JPS5910330B2 - Method for producing chlorinated derivatives of ethylene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to vinyl and vinylidene halides,
In particular, it relates to a method for producing chlorinated derivatives of ethylene, such as vinyl chloride.

Also closely related to this is the synthesis of chlorinated solvents from ethylene, chlorine and/or hydrogen chloride. Among such solvents are highly chlorinated ethylenes such as perchlorethylene, which can be used to convert ethylene and/or partially chlorinated ethane into catalytic oxyhydrochlorinated solvents using hydrogen chloride and oxygen. manufactured by a method that involves one or more steps in the production process. Vinyl chloride is produced from ethylene, elemental chlorine, and/or hydrogen chloride in a variety of ways, almost all of which involve the thermal decomposition of ethylene dichloride under pressure in the vapor phase to vinyl chloride and the byproduct hydrogen chloride. A disassembly process is adopted.

The latter is recovered in the oxyhydrochlorination step,
In this step, the hydrogen chloride reacts with further ethylene and oxygen to form dichloroethane, which in turn is recycled to the cracking step. In many ways,
A direct chlorination process has also been used in which ethylene and elemental chlorine are reacted in the liquid phase to form dichloroethane, which is then decomposed to vinyl chloride. In all of these known solvent and monomer preparation processes, the desired direct chlorination, oxyhydrochlorination, and/or decomposition step is carried out at a
00% selective, and as a result undesired chlorine-containing by-products are obtained as complex mixtures, the composition of which ranges from chloroform or ethyl chloride to trichloroethane and trichlorethylene, tetrachloroethane, hexachloroethane, hexachlorobutadiene, etc., as well as aromatic Compounds of this group range from

Clearly, these undesirable chlorine-containing by-products pose economic and socio-ecological problems for disposal.
Therefore, the thermal energy produced is utilized in the process and the production of unwanted chlorinated hydrocarbon by-products is substantially eliminated or the end result becomes less problematic due to the recycling of waste products during the process. It would be most desirable and advantageous to have a process for producing chlorinated derivatives of ethylene and chlorinated solvents from ethylene, chlorine, and/or hydrogen chloride. The inventors have discovered that the above-mentioned problems of conventional processes are such that the unwanted chlorinated hydrocarbon by-product is recovered for reuse in the form of essentially elemental chlorine-free hydrogen chloride and the chlorinated hydrocarbon impurities and has been found to be overcome or substantially eliminated by providing a process in which the hydrogen chloride is recycled to the production of chlorinated derivatives of ethylene.

Additionally, the inherent thermal energy of the crude by-product is returned to the process to preheat the raw and intermediate feeds of the process. In particular, the process of the present invention converts waste products containing unwanted chlorinated hydrocarbons into 90% to 50% Al2O3,S
passing a heated bed of catalyst containing 10% to 50% Cr2O3 over a combination support of iO2 or Al2O3 and SiO2, the catalyst bed being fixed or fluidized with air, thereby The waste products are converted to a combustion gas stream containing essentially only carbon oxides, water, inert gases and carbon chloride. As used herein, the terms ``chlorinated ethylene derivative'' and hexachlorinated ethylene synthesis method 1 refer to the reaction of ethylene with elemental chlorine and/or hydrogen chloride in one or multiple steps to produce vinyl chloride, vinylidene chloride, Ethyl, 1,1-dichloroethane, 1
・2-dichloroethane, trichloroethane, trichlorethylene, tetrachloroethane, verchlorethylene,
is a general term that includes various methods and products of producing chlorethylene or chloroethane type compounds such as and others.

Therefore, chlorinated ethylene synthesis methods include direct chlorination of ethylene or chlorinated ethylene derivatives, which converts ethylene or its chlorinated derivatives into products with higher chlorine content, and oxychlorination of ethylene or chlorinated ethylene derivatives. , and any step of decomposition (dehydrochlorination) or rearrangement of chlorinated ethylene derivatives to produce chlorinated ethylene derivatives with lower chlorine content. In the practice of the present invention, industrial waste containing chlorinated hydrocarbons is combined with 90% to 50% Al2O3 or SiO2 or Al2O3 and S
It is passed through a catalyst bed consisting of 10% to 50% Cr2O3 on a support in combination with iO2.

