JPH0765054B2 - Method for producing aromatic hydrocarbon - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for converting a light naphtha fraction into aromatic hydrocarbons, and more particularly to C ₅ and / or C ₆ aliphatic and / or naphthene-based carbonization. It relates to a method for producing an aromatic hydrocarbon in a high yield from a raw material containing at least 80% by weight of hydrogen.

[Conventional technology]

Generally, a mixture of aromatic hydrocarbons is widely used as a base material for gasoline blending and a petrochemical raw material.

Conventionally, it is known that a zeolite-based catalyst is effective in converting lower aliphatic hydrocarbons into aromatic hydrocarbons in the gasoline boiling range, and as an example, US Patent 4,528,
There are 412 and 4,548,619. The mechanism of this conversion reaction has not been fully clarified, but after the paraffin, which is the raw material, is olefinized with cracking, it is polymerized to become an oligomer of C ₆ or more, and is further aromatized by cyclodehydrogenation. It is thought to do. In the course of these reactions, a large amount of hydrogen, C _{1 to} C ₄ paraffins, olefins, and other gaseous products are produced as by-products together with aromatic hydrocarbons. In order to improve the yield of aromatic hydrocarbons, it is necessary to circulate this gaseous product again in the reaction zone for repeated reaction, but according to the disclosure of the above patent, C ₃ and C ₄ carbonization is required. It uses hydrogen as the main raw material and may contain a small amount of C ₂ and C ₅ components, but it is said that the C ₅ component is preferably at a practically minimum level. Further, in the above U.S. Patent 4,548,619,
The above-mentioned light gas by-product is mixed with C ₃ and heavier gas,
Disclosed is a method in which hydrogen, which is poor in reactivity, and lighter gases such as C ₁ and C ₂ are separated by a membrane separation method, the former is circulated in a reaction zone, and the latter is removed out of the system.

Further, according to the disclosure of JP-A-60-156793, an aromatic hydrocarbon is produced by a catalytic reaction of a C ₃ and C ₄ component in an amount of 50 wt% or more, preferably 70 wt% or more, with an aliphatic hydrocarbon catalyst. At this time, if 10 to 50% by weight of ethane is mixed into the raw material from outside the system or as a circulating gas after product separation, C ₃ and C ₄
It is stated to favorably affect the selectivity of conversion of the components to aromatic hydrocarbons.

However, in each of the above conventional techniques, since the amount of methane and ethane by-produced is large, the yield of aromatic hydrocarbons cannot be said to be satisfactorily high, and there is a problem that the catalyst life is short and frequent regeneration is required. there were.

On the other hand, for example, regarding a method using an aliphatic and / or naphthenic hydrocarbon having C ₇ or more as a raw material, it is known that it is possible to aromatize by a catalytic reforming technique using a platinum-supported alumina catalyst. are, but if a C ₆ aliphatic and / or naphthenic hydrocarbons as a raw material, it is known that in the catalytic reforming techniques can not be aromatized practical enough, C ₅ aliphatic Almost no reports have been found on the case of using naphthenic hydrocarbons as raw materials.

[Problems to be solved by the invention]

INDUSTRIAL APPLICABILITY The present invention relates to an effective use of a so-called light naphtha, a fraction mainly composed of C ₅ and / or C ₆ aliphatic and / or naphthenic hydrocarbons, the use of which has not been sufficiently exploited in terms of oil refining balance. As an object, it is intended to provide a method for converting it into an aromatic hydrocarbon having a high degree of usefulness, whereby various problems that are difficult to achieve in the above-mentioned prior art, that is, aromatic hydrocarbon The two problems of low yield and short catalyst life and frequent regeneration are to be solved.

[Means for solving problems]

The present invention provides a raw material 1 containing at least 80% by weight of C ₅ and / or C ₆ aliphatic and / or naphthenic hydrocarbons.
A mixture of 1 part by weight and a mixed hydrocarbon gas consisting mainly of methane and ethane, both of which and 0.05 to 1.0 parts by weight of ethylene is mixed at a temperature of 450 to 650.
Ga, Zn, Pd, Pt, T under the conditions of ℃, pressure normal pressure to 50Kg / cm ² G
A method for producing an aromatic hydrocarbon, which comprises catalytically reacting with a zeolite containing one or more of i, Cd, Ni, Cu, Re, Fe, Ge and Cr in the form of a compound or an ion. .

The raw material used in the present invention is typically so-called light naphtha, but contains at least 80% by weight of C ₅ and / or C ₆ aliphatic and / or naphthenic hydrocarbons, preferably
It contains 90% by weight, and the remaining components are mainly C ₄ or less, usually C ₃ and C ₄ hydrocarbons, and substantially all vaporize at a temperature of about 250 ° C. under normal pressure. If a raw material containing less than 80% by weight of C ₅ and C ₆ components is used, the conversion rate to aromatic hydrocarbons is lowered, which is not preferable. Regarding the composition of the C ₅ and C ₆ components, C ₆
The higher the content ratio of the component, the higher the conversion rate to the aromatic, but in the present invention, the constituent ratio of the C ₅ and C ₆ components is not particularly limited.

In the present invention, a mixed hydrocarbon gas consisting mainly of methane, ethane and propane, whose total amount is 0.05 to 1.0 part by weight per 1 part by weight of the above raw material, is mixed with the above raw material to 450 to 650 ° C. After heating, 0 to
It is subjected to the reaction under the condition of 50 kg / cm ² G. The proportion of the C ₁ and C ₂ components in the mixed hydrocarbon gas is preferably 50% by weight or more, more preferably 65% by weight or more. The mixed hydrocarbon gas may, of course, be obtained from another source, but preferably the circulating gas described below is used.

That is, according to the method of the present invention, the product that exits the reactor after the reaction, in addition to the target aromatic hydrocarbons, contains hydrogen and non-aromatic hydrocarbons of various carbon atoms, By cooling this to 0 to 50 ° C., aromatic hydrocarbons and non-aromatic hydrocarbons having C ₅ or more are condensed and separated as a liquid substance. Non liquefied gas is hydrogen, methane, C ₂ -C ₃ serves than hydrocarbons and small amounts of C ₄ -C ₅ hydrocarbons, is introduced into the membrane separation device of the gas to be described later this hydrogen therein And a small amount of C ₂ -C ₃ hydrocarbons unavoidably accompanied with methane are permeated through the membrane and discharged out of the system to mainly consist of methane, ethane, and propane. Since a gas containing a small amount of hydrogen (mainly butane) and having a total amount of methane, ethane and ethylene of 0.05 to 1.0 parts by weight per 1 part by weight of the raw material remains, it is used as a circulating gas for mixing with the raw material for the reaction. Is a preferred embodiment of the present invention.

The effect of mixing a mixed hydrocarbon gas mainly consisting of methane, ethane and propane with the raw material is that the by-products of C ₁ , C ₂ and C ₃ components such as methane, ethane and propane during the reaction are suppressed and the aroma is reduced. It is needless to say that the yield of the group is improved and the activity retention period of the catalyst, that is, the life is extended, and the effect of the above-described embodiment of performing gas membrane separation by the membrane separator is preferable from the viewpoint of energy saving. However, the gas containing the appropriate amount of methane, ethane and propane described above can be mixed and reused as a circulating gas in the raw material.

It should be noted that C _{2 to} C ₄ aliphatic hydrocarbons (for example, FCC exhaust gas) can be used together as the raw material.

The zeolite used as the catalyst in the present invention has an effective pore size of about 5 to 5 in order to produce an aromatic hydrocarbon having a gasoline boiling point range desirable from the viewpoint of its usefulness.
Aluminosilicates with a medium pore size in the range of 6.5Å are preferred, and typical examples of these are silicalite, ZSM-
5, ZSM-11, ZSM-38 and the like can be mentioned, but ZSM-5 is particularly preferable.

The SiO ₂ / Al ₂ O ₃ molar ratio of these zeolites is
From the viewpoint of stability and activity, 20 to 100 is preferable. These zeolites are substituted from the cation type to the hydrogen type according to a known method, and are further exchanged with cations of the following metals,
Alternatively, the compound contained in the form of the compound is used as the catalyst. The form of the metal compound is preferably an oxide or a sulfate.

As the metal, Ga, Zn, Ti, Cd, Ni, Cu, Pd, Re, Fe, Ge, Cr, Pt and the like can be used, but Ga, Zn, Pd are particularly preferable. Of course, two or more of these may be used in combination at an appropriate ratio. By thus containing the specific metal in the form of a compound or an ion, the catalyst has excellent aromatic selectivity. The metal content is 0.05 to 10% by weight of zeolite.
Can be added in a ratio of 0.05 to 4 and a preferable ratio is 0.05 to 4
% By weight.

The mixture of the raw material and the mixed hydrocarbon gas is heated and vaporized by a preheater to a desired temperature in a reactor filled with the above catalyst, and then introduced and reacted. Reaction temperature is 450-650 ° C, preferably 500
-600 ° C, reaction pressure is atmospheric pressure to 50 kg / cm ² G, preferably 1-
It is 10 kg / cm ² G. Since the reaction is accompanied by dehydrogenation, the lower the reaction pressure, the higher the aromatic selectivity, but it is desirable to select the above range from the viewpoint of space time yield (space time yield). As the reactor type, a fixed bed, a moving bed, a fluidized bed, etc. can be selected according to the scale of the equipment and the properties of the catalyst. Conversely, the particle size and particle size distribution of the catalyst can be selected according to the model. Can be selected. Further, the number of reactors may be one, but it is also possible to use several reactors in series. In the latter case, the mixed hydrocarbon gas mainly consisting of methane, ethane and propane is usually mixed in its entire amount with the raw materials. Although it is introduced into the reactor of the first stage through the post-preheater, it may be introduced into the reactors of the second stage and thereafter, or may be dividedly introduced into the reactors of each stage.

