JPS60186403A - Method of converting chlorinated hydrocarbon and metallic oxide into carbon oxide and metallic chloride - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel process for converting chlorinated hydrocarbons into metal chlorides and oxides of carbon. Undesirable chlorinated hydrocarbons (typically a by-product of industrial synthesis processes) are commonly dealt with by incineration. However, such operations are partially due to the need for fuel to maintain combustion.
Generally, it is something that costs money. Additionally, nitrogen oxides or other undesirable by-products may be formed. Therefore, it would be desirable to have a method for converting chlorinated hydrocarbons into useful products.

Coincidentally, by adding chlorine and maintaining the proper ratio of carbon to available oxygen, virtually all chlorinated hydrocarbons react essentially completely with suitable refractory metal oxides. It has now been found that.

According to the invention, chlorinated hydrocarbons other than carbon tetrachloride are converted into metal chlorides or metal oxychlorides and oxides of carbon by reaction with suitable metal oxides. The process involves contacting at least one chlorinated hydrocarbon with a sufficient amount of a refractory metal oxide and chlorine under reactive conditions to substantially eliminate (at least 90% of) the chlorinated hydrocarbon present in the chlorinated hydrocarbon. carbon atoms into carbon monoxide or carbon dioxide.

The chlorinated hydrocarbons reacted in this process are part of a vast swath of chlorinated hydrocarbons, but they are a well-known class of compounds. These compounds have the formula CxHyC4z, where X is an integer greater than 1, 2 is an integer greater than O, and y is an integer at least 0, where x = l
, y=Q, so5- and z=4 compound (CC4 tetrachloromethane)
It includes all known compounds corresponding to the following. Compounds that completely decompose to CCl4 under the reaction conditions are also excluded. However, mixtures of the chlorinated hydrocarbons can also be used, including mixtures with CCl4.

Preferably, the formula CxHyClz is such that z>y, and more preferably y=Q except when x=l. Preferred chlorinated hydrocarbons include hexachloro-1,3-butadiene and hexachloroethane. Particularly preferred is
Aromatic chlorinated hydrocarbons, such as hexachlorobenzene or polychlorinated piphenyl, are particularly difficult to treat by conventional methods. In certain embodiments of the invention, these preferred chlorinated hydrocarbons are formed during the reaction of carbon and chlorine with metal oxides of tetrachloromethane or other chlorinated hydrocarbon feedstocks.

Refractory metal oxides to be reacted with 6-monochlorinated hydrocarbons are also known in the art. For example, Kirk Osmer
Encyclopedia of Chemical Technology,
See 2nd edition, Vol. 19, pp. 227-267 (1968). Periodic table of standard elements ■b, vb, v+b, ■
b, l [a and IVa (excluding, of course, carbon) and oxides of metals selected from beryllium, magnesium,
Oxides of thorium and uranium can generally be used as long as the metal oxides are normally solid at the reaction temperatures used.

From a thermodynamic point of view, a metal chloride or oxychloride derived by chlorination of a metal oxide or mixture of oxides as a starting material has a desired operating range (on an equilibrium stoichiometric basis).
For example, at 500'-1200°C), it has a more positive free energy of formation of quips than the starting material. This means that metal oxides generally cannot be chlorinated by chlorine unless there is a carbon-containing material to be oxidized at the same time. However,
Iron oxides are an exception. Generally one of the metal oxide starting materials
The free energy of formation of the equivalent amount of oxygen in moles is more negative than the free energy of formation on a molar basis of metal chloride or metal oxychloride per two atoms of chlorine present in the product formula There should not be an absolute difference of 47,000 calories (197 kJ) at 500°C or 58,000 calories (243 kJ) at 1200°C).

The necessary thermodynamic data to evaluate the thermodynamics of a reaction are
JANAF Thermochemical Tables (available from the U.S. Government as American Bureau of Standards Publication 37) or other similar compilations.

Generally, non-chlorinated metal oxides are preferred, but
Partially chlorinated derivatives of these oxides can also be used and will be formed in-house during the chlorination of metal oxides.

The desired metal oxides include titanium (■), aluminum (■
), iron (■ and ■), zirconium (IV), tin (■ and ■), vanadium (III, ■ and ■) and chromium (
(2) and (2) oxides are included. Titanium dioxide and aluminum oxide (A1203) are preferred as metal oxides. Metal oxides can be used in purified form. Metal oxides present in crude mineral ores are generally usable and cheaper than refined materials.

