WO2025237773A1 - Apparatus for dehydrochlorination of chlorinated alkanes - Google Patents

Abstract

The present invention relates to an apparatus and a process for dehydrochlorination of chlorinated alkanes, in particular to a process for preparing vinyl chloride by catalytic thermal cracking of 1,2-dichloroethane, in which the heat required for the thermal cracking is supplied via a liquid or condensing heat transfer medium or by direct electrical heating, and hot process streams are additionally used for heating of heat sinks in the process of preparing 1,2-dichloroethane or vinyl chloride. The present invention further provides a plant for preparing vinyl chloride by catalytic thermal cracking of 1,2-dichloroethane, in which the heat required for the thermal cracking and for the preceding preheating, evaporation and optional superheating of the 1,2-dichloroethane is supplied via a liquid or condensing heat transfer medium or by direct electrical heating, comprising at least one heat exchanger for preheating a liquid 1,2-dichloroethane stream, at least one evaporation apparatus, consisting of a heat exchanger and, optionally, a phase separation vessel, for evaporating a liquid 1,2-dichloroethane stream, optionally at least one heat exchanger for superheating a gaseous 1,2-dichloroethane stream, and at least one reactor for thermal catalytic conversion of 1,2-dichloroethane to vinyl chloride and hydrogen chloride. The invention further relates to a plant for preparing vinyl chloride by catalytic thermal cracking, in which at least some of the apparatuses and devices detailed above are components of prefabricated modules.

Description

Device for the dehydrochlorination of chlorinated alkanes

The present invention relates to an apparatus and a method for the dehydrochlorination of chlorinated alkanes, in particular a method for the production of vinyl chloride by catalytic thermal cracking of 1,2-dichloroethane, in which the heat required for the thermal cracking is supplied via a liquid or condensing heat transfer medium or by direct electrical heating, and furthermore hot process streams are used to heat heat sinks in the process of producing 1,2-dichloroethane or vinyl chloride. The present invention further relates to a plant for the production of vinyl chloride by catalytic thermal cracking of 1,2-dichloroethane, wherein the heat required for the thermal cracking, as well as for the preceding preheating, evaporation and optionally superheating of the 1,2-dichloroethane is supplied via a liquid or condensing heat transfer medium or by direct electrical heating, comprising at least one heat exchanger for preheating a liquid 1,2-dichloroethane stream, at least one evaporation device, consisting of a heat exchanger and, optionally, a phase separation vessel, for evaporating a liquid 1,2-dichloroethane stream, optionally at least one heat exchanger for superheating a gaseous 1,2-dichloroethane stream and at least one reactor for the thermal-catalytic conversion of 1,2-dichloroethane to vinyl chloride and hydrogen chloride. Furthermore, the invention relates to a plant for the production of vinyl chloride by catalytic thermal cracking, in which the above-mentioned- ten apparatuses and devices are at least partially components of prefabricated modules.

The thermal cracking of 1,2-dichloroethane to produce vinyl chloride, which is especially needed for the production of polyvinyl chloride, follows the reaction equation shown below (1):

Pyrolysis is an endothermic reaction, and can occur either catalyst-free in the gas phase under high pressure (1 to 4 MPa) and at temperatures of 450 to 600 °C, or in catalytic processes that allow pyrolysis to be carried out at similar pressures but significantly lower temperatures, typically 230–350 °C. Even in catalytic processes, the reaction is predominantly carried out in the gas phase.

State of the art

EP 264 065 A1, for example, describes a process for the production of vinyl chloride by thermal cracking of 1,2-dichloroethane. In this process, 1,2-dichloroethane is heated in a first container, then transferred to a second container by vaporization at a lower pressure than in the first container without further heating. The gaseous 1,2-dichloroethane is then fed into a cracking furnace where it is cracked into vinyl chloride and hydrogen chloride. The temperature of the 1,2-dichloroethane upon exiting the second container is between 220 °C and 280 °C. Tubes in the cracking furnace, where the 1,2-dichloroethane is thermally cracked, are heated by burning a fuel. In the radiant zone of the cracking furnace, the gaseous 1,2-dichloroethane is heated to 525 °C or 533 °C.

EP 264065 Al also mentions that a tempering medium can be used to preheat the liquid, fresh 1,2-dichloroethane, which in turn mixes with the flue gas in the convection zone of the cracking furnace. The burner heating the cracking furnace is heated. Heated high-boiling liquids such as mineral oil, silicone oil, or molten diphenyl are suitable as the heating medium. However, this only preheats to a temperature of 150 to 220 °C, while the pyrolysis itself takes place at temperatures of approximately 530 °C. Therefore, this known process does not allow for pyrolysis to be carried out at temperatures in the range of 230 to 350 °C and for all the necessary heat to be supplied by a liquid or vaporous heat transfer medium or by direct electrical heating.

A typical vinyl chloride production plant complex consists of

- a plant for the production of 1,2-dichloroethane from ethene and chlorine ("direct chlorination")

- a plant for the production of 1,2-dichloroethane from ethene, hydrogen chloride and oxygen ("oxychlorination"),

- a plant for the distillative purification of 1,2-dichloroethane, consisting of

- a dewatering column for separating water and low-boiling substances from the 1,2-dichloroethane produced in the oxychlorination plant

- optionally an additional low-boiling column for the separation of byproducts boiling at lower than 1,2-dichloroethane

- a high-boiling column for the separation of byproducts boiling at higher than 1,2-dichloroethane

- a vacuum column for further concentration of the high-boiling by-products separated in the high-boiling column

- a plant for the distillative separation of hydrogen chloride and unreacted 1,2-dichloroethane and for the purification of vinyl chloride, consisting of

- an HCI column for separating hydrogen chloride from the reaction mixture of the 1,2-dichloroethane hydrolysis

- a vinyl chloride or VCM column for separating vinyl chloride from the reaction mixture of the 1,2-dichloroethane hydrolysis - a vinyl chloride or VC M stripper for separating traces of hydrogen chloride from the final product vinyl chloride,

- a plant for the recovery of hydrogen chloride by combustion of gaseous and liquid by-products of the production of 1,2-dichloroethane and vinyl chloride with subsequent absorption of the hydrogen chloride formed during combustion.

The hydrogen chloride obtained by thermal cracking of 1,2-dichloroethane can be recycled to the oxychlorination plant and reacted there with ethene and oxygen to form 1,2-dichloroethane again.

