温度对二氧化碳酸析提取黑液中木质素的影响

以碱法制浆的松木黑液为原料,用二氧化碳酸化黑液提取其中的木质素,考察了反应温度(40~80℃)对酸析木质素产率及其无机盐和糖分等含量的影响,采用凝胶渗透色谱(GPC)、离子色谱仪(IC)、元素分析仪和热重分析仪(TG)对木质素产物进行结构表征。结果表明,温度升高不利于木质素析出,产率下降;但较高温度下制备的木质素中无机盐、糖分及硫含量低,纯度高;同时温度越高,木质素相对分子质量越大,甲氧基含量增大,但酚羟基含量减小。TG和DTG曲线显示,反应温度升高木质素最大失重速率增加,残余量减少。     

Hydrodeoxygenation of lignin model compounds to alkanes over Pd–Ni/HZSM-5 catalysts

In this work, a bimetallic catalyst of Pd and Ni supported on HZSM-5 was designed and evaluated in the hydrodeoxygenation of model compounds representing various C–O bonds in lignin. The effects of temperature, holding time, and initial H₂ pressure on the catalytic performance of the Pd–Ni/HZSM-5 catalyst were investigated. The results indicated that the Pd–Ni/HZSM-5 catalyst exhibited superior catalytic activity towards the conversion of the model compounds to alkanes compared to its monometallic counterparts. Direct cleavage of the C–O bond in DPE was achieved under low H₂ pressure, mainly producing benzene and minor amounts of phenol and cyclohexane, while at high H₂ pressure, the reaction pathway was altered towards hydrogenation of the benzene ring, followed by then cleavage of the C–O bond to afford only cyclohexane. Moreover, the Pd–Ni/HZSM-5 catalyst showed high activities when applying other substrates including anisole, veratrole, guaiacol, benzyloxybenzene, phenethyl phenyl ether, and dibenzyl ether.     

Removal of water pollutants with activated carbons prepared from H3PO4 activation of lignin from kraft black liquors

Activated carbons with a high BET surface area and a well-developed porosity have been prepared from pyrolysis of H3PO4-impregnated lignin precipitated from kraft black liquors. Impregnation ratios within the range of 1-3 and activation temperatures of 623-873 K have been used, giving rise to carbons with different porous and surface chemical structure. Increasing the activation temperature and the impregnation ratio leads to a widening of the porous structure with a higher relative contribution of mesoporosity. The potential application of these carbons for the removal of water pollutants has been investigated by measuring their adsorption capacities for phenol, 2,4,5-trichlorophenol and Cr (VI) as representative of toxic contaminants found in industrial wastewaters. The results obtained compare well and even favorably with those reported in the literature for other activated carbons. An impregnation ratio and an activation temperature around 2 g H3PO4/g lignin and 700 K, respectively, are recommended as the best combination of operating conditions to prepare activated carbons for aqueous phase applications although at lower values of these two variables carbons with good adsorption capacities are also obtained.     

木质素磺化的研究

木质素磺酸盐是一种具有广泛用途的高分子物质,开发利用木质素磺酸盐具有很广阔的前途。对造纸黑液及酸析木质素的磺化进行了研究,得出了黑液及酸析木质素磺化的工艺条件。     

酶促木质素与酚共聚反应及产物表征

在反相微乳液系统中 ,用辣根过氧化物酶进行了酶促木质素与酚共聚反应 ,并进行了红外光谱分析及差示扫描量热分析。结果表明 ,由于在木质素分子间引入了聚甲酚片段 ,共聚物的热性能有较大改善。聚合物的重均分子量随反应温度的升高而增加     

Biomass yield and quality of an energy dedicated crop of poplar (Populus spp.) clones in the Mediterranean zone of Chile

The biomass of nineteen Populus spp. clones was measured and characterized as a feedstock for energy production. Biomass yield was estimated using the average volume and dry weight of each clone. Quality traits analyzed include higher heating value (HHV) and chemical composition. Biomass yield ranged between 0.31 and 9.54 kg individual⁻¹. HHV ranged between 17.69 and 20.75 MJ kg⁻¹. Total extractives varied between 11.78% and 19.62% (mass fraction% on dry basis), Klason lignin ranged between 14.31% and 20.92% and α-Cellulose ranged between 42.38% and 48.70%, both without extractives. The ash content ranged from 2.05% to 3.40%. The chemical composition of the clones reported here is slightly different to the previously reported for this genre, but this is attributed to the juvenile wood and the inclusion of bark in the samples. As a result of the biomass used in this study, the correlations between the chemical composition and extractives content on HHV are of very poor quality. Based on our results, an approach including both biomass yield and quality is required in order to ensure the most viable treatment for a sustainable utilization of the biomass for energy generation. For a direct combustion perspective, the preferred clones are those which a high combination of yield and heating value as Bocalari, Beaupre, Constanzo and Nmdv.     

