Phenolation Of Wood Decayed By Brown-rotted Fungi And Resinification Of Phenolated Wood Product

Liquefaction is one of the promising techniques for effective utilization of woody biomass,by which the lignocellulosics can be converted to liquid reactive materials. These materialscould be employed as alternative intermediates to the conventional petrochemical derivedphenol in the production of resin. The high cost and serious corrosion of equipment make itstill to have a long time being widely used. Wood was firstly pretreated by brown-rot fungi ofFuling before liquefaction so that wood can be liquefied easily. The main chemical components,crystallinity and 1ï¼…NaOH extractive content of wood decayed for different times wereinvestigated. Wood was liquefied by phenol under cid-catalyzed conditions. The variousreaction conditions, including wood with different levels of decay, catalyst, reactiontemperature, reaction time, charge ratio of phenol to wood (liquid ratio) and catalyst dosagehave been investigated. By means of GPC and HPLC analysis, the molecular weight and freephenol content of liquefied wood under different reaction conditions was investigated to tracethe change in the structural characteristics of the liquefied wood. The optimum condition ofnovolac phenol formaldehyde resin from liquefied decayed wood (PWF) was studied. Thestructures of PWF and traditional novolac phenol formaldehyde resin (PF) were compared byFTIR and ¹³C-NMR. Curing behaviors and kinetics analysis of PWF were examined by DSCand TG. The major research results are summarized as follows:(1) Fuling damaged wood by rapidly depolymerizing cellulose and hemicellulosecomponents. Lignin was modified until the later stages of decay. After wood was decayed for15 weeks, the holocellulose content, pentosan content and crystallinity decreased graduallyfrom 72.80ï¼…,14.95ï¼…and 40.3ï¼…for normal wood to 18.57ï¼…,8.58ï¼…and 6.1ï¼…, respectively.On the contrary, the acid-insoluble lignin content and 1ï¼…NaOH extractive content went upgradually from 27.30ï¼…and 12.89ï¼…to 43.88ï¼…and 70.07ï¼…, respectively.(2) The determination coefficients (RE) between holocellulose content, acid-insoluble lignincontent and 1ï¼…sodium hydroxide extractive or crystallinity were above 0.9. As for pentosan,R² was above 0.7. Both crystallinity and 1ï¼…NaOH extractive can be as an indicator to assesthe level of wood decay. The results showed wood can be easily liquefied when the contents of1ï¼…NaOH extractive and crystallinity were 54ï¼…and 28ï¼…, respectively.(3) Brown-rotted wood can be more easily liquefied than normal wood. When the weightratio of wood and Phenol to phosphoric acid was 1:2:0.16, the residue content of liquefieddecayed wood was only 7.6ï¼…for 0.5h. But for normal wood, the residue content was 26.2ï¼…for 2h. The properties of liquefied decayed wood were different from those of liquefied normal wood. The combined phenol content of the former was higher than that of the latter. Whereas,the weight-average molecular weight and polydispersity of the former was lower than those ofthe latter.(4) Wood could be liquefied into soluble reactive intermediates, which could further reactedwith phenol or by themselves. Phenolation and recondensation were a pair of competingreactions. Decomposition, phenolation and recondensation dominated the whole liquefactiondynamic process and determined the structural characteristics of liquefied wood. The phenolwas linked to wood components at its ortho or para positions to a phenolic hydroxy group.(5) The liquefied higher-molecular-weight substance could further decomposed duringresinification. The added formaldehyde reacted not only with the phenol which remained afterliquefaction, but also with the liquefied wood components with middle and lower molecularweight. High viscosity and steric hindrance affected the condensation and resulted in the lowerPolymerization extent. The content of higher-molecular-weight fraction in PWF was lower thanin PF and its fluidity was inferior to PF's.(6) The orthogonal test showed the product yield of resin was notably affected by pH andreaction temperature, and the softening point was significantly affected by charge ratio offormaldehyde to phenol and reaction time. The optimum condition of PWF prepared fromliquefied wood is: actual pH of liquefied wood without extra acid, 105℃, 150min and 0.7～0.8of ratio of formaldehyde to phenol.(7) The curing agent content had and great influence on curing process of PWF. When theratio of PWF to curing agent is 100 to 10, the apparent activation energy of the curing reactionof PWF and PF was 107.76 kJ·mol^-1 and 141.35 kJ·mol^-1, respectively. There was little effect ofcuring agent content on the level of the PWF curing reaction. The level of the PWF curingreaction (0.95) was same with that of PF curing reaction (0.95). The curing temperature ofPWF was about from 138 to 141℃by extrapolating Tp—β.(8) TG curve of cured PWF were same with that of cured PF during the range of 30 to 291℃.Both were thermal stable and had no weight loss before 200℃and they began to loss weightwith increasing temperature. The temperatures of thermal decomposability of cured PWF andPF were 291℃and 296℃, respectively.