CLIAMS:1. A process for separating petroleum products from clarified slurry oil (CSO), said process comprising the following steps:
a. deep vacuum fractionating CSO at a pressure range of 0.1 to1 mm Hg abs and at a temperature range of 270 to 550 °C;
b. separating a first fractional mass at a temperature range of 270 to 360 °C;
c. separating a second fractional mass at a temperature range of 360 to 430 °C;
d. separating a third fractional mass at a temperature range of 430 to 510 °C; and
e. separating a residual fractional mass at a temperature above 510 °C

2. The process of claim 1, wherein said first fractional mass separated comprises at least one compound from the group including diesel, light diesel oil (LDO) and wash oil.

3. The process of claim 1, wherein said second fractional mass separated comprises cycle oil.

4. The process of claim 1, wherein said third fractional mass comprises untreated rubber extender oil.

5. The process of claim 1, wherein said residual fractional mass comprises petroleum pitch.

6. The process of claim 1, wherein the rubber extender oil has an asphaltene content less than 1 wt % and a poly cyclic aromatic (PCA) content of more than 3 wt %.

7. The process of claim 1, wherein the cycle oil has an asphaltene content of less than 1 wt %.

8. The process of claim 5, wherein the petroleum pitch has Quinoline Insolubles (QI) of less than 0.8% and a softening point of in the temperature range of 85-110 °C. ,TagSPECI:Field

The present disclosure relates to a process for separating valuable petroleum products from clarified slurry oil (CSO).

Background

Fluid catalytic cracking (FCC) unit in a refinery cracks the heavy gas oils (boiling above 360 °C) obtained from primary units and/or secondary units after pre-treatment in Fluid catalytic cracker feed hydrotreaters. The FCC process is operated in a fluidized bed reactor with continuous regeneration of catalyst. The cracked product obtained is then separated through fractionation. The bottom material of the fractionation section after vacuum stripping and filtration (to remove the entrapped catalyst particles associated with cracked combined product from FCC reactor) is known as clarified slurry oil (CSO). CSO is normally used as carbon black feed stock or blended with a cutter stock for use as fuel oil. The CSO distils typically, between 310 to 610 °C (5% / 95% vol respectively).

CSO is normally filtered in a slurry settler or a Gulftronic filter to remove and recover the catalyst particles, which are recycled back into the catalyst riser by combining it with the FCC (Fluid catalytic cracker unit) feedstock oil. Thus, CSO has limited use and comparatively much lower value than the actual crude oil in a refinery.

CSO comprises complex mixtures of relatively high molecular weight compounds with typical molecular weight in the range of 250 to 1000. It contains greater proportions of highly condensed aromatics and asphaltenes, fewer mixed aromatics, as well as non-aromatic cyclo-parraffinic compounds depending on the operating severity of FCC unit.

Thus, CSO can serve as a rich source of high value petroleum products with higher aromatic content, for separation of Distillate Oil (LDO, Diesel or Wash Oil), cycle oil, rubber extender oil (REO), high viscosity Carbon Black Feed stock and/or Petroleum pitch.

Rubber manufacturing and processing requires rubber extender oils (REO) and rubber processing oils for improved processability and/or enhancing properties of natural as well as synthetic rubber. These applications typically use aromatic extracts obtained by solvent extraction process while producing lubricating oil from Heavy Gas Oils and/or natural mineral oils for the purpose. The REOs are mostly of naphthenic, paraffinic or aromatic type dark coloured oils used for processing natural or synthetic rubber. They are produced conventionally by extraction of lubricating base oil followed by secondary extraction and/or deep hydrogenation at refinery which increases its production cost.

Cycle oils are used in naphtha steam crackers to quench cracked gasses (as make up to the quench oil system) before further separation process. Preferably, during quenching of cracked effluents from a steam cracking furnace, precipitation of asphaltene needs to be avoided. To achieve this, therefore, cycle oil with lower asphaltene and high aromatic content is preferred.

