DE2558871A1 - Vinyl chloride prepn. from acetylene and hydrogen chloride - using mercuric chloride on active carbon catalyst in two reactors - Google Patents

Abstract

Vinyl chloride is prepd. from C2H2 and HCl, with heating, in the presence of HgCl2/active C catalysts. Initial gas mixt. is reacted incompletely, at 110-150 degrees c, in a 1st reactor packed with already spent catalyst. gas mixt. is then after-reacted in a 2nd reactor, packed with fresh catalyst, at 70-115 degrees C. Pref. reaction gas leaving 1st reactor may be cooled to 25-70 degrees C in a heat-exchanger, before after-reaction in a 2nd reactor. Initial gas mixt. pref. contains C2H2 and HCl in vol. ratio 1:1 to 1:1.2. Initial gas mixt. may contain, by vol. 42-50% C2H5, 45-54% HCl and 0-10% inert impurities, gaseous under the reaction conditions. Catalyst is used up better. Vinyl chloride quantity/kg fresh contact can be doubled.

Description

Process for the production of vinyl chloride

The invention relates to a process for the production of vinyl chloride from acetylene and hydrogen chloride at elevated temperature in the presence of mercury (II) -chloric1 / Activated carbon catalysts.

It is known to blow vinyl chloride under slight excess pressure (1 to 1.8 bar) at temperatures between 50 ° C and 250 ° C on catalysts, especially mercury (II) chloride on activated carbon, in tube or contact furnaces used for gasoline synthesis developed according to Fischer-Tropsch.

The disadvantage is the low long-term load capacity of the mercury (II) chloride / activated carbon catalyst. After a short running time, the residual acetylene content in the vinyl chloride formed increases at. Because of the high catalyst prices and the cumbersome for reasons of toxicity Cata lys ate exchange must be carried out with increasing inactivation of the catalyst increasing content of unreacted acetylene in vinyl chloride can be accepted. The separation and reprocessing of this residual acetylene are complex. The catalyst loses its effectiveness when the Silver (II) chloride leaks and by the clogging of the activated carbon pores with decomposition products and / or Polymeric products of vinyl chloride. Temperatures of more than 2500C lead therefore for rapid inactivation of the catalyst.

Because of the high level of activity and the high levels released during use Enthalpy of reaction can be a fresh mercury (II) chloride / activated carbon catalyst heat until embers until dark ro-i. Such a catalyst is then useless. There has therefore been no lack of proposals to change the procedure in order to improve its effectiveness c * s catalyst over long periods of time and the residual acetylene content in the Keep vinyl chloride small.

According to DT-PS 848 189, vaporous mercury was used with the starting gases Introduced into the contact furnace to reduce the loss of mercury salts on the catalyst Attempts were also made to balance the starting gases under a higher pressure of z. B. implement 2-7 bar. The reaction of acetylene and hydrogen chloride was also observed in the vortex: bed carried through. It was also suggested that the starting gases should be used first to conduct from top to bottom through the catalyst layer; after that when the catalyst has become inactive in the upper layer, the output gases should be in the opposite direction be sent through the catalyst layer.

A modification of this process aims to improve the catalyst take advantage of the fact that the starting gases are introduced at different points in the catalyst layer will.

However, all these measures were kauni suitable for the procedure Production of vinyl chloride from acetylene and hydrogen chloride on mercury (II) chloride / activated carbon catalysts to improve decisively.

DT-PS 1 123 661 describes a method according to which the starting gases in a single reactor, but in separate, coolable and heatable Reaction zones are implemented on different activated carbon catalysts. The disadvantage of the tubular reactor proposed here is to be seen in that upon inactivation of the first catalyst layer, e.g. B. HgCl2 / activated carbon, the entire reactor, including the second, more active catalyst layer, e.g. B. Hg-Vana dat / activated carbon e, must be emptied. In addition, the long-term load capacity is well known of the mercury vanadate / activated carbon catalyst even worse than that of the mercury (II) chloride / activated carbon catalyst, so that either a more frequent replacement of the entire catalyst filling is required or a larger content of residual acetylene remains in the vinyl chloride.

The aim of the present invention is to develop a method in which the long-term resilience of the mercury (II) chloride catalyst is low Residual acetylene content in the vinyl chloride is decisively improved.

The method of the invention is now characterized in that the starting gas mixture in a first, with already used catalyst filled reactor while maintaining temperatures between 110 and 150 ° C incompletely implemented and in a second reactor filled with fresh catalyst can react while maintaining temperatures between 70 and 1150C.