The catalyst bed may be fixed or fluidized, ie fluidized with air. The catalyst bed is maintained at a temperature ranging from about 300°C to about 450°C. Within the catalyst bed, the waste is combusted and essentially produces carbon oxides, water, inert gases,
and most importantly converted into a combustion gas stream containing only hydrogen chloride. The contact time between the waste and the catalyst bed is about 10 seconds to about 50 seconds. At the temperatures used, the catalyst causes essentially complete combustion of the chlorinated hydrocarbons in the waste stream, but limits the combustion so that the hydrogen atoms remain bound to the chlorine atoms of the hydrogen chloride. This allows the production of a gas stream that is virtually free of elemental chlorine. Elemental chlorine is undesirable and its formation should be avoided as much as possible. As complete combustion as possible is also important, since the presence of chlorinated hydrocarbons in the combustion gases also tends to increase by-product formation in the oxyhydrochlorination process. In producing the catalyst of the present invention, Cr(NO3)3.9H,0 or CrCl,.6H,0
is dissolved in distilled water and the solution is applied to the support, namely Al2O3
, SiO2 or a mixture of both.

The wet impregnated catalyst support is then dried with hot air and calcined to a powder at a temperature of 540 DEG C. for approximately 16 hours. The catalyst is then passed through an 80 to 325 mesh sieve and is ready for use in the manufacturing process. After the waste is introduced into the catalyst bed, it is volatilized and then cleanly combusted using the controlled method described herein.

Direct injection of a liquid waste stream, which is often viscous, tarry, and contains materials consisting of suspended carbon, does not damage the catalyst bed, nor does it affect its fluidity when a fluidized bed is used. It doesn't hurt. Feed of waste to the catalyst bed can be easily accomplished utilizing standard equipment such as gear pumps, mechanical transfer pumps, and others. In view of the temperatures used in the process of the present invention as described above, there are many conventional materials that can be used to house the catalyst bed and can withstand the corrosive environment encountered within the catalyst bed.
The pressure used in the combustion catalyst bed of the present invention is not critical.

For example, catalytic combustion reactions can be carried out at atmospheric pressure, especially if the combustion gases are not fed directly to the oxyhydrochlorination step or reaction. If the gas is fed directly, the gas must be prepressurized to the same pressure as the pressure of the oxyhydrochlorination reactor, since the oxyhydrochlorination reaction is usually carried out at a pressure higher than atmospheric pressure. Therefore, the gas in the combustion bed is approximately 25
It is desirable to maintain a pressure in the range of from about 40 to about 100 psig, preferably from about 40 to about 100 psig. In most cases, the pressure should be maintained only slightly higher than that maintained in the oxyhydrochlorination step to avoid the need to compress the combustion gases. Of course, atmospheric pressure is sufficient and convenient when performing experiments testing the catalytic combustion reaction of the present application using a simulated waste stream. This is because a pressurized device is not required. Combustion catalysts useful in the practice of this invention include from about 10% to about 50% by weight Cr2O3 and from about 90% to about 50% by weight Al2O3, SiO2, based on the total weight of the catalyst.
or a mixture of Al2O3 and SiO2. When such a mixture is used, the content is from 13% to 94% by weight Al2O3 and from 6% to 87% by weight SiO2. Furthermore, the catalyst used here has a large surface area, i.e. at least 10 and usually at least 50 square meters/gram (Trl/7m
) must have a surface area of The most active catalysts of this type range from about 175 I/Fm to about 600 m1/V
The catalyst has a surface area in the range of m. The most useful combustion catalysts for the present process are catalysts containing pores with an average size in the range of 30λ to 60λ in diameter. The most preferred catalysts contain 20% Cr2O3 and 80% Al2O3 or SiO2 and have a surface area of about 175 to about 550 i/Tm.
It is within the range of . The components of the catalyst used here are readily available commercially.

For example, especially when using a fluidized bed, good fluidity is required, i.e., the majority of the particles have an average diameter of less than 20 microns or larger than about 200 microns, with few if any particles having an average diameter of less than 20 microns or larger than about 200 microns. Al2O3 and SiO2 are readily available with a randomly wide range of size distributions ranging from about 40 to about 140 microns. Approximately 2
Very small particles, or "fine particles", with an average diameter of less than 0 microns, are very susceptible to loss from the reactor and should be avoided. Similarly, large particles, with an average diameter of more than about 200 microns, should be avoided. It is very difficult to flow and should be avoided. From the nature of the process it is clear that the catalyst material should not be brittle and should be as resistant to friction as possible. In the process of the invention , the corrosive action within the catalytic combustion chamber or reactor is very gradual.

