Process for Producing Hydrorefined Gas Oil, Hydrorefined Gas Oil, and Gas Oil Composition

Abstract

A process of the present invention for producing a hydrotreated gas oil has a step for obtaining a product oil having a total aromatic content of 3% by volume or less by hydrogenating a hydrotreated oil including 95% by volume or more of fraction having a boiling point range of 150-380° C., a sulfur content of 2-15 ppm by mass, a total aromatic content of 10-25% by volume, and a naphthene of 20-60% by volume in the presence of a hydrogenation catalyst; and a step for obtaining, by hydrogenating the above-described product oil in the presence of a hydrogenation catalyst containing a crystalline molecular sieve component, a product oil satisfying the conditions that the content of petroleum fraction having a boiling point range of lower than 150° C. is 16% by volume or less, and the sum of the total aromatic content and the total naphthene content is 80% or less relative to the sum of these in the hydrotreated oil.

Description

TECHNICAL FIELD[0001]The present invention relates to a process for producing a hydrotreated gas oil, a hydrotreated gas oil, and a gas oil composition.BACKGROUND ART[0002]Diesel engines are expected to serve a function in the reduction of carbon-dioxide emissions as global warming prevention measures because of a high energy efficiency thereof. On the other hand, demands for cleaner diesel engine exhaust gas has been tightened increasingly, and it is one of major challenges to remove such harmful substances as fine particle contents referred to as “particulate matter” and NOx. Of these, in order to remove the particulate matter, the loading of an exhaust gas clean up system such as a particulate removing filter is going to be promoted increasingly.[0003]However, it is indicated that, when a gas oil containing a lot of sulfur content is used as fuel, the deterioration of such exhaust gas clean up systems become significant. Responding to this, for transportation trucks having long t...

AI Technical Summary

Benefits of technology

[0023]According to the present invention, it is possible to provide a process for producing such hydrotreated gas oil excellent in both environmental properties and combustion properties that has a sulfur content of 1 ppm by mass or less and a total aromatic content of 3% by volume or less, and that, further, has a high cetane number, with a sufficient efficiency and reliability without setting special operation conditions and equipment investment.BEST MODES FOR CARRYING OUT THE INVENTION

[0024]Hereinafter, preferred embodiments of the present invention are described in detail.

[0025]The process of the present invention for producing a hydrotreated gas oil is a process for producing a hydrotreated gas oil by carrying out the hydrotreating of a feed oil, wherein the process has a first step for obtaining a first product oil having a total aromatic content of 3% by volume or less by using hydrotreated oil including a petroleum fraction of 95% by volume or more having a boiling point range of 150-380° C., a sulfur content of 2-15 ppm by mass, a total aromatic content of 10-25% by volume and a total naphthene content of 20-60% by volume as a feed oil, and by carrying out hydrotreating of the feed oil in the presence of a first hydrogenation catalyst; and a second step for obtaining a second product oil that satisfies the following conditions (1) and (2): (1) the content of petroleum fraction having a boiling point range of lower than 150° C. is 16% by volume or less, and (2) the sum of the total aromatic content and the total naphthene content is 80% or less relative to the sum of the total aromatic content and the total naphthene content in the feed oil, by carrying out the hydrotreating of the first product oil in the presence of a second hydrogenation catalyst containing a crystalline molecular sieve component.

[0027]A hydrotreated oil used as the feed oil in the present invention contains a petroleum fraction of 95% by volume or more having a boiling point range of 150-380° C., a sulfur content of 2-15 ppm by mass, a total aromatic content of 10-25% by volume, and a total naphthene content of 20-60% by volume.

[0028]Here, the term “boiling point range” herein means one that is measured according to the method as described in JIS-K-2254 “Petroleum products—Determination of distillation characteristics” or ASTM-D86. The term “sulfur content” herein means the mass content of sulfur on the basis of a total gas oil volume, which is measured according to the method as described in JIS-K-2541 “Crude oil and petroleum products-Determination of sulfur content” or ASTM-D5453.

[0029]Further, the terms “total aromatic content” and “polycyclic aromatic content,” which is described later, herein mean the content that is calculated from the volume percentage (% by volume) of respective aromatic contents to be measured according to the method as described in Journal of the Japan Petroleum Institute JPI-5S-49-97 “Petroleum products-Determination of hydrocarbon types-High performance liquid chromatography” published by The Japan Petroleum Institute. The terms “total naphthene content” and “olefin content,” which is described later, herein mean the content that is measured according to the method as described in ASTM-D2786-91 “Standard Test Method for Hydrocarbon Types Analysis of Gas-Oil Saturates Fraction by High Ionizing Voltage Mass Spectrometry.”

Problems solved by technology

On the other hand, demands for cleaner diesel engine exhaust gas has been tightened increasingly, and it is one of major challenges to remove such harmful substances as fine particle contents referred to as “particulate matter” and NOx.

However, it is indicated that, when a gas oil containing a lot of sulfur content is used as fuel, the deterioration of such exhaust gas clean up systems become significant.

Among sulfur compounds existing in a gas oil fraction which have been hydrodesulfurized with a hydrodesulfurization catalyst, dibenzothiophene derivatives having plural methyl groups as a substituent as represented by 4,6-dimethyldibenzothiophene have a very poor reactivity.

But, at relatively low reaction temperatures, since the reaction rate of the aromatic hydrogenation reaction is insufficient, reaction conditions other than reaction temperature and a catalyst are required for compensating that.

Consequently, in conventional techniques, when the reaction condition is set on a lower temperature side in order to accelerate the hydrogenation of aromatic compounds, the desulfurization activity is insufficient, and, as the result, it is very difficult to satisfy both the ultra low sulfur content and low aromatic content.

But, when combustion does not occur normally at the timing of blowing the gas oil, knocking may occur.

Accordingly, the improvement of the cetane number of gas oil is one of the important challenges for aiming to the high efficiency of diesel engines.

However, the conversion of naphthene to paraffin is accompanied, usually, with a cracking reaction, therefore lightening of a product oil as compared with the feed oil is inevitable, to lead to the substantial yield reduction of gas oil fraction.

However, even production processes as described in these Patent Documents do not exert a sufficient effect of decreasing both the sulfur content and aromatic content.

Specifically, even with such production processes as described in these Patent Documents, it is difficult to achieve simultaneously such a very high desulfurization and aromatics-removing levels as a sulfur content of 1 ppm by mass or less and an aromatic content of 1% by volume or less.

In such conventional production processes, when the operation severity in the first step is raised, it becomes difficult to continue economically the operation in the first step for satisfactory period of time.

Further, the rise of the reaction temperature in the first step results in the increase in the aromatics content in the product oil in the first step and hinders removing of aromatics in the second step.

Furthermore, there is the above-described equilibrium restriction on aromatics in the second step, therefore there are limitations on increasing the operation severity such as the rise of the reaction temperature etc.

However, in order to proceed with conversion of naphthene to paraffin, a high reaction temperature is required, and along with the increase in the severity of the reaction condition as the result of the raised reaction temperature, the yield of the generating gas oil fraction tends to decrease.