A novel method to determine the adsorption of water vapor on porous solids and supported ionic liquids by electrical sensors

离子液体在蒸发和分解过程中的热稳定性对纯离子液体和负载型离子液体(ILS)的应用具有重要意义。在两个PI即将完成的联合DFG项目中，成功地开发了基于射频(RF)的方法来检测离子液体的孔填充程度的电传感器。利用这种方法，可以测量蒸发和热分解的质量损失。在Pd-SCILL催化剂(具有离子液体层的固体催化剂)上丁二烯选择加氢制丁烯的过程中，这也是可能的。在应用的新研究项目中，作为第一个项目的继续，有前途的RF方法现在将转移到在多孔固体和负载在多孔固体上的离子液体上测量水蒸气的吸附。一般来说，这对于通过吸附干燥气体以及在催化中使用负载型离子液体是很重要的。如果可能，应该在吸附器(固定床)中轴向空间分辨地监测吸附过程。非常初步的实验表明，无论是对于纯多孔性固体还是涂有离子液体的多孔性固体，都可以用基于射频的方法来测量水蒸气的吸附和解吸。拟议项目的最终目标是开发一种新的电学方法来确定非接触式、操作式和空间分辨的吸附剂的水负荷。纯多孔二氧化硅以及涂有离子液体的二氧化硅将被研究。在后一种情况下，用离子液体同时测定水负荷和孔隙充填度也是本项目的目标。最后，这些研究的结果也应该应用于确定水(蒸汽)对SCILL催化剂的活性和选择性的影响，即以钯为活性金属的二氧化硅负载的IL[DMIM][DMP]。作为模型反应，应该再次使用丁二烯选择加氢为丁烯。在项目结束时，应该已经开发出一个模型，该模型允许定量地解释射频信号作为输入参数(水的暴露、温度)的函数，并从射频信号中推导出空间解析的水负荷。

The thermal stability of ionic liquids with regard to evaporation and decomposition is important for the application of pure and supported ionic liquids (ILs). In the course of the soon-finished joint DFG-projects of both PIs, electrical sensors have been successfully developed to detect the pore filling degree of ionic liquids by a radio frequency-based (RF-based) method. By means of this method, the mass loss by evaporation and thermal decomposition can be measured. This was also possible in operando during the selective hydrogenation of butadiene to butene on a Pd-SCILL-catalyst (solid catalyst with ionic liquid layer).Within the applied new research project, which is a continuation of the first project, the promising RF-method shall now be transferred to measure in operando the adsorption of water vapor on porous solids and ionic liquids supported on porous solids. This is in general important for drying of gases by adsorption as well as for the use of supported ionic liquids in catalysis. If possible, the adsorption process should be monitored space-resolved in axial direction in an adsorber (fixed bed).Very preliminary experiments show that the ad- and desorption of water vapor can be measured by the radio frequency-based method both for pure porous solids as well as for porous solids coated with an IL. The ultimate goal of the proposed project is the development of a new electrical method to determine the water load of adsorption agents contact-free, in operando, and space-resolved. Pure porous silica as well as silica coated with an IL will be investigated. In the latter case, the simultaneous determination of the water load and the pore filling degree with the ionic liquid is also a goal of the project. Finally, the results of these investigations should also be applied to determine the influence of water (vapor) on the activity and selectivity of a SCILL-catalyst, namely the IL [DMIM][DMP] supported on silica with palladium as active metal. As a model reaction, the selective hydrogenation of butadiene to butene should again be used.At the end of the project, a model should have been developed that allows to quantitatively explain the radio frequency signals as a function of the input parameters (exposure of water, temperature) and that derives the water load spatially resolved from the RF signals.