WO2017028905A1

WO2017028905A1 - Gold containing catalyst for the selective deoxygenation of quinone epoxides

Info

Publication number: WO2017028905A1
Application number: PCT/EP2015/068894
Authority: WO
Inventors: Pierre Dournel; Arnaud LEMAIRE
Original assignee: Solvay Sa
Priority date: 2015-08-18
Filing date: 2015-08-18
Publication date: 2017-02-23
Also published as: BR112018003025A2

Abstract

The invention relates to a process for the regeneration of a working solution employed in the production of hydrogen peroxide by an anthraquinone process, said working solution containing alkyltetrahydro-anthraquinone epoxides as degradation products and alkyltetrahydro-anthraquinones as active compounds which comprises treating at least a part of said working solution with a supported gold-based catalyst in the presence of hydrogen to at least partially convert said alkyltetrahydro-anthraquinone epoxides into active alkyltetrahydro-anthraquinones.

Description

GOLD CONTAINING CATALYST FOR THE SELECTIVE DEOXYGENATION OF QUINONE EPOXIDES

The invention relates to a selective epoxide deoxygenation catalyst (epoxide reversion catalyst), to the use of the selective deoxygenation catalyst for the conversion of epoxidized anthraquinone forms into the corresponding ordinary anthraquinone forms (selective epoxide reversion). The invention also relates to a process of converting epoxidized anthraquinone forms into the corresponding ordinary anthraquinone forms employing said selective epoxide deoxygenation catalyst. Furthermore, the invention relates to a process for the manufacture of hydrogen peroxide by the AO-process comprising a selective epoxide reversion wherein the selective epoxide deoxygenation catalyst of the present invention is employed in converting epoxidized anthraquinone forms into the corresponding ordinary anthraquinone forms.

Epoxides are very reactive cyclic ethers of an organic compounds with three ring atoms, wherein compared to cyclopropane one carbon atom in the ring is replaced by an oxygen atom. This epoxide ring approximately defines an equilateral triangle, which makes it highly strained. The strained ring makes epoxides more reactive than other ethers. Thus, epoxides are very reactive compounds and may be hazardous compounds that may be formed as undesired byproducts during oxidation reactions involving olefinic and/or aromatic organic compounds. Especially, due care must be taken in industrial processes, wherein the formation and accumulation of epoxides may occur as degradation or byproducts, in order to manage the associated risks, for example, by monitoring the level of undesired epoxides and appropriate measures like side- stream processes to decompose formed epoxides and/or to otherwise purify the reaction media from said epoxides in such industrial processes.

An industrially very important process, wherein undesired epoxides may play a role, is the manufacture of hydrogen peroxide by the anthraquinone auto- oxidation process (the so-called AO-process), wherein a solution of organic compounds like anthraquinones and/ tetrahydro anthraquinones in a suitable, usually organic, solvent (the so-called working solution) are used in a continuous hydro- genation and oxidation reaction cycle to produce hydrogen peroxide. In these industrial, including large scale, applications for the production of hydrogen peroxide the anthraquinones are hydrogenated to the corresponding dihydroquinones, which then transfer hydrogen to oxygen to form hydrogen peroxide. In this AO- process for the manufacture of hydrogen peroxide, in a cyclic process of hydro- genating the anthraquinone to the corresponding dihydroanthraquinone, subsequently oxidazing the dihydroanthraquinone to convert back into the anthra- quinone and thereby forming H₂O₂, which is then extracted with water, several billion kilograms of Η₂0₂ are produced annually.

In the industrial application of anthraquinones for the production of hydrogen peroxide commonly, as the so-called working compounds, 2-Alkyl-9,10- anthraquinone, especially 2-ethyl-9,10-anthraquinone and/or 2-amyl-9,10-anthra- quinone or other related alkyl derivatives are used, rather than the unsubstituted anthraquinone itself. Also, it is common to use the tetrahydro anthraquinones, eg. like 2-alkyl-9,10-tetrahydro-anthraquinone, especially 2-ethyl-9,10-tetrahydro anthraquinone and/or 2-amyl-9,10-tetrahydro anthraquinone or other related alkyl derivatives in the industrial production of hydrogen peroxide. Both, 2-alkyl anthraquinones and 2-alkyl tetrahydro anthraquinones, may also be used in combination in the industrial production of hydrogen peroxide.

The known anthraquinone process (AO-process), in which hydrogen peroxide is produced by reducing anthraquinones with hydrogen and subsequently oxidizing the dihydroanthraquinone with oxygen, is subjected to a number of complications caused by the repeated reductions and oxidations of the working solutions, which lead to a number of more or less known undesired by-products. Thus, continuous working of the cyclic process for producing hydrogen peroxide leads to formation of a degraded working solution containing a complex mixture of anthraquinone by-products and/or degradation products, which cannot take part in the production of hydrogen peroxide, and some of these degradation products are derived from the useful quinone content of the working solution. A class of such degradation products has been isolated and is described as quinone epoxides. It has been found in the state of the art that at least a portion of these by-products can be regenerated to hydrogen peroxide forming material, and numerous proposals have been described in literature for regenerating the degraded working solution and or otherwise treating the working solution containing the working compound, namely said anthraquinones and/ or tetrahydro anthraquinones, including proposals for mitigating the problem of undesired epoxides of the anthraquinones which must be eliminated from the cyclic AO- process in order to avoid epoxide accumulation and the risk of hazardous events by spontaneous decomposition of the epoxide ring. Such epoxides may particu- larly be formed in the AO-process for the manufacture of hydrogen peroxide if a working solution containing tetrahydro anthraquinones as a working compound is used, e.g. then tetrahydro anthraquinone epoxides may be formed. Also, if the working compound in the working solution is an anthraquinone, nevertheless tetrahydro anthraquinone epoxides may be formed because of incidental over- hydrogenation of the anthraquinone to tetrahydro anthraquinone and subsequent epoxide formation thereof. For sake of clarity, the term "degradation products", as used here in the context of the present invention does not apply to tetrahydro derivatives of the anthraquinone working compound, which may be formed during the hydrogenation step of the AO-process or which may intentionally be present in the working solution as the or one of the working compounds.

Thus, undesired epoxides of the anthraquinones may be formed which must be eliminated from the cyclic AO-process in order to avoid accumulation of epoxide and the risk of hazardous events by spontaneous decomposition of the epoxide ring. In order to avoid accumulation of unwanted anthraquinone products in the working solution, e.g. such like quinone epoxides, anthrones and oxanthrones, subsequent regeneration steps are necessary and described in the state of the art. For example, it is a commonly known technique to provide a side-stream of a hydrogenated working solution containing quinone epoxides in contact with basic alpha or gamma aluminum oxide at temperatures 50-140 °C. Also, it is known to treat the working solution with aluminium oxide. When the regeneration steps are performed by treating the working solution by aluminum oxide, remarkable amounts of aluminum oxide are needed. Furthermore, the aluminum oxide is deactivated by water formed in the regeneration step. The aluminum oxide is also gradually covered by polymeric aromatic by-products resulting from the polymerization of the aromatic compounds of the aromatic solvent commonly used in the working solution. Therefore, the aluminum oxide used for the regeneration steps must be changed occasionally. Regenerating the working solution is a costly and sometimes a limiting step of the process. Any improvement in increasing the effectivity of the regeneration steps or the life time of the aluminum oxide will result in substantial savings in the cost of the production of hydrogen peroxide.

Since the used aluminum oxide is contaminated by anthraquinone derivatives and by the phenolic derivatives, the purification of the used aluminum oxide discharged from the hydrogen peroxide process has been found too expensive to carry out. Being a relatively non-toxic material, it is commonly stored to landfill areas. However, the storage of the used aluminum oxide to landfill areas implicates an environmental problem at least by occupying a remarkable space in the landfill area. Therefore, also from an environmental point of view, it is extremely desirable to reduce the consumption of aluminum oxide in the production of hydrogen peroxide.

Further methods for the regeneration of the working solution used in the production of hydrogen peroxide, also appear in the more recent patent literature.

The US 6946061 (2005) describes a method of regenerating hydrogenated and/or oxygenated alkyl anthraquinones and/or alkyl anthrahydroquinones to alkyl anthraquinones and/or alkyl anthrahydroquinones, or a method for regenerating a working solution containing hydrogenation and/or oxidation products of said alkyl anthraquinones and/or alkyl anthrahydroquinones dissolved in at least one solvent, wherein the reaction is carried out in the presence of a catalyst under electromagnetic irradiation, e.g. microwave irradiation to convert the hydrogen- ation and/or oxidation products of alkyl anthraquinones and/or alkyl anthrahydroquinones to productive alkyl anthraquinones and/or alkyl anthrahydroquinones. The catalyst may be any material capable of absorbing the microwave irradiation, and for example, is selected from the group consisting of aluminium oxides, zeolites, magnesium oxide and silicates, wherein aluminium oxides are preferred. The regeneration is preferably carried out at temperatures of from 25 °C to 250 °C, wherein a portion of the working solution containing hydrogenation and oxidation products separated from the cyclic process for the production of hydrogen peroxide, as a side- stream, and the upgraded side- stream is then recirculated to the cyclic process, in order to ensure that the anthraquinone by- products are not accumulated in the cyclic AO-process.

The US 2009/0018013 patent application (2009) describes a catalyst for regenerating a working solution usable for producing hydrogen peroxide by an anthraquinone method, the catalyst being produced by a method, wherein active alumina is treated with a 20% by weight to saturated aqueous solution of a magnesium salt, treated with ammonia and the resultant substance is then burned. Preferably, the magnesium salt used is magnesium chloride, and the amount of magnesium supported to the active alumina as a result of treating the active alumina with the aqueous solution containing the magnesium salt is 1 to 50% by weight with respect to the weight of post-burning magnesium- supported active alumina. Furthermore, after burning, a metal compound containing at least one type of metal selected from the group consisting of palladium, rhodium, ruthenium and platinum is supported in an amount of 0.1 to 10% by weight with respect to the weight of post-burning magnesium- supported active alumina.

In the state of the art most widely a two-step solid reversion is applied for the epoxide reversion in the AO-process. This solid reversion is a reaction is per- formed in a column which is filled with a solid material of alumina or alumino- silicate and the reaction takes place at high temperature usually between 120 and 180 °C. In a first step, the alkyl tetrahydro anthraquinone epoxide (RTEQ) is reduced with a noble metal catalyst on a highly acidic or basic support in the presence of hydrogen in order to yield the corresponding hydroxy- form of the alkyl tetrahydro anthraquinone (RTHQ); in a second step, then hydroxy- form of the alkyl tetrahydro anthraquinone (RTHQ) is dehydrated, e.g. water is eliminated, to yield the alkyl tetrahydro anthraquinone (RTQ). The high temperatures are required in order to achieve the dehydration of the RTHQ into RTQ, e.g. of the ATHQ and/or ETHQ into the ATQ and/or ETQ. However, the problem of working at such high temperature is the formation of other by-products, e.g. such as polymeric compounds that contribute to quinone consumption. The solid material adsorbs progressively such by-products and becomes inactive on longer term. Finally, the inactive solid material cannot be reactivated and must be disposed. This disposal generates a solid waste, and to get rid of it, normally it is burned in a cement kiln. Although, the described two-step solid state deoxygen- ation process of the state of the art is satisfying if applied in common large to mega-scale hydrogen peroxide production AO-processes, it is difficult to scale said two-step solid state deoxygenation process down to medium and/or small- scale hydrogen peroxide production capacities.

Despite all the efforts in the prior art described here above, it has been found that the prior art regenerating processes cannot be satisfactorily employed in every type of cyclic process for the production of hydrogen peroxide by the anthraquinone process or still have disadvantages, and thus, there is yet a desire for improved regeneration processes and suitable means therefore.

Thus, it is an objective of the present invention to provide for improved regeneration processes, in particular for improved anthraquinone epoxide conversion processes, and means therefore capable of more effectively regenerating non-productive anthraquinones and anthraquinone derivatives of the hydrogen peroxide working solution, and in particular to convert anthraquinone epoxides, especially tetrahydro anthraquinone epoxides, present in the aged working solution to anthraquinones, especially tetrahydro anthraquinones, capable of producing hydrogen peroxide. It is a further objective of the present invention that said improved regeneration processes, in particular said improved anthraquinone epoxide conversion processes, and means therefore, in addition of being employable in a side-stream process for the regeneration of a working solution used in an AO-process for the production of hydrogen peroxide, are also suitable to be directly employed in the cyclic itself in a sustainable manner and also over a longer period of time. In particular in such improved anthraquinone epoxide conversion processes and means therefore should be suitable for AO-processes that do not involve a permanent regeneration step, especially not a permanent side-stream regeneration step, for the AO-process working solution. Yet a further objective of the present invention is that said improved regeneration processes and the means therefore are also applicable in small-to-medium size AO- processes for the production of hydrogen peroxide.

According to the invention these objectives are achieved by providing a selective epoxide deoxygenation catalyst, by the use of the selective epoxide deoxygenation catalyst for converting epoxide forms of anthraquinones back into the underlying anthraquinone form, the respective epoxide reversion process, and the process for the manufacture of hydrogen peroxide by the AO-process comprising said selective epoxide reversion, as each defined in the claims and as hereinafter described in more detail.

In summary the present invention relates to a method of regenerating epoxides of (alkyl) anthraquinones and/or (alkyl) anthrahydroquinones, or a working solution comprising said (alkyl) anthraquinone and/or (alkyl) anthrahydroquin- one epoxides, into the underlying quinone form in the presence of a catalyst. More specifically, in this regard the present invention also relates to a regeneration method of a working solution in a hydrogen peroxide production process utilizing an anthraquinone method, and wherein various by-products which do not participate in the hydrogen peroxide production may be formed in the ageing working solution. According to the invention these by-products, e.g. specifically the epoxides of (alkyl) anthraquinones and/or (alkyl) anthrahydroquinones, can efficiently be converted to the respective anthraquinones and/or anthrahydroquinones being effective as working compound in the production of hydrogen peroxide. While in this AO-process for the manufacture of hydrogen peroxide the hydrogenation and oxidation procedure is repeated, (alkyl) tetrahydro anthra- quinone epoxides, (alkyl) hydroxyanthrones (e.g. oxanthrone) and the like are produced by side reactions. The (alkyl) tetrahydro anthraquinone epoxides, (alkyl) hydroxyanthrones and the like compounds cannot produce hydrogen peroxide, even when repeatedly subjected to the reduction and oxidation. The production of these useless compounds is relatively small per occurrence of the reduction and oxidation. However, while the circulation is repeated, the above mentioned compounds are accumulated in the working solution and cause various troubles and/ or safety concerns.

