Research on catalytic pyrolysis of algae based on Py-GC/MS

Abstract

In order to improve the quality of catalysis products of algae, composite molecular sieve catalyst was prepared by digestion and crystallization of HZSM-5 to reduce the oxygen content of the catalytic products. According to the analysis of the pyrolysis products, the best preparation conditions were chosen of tetra propylammonium hydroxide (TPAOH) solution 2.0 mol l−1, cetyltrimethylammonium bromide (CTAB) solution 10 wt%, crystallization temperature 110°C, digestion–crystallization time: 24–24 h. The results indicate that the main function of catalysts is to promote the conversion of alcohols into hydrocarbons by reducing energy barriers. Catalysed by the composite molecular sieve, the content of alcohols in the pyrolysis products decreased from more than 30% to less than 10%, the content of hydrocarbons increased from 20% to nearly 60%, while all the adverse components remained at a low level, which indicates that the catalytic pyrolysis products are of high quality. The great deoxidation effect of composite molecular sieves is not only due to the expansion of the range of organic matter during re-pyrolysis, but also the increasing of the residence time of pyrolysis products inside the structure for the external mesoporous structure.

Effect of H-ZSM-5 and Al-MCM-41 Proportions in Catalyst Mixtures on the Composition of Bio-Oil in Ex-Situ Catalytic Pyrolysis of Lignocellulose Biomass

“…Then, the coke yield increased to 2.78 wt.% when using single H-ZSM-5 catalyst. The fluctuation of coke yield when using single H-ZSM-5 catalyst was caused by the microporosity structure of H-ZSM-5, which hindered the large molecule oxygenates to enter the pores and caused the growth of coke [9,12,17,18]. In the absence of Al-MCM-41 catalyst, there was no pathway to convert large oxygenates to small ones before reacting with H-ZSM-5 catalyst.…”

“…However, H-ZSM-5 catalyst is also known for its high coking formation and rapid catalyst deactivation [11,12,15,16]. Some high-molecular-weight oxygenates, which cannot enter the pores of microporous H-ZSM-5 catalyst, polymerize and form coke on the catalyst surface [9,12,17,18].…”

“…Al-MCM-41 is one of the mesoporous materials with high surface area and more accessible reaction sites than the traditional H-ZSM-5 catalyst [17,19]. However, products may escape before complete pyrolysis because the pore size is too large [18]. In addition, catalytic pyrolysis of biomass using Al-MCM-41 catalyst results in the formation of polycyclic aromatic hydrocarbons (PAHs), which is not a desirable product in the bio-oil [17,19,20].…”

Biogasoline Obtained Using Catalytic Pyrolysis of Desmodesmus sp. Microalgae: Comparison between Dry Biomass and n-Hexane Extract

“…sample, and such bed geometry was not obeyed in the case of n-hexane extracts simply dropped either in the reacting cup or in the reacting cup containing a defined quantity of alumina; (iv) the quantity of other C5-C12 products, generally associated with oxygenated and nitrogenated products, is always higher in presence of alumina; then, the alumina catalyst is helping the production of the desired pure hydrocarbons but also favours the formation of more complex molecules, in particular nitrogenated molecules and to a lesser extent some oxygenated products; (v) the nitrogenated products, essentially alkylated pyrroles, were produced to a rather large extent with the dry biomass but were under the detection limit when pyrolysing the extracts. This is an important result, as the reduction of the content of nitrogen compounds is a goal for increasing the quality of microalgae pyrolysis products [35].…”

Evolved Gas Analysis and Kinetics of Catalytic and Non-Catalytic Pyrolysis of Microalgae Chlorella sp. Biomass With Ni/θ-Al2O3 Catalyst via Thermogravimetric Analysis

“…However, many studies are available on the catalytic degradation of microalgae via pyrolysis processes to optimize biofuel production (Zhao et al, 2021). But still, it is difficult to establish its industrial-scale employment due to the lack of deep understanding of pyrolysis mechanism, conversion rate, the extent of conversion, and kinetic behavior (Ali et al, 2021).…”