木质素催化转化制取苯、甲苯和二甲苯

对HZSM-5、HY和MCM-22三种催化剂进行了比较,其中HZSM-5催化裂解木质素制备苯、甲苯和二甲苯（BTX）的结果最优．确定了木质素催化裂解的最佳反应条件,包括反应温度、载气流速、催化剂／木质素配比．当反应温度为550-600℃,载气流速为300mL／min,催化剂／木质素配比为2时,使用HZSM-5催化裂解制备BTX的最高C产率和芳香选择性分别可达25．3％和90．9％。     

Characterization of milled wood lignin and ethanol organosolv lignin from miscanthus

Ethanol organosolv lignin extracted from Miscanthus × giganteus (using the following conditions: T = 190 °C, t = 60 min, sulfuric acid = 1.2% w/w, EtOH/H₂O = 0.65) and milled wood lignin from Miscanthus × giganteus were subjected to a comprehensive structural characterization by ¹³C, ³¹P NMR, FTIR, UV spectroscopies and size exclusion chromatography. The results showed that Miscanthus lignin is an H/G/S type (4%, 52%, 44% respectively) with ∼0.41 β-O-4 linkage per aromatic ring and contains coumarylate linkages (0.1/Ar). It was shown that during organosolv treatment, cleavage of β-O-4 linkages and of ester bond (acetyl and coumaryl residues) was the major mechanisms of lignin breakdown but the process did not significantly change the core of the lignin structure.     

液体离子提取烟梗木质素的研究

本文研究了在温和的条件下利用四种离子液体对烟梗木质素的提取过程,结果表明1-乙基-3-甲基咪唑磷酸二乙酯盐([EMIM][DEP])的提取效果最佳. 通过80 °C的热水搅拌30 min的预处理过程可以有效脱除烟梗中含有的绝大多数糖分同时疏松了烟梗的微纤维结构,在此基础上使用[EMIM][DEP]在150 °C和反应时间4 h的条件下可以获得纯度90.21%的木质素,木质素的提取率达到85.38%.     

Simulation of SIMS for monomer and dimer of lignin under the assumption of thermal decomposition using QMD method

The thermal decomposition of the monomer and dimer of lignin has been simulated by a quantum molecular dynamics (DMD) method. In the calculation, we controlled the total energy of the system using Nóse-Hoover thermostats in the total energy range of 0.69-0.95 eV, and the sampling position data with a time step of 0.5 fs were carried out up to 3000 (1.5 ps) or 5000 (2.5 ps) steps in ab initio and semiempirical MO methods, respectively. We obtained the thermally decomposed fragments with positive, neutral and negative charges from SCF MO calculation at each data of the last MD step, and simulated the fragment distribution of the monomer and dimer lignins from the last step in 30-40 runs. Simulated mass numbers of positively and negatively charged fragments for lignin monomer and dimer showed considerably good accordance with the experimental results in TOF-SIMS observed by Saito and co-workers.     

Lignin adsorption on cellulose fibre surfaces: Effect on surface chemistry, surface morphology and paper strength

The adsorption of lignin on cellulose fibres at neutral pH and the effects of calcium ions and a cationic polyelectrolyte (PDADMAC) on the adsorption have been studied. The surface coverage by lignin was determined by electron spectroscopy for chemical analysis (ESCA). The morphology of the lignin layer was studied by atomic force microscopy (AFM). The effect of adsorbed polyelectrolyte and lignin on the strength properties of the paper was also studied. The adsorbed amount of lignin increased monotonically with lignin concentration. Addition of calcium ions resulted in a very high surface coverage by lignin. PDADMAC did not enhance the adsorption of lignin, but without addition of polyelectrolyte the lignin was very weakly attached to the fibre surface. PDADMAC formed complexes with lignin in solution. At high polymer/lignin concentration ratios the charge of the complex was positive and it adsorbed irreversibly as large blobs. At low ratios the complex was easily washed away from the fibre surface. When PDADMAC was pre-adsorbed on the fibre surface the lignin adsorbed as small granules at all lignin concentrations. Neither PDADMAC nor lignin alone increased the strength of pulp sheets significantly. However, together they increased the bonding between fibres.     

The conformational dynamics of humic polyanions in model organic and organo-mineral aggregates

Molecular mechanics calculations and simulated annealing were applied to model humic polyanions originating from lignin. The dynamic behavior of such oxidized lignins in model soil organic complexes, such as an oxidized lignin-carbohydrate complex (LCC) and humic (oxidized LCC)-clay aggregates, was analyzed. Neither ionization nor hydrogen bonding bring significant changes in the conformational properties of oxidized lignin and LCC. Oxidized lignin and LCC oligomers (humic substances in soil) bind to the mineral surfaces, a process that was exemplified in computational experiments on complexes with muscovite. Upon ionization, a lignin-derived oligomer develops strong attractive organo-mineral interactions through cation bridges. Without metal cations, electrostatic repulsion between negatively charged anions and the oxygen-mineral surface prevails, and the two parts of the organo-mineral complex drift apart. This tendency is typical of an oxidized lignin oligomer but not of a topological oxidized LCC.     

Radical synthesis of tetrameric lignin model compound

The lack of suitable lignin model compound limits the understanding of the characteristics of lignin, and hence hinders the efficient utilization of this kind of bioresource. A tetramer phenolic lignin model compound composed of 5-5, α-O-4 and β-5 linkages was prepared by a two-step of free radical reaction with hydrogen peroxide/horseradish peroxidase and S₂O₈^2- /Fe²⁺ as the initiator. Compared with enzymatic process, this synthetic process gives a higher yield of 33.8% within a shorter time. HRMS and ¹³C NMR spectroscopy show that synthesized model compound contains phenylpropane structure linked by 5-5, α-O-4 and β-5 bonds, which can mimic some chemical characteristics of lignin.     

Selectively transform lignin into value-added chemicals

Selective transformation of lignin into value-added chemicals is of strategic significance. Phenols, aldehydes, carboxylic acids, alkanes and arenes can be harvested from lignin with high selectivity under appropriate reaction condition.     

The efficacy of photostabilizers on the color change of wood filled plastic composites

In this study, we compared the performance of different hindered amine light stabilizers and ultraviolet absorbers as photostabilizers of wood plastic composites (WPC). We showed how their functional groups and molecular weights influence the photostabilization of WPC subjected to natural weathering for 2000 h. The changes were followed using color measurements and FTIR spectroscopy which provided insight into the photodegradation mechanism of weathered WPC.The results indicate that weathering causes color fading and changes in yellowing. We propose that WPC undergo two competing redox reactions upon UV exposure. The first is the oxidation of lignin which leads to the formation of paraquinone chromophoric structures which is dominant in the first 250 h of exposure. The second is the reduction of the paraquinone structures to hydroquinones which leads to photobleaching.High molecular weight diester HALS were found to be the most effective in controlling long term fading and yellowing changes. Furthermore, the addition of a benzotriazole ultraviolet absorber shows great synergism in controlling fading when added to a diester HALS.     

MoS2 decorated lignin-derived hierarchical mesoporous carbon hybrid nanospheres with exceptional Li-ion battery cycle stability

We developed a feasible self-assembly and carbonization method to prepare lignin-derived porous carbon nanosphere (PCN) and its efficient embedment of MoS₂ without any additives. The obtained hybrid nanocomposite provides a possible route to develop high performance Li-ion battery from natural biomass or organizational structures.