The present invention overcomes troubles and safety concern, and it also overcomes the disadvantage of solid waste of the prior process and it provides for a simple and selective epoxide reversion for converting undesired epoxide forms of anthraquinones, in particular epoxide forms of tetrahydro anthraquin- ones, especially epoxide forms of 2-alkyl-tetrahydro anthraquinone, e.g. such as 2-amyl-tetrahydro anthraquinone epoxide and/or 2- ethyl-tetrahydro anthraquinone epoxide, back into the underlying quinone form. Said epoxide reversion according to the invention can be applied as a side- stream to an industrial process and/or preferably directly in a cyclic industrial process itself, which process is in need of such conversion or such conversion is advisable. Preferably, the present invention is applied in such an industrial process which is a cyclic AO-process for the manufacture of hydrogen peroxide. A further achievement of the present invention is providing a simple and selective epoxide reversion for converting said undesired epoxide forms of an anthraquinone, in particular of an tetrahydro anthraquinone back into the underlying quinone form, wherein the epoxide reversion is easily scalable to a wide range of desired production capacities, and in particular also applicable for small-to-medium scale AO- processes for the manufacture of hydrogen peroxide. Yet another achievement of the present invention is providing an improved anthraquinone epoxide conversion processes and means therefore which are suitable for AO-processes that do not involve a permanent regeneration step, especially not a permanent side- stream regeneration step, for the AO-process working solution.

Also the present invention provides a selective epoxide deoxygenation catalyst (epoxide reversion catalyst), the use thereof for the conversion of epoxi- dized quinone forms into the corresponding ordinary quinone forms, to provide a process of converting epoxidized quinone forms into the corresponding ordinary quinone forms, and especially also to provide a process for the manufacture of hydrogen peroxide by the AO-process comprising a selective epoxide reversion wherein the selective deoxygenation catalyst of the present invention is employed in converting epoxidized quinone forms into the corresponding ordinary quinone forms, particularly for converting epoxidized anthraquinone forms into the corresponding ordinary anthraquinone forms.

Although, in the state of the art there is some recent scientific literature related to metal catalysts for the deoxygenation of epoxides in the context of organic synthesis exemplified by simple molecular structures, hitherto for more complex anthraquinone structures, especially tetrahydro anthraquinone structures, and in particular for those anthraquinones, especially tetrahydro anthraquinones, employed as working compounds in the working solution of an AO-process for the production of hydrogen peroxide, no such metal catalyst were yet available in the state of the art prior to this invention.

For example, Takato Mitsudome et al. have described supported gold and silver nanoparticles for catalytic deoxygenation of epoxides into alkenes for organic synthesis (Angew. Chem. Int. Ed. 2010, 49, 5545-5548); and Akifumi Noujima et al. similarly have described the selective deoxygenation of epoxides to alkenes with molecular hydrogen in organic synthesis using a hydrotalcite- supported gold catalyst, including a concerted effect between gold nanoparticles and basic sites on a support (Angew. Chem. Int. Ed. 2011, 50, 2986-2989). Other authors have described supported gold nanoparticles for the CO catalyzed or CO mediated deoxygenation of epoxides: see for example, Takato Mitsudome et al. describing the room-temperature deoxygenation of epoxides with CO catalyzed by hydrotalcite- supported gold nanoparticles in water (Chem. Eur. J. 2010, 16, 11818-11821); and Ji Ni et al. describing the mild and efficient CO-mediated eliminative deoxygenation of epoxides catalyzed by supported gold nanoparticles (Chem. Commun. 2011, 47, 812-814). However, none of the scientific literature, which is directed to mere organic synthesis, discloses nor indicates the suitability of supported gold-based catalysts for deoxygenation of epoxides of the more complex anthraquinone structures, nor their suitability in the more complicated industrial cyclic process of producing hydrogen peroxide by the AO-process. Contrary to said scientific literature, as described above and known from patent literature, the conversion of especially tetrahydro anthraquinone epoxides is conventionally performed in the state of the art with basic materials like alumina at relatively high temperatures of e.g. 120 °C to 160 °C. Although not intended being bound by theory, it is believed that in this conventional conversion of for example alkyl tetrahydro anthraquinone epoxides (e.g. RTEQ) to useful alkyl tetrahydro anthraquinone (RTQ), first the epoxide ring is easily opened to result in the hydroxy- form of the alkyl tetrahydro anthraquinone (RTHQ) from which then due to the high temperature of e.g. 120 °C to 160 °C water is eliminated to yield the alkyl tetrahydro anthraquinone (RTQ). Unfortunately, by-products are also formed leading to consumption of the alkyl tetrahydro anthraquinone over time, and tar is accumulating on the alumina. Surprisingly, it was found by the present invention that with a supported gold-based catalyst the alkyl tetrahydro anthraquinone epoxides (RTEQ) can be easily and selectively reduced in the presence of hydrogen to the useful alkyl tetrahydro anthraquinones (RTQ) at milder temperatures, e.g. below 120 °C, and thereby minimizing the risk of forming disadvantageous by-products like tar and other degradation products. The supported gold-based catalyst is highly selective in only reducing the epoxide without over-hydrogenating the anthraquinone ring and it is not able to reduce the quinone group to the dihydroquinone. Therefore, the present invention can be advantageously used for the selective conversion and elimination of anthraquinone epoxides in working solutions of AO-processes for the production of hydrogen peroxide, without negatively interfering with the AO-process itself, e.g. it does not negatively interfere with the hydrogenation step of an AO-process and may be even combined with said hydrogenation step.

In an embodiment the invention relates to a process for the regeneration of a working solution employed in the production of hydrogen peroxide by an anthraquinone process, said working solution containing alkyl tetrahydro anthraquinone epoxides as degradation products and alkyl tetrahydro anthraquinones as active compounds, which comprises treating at least a part of said working solution with a supported gold-based catalyst in the presence of hydrogen to at least partially convert said alkyl tetrahydro anthraquinone epoxides into active alkyl tetrahydro anthraquinones.

In another embodiment the invention relates also to the supported gold- based catalyst itself as defined hereinafter in the context of the process for the regeneration of a working solution employed in the production of hydrogen peroxide by an anthraquinone process, wherein said working solution contains alkyl tetrahydro anthraquinone epoxides as degradation products and alkyl tetrahydro anthraquinones as active compounds, and which supported gold-based catalyst is advantageous for treating at least a part of said working solution in the presence of hydrogen to at least partially convert said alkyl tetrahydro anthraquinone epoxides into active alkyl tetrahydro anthraquinones.

In the gold-based catalyst gold (Au) is present at least in a catalytically active amount. The catalyst may comprise optionally further catalytically active amounts of one or more other co-metals, especially of such co-metal being selected from the group consisting of any noble metal other than gold. Particularly such co-metals may be selected from one or more co-metals selected from the group consisting of Pd (palladium), Pt (platinum), Rh (rhodium) and Ru (ruthen- ium). Such co-metals may be present in a total amount of up to about 25 % by wt., preferably of up to about 15 % by wt., more preferably of up to about 10 % by wt., and most preferably of up to about 5 % by wt., each compared to the contained amount of gold. Accordingly, the co-metals may be present in a total amount of from about 0.1 to 25 % by wt., preferably of from about 0.1 to 15 % by wt., more preferably of from about 0.1 to 10 % by wt., and most preferably of from about 0.1 to 5 % by wt., each compared to the contained amount of gold. But preferably gold is the only catalytically active noble metal, and then the catalyst does not comprise any other noble metal. Most preferably, gold is the only catalytically active metal present in the supported catalyst.

