JPH0649873B2 - Light oil desulfurization method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a product gas oil that is used as a diesel fuel by desulfurizing a raw gas oil, and efficiently produces a desulfurized gas oil having a low sulfur content. Desulfurization method.

"Prior art" Desulfurization of light petroleum fractions such as naphtha and gasoline among petroleum fractions has made great progress so far and has reached a high level.

On the other hand, with regard to heavy petroleum fractions, further reduction of sulfur is being promoted as the momentum of global environmental protection increases. Particularly in recent years, sulfur oxides contained in exhaust gas emitted from diesel vehicles have been taken up as one of the causes of so-called "acid rain", and in order to reduce this, further reduction of sulfur in diesel fuel oil is required. Differentiation is being considered.

The raw gas oil used for diesel fuel is a so-called straight-run gas oil obtained by atmospheric fractionation of crude oil, and has a boiling point of about 200.
˜370 ° C. cut.

Conventionally, as a common method for naphtha, kerosene, and light oil, desulfurization of the light oil fraction obtained by the atmospheric fractionation is carried out by mixing the feed gas oil 1 with makeup hydrogen and circulating hydrogen as shown in FIG. After preheating in a heat exchanger and a heating furnace, a hydrodesulfurization reaction is performed in the reactor 2. A catalyst that causes a hydrodesulfurization reaction is housed in the reactor 2. As the catalyst, an alumina or silica-alumina carrier holding a metal sulfide is used, and the metal sulfide is C
It is a combination of o-Mo, Ni-Mo or Co-Ni-Mo. The reaction product oil leaving the reactor 2 is cooled by a heat exchanger and then gas-liquid separated in a high pressure separation tank. After re-flushing the liquid content in the low pressure separation tank to separate the gas,
H ₂ S and light hydrocarbons remaining in the stripper are removed and the product light oil is obtained by withdrawing from the bottom of the column. As a method of stripping, in addition to a method of using a heating furnace reboiler, a method of combining steam stripping and a reduced pressure dehydration tower has been generalized.

"Problems to be solved by the invention" However, the sulfur concentration in the product gas oil obtained by the conventional method is often 0.15 to 0.2 wt%. Furthermore, the sulfur concentration of commercial gas oil is about 0.4 wt% in actual value.

The sulfur concentration in light oil is 0.1 wt% or less, preferably 0.0
In order to reduce the amount to 5 wt% or less, it is necessary to make the reaction conditions severe, such as increasing the reaction temperature of the desulfurization reaction and lengthening the reaction time. As a result, the product light oil coloring,
There are inconveniences such as shortening the catalyst life and increasing the amount of catalyst used. In addition to this, there is no specific operating method for how to reduce the sulfur concentration by using the existing gas oil desulfurization facility.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for efficiently producing a product gas oil having a sulfur concentration of 0.05 wt% or less.

"Means for Solving the Problem" The present invention divides a raw material gas oil into a plurality of fractions, performs desulfurization treatment or desulfurization treatment and hue stabilization treatment for each fraction, and thereafter, The above problem was solved by mixing the distillates.

In addition, the raw gas oil is fractionated at a cut temperature set in the range of 270 ° C to 330 ° C, and divided into a low boiling fraction having a boiling point lower than the above cutting temperature and a high boiling fraction having a boiling point higher than the above cutting temperature. It is desirable that the low-boiling fraction is desulfurized, the high-boiling fraction is desulfurized, and then a hue stabilizing treatment is carried out, if necessary, and then both treated oils are mixed.

Furthermore, it is desirable that the hue stabilization treatment be a clay treatment or a hydrogenation treatment.

Hereinafter, the present invention will be described in detail.

One of the methods for reducing the sulfur concentration in light oil is to increase the treatment temperature of the desulfurization reaction. However, in this case, although the effect of removing sulfur is improved, destabilization of the hue occurs and coloring becomes easy. Measures such as increasing the reaction pressure are taken to suppress the occurrence of coloring to a low level. Further, by making LHSV (liquid space velocity) small, the sulfur concentration in light oil is made low.