The Distillate fraction (LDO/Diesel or Wash Oil) obtained by fractionation of CSO is used as Boiler fuel or as Wash oil in petrochemical complexes.

The distillation residue known as ‘Petroleum pitch’ obtained from CSO has Quinoline Insolubles (QI) of less than 0.8% and a boiling range above 510 oC and therefore, it can serve as a potential source of ‘Mesophase pitch’.

The petroleum pitch is suitable for use in Graphite and Aluminium Industry as Binder and/or Impregnation pitch. Mesophase pitches are mainly used to produce high value carbon fibres.

Accordingly, there is a need for simple and cost efficient process for separation of petroleum products from alternative sources such as clarified slurry oil.

Objects

Some of the objects of the present disclosure which at least one embodiment is adapted to provide, are described herein below:

It is an object of the present disclosure to provide a simple and efficient process for separation of useful and valuable petroleum products from CSO.

It is yet another object of the present disclosure to provide a process for separation of valuable petroleum products from CSO in single process step.

It is still another object of the present disclosure to provide valuable petroleum products from CSO which can be directly used in various processes.

Other objects and advantages of the present disclosure will be more apparent from the following description which is not intended to limit the scope of the present disclosure.
Summary

In accordance with the present disclosure there is provided a process for the separation of petroleum products from CSO, said process comprises the following steps: deep vacuum fractionating CSO at a pressure range of 0.1 to 1 mm Hg abs to separate fractional mass at different temperatures. A first fractional mass comprising of either diesel, light diesel oil (LDO) and/or wash oil is separated at a temperature range of 270 to 360 °C; a second fractional mass comprising Cycle Oil is separated at a temperature range of 360 to 430 °C; a third fractional mass comprising Rubber Extender Oil is separated at a temperature range of 430 to 510 °C; and a residual mass comprising pitch and heavies are separated at a temperature above 510 °C.

Detailed Description

In one aspect, the present disclosure provides a process for separation of valuable petroleum products from clarified slurry oil.

In one embodiment of the present disclosure the process comprises the following steps:
• deep vacuum fractionating of CSO at the pressure range of 0.1 to 1 mm Hg abs ;
• separating a first fractional mass at a temperature range of 270 to 360 °C;
• separating a second fractional mass at a temperature range of 360 to 430 °C;
• separating a third fractional mass at a temperature range of 430 to 510 °C; and
• separating a residual mass at a temperature above 510 °C.

CSO is rich in aromatics and hence, has a high Bureau of Mine Co-relation Index (BMCI, which effectively measures the degree aromaticity, i.e aromatic carbons and ultimately yield of carbon black), and high solvency power to hold asphaltene in solution. Culling out a particular fraction of CSO can facilitate availability of distillate aromatic extract (DAE) type oil (with excellent VGC) and can be effectively used in comparison to the current industry practice of using lubricating oil extracts for the same purpose. Hence, it is preferred that high cost/low BMCI lubricating extracts are replaced with rubber extender oil fraction derived from CSO. Therefore, there is a need for cost efficient and simple process for separation of valuable petroleum products such as diesel, light diesel oil, wash oil, cycle oil, rubber extender oil and the like from clarified slurry oil.

