Supported molybdenum oxides for the aldol condensation reaction of acetaldehyde

Rasmussen, Mathew J.; Najmi, Sean; Innocenti, Giada; Medford, Andrew J.; Sievers, Carsten; Medlin, J. Will

doi:10.1016/j.jcat.2022.03.002

Cited by 14 publications

(8 citation statements)

References 59 publications

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“…Under the optimum reaction conditions (400 °C; W/F, 5.6 g h mol –1 ; time-on-steam, 15 min), the selectivity of crotonaldehyde was only 60.6%. Rasmussen et al prepared a series of differently loaded molybdenum oxide catalysts for acetaldehyde condensation. The conversion of crotonaldehyde could only reach a maximum of 88 ± 3% after 10 h at 300 °C and WHSV = 1.4 h –1 .…”

Section: Resultsmentioning

confidence: 99%

Efficient Synthesis of C4 Compound with Low Carbon Emission from Acetaldehyde: Aldol Condensation Catalyzed by Regulable Acidic–Alkaline Al/Mg Sites of CuMgAlO

Yan

et al. 2022

Ind. Eng. Chem. Res.

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Aldol condensation is an optimal method for carbon growth free from the thermo-cleavage technique of fossil resources with high carbon emissions. To further develop a catalyst with high activity and selectivity, a CuMgAl layered double oxide, named X/CuMgAlO, is successfully obtained after calcinating the MgAl hydrotalcite precursor doped with Cu 2+ . The resulting sample is applied as a catalyst in the self-condensation of acetaldehyde to crotonaldehyde. On the basis of the investigation of the reaction conditions, sample 15/CuMgAlO has presented to be the optimal catalyst in the aldol condensation of acetaldehyde to form crotonaldehyde with the conversion and selectivity of 92.3% and 80.4%, respectively. NH 3 -TPD, CO 2 -TPD, IGC, and Py-IR were applied to investigate the synergistic effect of the acidic and alkaline sites. It has been verified that a suitable acidity could be regulated through the addition of Cu species, and more Lewis acidic sites from Al sites can be formed due to the Jahn−Teller effect, the enhanced electronegativity of Cu, and the shattered lamellar layer in the calcinated CuMgAlO. Besides, the relatively mild acid could guarantee high selectivity to the target crotonaldehyde. Considering that aldol condensation could create a new carbon bond without the use of fossil resources, carbon emissions are significantly reduced in the field of fine-chemical synthesis industry.

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Section: Resultsmentioning

confidence: 99%

Efficient Synthesis of C4 Compound with Low Carbon Emission from Acetaldehyde: Aldol Condensation Catalyzed by Regulable Acidic–Alkaline Al/Mg Sites of CuMgAlO

Yan

et al. 2022

Ind. Eng. Chem. Res.

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“…Based on the observed products, two primary pathways were identified to occur on MoO 3 : the direct HDO of acetone to propane and propylene and the chain coupling of acetone to C 6+ products, as previously demonstrated on MoO 3 -based catalysts. 24,38,39 It is likely that mesitylene and several other minor trimethylcyclohexene products are formed through a phorone intermediate from the triple condensation of acetone. Subsequent deoxygenation of these undetected C 9 H 14 O species leads to ring-closing and dehydrogenation, as previously seen on other metal oxide catalysts.…”

Section: Reaction Network Of Acetone Over Moomentioning

confidence: 99%

Kinetic Analysis of the Hydrodeoxygenation of Aliphatic Volatilized Lignin Molecules on Bulk MoO₃: Elucidating the Formation of Alkenes and Alkanes

Kohler,

Walter,

Shanks

2023

ACS Catal.

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Universal oxygen removal of depolymerized lignin molecules is a desirable route to funnel complex mixtures of bioderived molecules to high-demand “drop-in” petrochemical intermediates (aromatics and alkenes). Molybdenum oxide-based catalysts are of great interest for this valorization strategy, as they have shown proficiency in removing a wide range of oxygen functionalities without excess hydrogen consumption or aromatic ring saturation. Despite these advantages, MoO3 has demonstrated a propensity to saturate aliphatic molecules to low-value alkanes during deoxygenation, decreasing the economic potential of the conversion process. To better inform mitigation strategies, detailed kinetic experiments were applied to various alcohol-, aldehyde-, and ketone-containing model compounds to infer potential reaction pathways and mechanisms for forming alkene and alkane products. Consistent differences in product distribution, reaction rates, oxygenate, and H2 orders were observed to exist between carbonyls and their alcohol analogs, allowing for the determination that the hydrogenation of carbonyls to alcohols is required and kinetically limiting for HDO on MoO3. It is also proposed that carbonyls competitively adsorb at hydrogenation-active hydroxyl species, leading to aldol condensation reactions and a negative carbonyl order for the rate of HDO. Once adsorbed/formed on oxygen vacancies, MoO3 likely mediates hetero- and homolytic cleavage of alcohol C–O bonds to create a combination of carbocation and free radical intermediates. Both intermediates can then proceed through a dehydration or hydrogenolysis pathway to directly form alkenes or alkanes, respectively, at varying rates depending on the stabilization of the reactive carbon by electron-donating constituents. This effect led to primary oxygen functional groups yielding the lowest initial selectivity to alkenes (∼50%). Further, kinetic analysis of cyclohexene and 1-pentene feeds showed that alkenes weakly adsorb onto HDO-active oxygen vacancies to undergo a sequential hydrogenation reaction. This low adsorption strength of alkenes relative to those of oxygen-containing molecules prevents further conversion of the initial HDO products.

