FORM-2
THE PATENT ACT,1970
(39 OF 1970)
AND
THE PATENT RULES, 2003
(As Amended)
COMPLETE SPECIFICATION (See section 10;rule 13)
"PROCESS FOR IMPROVING QUALITY OF KEROSENE TYPE PETROLEUM DISTILLATES BY ADSORBENT TECHNIQUE"
NAYARA ENERGY LIMITED, a corporation organized and existing under the laws of India, of 39 KM Jamnagar-Okha Highway, Vadinar, Dist Devbhoomi Dwarka, Gujarat, India.
The following specification particularly describes the invention and the manner in which it is to be performed:

Title of Invention:
Process for improving quality of kerosene type petroleum distillates by
adsorbent technique
Field of the invention:
The present invention relates to crude oil refining process, more specifically to improve quality of kerosene type petroleum distillates that produced from crude oil, furthermore specific to petroleum product namely, mineral turpentine oil, aviation turbine fuel, superior kerosene oil, petroleum hydrocarbon solvent etc.
Background of the invention:
Crude oil is fossil fuel extracted from earth, sometime synthetic material also mixed with it. After exploration and cleaning process, crude oil mainly consists of mixture of hydrocarbon and trace quantity of water and sediments. Petroleum refiners process different types of crude oils and produce valuable gaseous and liquid fuels namely Liquefied Petroleum Gas (LPG), Motor Spirit (MS), Aviation Turbine Fuel (ATF), Superior Kerosene Oil (SKO), Mineral Turpentine Oil (MTO), Diesel, etc. and solid products like Sulphur and Petroleum Coke. The kerosene fraction of distillates are mainly used to produce ATF, MTO, SKO and petroleum hydrocarbon solvents.
Most of recent crude oil refiners process heavy crude oils by blending of multiple crude oils to earn higher profit. The kerosene fraction, many a time, has lower Saybolt color and an unstable Saybolt color which deteriorates faster, and the product becomes yellowish in color. The kerosene type petroleum distillate is produced through crude oil distillation (CDU) unit and is mostly processed through sweetening process called MERICHEM or MEROX treatment to remove impurities namely hydrogen sulphide, mercaptans, naphthenic acids and surfactants etc. This sweetening process further deteriorates 3 to 6 Saybolt color unit. Also, Saybolt color of kerosene distillate is an inherent property of hydrocarbon molecules which depends on crude oil as well as types of production process and process conditions. Hence many a times either product has inferior color (yellowish) or the product becomes yellowish in color after production due to deterioration (unstable), which is not acceptable in the market since Saybolt color is part of product specification or paint industry wants a product to use for manufacturing of white paint. The Saybolt colour requirement in different kerosene type petroleum products is tabulated in below Table-1,

Table 1:

Petroleum Product Saybolt Color Requirements Remarks
Petroleum Hydrocarbon Solvents, 125 to 240°C +21 min As per IS 1745
Superior Kerosene oil (SKO) +10 min As per IS 1459
Mineral Turpentine Oil (MTO) +25 min As per market requirements of paint industries
Aviation Turbine Fuel To report Minimum +18 is expected as per market trend.
Requirement of Saybolt Color for Kerosene type disti late products.
In these cases, product is downgraded or has to be used for other less valuable applications, which ultimately reduces profit margin of the refiner. Hydrotreatment can improve the Saybolt color but it is very costly, risky and complex process.
There is very limited literature available on methods to improve Saybolt color and improve stability of Saybolt color. One of such literature is the US patent no 6805790 B2 wherein the inventors have used molecular sieve modified clays for Saybolt color stability of petroleum hydrocarbon solvent produced from nitrogen rich crude oils. Also, WO2005075608A1 discloses de-nitrogenation of liquid fuel using ion-exchanged zeolite.
The Saybolt color of kerosene type distillate product purely depends on chemical composition of crude oil and refining process & technology used for production. As of today, there is no easy, efficient and economical process well known to the refining fraternity for production of kerosene type distillate with desired and stabilised Saybolt color.
Looking to the above problems, crude oil refiners are striving to improve and stabilize Saybolt color of kerosene type petroleum distillate by simple process. Therefore, it would be of great benefit to the refining fraternity if easy, efficient, and economical process is made available for them for said purpose. Hence, need arises to develop easy, efficient, and economical process to improve Saybolt color and stability of Saybolt color of kerosene type petroleum distillates.

Object of the Invention:
The main object of present invention is to improve quality of kerosene type petroleum distillates.
Further, object of the present invention is to provide a process to improve quality of kerosene type petroleum distillates by adsorbent technique.
Yet another object of present invention is to develop a process to improve Saybolt color & stability of color for kerosene type petroleum distillates.
Another object of present invention is to develop a process to improve Saybolt color & stability of color for kerosene type petroleum distillates and regeneration of adsorbent.
Another object of present invention is to improve Saybolt color, improve stability of Saybolt color, reduce organic nitrogen content, reduce moisture content, recover hydrocarbon and regenerate the used adsorbent of kerosene type petroleum distillates.
Yet another objective of the present invention is to develop a process to improve Saybolt color of kerosene type petroleum distillates having distillation range between 125 to 300°C or beyond of this range.
Yet another objective of the present invention is to develop a process to improve Saybolt color of kerosene type petroleum distillates using batch or continuous process.
Yet another objective of the present invention is to develop a process to improve Saybolt color of kerosene type petroleum distillates using ambient or any temperature.
Yet another objective of the present invention is to develop a process to improve Saybolt color of kerosene type petroleum distillates using ambient or any other pressure.
Yet another objective of the present invention is to develop a process to improve Saybolt color of kerosene type petroleum distillates using different flow rate.
Yet another objective of the present invention is to develop a process to improve Saybolt color of kerosene type petroleum distillates using single or multiple types of adsorbents.

