Method for preparing 3-methyl-2-butene-1-aldehyde

Abstract

The invention relates to a method for preparing 3-methyl-2-butene-1-aldehyde, wherein 2-methyl-3-butene-2-ol is reacted to form 3-methyl-2-butene-1-aldehyde in the presence of a catalyst, wherein the catalyst comprises a catalytically active metal and wherein the reaction is carried out at a pH of ≤7.

Description

[0001] The present invention relates to a process for preparing 3-methyl-2-butene-1-al by reacting 2-methyl-3-butene-2-ol in the presence of an oxidant and a catalyst, wherein the catalyst comprises a catalytically active metal and wherein the reaction is carried out at a pH of ≤7. Technical Background:

[0002] 3-Methyl-2-buten-1-al ("isopentenal") is an important chemical intermediate for the preparation of terpene flavors, such as citral, and for the preparation of vitamins, such as vitamin E, and is therefore of great technical and economic importance.

[0003] The most common procedure for preparing isopentanol uses isopentanol (3-methyl-2-butene-1-ol) or isopentanol (3-methyl-3-butene-1-ol) as starting compound. Therefore, EP 0 881 206 describes the oxidation of these starting compounds with oxygen in the gas phase using a silver catalyst. The selectivity of this method can be improved by further developing a catalytic system such as disclosed in WO 2008 / 037693. However, in order to obtain enough conversions and selectivities, the procedure in the gas phase must be carried out at a temperature of about 360° C. while maintaining a short contact time. This is required to ensure sufficient reactivity on the one hand and to prevent the decomposition reaction of sensitive reactants and products on the other hand. These conditions can only be achieved using expensive equipment.

[0004] The oxidation of prenol to prenaldehyde in the aqueous liquid phase is described in Green Chem. 2015, 17, 2325-2329; Green Chem. 2009, 11, 816-820; Adv. Funct. Mater. 2012, 22, 591-599 and Molecular Catalysis A: Chemical 2010, 331 (1-2). Prenol (3-methyl-2-butene-1-ol) can only be obtained by isomerization of prenyl alcohol (3-methyl-3-butene-1-ol), which itself can only be obtained on a large scale by the energy-consuming high-pressure reaction of isobutene and formaldehyde.

[0005] An object of the present invention is to provide a simple and effective method for preparing 3-methyl-2-butene-1-aldehyde, which is suitable for industrial scale preparation. The method should be easy to operate, provide high yield and high selectivity of 3-methyl-2-butene-1-aldehyde, and thus avoid excessive oxidation to the corresponding acid. In addition, the use of toxic or expensive reagents should be avoided. In addition, the method should allow high space-time yield (STY), which is crucial for economic applicability in industrial scale methods. Space-time yield (STY) is defined as the amount of product obtained per reaction volume per hour, expressed in g / l / h. Reaction volume is the volume of the reactor in which the reaction occurs. In the case where the reaction is carried out in a cylindrical reactor, the reaction volume is the volume of the cylindrical reactor in which the reaction occurs. Particularly interesting is a method that allows high space-time yield within the reaction time, wherein at least 40%, preferably at least 50% conversion is achieved. In addition, it is desirable to provide a method that can easily recycle aldehydes.

[0006] Furthermore, the process should allow a high specific activity (SA), which is essential for economic viability in industrial-scale processes. The specific activity (SA) is defined as the amount of product obtained per amount of catalytically active metal reacted per hour, expressed in g / g / h. Of particular interest are processes that allow a high specific activity over the reaction time, wherein a conversion of at least 40%, preferably at least 50%, is achieved. Summary of the invention:

[0008] It has now been found that these objects are achieved by a process in which 2-methyl-3-butene-2-ol is reacted to give 3-methyl-2-butene-1-al in the presence of an oxidizing agent and a catalyst, wherein the catalyst comprises a catalytically active metal and wherein the reaction is carried out at a pH of ≤7.

[0009] It has been surprisingly found that 3-methyl-2-butene-1-aldehyde can be obtained with excellent yield and selectivity using the method according to the present invention. The method according to the present invention is further associated with a series of advantages. The method according to the present invention can prepare 3-methyl-2-butene-1-aldehyde with high yield and high selectivity under the conditions of temperature and pressure being gentle, while only requiring a medium to low amount of catalyst. The method can be carried out with an oxidant. The method can be carried out without an organic solvent or with a low amount of an organic solvent, thereby avoiding or minimizing the waste stream that is problematic in the environment. The method can also simply separate 3-methyl-2-butene-1-aldehyde. Another advantage of the method of the present invention is to obtain 3-methyl-2-butene-1-aldehyde with a high concentration in the reaction mixture, thereby minimizing the downstream separation step.

[0010] The present invention therefore relates to a process for preparing 3-methyl-2-butene-1-al, wherein 2-methyl-3-butene-2-ol is reacted to 3-methyl-2-butene-1-al in the presence of an oxidizing agent and a catalyst, wherein the catalyst comprises a catalytically active metal and wherein the reaction is carried out at a pH of ≤7.

[0011] Without wishing to be bound by this theory, it is assumed that 2-methyl-3-buten-2-ol isomerizes to 3-methyl-2-buten-1-ol, which is subsequently oxidized to 3-methyl-2-buten-1-al.

[0012] General Definition:

[0013] In the present invention, unless otherwise specified, generally used terms are defined as follows:

[0014] Selectivity is defined as the number of moles of 3-methyl-2-butene-1-aldehyde formed divided by the number of moles of 2-methyl-3-butene-2-ol and 3-methyl-2-butene-1-ol consumed. The amount of 3-methyl-2-butene-1-aldehyde, 3-methyl-2-butene-1-ol and 2-methyl-3-butene-2-ol can be easily determined by GC analysis as specified in the experimental part.

[0015] The terms "perform" and "execute" are used synonymously.

[0016] Embodiments of the present invention

[0017] The remarks made below with regard to preferred embodiments of the reaction conditions of the process apply either alone or, more particularly, in any conceivable combination with one another.

[0018] 2-Methyl-3-butene-2-ol

[0019] The reactant of the inventive method is 2-methyl-3-butene-2-ol (DMVC, dimethyl vinyl carbinol). The reactant may further comprise 3-methyl-2-butene-1-ol. In one embodiment of the invention, the reactant comprises 2-methyl-3-butene-2-ol and 3-methyl-2-butene-1-ol.

[0020] 3-Methyl-2-butene-1-aldehyde

[0021] The product of the process of the present invention is 3-methyl-2-butene-1-aldehyde (isopentenal).

[0022] Reaction conditions

[0023] pH

[0024] The reaction according to the present invention is carried out at a pH equal to or lower than (≤) 7, preferably the reaction is carried out at a pH lower than 7, preferably equal to or lower than (≤) 6.

[0025] The pH of the reaction can be adjusted, for example, by adding an acid, such as an organic and / or inorganic acid. The pH of the reaction can be adjusted, for example, by adding an acid in liquid form and / or by adding an acid in solid form. The term "acid" includes one or more than one acid.

[0026] Examples of suitable acids are formic acid, acetic acid, phosphoric acid, sulfuric acid, hydrochloric acid, benzoic acid, citric acid, etc. Preferably, a pK a Acids having a value (measured in water at 25°C) below 5, preferably below 3, more preferably between 0 and 2.5.

[0027] The pH of the reaction can be adjusted, for example, by carrying out the process in the presence of a strongly acidic cation exchanger, for example a strongly acidic cation exchanger comprising or having sulfonic acid groups.

[0028] Strong acid cation exchangers, especially H( + ) form of cation exchange resin. Suitable examples are:

[0029] - strongly acidic cation exchangers (e.g. Amberlyst, Amberlite, Dowex, Lewatit, Purolite, Serdolit), which are based on polystyrene and contain copolymers of styrene and divinylbenzene as carrier matrix, with H( + ) in the form of a sulfonic acid group,

[0030] - Ion exchanger groups functionalized with sulfonic acid groups (-SO3H).

[0031] Ion exchangers differ in their polymer backbone structure and a distinction is made between gel-like and macroporous resins. Strongly acidic ion exchangers are usually regenerated with hydrochloric acid and / or sulfuric acid.

[0032] are perfluorinated polymeric ion exchanger resins from Dupont. These are perfluorinated ion exchanger materials containing a fluorocarbon base chain and perfluorinated side chains containing sulfonic acid groups. These resins are obtained by copolymerizing perfluorinated, terminally unsaturated and sulfonyl fluoride functionalized ethoxylates with perfluorinated ethylene. It belongs to gel-like ion exchange resin. Examples of such perfluorinated polymer ion exchange resins are NR-50.

[0033] Suitable H( +Strongly acidic cation exchangers of the form of ) are those in which the ion exchanger contains a polymer backbone having sulfonic acid groups and is gel-like or comprises a macroporous resin.

[0034] Furthermore, ion exchangers based on a polystyrene backbone with sulfonic acid groups or based on perfluorinated ion exchanger resins with sulfonic acid groups can be used.

[0035] Commercially available strongly acidic cation exchangers are known under the following trade names: (Lanxess), (The Purolite Company), (Dow Chemical Company), (Rohm and Haas Company),Amberlyst TM (Rohm and Haas Company).

[0036] Strongly acidic cation exchangers which can be used are, for example: K 1221, K 1461, K 2431, K 2620, K 2621, K 2629, K 2649, IR 120,Amberlyst TM 131,Amberlyst TM 15.Amberlyst TM 31,Amberlyst TM 35.Amberlyst TM 36,Amberlyst TM 39,Amberlyst TM 46,Amberlyst TM 70, SGC650, C100H, C150H, 50X8, red and NR-50.

[0037] Liquid Phase

[0038] It has surprisingly been found that the process according to the invention can be carried out in the presence of a liquid phase consisting of all components of the reaction mixture which are liquid at 20° C. and a pressure of 1 bar.

[0039] Depending on the catalyst and oxidant used, the process according to the invention is carried out in the liquid phase (catalyst and oxidant are part of the liquid phase, homogeneous catalytic process) or in the interphase between the liquid phase and the solid catalyst (heterogeneous catalytic process). The term "in the presence of a liquid phase" includes processes in the liquid phase as well as processes in the interphase.

[0040] The liquid phase may consist of one or more, for example two or three, separate liquid phases. The number of liquid phases may be selected by a person skilled in the art, for example depending on the concentration of the reactants, water or on the optional solvent.

[0041] The process according to the invention can be carried out in the presence of a liquid phase consisting of one liquid phase (monophase system). The process according to the invention can be carried out in the presence of a liquid phase consisting of more than one, for example two, three or more separate liquid phases (multiphase system).

[0042] All weight % relating to the liquid phase in the process according to the invention are based on the total weight of the liquid phase and are determined at a temperature of 20° C. and a pressure of 1 bar.

[0043] In case the process is carried out as a heterogeneous catalytic process, the solid catalyst is not liquid at a temperature of 20°C and a pressure of 1 bar and is therefore by definition not included in the weight % of the liquid phase. In case the process is carried out in the presence of a solid acid such as a strongly acidic cation exchanger, the solid acid is not liquid at a temperature of 20°C and a pressure of 1 bar and is therefore by definition not included in the weight % of the liquid phase. Water

[0044] Water may be present in the liquid phase. If present, water is generally present in an amount greater than 0.1 wt %, preferably 0.5 wt % to 99.5 wt %, of the liquid phase.

[0045] The process according to the invention can be carried out in the presence of a liquid phase consisting of one liquid phase, wherein the liquid phase contains at least 0.5% by weight, preferably at least 5% by weight, preferably at least 10% by weight, more preferably at least 20% by weight, more preferably at least 25% by weight of water, measured at a temperature of 20° C. and a pressure of 1 bar.

[0046] The process according to the invention is carried out in the presence of a liquid phase consisting of more than one liquid phase, wherein at least one separate liquid phase contains at least 0.5% by weight, preferably at least 5% by weight, preferably at least 10% by weight, more preferably at least 20% by weight, more preferably at least 25% by weight of water, based on the total weight of this separate liquid phase, measured at a temperature of 20° C. and a pressure of 1 bar.

[0047] The process according to the invention can be carried out in the presence of a liquid phase consisting of two or three separate liquid phases, wherein each separate liquid phase contains at least 0.5% by weight, preferably at least 5% by weight, preferably at least 10% by weight, more preferably at least 20% by weight, more preferably at least 25% by weight of water, measured at a temperature of 20° C. and a pressure of 1 bar, based on the total weight of this separate liquid phase.

[0048] In one embodiment of the invention, each separate liquid phase contains at least 0.5% by weight, preferably at least 5% by weight, preferably at least 10% by weight, more preferably at least 20% by weight, more preferably at least 25% by weight of water, based on the total weight of this separate liquid phase. The weight % of water is determined at a temperature of 20° C. and a pressure of 1 bar.

[0049] The following preferred ranges for the water content of the liquid phase apply correspondingly to the at least one or each separate liquid phase.

