Oxychlorination of Ethylene with Copper Chloride Catalyst*

Naoya Kominami**, Kusuo Kawarazaki**, Yoshiaki Yamazaki** Tokio Sakurai**

Summary: In the oxychlorination of C2H4, copper chloride on the active carbon has a higher activity than catalysts on other sorts of carrier. Examinations were made as to what relations exist between the selectivity of 1, 2-dichloroethane and composition of supplied gas and the reaction temperature. Two ranges in which the selectivity of 1, 2-dichloroethane does not vary and CO2 produced in large quantity were observed. The breaking point of both range depends on the mole ratio of HCl/C2H4 in the supplied gas and the reaction temperature. When the reaction is performed with the supplied gas having higher than 2 mole ratio of HCl/C2H4 the oxide-forming range does not appear. The forming rate of 1, 2-dichloroethane is shown by the following equation at chloride-forming range, r=kPC2H4PHCl0.2. Considering the rate equation shown above, the change of catalytic state and the results of the pulse technique, it is reduced that the mechanism of the oxychlorination of C2H4 with copper chloride catalyst is consisted of the follow- ing two equations, C2H4+2CuCl2→C2H4Cl2+Cu2Cl2 (a) Cu2Cl2+2HCl+1/2O2→2CuCl2+H2O (b)

and the former is rate determining step.

Introduction The authors have found that a high acti- As to synthesis of 1, 2-dichloroethane there vity at low temperatures can be obtained are many known methods using copper by using an active carbon carrier, and also chloride; for example, a method in which obtained some knowledge about the mecha- copper chloride is used as a chlorinating re- nism of the said catalyst, which are reported agent and the reduced copper chloride con- hereinafter. verted into the original copper chloride by Experimental hydrogen chloride and oxygen to be used Specimen again1) and a method in which 1, 2-dichloro- The used ethylene, oxygen, nitrogen and ethane is derived from ethylene, hydrogen hydrogen chloride were obtained on the chloride and oxygen with copper chloride as market, packed in cylinders. a catalyst2). These methods, however, re- Catalyst quire high reaction temperatures, so if there 100 grams of active chrbon (Sirasagi C can be obtained a high activity at lower of Takeda Yakuhin Co., Ltd.) which had reaction temperatures, it is more advantage- ous, commercially, from the standpoints of been washed thoroughly with acid and then with water and dried, were immersed in an materials of reactors, removal of heat, capa- aqueous solution of 50m. moles of copper city of apparatus and prevention of by- chloride, and after evaporating it to dryness products. on a water bath, it was used in the reaction. * Received December 1 , 1965. ** Research Laboratory of Technology The catalysts of silica gel and alumina car- , Asahi Chemical Industry Co., Ltd., 3-27-36, Nakadai-cho, Itabashi-ku, riers were prepared similarly to the catalyst Tokyo. of active carbon, with commercially obtained

Volume 8-June 1966 28 Kominami, Kawarazaki, Yamazaki and Sakurai:

ducing 1, 2-dichloroethane than the other two catalysts. The high selectivity of 1, 2- dichloroethane against the converted ethylene was found with each carrier, and no differ- ence was observed on the selectivity due to the catalysts. The third column of the table shows the surface area of each carrier me- asured by BET method. As clearly seen in the table, a co-relationship between the sur- face area of the carrier and the activity is hardly recognized, so the difference on the activity cannot be considered simply as the difference of the surface area of the carrier. It was found, particularly, that very high

Fig. 1 Apparatus activity could be obtained by using the active carbon carrier. obtained silica gel and γ-alumina. Factors for the Selectivity of 1, 2-dichloro- Apparatus ethane The ordinary following-type reactor shown The relations of the selectivity of 1, 2- in Fig. 1 was employed. 3.0c.c. of the ca- dichloroethane to the composition of supplied talyst diluted with 12c.c. of quarts sand gas and to the reaction temperature, with were filled in a U-type reaction tube of pyrex the catalyst of the active carbon carrier, glass having the inner diameter of about are shown in Fig. 2. The conversion of 10mm. It was heated by a nitre bath. Any difference between the temperatures of the nitre bath and the catalyst layer in the re- action tube was hardly observed. Analysis All samples were analysed by gas chro- matography except for the analysis of hydro- gen chloride which was by iodometry. The flowing rate was calibrated based on nitrogen as the inner standard.

Results and Discussion Influences of Carriers Experiments with various carriers were performed to clarify the effect of various carriers, and the results are shown in Table Fig. 2 Selectivity of 1, 2-dichloroethane 1. The catalyst of the activated charcoal ethylene was, of course, increased by raising carrier showed much higher activity of pro- the reaction temperature, but this relation is not shown in Fig. 2: Relations of the Table 1 Influences of Carriers reaction temperature to the conversion of ethylene and the one-pass yields of 1, 2- dichloroethane and carbon dioxide are shown in Fig. 3 in which the molar ratio of the supplied gas was HCl:C2H4:O2=2:2:1. Ac- cording to these results, the following can be pointed out: i) With the supplied gas having respective molar ratio, the curve of the selectivity of

