Effects of potassium additives on the combustion characteristics of graphite as a heating source of heat-not-burn tobacco

Abstract

“Heat-not-burn” tobacco with an external heating source is a cleaner alternative to conventional cigarettes due to its lower emission of nicotine, CO and tar in the smoke, and graphite is a promising carbon heating source for a “heat-not-burn” tobacco product yet is not easy to be fired. This work aims to improve the combustion properties of graphite using potassium catalysts. Thermal gravimetric analysis is performed to investigate the combustion properties, and a first-order kinetic model is applied to describe the combustion process. Scanning electron microscopy is used to observe the surface morphology, and the mineral and elemental composition are investigated by powder X-ray diffraction and energy dispersive spectrometry, respectively. The results indicate that the potassium additives can significantly decrease the ignition temperature of the graphite samples by 51–124 °C, and the promotion effects are closely related to the potassium and oxygen content of the additives. Further kinetic analysis implies that K and O can decrease the activation energy required for the oxidation reactions by 45.1% from 194.5 to 106.8 kJ mol⁻¹, thereby improving the graphite combustion. Moreover, potassium can play the role of “O₂ transfer”, which can transfer atmospheric oxygen to support graphite combustion. K₂CO₃ is a suitable catalyst for graphite combustion, and the suggested addition amount is 0.88% in weight.