Wu Chengjun, Ding Junhuan, Tindall Graham W, Pittman Zachariah A, Thies Mark C, Roberts Mark E
Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, SC 29634, USA.
Molecules. 2024 Aug 16;29(16):3879. doi: 10.3390/molecules29163879.
Over the past decade, the production of biofuels from lignocellulosic biomass has steadily increased to offset the use of fuels from petroleum. To make biofuels cost-competitive, however, it is necessary to add value to the "ligno-" components (up to 30% by mass) of the biomass. The properties of lignin, in terms of molecular weight (MW), chemical functionality, and mineral impurities often vary from biomass source and biorefinery process, resulting in a challenging precursor for product development. Activated carbon (AC) is a feasible target for the lignin-rich byproduct streams because it can be made from nearly any biomass, and it has a market capacity large enough to use much of the lignin generated from the biorefineries. However, it is not known how the variability in the lignin affects the key properties of AC, because, until now, they could not be well controlled. In this work, various fractions of ultraclean (<0.6% ash) lignin are created with refined MW distributions using Aqueous Lignin Purification using Hot Agents (ALPHA) and used as precursors for AC. AC is synthesized via zinc chloride activation and characterized for pore structure and adsorption capacity. We show that AC surface area and the adsorption capacity increase when using lignin with increasing MW, and, furthermore, that reducing the mineral content of lignin can significantly enhance the AC properties. The surface area of the AC from the highest MW lignin can reach ~1830 m/g (absorption capacity). Furthermore, single step activation carbonization using zinc chloride allows for minimal carbon burn off (<30%), capturing most of the lignin carbon compared to traditional burn off methods in biorefineries for heat generation.
在过去十年中，木质纤维素生物质生产生物燃料的产量稳步增长，以抵消石油燃料的使用。然而，为了使生物燃料具有成本竞争力，有必要提高生物质中“木质”成分（质量占比高达30%）的附加值。木质素的性质，在分子量（MW）、化学官能团和矿物杂质方面，常常因生物质来源和生物精炼工艺的不同而有所差异，这使得其成为产品开发中具有挑战性的前驱体。活性炭（AC）是富含木质素的副产品流的一个可行目标，因为它几乎可以由任何生物质制成，并且其市场容量大到足以利用生物精炼厂产生的大部分木质素。然而，目前尚不清楚木质素的变异性如何影响活性炭的关键性能，因为到目前为止，这些性能还无法得到很好的控制。在这项工作中，使用热剂水相木质素纯化法（ALPHA）制备了具有精细分子量分布的各种超纯（灰分<0.6%）木质素馏分，并将其用作活性炭的前驱体。通过氯化锌活化合成活性炭，并对其孔结构和吸附容量进行表征。我们发现，使用分子量增加的木质素时，活性炭的表面积和吸附容量会增加，此外，降低木质素的矿物质含量可以显著提高活性炭的性能。由最高分子量木质素制成的活性炭的表面积可达~1830 m²/g（吸附容量）。此外，与生物精炼厂中用于产生热量的传统燃烧方法相比，使用氯化锌进行单步活化碳化可使碳的烧失量降至最低（<30%），从而捕获大部分木质素碳。
