Instituto de Química, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
Instituto de Química, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
Talanta. 2018 Mar 1;179:828-835. doi: 10.1016/j.talanta.2017.12.022. Epub 2017 Dec 8.
Thermochemical processes can convert the biomass into fuels, such as bio-oil. The biomass submitted to pyrolysis process, such as fibers, are generally rich in silicon, an element that can lead to damages in an engine when there is high concentration in a fuel. High-resolution continuum source atomic absorption spectrometry (HR-CS AAS) is an interesting alternative for Si determination in the products and byproducts of the pyrolysis process because, besides the flame (F) and graphite furnace (GF) atomizers, it has enhanced the application of direct analysis of solid samples (SS) within GF. This study aimed the development of methods to determine Si in biomass samples, their products and byproducts using HR-CS AAS. A high-resolution continuum source atomic absorption spectrometer contrAA 700 equipped with F and GF atomizers was used throughout the study. HR-CS F AAS (λ = 251.611nm, 1 detection pixel, NO/CH flame) was used to evaluate Si content in biomass and ash, after a microwave-assisted acid digestion with HNO and HF. HR-CS GF AAS (T = 1400°C, T = 2650°C) has evaluated Si in pyrolysis water and bio-oil at 251.611nm, and in peach pit biomass and ash at 221.174nm using SS, both wavelengths with 1 detection pixel. Rhodium (300μg) was applied as permanent modifier and 10μgPd + 6μg Mg were pipetted onto the standards/samples at each analysis. Three different biomass samples were studied: palm tree fiber, coconut fiber and peach pit, and three certified reference materials (CRM) were used to verify the accuracy of the methods. The figures of merit were LOD 0.09-20mgkg, and LOQ 0.3-20mgkg, considering all the methods. There were no significant differences between the CRM certified values and the determined ones, using a Student t-test with a confidence interval of 95% (n = 5). Si concentration ranged from 0.11-0.92% mm, 1.1-1.7mgkg, 3.3-13mgkg, and 0.41-1.4%mm, in biomass, bio-oil, pyrolysis water and ash, respectively. Si remained mostly in the ash, leading to a mass fraction of up to 103%, even when the Si loss is not considered. Silicon concentration in bio-oil was below 1.7mgkg, which is suitable for its application as a fuel. The developed methods using HR-CS AAS are suitable for Si determination in biomass, bio-oil, pyrolysis water, and ash. The application of bio-oil as an alternative fuel would be possible evaluating its Si content due to its low levels. The mass balance for Si has proved to be an important tool in order to evaluate the correct disposal of pyrolysis process byproducts.
热化学过程可以将生物质转化为燃料，如生物油。用于热解过程的生物质，如纤维，通常富含硅，当燃料中硅浓度较高时，硅会对发动机造成损害。高分辨率连续光源原子吸收光谱法（HR-CS AAS）是一种测定热解过程产物和副产物中硅的有趣方法，因为它除了火焰（F）和石墨炉（GF）原子化器之外，还增强了直接分析 GF 中固体样品（SS）的应用。本研究旨在开发使用 HR-CS AAS 测定生物质样品及其产物和副产物中硅的方法。在整个研究过程中，使用了高分辨率连续光源原子吸收光谱仪 contrAA 700，配备了 F 和 GF 原子化器。使用 HR-CS F AAS（λ = 251.611nm，1 个检测像素，NO/CH 火焰）评估了经微波辅助消解后的生物质和灰分中的硅含量，所用酸为 HNO 和 HF。HR-CS GF AAS（T = 1400°C，T = 2650°C）在 251.611nm 处评估了热解水和生物油中的硅含量，在 221.174nm 处评估了桃核生物质和灰分中的硅含量，均采用 SS，两个波长均使用 1 个检测像素。在每次分析时，均将 300μg 的铑作为永久改性剂，以及 10μgPd+6μgMg 加入到标准/样品中。研究了三种不同的生物质样品：棕榈树纤维、椰子纤维和桃核，使用三种认证参考物质（CRM）来验证方法的准确性。所有方法的检出限为 0.09-20mgkg，定量限为 0.3-20mgkg。使用置信区间为 95%（n = 5）的学生 t 检验，CRM 认证值与测定值之间没有显著差异。生物质、生物油、热解水和灰分中的硅浓度分别为 0.11-0.92%mm、1.1-1.7mgkg、3.3-13mgkg 和 0.41-1.4%mm。硅主要留在灰分中，导致质量分数高达 103%，即使不考虑硅的损失也是如此。生物油中的硅浓度低于 1.7mgkg，适合用作燃料。使用 HR-CS AAS 开发的方法适用于测定生物质、生物油、热解水和灰分中的硅。由于其含量较低，因此可以评估生物油的硅含量，从而可以将其用作替代燃料。硅的质量平衡已被证明是评估热解过程副产物正确处理的重要工具。
