This study was performed for the development of a green and promising approach for the synthesis of methyl acrylate and acrylic acid by a one‐step aldol condensation reaction of dimethoxymethane and methyl acetate ov...This study was performed for the development of a green and promising approach for the synthesis of methyl acrylate and acrylic acid by a one‐step aldol condensation reaction of dimethoxymethane and methyl acetate over cesium oxide‐supported on ZSM‐35 zeolite catalysts; the effect of base sites as well as acid sites on the aldol condensation reaction was studied in detail. It was found that base sites were harmful for aldol condensation due to their failure in catalyzing the decomposition of dimethoxymethane precursor into formaldehyde, whereas the acid site was indispensable for the reaction to proceed. This reaction cannot take place without an acid site. Although acid sites in H‐form of the zeolite（HZSM‐35） are indispensable for the aldol condensation reaction, not all of them tend to favor this reaction. A strong acid catalyzes methanol‐to‐olefin‐like reactions resulting in hydrocarbon byproducts, which are finally transferred to hard coke. Medium strong acids and weak acids are great candidates for the target aldol condensation reaction with high activity and selectivity. A γ‐Al2O3 sample with abundant weak‐strength Lewis acid sites, together with a few medium‐strong‐strength acid sites, performs well with a high activity and considerable stability during the synthesis of methyl acrylate and acrylic acid.展开更多
Acrylic acid(AA)and its ester,methyl acrylate(MA),were produced by a green one‐step aldol condensation reaction of dimethoxymethane and methyl acetate.The reaction was conducted over ZSM‐35 zeolites with different c...Acrylic acid(AA)and its ester,methyl acrylate(MA),were produced by a green one‐step aldol condensation reaction of dimethoxymethane and methyl acetate.The reaction was conducted over ZSM‐35 zeolites with different concentrations of Bronsted acid,which were prepared by the sodium ion‐exchange process with H‐form zeolite.The acidic property of HZSM‐35 was studied in detail through infrared experiments.About 51%of all bridging OH groups were distributed in cages,while 23%and 26%,respectively,were distributed in 10‐and 8‐ring channels.The catalytic performance was enhanced by a high concentration of Bronsted acid,indicating that Bronsted acid is an active site for the aldol condensation reaction.The ZSM‐35 zeolite possessing a concentration of Bronsted acid as high as 0.049 mmol/g demonstrated excellent performance with a MA+AA selectivity of up to 73%.展开更多
文摘This study was performed for the development of a green and promising approach for the synthesis of methyl acrylate and acrylic acid by a one‐step aldol condensation reaction of dimethoxymethane and methyl acetate over cesium oxide‐supported on ZSM‐35 zeolite catalysts; the effect of base sites as well as acid sites on the aldol condensation reaction was studied in detail. It was found that base sites were harmful for aldol condensation due to their failure in catalyzing the decomposition of dimethoxymethane precursor into formaldehyde, whereas the acid site was indispensable for the reaction to proceed. This reaction cannot take place without an acid site. Although acid sites in H‐form of the zeolite（HZSM‐35） are indispensable for the aldol condensation reaction, not all of them tend to favor this reaction. A strong acid catalyzes methanol‐to‐olefin‐like reactions resulting in hydrocarbon byproducts, which are finally transferred to hard coke. Medium strong acids and weak acids are great candidates for the target aldol condensation reaction with high activity and selectivity. A γ‐Al2O3 sample with abundant weak‐strength Lewis acid sites, together with a few medium‐strong‐strength acid sites, performs well with a high activity and considerable stability during the synthesis of methyl acrylate and acrylic acid.
文摘Acrylic acid(AA)and its ester,methyl acrylate(MA),were produced by a green one‐step aldol condensation reaction of dimethoxymethane and methyl acetate.The reaction was conducted over ZSM‐35 zeolites with different concentrations of Bronsted acid,which were prepared by the sodium ion‐exchange process with H‐form zeolite.The acidic property of HZSM‐35 was studied in detail through infrared experiments.About 51%of all bridging OH groups were distributed in cages,while 23%and 26%,respectively,were distributed in 10‐and 8‐ring channels.The catalytic performance was enhanced by a high concentration of Bronsted acid,indicating that Bronsted acid is an active site for the aldol condensation reaction.The ZSM‐35 zeolite possessing a concentration of Bronsted acid as high as 0.049 mmol/g demonstrated excellent performance with a MA+AA selectivity of up to 73%.
