Hydrogenation of benzene to produce cyclohexane

 

Method for obtaining cyclohexane by hydrogenation of benzene, in which the reactor operates at a pressure at which the reaction mixture boils under low absolute partial pressure of hydrogen in the range from about 0.1 psi to less than 200 psi, the absolute pressure of the upper straps is from 0 to 350 psig. The catalyst is provided in the form of patterns for catalytic distillation, so that the reaction is occurring concurrently with distillation. Benzene is served by pipeline (1) in the above catalyst layer (12), and hydrogen serves in place below the catalyst layer (12), pipe (2). All top shoulder straps can be returned in the form of phlegmy to provide cooling inside the catalyst layer. Effect: increase the conversion of benzene to cyclohexane. 2 N. and 8 C.p. f-crystals, 1 Il., 1 PL.

Background of invention

The technical field to which the invention relates

The present invention relates to the hydrogenation of benzene to produce cyclohexane. More precisely, the invention relates to a method, in which the hydrogenation of benzene and addinformation, related to this application

Cyclohexane is a main starting material for obtaining of nylon products, and the need for it as such remains significant. Cyclohexane was first obtained by direct fractional distillation of the respective products of the refining of crude oil. Currently, a large portion of the cyclohexane is obtained by the direct hydrogenation of benzene. Usually, the reaction is carried out in the vapor or mixed phase using the reaction in a fixed bed. The temperature of the reactor is adjusted so that it was in the range of from 350 to 500F. higher temperatures can lead to thermodynamic limitations on conversion of benzene, thermal cracking and increase the amount of by-product.

Peterson in U.S. patent No. 2373501 reveals what is happening in the liquid phase process, the purpose of which is the hydrogenation of benzene to produce cyclohexane, and in which there is a temperature difference between the upper part of the catalyst layer, which serves benzene, and output, where is given essentially pure cyclohexane. The temperature difference occurs due to the change of the emitted heat of exothermic reaction in benzene. Namely, the upper part of the catalyst layer is at a higher temperature than the lower part of the catalyst layer. Hydrogen served in counter-current relative to the flow of benzene/cyclohexane. Coils for temperature control is located inside the reactor to maintain the temperature difference, if the exothermic heat of reaction is not sufficient, or for cooling the layer, if you select a too large amount of heat. Peterson acknowledges that despite the fact that a large part of the proposed reaction occurs in the liquid phase, a portion of the benzene and cyclohexane will evaporate, especially near the top of the reactor where the concentration of benzene is the largest and the conversion occurs in the maximum degree. Provides partial condenser hot irrigate intended for condensation condensation material and return it to the reactor. Thus, a significant portion of the heat of reaction is removed by condensation reagents, evaporating all the time during the reaction. In the solution according to the patent in the name of Peterson supported some level of liquid above the upper part of the catalyst layer, but provides the possibility of formation of free space for PA is kin and others, disclosed to any other occurring in the liquid phase process for the hydrogenation of benzene to obtain cyclohexane. However, in the decision in this patent uses high pressure (gauge pressure of 2500 pounds per square inch) to keep the reactants in the liquid state. In addition, in the patent, issued in the name of Larkin and others, reveals the use of the catalyst, the activity of which gradually increases with the decrease of the concentration of benzene for temperature regulation and undesirable side reactions.

In U.S. patent No. 4731496, issued in the name of Hui and others, reveals what is happening in the gas phase process for the hydrogenation of benzene to obtain cyclohexane over a particular catalyst. The catalyst reported in this patent, is a Nickel on the carrier from a mixture of titanium dioxide and zirconium dioxide.

Hydrogenation of benzene is also useful for removing aromatic compounds from the flow of gasoline. One example of this process is disclosed in U.S. patent No. 5210348, issued in the name of Hsieh and others, uses one hydrogenation of benzene fraction or in combination with alkylation. Describes the hydrogenation of benzene takes place in a standard reactor with a fixed bed for about what andartu ASTM D-86 (American society for testing and materials) defined in this way, that should be prevented by the presence of aromatic and unsaturated cyclic and polycyclic compounds in gasoline fuel mixture. This was identified as the source of the gasoline blend T-90 with the specified 90% limit in accordance with the standards of the American society for testing and materials. The resulting ndogoni (bottom remainders) T-90+, which are mostly unsaturated cyclic and polycyclic compounds must be removed, and hydrogenation them for more light, more saturated compounds for gasoline fuel mixture is a tempting alternative.

