JPH08333581A - Desulfurization of catalytically cracked gasoline - Google Patents

Abstract

PURPOSE: To prevent decline in catalytic activity due to coke deposition in conducting a hydrodesulfurization of catalytically cracked gasoline containing both sulfur compounds and olefin components, by scrubbing out a coke precursor as a byproduct during the reaction by using hydrocarbons in a liquid phase. CONSTITUTION: In conducting a hydrodesulfurization of catalytically cracked gasoline containing both sulfur compounds and olefin components, a coke precursor as a reaction byproduct subject to adherence to the catalyst is scrubbed out in a liquid phase by using hydrocarbons virtually free from olefin components and containing pref. >=80vol.% of paraffin components (esp. pref. rich in isoparaffins and/or naphthenes) to prevent decline in catalytic activity. It is preferable that the scrubbing operation is carried out by passing the hydrocarbons through the reaction unit while the reaction unit is standing packed with the catalyst; in this case, the catalytically cracked gasoline may be stopped passing through the reaction unit; or it may be passed simultaneously with the above-mentioned hydrocarbons along with carrying out the desulfurization.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for desulfurizing catalytically cracked gasoline. More specifically, when catalytically cracking gasoline containing a sulfur compound and an olefin component is hydrodesulfurized using a catalyst, the coke precursor adhering to the catalyst is washed and removed in a liquid phase using a hydrocarbon. However, the present invention relates to a desulfurization method for prolonging the life of the catalyst by preventing the activity of the catalyst from decreasing due to coke deposition.

[0002]

2. Description of the Related Art In the field of petroleum refining, there is catalytic cracking gasoline as a high octane gasoline material source containing a large amount of olefin components. This is a gasoline fraction obtained by catalytically cracking heavy petroleum fractions, for example, feedstock oil such as vacuum gas oil or atmospheric residual oil, and recovering and distilling catalytic cracking products. It is used as one of the sources.

However, the catalytically cracked feedstock oil originally has a relatively large content of sulfur compounds, and if this is directly subjected to catalytic cracking treatment, the content of sulfur compounds in the catalytically cracked product also increases. If this is used as a mixed source of automobile gasoline, environmental impact may become a problem. For this reason, the feedstock oil of the catalytic cracking apparatus is usually desulfurized in advance.

As the desulfurization treatment, a hydrodesulfurization treatment which has been conventionally carried out in the field of petroleum refining is generally used. This is an appropriate hydrogenation of a feed oil to be desulfurized in a high temperature and pressurized hydrogen atmosphere. The catalyst is brought into contact with the desulfurization treatment catalyst. In the case of hydrodesulfurization treatment of reduced pressure gas oil or atmospheric residual oil, which is a feedstock for catalytic cracking, the hydrodesulfurization catalyst is a group VIII or VI element such as chromium, molybdenum, tungsten, cobalt or nickel. A suitable substrate, for example one supported on alumina, is used. The conditions for the hydrodesulfurization treatment are generally temperatures of about 300 to 400.
℃, hydrogen partial pressure about 30-200 kg / cm2, liquid space velocity (L
HSV) about 0.1 to 10 1 / h is adopted.

However, in the case of hydrodesulfurization of heavy petroleum fractions such as vacuum gas oil and atmospheric residual oil, which are feedstocks for catalytic cracking, the processing conditions are high temperature and high pressure as described above, so There is a problem that the construction cost is high when a device is added in order to cope with a strict design condition and a lack of the device capacity. The catalytically cracked gasoline can be directly hydrodesulfurized, but in this case, the olefin component contained in the catalytically cracked gasoline is hydrogenated, and the octane number decreases as the content decreases. is there. Therefore, a desulfurization process is desirable while suppressing the olefin hydrogenation reaction as much as possible.

The catalyst used in the apparatus for hydrodesulfurizing catalytically cracked gasoline containing a sulfur compound and an olefin component is, like other desulfurization catalysts, a group VIII and group VI element,
For example, chromium, molybdenum, tungsten, cobalt,
An appropriate base material such as nickel supported on nickel is used. This catalyst is activated by pre-sulfurization, and the same method as the naphtha desulfurization catalyst can be used as the pre-sulfurization method. That is, a method is generally used in which naphtha is mixed with a sulfur compound such as dimethyl disulfide, heated to 150 to 350 ° C. with hydrogen, and then passed through a reaction tower filled with a catalyst. A sulfur compound such as dimethyl disulfide reacts with hydrogen on the surface of the active metal of the catalyst to be converted into hydrogen sulfide, and the hydrogen sulfide and the active metal further react to become a metal sulfide active in the desulfurization reaction.

