Thermal behavior and kinetics of co-pyrolysis of cellulose and polyethylene with the addition of transition metals

The influence of the addition of transition metals involving nickel (Ni), cobalt (Co), iron (Fe) and manganese (Mn) on the thermal behavior and kinetic of co-pyrolysis of cellulose (CL) together with polyethylene (PE) was investigated according to thermogravimetric analysis (TGA). It is found that the involvement of transition metals acting as catalysts could promote the decomposition of individual component (CL and PE) in the mixture. The initial decomposition temperature of CL and PE in the mixture is reduced by 91–136 °C and 8–15 °C, respectively, after the addition of transition metals in comparison with that of the mixture of CL and PE. Meanwhile, transition metals could intensify the synergistic interactions between CL and PE, especially during the pyrolysis stage assigned to CL decomposition. The maximum difference of weight loss in this stage is −9.30% to −14.10% for transition metals treated-mixtures while that of the mixture without transition metal treatment is −2.99%. Kinetic results show that the co-pyrolysis of transition metal-involved CL/PE mixtures can be well described as two consecutive first order reactions. The activation energy (E) of CL and PE in the mixture is reduced by 53.21–80.53 kJ/mol and 8.23–12.36 kJ/mol, respectively, as transition metals were involved. In addition, the content of transition metal makes a large influence on the thermal behavior and kinetics of co-pyrolysis of CL/PE mixture.