Yet another objective of the present invention is to develop a process to improve Saybolt color of kerosene type petroleum distillates using single or multiple adsorbent beds.
Yet another objective of the present invention is to develop a process to improve Saybolt color of kerosene type petroleum distillates using any particle size, shape and color of silica gel adsorbent.
Yet another objective of the present invention is to develop simple process to improve stability of Saybolt color of kerosene type petroleum distillates.
Yet another objective of the present invention is to develop a cost-effective process to improve Saybolt color of kerosene type petroleum distillates.
Yet another objective of the present invention is to develop simple and cost-effective process to improve stability of Saybolt color of kerosene type petroleum distillates.
Yet another objective of the present invention is to develop simple and cost-effective process to reduce moisture content of kerosene type petroleum distillates.
Yet another objective of the present invention is to develop simple and cost-effective process to reduce organic nitrogen content of kerosene type petroleum distillates.
Yet another objective of the present invention is to recover hydrocarbon from used adsorbent.
Yet another objective of the present invention is to reduce hydrocarbon hazard from used adsorbent.
Yet another objective of the present invention is to reduce fire hazard from used silica gel thus will improve operation safety.
Yet another objective of the present invention is to develop regeneration process for used adsorbent for reuse.
Yet another objective of the present invention is to develop regeneration process for used adsorbent at 500 to 1000°C and beyond this temperature range.

Yet another objective of the present invention is to develop regeneration process for used adsorbent with initially nitrogen or inert gas purging.
Yet another objective of the present invention is to develop regeneration process for used adsorbent with air purging.
Yet another objective of the present invention is to develop regeneration process for used adsorbent with hydrocarbon recovery.
Yet another objective of the present invention is to develop regeneration process using batch or continuous process.
Yet another objective of the present invention is to reduce volatile organic carbon hazards thus reduce air pollution.
Yet another objective of the present invention is to develop procedure to measure adsorbent Saybolt color improvement efficiency.
Summary of the Invention:
In order to achieve the afore-said objectives, present invention provides a novel process to improve Saybolt color, improve stability of Saybolt color, reduce organic nitrogen and reduce moisture content of kerosene type petroleum distillates, and process to recover hydrocarbon and regeneration of used adsorbent.
As per the first aspect the process of the present invention is a simple three step process comprising following steps:-Step-1: passing the kerosene type petroleum distillate through silica gel adsorbent bed to improve the Saybolt color, improve stability of Saybolt color, reduce organic nitrogen and reduce moisture content;
Step-2: recovering surface hydrocarbon from used silica gel by water washing; or recovering surface and adsorbed hydrocarbon by thermal regeneration; Step-3: regenerating used silica gel by thermal oxidation.
In one of the embodiment the present invention further provides the process for treating
kerosene type petroleum distillate comprising:
Step-1: passing kerosene type petroleum distillate through silica gel;

Step-2: recovering surface hydrocarbon from used silica gel by water washing;
Step-3: regenerating used silica gel obtained after Step-1 or after Step-2 by thermal
oxidation.
In another embodiment the present invention provides a process for thermal oxidation
comprises:
Step-1: raising furnace temperature from ambient to 350°C at the rate of 100°C per hour
while purging nitrogen;
Step-2: switching purging gas from nitrogen to air and raising furnace temperature up to
700 °C.
In another embodiment the present invention provides a process for treating kerosene type petroleum distillate, wherein the efficiency of Saybolt color improvement is ˜7000 Saybolt color unit per ml of sample per gm of silica gel.
In another embodiment the present invention provides the process for treating kerosene type petroleum distillate, wherein the process improves Saybolt color of the distillate, improves stability of Saybolt color of the distillate, reduces organic nitrogen of the distillate, reduces moisture content of the distillate, recovers hydrocarbon from used silica gel and regenerates used silica gel.
In another embodiment the present invention provides the process for treating kerosene type petroleum distillate, wherein the kerosene type petroleum distillate treated by silica gel is highly stable up to 60 days at 25 ± 2°C.
Description of the Drawings:
The foregoing and further objects, features and advantages of the present subject matter will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements.
It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter, and are therefore, not to be considered for limiting of its scope, for the subject matter may admit to other equally effective embodiments.

Figure 1: Illustrates the basic silica gel adsorbent process to improve the Saybolt color, improve stability of Saybolt color, reduce moisture, and reduce nitrogen content of kerosene type petroleum distillates.
Figure 2: Illustrates the basic process for recovery of surface hydrocarbon from used silica gel by water washing.
Figure 3: Illustrates the basic process for regeneration of used adsorbent with hydrocarbon recovery.
Figure 4: Image of white silica gel crystal used as adsorbent.
Figure 5: Image of lab scale 300 ml adsorbent bed for experiment.
Figure 6: Image of visual colour improvement before and after silica gel treatment.
Figure 7: Image of pilot skid for adsorbent treatment.
Figure 8: Image of used silica gel.
Figure 9: Image of lab scale water washing system to recover hydrocarbon from used silica gel.
Figure 10: Image of lab scale silica gel regeneration system.
Figure 11: Image of recovered hydrocarbon from water washing and regeneration system.
Figure 12: Image of regenerated silica gel.
Figure 13: Images of fresh, used and regenerated silica gel.
Detailed description of the invention:
The following presents a detailed description of various embodiments of the present subject matter with reference to the accompanying drawings.