With this in mind, a conventional heat exchange coil of conventional materials and design is inserted into the catalyst bed, where the coil provides steam for the feed stream of raw materials or intermediate materials for the production of chlorinated derivatives of ethylene. Works as a generating coil or preheating coil. Even in the case of chlorinated derivative production of ethylene, where only about 3% to 8% of the initial ethylene feed is converted to by-products, the annual savings in thermal energy are significant. Additionally, since the process operates at low temperatures, the resulting combustion gases can be fed directly to the oxyhydrochlorination reaction without intermediate cooling. As previously pointed out, the present process can be carried out using a fluidized catalyst and using air as the fluidizing agent or gas. When using such a fluidized bed catalyst system, the flow rate is such that the air is present in sufficient quantities and at a rate to not only completely fluidize the catalyst bed but also provide sufficient oxygen for the controlled combustion of hydrocarbons in the waste or byproduct stream. must be used in In order to ensure complete combustion of the waste stream τ, it is necessary to supply at least 2 moles of oxygen to the reaction system per mole of carbon in the waste stream. However, to ensure adequate oxygen supply to the fluidized catalyst bed, approximately 2
．． Sufficient air is supplied to the bed to provide from 5 moles to about 10,0 moles of O oxygen. If the air feed rate is such that it provides an excess of more than about 10.0 moles of oxygen per mole of carbon in the waste stream, a reduction in capacity and loss of catalyst will result, and more importantly. Hydrogen chloride increases the risk of oxidation to elemental chlorine, which, as pointed out earlier, must be avoided. If the air supply rate is such that it supplies less than about 2.0 moles of oxygen per mole of carbon in the waste, complete combustion is only about 80% to 85%. The preferred air supply rate is
From about 2.5 moles to about 5.0 moles per mole of carbon in the waste feed stream.
The rate is such that 5 moles of oxygen are supplied. The above air feed rates can be employed with fixed catalyst beds as well, although some minor adjustments may be necessary or desirable to achieve maximum performance. The contact time of the waste or by-product with the catalyst in the reactor can be varied considerably without significantly affecting combustion efficiency.

When using a fluidized bed reactor, contact between about 5 seconds and about 50 seconds, keeping in mind that only about half of the calculated contact time represents the time that the gas is actually in contact with the bed. The time is appropriate. This is because the remaining time the gas is away from the catalyst in the free space above the catalyst bed and in the cyclone separator section within the reactor. Best results were obtained when contact times ranged from about 10 to about 50 seconds. When using a fixed catalyst bed reactor, preferred contact times range from about 5 to about 25 seconds. As previously pointed out, the most important variables in the catalytic combustion process of the present invention are the reaction temperature and the catalytic efficiency of the catalyst.

For example, if the reaction temperature is below 300°C, complete combustion cannot be achieved with reasonable contact times. Reaction temperature is 450
At temperatures above 0.degree. C., the combustion reaction is so intense that some of the hydrogen chloride is oxidized to elemental chlorine; this is of course harmful and must be avoided. It has been found that most metal chlorides and metal oxides, when used alone, have some but varying degree of catalytic effect on combustion reactions.

The problem with using most of these compounds alone is that they act as DeacOn process catalysts, thus converting or rearranging at least a portion of the chlorine content in the waste. Some of this is the formation of new polychlorinated hydrocarbons that are more resistant to oxidation. When such metal catalysts are used as described above, the combustion gases generally contain significant amounts of polychlorinated and unsaturated by-products. In contrast,
The catalyst of the present invention has desirable catalytic activity and produces very little combustion gas, and under optimal conditions,
Essentially free of elemental chlorine and chlorinated hydrocarbons. Additionally, the catalyst of the present invention is inexpensive and has excellent resistance to friction and contamination by unburned carbon and trace amounts of metal content in the waste byproduct feed stream. The by-product streams separated in the various fractionation steps of many chlorinated ethylene syntheses contain up to 1-2% by weight of iron chloride as an impurity.

In the catalyst bed of the present invention, iron chloride and the like are oxidized to fine iron oxides and transported from the catalyst bed by the combustion gases and collected in a cyclone separator. The small amount of iron oxide left in the catalyst bed has little detrimental effect on the efficiency of the catalyst bed.
Also, the small amount of iron oxide carried by the combustion gases from the combustion reactor to the subsequent oxyhydrochlorination step does not affect the oxyhydrochlorination catalyst, which is usually supported on alumina. The only adverse effect of using the combustion gas produced in accordance with the present invention in the hydroxychlorination process is the large charge of inert gas from the combustion gas in the feed to the oxyhydrochlorination process. There is a very small increase in capacity due to When carrying out the process of the invention using a fluidized bed, the solid particulate catalyst is first charged to the combustion reactor.