These mineral ores may optionally contain silica or silicates. In other cases, the metal oxide may be partially hydrated, and activated alumina is an example of such a hydrate. A typical ore is forsterite,
Includes spinel, zircon and mullite. Preferred is rutile or ilmenite mineral ore.

Preferably, sufficient oxygen is available for the reaction and there is at least one oxygen atom for each carbon atom introduced. In some cases, but less preferably, less than the stoichiometric amount of oxygen may be available and some carbon may be produced. If sufficient chlorine moieties are produced by the chlorinated hydrocarbon, the oxygen participating in the reaction can be released by the metal oxide to replace the stoichiometric amount of oxygen. Alternatively, an oxygen-containing gas can be introduced directly into the reaction mixture to provide additional oxygen, or chlorine can be introduced to release additional oxygen from the metal oxide. A mixed gas of oxygen and chlorine can also be used.

Preferably, the ratio of carbon atoms to oxygen atoms available for reaction ranges from about 1:1 to 1:2. Introducing chlorine gas can create excess available oxygen, while a less than stoichiometric ratio will produce carbon.

The available oxygen is the sum of the introduced oxygen, the oxygen released from the metal oxide, or other oxygen-containing compounds present during the reaction, the introduced chlorine, and the chlorine from the chlorinated hydrocarbon. It is. Carbon or hydrocarbons may be introduced with or prior to the chlorinated hydrocarbons and oxidized to reach or maintain the desired operating temperature.

In a preferred embodiment of the invention, the aforementioned chlorinated hydrocarbons are introduced into a conventional prior art process for producing metal chlorides by reacting chlorine with metal oxides in the presence of carbon.

In this embodiment, the solids in the reaction zone will generally consist of about 10 to about 90 weight percent metal oxide and the balance carbon. Oxides of uranium can be present up to 95 wt%. Chlorine containing up to 50% by weight of chlorinated hydrocarbons is added to the reaction zone.

That hexachlorobenzene can be reacted in this way is particularly surprising, as examples have shown that hexachlorobenzene has been produced in the conventional process of producing titanium tetrachloride from titanium dioxide. be.

As has now been discovered, there was no suggestion in the prior art that hexachlorobenzene produced during the production of metal chlorides could be destroyed by recycling.

It is important that a sufficient amount of chlorine be present in order to convert the hydrogen moiety present in the chlorinated hydrocarbon to hydrogen chloride.

Hydrogen chloride can be easily separated from the product gas by conventional methods.

In some cases, it may be desirable to add hydrogen, hydrocarbons, or water to generate excess hydrogen chloride. At least a stoichiometric amount or preferably an excess of metal oxide should be present to ensure essentially complete reaction of the chlorine moiety derived from the chlorinated hydrocarbon. Generally, the hydrogen portion from the hydrocarbon feedstock is more reactive towards chlorine than the metal oxides. Therefore, the overall ratio of chlorine to hydrogen part is:
In cases where metal chlorides are generated, the ratio should be more than 1:1.

In one embodiment of the process, the chlorinated hydrocarbon and oxygen or chlorine or oxygen gas are first preheated as a mixture or separately to vaporize the chlorinated hydrocarbon. These reactants can be preheated by any conventional method known in the art. Preferably, once the process is running, at least a portion of the heat is obtained by heat exchange with the product gas. Alternatively, the liquid chlorinated hydrocarbon can be heated and introduced directly to a metal oxide bed where it can be vaporized, sublimated or reacted.

The chlorinated hydrocarbon and oxygen or chlorine gas are introduced into a packed or fluidized bed of refractory metal oxide, optionally together with a gas essentially inert to the reaction (such as ♀ element). Preferably,
The metal oxide is present as particles having a high surface area to volume ratio, but not so small that gas flow is undesirably impeded. Particles of Tyler sieve size from about 24 to about 325 (0.707 and 0.044w apertures, respectively) are preferred. Essentially inert filler materials can also be used to improve gas flow rate distribution.

13- The temperature during the contacting period of the chlorinated hydrocarbon and metal oxide is preferably within the range of about 700° to about 1200°C, more preferably about 900° to about 1100°C. Approximately 700℃
Lower temperatures generally result in undesirably slow reaction rates.

Temperatures higher than about 1200° C. are not necessary and require the use of expensive materials for the reactor and ancillary equipment.

