Optimization of Conversion of High Free Fatty Acid Jatropha curcas Oil to Biodiesel Using Response Surface Methodology

Table 1

Independent variables and levels used for CCD in transesterification process.

Serial number	Variables	Symbols	Levels
			−1	−0.5	0	0.5	1
1	Catalyst; concentration; (% w/w)	𝐴	0	0.5	1.0	1.5	2.0
2	Temperature (°C)	𝐵	35	40	45	50	55
3	Time (min)	𝐶	30	67.5	105	142.5	180
4	Methanol-to-oil ratio (w/w)	𝐷	6	7.5	9	10.5	12