The embodiments of the present subject matter are described in detail with reference to the accompanying drawings. However, the present subject matter is not limited to these embodiments which are only provided to explain more clearly the present subject matter to a person skilled in the art of the present disclosure. In the accompanying drawings, like reference numerals are used to indicate like components.
The specification may refer to “an”, “one”, “different” or “some” embodiment(s) in several locations. This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.
As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes”, “comprises”, “including” and/or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being “attached” or “connected” or “coupled” or “mounted” to another element, it can be directly attached or connected or coupled to the other element or intervening elements may be present. As used herein, the term “and/or” includes any and all combinations and arrangements of one or more of the associated listed items.
The figures depict a simplified structure only showing some elements and functional entities, all being logical units whose implementation may differ from what is shown.
The present invention provides a novel process to improve Saybolt color, improve stability of Saybolt color, reduce organic nitrogen and reduce moisture content of kerosene type petroleum distillates, and process to recover hydrocarbon and regeneration of used adsorbent.
The process of the present invention is a simple three step process comprising following steps:-Step-1: passing the kerosene type petroleum distillate through silica gel adsorbent bed to improve the Saybolt color, improve stability of Saybolt color, reduce organic nitrogen and reduce moisture content;

Step-2: recovering surface hydrocarbon from used silica gel by water washing; or recovering surface and adsorbed hydrocarbon by thermal regeneration; Step-3: regenerating used silica gel by thermal oxidation.
In one of the embodiment the present invention further provides the process for treating
kerosene type petroleum distillate comprising:
Step-1: passing kerosene type petroleum distillate through silica gel;
Step-2: recovering surface hydrocarbon from used silica gel by water washing;
Step-3: regenerating used silica gel obtained after Step-1 or after Step-2 by thermal
oxidation.
In another embodiment the present invention provides a process for thermal oxidation
comprises:
Step-1: raising furnace temperature from ambient to 350°C at the rate of 100°C per hour
while purging nitrogen;
Step-2: switching purging gas from nitrogen to air and raising furnace temperature up to
700 °C.
In another embodiment the present invention provides a process for treating kerosene type petroleum distillate, wherein the efficiency of Saybolt color improvement is ˜7000 Saybolt color unit per ml of sample per gm of silica gel.
In another embodiment the present invention provides the process for treating kerosene type petroleum distillate, wherein the process improves Saybolt color of the distillate, improves stability of Saybolt color of the distillate, reduces organic nitrogen of the distillate, reduces moisture content of the distillate, recovers hydrocarbon from used silica gel and regenerates used silica gel.
In another embodiment the present invention provides the process for treating kerosene type petroleum distillate, wherein the kerosene type petroleum distillate treated by silica gel is highly stable up to 60 days at 25 ± 2°C.
The present process provides improved Saybolt color, improved stability of Saybolt color, reduced organic nitrogen and reduced moisture content of kerosene type petroleum distillates, recovery of hydrocarbon and regeneration of adsorbent. The invented process is verified at laboratory scale and field level. The detailed description of process is as mentioned below.

Step-1 Process to Improve Saybolt Color:
As per Figure 1, the kerosene type petroleum distillate [1] that is produced at crude oil refinery is feed to the silica gel adsorbent bed [2] via valve [V1] and improved kerosene type distillate product is collected from outlet line [3] via valve [V2]. The process can be operated at ambient temperature and pressure, or these parameters can be adjusted as per requirements. The process can be also used with single (silica gel) or mixture with other adsorbent. The process can be also operated at single or multiple adsorbent beds based on requirements. The flow can be passed from top to bottom or from bottom to top. The experiments conducted at laboratory scale and at field level using pilot skid indicate that the present process is capable to improve Saybolt colour, improve stability of Saybolt colour, reduce nitrogen content and reduce moisture content as mentioned in experimental study work. After exhaustion of adsorbent life, close the bed inlet and outlet valves [V1 and V2] and open drain valve [V6] and vent valve [V5] to drain kerosene from bed. After draining of kerosene, close the drain valve [V6] and open side manhole to unload the used adsorbent. After unloading adsorbent, close the side manhole [6] and load the fresh silica gel adsorbent from top manhole [5].
Step-2 Process to Recover Surface Hydrocarbon:
As per Figure 2, take the used silica gel adsorbent into tank A and submerge with water. Circulate the water from bottom to top using pump, alternately air purging also can be used. Collect the floated hydrocarbon from top liquid layer of tank B and transfer it to slop oil system for reprocessing. Water washed adsorbent will be free from surface hydrocarbon hence it will reduce fuel loss, reduce chemical hazards, avoid adverse impact on environment by reducing volatile hydrocarbon release in air, therefore it will improve operational safety and easy for handling for regeneration or disposal. Also, it will make process more cost effective.
Step-3 Process to Regenerate Adsorbent:
As per Figure 3, take washed silica gel adsorbent into the regeneration furnace SS vessel. Start the nitrogen purging using valve [V2] and start furnace temperature raising from ambient to 350 °C at the rate of 100 °C per hour. Initially water and adsorbed hydrocarbon get vaporised and get condensed at condenser and collected in hydrocarbon recovery vessel between 100 to 350°C. Once hydrocarbon recovery is over, switch the purging gas from nitrogen to air and start further raising of furnace temperature up to 700 °C, at higher temperature in presence of air oxygen, all hydrocarbon impurities will get decomposed or oxidized and adsorbent get regenerated. This process is recovering

