JPH0414087B2 - - Google Patents

Description

[Detailed description of the invention]

Alkylaromatic compounds, such as ethylbenzene, ethyltoluene, isopropylbenzene, etc., are of great importance as precursors for the production of vinylaromatic monomers. The vinyl aromatic monomers produced are used to make a variety of useful polymeric materials, such as styrenic resins. Typical commercial methods are produced by catalytic alkylation at elevated temperatures. To date, there have been two major drawbacks in catalytic alkylation gas phase processes. The first major drawback is the production of undesirable by-products. For example, in the production of ethylbenzene, significant amounts of xylene isomers are also produced.
Even small amounts of xylene are undesirable because the separation of xylene isomers from ethylbenzene is very difficult due to the fact that the boiling points of ethylbenzene and xylene isomers are substantially the same.
Another problem is the incorporation of more alkyl groups into the aromatic nucleus than desired. For example, in the production of ethyltoluene, significant amounts of trimethylbenzene are also produced. Also, separation of the desired product from undesired by-products is very difficult. This phenomenon, referred to below as polyalkylation, further reduces the yield of the desired product. Therefore, this is necessary if it is possible to prevent the formation of xylene isomers or other undesirable by-product materials during the alkylation reaction. A second major drawback encountered with conventional catalytic alkylation methods is the rapid loss of catalyst activity. As the catalytic reaction progresses, the catalyst activity, expressed as the percentage of feedstock actually converted to the desired alkylaromatic product compounds, gradually decreases so that after a period of time, the alkylation is stopped and the catalyst is removed. It is necessary to replace or regenerate. The associated reduced productivity of the equipment used and the expense of catalyst replacement or regeneration substantially increase the cost of producing the desired alkyl aromatic compound. The term "stability" as used herein refers to the ability of a catalyst to convert feedstock to the desired product, measured as a function of time while the reaction is proceeding. Recently, synthetic aluminosilicate catalysts have been recognized as useful in alkylation processes. In particular, catalysts based on ZSM-5 are reported to offer advantages in alkylation processes. Such aluminosilicate materials are subject to deterioration due to caulking. Furthermore, these materials are reported to rapidly lose activity when steam or water is present during the reaction. It is generally believed that the activity of these catalysts is directly proportional to the aluminum concentration and that the water vapor gradually removes aluminum from the framework, thereby irreversibly deactivating the catalyst. It is also theorized that water combines with the aluminum present in such compositions and adversely affects the catalytically active sites of the catalyst. There continues to be a need for improved alkylation methods and apparatus that can overcome these problems associated with the prior art. It is therefore an object of the present invention to provide an improved method and apparatus for the alkylation of aromatic compounds. Another object of the present invention is to provide an improved method and apparatus for the production of alkylaromatic compounds, such that the formation of by-products such as xylene, trimethylbenzene and polymers is reduced. . It is also an object of the present invention to provide an improved process and apparatus for the production of alkyl aromatic compounds in which the alkylation catalyst loses its alkylation activity more slowly. Another object of the present invention is to provide a process and apparatus for the production of alkyl aromatic compounds that converts a relatively high percentage of the raw material to the desired alkyl aromatic product. Another object of the present invention is to provide a method and apparatus for producing alkyl aromatic compounds with extended cycle length. Yet another object of the present invention is to provide a method and apparatus that reduces the cost of producing the desired alkyl aromatic compounds. Yet another object of the present invention is to provide an improved process for the production of alkylaromatic compounds, which increases the productivity of the equipment used. Another object of the invention is to provide a process and apparatus for the alkylation of aromatic compounds, which has particular application in the production of ethylbenzene or ethyltoluene. These and other purposes are for aromatic compounds,
