A kinetic study on the effects of alkaline earth and alkali metal compounds for catalytic pyrolysis of microalgae using thermogravimetry

• Alkali and alkaline earth metals compounds can promote the degradation of microalgae organic matters.
• Alkali and alkaline earth metals compounds can increase the initial decomposition temperatures of microalgae pyrolysis.
• Alkali and alkaline earth metals compounds can affect the microalgae pyrolysis overall activation energy.

In this paper, thermogravimetric (TG) analysis and kinetic modeling are applied to study the effects of alkaline earth and alkali metal compounds on catalytic thermal decomposition of microalgae. When alkaline earth and alkali metal compounds are added, the initial thermal degradation temperatures increased by about 3.2–10.2 K, and the final temperatures reduced by about 3.5–9.4 K. The results show that CaO, MgO, K2CO3, BaCO3 and Na2CO3 may shorten the time of pyrolysis, implying that alkaline earth and alkali metal compounds may promote the process of thermal degradation of organic matters. The first maximum weight loss rate is in the order of Na2CO3 > CaO > K2CO3 > BaCO3 > MgO > no additive. Em (weight means activation energy) varies from 99.60 to 134.05 kJ mol−1, which implies ignorable overall activation energies (Em) after alkaline earth and alkali metal compounds are added.