Molecular Simulation of Non-hydrolyzable Organic Matter and its Hydrocarbon Generation Potential during Pyrolysis

Cyanobacteria-rich phytoplankton is very common in freshwater lake. It is rich in organic matter and could generate hydrocarbons during the pyrolysis. In this study, one cyanobacteria-rich phytoplankton sample (GP sample) was collected by using a continuous-flow centrifuge at 8000 rpm from the Liuhuahu Park in Guangzhou, China. And the hydrolyzable organic matter (lipid fraction, alkaline and acidic hydrolyzable fraction) was removed from the sample: nonhydrolyzable organic matter (NHOM) was left. The NHOM was analyzed by ¹³C NMR (CP/TOSS), XPS, Rock-Eval and closed pyrolysis to research its chemical structure and its generation mechanisms of bio-crude oil. And a type Ⅰ kerogen sample was used to be a contrast with the NHOM in this study.

Through the pyrolysis, gas (C_1-5) and soluble hydrocarbon (C_6-14, C₁₄₊)generated from NHOM. Comparing with the kerogen sample, the NHOM hydrocarbon production was less in low maturity, but with the temperature increasing, two samples' hydrocarbon production rate turns to same. This indicated that, NHOM could generate the oil-crude, however, its capability was less than type Ⅰ kerogen.

To reflect the chemical characteristic of NHOM, the NHOM average molecular structure was established. The NHOM chemical structure was similar with the kerogen: both of them have long aliphatic carbon chains and small aromatic clusters. A single NHOM aliphatic chain could contain more than twenty carbon atoms, this meaning that NHOM has a even more hydrocarbon generation potential than type Ⅰ kerogen in perspective of molecular structure simulation.

This study took the NHOM from cyanobacteria-rich phytoplankton as experiment object, characterized it chemical structure by analysis and molecular simulation, researched it hydrocarbon generation potential in pyrolysis process, and revealed it relationship with kerogen.