hydrocarbon and regenerating adsorbent hence it will reduce fuel loss, avoid generation of waste, avoid adverse impact on environment, therefore it will improve operational safety and reduce operational cost. Alternately, user can avoid step-2 and take directly feed from step-1.
Various laboratory scale qualitative and quantitative experiments were conducted on actual kerosene type petroleum distillate samples collected from crude oil refinery and silica gel adsorbent purchased from market. In this experimental study work following aspects are studied:
1) Development of process for Saybolt colour improvement in kerosene type petroleum distillate.
2) Experimental work to check stability of Saybolt color.
3) Experimental work to check the effect on organic nitrogen content.
4) Experimental work to check the effect on moisture content.
5) Experimental work to check the effect on key quality parameters of ATF, SKO and MTO products.
6) Development of process for recovery of surface hydrocarbon from used adsorbent.
7) Development of process for regeneration of used adsorbent.
8) Experimental work at Laboratory scale.
9) Experimental work at field using pilot skid.
10) Feasibility of invented process with respect to cost, availability of technology,
availability of material (adsorbent), operational safety, impact on environment and
easy implementation in the field.
Details of Equipment and Materials Used for Experimental Work:
Adsorbent: The different grades of white silica gel crystal purchased from market. Figure 4 represent the image of fresh white silica gel crystal that used as adsorbent. The technical specification of white silica gel is mentioned in the below table-2.
Table 2:

TECHNICAL SPECIFICATION
DESCRIPTION SILICA GEL WHITE
TYPE Non-Indicating
ASSAY(as SiO2),% 97-99
pH 5.5 - 7.0

Bulk Density, gm/ml 0.600 - 0.700
Loss on Drying,% 5 - 6
Adsorption Capacity at 100% humidity , % 27 - 35
Friability 99.5
Chloride (as Nacl),% Max 0.5
Sulphates (Na2So4),% Max 0.5
Ammonium Compound (NH3), % 0
Particle Size, mm 0 to 1, 1 to 2, 2 to 4 and 4 to 8
Chemical Formula SiO2 + H2O
White Silica Gel Specification
Kerosene Type Distillates: All product samples namely Aviation Turbine Fuel (ATF), superior Kerosene oil (SKO), Mineral Turpentine Oil (MTO) and petroleum hydrocarbon solvents were collected from M/s Nayara Energy petroleum refinery, Vadinar, Dist. Devbhoomi Dwarka, State - Gujarat, India.
Saybolt Colorimeter: Instrument comply with the requirements of Test Method ASTM D 156 (manual method) and Tintometer (automated method).
Moisture Analyser: Instrument comply with the requirements of Test Method ISO 12937 – (Microcoulometry).
Nitrogen Analyser: Instrument comply with the requirements of Test Method ASTM D 4629 – (Oxidative combustion with chemiluminescence detection).
Glass Wares: Glass Bottles (200, 500 and 2000ml capacity), cylinders (100, 500 and 1000ml), separating funnels, test tubes, volumetric flask etc.
Balance for sample weight: 0 to 210 gm and 0 to 5kg.
Magnetic Stirrer: Capable to control from 0 to 500 RPM with magnetic needle.
Adsorbent Glass Column: 500 ml capacity glass column as shown in figure- 5.
Adsorbent skid: 10 lit capacity SS skid as shown in figure- 7.

Hydrocarbon Recovery System: Glass assembly for recovery of hydrocarbon from used silica gel by water washing as shown in figure - 9 and figure-2.
Adsorbent Regeneration System: Muffle furnace with heating capacity up to 1000°C and SS 300 ml assembly with glass condenser and hydrocarbon receiver as shown in figure- 10 and figure-3.
Testing methods: Various testing methods used are recommended by standard product specifications.
The inventors have conducted various laboratory experiments to conclude the performance parameters of new process for improving quality of kerosene type petroleum distillate. Out of many such laboratory / field experiments, some of important experiments are explained below for evidence and reference of laboratory / field experimental work. However, the scope of the invention should not be limited to said examples.
Experimental Work:
1. Lab Experiments:
1.1 Determination of Improvement of Saybolt Color by Silica Gel Adsorbent:
Aim: To check the effect of white silica gel on Saybolt color of kerosene type petroleum distillate.
Experiment Condition / Procedure: Kerosene type petroleum distillate samples were collected from refinery product tank and passed through 300 ml white silica gel bed prepared in glass column at laboratory. Kerosene is tested for Saybolt colour before and after treatment. Test results are tabulated in below table- 3. The figure- 4 represent the white silica gel crystal used as adsorbent and figure - 5 represent the image of lab scale 300 ml adsorbent bed.
Table 3: Test results

Sample Details Saybolt Color Saybolt Color Improvement
before After Treatment in Saybolt
Treatment (A) (B) Color (B-A)

MTO-350C-12.07.21 +22 +30 +8
ATF from KMU 11.01.21 +16 +30 +14
SKO Tank (Old material) +11 +30 +19
Saybolt Color Test Results before and after treatment.
Observations: From the above test results, it is observed that, white silica gel is capable to improve Saybolt color of kerosene type hydrocarbon (MTO, ATF and SKO) produced from crude oils. Figure 6 represent the image of visual color improvement before and after treatment.
1.2 Determination of Saybolt Color Improvement Efficiency of Silica Gel Adsorbent:
Aim: To check the efficiency of silica gel for Saybolt color improvement.
Experiment Condition / Procedure: Take 200ml kerosene type petroleum distillate sample in clean and dry glass bottle, check the Saybolt color of sample and record as initial color, add 0.2 gm of silica gel adsorbent and record the weight of adsorbent in gm, put the Teflon coated magnetic stirrer and stir the sample for four hours at 100 to 120 RPM at ambient temperature (22 to 26°C). Check the Saybolt color of treated sample and record as improved Saybolt color. Calculate the Saybolt color improvement efficiency as per below mentioned formula.
Calculation for Saybolt Color Improvement Efficiency:
[(Improved Saybolt color – Initial Saybolt color) X sample Volume in ml]/ Wt. of adsorbent in gm
For Example: Initial Saybolt color is 10, Improved Saybolt color is 20, sample volume is 200 ml and adsorbent weight is 0.2 gm, then adsorbent Saybolt Color Improvement efficiency would be calculated as follow: [(20 -10) X 200]/0.2 = 10000 Saybolt color unit/ ml of sample / gm of adsorbent.
Test Results: Various kerosene type distillate sample were tested and few of them are tabulated in below table-4,