It is possible to improve the desulfurization efficiency of the desulfurization operation as a whole by performing some appropriate pretreatment on the raw gas oil side while making improvements such as catalyst improvement on the side of such processing conditions. .

Desulfurization of feed gas oil is improved by tightening the treatment conditions, which means that various sulfur compounds, from easily decomposed sulfur compounds that are easily decomposed by hydrodesulfurization to relatively difficultly decomposed sulfur compounds, are used. It suggests that it contains sulfur compounds.

So after distilling crude gas oil (raw gas oil) and fractional distillation at each temperature,
Hydrodesulfurization was carried out for each fraction under certain conditions, and the difficulty of desulfurization of each fraction was investigated. As a result, it was confirmed that the desulfurization effect of the fraction on the high boiling point side was low and the sulfur compound contained therein was difficult to hydrocrack. Ie 310
When the temperature near ℃ is used as a boundary and it is divided into a fraction having a higher boiling point and a fraction having a lower boiling point than that, the refractory sulfur compound is concentrated in a fraction having a higher boiling point.

The present invention divides the raw gas oil into a plurality of fractions, performs desulfurization treatment or desulfurization treatment and hue stabilization treatment according to the desulfurization difficulty of each fraction, and then mixes each fraction. Is a method for producing a product gas oil having an extremely low sulfur concentration.

Next, an example of the method of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram for explaining an example of the method of the present invention. In the figure, reference numeral 10 is a distiller for distilling the raw gas oil 1 at atmospheric pressure, 11 and 12 are desulfurization reactors, and 13 is a hue. It is a stabilizing device.

In the desulfurization treatment of light oil according to this example, first, the light oil feedstock 1 having a boiling point range of about 200 to 370 ° C. obtained by atmospheric distillation of petroleum is supplied to the distiller 10 and distilled at a predetermined cut temperature to obtain the cut temperature. It fractionates into a fraction on the higher boiling point side (referred to as a high boiling point fraction) and a fraction on the lower boiling point side (referred to as a lower boiling point fraction).

In this example, the feed gas oil 1 is fractionated into the above-mentioned two fractions (high-boiling fraction and low-boiling fraction), and the cutting temperature in this case is set in the range of 270 ° C to 330 ° C. And particularly preferably set to a temperature around 300 to 320 ° C.

If this cutting temperature is lower than 270 ° C., the amount of low-boiling fractions is small and the amount of high-boiling fractions is large, and after the respective desulfurization treatments are appropriately desulfurized, the splitting effect when mixing the two components is sufficient. You won't get it. Meanwhile, the cut temperature is 330 ° C
With the above, as the low-boiling fraction increases, the refractory sulfur compound migrates to the low-boiling fraction side, and it becomes necessary to tighten the conditions for the desulfurization treatment of the low-boiling fraction, and the desulfurization efficiency cannot be improved. .

By setting the cutting temperature in the range of 270 ° C to 330 ° C, particularly preferably in the vicinity of 300 to 320 ° C,
The raw gas oil 1 can be fractionated into a high boiling fraction 14 rich in hardly decomposed sulfur compounds (such as dibenzylthiophenes) and a low boiling fraction 15 containing easily decomposed sulfur compounds (such as benzylthiophenes).

The high-boiling fraction 14 and the low-boiling fraction 15 are sent to desulfurization reactors 11 and 12, respectively, and mixed with hydrogen for hydrodesulfurization treatment.
(Hereinafter referred to as desulfurization treatment). This desulfurization treatment may be set so that the sulfur concentration of the oil after desulfurization treatment of both fractions becomes the target sulfur concentration of the product gas oil, or even if one sulfur concentration is equal to or higher than the target sulfur concentration. By making the other sulfur concentration extremely low, it is possible to set the sulfur concentration of the oil in which both fractions are mixed so as to meet the target value.

