The Solvent Extraction Method Biology Essay

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Since the oil soluble compounds, mainly low molecular weight chelates of vanadium and nickel, were not removed by centrifuge method, an attempt was made to remove these by solvent extraction method. Solvents chosen for this study varied from non polar (n-C6, n-C7) to polar (ethyl acetate) and highly polar (ethyl acetate with 0.1 to 1.0 % H2SO4 or H3PO4). Properties of PDR are given in chapter-7.

Petroleum distillation residue was deasphalted-demetallated by n-C5, n-C6 and C7 alkanes. Demetalation increased as carbon number of n-alkanes decreased, hence n-pentane gave highest 85 and 90 percent vanadium and nickel respectively removal. Ethyl acetate gave the second highest metal (V + Ni) removal of 82 and 88 wt. % (Table 10.1 and 10.2). All solvents were found to be effective in removing water soluble salts; hence 100% sodium from PDR has been removed by all solvents. It was noted that rate of demetalation was varying with samples, which was probably depending on the type of metal complex in the oil. Hence, solvent extraction by ethyl acetate removed 82% vanadium and 88% nickel from PDR contains 35.0 ppm vanadium and 13.0 ppm nickel, removed 73% vanadium and 83% nickel from PDR contains 25.5 ppm vanadium and 3.6% nickel, and removed 57% vanadium from PDR contains 122.0 ppm vanadium (Table-10.3).

However, when sulfuric acid was added (0.1-1.0 %) in ethyl acetate there was no improvement in percent metal removal by solvent extraction. In fact it was found to decrease with increase in the amount of sulfuric acid (0.1 - 1.0). Similarly, addition of small amounts of phosphoric acid (0.1 to 1.0%) to ethyl acetate did not show any improvement for metal removal (Table 10.4).

Removal of vanadium increased with time up to 91%, which is due to chemical demetalation of vanadium porphyrins by H2SO4. Contacting time less effects on removal of Ni then on removal of vanadium, represent in Figure-10.1 Results of reaction time effect are summarized in Table 10.5.

Although solvent ratio higher than eight increases metal removal percent, the solvent recovery losses and process economy do not favor such ratios. The weight ratios of liquid solvent to oil, extraction temperature, recovery of solvent, and recovery of oil from residue are important factors in using solvent extraction methods. Moreover, the results show that processes employing hydrocarbon solvents (nC5,nC6 and nC7), used to modify the oily matrix solubility parameter in such a way that asphaltenes are separated, deasphaltation implies partial demetalation. Processes using polar solvents, scarcely miscible with petroleum are able to selectively extract from it metallic complexes of heteroatomic legends (e.g. metalloporphyrins).

The results for solvent extraction by mixtures of polar (ethyl acetate) and Non-Polar (n-heptane) solvents are presented in Table 10.6. Demetalation was found to decrease with mixture of the two solvents and demetalation becomes zero when ratio of n-heptane and ethyl acetate reaches between 70:30 and 50:50. It is also found that demetalation by ethyl acetate is equals to the demetalation results when we extract oil with n-heptane and ethyl acetate simultaneously.

HPCO is a high viscosity, gravity oil contain high asphaltene vanadium and nickel contents. This heavy Pakistani crude oil was demetalated and deasphalted by solvent extraction with n-pentane, n-hexane and CPCO. CPCO is a light Pakistani crude oil having high abundance of alkanes (especially normal alkanes). Removal of asphaltene by solvent extraction was increased as molecular weight of solvent decreased. In same pattern metalo organic compounds are concentrated in asphaltenes Hence, n-pentane gave highest removal of asphaltene 21.8%. n-hexane removed 17.7% and CPCO removed 13.7% asphaltene from HPCO. Similarly highest 100% and 97% vanadium and nickel were removed with n-pentane. N-hexane removed 98% and 95% vanadium and nickel respectively. Extraction with CPCO gave 53% and 45% vanadium and nickel removal when the mixture was not heated. Because normal alkanes of C9 to C14 are abundant in CPCO; it support the high reaction temperature. 99% and 83% vanadium and nickel respectively were removed when the mixture was boil for 30 minutes (Table 10.7).

