United States Patent [1911 [111 3,887,490 Schreyer Et Al

United States Patent [1911 [111 3,887,490 Schreyer et al. [45] June 3, 1975

[54] PROCESS FOR REGENERATING NOBLE METAL CATALYST FOR THE SYNTHESIS [56] References Cited OF HYDROGEN PEROXIDE ACCORDING UNITED STATES PATENTS TO THE ANTHRAQUINONE PROCESS 2,657,980 11/1953 Spraver ...... 423/590 [751 Inventors: Gerd Schreyer; Ferdinand Theissen, 2,692,240 '10/ 1954 Sprauer ...... 252/414 both of Grossauheim; Otto Weiherg, 3,635,841 1/1972 Keith et a1...... 423/588 Neuisenburg; Wolfgang Weigert, Offenbach, all of Germany FOREIGN PATENTS OR APPLICATIONS 922,021 3/1963 United Kingdom ...... 252/415 [731 Assignee: Deutsche Gold- und Silber-Scheideanstalt vormals Primary Examiner—Winston A. Douglas Roessler, Germany Assistant Examiner-P. E. Konopka [22] Filed: Aug. 20, 1973 Attorney, Agent, or Firm-Cushman, Darby & Cushman [21] Appl. No.: 389,543 Related U.S. ‘Application Data ABSTRACT [63] Continuation of Ser. No. 174,234, Aug. 23, 1971, In situ regeneration of noble metal catalysts for the abandoned. ' synthesis of hydrogen peroxide by the anthraquinone process is provided by employing as the working solu [30] Foreign Application Priority Data tion coming from the extraction or desorption step Aug. 27, 1970 Germany ...... 2042523 and being introduced into the hydrogenation step a solution which contains at least 250 mg/liter of hydro [52] U.S. Cl...... 252/414; 423/588; 423/589; gen peroxide, to thereby completely regenerate the 423/590 noble metal catalyst by full capacity of the hydrogena [51] Int. Cl...... Bolj 11/18; COlb 15/02 tion step. [581 Field of Search ...... 252/414, 412; 423/588, 423/589, 590 7 Claims, No Drawings 3,887,490 1 2 PROCESS FOR REGENERATING NOBLE METAL reactive hydrogen peroxide of at least 250 mg/liter and CATALYST FOR THE SYNTHESIS OF HYDROGEN up to 30,000 mg/liter. PEROXIDE ACCORDING TO THE Preferably the working solution has 300-1000 mg ANTHRAQUINONE PROCESS Hzog/llter. ' This amount of hydrogen peroxide can remain in the This is a continuation, of application Ser. No. working solution either by a correspondingly small ex 174,234 filed Aug. 23, 1971 now abandoned. traction with'water or desorption with organic solvent The invention is directed to a process for the in situ vapors or it can be reinserted in the working solution regeneration of noble metal catalysts employed in the after the extraction or desorption, either by addition of anthraquinone process in which there is employed as a side stream from the oxidation or by addition of 100% the active metal a metal or mixture of metals of the hydrogen peroxide or highly concentrated aqueous so platinum group of the periodic system. Preferably the lutions. These highly concentrated aqueous solutions catalyst is added on a carrier. can be produced most simply and economically by ex The noble metal catalysts include platinum, palla traction of the solutions of Schreyer et al. applications dium, iridium, rhodium and ruthenium for example. 856,070 ?led Sept. 8, 1969 now abandoned and 79,315 As is known hydrogen peroxide can be produced in ?led Oct. 8, 1970, now US. Pat. No. 3,707,444 (and a cyclic process in which anthraquinone compounds corresponding German published applications P 18-02 are alternately hydrogenated and oxidized. Reduction 003.6 and P 19 51 211.9) and German published appli and oxidation occur in an organic solvent or solvent cation P 20 25 237.3 with correspondingly small mixture that contains both the anthraquinone and the 20 amounts of water as set forth in our application ?led on anthrahydroquinone compounds in solution. The hy even date entitled “Process for the Production of Very drogen peroxide formed by the oxidation of the hydro Pure Aqueous Hydrogen Peroxide Solutions” (corre quinone to quinone is isolated from the organic phase sponding to German application P 20 42 522.3). The entire disclosures of the Schreyer et al. United States by known processes and the anthraquinone compound 25 containing working solution is returned to the cycle in application Ser. Nos. 856,070 and 79,315 as well as the hydrogenation. the Schreyer et al. application of even date are hereby incorporated by reference. . In this cyclic process there are undesired side reac It is only essential that the working solution before tions in which compounds of various types are formed. entering the hydrogenation tower possess the reactive As especially disturbing there have been found resini? 