[0050] In one embodiment of the invention, the method is carried out in a liquid phase containing at least 30% by weight, preferably at least 40% by weight, more preferably at least 50% by weight of water. In a further embodiment, the method can be carried out in a liquid phase containing at least 60% by weight, preferably at least 70% by weight, more preferably at least 80% by weight, more preferably at least 90% by weight, more preferably at least 95% by weight of water. According to one embodiment of the invention, the method can be carried out in a liquid phase containing 99.5% by weight of water. All % by weight are based on the total weight of the liquid phase (or in the case of more than one liquid phase, the at least one or each discrete liquid phase).

[0051] In one embodiment of the invention, the process is carried out in a liquid phase which contains 50 to 99.9 wt. %, preferably 60 to 99.5 wt. %, preferably 70 to 99 wt. %, preferably 75 to 95 wt. % of water. All wt. % are based on the total weight of the liquid phase (or, in the case of more than one liquid phase, the at least one or each discrete liquid phase).

[0052] In another embodiment of the invention, the method is carried out in a liquid phase containing 0.1 wt % to less than 25 wt %, or 0.1 wt % to less than 50 wt %, or 0.5 wt % to less than 60 wt %, or 1 wt % to less than 70 wt %, or 5 wt % to less than 75 wt %, or 5 wt % to less than 99.5 wt % water. All wt % are based on the total weight of the liquid phase (or in the presence of more than one liquid phase, the at least one or each discrete liquid phase).

[0053] Reactants and Products

[0054] The liquid phase generally contains from 0.5 to 99.5% by weight, preferably from 10 to 90% by weight, of reactants and products.

[0055] The process according to the invention can be carried out in the presence of a liquid phase consisting of one liquid phase, wherein the liquid phase contains at least 0.5% by weight, preferably at least 5% by weight, preferably at least 10% by weight, more preferably at least 20% by weight, more preferably at least 25% by weight of reactants and products.

[0056] The process according to the invention can be carried out in the presence of a liquid phase consisting of more than one liquid phase, wherein at least one separate liquid phase contains at least 0.5% by weight, preferably at least 5% by weight, preferably at least 10% by weight, more preferably at least 20% by weight, more preferably at least 25% by weight of reactants and products, based on the total weight of this separate liquid phase.

[0057] The process according to the invention can be carried out in the presence of a liquid phase consisting of two or three separate liquid phases, wherein each separate liquid phase contains at least 0.5% by weight, preferably at least 5% by weight, preferably at least 10% by weight, more preferably at least 20% by weight, more preferably at least 25% by weight of reactants and products, based on the total weight of this separate liquid phase, measured at a temperature of 20° C. and a pressure of 1 bar.

[0058] In one embodiment of the invention, each separate liquid phase contains at least 0.5% by weight, preferably at least 5% by weight, preferably at least 10% by weight, more preferably at least 20% by weight, more preferably at least 25% by weight of reactants and products, based on the total weight of this separate liquid phase. The weight % of water is determined at a temperature of 20° C. and a pressure of 1 bar.

[0059] The following preferred ranges for the weight % of reactants and products in the liquid phase apply to the liquid phase of a single-phase system or to at least one individual discrete liquid phase of a multiphase system.

[0060] In one embodiment of the invention, the liquid phase contains at least 30 weight %, preferably at least 50 weight %, preferably at least 60 weight %, preferably at least 70 weight %, preferably at least 75 weight %, preferably at least 80 weight %, preferably at least 85 weight %, preferably at least 90 weight %, preferably at least 95 weight % of reactants and products, based on the total weight of the liquid phase for a single-phase system or at least one separate liquid phase for a multi-phase system.

[0061] In one embodiment of the invention, the process is carried out in a liquid phase containing from 50 to 99.9 wt %, preferably from 60 to 99.5 wt %, preferably from 70 to 99 wt %, preferably from 75 to 95 wt % of reactants and products. All wt % are based on the total weight of the liquid phase (or, in the case of more than one liquid phase, the at least one or each discrete liquid phase).

[0062] In another embodiment of the present invention, the method is carried out in a liquid phase containing 0.1 wt % to less than 25 wt %, or 0.1 wt % to less than 50 wt %, or 0.5 wt % to less than 60 wt %, or 1 wt % to less than 70 wt %, or 5 wt % to less than 75 wt %, or 5 wt % to less than 99.5 wt % of reactants and products. All wt % are based on the total weight of the liquid phase (or in the presence of more than one liquid phase, the at least one or each discrete liquid phase).

[0063] Oxidants

[0064] The process according to the invention is carried out in the presence of at least one oxidizing agent.

[0065] The term "oxidant" includes one or more than one oxidant.

[0066] Suitable oxidizing agents are, for example, selected from the group consisting of halogens, oxygen, oxyanions of chlorine, oxyanions of bromine, oxyanions of iodine, dialkyl peroxides, organic and inorganic peroxyacids, peresters, hydroperoxides and hydrogen peroxide.

[0067] Suitable halogens are, for example, fluorine or chlorine. Suitable chlorine oxygen-containing anions are, for example, hypochlorite, chlorate, chlorate or perchlorate. Suitable bromine oxygen-containing anions are, for example, hypobromite, bromate or perbromate. Suitable iodine oxygen-containing anions are, for example, hypoiodite, iodite, iodate or periodate. Suitable dialkyl peroxides are, for example, diisopropyl peroxide or di(tert-butyl) peroxide. Suitable organic or inorganic peroxyacids are, for example, metachloroperbenzoic acid or peracetic acid, peroxydisulfuric acid or peroxymonosulfuric acid. Suitable peresters are, for example, peracetic acid esters, such as tert-butyl peracetate or tert-butyl phenylperacetate. Suitable hydroperoxides are, for example, tert-butyl hydroperoxide, 1-phenylethyl hydroperoxide (ethylbenzene hydroperoxide), 2-prop-2-ylbenzene hydroperoxide (cumyl hydroperoxide), cyclohexyl hydroperoxide or 1-methyl-1-(4-methylphenyl)ethyl hydroperoxide (p-cymene hydroperoxide).

[0068] For the purposes of the present invention, the expressions "hypochlorite", "chlorite", "chlorate" or "perchlorate" refer to a chlorate containing the oxygen-containing anion ClO, respectively. - (Hypochlorite), ClO2 -(chlorite), ClO3 - (chlorate) or ClO4 - (perchlorate), for example an alkali metal or alkaline earth metal salt.

[0069] For the purposes of the present invention, the expressions "hypobromite", "bromite", "bromate" or "perbromate" refer to a bromate containing the oxyanion BrO - (Hypobromite), ClO2 - (bromite), ClO3 - (bromate) or ClO4 - (perbromate), for example an alkali metal or alkaline earth metal salt.

[0070] For the purposes of the present invention, the expressions "hypoiodite", "iodite", "iodate" or "periodate" refer to a molecule comprising an oxyanion IO - (Hypoiodite), IO2 - (iodite), IO3 - (iodate) or IO4 - / IO6 5- (periodate), for example an alkali metal or alkaline earth metal salt.

[0071] Preferably, the oxidizing agent is selected from hydroperoxides, hydrogen peroxide and oxygen.

[0072] In a preferred embodiment, the oxidizing agent is selected from tert-butyl hydroperoxide, 1-phenylethyl hydroperoxide (ethylbenzene hydroperoxide), 2-propan-2-ylbenzene hydroperoxide (cumyl hydroperoxide), cyclohexyl hydroperoxide, 1-methyl-1-(4-methylphenyl)ethyl hydroperoxide (p-cymene hydroperoxide), hydrogen peroxide and oxygen.

[0073] The method according to the invention can be carried out with oxygen and / or hydrogen peroxide as oxidant. The oxygen can be used undiluted or diluted. The oxygen can be diluted with other inert gases such as N2, Ar or CO2, for example in the form of air. In a preferred embodiment of the invention, the oxygen is used undiluted. Hydrogen peroxide can be used as an aqueous solution.

[0074] In a preferred embodiment of the present invention, oxygen is used as oxidant.

[0075] Solvents

[0076] The process according to the invention can be carried out in the presence of a liquid phase which consists essentially of reactants, products, water, acid and oxidant.

[0077] The process according to the invention can be carried out as a heterogeneous catalytic process in the presence of a liquid phase, which consists essentially of reactants, products, water and oxidant. Depending on the acid selected, the acid can be part of the liquid phase or can be part of the solid phase.

[0078] The process according to the invention can be carried out as a homogeneous catalytic process in the presence of a liquid phase, which consists essentially of reactants, products, water, acid, oxidant and catalyst.

[0079] In these embodiments, the liquid phase is free of solvent.

[0080] The term "solvent" includes any component other than reactants, products, water, oxidant, catalyst or acid, which is liquid at a temperature of 20°C and a pressure of 1 bar and which is therefore part of the liquid phase.

[0081] One of the advantages of the present invention is that the process can be carried out in the presence of a liquid phase comprising less than 75% by weight, preferably less than 70% by weight, of solvent, based on the total weight of the liquid phase.

[0082] In case a solvent is used, a suitable solvent may be selected depending on the reactants, products, catalyst, oxidant, acid and reaction conditions. The term "solvent" includes one or more than one solvent.

[0083] The following preferred ranges for the solvent content of the liquid phase apply to the liquid phase (for a single-phase system) or to at least one separate liquid phase (for a multi-phase system).

[0084] In a preferred embodiment of the present invention, the process is carried out in a liquid phase which contains less than 70% by weight, preferably less than 60% by weight, preferably less than 50% by weight, preferably less than 40% by weight, preferably less than 30% by weight, more preferably less than 20% by weight, more preferably less than 10% by weight of solvent, based on the total weight of the liquid phase (for a single-phase system) or of at least one separate liquid phase (for a multiphase system).

[0085] Advantageously, the process according to the invention can be carried out in the presence of a liquid phase containing less than 5% by weight of solvent, based on the total weight of the liquid phase (for a monophasic system) or at least one separate liquid phase (for a multiphasic system). In one embodiment of the invention, the process is carried out in the presence of a liquid phase containing less than 3% by weight, preferably less than 1% by weight of solvent. In one embodiment of the invention, the process is carried out in the presence of a solvent-free liquid phase.

[0086] In case a solvent is used, suitable solvents are, for example, protic or aprotic solvents.

[0087] Where a solvent is used, it has been found to be advantageous to use an aprotic organic solvent.

[0088] When a solvent is used, it is preferred that the boiling point of the solvent is higher than 50°C, for example in the range of 50 to 200°C, especially above 65°C, for example in the range of 65 to 180°C, especially above 80°C, for example in the range of 80 to 160°C.

[0089] Aprotic organic solvents useful herein include, for example, aliphatic hydrocarbons such as hexane, heptane, octane, nonane, decane and petroleum ether, aromatic hydrocarbons such as benzene, toluene, xylene and mesitylene, aliphatic C3-C8 ethers such as 1,2-dimethoxyethane (DME), diethylene glycol dimethyl ether (diglyme), ethyl ether, dipropyl ether, methyl isobutyl ether, tert-butyl methyl ether and tert-butyl ethyl ether. , dimethoxymethane, diethoxymethane, dimethylene glycol dimethyl ether, dimethylene glycol diethyl ether, 1,3-propylene glycol dimethyl ether, 1,3-propylene glycol diethyl ether, 1,4-butanediol dimethyl ether, alicyclic hydrocarbons such as cyclohexane and cycloheptane, alicyclic C3-C6 ethers such as tetrahydrofuran (THF), tetrahydropyran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxolane and 1,4-dioxolane Alkane, 1,3,5-tri Alkanes, short-chain ketones, such as acetone, methyl ethyl ketone and methyl isobutyl ketone, C3-C6 esters, such as methyl acetate, ethyl acetate, methyl propionate, dimethyl oxalate, methyl methoxyacetate, ethylene carbonate, propylene carbonate, ethylene glycol diacetate and diethylene glycol diacetate, C3-C6 amides, such as dimethylformamide (DMF) and dimethylacetamide and N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), C3-C6 nitriles, such as acetonitrile, propionitrile, or mixtures of these solvents with each other.

[0090] According to one embodiment of the present invention, preference is given to those of the above-mentioned aprotic solvents which have a boiling point above 50°C, such as in the range of 50 to 200°C, in particular above 65°C, such as in the range of 65 to 180°C, especially above 80°C, such as in the range of 80 to 160°C.

[0091] If used, more preferably the solvent is selected from 1,2-dimethoxyethane (DME), diethylene glycol dimethyl ether (diglyme), diethoxymethane, dimethylene glycol dimethyl ether, 1,3-propylene glycol dimethyl ether, 1,4-butanediol dimethyl ether, 1,3-dioxolane, 1,4-di Alkane, 1,3,5-tri Alkanes, dimethylacetamide, methyl acetate, dimethyl oxalate, methyl methoxyacetate, ethylene carbonate, propylene carbonate, ethylene glycol diacetate and diethylene glycol diacetate, toluene, xylenes, 1,3,5-trimethylbenzene, C7-C10 Alkanes such as octane or nonane, THF, 1,4-dihydro Alkanes and mixtures thereof, in particular selected from toluene, o-xylene, m-xylene, p-xylene and 1,3,5-trimethylbenzene.