The process described in DE 102 52 891 Al for the cracking of 1,2-dichloroethane into vinyl chloride and hydrogen chloride uses a catalyst that allows the operating temperature during endothermic cracking to be lowered. However, in this process, too, the tubular reactor is fired with a primary energy carrier such as oil or gas, with the furnace being divided into a radiation zone and a convection zone. In the radiation zone, the heat required for pyrolysis is transferred to the reaction tube primarily by radiation from the burner-heated furnace walls. In the convection zone, the energy content of the hot flue gases exiting the radiation zone is utilized by convective heat transfer, which allows the 1,2-dichloroethane, as the reactant of the pyrolysis reaction, to be preheated, vaporized, or superheated.

Various energy-saving and heat recovery measures for 1,2-dichloroethane production plants are known from the state of the art. Such measures lead to a significant reduction in operating costs and thus contribute substantially to the plant's economic efficiency and its CO2 emissions. These include, for example, measures that utilize the heat of reaction from exothermic reaction steps to heat heat sinks within the process. WO 2014/108159 Al lists various known heat recovery measures for vinyl chloride production plants and cites the relevant literature. EP 0002 021 Al describes a process for the catalytic dehydrohalogenation of 1,2-dichloroethane to vinyl chloride, using zeolitic catalysts treated with a Lewis acid. Using such catalysts, the reaction can be carried out at elevated pressure and temperatures in the range of 200 °C to 400 °C, and thus at considerably lower temperatures than in the conventional pyrolysis of 1,2-dichloroethane.

US Patent 10,239,803 describes a process using a catalytic system containing catalytic components for both the dehydrochlorination of 1,2-dichloroethane and the hydrochlorination of acetylene, a precursor to coke produced as a byproduct of thermal cracking. In this process, the acetylene is hydrochlorinated to vinyl chloride by means of the hydrogen chloride present in the reaction system as a cracking product of 1,2-dichloroethane, thereby suppressing coke formation.

Like the measures described in WO 2014/108159A1 mentioned above, the thermal-catalytic cracking of 1,2-dichloroethane also represents a heat recovery and energy-saving measure. One reason for this is that in catalytic processes, the heat of reaction can be supplied at significantly lower reaction temperatures than in purely thermal processes, thus requiring considerably less energy to heat the 1,2-dichloroethane to the reaction temperature. A further advantage of a catalytic process is that the reaction temperature range is accessible to heating with commercially available heat transfer media, primarily heat transfer fluids, especially mineral or synthetic heat transfer oils.

Heating with heat transfer fluids allows the use of heat sources within the 1,2-dichloroethane production process. Such a process is described, for example, in DE 10 2019 206 154 A1. This patent describes the use of waste heat from a plant for the combustion of gaseous and liquid byproducts from the production of 1,2-dichloroethane and vinyl chloride, respectively. used to heat a heat transfer fluid, wherein the heated heat transfer fluid is used to heat a catalytic-thermal 1,2-dichloroethane cracking process.

Similarly, the use of a heat transfer fluid allows for mixed heating. Thus, part of the energy required to heat the heat transfer fluid can be supplied, at least partially, by heating with sustainably generated electricity, and the remaining part by burning a fuel. This approach, described in WO 2020/221638 Al, enables great flexibility in heating a catalytic 1,2-dichloroethane hydrolysis process and, in particular, the use of sustainably generated electricity when it is available in sufficient quantity or surplus.

Finally, DE 10 2022 208 894.8 discloses the use of a heat transfer fluid for heating a catalytic 1,2-dichloroethane cracking reaction, wherein the heat transfer fluid was previously heated, at least partially, by the combustion of hydrogen or an ammonia-hydrogen mixture. When using hydrogen or ammonia produced from sustainable energy sources, this method also contributes to a significant reduction in CO2 emissions from the vinyl chloride production process.

Although various catalyst systems and the energy-saving measures described above have been described in the literature, there is a need for a commercially applicable process for the thermal-catalytic cleavage of 1,2-dichloroethane.

The object of the present invention is to provide such a process for the production of vinyl chloride by thermal cracking of 1,2-dichloroethane and a corresponding apparatus for carrying out such a process, in which a reduction in operating costs and a significant reduction in CO2 emissions are achieved.

This problem is solved by the features of claim 1, wherein the dependent claims represent advantageous developments. The invention thus relates to a device for the catalytic dehydrochlorination of chlorinated alkanes, comprising at least one catalytic dehydrochlorination reactor designed to be supplied with thermal energy by means of a liquid or vaporous heat exchanger medium or by direct electrical heating, wherein the catalytic dehydrochlorination reactor has at least one inlet for gaseous chlorinated alkane and at least one outlet for a product mixture obtained by dehydrochlorination of the chlorinated alkane carried out in the at least one catalytic dehydrochlorination reactor, at least one evaporator is connected upstream of the at least one catalytic dehydrochlorination reactor, the evaporator being in fluidic communication with the at least one catalytic dehydrochlorination reactor via a supply line and being designed to evaporate liquid chlorinated alkane, wherein liquid chlorinated alkane is supplied to the at least one evaporator via a supply line, and at least one heat exchanger is connected upstream of the at least one evaporator, by means of which thermal energy is transferred into the product mixture obtained by means of the catalytic dehydrochlorination reactor. Liquid chlorinated alkane can be introduced via a feed line.

According to the present invention, a second heat exchanger is provided to thermally interact with the product mixture discharged through the at least one outlet from the at least one catalytic dehydrochlorination reactor and is designed to remove thermal energy from the product mixture and supply it to the liquid chlorinated alkane carried in the feed line, wherein the second heat exchanger is arranged at a point in the feed line that is upstream of the at least one evaporator.

The present invention thus enables efficient utilization of the thermal energy of the product streams by preheating the reactant stream entering the catalytic dehydrochlorination reactor. The possible catalysts used for the purposes of the present invention are... These possibilities are known from the prior art, as described, for example, in US 10,239,803.

An advantageous further development provides that the supply line, in addition to the heat exchanger mentioned above, has at least one further heat exchanger and thus at least two heat exchangers, which are designed to supply thermal energy to the liquid chlorinated alkane carried in the supply line by means of a liquid or vaporous heat exchange medium or by direct electrical heating, in particular via a first and a second heat exchanger.