Table 4:

Sample Details Initial
Saybolt
Color Improved
Saybolt
Color Weight of Silica Gel, In gm Sample Volume, In ml Saybolt Color Improvement Efficiency, ml Sample / gm Adsorbent
SKO- T- 350B 16 23 0.2047 200 6839
SKO- T- 350B 16 23 0.2014 200 6951
SKO- T- 350B 16 24 0.2023 200 7909
ATF-T- 450A 22 26 0.1030 200 7767
ATF-T- 450A 22 27 0.1523 200 6566
Test Results of Saybolt Color Improvement Efficiency of silica Gel Adsorbent.
Observations: From the table-4 test results, it is observed that silica gel is having efficiency to improve approximately 7000 Saybolt color unit per ml of sample per gm of silica gel adsorbent at laboratory scale batch experiments.
1.3 Determination of Improvement in Stability of Saybolt Color:
Aim: To verify the relative improvement in stability of Saybolt color after silica gel treatment.
Experiment Condition / Procedure: Kerosene type petroleum distillate sample passed through silica gel bed and then both (treated and untreated) sample were tested for Saybolt color, recorded as initial Saybolt color. Both the samples were kept for color stability check (deterioration) at same laboratory condition for six days at 25 ± 2°C and again tested for Saybolt color, test results were recorded as stabilised Saybolt color. Various laboratory scale experiments were carried out and few of them are tabulated in below table-5.
Table 5:

Initial Saybolt Difference Saybolt
Exp.
Saybolt Color in Saybolt Color
Start Sample Details
Color after Six Color Stability %
Date
(A) Days (B) (A-B) (B)*100/(A)

Kerosene of Eocene
21.02.22 Crude oil (IBP: 145 °C, FBP:220 °C), date: 21.02.22 30 25 5 83
After passing through
21.02.22 Silica gel: Kerosene of Eocene Crude oil (IBP: 145 °C, FBP:220 °C) 30 28 2 93
Light Kerosene from
18.04.22 CDU-1 Unit, Date: 18.04.22 24 15 9 63
After passing through
18.04.22 Silica gel: Light Kerosene CDU-1, Date: 18.04.22 30 30 0 100
Light Kerosene from
20.04.22 CDU-1 Unit, Date: 20.04.22 24 16 8 67
After passing through
20.04.22 Silica gel: Light Kerosene CDU-1, Date: 20.04.22 30 30 0 100
Improvement in Stability of Saybolt Color
Observations: From the Saybolt color stability test results, it is observed that, after passing kerosene type petroleum distillate from silica gel, Saybolt color stability of sample was increased drastically in most of cases.
1.4 Long Term Saybolt Color Stability Study of Treated Sample:
Aim: To check the long term Saybolt color stability of kerosene type distillate sample that treated by silica gel.
Experiment Condition / Procedure: Kerosene type petroleum distillate sample passed through silica gel bed and then tested for Saybolt color, test results were recorded as initial Saybolt color. Treated samples were kept for color stability check (deterioration) at laboratory condition for 60 days at temperature 25 ± 2°C. The Saybolt color of study sample was tested at every 10 days interval and test results were recorded. Two samples

were studied for long term Saybolt color stability study and observed test results are tabulated in below table-6.
Table 6:

Color Reading Recorded on Days Silica Gel Treated
MTO Sample,
Exp. Start Date: 12.07.21 Silica Gel Treated SKO
Sample,
Exp. Start Date: 12.07.21
0 +30 +30
10 +30 +30
20 +30 +30
30 +30 +30
60 +30 +30
Color Stability % => 100 100
Test Results of Long Term Saybolt Color Stability Study
Observations: From test results of above experiments, it is observed that kerosene type petroleum distillate treated by silica gel is found to be highly stable up to 60 days at laboratory condition.
1.5 Relative Saybolt Color Stability in Sunlight for Hydro-treated Vs Silica Gel Treated Kerosene Type Petroleum Distillate:
Aim: To check the relative Saybolt color stability by exposure of sunlight on Hydro-treated and silica gel treated kerosene type petroleum distillate. It is experienced that, direct exposure of sunlight is deterioration Saybolt color very fast, hence this relative study is very important to predict very long term color stability.
Experiment Condition / Procedure: Kerosene type petroleum distillate samples namely silica gel treated ATF and hydro-treated MTO were filled in 1000 ml transparent glass bottles and kept for sunlight exposure in open ground for 8 hrs. The weather on the day of experiment was clear without cloud. Both the samples were tested for Saybolt color reading after every 2 hours of interval and observed Saybolt color test results are tabulated in below Table-7.

