CH439284A - Process for carrying out a catalyzed chemical reaction - Google Patents

Description

Process for carrying out a catalyzed chemical reaction The subject of the present invention is a process for carrying out a catalyzed chemical reaction, by passing a gas stream of the materials from bottom to top through a fluidized bed of catalyst particles. This process is particularly applicable to the oxychlorination of hydrocarbons.

The term oxychlorination refers to metal halide catalyzed processes in which gaseous hydrochloric acid serves as the chlorinating agent. These methods include the oxychlorination of hydrocarbons and/or chlorohydrocarbons with hydrochloric acid and elemental oxygen or an oxygen-containing gas, such as Air.

The process is carried out in the presence of a metal halide catalyst such as a suitable carrier impregnated with cupric chloride. It is assumed that in these oxychlorinations the hydrochloric acid is oxidized to chlorine and water, and that the chlorine reacts with the organic matter present in the feed gas.

In a variation of the oxychlorination process, an employs elemental chlorine as the chlorine source. In this case, hydrochloric acid is produced by chlorination of the hydrocarbon and/or chlorohydrocarbon with elemental chlorine. 0n passes 1e free chlorine; the gas containing oxygene, a hydrocarbon and/or a chlorohydrocarbon to be chlorided in contact with a metal halide catalyst bed. The chlorine reacts with the hydrocarbon or chlorohydrocarbon to produce hydrochloric acid and the product Chloride of the hydrocarbon or a derivative plus Chloride of the chlorohydrocarbon. The chlorine content of the hydrochloric acid produced in this manner is then used to effect further chlorinations of the hydrocarbon and/or chlorohydrocarbons present in the reaction zone through oxidation of the hydrochloric acid to elemental chlorine. The term fluidized bed refers to processes in which a gas is passed through a bed of solid material whose state depends on various factors such as gas velocity, particle size, and the like. Thus, if the gas velocity is too low, the bed of solid elements remains practically static; the gas simply passes through the pores of the bed and nothing happens among the particles of the bed. If the gas velocity is increased, at least some of the particles enter dynamically into the suspension RTI ID="0001.0270" WI="16" HE="4" LX="1453" LY="1641"> of rising gas, and the height of Et increases. Such a bed is called a dynamic bed. If Fon further increases the speed of the gas, all the particles go into suspension and the bed expands further. Eventually the bed may find itself in a state of strong turbulence, a state which in many respects resembles that of a boiling liquid.

The present process is especially intended for reactions carried out in catalyst beds where gas velocities result in the formation of dynamic and fluidized beds. The formation of these beds depends on factors such as particle size, components, gas velocity, particle density, etc. Wilhelm & Kwauk, Chemical Engineering Progress, Volume 44, Page 201 (1948) have equated the various factors necessary for bed fluidization and beds of desired conditions can be achieved by following the principles given in their article. For the implementation of the present process, a fluidized bed is used rather than a dynamic bed.

During the use of fluidized beds, the wear by friction of the particles of the catalyst, which normally occurs during the operation, gives rise to a considerable quantity of fine material which, according to the speeds, is entrained in greater or lesser quantity. - lifted out of the bed by ascending gas currents coming out of the reaction zones. These fine materials carry with them the catalyst, it naturally results from these losses a reduction in the activity of the catalyst. The recovery of the fine materials removed from the catalytic beds often presents many difficulties due to the corrosive nature of the gases leaving these beds. The usual techniques, such as filtration or condensation outside the reactor in a suitable dust collector, are not applicable because of the corrosive properties of the exiting gases.

The present invention avoids several problems relating to the removal of gases and fine materials as well as the recovery of catalytic material from fluidized beds. By means of the present invention, it is now possible to recover entrained catalyst from such beds while simultaneously eliminating many of the deleterious effects generally associated with such recovery. It also makes it possible to substantially reduce the quantity of material removed or carried out of the fluidized oxychlorination bed.