Another advantageous feature of the aforementioned embodiment is that the first heat exchanger can be bypassed if necessary, particularly if the supplied stream of a chlorinated alkane is already heated before being supplied.

In the reactor, heat is preferably supplied via a liquid or condensing heat transfer medium. Purely electric heating is another advantageous embodiment.

Preferably, the at least one dehydrochlorination reactor is designed as a vertical tube bundle reactor comprising a catalyst bed arranged in the tubes, with electrical heating elements attached to the outside of the tubes. These heating elements can be, for example, inductive or resistive electrical heating elements and/or the tube bundle can be designed such that the reactor tubes can be heated by an electric current flowing through them due to their own ohmic resistance.

In particular, the system is designed to include several dehydrochlorination reactors that can be operated in parallel or alternately. This allows, for example, the catalyst to be changed in the dehydrochlorination reactor that is not currently in operation, while the entire plant continues to operate, thus enabling quasi-continuous operation. It is further advantageous if the at least one evaporator has a first phase separation zone in which a separation of liquid and gaseous chlorinated alkane takes place, as well as a bottom-side discharge through which liquid chlorinated alkane can be discharged from the phase separation zone, and a fourth heat exchanger designed to supply thermal energy to the liquid chlorinated alkane taken from the discharge of the phase separation zone by means of a liquid or vaporous heat exchanger medium or by direct electrical heating, and a return of the chlorinated alkane to the phase separation zone.

In particular, the exhaust system has a discharge line to prevent the accumulation of high-boiling components in the evaporator.

It is further preferred that a fifth heat exchanger is arranged between the at least one evaporator and the at least one dehydrochlorination reactor, which is designed to supply thermal energy to the gaseous chlorinated alkane taken from the evaporator by means of a liquid or vaporous heat exchanger medium or by direct electrical heating and to provide a vapor line for conveying the gaseous chlorinated alkane into the dehydrochlorination reactor.

It may also be provided that the at least one dehydrochlorination reactor has at least one gas supply, in particular hydrogen and/or inert gas and at least one exhaust gas line.

For example, at least one second heat exchanger can be followed by at least one second phase separation zone, which is in fluidic communication with the at least one second heat exchanger via a line, into which the product mixture discharged and cooled from the at least one second heat exchanger is fed, wherein the at least one second phase separation zone is designed to separate the fed product mixture into a liquid and gaseous phase and has a first top-side discharge for gaseous products and a first bottom-side discharge for liquid products. Possible design forms of the at least one second phase separation zone include the formation

• as a phase separation tank,

• has an inlet tube open to the downwards inside, which is immersed in a liquid phase inside the first phase separation zone (20) particularly during operation of the device,

• has a settling zone for any catalyst abrasion or coke particles that may accumulate,

• has a conical bottom,

• has an inert gas supply, an exhaust pipe and a heating jacket,

• is equipped with spray nozzles and/or column trays that can be supplied with liquid and/or

• a liquid drain is arranged above a liquid inlet.

Any combination of the aforementioned design options is possible.

Preferably, the first bottom-side outlet has a pressure relief device, in particular a pressure relief valve.

It is also advantageous if the first bottom-side discharge leads into a distillation zone where the liquid products are separated into a gaseous overhead stream and a liquid bottom stream.

The distillation zone preferably has a heating system by which a partial flow of the bottoms stream is heated and returned to the distillation zone.

It is also advantageous to remove the liquid bottom stream using a bottom pump. This product stream can, for example, be fed into a vacuum column of a plant for the distillative purification of 1,2-dichloroethane, where the 1,2-dichloroethane can be recovered. The distillation zone can be preceded by at least one third phase separation zone into which the discharge leads. This third phase separation zone is designed to separate the product mixture into liquid and gaseous phases and has a third top-side discharge for gaseous products and a third bottom-side discharge for liquid products. Both the bottom-side and top-side discharges lead into the distillation zone. Specifically, the product streams from the top-side and bottom-side discharges are introduced into the distillation zone at different vertical positions (e.g., onto different trays), which further enhances the separation of the components. The two product streams from the top-side and bottom-side discharges have different boiling points and can therefore be introduced onto different trays in the distillation zone.

Preferably, at least one third phase separation zone is designed in the same way as the second phase separation zone.

The overhead stream can be fed to a condenser designed to condense gaseous products contained in the overhead stream. A collection vessel (30) is connected downstream of the condenser (29). The collection vessel (30) has an exhaust line (32) at the top, through which non-condensable components can be fed for thermal utilization, and a bottom outlet. The outlet is divided into two streams, one of which is returned to the distillation zone (24), and the other of which is fed as feed stream to an HCI column designed to remove hydrogen chloride from a reaction mixture during the cracking of a chlorinated alkane.

Preferably, a pump is arranged in the process flow.

In the device according to the invention, it can further be provided that the first head-side discharge leads to at least one further heat exchanger, which is designed to transfer the product stream supplied via the discharge. to extract thermal energy, followed by at least one fourth phase separation zone, wherein the at least one fourth phase separation zone is configured to separate the fed product mixture into a liquid and gaseous phase and has a third top-side discharge for gaseous products and a second bottom-side discharge for liquid products, each of which is fed to an HCI column designed to remove hydrogen chloride from a reaction mixture of a cracking of a chlorinated alkane.

Preferably, the at least one third heat exchanger is designed to supply thermal energy, extracted from the product stream in the discharge, to a product stream that is the overhead stream of an HCI column designed to remove hydrogen chloride from a reaction mixture of a cracking of a chlorinated alkane, and wherein the product stream is subsequently fed as a preheated feed stream to an oxychlorination plant.

For example, it may be provided that a pump for supplying chlorinated alkane to the at least one dehydrochlorination reactor is arranged in the supply line.

According to a particularly preferred embodiment of the present invention, the device has a modular design. This means that various components of the device, such as the dehydrochlorination reactor, the various heat exchangers, or phase separation zones, can be arranged in specific compartments, allowing for flexible exchange of the respective device components. It can also be provided that empty compartments or modules are included into which components of the device can be received by removing them from the device and moving them into the empty compartments or modules on suitable devices such as tracks or rails. In particular, the modular design can be such that a first module can comprise the at least one evaporator, a second module the at least one dehydrochlorination reactor, and the a second heat exchanger may be included, a third module which may have a receiving option for the at least one dehydrochlorination reactor arranged in the second module, the second module and the third module may be arranged adjacent to each other and the at least one dehydrochlorination reactor may be reversibly led from the second module to the third module.

