Phenylalanine （Phe） is a significant amino acid that cannot be synthesized by human themselves but must be taken from environment. It was initially found that the nanosized amorphous Ni-B/SiO2 alloy prepared by the ...Phenylalanine （Phe） is a significant amino acid that cannot be synthesized by human themselves but must be taken from environment. It was initially found that the nanosized amorphous Ni-B/SiO2 alloy prepared by the chemical reduction method was an effective catalyst for the preparation of Phe from phenylpyruvic acid （PPA） by amination and hydrogenation. It has been found that the amorphous Ni-B/SiO2 alloy catalyst exhibits superior activity and selectivity to the traditional catalysts Raney Ni and Urushibara nickel. The effects of reaction time, amounts of catalysts and ammonia solution, reaction temperature, and H2 pressure on the reaction have been investigated systematically. The results indicated that the yield of Phe was 97.9%, and the selectivity for Phe reached 98.9% when the reaction was carried out for 3 h at 333 K and 2.0 MPa of H2 with m（Cat.） ： m（PPA） = 0.6 ： 1.0 and n（NH3） ： n（PPA） = 3 ： 1. The catalysts were characterized by XRD, AAS, XPS, BET, and TEM, and the relationship between the catalyst structure and the catalytic activity was discussed in detail. It was found that the reason why Ni-B/SiO2 amorphous alloy catalyst was much more active for the preparation of Phe could be accounted for by the presence of electron-rich Ni due to electron donation from alloying B; the smaller size of Ni-B particles, the larger specific surface area of Ni-B/SiO2.展开更多
Ultrafine and highly dispersed Pd nanoparticles have drawn considerable attention with high activity,selectivity and atomic efficiency.In this paper,amorphous Pd(II)-complex solid spheres with-5 nm Pd nanoparticles lo...Ultrafine and highly dispersed Pd nanoparticles have drawn considerable attention with high activity,selectivity and atomic efficiency.In this paper,amorphous Pd(II)-complex solid spheres with-5 nm Pd nanoparticles loaded on were successfully achieved through a simple and gentle one-pot solution method with vitamin B1 simultaneously as complexing agent and reducing agent.An ultrathin mesoporous SiO_(2) shell was then coated at the surface of Pd(II-O)spheres as the armor which could prevent the dissolution of Pd(II)during the catalytic process.The combination of Pd(II)and Pd(0)endowed Pd(II-0)@m-SiO_(2) catalyst an excellent performance in eco-friendly aqueous media Suzuki reactions.The high activity,productivity and recyclability were all comparable with the best Pd catalysts ever reported.The ingenious formation of amorphous Pd(II)/crystal Pd(0)with enhanced catalytic performances provides a new,scalable strategy to practical promotion of Suzuki cross-coupling reactions.展开更多
基金Fundamental research project of South-Central University for Nationalities (No. YZZ05010)
文摘Phenylalanine （Phe） is a significant amino acid that cannot be synthesized by human themselves but must be taken from environment. It was initially found that the nanosized amorphous Ni-B/SiO2 alloy prepared by the chemical reduction method was an effective catalyst for the preparation of Phe from phenylpyruvic acid （PPA） by amination and hydrogenation. It has been found that the amorphous Ni-B/SiO2 alloy catalyst exhibits superior activity and selectivity to the traditional catalysts Raney Ni and Urushibara nickel. The effects of reaction time, amounts of catalysts and ammonia solution, reaction temperature, and H2 pressure on the reaction have been investigated systematically. The results indicated that the yield of Phe was 97.9%, and the selectivity for Phe reached 98.9% when the reaction was carried out for 3 h at 333 K and 2.0 MPa of H2 with m（Cat.） ： m（PPA） = 0.6 ： 1.0 and n（NH3） ： n（PPA） = 3 ： 1. The catalysts were characterized by XRD, AAS, XPS, BET, and TEM, and the relationship between the catalyst structure and the catalytic activity was discussed in detail. It was found that the reason why Ni-B/SiO2 amorphous alloy catalyst was much more active for the preparation of Phe could be accounted for by the presence of electron-rich Ni due to electron donation from alloying B; the smaller size of Ni-B particles, the larger specific surface area of Ni-B/SiO2.
基金support from Beijing Natural Science Foundation(No.2194077)the National Natural Science Foundation of China(Nos.51532001 and 52002010)+1 种基金the National Postdoctoral Program for Innovative Talents(No.BX20180020)the China Postdoctoral Science Foundation Funded Project(No.2018M640041).
文摘Ultrafine and highly dispersed Pd nanoparticles have drawn considerable attention with high activity,selectivity and atomic efficiency.In this paper,amorphous Pd(II)-complex solid spheres with-5 nm Pd nanoparticles loaded on were successfully achieved through a simple and gentle one-pot solution method with vitamin B1 simultaneously as complexing agent and reducing agent.An ultrathin mesoporous SiO_(2) shell was then coated at the surface of Pd(II-O)spheres as the armor which could prevent the dissolution of Pd(II)during the catalytic process.The combination of Pd(II)and Pd(0)endowed Pd(II-0)@m-SiO_(2) catalyst an excellent performance in eco-friendly aqueous media Suzuki reactions.The high activity,productivity and recyclability were all comparable with the best Pd catalysts ever reported.The ingenious formation of amorphous Pd(II)/crystal Pd(0)with enhanced catalytic performances provides a new,scalable strategy to practical promotion of Suzuki cross-coupling reactions.