30 amount of hydrogen peroxide of the invention speci?ed cation and decomposition products of undetermined above. ' composition. These compounds for example cause the It could not be perceived that an amount of hydrogen gradual reduction of the activity in the activity of the peroxide of the speci?ed height could maintain the ac hydrogenation catalyst which can lead to excessively tivity of the catalyst during the hydrogenation or again high catalyst costs in comparison to the total product produce such activity. Until now it was only known to costs of the hydrogen peroxide. Customarily a catalyst increase the catalyst activity by insertion of a specified which is exhausted or has its activity reduced is re- _ water content to the working solution, see US. Pat. No. moved from the plant and subjected to a working up for 2,867,507. By this procedure, however, there can not reactivation. At least the hydrogenation tower is dis be prevented the gradual reduction in the course of connected during the regeneration. Especially in work‘ 40 time of activity obtained in this manner by poisons in ing with solid bed hydrogenation catalysts these meth - the course of time which are brought in with the work ods of operation are time consuming and noticeably ing solution. According to the process of the invention costly. ‘ ' these reductions in activity, however, are prevented by Until the present no truly useful processes for the re inclusion of the recited amounts of hydrogen peroxide. activation of the catalyst in situ have been known. 45 The experts in art until now were of the opinion that To be sure German Pat. No. 1,055,513 speci?es a uncharged hydrogen peroxide as well as the active oxy process of revival for a hydrogenation catalyst of the gen were detrimental to the hydrogenation catalyst. anthraquinone process according to which the catalyst Even the working solution should be changed in the in the hydrogenation step is subjected to a periodic re regular cyclic procedure by the constant presence of duction of the hydrogen peroxide pressure with simul 50 hydrogen peroxide. On the contrary it has surprisingly taneous introduction of an inert gas. However, the hy been shown that in the presence of hydrogen neither drogenation itself must either be very greatly slowed the catalyst nor the working solution becomes at down or even completely interrupted. tacked. Also according to the regular cyclic process the Until now it has not been known how to undertake working solution was intact. The catalyst retains its the regeneration of the hydrogenation catalyst at its 55 original activity and selectivity. complete normal rate in the hydrogenation step itself. It is even possible to regenerate to the old value a cat It has now been found that noble metal catalyst in alyst whose activity has been reduced by the recycling which a metal of the platinum group of the periodic sys of the until now customary working solution by addi tem (such as those set forth above), preferably palla tion of H202 in the speci?ed amounts to the working dium, in a given case in admixture with other metals of solution. In this manner in‘ existing plants there is the platinum group, e.g., platinum, iridium, rhodium or avoided the costly regeneration apparatus which also ruthenium, is deposited on a carrier, e.g., alumina, sil require expensive maintenance. ica, alumium silicate or the like, is directly regenerated As carriers for the catalyst there are used silica con taining materials as well as aluminum oxideand acti during the hydrogenation at complete driving capacity 65 in the hydrogenation step, if the working solution com vated carbon. ing from the extraction or desorption step which is re The catalysts can be employed either as suspension turned again to the hydrogenation step has a content of catalysts or as solid bed catalysts. 