Upon introduction of air or fluidization, the catalyst bed expands to almost completely fill the internal volume of the reactor. The catalyst bed is fluidized as described above before introducing the waste byproducts. If the by-product stream is fed to the reactor, it is introduced at the bottom of the reactor, slightly above the air inlet. Preferably, the waste stream is introduced into the reactor through a water-cooled nozzle that prevents the by-products from evaporating and/or scorching before contacting the bed catalyst. Specific examples are provided below to further illustrate the invention. It is understood that these are merely intended to be illustrative and not to limit the invention. In the examples, all parts and percentages are by weight unless otherwise indicated. Example 1 In this example a catalyst was prepared from chromium chloride supported on alumina.

The prepared catalyst contained 20 wt% Cr2O3 and 80%
% Al2O, by weight, and had a surface area of 220 I/TWL. The catalyst was charged to a fluidized bed maintained at atmospheric pressure. A simulated chlorinated hydrocarbon mixture was prepared and fed to the reactor at a rate of 1.5 ml/hr. Similarly, air was fed to the reactor at a rate of 5.24 liters/hour to fluidize the catalyst bed. The feed rate of the mixture was kept constant to maintain a contact time of 18 seconds between the mixture and the catalyst. The oxygen to carbon (as C2) ratio was 2.85 and the hydrogen to chlorine ratio was 1.309. The temperature inside the reactor was adjusted to 350°C and later increased to 375°C. Data regarding feed and conversion are shown in the following table. The carbon balance (CarbOnbalsenCe) of this reaction is 9,5-
121% and chlorine balance (as hydrogen chloride) 86-10
It was 9%.

The exhaust gas from the top of the reactor was analyzed by chromatography.

The composition of the exhaust gas at 375°C was: This means that essentially 100% conversion or recovery of hydrogen chloride was obtained.

This exhaust gas stream could be used directly in the oxyhydrochlorination reaction. Example 2 The process of Example 1 was repeated using a catalyst consisting of 20% Cr2O3 and 80% Al2O3 with a surface area of 220 I/Ym.

The pressure in the reactor was maintained at atmospheric pressure and the reaction was carried out at 375°C. Using the same chlorinated hydrocarbon as in Example 1,
．． It was fed to the reactor at a rate of 0 d/h. 8.5 air
A rate of 1 liter/h was fed to the bottom of the reactor. The mixture was fed such that the contact time between the mixture and the catalyst was 11.2 seconds. The oxygen to carbon (as C2) ratio was 3.2. Data regarding feed and conversion are shown in the following table. The carbon balance for this reaction was 100.37% and the chlorine balance (as hydrogen chloride) was 97.3%. Carbon (as C2) conversion was 80.69% and oxygen conversion was 30.74%. This example illustrates the sensitivity of the catalyst to contact time. When the contact time was decreased from 18 seconds to 11.2 seconds, the conversion decreased to 80.69%. As shown in Table 21 above, the majority of the material that was not converted was cis- and trans-1,2-dichloroethylene. This is because they form from the 1,1,2-trichloroethane present in high concentrations in the feed stream. Example 3 The process of Example 1 was repeated using a catalyst consisting of 20% Cr2O3 and 80% Al2O3 and having a surface area of 220 m1/Ym.

The pressure in the reactor was maintained at atmospheric pressure and the reaction was carried out at 350°C. The chlorinated hydrocarbon mixture was fed into the reactor at a rate of 1.5 ml/hour and air was fed from the bottom of the reactor at a rate of 5.24 liters/hour. The feed rate of the mixture was such that the contact time between the mixture and the catalyst was 18 seconds. The ratio of oxygen to carbon (as C2) is 2.7
1 and the hydrogen to chlorine ratio was 1.23.
Data regarding feed and conversion are shown in the following table. Note that the simulated mixtures used were slightly different from each of the previous examples. The carbon balance of this reaction is 92.63-94.45%
and the chlorine balance (as hydrogen chloride) is 99.54
-102.8%.

Example 4 The process of Example 3 was repeated using the same catalyst and reactor pressure as in Example 3 and using a reaction temperature of 375°C.

