SK282850B6 - Device and use thereof for oxi-chlorination - Google Patents

Abstract

The production of 1,2-dichloroethane from ethylene, hydrogen chloride and oxygen or an oxygen-containing gas (oxi-chlorination) is done advantageously in a reactor with a lower boundary for a catalyst-fluidised bed, a first gas inlet duct (distributor pipes) (4) being provided above the boundary within the catalyst-fluid bed. The first gas inlet duct is provided with nozzles (5) distributed over the entire cross-section of the reactor; these nozzles open out into pipes (6) which conduct the emerging gas stream in a direction essentially opposed to that of the gas stream which fluidises the catalyst after entering via a second gas inlet duct (7) below the boundary.

Description

Technical field

By oxychlorination is meant the conversion of ethylene by hydrogen chloride and oxygen or oxygen-containing gas to give 1,2-dichloroethane (EDC). The hydrogen chloride produced by the thermal cleavage of EDC into vinyl chloride is generally used.

BACKGROUND OF THE INVENTION

Catalysts containing metal halides, preferably copper (I) chloride, on powdered supports such as alumina are used for oxychlorination. The catalyst particles in this case have an average diameter of about 50 [mu] m and form a fluidized bed which is carried either by the reaction gas flow, optionally with an inert gas fraction, or by an additional gas stream in the circuit. In this process, the heat of reaction is received in the fluidized bed and removed through the cooling surfaces to achieve a uniform temperature distribution in the fluidized bed reactor. The catalyst particles must have a high abrasion resistance. This property is essentially due to the carrier material for which silicic acid, diatomaceous earth or pumice are also used in addition to the alumina. In the case of insufficient abrasion resistance, the catalyst particles are broken down, in particular by the action of gas streams from the gas supply device, and the resulting catalyst support dust is discharged from the oxychlorination reactor in the downstream process. This results in not only loss of catalyst but also increased abrasion of the apparatus.

However, the use of abrasion-resistant carrier material results in increased wear of the gas supply device, leading to more frequent replacement thereof, which entails considerable costs and additional costs due to production interruptions.

In addition to the necessary balance between the stability of the catalyst particles and the abrasion associated therewith, it should also be borne in mind that there is no agglomeration of the catalyst particles, which would lead to crumbling and thus fluid bed failure. This would result in an uneven temperature distribution in the fluidized bed with a correspondingly unfavorable course of the reaction, as well as eventual clogging of bottlenecks in the apparatus, for example in cyclones for dust separation above the fluidized bed or in downcomers to convey dust from these cyclones back to the fluidized bed. This tendency to clumping depends, in addition to the properties of the catalyst and its distribution on the catalyst support, particularly the concentration of the reaction gases in the fluidized bed.

EP-A-0 446 379 discloses a reactor for the production of .alpha.-unsaturated nitrile in which a gas inlet for olefin or tertiary butyl alcohol is arranged horizontally, with a plurality of nozzles arranged at the lower side of the gas inlet as well as a further inlet for an oxygen-containing gas arranged upstream and parallel to the first gas inlet, the distance between the two gas inlets being 25 to 300 mm. Too short a spacing can lead to melting of the gas feeds due to an unexpected reaction, while at too long spacing the olefin or tertiary butyl alcohol is not mixed sufficiently with the oxygen-containing gas, reducing the nitrile yield.

GB-A-1 265 770 discloses a fluidized bed reactor with a separating plate at the bottom of the reactor below which a gas inlet is arranged, with a further gas inlet in the peripheral region of the reactor vessel above and near the distributor plate. This additional gas supply ensures that the catalyst does not settle in the edge region. This measure serves in particular to prevent the catalyst being reduced. An additional gas supply may be provided within the fluidized bed at the bottom of the reactor to provide good mixing of the reactants in the fluidized bed.

WO 94/19099 discloses an oxychlorination plant characterized by a reactor 1, a lower boundary 2 for a fluidized bed catalyst 3, a gas inlet 4 (a manifold) comprising nozzles 5, the nozzles 5 opening into tubes 6 which lend to the outgoing gas stream a horizontal component in the flow direction, and a gas inlet 9 below the boundary 2.

Preferred embodiments are directed to the tubes having a nozzle opening having control devices having outlet openings at the end, or that the tubes are disposed obliquely upward or in a horizontal direction or obliquely downwardly, the tubes they terminate freely in the catalyst bed or that the tubes are arranged with respect to the outlet openings of the adjacent tube so that the outgoing gas streams do not face each other face-to-face and / or do not meet the adjacent pipe. Further preferred embodiments are directed to tubes passing through the boundaries in which the nozzles are arranged below the boundary but above the lower end of the tube, the nozzles preferably being below half the length of the respective tube, in particular at a distance of about one tube diameter from the lower. end.

SUMMARY OF THE INVENTION

It has now been found that these known devices have a certain abrasion in the gas supply device during long operation and high load, i.e. high gas velocity. Surprisingly, it has further been found that this abrasion does not occur, or occurs only to a substantially reduced extent, when the tubes into which the nozzles exit lead the outgoing gas stream substantially upstream of the gas which holds the catalyst in the form of a fluidized bed.

Accordingly, the present invention relates to an oxychlorination apparatus characterized in that it comprises:

- reactor 1,

- a lower boundary 2 for the fluidized bed catalyst 3,

- above the boundary 2 and inside the catalyst in the fluidized bed 3 a gas inlet 4 (manifold) equipped with nozzles 5 distributed over the entire cross-section of the reactor 1,

- wherein the nozzles 5 open into tubes 6 which guide the exiting gas stream substantially upstream of the gas stream which fluidises the catalyst, and

- gas inlet 7 below boundary 2.