In particular, it is possible that the second module and the third module have at least one device for moving the at least one dehydrochlorination reactor, in particular a mobile frame or tracks.

Particularly preferred is a further module comprising at least one further dehydrochlorination reactor which, when the at least one dehydrochlorination reactor is removed from the second module, can be inserted into the second module in place of this at least one dehydrochlorination reactor.

The invention is not limited to the above-described assignment of apparatus to specific modules.

The present invention is described below using the non-limiting example of a device and a process for the thermal-catalytic ethylene dichloride (EDC) cleavage. An exemplary embodiment of a device according to the invention is shown in the figures.

In this example, the process consists of the following steps:

- (Optional) Preheating of liquid 1,2-dichloroethane by means of a heat exchanger heated by steam or a liquid or vaporous heat transfer medium or directly by electricity.

- Further preheating of the liquid 1,2-dichloroethane by means of a heat exchanger in countercurrent flow with the reaction mixture from Outlet of the catalytic 1,2-dichloroethane fission reactor

- Evaporation of liquid 1,2-dichloroethane by means of an evaporation device, wherein the heat of vaporization is supplied by a liquid cider, vaporous heat transfer fluid, or by direct electrical heating.

- Optional superheating of the vaporized 1,2-dichloroethane by means of a heat exchanger, wherein the heat for superheating is supplied by a liquid or vaporous heat transfer fluid or by direct electrical heating.

- Catalytic dehydrochlorination of 1,2-dichloroethane to vinyl chloride and hydrogen chloride, wherein the heat of reaction is supplied by a liquid cider, vaporous heat transfer fluid, or by direct electrical heating.

- Cooling of the reaction mixture in countercurrent flow with liquid 1,2-dichloroethane via partial condensation

- Separation of the reaction mixture into a gaseous and a liquid phase using a phase separation device

- Distillative separation of the resulting liquid phase into an overhead product and a bottoms product, wherein the overhead product is fed as feed stream to an HCI column and the bottoms product is fed as feed stream to a vacuum column.

- Optional cooling of the gaseous fraction from the phase separation device by preheating a hydrogen chloride stream, which is supplied as input stream to an oxychlorination plant, whereby part of the gaseous fraction from the phase separation device condenses.

- Optionally, further cooling of the gaseous fraction from the phase separation device by means of an air cooler, whereby a further part of the gaseous fraction from the phase separation device condenses.

- Cooling of the gaseous fraction from the phase separation device by means of a heat exchanger using cooling water, whereby a further part of the gaseous fraction from the phase separation device condenses. - Optionally, the resulting two-phase current can be separated into a gaseous and a liquid current using a second phase separation device.

- Feeding the gaseous and liquid components of the resulting two-phase stream as feed streams to an HCI column.

The invention also relates to a device for carrying out the method according to the invention, consisting of:

- Optionally, a first heat exchanger heated by steam or a liquid cider vaporous heat transfer fluid or directly electrically heated for preheating liquid 1,2-dichloroethane

- A second heat exchanger for further preheating of liquid 1,2-dichloroethane using sensible and/or latent heat from the outlet stream of a catalytic reactor for the dehydrochlorination of 1,2-dichloroethane.

- An evaporation device for evaporating liquid 1,2-dichloroethane using a liquid or vaporous heat transfer medium or by direct electrical heating, wherein this device preferably consists of a heat exchanger and a phase separation vessel

- Optionally, a heat exchanger for superheating vaporous 1,2-dichloroethane using a liquid or gaseous heat transfer medium or by direct electrical heating.

- At least one reactor for the thermal-catalytic dehydrochlorination of 1,2-dichloroethane, wherein the at least one reactor is preferably designed as a tube bundle reactor and the catalyst is located in the tubes and the tubes are heated on the shell side by means of a vaporous or liquid heat transfer medium or by means of direct electrical heating

- A first phase separation vessel for separating the reaction mixture from the reactor outlet into a liquid and a vapor phase - A pressure relief device consisting of a pressure relief valve and optionally a downstream second pressure relief vessel for the partial pressure relief evaporation of the liquid phase from the first phase separation vessel and the separation into a liquid and a vapor phase.

- A distillation zone for the distillative processing of the liquid and vapor phases from the flash evaporation of the liquid phase of the first phase separation vessel.

- Optionally, a first heat exchanger for cooling the vaporous stream from the first phase separation vessel by preheating a gaseous hydrogen chloride stream from the top of an HCI column

- Optionally, an air cooler for further cooling of the vaporous stream from the first phase separation vessel

- A heat exchanger for (further) cooling of the vaporous stream using cooling water.

The process according to the invention comprises, in addition to heating the catalytic-thermal cracking reaction by means of a liquid or condensing heat transfer medium, also heating the upstream preheating, evaporation, or superheating of the 1,2-dichloroethane by means of this heat transfer medium. It is not necessary for all of these steps to be heated by means of the heat transfer medium. The process according to the invention includes heating at least one, up to any combination thereof, of the aforementioned partial steps, wherein the individual partial steps can in turn be subdivided (by apparatus) into further steps. In particular, certain partial steps can also be heated by cooling a liquid heat transfer medium using its sensible heat, while other partial steps are heated by condensing a vaporous heat transfer medium. Any combination of the heating modes "liquid/sensible heat" and "vaporous/latent heat" for different process steps is also possible. Furthermore, the invention also includes the direct heating of the individual process steps using electrical energy. In this embodiment, the preheating, evaporation, and superheating of the feedstock are carried out by electrically heated heat exchangers, in which, for example, the product-carrying tubes are embedded in or equipped with electrical heating elements. Inductive heating of the heat exchanger tubes or direct resistance heating is also possible, by passing an electric current through the heat exchanger or reactor tubes. The reactor tubes of the catalytic dehydrochlorination reactor can be heated in the same manner. The direct electrical heating of the process steps is preferably carried out with sustainably generated electricity.

