Table 1 Experimental matrix and experimental plan of the face centered composite design
Number of experiments | Experimental variables | |||||||
|---|---|---|---|---|---|---|---|---|
X1 | X2 | X3 | X4 | Volume of EAA (ml) | Volume of H2SO4(ml) | Temperature (°C) | Heating time (min) | |
1 | 1 | 0 | −1 | −1 | 0.3 | 1.5 | 25 | 10 |
2 | 0 | 1 | 1 | 1 | 0.2 | 2.5 | 55 | 30 |
3 | 1 | −1 | −1 | 1 | 0.3 | 0.5 | 25 | 30 |
4 | 0 | 0 | 0 | 0 | 0.2 | 1.5 | 40 | 20 |
5 | −1 | 1 | 0 | −1 | 0.1 | 2.5 | 40 | 10 |
6 | −1 | 0 | −1 | 0 | 0.1 | 1.5 | 25 | 20 |
7 | 0 | 0 | 0 | 0 | 0.2 | 1.5 | 40 | 20 |
8 | 0 | −1 | 1 | 0 | 0.2 | 0.5 | 55 | 20 |
9 | 1 | 1 | 1 | −1 | 0.3 | 2.5 | 55 | 10 |
10 | −1 | −1 | 0 | 1 | 0.1 | 0.5 | 40 | 30 |
11 | 0 | 0 | 0 | 0 | 0.2 | 1.5 | 40 | 20 |