Cascade Reaction of Ethanol to Butadiene over Multifunctional Silica-Supported Ag and ZrO₂ Catalysts

Abstract

Although butadiene is currently a byproduct of naphtha cracking, interest in producing butadiene from biobased ethanol has increased because of the lower environmental impact of the ethanol to butadiene reaction. This work explores a multifunctional catalyst system composed of silica-supported Ag and ZrO2 used for the cascade reaction of ethanol to butadiene at 573 K. The Ag and ZrO2 components were synthesized on separate support particles, enabling the characterization of each component without interference from the other. High selectivity to butadiene (65%) at high ethanol conversion (75%) was achieved with an appropriate ratio of Ag and ZrO2 in the reactor. Silver catalyzed the initial dehydrogenation of ethanol to acetaldehyde, while ZrO2 catalyzed the C–C coupling and subsequent dehydration reactions. The silica-supported ZrO2 exhibited superior selectivity relative to bulk ZrO2 in the Ag-promoted ethanol to butadiene reaction. Results from Zr K-edge X-ray absorption spectroscopy and UV–vis spectroscopy showed that ZrO2 was highly dispersed on the silica support over a range of loadings. Infrared spectroscopy of adsorbed pyridine, CO, and CO2, and kinetics of probe reactions 1-butene double bond isomerization, 2-propanol decomposition, and ethanol hydrogenation of acetone were used to compare the acid–base nature and chemical reactivity of silica-supported ZrO2 to bulk ZrO2.

Laser‐assisted preparation of monolithic acidic catalysts for biomass conversion

“…B and L acid signals appear at 1542 and 1476 cm −1 , respectively (Figure 5C); the B and L acid sites were determined to be present at 16.71 and 13.9 μmol/g, respectively, at 150°C (Table S3). The characteristic hydroxyl band is observed at 3661 cm −1 in the absence of pyridine adsorption, consistent with the adsorption of water molecules on the surface 47 (Figure 5D), which also provides a reason for the existence of the B acidic sites 48 …”

Cascade Reaction of Ethanol to Butadiene over Ag-Promoted, Silica- or Zeolite-Supported Ta, Y, Pr, or La Oxide Catalysts

“…For example, 0.1 g of Ag-SiO 2 was physically mixed with 0.4 g of 2Y-SiO 2 while an analogous HBZ-based catalyst utilized a physical mixture of 0.1 g of Ag-SiO 2 with 0.05 g of 2Y-HBZ. To be consistent with our prior work, the mass ratio of Ag-SiO 2 to M-SiO 2 was chosen to be 1:4; however, this ratio was adjusted for M-HBZ samples as their relative activity was an order of magnitude greater than that of their silica analogues. c o n v e r s i o n false( C 0.25em % false) = 100 % · ( ∑ n i M i 2 M 0 ) selectivit y i 0.25em ( C % ) = 100 % · ( n i M i ∑ n i M i ) ST Y i = ( M i M m ) …”

“…Direct comparisons among Lewis acid cations and supports used in the valorization of ethanol to C 4 and C 4+ products have been limited because the co-impregnation of components such as Zn and/or Cu have been previously shown to exhibit Lewis acid character of their own when supported on β zeolite . Previously, our group has shown that a co-impregnated Ag-ZrO x -SiO 2 catalyst behaves similarly to that of a catalyst system composed of a physical mixture of Ag-SiO 2 and ZrO x -SiO 2 . The physical separation of Ag metal and ZrO x on different support particles allowed for a direct evaluation of performance of the different components without mutual interference.…”

Sustainable Synthesis of Drop-In Chemicals from Biomass via Chemical Catalysis: Scopes, Challenges, and the Way Forward

“…However, with a plentiful supply of inexpensive petroleum and the steam-cracking of naphtha developed in the 1960s, the research on converting ethanol to BDE fell out of favor. Converting bioethanol into BDE selectively over a multifunctional catalyst has received renewed interest in the 21st century . The resurgence of this research interest over the past decade is fuelled by the incentives in sustainable technologies, stricter environmental regulations, and inexpensive bioethanol from nonfood cellulosic and algal biomasses .…”

“…Converting bioethanol into BDE selectively over a multifunctional catalyst has received renewed interest in the 21st century. 119 The resurgence of this research interest over the past decade is fuelled by the incentives in sustainable technologies, stricter environmental regulations, and inexpensive bioethanol from nonfood cellulosic and algal biomasses. 120 The mechanism of transforming ethanol into BDE involves the dehydrogenation of ethanol into acetaldehyde, which then undergoes an aldol reaction to form acetaldol.…”