A product which mainly comprises C _{6 to} C ₁₀ aromatic hydrocarbons by introducing the reaction product into a condenser and cooling to 0 to 50 ° C, and inevitably carries a small amount of C ₅ or more non-aromatic hydrocarbons. Since it will be condensed, it can be separated with a gas-liquid separator and taken out of the system, and can be widely used as a base material for gasoline mixing and a petrochemical raw material. Incidentally, the non-aromatic hydrocarbon having a C of ₅ or more, which is condensed with a small amount, may be rectified and separated, if necessary, and recycled to the raw material system.

Uncondensed gaseous products are hydrogen, methane, C ₂ −
It is composed of C ₃ hydrocarbons and a small amount of C ₄ -C ₅ hydrocarbons, which can be used for petrochemical feedstocks, fuels, etc. It is as described above that the gas is separated into gas and the unpermeable gas is circulated to mix with the raw material.

This preferred embodiment is specifically carried out as follows. That is, the uncondensed gas is introduced into the gas membrane separator through the compressor and the preheater under the conditions of temperature 0 to 150 ° C. and pressure 0 to 50 kg / cm ² G. The membrane to be used may be a non-porous membrane such as cellulose acetate, polyimide, polysulfone, polyethylene, polyethylene terephthalate or polymethyl acrylate membrane, or a porous membrane such as other porous glass (for example, Corning Vycor glass). . The separation membrane has a separation coefficient of H ₂ / CH ₄ , that is (H ₂
/ CH ₄ partial pressure ratio) / (supply side H ₂ / CH ₄ partial pressure ratio) is preferably 70 or less, and an appropriate membrane separation unit such as a hollow fiber type or a spiral type is used.

In addition, the membrane separation device may have a plurality of containers (modules) containing separation membranes installed in parallel in the flow path according to the throughput,
It may be installed or used in multiple stages depending on the purpose of separation, and all of these aspects are referred to as a membrane separation device in the present invention.

The permeation side of the membrane is 50 Torr to 10 Kg / cm ² G, and hydrogen and a small amount of C _2-
The C ₃ hydrocarbon becomes a permeate gas and is discharged to the outside of the system, and the remaining gas containing methane, ethane and propane as the main components has a molar ratio of methane to ethane of 10:90 to 90:10. A total of 70% or more of the total and a small amount of other small amounts of lower hydrocarbons (mainly butane) and hydrogen are contained, and it is a preferred embodiment of the present invention to circulate this and mix it with the raw material. Judging from the results of the examination by the present inventors regarding the effect of circulating this unpermeated gas in the reactor, it seems that methane does not directly participate in the reaction, but it has the effect of suppressing the production of methane due to cracking during the reaction. It is presumed that, together with hydrogen, it also has the effect of suppressing the deterioration of catalyst activity over time. Therefore, as another embodiment of the present invention, a mixed gas containing methane, ethane, and propane as main components obtained from another source is introduced into the reaction system together with the raw materials, even if the circulating gas from the membrane separation device is not used. It may be as described above.

In the prior art, hydrogen, methane, and most of ethane were separated from the gaseous product and removed outside the system, and the effect of circulating these into the reaction system was not examined. JP-A-60-156793 mentions the use of ethane, but in this case, it is an example of a system using a raw material in which the C ₃ and C ₄ components account for the majority, and is a technique different from the present invention. Is.

In the present invention, a raw material containing C ₅ and / or C ₆ aliphatic hydrocarbons and / or naphthenic hydrocarbons as a main component is mixed with a mixed hydrocarbon gas mainly composed of methane, ethane and propane to cause a reaction. It suppresses by-products and enhances the aromatization yield by the overall effects such as promoting the aromatization of ethane, and further suppresses the deterioration of the catalytic activity over time and retains its high activity for a relatively long time. can do.

Further, if the above-mentioned membrane separation technique is used as an embodiment,
It consumes less energy than the commonly used separation methods such as rectification method and cryogenic separation method, and it is not only easy to maintain and manage the equipment, but also the aromatization of overalls by recycling by-product gas. The rate is also increasing, and the economic effect is extremely large.

Regarding the mixing ratio of the raw material and the mixed hydrocarbon gas, it is desirable that the total amount of methane, ethane and propane in the latter is 0.05 to 1.0 part by weight with respect to 1 part by weight of the former. If it is less than 0.05 part by weight, ethane is discharged out of the system without sufficiently reacting. On the other hand, when the amount exceeds 1 part by weight, the above-mentioned effect of the present invention reaches the saturation point, and in the case of the embodiment of gas circulation using the membrane separation technique, the equipment is unnecessarily enlarged for gas circulation and wasteful energy is consumed. Is not desirable.