This is achieved by providing a method for producing an alkyl aromatic compound comprising passing a reactive alkene and an effective amount of water through a bed of a silicalite alkylation catalyst at alkylation conditions and recovering the alkyl aromatic compound produced. Ru. The objects of the invention further provide: a reaction zone means; a silicalite alkylation catalyst bed in the reaction zone means; a means for adding and contacting an aromatic substrate compound feed to the catalyst bed in the reaction zone means; means for adding an alkene feedstock to and contacting the catalyst bed in the reaction zone means; means for adding a controlled amount of water vapor into the reaction zone means; and alkyl aromatic compound-containing product stream to the reaction zone means. This is achieved by providing an apparatus for producing an alkyl aromatic compound comprising means for removal from the zone means. It is truly unexpected and surprising that the objects of the present invention can be successfully achieved using the combination of a silicalite alkylation catalyst and an effective amount of water, which is in the form of steam under the reaction conditions. The reason is that most alkylation catalysts in the prior art are very moisture sensitive, and the presence of ppm amounts of moisture during catalytic alkylation virtually destroys the catalyst activity and reduces the useful This is because it has been found to prevent reactions from occurring. The method of the present invention can be applied to various aromatic raw materials. Suitable raw materials include benzene, toluene, ethylbenzene, naphthalene and similar compounds. Various reactive alkenes can also be used. Suitable alkene sources include ethylene and propylene. A silicalite alkylation catalyst is used in the present invention. Silicalites are crystalline silica materials that have a network of molecular-sized pores that act as catalytically active sites. Such catalysts are known in the art; see, eg, US Pat. No. 4,061,724, the entire disclosure of which is incorporated herein by reference. These materials are polymorphs as opposed to aluminosilicates. As it is, their Si/Al ratio is very high since the alumina present is only an impurity of the starting material used to produce it. Generally, the reaction is carried out with a substantial molar excess of aromatic substrate to further reduce the occurrence of polyalkylation. Desirably, the molar ratio of aromatic substrate to alkene feedstock will be between about 2:1 and about 20:1, preferably between about 7:1 and about 20:1. Water is usually added in the form of superheated steam. It should be recognized that water is present in varying amounts in aromatic feedstocks. For example, saturated benzene contains about 700 ppm under indoor conditions.
The use of a steam co-feedstock to add more water than would normally be present in the reactor along with the reactants themselves is reflected by the percent conversion to the desired product over time. effectively increasing the stability of such catalysts and reducing the amount of undesirable by-products produced. Therefore, as used herein, the term "effective amount of steam" refers to improved stability under reaction conditions compared to the performance of the same catalyst in the absence of a steam co-feedstock under the same reaction conditions. refers to the amount of water or moisture that is sent into the reactor along with the aromatic and alkene feed materials that will result in the specific silicalite catalyst used to exhibit reduced properties and/or by-product production.
Preferably between about 20,000 ppm and about 100,000 ppm,
Most preferably between about 20,000 ppm and about 60,000 ppm,
Add steam. The alkylation reaction takes place at elevated temperatures. To maintain an appreciable reaction rate, at least approximately
A minimum temperature of 300°C should be used. Temperatures above about 600°C are desirably avoided in order to prevent undesirable side reactions that may occur more easily at higher temperatures. Preferably, the inlet temperature of the alkylation reaction is maintained between about 350<0>C and about 500<0>C, most preferably between about 400<0>C and about 460<0>C. If desired, the operating temperature can be increased as the catalyst is gradually deactivated. The operating pressure within the alkylation reaction zone can be varied over a substantial range. Generally, the pressure is between about atmospheric pressure and about 25 atmospheres. Preferably,
The pressure is maintained between about 10 and about 15 atmospheres. Referring now to the drawings, reference numeral 1 designates a reaction vessel 1 defining an alkylation reaction zone. Inside the reactor 1 is a bed of silicalite alkylation catalyst 2. Although only one catalyst bed is shown in the drawings, it will be understood that a multi-bed system comprising any desired number of catalyst beds can also be used. Aromatic feed is added into the alkylation reactor through inlet tube 3. The alkene feed is added to the aromatics stream via tube 4, which flows into tube 3. Similarly, a controlled proportion of superheated steam is added to the mixed aromatics and alkene feed through tube 5, which is led into tube 3. Valve means 6
