JPH04348187A - Method for stabilizing gas oil produced by catalytic cracking, produced gas oil, and composition containing the stabilized gas oil - Google Patents

Abstract

PURPOSE: To improve the oxidation stability of gas oil generated by catalytic decomposition.

CONSTITUTION: Oxidized or non-oxidized gas oil obtained at a time of catalytic decomposition is subjected to liquid-liquid extraction by using a mixture of alcohol and water and, succeedingly, the gas oil and alcohol extract is separated to remove only an aromatic component having high polarity causing unstability.

COPYRIGHT: (C)1992,JPO

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION The present invention relates to a method for stabilizing gas oil obtained by catalytic cracking.

0002

BACKGROUND OF THE INVENTION Refining technology has undergone rapid development in recent years with the proliferation of catalytic crackers and viscosity control equipment. Heavy distillate from refineries cannot be used as is and is subjected to catalytic cracking treatment on a fluidized bed. This process allows the recovery of a gas liquefied petroleum (GPL) fraction, a main fraction of gasoline, and a middle distillate corresponding to the gas oil cut (coupe gazole). Such gas oil cut obtained by catalytic cracking is generally called LCO from the English name "light cycle oil". For convenience, the abbreviation LCO is used below.

Generally, LCO has a lower distillation temperature range and less viscosity than directly distilled gas oil. Due to the high aromatic content, the density is also relatively high.

Based on the sulfur content, LOC is LCO-
It is divided into BTS, ie, low sulfur type, and LCO-HTS, ie, high sulfur type. Products with a sulfur content of 1% or less usually belong to LCO-BTS.

Traditionally, LCO has been used to dilute distillation residues to prepare heavy fuel oils and adjust their viscosity to specified values. In France, the above viscosity is No. 2 fuel oil, it is specified to be 4 x 10-6 m2/s or less at 100°C.

Current emphasis is on improving catalytic cracking performance, particularly increasing the amount of processed heavy distillate and limiting the use of heavy fuel oils. Therefore, when LCO-HTS is commonly used as a diluent or solvent for heavy fuel oil, it is placed in the category of gas oil.

[0007] Gas oil has two main fields of use, one of which is for thermal use as a domestic fuel for boilers, and the other as a fuel for diesel engines. This fuel is sold under the name automotive gas oil in this case.

[0008]

[Problems to be Solved by the Invention] When gas oil is used as a fuel, it must meet required standards to ensure satisfactory ignition and combustion in the engine. For this purpose, the cetane number of diesel fuel needs to be at least 48, and since the cetane number of LCO is too low, a large amount of LCO cannot be introduced into automobile gas oil.

[0009] LCO is therefore primarily incorporated into household fuel compositions whose use is limited only by sulfur content.

On the other hand, as in the case of gas oil, when LCO is added to household fuels, the stability of the fuel substance is impaired, causing a major problem. Fact, L
It is known that the CO cut fraction exhibits reactivity. Due to the oxidation reaction that occurs during storage, it forms a rubbery substance,
It may also appear pale yellow, dark brown, or even black.

The produced rubber may begin to precipitate and partially precipitate and is called insoluble rubber, or may accumulate on the walls of the storage structure and is called adhered rubber. Both of these forms of rubber are collectively referred to as total rubber.

The exact nature of the expandable compounds that induce coloration and gummy formation is unknown. However, at least some of the obvious problems are that indene, phenalene (phe
the presence of fused cyclic aromatic compounds such as nalene, or azulene. Fused rings include indole, isoindazole, benzoxazole, carbazole, anthranyl, and the like. In particular, compounds containing heteroatoms are easily oxidized and cause instability of LCO.

[0013] Rubbery precipitation is promoted by mixing LCO and gas oil. Since LCO has strong aromatic properties, it can be solubilized even when the aromatic heterocycle is oxidized. On the other hand, when LCO is mixed with a paraffin cut such as gas oil, strongly colored compounds that are insoluble in alkanes precipitate out.

