JPS6118597B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for selective hydrotreating of pyrolyzed gasoline, and more specifically to a method for selectively hydrotreating pyrolyzed gasoline, and more specifically, by pyrolyzing hydrocarbons having a boiling point of _C4 butane or higher, such as light petroleum fractions such as naphtha and kerosene, at high temperatures and producing petrochemical When producing ethylene, propylene, butadiene _, etc., which are useful for For the purpose of producing gasoline for automobiles, diolefin hydrocarbons are selectively hydrogenated to monoolefins, and further unsaturated compounds of alkenyl group-substituted aromatics (hereinafter referred to as styrenes) contained in pyrolyzed gasoline are The present invention relates to a method for selectively hydrogenating. This pyrolysis gasoline contains a considerable amount of isoprene,
Includes diolefins such as cyclopentadiene and aliphatic olefins such as pentene, hexene, heptene, and alkenyl aromatics such as styrene, α-methylstyrene, allylbenzene, crotonylbenzene. This fraction is generally given a research octane number (hereinafter referred to as
Although it exhibits a high octane number (referred to as RON) (unleaded) of 90 or higher, which is suitable for automobile gasoline, it contains large amounts of various diolefin hydrocarbons and monoolefin hydrocarbons, and its properties include, for example, a diene number of 20 or higher and a bromine number of 50 or higher. shows. Also
The oxidation stability is poor, as shown by the ASTM method of 20 mg/100 c.c. or more of actual gum and an induction period of 1 hr or less, so it cannot be used as gasoline as is. Therefore, large amounts of diolefin and styrene,
The presence of styrenes such as α-methylstyrene in pyrolysis gasoline is undesirable. Such diolefins and styrenes are unstable and tend to polymerize into higher molecular compounds. The tendency of diolefins to polymerize is particularly influenced by air and light. When pyrolyzed gasoline containing diolefins and styrenes is mixed and used as a fuel in an internal combustion engine, the rubbery substances formed tend to deposit in the fuel supply system, in the carburetor, valves, etc. In order to use pyrolysis gasoline as a blending gasoline, almost all of the diolefins and styrenes must be removed, which requires hydrogenation to convert the styrenes to their corresponding aromatic compounds and conjugated diolefins to their corresponding aromatic compounds. This is achieved by making a monoolefin. In fact, for gasoline formulation it is undesirable to hydrogenate diolefins to completely saturated hydrocarbons. This is because paraffinic saturated hydrocarbons typically have lower octane numbers than their monoolefin counterparts. Conventional methods for selectively hydrogenating diolefins by hydrotreating pyrolysis gasoline can be broadly classified into two types. The method of the first category is used by pre-sulfurizing a catalyst in which active metal components such as Ni, W--Ni, Ni--Mo, and Co--Mo are supported on high surface area alumina. Normal reaction temperature 140~240℃, 0.5~3V/H/V
Since it is used under somewhat harsh operating conditions such as a small space velocity, it has the disadvantage that the catalyst regeneration cycle is short, at 0.6 to 1 year. The second category method uses a catalyst in which a noble metal is supported on alumina, and palladium alone or a palladium catalyst with Cu, Cr, etc. as a co-catalyst is usually used. This type of catalyst generally has high activity at low temperatures, so the reaction temperature is used at 50-90°C, and the space velocity is 1.
Used at ~5V/H/V. In addition, this catalyst is used for the selective hydrogenation of coexisting conjugated diolefins without causing much aromatic nuclear hydrogenation, but sufficient measures have been taken to control the reaction temperature, and further improvements have been made in its usage. There are some suggestions as follows. First, it is well known to selectively hydrogenate conjugated diolefins and styrene in pyrolyzed gasoline (Japanese Patent Publication No. 30601/1983). In this method, a hydrogenation reactor type is proposed in which the reaction temperature can be adjusted within a narrow temperature range that is optimal for selective hydrogenation. That is, using a noble metal catalyst in the liquid phase and operating at a temperature of about 49-204° C. and a pressure of 14-70 Kg/cm ² g, depending on the sulfur content and hydrogen purity (i.e. methane content) in the feedstock. The new feedstock for the reactor is mixed directly with the recycled hydrogen treated gasoline from the bottom of the reactor and then fed into the reactor from the top, flowing along with the hydrogen. However, as a practical problem, when the content of conjugated diolefins and olefins is high, the calorific value is large and hydrogenation of a considerable amount of monoolefins occurs, leading to a sharp decrease in the RON of the hydrogenated gasoline. On the other hand, in order to control the reaction heat generated by the reaction, even if hydrogenated gasoline is recycled in large quantities and used, the selectivity is poor and a considerable amount of aliphatic olefins are hydrogenated, causing hydrogenation of only conjugated diolefins and styrenes. has its drawbacks. Next, it is well known that the selectivity of conjugated diolefins can be improved by coexisting a sulfur compound (H ₂ S, CS ₂ ) in a reaction system using a palladium-based catalyst. (U.S. Patent No. 3,309,307). This method does not use a pre-sulfided catalyst and therefore does not produce superior cracked gasoline. Next, it is well known to selectively hydrogenate diolefin hydrocarbons and monoolefin hydrocarbons in cracked gasoline using a catalyst containing palladium as a main component and chromium, copper, etc. as auxiliary components. Publication No. 42-7254). However, this publication states that palladium-based catalysts deteriorate due to sulfur.
Furthermore, a presulfurized catalyst is not used. In fact, when a catalyst that does not undergo pre-sulfurization as used in the present invention is used, it is not possible to obtain gasoline with a sufficiently high octane number, as shown in the comparative examples described later. The present inventors conducted intensive research to develop a method for selectively hydrogenating diolefin hydrocarbons and styrenes for the purpose of producing automobile gasoline with good stability. We have discovered that by hydrogenating pyrolyzed gasoline using a palladium-based catalyst, conjugated diolefins and styrenes in pyrolyzed gasoline can be selectively hydrogenated, and sulfur compounds in pyrolyzed gasoline can also be desulfurized. . That is, the present invention provides a selective hydrogenation method for pyrolysis gasoline with a total pore volume of 0.4 to 1.0 cc/g, B.
A palladium-based catalyst with an ET surface area of 50 to 200 m ² /g was heated in advance with hydrogen gas containing hydrogen sulfide (hydrogen sulfide,
The sulfur content in the catalyst is reduced by presulfiding using naphtha (30 to 100 wtppm as sulfur) to which at least one sulfur-containing compound selected from carbon disulfide, mercaptans, and sulfides has been added. 0.1~1.0wt% of active metals
Using a sulfur catalyst with a CO chemisorption amount of 20 to 80 c.c./gPd, pyrolyzed gasoline was heated to 50 to 50% hydrogen sulfide at a temperature of 70 to 150°C and a pressure of 10 to 80 Kg/ ^cm2.
A method for hydrogenating pyrolyzed gasoline, which is characterized by hydrogenating with hydrogen added at 500 molppm to selectively hydrogenate conjugated diolefins and alkenyl aromatics in pyrolyzed gasoline to produce olefins and alkyl aromatics, respectively. be. The pyrolysis gasoline referred to in the present invention is a hydrocarbon with a carbon number of 4 or more, preferably 5 or more, and a boiling point of 220°C or less, which is produced as a by-product when petroleum is pyrolyzed and steam cracked to produce lower olefins. with a mixture,
Usually, the residue obtained by substantially removing from the cracked oil mixture those boiling points lower than C ₃ , preferably those boiling lower than C ₄ , and those boiling higher than 220° C. is used. The catalyst used in the present invention has palladium supported on alumina in an amount of 0.2 to 1.0 wt% as a main component, and has a total pore volume of 0.4 to 1.0 cc/g, preferably 0.5 to 0.8 cc/gB.
