Chemistry of hydrocarbon compounds – Alicyclic compound synthesis – Polycyclic product
Reexamination Certificate
2000-08-02
2002-11-12
Dang, Thuan D. (Department: 1764)
Chemistry of hydrocarbon compounds
Alicyclic compound synthesis
Polycyclic product
C585S318000, C585S354000, C422S187000, C422S186220, C422S186220
Reexamination Certificate
active
06479719
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process and to a reactor for the manufacture of norbornene (1,2,2-bicyclo[2.2.1]hept-2-ene) from dicyclopentadiene (DCPD) and ethylene.
BACKGROUND OF THE INVENTION
The synthesis of norbornene was described for the first time in 1941 by L. M. Joshel and L. W. Butz (J. Am. Chem. Soc., 63, 3350).
U.S. Pat. No. 2,340,908 discloses the reaction of DCPD and ethylene at a temperature of approximately 200° C. under a pressure of 50 to approximately 100 bar.
U.S. Pat. No. 3,007,977 discloses the synthesis of norbornene from a mixture of cyclopentadiene (CPD) and DCPD, the use of the mixture being regarded as favouring the control of the reaction conditions.
U.S. Pat. No. 3,763,253 discloses a highly selective process for the manufacture of norbornenes which consists of:
(1) introducing a mixture of a lower olefin and of DCPD having a temperature of greater than approximately 190° C., in particular of approximately 200-325° C., into a reactor with a substantial excess of olefin, for example at an olefin/DCPD molar ratio of 1:0.5 to 40:1,
(2) maintaining the conditions of temperature, of pressure and of residence time in the reactor so that the reactants and the products remain in the vapour phase and so that the formation of the norbornenes is favoured, in particular at a temperature of 200-325° C., a pressure of 6.8 to 136 Pa (100 to 2000 psi) and a residence time of 0.5 to 20 minutes, and
(3) recovering the norbornenes.
Patents DD-140,874 and DE-203,313 disclose a continuous process for the manufacture of norbornene by reaction of DCPD and/or CPD and ethylene under reaction conditions under which not only the reactants but also the desired norbornene are obtained in the gas phase, according to which process 1 mol of DCPD is mixed with 2-50 mol of ethylene and the reaction is carried out at 250-340° C. under a pressure of 2-20 MPa, excess ethylene being conveyed, before the reaction region, under the reaction pressure at a temperature of less than 190° C., through the liquid DCPD and then reacting to give the norbornene in the reaction region, the norbornene being withdrawn in the gaseous form at the top of the reaction region; according to DD-140,874, liquid compounds with high boiling points are withdrawn below the reaction region at temperatures of 150-220° C. in an amount of less than 3% by weight with respect to the DCPD introduced into the reaction system, their composition being regulated so as to comprise less than 1% by weight of norbornene; according to DE-203,313, liquid compounds with high boiling points are withdrawn from the region for mixing the DCPD with the ethylene, the liquid DCPD having a mean residence time in the mixing region of less than 60 minutes.
German Patent DD-144, 257 relates to a reactor for the synthesis of norbornene from DCPD and ethylene, the reaction space being divided by two concentrically positioned pipes into an annular space, in which cleavage of the DCPD predominantly takes place, and into an internal space, in which synthesis of the norbornene predominantly takes place.
German Patent DD-215, 078 relates to a process for the continuous manufacture of pure norbornene under reaction conditions according to which not only the reactants CPD and ethylene but also the norbornene are maintained in the gas phase; 1 mol of CPD is reacted with 1 to 25 mol of ethylene at 523-613° K. and under a pressure of 2-20 MPa; a DCPD concentrate, which comprises up to 20% of codimers of CPD with methylcyclopentadiene, piperylene, isoprene and butadiene, is mixed with the ethylene in a mixing region at 433-473° K. with a residence time of 10 to 30 minutes; the compounds with high boiling points formed in the mixing region are withdrawn at the lower end; the conversion to norbornene takes place in a reaction region following the mixing region and the reaction products are withdrawn at the top of the reaction region; the reaction products are separated in a two-stage distillation region which follows, so that methylnorbornene, methyltetrahydroindenes, DCPD and other by-products with high boiling points are withdrawn at the bottom of the first distillation stage and the light substances, such as CPD and small amounts of isoprene, of piperylene and of butadiene, are withdrawn at the top of the second distillation stage and norbornene of high purity is withdrawn at the bottom of the second distillation stage.