[0014]LCO is treated by hydrogen treatment (hydrotrain).
tment). This method requires a large amount of hydrogen as the hydrogen processing capacity increases, and this is expected to be a problem for some refineries.

[0015] Furthermore, the stability of LCO can be increased by using an antioxidant.

Generally, a non-aromatic secondary or tertiary amine mixture is used which is combined with a metal deactivator such as N,N'-disalicylidenepropane-1,2-diamine, and/or a non-aromatic secondary or tertiary amine mixture. Alternatively, a dispersant such as polyacrylate or polymethacrylate is often combined. Commercial additives that can be used include FOA 3, 11, and 310
(manufactured by DuPont), KEROPON 5257 (BA
(manufactured by SF Corporation), and HITEC 4235 (manufactured by Esil Corporation).

Additives slow, but do not prevent, rubber formation and precipitation. Furthermore, it has virtually no effect on coloring.

[0018]

[Means for solving the problem] Therefore, the present inventors
We have discovered a method for stabilizing gas oil obtained by catalytic cracking. The gas oil treated according to the invention has a strong oxidation resistance, which is evidenced by the reduction in the degree of deposits and color development. This treated gas oil has no nauseating odor. This gas oil usually becomes more stable when mixed with paraffin cuts. The treatment of LCO has a positive effect on the quality of blends such as automotive gas oil and household fuel oil. This mixture has a constant cetane number and exhibits excellent combustion characteristics in the best diesel engines.

In the absence of impurities, the action of the additive during low-temperature operation is improved, the life of the diesel filter is increased, and the tendency to rubberize the injectors is reduced.

The stability of the LCO treated according to the invention is further improved by customary additives. The treatment according to the invention makes the LCO more sensitive to the action of antioxidants and stabilizers, reducing the formation of precipitates and at the same time improving the color. LCO not treated according to the invention
It was found that the additives had no effect on the color development.

The method of the invention can also be used to treat oxidized gas oils, which result, for example, in long-term storage. Oxidized gas oil restores its original appearance and quality.

The method according to the invention for stabilizing gas oil obtained during oxidized or unoxidized catalytic cracking involves liquid-liquid extraction of said gas oil using a mixture of alcohol and water, followed by a combination of gas oil and alcohol. including separating the extract from the extract.

The aromaticity of the gas oil produced during catalytic cracking is extremely high, and complete extraction of all aromatic components by pure alcohol is probably not an economically viable process.

The solvent action of alcohol can be suppressed by the presence of water. Therefore, the water content is adjusted to extract only highly polar aromatic components that cause instability, and to prevent loss of aromatic components that do not contribute to instability.

The alcohols used are usually linear or branched aliphatic C1-C6 alcohols. The use of methanol appears to be advantageous.

The alcohol-water mixture contains 1 of the gas oil.
5 to 35% by weight, preferably 20 to 30% by weight.

The water content in the alcohol varies depending on the composition of the gas oil to be treated. Generally, the water content in the alcohol-water mixture is between 1 and 10% by weight, preferably 3% by weight.
7% by weight.

Processing efficiency can be increased by using an aqueous soda solution instead of water. The soda content in this aqueous solution is 10 to 30% by weight, preferably 15% by weight.
25% by weight.

If the content of sulfur products in the mixture is very high, ie corresponding to LCO-HTS, the extraction according to the invention can be carried out by meroxage.
Alternatively, it may be combined with hydrogen treatment. In this case, the hydrogen treatment can be performed relatively gently at a lower hydrogen pressure than in the hydrogen treatment of a material that has not been previously subjected to an extraction treatment. The relatively low hydrogen pressure reduces catalyst coking while increasing catalyst life. It goes without saying that hydrogen consumption can also be reduced.

The extraction is carried out continuously or discontinuously, using extraction apparatuses operating in co-current or counter-current mode.

Various techniques can be used, such as plate columns, packed columns, or extractors, which utilize thin film liquid-liquid exchange principles.