The term "catalytically active amount", or comparable or similar terms like

"catalytic quantity", as used herein refers to an amount which can bring about regeneration, e.g. the conversion of an anthraquinone epoxide into the underlying anthraquinone, without having a retarding effect on the anthraquinone process, i.e. an amount sufficient to enable a workable regenerated working compound or working solution to be obtained but insufficient to adversely affect its operabi- lity. The abbreviation "by wt." has the meaning "by weight" throughout the present application hereinbefore and hereinafter.

Thus, in the process according to the invention, the catalytically active amount of gold, and, if applicable, of the optional one or more co-metals, is adapted to the operating conditions such that the working solution is treated in a temperature range of from 30 °C to 150 °C. Preferably the process of the invention is operated at a temperature of from 40 °C to 100 °C, and more preferably at a temperature corresponding to temperatures conventionally used in the anthraquinone process. A most preferred temperature is in the range of from 50 °C to 90 °C, and in a practical example the temperature is at about 80 °C.

Generally, the meaning of the term "about" in the context of the present invention is that a figure, value or parameter and the like may somewhat vary around a given value. For example, regarding temperature "about 80 °C" may mean in a broader sense 80 +/- 5 °C, and in a narrower sense e.g. 80 +/- 4 °C, 80 +/- 3 °C, preferably 80 +/- 2 °C, more preferably 80 +/- 1 °C, and most preferably 80.0 +/- 0.5 °C. The catalyst employed in the present invention is a so-called supported catalyst. The term "support" means a catalyst carrier, e.g. a material onto which the catalytically active amount of gold and, if applicable, any of the one or more co-metals are deposited. In the context of the present invention the term

"support" usually denotes a "dehydrated support", since it is known to the skilled person that support materials always may contain some adsorbed water. The catalyst support or carrier may be a "slurry support" for a slurry type process or it may be a "fixed-bed support" for a fixed-bed type process. Thus, according to the invention, the catalytically active amount of gold, and, if applicable, of the optional one or more co-metals, is adapted to the type of the support, e.g. to a slurry support or to a fixed-bed support. For example, then the process or the catalyst, respectively, according to the invention is characterized in that a) if the support is a slurry support, the gold (Au) is loaded onto the slurry support in an amount of up to about 5 % by wt., preferably with an Au amount of from 1 to 3 % by wt., and more preferably with an Au amount of about 2 % by wt.; or

b) if the support is a fixed-bed support, the gold (Au) is loaded onto the fixed- bed support in an amount of up to about 1 % by wt., preferably with an Au amount of from 0.1 to 0.8 % by wt., more preferably with an Au amount of from 0.2 to 0.5 % by wt. most preferably with an Au amount of about 0.3 % by wt.

The meaning of the term "about" is that the amount of gold in the (fresh) catalyst may somewhat vary around the given values. For example, if the support is a slurry support, the given values may vary by e.g. up to +/- 0.2% by wt., preferably by up to +/- 0.1% by wt., and more preferably up to +/- 0.05% by wt., each with respect to the total weight of the catalyst. Thus, a slurry catalyst with an amount of 2% (2.0%) by wt. may slightly vary in the exact amount of gold such as 2% (2.0%) +/- 0.2% by wt., preferably such as 2% (2.0%) +/- 0.1% by wt., preferably such as 2% (2.0%) +/- 0.05% by wt., each with respect to the total weight of the catalyst. For example, if the support is a fixed-bed support, the given values may vary by e.g. up to +/- 0.1% by wt., however provided that in respect of variation of the given minimum amounts the gold still must be present in a catalytic quantity, preferably by up to +/- 0.01% by wt., and more preferably up to +/- 0.005% by wt., each with respect to the total weight of the catalyst. Thus, a fixed-bed catalyst with an amount of 1% (1.0%) by wt. may slightly vary in the exact amount of gold such as 1% (1.0%) +/- 0.1% by wt., preferably such as 1% (1.0%) +/- 0.01% by wt., preferably such as 1% (1.0%) +/- 0.005% by wt., each with respect to the total weight of the catalyst. The same variation applies analogously to the amounts indicated above for any of the one or more co- metals, if present in the catalyst.

In a preferred embodiment of the invention, in the catalysts of the present invention, in particular in those employed in a process according to the invention, the gold is deposited on a support in particulate form. Preferably the deposited gold is in nano-particulate form. In a more preferred embodiment of the invention the deposited gold is in nano-particulate form of from about 0.5 to 20 nm gold particle size, in particular of from about 1 to 20 nm gold particle size, even more preferably of from about 1 to 10 nm gold particle size. Most preferably the deposited gold is in nano-particulate form of form about 1.5 to 3.0 nm gold particle size.

In the embodiments of the invention, e.g. in the catalysts of the present invention, in particular in those employed in a process according to the invent- ion, the gold may be deposited within the porosity of the support and/or onto the surface of the support, preferably onto the surface of the support in an eggshell configuration.

Typically, in the invention aluminium oxide (AI₂O₃), especially gamma- aluminium oxide (gamma- AI₂O₃) or delta-alumina (delta- AI₂O₃) or a mixture of both, gamma and delta alumina, titanium dioxide (amorphous, anatase, brookite, rutile or any crystalline mixtures), hydrotalcite, alumino silicate and magnesium oxide, and any combination thereof can be used as a catalyst support. In general, this catalyst support in the present invention can be in a crystalline, partially crystalline, amorphous or partially amorphous form, but advantageously the catalyst support has, at least in a portion thereof, a morphology as particularly described further below in the context of the preferred alkaline catalyst supports. The skilled person knows how to provide the required support materials and to determine the morphology, as this is well established in the art.

The catalysts of the present invention, in particular in those employed in a process according to the invention, in preferred embodiments of the invention are characterized in that the supported gold-based catalyst comprises gold deposited on an alkaline support, preferably deposited on an alkaline support selected from the group consisting of alumina, titanium dioxide, hydrotalcite, alumino silicate and magnesium oxide, and any combination thereof. The term "alkaline", e.g. as used herein in the context of preferred supports, means a material or compound that exhibit some Bronsted and/or Lewis basic sites, i.e. able to adsorb acid gaseous probes such as C0₂ or S0₂ (measurements through Fourier-transform Infra- Red Spectroscopy (FT-IR) and/or Temperature Programmed Desorption (TPD) studies).

Preferably, the alkaline support is alumina, in particular γ-alumina, or gamma-aluminium oxide (gamma- A1₂0₃) or delta-alumina (delta- A1₂0₃) or a mixture of both gamma- and delta-alumina. Said alumina supports may optionally be coated with an amount of up to about 20 % by wt., preferably with an amount of up to about 15 % by wt., titanium dioxide (Ti0₂, amorphous, anatase, brookite, rutile or any crystalline mixtures). In particular, the alumina supports may optionally be coated with an amount of Ti0₂ from about 1 to 20 % by wt., and more preferably the alumina supports may optionally be coated with an amount of Ti0₂ from about 5 to 15 % by wt.

The morphology of the particulate catalyst support, particularly of the preferred particulate alkaline support, is a further characteristic of preferred embodi- ments of the invention. Thus, in the catalysts of the present invention, in particular in those employed in a process according to the invention, the support morphology, in particular the preferred alkaline support morphology, is particulate and in the shape of irregular particles, trilobes, extrudates, or pellets. Preferably the morphology of the particulate support, in particular the preferred alkaline support morphology, is displayed in a particulate and spherical or cylindrical shape, more preferably in a particulate shape of spheres, and most preferably in particulate shape of spheres that are suitable to be used as a fixed-bed catalyst.