[0092] In a preferred embodiment, the solvent, if used, is selected from solvents having a water solubility greater than 150 g / L at 20°C. In a preferred embodiment, the solvent, if used, is selected from solvents having a vapor pressure less than 100 mbar at 20°C.

[0093] In a preferred embodiment, if used, the solvent is selected from diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and dimethylacetamide, general formula (III) H3C-O-(CH2O) n -CH3 (wherein n=3 to 8) polyoxymethylene dimethyl ether, dimethyl oxalate, methyl methoxyacetate, ethylene carbonate, propylene carbonate, ethylene glycol diacetate and diethylene glycol diacetate.

[0094] catalyst

[0095] The process according to the invention is carried out as a heterogeneously catalyzed process or as a homogeneously catalyzed process.

[0096] In a preferred embodiment of the invention, the method is carried out as a heterogeneous catalytic process. In this heterogeneous catalytic process, the catalyst and reactants / products are in different phases, which contact each other. The reactants / products are in the liquid phase, and the catalyst is at least partially in the solid phase. The reaction will occur in the interphase between the liquid phase and the solid phase.

[0097] The method according to the invention is carried out in the presence of a catalyst. The catalyst comprises at least one catalytically active metal. In the method according to the invention, the catalytically active metal may be selected from elements of the 8th, 9th, 10th and 11th groups of the periodic table (according to the IUPAC nomenclature). Elements of the 8th, 9th, 10th and 11th groups of the periodic table include iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, silver and gold.

[0098] In a preferred embodiment, the catalytically active metal is selected from the elements of Groups 10 and 11 of the Periodic Table of the Elements (according to IUPAC nomenclature).

[0099] In a preferred embodiment, the catalytically active metal is selected from elements selected from platinum, palladium and gold.

[0100] In a preferred embodiment of the present invention, the catalytically active metal is platinum.

[0101] The catalytically active metal can be used in any form, for example unsupported or on a support. The catalytically active metal can be used in unsupported form, for example as a powder, screen, sponge, foam or mesh. In a preferred embodiment, the catalytically active metal is on a support.

[0102] The catalyst may optionally contain one or more so-called promoters which enhance the activity of the catalytically active metal. Examples of such promoters are bismuth (Bi), antimony (Sb), lead (Pb), cadmium (Cd), tin (Sn), tellurium (Te), cerium (Ce), selenium (Se) or thallium (Tl).

[0103] In a preferred embodiment, the catalyst comprises at least one promoter selected from bismuth (Bi), antimony (Sb), lead (Pb), cadmium (Cd), tin (Sn) and tellurium (Te). In a preferred embodiment, the catalyst comprises at least one promoter selected from bismuth (Bi), lead (Pb) and cadmium (Cd). In a preferred embodiment, the catalyst comprises bismuth (Bi).

[0104] The promoters can be used, for example, as metals, nitrates, acetates, sulfates, citrates, oxides, hydroxides or chlorides and mixtures thereof.

[0105] In a preferred embodiment, the catalytically active metal is platinum and the promoter is bismuth.

[0106] In case a promoter is used, a suitable molar ratio of catalytically active metal to promoter is from 1:0.01 to 1:10, preferably from 1:0.67 to 1:5, preferably from 1:0.5 to 1:3, more preferably from 1:0.1 to 1:2.

[0107] The promoter may, for example, be present on a support or may be added separately to the process.

[0108] The term "on a support" includes that the catalytically active metals and / or promoters may be located on the outer surface of the support and / or the inner surface of the support. In most cases, the catalytically active metals and / or promoters will be located on the outer surface of the support and on the inner surface of the support.

[0109] In the case of a catalytically active metal on a support, the catalyst comprises the catalytically active metal, the support and optionally a promoter.

[0110] In one embodiment of the invention, the process is carried out as a batch process and the molar ratio of catalytically active metal to alcohol of formula (II) is from 0.0001:1 to 1:1, more preferably from 0.001:1 to 0.1:1, even more preferably from 0.001:1 to 0.01:1.

[0111] In one embodiment of the present invention, the process is carried out as a continuous process and the catalyst loading (defined as the total amount of alcohol of formula (II) / the total amount of catalytically active metal in the reactor / time unit) is from 0.01 to 100 grams of alcohol of formula (II) / gram of catalytically active metal / hour, more preferably from 0.1 to 20 grams of alcohol of formula (II) / gram of catalytically active metal / hour.

[0112] In one embodiment of the present invention, the process is carried out as a continuous process and the catalyst loading (defined as the total amount of alcohol of formula (II) / the total amount of catalytically active metal in the reactor / time unit) is from 30 to 40000 g of alcohol of formula (II) / g of catalytically active metal / hour, more preferably from 1000 to 9000, more preferably from 1200 to 5000, preferably from 1500 to 4000, preferably from 1650 to 3500 g of alcohol of formula (II) / g of catalytically active metal / hour.

[0113] In the case of catalytically active metals on a support, the support may be, for example, a powder, a shaped body or a mesh tempered in the presence of oxygen, for example an iron-chromium-aluminum (FeCrAl) mesh (available under the trademark purchased).

[0114] In a preferred embodiment of the invention, the catalytically active metal is used on a support. In a preferred embodiment, the catalytically active metal is used on a support and the support is selected from powders and shaped bodies. In the case of using a support in powder form, this powder generally has a particle size of 1 to 200 μm, preferably 1 to 100 μm. The shaped body can be obtained, for example, by extrusion, pressing or tableting and can be of any shape, such as strands, hollow strands, cylinders, tablets, rings, spherical particles, trilobes, stars or spheres. Typical sizes of shaped bodies range from 0.5 mm to 250 mm.

[0115] In a preferred embodiment, the diameter of the carrier is from 0.5 to 20 mm, preferably from 0.5 to 10 mm, more preferably from 0.7 to 5 mm, more preferably from 1 to 2.5 mm, preferably from 1.5 to 2.0 mm.

[0116] In a preferred embodiment, the carrier is obtained by extrusion and is in the form of a strand or hollow strand. In one embodiment, a carrier with a strand diameter of 1 to 10 mm, preferably 1.5 to 5 mm, is used. In one embodiment, a carrier with a length of 2 to 250 mm, preferably 2 to 100 mm, preferably 2 to 25 mm, more preferably 5 to 10 mm is used. In one embodiment, a carrier with a strand diameter of 1 to 2 mm and a strand length of 2 to 10 mm is used.

[0117] In a preferred embodiment, the catalytically active metal is employed on a support, wherein the support is selected from carbonaceous and oxidic materials.

[0118] Suitable support materials are, for example, carbonaceous or oxidic materials. A preferred carbonaceous material is activated carbon. The surface area of ​​the carbonaceous support material is preferably at least 200 m 2 / g, preferably at least 300m 2 / g. In the case of using a carbonaceous carrier, it has at least 300m 2 Activated carbon with a surface area of ​​at least 300 m / g is preferred. In a preferred embodiment, the catalytically active metal (preferably platinum) is used on an activated carbon support, preferably one having a surface area of ​​at least 300 m / g. 2 / g of surface area of ​​activated carbon support.

[0119] In the case of using an oxidic support, oxides of the following elements can be used: Al, Si, Ce, Zr, Ti, V, Cr, Zn, Mg. The present invention also includes the use of mixed oxides containing two or more elements. In one embodiment of the present invention, a mixed oxide selected from (Al / Si), (Mg / Si) and (Zn / Si) mixed oxides is used as a support. In a preferred embodiment, an oxidic support selected from alumina and silica is used. Alumina can be used in any phase, such as α-alumina (α-Al2O3), β-alumina (β-Al2O3), γ-alumina (γ-Al2O3), δ-alumina (δ-Al2O3), η-alumina (η-Al2O3), θ-alumina (θ-Al2O3), χ-alumina (χ-Al2O3), κ-alumina (κ-Al2O3) and mixtures thereof. The term β-alumina (β-Al2O3) describes the compound Na2O·11Al2O3.

[0120] In a preferred embodiment, the oxidic support is selected from alpha alumina (α-Al2O3), beta alumina (β-Al2O3), gamma alumina (γ-Al2O3), delta alumina (δ-Al2O3) and theta alumina (θ-Al2O3).

[0121] In a preferred embodiment, the oxidic support is selected from the group consisting of alpha alumina (α-Al2O3), beta alumina (β-Al2O3) and gamma alumina (γ-Al2O3).

[0122] In one embodiment, the oxidic support is gamma alumina (γ-Al2O3).

[0123] Commercially available gamma alumina (γ-Al 2 O 3 ) may be treated at a temperature of 500 to 700° C., preferably 550 to 600° C., to ensure that all of the Al 2 O 3 is in the γ-phase.

[0124] In one embodiment, the oxidic support may have a m 2 / g BET surface area (BET, Brunnauer-Emmet-Teller, according to DIN 66131, determined by N2 adsorption at 77 K). The oxidic support preferably has a surface area of ​​at least 0.1 m 2 / g, preferably at least 1m 2 / g, preferably at least 10m 2 / g, more preferably at least 30m 2 / g, more preferably at least 50m 2 / g, more preferably at least 75m 2 / g, preferably at least 100m 2 / g, preferably at least 150m 2 / g, particularly preferably at least 200m 2 / g of BET surface area.

[0125] In another embodiment, the oxidic support has a molecular weight of 1 to 50 m 2 In another embodiment, the oxidic support has a BET surface area of ​​10 to 300 m 2 / g, preferably 20 to 100 m 2 In another embodiment, the oxidic support has a BET surface area of ​​100 to 300 m 2 / g, preferably 150 to 300m 2 / g of BET surface area.

[0126] In a preferred embodiment, the support is Al2O3 with a BET surface area of ​​100 to 300 m 2 / g.

[0127] In one embodiment, the catalyst comprises platinum on a support.

[0128] In one embodiment, the catalyst comprises platinum on a support, wherein the support is selected from the group consisting of carbonaceous and oxidic materials.

[0129] In one embodiment, the catalyst comprises platinum on a support, wherein the support is selected from carbonaceous and oxidic materials, and wherein the oxidic material is selected from oxides of elements selected from Al, Ce, Zr, Ti, V, Cr, Zn, and Mg.

[0130] In one embodiment, the catalyst comprises platinum on a support, wherein the support is selected from carbonaceous materials and oxidic materials, and wherein the oxide is selected from oxides of elements selected from Al, Ce, Zr, and Ti.

[0131] In a preferred embodiment, the catalyst is selected from platinum / carbon (Pt / C) and platinum / alumina (Pt / Al2O3).

[0132] In a preferred embodiment, the catalyst comprises platinum on alumina, wherein the alumina is selected from alpha alumina (α-Al2O3), beta alumina (β-Al2O3), gamma alumina (γ-Al2O3), delta alumina (δ-Al2O3), eta alumina (η-Al2O3), theta alumina (θ-Al2O3), chi alumina (χ-Al2O3) and kappa alumina (κ-Al2O3).

[0133] In the case of catalytically active metals on a support, the catalytically active metal content of the catalyst is generally from 0.1 to 20% by weight, preferably from 0.1 to 15% by weight, preferably from 0.5 to 10% by weight.

[0134] In the case of a catalytically active metal on a support, the catalyst can be prepared, for example, by a deposition-reduction process, in which a metal compound is first deposited on a support and then reduced to the catalytically active metal. The reduction can be carried out by any known method, for example in the gas phase or liquid phase.

[0135] In a preferred embodiment of the present invention, the catalyst can be obtained by:

[0136] a) Provide carrier

[0137] b) Providing metal compounds

[0138] c) Depositing the metal compound on the support

[0139] d) optionally calcining the catalyst precursor thus obtained

[0140] e) Reduction of catalyst precursor

[0141] f) optionally recovering the catalyst.

[0142] In a preferred embodiment of the present invention, the catalyst is obtained by:

[0143] a) Provide carrier

[0144] b) Providing metal compounds

[0145] c) Depositing the metal compound on the support

[0146] d) optionally calcining the catalyst precursor thus obtained

[0147] e) Reduction of catalyst precursor

[0148] f) optionally recovering the catalyst.

[0149] Step a) Providing a carrier

[0150] A suitable support is provided, for example, by adding the support in the form of a powder or shaped body directly to the reactor vessel or by providing the support as a slurry (in the case where the support is in the form of a powder).

[0151] Step b) providing a metal compound

[0152] The metal compound is a precursor of the catalytically active metal. The catalytically active metal is obtained by reducing the metal compound.

[0153] The metal compound can be used as a solution, for example as an aqueous solution of a water-soluble salt of the metal compound or as a non-aqueous solution. The metal compound can also be used as a colloid, in which the undissolved metal compound is dispersed in a liquid phase.

[0154] In a preferred embodiment, the metal compound is used as a salt. Depending on the solubility of the salt, an aqueous solution or a non-aqueous solution can be used.

[0155] Suitable salts of metal compounds include nitrates, acetates, sulfates, citrates, oxides, hydroxides and chlorides and combinations thereof. Preferably, water soluble salts are used.

[0156] In a preferred embodiment, the metal compound is selected from platinum salts. Depending on the solubility of the platinum salt, an aqueous or non-aqueous solution of the platinum salt can be used. Examples of suitable platinum salts are H2PtCl6, PtCl4, Pt(NH3)2(NO3)2, Pt(NO2)2(NH3)2 / NH4OH, Pt(NO3)2, platinum hydroxides such as Pt(OH)2, Pt(OH)4 or H2Pt(OH)6, all of which are stable in amines, for example in monoethanolamine, PtO2, bis(2,4-pentanedione)platinum(II)=Pt(C5H7O2)2, K2PtCl4, NaPtCl4, (NH4)2PtCl4.

[0157] In a preferred embodiment, the platinum salt is selected from H2PtCl6, Pt(NH3)2(NO3)2, Pt(NO2)2(NH3)2 / NH4OH and Pt(NO3)2.

[0158] Typically, the deposition step c) will be performed before the reduction step e). The present invention also encompasses embodiments in which the catalytically active metal can be reduced in situ from a metal compound and then deposited on the support.

[0159] In the case of using promoters, they can be used, for example, as promoter compounds, which are subsequently converted (by oxidation and / or reduction) to the promoter. The promoter compounds can be used as solutions, for example as aqueous solutions of water-soluble salts of the promoter compounds or as non-aqueous solutions of the promoter compounds. The promoter compounds can also be used as colloids, wherein the undissolved promoter compound is dispersed in the liquid phase.

[0160] Suitable salts of the promoter compound include nitrates, acetates, sulfates, citrates, oxides, hydroxides and chlorides and combinations thereof. Preferably water soluble salts are used.

[0161] In the case of using promoter compounds, they can be added to the metal compound. In this embodiment, the metal compound and the promoter compound are deposited on the support together. In another embodiment, the metal compound and the promoter compound can be deposited on the support separately.

[0162] After one or more deposition steps, both the promoter compound and the metal compound are then converted to promoter and catalytically active metal.

[0163] In a preferred embodiment, the promoter compound is selected from Bi salts, Cd salts and Pb salts.

[0164] Step c) Deposition step

[0165] The deposition of the metal compound on the support can be carried out by any known method, for example by chemical or physical vapor deposition or by contacting and mixing the support with the metal compound (= impregnation) or by spraying the metal compound onto the support.

[0166] In a preferred embodiment, deposition is carried out by dipping and / or spraying.

[0167] In the case of deposition by impregnation or spraying, the metal compound can be used as a solution or colloid or a colloid generated in situ during the impregnation or spraying process. Deposition by impregnation or spraying can be carried out at a temperature of 1 to 100° C. The pH value for the deposition step can be selected depending on the metal compound used. The deposition can be carried out for 0.1 to 24 hours, typically 0.5 to 2 hours. The deposition can be carried out at different pressures, for example at a pressure of 1 to 1000 mbar (atmospheric pressure), suitable pressures being, for example, 50 mbar, 70 mbar, 100 mbar, 250 mbar, 500 mbar or atmospheric pressure. The catalyst precursor thus obtained can be optionally dried and / or calcined before the reduction step.

[0168] In case the deposition step is carried out by impregnation or spraying, the volume of the solution or colloid of the metal compound is ideally chosen so that at least 90%, preferably 100%, of the pore volume of the support will be filled with the solution or colloid (the so-called "incipient wetness" process). The concentration of the metal compound is ideally chosen so that after deposition and reduction, a catalyst having the desired catalytically active metal content is obtained.

[0169] The deposition step can be carried out in one step or in a plurality of consecutive steps. The deposition step can also be carried out as a combination of spraying and dipping.

[0170] The catalyst precursor may then be recovered by suitable separation methods such as filtration and / or centrifugation.The catalyst precursor may then be washed with water, preferably until a conductivity of less than 400 μS / cm, preferably less than 200 μS / cm is obtained.

[0171] In one embodiment, the deposition step c) may be followed by a drying step and / or a calcination step d).

[0172] The calcination step d) can be carried out in conventional furnaces, for example in a rotary furnace, a chamber furnace, a tunnel furnace or a belt calciner.

[0173] The calcination step d) may be carried out at a temperature of from 200 to 1150° C., preferably from 250 to 900° C., preferably from 280 to 800° C., more preferably from 500 to 800° C., preferably from 300 to 700° C. Calcination is suitably carried out for 0.5 to 20 hours, preferably 0.5 to 10 hours, preferably 0.5 to 5 hours.

[0174] The calcination of the catalyst precursor in step d) serves primarily to stabilize the metal compound (and, if present, the promoter compound) deposited on the support and to remove undesired components.

[0175] Step e) Reduction step

[0176] The catalyst precursor thus obtained can then be reduced, for example by treatment with a gas (gas phase reduction) or by treating the catalyst precursor with a solution of a reducing agent (liquid phase reduction).

[0177] The gas phase reduction of the catalyst precursor can be carried out by treating the catalyst precursor with hydrogen and / or CO. Hydrogen and / or CO may further contain at least one inert gas, such as helium, neon or argon, N2, CO2 and / or lower alkanes, such as methane, ethane, propane and / or butane. Preferably N2 is used as the inert gas. The gas phase reduction can be carried out at a temperature of 30 to 200°C, preferably 50 to 180°C, more preferably 60 to 130°C. Typically, the gas phase reduction is carried out for 1 to 24 hours, preferably 3 to 20 hours, more preferably 6 to 14 hours.

[0178] Liquid phase reduction of the catalyst precursor is carried out by treating the catalyst precursor with a reducing agent solution. Suitable reducing agents are quaternary alkylammonium salts; formic acid; formates such as sodium formate, potassium formate, lithium formate or ammonium formate; citric acid; citrates such as sodium citrate, potassium citrate, lithium citrate, ammonium citrate; ascorbic acid; ascorbates such as sodium ascorbate, potassium ascorbate, lithium ascorbate and ammonium ascorbate; tartaric acid; tartrates such as sodium tartrate, potassium tartrate, lithium tartrate and ammonium tartrate; oxalic acid; oxalates such as potassium oxalate, sodium oxalate, lithium oxalate and ammonium oxalate; ammonium bicarbonate (NH4HCO3); hydroxylamine; hypophosphorous acid; hypophosphites such as sodium hypophosphite (NaH2PO2); sodium sulfite ( Na2SO3); hydrazine; benzene; C1-C4 alcohols, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, isobutanol (2-methyl-1-propanol), 2-butanol; diols; polyols; reducing sugars, such as glucose, fructose; borohydrides, such as LiBH4, NaBH4, NaBH3CN, KBH4, KBH(C2H5)3, LiBH(C2H5)3; lithium aluminum hydride (LiAlH4); formaldehyde; N-vinylpyrrolidone (NVP), polyvinylpyrrolidone (PVP); phenol; sodium thiocyanate; iron (II) sulfate; sodium amalgam; zinc amalgam.

[0179] The liquid phase reduction can be carried out at a temperature of 10 to 95° C., preferably 50 to 90° C. The pH of the reduction step can be selected depending on the reducing agent used.

[0180] In a preferred embodiment, the reducing step is performed by treating the catalyst precursor with a solution of a reducing agent.

[0181] In a preferred embodiment, the reduction step is carried out by treating the catalyst precursor with a solution of a reducing agent, wherein the reducing agent is selected from: quaternary alkylammonium salts; formic acid; formates such as sodium formate, potassium formate, lithium formate or ammonium formate; citric acid; citrates such as sodium citrate, potassium citrate, lithium citrate, ammonium citrate; ascorbic acid; ascorbic acid salts such as sodium ascorbate, potassium ascorbate, lithium ascorbate and ammonium ascorbate; tartaric acid; tartrates such as sodium tartrate, potassium tartrate, lithium tartrate and ammonium tartrate; oxalic acid; oxalates such as potassium oxalate, sodium oxalate, lithium oxalate and ammonium oxalate; ammonium bicarbonate (NH4HCO3); hydroxylamine; hypophosphorous acid; hypophosphites such as hypophosphite Sodium phosphate (NaH2PO2); sodium sulfite (Na2SO3); hydrazine; benzene; C1-C4 alcohols, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, isobutanol (2-methyl-1-propanol), 2-butanol; diols; polyols; reducing sugars, such as glucose, fructose; borohydrides, such as LiBH4, NaBH4, NaBH3CN, KBH4, KBH(C2H5)3, LiBH(C2H5)3; lithium aluminum hydride (LiAlH4); formaldehyde; N-vinylpyrrolidone (NVP), polyvinylpyrrolidone (PVP); phenol; sodium thiocyanate; iron (II) sulfate; sodium amalgam; zinc amalgam.

[0182] In a preferred embodiment, the reduction step is carried out by treating the catalyst precursor with a reducing agent solution, wherein the reducing agent is selected from sodium formate, sodium citrate, sodium ascorbate, polyols, reducing sugars, formaldehyde, methanol, ethanol, 2-propanol, KBH(C2H5)3 and LiBH(C2H5)3.

[0183] The catalyst can then be recovered by suitable separation methods such as filtration and / or centrifugation. Typically, the catalyst is then washed with water, preferably until a conductivity of less than 400 μS / cm, preferably less than 200 μS / cm, is obtained.

[0184] The drying step can be carried out, for example, after step c) and / or after step e). The drying of the catalyst precursor obtained in step c) or the catalyst obtained in step e) can generally be carried out at a temperature above 60° C., preferably above 80° C., more preferably above 100° C. The drying can be carried out, for example, at a temperature of 120 to 200° C. Drying is generally carried out until substantially all of the water has evaporated. Typical drying times vary from 1 hour to up to 30 hours, depending on the drying temperature. The drying step can be accelerated by using a vacuum.

[0185] In one embodiment of the present invention, the catalyst comprises at least one catalytically active metal and at least one promoter.

[0186] The catalyst can comprise at least one catalytically active metal and at least one promoter in any structure, for example unstructured (random distribution of catalytically active metal and promoter) or in an ordered or partially ordered structure [= as an intermetallic compound (IMC)] and in different proportions of these states.

[0187] In one embodiment of the present invention, at least 50% by weight, at least 60% by weight, at least 70% by weight, preferably at least 85% by weight, preferably at least 90% by weight and more preferably at least 95% by weight of the at least one catalytically active metal and the at least one promoter are in the structure of the intermetallic compound.

[0188] In one embodiment of the present invention, the catalyst comprises at least one catalytically active metal A and at least one promoter B as a general formula A x B y intermetallic compounds, among which

[0189] A x B y wherein x is in the range of 0.05-10, preferably 0.1-5, preferably 0.2-4, more preferably 0.25-3, more preferably 0.5-2, more preferably 0.67-1.

[0190] A x B y The y in the range is 0.05-10, preferably 0.1-5, preferably 0.2-4, more preferably 0.25-3, more preferably 0.5-2, more preferably 0.67-1.

[0191] In one embodiment of the present invention, the catalyst comprises at least one catalytically active metal A and at least one promoter B as a general formula A x B y intermetallic compounds, among which

[0192] A is one or more elements selected from Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, Ag and Au,

[0193] B is one or more elements selected from Bi, Sb, Pb, Cd, Sn, Te, Ce, Se and Tl

[0194] A x B y wherein x is in the range of 0.05-10, preferably 0.1-5, preferably 0.2-4, more preferably 0.25-3, more preferably 0.5-2, more preferably 0.67-1.

[0195] A x B yThe y in the range is 0.05-10, preferably 0.1-5, preferably 0.2-4, more preferably 0.25-3, more preferably 0.5-2, more preferably 0.67-1.

[0196] More preferably, the general formula A x B y intermetallic compounds, among which

[0197] A is one or more elements selected from Pd, Pt and Au,

[0198] B is one or more elements selected from Bi, Pb and Cd,

[0199] A x B y wherein x is in the range of 0.05-10, preferably 0.1-5, preferably 0.2-4, more preferably 0.25-3, more preferably 0.5-2, more preferably 0.67-1.

[0200] A x B y The y in the range is 0.05-10, preferably 0.1-5, preferably 0.2-4, more preferably 0.25-3, more preferably 0.5-2, more preferably 0.67-1.

[0201] More preferably, the general formula A x B y intermetallic compounds, among which

[0202] A is Pt,

[0203] B is one or more elements selected from Bi, Pb and Cd,

[0204] A x B y wherein x is in the range of 0.05-10, preferably 0.1-5, preferably 0.2-4, more preferably 0.25-3, more preferably 0.5-2, more preferably 0.67-1.