are installed on the pipe 5 to ensure positive adjustment of the proportion of water vapor added into the feed stream.
The aromatic substrate compound and the alkene feed are contacted with the catalyst in the presence of water vapor and at a temperature sufficient to cause alkylation in the reaction zone. The alkyl aromatic product compound formed is removed from the reactor 1 through tube 7 and sent to a fractionation section 8 where excess aromatic substrate is separated from the alkyl aromatic product. Excess aromatic substrate is removed from fractionation zone 8 as a superheated fraction through tube 9 and recycled to tube 3. The crude alkyl aromatic product fraction is removed from fractionation section 8 through tube 10 as a bottom stream. By request,
Heavy materials, such as diethylbenzene, produced as by-products during ethylbenzene production can be recovered and recycled to the inlet pipe 3 for economical operation. In a preferred embodiment, the process of the present invention, which combines the use of a silicalite catalyst and a steam co-feedstock in the alkylation reaction, thereby reduces the amount of xylenes, trimethylbenzene and other undesirable by-products that are difficult to separate from the product mixture. A particularly effective process for producing ethylbenzene and ethyltoluene is provided. More dramatically, however, the use of an effective amount of steam co-feed improves the stability of the silicalite catalyst in that higher conversions are obtained when no steam is used, and it is retained over a relatively long period of time. ramp up. This allows the cycle length of the catalyst to be extended, which of course has great commercial advantages. moreover,
The use of steam co-feedstock and silicalite catalyst has little or no irreversible deactivation effect on the catalyst. In other words, the same catalyst can be reused after regeneration without substantial loss of activity. When using the process of the present invention to produce ethylbenzene or ethyltoluene from benzene and toluene aromatic feedstocks, suitable silicalite catalysts are those having a crystalline size of less than about 8 microns and a silica to alumina ratio of at least about 200. It is. It is advantageous to use with these catalysts a steam co-feedstock in the range of about 20,000 to about 60,000 ppm based on the amount of aromatics. about
The use of 40000 ppm steam co-feedstock is most preferred. Although inlet temperatures of about 350° to about 500°C can be used,
Particularly effective is a temperature range of about 410° to about 475°C. Preferred reactant ratios (aromatics/alkenes) are from about 7:1 to about 20:1;
WHSV ranges from about 100 to about 150. Operating pressures between about atmospheric pressure and about 25 atmospheres can be used, and between about 10 and about
A range of 13 is preferred. The invention will be explained in more detail with reference to the following non-limiting examples. Example 1 Benzene and ethylene were added into a reaction zone containing a bed of silicalite catalyst material having a particle size between 12 and 20 meshes and a Si/Al ratio greater than about 300. The depth of the floor was approximately 8.25 cm.
The molar feed ratio of benzene to ethylene was approximately 16:1. The operating conditions are approximately 410°C at the inlet of the catalyst bed.
The temperature was approximately 110 °C and the outlet pressure was approximately 11 atm, containing a benzene WHSV of approximately 110 °C. 7th hour of operation ~
For the 14th hour, a flow of about 20,000 ppm based on the weight of the benzene feed was added. Between the 16th and 24th hour of operation, approximately 60,000 ppm flow was used. 40000ppm during the 26th to 34th hours of operation
A steam co-raw material was used. Finally, from hours 36 to 43 of the operation, less than about 100 ppm of steam co-feedstock was used. The product stream from the alkylation reaction zone was analyzed by gas chromatography. Catalytic activity was measured both at the beginning and at the end of the experiment according to the following formula: % conversion = number of moles of target alkyl aromatic compound / number of moles of reactive alkene fed to the reactor x 100 % selectivity was determined according to the following formula: Selectivity=weight of target alkyl aromatic compound/weight of total product x 100% After 100 hours of experimental time, the reaction was stopped. Calculating the initial catalyst activity gives a conversion rate of 99.9%,
And the final catalyst activity was 89.7% conversion.
The initial selectivity was 98%, and at the end of the experiment the selectivity increased to virtually 99%. The results of each of these experiments using one catalyst sample are shown below:

Table: These experiments demonstrate that steam co-feedstock significantly reduces the amount of xylene byproduct produced, even when comparing fresh and spent catalyst materials. It should be noted that although the xylene content was relatively high during the first run, the conversion rate during that run was considerably higher than in the last run. Example 2 Toluene and ethylene were added into a reaction zone containing a bed of silicalite catalyst material having a particle size between 12 and 20 meshes and a Si/Al ratio greater than about 300. The depth of the floor was approximately 8.0 cm. The molar feed ratio of toluene to ethylene was approximately 16:1. Operating conditions include an outlet pressure of about 11 atm and an outlet pressure of about 130
Toluene WHSV was included. Two separate experiments were conducted, one with a steam co-feedstock and one without a steam co-feedstock. The inlet temperature for each experiment was initially approximately
490°C, and then for about the next 24 hours about
The temperature dropped to 470℃. The results of these experiments are shown below:

TABLE These experiments demonstrate that the steam co-feed significantly reduced the amount of trimethyl-benzene byproduct produced. Example 3 Toluene and ethylene in a 7:1 molar ratio at a temperature in the range of about 450-490°C at the catalyst bed inlet, about
The reaction was carried out at a pressure of 11 atmospheres and a toluene WHSV of approximately 130. The catalyst used had a mesh size between 12 and 20 mm and a bed depth of about 7.5 cm.
The first experiment was conducted using the new catalyst and without steam co-feedstock. The initial conversion rate is 98%
and 39% after 100 hours of operation.
A second experiment was conducted under the same reaction conditions but using a new catalyst of the same type and adding an additional 40,000 ppm of steam co-feedstock (based on toluene) into the reaction. The initial conversion rate for this experiment was 96.8%
, and this was reduced to 57% after 258 hours of operation. This shows that when an effective amount of steam was co-fed in the process, the conversion (a measure of catalyst activity) remained at a high level after 2 1/2 times the period of use of the catalyst. Example 4 In this experiment, an inlet temperature of 450° to 480°C, approx.
A pressure of atmospheres and an aromatic to alkene molar feed ratio of about 8:1 was used. Benzene was used as the aromatic feedstock and ethylene as the alkene. Benzene WHSV was 110. moreover,
40000ppm water (based on benzene feedstock) was used. The catalyst had a mesh of between 12 and 20 mm and a bed depth of about 8 cm. Conversion remained at a high level of approximately 99% during the first 100 hours of operation. Similarly, the selectivity was about 99% after 100 hours of operation. The same catalyst used in the above experiment was then regenerated. The regeneration process used here is generally described below. First, the catalyst material was heated to 480 °C in the presence of nitrogen gas.
heated to ℃. After 3 hours of treatment, remove water vapor.
Added at a rate of 28WHSV. After 30 minutes, nitrogen
It was returned to 12WHSV, and the water vapor was set to 5WHSV.
After 10 hours, the water vapor was raised again to a level of 28WHSV, the nitrogen to 24WHSV, and the air flow was increased.
Added at 0.5WHSV. Thereafter, water vapor and nitrogen were slowly removed from the system, and air flow was increased stepwise over a period of 3 hours. Total playing time is approx.
It was hot for 18 hours. Using the regenerated catalyst used in the previous experiment, a second experiment was carried out from 450° without the steam co-feedstock.
Inlet temperature in the range of 500℃, pressure of about 11 atm and 16
A second experiment was conducted at the toluene to ethylene molar feed ratio. Toluene WHSV was 130.
Conversion rates are higher during 160 hours of operation using regenerated catalyst.
It was maintained at over 98%. This indicates that the use of a steam co-feedstock does not substantially adversely affect the activity of the silicalite catalyst material. However, selectivity ranged from about 88% initially to a final 92% after 161 hours of operation. The embodiments described above are presented merely as examples of the invention and are not intended to be limiting. Since modifications may be made to the disclosed embodiments by those skilled in the art that encompass the spirit and substance of the invention, the scope of the invention should be construed in accordance with the following claims.

[Brief explanation of drawings]

The drawing schematically represents an apparatus for producing alkyl aromatic compounds according to the invention. In the figure, 1 is the reactor, 2 is the catalyst bed, 6 is the valve means, 8 is the fractionation zone, 3, 4, 5, 7, 9 and 1
0 represents a tube, respectively.

Claims (1)

[Claims] 1. The following formula In the formula, R ¹ represents hydrogen or lower alkyl,
An aromatic compound of the following formula _CH2 =CH- ^R2 , where ^R2 represents hydrogen or lower alkyl,
of the reactive alkene and the alkyl aromatic compound characterized in that 20,000 ppm to 100,000 ppm of water, based on the weight of the reactive alkene and the aromatic compound, is passed through the silicalite alkylation catalyst bed at alkylation conditions and the resulting alkyl aromatic compound is recovered. A method for producing aromatic compounds. 2. The method of claim 1, wherein the water is added in the form of superheated steam. 3. The method of claim 1, wherein the aromatic compound, the reactive alkene, and the water are mixed before being added to the reaction zone containing the alkylation catalyst bed. 4. The method of claim 1, wherein a molar excess of the aromatic compound is added into the reaction zone. 5 The molar ratio of aromatic compound to reactive alkene is 2
5. The method of claim 4 in the range of .about.20. 6. The method of claim 1, wherein the reactive alkene is ethylene. 7. The method according to claim 6, wherein the aromatic compound is benzene. 8. The method according to claim 6, wherein the aromatic compound is toluene. 9. The method of claim 1, wherein the temperature in the reaction zone is maintained between 300°C and 600°C. 10. The method of claim 9, wherein the temperature in the reaction zone is maintained between 400<0>C and 460<0>C. 11. The method of claim 1, wherein the pressure in the reaction zone is maintained between 3 and 25 atmospheres. 12. The method of claim 11, wherein the pressure in the reaction zone is maintained between 10 and 15 atmospheres. 13 40000ppm based on the weight of aromatic compounds
of water is added into the reaction zone.
The method described in section. 14 Reaction zone means; silicalite alkylation catalyst bed in the reaction zone means; In the formula, R ¹ represents hydrogen or lower alkyl,
means for adding and contacting the aromatic substrate compound feedstock with the catalyst bed in the reaction zone means; in the following formula _CH2 =CH- ^R2 , ^R2 represents hydrogen or lower alkyl;
means for adding and contacting the catalyst bed in the reaction zone means with a reactive alkene feedstock of from 20,000 ppm to 20,000 ppm based on the weight of the aromatic compound;
An apparatus for producing an alkyl aromatic compound, characterized in that it has means for adding 100,000 ppm of water vapor into the reaction zone means; and means for removing an alkyl aromatic compound-containing product stream from the reaction zone means. . 15. The apparatus of claim 14, further comprising means for separating excess aromatic substrate compounds from the alkyl aromatic compound-containing product stream. 16. The apparatus of claim 15 further comprising means for recycling separated aromatic substrate compounds to said aromatic feedstock means.