A typical problem in the hydrogenation of benzene to obtain cyclohexane are simultaneously occurring reactions. Particularly undesirable isomerization to Methylcyclopentane. In addition, at higher temperatures there is a destruction of a cyclic structure, leading to the formation of undesirable5and lighter products. In U.S. patent No. 5773670 disclosed a process in which unsaturated cyclic and polycyclic compounds (in particular, benzene) are subjected to hydrogenation. With the method described in this patent, the hydrogen and Nanase is in the distillation column reactor type. In addition, to achieve complete conversion of benzene to cyclohexane was necessary reactor for thin clearing.

In U.S. patent No. 5856602 disclosed hydrogenation of selected aromatic compounds contained in the naphtha stream by the flow of naphtha and hydrogen in a distillation column reactor type below the layer containing the catalyst.

It was found that the catalytic distillation reactor in a downward direction, that is, one in which a stream containing benzene, served over an area of catalyst, provides a very high degree of conversion. The main by-product of normal reactions is Methylcyclopentane, which is absent in the reaction according to the present invention.

Summary of the invention

The present invention includes the supply of benzene in the distillation reactor column type in the space above the layer of catalyst and the hydrogen stream under absolute partial pressure of hydrogen, comprising from at least about 0.1 psi to less than 200 psig, preferably comprising less than 170 pounds per square inch and at a range of 75 to 150 pounds per square inch, in a distillation column reactor t the element structure for distillation, and the hydrogenation essentially all of the benzene.

The flow rate of hydrogen must be adjusted so that it was sufficient for the maintenance of the hydrogenation reaction and compensation of the loss of hydrogen from the catalyst, but it should be kept below this value, which leads to zachlapywaniu columns, however, this consumption is understood as operate the amount of hydrogen in the sense in which the term is used in this description. Typically, the molar ratio of hydrogen to benzene in the original reaction mixture supplied to the fixed layer, the present invention will be from about 3:1 to 15:1, preferably up to about 10:1.

The term “reactive distillation” is used to describe a parallel reaction and fractionation in the column. For the purposes of the present invention, the term “catalytic distillation” includes reactive distillation and any other process parallel reaction and fractional distillation in a column regardless of its destination.

The drawing shows a process flow diagram according to one variant embodiment of the invention.

Detailed description of the invention

To the provisions of the reaction liquid boils inside the distillation column reactor type. The top straps are discharged and condensed, with some portion of the condensate is returned into the distillation column reactor type of phlegmy. The advantage of the method according to the present invention is that due to continuous irrigation of a portion of the benzene always condenses on the catalytic structure.

The hydrogenation according to the present invention can be performed to obtain essentially pure cyclohexane from benzene.

Described here hydrogenation is an exothermic reaction. Earlier the temperature was regulated by a sharp cooling in strategic locations inside the reactor by adding low-temperature hydrogen. The addition of hydrogen also served to maintain a molar excess of hydrogen inside the reactor to prevent coking and other undesirable side reactions. I think that with the reaction of the present invention the catalytic distillation has the advantage, because all the components are in a fluidized state, resulting in the regulation of the reaction temperature on the level of the boiling temperature of the mixture when the system pressure, and the reaction and distillation occur in parallel in one and the cation pair, but does not increase the temperature at a given pressure.

In accordance with the present invention the method is implemented in a column type reactor filled with a catalyst, which is rational from the point of view that it contains a steam phase and some liquid phase, as in any distillation. Distillation column type reactor operates at such pressure that the reaction mixture boils in the catalyst bed. The process of hydrogenation of benzene according to the present invention occurs at a gauge pressure of upper straps of the specified distillation reactor column type, which is in the range from 0 to 350 psig and preferably is 200 pounds per square inch or less, for example, from 75 to 200 psig, and at temperatures within the specified area resulting from the distillation and reaction precipitate, which range from 100 to 500°F, preferably from 280 to 380°F. Average hourly feed rate of the feedstock, which in this case is understood as the ratio of the unit weight of the feedstock entering the hours in the reaction distillation column to a unit weight of catalyst structures for catalytic distillation may vary in oannot the way to regulate the temperature due to the operation of the reactor at a predetermined pressure to allow the partial evaporation of the reaction mixture. Thus, the exothermic heat of reaction is dissipated due to the latent heat of vaporization of the mixture. The evaporated portion is taken as the upper shoulder straps, and condensed material is subjected to condensation and return to the column in the form of phlegmy.