Table 7:

Time in Hrs Weather Condition Reading Time on Dt. 13.01.22 Silica Gel Treated ATF Sample, Dt. 12.01.22 Hydro-treated MTO Sample, Dt. 13.01.22
0 Clear weather
without any
cloud 9:00 AM +29 +30
2
11:00 AM +28 +29
4
1:00 PM +26 +25
6
3:00 PM +22 +23
8
5:00 PM +19 +21
Saybolt color unit deterioration 10 9
Test Results of Relative Saybolt Color stability in Sunlight.
Observations: From the above test results, it is observed that silica gel treated kerosene type petroleum distillate having Saybolt color stability in sunlight comparable with same type of hydro-treated material. Hence it is expected that, silica gel treated kerosene type petroleum distillate will have very long term Saybolt color stability.
1.6 Effect of Silica Gel Adsorbent on Organic Nitrogen and Moisture:
Aim: To check the effect of adsorbent on organic nitrogen and moisture content of kerosene type petroleum distillate.
Experiment Condition / Procedure: Kerosene type petroleum distillate sample passed through silica gel bed and then both samples (treated and untreated) were tested for organic nitrogen by test method ASTM D 4629 and moisture by test method ISO 12937. Various laboratory scale experiments were carried out and few of them are tabulated in below table-8 and table-9 for organic nitrogen and moisture content respectively.
Table 8:

Sample Detail Organic Nitrogen, wt. ppm Organic Nitrogen Reduction %

Before Treatment After Treatment

ATF R/D-10.09.21 2.39 0.66 72
ATF R/D-15.09.21 1.65 0.46 72
ATF R/D-12.10.21 3.95 0.75 81
LK- CDU-1, 18.04.22 1.78 0.07 96

LK- CDU-1, 20.04.22 1.56 0.1 94
LK- CDU-1, 02.05.22 1.40 0.06 96
Test Results of Organic Nitrogen Before and After Treatment
Table 9:

Sample Detail Moisture, wt. ppm Moisture Reduction %

Before Treatment After Treatment

ATF R/D-12.10.21 125 17 86
LK- CDU-1, 18.04.22 222 84 62
LK- CDU-1, 20.04.22 209 96 54
LK- CDU-1, 02.05.22 330 125 62
Test Results of Moisture Content Before and After Treatment.
Observations: From the above test results, it is observed that silica gel is reducing organic nitrogen and moisture content of kerosene type petroleum distillate. The moisture test is very sensitive to atmospheric humidity hence should be tested immediately and take proper care to avoid contact of air with test sample.
1.7 Impact of Silica Gel Adsorbent on Other Properties of Kerosene Type Distillate:
Aim: To check the impact of silica gel adsorbent on other key properties of kerosene type products.
Experiment Condition / Procedure: Kerosene type petroleum distillate sample passed through silica gel bed and then both samples (treated and untreated) were tested for key properties of ATF / SKO / MTO specification. Observed test results are tabulated in below table-10.
Table 10:

Parameters Unit Before Treatment, Test Results After Treatment, Test Results
Color Saybolt +17 + 25
Total Sulphur % mass 0.18 0.17
RSH PPM 24 24

IBP Deg. C 153.5 152.1
10% Deg. C 173.2 173.5
50% Deg. C 191.1 191.7
90% Deg. C 214.6 215.3
FBP Deg. C 230.9 231
Loss % Vol 0.6 0.7
Residue % Vol 1.4 1.4
Cu corrosion Class 1b 1b
Acidity mg KOH/gm 0.006 0.006
Naphthalene %v/v 0.74 0.73
Test Results of Key Properties Before and After Treatment.
Observations: From above test results, it is observed that, there is no significance impact on other key properties of kerosene type petroleum distillate sample. Hence silica gel can be use as adsorbent for color improvement for kerosene type products namely SKO, MTO, ATF and hydrocarbon solvents.
2. Field Experiments Using Pilot Skid:
Aim: The test results of laboratory scale batch process was found very interesting and useful, hence before going for large scale design it was decided to verify the performance of silica gel adsorbent using pilot skid on continuous flow process at field condition. Figure- 7 represent the image of pilot skid used for field experiments.
Pilot Skid Details:
1) Capacity: 10 Litre Volume, single cylindrical bed, 100 MM ID and 1500 mm Height.
2) Material of construction: Stainless Steel.
3) Facility: Pressure gage, valve and sample point at inlet and outlet.
4) Electrical pump with flow control mechanism.
5) Trolley mounted with four castor wheels for easy movement as shown in Figure 7.
Experiment Condition / Procedure: Pilot skid was installed at ATF filter area of product intermediate tank farm at Nayara Energy refinery. The pilot skid was filled up with 6.35 kg of fresh white silica gel material having 1 to 2 mm particle size. The ATF material was taken as inlet from ATF run down line through flow controllable pump. The ATF flow was monitored shift wise and maintained in the range of 40 to 50 litre per hour. The field trial run was carried out for 15 days. The inlet and outlet samples were collected

shift wise and analysed for Saybolt color at laboratory. Total 16349 litres of ATF material was passed through pilot skid bed to see the performance of adsorbent at field level with continuous operation.
Test Results: Test results of field trial are mentioned in below table-11.
Table 11:

