater the significant advantage, even if it is smaller.

[0052] Example 5 and Comparative Sample C

[0053] Although adding ferric chloride to the nitrobenzene reduction reaction described in the previous example significantly improves the reaction rate, the presence of chloride ions results in the formation of unwanted byproducts in certain reactions. Therefore, for reducing a nitrogen compound to a corresponding amine, an iron(III) compound that is almost free of any halide ions is preferred.

[0054] Ferric chloride and activated carbon were combined in the presence of water at a weight ratio of iron to carbon of 1:20. Sodium bicarbonate was added, which reacted with ferric chloride to produce basic ferric carbonate, which precipitated as activated carbon and sodium chloride. The iron carbonate-activated carbon particles were separated from the liquid phase and heated at 80°C for 30 minutes to decompose the iron carbonate into ferric hydroxide. Afterward, the particles were washed, filtered, and dried.

[0055] Comparative sample C is performed according to the general reaction time procedure described above. The catalyst is a spent palladium-iron catalyst from a commercial aniline production facility, prepared according to the method originally described in U.S. Patent No. 2,823,235.

[0056] In Example 5, the same mixture of spent catalyst and ferric hydroxide-activated carbon particles is used. The mixture is formed by separately adding the spent catalyst and ferric hydroxide-activated carbon particles to a reactor. By adding the ferric hydroxide-activated carbon particles sufficiently, about 4 wt-% of iron is supplied based on the weight of the spent catalyst particles. The total iron content in the combined spent catalyst and ferric hydroxide-activated carbon particles is 5 to 6.25 wt% of the spent catalyst particles. The results are shown in Table 2 along with the results of Comparative Sample A.

[0057] [Table 2]

[0058]

[0059] As demonstrated by the data in Table 2, the addition of iron in the form of iron hydroxide supported on activated carbon restores the catalytic activity to approximately the level of a new catalyst. There are no unwanted reaction byproducts.

Claims

Claim 1 A catalytic process for producing one or more chemical products, comprising: a) a step of carrying out a chemical reaction by subjecting one or more starting compounds to reaction conditions in the presence of a precious metal-iron catalyst comprising platinum, palladium, or a mixture thereof supported on a carbonaceous support, wherein under said reaction conditions the one or more starting compounds react to form one or more chemical products, and said reaction continues for a certain period of time until said precious metal-iron catalyst is at least partially consumed; and b) a step of adding an iron (III) compound to a reaction vessel one or more times, wherein 10 weight percent or less of a precious metal is added based on the weight of iron in the added iron (III) compound, and then continuing to perform a chemical reaction in the presence of at least partially a waste precious metal-iron catalyst and the added iron (III) compound, wherein the iron (III) compound is an iron halide (III), an iron oxide, a basic iron carbonate (III), an iron carbonate (III), or an iron hydroxide (III), wherein the added iron (III) compound is not supported and is physically independent from 10 weight percent or less of the precious metal, and wherein the chemical reaction is one or more of an oxidation reaction, a dechlorination or dehydrochlorination reaction; a hydrogenation / deoxidation reaction; a reduction reaction or a hydrogenation reaction. Claim 2 A process for manufacturing an aromatic amine comprising: a) continuously or intermittently introducing a starting nitrogen aromatic compound and hydrogen into a reaction vessel in the presence of a precious metal-iron catalyst comprising platinum, palladium, or a mixture thereof supported on a carbonaceous support; and continuously or intermittently removing the aromatic amine and water produced by the reaction of the starting nitrogen aromatic compound and the hydrogen from the reaction vessel to perform a continuous reduction reaction, wherein the reduction reaction continues for a certain period of time until the precious metal-iron catalyst is at least partially consumed; and b) a step of adding an iron (III) compound to a reaction vessel one or more times, wherein 10 weight percent or less of a precious metal is added based on the weight of iron in the added iron (III) compound, and then continuing to perform a continuous reduction reaction in the presence of at least partially a waste precious metal-iron catalyst and an iron (III) compound, wherein the iron (III) compound is an iron halide (III), an iron oxide, a basic iron carbonate (III), an iron carbonate (III), or an iron hydroxide (III), and wherein the added iron (III) compound is not supported and is physically independent from 10 weight percent or less of the precious metal. Claim 3 In paragraph 2, the carbonaceous support has a porosity of at least 3,000 m when measured by a gas deposition method. 2 A process containing activated carbon in g. Claim 4 A process according to claim 2 or 3, wherein the precious metal-iron catalyst is a carbon-supported palladium-iron or palladium-platinum-iron catalyst containing 3% to 7.5% by weight of palladium and / or platinum and an equal amount of iron based on the total dry weight of the new catalyst supported in the new state. Claim 5 A process according to claim 2 or 3, wherein the precious metal-iron catalyst is a palladium iron catalyst; the iron(III) compound is ferric chloride or ferric hydroxide; and / or the iron(III) compound is added in an amount sufficient to provide 1 to 4 parts by weight of iron per 100 parts by weight of spent palladium iron catalyst. Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 delete Claim 10 delete Claim 11 delete Claim 12 delete Claim 13 delete Claim 14 delete Claim 15 delete

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