Study On The Mechanism Of Liquefaction Of Woody Biomass In The Presence Of Phenol With Sulfuric Acid As The Catalyst And The Characteristics Of Its Products

With the short of petrochemical resources, woody biomass, as a renewable resource,has been taken much attention in the world. Thermolchemical liquefaction technology hasbeen used widely, which is one of effective ways of woody biomass utilization. Based onthe three main components （cellulose, lignin, hemicellulose） of the woody biomass,microcrystal cellulose, xylan and alkali-lignin were used as the model samples and theliquefaction of them in the presence of phenol was investigated in this paper. Thecharacterization of the solid residue, gas proucts and liquid products at different reactiontemperature and reaction time in the liquefaction was studied by using the moderninstrument technologies, such as FTIR、TG、GC、GC/MS、HPLC、GPC、¹H-NMR and¹³C-NMR. Meanwhile, the liquefaction mechanism of three main components of woodybiomass in the presence of phenol with sulfric acid as the catalyst and the characteristics oftheir liquefied products were discussed. The results showed that:（1）With increasing of reation temperature and prolonging of reaction time, theconversion rate, yield of gas products and liquid products of microcrystal cellulose、xylan,alkali-lignin and their mixtures （cellulose/xylan/lignin=6/2/2, w/w） increased generallywhether with or without sulfuric acid catalyst.（2）From the FTIR spectra, the structure characteristics of the solid residue ofmicrocrystal cellulose in the liquefaction before reaction time of30min are similar tocellulose. But the FTIR spectra characteristics of the solid residue after30min have beenchanged evidently, which was quite different from the cellulose. There were a lot ofobvious differences in the FTIR spectra characteristics between the solid residue and thexylan, whether how long the reaction time was. For the alkali-lignin, the characteristics ofFTIR spectra of the solid residue are similar to the model sample during the liquefaction.（3）From the results of pyrolysis characteristics of the solid residue obtained from theliquefaction of cellulose, the solid residue showed a better thermal stability with increasingof reaction temperature and prolonging of reaction time with H₂SO₄as the catalyst.（4）With increasing of reaction temperature and prolonging of reaction time, thedegradation of microcrystal cellulose, xylan, alkali-lignin and their mixtures in thepresence of phenol with H₂SO₄as the catalyst became vigorous. And the yield of the gasproducts increased gradually. The main component of the gas from the liquefacion ofcellulose was CH4. The main component of the gas from the liquefacion of xylan、ligninand the three-main-component mixtures was almost CO₂.（5）The content of combined phenol in the liquid products from the liquefaction ofmicrocrystal cellulose, xylan, alkali-lignin and their mixtures increased with increasing ofreaction temperature and prolonging of reaction time with H₂SO₄as the catalyst. Moreover,the content of combined phenol in the liquid products from the liquefaction of xylan and the three-main-component mixtures increased obviously, particularly in the initial stage ofthe liquefaction （before2min）.（6）The characteristics of FTIR spectra of the liquid products from the liquefaction ofmicrocrystal cellulose, xylan, alkali-lignin and their mixtures in the presence of phenolwith H2SO4as the catalyst were similar, whether how high the reaction temperature andhow long the reaction time was. And all of the liquid products were resulted from thereaction between degradated products of biomass and phenol.（7）The molecular weight of the liquid products from the liquefaction of microcrystalcelloluse, xylan, alkali-lignin and their mixtures reduced rapidly with increasing ofreaction temperature and prolonging of reaction time, but the molecular weight distributionof the liquid products changed a little.（8）From the results of NMR spectra of the liquid products from the liquefaction ofmicrocrystal cellulose, xylan and alkali-lignin in the presence of phenol under acidcondition: The degradation reactions of the three-main components of woody biomassoccurred mainly in the initial stage of liquefaction （2min）. As the result, some intermediateproducts with low molecular weight were produced, such as glucose, xylose, etc. Theproducts in the later stage of liquefaction were mainly resulted from the reaction betweendegradated products of biomass and phenol.（9）Compared with the results of the liquefaction of microcrystal cellulose, xylan andalkali-lignin alone, there was a synergetic mechanism in the liquefaction of thethree-main-components mixtures in the presence of phenol under acid condition.（10）The liquefaction mechanism of woody biomass in the presence of phenol withsulfuric acid as the catalyst was summarized as the following: The main components, suchas cellulose、xylan and lignin in woody biomass were degradated firstly. Some gasproducts such as CH4、CO2and some low molecular intermediate products such as glucose,xylose were produced at the same time. Meanwhile, the liquid intermediate productsreacted with the reactive phenol which was the liquefaction reagent. Finally, a largenumber of stable complex compounds dissolved in the liquefaction reagent of phenolbecame the liquid products of the liquefaction system.