Table 3.

Results of designed experiments.

Run	Catalyst (%v/v)	Temperature ($°C$)	Retention time (h)	Relative viscosity reduction Δη (%)
1	0.2	80	39	2.56
2	0.4	90	55	2.08
3	0.4	90	22	4.53
4	0.4	70	22	10.20
5	0.4	70	55	−35.35a
6	0.6	80	6	3.47
7	0.6	100	39	−31.24a
8	0.6	80	39	9.10
9	0.6	80	39	8.22
10	0.6	80	72	4.10
11	0.6	80	39	10.13
12	0.6	80	39	9.27
13	0.6	60	39	4.66
14	0.8	70	22	9.05
15	0.8	70	55	4.66
16	0.8	90	22	10.52
17	0.8	90	55	1.62
18	1.0	80	39	8.05

^aNegative numbers indicate an increase of viscosity.