The feed rate of the mixture was 1.5 WL1/h (4) and the air feed rate was 5.24 l/h.
The feed rate of the mixture is such that the contact time between the mixture and the catalyst is 18
It was set to seconds. In this case as well, simulated mixtures were prepared with different compositions from those of the previous examples. Oxygen vs. carbon (as C2)
The ratio of is 2.225 and the ratio of hydrogen to chlorine is 1
．． It was 475. Data regarding feed and conversion are shown in the following table. The carbon balance for this reaction was 95.9% and the chlorine balance (as hydrogen chloride) was 100.38%. The oxygen conversion rate was 60.27%. It is particularly noteworthy that in Examples 3 and 4, the conversion of all components of the simulated mixture or waste stream was complete or 100%. ◆? Example 5 In this example the catalyst contained 20% Cr2O3 and 80% Al2O3 by weight and was charged to a fluidized bed reactor maintained at 75 psig.

A simulated chlorinated hydrocarbon mixture was prepared with the following composition. This mixture was then fed to the reactor.

Similarly, air was fed to the reactor at a rate sufficient to fluidize the catalyst bed. The feed rate of the mixture was kept constant such that the contact time between the mixture point and the catalyst was 12 seconds. Using this mixture, four experiments were conducted at different temperatures and the following results were obtained. In Table 6, the combustion gases were analyzed by gas chromatography and the results were used to calculate the overall mass balance.

The carbon conversion rate is the total emission carbon (TOtalcarbOnOu
The ratio of CO and CO2 to t) was calculated.

Hydrogen and chlorine conversions were calculated by comparing the amount of unconverted hydrocarbons to the amount known to be present in the feed, based on the feed composition and total exhaust carbon. Since no Cl2 was observed, all converted chlorine remained as HCI and all converted hydrogen remained as HCI or H2O. Oxygen as H2O, CO and C
Added to oxygen measured as O2. By comparing this sum with the amount calculated as being charged with the measured nitrogen, an oxygen balance was obtained to check the reliability of the data. This value indicates that the oxygen balance was good. Example 6 Using the same simulated chlorinated hydrocarbon mixture as used in Example 5 and the same catalyst and reaction conditions as in Example 5, the contact time of the mixture with the catalyst was 18 seconds instead of 12 seconds. , conducted a series of experiments.

The following results were obtained from seven experiments conducted at different temperatures. *(W/F) ratio = monthly oxygen balance between catalyst and feed (mixture) was good, indicating the reliability of this data.

The present invention provides a new and improved method for treating undesirable chlorinated by-products commonly obtained in the production of ethylene chlorinated derivatives, such as the production of vinyl chloride.

The process of the invention converts the chlorine contained in the waste by catalytic oxidation into hydrogen chloride, which can then be used in the oxyhydrochlorination step in the production of chlorinated ethylene derivatives.
This is a further advance in that it can be recovered and recovered as Traditionally, hydrogen chloride has been recovered from unwanted chlorination byproducts by torrefaction using methane as fuel.

However, this method is very costly and unreliable. Furthermore, such a method is completely impractical since the recovery cost is more than five times the market price of hydrogen chloride. On the other hand, the method of the present invention is economical since no additional fuel is required, thus substantially reducing recovery costs. The new process is also advantageous in that the temperatures used can be exchanged to generate steam and the thermal energy generated can be used for preheating the feed stream in the production of chlorinated ethylene derivatives. Another advantage of the present invention is that there is little corrosion of the equipment since substantially no elemental or free chlorine is produced. Many other advantages of the invention will be readily apparent to those skilled in the art. Although the invention has been described with reference to specific embodiments, these modifications and equivalent substitutions will be apparent to those skilled in the art and are within the scope of the invention.

Claims (1)

[Claims] 1. In a process for producing chlorinated ethylene derivatives comprising an oxyhydrochlorination step in which hydrogen chloride reacts with oxygen and ethylene or chlorinated ethylene derivatives; unneeded chlorinated ethylene derivatives and others in the flow from the production process. By-products of 10-50 wt% Cr_2O_3 and Al_2O_3 and SiO_2 and A
This stream is injected into a combustion catalyst bed consisting of 90-50% by weight of a material selected from the group consisting of a mixture of l_2O_3 and SiO_2; C. to about 450.degree. C. to produce a hot combustion gas mixture containing essentially hydrogen chloride and essentially free of elemental chlorine and chlorinated hydrocarbon materials; A manufacturing method characterized by recycling to the oxyhydrochlorination step.