Without limiting the scope of the invention, it is assumed that the mechanism that ensures the effectiveness of the method according to the present invention is the condensation of a part of the vapors in the reaction system, which ensures the absorption of a sufficient quantity of hydrogen condensed liquid to achieve the necessary close contact between hydrogen and benzene in the presence of a catalyst, which leads to their hydrogenation. In addition, evaporation of the liquid source of the reaction mixture leads to the diversion of a significant quantity of exothermic heat of reaction. Since the liquid in the reactor is at boiling point, the temperature can be adjusted via pressure. The increase in pressure leads to an increase in temperature and decrease in pressure causes a decrease in temperature.

The current down the liquid causes more condensation inside the reactor, which is normal in any distillation. Contact of the liquid, causing condensation inside the parallel transfer of the reaction mixture to locations of the catalyst. I believe that this mode of condensation leads to a very good conversion and selectivity of the current process and allows operation at lower partial pressures of hydrogen and the temperature of the reactor. An additional advantage that the reaction can be obtained from the catalytic distillation consists in leaching the impact that domestic irrigation has on the catalyst, resulting in reduced formation of polymers and coking. The ratio of inner irrigation can vary in the range from 0.2 to 20 L/D (mass fraction of fluid directly under the layer of catalyst/mass fraction of distillate), which gives excellent results.

The preferred implementation is designed to produce cyclohexane by hydrogenation of benzene. In that case, if the product is cyclohexane, the initial reaction mixture containing benzene, characterized in that it preferably contains benzene in an amount corresponding to its mass fraction, at least from 5 to 100%. Other components usually are5C6and C7-hydrocarbons. Because other unsaturated compounds may be hydrogenised cyclohexane. Preferably, the share of other unsaturated compounds in the original reaction mixture should be less than 30%. Cyclohexane is a preferred solvent because it is a product that is desirable to obtain. However, acceptable are other inert substances, such as other alkanes, such as alkanes from C5to C9.

The method according to the present invention are also quite well suited for removal of benzene from the product streams of the reforming process by selective hydrogenation, so that these products can be used as a gasoline fuel mixture. The operation of distillation column reactor type, the maintenance of the desired aromatic fractions active in the reaction zone is described in U.S. patent No. 5856602, which is included in this description in its entirety.

As described, the catalytic material used in the process of hydrogenation, has an appearance which allows it to serve as a distillation head. In a broad sense, the catalytic material is a component of a distillation system, serving both as a catalyst and distillation of the nozzle is a nozzle for distillation columns, it is painted as a heterogeneous, because the catalyst remains a separate structural element. Can be used any suitable hydrogenation catalyst, for example, metals of group VIII of the Periodic table of elements as a main catalytic component separately or together with promoters and modifiers, such as palladium/gold, palladium/silver, cobalt/zirconium, Nickel, preferably deposited on a carrier such as alumina, refractory brick, pumice, carbon, silica, resin, or etc.

Among the metals that are known to catalyze the hydrogenation reaction, you can specify platinum, rhenium, cobalt, molybdenum, Nickel, tungsten and palladium. Typically, for commercial production types of catalysts are the oxides of these metals deposited on the media. The oxide is reduced to the active form or in front by using a reductant, or during use of the hydrogen contained in the initial reaction mixture. These metals also catalyze other reactions, most notably it is shown for the reaction of dehydrogenation at elevated temperatures. In addition, they can stimulate the reaction of olefinic compounds with themselves or>utilizator can be prepared in the form of patterns for catalytic distillation. More precisely, the hydrogenation catalyst, as a rule, is a metal deposited on a carrier of alumina in the form of molded particles or spheres. These particles or spheres placed in a porous container and have the appropriate media in the distillation reactor column type, to allow flow of steam through the layer while providing sufficient surface area for catalytic contact.

Component constituting the catalyst may have a number of forms. In the case of catalytic material in the form of particles with a size typically from 60 mm to about 1 mm and below to a powder, particles, this material is enclosed in a porous container, such as container of mesh wire or polymeric mesh. The material used to create the container, must be inert to the reagents and the conditions in the reaction system. The grid wire may be a wire made of aluminum, steel, stainless steel, etc., Polymeric mesh may be made of nylon, Teflon or similar Mesh [number of holes in the sieve one inch] isator retained therein and will not pass through the holes in the material. The catalyst particles size of about 0.15 mm or powders can be used, and the particle diameter of up to about 1/4 of an inch can be used in containers.

