In situ and Ex situ Catalytic Pyrolysis of Microalgae and Integration With Pyrolytic Fractionation

Area of Science:

• Biomass Thermochemical Conversion
• Catalytic Pyrolysis
• Biofuel Production

Background:

• Microalgae are promising feedstocks for biofuels due to high lipid content.
• Thermochemical conversion of microalgae faces challenges with non-lipid components (starch, protein) producing undesirable byproducts.
• Zeolite catalysts, like HZSM-5, show potential for upgrading pyrolysis products.

Purpose of the Study:

• To investigate the in situ and ex situ catalytic pyrolysis of lipid-rich Chlorella sp. using HZSM-5.
• To optimize aromatic hydrocarbon production from microalgae biomass.
• To evaluate a two-step fractional pyrolysis approach for selective product recovery.

Main Methods:

• Catalytic pyrolysis of Chlorella sp. with HZSM-5 at temperatures ranging from 450-550°C.
• Comparison of in situ and ex situ catalytic upgrading strategies.
• Assessment of a two-step fractional pyrolysis followed by catalytic upgrading.

Main Results:

• Both in situ and ex situ pyrolysis yielded similar product compositions, with benzene, toluene, and xylene as primary aromatics.
• Aromatic yields and selectivity increased with temperature, peaking at 550°C (36.4% aromatics/g ash-free microalgae).
• At 550°C, ex situ pyrolysis produced liquid products free of oxygenates and nitrogenous compounds. The two-step process yielded comparable results to single-step pyrolysis.

Conclusions:

• Catalytic pyrolysis with HZSM-5 is effective for producing hydrocarbon-rich bio-oil from microalgae.
• Higher pyrolysis temperatures (up to 550°C) favor aromatic hydrocarbon formation.
• Fractional pyrolysis coupled with catalytic upgrading offers a viable strategy for separating and recovering valuable products from different microalgal biomass components.