HEAVIES AND HYDROGEN CHLORIDE FROM ETHANE

The present invention relates to a method of producing heavies and hydrogen chloride by chlorinating ethane using chlorine (Cl ₂ ) as the chlorinating agent and the invention further relates to the recycle to extinction of ethylene, vinyl chloride monomer (VCM) and ethyl chloride.

US 3,706,816 discloses that a feed material which is basically ethane and/or 1,1 - dichloroethane may be chlorinated to give 1,1,1-tricliloroethane but such processes are not very satisfactory in that use of ethane is associated with evolution of large amounts of HC1 and in any event the yields of 1 ,1,1-trichloroethane are not high.

The present invention solves the problem of the art by providing a process having a >95 yield of product while still employing ethane as the main reactant.

It is therefore an object of the present invention to provide a method for the chlorination of ethane that overcomes the disadvantages of the conventional methods.

The present invention provides a continuous process for producing heavies and hydrogen chloride comprising:

a. reacting a feed comprising chlorine with ethane in a reaction zone to

produce a crude product comprising

i. product components comprising heavies and hydrogen chloride and

ii. an extinction recycle fraction comprising ethylene, vinyl chloride, and ethyl chloride:

b. separating from the crude product the extinction recycle fraction; and c. separating from the crude product the product components.

As used herein "adiabatic" means: the chlorination process or reaction occurs without transfer of heat between the reactor and its surroundings. The process is said to be nearly adiabatic because the reactor is insulated or designed in such a manner that heat is not intentionally added or removed from the reactor.

As used herein "exit temperature" means: the temperature of reactor effluent. The chlorine to ethane feed ratio is one of the variables used to control the exit temperature. This chlorine: ethane molar ratio ranges from 1.0 mol. to 5.0 mol., alternatively from 1.5 mol. to 4. mol. The exit temperature ranges from 350 - 700 °C, alternatively from 375 - 675 °C, further alternatively from 400 - 650 °C.

As used herein "extinction recycle" means: primarily ethylene, vinyl chloride, and ethyl chloride.

As used herein "heavies" means: primarily trans - 1,2-dichloroethylene, cis -1,2- dichloroethylene, vinylidene chloride (1,1-dichloroethylene), 1, 1,2-trichloroethane, 1,1, 1- trichloroethane, 1 , 1 -dichloroethane

As used herein "inlet temperature" means: the mixed or mixture temperature of all the feed components as they enter the reactor wherein the feed components comprise primarily ethane, and/or extinction recycle fraction, and chlorine. The inlet temperature ranges from 200°C to 350°C, alternatively from 250 - 330 °C, further alternatively from 260 - 320 °C.

As used herein "product components" means: 1,2-dichloroethylene, vinylidene chloride, 1,1,2-trichloroethane, 1,1 ,1-trichloroethane, and hydrogen chloride.

As used herein "recycle to extinction" means: when a byproduct or an intermediate product is recycled at the same mass rate as produced and thus at steady state the intermediate or byproduct species is not removed or produced from the process. The extinction recycle fraction is optionally recycled to extinction.

All range values provided herein are inclusive and combinable. All percentages are percentages by weight.

FIG. 1 is a schematic view of the operation of a preferred embodiment of the process of the invention. Referring to the Figure, the process of the present invention is carried out as follows.

A feed containing feed components of ethane and chlorine is fed to a reactor ("reaction zone"). The feed may be substantially free of ethylene, alternatively free of ethylene. The feed components are preheated either individually or in combination in any manner and at any time prior to entry into the reactor 10. Prior art reference, CA 2097434 premixes ethane and chlorine below 200°C and heats the mixture after adding it to the reactor. This method requires heat exchangers and thus is more capital intensive than the process of the present invention which uses a reactor 10 that is nearly adiabatic. Chlorine may be preheated to the inlet temperature or alternatively may comprise a temperature ranging from 20° to 80°C before it is combined with the feed preheated at higher temperature to reach the desired inlet temperature. The chlorine may be co-fed into the reactor 10 with ethane, mixed with the ethane and then added to the reactor 10, or added by other conventional means of introducing materials into a reactor.

