TY - JOUR
T1 - Improving the selectivity to C4 products in the aldol condensation of acetaldehyde in ethanol over faujasite zeolites
AU - Zhang, L.
AU - Pham, Tu N.
AU - Faria, Jimmy
AU - Resasco, Daniel E.
PY - 2015/9/5
Y1 - 2015/9/5
N2 - The selective conversion of acetaldehyde to C4 products, minimizing the production of secondary (C6, C8) condensation products, could be a potential path in the production of butadiene from ethanol, a process of commercial interest. Therefore, we have investigated the selective aldol condensation of acetaldehyde in liquid phase over faujasite zeolites, NaX and NaY. Specifically, we have examined the influence of the number and location of the exchangeable cations, type of cations, and post-synthesis treatments on product selectivity. At 230 °C, NaY results in higher C4/(C6 + C8) product ratio than NaX, which can be explained in terms of the strength, density, and accessibility of basic sites, which are less favorable in NaX than NaY. In fact, the CO2 TPD measurements indicate the presence of three types of basic sites of varying strength, of which those with weak and medium strength are most important for the selective condensation. A confinement effect is observed when adding K to the NaY zeolite. The observed selectivity changes suggest that when larger cations partially occupy the supercages, the production of C8 products decreases, while C6 products increase. Also, post-synthesis washing treatments show significant variations in selectivity, which demonstrate the effects of partial occupation of the zeolite pores in the reaction. It is also shown that at a given conversion, the C4/(C6 + C8) ratio can be adjusted by modifying the micro/mesoporosity balance in the zeolite.
AB - The selective conversion of acetaldehyde to C4 products, minimizing the production of secondary (C6, C8) condensation products, could be a potential path in the production of butadiene from ethanol, a process of commercial interest. Therefore, we have investigated the selective aldol condensation of acetaldehyde in liquid phase over faujasite zeolites, NaX and NaY. Specifically, we have examined the influence of the number and location of the exchangeable cations, type of cations, and post-synthesis treatments on product selectivity. At 230 °C, NaY results in higher C4/(C6 + C8) product ratio than NaX, which can be explained in terms of the strength, density, and accessibility of basic sites, which are less favorable in NaX than NaY. In fact, the CO2 TPD measurements indicate the presence of three types of basic sites of varying strength, of which those with weak and medium strength are most important for the selective condensation. A confinement effect is observed when adding K to the NaY zeolite. The observed selectivity changes suggest that when larger cations partially occupy the supercages, the production of C8 products decreases, while C6 products increase. Also, post-synthesis washing treatments show significant variations in selectivity, which demonstrate the effects of partial occupation of the zeolite pores in the reaction. It is also shown that at a given conversion, the C4/(C6 + C8) ratio can be adjusted by modifying the micro/mesoporosity balance in the zeolite.
KW - Acetaldehyde
KW - Aldol condensation
KW - Biomass
KW - Butadiene
KW - Crotonaldehyde
KW - Ethanol
KW - Faujasite
UR - http://www.scopus.com/inward/record.url?scp=84942368798&partnerID=8YFLogxK
U2 - 10.1016/j.apcata.2014.11.018
DO - 10.1016/j.apcata.2014.11.018
M3 - Article
AN - SCOPUS:84942368798
VL - 504
SP - 119
EP - 129
JO - Applied catalysis A: general
JF - Applied catalysis A: general
SN - 0926-860X
ER -