Mineral oils: processes and products – Refining – With solid catalyst or absorbent
Reexamination Certificate
2002-03-04
2004-10-19
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Refining
With solid catalyst or absorbent
C208S31000R, C208S31000R, C585S820000, C585S823000, C585S824000
Reexamination Certificate
active
06805790
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a novel process and an apparatus for the production of petroleum hydrocarbon stream with desired colour stability. Particularly, the invention relates to a process and an apparatus for the production of petroleum hydrocarbon stream from crude oil having high concentration of nitrogenous compounds. More particularly, the invention relates to a process and an apparatus for the production of Mineral Turpentine Oil (MTO) of boiling range 145-205 deg. C from crude oil having high concentration of nitrogenous compounds.
BACKGROUND OF THE INVENTION
In general, petroleum hydrocarbon solvents are manufactured in oil refineries. Originally fractions are obtained by drawing off suitable streams from crude oil atmospheric distillation columns, followed by various treatments to reduce the odorous and /or corrosive impurities. For many applications, solvents obtained by straight atmospheric distillation and hence, having the hydrocarbon composition typical of that of feedstock, from which they have been made, are used as such and thus no chemical conversion or separation is required.
More particularly, Mineral Turpentine Oil (MTO) is produced in the refinery by distilling the Kerosene (Kero)/Aviation Turbine Fuel (ATF) cut obtained from crude oil distillation column followed by treatment in Merox unit for the removal of Mercaptan. The Kero I ATF cut is sent to MTO splitter column having 26 valve trays. In this splitter, Kero/ATF is fed on tray 10 of the splitter and is fractionated in three streams viz. overhead stream, side stream or MTO product and bottom streams. MTO product is withdrawn from the tray above tray 20 by MTO product pumps. The overhead and bottom streams are always routed again with Kero/ATF product stream, bypassing Merox unit. The MTO splitter operates at the top pressure of 1.1 kg/cm
2
g. The heat required for distillation is supplied in a MTO splitter reboiler using Heavy vacuum gas oil (HVGO) circulating reflux as heating medium. The MTO product thus obtained is sent under flow control to air cooler where it is cooled and finally the cooled material is sent for storage. This product so obtained has the specifications given in Table-1.
TABLE 1
Specifications of MTO
Bureau of
Indian Specification
S. No.
Property
IS-1745-1978 (grade-II)
1
Density at 15° C. g/ml
To report
2
Color (saybolt), min
+20
3
Flash Point(Abel)° C., Min
35
4
Distillation
a) IBP, ° C., Min
145
b) 50% vol rec @ ° C.
to report
c) 95% vol rec @ ° C.
to report
d) FBP, ° C., Min
205
5
Aromatic contents % V, Max
40
6
Copper corrosion @ 50° C. for 3 Hrs
Not worse than No 1
7
Residue on evaporation, mg/100 ml
5
In general, MTO is manufactured in refineries using crude oils containing very low nitrogen and/or sulphur contents and the product meets the IS 1745-1978 specifications. The typical data of such crude oils is given in Table-2. In order to maximize the refinery profit margins, the Applicants attempted making MTO from Nigerian low sulfur and Persian Gulf (PG) mix high sulfur crude oils which is very cheap. The typical data of such crude oils is also given in Table-2. MTO produced from these crude oils was evaluated against IS 1745-1978 specifications and the data is tabulated in Table-3.
TABLE 2
Typical properties of Low and High nitrogen crude oils
Low nitrogen
crude oils
High nitrogen
Sr.
CHAR-
Bombay
South
crude oils
No
ACTERISTICS
high
Gujarat
Nigerian
PG mix
1
Density @ 15 deg.
0.8284
0.8004
0.8465
0.8745
C gm/ml
2
Total Sulfur % wt
0.15
0.07
0.15
2.8
3
Total
150
190
667
1300
Nitrogen . ppm
TABLE 3
Analysis Data of MTO produced from Nigerian Crude
Specification
S.
IS-1745-1978
No.