When selecting an extraction device, operating conditions include temperature, pressure, extraction time, and amount of solvent.

To avoid heat loss, the LCO is normally used at the exit temperature of the cracker. Other conditions are adjusted according to predetermined specifications.

The efficiency of the extraction device should correspond to at least about 10 theoretical stages.

After extraction, the mixture is sent to a slurry tank 2
Separate into phases. The floating phase consists of alcoholic extracts of polar aromatic compounds that cause instability. This phase also contains water or soda solution. The decantation phase consists of stabilized LCO containing traces of methanol.

The floating phase is sent to a "flash" distillation column to remove methanol, followed by separation of the water or soda solution by a decantation operation. After a decantation operation followed by washing, the aromatic extract is added to the heavy fuel oil. If an aqueous soda solution is used in the extraction operation, the aqueous soda solution is sent to one column to remove volatile substances. The aqueous soda solution recovered from the bottom of this column is replenished with fresh soda and recycled into the process.

The decantation phase consisting of LCO is washed to remove traces of methanol and the stabilized LCO is recovered after decantation. Cleaning water is "flush"
Distill to recover methanol. All methanol recovered during the process can be recycled.

The ratio of stabilized LCO to extracted aromatics varies depending on the composition of the LCO undergoing treatment. Generally, the amount of aromatics removed will vary from 3 to 5% by weight. The proportion of LCO stabilized is therefore between 95 and 97% by weight.

The LCO stabilized according to the invention is added to the gas oil by direct distillation. The composition comprises a major proportion of direct distillation gas oil and 10 to 30% by weight, preferably 15 to 25% by weight, of gas oil produced by catalytic cracking and stabilized according to the invention.

The composition exhibits excellent oxidative stability on storage.

However, if the stability of the composition is insufficient, conventional antioxidants may be used. According to a preferred feature of the invention, the composition is highly amenable to additives.

As mentioned above, additives have little effect on preventing coloring of LCO-containing compositions.

Comparing the degree of coloring and the amount of rubber produced after the oxidation promotion treatment, it was found that the composition according to the present invention has higher stability and superior antioxidant effect than the composition obtained from untreated LCO. I know that there is.

[0044] In general, a very small amount of antioxidant, such as 0.0001 to 1% by weight, preferably 0.001 to 0.02% by weight, exhibits a sufficient effect.

Examples of the present invention are shown below, but the present invention is not limited thereto. Unless otherwise indicated, the proportions used are expressed in % by weight.

[0046]

[Example] Table 1 shows the characteristics of LCO before treatment, classified again.

Table 1

Distillation temperature range

197-352℃ sulfur (%)
0.5
7 Total nitrogen (ppm)
650 basic nitrogen (ppm)
65
.

800 g of LCO and 200 g of solvent were introduced into the extractor. Solvent composition: 97% methanol and 5%
It was a 3% N soda solution.

The extractor was a thin film liquid-liquid exchange type device with a rotating cone. This was used in batch mode.

[0050] The temperature inside the extractor was 20°C, and the residence time was 1 minute.

After extraction, the mixture was sent to a decanter where it was separated into two phases.

The floating phase was separated and methanol was recovered after flash distillation. The extracted aromatic compounds were separated from the soda aqueous solution by decantation. After washing with water, 30 g of aromatic compound was recovered by decantation separation.

The decantation phase was washed with water to recover a trace amount of methanol. 768g LC after decantation
O was collected.

Table 2 summarizes the contents of basic nitrogen (NB), total nitrogen (NT), and sulfur in LCO before and after extraction, and the contents of each of the above components in the aromatic extract.

[0055] The coloring state was compared by hue level based on the ASTM-D-1500 standard.

Table 2


NB (ppm)
NT (PPM) S (%) Hue
LCO (before treatment) 65
650 0.57 Orange yellow LCO
(After processing) 2 450
0.55 Yellow extract
>900 1400
- Dark maroon.

[0057] NT and NB, which are factors of instability, show high values in the extract.