The method of the invention can be further optionally characterized be that a) the reaction gas leaving the first reactor in a heat exchanger cools to 25 to 70 ° C. and only then reacts in the second reactor leaves.

b) the starting gas mixture acetylene and hydrogen chloride in a volume ratio contains from 1: 1 to 1: 1.2.

c) the starting gas mixture 42-50 volume% acetylene 45-54 volume Hydrogen chloride and 0-10% by volume gaseous, inert under reaction conditions Contains accompanying substances.

d) the reaction gas leaving the first reactor and optionally cooled up to 20 volume 0 / a of a gas mixture of 42 - 50 volume acetylene, 45 - 54 volume% Hydrogen chloride and 0-10 volume under reaction conditions gaseous, inert Accompanying substances, the volume ratio of acetylene to hydrogen chloride from 1 to 1: -1.2 is added and the mixture is fed to the second reactor.

e) leaving the several first reactors connected in parallel Reaction gases are mixed and the mixture is one or more connected in parallel second reactors feeds.

f) the mixture of the reaction gases in a heat exchanger on 25 Cools down to 70 ° C and only then reacts in the second reactor or reactors leaves.

g) the mixture of the optionally cooled reaction gases up to 20% by volume a gas mixture of 42-50 volumes of acetylene, 45-54 volume% of hydrogen chloride and 0 - 10 volume% under reaction conditions gaseous, inert accompanying substances, wherein the volume ratio of acetylene to hydrogen chloride is 1: 1 to 1: 1.2, admixed and the mixture fed to the second reactor or reactors.

The process of the invention has the advantage that the catalyst can be used much better. Now can do every kilogram of fresh contact double the amount of vinyl chloride can be produced. When using HgCl2 / activated carbon catalyst in the "first reactor" is exhausted, d. H. if only about half of the with that Starting gas introduced acetylene is converted to vinyl chloride, this is catalyst filling changed. The now with fresh, active mercury (II) chloride / active carbon catalyst filled reactor is now called a "second reactor" with partially already implemented Reaction gas applied. The reactor previously operated as a "second reactor" with now used catalyst is now used as "ester reactor".

The starting gas can consist of acetylene and hydrogen chloride. Often, however, the starting gas also contains accompanying substances, e.g. B. up to 10 volume%, which are gaseous and inert under the reaction conditions. About these accompanying substances include N2, O2, H2, CO and C02, which are the impurities of acetylene and hydrogen chloride be introduced, but also the vinyl chloride to be produced itself and 1,2- and 1,1-dichloroethane, which from the Acetylene work-up originate and get into the starting gases as a result of the usual circulation. According to the invention can be used at pressures of 1-7 bar, preferably 1.1-1.8 bar.

The flow sheet of the drawing illustrates the process. By the line (8), the four-way valve (11) and the line (10) get the output gases into the first reactor (1), which has an already used mercury i = hlo.rid / activated carbon catalyst contains. The reactor (1) is by indirect cooling or heating with the help of Heat exchanger (4) and the circulation pump (6) kept at a predetermined temperature. The hot reaction gas partially converted to vinyl chloride is passed through the line (15), the four-regulating valve (14) and the line (18) fed to the heat exchanger (3), in which it is cooled to a predetermined temperature in indirect heat exchange can be. The optionally cooled reaction gas is passed through line (19), the four-way valve (11) and the line (9) fed to the second reactor (2), the fresh, active one Contains mercury (II) chloride / activated carbon catalyst and with the help of the heat exchanger (5) and the circulation pump (7) is kept at a predetermined temperature. That - based on acetylene - almost completely converted reaction gas leaves the reactor (2) through the line (16), the four-way valve (14) and the line (17) to the further Work-up, e.g. B. according to DT-PS 1 254143.

To increase the acetylene content in the partially converted reaction gas can through valve (13) fresh starting gas from line (8) into line (9) be dosed.

If the used mercury (II) chloride / active catalyst of the first reactor (1) is exhausted, it is replaced by a fresh, active mercury (II) chloride / Activated carbon catalyst replaced. Reactor (1) is now used as the second reactor operated. The reactor (2), previously operated as a swaiter reactor, now contains one used catalyst and is switched as the first reactor. The switchover takes place with the two four-way valves (11) and (14).

The output gases therefore flow from line (8) via line (9) through reactor (2) and further as reaction gases via lines (16) and (18) Heat exchanger (3), lines (19) and (10) through reactor (1s, lines (15) and (17). In an analogous manner, fresh starting gas can be discharged from the valve (12) Line (8) are metered into line (10).

Example 1 The reactor (1) was with 1100 Nm5 / h starting gas of 2000 applied. The pressure in the reactor (1) was 1.6 bar.

The reactor (1) contained 2,500 kg of an originally fresh, now but as used to be designated mercury (II) chloride / activated carbon catalyst with 9.8% by weight HgC12 and was already during a previous period as a downstream, Second reactor in operation. In this previous period there was partially converted reaction gas passed over the catalyst in an amount corresponding to 9,300 tons of vinyl chloride been. Before the downstream, "second" reactor as the "first" reactor with fresh Output gas was operated, had the "second" reactor leaving Reaction gas contains 0.3% by volume of acetylene.