[0205] A x B y The y in the range is 0.05-10, preferably 0.1-5, preferably 0.2-4, more preferably 0.25-3, more preferably 0.5-2, more preferably 0.67-1.

[0206] More preferably, the general formula A x B y intermetallic compounds, among which

[0207] A is Pt, B is Bi,

[0208] A x B ywherein x is in the range of 0.05-10, preferably 0.1-5, preferably 0.2-4, more preferably 0.25-3, more preferably 0.5-2, more preferably 0.67-1.

[0209] A x B y The y in the range is 0.05-10, preferably 0.1-5, preferably 0.2-4, more preferably 0.25-3, more preferably 0.5-2, more preferably 0.67-1.

[0210] For the purposes of the present invention, an intermetallic compound (IMC) is a compound made of at least two different metals in an ordered or partially ordered structure with a defined stoichiometry. The structure may be similar to or different from the structure of the pure constituent metals. Examples of intermetallic compounds are ordered, partially ordered and eutectic alloys, Laves phases, Zintl phases, Heussler phases, Hume-Rothary phases, and other intermetallic compounds known to those skilled in the art. Also included are compounds containing elements belonging to the semimetal family, such as selenides, tellurides, arsenides, antimonides, silizides, germanides, and borides.

[0211] The term intermetallic compound (IMC) also includes compounds of the general formula A as described above. x B y A mixture of different intermetallic compounds.

[0212] Examples of intermetallic compounds according to the present invention are RhPb, RhPb2, Rh4Pb5, Rh2Sn, RhSn, RhSn2, RhSn4, Rh2Sb, RhSb, RhSb2, RhSb3, IrPb, IrSn, Ir5Sn7, IrSn2, Ir3Sn7, IrSn4, IrSn, Ir5Sn7, IrSn2, Ir3Sn7, IrSn4, Pd3Pb, Pd 13 Pb9, Pd5Pb3, PdPb, Pd3Sn, Pd 20 Sn 13 , Pd2Sn, PdSn, Pd5Sn7, PdSn2, PdSn3, PdSn4, Pd3Sb, Pd 20Sb7, Pd5Sb2, Pd8Sb3, Pd2Sb, PdSb, PdSb2, Ru2Sn3, RuSn2, Ru3Sn7, RuSb, RuSb2, RuSb3, NiPb, Ni3Sn4, Ni3Sn2 , Ni3Sn, NiSn, Ni5Sb2, Ni3Sb, NiSb2, NiSb3, PtBi, PtBi2, Pt2Bi3, PtPb, Pt3Pb, PtPb2, PtPb4, PtSb, PtSb2, Pt 0.3 Sb 0.7 ,Pt3Sb,Pt3Sb2,Pt7Sb,PtSn,Pt 0.9 Sn 0.1 , Pt 0.94 Sn 0.06 , PtSn2, PtSn4, Pt2Sn3 and Pt3Sn.

[0213] Preferred intermetallic compounds are selected from PtBi, PtBi2, Pt2Bi3, PtPb, Pt3Pb, PtPb2, PtPb4, PtSb, PtSb2, Pt 0.3 Sb 0.7 ,Pt3Sb,Pt3Sb2,Pt7Sb,PtSn,Pt 0.9 Sn 0.1 , Pt 0.94 Sn 0.06 , PtSn2, PtSn4, Pt2Sn3 and Pt3Sn

[0214] Preferred intermetallic compounds are selected from PtBi, PtBi2 and Pt2Bi3.

[0215] The presence of intermetallic compounds can be detected by standard methods for characterizing solids, such as electron microscopy, solid-state NMR, XPS (X-ray photoelectron spectroscopy) or powder X-ray diffraction (PXRD). PXRD analysis can be preferably used for unsupported intermetallic compounds, while XPS analysis is preferably used for the analysis of supported intermetallic compounds. PXRD-analysis can be performed, for example, as described in Zhang et al., J. Am. Chem. Soc. (2015) 137, p. 6264 "Characterization of Pt-Bi intermetallic NPs" or as described in Cui et al., J Am. Chem. Soc. (2014), 136, 10206-10209 and its supporting information. XPS can be performed, for example, as described in the following examples.

[0216] Preparation of IMCs

[0217] IMC can be prepared by standard methods, for example as described in Zhang et al., J. Am. Chem. Soc. (2015) 137, 6263-6269; Zhang et al., Electrochemistry Communications (2012) 25, 105-108 or Furukawa et al., RSC Adv. (2013), 3, 23269-23277. IMC can also be prepared by the so-called "DiSalvo" method, as described in Cui et al., J. Am. Chem. Soc. (2014), 136, 10206-10209 or Chen et al. (2012), J. Am. Chem. Soc. 134, 18453-18459. IMC can also be prepared, for example, as described in WO 2018073367.

[0218] Step g) Preparation of IMC

[0219] In one embodiment, the intermetallic compound (IMC) can be obtained as follows:

[0220] g-1) providing a composition comprising the at least one metal compound and the at least one co-catalyst compound

[0221] g-2) reducing the composition

[0222] g-3) Annealing step

[0223] g-4) optionally recovering the IMC.

[0224] Within the scope of the present invention, IMC can be obtained in a reaction combining steps g-1) and g-2) or steps g-2) and g-3).

[0225] Step g-1)

[0226] The metal compound and the co-catalyst compound may for example be provided as described above in step-b).In a preferred embodiment, the metal compound and the co-catalyst compound are provided in a solvent, preferably in an aprotic solvent as described above.

[0227] In one embodiment of the present invention, the metal compound and the promoter compound are provided in the form of chlorides.

[0228] Step g-2)

[0229] Reduction of the composition to reduce the catalyst precursor is preferably carried out as described above in step e).

[0230] In case the reducing agent in step g-2) is provided in a solvent, preferably the solvent is the same as the solvent of the composition provided in step g-1).

[0231] It is within the scope of the present invention to use stabilizers and / or solvents which also serve as reducing agents.

[0232] In one embodiment of the present invention, the reducing agent is selected from potassium triethylborohydride (K(C2H5)3BH) and lithium triethylborohydride (Li(C2H5)3BH).

[0233] In one embodiment of the present invention, step g-1) and step g-2) are carried out in a one-pot reaction.

[0234] In one embodiment of the present invention, step g-1) and step g-2) are carried out in a one-pot reaction, the metal compound and the co-catalyst compound are provided in the form of chlorides, and the reducing agent is selected from potassium triethylborohydride (K(C2H5)3BH) and lithium triethylborohydride (Li(C2H5)3BH). In this embodiment, the insoluble byproduct KCl or LiCl produced is then used as a matrix to stabilize the produced IMC and minimize agglomeration. Typically, this one-pot reaction is carried out in an aprotic solvent, such as THF.

[0235] In order to control the size of the IMC and / or prevent agglomeration, a stabilizer, preferably an inorganic stabilizer, may be added to the composition in step g-2), or a reducing agent which also acts as a stabilizer may be used. Likewise, a solvent (e.g., ethylene glycol) which also acts as a stabilizer may be used in step g-4.

[0236] Step g-3) Annealing step

[0237] The annealing step is preferably carried out by treating the composition obtained in step g-2) at a temperature of 200 to 700°C.

[0238] In another embodiment, steps g-2) and g-3) can be combined into a single step by subjecting the composition obtained in step g-1) to a thermal treatment in the presence of a reducing agent or at a temperature at which reduction occurs.

[0239] Step g-4) Recovery of IMC

[0240] In one embodiment, the IMC can be used directly after the annealing step. In an alternative embodiment, the IMC can be recovered, for example by a suitable separation method, such as filtration and / or centrifugation. The recovery step is preferably carried out in the presence of a stabilizer such as PVP or ethylene glycol.

[0241] The IMCs obtainable in this way may have various sizes, for example 1 to 50 nm, preferably 5 to 30 nm, but also sizes in μm (agglomerates). The size of the IMCs can be adjusted by methods known to those skilled in the art, for example by selecting the solvent and / or stabilizer and / or the time of the annealing step. The structure of the IMCs is usually adjusted by varying the temperature of the annealing step.

[0242] The at least one catalytically active metal and the at least one promoter as intermetallic compound (IMC) can be used in any form, for example unsupported or on a support.

[0243] In the case of at least one catalytically active metal and at least one promoter as an intermetallic compound (IMC) on a support, the catalyst can be prepared, for example, by the following steps:

[0244] - Providing a carrier, as described in step a) above

[0245] - Providing an IMC, preferably prepared as described in step g) above

[0246] - Depositing the IMC on the support, as described in step c) above

[0247] - Optional drying step

[0248] In one embodiment of the present invention, the catalyst can be obtained by the following steps:

[0249] - Provide carrier

[0250] - providing the at least one catalytically active metal and the at least one promoter as an intermetallic compound (IMC),

[0251] - depositing said IMC on said support,

[0252] - Optional drying step

[0253] In one embodiment of the present invention, the catalyst can be obtained by the following steps:

[0254] - providing a carrier, preferably as described in step a) above,

[0255] - providing the at least one catalytically active metal and the at least one promoter as an intermetallic compound (IMC), preferably prepared as described in step g) above

[0256] - depositing the IMC on the support, preferably as described in step c) above

[0257] - Optional drying step

[0258] In the case of at least one catalytically active metal and at least one promoter as an intermetallic compound (IMC) on a support, in an alternative embodiment, the catalyst may be prepared by the following steps

[0259] (i) providing a vector, as described in step a) above

[0260] (ii) providing a composition comprising at least one metal compound and at least one promoter compound, as described in step b) above

[0261] (iii) depositing the composition on a support, as described in step c) above

[0262] (iiia) optionally carrying out a drying and / or calcining step

[0263] (iv) reducing the catalyst precursor thus obtained, as described in step e) above, and

[0264] (v) performing an annealing step, preferably at a temperature of 200 to 700°C.

[0265] In one embodiment of the present invention, the catalyst can be obtained by the following steps:

[0266] (i) Providing a carrier

[0267] (ii) providing a composition comprising said at least one metal compound and said at least one promoter compound

[0268] (iii) depositing the composition on a support

[0269] (iiia) optionally carrying out a drying and / or calcining step

[0270] (iv) reducing the catalyst precursor thus obtained, and

[0271] (v) performing an annealing step.

[0272] In one embodiment of the present invention, the catalyst can be obtained by the following steps:

[0273] (i) providing a carrier, preferably as described in step a) above

[0274] (ii) providing a composition comprising at least one metal compound and at least one promoter compound, preferably as described in step b) above

[0275] (iii) depositing the composition on a support, preferably as described in step c) above

[0276] (iiia) optionally carrying out a drying and / or calcining step, as described in step d) above

[0277] (iv) reducing the catalyst precursor thus obtained, preferably as described in step e) above, and

[0278] (v) performing an annealing step, preferably at a temperature of 200 to 700°C.

[0279] Annealing step (v)

[0280] The annealing step is preferably carried out by treating the catalyst obtained in step (iv) at a temperature of 200-700°C.

[0281] In another embodiment, steps (iv) and (v) may be combined into a single step by thermally treating the precursor obtained in step (iii) in the presence of a reducing agent or at a temperature at which reduction occurs.

[0282] Annealing step g-3) or (v)

[0283] The annealing step is preferably carried out at a temperature between 200 and 700° C., preferably under chemically inert conditions.

[0284] The annealing step is the step that primarily produces the IMC structure. The extension of the IMC structure can be adjusted, for example, by varying the temperature or duration of the annealing step.

[0285] The extent to which the IMC structure is achieved can be monitored by, for example, PXRD analysis. If necessary, the temperature and / or time of the heat treatment can be adjusted to achieve the desired extension of the IMC structure.

[0286] Typically, the annealing step g-3) or (v) is carried out by heating the composition obtained in step g-2) or the catalyst obtained in step (iii) to the desired temperature under chemically inert conditions, wherein the gas mixture present does not contain any reactive components that can chemically react with the composite material. In particular, the mixture should not contain oxidants, such as oxygen, water, NO x , halides, etc. Heating can be carried out by any method suitable for hot solids or wet solids, such as heating in a muffle furnace, microwave oven, rotary kiln, tube furnace, fluidized bed and other heating devices known to those skilled in the art.

[0287] Distribution on the carrier

[0288] In the case of a catalytically active metal on a support, the catalytically active metal may be uniformly distributed on the support or may be non-uniformly distributed on the support. The catalytically active metal may, for example, be concentrated in a core or in a defined layer of the support. The catalytically active metal may be partially or completely located on the inner surface of the support, or may be partially or completely located on the outer surface of the support.

[0289] For all embodiments of the present invention, where the catalyst comprises a catalytically active material and a promoter, the catalytically active material and the promoter may be of any structure, such as unstructured or ordered or partially ordered structures [as intermetallic compounds (IMCs)] as well as different proportions of these states as described above.