At the aforementioned reaction temperatures, the reaction rate is generally quite fast. Thus, essentially complete conversion of most chlorinated hydrocarbons will typically be achieved with a residence time of less than 1 second in the reaction zone. Under less favorable conditions a distribution of residence times may be necessary. Of course, the actual reaction time depends on the reaction temperature,
Depending on the size of the metal oxide particles, the identity of the chlorinated hydrocarbon, and other factors, it may be longer or as short as o, oi seconds or less.

The pressure in the reaction zone is generally not critical. Absolute pressures of about 0.1 to 14 to about 10 atmospheres (10,1 to 1010 kPa) are convenient, with pressures of about 1 atmosphere (101 kPa) being preferred.

The metal chloride or metal oxychloride produced in a preferred embodiment of the process has greater economic value than the starting metal oxide. Metal chlorides can be recovered by methods known in the prior art. Generally, the metal chloride produced will vaporize or sublimate under the reaction conditions and can be easily recovered from the product gas stream by condensation. Preferably, excess metal oxide is used in the process to prevent chlorinated hydrocarbons from blowing through the reaction bed. Preferably, the process is carried out continuously, with additional metal oxide being introduced into the reaction zone as the metal chloride exits into the gas phase.

The following examples are presented to further illustrate the invention. Unless otherwise specified, parts and percentages are by weight.

Examples 1-8 Hexachlorobenzene was placed in a round bottom flask equipped with a thermometer, a sparge tube to introduce the gas into the hexachlorobenzene, and a Vycor column packed with a refractory metal oxide. The outlet of the Vykol column is connected to a sixth flask kept at a temperature of 150°C, a second flask kept at a temperature of about 25°C, and a gas containing a 0.31 molar KI aqueous solution.
They are connected one after another to the scrubber.

Vycor tube approximately 700°, 800° or 90°
Heated to a temperature of 0°C. Chlorine gas was introduced into the liquid hexachlorobenzene in the round bottom flask at a rate determined by a flow meter. Hexachlorobenzene in the gas introduced into the Vycor column was determined experimentally by mass transfer at specific operating temperatures and chlorine gas flow rates. The residence time of the gas in the packed bed was calculated from the porosity of the column and the apparent raw material gas volume.

The chlorinated hydrocarbons that passed through the packed column condensed into 11 or 2 flasks arranged after the column.

Cyclohexane and water were added to the contents of each of these two flasks. Metal and chloride ions were analyzed by conventional methods to confirm the presence of metal chlorides in the aqueous phase. Chlorinated hydrocarbons present in the organic phase were also analyzed. The amount of chlorine recovered by the scrubber was also measured using standard methods. Therefore, chlorine efficiency depends on the chlorine content of metal chlorides,
It was divided by the sum of the metal chlorides, the chlorine content of the recovered chlorinated hydrocarbons, and the chlorine in the scrubber.

, 1 Table 1 shows metal oxide, caczs flow rate, chlorine flow rate,
Packed bed temperature, gas residence time, run time, chlorine efficiency, and amount of unreacted chlorinated hydrocarbons are displayed for each of the eight experiments.

The data in Table 1 show that hexachlorobenzene can be reacted essentially completely with various metal oxides in the presence of chlorine to form metal chlorides.

17-Table 1 1 Rutile (50F) 5-8 7-242 Rutile (25F) 1.5-7 5-93 Rutile (20
F) 2-5 10-154 Rutile (15r) 0
．． 8 2.85 Activated alumina (12y) 0.7 3
．． 26 Magnetite (30r) 0.7-1.5
6-87 Roasted alumina (9F) 0.7 58 Rutile (68y) 7 1O N, D, - Not detected > 95% FezO3.

Coming to America - Section 80 - Al2O2 Temperature Residence time Experiment time Ct2 efficiency Recovery 80
0 2-5 195 94% N, D.

800 3-7 270 N, D, N, D.

800 2-3 200 94% 0.36800 6
260 91% Trace 800 50 300 95% 0.03500-80
0 7 260 N, D, 0.2900 9 28
5 96 0.09800 6 110 96% - 1 18 = Examples 9-12 The other points were the same as in Example 1, except that hexachlorobenzene was reacted with rutile in the presence of air instead of chlorine.

The operating parameters and weights of metal chlorides and chlorinated hydrocarbons recovered are summarized in Table 2. No oxides of nitrogen were detected in the product gas.

The data in Table 2 shows that hexachlorobenzene can be reacted essentially completely with rutile or At203 in the presence of air.

