Separation and Purification of Essential Oil by Supercritical Pressure Swing Adsorption

提出了一种提取柑桔油的新工艺。以硅胶为吸附剂，研究了超临界二氧化碳（SC-C0_2）的变压吸附工艺。采用示踪响应技术和突破分析对橙油011硅胶中主要溶质的吸附-解吸过程进行了评价。芳樟醇（香气）在硅胶上的选择性吸附优于柠檬烯（萜烯）。吸附平衡常数随温度升高或压力降低而增大。根据范霍夫图计算表观吸附热。芳樟醇的颗粒内有效扩散系数大于柠檬烯。质量输运特性表明，轴向扩散阻力对色谱响应峰展宽的贡献随雷诺数的增加而减小，表明颗粒内扩散阻力相对重要。在313 K和8.8 MPa条件下，通过突破分析得到了橙油的吸附等温线。吸附等温线用Langmuir方程表示。吸附平衡常数的密度依赖性使我们能够对各种条件进行外推。测定了在313 K和8.8 MPa温度下SC-C0_2对橙油的吸附动力学行为和在313 K和19.4 MPa温度下溶质的解吸动力学行为。用硅胶吸附剂在SC-CO_2中处理柑橘油，研究了在低压吸附和高压解吸之间的连续循环操作（变压吸附），包括漂洗步骤，以去除吸附器空隙区域的溶质。研究了进料浓度和半循环时间对含氧化合物浓度因子的影响。通过解吸和排空两个步骤，成功地得到了无萜柑橘油。半循环时间的增加使浓度因子增加。获得了较高的富集系数，可达25，达到了工业要求。变压吸附SC-CO_2处理柑橘油的数学模型与实验结果吻合较好。计算出的柱内溶质浓度分布表明，吸附剂再生不充分，循环使用吸附剂的比例很小。在解吸过程中，以较高的CO_2流速进行吸附，可以回收吸附的有价溶质。实验结果表明，循环吸附过程连续运行是可行的。少

A new technique for fractionation of citrus oil was proposed. A pressure swing adsorption process in supercritical carbon dioxide (SC-C0_2) was developed with silica gel as adsorbent. The adsorption-desorption process of major solutes in orange oil 011 silica gel was evaluated by the tracer response technique and the breakthrough analysis. Linalool (aroma) was more selectively adsorbed on silica gel than limonene (terpene). The adsorption equilibrium constant was increased with the increase in temperature or the decrease in pressure. The apparent heat of adsorption was calculated from the van't Hoff plot. The intraparticle effective diffusivity for linalool was larger than that of limonene. Mass transport properties showed that the contribution of axial dispersion resistance on the broadening of the chromatographic response peak decreased with the increase in Reynolds number, resulting in the relative importance of intraparticle diffusion resistance. Adsorption isotherm of orange oil w … More as obtained by breakthrough analysis at 313 K and 8.8 MPa. The adsorption isotherm was represented by the Langmuir equation. The density dependency of the adsorption equilibrium constant enabled the extrapolation to the various conditions. Dynamic behaviors of adsorption of orange oil in SC-C0_2 at 313 K and 8.8 MPa and desorption of solutes at 313 K and 19.4 MPa were measured.A continuous cyclic operation (Pressure Swing Adsorption) between the adsorption at a lower pressure and the desorption at a higher pressure, involving the rinse step to remove the solutes in the void region of the adsorber, was demonstrated for citrus oil processing with silica gel adsorbent in SC-CO_2. Effects of feed concentration and half cycle time on the concentration factor of oxygenated compounds were studied. Terpeneless citrus oil was successfully obtained in the desorption step and blowdown step. The increase in half cycle time increased the concentration factor. Higher concentration factor up to 25 was obtained, and tile concentration factor satisfied the commercially required value. The mathematical model for the citrus oil processing by a pressure swing adsorption in SC-CO_2 agreed well with the experimental results. Calculated concentration profile of the solutes in the column showed that the regeneration of the adsorbent was not sufficient and the portion of the utilized adsorbent for tile cyclic operation was small. Adsorption process operated at a higher flow rate of CO_2 during the desorption step may recover the adsorbed valuable solutes. The proposed system showed the feasibility of the continuous operation of the cyclic adsorption process. Less