Search

Recently we mentioned that the surface of solids often exerts Pauli repulsion on the interstitial/substitutional hydrogen, which markedly changes the properties of H, and increases its chemical activity, which is referred to as ‘Pauli activation of interstitial H’ for short. The purpose of this paper is to further confirm the reality of this activation mechanism at a quantitative level. We particularly mention the importance of the H-dipole of the interstitial hydrogen induced by Pauli activation for this catalysis, which is the key to understand the principle of this catalysis mechanism. Taking a simple diatomic molecule as an example, we first illustrate what are the prerequisites for forming a molecular covalent bond, when the two atoms are in close contact. Then we argue that, the Pauli-activated H at solid surface just meets these prerequisites due to the dual modulation effect of the induced H-dipole on both the energy and the spatial orientation of a foreign atom/molecule in the bonding process with H, thus accelerates the hydrogenation. Moreover, we emphasize that the size of the depression/hole at solid surface, where the interstitial H sited(simply referred to as ‘Pauli hole’), must match the radius of H to ensure the effectiveness of Pauli activation of H. Accordingly it provides a criteria for selecting a suitable catalysts for the specific chemical reaction, which would be useful in practical applications. Taking a common chemical reaction as an example, we make a calculation and quantitative analysis of the synthesis of MgH2, using Ni as the heterogeneous catalyst. Details of how to select a suitable catalyst are given in this reaction. And why and how the dual modulation effect of the induced H-dipole of interstitial H promotes the realization of the prerequisites, thus facilitates the formation of the covalent bond Mg-H. Therefore the rationality of the Pauli activation-catalysis is confirmed theoretically.

TS-1 zeolite has outstanding performance in the catalytic reactions with hydrogen peroxide as catalytic promoter. However, the narrow pore size (< 1.0 nm) of traditional TS-1 makes it difficult for bulky organic compounds to contact with the active sites in the pores, which seriously limits application of TS-1. Recently, the introduction of mesoporous structure into microporous TS-1 becomes a hot research topic. Meanwhile, the huge synthesis cost of TS-1 is another main reason hindering its industrial application. In this paper, mesoporous TS-1 was successfully synthesized using sodium silicate as silicon source and titanium trichloride as titanium source under the template conditions of tetrapropylammonium hydroxide (TPAOH) and cationic polymer. The mesoporous TS-1 was characterized by X-ray diffraction (XRD), N2 adsorption, scanning electric microscopy (SEM), transmitting electric microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and UV-Vis Spectrum spectra (UV-Vis). Results show that the synthesized TS-1 zeolites have good crystallinity and tetra-coordinated framework Ti atoms, and there are abundant mesoporous structures in the zeolite crystals. The results of oxidation experiments show that conversion of diphenyl sulfide and dibenzyl sulfide with mesoporous TS-1 are 97.3 % and 85.3 % respectively, while that conversion with microporous TS-1 are 75.7 % and 63.5 respectively.