贵金属催化剂上两步法选择性降解有机溶剂型木质素(英文)

Abstract

使用担载型贵金属催化剂和磷酸在不同温度下通过两步法加氢降解二氧六环木质素.第一步反应使用Rh/C和浓度为1%(w)的磷酸为催化剂,在270°C和4MPa氢气气氛下反应后通过气相色谱(GC)和气相色谱-质谱(GC-MS)分析木质素单体和二聚体,总收率最高可达16.9%.通过傅里叶变换红外(FTIR)光谱、X射线光电子能谱(XPS)、元素分析(EA)和凝胶渗透色谱(GPC)等方法研究第一步反应产物的变化.结果发现,二氧六环木质素中的C-O-C键被打断,木质素分子量降低,部分羰基和羧基被脱除.随着反应温度的上升,产物的含氧量不断下降,在270°C反应10h后氧含量从35%(w)降低至21%(w).结...

Dioxane lignin, a typical organosolv lignin, was degraded by supported noble metal catalysts and phosphoric acid by a two-step method at different temperatures. The results showed that under 4 MPa H-2 at 270 degrees C using Rh/C and 1% (w) phosphoric acid as catalysts, the highest total yield of the monomers and dimer was 16.9% after the first step, based on gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) analyses. Moreover, the raw products from the first step were analyzed by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), element analysis (EA), and gel permeation chromatography (GPC) to improve the understanding of the chemical transformations involved. The results indicated that the C-O-C bond linkages in the dioxane lignin were cleaved to form lower molecular-weight products, resulting in the degradation of lignin, and the carbonyl and carboxyl groups were partly removed. Oxygen content was reduced dramatically with increasing reaction temperature, from 35% (w) to 21% (w) after reacting at 270 degrees C for 10 h. Based on the analysis results, a reaction pathway for the degradation of lignin was proposed. Finally, the products from the first step could be hydrodeoxygenated to alkanes with carbon numbers in the range of gasoline and diesel with high selectivity catalyzed by Pd/C and phosphoric acid at 250 degrees C.