The process of the present disclosure is described hereinafter. The bulk temperature of the process fluid in accordance with the present disclosure does not exceed 340 °C especially in the first step of deep vacuum fractionation and has a lowest possible residence time in order to minimize undesired side reactions/cracking of the process fluid. A mild hydrogenation step followed by stripping of light ends is envisaged to impart product stability as well as compliance with the volatility specification of the rubber extender oil (REO). Therefore the present invention deals with a simple and cost efficient process for separation of valuable petroleum products such as cycle oil, wash oil, light diesel oil, rubber extender oil and the like from clarified slurry oil using deep vacuum distillation.
The Cycle oil is mainly used in Naphtha crackers, whereas the Wash oil is used in gas and naphtha crackers. Diesel/LDO fraction is used as a fuel in boilers and furnaces. The last heavy cut of the cycle oil that is the petroleum pitch can be used as a potential source of high value Mesophase pitch which can be used for the preparation of carbon fibers, carbon foam etc. and/or used as ‘Binder Pitch’ or ‘Impregnating Pitch’ in the Aluminum and Graphite Industry.
Accordingly, the CSO feed is first fractionated under deep vacuum (pressure of 0.1 – 1 mm Hg abs).
Non-limiting examples of evaporators for the fractionation include degassers, falling film evaporators, thin film evaporators, short path distillation units and any combination thereof.
The deep vacuum fractionation of CSO results in separation of CSO into four cuts namely, light ends (up to 360 °C; this is atmospheric equivalent temperature and in actual operation it will be lower, owing to deep vacuum conditions), cycle oil (360 to 430 °C cut), Rubber extender oil (430 to 510 °C cut) and petroleum pitch (510 °C plus). The maximum bulk temperature of the process thermic fluid is maintained at or below 340 °C and a limited residence time at high temperature of few minutes to avoid cracking of the feed oil.
While, the light ends and cycle oil can be used directly in various applications, the rubber extender oil fraction of CSO is either used as such in untreated form or further treated to obtain treated REO. Treatment of untreated REO comprises mild hydro-treating or hydro-finishing to achieve olefin saturation followed by subsequent stripping of light ends to attain appropriate flash point of final product.

The hydro-treatment stage shall be milder, sufficient to saturate the olefins present in the CSO fractions and impart stability on long term storage as well. An optional step of blending with other types of REO can also be carried out to improve the quality of rubber extender oil based on specific end application.

In one of the embodiments of the present disclosure, the untreated rubber extender oil is subjected to mild hydro-treatment at a temperature range of 270 to 320 °C and at a moderate pressure range of 28 to 30 bar using 430 to 470 nm3 of hydrogen gas per m3 of oil at 1 to 2 hour-1 liquid hourly space velocity of untreated rubber extender oil.

The catalyst for the hydro-treatment step is at least one from the group consisting of cobalt-molybdenum (Co-Mo) and nickel-molybdenum (Ni-Mo).
The light saturated hydrocarbons evolved during mild hydro-treatment step are separated either by stripping or distillation to impart product stability as well as compliance with the volatility specification of the rubber extender oil (REO).
The rubber extender oil obtained after stripping or distillation step comprise a polycyclic aromatics (PCA) content of more than 3 wt %.

In an exemplary embodiment of the present disclosure the rubber extender oil and cycle oil comprise less than 1wt % of asphaltene content.

The Petroleum Pitch obtained as a last fraction in vacuum distillation process, is suitable to use as ‘Binder Pitch’ or ‘Impregnation Pitch’ in aluminum and graphite industry as such or with further treatment.
In yet another application, the blend of Lighter ends, REO and Petroleum Pitch streams obtained after separation of Cycle Oil fraction from CSO is found suitable as high viscosity grade Carbon Black Feed Stock (CBFS).

Technical advances
- The present disclosure provides a simple and economic process for the separation of valuable petroleum products from CSO using deep vacuum fractionation with gradual increase in temperature of the fractionation column.
- The present disclosure also provides a process for the separation of petroleum products including Lighter fractions (comprising either/or Diesel, Light Diesel Oil, Wash Oil), Cycle oil, Rubber extender oil (REO), Petroleum pitch and like from CSO.
- The present disclosure provides rubber extender oil and cycle oil comprising less than 1 wt % asphaltene content.
- The process of the present disclosure can be carried out in the absence of expensive conventional solvent extraction processes used for the separation of rubber extender oil and cycle oil from lubricating oil.

The exemplary embodiments herein quantify the benefits arising out of this disclosure and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the description.

Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.