The structure of milled wood lignin（MWL）, isolated via the Bjrkman procedure, was studied by means of 1H NMR spectroscopy and Fourier transform infrared spectroscopy, and then its pyrolytic product distribution was ...The structure of milled wood lignin（MWL）, isolated via the Bjrkman procedure, was studied by means of 1H NMR spectroscopy and Fourier transform infrared spectroscopy, and then its pyrolytic product distribution was investigated on a pyrolysis device. MWL obtained from Manchurian Ash（MA） contained more methoxyl and free phenolic hydroxyl groups per C9 unit than MWL from Mongolian Pine（MP） due to the existence of both guaiacyl and syringyl units, which have a major influence on the pyrolysis behavior of lignin. The results of pyrolysis show that MWL from MA generated a higher yield of bio-oil, mainly composed of phenols, guaiacols, syringols and catechols, and a less yield of char, in addition to the gaseous products CO, CO2, methane and methanol, compared with MWL from MP. Guaiacol and syringol were the typical products from G-lignin and S-lignin, probably attributed to the easier cleavage of the aryl-alkyl linkage in the side chain compared with the C―OCH3 bond in the benzene ring. The degradation of MWL from MP was dominated by the demethylation reaction and the cleavage of aliphatic ―CH2OH at the γ-position, followed by the cracking of the Cα―Cβ and C4―Cα bonds.展开更多
In order to understand the structural characteristics of lignin in triploid clones ofPopulus tomentosa and its changes in the processes of pulping and bleaching, milled wood lignin （MWL）, lignin carbohydrate complex...In order to understand the structural characteristics of lignin in triploid clones ofPopulus tomentosa and its changes in the processes of pulping and bleaching, milled wood lignin （MWL）, lignin carbohydrate complex （LCC） and the residual lignin from kraft pulp （KP） and sulfite pulp （SP） were isolated and analyzed by Fourier transform infrared （FTIR） spectrum and ^13C nuclear magnetic resonance （NMR）. The most diagnostic peaks were assigned and the differences were discussed. The spectral patterns reveal that triploid P tomentosa shows the specific features of hardwood from temperate areas, but in the spectrum of FTIR, the strength ratio orAl270 cm^-1 to A1226 cm^-1 is 0.88, higher than the average of hardwood from temperate areas, which will make the lignin delignification more difficult during pulping and bleaching. The LCC from triploid P tomentosa is mainly composed of xyloglucan and glucuronic acid, and other glucides have much lower ratio. In LCC FTIR, there are three peaks at 1 427, 1 329 and 1 046 cm^-1, indicating that both semi-cellulose and cellulose could exist in LCC, and that there might be relationships between cellulose and lignin. Compared with the residual lignin from KP and SP, the condensed structure in KP is more than that in SP.展开更多
The Structural nature of Tctracctron sinense MWL is characterized by means of Chemical analysis.GC,IR,’H NMR and <sup>C</sup>（13） NMR spectra.The researches indicated that the MWL is of guaiacyl—syring...The Structural nature of Tctracctron sinense MWL is characterized by means of Chemical analysis.GC,IR,’H NMR and <sup>C</sup>（13） NMR spectra.The researches indicated that the MWL is of guaiacyl—syringyl type.The main connective form between structural units is β—O—4aryl ether bonds.The quantity of β—O—4 and 5—5 substructures is 0.53/C<sub>9</sub> and 0.06/C<sub>9</sub>,respectively.The alipatic and phenolic hydroxy contents are respectively.The OCH<sub>3</sub> content is estimated by <sup>C</sup>（13）NMR is spectrum （1.14/C<sub>9</sub>）,which is con-sistent with chemical method（1.11/C<sub>9</sub>） The degree of condensetion of the MWL is 0.51/C<sub>9</sub>（from ’HNMR）,which is consistent with the result from <sup>C</sup>（13）NMR.展开更多
According to calculation on available data, higher δ18O exists in atmospheric precipitation of southeastern and northwestern part of China, and the lower in Northeast China and the southern QinghaiTibet Plateau. In C...According to calculation on available data, higher δ18O exists in atmospheric precipitation of southeastern and northwestern part of China, and the lower in Northeast China and the southern QinghaiTibet Plateau. In China temperature effect appears mainly in the inner continent of midhigh latitudes and the amount effect appears in southeastern coastal regions, the YunnanGuizhou Plateau and QinghaiTibet Plateau where the influence of monsoon climate is obvious. The meteoric water lines (MWLs) of different regions are of certain divergence, which is closely related to the stable isotopic fractionations of the two processes, namely the evaporation of origins and the precipitating of vapor.展开更多