3,887,490 3 4 The regeneration according to the invention, as said, can be used, for example, methyl neodecanoate, ethyl is suited for a plant using water extraction or a plant neodecanoate, methyl neotridecanoate. using desorption of the hydrogen peroxide by organic Particularly preferred are esters of aliphatic alcohols, vapors. 1n the last case it is especially effective since the especially methyl to butyl alcohols with acids where R, hydrogenation catalyst according to experience is there is an alkyl group with l-3 carbon atoms and R2 and R3 more quickly exhausted than in the water extraction. are alkyls of l to 2 carbon atoms. Most preferred are As working solutions there can be employed solu methyl to butyl esters of pivalic acid (trimethyl acetic tions of one or more alkyl anthraquinones in a high acid). in addition to the speci?c esters just mentioned boiling solvent stable to oxygen and hydrogen perox there can be used, for example, the methyl ester of 2,2 ide. As alkyl anthraquinones, there are employed, for dimethyl valeric acid and the ethyl ester of 2,2-diethyl example, alkyl derivatives thereof, such as 2-methyl an butyric acid. thraquinone, Z-ethyl anthraquinone, Z-butyl anthraqui There also can be used allyl acetate as well as esters none, 2-isopropy_l anthraquinone, anthraquinone, 2 of cycloaliphatic alcohols such as cyclohexyl acetate, sec. amyl anthraquinone, 1,3-dimethyl anthraquinone, cyclohexyl butyrate, cyclohexyl pivalate, cyclohexyl 2,7-dimethyl anthraquinone and mixtures of them as formate, methyl cyclohexyl acetate and cyclopentyl ac well as their partially nuclear hydrogenated derivates, etate. e.g., the tetrahydro anthraquinones such as Z-ethyl tet Additionally there can be used as stripping agents rahydro anthraquinone. As solvents there have been mixtures of carboxylic acids, esters, ketones or alcohols used, among others, alkyl benzenes such as tetramethyl with aromatic or aliphatic hydrocarbons or hydrocar benzene, paraf?ns, higher alcohols, naphthalenes such 20 bon fractions boiling up to 160°C. Illustrative of such as tetralin (tetrahydronaphthalene), methyl naphtha a mixture is 60% acetic acid and 40% n-propyl ether. lene, dimethyl naphthalene and esters such as methyl Besides there can be used aliphatic ethers with 4-10 cyclohexyl acetate, trioctyl phosphate, tributyl phos carbons atoms such as diethyl ether, diisopropyl ether, phate. dibutyl ether, diisobutyl ether, di sec. butyl ether, dia For stripping (desorbing) there are best suited vapors 25 myl ether, di-isoamyl ether, ethyl propyl ether, propyl of substances which dissolve hydrogen peroxide and butyl ether, ethylene glycol dimethyl ether, propylene are not attacked by hydrogen peroxide under the pro glycol dimethyl ether, methyl ethyl ether of ethylene cess conditions. For these materials, depending on the glycol, methyl ethyl ether of propylene glycol. later intended use, carboxylic acids, esters, alcohols 30 Also there can be used aliphatic ketones with 3-7 and esters having 4 to 10, preferably 4 to 8 carbon carbon atoms, for example acetone, methyl ethyl ke atoms, ketones having 3 to 7 carbon atoms, have tone, methyl isobutyl ketone, cyclohexanone, di proven suitable. Thus, there can be used carboxylic isopropyl ketone. acids such as formic acid, acetic acid, propionic acid, Additional examples of mixtures of stripping agents butyric acid, isobutyric acid, pivalic acid, esters such as 35 include, for example, acetic acid-di-n-propyl ether, ethyl acetate, propyl acetate, butyl acetate, ally] ace acetic acid-methyl ethyl ethylene glycol ether, di tate, propyl formate, butyl formate, isobutyl acetate, isopropyl ether-t~buty1 acetate, di-isopropyl ether-t amyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, methyl butyl acetate-benzene, acetic acid-n-butyl acetate, ace valerate, methyl isovalerate, isopropyl acetate, 2 tone-benzene, propionic acid-propyl propionate, pro ethylbutyl acetate, sec-hexyl acetate, propyl propio 40 pyl acetate-acetic acid, propyl acetate-propanol. For nate, isopropyl propionate, butyl propionate, isobutyl example, in each of the two and three component mix propionate, amyl