ET surface area is 50-200m ² /g, preferably 80-
150 m ² /g, and may contain 0.2 to 2 wt% of chromium, 0.1 to 2 wt% of copper, or 0.2 to 4 wt% of chromium-copper as auxiliary components in addition to palladium. Furthermore, before using the catalyst in the hydrogenation reaction, we used naphtha to which hydrogen sulfide, carbon disulfide, or sulfur-containing compounds (concentration 100 to 300 ppm) such as mercaptans and sulfides were added to the hydrogen stream, and the sulfurization temperature was 50. The sulfur content in the catalyst can be reduced from 0.1 to 0.1 by presulfiding at ~200°C for 4 to 10 hours.
1.0wt%, preferably 0.3-0.8wt% of active metal
CO chemisorption amount from 20 to 80 c.c./gPd, preferably 30
Adjust to ~60c.c./gPd. Examples of the mercaptans or sulfides used as the sulfur-containing compound for the above-mentioned presulfurization include alkyl mercaptans such as methyl mercaptan and ethyl mercaptan, and dialkyl sulfides such as dimethyl sulfide and diethyl sulfide. If the sulfur content in the catalyst is 0.1 wt% or less and the active metal CO chemisorption amount is 80 c.c./gPd or more, the hydrogenation reaction of aliphatic olefins will proceed and the RON will decrease. Further, if the sulfur content in the catalyst is 1.0 wt% or more and the active metal CO chemical adsorption amount is 20 c.c./gPd or less, the activity of the catalyst decreases and the hydrogenation of diolefins and alkenyl aromatics is suppressed. Measurement of CO chemisorption amount of the above active metals is available in Journal
of Catalysis 1, 85-92 (1962). That is,
The sample (catalyst) was reduced with hydrogen at 200℃, then vacuum degassed at 400℃, then cooled to room temperature, and then exposed to a predetermined amount of CO2.
to determine the amount of CO chemical adsorption. The selective hydrogenation reaction of the present invention uses a pre-sulfurization catalyst to process the pyrolyzed gasoline fraction at a reaction temperature of 50 to 150°C.
Preferably 60~130°C, and pressure 10~80Kg/ ^cm2 ,
Preferably 50-500 molppm of hydrogen sulfide in a hydrogen stream under conditions of 20-60 Kg/ ^cm2 , preferably 100-500 molppm
It is preferable to carry out the reaction by adding 350 mol ppm, with a feedstock oil supply rate (per catalyst) of 0.5 to 5.0 V/H/V, and a hydrogen/stock oil ratio of 50 to 500 l/l. The reaction temperature is preferably controlled to the above temperature at the inlet of the reactor. The hydrogenation treatment is carried out under such reaction conditions to selectively hydrogenate conjugated diolefins and styrenes, and at this time, preferably desulfurizes at least 3% or more, especially 5% or more of the sulfur compounds in the pyrolyzed gasoline, and desulfurizes the olefins, respectively. and alkylaromatics. According to the present invention, the advantages of hydrotreating pyrolyzed gasoline are that conjugated diolefins and styrenes are selectively hydrogenated by hydrogenating pyrolyzed gasoline, and the RON of the hydrogenated gasoline hardly decreases; It can be used for manufacturing or blending automobile gasoline with excellent oxidation stability. In addition, the amount of polymer by-products produced by the hydrogenation process is extremely small, reducing catalyst contamination, making it possible to withstand long-term use and significantly reducing the gum quality of hydrogenated gasoline. Furthermore, since it has almost no hydrogenation ability for aliphatic olefins, the amount of hydrogen chemically consumed is small, and the reaction temperature can be easily controlled. On the other hand, it contains a high concentration of diolefin (DV50
degree) When pyrolyzed gasoline is hydrogenated, it is possible to partially recycle the hydrogenated gasoline for the purpose of controlling the reaction temperature and operate without diluting the diolefin. Therefore, it can be said that this process is quite favorable in terms of energy saving. The present invention will be explained in more detail below with reference to Examples. Examples 1 and 2 In this example, a nichrome wire heater was wrapped around the outside of a stainless steel reaction tube with an inner diameter of 2.5 cm and a length of 150 cm, and a carborundum filling was placed at the top and bottom of the reaction tube. 0.3wt into the liquid phase hydrogenation equipment which was filled and the raw material was sufficiently preheated.