According to the invention, an reduces, in a zone occupied by the gases and located above the bed, the velocity of the gases produced leaving the bed, then raises the velocity of the gases above that at which they leave the bed by imparting to them a circular movement to deposit, in the zone of increased speed, the entrained fine particles; and removes reaction gases substantially free of fine particles from said zone by maintaining the increased velocity zone at a temperature above the dew point of the gases. The increased velocity zone may be in a cyclone, or similar dust collecting device, disposed in the space occupied by the gases, and maintained at the reaction temperature. Maintaining gases at a temperature above their dew point is important because lowering the temperature below the dew point can lead to many deleterious corrosion effects. The velocity of gases entering the dust collection device is greatly increased to produce a swirling action and rapid deposition of gas-entrained solid particles before the gases leave the dust collection device.

In the rest of this presentation, the invention will be described more particularly in its application to the catalytic oxychlorination of aliphatic hydrocarbons in a fluidized bed. For such oxychlorination, one can proceed as follows: the material to be chlorided, that is to say a lower aliphatic hydrocarbon containing 1 to 4 carbon atoms and/or a partially chlorinated lower aliphatic hydrocarbon, is introduced. having from 1 to 4 carbon atoms, the elemental chlorine and/or HCl, in the lower part of a fluidized bed of metal halide based oxychlorination catalytic particles. The oxygen with the hydrocarbons and the chlorine or HCl is introduced into the bed, while the gaseous reaction products are withdrawn from the upper part of the bed. During the reaction, the inlet rate of chlorine and/or HCl, oxygen, hydrocarbon and/or chlorohydrocarbon is maintained high enough to at least wet the catalyst particles in suspension so as to produce a dynamic bed or a fluidized bed in the reaction zone. It has been found that by operating in this manner it readily converts hydrocarbons such as methane, ethanol, propane, ethylene, and chlorohydrocarbons such as 1,2-dichloroethane, tetrachloroethane and other similar partially chlorinated hydrocarbons. into chlorohydrocarbons and chlorohydrocarbons with a higher degree of chlorination, respectively.

It is preferable to use elemental Foxygene, especially when dealing with unsaturated aliphatic hydrocarbons such as ethylene. In this case, a gas containing oxygen can be used, such as air, although it is preferable to use oxygen. With aliphatic hydrocarbons such as ethane or methane, the use of Air does not offer any particular disadvantages except as regards the large quantities of inert matter contained in the air which must be treated in the process. recovery device. The quantity of oxygen used in the oxychlorination beds or zones according to the invention is the stoichiometric quantity necessary to oxidize all the HCl contained in the zone into water and elemental chlorine, according to the formula <B>2110</B> -I- 1/202 =H20 -I- C4 The temperature of the reaction zones can vary considerably in the first process according to the invention. It depends to some extent on the starting hydrocarbon and/or chlorohydrocarbon. Generally reaction temperatures between 287 and 5660 C give the best results for most lower aliphatic hydrocarbons and their partially chlorinated derivatives. As a general rule, unsaturated hydrocarbons tend to react at lower temperatures than saturated hydrocarbons, and this fact can be taken into account in determining the best temperature conditions for a reaction zone or process. particular fluidized bed. Thus, for example, to oxychloride ethylene to 1,2-dichloroethylene, preferably employs a temperature between 287 and 316 C. To oxychloride 1,2-dichloroethane to perchloroethylene and trichloroethylene, temperatures between 398 and 455o C.

In oxychlorination reactions, the contact time, ie the time during which the supplied materials are in the reactor, can be varied considerably. Contact times can be from 4 to 25 seconds or even longer. Ordinarily, these times are adjusted so that the supplied materials remain 5 to 15 seconds in the reaction zones.

The oxychlorination reactions carried out in the fluidized beds being exothermic, they must be cooled in order to maintain the reaction temperature at a suitable value. This control is usually effected by means of reactors with suitable cooling jackets, by spraying cooling agents into the reaction zones or by placing cooling coils in the reaction beds. It is also possible to employ, alone or in combination, bionnette refrigerators and other heat exchange devices suitable for fluid bed reactors.