Advantageously, the device according to the invention is designed in such a way that an equal number of tubes 6 are arranged uniformly over the cross-section of the reactor against a plurality of tubes 8

1. In particular, the interconnection of one tube 8 and 6 gives a particular connection of the reacting gases from the tubes 8 and 6.

In another embodiment of the device according to the invention, the same amounts of tubes 8 and 6 are displaced relative to one another. This geometry causes the least erosion of the tubes 6 by the gas stream exiting the tubes 8. Further, by this arrangement, the reactants exiting the tubes 8 and 6 in the catalyst in the fluidized bed 3 are immediately exposed to the direct contact with the catalyst. This favors the desired reaction in the direction of EDC formation, and side reactions such as the combustion of ethylene with oxygen are suppressed.

Another embodiment of this device leaves more freedom for its sizing and construction. In this embodiment, the number of tubes 6 differs from the number of tubes 8. However, it is also important here to distribute these tubes as evenly as possible into the cross-section of reactor 1. This form provides the possibility to change the number of tubes 6 in an existing reactor without having to adapt the tubes at the same time. 8, which may entail considerable costs.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail by means of the following exemplary embodiment shown in the drawing.

DETAILED DESCRIPTION OF THE INVENTION

In the example, the apparatus of FIG. 1. Gaseous reactants preheated to 160 ° C are introduced into reactor 1 with a diameter of 2.8 m and a height of 26 m. A mixture of 5974 kg / h of hydrogen chloride and 1417 kg / h of oxygen flows through the gas inlet 4 through the nozzles 5 and the tubes 6 to the fluidized bed catalyst 3. The nozzles 5 have different diameters in order to achieve the gas distribution as uniformly as possible. Reactor cross-section 1. The diameter of the nozzles 5 increases in the gas inlet 4 downstream from 8.6 mm to 9.3 mm and further to 10 mm in order to compensate for different pressure losses along the gas inlet to the individual nozzles 5. Tubes 6 with internal diameter 40 mm have a length of 300 mm. 2380 kg / h of ethylene flows through the gas inlet 7 and the tube 8 with the nozzles 9 through the lower limit 2. In the reactor 1, the catalyst in the fluidized bed 3 is copper chloride on alumina as the support. The reactants are introduced into the fluidized bed. For fluidizing the fluidized bed, an additional 8780 kg / h of gas flows from the gas circuit through the gas inlet 7 and the tubes 8 through the lower boundary 2 to the reactor 1. The upper ends of the tubes 8 are aligned with the lower boundary 2. . In this section, the reactants are separated after the cross-section of the reactor, and the mixing zones of the individual reactants and the catalyst are formed. The ethylene and the gas from the circuit flow in the reactor from bottom to top. In this way, they encounter hydrogen chloride and oxygen and react with EDC and water with the assistance of the catalyst present. The reaction heat of 238.5 kJ / mol produced thereby is removed by means of a catalyst in the fluidized bed 3 through a cooling coil 12, in which the water is converted to steam at 183 ° C. The reaction temperature is 225 ° C at a pressure of 3.2 bar in the reactor. The gas stream in the reactor head, consisting of the reaction products and the gas from the circuit, leaves the reactor 1 through three cyclones for further processing (not shown in the figure). The three series cyclones serve to separate the entrained catalyst dust from the gas stream in the reactor head above the fluidized bed catalyst.

Claims (8)

PATENT CLAIMS Oxychlorination plant, characterized in that it comprises a reactor (1), a lower boundary (2) for the fluidized bed catalyst (3), above the boundary (2) and inside the catalyst in the fluidized bed (3) an inlet (4) ) a gas (manifold), which is provided with nozzles (5) distributed over the entire cross-section of the reactor (1), the nozzles (5) flowing into tubes (6) which guide the outgoing gas stream substantially upstream of the gas stream which fluidizes the catalyst and a gas supply (7) below the boundary (2) and a pipe (8) passing through the boundary (2), the space between the upper ends of the tubes (8) and the lower ends of the tubes (6) forming a mixing area which is sized so large mixing the reactants coming out of these tubes (6, 8) with the catalyst. Apparatus according to claim 1, characterized in that tubes (8) extend through the boundary (2), in which nozzles (9) are arranged below the boundary (2) but not below the lower end of the tube (8). Apparatus according to claim 2, characterized in that the nozzles (9) are arranged at such a large distance from the upper end of the tube (8) that the flow rate of the gas streams directed upwards from the nozzles (9) before reaching the upper end of the tube (8) always aligns the pipe (8). Device according to claim 3, characterized in that the nozzles (9) are arranged at a distance of about one diameter of the tube (8) from the lower end of the tubes (8). Device according to claim 1, characterized in that the length of the tubes (6) is so large that the flow rate of the downstream gas streams from the nozzles (5) before reaching the lower end of the tube (6) in the tube cross-section (6) always equalizes. Apparatus according to claims 1 and 5, characterized in that the nozzles (5) have different diameters to distribute the amount of gas supplied by the inlet (4) evenly across the cross-section of the reactor (1). Apparatus according to claims 1 to 6, characterized in that the space between the upper ends of the tubes (8) and the lower ends of the tubes (6) is dimensioned so as to avoid a large erosive interaction of the tubes (4,6, 8) and bottom border (2). Use of a device according to claims 1 to 7 for converting ethylene with hydrogen chloride and oxygen or oxygen-containing gas into 1,2-dichloroethane.