"Heating" in the context of the process according to the invention means the transfer of heat to the starting material 1,2-dichloroethane and/or the reaction mixture by means of a heat transfer medium. The starting material 1,2-dichloroethane can be heated, vaporized, or superheated. Heat can be supplied to the reaction mixture in the reactor at a constant temperature level (isothermal reaction). The reaction mixture can also be heated further, with the heat supplied by the heating being used partly to meet the reaction heat requirement and partly to further heat the reaction mixture. Finally, the heat supply to the reaction mixture by heating can be adjusted so that at least part of the sensible heat content of the reaction mixture is used to meet the reaction heat requirement, and the reaction mixture in the reactor cools down compared to the reactor inlet temperature.

Heating devices for the 1,2-dichloroethane or the reaction mixture can be any type of heat exchanger known to a person skilled in the art, for example, but not limited to: shell and tube heat exchangers, plate heat exchangers, double tube heat exchangers, spiral heat exchangers, natural circulation evaporators or forced circulation evaporators.

Heat transfer media or fluids within the meaning of the invention Examples of methods include mineral and synthetic thermal oils, silicone oils, and molten salts.

Figure 1 describes the method according to the invention. Devices for heating a heat transfer medium and the heat transfer-side circuitry of heat exchangers, including devices for temperature control, both when heating with a liquid heat transfer medium and when heating with a vaporous heat transfer medium, are known to those skilled in the art and are not shown or described separately.

Liquid 1,2-dichloroethane 1 is pumped by a feed pump 2 to a first heat exchanger 3 for preheating. If the 1,2-dichloroethane is supplied directly from a column and is already warm, this step can be omitted. In this case, the first preheater is bypassed by means of a bypass line 4.

If the 1,2-dichloroethane is obtained from a storage tank at ambient temperature, for example, a first preheating step takes place in the first heat exchanger 3 using a heat transfer medium 5.

The liquid 1,2-dichloroethane now flows to a second heat exchanger 6 by means of which it is further heated by the sensible and/or latent heat of the hot reaction mixture 8 exiting the catalytic dehydrochlorination reactor 7.

Finally, the liquid 1,2-dichloroethane is preheated again in a third heat exchanger 9 until the selected evaporation temperature is reached. This step is optional, as the downstream evaporation device 10 can be designed to perform the preheating task simultaneously with the evaporation task, without requiring separate preheating.

In the evaporation device 10, the liquid 1,2-dichloroethane is evaporated. The evaporation device 10 consists of at least one four- The invention comprises a heat exchanger 11 and a phase separation zone 12, in which the vaporized 1,2-dichloroethane is separated from the liquid 1,2-dichloroethane. The evaporation device is shown in Fig. 1 as a vertical vessel with a vertical circulating evaporator, whereby a falling film evaporator can also be used. However, the invention is not limited to this arrangement – horizontal arrangements can also be used in which the phase separation zone is located above the heat exchanger. Furthermore, evaporation devices can also be used in which the heat exchanger and phase separation zone are designed as a single unit, such as kettle evaporators.

The evaporation device 10 also has a discharge line 13 through which high-boiling substances can be discharged from the evaporation device.

The vaporous 1,2-dichloroethane 14 now passes through a fifth heat exchanger 15, by means of which it is superheated to the reaction temperature. This step is also optional, since the evaporation temperature in the evaporation device 10 can be selected so that superheating of the vaporized 1,2-dichloroethane is no longer necessary.

The vaporous, possibly superheated, 1,2-dichloroethane now enters the at least one catalytic dehydrochlorination reactor 7, where the catalytic conversion to vinyl chloride and hydrogen chloride takes place. The heat of reaction from the endothermic reaction is supplied by means of the vaporous or liquid heat transfer medium.

The dehydrochlorination reactor 7 is preferably designed as a vertical tube bundle reactor, wherein the catalyst bed is located inside the tubes and the heat transfer medium 5 is on the outside of the tubes. In a further preferred embodiment of the invention, several dehydrochlorination reactors can also be connected in parallel, wherein these reactors can each be shut off separately on the product side and heating side, so that, for example, a catalyst change can take place in one or more reactors. This can be done without having to take the remaining reactors out of service.

The invention also includes a method in which the reaction temperature is adjusted depending on the catalyst activity. Thus, a lower temperature can be set at the beginning of the catalyst run time when catalyst activity is high than at the end of the catalyst run time when catalyst activity is lower.

The invention also includes a method in which the heated side of the reactor is divided into several zones, the temperature of which can be set independently of one another. This can be achieved, for example, by dividing the shell space of the tube bundle reactor into at least two shell-side compartments or by connecting several tube bundle reactors in series.

The dehydrochlorination reactor 7 also has a feed line 16 for the activation of the catalyst, which allows the flow of, for example, hydrogen or a hydrogen-containing gas mixture through the reactor if a metal- or precious-metal-containing catalyst is used that requires activation.

Furthermore, the dehydrochlorination reactor 7 has a supply line for an inert gas 17 in order to desorb adsorbed components such as 1,2-dichloroethane, vinyl chloride and hydrogen chloride before a catalyst change, whereby the desorption process can be supported by heating the reactor.

The activation gas - or in the case of desorption prior to a catalyst change - the inert gas loaded with components of the reaction mixture from the reactor outlet - is fed via an exhaust gas line 18 to a suitable exhaust gas treatment device, preferably a combustion plant for the thermal recovery of hydrogen chloride.

The hot reaction mixture 8 from the outlet of the dehydrochlorination reactor 7 The fluid flows through the second heat exchanger 6 and preheats liquid 1,2-dichloroethane. The reaction mixture partially condenses, resulting in a two-phase current 19 at the outlet of the preheater 6.

The current 19 enters a first phase separation zone 20, which is shown in Fig. 1 as the simplest embodiment of a phase separation vessel. Further preferred embodiments of the first phase separation zone include designs in which:

The phase separation device has an inlet tube open at the bottom inside.

The inlet tube is submerged in the liquid phase inside the container.

The container has a settling zone for any catalyst abrasion or coke particles that may accumulate.

The container has a conical bottom to allow for better removal of catalyst abrasion and/or coke particles.

The container has an inert gas supply, an exhaust gas line and a heating jacket to desorb adsorbed components of the reaction mixture before opening the container for cleaning purposes.

The container is equipped with spray nozzles and/or column trays that can be sprayed with liquid to wash out catalyst debris, coke particles, or tar-like byproducts from the gas stream.

The spray nozzles and/or column trays are supplied with liquid, which is condensed out of the reaction mixture by cooling during the further course of the process.

