Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
  • C07B35/00—Reactions without formation or introduction of functional groups containing hetero atoms, involving a change in the type of bonding between two carbon atoms already directly linked
  • C07B35/02—Reduction
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
  • C07C5/02—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by hydrogenation
  • C07C5/10—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by hydrogenation of aromatic six-membered rings
  • C07C5/11—Partial hydrogenation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
  • C07C2523/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of noble metals
  • C07C2523/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of noble metals of the platinum group metals
  • C07C2523/46—Ruthenium, rhodium, osmium or iridium
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2527/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
  • C07C2527/24—Nitrogen compounds
  • C07C2527/25—Nitrates

Definitions

• the present invention relates to a process for hydrogenating at least one organic substrate in at least two liquid phases which are at least partially immiscible with one another using a catalyst, wherein at least one of the two or more liquid phases contains at least the following further components: (i) at least one surface-active substance and (ii) at least one salt which is at least partially soluble in at least one of the liquid phases.
• the present invention is in the fields of catalysis and of multiphase reactions.
• catalysts a distinction is made between homogeneous and heterogeneous catalysts.
• homogeneous catalysis in which all reactants are present in one phase
• heterogeneous catalysis reactants and products are present in a different phase from the catalyst.
• the advantage of heterogeneous catalysis over homogeneous catalysis is the greater ease with which the catalyst can be separated off and the resulting lower costs for purifying the product obtained and for regenerating and/or removing the catalyst.
• the heterogeneously catalysed hydrogenation of an organic substrate in the liquid phase described in the present invention is a multiphase reaction in which at least the following three phases are present: a gas phase and at least two liquid phases which are at least partially immiscible with one another.
• Two phases which are at least partially immiscible with one another e.g. an "oil phase” (hydrophobic, immiscible with water) and a “water phase” (hydrophilic, miscible with water) , are regarded as different phases for the purposes of the invention.
• an "oil phase” hydrophobic, immiscible with water
• water phase hydrophilic, miscible with water
• EP 0 554 765 Al describes a process for preparing cyclohexene by partial hydrogenation of benzene by means of hydrogen in the presence of water and a ruthenium catalyst which is modified with nickel.
• the document focuses on an improved catalyst and provides no teachings regarding the addition of further substances which are at least partially soluble in the liquid phase.
• US 5 969 202 pays particular attention not only to the catalyst but also to the composition of the liquid phase.
• the starting materials and products are preferentially present in the oil phase while the aqueous phase comprises mostly the cosolvent water.
• Control of this phase separation makes it possible to control the selectivity to individual products, in this case cyclic olefin relative to cyclic alkane, for example by addition of zinc sulphate.
• cyclic olefin relative to cyclic alkane
• no further substances for controlling the phase behaviour and the selectivity are disclosed.
• a further document which describes the addition of salts is, for example, US 5 973 218.
• phase transfer catalysis is the acceleration of reactions in two-phase systems (e.g. water/organic solvent) in which the substrate is present in the lipophilic (hydrophobic) organic phase and the reagent is, for example * , present in the aqueous or solid phase. Transport of the reagent through the phase boundary to the substrate is then effected by phase transfer catalysis.
• two-phase systems e.g. water/organic solvent
• the substrate is present in the lipophilic (hydrophobic) organic phase
• the reagent is, for example *
• phase transfer catalysts belong to the class of surface-active substances as are defined further below in the present invention.
• phase transfer catalyst for the (partial) hydrogenation of organic substrates
• an Ru complex i.e. not a solid and thus not a heterogeneous catalyst
• gaseous hydrogen, water, an organic solvent and a phase transfer catalyst of the abovementioned type are used.
• the object of the invention is achieved by providing the following process: hydrogenation of at least one organic substrate in at least two liquid phases which are at least partially immiscible with one another using a catalyst, wherein at least one of the two or more liquid phases contains at least the following further components: (i) at least one surface-active substance and (ii) at least one salt which is at least partially soluble in at least one of the liquid phases.
• the substrate used can in principle be any organic compound which reacts with hydrogen. Preference is given to using compounds which have at least one bond selected from the following group: C-C double bonds, C-C triple bonds, aromatic systems, C-N double bonds, C-N triple bonds, C-0 double bonds and C-S double bonds. These bonds can be present in a monomer or a polymer.
• aromatic hydrocarbons are particularly preferred.
• the aromatic substrate or substrates can be selected from the group consisting of benzene, benzene substituted on the ring by at least one hydroxy, carboxy or amino group, benzene derivatives having at least one alkyl group, polycyclic aromatics, fused aromatics, heteroaromatics, multinuclear aromatics and also nonbenzenoid aromatics. Benzene and toluene and their derivatives are particularly preferred.
