Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
1995-06-07
2001-03-20
Siegel, Alan (Department: 1721)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
Reexamination Certificate
active
06204419
ABSTRACT:
DESCRIPTION
In the so-called direct chlorination process, 1,2-di-chloroethane, referred to below as EDC, is obtained by reaction of ethylene with chlorine. This addition reaction is catalyzed by metal halides which behave as Lewis acids and a halide of a metal of the first main group of the Periodic Table.
In the process described in NL-A 6901398 the metal halide having Lewis acid behavior is preferably iron(III) chloride. The metal of the first group of the Periodic Table preferably has an atomic number of at most 12 (sodium) and is in particular lithium. The molar ratio of the halide having Lewis acid behavior and the halide of the metal of the first group of the Periodic Table is between 1:2 and 2:1.
U.S. Pat. No. 4,774,373 describes a process in which the catalyst used is an anhydrous tetrachloroferrate, for example sodium tetrachloroferrate, or the corresponding components are used in stoichiometric amounts. In DE 41 03 281 Al the catalyst used is iron(III) chloride mixed with sodium chloride in a molar ratio of 1:1.5 to 1:2.
It has now been found that the direct chlorination of ethylene proceeds particularly advantageously when during the total reaction the molar ratio of sodium chloride to iron(III) chloride is kept below 0.5. Maintenance of this condition allows the reaction to be carried out in such a way as to produce EDC of sufficiently high purity to be used directly to form vinyl chloride without distillative removal of high boilers. In addition, the process of the invention is not very costly in terms of equipment and energy consumption. Preferred embodiments of the invention and the associated advantages will now be explained in more detail.
The reaction medium used is advantageously liquid EDC, the reactants being fed into the circulating EDC. Here it is not necessary to use chlorine in liquid form, since the process of the invention can be carried out under such mild conditions, particularly such low pressures, that gaseous chlorine can be used. Thus the pressure is advantageously a maximum of 1 bar gauge pressure, preferably between 0.4 and 0.6 bar gauge pressure, which is advantageously set by means of inert gas, preferably nitrogen, blanketing.
The reaction temperature is from 50 to 105° C., advantageously from 70 to 90° C. Pressure and temperature are adapted to each other in such a way that the reaction is carried out below the boiling point of EDC.
In a preferred embodiment of the invention, all or preferably only some of the EDC is passed into an expansion vessel maintained under vacuum, the heat content of the EDC stream leading to the vaporization of part of the EDC. The vaporized EDC is free of catalyst and after condensation has a purity of at least 99.9%, so that it can be fed directly to the cleavage reaction to form vinyl chloride. This allows the omission of the water-scrubbing that is necessary for removal of the catalyst in conventional processes, carried out without pressure letdown or EDC vaporization, and also of the subsequently required distillative drying of the EDC.
The pressure in the expansion vessel is advantageously from 0.2 to 0.7 bar absolute. This reduced pressure is produced and maintained by means of customary fans or pumps, referred to below as a vacuum pump. If this vacuum pump is not also to be used for conveying the gaseous EDC the latter is condensed by means of a suitable apparatus, referred to below as a cooler, and collected in a vessel.
The exploitation of the heat of reaction for the partial vaporization of the EDC and for maintaining the reaction temperature in the stated preferred range results in a substantially reduced need for coolant.
The unvaporized catalyst-containing part of the EDC remaining in the expansion vessel is returned to the EDC circuit. This is made possible by the reaction forming only a very small proportion of byproducts and the EDC return containing only inconsequential amounts of hydrogen chloride.
The waste gas is practically free of chlorine. The particularly preferred operating mode, in which only some of the EDC, preferably a relatively small amount, is passed into the expansion vessel, has the further advantage that a secondary reactor for the conversion of the remaining ethylene is not necessary. However, devices for the removal and recirculation thereof can be provided even in this preferred embodiment of the invention, since they are not very costly.
Thus the ethylene yield can be further increased or the ethylene losses further reduced by returning the ethylene-containing expansion vessel waste gas to the reaction from a point downstream of the vacuum pump by means of a suitable compressor, preferably a liquid-jet compressor, which is advantageously fitted at the bottom of the reactor, and rereacting the ethylene with chlorine. The driving jet for the preferred compressor is advantageously a bleed stream (partial stream) of the circulating EDC.
The residual amounts of ethylene can, however, also be used for producing energy by waste gas incineration, preferably for hydrogen chloride recovery.
REFERENCES:
patent: 3214482 (1965-10-01), Caropreso et al.
patent: 3496243 (1970-02-01), Berkowitz et al.
patent: 3864411 (1975-02-01), Mueller
patent: 3911036 (1975-10-01), Di Flore et al.
patent: 4672142 (1987-06-01), Hundeck et al.
patent: 4103281 (1992-08-01), None
patent: 41 03 281 (1992-08-01), None
patent: 41 33 810 (1993-04-01), None
Eichler Jurgen
Krumbock Reinhard
Kuhn Wenzel
Mielke Ingolf
Schwarzmaier Peter
Connolly Bove & Lodge & Hutz LLP
Siegel Alan
Vinnolit Technologie GmbH & Co. KG
LandOfFree
Process and apparatus for preparing 1,2-dichloroethane by... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process and apparatus for preparing 1,2-dichloroethane by..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and apparatus for preparing 1,2-dichloroethane by... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2475187