The container is arranged such that the liquid outlet is located above the liquid inlet of the phase separation vessel 23. The liquid phase from the phase separation zone 20 enters an expansion device 21, whereby a vaporous phase or a two-phase current 22 is formed by expansion evaporation. Optionally, a second phase separation zone 23 can be connected downstream of the expansion device, which is shown in Fig. 1 as the simplest embodiment of a phase separation vessel. Further preferred embodiments of the second phase separation zone 23 include configurations in which:

The phase separation device has an inlet tube open at the bottom inside.

The inlet tube is submerged in the liquid phase inside the container.

The container has a settling zone for any catalyst abrasion or coke particles that may accumulate.

The container has an inert gas supply, an exhaust gas line and a heating jacket to desorb adsorbed components of the reaction mixture before opening the container for cleaning purposes.

The phase separation vessel is arranged such that the liquid outlet is located above the liquid inlet of the distillation column 24.

The two-phase current 22 from the expansion device 21 is now fed into a distillation zone 24. If the second phase separation zone 23 is used, the liquid and gaseous components are fed separately into the distillation zone 24. The distillation zone 24 has at least one separation stage and a heating device 25.

The distillation zone 24 is shown in Fig. 1 as a distillation column with a circulating evaporator. However, the invention is not limited to this embodiment. Another preferred embodiment consists of a horizontal or vertical vessel without column trays and with a circulating evaporator. The bottom stream 26 of the distillation zone 24, consisting mainly of 1,2-dichloroethane, is fed by means of a bottom pump 27 to a further distillative work-up, preferably in the vacuum column - a plant for the purification of 1,2-dichloroethane, as described above.

The overhead stream 28 from the distillation zone 24 is condensed by means of the overhead condenser 29, collected in the reflux tank 30, and pumped by the reflux pump 31 as feed stream to the HCI column. Non-condensable components are fed via an exhaust gas line 32 to a combustion plant for thermal HCI recovery.

The gas phase 33 from the first phase separation zone flows through a heat exchanger 34 to preheat the hydrogen chloride stream 35 from the top of the HCI column, which is fed to the oxychlorination plant as a preheated feed stream 36.

The product-side outlet stream 37 of the HCI preheater 34 now flows successively through an air cooler 38 and a heat exchanger 39 cooled by means of cooling water.

The steps of HCI preheating and cooling in an air cooler are optional: If no heat recovery is to be implemented or sufficient cooling water is available, the gas phase 33 from the first phase separation zone can also be cooled solely with the cooling water-operated heat exchanger 39.

During the cooling step(s) in the heat exchangers 34, 38 and 39, a portion of the gas stream 33 condenses. After passing through a third phase separation zone 40, the resulting gas and liquid phases are fed to the HCI column as feed streams 41 and 42.

The invention also relates to a device for splitting 1,2-dichloroethane, in which apparatus components are combined (steel) on-site into prefabricated modules, which offers significant advantages both in the construction and in the maintenance of the device. Figure 1b shows an exemplary embodiment of a catalytic dehydrochlorination reactor 7. This reactor has an inlet 14 at the top for gaseous 1,2-dichloroethane, which flows through the reactor 7 from top to bottom. Also at the top is an exhaust line 18 through which gaseous byproducts, e.g., HCl, can be discharged from the reactor. The reactor 7 also has supply lines for gases for catalyst activation 16 or for desorption 17 of products or reactants remaining on the catalyst. The tube bundles are indicated by the vertical lines or the reference numeral 72.

The tube bundle reactor is divided into several shell-side compartments by partitions 73, analogous to a tube bundle heat exchanger. Each of these is equipped with an inlet 75 and an outlet 76 for a heat transfer medium.

Fig. 2a shows an example of such an arrangement. The figure serves only for illustration; the invention is not limited to the components and arrangements shown and includes any arrangements of the apparatus components required for carrying out the method according to the invention, as well as any number of modules required for this purpose.

In particular, only parts of a device for carrying out the process according to the invention can be modularly constructed, while other parts are constructed in a conventional manner. This is particularly advantageous if, for example, an existing plant for the thermal cracking of 1,2-dichloroethane is to be converted to a thermocatalytic process and existing plant components are to continue to be used (revamp option).

Fig. 2a shows three steel construction modules 43, 44 and 45 as examples. Module 43 contains the evaporation device 10 with the heat exchanger 11 and the phase separation zone 12 for the evaporation of 1,2-dichloroethane as well as the heat exchanger 15 for the superheating of the vaporous 1,2-dichloroethane. The outlet of the superheater 15 is connected via the vapor line 46 to the inlet of the catalytic dehydrochlorination reactor 7 in module 44. In the arrangement shown, module 44 contains both the reactor 7 and the heat exchanger 6 for preheating liquid 1,2-dichloroethane using the reaction mixture from the outlet of reactor 7.

The invention also relates to a device for the thermal-catalytic decomposition of 1,2-dichloroethane, in which apparatus components can be moved between modules for maintenance purposes or, to save time during necessary maintenance work, can also be replaced by a spare component. Figures 2a and 2b illustrate this by way of example for the dehydrochlorination reactor 7. However, the invention is not limited to this apparatus – other apparatus components can also be moved between different modules for maintenance or cleaning purposes.

In the example shown in Figs. 2a and 2b, the reactor 7 can be moved into the empty module 45 for catalyst replacement using a suitable device, for example a mobile frame 50 on tracks 51. After moving it into the empty module 45, the used catalyst 48 can be emptied into a suitable container 49 and then the reactor can be refilled with fresh catalyst.

To further shorten maintenance procedures, as shown in Fig. 2b, a device requiring maintenance can be exchanged for a readily available replacement device. For example, reactor 7 can be moved into an empty module for emptying and refilling and exchanged for the already refilled reactor 47.

The invention also includes a device for the thermal-catalytic cleavage of 1,2-dichloroethane, in which apparatus (steel) components are combined on-site into prefabricated modules and the modules are designed to be disassembled into subunits, the subunits of which in turn may contain apparatus components.

For example, the upper part of module 44 with the contents within it can be Reactor 7 can be lifted from the lower section, including the preheater 6 located therein, by means of a crane and placed on a frame for maintenance purposes. This frame can, for example, correspond to the lower section of module 45. This procedure is described here using reactor 7 as an example; however, the invention is not limited to this apparatus.

