APPLICATION OF IMIDAZOLINES BASED ON TALL OIL FATTY ACIDS AND THEIR QUATERNARY SALTS FOR THE SEPARATION OF THE BINARY NON-AQUEOUS AZEOTROPE SYSTEMS

Методом экстрактивной (в том числе солевой) ректификации с использованием имидазолинов и четвертичных солей на их основе разделены на компоненты неводные двойные азеотропные системы. В качестве разделяющих агентов выбраны: промышленный продукт 1-гидроксиэтил-2-алкенил-2-имидазолин на основе жирных кислот таллового масла, а также его четвертичные соли - хлорид и тетрафторборат 1-гидроксиэтил-2-алкенил-3-бензил-2-имидазолиния. Для разделения были использованы неводные азеотропные системы: ацетон-метанол, метилацетат-метанол, этилацетат-этанол и хлороформ-метанол. Равновесие жидкость-пар в соответствующих тройных системах исследовано в модифицированном приборе Отмера при 101,3 кПа, состав жидкой и паровой фаз определен газохроматографическим методом анализа. Минимальные концентрации (в мольных долях) имидазолина и имидазолиниевых солей для разрушения азеотропов составили 0,156-0,264. Для корреляции экспериментальных данных о парожидкостном равновесии в системах, содержащих имидазолиниевые соли использована электролитная модель NRTL. Средние абсолютные отклонения расчетных данных от экспериментальных значений мольного содержания растворителей в паровой фазе и температуры в системах составили 0,007-0,008 и 0,25-0,35 К, соответственно. The non-aqueous binary azeotrope systems have been separated into components by the method of extractive rectification (and salt rectification) using imidazolines and their quaternary salts. The following were selected as separating agents: industrial product 1-hydroxyethyl-2-alkenyl-2-imidazoline based on tall oil fatty acids, as well as its quaternary salts - chloride and tetrafluoroborate 1-hydroxyethyl-2-alkenyl-3-benzyl-2-imidazolinium. Non-aqueous azeotrope acetone - methanol, methyl acetate - methanol, ethyl acetate - ethanol, and chloroform - methanol systems were used for separation. The vapor-liquid equilibrium in the corresponding ternary systems was investigated in a modified Othmer still at 101.3 kPa, the composition of the liquid and vapor phases was determined by gas chromatographic analysis. The minimum concentrations (in molar fractions) of imidazoline and imidazolinium salts for the azeotrope breaking were 0.156-0.264. The mean absolute deviations between experimental and calculated data for the solvent mole fraction in the vapor phase and temperature in the imidazolinium salt containing systems were 0,007-0,008 and 0,25-0,35 К respectively.

Comparison of the Economy and Controllability of Pressure Swing Distillation with Two Energy-Saving Modes for Separating a Binary Azeotrope Containing Lower Alcohols

The pressure swing distillation (PSD) with two different energy-saving modes are put forward to separate a binary azeotrope containing lower alcohols: benzene/methanol. A comparison of the economy and controllability for the partial and fully heat integrated pressure swing distillation (HIPSD) is made by detailed simulation analysis. The optimal operating parameters of partial and fully HIPSD processes are obtained by minimizing total annual cost (TAC). These results show that the fully HIPSD mode saves 5.88% TAC compared with the partial HIPSD mode. Meanwhile, this paper proposes that the composition slope profile can help to select the temperature control stage (TCS), when the temperature profile in the column is rising rapidly near the bottom and the maximum of temperature slope value occurs in the bottom of the column. Several control structures are developed to check the rationality of the selection of the TCS and evaluate the industrial application. These results illustrate the composition/temperature cascade control structure for the PSD with two energy-saving modes can both get good control performances, and the purities of benzene and methanol can be brought close back to the initial value. However, the fully HIPSD mode can only handle much smaller composition disturbances (<10%) compared with the partial HIPSD mode. Therefore, the selection of energy-saving modes for the separation process should weigh economy against controllability.