The size of the catalyst support used in the context of the invention as such is not critical to a general practice of the invention for converting quinone epoxides into the corresponding quinone, but in the more specific practice of the invention for converting quinone epoxides into the corresponding quinone in an AO-process for the manufacture of hydrogen peroxide, controlling the size of the catalyst support may be important to the effective and/or efficient use of the epoxide conversion catalyst.

Thus, in preferred embodiments of the invention, the particulate support, especially the particulate alkaline support, if the support is a slurry support, is of a mean particle size of about 25 μιη to 200 μιη, preferably of a mean particle size (in diameter) of about 50 μιη to 160 μιη, more preferably of a mean particle size of about 70 μιη to 140 μιη, and most preferably of a mean particle size of about 125 μιη. Or otherwise, in preferred embodiments of the invention, the particulate support, especially the particulate alkaline support, if the support is a fixed-bed support, is of a mean particle size (in diameter) of about 0.5 mm to 5.0 mm, preferably of a mean particle size of about 1.0 mm to 3.5 mm, more preferably of a mean particle size of about 2.0 mm. Particularly in fixed bed reactors, a suitable support size would generally be about, 1.0 to 5.0 mm, preferably about 1.0 to 4.0 mm or about 1.0 mm to 3.5 mm, and most preferably about 1.5 to 2.5 mm, in diameter, and especially about 2 mm. The support morphology may vary and can be described, e.g., as irregular particles, trilobes, and more preferably as spherical or cylindrical shapes. The given particle size for fixed bed reactions generally have the meaning of mean particle diameter. The meaning of the term "about" is that the particle size of the (fresh) catalyst may somewhat vary around the given values by e.g. up to +/- 0.02 mm, preferably up to +/- 0.01 mm. Thus, for example, in a catalyst of the present invention the particle size of the catalyst can be 0.5 to 5.0 mm +/- 0.02 mm (preferably 0.5 to 5.0 mm +/- 0.01 mm) or 1.0 to 5.0 mm +/- 0.02 mm (preferably 1.0 to 5.0 mm +/- 0.01 mm), preferably 1.0 to 4.0 mm +/- 0.02 mm (preferably 1.0 to 4.0 mm +/- 0.01 mm), and most preferably about 1.0 to 3.5 mm +/- 0.02 mm (preferably 1.0 to 3.5 mm +/-0.01 mm) or 1.5 to 2.5 mm +/- 0.02 mm (preferably 1.5 to 2.5 mm

+/-0.01 mm), and especially about 2 mm +/- 0.02 mm (preferably 2 mm

+/-0.01 mm).

The particle size of the catalyst and/or support in the context of the present invention can be determined by methods well known by the skilled person.

Preferably, the standard particle size distribution for a fixed bed type catalyst is adjusted such that, in % by wt., at least 99 , preferably at least 95 , of the particles are ranging from 0.5 to 5.0 mm or 1.0 to 5.0 mm, more preferably at least 95 % of the particles are in a fraction from 1.0 to 4.0 mm, and most preferably at least 90 % of the particles are in a fraction from 1.0 to 3.5 mm.

Furthermore, in a preferred embodiment, the supported gold-based catalyst as defined hereinabove, is a supported gold-based catalyst, which is further characterized in that the support comprises or consists of a porous support with a BET surface area in the range of from 5 m²/g to 1200 m²/g, preferably from 50 m 2 /g to 800 m 27g, and very preferably with a BET surface area in the range of from 100 m 2 /g to 500 m 2 /g. Methods to determine the BET surface area are well- known to those skilled in the art. The supported gold-based catalyst of the invention may be prepared by methods well-known to those skilled in the art. However, in a further aspect the invention also provides for a very suitable method for preparing a supported gold-based catalyst of the invention as defined hereinabove, said method comprising

a) if the support is a slurry support, suspending beads of a slurry support, preferably a slurry support selected from the group of alkaline slurry support as defined in any of the claims 7 to 9, in demineralized water, warming up the obtained suspension to a temperature of from 40 °C to 90 °C, preferably to a temperature of about 70 °C, then dissolving sodium carbonate (Na₂C0₃) in the suspension followed by dropwise adding of an aqueous solution of

tetrachloroaurate acid (HAuCU) over a period of time, subsequently separating off the solids from the suspension and washing the separated-off solids with demineralized water to completely remove alkaline excess, drying the washed solids, then calcinating said solids under oxygen at a temperature in the range of from 300 °C to 700 °C, preferably at a temperature of about 500 °C, and subsequently reducing the calcinated solids with a reducing agent, preferably with hydrogen as reducing agent at a temperature in the range of from 200 °C to 700 °C, preferably at a temperature of about 450 °C, to yield the slurry supported gold-based catalyst; or

b) if the support is a fixed-bed support, impregnating beads of a fixed-bed support preferably a fixed-bed support selected from the group of alkaline fixed- bed support as defined in any of the claims 7 to 9, with a solution of sodium carbonate (Na₂C0₃) dissolved in demineralized water, evaporating the water at a temperature of from 85 °C to 140 °C, preferably at a temperature of about 120 °C, from the mixture containing the impregnated beads followed by dropwise adding of an aqueous solution of tetrachloroaurate acid (HAuCU) over a period of time while continuously further evaporating the water, and subsequently washing the resulting solids with demineralized water to completely remove alkaline excess, drying the washed solids, then calcinating said solids under oxygen at a temperature in the range of from 300 °C to 700 °C, preferably at a temperature of about 500 °C, and thereafter reducing the calcinated solids with a reducing agent, preferably with hydrogen as reducing agent at a temperature in the range of from 200 °C to 700 °C, preferably at a temperature of about 450 °C, to yield the fixed-bed supported gold-based catalyst. The supported gold-based catalyst of the invention as defined above is very suitable for (a) use as an epoxide reversion (deoxygenation) catalyst for deoxygenating alkyl tetrahydro anthraquinone epoxides into active alkyl tetrahydro anthraquinones, as described herein; and/or for (b) use in the process for the regeneration, in the sense of epoxide reversion (deoxygenation), of a working solution as defined herein; and/or for (c) use as an epoxide reversion (deoxygenation) catalyst in a process for the manufacture of hydrogen peroxide by an anthraquinone process as defined herein.

The gold-based catalyst described above for the process of the present invention for the regeneration, in the sense of epoxide reversion (deoxygenation), of a working solution employed in the production of hydrogen peroxide by an anthraquinone process, said working solution containing alkyl tetrahydro anthraquinone epoxides as degradation products and alkyl tetrahydro anthraquinones as active compounds, which anthraquinone process comprises treating at least a part of said working solution with the said supported gold-based catalyst in the presence of hydrogen to at least partially convert said alkyl tetrahydro anthraquinone epoxides into active alkyl tetrahydro anthraquinones, may be also used in combination with other catalysts. Thus, in a particular embodiment of the present invention the gold-based catalyst is used in combination with a supported hydrogenation catalyst for the hydrogenation step in the anthraquinone process, preferably in combination with a supported palladium (Pd) hydrogenation catalyst for the hydrogenation step in the anthraquinone process for the manufacture of hydrogen peroxide. More preferably the gold-based catalyst of the invention is used in combination with a SiCVsupported palladium (Pd) hydrogenation cata- lyst for the hydrogenation step in the anthraquinone process for the manufacture of hydrogen peroxide, and most preferably in combination with a SiCVsupported palladium (Pd) hydrogenation catalyst for a fixed-bed anthraquinone process for the manufacture of hydrogen peroxide.

