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This work unveils a route for a new generation of heterogeneous polyoxometalate (POMs) based catalysts associated to the preparation of hybrid materials as a triad of POMs, mesoporous silica (SBA‐15) and microporous MOF structures (MOF‐808). The prepared catalyst, PMo12@MOF‐808@SBA‐15, with the main active center the phosphomolybdic acid (PMo12), was successfully applied for the desulfurization of a multicomponent fuel. Its oxidative catalytic performance showed to be considerable superior to the isolated POM@MOF and able to be recycled for more catalytic cycles without active loss. The higher catalytic performance seems to be directly related with the preparation of a more amorphous MOF structure within the channels of SBA‐15, in the presence of active POM guests. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have been the subject of extensive scientific investigation in the last three decades and, currently, they make up one of the types of compounds most studied for their potential application in a wide range of distinct catalytic processes. Pristine MOF compounds provide several intriguing benefits for catalytic applications, including large interior surface areas and high densities of active sites; high catalytic reaction rates per volume; post-synthesis modifications with complementary catalytic groups; and the ability for multiple functional groups to catalyze the reaction. For most large-scale catalytic applications, including those in fuel processing, gas emission reduction, and chemical synthesis, pristine MOFs often show limited stabilities and opportunities for regeneration at high temperatures. As a result, the real applications of MOFs in these technologies are likely to be constrained, and a controlled thermal modification to prepare MOF-derivative compounds has been applied to induce crystalline structural changes and increase the structural stability of the MOFs, enhancing their potential applicability in more severe catalytic processes. Recent advances concerning the use of this strategy to boost the catalytic potential of MOF-derivative compounds, particularly for stable Zr-based MOFs, are outlined in this short review article. [ABSTRACT FROM AUTHOR]

A binuclear dioxomolybdenum catalyst [(MoO2Cl2)2(L)] (1) (with L (1S,2S)-N,N′-bis(2-pyridinecarboxamide)-1,2-cyclohexane) was prepared and used as catalyst for the desulfurization of a multicomponent model fuel containing the most refractory sulfur compounds in real fuels. This complex was shown to have a high efficiency to oxidize the aromatic benzothiophene derivative compounds present in fuels, mainly using a biphasic 1:1 model fuel/MeOH system. This process conciliates catalytic oxidative and extractive desulfurization, resulting in the oxidation of the sulfur compounds in the polar organic solvent. The oxidative catalytic performance of (1) was shown to be influenced by the presence of water in the system. Using 50% aq. H2O2, it was possible to reuse the catalyst and the extraction solvent, MeOH, during ten consecutive cycles without loss of desulfurization efficiency. [ABSTRACT FROM AUTHOR]

The removal of sulfur- and nitrogen-containing compounds present in fuels is and will be crucial to accomplish actual strict regulations to avoid environmental and humanity health adversities. The conventional hydrodesulfurization and hydrodenitrogenation processes conducted by refineries are limited due to severe operating conditions, and even more importantly, they are inefficient for simultaneously removing nitrogen- and sulfur-containing compounds in fuels. On the other hand, non-hydrogen technologies are beneficial in terms of mild operating conditions, and during the last two decades, some successful works have shown that these can be highly effective at efficiently removing both sulfur- and nitrogen-containing compounds from liquid fuels. For more than four decades, extensive research (thousands of publications since the 1980s) has been dedicated to developing remote desulfurization technologies without taking into consideration the presence of a complex fuel matrix, or even taking into account the presence of other harmful pollutant elements, such as nitrogen. Even more recently, several effective non-hydrogen denitrogenation processes have been reported without considering the presence of sulfur compounds. This review paper is a reflection on the limited work that has been successfully performed to simultaneously remove sulfur- and nitrogen-containing compounds from fuels. An evaluation of different methodologies (adsorption, extraction, oxidative (photo)catalysis, ultrasound-assisted oxidation) is presented here. Furthermore, this review intends to define new future strategies that will allow the design of more suitable and economical technologies, effectively conciliating desulfurization and denitrogenation processes to produce more sustainable fuels. [ABSTRACT FROM AUTHOR]