镉掺杂类水滑石催化剂的制备及其在木素超临界催化解聚中的初步应用
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摘要
采用化学共沉淀法制备不同镉掺杂量的镉镁铝类水滑石催化剂,并将其用在杨木乙醇木素超临界催化解聚中,解聚溶剂体系为乙醇。通过X射线衍射、热重分析、傅里叶变换红外光谱等方法对催化剂进行表征,确定了可形成镉镁铝类水滑石结构的最佳摩尔比。解聚产物GC-MS分析结果表明,木素超临界解聚产物复杂,主要为酯类和含苯环类物质。随着镁离子与镉离子摩尔比的增大,水滑石的结晶度先升高随后降低,其比值为8时结晶度最高,产物中酯类和苯环类物质含量最高,催化剂起到定向解聚的作用。
A series of hydrotalcite-like catalysts with various Cd2+were prepared by chemical co-precipitation.The catalytic depolymerization of aspen alcohol lignin was conducted in supercritical ethanol with catalysts.The catalysts were characterized by X ray diffraction,thermogravimetric analysis and FT-IR spectrometer,and the best mole ratios were obtained.The affecting changes in product distributions were characterized by GC-MS and the results showed that the degraded products of lignin mainly contained esters and benzene ring.The hydrotalcite crystallinity increased with mole ratio of magnesium and cadmium ions at first,and then decreased.The highest crystallinity was obtained when the specific value was eight,and the selectivity depolymerization products had high contents of esters and aromatic molecular species,indicating the catalyst played a role of directional depolymerization.
A series of hydrotalcite-like catalysts with various Cd2+were prepared by chemical co-precipitation.The catalytic depolymerization of aspen alcohol lignin was conducted in supercritical ethanol with catalysts.The catalysts were characterized by X ray diffraction,thermogravimetric analysis and FT-IR spectrometer,and the best mole ratios were obtained.The affecting changes in product distributions were characterized by GC-MS and the results showed that the degraded products of lignin mainly contained esters and benzene ring.The hydrotalcite crystallinity increased with mole ratio of magnesium and cadmium ions at first,and then decreased.The highest crystallinity was obtained when the specific value was eight,and the selectivity depolymerization products had high contents of esters and aromatic molecular species,indicating the catalyst played a role of directional depolymerization.
引文
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[2]TENORIO M J,CABAAS A,PANDO C,et al.Solubility of Pd(hfac)2and Ni(hfac)2·2H2O in supercritical carbon dioxide pure and modified with ethanol[J].The Journal of Supercritical Fluids,2012,70:106-111.
[3]SHU R Y,LONG J X,YUAN Z Q,et al.Efficient and product-controlled depolymerization of lignin oriented by metal chloride cooperated with Pd/C[J].Bioresource Technology,2015,179:84-90.
[4]PI′NKOWSKA H,WOLAK P,ZOCI′NSKA A.Hydrothermal decomposition of alkali lignin in suband supercritical water[J].Chemical Engineering Journal,2012,187:410-414.
[5]DAS N N,SRIVASTAVA S C.Catalytic characterization of bi-functional catalysts derived from Pd-MgAl layered double hydroxides[J].Bulletin of Materials Science,2002,25(4):283-289.
[6]BASILE F,FORNASARI G,GAZZANO M,et al.Thermal evolution and catalytic activity of Pd/Mg/Al mixed oxides obtained from a hydrotalcite-type precursor[J].Applied Clay Science,2001,18(1):51-57.
[7]LI H,MCDONALD A G.Fractionation and characterization of industrial lignins[J].Industrial Crops and Products,2014,62:67-76.
[8]CHENG S N,WILKS C,YUAN Z S,et al.Hydrothermal degradation of alkali lignin to bio-phenolic compounds in sub/supercritical ethanol and waterethanol co-solvent[J].Polymer Degradation and Stability,2012,97(6):839-848.
[9]卫瑾瑾,刘健,甘礼惠,等.竹木质素的NaOH-乙醇水溶液热降解及产物分析[J].新能源进展,2014,2(4):254-259.