Date Time Flow Lit /Hrs [A] Total
Materia
l
Passed
in Lit
[B] Inlet Saybolt Color, [C] Outlet Saybolt Color, [D] Bed Volume = [B] / 6.35 Total Colour Unit Improvement per litre per Kg Ads. = ([D-C]*B)/ 6.35
15.09.2021 16:45 43 - - - - -
15.09.2021 21:00 41 171 22 30 27 215
16.09.2021 05:00 43 345 22 29 54 380
16.09.2021 13:00 42 337 21 26 53 265
16.09.2021 13:30 44 351 21 27 55 332
16.09.2021 21:00 42 333 21 25 52 210
17.09.2021 05:00 44 351 21 26 55 277
17.09.2021 13:00 40 320 20 25 50 252
17.09.2021 21:00 44 349 21 25 55 220
18.09.2021 05:00 44 351 20 25 55 277
18.09.2021 13:00 41 329 20 25 52 259
18.09.2021 21:00 44 356 21 25 56 224
19.09.2021 05:00 44 349 22 25 55 165
19.09.2021 13:00 51 409 22 25 64 193
19.09.2021 21:00 40 322 22 25 51 152
20.09.2021 05:00 41 329 22 25 52 156
20.09.2021 13:00 41 329 22 24 52 104
20.09.2021 21:00 42 337 22 25 53 159
21.09.2021 05:00 44 353 23 26 56 167
21.09.2021 13:00 42 339 23 25 53 107
21.09.2021 21:00 45 360 22 25 57 170
22.09.2021 05:00 44 349 22 24 55 110
22.09.2021 13:00 46 367 21 23 58 116
22.09.2021 21:00 41 329 22 25 52 156

23.09.2021 05:00 41 327 23 25 52 103
23.09.2021 13:00 42 339 22 23 53 53
23.09.2021 21:00 41 331 21 25 52 209
24.09.2021 05:00 47 379 24 27 60 179
24.09.2021 13:00 46 365 23 25 57 115
24.09.2021 21:00 42 339 21 23 53 107
25.09.2021 05:00 46 367 20 28 58 462
25.09.2021 13:00 46 365 21 24 57 172
25.09.2021 21:00 45 362 20 27 57 399
26.09.2021 05:00 47 379 22 26 60 239
26.09.2021 13:00 43 343 20 25 54 270
26.09.2021 21:00 41 327 23 27 52 206
27.09.2021 05:00 46 365 22 28 57 344
27.09.2021 13:00 45 360 20 25 57 283
27.09.2021 21:00 40 320 20 27 50 353
28.09.2021 05:00 43 347 24 27 55 164
28.09.2021 13:00 45 358 21 22 56 56
28.09.2021 21:00 45 362 21 24 57 171
29.09.2021 05:00 46 367 21 24 58 173
29.09.2021 21:00 48 768 22 23 121 121
30.09.2021 05:00 46 365 22 24 57 115
30.09.2021 13:00 46 369 22 24 58 116
30.09.2021 21:00 48 381 22 24 60 120
Total 16349 Avg.=21 .6 Avg.=25 .3 2575 9195
Test Results of Initial and at end of field trials using pilot skid.
Observations:
a) Filed trial for improvement of Saybolt color from kerosene type petroleum distillate were found successful using silica gel bed in pilot skid and performance was found superior than laboratory scale trials.
b) Total 16349 litres of Kerosene type petroleum distillate (ATF / MTO / SKO) was passed through 6.35 kg of silica gel bed which is equal to 2575 bed volume per weight of silica gel.
c) The average feed Saybolt color was 21.6 and average product color found 25.3.
d) Total 9195 colour unit improved per litre of sample per kg of silica gel adsorbent.

3. Experiments for Used Silica Gel Adsorbent:
Aim: To develop process for recovery of surface hydrocarbon and regeneration of used silica gel adsorbent.
To achieve above aspects, following experiments were done using used silica gel, Figure-8 represent the image of used silica gel collected after field trial.
3.1 Recovery of Surface Hydrocarbon from Used Silica Gel Adsorbent:
Aim: To develop process for recovery of surface hydrocarbon from used silica gel.
Experiment Condition / Procedure: Laboratory scale experiments were carried out using used silica gel in glass assembly, water was circulated from bottom to top and floated hydrocarbon volume was measured. The hydrocarbon concentration calculated and tabulated in below table-12. Figure -2 & 9 represent the image of laboratory scale surface hydrocarbon recovery system. Figure 11 represent the image of recovered hydrocarbon.
Table 12:

Used Silica Gel, Wt. in gm Hydrocarbon Recovered in ml Hydrocarbon Recovered in % Vol. / Wt.
100 14 14
150 17 11
Hydrocarbon Recovery from Used silica Gel.
Observations: From the above test results, it is observed that, used silica gel is having considerable amount of surface hydrocarbon in the range of 11 to 14 % Volume per weight of used adsorbent and simple water washing process can recover the same. The recovery of surface hydrocarbon from used silica gel will have many benefits for downstream activities like, regeneration or disposal of waste adsorbent,
a) It will reduce hazard contamination hence handling of waste will be safe.
b) It will recover hydrocarbon hence will reduce fire hazard, reduce releasing of volatile organic matter in air, and also reduce quantity of waste.
c) Recovered hydrocarbon will be reprocessed hence will realize fuel price from waste.
d) Water washed silica gel can be either send for regeneration or disposal.
3.2 Regeneration of Used Silica Gel Adsorbent:

Aim: To develop process for regeneration of used silica gel along with recovery of hydrocarbon.
Experiment Condition / Procedure: Take used silica gel (after water washed or without water wash) in laboratory scale regeneration assembly as shown in figure- 10. The laboratory scale experiments were conducted to verify the process performance using muffle furnace at 700 °C temperature, nitrogen / air flow 400 to 500 ml per minute, run time 100 minute in batch process. The observed test results are tabulated in below table-13. Figure- 3 & 10 represent the image of laboratory scale regeneration system, Figure-8 represent the image of used silica gel, figure-12 represent the image of regenerated silica gel and figure-11 of recovered hydrocarbon oil during thermal regeneration.
Table 13:

Silica Gel Details Silica Gel Wt. In gm Recovered Hydrocarb on In gm Recovered Hydrocarbon In % Vol. /Wt. Appearance of regenerated silica gel
Used silica gel with water washed 100 4 4 Dark brown silica gel become slight brownish white
Used silica gel without water wash 93.4 21 22.5

Used silica gel without water wash 100 21 21

Regeneration of used Silica Gel by Thermal air oxidation with recovery of hydrocarbon.
Observations: From above test results, it is observed that used silica gel can be easily regenerated by thermal air oxidation. The process is also recovering considerable amount of hydrocarbon (surface and adsorbed) up to 22.5 % volume per weight of adsorbent. The process is avoiding generation of waste as well as avoiding loss of precious hydrocarbon oil hence it make process more economical.
3.2.1 Performance of Regenerated Silica Gel:
Aim: To check the performance (efficiency) of regenerated silica gel for color improvement application.