Here, gas oil by direct distillation (GO
) and 30% untreated LCO or 30% LCO treated according to the invention. These compositions were subjected to accelerated aging tests to test their stability. This test followed the method of ASTM D-2274. First, take 350 ml of sample into a glass tube and add 3 liters of pure oxygen.
Oxidation was carried out for 2 hours at a temperature of 120° C. while feeding at a rate of /hour. Oxygen was bubbled into the sample. The glass tube was then cooled to room temperature and exposed to 800 nm (8×
10-7 m) and a diameter of 4.7 cm. When washed with pentane, dried, and weighed, an insoluble rubber substance of about several mg/100 ml was produced from the sample.

The pentane-washed tube was washed with three kinds of solvents (1/3 each of toluene, acetone, and methanol) in order to dissolve the rubbery substance adhering to the tube. After evaporating the three solvents in an analytical furnace, the residual product was weighed. This amount corresponds to the amount of adhered rubber per 350 ml of gas oil. Add this value to 100m of gas oil.
Calculated per liter. The sum of the insoluble rubber and adherent rubber is called latent rubber or total rubber.

Similarly, the effect of antioxidants on the compositions was also measured.

The antioxidant used in the experiment was an additive auxiliary agent (FOA-3 manufactured by DuPont) consisting of a non-aromatic amine.
A mixture of 4 ppm and 4 ppm of a metal deactivator (DMD manufactured by DuPont) was used.

Table 3 summarizes the effect of the accelerated aging test on LCO and a comparison of compositions containing LCO treated according to the invention and without LCO.

Table 3


Before aging After aging Whole rubber

hue hue
mg/100ml


Untreated LCO
2.5 7.0 0
．． 1730% untreated LCO 2
．． 5 6.5 13.8
70% GO 30% untreated LCO 2.5
5 3.087
0% GO LCO treated with antioxidant 2.5
4.5 0.1230
% treated LCO 2.5
3.5 0.3770% GO 30% treated LCO 2.5
3 0.0970%
GO Antioxidant addition

.

Table 3 shows the LCs treated according to the present invention.
It is shown that an excellent antioxidant effect is observed only in mixtures of directly distilled gas oil with O and LCO treated according to the invention.

Claims (11)

[Claims] 1. A method for stabilizing gas oil produced during oxidized or unoxidized catalytic cracking, comprising extracting the gas oil to be treated with a mixture of alcohol and water and subsequently extracting the stabilized gas oil and the alcohol extract. A method comprising: separating the [Claim 2] Claim 1, wherein the alcohol is a linear or branched aliphatic C1-C6 alcohol.
the method of. 3. The method of claim 2, wherein the aliphatic alcohol is methanol. 4. The alcohol-water mixture comprises 15 to 35% by weight of the gas oil, preferably 20 to 30% by weight.
, any one of claims 1 to 3 characterized in that
Claimed Method. 5. Process according to claim 1, characterized in that the water content in the alcohol-water mixture is between 1 and 10% by weight, preferably between 3 and 7% by weight. . [Claim 6] 10 to 30% by weight of soda in water;
6. A method according to claim 1, characterized in that the content is preferably between 15 and 25% by weight. 7. Process according to claim 1, characterized in that the extraction operation is carried out in an extraction apparatus which is operated continuously or discontinuously, in co-current or counter-current mode. 8. Process according to claim 1, characterized in that the efficiency of the extraction device corresponds to at least about 10 theoretical stages. 9. Gas oil obtained by catalytic cracking, characterized in that it has been stabilized by the method according to any one of claims 1 to 8. 10. A composition according to claim 9, comprising a major proportion of gas oil obtained by direct distillation, from 10 to 30% by weight, preferably from 15 to 25% by weight. 11. The composition according to claim 10, characterized in that it contains 0.0001 to 1% by weight, preferably 0.001 to 0.02% by weight, of an additive exhibiting an antioxidant effect and/or a stabilizing effect. thing.