The preferred structure of the catalyst for hydrogenation of benzene includes at least one set of flexible, semi-rigid open mesh tubular elements filled with a catalytic material, the catalytic component) in the form of particles and tightly closed at both ends, is closely connected with a wire sieve and based on this wire mesh, rolled into a spiral having a longitudinal axis, with the specified tubular element is located in a particular order at an angle to the longitudinal axis, thereby forming the stack, and is described in detail in U.S. patent 5431890. Flexible, semi-rigid open mesh tubular element filled with a catalytic material in the form of particles, preferably has fastening means every 1-12 inches along the length of the tube for the formation of patterns for catalytic distillation in the form of multiple links. The links are formed with fastening means may be evenly or unevenly distributed.

Patterns for the catalytic distillate Lochem the sieve, such as demister [separator of small droplets of mist] wire mesh, diagonally, so that when you wrap a wire sieve folded structure forms a new and improved structure for catalytic distillation. Additional options for implementation include the design of many feet, formed of alternating wire mesh and tubular elements, which are collapsed into a new structure for catalytic distillation in the form of bales. Tubular elements in alternating layers preferably are located on a wire sieve in a certain order in opposite directions, so their trails intersect. Each tubular element forms a spiral inside the bale.

The most preferred structure of the catalyst for hydrogenation is described in U.S. patent No. 5730843. This document disclosed a contact structure suitable as a framework for distillation, which has a rigid frame made of two essentially vertical double grating located at a certain distance from each other and rigidly held by means of many essentially horizontal rigid elements, and a lot essentially horyzontalnymi tubes. At least part of the tube of wire mesh contains catalytic material in the form of particles. The catalyst inside the tubes creates a reaction zone, which may occur catalytic reaction, and wire mesh forms a surface for mass transfer for the implementation of fractional distillation. The placement of elements in space provides the variation of the density and loading of the catalyst, as well as structural integrity.

The drawing shows a process flow diagram illustrating the hydrogenation of benzene. Benzene is served by line 1 in the space above the catalyst layer 12, and the hydrogen serves on highway 2 in place under layer 12 of the catalyst contained in the distillation column reactor 10 of the type. If desired, the source submitted benzene can be diluted with cyclohexane. The heat necessary to initiate and balancing process is provided by the circulation flow 4 sediment through the reboiler 50 and highway 5 return. The benzene passes down into the layer, where part of it reacts with rising hydrogen with formation of a reaction mixture containing cyclohexane, representing the product of the reaction, unreacted benzene is Finance vapor from the reaction mixture, while the evaporated part of it comes from the column as the top straps through line 7 to flow. Unreacted hydrogen is also released along with the top shoulder straps. Gaseous top shoulder straps, containing unreacted benzene, cyclohexane, lighter compounds and hydrogen are passed through a condenser 30, in which essentially all of the benzene and essentially all condensed cyclohexane. Thereafter, the flow of the upper straps are served in receiver/separator 40, in which the gas, which mostly represents hydrogen, is separated, and the liquid is collected. The gas is removed through line 9 for recycling or use later in the process.

All of the condensed liquid through line 6 to the thread is returned to the distillation column in the form of phlegmy, provides additional cooling and condensation inside the column. The precipitate [ndogoni], containing a small amount of benzene and cyclohexane is removed through line 4 to flow while part of it is recycled through the reboiler 50 and highway 5 for a thread. There is no selection of the product constituting the liquid from the upper straps. The entire product divert as sludge through line 8 for the stream.

Pic and slightly lower temperature in comparison with the previously known methods for obtaining the same results namely, what happens conversion of approximately 100% of benzene in cyclohexane with 100% selectivity.

Example 1

Was used distillation reactor column type with a diameter of three inches. The rigid structure of the catalyst was filled 6,77 pounds of catalyst Crosfield HTC-400 (12% Nickel on alumina), as described above, and placed in the middle part of the reactor, the length of which was 9 feet, in the form of a nozzle, as described in U.S. patent No. 5730843. The lower part of the reactor, the length of which was 50 feet, was filled with inert nozzle for distillation.

The standard conditions and the results are shown in the table.

