HRTEM image changes on heating and thermogravimetric characteristics of barkinite

Barkinite, one of Chinese special maceral, was chosen to study its peculiar thermal characteristics based on thermogravimetric analysis and Rock-eval analysis by comparing vitrinite with bark coal. The changes of chemical structure by heat-treatment of barkinite were discussed by HRTEM. The distribution of functional group of barkinite was studied by Micro-FTIR method. The results show that barkinite has the highest mass loss and the maximum rate of mass loss among these three samples. Barkinite and vitrinite have both orientated layers after temperature above 350℃. With the increasing of temperature, the orientation in aromatic layer is obviously improved and some layers in stacks increase. At the same temperature, for barkinite and vitrinite, three fringes show the greatest abundance, namely, naphthalene, 2×2, and 3×3 fringes, following by 4×4 and 5×5 fringes. Barkinite has a higher abundance of naphthalene than vitrinite and has lower abundances of larger aromatic fringes than vitrinite, for instance, 3×3, 4×4, and 5×5 fringes. With the increasing of temperature, the content of naphthalene in barkinite and vitrinite is increased. Their abundance reaches the highest at 450℃ that is also the temperature of the maximum mass loss rate of barkinite, which indicates that the thermal characteristics of barkinite is related to the abundance of naphthalene in the chemical structure of barkinite.