• the organic substrate and optionally a solvent in which this substrate is at least partially soluble is referred to as solvent.
• the solvent in question is at least partially immiscible with the cosolvent described below.
• the solvent is typically the hydrophobic "oil phase" .
• the liquid which is at least partially immiscible with the organic substrate or is less soluble with the organic substrate is referred to as cosolvent for the purposes of the present invention.
• Figure 1 shows, by way of example, the influence of the use of monools and polyols on the reaction rate in the hydrogenation of toluene in the presence of different proportions of cosolvent.
• the homologous series methanol, glycol and glycerol was examined here. Water serves as comparative system in this case and also for the examples described below, since the hydrogenation of benzene, for example, is carried out industrially in a water phase.
• any ratio of cosolvent to solvent i.e., for example, the ratio of water to toluene
• the hydrogenation can in principle be carried out using any hydrogen-donating substance.
• the hydrogen can be introduced into the reaction system from the outside as gas, preferably as hydrogen gas or as a gas mixture containing hydrogen.
• the hydrogen can also be generated in the liquid phase by reaction or from precursor compounds, for example as nascent hydrogen.
• the hydrogenation reaction can be any reaction in which an organic substrate reacts with at least one of the above-described hydrogenating agents.
• selective hydrogenations are particularly preferred.
• a selective hydrogenation is any hydrogenation in which at least one target product is formed in higher yield than any other single product, including by-products and/or waste products.
• Complete hydrogenation is explicitly included as a possibility, but a partial hydrogenation is preferred.
• a partial hydrogenation is, for the purposes of the present invention, any hydrogenation which does not lead to complete hydrogenation of the substrate.
• the catalyst to be used for the hydrogenation is, for the purposes of the present invention, not subject to any restrictions at all.
• the catalyst can in principle also be homogeneous, i.e. be present as a solution in one of the liquid phases.
• An advantage of the present invention is, in particular, that catalysts which do not come into question for industrial processes, e.g. hydrogenation processes, due to nonoptimal activity and/or selectivity can also be used industrially as a result of the additives employed according to the invention.
• the catalysts used according to the invention comprise at least one metal, preferably a catalytically active metal ("active metal") selected from the group consisting of metals of the main groups and transition groups of the Periodic Table of the Elements.
• active metal a catalytically active metal
• the metal or metals is or are applied to a porous support or is or are a constituent of a porous material.
• porous (support) material in principle any material which is porous and withstands the conditions occurring during use of the catalyst can be used.
• Refractory i.e. nondecomposing, oxides and also related mixed oxides and/or oxide mixtures are of particular importance.
• silicates in particular aluminosilicates and more preferably zeolites and also titanium oxides, aluminium oxides, silicon oxides, zirconium oxides, carbon-containing materials, carbon modifications and especially activated carbon, or mixtures of at least two of the abovementioned substances.
• Grids, meshes, braided materials, honeycombs or compositions of metals or of composite materials containing metals and/or ceramics are likewise conceivable.
• the use of a nonporous support and/or application of the catalytically active material, for example at least one active metal, as a film or layer to a support is likewise conceivable.
• the catalytically active transition metals are preferably used in the form of their salts and particularly preferably in the form of their oxides or sulphides as supported catalysts or as pure metal in the form of all-active or supported catalysts.
• These catalysts can be used as powder catalysts which are present in the reactor as a fine suspension or as pellets, tablets or granules.
• the catalysts to be used should be at least not completely soluble in the liquid phase. Greater preference is given to the heterogeneous catalyst not being soluble at all, i.e. it has a low solubility product as is typical for a transition metal oxide, both in the solvent and in the cosolvent.
• surface- active substances are all substance which, in liquid systems, accumulate or are depleted at at least one phase boundary selected from the group consisting of liquid/gas, liquid/liquid and liquid/solid phase boundaries.
• surfactant and “surface-active substance” are used synonymously for the purposes of the present invention.
• a characteristic embodiment of surfactants comprises bipolar compounds in which the hydrophilic part comprises one or more polar groups.
• the hydrophobic part preferably comprises a chain of carbon atoms .
• anionic, cationic, nonionic and ampholytic surfactants preference is given to anionic, cationic, nonionic and ampholytic surfactants.
• Anionic surfactants are particularly preferred for the purposes of the present invention.
• Anionic surfactants may have carboxylate, sulphate or sulphonate groups.
• cationic surfactants having at least one quaternary ammonium group or nonionic surfactants is also conceivable.
