Study On The Effect Of Different Solvents On The Degree Of Re-permeation And Pyrolysis Characteristics Of Tobacco Stem

As one of the main raw materials of cigarette,tobacco stem were processed to obtain a higher filler value and better combustibility,which plays a very important role in reducing harm and coke,reducing formula cost and improving cigarette physical quality.However,besides used as cigarette raw material,most of the tobacco stem can not be fully utilized,but are disposed of landfill or direct incineration,resulting in the waste of resources and environmental pollution problems.In this paper,tobacco stem was used as raw material,a quantitative characterization method of tobacco stem re-permeation degree based on texture analyzer was established and the effects of different solvents on tobacco stem permeability and pyrolysis characteristics was investigated,in order to lay a foundation for accurate and objective evaluation of tobacco stem re-permeation degree,improving the pyrolysis characteristics and product distribution of tobacco stem raw materials,and promoting the multi-purpose development of tobacco stem.The main conclusions are as follows:(1)The test parameters of the quantitative characterization method of tobacco stem repermeation degree based on texture analyzer are: the probe model is HDP / BSK shear probe,the pre-test,test and return speeds are 1.0 mm / s respectively,the trigger force is 15 g and the strain is 170%.The influence of various factors on the degree of permeability is strain > test speed > trigger force.The intra day and intra day precision of this method are 6.44% and 4.26%respectively,which can be used to quantitatively characterize the degree of re-permeability of tobacco stem.(2)The degree of re-permeability of tobacco stem in the four regions decreased with the increase of stem years,length and diameter,increased with the increase of stem washing time and stem washing temperature,and first increased and then decreased with the increase of stem storage time.Under the same treatment conditions,the order of the degree of re-permeability after treatment with four solvents was hydrochloric acid > sodium hydroxide > water > ethanol.(3)Among the four solvents,hydrochloric acid,sodium hydroxide and water had a greater effect on the composition and structure of tobacco stem,while ethanol had a smaller effect.After solvent treatment,the mass retention rate of tobacco stem was alcohol washing > alkali washing > acid washing > water washing.Elemental composition analysis showed that acid washing increased the carbon content and showed a high removal rate of inorganic species.The microstructure,pore structure and surface chemical structure after solvents treatment showed that acid,alkali and water washing changed the internal structural characteristics of tobacco stems to a certain extent.(4)After solvents treatment,the unstable volatile components in the tobacco stem are reduced,which leads to the increase of the initial pyrolysis temperature of the tobacco stem.Meanwhile,hydrochloric acid pretreatment increased the maximum pyrolysis rate temperature of cellulose decomposition stage and decreased the char residues due to the large removal of inorganic species,while alkali treatment produced the opposite result.After acid,alkali and water washing,the comprehensive pyrolysis index of tobacco stems increased significantly,indicating that the corresponding solvent treatment had a positive effect on the pyrolysis characteristics.The released gaseous products during the pyrolysis process were also monitored by using TG-FTIR technique,and the gaseous release behavior was diferent from each other.Pyrolysis kinetic analysis based on Coats-Redfern method showed that F1.5 chemical reaction model can be used to describe the pyrolysis stages of tobacco stem samples and a decreased activation energy was observed during the decomposition of cellulose stage for the acid,alkali and water washed samples.