Transition metal-catalyzed carbonylation reactions represent a direct and atom-economical approach to synthesize carbonyl compounds or their derivatives by using CO as a cheap and readily available C1 feedstock.While ...Transition metal-catalyzed carbonylation reactions represent a direct and atom-economical approach to synthesize carbonyl compounds or their derivatives by using CO as a cheap and readily available C1 feedstock.While carbonylation of C(sp^(2))-hybridized electrophiles (e.g.,aryl halides) is well developed,carbonylation of less reactive unactivated alkyl electrophiles remains challenging.Recently,the use of earth-abundant base metals including Cu,Co,Mn,Fe,Ni as catalysts has enabled advances in carbonylative coupling of alkyl electrophiles for approaching diverse carbonyl compounds or their derivatives,notably,some of which are of synthetic importance but difficult to be synthesized through previous reported methods.Herein,we have summarized and discussed these recent achievements in base-metal-catalyzed carbonylative C—C,C—N,C—O,C—X coupling and other carbonylation reactions of unactivated alkyl electrophiles using CO as C1 source.展开更多
考察了添加在镍基催化剂中的碱土金属助剂对甲烷与空气制合成气的催化反应性能的影响。并对催化剂用TPO、TPR、CO2 TPD、XPS及CO脉冲色谱对催化剂进行了表征。实验表明 ,碱土金属助剂对降低催化剂结炭有一定的作用 ,催化剂抗积炭顺序为...考察了添加在镍基催化剂中的碱土金属助剂对甲烷与空气制合成气的催化反应性能的影响。并对催化剂用TPO、TPR、CO2 TPD、XPS及CO脉冲色谱对催化剂进行了表征。实验表明 ,碱土金属助剂对降低催化剂结炭有一定的作用 ,催化剂抗积炭顺序为Ni BaO CaO Al2 O3>Ni SrO CaO Al2 O3>Ni MgO CaO Al2 O3>Ni CaO Al2 O3。而且 ,添加了碱土金属催化剂的Ni晶粒减小、结合能负位移和催化剂吸附CO2 的能力变化顺序都与积炭量减少顺序一致。其中尤以Ni BaO CaO Al2 O3 催化剂既有较高的活性 。展开更多
Melting temperature, spreadability, mechanical properties and the microstructures of joints brazed with silver-base filler metals including different amounts of Ga and/or In were studied respectively in this paper, an...Melting temperature, spreadability, mechanical properties and the microstructures of joints brazed with silver-base filler metals including different amounts of Ga and/or In were studied respectively in this paper, and the results show that the melting temperature of the silver-base filler metals is decreased, spreadability of the silver-base filler metals is improved, and the microstructures of silver-base filh, r metals are refined obviously with the addition of Ga and/or In. Using copper and brass plates as base metal and brazing with flame method, the mechanical properties of the lap-joint and butt joint were also examined and analyzed respectively, and the results indicate that the fracture position of two kinds of brazed joints occurred on the base metal, except for the lap-joint of brass, which shows better mechanical properties of the joints brazed with the silver- based filler metals including Ga. For the lap-joint of brass, the tensile strength gradually increased with the increase of Ga content, while the addition of In has little effect on mechanical properties. It is also found that the best comprehensive properties of cadmium-free Ag-Cu-Zn filler metals are obtained when Ga content is about 3.0 wt. % and In content is between 1.5 wt. % and 2. 0 wt. %.展开更多
基金Fundamental Research Funds for the Central Universities and Natural Science Foundation of Hunan Province(2022JJ30122,2023JJ10003)for financial support.
文摘Transition metal-catalyzed carbonylation reactions represent a direct and atom-economical approach to synthesize carbonyl compounds or their derivatives by using CO as a cheap and readily available C1 feedstock.While carbonylation of C(sp^(2))-hybridized electrophiles (e.g.,aryl halides) is well developed,carbonylation of less reactive unactivated alkyl electrophiles remains challenging.Recently,the use of earth-abundant base metals including Cu,Co,Mn,Fe,Ni as catalysts has enabled advances in carbonylative coupling of alkyl electrophiles for approaching diverse carbonyl compounds or their derivatives,notably,some of which are of synthetic importance but difficult to be synthesized through previous reported methods.Herein,we have summarized and discussed these recent achievements in base-metal-catalyzed carbonylative C—C,C—N,C—O,C—X coupling and other carbonylation reactions of unactivated alkyl electrophiles using CO as C1 source.
文摘考察了添加在镍基催化剂中的碱土金属助剂对甲烷与空气制合成气的催化反应性能的影响。并对催化剂用TPO、TPR、CO2 TPD、XPS及CO脉冲色谱对催化剂进行了表征。实验表明 ,碱土金属助剂对降低催化剂结炭有一定的作用 ,催化剂抗积炭顺序为Ni BaO CaO Al2 O3>Ni SrO CaO Al2 O3>Ni MgO CaO Al2 O3>Ni CaO Al2 O3。而且 ,添加了碱土金属催化剂的Ni晶粒减小、结合能负位移和催化剂吸附CO2 的能力变化顺序都与积炭量减少顺序一致。其中尤以Ni BaO CaO Al2 O3 催化剂既有较高的活性 。
文摘Melting temperature, spreadability, mechanical properties and the microstructures of joints brazed with silver-base filler metals including different amounts of Ga and/or In were studied respectively in this paper, and the results show that the melting temperature of the silver-base filler metals is decreased, spreadability of the silver-base filler metals is improved, and the microstructures of silver-base filh, r metals are refined obviously with the addition of Ga and/or In. Using copper and brass plates as base metal and brazing with flame method, the mechanical properties of the lap-joint and butt joint were also examined and analyzed respectively, and the results indicate that the fracture position of two kinds of brazed joints occurred on the base metal, except for the lap-joint of brass, which shows better mechanical properties of the joints brazed with the silver- based filler metals including Ga. For the lap-joint of brass, the tensile strength gradually increased with the increase of Ga content, while the addition of In has little effect on mechanical properties. It is also found that the best comprehensive properties of cadmium-free Ag-Cu-Zn filler metals are obtained when Ga content is about 3.0 wt. % and In content is between 1.5 wt. % and 2. 0 wt. %.
