基于密度泛函理论研究木质素二聚体C_α-OH基团的修饰对其热解均裂历程的影响  

Density functional theory study on the effect of C_α-OH functional group modification on the homolytic cracking reaction routes during the pyrolysis of lignin dimer

作　　者：段毓 程皓[1,2] 武书彬 DUAN Yu;CHENG Hao;WU Shu-bin(State Key Laboratory of Pulp and Paper Engineering,South China University of Technology,Guangzhou 510640,China;Experimental Teaching Demonstration Center of Light Industry and Food Science,South China University of Technology,Guangzhou 510640,China)

机构地区：[1]华南理工大学制浆造纸工程国家重点实验室,广东广州510640 [2]华南理工大学轻工与食品国家级实验教学示范中心,广东广州510640

出　　处：《燃料化学学报》2019年第12期1440-1449,共10页Journal of Fuel Chemistry and Technology

基　　金：国家自然科学基金(31870558,31670582)资助~~

摘　　要：采用等体积浸渍法将Pd、Mo和P元素负载在γ-Al2O3上制得PdMoP/γ-Al2O3催化剂,通过XRD、NH3-TPD、XPS、Py-FTIR、氮吸附和STEM-EDS等手段对催化剂进行了表征,以大豆油甲酯为原料考察了催化剂的催化加氢脱氧性能,并进行了加氢脱氧工艺条件的优化。结果表明,Pd、Mo、P三种元素相结合能够有效地调节催化剂的酸性;Mo元素可降低催化剂的强酸酸性;P元素可增强催化剂的弱酸酸性,使得催化剂弱酸的B/L值减小、强酸的B/L值略有增大。经优化后的加氢工艺条件为:315℃、1.5 MPa、WHSV为0.5 h-1、H2/esters体积比为1100,大豆油甲酯的转化率达到98.4%,C15-18烷烃收率达到91.5%。Density functional theory method was used to calculate the bond dissociation energies of the C aromatic-Cα,Cα-Cβ,Cβ-O bond,and C aromatic-O bonds in four lignin dimer model compounds,viz.,(2-(2-methoxyphenoxy)-1-phenylethan-1-ol,2-(2-methoxyphenoxy)-1-phenylethan-1-one,1-methoxy-2-(2-methoxy-2-phenylethoxy)benzene,and 2-(2-methoxyphenoxy)-1-phenylethyl acetate;the homolytic cracking reaction during pyrolysis of these dimers was then invetigated and the formation pathways of pyrolysis products of different dimers were analyzed.The results show that the homogenization of Cβ-O bond is the main reaction in the initial pyrolysis of dimer,whereas the homolysis of Cα-Cβbond is a competitive reaction.After the oxidation and acetylation of Cα-OH,the bond dissociation energy of Cβ-O bond decreases,whereas the dissociation energy of Cα-Cβbond increases,ccompanied with an increase in the probability of the Cβ-O bond dissociation and a decrease in the competitive ability of Cα-Cβbond homolysis.For the pyrolysis of four model compounds,the main aromatic products include benzyl alcohol,toluene,benzaldehyde,guaiacol,etc.The selective modification of the Cα-OH functional groups can regulate the types of pyrolysis products.In particular,the product types for the pyrolysis of model compounds modified by oxidation become less,accompanied with an increase in the selectivity to ceratin products.Ethylbenzene and toluene can be produced from the hydrolysis of dimers modified by methylation and acetylation.

关 键 词：木质素 热解 均裂 Cα-OH官能团 β-O-4连接 密度泛函理论 

分 类 号：TK6[动力工程及工程热物理—生物能]