19-20- Example 13 Hexachloro-1,3-butadiene at 900°C, 58
The reaction was otherwise similar to Example 1 with a packed bed of rutile of Example 2. For 26 minutes, the flow rate of C, CIA and C42 was 3Q, 77 m for each gas,
5M/'IIa for each gas for the next 24 minutes.
It increased to During this 50 minute period, 20 ctA/wig of nitrogen was also introduced. Essentially all of the C4C16 introduced was converted to metal chlorides and oxides of carbon.

Example 14 Hexachloroethane at 900° C. with a packed bed of 352 rutile and no chlorine gas introduced but instead a volume of 4 M/m nitrogen as carrier, but otherwise Example 1
was reacted in the same manner. Gas residence time in the bed is approximately 1
It was seconds.

Only 0.04 r of chlorocarbon was separated from the gas product stream, but about 10 f of metal chloride was recovered. The recovered chlorocarbon was mainly hexachlorobenzene.

Example 15 Diameter 2.2c! A ceramic frit was attached to one end of the 34 cr++ long column and placed vertically.

Approximately 10 f of Vycor (high silica glass) chips were placed on the frit, followed by 48 tie-y-mesh (48 mesh (Tyler) sieve opening = 0.297M) 101 of Al2O3. Next to the column was a spherical, h-inch diameter aluminum silicate packing obtained from Two-Tone;
162.72 of DENSTONE57 and liquid purchase 1
A packed fluidized bed with a height of 32c1n was created by adding 38.1f of 203. Both ends of the column were connected to a truncated cone to allow the column to be connected to smaller diameter gas inlets and outlets while maintaining good gas flow-distribution.

A gas mixture of hexachlorobenzene and chlorine was introduced at various gas flow rates into a packed fluidized bed maintained at 900°C. The operating parameters and products recovered in consecutive experiments using the same bed are summarized in Table 3.

123= 24- Continuation of page 1 ■Int, C1,' Identification symbol Internal docket number procedure amendment form C method) % formula % 1. Indication of the case 1982 Patent Application No. 38893 2. Name of the invention Chlorine Method for converting carbonized hydrocarbons and metal oxides into total carbon oxides and metal chlorides 3. Relationship with the amended case Patent applicant name The Dow Chemical Company Akasaka Taisei Building (
Telephone 582-7161) Handwritten specification attached to the application 6, contents of amendment

Claims (1)

[Claims] 1. In a method for converting metal oxides into metal chlorides and metal oxychlorides using chlorinated hydrocarbons, at least one of the formula CxHyCt2 (provided that "x"
is an integer greater than 1, 92'' is an integer greater than 0, and y is an integer at least equal to 0)
of a gaseous chlorinated hydrocarbon with an amount of a suitable refractory metal oxide and a sufficient amount of chlorine to convert substantially all the carbon atoms of the chlorinated hydrocarbon to carbon monoxide or carbon dioxide. and the ratio of carbon atoms present to oxygen atoms available for reaction is in the range of about 1:1 to 1:2, and the metal oxide is chlorinated at the same time as the chlorinated hydrocarbon is oxidized. A method for converting metal oxides into metal chlorides and metal oxychlorides. 2. Metal oxides include titanium (IV), aluminum (l[
l), iron (■ and III), zirconium (■), tin (
■ and ■), vanadium (■, ■ and ■) and chromium (■
The method according to claim 1, wherein the oxide is selected from the oxides of (1) and (1). 3. The method according to claim 1, wherein the metal oxide is titanium dioxide or aluminum oxide. 4. The method according to claim 3, wherein titanium dioxide is present in the form of rutile or ilmenite. 5. The method according to claim 1, wherein the metal oxide is silica or a silicate. 6. The method of claim 1, wherein the chlorinated hydrocarbon has at least one aryl moiety. 7. The method according to claim 1, in which z>y in the formula CxH7Ct2. 8. The method according to claim 7, wherein the chlorinated hydrocarbon is hexachlorobenzene, polychlorinated biphenyls, or a mixture thereof with other chlorinated hydrocarbons. 9. The method according to claim 7, wherein the chlorinated hydrocarbon is hexachloro-1,3-butadiene or hexachloroethane. 10. The method according to claim 8, wherein the metal oxide is aluminum oxide or titanium dioxide. 11. The method according to claim 9, wherein the reaction temperature is in the range of 900° to 1200°C. 2. The method of claim 1, wherein carbon is added to the reaction medium. 13. The method of claim 1, wherein carbon and metal oxides are present in the bed and 10 to 90% of the solids in the bed are metal oxides and the remaining solids are carbon. 14. The method of claim 1, wherein chlorinated hydrocarbons are recycled from the product gas produced during the chlorination of metal oxides.