The catalyst used for the oxychlorination reactions described herein can comprise any common Deacon-type oxychlorination catalyst impregnated with a suitable vehicle or support. Catalysts of this type are generally metal halides, preferably chlorides of polyvalent metals such as copper, iron, chromium, etc. These metal halides, usually chlorides, can be used alone or in combination with other metal compounds such as alkali metal chlorides and alkaline earth metal chlorides or with mixtures of these chlorides. In general, any effective metal halide catalyst of the Deacon type produces chlorinated hydrocarbons satisfactorily. . A particularly effective catalyst for these oxychlorination reactions is a mixture of copper chloride and potassium chloride. This catalyst is particularly suitable when the reactions are carried out at high temperatures, that is to say at temperatures between 260 and 500 C. Another effective catalyst is a mixture of copper chloride, zinc chloride, calcium chloride . Preferably, a catalyst containing a substantial amount of copper chloride is employed. By substantial amount an is meant a catalyst particle containing about 6 to 12 weight percent copper.

Various materials such as silica, alumina, fuller's earth, kieselguhr, pumice and the like can be employed as the catalyst support. The choice of a particular type of support depends to a large extent on the turbulence of the bed, the gas velocity, the allowable amounts of burnt material and other similar considerations. Losses due to attrition being particularly undesirable in operations carried out in fluid beds, the preferred particulate support material is Florex (treated fuller's earth manufactured by Floridin Corporation). The particular technique applied to place the catalyst on the support is variable, but the one which makes it possible to effect the most uniform distribution of the catalyzing material on the support is preferred. One can simply immerse the carrier in solutions containing the catalyst and evaporate the aqueous solution impregnating the carrier particles after removing them from the solution. Ort can also spray the catalytic material onto the particles in a device such as a rotating drum, ribbon mixer or similar device. Another effective method for impregnating carrier particles with the catalyst material is to spray a solution of the catalyst into a fluidized bed of carrier particles. During the fluidization and the impregnation of the support particles, an heats the fluidized bed by means of hot inert gases in order to vaporize the water of the solution and to obtain a fluidized bed of particles uniformly impregnated with the catalyzing material. It is also possible to resort to indirect heat exchange by means of sleeves or coils.

By employing in the fluidized beds very large quantities of inert matter, such as sand; an can significantly reduce the amount of oxidized or burned organic matter. 0n rule in g6n6- ral dilution of catalytic beds with. particles of sand so that the bed contains no more than 50 percent by volume of sand or other inert diluent. Although diluents are effective in reducing combustion, one can of course put beds into service without using diluent.

Oxychlorinations in fluidized beds can be carried out under atmospheric pressure or under considerable pressure. When feasible, an applies pressure to increase productivity.

The reaction products of the operations carried out in such fluidized beds are collected from the upper part of the bed and the gases removed from the reaction zone. Ordinarily the first ascending current of gases entrains the reaction products with any inert constituents. The reaction products include various chlorinated organic derivatives of the permitted hydrocarbons and/or chlorohydrocarbons. To collect the products, an usually condenses and/or absorbs them. After purification and removal of water by the usual methods, the chlorinated hydrocarbon products are separated from each other by the use of fractional distillation, selective absorption and desorption, and other similar separation methods. It is in the removal of the reaction products from the reaction zones that the greatest difficulty is encountered. These products, entrained by the gases in the space occupied by the vapors above the fluidized bed, carry considerable quantities of fine particles of catalyst from the fluidized bed. By operating the process under or near stoichiometric conditions for the particular hydrocarbon fed to the reaction zone, it is found that the velocity of the gas delivered to the reaction zone is considerably reduced in the vapor space above the fluid bed. This reduction substantially decreases the amount of solid matter removed from the bed by rising gases leaving its upper level. Large particles tend to fall by gravity into the fluid bed due to the decrease in velocity of the gas stream passing from the surface of the fluid bed to the vapor space above. RTI ID="0003.0551" WI="6" HE="4" LX="1927" LY="1038"> gases, which move relatively slowly, pass to an upper part of the space occupied by the vapors where they penetrate the narrow inlet orifice of a dust collector or cyclone, their speeds thus increase considerably by the venturi effect. After passing through the constricted orifice, the gases swirl at high speed to the bottom of the dust collector (preferably a cyclone-type separator) where fine particles are forced by centrifugal force out of the gas stream. before it reaches the outlet end of the cyclone.