Therefore, the supported gold-based catalyst described above is also very suitable in a process for the manufacture of hydrogen peroxide by an anthraquinone process. Accordingly, the invention also relates to a process for the manufacture of hydrogen peroxide by an anthraquinone process, wherein a working solution is employed that comprises alkyl tetrahydro anthraquinones as active compounds and wherein alkyl tetrahydro anthraquinone epoxides may be formed as degradation products, and said anthraquinone process being characterized in that the anthraquinone process involves a process for the regeneration, in the sense of epoxide reversion (deoxygenation), of the said working solution as defined above in the context of the present invention.

When used in the AO-process such a combination of the supported gold- based catalyst with an AO-process hydrogenation catalyst may be implemented in various manners. For example, the supported gold-based catalyst of the invention, on the one hand, and supported hydrogenation catalyst for the hydrogenation step in the anthraquinone process, on the other hand, may be placed in the same reactor (hydrogenator) in any order or mixture; or they may be placed separately in different reactors in any order. In these options the regeneration, in the sense of epoxide reversion (deoxygenation), of the working solution in the anthraquinone process (AO-process) is integrated part of the AO-process cycle (AO-process loop). If the supported gold-based catalyst (epoxide deoxygenation catalyst) of the invention and the AO-process hydrogenation catalyst are placed in the same reactor, that is to say in the hydrogenator, preferably the circulating working solution and the hydrogen feed are first passing the epoxide deoxygenation catalyst of the invention and then the AO-process hydrogenation catalyst. If the epoxide deoxygenation catalyst of the invention and the AO-process hydrogenation catalyst are placed separately in different reactors, the reactor with the epoxide deoxygenation catalyst of the invention may be integrated part of the of the AO-process cycle, e.g. the reactor is arranged within the AO-process loop, preferably before the AO-process hydrogenator, or the reactor with the epoxide deoxygenation catalyst of the invention may be operated as a side- stream reactor. A combination of side-stream operation and operation of the epoxide deoxygenation catalyst of the invention within the AO-process loop, e.g. in a separate reactor and/or in the same reactor as the AO-process hydrogenation catalyst in the AO-process loop, is possible, too.

Although both arrangements, that within the AO-process loop or that as a side- stream, generally can be chosen for any type and size of the AO-process for the manufacture of hydrogen peroxide, usually the reactor with the epoxide deoxygenation catalyst of the invention will be operated in a side-stream if the AO-process is a large-to-mega scale hydrogen peroxide production process, whereas, if the AO-process is a small-to-medium scale hydrogen peroxide production process the reactor with the epoxide deoxygenation catalyst of the invention can be preferably integrated part of the AO-process cycle, e.g. then the epoxide deoxygenation catalyst may be placed in a separate reactor and/or in the same reactor as the AO-process hydrogenation catalyst in the AO-process loop. Particularly, the invention is very suitable to be applied in AO-processes for the manufacture of hydrogen peroxide. The invention may be employed in any type and size of the AO-process for the manufacture of hydrogen peroxide, and is advantageously employed especially in small-to-medium scale hydrogen peroxide production AO-processes and/or hydrogen peroxide production AO- processes that do not have a permanent (conventional) regeneration of the working solution. Thus, in an embodiment the invention also relates to a process for the manufacture of hydrogen peroxide by an anthraquinone process employing a supported gold-based catalyst for the regeneration, in the sense of epoxide reversion (deoxygenation), of the working solution according to the invention, characterized in that

(a) the regeneration, in the sense of epoxide reversion (deoxygenation), of the working solution is performed permanently or intermittently, preferably characterized in that the regeneration of the working solution is performed as continuous regeneration; and/or

(b) the anthraquinone process (AO-process) is a small-to-medium scale AO- process which is run with a capacity of up to 20 ktpa, preferably with a capacity of up to 10 ktpa, (as 100 %) hydrogen peroxide production, and most preferably with a capacity of up to 7.5 ktpa, (as 100 %) hydrogen peroxide production, in particular with a capacity of 2 to 7.5 ktpa, (as 100 %) hydrogen peroxide production.

In case of a small-to-medium scale AO-process which is run with a capacity as indicated hereinbefore, e.g. a small-to-medium scale AO-process which is run with a capacity of up to 20 ktpa or with any other capacity or capacity range as indicated hereinbefore, the present invention is very useful if such small-to-medium scale AO-process are performed without a conventional reversion unit for continuous reversion of the working solution, e.g. without a reversion unit that is typically continuously applied in industrial large-to-mega scale production facilities for the manufacture of hydrogen peroxide by the AO- process. Such a small-to-medium scale AO-process for the production of hydrogen peroxide without a reversion (regeneration) unit is described in the PCT patent application PCT/EP2012/069414 (filed on October 2, 2012), which hereby is incorporated by reference. Therefore, the present invention also relates to a process for the manufacture of hydrogen peroxide by the AO-process comprising the two alternate essential steps of

(a) hydrogenation of a working solution in a hydrogenation unit in the presence of a catalyst, wherein said working solution contains at least one alkyl anthraquinone dissolved in at least one organic solvent, to obtain at least one corresponding alkyl anthrahydroquinone compound; and

(b) oxidation of said at least one alkyl anthrahydroquinone compound to obtain hydrogen peroxide in an oxidation unit; and further comprising the step of

(c) extracting the hydrogen peroxide formed in the oxidation step in an extraction unit,

characterized in that the hydrogenation, oxidation and extraction steps are performed in an reactor system which is designed as a compact modular system of a hydrogenation unit, an oxidation unit and an extraction unit, and wherein said reactor system is configured to operate without a reversion unit, in particular without a reversion unit for continuous reversion of the working solution, as a small to medium scale AO-process with a production capacity of hydrogen peroxide of up to 20 kilo tons per year, wherein the working solution and/or the catalyst are replaced and/or treated for regeneration or reactivation only intermittently or periodically.

This small-to-medium scale AO-process is especially performed such that the working solution and/or the catalyst are only intermittently with low frequency or periodically with low frequency replaced for regeneration or reactivation, e.g. only after periods of several months operation, and wherein preferably the working solution is replaced and/or treated for regeneration only intermittently or periodically with a low frequency of only about monthly periods, preferably only after periods of at least 3 months in the loop of the AO- process steps (a), (b) and (c). In particular, this small-to-medium scale AO- process for the manufacture of hydrogen peroxide is performed such that the working solution is replaced and/or treated for regeneration only intermittently or periodically after periods of at least 6 month, preferably at least 9 months, and more preferred at least 12 months

Furthermore, in case of a small-to-medium scale AO-process which is run with a capacity as indicated hereinbefore, e.g. a small-to-medium scale AO- process which is run with a capacity of up to 20 ktpa or with any other capacity or capacity range as indicated hereinbefore, the present invention is very useful if such small-to-medium scale AO-process is remotely controlled. Such a small-to- medium scale AO-process for the production of hydrogen peroxide without a reversion (regeneration) unit is described in the PCT patent application

PCT/EP2012/069408 (filed on October 2, 2012), which hereby is incorporated by reference. Therefore, the present invention also relates to a process for the manufacture of hydrogen peroxide by the AO-process for the manufacture of hydrogen peroxide comprising the two alternate essential steps of

(b) oxidation of said at least one alkyl anthrahydroquinone compound to obtain hydrogen peroxide in an oxidation unit;

and further comprising the step of

(c) extracting the hydrogen peroxide formed in the oxidation step in an extraction unit, wherein the units of step (a) to (c), optionally together with further ancillary units as appropriate, constitute a hydrogen peroxide production site,

characterized in that one or more of said units are equipped with one or more sensors for monitoring one or more AO-process parameters, optionally involving at least one chemical AO-process parameter, at the hydrogen peroxide production site, said sensors being interconnected with one or more first computers at the hydrogen peroxide production site, said first computers being linked via a communication network to one or more second computers in a control room being remote from the hydrogen peroxide production site, and wherein said control room is remotely controlling, particularly remotely operating and controlling, said hydrogen peroxide production site.

