Optimized diethanolamide surfactant production from waste cooking oil using K2CO3/zeolite catalyst

The diethanolamide surfactant from waste cooking oil using zeolite supported potassium carbonate (K2CO3/zeolite) catalyst was successfully synthesized. The zeolite was activated by acid treatment followed by impregnation of K2CO3 at various K2CO3−to-zeolite ratios of 2:1, 4:1, and 6:1. K2CO3/zeolite catalysts were analyzed by Fourier transform infrared spectrophotometer (FTIR) and X-ray diffractometer (XRD). The transesterification reaction was performed to convert waste cooking oil into methyl ester using potassium hydroxide (KOH) catalyst. The transesterification product was confirmed by FTIR spectrophotometer and gas chromatography-mass spectrometer (GC-MS). The obtained methyl ester and diethanolamine solution were refluxed over K2CO3/zeolite catalyst to produce diethanolamide surfactant. The formation of diethanolamide was monitored using FTIR spectrophotometer. The surface-active properties of diethanolamide surfactant were assessed in terms of foam stability, emulsion index, and surface tension. The reaction of methyl ester and dietanolamine using K2CO3/zeolite with K2CO3−to-zeolite ratio of 2:1, 4:1, and 6:1 successfully produced diethanolamide surfactant with total conversion of 86, 92, and 89%, respectively. K2CO3/zeolite (6:1) catalyst produced the highest foam volume and emulsion index of 33.91 cm3 and 68.60%, respectively. The diethanolamide surfactant produced from amidiation reaction over K2CO3/zeolite (6:1) catalyst showed stable foam and emulsion with the reduction of surface tension of 8.46 dyne/cm.