Dehydrogenation of Isopropanol on Copper-Containing Mesoporous Catalysts

Abstract

Copper-containing mesoporous catalysts with an MCM-41 type structure have been prepared using direct hydrothermal synthesis and characterized using XRD, AAS, N 2 adsorption-desorption, DRUV-vis, and TEM. All of the samples showed high structural regularity and surface area. Three copper species are presented in these materials: isolated mononuclear Cu δ+ species, oligonuclear [Cuand bulky CuO oxides. These materials were catalytically tested in isopropanol dehydrogenation, showing good activity and very high selectivity to propanone at 300 °C. A further reduction treatment of the samples allowed us to suggest possible active species. Both the [Cu δ+and the isolated Cu δ+ cations seem to be the species responsible for isopropanol dehydrogenation.

Pd–Cu interaction in Pd/Cu-MCM-41 catalysts: Effect of silica source and metal content

“…Reflections shift toward lower • 2Â values with increases in the total metal content. This behavior has been previously associated with the inclusion of copper and palladium cations in the MCM-41 framework by Bálsamo et al [31] and Papp et al [34]. In the present work we observed that most of the Pd and Cu species during the template removal were present as oxides on the external surface of MCM-41 particles (see below).…”

“…DFT analysis confirms that the total volume adsorbed in the 4.3 nm mesopores is lower in comparison to other samples, and that 6-7 nm pores are also present in this sample. The presence of large copper and palladium oxide particles may be responsible for the change in the sample textural properties [31,34].…”

“…When dealing with MCM-41 materials containing Cu and Pd, the main drawback to be avoided is the segregation of large Cu [26][27][28][29][30][31][32] and Pd [33][34][35][36][37][38][39] oxide or metallic particles during the catalyst preparation, which is well-known to be dependent on the incorporation method. In bimetallic Pd/Cu-MCM-41 catalysts, we observed that the nature and size of active species depend on the synthesis procedure, namely co-impregnation of PdCl 2 and CuCl 2 and addition of Pd and Cu during the MCM-41 synthesis as cations or as preformed nanoparticles [6,7].…”

The impact of the copper source on the synthesis of meso-structured CuTUD-1: a promising catalyst for phenol hydroxylation

“…27, 33 In addition, very broad peak at above 400 nm is assigned to pseudo-octohedral ligand oxygen 10 environment of copper. 17,18,23,24,33 Among the three samples, CuTA showed an intense absorption peak at 310 nm, which indicate of presence of oligonuclear CuO clusters 18 and also an indirect evidence for lesser incorporation of Cu 2+ into the silica matrix. Furthermore, for all the CuTUD-1 samples a relative 15 percentage of Cu species were estimated from the respective absorption peak areas.…”

“…12 Though the high content of divalent metal ions such as Cu 2+ are difficult to incorporate into the 50 mesoporous silica, many research groups have devoted to pack the Cu 2+ sites as complex or direct incorporation into silica framework. [13][14][15][16][17][18] It has been well known that one of the important factor that determines the dispersion of Cu 2+ active site which are in turn influenced in the direct synthesis method by structural 55 nature of copper precursors, coordinative environment, rate of hydrolysis and solubility. Hence, the selection of copper source is of prime concern in the copper based mesoporous material synthesis.…”