Degradation Of Alkali Lignin By Photochemi Calcatalysis Over Fe-TiO₂

This paper proposes the integration technology of photocatalytical degradation ofalkali lignin solution in corrugated plate reactor and cyclic extraction of products. Thephoto catalyst of Fe doping TiO2was prepared by sol–gel method and coated on the innersurface of corrugated plate with Fe-TiO2film. The phase transformation, crystallite size andweight percent of anatase/rutile phase ratio of Fe-TiO2were determined by XRD andsurface morphology were observed by SEM. The corrugated plate coated with Fe-TiO2filmwas placed in the reactor tube with parallel orientations. During the cyclic process, thealkali lignin solution was put into the reactor and degraded by UV radiation over Fe-TiO2catalyst, mixture of alkali lignin solution and products was transported by water pump tothe extraction apparatus, and then the alkali lignin flowed to the photocatalytic reactor.The concentrated extracts were separated with silica gel column chromatography togive the pure products.1H NMR，13C NMR spectra and GC-MS analysis were confirmedthe products. The products were analyzed following an internal standard method on the gaschromatography instrument. The other extracts were analyzed with a Trace DSQ GC/MSsystem. At the end of the photocatalytic degradation, the lignin residue was comparativelyanalysis with functional groups by FT-IR. The reaction time, lignin concentration, Fe dopedcatalyst, catalyst film layers and folded plate angle were also investigated.Experimental results show that Fe-TiO2catalyst with anatase structure has muchhigher photochemical oxidation. The main products of photocatalysis degradation of ligninwere2,6-bis(1,1-dimethylethyl)-4-methylphenol (BHT), dibutyl phthalate (DBP) anddiisobutyl phthalate (DIBP). The optimum condition for lignin degradation to BHT wasreaction time5h, lignin concentration of30g/L, the doping amount of Fe2%,8layers,folding plate angle63°, and final BHT concentration up to1.12g/L. While the optimumcondition of DIBP and DBP were reaction time6h, lignin concentration of30g/L, theamount of Fe doping5%, the film layers9and folded plate angle of63°, the concentrationof DIBP and DBP were0.74g/L and1.57g/L, respectively. Other un-separated productswere assigned to guaiacyl and syringyl derivatives, aromatic derivatives and some saturatedhydrocarbon compounds.