Should the disclosure of any of the patents, patent applications, and publications that are incorporated herein by reference be in conflict with the present description to the extent that it might render a term unclear, the present description shall take precedence over them.

The following examples are intended to explain the invention further without the intent to limit it.

EXAMPLE 1

Synthesis of a Gold-based Catalyst (precipitation, 1 mm large beads) for Fixed-bed

50 g of carrier (1 mm large beads of typically AI₂O₃, hydrotalcite, T1O₂, MgO, alumino silicate) were impregnated with a solution of 5 g of sodium carbonate (Na₂C0₃) dissolved in 100 ml of demineralized water. The solvent was then evaporated from the warmed mixture (120°C) in rotavapor. 300 g of an aqueous solution of hydrogen tetrachloroaurate (HAuC ) was added dropwise over a period of 4 hours with a constant evaporation of water. The resulting solids were then washed with demineralized water until the total removal of alkaline excess. The catalyst was finally dried at 110°C, calcined at 500°C under 0₂ for 4 hours, then reduced under H₂ for 4 hours at 450°C.

The characteristics of the resulting support and the supported catalyst were: The catalysts comprised an amount of gold from 0.1 to 0.8% +/- 0.02% by weight, preferably in an amount of 0.3% (0.30%) +/- 0.01% by weight. The Au loading on supports have been determined by the ICP-OES method. Preferably, Au was dispersed on the outer surface of the support (eggshell type), with an Au thickness inferior to 500 nm, more preferably inferior to 20 nm. The Au profile in the support was characterized by Energy Dispersive X-ray coupled with a Scanning Electronic Microscope (SEM-EDX). Preferably, the Au nanoparticles size was ranging from 0.5 to 5 nm, and preferably narrowly centered on 2 nm. The nanoparticles size distribution was assessed by High-Resolution

Transmission Electronic Microscope (HR-TEM). Preferably, the catalyst particle size was ranging from 0.2 to 5 mm large, more preferably narrowly centered on 2 mm. The catalyst granulometry was determined either by sieving granulometry or laser granulometry. Accessible surface areas (BET method), porous volume and pore size distribution (BJH method) were respectively and preferably ranging from 100 to 500 m²/g, 0.1 to 0.8 cm³/g and 2 to 30 nm. Textural properties were determined by N₂ adsorption-desorption method.

EXAMPLE 2

Synthesis of a Gold-based Catalyst (precipitation, 120 μηι large beads) for Slurry- reactor

50 g of carrier (125 μιη large beads of typically A1₂0₃, hydrotalcite, Ti0₂, MgO, alumino silicate) were suspended in 350 ml of demineralized water warmed and kept at 70°C. 10 g of sodium carbonate (Na₂C0₃) were dissolved in the mixture. 50 ml of an aqueous solution of tetrachloroaurate acid (HAuC ) was added dropwise over a period of 1 hour. The solids were then filtered and washed with demineralized water until the total removal of alkaline excess. The catalyst was finally dried at 110°C, calcined at 500°C under 0₂ for 4 hours, then reduced under H₂ for 4 hours at 450°C.

The characteristics of the resulting support and of the supported catalyst were: The catalyst comprised an amount of gold from 1 to 3% +/- 0.2% by weight, preferably in an amount of 2% (2.0%) +/- 0.1% by weight. The Au loading on supports have been determined by the ICP-OES method. Preferably, Au was dispersed on the outer surface of the support (eggshell type), with an Au thickness inferior to 500 nm, more preferably inferior to 20 nm. The Au profile in the support was characterized by Energy Dispersive X-ray coupled with a Scanning Electronic Microscope (SEM-EDX). Preferably, the Au nanoparticles size is ranging from 0.5 to 5 nm, and preferably narrowly centered on 2 nm. The nanoparticles size distribution was assessed by High-Resolution Transmission Electronic Microscope (HR-TEM). Preferably, the catalyst particle size was ranging from 25 to 200 μιη large, more preferably narrowly centered on 125 μιη. The catalyst granulometry was determined either by sieving granulometry or laser granulometry. Accessible surface areas (BET method), porous volume and pore size distribution (BJH method) were respectively and preferably ranging from 100 to 500 m²/g, 0.1 to 0.8 cm³/g and 2 to 30 nm. Textural properties were determined by N₂ adsorption-desorption method.

EXAMPLE 3

Evaluation of Activity and Selectivity of Catalysts of the Invention

A catalyst of Example 1 (gold 0.2% on 1 mm large δ-Α1₂0₃ beads) was evaluated from the viewpoint of its activity and of its selectivity in the reduction of amyl tetrahydro anthraquinone epoxides (RTEQ) in a batch reactor according to the following procedure; the working solution (150 g), composed of 65 g/kg of amyl tetrahydro anthraquinone epoxides dissolved in the Diisobutlcarbinol-Solvesso mixture (20/80 ratio by weight), which was saturated with water, was hydrogenated at 80°C under a constant pressure of 1.2 bar absolute by a continuous recirculation throughout a bed of catalyst. The catalyst (53 g/kg working solution) was packed in a fixed-bed and the working solution is injected in the hydrogenator co-currently with H₂ in a downflow mode. Conversions of ATEQ and selectivity were assessed by 5 HPLC measurements executed during the hydrogenation course.

The Table 1 exhibits the typical conversion of amyl tetrahydro

anthraquinone epoxides (ATEQ) as a function of the time. ATEQ was quantitatively converted into amyl tetrahydro anthraquinone (ATQ) without formation, through HPLC analyses, of amyl tetrahydro hydroxyanthraquinone (ATHQ) or other non-useful quinones. The ATEQ conversion, with the concomitant production of ATQ, is presented in the following Table 1. Table 1: Conversion table of ATEQ

EXEMPLE 4

A Method for Determining the Particle Size of 1 mm Large Beads

Alumina beads were dispersed into methanol and the particle size distribution was determined during 90 seconds through laser granulometry (Beckman Coulter LS 230). Table 2 shows data exemplifying suitable particle sizes and

distributions. Mean diameter is around 982.7 μιη.

Table 2: Particle size distribution (1 mm)

Size distribution (μιη) Fraction (%) Cumul. fraction (%)

< 780 0 0

786.9 8.24 0

863.9 28.7 8.24

948.3 38 37

1041 21.1 75

1143 3.98 96.1

1255 0 100

> 1377 0 100

Claims

C L A I M S

1. A process for the regeneration of a working solution employed in the production of hydrogen peroxide by an anthraquinone process, said working solution containing alkyl tetrahydro anthraquinone epoxides as degradation products and alkyl tetrahydro anthraquinones as active compounds, which comprises treating at least a part of said working solution with a supported gold- based catalyst in the presence of hydrogen to at least partially convert said alkyl tetrahydro anthraquinone epoxides into active alkyl tetrahydro anthraquinones.