[0007]

When hydrocracking catalytically cracked gasoline containing an olefin component, it is necessary to suppress the hydrogenation reaction of the olefin as much as possible, and thus the hydrogen partial pressure is usually about 5 to 30 kg / cm2. It is performed at low pressure. Therefore, the supply of hydrogen to the surface of the catalyst is suppressed, and it becomes difficult to suppress the polymerization reaction of the olefin that occurs at the Lewis acid points on the surface of the catalyst. The polymerization reaction of olefins is a sequential reaction and not only becomes heavy with a dimer and a trimer, but also dehydrogenates and cyclizes to an aromatic hydrocarbon, which eventually becomes a coke by dehydrogenative condensation. It grows and reduces the activity of the catalyst. As described above, a polymer such as an olefin dimer or trimer produced on the surface of the catalyst during the reaction or a dehydrogenated / cyclized aromatic hydrocarbon is a substance that causes coke formation, that is, coke. It becomes a precursor. Since the desulfurization reaction of catalytically cracked gasoline is usually carried out by a gas phase reaction, the produced coke precursor accumulates on the catalyst surface without being washed away from the catalyst surface by the liquid phase.

On the other hand, as compared with the desulfurization reaction of catalytically cracked gasoline, ordinary naphtha desulfurization targets straight-run gasoline containing almost no olefin component, so that the decrease in activity due to coke hardly poses a problem. When desulfurizing catalytic cracking light / gas oil, the content of olefin components in catalytic cracking light / gas oil is smaller than that in catalytic cracking gasoline, and for kerosene / light oil, it is better to hydrogenate olefins to paraffin. Excellent hydrogen partial pressure of 30
The desulfurization is performed under the condition that the olefin is hydrogenated by setting it as high as kg / cm2 or more. Therefore, the contact decomposition lamp
Also for desulfurization of light oil, the decrease in activity due to coke does not pose a problem. That is, the problem of catalyst deterioration is a problem peculiar to the desulfurization reaction of catalytically cracked gasoline containing an olefin component.

An object of the present invention is to suppress coke deposition on a catalyst and maintain a high desulfurization activity for a long period of time during hydrodesulfurization of a catalytically cracked gasoline containing a sulfur compound and an olefin component. It is to provide a desulfurization treatment method capable of

[0010]

The inventors of the present invention have conducted extensive studies in order to solve the above-mentioned problems, and as a result, catalytically cracked gasoline containing a sulfur compound and an olefin component was hydrodesulfurized using a catalyst. In this case, it is an epoch-making technology to prevent the catalyst activity from decreasing due to coke deposition by washing and removing the coke precursor, which is by-produced during the reaction and adheres to the catalyst, in the liquid phase using hydrocarbon. Came to invent the invention.

As described above, the coke deposition is caused by the dehydrogenative condensation of the coke precursor by-produced by the olefin polymerization reaction occurring at the Lewis acid points on the catalyst surface to grow into coke. . The hydrodesulfurization treatment of catalytically cracked gasoline is a gas phase reaction, and there is a problem that the produced coke precursor becomes coke without moving from the catalyst surface. The coke precursor is a stage before polycondensation proceeds and has a molecular weight of 300.
It is a low molecular weight compound of 0 or less. Therefore, the coke precursor has a characteristic of being easily dissolved in liquefied hydrocarbon, and can be removed from the catalyst surface by washing the catalyst with liquefied hydrocarbon.

When the catalyst is washed with a hydrocarbon to remove the coke precursor, the catalyst may be taken out of the reactor, washed, and charged again in the reactor. It is simpler to wash the coke precursor in the liquid phase by passing hydrocarbon through it while it is filled. While the reactor is filled with catalyst, hydrocarbons are passed through to wash the coke precursor in the liquid phase.
When removing, the oil passage system may be either a down flow or an up flow, but it can be determined in consideration of the shape of the device and the cleaning efficiency.