Thus, by the effect of a reduction in the velocity of the gases leaving the upper level of the fluid bed, and by the effect of an increase in the velocity of the gases entering the dust collecting device, the large particles fall directly back into the bed at from the space occupied by the vapors, while the small particles are removed from the dust collecting device or cyclone, and are reintroduced into the bed by direct contact of the cyclone with the bed. This last operation is normally carried out by means of a dip tube fixed to the bottom of the cyclone and submerged for an appreciable length below the upper level of the fluidized bed. It is important that the tube dip well below the upper level of the fluidized bed so as to prevent gas leakage through this tube. Ort usually mounts the cyclone dip tube so that its lower end is at least six inches below the top level of the fluidized bed. It has been found that the gases exiting the reactor contain few or no catalyst particles, and can be condensed in the usual way to recover the products of the reaction.

If necessary, the cyclone or dust collector can be fitted with an auxiliary heater so that the temperature inside the cyclone can be maintained at or above the dew point of the gases passing through it. rose. Maintaining the temperature of the cyclone above the dew point of the gases is an important factor in the implementation of the process according to the invention, because if one operates below this point, there are external problems. serious about corrosion of the dust collector or cyclone.

Example <I>1:</I> Ort prepares the catalyst by dissolving 1316 g of CuC12.2H20 and 688 g of KCl in 2 liters of water. Ort pours this concentrated solution evenly over 4.53 kg of Florex particles of 30 to 60 mesh size (Florex is a calcined fuller's earth manufactured by Floridin Corporation). The solution contains just enough water to thoroughly wet all of the Florex particles. The wet catalyst particles are dried in a steam heated tray dryer. The dry particles have a solid salt loading of 30.6 weight percent which corresponds to 7.5 weight percent copper and 5.5 weight percent potassium.

Ort uses, for the ethylene oxychlorination reaction with HCl and Foxygene, a fluidized bed reactor comprising a nickel tube 2.90 m long and 38 cm in diameter. The reactor is surrounded by a 50.8 cm diameter steel jacket to which is attached a reflux condenser containing orthodichlorobenzene as a heat exchanger. At the top of the reactor is a nickel cyclone, 20.3 cm in diameter, provided at its upper part with a vent presenting a dip tube of sufficient length to reach a depth of 20.3 cm in the fluidized bed. in the expanded state. A distributor plate 44.45 cm in diameter is placed at the bottom of the reactor, it is pierced with 88 holes 1.4 mm in diameter, arranged in a triangular pattern. A condensing coil, consisting of a nickel tube 30.48 m de Jong and 1.27 cm in diameter, is placed at the top of the fluid bed. Below the distributor plate is an enclosed chamber serving as a wind box to which the reacting bodies are sent through a common 2.54 cm diameter supply conduit. Three 1.27 cm lines are connected to the common supply line by a T-mixer and the ethylene, Foxygene and HCl are fed separately to the common line through these three lines. A charge of 131.5 kg of the catalyst of Example 1 is placed in the reactor and the ortho-dichlorobenzene is heated to 216° C. by means of electric ribbon heaters placed against the bottom of the shell. Air at 1210 C is used to fluidize the bed until its temperature reaches about 2161) C. At this temperature, an admits oxygen to the wind box and shuts off the air intake. Ort sends HCI Jans the crate to RTI ID="0004.0276" WI="7" HE="4" LX="195" LY="2069"> wind and finally ethylene. The envelope temperature is maintained during the reaction at 1770° C. with a layer of nitrogen. The coils are operated to maintain the bed temperature at 288°C during the reaction. For this purpose, water, previously heated, is vaporized at 1040 C under a vapor pressure of 2.11 kg/cm@ in the coils. The gases leaving the reactor pass through a condenser and are cooled to 32-38 C. A second condenser reduces the temperature of the gases to 20 C. After condensation, the gases are purified with water and evacuated. Ort combines the condensates of the two condensers and separates the phases. The organic phase is distilled and 1,2-dichloroethane is obtained. The reactor is fed with ethylene, HCl and air in a molecular proportion of 1.0 to<B>1.89</B> to. 2.6.

The table below shows the results of this operation.

Table I Percent 1,2-dichloroethane (/o by weight of organic bodies recovered). . . . . . . . 89.2 Use of ethylene (in the form of chlorinated organic bodies) . . . . . . . . 81.8 Use of HCl (as Chlorinated Organic Bodies) . . . . . . . . 90.5 Example <I>2:</I> The apparatus, catalyst and process of Example 1 are used and ethylene, HCl and oxygen are fed into the reactor in a molecular proportion of 1 to 1, 89 to 0.55. The table below shows the results of this operation.