• ampholytic surfactants i.e. surface-active substances which contain both anionic and cationic groups and accordingly behave as anionic or cationic surface-active compounds depending on the pH.
• surface-active substances selected from the group consisting of block copolymers, poly (alkylene oxide) triblock copolymers; alkylpoly (ethylene oxides); lipids, phospholipids; and also combinations of two or more of the abovementioned substances are also preferred.
• nonionic surface-active substances preference is given to compounds containing at least one ether group.
• Polyethers such as polyethylene glycol or polypropylene glycol are particularly preferred.
• polyethylene-block-poly ethylene glycol
• poly (ethylene glycol) 4-nonylphenyl 3-sulphopropyl diether poly (ethylene glycol) monolaurate
• hexadecyl- trimethylammonium acetate hexadecyltrimethylammonium nitrate
• trimethylammonium bromides for example hexadecyltrimethylammonium bromide (CTAB)
• the proportion of surface-active substance to be used is in principle not subject to any restrictions. In principle, preference is given to the value at which the optimum value of the desired parameter, e.g. the selectivity, is achieved. Values of from 0.1% by weight to 30% by weight are preferred. However, in realistic industrial operation, the comparatively high costs of some surfactants have to be taken into account. In such a case, the surfactant content is preferably from 0.1 to 2 % by weight, particularly preferably from 0.1 to
• the multiphase systems occurring in the process of the present invention and comprising at least one hydrophilic ("aqueous") phase and at least one phase which is not completely miscible with water are also referred to as emulsions.
• the industrially most important emulsions generally comprise a water phase and an organic phase, which is usually referred to as "oil phase” .
• the internal phase is, in this sense, the part of the system which is present in small droplets.
• Each such system can exist in two different forms in which water or oil can be the internal phase. Accordingly, a distinction is made between water-in-oil and oil-in- water emulsions.
• the present invention applies to all binary liquid systems which are known to those skilled in the art and are not completely miscible, including the abovementioned emulsions and in particular micro- emulsions .
• the system described in the present invention which comprises a heterogeneous catalyst and also a liquid substrate phase and a cosolvent which is at least partially immiscible therewith
• it can, for example, be useful for the aqueous phase, here the cosolvent, to be preferentially adsorbed on the heterogeneous catalyst and possibly block active centres.
• Such an effect can be of assistance in controlling the selectivity and it may be expected that the use of additives could influence the interfaces in question so as to increase the activity and/or selectivity.
• a possible embodiment of the substrate (possibly with solvent) /cosolvent system is a microemulsion.
• This is a macroscopically homogeneous, optically transparent, low-viscosity, thermodynamically stable mixture of two liquids which are immiscible with one another using at least one nonionic or ionic surfactant. If an ionic surfactant having only a hydrophobic radical is added to the two mutually insoluble components, a cosurfactant is additionally needed to form the microemulsion. Short-chain aliphatic alcohols are preferred here. Due to their extremely large surface area per unit volume, microemulsions offer an ideal "solvent" for chemical reactions in which mass transfer through interfaces plays a role.
• a salt is any at least partially charged compound, i.e. any compound which is not neutral in terms of its charge distribution.
• Ionic compounds which are at least partially soluble in the aqueous phase and break up into anions and cations which may be partially solvated are particularly preferred.
• Metal salts are more preferred and metal salts having at least doubly charged cations are further preferred.
• a low salt content i.e. a salt content of from 10 "7 to 1 mol/1
• a value of from 10 "5 mol/1 to 10 "2 mol/1 is preferred.
• the proportions are based on litres of the aqueous phase.
• the type and proportion of cosolvent and also the type and proportion of the surface-active substance and the type of salt and possibly also other parameters and/or additive are varied in a multidimensional parameter matrix so as to optimize the selectivity and/or the yield.
• the process of the present invention for hydrogenating organic substrates comprises bringing the above- described substances, but at least (i) at least one organic substrate, (ii) at least one cosolvent, (iii) at least one surface-active substance and (iv) at least one salt which is at least partially soluble in the liquid phase into contact with a hydrogenating agent.
• the conditions under which this occurs, the order in which the components are combined and/or brought into contact with one another and the containers are subject to no particular restrictions according to the present invention.
• the reaction conditions for the hydrogenation of aromatics which are known to those skilled in the art in organic chemistry in general and in industrial organic chemistry in particular are particularly preferred. Further preference is given to the conditions which are known for the selective hydrogenation of aromatics.
• Figure 1 shows the influence of the use of monools and polyols on the reaction rate in the hydrogenation of toluene (for different proportions of cosolvent).
• Figure 2 shows the reaction rates for the hydrogenation of toluene (different proportions by volume of various cosolvents added) .
