Carbonization of waste organic matrices in zinc-based molten salts

Molten salt driven catalytic carbonisation offers a new and emerging technology approach for treating organic wastes to achieve negative CO2 emissions and a circular carbon economy by converting the low-value carbon content of the waste into high value solid carbon materials which can be reused, and also converting the hydrogen content of the waste into a low-carbon hydrogen-rich fuel gas. In the work herein, a methodology to handle pure ZnCl2 (and load it into batch reactors) was built. The ZnCl2 used to this purpose was provided by VWR Chemicals (>97% of purity). Pellets of HDPE were provided by polymer testing laboratory. After that, some experimental trials on molten salts assisted pyrolysis using ZnCl2 in mixture with HDPE were conducted. Then the HDPE pellets were milled to obtain filaments with dimensions of 1mm x 2mm. The preliminary collected outcomes showed that, when the reaction temperature increased from 300 to 380 °C for 30 min, the gaseous products yield increased from values below 1%w/w to 3%w/w. In both experiments hydrogen was the main component (90 % mol). With an increase of the reaction time from 30 min to 3 h an enhancement in the production of light olefins in the place of hydrogen was observed. TGA analyses were conducted of ZnCl2, of HDPE and of HDPE in the presence of ZnCl2 and the catalytic activity of ZnCl2 was demonstrated by an improvement of the mass loss rate.