Abstract

Galactomannans can be extracted from various plant species, including those of the Cassia grandis Linn. f. (Fam. Caesalpiniaceae), a native Brazilian tree. The objective of this work was to obtain galactomannans by three different extraction methods and to characterize them owing to structure and rheological behavior in aqueous saline fluids that are typically applied for enhanced oil recovery. The largest yield obtained was 23.4 wt% and the mannose/galactose ratios were between 1.1 and 1.5. All the gums extracted were characterized by Proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, Elementary Analysis (CHN) and X-Ray Diffraction demonstrating their galactomannan structures. Thermogravimetric analyses allowed determining the real concentration of organic matter present in the final extraction product, which was near 70 wt%. The greatest molar mass of the Cassia gum was Mw = 1.01 × 10⁶ g/mol, determined by Size-exclusion chromatography and since it is a nonionic biopolymer, it was not influenced by the salinity of the prepared synthetic aqueous solutions with high salt concentrations (TDS = 29,711 mg/L and 68,317 mg/L), including the solutions containing divalent cations. Under a shear rate of 7.3 s⁻¹, Cassia gum from method A showed the highest apparent viscosity values that were approximately 158, 78 and 55 mPa s, at concentration of 5,000 ppm and temperatures of 25, 60 and 80 °C, respectively. Thus, Cassia gum stood as a promising biopolymer for enhanced oil recovery application.

摘要

半乳甘露聚糖可以从各种植物物种中提取，包括Cassia grandis Linn 的植物物种。F。(Fam. Caesalpiniaceae)，一种巴西本土树。这项工作的目的是通过三种不同的提取方法获得半乳甘露聚糖，并根据通常用于提高石油采收率的含水盐水流体中的结构和流变行为来表征它们。获得的最大产量为 23.4 wt%，甘露糖/半乳糖比在 1.1 和 1.5 之间。所有提取的树胶均通过质子核磁共振、傅里叶变换红外光谱、元素分析 (CHN) 和 X 射线衍射表征其半乳甘露聚糖结构。热重分析允许确定最终提取产品中存在的有机物质的实际浓度，接近 70 wt%。决明子胶的最大摩尔质量为 Mw = 1.01 × 10 ⁶g/mol，通过尺寸排阻色谱法测定，并且由于它是一种非离子生物聚合物，因此它不受制备的高盐浓度（TDS = 29,711 mg/L 和 68,317 mg/L）合成水溶液盐度的影响，包括含有二价阳离子的溶液。在 7.3 s ^-1的剪切速率下，来自方法 A 的决明胶在浓度为 5,000 ppm 和温度为 25、60 和 80°C 时显示出最高的表观粘度值，分别约为 158、78 和 55 mPa s。因此，决明胶是一种用于提高石油采收率应用的有前途的生物聚合物。