Processes for the synthesis of norbornene from DCPD or CPD have been provided in the literature but, in reality, such a synthesis is very difficult to carry out industrially because, due to the low reactivity of ethylene, it requires severe operating conditions. These operating conditions are very close to the conditions for the explosive thermal decomposition of (D)CPD. This is the reason why several industrial plants intended for the synthesis of norbornene have had to cease operations as a result of explosions.
The aim of the present invention is therefore to provide means which make it possible to carry out the industrial synthesis of norbornene under satisfactory safety conditions.
The difficulties of this synthesis will be set out in more detail in what follows.
Pure DCPD is solid at ambient temperature (M.p.=305.15° Ki). DCPD is a dimer in equilibrium with its monomer, CPD, via a Diels-Alder reaction. The proportions of the two opposing products depends on the temperature and pressure conditions. The monomerization reaction is endothermic.
The reaction for the synthesis of norbornene is a Diels-Alder reaction between CPD (the diene) and ethylene (the dienophile).
This reaction is an equilibrium reaction and theoretically results in a mixture of norbornene (Nor), CPD and DCPD being obtained.
The chemical factors which favourably influence the Diels-Alder reactions are:
a cyclic diene with a high ring strain, which is certainly the case with CPD;
a dienophile activated by an electron-withdrawing group, which is not the case with ethylene.
The reaction conditions have to be adjusted in order to compensate for this lack of reactivity of ethylene. The increase in pressure is a favourable thermodynamic and kinetic factor. The increase in temperature is a favourable kinetic factor but an unfavourable thermodynamic factor. The increase in the ethylene/CPD ratio is a favourable thermodynamic and kinetic factor.
The instability of the products introduces an additional constraint: safety. This is because it is recognized that the synthesis of norbornene is a risky reaction. The low reactivity of ethylene makes it necessary to operate under conditions which are close to the conditions for the explosive thermaldecomposition of the products.
The reaction between ethylene and CPD is strongly exothermic: &Dgr;H°
298
=−22 kcal/mol ideal gas.
CPD is, in comparison with ethylene, the more sensitive product with regard to these explosive reactions. In 1991, a Union Carbide team (M. Ahmed and M. Lavin, Plant/Operation Progress, 1991, Vol., No. 3, pages 143-154) showed by DSC (differential scanning calorimetry) tests that CPD, heated under pressure, can successively give exothermic reactions at temperatures of:
250° C., formation of DCPD oligomers (&Dgr;H=−66 kcal/mol);
340° C., conversion of the oligomers to polymers (&Dgr;H=−80 kcal/mol);
440° C., decomposition of the polymers, resulting in the production of large amounts of gas (&Dgr;H=−90 kcal/mol).
The above recited temperatures are variable according to the source of the DCPD, without it having been possible to find an explanation for these variations, which can reach 30° C. ARC (accelerating rate calorimetry) tests were carried out and made it possible to record the pressure and temperature variations. In these tests, the final decomposition reaction stated at temperatures of 350° C. and resulted in increases in pressure of 5 bar (300° C.) to 210 bar (460° C.).
The reaction conditions are such that other condensation reactions come into play. Thus it is that dimethanooctahydronaphthalene (DMON) i
Kotwica Roland
Marbach Andre
Atofina
Dang Thuan D.
Millen White Zelano & Branigan P.C.
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