Claims

1. The method of producing cyclohexane by hydrogenation of benzene, including the following:

(a) feeding a first stream containing benzene distillation column type reactor containing a bed of the catalyst hydrogenation; (b) feeding a second stream containing hydrogen, the distillation reactor column type in the space below the specified layer; (c) contacting benzene and hydrogen at a partial absolute hydrogen pressure of 0.1 to 200 pounds per square inch the kind with the formation of the reaction mixture, containing cyclohexane and unreacted hydrogen and unreacted benzene; (d) maintaining the pressure in the distillation column reactor type at this level, that part of the reaction mixture was kept in a fluidized state; (e) removing the gaseous top straps, components of the reaction mixture and hydrogen from the distillation column reactor type; (f) the condensation of part of the upper straps of the distillation column reactor type; and (q) the return part of the condensed top straps in the distillation reactor column type in the form of phlegmy, characterized in that said first stream is served in place, above the specified layer of the catalyst for hydrogenation.

2. The method according to p. 1, in which the gauge pressure of the upper straps distillation reactor column type is from 0 to 350 psig.

3. The method according to p. 1, in which the absolute partial pressure of hydrogen is from 0.1 to 170 pounds per square inch.

4. The method according to p. 3, in which the absolute partial pressure of hydrogen is from 75 to 150 pounds per square inch.

5. The method according to p. 4, in which the gauge pressure of the upper straps distillation reactor column type is from 0 to 350 pounds on the square inch, the reaction temperature in the specified layer is approximately 346-383°F and above 90% benzene reacts with hydrogen to form cyclohexane.

7. The method according to p. 1, in which the molar ratio of hydrogen to benzene feedstock ranges from approximately 3.0 to 15.0:1.

8. The method according to p. 1 which includes the upper shoulder straps contain benzene, cyclohexane and hydrogen, and all the benzene and cyclohexane from the upper straps condense and return to the distillation column reactor type of phlegmy.

9. The method according to p. 8, in which a liquid product that represents a residue containing a benzene and cyclohexane, away from distillation reactor column type.

10. The method of producing cyclohexane by hydrogenation of benzene, comprising the following operations: (a) feeding a first stream containing benzene distillation column type reactor containing a bed of the catalyst hydrogenation; (b) feeding a second stream containing hydrogen, the distillation reactor column type in the space below the specified layer, while the molar ratio of the specified hydrogen to benzene is from 3.0 to 10.0; (c) contacting benzene and hydrogen with a full gauge pressure of ver hydrogen pressure, in the range from 75 to 150 psig, and the reaction temperature from 280 to 380°F in the presence of a hydrogenation catalyst prepared in the form of patterns for catalytic distillation, resulting in essentially all of the benzene reacts with part of the hydrogen with the formation of a reaction mixture containing cyclohexane and unreacted hydrogen; (d) maintaining the pressure in the distillation column reactor type at this level, that part of the reaction mixture was kept in a fluidized state at the reaction temperature in the specified layer; (e) removal of gaseous benzene, cyclohexane and hydrogen in the form of the upper straps of the distillation column reactor type; (f) condensation, essentially all of the benzene and essentially all of the cyclohexane is removed in the form of the upper straps of the distillation column reactor type; (g) return essentially all of the condensed benzene and essentially just condensed cyclohexane distillation reactor column type in the form of phlegmy; and (h) the withdrawal of liquid product that represents a residue containing a cyclohexane from the distillation column, characterized in that said first stream is served in place, above indicated

 

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SUBSTANCE: isopropyl alcohol production process comprises hydrogenation of starting acetone including from 0.01 to 10000 ppm benzene in presence of hydrogen and catalyst to give isopropyl alcohol and benzene hydrogenation products, acetone and benzene contained in feedstock being hydrogenated simultaneously. In its second embodiment, isopropyl alcohol production process comprises product separation stage. Process of producing phenol and isopropyl alcohol containing benzene hydrogenation products comprises stages: alkylation of benzene with isopropyl alcohol and/or propylene to form cumene, oxidation of resulting cumene into cumene hydroperoxide, acid cleavage of cumene hydroperoxide to produce phenol and acetone including from 0.01 to 10000 ppm benzene, preferably concentration of produced benzene-polluted acetone, and catalytic hydrogenation of benzene-polluted acetone into isopropyl alcohol containing benzene hydrogenation products, hydrogenation of benzene and acetone proceeding simultaneously.

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