• Figure 3 shows the dependence of the selectivity for the hydrogenation of toluene to methylcyclohexene using lanthanum nitrate as additive.
• Figure 4 shows the effect of the combined addition of a salt and a surface-active substance on the selectivity.
• Figure 5 shows the effect of adding nonionic, cationic and anionic surfactants at the same mole fraction of zinc salt, respectively.
• Figure 6 shows the effect of high proportions of surface-active substances on the olefin yield
• the autoclaves are equipped with four-blade stirrers .
• the stirrer speed can be varied in a range from 50 to 2 000 revolutions per minute.
• the experiments described here were carried out at 1 200 rpm.
• the autoclave can be cooled or heated within a temperature range from 20°C to 200°C.
• the autoclaves comprise the actual reaction vessel, an upper part (lid) and a sleeve which can heat or cool the reaction vessel. A rubber seal between the reaction vessel and lid ensures that the apparatus is gastight.
• Surfactant 1 Polyethylene-block-poly (ethylene glycol): molar mass 920 g/mol; 20% of ethylene oxide in the monomer;
• Surfactant 2 Polyethylene-block-poly (ethylene glycol): molar mass 575 g/mol; 20% of ethylene oxide in the monomer ; Surfactant 3: Poly (ethylene glycol) 4-nonylphenyl 3-sulphopropyl diether;
• Surfactant 4 Polyethylene-block-poly (ethylene glycol): molar mass (M) 875 g/mol; 20% of ethylene oxide in the monomer;
• Surfactant 5 Poly (ethylene glycol) monolaurate: (M: 400 g/mol) ;
• Surfactant 6 Poly (ethylene glycol) monolaurate: (M: 600 g/mol) ;
• Surfactant 7 Hexadecyltrimethylammonium acetate
• Surfactant 8 Hexadecyltrimethylammonium nitrate.
• Example 1 Hydrogenation of toluene over an Ru/C catalyst using a cosolvent
• Figure 2 shows the reaction rates obtained when different proportions by volume of each of the various cosolvents were added.
• the shape of the reaction rate versus proportions by volume curve is virtually identical for methanol, ethanol and 1-propanol: as the proportion of cosolvent increases, an increase in the reaction rate is observed until finally the maximum reaction rate is achieved at about 50% by volume. Since it is more economical in practice to employ relatively small proportions of cosolvent, a proportion of cosolvent of 30% by volume was chosen for the experiments described below.
• Example 2 Selectivity of the hydrogenation of toluene when using an Ru-C catalyst system, water as cosolvent and with addition of a salt (comparative example)
• the selectivity to methylcyclohexene can be increased by addition of a salt.
• a similar shape of the selectivity versus conversion curve was found in each case: as the degree of conversion increases, the selectivity to methylcyclohexene drops, but the selectivity at a conversion of 20% is in each case increased from 1% to 2% when using lanthanum nitrate compared with the use of water as cosolvent without salt. In comparison, the selectivity when zinc nitrate is added is about 1.3%.
• Example 3 Effect of the simultaneous addition of salt and of surface-active substance on activity and selectivity in the hydrogenation of toluene (process of the invention)
• Figure 4 shows the effect of the combined addition of a salt and a surface-active substance (here an anionic surfactant) on the selectivity.
• Figure 4 shows the dependence of the selectivity to methylcyclohexene on degree of conversion for the combination of surfactant 3 and zinc salt. It is found that the combination of poly (ethylene glycol) 4-nonyl- phenol 3-sulphopropyl diether and zinc nitrate has a selectivity-increasing effect, since the yield of methylcyclohexene was able to be increased significantly.
• the shape of the selectivity/conversion curve is similar to that found above when using the salt alone: a decrease in the selectivity to the olefin is found as the degree of conversion increases.
• Example 4 Comparison of anionic, cationic and nonionic surfactants in the presence of zinc salts for increasing the selectivity of the hydrogenation of toluene (process of the invention)
• Example 5 The process of the invention at high proportions of surface-active substances
• Figure 6 shows the effect of high proportions of surface-active substances on the olefin yield. In comparison with small concentrations of surface-active substances, significantly higher olefin yields were able to be achieved when relatively large amounts of surface-active substances were added. The additional addition of lanthanum nitrate produced a further increase in the selectivity.
• the maximum olefin yields obtained were 3% of methylcyclohexene at a conversion of 18% with addition of 5 per cent by weight of surfactant 1 and 10 ⁇ 3 mol of lanthanum nitrate.

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• 2002
  • 2002-05-21 DE DE2002122385 patent/DE10222385B4/de not_active Expired - Fee Related
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