Li Shuai, Ogunkoya Dolanimi, Fang Tiegang, Willoughby Julie, Rojas Orlando J
Bio-based Colloids and Materials (BiCMat), School of Chemical Technology, Aalto University, P.O. Box 16300, Espoo 00076, Finland; Department of Forest Biomaterials, North Carolina State University, P.O. Box 8005, Raleigh, NC 27695, United States.
Department of Mechanical and Aerospace Engineering, North Carolina State University, P.O. Box 8005, Raleigh, NC 27695, United States.
J Colloid Interface Sci. 2016 Nov 15;482:27-38. doi: 10.1016/j.jcis.2016.07.063. Epub 2016 Jul 26.
Kraft and organosolv lignins were subjected to carboxymethylation to produce fractions that were soluble in water, displayed a minimum surface tension as low as 34mN/m (25°C) and a critical aggregation concentration of ∼1.5wt%. The carboxymethylated lignins (CML), which were characterized in terms of their degree of substitution ((31)P NMR), elemental composition, and molecular weight (GPC), were found suitable in the formulation of emulsions with bitumens of ultra-high viscosity, such as those from the Canadian oil sands. Remarkably, the interfacial features of the CML enabled fuel emulsions that were synthesized in a very broad range of internal phase content (30-70%). Cryo-replica transmission electron microscopy, which was used here the first time to assess the morphology of the lignin-based emulsions, revealed the droplets of the emulsion stabilized with the modified lignin. The observed drop size (diameters<2μm) was confirmed by light scattering, which revealed a normal size distribution. Such characteristics led to stable emulsified systems that are amenable for a wide range of applications. Emulsification with CML afforded bitumen emulsions with very high colloidal stability (no change was noted for over one month) and with a strong shear thinning behavior. Both features indicate excellent prospects for storage, transport and spraying, which are relevant in operations for power generation, which also take advantage of the high heating value of the emulsion components. The ability of CML to stabilize emulsions and to contribute in their combustion was tested with light fuels (kerosene, diesel, and jet fuel) after formulation of high internal phase systems (70% oil) that enabled operation of a fuel engine. A significant finding is that under certain conditions and compared to the respective pure fuel, combustion of the O/W emulsions stabilized by CML presented lower NOx and CO emissions and maintained a relatively high combustion efficiency. The results highlight the possibilities in high volume application for lignin biomacromolecules.
对硫酸盐木质素和有机溶剂木质素进行羧甲基化处理，以制备可溶于水的馏分，其最低表面张力低至34mN/m（25°C），临界聚集浓度约为1.5wt%。通过取代度（（31）P NMR）、元素组成和分子量（凝胶渗透色谱法）对羧甲基化木质素（CML）进行了表征，结果表明其适用于配制具有超高粘度的沥青乳液，如来自加拿大油砂的沥青乳液。值得注意的是，CML的界面特性使得能够在非常宽的内相含量范围（30 - 70%）内合成燃料乳液。低温复型透射电子显微镜首次用于评估木质素基乳液的形态，结果显示乳液液滴由改性木质素稳定。通过光散射证实了观察到的液滴尺寸（直径<2μm），其显示出正常的尺寸分布。这些特性导致形成了适用于广泛应用的稳定乳化体系。用CML进行乳化得到的沥青乳液具有非常高的胶体稳定性（一个多月内无变化）和强烈的剪切变稀行为。这两个特性表明其在储存、运输和喷雾方面具有良好的前景，这在发电操作中很重要，发电操作也利用了乳液成分的高热值。在配制了能够使燃料发动机运行的高内相体系（70%油）后，用轻质燃料（煤油、柴油和喷气燃料）测试了CML稳定乳液并促进其燃烧的能力。一个重要发现是，在某些条件下，与相应的纯燃料相比，由CML稳定的O/W乳液燃烧时NOx和CO排放量更低，并且保持了相对较高的燃烧效率。这些结果突出了木质素生物大分子在大规模应用中的可能性。
