Experimental & Theoretical Studies of Selectivity & Heats of Adsorption of Gaseous Mixtures in Zeolites: Effect of Pore Size and Electric Field

PIs建议发展多组分吸附理论，使其能够可靠地预测选择性和吸附热。由于缺乏可靠的实验数据，本提案的目标是测量热力学过剩函数：过量吉布斯自由能（Ge）和混合热（He）。过量吉布斯自由能包含了吸附相活度系数和选择性的信息；在变压吸附（PSA）绝热过程中，需要用混合热来确定系统温度的变化。被吸附混合物的这些多余功能将用微量热计来测定，微量热计同时测量混合物组分的选择性和各自的吸附热。吸附的统计力学理论自然导致对超额函数理论值的预测。因此，对选定的实际措施的精确实验数据是可取的，作为测试材料，可以判断竞争理论的有用性。初步研究选择的系统是：1。低负荷时硅酸盐中的CH4和C2H6。2. NaX中的CO2和C2H6。3. NaX中的CO2和C2H4。4. X和Y分子筛中Li、Na、K、Rb、Cs阳离子交换形式的CHF2CHF2 （HFC-134）和CF3CH2F （HFC-134a）。5. CH4和SF6在由10、12和14元环组成的圆柱形一维孔中。选择这五种体系来分离决定选择性的主要变量：沸石微孔内的孔径和电场以及吸附质分子的极性、大小和形状。所提出的测量的意义在于，它们将提供一种系统的方法来处理单气体和多组分混合物吸附的温度依赖性，这对吸附分离过程的设计至关重要。

Abstract CTS 9610030 The PIs propose to develop theories of multicomponent adsorption capable of making reliable predictions of selectivity and heats of adsorption. Since reliable experimental data are scarce, the objective of this proposal is to measure thermodynamic excess functions: the excess Gibbs free energy ((Ge) and heat of mixing ((He). The excess Gibbs free energy contains information about adsorbed-phase activity coefficients and the selectivity; the heat of mixing is needed to determine the change in temperature of the system during adiabatic operation of pressure-swing-adsorption (PSA) processes. These excess functions of adsorbed mixtures will be determined with a microcalorimeter which measures simultaneously the selectivity and the individual heats of adsorption of the components of the mixture. Statistical mechanical theories of adsorption lead naturally to the prediction of theoretical values of excess functions. Therefore precise experimental data on selected real measures are desirable as test material against which the usefulness of competing theories can be judged. The systems chosen for initial studies are: 1. CH4 and C2H6 in silicate at low loading. 2. CO2 and C2H6 in NaX. 3. CO2 and C2H4 in NaX. 4. CHF2CHF2 (HFC-134) and CF3CH2F (HFC-134a) in Li, Na, K, Rb, Cs cation-exchanged forms of X and Y zeolites. 5. CH4 and SF6 in cylindrical, one-dimensional pored composed of 10, 12, and 14 membered rings. These five systems were selected to isolate the principal variables which determine selectivity: the pore size and electric field inside the micropores of the zeolite and the polarity, size, and shape of the adsorbate molecules. The significance of the proposed measurements is that they will provide a systematic way of handling the temperature dependence of adsorption of single gases and multicomponent mixtures, which is critical for the design of adsorptive separation processes.