Studies on thermal decomposition behaviors of demineralized low-lipid microalgae by TG-FTIR

In this work, dilute acid washing of typical low-lipid microalgae has been performed to remove ash-forming inorganics for mitigating the negative consequences during pyrolysis process. In order to investigate the potential influence of demineralization, the kinetics and pyrolysis behaviors of pretreated Chlorella vulgaris was systematically studied using thermogravimetric analysis coupled by fourier transform infrared spectrometer (TG-FTIR). TG analysis showed that the temperatures corresponding to decomposition peaks for pretreated samples shifted to the low temperature zone. Comparing with the removal of inorganics, the physiochemical structure changes of microalgae played the dominant role in decomposition of carbohydrate and protein fractions. For evolved gas, acid washing suppressed the formation of CO2 and increased the generation of C-H. It was noteworthy that the production of HCN by cracking of dipeptides was promoted clearly. HCl-5% had the lower average activation energy, residual mass (22.97%) and more desired gaseous products (pyrolysis effectiveness index S = 0.32).