propionate, propyl butyrate, isobutyl tures just mentioned there can be used equal parts by butyrate, methyl isobutyrate, ethyl isobutyrate, propyl volume of each component of the mixture. isobutyrate, isopropyl isobutyrate, isobutyl isobutyrate, Unless otherwise indicated all parts and percentages amyl isobutyrate, ethyl valerate, methyl isovalerate, 45 are by weight. propyl isovalerate, methyl caproate, alcohols such as EXAMPLE 1 propanol, butanol, isobutyl alcohol, amyl alcohol, A working solution consisting of 150 grams/liter of hexyl alcohol, cyclohexanol. ethyl anthraquinone and 150 grams/liter of tetrahydro An especially preferred class of stripping agents are 50 esters of acids of the formula ethyl anthra-quinone in a mixture of 60 vol. parts of tri butyl phosphate/4O vol. parts methyl naphthalene (a technical mixture of the 1 and 2 isomers) was hydroge R1 nated at 60°C. over a solid bed catalyst (0.3% pd on sil C-COOH ica pebbles) corresponding to an H202 content of 30 R2 55 g/liter and after ?ne filtration oxidized back with air at 60°C to the anthraquinone/tetrahydroanthraquinone R3 and H202 in an oxidation tower. The H202 was de sorbed with butyl acetate in the manner set forth in ap plication Ser. No. 79,315 to obtain a working solution where R1, R2, and R3 are lower alkyl i.e., R1 are alkyls 60 with 1 to 4 carbon atoms and R2 and R3 alkyls with 1 substantially freed of H202 but having a residual con to 4 carbon atoms. Thus, there can be used esters of pi tent of 0.3 grams/liter of H202 was returned to the hy valic acid, 2,2-dimethylpentanoic acid, neodecanoic drogenation tower. (In the event the residual H202 con acid, neotridecanoic acid, 2,2,4,4-tetramethyl valeric tent is below 0.3 g/l it can be raised to that value either by means of adding a side stream from the oxidation acid. Most preferred are lower alkyl esters of pivalic 65 acid such as methyl pivalate, ethyl pivalate, propyl step or by adding 10% H202 in butyl acetate.) After pivalate, isopropyl pivalate, butyl pivalate, sec. butyl 1,200 hours the hydrogenation catalyst showed no loss pivalate, amyl pivalate and hexyl pivalate. There also of activity. 3,887,490 5 6 2. A process according to claim 1 wherein the cata EXAMPLE 2 lyst includes palladium. A working solution of the type set forth in example 3. A process according to claim 1 wherein the work 1 was freed of H202 to a‘residual content of 0.00lg/liter ing solution is extracted or desorbed to reduce the of H202. After 12 hours the degree of hydrogenation H202 content to 300 mg/liter up to 1,000 mg/liter prior had fallen to the extent that it only corresponded to to its introduction into the hydrogenation step. 20g/liter of H202. Then the working solution was de 4. A process according to claim 3 wherein the pro sorbed up to a residual content of 0.5-0.8 g H2O2/liter cess is carried out at 60°C. of working solution and returned to the working solu 5. A process according to claim 1 wherein the pro tion. After a further 12 hours the complete hydrogena 10 cess is carried out at 60°C. tion activity was again attained. 6. A process according to claim 1 wherein the work What is claimed is: ing solution introduced into the hydrogenation step to 1. A process for the in situ regeneration of noble regenerate the catalyst directly in the hydrogenation metal catalyst of the platinum group of the periodic sys step and the hydrogenated working solution is returned tem for the synthesis of hydrogen peroxide by the an to the oxidation step to form further hydrogen perox thraquinone process, said catalyst being deposited on ide, the thus formed oxidized working solution is ex a catalyst consisting of silica, said process comprising tracted or desorbed to reduce the H2O2 content to introducing into the hydrogenation step of the anthra 300—1,000 mg/liter and is then again reintroduced quinone process an anthraquinone working solution into the hydrogenation step. still containing 300 mg/liter up to 1,000 mg/liter of hy 20 7. A process according to claim 6 which is carried out drogen peroxide to thereby completely regenerate the at 60°C. noble metal catalyst to full hydrogenation capacity.