Preparation and Characterization of Alkaline and Acidic Heterogeneous Carbon-Based Catalysts and Their Application in Vegetable Oil Transesterification to Obtain Biodiesel

Table 2

Elemental composition obtained from the XRF analysis of alkaline and acidic catalyst samples.

Elements	Catalyst samples
	1K	2K	3K	3TA	3SA	3CA
CH2	90.95	89.02	85.58	92.47	91.09	76.35
Ca	7.38	7.83	12.41	7.25	4.79	23.29
K	0.50	2.01	1.19	0.17	0.13	—
S	0.09	0.09	0.06	0.11	2.38	0.03