Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
  • C07C29/132—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group
  • C07C29/136—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group of >C=O containing groups, e.g. —COOH
  • C07C29/14—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group of >C=O containing groups, e.g. —COOH of a —CHO group
  • C07C29/141—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group of >C=O containing groups, e.g. —COOH of a —CHO group with hydrogen or hydrogen-containing gases

Definitions

• the present invention relates to a process for the continuous selective hydrogenation of citronellal to citronellol (Scheme 1).
• Citronellol is used as a fragrance and aroma substance.
• US 3,346,650 discloses a process for the production of citronellol by hydrogenating a mixture of geraniol and nerol over a copper chromate catalyst.
• Catalytic hydrogenations on heterogeneous catalysts are often carried out using fixed bed reactors in order to obtain the advantages of a continuous process.
• specially prepared catalysts have to be produced and used for this purpose, which have to be replaced or regenerated in a complex manner if activity is lost - often after a shorter period of time - which is usually not only the case when the hydrogenation system is switched off, but also afterwards Processing stages is connected.
• a heterogeneously catalyzed hydrogenation can be carried out in the form of a suspension reaction, the hydrogenation catalyst being suspended in a liquid phase by supplying mechanical energy, for example in a stirred tank, cf. eg Ullmann's Encyclopedia of Technical Chemistry, 4th Edition, Volume 13, 1997, p. 138, Verlag Chemie Weinheim.
• mechanical energy for example in a stirred tank, cf. eg Ullmann's Encyclopedia of Technical Chemistry, 4th Edition, Volume 13, 1997, p. 138, Verlag Chemie Weinheim.
• Fluidized or fluidized bed reactors allow higher relative speeds, but require the use of significantly larger catalyst particles so that a more or less strongly expanded catalyst bed is present during operation.
• the smaller volume-related surface area of larger catalyst particles limits the material conversion and thus compensates for the effect of the higher relative speed.
• EP-A 798 039 discloses a process for carrying out catalytic reactions in a reactor which contains a liquid phase in which at least one catalyst is suspended. The hydrogenation of hydrodehydrolinalool to hydrolinalool and further to tetrahydrolinalool is described. Hydrodehydrolinalool contains only a triple bond as the functional group to be hydrogenated, so that the person skilled in the art would not have taken any suggestion regarding selective hydrogenation.
• the present invention has for its object to provide a process for the selective hydrogenation of citronellal to citronellol, which combines the advantages of a high space-time yield and a simple catalyst exchange.
• the object is achieved according to the invention by a process in which a liquid phase in which the citronellal is dissolved and suspended in the particles of a catalyst is used for the preferential hydrogenation of carbon-oxygen double bonds before carbon-carbon double bonds is capable, in the presence of a hydrogen-containing gas, through a device which inhibits the transport of the catalyst particles.
• a higher relative speed of the liquid phase compared to the catalyst particles is generated because the transport of the catalyst particles is inhibited by suitable means, such as internals in a reactor, i.e. the particles are held back more strongly by the surrounding liquid.
• suitable means such as internals in a reactor, i.e. the particles are held back more strongly by the surrounding liquid.
• high space-time yields are achieved as a result.
• the device which inhibits the transport of the catalyst particles preferably has openings or channels whose hydraulic diameter is 2 to 2000 times, in particular 5 to 500 times, particularly preferably 5 to 100 times the average diameter of the catalyst particles.
• the hydraulic diameter is a parameter familiar to the person skilled in the art for describing the equivalent diameter of non-circular channel structures.
• the hydraulic diameter of an opening is defined as the quotient of 4 times the cross-section of the opening and its circumference.
• the hydraulic diameter can be as
• Devices suitable for the openings or channels generally have a hydraulic diameter of 0.5 to 20 mm, preferably 1 to 10 mm, particularly preferably 1 to 3 mm.