When a hydrocarbon is passed through while the reactor is filled with the catalyst, the catalytic cracking gasoline is stopped from passing through the coke.
It is also possible to carry out the washing / removing operation of the precursor of the liquefied carbon, and to wash / remove the coke precursor produced while carrying out the desulfurization reaction by passing oil through catalytic cracking gasoline and hydrocarbons at the same time. . When the oil passage of the catalytically cracked gasoline is stopped, the oil passage temperature can be arbitrarily set within the temperature condition range in which the hydrocarbon to be passed is in the liquid phase. That is, it is possible to use a high boiling point hydrocarbon to pass oil while keeping the temperature at the desulfurization reaction temperature, or to lower the temperature once and use a low boiling point hydrocarbon. It is desirable that the frequency of passing the cleaning hydrocarbon is determined at regular intervals in consideration of the degree of adhesion of the coke precursor. When the catalytically cracked gasoline and the hydrocarbon for cleaning are simultaneously passed, there is an advantage that the coke precursor can be efficiently cleaned and removed without interrupting the desulfurization reaction, but the catalytically cracked gasoline and the carbonized for cleaning are A distillation operation for separating hydrogen is required. The passage of the cleaning hydrocarbon may be carried out continuously or discontinuously and periodically.

As the cleaning hydrocarbon, those which dissolve the coke precursor well are preferable, and those containing a large amount of paraffin components, particularly isoparaffin and naphthene are desirable. A compound containing an aromatic compound can be used, but it becomes a coke precursor 2.
Those which do not contain aromatic rings or rings are preferred. Those containing a large amount of olefin components do not contain olefin components because they stop the desulfurization reaction and pass oil at low temperatures, but when oil is passed at temperatures of 200 ° C or higher, the olefin components polymerize. Hydrocarbons are preferred. The cleaning hydrocarbon that is passed through the oil at a temperature of 200 ° C. or higher does not substantially contain an olefin component, and the ratio of the paraffin component is 8
It is preferably 0% by volume or more.

As the catalyst used in the hydrodesulfurization apparatus to which the present invention can be applied, a hydrodesulfurization catalyst, which is a porous inorganic oxide carrier on which a desulfurization active metal is supported, and which is usually used in the field of petroleum refining, is used. You can Examples of the porous inorganic oxide carrier include alumina, silica, titania,
Magnesia and the like can be used, and these can be used alone or in the form of a mixture. Alumina and silica-alumina are preferably selected.

Examples of the desulfurization active metal include chromium, molybdenum, tungsten, cobalt and nickel, and these can be used alone or in the form of a mixture. Preferably, cobalt-molybdenum or nickel-cobalt-molybdenum is selected. These metals can be present on the support in the form of metals, oxides, sulfides, or mixtures thereof. As a method of supporting the active metal, an impregnation method,
A known method such as a coprecipitation method can be used.

The type of the reaction column may be any of a fixed bed, a fluidized bed and a boiling bed, but a fixed bed is particularly preferable. Contact between the catalytically cracked gasoline and the catalyst may be either up-flow or down-flow. These individual operations are known in the field of petroleum refining and can be arbitrarily selected and carried out. The desulfurization reaction condition is a temperature of about 200 to 350.
℃, hydrogen partial pressure about 5 to 50 kg / cm2, liquid hourly space velocity (LHS
V) about 1 to 10 1 / h, hydrogen / oil ratio about 200 to 3000 s
Can be set with cf / bbl.

[0018]

EXAMPLES The present invention will be described in more detail by way of examples. (Comparative example) In a fixed bed / downflow type small reactor,
4.5 wt% CoO and 15 wt% MoO on alumina carrier
Extruded commercial catalyst carrying 3 is crushed to 0.5-1
The particle size was adjusted to mm, and 2.7 g (4.0 ml) was charged. JIS1 containing 5% by weight of dimethyl disulfide
No. industrial gasoline 300 ℃, pressure 15 kg / cm2,
Pre-sulfurization was performed for 5 hours at LHSV21 / h and hydrogen / oil ratio of 500 scf / bbl. 80 obtained by catalytically cracking a feedstock oil containing atmospheric residual oil as catalytically cracked gasoline after completion of sulfidation
Catalytic cracking gasoline of 〜220 ℃ fraction (density 0.781 g
/ cm3 @ 15 ℃, sulfur content 248 ppm by weight, olefin content 3
A desulfurization reaction test was carried out using 1% by volume and a Lisa-thiooctane number of 87.0). The reaction conditions are temperature 250 ° C., hydrogen partial pressure 15 kg / cm 2, LHSV 7 1 / h, hydrogen / oil ratio 2000 scf.
/ bbl. The desulfurization rate was 77% 3 days after the start of the reaction,
The desulfurization rate was 68% 14 days after the start of the reaction.