[0290] In the case where the catalytically active metal is located entirely on the inner surface of the support, the outer surface of the catalyst is identical to the outer surface of the support.

[0291] The distribution of catalytically active metals can be measured with scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDXS). Distribution can be determined, for example, by preparing a cross section of the catalyst. In the case where the catalyst is spherical, a cross section can be prepared by the center of the sphere. In the case where the catalyst is a wire material, a cross section can be prepared by cutting the wire material at right angles to the wire material axis. By backscattered electrons (BSE), the distribution of catalytically active metals in the catalyst can be seen. The amount of catalytically active metals can then be quantified by EDXS, thus typically using an accelerating voltage of 20 kV.

[0292] In a preferred embodiment of the invention, a catalyst is used in which the catalytically active metal is located in the outer shell of the catalyst. In this embodiment, the catalytically active metal is mainly located in the outer shell of the catalyst.

[0293] In one embodiment, the outer shell of the catalyst is the space from the outer surface of the catalyst to a depth of X from the outer surface of the catalyst, where X is 15% of the distance from the outer surface of the catalyst to the center of the catalyst. For example, in the case of a spherical catalyst with a diameter of 1.5 mm, the outer shell is the space from the outer surface to a depth of 112.5 μm from the outer surface.

[0294] In one embodiment, the outer shell of the catalyst is the space from the outer surface of the catalyst to a depth of X from the outer surface of the catalyst, where X is 30% of the distance from the outer surface of the catalyst to the center of the catalyst. For example, in the case of a spherical catalyst with a diameter of 1.5 mm, the outer shell is the space from the outer surface to a depth of 225 μm from the outer surface.

[0295] In one embodiment, the outer shell of the catalyst is the space from the outer surface of the catalyst to a depth of 100 μm from the outer surface of the catalyst.

[0296] In one embodiment, the outer shell is a space from the outer surface of the catalyst to a depth of 400 μm, preferably 300 μm, preferably 200 μm from the outer surface of the catalyst.

[0297] In a preferred embodiment, at least 50% by weight, preferably at least 70% by weight, preferably at least 80% by weight, preferably at least 90% by weight, preferably at least 95% by weight of the catalytically active metal is located in the outer shell of the catalyst, wherein the outer shell of the catalyst is the space from the outer surface of the catalyst to a depth X from the outer surface of the catalyst, wherein X is 15% of the distance from the outer surface of the catalyst to the center of the catalyst.

[0298] In a preferred embodiment, at least 70% by weight, preferably at least 80% by weight, preferably at least 90% by weight, preferably at least 95% by weight of the catalytically active metal is located in the outer shell of the catalyst, wherein the outer shell of the catalyst is the space from the outer surface of the catalyst to a depth X from the outer surface of the catalyst, wherein X is 30% of the distance from the outer surface of the catalyst to the center of the catalyst.

[0299] In another embodiment of the present invention, at least 50% by weight, preferably at least 70% by weight, preferably at least 80% by weight, preferably at least 90% by weight, preferably at least 95% by weight of the catalytically active metal is located in the outer shell of the catalyst, wherein the outer shell of the catalyst is the space from the outer surface of the catalyst to a depth of 100 μm from the outer surface of the catalyst.

[0300] In another embodiment of the present invention, at least 70% by weight, preferably at least 80% by weight, preferably at least 90% by weight, preferably at least 95% by weight of the catalytically active metal is located in the outer shell of the catalyst, wherein the outer shell of the catalyst is the space from the outer surface of the catalyst to a depth of 400 μm, preferably 300 μm, preferably 200 μm from the outer surface of the catalyst.

[0301] In a further embodiment of the invention, catalysts are used in which the degree of dispersion of the catalytically active metal is on average from 10% to 100%, preferably from 30% to 95% (determined by CO adsorption to DIN 66136-3).

[0302] Catalysts in which the catalytically active metal is located in the catalyst shell can be obtained, for example, by a deposition-reduction method as described above. The distribution of the catalytically active metal in the catalyst shell can be achieved, for example, by selecting the deposition method and / or selecting deposition parameters such as temperature, pH and time and combinations of these parameters. A description of different preparation methods can be found, for example, in the "Handbook of Heterogeneous Catalysis", G. Ertl, H. J. Weitkamp, ​​ed., Volume 1, Wiley-VCH, 1997, Chapter 2, Section 2.2.1.1, Impregnation and Ion Exchange, by M. Che, O. Clause and Ch. Marcilly, pp. 315-340.

[0303] The promoter may be uniformly distributed on the support or may be non-uniformly distributed on the support. In a preferred embodiment, the promoter is distributed in the same manner as the catalytically active material on the support.

[0304] One embodiment of the present invention relates to a process for preparing 3-methyl-2-butene-1-al, wherein 2-methyl-3-butene-2-ol is reacted to 3-methyl-2-butene-1-al in the presence of an oxidizing agent and a catalyst, wherein the catalyst comprises a catalytically active metal, preferably selected from platinum, palladium and gold, and wherein the reaction is carried out at a pH of ≤7, and wherein a catalyst is used which can be obtained by the following steps:

[0305] a) Provide carrier

[0306] b) Providing metal compounds

[0307] c) Depositing the metal compound on the support

[0308] d) optionally calcining the catalyst precursor thus obtained

[0309] e) reducing the catalyst precursor, preferably by treating the catalyst precursor with a reducing agent solution

[0310] f) optionally recovering the catalyst.

[0311] One embodiment of the present invention relates to a process for preparing 3-methyl-2-butene-1-al, wherein 2-methyl-3-butene-2-ol is reacted to 3-methyl-2-butene-1-al in the presence of an oxidizing agent and a catalyst, wherein the catalyst comprises a catalytically active metal, preferably selected from platinum, palladium and gold, and wherein the reaction is carried out at a pH of ≤7, and wherein a catalyst obtained by the following steps is used:

[0312] a) Provide carrier

[0313] b) Providing metal compounds

[0314] c) Depositing the metal compound on the support

[0315] d) optionally calcining the catalyst precursor thus obtained

[0316] e) reducing the catalyst precursor, preferably by treating the catalyst precursor with a reducing agent solution

[0317] f) optionally recovering the catalyst.

[0318] In preferred embodiments of these methods, the catalyst comprises platinum as the catalytically active metal. In preferred embodiments of these methods, the support is selected from alpha alumina (α-Al2O3), beta alumina (β-Al2O3) and gamma alumina (γ-Al2O3). In preferred embodiments of these methods, the oxidant is oxygen and / or hydrogen peroxide.

[0319] One embodiment of the present invention relates to a process for preparing 3-methyl-2-butene-1-al, wherein 2-methyl-3-butene-2-ol is reacted to 3-methyl-2-butene-1-al in the presence of an oxidant and a catalyst, wherein the catalyst comprises a catalytically active metal, preferably selected from platinum, palladium and gold, and wherein the reaction is carried out at a pH of ≤7, and wherein a catalyst is used, the catalyst comprising a catalytically active metal on a support, and wherein the catalytically active metal is predominantly located in the outer shell of the catalyst.

[0320] One embodiment of the present invention relates to a process for preparing 3-methyl-2-butene-1-al, wherein 2-methyl-3-butene-2-ol is reacted to 3-methyl-2-butene-1-al in the presence of an oxidant and a catalyst, wherein the catalyst comprises a catalytically active metal, preferably selected from platinum, palladium and gold, and wherein the reaction is carried out at a pH of ≤7, and wherein a catalyst is used, the catalyst comprising a catalytically active metal on a support, and wherein at least 50% by weight, preferably at least 70% by weight, preferably at least 80% by weight, preferably at least 90% by weight, preferably at least 95% by weight of the catalytically active metal is located in the outer shell of the catalyst, wherein the outer shell of the catalyst is the space from the outer surface of the catalyst to a depth X from the outer surface of the catalyst, wherein X is 15% of the distance from the outer surface of the catalyst to the center of the catalyst.

[0321] One embodiment of the present invention relates to a process for preparing 3-methyl-2-butene-1-al, wherein 2-methyl-3-butene-2-ol is reacted to 3-methyl-2-butene-1-al in the presence of an oxidant and a catalyst, wherein the catalyst comprises a catalytically active metal, preferably selected from platinum, palladium and gold, and wherein the reaction is carried out at a pH of ≤7, and wherein a catalyst is used, the catalyst comprising a catalytically active metal on a support, and wherein a catalyst is used, the catalyst comprising a catalytically active metal on a support, and wherein at least 70% by weight, preferably at least 80% by weight, preferably at least 90% by weight, preferably at least 95% by weight of the catalytically active metal is located in the outer shell of the catalyst, wherein the outer shell of the catalyst is the space from the outer surface of the catalyst to a depth X from the outer surface of the catalyst, wherein X is 30% of the distance from the outer surface of the catalyst to the center of the catalyst.

[0322] One embodiment of the present invention relates to a process for preparing 3-methyl-2-butene-1-aldehyde, wherein 2-methyl-3-butene-2-ol is reacted to 3-methyl-2-butene-1-aldehyde in the presence of an oxidant and a catalyst, wherein the catalyst comprises a catalytically active metal, preferably selected from platinum, palladium and gold, and wherein the reaction is carried out at a pH of ≤7, and wherein a catalyst is used, the catalyst comprising a catalytically active metal on a support, and wherein at least 50% by weight, preferably at least 70% by weight, preferably at least 80% by weight, preferably at least 90% by weight, preferably at least 95% by weight of the catalytically active metal is located in the outer shell of the catalyst, wherein the outer shell of the catalyst is the space from the outer surface of the catalyst to a depth of 100 μm from the outer surface of the catalyst.

[0323] One embodiment of the present invention relates to a process for preparing 3-methyl-2-butene-1-aldehyde, wherein 2-methyl-3-butene-2-ol is reacted to 3-methyl-2-butene-1-aldehyde in the presence of an oxidant and a catalyst, wherein the catalyst comprises a catalytically active metal, preferably selected from platinum, palladium and gold, and wherein the reaction is carried out at a pH of ≤7, and wherein a catalyst is used, the catalyst comprising a catalytically active metal on a support, and wherein at least 70% by weight, preferably at least 80% by weight, preferably at least 90% by weight, preferably at least 95% by weight of the catalytically active metal is located in the outer shell of the catalyst, wherein the outer shell of the catalyst is the space from the outer surface of the catalyst to a depth of 400 μm, preferably 300 μm, preferably 200 μm from the outer surface of the catalyst.

[0324] In preferred embodiments of these methods, the catalyst comprises platinum as the catalytically active metal. In preferred embodiments of these methods, the support is selected from alpha alumina (α-Al2O3), beta alumina (β-Al2O3) and gamma alumina (γ-Al2O3). In preferred embodiments of these methods, the oxidant is oxygen and / or hydrogen peroxide.

[0325] Method Pattern

[0326] The embodiments of the method modes described below can be appropriately applied to all the methods described above.

[0327] The pH of the process can be adjusted by any means known to those skilled in the art, for example by the amount of acid added to the process and the selection or by the amount of strongly acidic cation exchanger loaded into the reactor.

[0328] The method according to the invention can be carried out in a conventional reaction vessel for such reactions, which can be configured as a continuous, semi-batch or batch mode. Generally speaking, the particular reaction is carried out at atmospheric pressure. However, the method can also be carried out under reduced or increased pressure.

[0329] The process according to the invention can be carried out under pressure, preferably at a pressure of more than 1 to 15 bar (absolute), preferably more than 1 to 10 bar (absolute).

[0330] When oxygen is used as the oxidant, the process according to the invention can be carried out at an oxygen partial pressure of 0.1 to 15 bar, preferably 0.2 to 10 bar, preferably 0.2 to 8 bar, more preferably 0.2 to 5 bar, more preferably 1 to 3 bar, preferably 1 to 2.5 bar, more preferably 1.2 to 2 bar.

[0331] In a preferred embodiment of the present invention, the process according to the invention is carried out at a pressure of 1 to 3, preferably 1 to 2.5, more preferably 1.2 to 2 bar.

[0332] In a preferred embodiment of the present invention, the process is carried out as a batch process. In a preferred embodiment of the present invention, the process is carried out as a semi-batch process. In a preferred embodiment of the present invention, the process is carried out as a continuous process.

[0333] In a preferred embodiment of the invention, the process is carried out with a fixed bed catalyst. In case the process according to the invention is carried out with a fixed bed catalyst, a suitable fixed bed reactor may be selected from trickle bed reactors, bubble pack reactors, multi-tube reactors and plate reactors.

[0334] The process according to the invention can be carried out in a fixed bed reactor or can preferably be carried out in more than one, preferably more than two, more preferably more than three, preferably 3 to 5 fixed bed reactors. The one or more fixed bed reactors can be arranged in series or in parallel.

