Optimization to Hydrothermal Liquefaction of Low Lipid Content Microalgae Spirulina sp. Using Response Surface Methodology

Table 6

The main FT-IR function group composition of biocrude from HTL of Spirulina sp.

Frequency range cm^−1	Frequency cm^−1	Assignment
550–450	537	S–S stretching
750–650	617, 697, 745	Secondary amid N–H wagging
915–650	835, 903	O–H bending
965–930	962	Oxime N–O stretching
1,060–1,020	1,025	S=O stretching
1,070–1,050	1,064	CH2 twisting
1,300–1,100	1,151, 1,177	C–O stretching
1,370–1,330	1,365	Aromatic nitro compound NO2 symmetric stretching
1,400–1,450	1,448	Azo compound N≡N stretching
1,540–1,500	1,490	Aromatic nitro compound NO2 asymmetric stretching
1,560–1,530	1,535	Secondary amide N–H bending, C–N stretching
1,615–1,565	1,598	Pyridine C–N stretching, C=C stretching
1,640–1,680	1,662	Primary and secondary amide C=O stretching
2,130–2,100	2,102	Aromatic isonitrile–N–C stretching
2,180–2,110	2,186	Aliphatic isonitile-N–C stretching
3,000–2,800	2,846, 2,909	C–H3 stretching
3,105–3,000	3,019, 3,066, 3,051	CH2 stretching
3,190–3,170	3,179	Primary amide NH2 symmetric stretching