Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2003-01-02
2004-06-29
Owens, Amelia (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
active
06756503
ABSTRACT:
This application is a 371 of PCT/EP01/07716 filed Jul. 5, 2001.
The present invention relates to a process for the preparation of propylene oxide from propene and hydrogen peroxide in the presence of methanol. After the reaction of the propene with hydrogen peroxide in the process according to the invention, a mixture comprising methanol, water and unreacted hydrogen peroxide is separated off from the reaction discharge, and this mixture is subjected to a separation process which gives a further mixture comprising methanol and methyl formate.
Processes for the preparation of propylene oxide from propene are known from the prior art. In these processes, the problem generally occurs that a certain amount of hydrogen peroxide is not reacted during the reaction and arises on subsequent removal of propylene oxide from the reaction discharge.
In order to remedy this problem, it has been proposed, inter alia, to separate off hydrogen peroxide, in an intermediate separation step, from the reaction discharge from a first reaction step and to react it again with alkene in a second reaction step. Such processes are described, for example, in PCT/EP99/05740 and DE-A 100 15 246.5. Although it is possible here to achieve virtually one hundred per cent hydrogen peroxide conversion in the second reaction step, the second reaction step does mean, however, that increased complexity is necessary.
It is an object of the present invention to provide a process in which the problem of the unreacted hydrogen peroxide arising is solved inexpensively and efficiently.
We have found that this object is achieved by a process for the preparation of propylene oxide in which
(i) propene is reacted with hydrogen peroxide in the presence of methanol to give propylene oxide, giving a mixture (Gi) comprising propylene oxide, methanol, water and unreacted hydrogen peroxide,
(ii) a mixture (Gii) comprising methanol, water and hydrogen peroxide is separated off from the mixture (Gi), giving a mixture (Ga) comprising propylene oxide, and
(iii) water is separated off from the mixture (Gii), giving a mixture (Giii) comprising methanol and methyl formate.
Methanol is particularly preferably employed as solvent. It is also possible here to employ one or more further solvents in addition to methanol. In principle, all solvents which are suitable for the respective reaction can be employed as such further solvents. Inter alia, preference is given, for example, to
water,
alcohols, preferably lower alcohols, further preferably alcohols having less than 6 carbon atoms, for example ethanol, propanols, butanols and pentanols,
diols or polyols, preferably those having less than 6 carbon atoms,
ethers, for example diethyl ether, tetrahydrofuran, dioxane, 1,2-diethoxyethane and 2-methoxyethanol,
esters, for example methyl acetate or butyrolactone,
amides, for example dimethylformamide, dimethylacetamide and N-methylpyrrolidone,
ketones, for example acetone,
nitrites, for example acetonitrile,
or mixtures of two or more of the above-mentioned compounds.
In the process according to the invention, the reaction of propene with hydrogen peroxide is preferably carried out in the presence of a catalyst. Feasible catalysts for the conversion of propylene into propylene oxide are in principle all catalysts, preferably all heterogeneous catalysts, which are suitable for the respective reaction.
Preference is given to catalysts which comprise a porous oxidic material, for example a zeolite. Preference is given to catalysts in which the porous oxidic material is a titanium-, vanadium-, chromium-, niobium- or zirconium-containing zeolite.
In particular, zeolites which contain no aluminum and in which some of the Si(IV) in the silicate lattice have been replaced by titanium as Ti(IV) exist. The titanium zeolites, in particular those having a crystal structure of the MFI type, and possibilities for their preparation are described, for example, in EP-A 0 311 983 and EP-A 0 405 978.
Titanium zeolites having an MFI structure are known for the fact that they can be identified via a certain pattern in the determination of their X-ray diffraction diagrams and in addition via a skeletal vibration band in the infrared region (IR) at about 960 cm
−1
and thus differ from alkali metal titanates or crystalline or amorphous TiO
2
phases.
Suitable here are, in detail, titanium-, vanadium-, chromium-, niobium- and zirconium-containing zeolites having a pentasil zeolite structure, in particular the types with X-ray assignment to the ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, ANA, APC, APD, AST, ATN, ATO, ATS, ATT, ATV, AWO, AWW, BEA, BIK, BOG, BPH, BRE, CAN, CAS, CFI, CGF, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EMT, EPI, ERI, ESV, EUO, FAU, FER, GIS, GME, GOO, HEU, IFR, ISV, ITE, JBW, KFI, LAU, LEV, LIO, LOS, LOV, LTA, LTL, LTN, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MON, MOR, MSO, MTF, MTN, MTT, MTW, MWW, NAT, NES, NON, OFF, OSI, PAR, PAU, PHI, RHO, RON, RSN, RTE, RTH, RUT, SAO, SAT, SBE, SBS, SBT, SFF, SGT, SOD, STF, STI, STT, TER, THO, TON, TSC, VET, VFI, VNI, VSV, WEI, WEN, YUG or ZON structure and to mixed structures consisting of two or more of the above-mentioned structures. Also feasible for use in the process according to the invention are titanium-containing zeolites having the UTD-1, CIT-1 or CIT-5 structure. Further titanium-containing zeolites which may be mentioned are those having the ZSM-48 or ZSM-12 structure.
Ti zeolites having the MFI, MEL or MFI/MEL mixed structure are regarded as particularly preferred for the process according to the invention. Preference is furthermore given, in detail, to the Ti-containing zeolite catalysts generally known as “TS-1”, “TS-2” and “TS-3”, and Ti zeolites having a skeletal structure which is isomorphous with beta-zeolites.
In the process according to the invention, particular preference is given to a heterogeneous catalyst comprising the titanium-containing silicalite TS-1.
Accordingly, the present invention also relates to a process as described above in which, for the preparation of the propylene oxide, a zeolite catalyst, preferably a titanium silicalite catalyst and in particular a titanium silicalite catalyst of the structure TS-1, is employed.
The removal of water from the mixture (Gii) is in the process according to the invention preferably carried out by distillation, it being possible to use one or alternatively a plurality of distillation columns. Use of one or two distillation columns is preferred. In the case that heat recovery is unnecessary, one distillation column is preferably used. Two or more distillation columns are preferably used if particularly good heat integration in the process is to be ensured.
Regarding the physical parameters, such as temperature or pressure, there are no particular restrictions during removal of water from the mixture (Gii) by distillation, so long as it is ensured that hydrogen peroxide is degraded during the distillation and a mixture (Giii) comprising methyl formate and methanol is obtained.
If only one column is employed for the removal of water from the mixture (Gii) in the process according to the invention, this preferably has at least 5, preferably at least 20 and further preferably at least 30 theoretical plates. The distillation is preferably carried out at pressures in the range from 0.5 to 40 bar, preferably from 1.0 to 20 bar and particularly preferably from 2 to 15 bar.
If two columns are employed for the removal of water from the mixture (Gii) in the process according to the invention, the pressures are then selected in such a way that the heat of condensation at the top of the columns can be used to heat other process streams. This is achieved, for example, by cooling the condenser of at least one column using, for example, water and employing the hot water resulting from the cooling or the steam resulting from the cooling to heat one or more steps of the process according to the invention or even one or more other processes.
The first distillation column is preferably opera
Bassler Peter
Rehfinger Alwin
Rieber Norbert
Rudolf Peter
Teles Joaquim Henrique
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Owens Amelia
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