DE1946429C3 - Process for the production of malonic dinitrile - Google Patents

Description

Molar ratio Maximum tempn: - Medium g malononitrile Reynolds nis cyanogen chloride too rature Dwell time per hour and I. number Acetonitrile ⁰ C lake Reactor volume 1: 4 860-890 3.5 99 1063 1: 5 890-910 1.5 189 2481 1: 6 890-920 1.0 242 3722 1: 7 900-930 0.8 262 4652 1: 8 890-930 0.8 233 4652 1: 9 860-920 1.0 170 3722

In the first attempt the Reynolds number is only 1063, and the flow is still laminar. If the residence time is relatively long, the throughput (yield) is low. However, if the flow velocity is increased to 2481 and higher, i.e. in the limit area of laminar and turbulent or turbulent flow, the throughput and the yield are increased.

It was extremely surprising to find that it was possible. at temperatures in the range of over 780 ° C up to I200 ° C without being able to work

that decomposition occurs. In contrast to the expected decomposition that occurs when working after the The process of the invention does not occur, it is now even possible to carry out the process of the invention Increase yields.

attempt

In a up to a maximum temperature of 900 ⁰ C heated Quarzröhr mm with an inner diameter of 90 m in which a length of 2.03, the reaction temperature was maintained, cyanogen chloride and acetonitrile in a molar ratio of 1: introduced 4.69, wherein 7.5 kg of acetonitrile and 2.4 kg of cyanogen chloride were reacted within one hour, with a throughput of 770 g of starting mixture per hour and liter of reactor volume. The residence time was 2.13 seconds. The reaction products were continuously cooled and freed from hydrogen chloride and unconverted acetonitrile. The reaction mixture contained 1.83 kg of malononitrile, which corresponds to a yield, based on cyanogen chloride used, of 71.2% of theory. The Reynolds number was 1747, the flow is accordingly as still to be called laminar.

Examples

The procedure was as in the experiment, but - with the exception of Example 10 - longer reactors were used. The examples can be the influence of the temperature and especially the molar ratio on the Yields are taken.

Examples 6 and 9 show that when the Molar ratio, the yields drop sharply.

Example molar ratio No. of cyanogen chloride too

Acetonitrile

Maximum temperature

⁰ C

Mean residence time

Yield in% of theory

Pipe length

Reynolds number

1 2 3 4th 5 6th 7th 8th 9 10

1: 4.65 1: 4.73

1: 8.76 1: 4.24 1: 2.97 1: 8.76 1: 9.42 1: 1.43 1: 7

860 945 863 904 804 860 900 879 800 990

754 6 ', 9 81.6 793 733 673 79.8 78.6 39.6 62.0

6 4 6 4 6 4 4 4 6 2

2700 3160 2466 2366 2316 2151 2236 2676 2340 4600

Claims (1)

Claim: Process for the production of malononitrile from acetonitrile and cyanogen chloride in the gas phase, characterized in that the reaction of acetonitrile and cyanogen chloride is carried out at temperatures from 780 to 1200 ⁰ C and the reactants are passed through the reactor at such a high rate that they are the Flow through the reactor in the area between laminar and ι urbulent flow or in the area of turbulent flow. 15th The invention relates to a method of manufacture of pure malononitrile in high concentrations from acetonitrile and cyanogen chloride. The implementation of acetonitrile with cyanogen chloride too Malononitrile in the gas phase is known from US Pat. No. 25 53 406. This process however, only delivers malononitrile in a yield of not more than 18%, based on the amount consumed Cyanogen halide. This reaction occurs at one temperature of at least 600 ° C, preferably at 650 to 700 ° C and with optimal yield at 675 ° C. It is indicated that the yield of the end product is reduced at higher temperatures. These disadvantages are to be solved according to the US Pat. No. 26 06 917 by the fact that the implementation in Presence of an inert gas such as carbon dioxide. Nitrogen or steam. But also however, this measure does not improve the yield. At a molar ratio of cyanogen chloride to Acetonitrile to carbon dioxide = 1: 3: 7.2, a reaction temperature of 650 ° C. and a contact time of The yield of malononitrile according to Example 7 of this patent is likewise only 6 seconds 16.5%. An improvement in the yields is achieved according to the published Japanese patent application 16 506/1966 obtained by adding to the gaifo-shaped Reaction components (acetonitrile and cyanogen chloride) initiated a small amount of chlorine as a catalyst will. This improves the yield, which is around 70%. By applying before chlorine as However, large amounts of fumaric acid dinitrile and maleic acid dinitrile are formed as by-products as the catalyst. A separation of the same from malononitrile can only be carried out with difficulty. Furthermore, the Use of chlorine requires a lot of equipment. In the known processes, the reactants flow through the reactors in a laminar flow. Tubular vessels such as quartz tubes, metal tubes and the like can be used as reactors. The present invention is now intended to remedy these disadvantages and good yields of the desired product without the use of chlorine. According to the invention it has now been found that yields of up to over 80% of theory are obtained at high yields Throughputs can be achieved if you carry out the reaction of acetonitrile and cyanogen chloride at temperatures of 780 to I200 ° C and the reactants at such a high rate through the reactor directs that they the reactor in the area between laminar and turbulent flow or in the area of flow through turbulent flow. The residence times can be increased when the temperature is increased be kept lower. It is expediently less than 5 seconds above 850 ° C. At around 900 to 1100 ° C are dwell times of 4 to 0.01 seconds applied. In order to obtain the highest possible yields, molar ratios of cyanogen chloride to acetonitrile are preferred from 1 to over 4 applied. Molar ratios in the range from 1: 6 to 19 have proven to be particularly favorable proven. Higher molar ratios, such as 1:10, have no further advantages. The products obtained after the reaction are immediately heated to temperatures of 20 to 50 ° C., preferably 25 to 30 ° C, cooled. In order to avoid destruction of the resulting malonic acid dinitrile, it is useful from the liquid reaction mixture the unreacted acetonitrile and the dissolved hydrogen chloride continuously, for example by peeling off in a vacuum to remove. About the: Dependence of the yields on the molar ratio, on the temperature and mean residence time can generally be said as follows. ) The higher the temperature, the shorter the residence times must be applied. The molar ratio also plays a role. So z. B. arise using of the reactor used in the following experiment for an average yield of about 70% the following values: