Mechanisms, challenges, and future perspectives of adsorptive desulfurization using zeolite-based adsorbents: a review

This review is a comprehensive description of adsorptive desulfurization (ADS) by metal-modified zeolites, particularly the elimination of sulfur compounds from gasoline, diesel, kerosene, jet fuel, and heavy petroleum fuel. The seven largest zeolite structures (HEU, Composite, MWW, FAU, MFI, LTA, and BEA) were modified with metals such as copper, cerium, nickel, vanadium, zinc, and titanium and compared under different working conditions. It is determined by the results that CuCeY and modified CeY removed sulfur by 88.4% with an adsorption capacity of 4.49 mg S/g in model gasoline (thiophene, 500 ppm). CuHUSY and LaHUSY in model jet fuel (benzothiophene, 500 ppm) were removed by 83.9% and adsorbed by 7.16 mg S/g. For diesel fuel (dibenzothiophene, 500 ppm), LaNaY and CuNaY registered sulfur removal capacities of up to 99.9% and adsorption capacity of 24.6 mg S/g. Moreover, nickel, zinc, and tungsten-containing zeolites registered maximum removal capacities of up to 99% in heavy petroleum and model fuels like iso-octane and hexadecane, even under reduced contact times at room temperatures. In kerosene, Cu and TiO₂-modified clinoptilolite zeolites adsorbed 45-99.9% of sulfur based on the process conditions. This study also provides information on the regeneration of zeolites, the possibility of coupling modified zeolites with oxidants and solvents in the production of low-impact clean fuels, and mechanistic insights by Langmuir and Freundlich isotherms and pseudo-second-order kinetics. This study's findings help develop greener ways for fuel production processes.

Supported Ionic Liquid Catalysts for the Oxidation of S- and N-Containing Compounds—The Effect of Bronsted Sites and Heteropolyacid Concentration

In this article, a series of effective catalysts based on betaine and sulfuric or phosphomolybdic acids was obtained. These compositions were characterized by various physicochemical methods and tested in the oxidation of sulfur- and nitrogenous-containing compounds by H2O2. An increase in the amount of heteropolyacid (HPA) leads to a non-linear change in acidity, and the degree of removal of sulfur-containing compounds correlates with the concentration of Bronsted acid sites on the surface. On the contrary, the degree of pyridine removal is determined primarily by the content of heteropolyacids in the catalyst.