Table II Percent 1,2-dichloroethane (/o by weight of organic bodies recovered). . . . . . . . 93.0 Use of Ethylene (as Chlorinated Organic Bodies). . . . . . . . 88.4 Use of HCl (as Chlorinated Organic Bodies) . . . . . . . . 95.9 Example <I>3:</I> The device, catalyst and process of Example 1 are used and 1.2 -dichloroethane, chlorine and Foxygene. The feed molecular ratio of 1,2-dichlorothane to chlorine at Foxygene is maintained at 1 at 0.60 at<B>1.05.</B> 12.2 cm per second. Ort produces, under these conditions, perchloroethylene and trichloroethylene in good yields and with a 1,2-dichloroethane utilization of about 75 percent.

Example <I>4:</I> Uses the reactor, catalyst and process of Example 1, and feeds methane, HCl and Air to the fluidized bed reactor. Ort makes them react at temperatures between 510 and 5350 C. The molecular charge ratio of methane to HCl to Air is maintained at 1 to <B>2.15</B> to 7.5. Carbon tetrachloride, chloroform, methylene chloride and methyl chloride are thus produced in good yields and with the use of 92 percent HCl.

Example S Ort uses the catalyst, reactor and process of Example 1 and reacts ethane, chlorine and Air in the fluidized bed of catalyst particles maintained at temperatures between 477 and 4860 C. The RTI ID="0004.0533" WI="12" HE="4" LX="1310"LY="2672"> molecular feed ratio of ethanol to chlorine to air is maintained at 1 to 0, 5 to 4.3. By proceeding in this manner, vinyl chloride is prepared in good yields and with good chlorine utilization.

Example <I>6:</I> The catalyst, reactor and process of Example 1 are used, and ethane, HCl and fair are fed to the reactor, the fluidized bed of particles being maintained between 485 and 4880 C. The molecular charge ratio of ethane to HCl was maintained at Fair 1 to 1 to 4.3 during the reaction. By proceeding in this way, vinyl chloride is obtained with good yields and with good use of the HCl.

Example <I>7:</I> Using the catalyst, reactor, and process of Example 1, and feeding ethane, HCl, chlorine, and air to the reactor, the fluidized bed of particles of catalyst being maintained during the reaction at a temperature between 485 and 4880 C. The molecular ratio of ethane to HCl to chlorine is maintained at 1 to 0.5 to 0.05 to 4.3 during the reaction. By proceeding in this way, vinyl chloride is obtained with a good yield and with a satisfactory use of HCl and chlorine.

It can be seen from the above examples that operating the oxychlorination reactor in the manner shown gives adequate conversion of ethylene to 1,2-dichloroethane while keeping catalyst losses at a reasonable rate. .

Similar results can be obtained using other hydrocarbons and/or chlorohydrocarbons as feed. It is thus possible to feed the oxychlorination fluid bed, operating in the manner indicated in Example 2, with methane, ethane, propane, butane and obtain advantageous results such as a high yield of chlorohydrocarbon and good use of the agent. chlorinating. Similarly, chlorinated hydrocarbons such as 1,2-dichloroethane can be fed to a reaction zone such as that described in Example 2 to produce higher chlorination hydrocarbons in good yields.

Claims (1)

CLAIMS I. Process for carrying out a catalyzed chemical reaction, by passage of a gaseous current of the starting materials from the bottom upwards through a fluidized bed of catalyst particles, characterized in that Fon reduces, in a zone occupied by the gases and located above the bed, the velocity of the gases produced leaving the bed, then raises the velocity of the gases above that at which they leave the bed by imparting to them a circular motion to deposit, Jans the increased velocity zone entrains fine particles, and removes reaction gases from said zone substantially free of fine particles by maintaining the increased velocity zone at a temperature above the dew point of the gases. II. Application of the process according to claim I to the preparation of chlorinated aliphatic hydrocarbons, by oxidation of hydrochloric gas into chlorine and water and addition of the chlorine to the double bond of a non-chlorinated or incompletely chlorine olefinic hydrocarbon. SUB-CLAIM Application according to claim II, to the preparation of 1,2-dichloro-ethane from ethylene.