Study On The Mechanism Of Oxygen-alkali Pulping Of Rice Stra

Non-wood fiber materials have become the focus of the pulp and paper research with the increasing demand for pulp and the lack of paper-making materials.Straw which has the features of low cost,sheer volume and relatively concentrated distribution is to be China’s major crop residues and becomes rare papermaking raw materia ls.Yet it’s always been of great concern for energy conservation,reducing consumption and clean technology of pulping.Oxygen alkaline pulping is raised by the high whiteness puree and liquor tractability as a new method for grasses raw pulping,and only it can be achieved industrial production,a promising way will certainly be provided for sustainable development of non-wood pulp and paper fiber materials.Currently,the research method of oxygen alkaline pulping still remains in the theoretical level and still needs further study in China.This paper selected straw as raw materials using oxygen alkaline for pulping and compared to the traditional alkaline pulping,and quantification and qualitative analysis offorage or slurry and black liquor respectively after reaction.Revealing advantages of straw alkali-oxygen pulp yield and delignification,and then drawing the mechanism of oxygen delignification.The results are as follows:(1)Research on traditional alkaline and oxygen alkaline precooking of straw shows that oxygen alkaline precooking has a relatively large effect on the chemical composition of fodder or slurry when the material raises from room temperature to 70℃～120℃,the oven-dried ingredients were gradually reduced from 42.04g and 38.83g to 33.94g and 32.20g,ash declined lower than the traditional method,silicon dioxide was on the contrary.Oxygen-alkali delignification effect was significantly higher than traditional soda.(2)Black liquor pH,residual alkali and total solids of oxygen precooked changed significantly with the increasing temperature witch significantly accelerated the precooking reaction process compared with the traditional method.The content of lignin was 13.1842g at 120℃ by oxygen alkaline,while conventional alkali was only 7.4676g,carbohydrate is corresponding to 5.5877g and silicon dioxide was 7.3610g.(3)The research of soda-oxygen cooking of rice straw shows:silicon dioxide content increased first and then decreased gradually in black liquor,the degree of delignification was enhanced,and 45.01%lignin was obtained with the temperature of 120℃ for 140min.(4)Tracking and analysis of black liquor dissolved oxygen see:dissolved oxygen concentration is very low in 80-100min due to relatively strong alkali-oxygen reaction,oxygen delignification is remarkable.(5)Hemicellulose and lignin FT-IR analysis of straw black liquor shows that hemicellulose absorption peak is weak at 1169cm-1,the absorption peak at 1157cm-1 is sharp,a large differences between hemicellulose structure.Lignin contains paraben,guaiac wood-based and lilac group,and guaiac wood-based of lignindissolve faster than condensationlilac structural unit.(6)Hemicellulose and lignin 1H-NMR and 13C-NMR analysis of straw black liquor shows:hemicellulose sugar ring structure mainly is composed by pyran ring structure of β-glycoside linkage.The lignin structures of β-1,β-5,β-β and ether linkages have a high reactivityfor the cook drugs at higher cooking temperatures,andβ-formaldehyde elimination reaction also increases.Straw lignin structure forms a large amount of carboxyl groups which mainly non-conjugated carboxyl group during alkali-oxygen cooking process.Lignin condensed structure has been destroyed,aromatic ring of containing substituents and no substituen is in varying degrees of degradation.β-O-4 bond reactivity increases with the temperature rising,and accelerates the removal of lignin and fragmented.(7)Alkali-oxygen delignification kinetics shows:with respect to residual lignin content and the losses of raw material,experimental results showed that the reaction kinetics of staw alkali-oxygen delignification followed pseudo-first-order rate models.Finally,determination of the bulk delignification activation energy was 19.7686 kJ/mol,supplementary delignification activation energy was 39.7677 KJ/mol,and the residual delignification activation energy was 42.9863 kJ/mol according to the Arrhenius equation.