Study On Degradation Technology Of Lignin In Tobacco Stem

Papermaking reconstituted tobacco sheet is made of tobacco stem, powder and wasted leaves in the production of cigarette according to the theory of pulping and papermaking manufacturing process, the property of the sheet is close to the one made from natural tobacco leaves and the sheet has characteristics of low tar content, good filling performance and so on. However, due to the high content of lignin in tobacco stem, the quality and safety of cigarette were affected since lignin pyrolysis can produce phenol, catechol, alkyl catechins, causing harshtaste and carcinogenic effect. As the voice of reducing tar contentis is ever-increasing, lignin must be degraded so that the quality of tobacco can be improved. In this paper, acetic acid, glycerin alkaline, oxygen alkaline treatment process were mainly researched, aimed to reduce the lignin content in the tobacco stem. The tobacco slice was made from treated tobacco stem, and the changes of the harmful components in flue gas were studied by Py-GC/MS, the results are as follows:1. The optimal conditions of acetic acid method were: liquid-solid ratio of acetic acid and tobacco stem 15 mL·g-1, the concentration of acetic acid 70%(v/v), the dosage of catalyst HCl 1.5%, reaction time 2h, the content of lignin is 6.29% and the pulp yield is 73.4%, compared with the industrial pretreatment of water soaking process, the content of lignin reduced by 29.2%, the content of pyrocatecholin cracking gas decreased by 22.5%, as one of seven harmful ingredients in cigarette smoke—phenol content decreased by 19.4%, and the total content of harmful substance reduced by 37.1%.2. The optimal conditions of glycerin alkaline method were: dosage of potassium hydroxide 45%, reaction temperature 200℃, liquid-solid ratio 11:1, reaction time 0.5 h, the content of lignin is 5.06% and the pulp yield is 37.1%, compared with the industrial pretreatment of water soaking process, the content of lignin reduced by 43.0%. The content of harmful substance in cracking gas decreased significantly, the content of phenol and pyrocatecholin cracking gas decreased by 52.6% and 31.3% respectively and the total content of harmful substance reduced by 38.1%.3. The optimal conditions of oxygen alkaline method were: liquid-solid ratio 10 m L?g-1, dosage of potassium hydroxide 35%, reaction temperature 120℃, reaction time 40 minutes, oxygen pressure 0.6 MPa, and usage of protective agent MgCO3 0.5%, the content of lignin is 4.63% and the pulp yield is 39.8%, compared with the traditional pretreatment of water soaking process, the content of lignin reduced by 47.8%, the content of phenol and pyrocatecholin cracking gas decreased by 60.8% and 25.0% respectively and the total content of harmful substance reduced by 37.6%. The addition of protective agent MgCO3 can effectively increase the content of holocellulose in tobacco stem thus increase the pulp yield.4. The content of phenolic compounds in cracking gas increased with the rising of lignin content, and the content of ketones and aldehydes decreased with the rising of lignin content. The peak area of phenol, guaiacol, 4-vinylguaiacol, paraethyl phenol, eugenol and vanillin in cracking gas has good linear correlation with the content of lignin.