• catalyst particles with an average diameter of 0.0001 to 2 mm, preferably 0.001 to 1 mm, particularly preferably 0.005 to 0.1 mm are used.
• the device which inhibits the transport of the catalyst particles can consist of a bed, a knitted fabric, or an open-celled one
• Foam structure preferably made of plastic e.g. Polyurethane or melamine resin, or ceramic, or a packing element as is basically, i.e. its geometrical shape, already known from the distillation and extraction technology, exist.
• the packs generally have a hydraulic diameter which is smaller by a factor of 2 to 10 than that of comparable internals in the area of distillation and extraction technology.
• Metal mesh packs or wire mesh packs are particularly suitable as packing elements.
• packs made of other woven, knitted or felted materials can also be used.
• Packs of flat or corrugated metal sheets are also suitable, preferably without perforation or other larger openings, for example in accordance with the Montz Bl or Sulzer Mellapak types.
• Packings made of are also advantageous Expanded metal, such as packs of the type Montz BSH. What is decisive for the suitability of a package in the context of the present invention is not its geometry, but rather the opening sizes or channel widths in the package which arise for the current conduction.
• the surfaces of the device facing the liquid phase have a roughness in the range from 0.1 to 10 times, preferably from 0.5 to 5 times, the average diameter of the catalyst particles.
• Materials are preferred whose surfaces have a mean roughness value R a (determined according to DIN 4768/1) of 0.001 to 0.01 mm.
• R a determined according to DIN 4768/1
• a corresponding surface roughness can be achieved when using wire mesh packings made of stainless steel by thermal treatment in the presence of oxygen, for example by tempering the tissue in air at a temperature of about 800 ° C.
• the process according to the invention is generally carried out at a pressure between 1 and 100 bar, preferably 1 and 60 bar, particularly preferably 1 and 50 bar.
• the reaction temperatures are usually between 40 and 120 ° C, preferably between 60 and 100 ° C, particularly preferably between 70 and 90 ° C.
• the liquid phase preferably comprises an inert diluent, in particular a C 1 -C 6 -alkanol, particularly preferably a C 1 -C 6 -alkanol, such as, in particular, methanol.
• the liquid phase also preferably comprises ammonia, a primary, secondary and / or tertiary amine, of which tertiary amines, for example tri (C 1 -C 4 -alkyl) amines, in particular trimethylamine, are particularly preferred.
• the concentration of citronellal in the liquid phase is preferably 50 to 90% by weight, particularly preferably 60 to 80% by weight, that of the diluent 40 to 5% by weight, preferably 20 to 35%, that of the ammonia / Amine 1 to 15 wt .-%, preferably 1 to 8 wt .-%.
• Hydrogen gas with a purity of at least 99.5% by volume is generally used as the hydrogen-containing gas. It is used in an at least stoichiometric amount, based on the carbonyl compound contained in the liquid phase, usually in an excess of 1 to 20%.
• a commercially available suspension catalyst which is capable of preferentially hydrogenating carbon-oxygen double bonds over carbon-carbon double bonds can be used as the catalyst.
• Catalysts which contain at least ruthenium as the active component are particularly suitable.
• the catalyst can also contain other active components, such as iron.
• the catalyst can be used in metallic and / or oxidic form.
• the active components are preferably applied to a carrier material. Suitable carrier materials are, for example, Si0 2 , Ti0, ZrO 2 , Al 2 0 3 or carbon such as graphite, carbon black or activated carbon. Activated carbon is preferred due to its easy suspendability.
• the ruthenium content is preferably 0.1 and 10% by weight
• the iron content is preferably 0.1 and 5% by weight, in particular 0.5 and 1.5% by weight, based on the total weight of the catalyst ,
• the suspended catalyst material can be introduced into the liquid phase and distributed therein using conventional techniques.
• the device which inhibits the transport of the catalyst particles is usually built into a reactor which is arranged in such a way that the reaction mixture is forced through the device as it passes through the reactor, i.e. the internals usually fill the entire free cross-section of the reactor.
• the internals preferably, but not necessarily, extend over the entire extent of the reactor in the direction of flow of the liquid phase.