Property
(grade-II)
Results
1
Density at 15° C. g/ml
To report
0.7890
2
Color (saybolt), min (ASTM D156)
+20
+10
3
Flash Point(Abel)° C., Min
35
46
4
Distillation
a) IBP, ° C., Min
145
160.7
b) 50% vol rec @ ° C.
to report
177.3
c) 95% vol rec @ ° C.
to report
199.7
d) FBP, ° C., Min
205
204.9
5
Aromatic contents % V, Max
40
16.1
6
Copper corrosion @ 50° C. for 3 Hrs
Not worse than
1
No 1
7
Residue on evaporation, mg/100 ml
5
0.6
It is evident from Table-3 that the MTO sample is generally meeting all the specifications except the color, which is +10 against the requirement of +20(min). Colored MTO is not acceptable to the customers using the same for dry cleaning purpose and in the paint industry. It is also reported that the colored MTO affects the catalyst and therefore above MTO cannot be used in the process involving catalysts.
The applicants therefore, took up a systematic study to ascertain the genesis of color in MTO and also to develop economically viable and operationally feasible process for the intended purpose. The MTO sample produced from Nigerian crude as well as mixture of Nigerian and PG mix crude was thoroughly analysed for other properties such as trace metal impurities, sulfur and nitrogen contents. The result of this analysis in tabulated in table 4. The Applicants found that apart from small amount of iron (Fe) no other trace metals were detected. However, total nitrogen of 5.2 ppm with basic nitrogen content of 3ppm was observed along with 0.136% of sulfur and 2.5 ppm of mercaptans. These analysis data indicate that nitrogenous compounds and mercaptans present in the MTO may be responsible for coloration of the product.
TABLE 4
Analysis Data of MTO produced from Nigerian Crude
S. No.
Property
Results
1
Total nitrogen/Basic Nitrogen
5.2 ppm/5 ppm
(UOP 269-70T)
2
Total sulfur, % wt
0.136
3
Elemental analysis
Fe, <0.5 ppm
No element was found in
significant amount
4
H
2
S/Mercaptans
Nil/2.5 ppm
In order to prove the above hypothesis, the crude oils (Nigerian low sulfur and Persian Gulf (PG) mix high sulfur crude oils) being processed at the refinery were subjected to distillation and various cuts were produced. It was observed that 180-205° C. cut had +13 saybolt color rating. The nitrogen contents of 180-205° C. cut was 8.5 ppm. This infers that nitrogenous compounds and mercaptans are responsible for the color instability of MTO. The detailed analysis data of these samples are summarized in Table-5.
TABLE 5
Analysis Data of Fractions Prepared at R&D Center
Nigerian low
PG mix high
sulfur crude
Sulfur crude
S. No.
Property
180-205 cut
180-205 cut
1
Color (saybolt)
+13
+14
2
Copper corrosion @ 50° C.
1
1
for 3 Hrs
3
Total nitrogen, ppm
8.5
8.3
4
Total sulfur, % wt
5
Mercaptans, ppm as Sulfur
27
20
From the analysis data it is concluded that nitrogenous compounds in conjunction with mercaptans are imparting color instability to MTO. Therefore, removal of nitrogenous compounds would result in avoiding complex formation with mercaptans and is likely to result into improvement in color of MTO as well as the color stability on storage.
Following methods are generally employed for the removal of nitrogen impurities from hydrocarbon streams:
1. Treatment with sulfuric acid is used for partial or complete removal of unsaturated hydrocarbons, sulfur, nitrogen, and oxygen impurities, and other resinous and asphaltic compounds. It is used to improve the odor, color, stability, carbon residue, and other properties of the oil.
2. Caustic treatment using sodium (or potassium) hydroxide is used to improve odor and color by removing organic acids (naphthenic acids, phenols) and sulfur compounds (mercaptans, H
2
S). By combining caustic soda solution with various solubility promoters (e.g., methyl alcohol and cresols), up to 99% of all mercaptans as well as oxygen and nitrogen compounds can be removed from petroleum fractions.
3. Another method used by refineries for the removal of nitrogenous impurities is by catalytic hydro-treatment. This is a hydrogenation process used to remove about 90% of contaminants such as nitrogen, sulfur, oxygen, and metals from liquid petroleum fractions. These contaminants, if not removed from the petroleum fractions can have detrimental effects on the equipment, the catalyst efficiency and effective life, and the quality of the finish
Bhatnagar Akhilesh Kumar
Gupta Anurag Ateet
Misra Ambrish Kumar
Puri Suresh Kumar
Rajesh Muniaswamy
Griffin Walter D.
India Oil Corporation Limited
Nguyen Tam M.
Ohlandt Greeley Ruggiero & Perle L.L.P.
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