[0335] The process according to the invention can be carried out at typical values ​​of the weight hourly space velocity (WHSV), which is defined as the mass flow rate of process feed (in kg / h) per hour / catalyst (in kg). The process can be carried out, for example, at WHSV values ​​of 1 to 20,000, preferably 10 to 10,000, preferably 20 to 5,000, preferably 20 to 500, more preferably 50 to 100 kg / kg / h.

[0336] The method according to the invention can be carried out in one or more fixed bed reactors with or without heat exchange. In one embodiment of the invention, the fixed bed reactors can be operated to maintain a constant temperature on one, some or all fixed bed reactors. In one embodiment of the invention, the fixed bed reactors can be operated to maintain a defined temperature gradient on one, some or all fixed bed reactors without heat supply or heat removal. In one embodiment of the invention, the fixed bed reactors can be operated with a temperature controlled profile, wherein a defined temperature profile is maintained on one, some or all fixed bed reactors with internal or external heat supply or heat removal.

[0337] In a preferred embodiment of the invention, the process is carried out in a trickle bed reactor with a fixed bed catalyst. In one embodiment of the invention, the process is carried out in more than one, preferably more than two, more preferably more than three trickle bed reactors arranged in series or in parallel, preferably in series. In one embodiment, the process is carried out with 3 to 5 trickle bed reactors arranged in series. In one embodiment, a liquid recycle stream may be provided for one or more, preferably each trickle bed reactor.

[0338] In a preferred embodiment of the trickle bed reactor, the components of the reaction may be introduced into the reactor in parallel, meaning that the liquid phase and the gas phase comprising the oxidant oxygen are introduced into the reactor at the same side, preferably at the top of the reactor.

[0339] In one embodiment of the invention, the method is carried out in a bubble pack reactor with a fixed bed catalyst. In one embodiment of the invention, the method is carried out in more than one, preferably more than two, more preferably more than three bubble pack reactors arranged in series or in parallel, preferably in series. In one embodiment, the method is carried out with 3 to 5 bubble pack reactors arranged in series.

[0340] In one embodiment of the bubble pack reactor, the components of the reaction can be introduced into the reactor in parallel, meaning that the liquid phase and the gas phase containing the oxidant oxygen are introduced into the reactor on the same side, preferably at the bottom of the reactor. In one embodiment of the bubble pack reactor, the components of the reaction can be introduced into the reactor in countercurrent, meaning that the liquid phase and the gas phase containing the oxidant oxygen are introduced into the reactor on opposite sides. In one embodiment, the liquid phase is introduced into the reactor at the bottom of the reactor, while the gas phase containing oxygen as the oxidant is introduced at the top of the reactor. In one embodiment, the liquid phase is introduced into the reactor at the top of the reactor, while the gas phase containing oxygen as the oxidant is introduced at the bottom of the reactor.

[0341] In a preferred embodiment of the present invention, the process is carried out as a slurry process. The process can be carried out in a slurry type system, such as a stirred tank reactor or a slurry bubble column.

[0342] The reaction can be carried out by contacting 2-methyl-3-buten-2-ol, water, an acid, a catalyst, an oxidant and other components, such as one or more solvents, under suitable reaction conditions.

[0343] The components can in principle be brought into contact with one another in any desired order. For example, the 2-methyl-3-butene-2-ol can be charged first, dissolved in water or a solvent as appropriate or in dispersed form, and mixed with the catalyst, or vice versa, the catalytic system can be charged first and mixed with the 2-methyl-3-butene-2-ol and water. Alternatively, the components can also be added to the reaction vessel simultaneously.

[0344] As an example of a batch slurry process, a stirred tank reactor can be used, in which the catalyst, reactants, water, acid, oxidant and optional solvent are loaded. In the case of using oxygen as the oxidant, the reactor is then pressurized with oxygen. The reaction is then carried out until the desired conversion is achieved.

[0345] As an example of a batch slurry process, a stirred tank reactor can be used, wherein the catalyst is loaded, 2-methyl-3-butene-2-ol, water, acid, oxidant and optionally one or more solvents are dissolved in water or solvent or in dispersed form. In the case of using oxygen as the oxidant, the reactor is then pressurized with oxygen. The reaction is then carried out until the desired conversion is achieved.

[0346] As an example of a semi-batch process, a stirred tank reactor can be used, in which catalyst, 2-methyl-3-butene-2-ol, water, acid, oxidant and optional solvent are loaded. In the case of using oxygen as an oxidant, oxygen is then continuously fed into the reactor until the desired conversion is achieved. As another example of a semi-batch process, a fixed bed catalyst in a trickle bed reactor can be used. Then a solution of 2-methyl-3-butene-2-ol, water, acid, oxidant, optionally containing a solvent, is circulated through the catalyst. In the case of using oxygen as an oxidant, oxygen is passed through the reactor as a continuous stream. In one embodiment of the invention, oxygen can be added in excess, and the excess is released into the exhaust gas, or oxygen can be added in an amount required to supplement the consumed oxygen.

[0347] As an example of a continuous slurry process, a continuous stirred tank reactor can be used in which a catalyst is present. A solution of 2-methyl-3-butene-2-ol, water, an acid, optionally containing a solvent, and an oxidant are added continuously. In the case of using oxygen as an oxidant, oxygen can be added in excess and then the exhaust gas is discharged continuously. In another embodiment, oxygen can be added in an amount to supplement the consumed oxygen. The liquid reaction product can be continuously taken out through a filter to keep the catalyst in the reactor.

[0348] In another example of a continuous fixed bed process, a solution of 2-methyl-3-butene-2-ol and an oxidant are both continuously fed into a trickle bed reactor containing a catalyst. In this case, the gas (when oxygen is used as the oxidant) and / or the liquid can be partially or completely recycled back to the reactor to achieve the desired conversion of the reactants and / or oxygen (when oxygen is used as the oxidant).

[0349] In a preferred embodiment, the process according to the invention is carried out in continuous mode.

[0350] It has surprisingly been found that the process according to the invention results in a selectivity to 3-methyl-2-buten-1-al of more than 90%, preferably more than 93%, preferably more than 95%, preferably more than 97%, more preferably more than 99%.

[0351] The process according to the invention is preferably carried out until a conversion of 2-methyl-3-butene-2-ol of 10 to 99.99%, preferably 30 to 95%, most preferably 50 to 80% is obtained.

[0352] The process according to the invention is preferably carried out at a temperature of 1 to 250° C., preferably 5 to 150° C., preferably 20 to 100° C., 20 to 70° C., more preferably 25 to 80° C., preferably 30 to 70° C., more preferably 35 to 50° C. In one embodiment of the invention, the process is carried out at a temperature of 40 to 80° C.

[0353] The crude product obtained can be subjected to conventional purification measures, including distillation or chromatography or a combination of measures. Suitable distillation apparatuses for purifying the product include, for example, distillation columns, such as plate columns optionally equipped with bubble cap trays, sieve plates, sieve trays, plugging or packing materials, or spinning belt columns, such as thin film evaporators, falling film evaporators, forced circulation evaporators, wiped film (Sambay) evaporators, etc. and combinations thereof.

[0354] The invention is further illustrated by the following non-limiting examples.

[0355] Example - Catalyst Preparation

[0356] Example C1

[0357] Step a): Support: 50 g of alumina (γ-Al2O3 strands with an average diameter of 1.5 mm (commercially available from Exacers.rl Italy) were heated to 550°C in 4 hours and kept at 550°C for 1 hour.

[0358] Step b): 6.68 g of a 15.4 wt. % Pt(NO3)2 solution in 10 wt. % nitric acid and 1.29 g Bi(NO3)3 were added to 95.21 g water at room temperature.

[0359] Step c): A flask was charged with 50 g of the alumina obtained in step a), immersed in the Pt / Bi solution obtained in step b), and stirred at 70 mbar for 0.5 hours while the mixture was heated to 80° C. At 80° C., the solvent was removed within 30 minutes.

[0360] Dry in a rotary evaporator at 80°C for 60 minutes.

[0361] Step d): The catalyst precursor thus obtained was placed in a muffle furnace and heated to 450° C. over a period of 5 hours. The temperature of 450° C. was maintained for 1 hour.

[0362] Step e): Reduction of the catalyst precursor is carried out by treating the catalyst precursor with a reducing agent solution. 50 g of the catalyst precursor obtained in step d) is added to 400 g of water and heated to 60° C. An aqueous sodium formate solution (34.87 g of sodium formate (97%) plus 88.38 g of water) is prepared and added dropwise to the catalyst precursor over a period of 10 minutes. The reaction mixture is maintained at 60° C. for 140 minutes and then cooled to room temperature under N2.

[0363] The catalyst was recovered by filtration and washed with water to a conductivity of less than 170 μS / cm, followed by drying at 80° C. for 4 hours. The catalyst thus obtained had a Pt content of 1.4% by weight and a Pt:Bi molar ratio of 1:0.5. The distribution of the catalytically active metal Pt was determined in a cross section of the wire material by SEM-EDXS: most of the Pt was located within 100 μm from the outer surface of the catalyst.

[0364] Example C2

[0365] Example C1 was repeated, step c) was changed as follows:

[0366] Step c): A flask was charged with 50 g of the alumina obtained in step a) and impregnated with the Pt / Bi solution obtained in step b) and stirred for 10 minutes at 70 mbar. The catalyst precursor was recovered by filtration.

[0367] The catalyst thus obtained had a Pt content of 1.4 wt % and a Pt:Bi molar ratio of 1:0.5. The distribution of the catalytically active metal Pt was determined in a cross section of the strand by SEM-EDXS: most of the Pt was located within 100 μm of the catalyst outer surface.

[0368] Example C3

[0369] Step a): Support: 50 g of alumina (γ-Al2O3 strands with a diameter of 1.5 mm (commercially available from Exacer srl Italy) were heated to 550°C in 4 hours and kept at 550°C for 1 hour.

[0370] Step b): 6.63 g of a 15.4 wt. % Pt(NO3)2 solution in 10 wt. % nitric acid and 5.09 g Bi(NO3)3 were added to 29.6 g water at room temperature.

[0371] Step c): A flask was charged with 50 g of the aluminum oxide obtained in step a) and rotated at 70 mbar. The Pt / Bi solution obtained in step b) was added to the injection nozzle via a dropping funnel and sprayed onto the support. The deposition step was carried out with mixing at room temperature for 30 minutes. Drying was carried out in a rotary evaporator at 80° C. for 60 minutes.

[0372] Step d): The catalyst precursor thus obtained was placed in a muffle furnace and heated to 450° C. over a period of 5 hours. The temperature of 450° C. was maintained for 1 hour.

[0373] Step e): Reduction of the catalyst precursor is carried out by treating the catalyst precursor with a reducing agent solution. 50 g of the catalyst precursor is added to 400 g of water and heated to 60° C. An aqueous sodium formate solution (34.87 g of sodium formate (97%) plus 88.38 g of water) is prepared and added dropwise to the catalyst precursor over a period of 15 minutes. The reaction mixture is maintained at 60° C. for 120 minutes and then cooled to room temperature under N2.

[0374] The catalyst was recovered by filtration and washed with water to a conductivity of less than 170 μS / cm, followed by drying at 80° C. for 4 hours. The catalyst thus obtained had a Pt content of 1.6% by weight and a Pt:Bi molar ratio of 1:2. The distribution of the catalytically active metal Pt was determined in a cross section of the wire material by SEM-EDXS: most of the Pt was located within 100 μm from the outer surface of the catalyst.

[0375] Example C4

[0376] Example C3 was repeated, step b) being modified as follows: 2.55 g (instead of 5.09 g) of Bi(NO3)3 were added to the solution.

[0377] The catalyst thus obtained had a Pt content of 1.6% by weight and a Pt:Bi molar ratio of 1:1.

[0378] The distribution of the catalytically active metal Pt was determined in a cross section of the strands using SEM-EDXS: most of the Pt was located within 100 μm from the outer surface of the catalyst.

[0379] Example C5

[0380] Example C3 was repeated, step b) being modified as follows: 1.27 g (instead of 5.09 g) of Bi(NO3)3 were added to the solution.

[0381] The catalyst thus obtained had a Pt content of 1.6 wt % and a Pt:Bi molar ratio of 1:0.5. The distribution of the catalytically active metal Pt was determined in a cross section of the strand by SEM-EDXS: most of the Pt was located within 400 μm of the catalyst outer surface.

[0382] Example C6

[0383] Step a): 40 g of gamma-alumina (strands with a diameter of 1.5 mm) were heated to 550° C. over 4 hours and kept at 550° C. for 1 hour.

[0384] Step b): A 15.7 wt% Pt(NO3)2 solution in 10 wt% nitric acid was prepared.

[0385] Step c): A rotating plate was equipped with 40 g of the aluminum oxide obtained in step a), rotated and heated to 100° C. 15.95 g of a 15.7 wt. % Pt(NO3)2 solution in 10 wt. % nitric acid were sprayed onto the support using an injection nozzle over a period of 1 hour and 6 minutes. After the addition was complete, the mixture was rotated on the hot rotating plate for a further 10 minutes and then dried.