2. A process according to claim 1, characterized in that the working solution is treated in a temperature range of from 30 °C to 150 °C, preferably at a temperature of from 40 °C to 100 °C, more preferably at a temperature corresponding to temperatures conventionally used in the anthraquinone process, most preferably at a temperature in the range of from 50 °C to 90 °C, in particular at about 80 °C. 3. A process according to any of the claims 1 to 2, characterized in that a) if the support is a slurry support, the gold (Au) is loaded onto the slurry support in an amount of up to 5 % by wt., preferably with an Au amount of from 1 to 3 % by wt., and more preferably with an Au amount of about 2 % by wt.; or b) if the support is a fixed-bed support, the gold (Au) is loaded onto the fixed- bed support in an amount of up to 1 % by wt., preferably with an Au amount of from 0.1 to 0.8 % by wt., more preferably with an Au amount of from 0.2 to 0.5 % by wt. most preferably with an Au amount of about 0.

3 % by wt.

4. A process according to any of the claims 1 to 3, characterized in that the gold is deposited on the support in particulate form, preferably nano-particulate form, more preferably in nano-particulate form of from 0.5 to 20 nm particle size, in particular of from 1 to 20 nm particle size, even more preferably of from 1 to 10 nm particle size, and most preferably in nano-particulate form of 1.5 to 3.0 nm particle size.

5. A process according to any of the claims 1 to 4, characterized in that the gold is deposited within the porosity of the support and/or onto the surface of the support, preferably onto the surface of the support in an eggshell configuration.

6. A process according to any of the claims 1 to 5, characterized in that the supported gold-based catalyst comprises gold deposited on an alkaline support, preferably deposited on an alkaline support selected from the group consisting of alumina, titanium dioxide, hydrotalcite, alumino silicate and magnesium oxide, and any combination thereof.

7. A process according to claim 6, characterized in that the alkaline support is alumina, preferably γ-alumina, or gamma-aluminium oxide (gamma- A1203) or delta-alumina (delta- A1203) or a mixture of both gamma- and delta- alumina, optionally coated with an amount of up to 20 % by wt., preferably with an amount of up to 15 % by wt., titanium dioxide (Ti02 , amorphous, anatase, brookite, rutile or any crystalline mixtures), preferably with an amount of Ti02 from 1 to 20 % by wt., more preferably with an amount of Ti02 from 5 to 15 % by wt.

8. A process according to any of the claims 6 to 7, characterized in that the alkaline support morphology is particulate and in the shape of irregular particles, trilobes, extrudates, pellets, preferably particulate and in a spherical or cylindrical shape, more preferably particulate and in the shape of spheres, and most preferably particulate and in the shape of spheres that are suitable to be used as a fixed-bed catalyst.

9. A process according to claim 8, characterized in that the particulate alkaline support is of a mean particle size

a) if the support is a slurry support, of 25 μιη to 200 μιη, preferably of a particle size of 50 μιη to 160 μιη, more preferably of a particle size of 70 μιη to 140 μιη, and most preferably of a particle size of about 125 μιη; or

b) if the support is a fixed-bed support, of 0.5 mm to 5.0 mm, preferably of a particle size of 1.0 mm to 3.5 mm, more preferably of a particle size of about 2.0 mm.

10. A process according to any of the claims 1 to 9, characterized in that the gold-based catalyst is used in combination with a supported hydrogenation catalyst for the hydrogenation step in the anthraquinone process, preferably in combination with a supported palladium (Pd) hydrogenation catalyst for the hydrogenation step in the anthraquinone process, more preferably in combination with an Si02-supported palladium (Pd) hydrogenation catalyst for the hydrogenation step in the anthraquinone process, most preferably in combination with a Si02-supported palladium (Pd) anthraquinone process hydrogenation catalyst for a fixed-bed anthraquinone process.

11. A process for the manufacture of hydrogen peroxide by an

anthraquinone process, wherein a working solution is employed that comprises alkyl tetrahydro anthraquinones as active compounds and alkyl tetrahydro anthraquinone epoxides as degradation products, characterized in that the anthraquinone process involves a process for the regeneration of the said working solution according to anyone of the claims 1 to 10.

12. A process for the manufacture of hydrogen peroxide by an

anthraquinone process according to claim 11, characterized in that

(a) the regeneration of the working solution is performed permanently or intermittently, preferably characterized in that the regeneration of the working solution is performed as continuous regeneration; and/or

(b) the anthraquinone process (AO-process) is a small- to-medium scale AO- process which is run with a capacity of up to 20 ktpa, preferably with a capacity of up to 10 ktpa, (as 100 %) hydrogen peroxide production, and most preferably with a capacity of up to 7.5 ktpa, (as 100 %) hydrogen peroxide production, in particular with a capacity of 2 to 7.5 ktpa, (as 100 %) hydrogen peroxide production.

13. A supported gold-based catalyst as defined in any of the claims 3 to 9, preferably a supported gold-based catalyst as defined in any of the claims 3 to 9, which is further characterized in that the support comprises or consists of a porous support with a BET surface area in the range of from 50 m2/g to 800 m2/g, preferably with a BET surface area in the range of from 100 m2/g to 500 m2/g.

14. A method for preparing a supported gold-based catalyst as defined in claim 13, said method comprising

a) if the support is a slurry support,

suspending beads of a slurry support, preferably a slurry support selected from the group of alkaline slurry support as defined in any of the claims 7 to 9, in demineralized water, warming up the obtained suspension to a temperature of from 40 °C to 90 °C, preferably to a temperature of about 70 °C, then dissolving sodium carbonate (Na2C03) in the suspension followed by dropwise adding of an aqueous solution of tetrachloroaurate acid (HAuC14) over a period of time, subsequently separating off the solids from the suspension and washing the separated-off solids with demineralized water to completely remove alkaline excess, drying the washed solids, then calcinating said solids under oxygen at a temperature in the range of from 300 °C to 700 °C, preferably at a temperature of about 500 °C, and subsequently reducing the calcinated solids with a reducing agent, preferably with hydrogen as reducing agent at a temperature in the range of from 200 °C to 700 °C , preferably at a temperature of about 450 °C, to yield the slurry supported gold-based catalyst; or

b) if the support is a fixed-bed support,

impregnating beads of a fixed-bed support preferably a fixed-bed support selected from the group of alkaline fixed-bed support as defined in any of the claims 7 to 9, with a solution of sodium carbonate (Na2C03) dissolved in demineralized water, evaporating the water at a temperature of from 85 °C to

140 °C, preferably at a temperature of about 120 °C, from the mixture containing the impregnated beads followed by dropwise adding of an aqueous solution of tetrachloroaurate acid (HAuC14) over a period of time while continuously further evaporating the water, and subsequently washing the resulting solids with demineralized water to completely remove alkaline excess, drying the washed solids, then calcinating said solids under oxygen at a temperature in the range of from 300 °C to 700 °C , preferably at a temperature of about 500 °C, and thereafter reducing the calcinated solids with a reducing agent, preferably with hydrogen as reducing agent at a temperature in the range of from 200 °C to 700 °C, preferably at a temperature of about 450 °C, to yield the fixed-bed supported gold-based catalyst.

15. Use of a supported gold-based catalyst as defined in claim 13:

(a) as an epoxide reversion (deoxygenation) catalyst for deoxygenating alkyl tetrahydro anthraquinone epoxides into active alkyl tetrahydro anthraquinones; and/or

(b) in the process for the regeneration of a working solution as defined in any of the claims 1 to 10;

(c) and/or as an epoxide reversion (deoxygenation) catalyst in a process for the manufacture of hydrogen peroxide by an anthraquinone process as defined in any of the claims 11 to 12.