HPCO was demetalated by 1% maleic acid in CPCO. HPCO and 1% maleic acid in CPCO in a ratio of 1:10 was boiled to reflux for 30 minutes. The mixture was cooled and filtered. Together dechealation and solvent extraction gave 100 removals of vanadium and nickel. Results are summarized in Table-10.7. Demetalation and deasphaltation with CPCO will be economical then solvent extraction with pure solvents. Handling and transportation problems may also be countered with this method.

Table 10.1

Solvent Extraction of Petroleum Distillation Residue (35ppm Vanadium)

Vanadium (ppm)

% Demetalation or Decrease in Vanadium

Solvent

Soluble Part

(Maltene)

Insoluble Part

(Asphaltene)

n-Pentane

5.25

595

85

n-Hexane

10.5

490

70

n-Heptane

13

464

62

Ethyl acetate

6.3

197

82

Table 10.2

Solvent Extraction of Petroleum Distillation Residue (13ppm Nickel)

Nickel (ppm)

% Demetalation or Decrease in Nickel

Solvent

Soluble Part

(Maltene)

Insoluble Part

(Asphaltene)

n-Pentane

1.30

234

90

n-Hexane

3.25

195

75

n-Heptane

3.50

100

73

Ethyl acetate

1.56

215

88

Table 10.3

Solvent Extraction by Ethylacetate of three different Samples of PDR

 

Vanadium

Nickel

Sample

 

PPM

% Removal

PPM

% Removal

PDR

Vanadium =35.0 ppm, Nickel=13.0ppm

Soluble

6.3

82

0.3

88

Insoluble

197.0

-

54.0

-

PDR

Vanadium =25.5 ppm,

Nickel=3.6ppm

Soluble

6.9

73

0.6

83

Insoluble

411.0

-

70.0

-

PDR

Vanadium =122.0 ppm

Soluble

52.0

57

*

-

Insoluble

723.0

-

*

-

* Not analysed

Table 10.4

Solvent Extraction by Ethyl acetate

Reagent/Acid

% Removal Vanadium

% Removal Nickel

1

No reagent

73

83

2

H2SO4 0.1%

74

75

3

H3PO4 0.1%

55

67

4

H2SO4 1.0%

66

68

5

H3PO4 1.0%

51

55

Table 10.5

Effect of time on Demetallization of PDR by Solvent Extraction with Ethyl acetate 1% H2SO4

(Solvent Sample Ratio 20:1)

 

Removal %

 

Vanadium

Nickel

Day 1

67

 68

Day 11

71

77

Day 30

75

79

Day 38

77

80

Day 91

91

83

Table 10.6

Solvent Extraction with mixture of polar and non-polar solvent

Heptane : EtOAc

% Removal Vanadium

% Removal Nickel

1

100:0

62

73

2

90:10

25

25

3

80:20

5

13

4

70:30

0

0

5

60:40

0

0

6

50:50

0

0

7

40:60

18

3

8

30:70

30

17

9

20:80

48

55

10

10:90

73

80

11

0:100

82

88

Table 10.7

Solvent Extraction of Heavy Pakistani Crude Oil

(Contact Time 30 minutes &

Sample Solvent Ratio 1:10)

S.No

Solvent

Temperature ËšC

Asphaltne %

Removal % Vanadium

Removal%

Nickel

1

n-Pentane

~36

21.84

100

97

2

n-Hexane

~69

17.60

98

95

3

CPCO

~25-30 °C

13.70

53

45

4

CPCO

~160

*

99

83

5

CPCO with 1% Maleic Acid

~160

*

100

100

* Not checked

Figure 10.1

Effect of time on Demetallization of PDR by Solvent Extraction with Ethyl acetate 1% H2SO4

(Solvent Sample Ratio 20:1)

Figure 10.2

Solvent Extraction with mixture of polar

and non polar solvent

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