National Research Council of Canada, Energy Mining and Environment Portfolio, 1200 Montreal Road, Ottawa, ON K1A 0R6, Canada.
National Research Council of Canada, Energy Mining and Environment Portfolio, 1200 Montreal Road, Ottawa, ON K1A 0R6, Canada.
Ultrason Sonochem. 2022 Feb;83:105929. doi: 10.1016/j.ultsonch.2022.105929. Epub 2022 Jan 21.
Propelled by enormous increase in demand for fuel sources, Canadian oil sands are becoming increasingly important as a fuel source due to their abundance and upgrading capability. However, extraction of bitumen, a high acid crude (HAC) oil, requires 2-3 units of water per unit of oil resulting in naphthenic acid (NA)-rich oil sands process affected water (OSPW) collected in effluent ponds. This study illustrates the role of sonochemistry in the accelerated degradation through H-abstraction and subsequent decarboxylation of aromatic and alicyclic naphthenic acid model compounds. Benzoic acid and 3-methylcyclohexane carboxylic acid were selected as model NA compounds to investigate the mechanism of hydroxyl radical (OH) initiated carboxylic acid degradation in 378 KHz sonochemical reactor. Established FTIR methods with low resolution LCMS spectroscopy confirmation were applied to determine the extent of carboxylic acid degradation and identify the formation of products. FTIR monitoring showed a non-linear degradation of carboxylic acids with formation of many intermediates highlighting the shift from cyclic carboxylic acids to cyclic alcohols during BA degradation. Subsequent decrease in carboxylic acid groups signifies scission of cyclic structures before complete mineralization. This is confirmed with the LCMS identification of products such as: 3-hydroxybenzoic acid and phenol. This study postulated new breakdown pathways for degradation of benzoic acid with complete mineralization at a sonochemical reaction time (SRT) of 4 h. A radical quenching process was also inferred through the formation of conglomerates during sonochemical degradation of BA. Extension of the study to 3-methylcyclohexane carboxylic acid (3mCHA) shows similar non-linearity with an increase in carboxylic acid groups indicating H-abstraction followed by ring-opened compounds. However, due to the complex nature of 3mCHA's ring-opened compounds, complete mineralization is not achieved. The putative role of sonochemistry is a promising and sustainable degradation method for mitigating NAs in OSPW, but sonication periods need to be considered carefully to ensure adequate mineralization of their constituents and combinatorial methods with other advanced oxidation methods may be needed to enhance industrial application. In Part II, an in silico screening approach using first principles is reported to identify the breakdown of the organic compounds and determine molecular rates of reaction to confirm the mechanistic origins of the compounds formed.
受燃料需求大幅增长的推动，由于油砂资源丰富且具有升级能力，加拿大油砂作为燃料来源的重要性日益凸显。然而，沥青（一种高酸原油（HAC））的开采需要每单位油使用 2-3 个单位的水，导致在流出物池中收集到富含环烷酸（NA）的油砂加工影响水（OSPW）。本研究通过 H 原子的夺取和随后的脱羧作用，说明了声化学在加速芳香族和脂环族环烷酸模型化合物的降解中的作用。选择苯甲酸和 3-甲基环己烷羧酸作为 NA 模型化合物，以研究 378 KHz 声化学反应器中羟基自由基（OH）引发的羧酸降解的机理。应用具有低分辨率 LCMS 光谱确认的成熟 FTIR 方法来确定羧酸降解的程度并鉴定产物的形成。FTIR 监测表明，羧酸的降解是非线性的，形成了许多中间体，这突出表明在 BA 降解过程中，环状羧酸向环状醇的转变。随后，羧酸基团的减少表明在完全矿化之前，环状结构的断裂。这通过 LCMS 鉴定产物（如 3-羟基苯甲酸和苯酚）得到证实。该研究提出了苯甲酸在声化学反应时间（SRT）为 4 小时时完全矿化的新的降解途径。通过 BA 声化学降解过程中形成的聚集体，还推断出了自由基猝灭过程。将研究扩展到 3-甲基环己烷羧酸（3mCHA），可以看到类似的非线性，随着羧酸基团的增加表明发生了 H 原子的夺取和开环化合物的形成。然而，由于 3mCHA 的开环化合物的复杂性质，没有实现完全矿化。声化学的作用是一种有前途且可持续的降解 OSPW 中环烷酸的方法，但需要仔细考虑超声时间，以确保其成分的充分矿化，并且可能需要与其他高级氧化方法结合使用组合方法来增强工业应用。在第二部分中，报告了一种使用第一性原理的计算筛选方法，以识别有机化合物的分解并确定分子反应速率，以确认形成的化合物的机械起源。