Physical–chemical characteristics of lignins separated from biomasses for second-generation ethanol

Lignin was extracted by two extraction methods from two biomasses for energy (Mischantus and Giant Reed) and a lignocellulosic material resulting from a microbial treatment of giant reed. One method of extraction involved the use of H₂SO₄ (SA), providing a highly aromatic water-insoluble material, while a second method employed H₂O₂ at alkaline pH (Ox), resulting in a water-soluble lignin. Extraction yields were related to the total Klason lignin measured for the three materials. We compared the physical–chemical features of the isolated lignins, by employing solid-state nuclear magnetic resonance spectroscopy (¹³C-CPMAS spectra and derived T1ρH relaxation times), thermogravimetric analyses, infrared spectrometry and high performance size exclusion chromatography (HPSEC). We found that lignin separated by the Ox method owned a more mobile molecular conformation, and was largely more water-soluble and fragmented than the lignin obtained by the SA treatment. In line with T1ρH-NMR and thermogravimetric results, the HPSEC of Ox lignins showed nominal molecular weights less than 3 kDa, indicating well depolymerized materials. Such low-molecular weight and fragmented lignin obtained from biomasses for energy may become useful for application of recycled products in agriculture and in green chemistry reactions, thereby promoting an increase in the economic sustainability of biorefineries.     

Growth environment,harvest management and germplasm impacts on potential ethanol and crude protein yield in alfalfa

An alfalfa (Medicago sativa L) biomass energy production system would produce two products. Leaves would be separated from stems to produce a protein feed for livestock while stems would be processed to produce ethanol. Therefore, maximum yields of both leaves and stems are essential for profitability of this biomass production system. Our objective was to evaluate the impact of growth environment (locations, years and plant density) and harvest maturity stage (early bud (4 annual cuts) and late flower (3 annual cuts)) on leaf crude protein and potential ethanol yields for four alfalfa germplasms, two with high forage quality, and two non-lodging biomass types. Potential ethanol yield was greater at late flower compared to early bud, while leaf crude protein concentration was similar at the two harvest maturity stages at both locations. Leaf crude protein yield was greater at the Minnesota (MN) site compared to Wisconsin (WI) site. The two non-lodging biomass germplasms had greater potential ethanol yield compared to the high forage quality cultivars in WI, but no differences among the alfalfa germplasms were found for ethanol yield at MN. In WI, no differences were found among the germplasms for leaf crude protein yield, but the high quality cultivars had greater leaf crude protein yield than the non-lodging germplasms in MN. While germplasm differences were found for leaf crude protein and potential ethanol yields, the environmental influences of harvest date and locations had the greatest impact on these two alfalfa biomass energy products.     

Impact of PEF treatment on quality parameters of white asparagus (Asparagus officinalis L.)

Pulsed Electric Field (PEF) application on white asparagus (Asparagus officinalis L.) was exercised to examine influence of electroporation on spear characteristics as composition and texture. PEF treated spears showed altered storage behaviour, which was noticed by increased mass transfer as higher water loss as well as the decrease of the Maillard reaction substrate glucose. Cell disintegration measurement revealed significant influence of electric field orientation on electroporation. Since the anisotropy of asparagus tissue, PEF processing in longitudinal direction of the spear axis resulted in 9.06% higher cell membrane permeabilization than treatment in transverse direction. Furthermore, total solids inclusive lignin content were measured to obtain textural improvements of asparagus spears. It could be shown that dry weight as well as the amount of lignin was reduced after PEF implementation. Lignin degradation (− 2.4%) might be attributed to the PEF induced interference of electrostatic dipole–dipole interactions between lignin and cellulose and subsequent delignification.

Industrial relevance

Since three decades the technology of Pulsed Electric Fields (PEF) received considerable relevance in food — and bioengineering as well as in medicine. Besides the use of PEF to inactivate microorganisms main focus is put on the disintegration of biological cell material to enhance mass transfer in drying or extraction processes. Although the effects of PEF on various plant cell materials are well studied only scarce knowledge exists concerning the impact of PEF on white asparagus. In the study undertaken the PEF-induced changes in asparagus texture and composition were examined. The investigations shall help to reduce unfavored intra- and extracellular components to gain food safety as well as softer spear texture.     

Co(salen)/SBA-15 catalysed oxidation of a β-O-4 phenolic dimer under microwave irradiation

The microwave-assisted oxidative degradation of a lignin model phenolic dimer [1-(4-hydroxy-3-methoxyphenoxy)-2-(2-methoxyphenoxy)-propane-1,3-diol, 1] catalysed by Co(salen)/SBA-15 is reported. The investigated model compound 1 was prepared through a multistep synthesis and characterized by ¹H,¹³C NMR, and GC–MS studies. The catalyst was prepared by immobilizing [N,N′-bis(salicylidene)ethane-1,2-diaminato]Cobalt(II), Co(salen) complex onto the periodic mesopore channels of siliceous SBA-15. The activity of the Co(salen)/SBA-15 was investigated in the oxidation of 1 in the presence of hydrogen peroxide as oxidant, both under microwave irradiation and conventional heating. The phenolic dimer was selectively oxidized to 2-methoxy phenol with very high TON under microwave activation conditions. Comparatively, reactions run under conventional heating led to oligomerisation of the dimer and resulted in a mixture of products.