Electro-catalytic Hydrocracking Of Bamboo Lignin To 1,3-diethylbenzene In Alkali Aqueous Solution

This paper presented a new procedure for production of 1,3-diethylbenzene by electro-catalytic degradation of alkaline bamboo lignin and hydrocracking intermediate in basic aqueous solution with a three-dimensional reactor. In this three-dimensional reactor, the self-fabricated anode was Ti/SnO₂-Sb2O₃/α-Pb O₂/β-Pb O₂, the cathode was copper mesh, the third electrode was the ceramic particles which were fulfilled between the anode and cathode. The electro-catalytic hydrocracking of bamboo lignin was zero-order kinetic reaction, which had been used to explain the electro-catalytic hydrogenation mechanism. The morphology and characters of electrodes were determined by X-ray diffraction（XRD）, scanning electron microscope（SEM）. The chemical performance of the three-dimensional system for electro-degradation lignin was recorded by cyclic voltammetry（CV）, which indicated the electro-catalytic hydrogenation reaction occurred on the surface of the electrodes. Some organic solvents such as ethyl acetate, anisole, methylbenzene and dichloromethane were used to extract the degradation products according to their different polarities. Two methods of reduced pressure distillation and column chromatography were employed to separate and purify the products. Gas chromatography-mass spectrography was used to qualitative analysis of the extractive products and the separated products. Gas chromatography and ultraviolet spectrophotometry were used to quantitative analysis of the separated products. The operation conditions of this procedure such as current density, lignin concentration, reaction temperature and the ceramic dosage had been optimized intensively. The experimental results bring some conclusions as following.（1） 1,3-Diethylbenzene was selectively produced by hydrocracking of bamboo lignin intermediate in basic aqueous solution within the three-dimensional reactor of which anode was Ti/SnO₂-Sb2O₃/α-Pb O₂/β-Pb O₂, cathode was copper mesh, third electrode was the ceramic particles fulfilled between the anode and cathode. The reaction was fitted zero reaction kinetics.（2） The ceramic particles had the synergy in electro-degradation and electro-catalytic hydrogenation of bamboo lignin and lignin intermediate.（3） In this electro-catalytic hydrogenation procedure, the accumulated total yield of products reached 37.5 g/L while 50 g/L bamboo lignin solution was completely decomposed by electro-catalytic hydrogenation for duration 10 h. Among the products, 1,3-diethylbenzene, p-xylene and o-xylene were obtained by reduced pressure distillation.（4） The procedure was optimized by investigating the factors of current density, lignin concentration, react temperature and the ceramic dosage. It was found 1,3-diethylbenzene reached up to 0.361 g/g-lignin with lignin concentration of 30 g/L, current density of 25 m A/cm2 at 25 °C assisted with 25 g ceramic particles.