In the desulfurization process of high boiling fractions rich in persistent sulfur compounds such as dibenzylthiophenes, the reaction time is long, so the amount of catalyst used per treated oil is large, but on the other hand, easily decomposable sulfur compounds such as benzylthiophenes are used. The desulfurization treatment of the low boiling point fraction containing the is extremely high, and the amount of the catalyst used at that time is small. Therefore, as a whole, compared with the case of directly desulfurizing the raw gas oil 1 without fractionating, the catalyst The amount used can be reduced considerably.

As the desulfurization catalyst used in the desulfurization reactors 11 and 12, alumina or silica-alumina is used as a carrier, and Co-Mo system, Ni-Mo system or Co-N is used as the carrier.
For example, a material holding each i-Mo-based metal sulfide is used.

Of the oils 16 and 17 that have been desulfurized, the oil 16 on the high boiling point fraction side tends to have an unstable hue as a result of the desulfurization reaction.
Then, the color stabilization process is performed. For this hue stabilization treatment, oil 16 is applied to an adsorber filled with an adsorbent such as activated clay.
And a hydrogenation decolorization method in which hydrogen is mixed and the hydrogenation decolorization reaction is preferably carried out at a temperature of about 200 ° C.

Next, the oil 18 on the high boiling point fraction side that has undergone desulfurization and hue stabilization processing and the oil 17 on the low boiling point fraction side that has completed desulfurization processing are mixed and introduced into a high pressure separator (not shown). . The hydrogen-rich gas generated in this high-pressure separator is circulated and reused.
On the other hand, the liquid portion from the high pressure separator is cooled and then introduced into a low pressure separator (not shown) to separate hydrogen sulfide and other lower hydrocarbon gas. After this low-pressure separation, the product gas oil 19 is obtained as the liquid part.

There are no particular restrictions on the conditions and reaction mode of the desulfurization treatment, the hue stabilization treatment, or the final treatment of the mixed oil (in the above example, high-pressure separation is followed by low-pressure separation). Usual reaction conditions and reaction formats used in the desulfurization treatment can be adopted.

Hereinafter, the effects of the present invention will be further clarified by examples.

"Example" (Comparative example) A desulfurization treatment of a light oil feedstock was performed by a conventional method.

Crude gas oil (raw gas oil) having a sulfur concentration of 0.83 wt% was directly desulfurized as shown in FIG.

The desulfurization conditions were as follows: raw material flow rate: 100 m ³ / Hr (= 1500 BPSD) Reaction temperature: 340 ° C. Reaction pressure: 50 Kg / cm ² G catalyst: Alumina carrier / Co-Mo sulfide, target sulfur concentration of 0. The residence time and the amount of catalyst required to obtain 05 wt% product gas oil were determined. As a result, the residence time was 0.51 hr and the catalyst amount was 51.0 m ³ .

(Example) Using the same crude gas oil as in the above-mentioned comparative example, it was distilled at a cut temperature of 310 ° C to be divided into two fractions, a high-boiling fraction and a low-boiling fraction. The ratio of each fraction at this time is about 35 vo
1% and the low boiling fraction was about 65 vol%. The sulfur concentration of each of these fractions was 1.41 wt% for the high boiling fraction and 0.52 wt% for the low boiling fraction.

Next, these two fractions were desulfurized so that the sulfur concentration in the oil obtained by mixing the oil of each fraction after desulfurization was 0.05 wt%. The desulfurization conditions are as follows: [High boiling point fraction] Raw material flow rate …… 35 m ³ / Hr Reaction temperature …… 340 ° C. Reaction pressure …… 50 kg / cm ² G catalyst …… Alumina carrier / Co-Mo sulfide [Low boiling point fraction Minute] Raw material flow rate ... 65 m ³ / Hr Reaction temperature ... 340 ° C. Reaction pressure ... 50 Kg / cm ² G catalyst ... Alumina carrier / Co-Mo sulfide.