Example 1 Using the same reactor and catalyst as in the comparative example, presulfiding was carried out in the same manner. When the desulfurization reaction was performed under the same conditions using the same catalytically cracked gasoline as in the comparative example, the desulfurization rate was 68% 15 days after the start of the reaction. After lowering the temperature to 100 ° C, stop the passage of catalytically cracked gasoline, and transfer straight-run gasoline of 60 to 100 ° C fraction to LHSV71.
Oil was passed for 6 hours at a hydrogen partial pressure of 15 kg / cm <2> / h. After that, catalytic cracking gasoline was passed again to raise the temperature to 250 ° C., and the desulfurization reaction was performed under the same conditions.
Recovered to%.

(Example 2) The same reaction apparatus and catalyst as in the comparative example were used and presulfiding was carried out in the same manner. Using the same catalytically cracked gasoline as in the comparative example, the desulfurization reaction was performed under the same conditions.
After reacting for 6.5 days, the oil feed of catalytically cracked gasoline was stopped, and the diesel oil fraction (250-330 ° C fraction obtained by hydrocracking vacuum diesel oil with the reactor temperature kept at 250 ° C). , Paraffin content 86% by volume, sulfur content 6 ppm) LH
Oil was passed for 12 hours at SV7 1 / h. After that, the passage of the hydrocracked gas oil fraction was stopped, and the desulfurization reaction of the catalytically cracked gasoline was further performed under the same conditions for 6.5 days. After that, the catalytic cracking gasoline was stopped again and the hydrocracked gas oil was passed at 250 ° C. for 12 hours. Then, when the catalytically cracked gasoline is passed through again (the total oil passing time from the start of the reaction is 14
The desulfurization rate of (day) was 75%.

(Example 3) The same reaction apparatus and catalyst as in the comparative example were used and presulfiding was carried out in the same manner. Using the same catalytically cracked gasoline as in Example 1, the desulfurization reaction was performed under the same conditions.
After reacting for 6.5 days, the oil flow rate of catalytically cracked gasoline is changed to L
The HSV was 3.5 1 / h, and in addition, the hydrocracked gas oil fraction used in Example 2 was passed at LHSV 3.5 1 / h for 12 hours. (It means that a 1: 1 volume mixture of catalytically cracked gasoline and hydrocracked gas oil fraction was passed at LHSV7 1 / hr.) After that, the passage of this hydrocracked gas oil was stopped and contact was continued for another 6.5 days. The cracked gasoline was desulfurized under the conditions of LHSV71 / h. After that, the desulfurization rate was 7 when the catalytically cracked gasoline was passed again (total oiling time 14 days from the start of the reaction).
It was 3%.

The catalyst used in Comparative Examples and Examples was taken out, dried under reduced pressure at 50 ° C. and 50 mmHg for 2 hours, and then the catalyst deposit (coke precursor) was quantified by Soxhlet / toluene extraction. Then, the coke deposited on the catalyst surface was analyzed. The results are shown in Table 1.

[0023]

[Table 1]

[0024]

EFFECTS OF THE INVENTION When a catalytic cracking gasoline containing a sulfur compound and an olefin component is hydrodesulfurized, a coke precursor that is by-produced during the reaction and adheres to the catalyst is used in a liquid phase by using hydrocarbon. By washing and removing, the reaction can be carried out while preventing the catalyst activity from decreasing due to coke deposition.

Front Page Continuation (72) Inventor Satoshi Hikida 4-10-6-305 Sumida-ku, Tokyo 4-10-6-305

Claims (5)

[Claims] 1. When a catalytic cracking gasoline containing a sulfur compound and an olefin component is hydrodesulfurized, a coke precursor that is by-produced during the reaction and adheres to the catalyst is used in a liquid phase by using a hydrocarbon. A method for desulfurizing catalytically cracked gasoline, characterized by carrying out a reaction while washing / removing and preventing a catalyst activity reduction due to coke deposition. 2. The method for desulfurizing catalytically cracked gasoline according to claim 1, wherein hydrocarbon is passed through while the catalyst is being charged in the reactor, and the catalyst is washed in a liquid phase. 3. The method for desulfurizing catalytically cracked gasoline according to claim 2, wherein when the coke precursor is washed / removed in a liquid phase using hydrocarbon, the passage of catalytically cracked gasoline is stopped. . 4. The coke precursor is washed and removed while a hydrocarbon that becomes a liquid phase under a desulfurization reaction condition is passed through together with catalytically cracked gasoline to carry out a desulfurization reaction. Method for desulfurization of catalytically cracked gasoline. 5. The coke precursor is washed and removed using a hydrocarbon which does not substantially contain an olefin component and has a paraffin component ratio of 80% by volume or more. 4. The method for desulfurizing catalytically cracked gasoline according to any one of 4 to 4.