Abstract
Metal-Organic Framework (MOF) materials are often modified or functionalized, and then the crystal size and morphology of MOF materials are changed. In the process of preparing UiO-66 confined phosphomolybdic acid (PMA) composites (PU), the TiF4-modified PU (PMA + UiO-66) composite catalyst (TiF4-PU) was successfully synthesized by adding titanium tetrafluoride, and the catalytic desulfurization activity was excellent. Similarly, the reaction mechanism was investigated by means of infrared spectroscopy, Raman spectroscopy, XPS, and UV/Vis spectroscopy. The results show that the addition of TiF4 not only changes the appearance and color of the catalyst, but also changes the valence distribution of the elements in the catalyst. The number of oxygen vacancies in the MOF increases due to the addition of TiF4, and more electrons are transferred from the Zr-MOF to PMA to form more Mo5+, which improved the performance of oxidative desulfurization in comparison. Thus, a stronger strong metal-support interaction (SMSI) effect is observed for TiF4-modified PU catalysts. In addition, the quenching experiment of free radicals shows that ·OH radical is the main active substance in the oxidative desulfurization reaction over TiF4-PU catalyst.
Highlights
Petroleum, as a major source of the world’s energy, consists of various sulfur compounds; the combustion can emit amounts of sulfur oxides, eventually causing acid rain [1]
We have previously reported the synthesis of PU-200 by confining phosphomolybdic acid (PMA) with UiO-66 using the one-pot method [10]
The difference for the synthesis of TiF4 -PU is the addition of TiF4 to the solution using the same one-pot method
Summary
As a major source of the world’s energy, consists of various sulfur compounds; the combustion can emit amounts of sulfur oxides, eventually causing acid rain [1]. To solve this problem, different techniques are applied to the desulfurization of crude oil [2]. Polyoxometalates (POMs) are composed of heteroatoms (such as P, Si, Fe, Co, etc.) and polyatoms (such as Mo, W, V, Nb, Ta, etc.) according to certain structures [4]. POMs show acidity and redox ability, and act as new green multifunctional catalysts with good structural stabilities [5]. The superiority of the structural certainty behaves as follows: (1) POMs involve the main structural characteristics of both coordination complexes and metal oxides. (2) POMs show the storage and transfer abilities of electrons and protons [6]. (3) Different heteroatoms and polyatoms result in different
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