[0386] Step d): The catalyst precursor thus obtained was placed in a muffle furnace and heated to 450° C. over a period of 3 hours. The temperature of 450° C. was maintained for 1 hour.

[0387] Step e): Reduction of the catalyst precursor is carried out by treating the catalyst precursor with a reducing agent solution. 41.97 g of the catalyst precursor is added to 399.94 g of water and heated to 60° C. An aqueous sodium formate solution (29.32 g of sodium formate plus 74.13 g of water) is prepared and added dropwise to the catalyst precursor over a period of 15 minutes. The reaction mixture is maintained at 60° C. for 120 minutes and then cooled to room temperature under N2.

[0388] The catalyst was recovered by filtration and washed with water to a conductivity below 132.5 μS / cm, followed by drying at 80°C for 4.5 hours.

[0389] The catalyst thus obtained had a Pt content of 2.6% by weight. The distribution of the catalytically active metallic Pt was determined in a cross section of the strand by means of SEM-EDXS: the majority of the Pt was located within 100 μm of the catalyst surface.

[0390] Figure 1 and 2 The Pt distribution in the catalyst of Example C6 is shown. Figure 2 In FIG. 1 , the Y axis shows the local Pt concentration (wt. %) measured by EDX, while the X axis shows the position of the measurement. The distance is taken along the dashed line in the upper photo 1, with the zero point being on the left.

[0391] Example C7

[0392] C7A-IMC preparation (step g) PtBi was synthesized as follows (steps g-1 to g-3):

[0393] 1.2 mmol PtCl4 and 1.2 mmol BiCl3 were weighed in an argon-filled glove box and dissolved in 10 mL THF by stirring. An excess of 30 mol% of the reducing agent potassium triethylborohydride KBH(C2H5)3 (1.0 M in THF, Sigma-Aldrich) was mixed with THF to form a 15 mL solution. The solution was then drawn into a syringe and injected into the reducing agent solution under vigorous stirring. The sample was dried under vacuum until most of the THF disappeared. Hexane was then added to precipitate the PtBi-KCl powder. The sample was then washed three times with THF and hexane without contact with air. The product was then dried under vacuum for 2 hours and transferred to a glove box. The product was placed in a silicon tube, sealed under vacuum, and then annealed at 400°C for 6 hours. The resulting PtBi-KCl powder was analyzed by PXRD as described below. P-XRD analysis confirmed the IMC structure.

[0394] The KCl containing powder was then mixed with water and centrifuged until the solution was free of any chloride (AgNO3 test of the washing solution). PVP was then added and the solution was sonicated.

[0395] Preparation of C7B-supported IMC catalyst

[0396] Step a): Support: 8.25 g of alumina (γ-Al2O3 bundles with an average diameter of 1.5 mm (commercially available from Exacers.rl, Italy) were heated to 550°C for 4 hours and kept at 550°C for 1 hour.

[0397] Step c): 6.19 g of an aqueous suspension obtained in Example C7A containing 0.165 g of PtBi IMC and 0.017 g of PVP was sonicated for 10 minutes. The suspension was then added to 8.25 g of the support and mixed with a spatula for about 15 minutes. The catalyst was then dried at 80° C. for 1 hour.

[0398] The distribution of the catalytically active metal Pt was determined by SEM-EDXS in the cross section of the chain: most of the Pt was located within 100 μm from the outer surface of the catalyst. The resulting catalyst was examined by XPS as described below. The XPS analysis confirmed the IMC structure.

[0399] Example C8

[0400] C8A-IMC preparation (step g) / Pt2Bi3 was synthesized as follows (steps g-1 to g-3):

[0401] 0.6mmol PtCl4 and 0.9mmol BiCl3 were weighed in an argon-filled glove box and dissolved in 10mL THF by stirring. An excess of 30mol% of the reducing agent potassium triethylborohydride KBH(C2H5)3 (1.0M in THF, Sigma-Aldrich) was mixed with THF to form a 15mL solution. The solution was then drawn into a syringe and injected into the reducing agent solution under vigorous stirring. The sample was dried under vacuum until most of the THF disappeared. Hexane was then added to precipitate the Pt2Bi3-KCl powder. The sample was then washed three times with THF and hexane without contact with air. The product was then dried under vacuum for 2 hours and transferred to a glove box. The product was placed in a silicon tube, sealed under vacuum, and then annealed at 400°C for 6 hours. The resulting Pt2Bi3-KCl powder was analyzed by PXRD as described below. P-XRD analysis confirmed the IMC structure.

[0402] The KCl containing powder was then mixed with water and centrifuged until the solution was free of any chloride (AgNO3 test of the washing solution). PVP was then added and the solution was sonicated.

[0403] Preparation of C8B-supported IMC catalyst

[0404] Step a): Support: 12.9 g of alumina (γ-Al2O3 bundles with an average diameter of 1.5 mm (commercially available from Exacers.rl, Italy) were heated to 550°C for 4 hours and kept at 550°C for 1 hour.

[0405] Step c): 9.6 g of an aqueous suspension obtained in Example C8A containing 0.258 g of Pt2Bi3IMC and 0.026 g of PVP were sonicated for 10 minutes. The suspension was then added to 12.9 g of the support, which was spray-impregnated in a rotary evaporator at 500 mbar for 15 minutes. The catalyst was subsequently dried at 80° C. for 1 hour.

[0406] The distribution of the catalytically active metal Pt was determined by SEM-EDXS in the cross section of the chain: most of the Pt was located within 100 μm from the outer surface of the catalyst. The resulting catalyst was examined by XPS as described below. The XPS analysis confirmed the IMC structure.

[0407] Example C9

[0408] C9A-IMC preparation (step g) / PtBi2 was synthesized as follows (steps g-1 to g-3):

[0409] 1.2mmol PtCl4 and 2.4mmol BiCl3 were weighed in an argon-filled glove box and dissolved in 10mL THF by stirring. An excess of 30mol% of the reducing agent potassium triethylborohydride KBH(C2H5)3 (1.0M in THF, Sigma-Aldrich) was mixed with THF to form a 15mL solution. The solution was then drawn into a syringe and injected into the reducing agent solution under vigorous stirring. The sample was dried under vacuum until most of the THF disappeared. Hexane was then added to precipitate the PtBi2-KCl powder. The sample was then washed three times with THF and hexane without contact with air. The product was then dried under vacuum for 2 hours and transferred to a glove box. The product was placed in a silicon tube, sealed under vacuum, and then annealed at 400°C for 6 hours. The resulting PtBi2-KCl powder was analyzed by PXRD as described below. P-XRD analysis confirmed the IMC structure.

[0410] The KCl containing powder was then mixed with water and centrifuged until the solution was free of any chloride (AgNO3 test of the washing solution). PVP was then added and the solution was sonicated.

[0411] Preparation of C9B-supported IMC catalyst

[0412] Step a): Support: 14.65 g of alumina (γ-Al2O3 bundles with an average diameter of 1.5 mm (commercially available from Exacer srl, Italy) were heated to 550°C for 4 hours and kept at 550°C for 1 hour.

[0413] Step c): 10.99 g of an aqueous suspension obtained in Example C9A containing 0.293 g of PtBi2IMC and 0.029 g of PVP was sonicated for 10 minutes. The suspension was then added to 14.65 g of the support, which was impregnated in a rotary evaporator at 500 mbar for 15 minutes. The catalyst was subsequently dried at 80° C. for 1 hour.

[0414] The distribution of the catalytically active metal Pt was determined by SEM-EDXS in the cross section of the chain: most of the Pt was located within 100 μm from the outer surface of the catalyst. The resulting catalyst was examined by XPS as described below. The XPS analysis confirmed the IMC structure.

[0415] PXRD analysis

[0416] The phase purity and structure of the Pt-Bi material were analyzed by XRD using a Bruker D8 Advance diffractometer from Bruker AXS GmbH, Karlsruhe, using a variable slit from 10° to 90° 2θ, the diffractometer being equipped with a Lynxye XE 1D-detector. The anode of the X-ray tube consisted of copper. To suppress Cu radiation, a nickel filter was used. The following parameters were used: voltage: 40 kV, current: 40 mA, step size: 0.02° 2θ, scanning speed 0.2 s / step, Soller slit (primary side): 2.5°; Soller slit (secondary side): 2.5°; divergence slit: 0.17°.

[0417] The phases present in each sample were identified by searching and matching data available from the International Center for Diffraction Data (ICDD, 2015 edition).

[0418] XPS analysis

[0419] XPS analysis was performed with a Phi Versa Probe 5000 spectrometer using monochromatic Al Kα radiation (50.4 W) with a spot size of 200 × 200 μm, standard configuration. The instrument work function was calibrated to obtain a binding energy (BE) of 84.00 eV for the Au 4f7 / 2 line metallic gold, and the spectrometer dispersion was adjusted to obtain a BE of 932.62 eV for the Cu 2p3 / 2 line metallic copper. All samples used the built-in Phi charge neutralizer system. To minimize the effects of differential charging, all samples were mounted insulated from ground. The survey scan analysis was performed with a pass energy of 117.4 eV and an energy step size of 0.5 eV. High-resolution analysis was performed on the same analysis area with a pass energy of 23.5 eV and an energy step size of 0.1 eV. The spectrum has been charge corrected to the main line of the carbon 1s spectrum, which was set to 284.8 eV as a typical value for the energy reference of the peaks of exotic hydrocarbons. All spectra were analyzed using CasaXPS software version 2.3.20 with Shirley background subtraction. Quantification was performed using the relative sensitivity factors and transmission functions provided by the instrument manufacturer.

[0420] Example - Method

[0421] Gas chromatography analysis:

[0422] GC system and separation method:

[0423] GC system: Agilent 7890A

[0424] GC tower: RTX-200 (60m (length), 0.32mm (ID), 1.0μm (membrane))

[0425] Temperature program: 10 minutes at 60°C, 6°C / min from 60 to 280°C, 10 minutes at 280°C

[0426] Example 1

[0427] A 0.27 L metal autoclave was charged with 4 g of 2-methyl-3-butene-2-ol (DMVC, dimethylvinyl carbinol, from BASF), 76 g of demineralized water and 0.9 g of platinum on alumina (5 w / w% Pt on Al2O3 from Strem (ESCAT 2941), corresponding to 0.5 mol% platinum based on DMVC). Finally, 4 drops of H3PO4 (85 w / w-%) were added to the reactor, the solution was stirred at 1000 rpm and heated to 70° C., and O2 (5.9 l / h) was metered into the reactor at a constant O2 pressure of 2 bar at a rate to keep the pressure constant (no offgassing) for 6.5 hours. At the end of the reaction, the autoclave was cooled to room temperature and depressurized before opening. The reaction mixture was then filtered to remove the catalyst, and the filtrate was analyzed by gas chromatography using an FID detector, showing that it contained 55 area % of unconverted 2-methyl-3-butene-2-ol (DMVC), 7 area % of 3-methyl-2-butene-1-ol (isopentenol), 36 area % of 3-methyl-2-butene-1-aldehyde (isopentenol) and 1 area % of 3,3-dimethylacrylic acid. This corresponds to a conversion of DMVC plus isopentenol of 37.8% and a selectivity to isopentenal of 97.7%.

Claims

1. A process for preparing 3-methyl-2-butene-1-al, wherein 2-methyl-3-butene-2-ol is reacted to 3-methyl-2-butene-1-al in the presence of oxygen and a catalyst, wherein the catalyst comprises a catalytically active metal selected from elements of Groups 8, 9, 10 and 11 of the Periodic Table of the Elements on a support, and wherein the reaction is carried out in the presence of a liquid phase at a pH of ≤6, wherein the liquid phase contains at least 25% by weight of water, wherein the catalytically active metal is platinum.

2. The process according to claim 1, wherein the support is alumina.

3. The process according to claim 1, wherein the reaction is carried out at a temperature of 20 to 100°C.

4. The process according to claim 2, wherein the reaction is carried out at a temperature of 20 to 100°C.

5. The process according to claim 1, wherein the reaction is carried out in the presence of a liquid phase, wherein the liquid phase contains at least 50% by weight of water.

6. The process according to any one of claims 1 to 4, wherein the reaction is carried out at an oxygen partial pressure of 0.2 to 8 bar.

7. The process according to claim 5, wherein the reaction is carried out at an oxygen partial pressure of 0.2 to 8 bar.

8. The process according to any one of claims 1 to 4 and 7, wherein the catalyst comprises one or more promoters.

9. The process according to claim 5, wherein the catalyst comprises one or more promoters.

10. The process according to claim 6, wherein the catalyst comprises one or more promoters.

11. The process according to claim 8, wherein the promoter is bismuth.

12. The process according to claim 9, wherein the promoter is bismuth.

13. The process according to claim 10, wherein the promoter is bismuth.

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