The multicomponent reactions (MCRs) consist of two or more synthetic steps which are carried out without isolation of any intermediate thus reducing time, saving money, energy and raw materials. The development of MCRs in the presence of molecular iodine is an efficient approach that meets with the requirements of sustainable chemistry. The aim of this review is to highlight the synergistic effect of the combined use of MCRs and molecular iodine for the development of new eco-compatible methodologies for organic chemistry.
Nickel/gamma-alumina (Ni/γ-Al 2 O 3 ) catalysts promoted with Cu and La were prepared by the impregnation method and characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). XRD and HRTEM indicated that the addition of La and Cu was helpful to decrease the size of active particles and increase the dispersion of Ni species. TPR showed that Cu can effectively decrease the reduction temperatures of its own and Ni oxides, whereas La can change the proportion of various Ni species and increase the content of easily reducible Ni species. XPS and UV-vis DRS indicated that electron shift occurred on the Ni-based sample modified by Cu and enhanced remarkably by adding La. These findings suggest that Cu and La species induce both structural and electronic promotion effects, resulting in smaller particle size and weaker interaction between active components and the support, higher dispersions, and reducibility of active phases, ultimately enhancing the crude 2-ethylhexanol hydrotreating catalytic performance.
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