Figure 3 shows several possible embodiments of the phase separation zone 20 for illustrative purposes. The features shown in Figures 3a - 3e can be combined in any way - the invention is not limited to the examples shown.

In Fig. 3a, the phase separation zone is shown as a phase separation vessel with a conical bottom 52 and – optionally – a tapered, cylindrical vessel section 53 adjoining the conical bottom. The lid 54 connects either directly to the conical vessel bottom 52 or to the cylindrical vessel section 53 and can be removed for easier removal of solids deposited in the vessel.

The reaction mixture 19 enters the vessel via an inlet tube 55, which is open or perforated at the bottom and located above the liquid level 56. The gas phase 33 is drawn off at the top, and the liquid phase 57 at the bottom of the phase separation zone 20.

Fig. 3b shows another embodiment of the phase separation zone 20, in which the reaction mixture 19 is introduced via a perforated inlet tube 58, the inlet tube 58 being located below the liquid level 56.

Fig. 3c shows a further embodiment of the phase separation zone 20, in which the reaction mixture is introduced via a perforated inlet tube 58, the inlet tube 58 being located below the liquid level 56. Additionally, the phase separation zone 20 is equipped with spray nozzles 59, which can be supplied, for example, with a partial flow 60 of the liquid flow 41 in order to wash out any solid particles that may have been carried out of the gas phase 33. Fig. 3d shows a further embodiment of the phase separation zone 20, in which the reaction mixture is introduced via a perforated inlet tube 58, the inlet tube 58 being located below the liquid level 56. Additionally, the phase separation zone 20 is equipped with column trays 61, which can be supplied, for example, with a partial stream 60 of the liquid stream 41 in order to wash out any solid particles that may have been carried out of the gas phase 33.

Fig. 3e shows a further embodiment of the phase separation zone 20, in which the reaction mixture is introduced via a vertical, perforated inlet pipe 58, the inlet pipe 62 being immersed in the liquid. Additionally, the phase separation zone 20 is equipped with at least one partition 63, which divides the liquid volume into an inlet zone 63 and a settling zone 65. In this embodiment, the liquid phase 57 is drawn off from the settling zone 65. Solids that settle in the lower part of the vessel can remain there until the system is serviced and removed during servicing. If necessary, the solids can also be drawn off from the vessel via the discharge line 66 and sent for suitable processing.

For the desorption of adsorbed components such as hydrogen chloride and chlorinated hydrocarbons from settled solids, this embodiment also includes a heating jacket 67 with an inlet 68 and an outlet 69 for a heating medium. The term "heating jacket" also includes direct electrical heating of the container by means of electrical heating elements attached to the outside of the container (not shown in the figure).

Furthermore, this embodiment includes supply lines 70 for an inert gas and an exhaust line 71 for inert gas loaded with desorbed components. By heating the container and purging it with inert gas, adsorbed components can be desorbed from any solids that may be present before the container is opened.

