Characteristics and Evolution of Nitrogen in the Heavy Components of Algae Pyrolysis Bio-Oil

Abstract

Algae pyrolytic bio-oil contains a large quantity of Ncontaining components (NCCs), which can be processed as valuable chemicals, while the harmful gases can also be released during bio-oil upgrading. However, the characteristics of NCCs in the bio-oil, especially the composition of heavy NCCs (molecular weight ≥200 Da), have not been fully studied due to the limitation of advanced analytical methods. In this study, three kinds of algae rich in lipids, proteins, and carbohydrates were rapidly pyrolyzed (10−25 °C/s) at different temperatures (300−700 °C). The biooil was analyzed using a Fourier transform ion cyclotron resonance mass spectrometer equipped with electrospray ionization, and the characteristics and evolution of nitrogen in heavy components were first obtained. The results indicated that the molecular weight of most heavy NCCs was distributed in the 200−400 Da range. N 1−3 compounds account for over 60% in lipid and protein-rich samples, while N 0 and N 4 components are prominent in carbohydrate-rich samples. As temperature increases, most NCCs become more aromatic and contain less O due to the strong Maillard and deoxygenation reactions. Moreover, the heavier NCCs were promoted to form lighter compounds with more nitrogen atoms through decomposition (mainly denitrogenation and deoxygenation). Finally, some strategies to deal with the NCCs for highquality bio-oil production were proposed.a Calculated by difference. Carbohydrates = 100%moisture−ash− lipid−proteins.

Characteristics and evolution of heavy components in bio-oil from the pyrolysis of cellulose, hemicellulose and lignin

“…The oil yields of three samples. 27,28,[35][36][37][38][39]. Considering that the bio-oil is generally acidic and oxygen-contained, the ESI ionization source which is more sensitive to polar substances was chosen [40].…”

“…Considering that the bio-oil is generally acidic and oxygen-contained, the ESI ionization source which is more sensitive to polar substances was chosen [40]. Furthermore, the negative ion mode (ESI (− ) ) was chosen instead of the positive one (ESI (+) ) because the bio-oil obtained from model compounds has little nitrogen and sulfur, which are preferred by ESI (+) [39]. The details of basic instrument setting have been mentioned in our previous study [39].…”

“…Furthermore, the negative ion mode (ESI (− ) ) was chosen instead of the positive one (ESI (+) ) because the bio-oil obtained from model compounds has little nitrogen and sulfur, which are preferred by ESI (+) [39]. The details of basic instrument setting have been mentioned in our previous study [39]. Before analysis, the bio-oil was diluted with CH 3 OH (LC/MS grade) to 0.4 mg/ml for a better ionization and separation in the FT-ICR-MS [39,41,42], and the instrument was calibrated by NaCOOH solution [43].…”

“…The details of basic instrument setting have been mentioned in our previous study [39]. Before analysis, the bio-oil was diluted with CH 3 OH (LC/MS grade) to 0.4 mg/ml for a better ionization and separation in the FT-ICR-MS [39,41,42], and the instrument was calibrated by NaCOOH solution [43]. Then the sample was infused into the MS at a rate of 120 μml/h.…”

“…After testing, those signal with a S/N ≥ 3 were selected [28] for further calculation using MATLAB script [39] and their chemical formulas were determined by several rules listed in Table 2. Besides, the solvent used to dilute the oil sample was also analyzed, and the prominent signals in solvent mass spectrum were abandoned in the experiment results.…”