We report a demonstration of a fast wavelength tunable source (TWS) based on the laser diode array coupled to the arrayed waveguide grating (AWG) multiplexer. The switching and optical characteristics of TWS make it a...We report a demonstration of a fast wavelength tunable source (TWS) based on the laser diode array coupled to the arrayed waveguide grating (AWG) multiplexer. The switching and optical characteristics of TWS make it a candidate for implementing the wavelength-division space switch fabric for an optical packet/burst switching.展开更多
基金Supported by the National High Technology Research and Development Program of China(No.2009AA05Z407)the International Science and Technology Cooperation Program(No.2009DFA61050)+2 种基金the National Natural Science Foundation (No.90610035)the National Basic Research Program of China(No.2007CB210200)the Doctoral Foundation of the Ministry of Education of China(No.20090101110034)
文摘The structure of milled wood lignin（MWL）, isolated via the Bjrkman procedure, was studied by means of 1H NMR spectroscopy and Fourier transform infrared spectroscopy, and then its pyrolytic product distribution was investigated on a pyrolysis device. MWL obtained from Manchurian Ash（MA） contained more methoxyl and free phenolic hydroxyl groups per C9 unit than MWL from Mongolian Pine（MP） due to the existence of both guaiacyl and syringyl units, which have a major influence on the pyrolysis behavior of lignin. The results of pyrolysis show that MWL from MA generated a higher yield of bio-oil, mainly composed of phenols, guaiacols, syringols and catechols, and a less yield of char, in addition to the gaseous products CO, CO2, methane and methanol, compared with MWL from MP. Guaiacol and syringol were the typical products from G-lignin and S-lignin, probably attributed to the easier cleavage of the aryl-alkyl linkage in the side chain compared with the C―OCH3 bond in the benzene ring. The degradation of MWL from MP was dominated by the demethylation reaction and the cleavage of aliphatic ―CH2OH at the γ-position, followed by the cracking of the Cα―Cβ and C4―Cα bonds.
文摘In order to understand the structural characteristics of lignin in triploid clones ofPopulus tomentosa and its changes in the processes of pulping and bleaching, milled wood lignin （MWL）, lignin carbohydrate complex （LCC） and the residual lignin from kraft pulp （KP） and sulfite pulp （SP） were isolated and analyzed by Fourier transform infrared （FTIR） spectrum and ^13C nuclear magnetic resonance （NMR）. The most diagnostic peaks were assigned and the differences were discussed. The spectral patterns reveal that triploid P tomentosa shows the specific features of hardwood from temperate areas, but in the spectrum of FTIR, the strength ratio orAl270 cm^-1 to A1226 cm^-1 is 0.88, higher than the average of hardwood from temperate areas, which will make the lignin delignification more difficult during pulping and bleaching. The LCC from triploid P tomentosa is mainly composed of xyloglucan and glucuronic acid, and other glucides have much lower ratio. In LCC FTIR, there are three peaks at 1 427, 1 329 and 1 046 cm^-1, indicating that both semi-cellulose and cellulose could exist in LCC, and that there might be relationships between cellulose and lignin. Compared with the residual lignin from KP and SP, the condensed structure in KP is more than that in SP.
文摘The Structural nature of Tctracctron sinense MWL is characterized by means of Chemical analysis.GC,IR,’H NMR and <sup>C</sup>（13） NMR spectra.The researches indicated that the MWL is of guaiacyl—syringyl type.The main connective form between structural units is β—O—4aryl ether bonds.The quantity of β—O—4 and 5—5 substructures is 0.53/C<sub>9</sub> and 0.06/C<sub>9</sub>,respectively.The alipatic and phenolic hydroxy contents are respectively.The OCH<sub>3</sub> content is estimated by <sup>C</sup>（13）NMR is spectrum （1.14/C<sub>9</sub>）,which is con-sistent with chemical method（1.11/C<sub>9</sub>） The degree of condensetion of the MWL is 0.51/C<sub>9</sub>（from ’HNMR）,which is consistent with the result from <sup>C</sup>（13）NMR.
文摘According to calculation on available data, higher δ18O exists in atmospheric precipitation of southeastern and northwestern part of China, and the lower in Northeast China and the southern QinghaiTibet Plateau. In China temperature effect appears mainly in the inner continent of midhigh latitudes and the amount effect appears in southeastern coastal regions, the YunnanGuizhou Plateau and QinghaiTibet Plateau where the influence of monsoon climate is obvious. The meteoric water lines (MWLs) of different regions are of certain divergence, which is closely related to the stable isotopic fractionations of the two processes, namely the evaporation of origins and the precipitating of vapor.
文摘We report a demonstration of a fast wavelength tunable source (TWS) based on the laser diode array coupled to the arrayed waveguide grating (AWG) multiplexer. The switching and optical characteristics of TWS make it a candidate for implementing the wavelength-division space switch fabric for an optical packet/burst switching.