〔Example〕

The following examples were carried out by the test apparatus whose flow is outlined in FIG. 1, and will be described with reference to FIG.

Example 1 Raw light naphtha having the composition shown in Table 1 is supplied at 1.0 kg / hour from the conduit 2 and is circulated from the membrane separation device 14 through the conduit 3 Unpermeable gas having the composition shown in Table 1 0.693 Nm ³ / hour (0.833k
g / h) (the total amount of methane and ethane in the unpermeated gas is 0.793 parts by weight per 1 part by weight of the raw material gas), heated to 560 ° C. in the preheater 1 and passed through the conduit 4 to Ga-ZSM-
5 catalyst (extruded product having a diameter of about 1.6 mm (1/16 inch) and a length of 10 mm manufactured according to British Patent 1561590 Example 5; Ga3.0Wt
% Content; SiO ₂ / Al ₂ O ₃ molar ratio = 50) 0.8 kg was filled, 560
Introduced into the reactor 5 kept at ℃, reaction pressure 3Kg / cm ² G
After the reaction, the reaction product enters the condenser 7 through the conduit 6, is cooled to 6 ° C. here, and is separated into the condensed liquid and the uncondensed gas by the separator 8, and the condensed liquid is reduced in pressure through the conduit 9. Valve 10
After depressurization, 0.643 kg / hour was drained as a product. As shown in Table 1, the liquid composition was mostly aromatic hydrocarbons.

The uncondensed gas enters the compressor 11 via the conduit 12 and is pressurized to 4 kg / cm ² G, then heated to 60 ° C by the preheater 13 and then the membrane separation device.
I entered 14. The membrane separator 14 comprises a module of hollow fiber made of cellulose acetate having a membrane area of 5 m ² , and the composition of the permeated gas is also shown in Table 1. The retentate gas was circulated by conduit 3 to the inlet of preheater 1.

The liquid yield was 64.3 Wt%, and the reaction was continued for 8 days, but the decrease in the liquid yield during that period was only 3 Wt%.

Example 2 Instead of the circulating gas from the conduit 3 in Example 1, a second
1.1452 kg / hour of C ₂ and C ₃ mixed gas having the composition shown in the table was mixed with 1.0 kg / hour of raw light naphtha and reacted under the same conditions as in Example 1, and then the reaction product was cooled in the same manner to obtain a liquid product. And separated into uncondensed gas. The respective compositions are shown in Table 2. The total number of moles of the raw material and the mixed gas was the same as in Example 1.

The liquid yield was 58.0 Wt%, but when the reaction was continued for 8 days, the liquid yield was reduced by 9 Wt% during that period due to the decrease in catalytic activity.

Example 3 The same operation as in Comparative Example 1 was carried out except that 1.3618 kg / hr of propane was used instead of the C ₂ and C ₃ mixed gas of Example 2. The experimental results are shown in Table 3. The total number of moles of the raw material and propane was the same as in Example 1.

The liquid yield was 55.4 Wt%, but when the reaction was continued for 8 days, the liquid yield decreased by 15 Wt% during that period due to the decrease in catalytic activity.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a flow showing an example of an embodiment of the present invention. In the figure, the solid line indicates liquid and the broken line indicates gas. 1 ... Preheater, 5 ... Reactor, 7 ... Condenser, 8 ... Separator, 10 ... Pressure reducing valve, 11 ... Compressor, 13 ... Preheater, 14
...... Membrane separation device.

Claims (1)

[Claims] 1. A hydrocarbon containing at least 80% by weight of at least one of the following components: A: C ₅ aliphatic hydrocarbon, C ₆ aliphatic hydrocarbon and naphthene hydrocarbon. B: methane, ethane. , A mixed hydrocarbon consisting of ethylene and propane in an amount of 0.05 to 1.0 part by weight at a temperature of 450 to 650 ° C and a pressure of atmospheric pressure to 50 kg.
contact with zeolite containing one or more of Ga, Zn, Pd, Pt, Ti, Cd, Ni, Cu, Re, Fe, Ge and Cr in the form of compound or ion under the condition of / cm ² G The reaction product obtained by the reaction is subjected to the following steps: (1) cooling to 0 to 50 ° C to separate a condensate containing an aromatic as a main component (2) uncondensation by the above step (1) The step of introducing the residual gaseous product of 1. into the membrane separation device, and separating the gaseous product into a component consisting of hydrogen and methane that permeates the device separation membrane and a component that does not permeate the device separation membrane (3) A process for producing an aromatic hydrocarbon, which comprises treating the component B which does not pass through the separation membrane according to 2) with the component B.