Mineral oils: processes and products – Chemical conversion of hydrocarbons – With preliminary treatment of feed
Reexamination Certificate
1999-12-14
2002-07-02
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
With preliminary treatment of feed
C208S027000, C208S058000, C208S060000, C208S21600R, C208S217000
Reexamination Certificate
active
06413412
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for producing diesel oils, more particularly, to a process for producing diesel oils of superior quality and low solidifying point from fraction oils of inferior quality.
BACKGROUND OF THE INVENTION
In recent years, fraction oils are becoming more and more inferior in quality as the raw oils are becoming worse in quality, and the processing of heavy and/or residual oils is becoming deeper and deeper, and the like, and moreover, stricter requirement for quality of the products shall be met according to the relevant environmental protection laws. Therefore, it needs urgently to find a new technological process suitable for producing diesel oils of superior quality from fraction oils of inferior quality.
At present, a conventional process for treating fraction oils of inferior quality is a hydrorefining process, which is low in the technological investment and mature in technique, and is an important means widely used in the industry for improving the quality of oil products. The catalyst commonly used in the hydrorefining process comprises 10-25 wt % of MoO
3
(or WO
3
) and 3-5 wt % of NiO (or CoO) supported on &ggr;-Al
2
O
3
as carrier. However, this process has a disadvantage that the solidifying point of diesel oils cannot be effectively reduced to produce diesel oils of superior quality.
On the other hand, a hydrodewaxing process can provide oil products of low solidifying point by selectively cracking the constituents having high solidifying point, such as paraffins, alkanes with short branched chains, naphthenes with long branched chains and the like, in feedstocks, into small molecules under the conditions at a given temperature and hydrogen partial pressure and using a molecular sieve catalyst having unique pores and adequate acid sites. However, the product obtained by the process has the disadvantages of high sulfur content and poor stability, therefore it does not meet the new standards for diesel oil products. In addition, the catalyst for the hydrodewaxing process has only weak activity for hydrogenation, so, when used for treating fraction oils of inferior quality, the catalyst is deactivated by the poisonous impurities contained in feedstocks at a relatively fast rate and consequently the service life of the catalyst becomes shorter.
U.S. Pat. No. 4,436,614 teaches a process for producing base oils of lubricating oils or middle fraction oils of low solidifying point from fraction oils, comprising a single-stage technological process of desulfurization combined in series with dewaxing, wherein the desulfurization reaction of hydrocarbon feedstocks having a distillation range of 200-600° C. is carried out over a desulfurizing catalyst on the upper bed of a reactor while an inert diluting gas is introduced into the reactor to reduce the hydrocarbon gas partial pressure to 0.2 MPa, and the dewaxing reaction is carried out over a molecular sieve type of nonhydrodewaxing catalyst on the lower bed of the same reactor under a hydrocarbon gas partial pressure of less than 0.2 MPa. The dewaxing reaction occurring in the lower part of the reactor belongs to nonhydrodewaxing reaction carried out in absence of hydrogen, and the catalyst used contains no hydrogenation components, so the olefins and nonhydrocarbons in the feedstock cannot be saturated by the dewaxing reaction. Especially, as a large amount of olefins is formed in the nonhydrodewaxing process, the colour of the products consequently becomes darker. Therefore the product obtained by the nonhydrodewaxing process has poor stability, and since a large quantity of coked deposits is formed in the catalytic process of non-hydrodewaxing, the running period of the catalyst is shortened significantly.
U.S. Pat. No. 4,743,354 discloses a process for converting a waxy hydrocarbon feedstock into lube oils or diesel oils having a reduced content of normal paraffins by using a single-stage process of a catalytic dewaxing step combined with a hydrocracking step in series, in which the feedstock is reduced in the dewaxing step by selectively converting waxy paraffins into lower molecular weight hydrocarbons, and at least a portion of the effluent from the dewaxing zone is then passed to a hydrocracking zone where it is further cracked to produce with a comparatively high yield lube oils or diesel oils having a low normal paraffin content. When the desired product is a lube oil, the overall conversion to components boiling at or below about 343° C. is no more than 20 vol %, preferably 10 vol %; and when the desired product is a diesel oil, the overall conversion to components boiling below about 149 C. is no more than 25 vol %, preferably 15 vol %. It is also mentioned in the patent that a single-stage process of hydrotreating, hydrodewaxing combined with hydrocracking in series may be used for treating some feedstocks of inferior quality to produce the objective products. However, where the process is used for producing diesel oils of superior quality, the hydrorefined feedstock is subjected to hydrodewaxing reaction and results in forming some alkenes, which will be saturated in the subsequent hydrocracking reaction, and subsequently will compete with and bring about adverse effects on the saturation of aromatics and the ring-opening reactions, thus the cetane number of the product can not be boosted effectively. In addition, the patent only teaches in general that the process can produce a comparatively high yield of products having a lower solidifying point, without mentioning other properties showing the product quality and examples, and the catalysts used in this patent are not specifically defined.
U.S. Pat. No. 4,664,775 relates to a method by using a catalyst comprising a zeolite TSZ for manufacturing a low pour point petroleum product, such as the insulating oil, the lubricating oil used for various types of solidifying devices, or the base oil for such lubricating oil, from a paraffin-based crude oil as the starting material. In one embodiment of the process, the raw oil is at first catalytically dewaxed, then distilled, and then the fractions boiling at more than 288° C. are hydrorefined, and the stream is then separated in a distillation system to obtain the objective products. In a second embodiment of the process, the raw oil is at first catalytically dewaxed, and then hydrorefined, and the stream is then separated in a fractionating system to obtain products boiling at more than 288° C. In a third embodiment of the process, the raw oil is at first hydrorefined, then separation of liquid from gas is carried out in a separating system, and the stream is then catalystically dewaxed, and distilled to obtain products boiling at more than 288° C. All these embodiments of the process involve a complicated two-stage process, and when practically used in industry, it is inconvenient to operate and the production costs and investment in the process are high.
Therefore, there is a need in the art to develop a simple and feasible process convenient to operate for producing diesel oils which meet the new standards for diesel oils.
DISCLOSURES OF THE INVENTION
The object of the present invention is to overcome the technical problems existing in the prior art and to develop a simple and feasible process for producing diesel oils of superior quality and low solidifying point from fraction oils of inferior quality, and the product obtained has an improved quality and can meet the new standards for diesel oil products, and can even achieve a cetane number boost.
After extensive studies and experiments, the inventors have developed a practicable single-stage process comprising a hydrorefining step and a hydrodewaxing step combined in series. And when necessary, the process may optionally comprise a further hydroupgrading step between the two steps. That is, the process comprises a hydrorefining step, optionally a hydroupgrading step, and a hydrodewaxing step combined in series. In order to simplify the apparatus and make operation easier, when the process is used in
Fang Weiping
Liu Lizhi
Meng Xianglan
Peng Yan
Zhang Lixiu
China Petro-chemical Corporation
Griffin Walter D.
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