The starting gas had the following chemical composition in% by volume: 43.2% C2H2 51.2% HCl 3.3% N2 0.4% O2 0.3% H2 0.1% CO, CO2 0.8% vinyl chloride 0.6% other organic components 240 ppm H20 Via the heat exchanger (4) and the circulation pump (6) was the coolant of the reactor (1) at a temperature of Maintained 150 ° C. The reaction gas partially converted in the reactor (1) was in the heat exchanger (3) cooled from 1500C to 50 0C. It had the following chemical composition in% by volume: 6.2% C2H2 19.4% HCl 5.4% N2 1.3% O2, H2, CO, CO2 350 ppm H20 rest: Vinyl chloride and other organic components.

87.9% of the acetylene charged into the reactor (1) became therein implemented.

The coolant was passed through the heat exchanger (5) and the circulation pump (7) of the reactor (2) kept at 1080C. The reactor (2) contained 2,500 kg of one for The time of the experiment still to be designated as fresh mercury (II) chloride / activated carbon catalyst with 9.8% by weight HgCl2. At the time of the experiment, this catalyst was in the "second", downstream reactor (2) already partially converted reaction gas in a Amount corresponding to 1,430 tons of vinyl chloride was passed.

The reaction gas leaving the reactor (2) had the following chemical properties Composition in% by volume: 0.1% C2H2 14.1% HCl 5.8% N2 1.4% 02, H2, CO, CO2 350 ppm H20 remainder: vinyl chloride and other organic components.

99.8% of the acetylene introduced were in the reactors (1) and (2) implemented. The yield of pure vinyl chloride, based on the converted acetylene, was 98.2 Ω.

In the table below, in addition to example 1, there are further examples 2-6 summarized, which were carried out essentially analogously to Example 1.

The temperature of the outlet flowing into the first reactor (1) gases is consistently 200C-.

Tabel (1) (2) (3) (4) Example C2H2 HCl C2H2 ° C ° C C2H4 ° C Remarks 1 43.2 51.2 6.2 150 50 0.1 108 2 45.5 52.6 5.8 145 70 0.0 105 3 46.8 50.3 8.8 135 40 0.2 105 4 42.9 48.0 4.2 140 50 0.0 115 admixture of 10% fresh starting gas via line (12) in line (10) 5 43.2 49.2 12.3 110 110 0.1 110 without starting up the heat exchanger (3) 6 43.5 47.0 10.1 135 45 0.3 90 Explanations: (1) = composition of the starting gases fed into the reactor (1) in% by volume (2) = acetylene content in% by volume and temperature of the reaction gases leaving the reactor (1) (3) = temperature of the reaction gases flowing into the reactor (2) Reaction gases (4) = acetylene content in% by volume and temperature of the reaction gases leaving reactor (2) As a result of the volume contraction in the reaction C2H2 + HCl # CH2 = CHCl, the volume% figures in columns (2) and (4) relate to decreasing volumes.

Claims (8)

Claims: m 1) Process for the production of vinyl chloride aas acetylene and hydrogen chloride at elevated temperature in the presence of mercury (II) chloride / activated carbon catalysts, characterized in that the starting gas mixture in a first, with already used catalyst-filled reactor while maintaining temperatures between 110 and 1500C incomplete and sets and in a second, with fresh Catalyst-filled reactor while maintaining temperatures between 70 and 115 ° C allowed to react. 2) Method according to claim 1, characterized in that the Reaction gas leaving the first reactor in a heat exchanger to 25 to 70 ° C cools and only then allowed to react in the second reactor. 2 The method according to claim 1 or 2, characterized in that the Starting gas mixture acetylene and hydrogen chloride in a volume ratio of 1: 1 contains up to 1: 1.2. 4) Method according to claim 3, characterized in that the starting gas mixture 42-50 volume% acetylene, 4 45-54 volume% hydrogen chloride and 0-13 volume% Contains inert accompanying substances gaseous under reaction conditions. 5) Method according to one of claims 1 to 4, characterized in that that one leaves the first reactor and optionally cooled reaction gas up to to 20 volumes a gas mixture of 42 - 50 volume% acetylene, 45-54 volume% hydrogen chloride and 0-10 volume under reaction conditions gaseous, inert accompanying substances, the volume ratio of acetylene to Chlorine hydrogen £ 1 1 1 to 1: 1.2 is added and the mixture to the second Reactor feeds. 6) Method according to one of claims 1 to 5, characterized in that that one leaves the several parallel-connected first reactors reaction gases mixes and the mixture one or more second reactors connected in parallel feeds. 7) Method according to claim 6, characterized in that the Mixing the reaction gases in a heat exchanger is cooled to 25 to 70 ° C and only then allowed to post-react in the second reactor or reactors. 8) Method according to claim 6 or 7, characterized in that one the mixture of the optionally cooled reaction gases up to 20% by volume of a gas mixture from 42 volume% acetylene, 45 - 54 volume% hydrogen chloride and 0 - 10 volume% inert accompanying substances which are gaseous under reaction conditions, the volume ratio of acetylene to hydrogen chloride is 1: 1 to 1: 1.2, admixed and the mixture feeds to the second reactor or reactors.