A catalyst with a total pore volume of 0.6 cc/g and a surface area of 120 m ² /g obtained by impregnating alumina with % palladium.
Fill the tank with 100 c.c., raise the temperature while flowing electrolytic hydrogen, and maintain it at 100°C. Next, for hydrogen gas
Add hydrogen sulfide to 200molppm,
Hold at ℃ for 4 hours, and finally raise the temperature to 150℃ for 2 hours.
The reaction was continued and pre-sulfurization treatment was performed. The sulfur content of this presulfurized catalyst was 0.16 wt%, and the amount of CO chemically adsorbed by the active metal was 30 c.c./gPd. Next, under the reaction conditions shown in the table, the specific gravity is 0.845, and the boiling point range is 40.
~180℃, RON (lead free) 101, real gum 20mg/100
cc, conjugated diene content 9.8wt%, monoolefin content 15.7wt%, induction period 0.85hr, total sulfur content
Crude pyrolyzed gasoline obtained by pyrolysis of straight-run naphtha from Arabian light oil, which has an extremely low grade of 0.02 wt%, is preheated with hydrogen mixed with 200 to 300 ppm of hydrogen sulfide and passed over the above catalyst. The reaction was carried out. Note that the catalyst activity experiment was conducted for about one week. As a result, as shown in the table, pre-sulfurization treatment was performed, and during the reaction, hydrogen sulfide was added to
When the reaction was carried out in the coexistence of 300 ppm, the reaction between the conjugated diolefin and styrene proceeded extremely smoothly, while hydrogenation of the aliphatic olefin was suppressed. The obtained hydrogenated gasoline had a high RON of 101, and also had a good induction period of 7 hours or more. Comparative Example 1 A comparative experiment was conducted using the apparatus and raw materials described in Examples 1 and 2, and a catalyst that was not presulfurized, under the reaction conditions shown in the table. As a result, as shown in the table, when the catalyst is used without sulfidation, even if 250 ppm of hydrogen sulfide coexists in the hydrogen gas during the reaction, hydrogenation of aliphatic olefins occurs simultaneously, resulting in hydrogenation. of gasoline
RON dropped to 93-96. Comparative Example 2 A comparative experiment was conducted using the apparatus, raw materials, and presulfurized catalyst described in Examples 1 and 2 under the reaction conditions shown in the table without adding hydrogen sulfide to the hydrogen gas. As a result, hydrogenation of aliphatic olefins occurred, and the RON of hydrogenated gasoline decreased to about 90-93. Comparative Example 3 A comparative experiment was conducted using the apparatus, raw materials, and presulfurized catalyst described in Examples 1 and 2, adding hydrogen sulfide to hydrogen gas, and under the reaction conditions shown in the table. Despite presulfidation and the coexistence of hydrogen sulfide in hydrogen, hydrogenation of aliphatic olefins occurs at a high temperature of 170°C, and the RON of hydrogenated gasoline decreases.
It dropped to around 90.

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Claims (1)

[Claims] 1 In the selective hydrogenation method of pyrolysis gasoline,
Total pore volume 0.4~1.0cc/g, BET surface area 50~
200 m ² /g of palladium-based catalyst was added to hydrogen gas containing hydrogen sulfide (100 to 300 molppm hydrogen sulfide) or naphtha (as sulfur) to which at least one sulfur compound selected from carbon disulfide, mercaptans, and sulfides was added. 30~100wtppm) to pre-sulfurize the sulfur content in the catalyst from 0.1~
1.0wt%, active metal CO chemisorption amount 20~80c.c./
Using a sulfurized catalyst called gPd, pyrolysis gasoline is hydrogenated with hydrogen containing 50 to 500 molppm hydrogen sulfide at a temperature of 70 to 150℃ and a pressure of 10 to 80Kg/cm ² to select conjugated diolefins and alkenyl aromatics in pyrolysis gasoline. 1. A method for hydrogenating pyrolysis gasoline, the method comprising hydrogenating pyrolysis gasoline to produce olefins and alkyl aromatics, respectively.