Conventional reactors may be used. One suitable example of a reactor is a jet-stirred reactor. The temperature of the reactor 10 at the time of entry of the feed ("inlet temperature") ranges from 200 - 350 °C, alternatively from 250 - 330 °C, further alternatively from 260 - 320 °C. The thermal chlorination reaction is carried out in the reactor 10. The chlorine is highly reactive with the ethane and reacts to produce a crude product comprising an extinction recycle fraction and product components.

With the near adiabatic reactor condition, the exothermic reaction increases the crude product to temperature higher than 350°C up to 700°C to produce a vapor reaction product components. This vapor crude product is cooled to produce vapor phase and liquid reactor effluent. Suitable cooling methods include heat exchanging with coolant or by adjusting feed ratios.

The vapor phase and liquid reactor effluent are cooled further in a condenser 20 by quenching with product components or heavies stream to condense the liquid. The liquid is provided preferably to a distillation column 40, or alternatively to a separation column 50. The vapor phase is compressed at a pressure greater than or equal to 689 kPa, alternatively greater than or equal to 1378 kPa and further alternatively greater than or equal to 1930 kPa in compressor 30 to enable efficient separation of the extinction recycle fraction comprising ethylene and HCl from the crude product vapor stream in the distillation column 40. The extinction recycle fraction or column 40 overhead stream comprising ethylene and HCl is further fed to column 45 where the overhead stream containing mostly ethylene is recycled back to reactor 10. The bottom stream of column 45 containing HCl is recovered as byproduct for use in a downstream process. Instead of a distillation column, column 45 may also be an absorber unit where water may be used to remove HCl and recovered as an aqueous HCl stream as required by the downstream use.

The column 40 bottom stream comprising extinction recycle fraction is fed to column 50 where VCM and ethyl chloride is recovered in the overhead stream. This overhead stream is returned to the reaction zone 10. The extinction recycle fraction recycle streams of column 50 overhead and column 45 overhead comprising ethylene is effectively recycled to extinction as it continuously undergoes thermal chlorination with ethane and chlorine to produce the same amount of ethylene as recycled. The rest of the chlorination product components comprises primarily 1,2-dichloroethylene, vinylidene chloride, 1,1,2-trichloroethane, 1,1,1-trichloroethane, and hydrogen chloride.

The reaction of the present invention is highly efficient as greater than 95%, alternatively greater than 99% of the chlorine and ethane are converted during the reaction. The process of the present invention, specifically, the chlorination reaction of ethane, and recycled extinction fraction is part of a continuous process.

The bottom stream of separation column 50 comprising the product components are further fed to column 60 where the product components are purified in the overhead stream. A fraction of column 60 bottom stream comprising tetrachloroethanes and perchloroethylene is used to help condense the product effluent in unit 20. The rest of the heavies can be fed to other chlorination processes to produce trichloroethylene and perchloroethylene.

EXAMPLE

Process for the Chlorination of Ethane

Ethane is chlorinated to produce HC1 and heavies in a thermal chlorination jet-stirred reactor. The jet- stirred reactor was simulated as described in Chapter 8.7 in "Cleaner

Combustion: Developing Detailed Kinetics Models," F. Battin-Leclerc, J.M. Simrnie, E. Blurock (Ed) (2013)) using kinetics reported by Dahl et al. [Ind. Eng. Chem. Res. 2001, 40, 2226-2235]. The thermodynamic properties were obtained from reported literature values (see

http://webbook.nist.gov/chemistry/) and thermochemical kinetics approach (see S.W. Benson "Thermochemical Kinetics: Methods for the Estimation of Thermochemical Data and Rate Parameters," 1976). The reactor model was imbedded inside a process flow sheet simulation (see http ://www . aspentech . com/products/aspen-plus . aspx) such that impacts of recycle were evaluated.

The reactor has pressure of 40psia and the feed is preheated to higher than 200°C. The reactor exit temperature is maintained by adjusting chlorine flow rate. The residence time is about 0.5 sec to 1 second depending on whether outlet or inlet flow rate is used, respectively. The crude liquid product composition is given below in Error! Reference source not found.. Table 1. Process Operating Conditions and Product Composition