• reactors such as jet nozzle reactors, bubble columns or tube bundle reactors.
• a vertically arranged bubble column or a tube bundle reactor in which the internals are accommodated in the individual tubes are particularly suitable.
• the hydrogen-containing gas and the liquid phase are preferably passed through the reactor in cocurrent, preferably counter to the direction of gravity.
• the gas phase is intimately mixed with the liquid phase, for example by means of an injector nozzle.
• the empty tube velocity of the liquid phase is preferably more than 100 m 3 / m 2 h, in particular 100 to 250 m 3 / m 2 h, that of the gas phase is preferably more than 100 Nm 3 / m 2 h, in particular 100 to 250 Nm 3 / m 2 h.
• the catalyst particles suspended in the hydrogenation discharge are separated off by customary methods, for example by sedimentation, centrifugation, cake filtration or crossflow filtration.
• the hydrogenation according to the invention can be carried out either continuously or batchwise, but it is preferably continuous.
• FIG. 1 shows schematically a plant suitable for carrying out the process according to the invention with a reactor (bubble column) 1 with a packing 2 which inhibits the transport of the catalyst particles.
• Liquid is introduced into the rector 1 via the lines 3 and hydrogen gas is introduced via the line 4.
• the circulating gas 5 is mixed in with the mixing nozzle 6 with fresh gas and the suspension 11 circulated by the pump 14.
• the reactor discharge is fed via line 7 into the separating vessel 8, in which the gas phase is separated off and discharged via line 9.
• a partial stream of this gas quantity is withdrawn via line 10 and the remaining amount is fed via line 5 into the reactor.
• the suspended catalyst remains in the reactor system in that it is retained by a crossflow filter 12 and only catalyst-free liquid phase emerges via line 13 and is removed.
• the temperature in the reactor system can be set in a targeted manner via the heat exchanger 15.
• FIG. 2 shows schematically a layer of a folded fabric. Packs which can be used according to the invention are obtained if several of these layers are arranged one above the other. Each layer comprises channels with a cross section in the form of an isosceles triangle with the leg length s, the base b and the height h.
• FIG. 1 A system was used as shown in FIG. 1, which comprised a bubble column (3000 mm long, 27.3 mm in diameter) equipped with a Montz AI 1200 type tissue pack.
• the package consisted of layers of a fabric of stainless steel wires, which were folded so that channels with a cross section in the shape of an isosceles triangle were formed, the leg length 3.1 mm, the base 5.1 mm and the height 1.8 mm was, corresponding to a hydraulic diameter of 1.62 mm.
• a mixture of 70% by weight of citronellal, 27% by weight of methanol and 3% by weight of trimethylain served as the feed.
• An Ru / Fe carbon suspension catalyst which contained 5% ruthenium and 1% iron, was suspended in the feed contained on activated carbon and a medium Grain size of about 50 microns.
• the reaction was carried out continuously under a hydrogen pressure of 20 bar and a temperature of 80 ° C.
• the liquid with the suspended catalyst and the gas were introduced from below into the packed reactor at an empty tube speed of 5,200 m3 / m2h.
• the conversion was more than 95% with a selectivity of 96% for citronellol.
• the catalyst loading was 40.2 kgc rone ii a i kg Rh -h, the space-time yield 233 kg C i trone ii o i " 3 .h. 0

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

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• 2002
  • 2002-07-15 DE DE10231942A patent/DE10231942A1/de not_active Withdrawn
• 2003
  • 2003-07-14 WO PCT/EP2003/007599 patent/WO2004007411A1/de not_active Ceased
  • 2003-07-14 CA CA2492261A patent/CA2492261C/en not_active Expired - Lifetime
  • 2003-07-14 EP EP03763837A patent/EP1523464B1/de not_active Expired - Lifetime
  • 2003-07-14 DE DE50309035T patent/DE50309035D1/de not_active Expired - Lifetime
  • 2003-07-14 ES ES03763837T patent/ES2298577T3/es not_active Expired - Lifetime
  • 2003-07-14 AT AT03763837T patent/ATE384034T1/de not_active IP Right Cessation
  • 2003-07-14 AU AU2003254347A patent/AU2003254347A1/en not_active Abandoned
  • 2003-07-14 JP JP2004520615A patent/JP2005538078A/ja active Pending
  • 2003-07-14 CN CN03817019.1A patent/CN1281564C/zh not_active Expired - Lifetime
  • 2003-07-14 US US10/519,686 patent/US7005554B2/en not_active Expired - Lifetime

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