期刊
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
卷 22, 期 24, 页码 -出版社
MDPI
DOI: 10.3390/ijms222413665
关键词
heterogeneous catalyst; natural phosphate; fluorapatite; quinoxalines; apatite; nano-bio-chemistry
资金
- Australian College of ACK [IRC-2020/2021-SOE-ME-PR05, PR06]
Natural phosphate and synthetic fluorapatite phosphate have been proposed as stable, inexpensive, readily available, and recyclable catalysts for the synthesis of quinoxaline at room temperature. Natural phosphate showed higher catalytic activity compared to synthetic fluorapatite phosphate, and the recycling process did not significantly impact the catalytic property of natural phosphate.
Natural phosphate (NP) and synthetic fluorapatite phosphate (SFAP) were proposed as stable, inexpensive, readily available and recyclable catalysts for the condensation of 1,2-diamines with 1,2-dicarbonyls in methanol to afford quinoxaline at room temperature. NP provided as high as 92-99% yield for quinoxalines in short reaction times (i.e., 1-45 min), while SFAP created quinoxalines with 87-97% yield in 60-120 min. From the chemical analyses, X-ray fluoresecency, X-ray diffraction, energy dispersive X-ray and Fourier-transform infrared spectroscopy methods, two main phases (CaO, P2O5) appeared in NP together with other low content phases (SiO2, Fe2O3). Compared to other phases, apatite (CaO and P2O5 as Ca10(PO4)(6)) played a major role in the catalytic activity of NP. SFAP with similar Ca/P atomic ratio showed a relatively lower catalytic activity than NP for the condensation of 1,2-diamine with 1,2-dicarbonyl in methanol at ambient temperature. To investigate the recyclability of catalysts, the surface properties of NP and 6-recycled NP were investigated using scanning electron microscopy, energy dispersive X-ray and Brunauer-Emmett-Teller and Barrett-Joyner-Halenda methods. Some differences were observed in NP and 6-recycled NP's particle size, surface area, the volume and size of pores, and the content of elements; nevertheless, the use-reuse process did not noticeably change the catalytic property of NP.
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