Abstract
A Cu-based nano-catalyst has been widely used in the ethynylation of formaldehyde; however, the effects of the presence of Cu on the reaction have not yet been reported. CuO/SiO2 catalysts with different Cu species were prepared by impregnation (IM), deposition–precipitation (DP), and ammonia evaporation (AE). The structural evolution of the Cu species in different states of the ethynylation reaction and the structure–activity relationship between the existence state of the Cu species and the catalytic properties of the ethynylation reaction were studied. The results show that the Cu species in the CuO/SiO2 (IM), prepared using the impregnation method, are in the form of bulk CuO, with large particles and no interactions with the support. The bulk CuO species are transformed into Cu+ with a low exposure surface at the beginning of the reaction, which is easily lost. Thus, this approach shows the lowest initial activity and poor cycle stability. A high dispersion of CuO and copper phyllosilicate exists in CuO/SiO2 (DP). The former makes the catalyst have the best initial activity, while the latter slows release, maintaining the stability of the catalyst. There is mainly copper phyllosilicate in CuO/SiO2 (AE), which is slowly transformed into a highly dispersed and stable Cu+ center in the in situ reaction. Although the initial activity of the catalyst is not optimal, it has the optimal service stability.
Highlights
Catalytic ethynylation of formaldehyde is an important initial chemical process for the mass production of high-value intermediates such as 1,4-butynediol (BD) and propargyl alcohol (PA) and downstream chemicals such as 1,4-butanediol (BDO), 3-butene-1-alcohol (BTO), tetrahydrofuran (THF), polytetramethylene ether glycol (PTMEG), γ-butyrolactone (GBL), poly butylenes succinate (PBS), and polybutylene terephthalate (PBT)
Stimulated and driven by the demand for downstream products, such as new materials made of PBS, the demand for 1,4-butynediol is increasing every year [6]
The Cu2+ precursors in the above catalysts must be transformed in situ into a cuprous acetylide active phase through a complex chemical process
Summary
Catalytic ethynylation of formaldehyde is an important initial chemical process for the mass production of high-value intermediates such as 1,4-butynediol (BD) and propargyl alcohol (PA) and downstream chemicals such as 1,4-butanediol (BDO), 3-butene-1-alcohol (BTO), tetrahydrofuran (THF), polytetramethylene ether glycol (PTMEG), γ-butyrolactone (GBL), poly butylenes succinate (PBS), and polybutylene terephthalate (PBT). Our research group has found that the interaction of Cu species with other components can effectively inhibit the formation of inactive metal Cu and improve the stability of Cu+ active species. Examples of this effect include the electron-assisted action of Bi2O3, Fe3O4, and the strong interaction between CuO and a SiO2–MgO aerogel support [17,18]. The structural evolution and catalytic performance of the copper species in formaldehyde acetylation were studied
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