Bulletin of the Japan Petroleum Institute Oxychlorination of Ethylene with Copper Chloride Catalyst 29

of 1, 2-dichloroethane in the oxide-forming range is influenced by the molar ratio of HCl/C2H4 in the supplied gas. v) The selectivity of 1, 2-dichloroethane in the chloride-forming range is gradually decreased with the increase of the molar ratio of HCl/C2H4 in the supplied gas. It is due to the increase of the conversion ratio of ethyl chloride. vi) When the reaction is performed with the supplied gas having higher than 2 molar ratio of HCl/C2H4, which is the stoichiometric molar ratio according to the present reaction, Fig. 3 Temperature dependency no oxide is formed. Though the breaking 1, 2-dichloroethane in the figure shows a point is found on the curve (5) in Fig. 2, in breaking point at the reaction temperature, the descending range in the right side of the and the point divides the range into two point, the consecutive reaction product of 1, 2-dichloroethane or vinyl chloride is in- parts: one is the range in which the se- lectivity of 1, 2-dichloroethane is not varied creased, and the selectivity of 1, 2-dichloro- and the curve is flat, and 1, 2-dichloroethane ethane is decreased apparently. 1, 1, 2-tri- is the main product; this range is named as chloroethane and 1, 2-dichloroethylene are the chloride-forming range. The other is the main consecutive reaction products. range in which the selectivity of 1, 2-dichloro- Influences of Space Velocity and Reaction ethane is steeply sloped down with the raising Temperature of the reaction temperature, and the se- The reaction was carried out by varying lectivity of carbon dioxide and carbon monoxide the space velocity at each reaction temper- is increased: this range is named as the ature and the results are shown in Fig. 4 oxide-forming range. and Fig. 5. Fig. 4 and Fig. 5 show the re- ii) As clearly seen in Fig. 3, the conver- sion of ethylene is increased with the rise in the temperature. However, though the one-pass yield of 1, 2-dichloroethane is in- creased similarly to the conversion ratio of ethylene, the one-pass yield of 1, 2-dichloro- ethane is hardly increased at temperatures higher than 180℃. At the reaction temper- ature of 180℃ carbon dioxide begins to form, and its one-pass yield almost coincided with twice the increased value of the conver- Fig. 4 Ethylene conversion sion of ethylene: that is, formation of carbon dioxide and carbon monoxide in the oxide- forming range is due to oxidation of ethylene of the raw material, but not to the combus- tion of active carbon used as a carrier. iii) The said breaking point is transferred to the higher temperature side with the increase of the molar ratio of HCl/C2H4, in the supplied gas; that is, the position of the breaking point is determined by the molar ratio of HCl/C2H4 in the supplied gas.

iv) The descending slope of the selectivity Fig. 5 Selectivity of 1, 2-dichloroethane

Volume 8-June 1966 30 Kominami, Kawarazaki, Yamazaki and Sakurai: Oxychlorination of Ethylene with Copper Chloride Catalyst

lations of the conversion of ethylene and of reaction deviates to the side of the product the selectivity of 1, 2-dichloroethane to the system at temperatures near 300℃3); there- space velocity and the temperature, re- fore, it is assumed that oxychlorination with spectively. From these figures, it is found the present catalyst is not progressed via that by increasing the space velocity, the Deacon reaction. conversion of ethylene is decreased in each When introducing ethylene over the pre- case, but the selectivity of 1, 2-dichloroethane sent catalyst, 1, 2-dichloroethane is produced is increased. Then these results axe sum- and cupric chloride is reduced to cuprous marized as shown in Fig. 6, in which the chloride. When feeding only hydrogen chloride or oxygen over the catalyst of which 1, 2- dichloroethane forming activity has been lost due to almost all of cupric chloride having been converted to cuprous chloride, 1, 2- dichloroethane forming activity is not re- covered, but on feeding the gas mixture of hydrogen chloride and oxygen, the reactivity is recovered and, in that case, the catalyst is changed to cupric chloride. The effect of the partial pressures of the components on the reaction rate was studied by a series of experiments by varying the Fig. 6 Specific diagram on relation between partial pressure of one of the components of conversion and space velocity the gas, that is, ethylene, hydrogen chloride ordinate is the reaction temperature and the and oxygen, while keeping the partial pres- abscissa is the logarithm of the space velo- sure of the other components constant by city. The curve of Q-95 in the figure shows nitrogen-diluting method. The reaction was the relation of the reaction temperature to performed at 175℃ with the space velocity the space velocity on 95% of the conversion of 1,500hr-1 with the molar ratio of the of ethylene being obtained, and with the supplied gas in the chloride-forming range; conditions above the curve the conversion of and it was found that the forming rate of ethylene is higher than 95%. The curve of 1, 2-dichloroethane was dependent solely on S-95 shows the relation of the reaction the partial pressure of ethylene. temperature to the space velocity to obtain 95% of the selectivity of 1, 2-dichloroethane and with the conditions under the curve the The catalyst during the said reaction re- selectivity of 1, 2-dichloroethane is higher mained almost in the form of cupric chloride. than 95%. Therefore, with the conditions According to the results described above, within the range enclosed with the said two it is considered that oxychlorination of curves, the one-pass yield of 1, 2-dichloro- ethylene is consisted of two reactions shown ethane is higher than 90.3%. The maximum by equations (a) and (b), and in the case of effect of the catalyst to obtain 90.3% of the the copper chloride catalyst, the reaction of one-pass yield of 1, 2-dichloroethane is obtained (a), that is, the reaction of ethylene with with the condition shown by the cross point copper chloride, is the rate determining step. of the said two curves. (Point A in the C2H4+CuCl2→C2H4Cl2+CuCl2-x (a) figure.) CuCl2-x+HCl+O2→CuCl2+H2O (b) Reaction Mechanism To the present catalyst, the gas mixture References having the HCl/C2H4 molar ratio from 2 to 1) U. S. 2, 752,402; 2, 407, 828 etc. 4 was fed at 300℃ with the space velocity 2) Brit. 781, 414; 2, 783, 286 etc. of 1,500hr-1, and chlorine was not recognized 3) Arnold, C. W., Kobe, K. A., Chem. Eng. Process, at the outlet. The equilibrium in Deacon 48, 293 (1952).

Bulletin of the Japan Petroleum Institute