Legend of the characters: 1 Supply line 1,2-Dichloroethane, liquid

2 Feed pump

3 Heat exchangers 1 (preheating step 1).

4 Bypass line preheater 1

5 Heat transfer fluid

6 Heat exchangers 2 (preheating step 2)

7 Catalytic Dehydrochlorination Reactor

8 Reaction mixture, hot, to heat exchanger 2

9 Heat exchangers 3 (preheating to evaporation temperature)

10 evaporators

11 Heat exchangers 4 (evaporators)

12 First phase separation zone in 1,2-dichloroethane evaporation

13 Delivery Management

14 1,2-Dichloroethane, vaporous

15 Heat exchangers 5 (superheating)

16 Supply line for catalyst activation

17 Inert gas supply line for desorption

18 Exhaust pipe from the dehydrochlorination reactor

19 Two-phase reaction mixture from the preheater

20 Second phase separation zone

21 Relaxation device

22. Outlet flow from pressure relief device

23 Third phase separation zone

24 Distillation zone

25 Heating device

26 Bottom stream of the distillation zone

27 Pump for sump flow 28 Headstream of the distillation zone

29. Distillation zone head condenser

30 collection containers

31 Return pump of the distillation zone

32 Exhaust pipe

33 Gas phase from the second phase separation zone

34 HCI preheaters

35 HCl from the top of the HCI column

36 HCl, preheated, for oxychlorination

37 Product-side outlet flow of the HCI preheater

38 air coolers

39 Condenser, water-cooled

40 Fourth phase separation zone

41 Liquid stream to the HCI column

42 Gas flow to the HCI column

43 Steel construction module

44 steel construction module

45 steel construction module

46 Brøddenleitung

47 Replacement apparatus (reactor)

48 Catalytic converter, used

49 containers for used catalytic converters

50 Device for moving the reactor (mobile frame)

51 Device for moving the reactor (track)

52 conical base

53 cylindrical container part

54 lids 55 perforated inlet pipe

56 Fluid levels

57 liquid product

58 Inlet pipe

59 spray nozzles

60 partial current

61 column trays

62 Inlet pipe

63 Introduction zone

65 Calming Zone

66 Discharge Management

67 Heating jacket

68 Supply line

69 Derivation

70 supply lines

71 Exhaust pipe

72 tube bundles

73 Pipe floor or wall of a compartment

74 deflection plates

75 Supply line for heat transfer medium

76 Drainage for heat transfer medium

Claims

Patent claims 1. Device for the catalytic dehydrochlorination of chlorinated alkanes, comprising at least one catalytic dehydrochlorination reactor (7, 47) designed to be supplied with thermal energy by means of a liquid or vaporous heat exchanger medium (5) or by direct electrical heating, wherein the catalytic dehydrochlorination reactor (7, 47) has at least one inlet for gaseous chlorinated alkane and at least one outlet (8) for a product mixture obtained by dehydrochlorination of the chlorinated alkane carried out in the at least one catalytic dehydrochlorination reactor (7, 47), at least one evaporator (10) is connected upstream of the at least one catalytic dehydrochlorination reactor (7, 47), the evaporator being in fluidic communication with the at least one catalytic dehydrochlorination reactor (7, 47) via a feed line (14) and being designed to evaporate liquid chlorinated alkane, wherein Liquid chlorinated alkane is supplied to at least one evaporator (10) via a feed line (1), and at least one heat exchanger (3, 6, 9) is connected upstream of the at least one evaporator (10), by means of which thermal energy can be introduced into the liquid chlorinated alkane carried in the feed line (1), characterized in that a second heat exchanger (6) is in thermal interaction with the product mixture discharged through the at least one outlet (8) from the at least one catalytic dehydrochlorination reactor (7, 47) and is configured to remove thermal energy from the product mixture and supply it to the liquid chlorinated alkane carried in the feed line (1), wherein the second heat exchanger (6) is connected to is arranged at a point in the supply line (1) which is upstream of the at least one evaporator. 2. Device according to claim 1, characterized in that the supply line (1) has at least one further heat exchanger (3, 9) which is designed to supply thermal energy to the liquid chlorinated alkane carried in the supply line (1) by means of a liquid or vaporous heat exchanger medium (5) or by direct electrical heating, in particular via a first (3) and a second (9) heat exchanger. 3. Device according to one of the preceding claims, characterized in that the at least one catalytic dehydrochlorination reactor (7, 47) is designed as a vertical tube bundle reactor comprising a catalyst bed arranged in the tubes, wherein the heat exchange medium (5) is guided on the outside of the tubes. 4. Device according to one of the preceding claims, characterized in that the at least one catalytic dehydrochlorination reactor (7, 47) is designed as a vertical tube bundle reactor comprising a catalyst bed arranged in the tubes, with electrical heating elements attached to the outside of the tubes. 5. Device according to the preceding claim, characterized in that the heating elements are designed as inductive or resistive electrical heating elements and/or the tube bundle is designed such that the reactor tubes can be heated by electric current flowing through them and by their own ohmic resistance. 6. Device according to one of the preceding claims, characterized in that the device comprises several dehydrochlorination reactors (7, 47) which can be operated in parallel to each other or alternately. 7. Device according to one of the preceding claims, characterized in that the at least one evaporator (10) has a first phase separation zone (12) in which a separation of liquid and gaseous chlorinated alkane takes place, and a bottom-side discharge through which liquid chlorinated alkane can be discharged from the phase separation zone, and a fourth heat exchanger (11) which is designed to supply thermal energy to the liquid chlorinated alkane taken from the discharge of the phase separation zone (12) by means of a liquid or vaporous heat exchange medium (5) or by direct electrical heating, and to return the chlorinated alkane to the phase separation zone (12). 8. Device according to one of the preceding claims, characterized in that a fifth heat exchanger (15) is arranged between the at least one evaporator (10) and the at least one dehydrochlorination reactor (7, 47), which is designed to supply thermal energy to the gaseous chlorinated alkane taken from the evaporator (10) by means of a liquid or vaporous heat exchange medium (5) or by means of direct electrical heating and to provide a vapor line (46) for conveying the gaseous chlorinated alkane into the dehydrochlorination reactor (7, 47). 9. Method according to one of the preceding claims, characterized in that the at least one dehydrochlorination reactor (7, 47) has at least one feed (16, 17) for gases, in particular hydrogen and/or inert gas and at least one exhaust gas line (18). 10. Device according to one of the preceding claims, characterized in that at least one second heat exchanger (6) is connected downstream of at least one second phase separation zone (20), which is in fluidic communication with the at least one second heat exchanger (6) via a line (19), into which the product mixture discharged and cooled from the at least one second heat exchanger (6) is fed, wherein the at least one second phase separation zone (20) is configured to separate the fed product mixture into to separate a liquid and gaseous phase and has a first top-side discharge (33) for gaseous products and a first bottom-side discharge (22) for liquid products. 11. Device according to the preceding claim, characterized in that the first bottom-side discharge (22) has a pressure relief device (21), in particular a pressure relief valve. 12. Device according to one of the two preceding claims, characterized in that the first bottom-side discharge (22) opens into a distillation zone (24) in which the liquid products are separated into a gaseous top stream (28) and a liquid bottom stream (26). 13. Device according to the preceding claim, characterized in that at least one third phase separation zone (23) is arranged upstream of the distillation zone (24), into which the discharge (22) opens, wherein the at least one third phase separation zone (23) is configured to separate the fed product mixture into a liquid and gaseous phase and has a third top-side discharge for gaseous products and a third bottom-side discharge for liquid products, wherein the third bottom-side discharge and the third top-side discharge are led into the distillation zone (24). 14. Device according to one of claims 12 to 13, characterized in that the overhead stream (28) is fed to a condenser (29) designed to condense gaseous products contained in the overhead stream (28), wherein a collection vessel (30) is connected downstream of the condenser (29), wherein the collection vessel (30) has an exhaust line at the top end^), through which non-condensable components can be supplied for thermal utilization and a collection vessel outlet at the bottom, wherein the outlet is divided into two streams, wherein one partial stream is returned to the distillation zone (24) and the other partial stream is fed as feed stream to an HCI column designed to remove hydrogen chloride from a reaction mixture of a cleavage of a chlorinated alkane. 15. Device according to one of claims 10 to 14, characterized in that the first top-side discharge (33) leads to at least one further heat exchanger (34, 38, 39) designed to extract thermal energy from the product stream supplied via the discharge (33), followed by at least one fourth phase separation zone (40), wherein the at least one fourth phase separation zone (40) is configured to separate the fed product mixture into a liquid and gaseous phase and has a third top-side discharge (42) for gaseous products and a second bottom-side discharge (41) for liquid products, each of which leads to an HCI column designed to remove hydrogen chloride from a reaction mixture of a cleavage of a chlorinated alkane. 16. Device according to the preceding claim, characterized in that the at least one third heat exchanger (34, 38, 39) is designed to supply thermal energy to a product stream (35), which is the overhead stream of an HCI column designed to remove hydrogen chloride from a reaction mixture of a cracking of a chlorinated alkane, which was taken from the product stream in the discharge (33), and wherein the product stream (35) is subsequently supplied as a preheated feed stream (36) to an oxychlorination plant. 17. Device according to one of the preceding claims, characterized in that it is modularly constructed (43, 44, 45), wherein in particular a first module (43) comprises the at least one evaporator (10), a second module (44) comprises the at least one dehydrochlorination reactor (7, 47) and the second heat exchanger (6), a third module which has a receiving option for the at least one dehydrochlorination reactor (7, 47) arranged in the second module, and wherein the second module (44) and the third module (45) are arranged adjacently and the at least one dehydrochlorination reactor (7, 47) can be reversibly led from the second module (44) to the third module (45).