The sulfur concentration of each of these fractions after desulfurization treatment was appropriately set as shown in Table 1, and the residence time and total amount of each catalyst were determined.

The results are shown in Table 1.

From Table 1, the required catalyst amount when the sulfur concentration after desulfurization of the high-boiling fraction and the sulfur concentration after desulfurization of the low-boiling fraction were treated as the target sulfur concentration of 0.05% was 34.
A 2m ^3, it was possible to obtain a sulfur concentration 0.05 wt% of the product gas oil with much smaller amount of catalyst than the required amount of catalyst 51m ³ of the comparative example described above.

Furthermore, the condition (minimum point) where the amount of catalyst used is the smallest is that the sulfur concentration after desulfurization of the high boiling fraction is 0.1 w
t%, and the sulfur concentration after desulfurization of the low boiling fraction is about 0.023
It was when it was wt%.

Next, the cutting temperature is 270 ° C, 290 ° C, 310 ° C, 3
The feed gas oil was fractionally distilled at 30 ° C. and 350 ° C. and divided into two fractions, a high-boiling fraction and a low-boiling fraction, and the sulfur concentration and fraction yield of each fraction were investigated. Also desulfurized 2
When the two fractions were mixed, the sulfur content was 0.
The treatment conditions of each fraction to obtain the amount of 05 wt%, the sulfur concentration of the treated oil, and the required catalyst amount were determined. The results are shown in Table 2.

As is clear from Table 2, when the feed gas oil is divided into two fractions, a high-boiling fraction and a low-boiling fraction, if the cut temperature is set to 330 ° C. or lower, the effect of reducing the amount of the required catalyst is reduced. It became higher, and was particularly good when the cutting temperature was 310 ° C.

"Effects of the Invention" As described above, the present invention is to fractionate raw gas oil and divide it into a plurality of fractions. By carrying out the treatment and then mixing the respective fractions, it is possible to efficiently produce a stable product gas oil having a hue with an extremely low sulfur concentration.

Also, by performing desulfurization treatment or desulfurization treatment and hue stabilization treatment according to the desulfurization difficulty of each fraction, the amount of catalyst used as a whole can be reduced as compared to the case of directly desulfurizing raw gas oil. .

Furthermore, by dividing the raw gas oil into a part where the desulfurization conditions are severe and a part where desulfurization is easy, and by performing desulfurization treatment according to the degree of difficulty of desulfurization of each fraction, the occurrence of unstable factors of hue is reduced. can do.

[Brief description of drawings]

FIG. 1 is a flow sheet for explaining an example of the gas oil desulfurization method of the present invention, and FIG. 2 is a flow sheet showing a conventional gas oil desulfurization method. 1 ... Raw gas oil, 10 ... Distiller, 11, 12 ... Desulfurization reactor, 13 ... Hue stabilization treatment device, 14 ... High boiling fraction, 15 ... Low boiling fraction, 19 ... Product Light oil.

Claims (3)

[Claims] 1. A raw gas oil is fractionally fractionated into a plurality of fractions,
A desulfurization method for light oil, characterized by performing desulfurization treatment or desulfurization treatment and decolorization treatment on each fraction, and then mixing each fraction. 2. A raw gas oil is fractionally distilled at a cutting temperature set in the range of 270 ° C. to 330 ° C., a low boiling fraction having a boiling point lower than the above cutting temperature and a high boiling fraction having a boiling point higher than the above cutting temperature. A desulfurization method for light oil, characterized in that the low-boiling fraction is desulfurized, and the high-boiling fraction is desulfurized, followed by a hue stabilization treatment, and then both treated oils are mixed. . 3. The desulfurization method of gas oil according to claim 2, wherein the hue stabilization treatment is a clay treatment or a hydrogenation treatment.