Catalysis of Organic..

Hu et al. 93Results and DiscussionMetal Leaching TestThe leaching behavior of immobilized homogeneous catalyst was measured beforecommencing activity testing. It is highly desirable that the immobilized Co(II)catalyst, designated as Co(II)-IL/SiO 2 , exhibits minimum or zero metal leachingbehavior. Leaching tests were carried out under the following three conditions in thepresence of toluene and cyclohexane, respectively:1. Static Leaching Test at room temperature, no agitation2. Reflux Leaching Test at boiling points of the solvents under agitation3. High Temperature Leaching Test at 150 o C and 85 psig in a closed bombreactor with shakingIn each leach test, IL containing dissolved cobalt source was exposed to organicphase under the time and temperature conditions shown.All of organic phase leaching solutions were analyzed using a UV-Visspectrometer for Co(II) concentration. In our investigation, the level of Co (II) inleaching solution remained below detection limit of 0.1 ppm. Figure 1 illustratescomparison between leaching solution and standards. It provides a visual judgmenton whether metal is leached significantly into organic. In general, the successfulimmobilization of the Co(II) catalyst is accomplished by means of strong adhesion ofionic liquid on SiO 2 support and the insolubility of the Co(II)-IL complex in theorganic media.Figure 1. Comparison of leaching solution with standards using UV-Visspectrometer. (Leaching test was carried out at 150 o C, and 85 psig pressure).