Experiment Condition / Procedure: The performance (efficiency) of regenerated silica gel was carried out at laboratory by using same experimental condition as mentioned in experiment 1.2. The observed test results are tabulated in below table-14.
Table 14:

Sample Details Initial
Saybolt
Color Improved
Saybolt
Color Weight of Silica Gel, gm Sample
Volume,
ml Saybolt Color Improvement Efficiency, ml Sample / gm Adsorbent
SKO- T- 350B 16 23 0.2105 200 6651
SKO- T- 350B 16 22 0.1914 200 6270
SKO- T- 350B 16 23 0.2035 200 6880
Relative Performance of Regenerated Silica Gel
Observations: From above test results, it is observed that color improvement efficiency of regenerated silica gel is very close to the efficiency of fresh silica gel (table-4) for kerosene type petroleum distillate.
3.2.2 Quality of Recovered Hydrocarbon:
Aim: To check the quality of hydrocarbon oil that recovered from water washing or thermal regeneration process.
Testing of Quality Parameters: The recovered hydrocarbon oil was tested for key quality parameters and observed test results are summarised in below table-15. Figure 11 represent the image of recovered hydrocarbon oil.
Table 15:

Quality Parameters UOM Test Results
Density at 15 Deg. C gm/ cc 0.81 to 0.82
Total Sulphur % Wt. 0.66 to 0.84
Total Organic Nitrogen ppm Wt. 1200 to 2000
IBP Deg. C 68 to 78
FBP Deg. C 302 to 366
Quality of Hydrocarbon Oil Recovered from Water Washing or Thermal Regeneration

Observation: Above quality information of recovered oil can be useful for reprocessing of recovered hydrocarbon with refinery slop oil.
Advantages of the Invention:
The present invention is globally applicable to crude oil petroleum refining industries to improve Saybolt color, improve stability of Saybolt color, reduce organic nitrogen content, and reduce moisture content of kerosene type petroleum distillates. Furthermore, present invention also useful to recover hydrocarbon from used adsorbent and regenerate used adsorbent, hence present invention has many benefits to crude oil refining industries. Based on various experimental test results and observations, following benefits are envisaged,
1) Invented process is capable to improve Saybolt color of kerosene type distillate up to +30.
2) Silica gel is capable to adsorb up to 9000 Saybolt colour unit per litre kerosene type distillate per Kg of silica gel adsorbent.
3) Invented process is capable to improve Saybolt color stability comparable with hydro-treated kerosene type distillate.
4) Invented process is improving stability of Saybolt color hence it will reduce chance of kerosene type distillate product failure after production.
5) Invented process is capable to reduce organic nitrogen content.
6) Invented process is capable to reduce moisture content.
7) Sr. No. 1 to 6 indicate the improvement in quality of kerosene type distillate product.
8) Invented process is capable to recover surface hydrocarbon up to 14% volume by water washing.
9) Invented process is capable to recover surface and adsorbed hydrocarbon up to 22.5% volume by thermal regeneration process.
10) Invented process is capable to regenerate adsorbent, hence it is avoiding generation of hazardous waste.
11) Adsorbent used in process is easily available in the market at reasonable cost hence process is feasible and cost effective.
12) Invented process is recovering hydrocarbon and regenerating adsorbent, hence process is become more economical.

13) Invented process is operated at ambient temperature and pressure hence it is easy and safe to operate in the field.
14) The recovered hydrocarbon can be reprocessed, hence it will realize fuel price from waste.
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present invention as defined.

We claim:
1. A novel process for treating kerosene type petroleum distillate comprising:
i. passing kerosene type petroleum distillate through silica gel;
ii. recovering surface hydrocarbon from used silica gel by water washing; or
recovering surface and adsorbed hydrocarbon by thermal regeneration; and
iii. regenerating used silica gel obtained after Step-1 or after Step-2 by thermal oxidation.
2. The process as claimed in claim 1, wherein step ii, may be skipped.
3. The process as claimed in claim 1, wherein the thermal oxidation comprises:
i. raising furnace temperature from ambient to 350°C at the rate of 100°C per hour
while purging nitrogen; ii. switching purging gas from nitrogen to air and raising furnace temperature up to
700 °C.
4. The process as claimed in claim 1, wherein the efficiency of Saybolt color improvement is ˜7000 Saybolt color unit per ml of sample per gm of silica gel.
5. The process as claimed in claim 1, wherein the process improves Saybolt color of the distillate, improves stability of Saybolt color of the distillate, reduces organic nitrogen of the distillate, reduces moisture content of the distillate, recovers hydrocarbon from used silica gel and regenerates used silica gel.
6. The process as claimed in claim 1, wherein the kerosene type petroleum distillate treated by silica gel is found to be highly stable up to 60 days at 25 ± 2°C.