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“…For this purpose, Fourier Transform Infrared spectroscopy (FTIR) has been used for decades as a powerful and effective tool [19–21] . In the most common approach, a pulse of the molecule of interest is admitted into a cell containing the activated catalyst, and the surface reactions of the molecule are followed [22–30] . Pulse studies have been performed with reasonably complex molecules, such as ethyl pyruvate [23] or phenol [31] .…”

Section: Introductionmentioning

confidence: 99%

“…[19][20][21] In the most common approach, a pulse of the molecule of interest is admitted into a cell containing the activated catalyst, and the surface reactions of the molecule are followed. [22][23][24][25][26][27][28][29][30] Pulse studies have been performed with reasonably complex molecules, such as ethyl pyruvate [23] or phenol. [31] However, they are not well representative for catalysts under reaction conditions as the surface coverage may differ and fresh reactant is continuously fed to the catalyst surface.…”

Section: Introductionmentioning

confidence: 99%

Reaction Mechanism of Tetrahydrofurfuryl Alcohol Hydrogenolysis on Ru/SiO₂ Studied by In‐Situ FTIR Spectroscopy

et al. 2022

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In situ infrared spectroscopy is used to gain a deep understanding of the surface reactions during the hydrogenolysis of tetrahydrofurfuryl alcohol vapor on Ru/SiO2 and SiO2 and to identify intermediates that lead to catalyst deactivation. Time‐resolved in situ infrared spectroscopy experiments elucidate the formation and consumption of different surface species. Hydroxy valeraldehyde is the key intermediate and can undergo hydrogenation or the Tishchenko reaction. Both reactions yield 1,5‐pentanediol, but the latter also produces hydroxy valeric acid, which can polymerize on the catalyst surface. Finally, hydroxy‐valeraldehyde can also participate in fouling by means of aldol condensation. The same reaction intermediates are found both on Ru/SiO2 and SiO2 suggesting that the support plays a role in retaining the molecules on the surface and favoring the multi‐step reaction mechanism on the surface rather than the direct ring opening mechanism.

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Supported molybdenum oxides for the aldol condensation reaction of acetaldehyde

Cited by 14 publications

References 59 publications

Efficient Synthesis of C4 Compound with Low Carbon Emission from Acetaldehyde: Aldol Condensation Catalyzed by Regulable Acidic–Alkaline Al/Mg Sites of CuMgAlO

Efficient Synthesis of C4 Compound with Low Carbon Emission from Acetaldehyde: Aldol Condensation Catalyzed by Regulable Acidic–Alkaline Al/Mg Sites of CuMgAlO

Kinetic Analysis of the Hydrodeoxygenation of Aliphatic Volatilized Lignin Molecules on Bulk MoO₃: Elucidating the Formation of Alkenes and Alkanes

Reaction Mechanism of Tetrahydrofurfuryl Alcohol Hydrogenolysis on Ru/SiO₂ Studied by In‐Situ FTIR Spectroscopy

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Supported molybdenum oxides for the aldol condensation reaction of acetaldehyde

Cited by 14 publications

References 59 publications

Efficient Synthesis of C4 Compound with Low Carbon Emission from Acetaldehyde: Aldol Condensation Catalyzed by Regulable Acidic–Alkaline Al/Mg Sites of CuMgAlO

Efficient Synthesis of C4 Compound with Low Carbon Emission from Acetaldehyde: Aldol Condensation Catalyzed by Regulable Acidic–Alkaline Al/Mg Sites of CuMgAlO

Kinetic Analysis of the Hydrodeoxygenation of Aliphatic Volatilized Lignin Molecules on Bulk MoO3: Elucidating the Formation of Alkenes and Alkanes

Reaction Mechanism of Tetrahydrofurfuryl Alcohol Hydrogenolysis on Ru/SiO2 Studied by In‐Situ FTIR Spectroscopy

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Product

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Kinetic Analysis of the Hydrodeoxygenation of Aliphatic Volatilized Lignin Molecules on Bulk MoO₃: Elucidating the Formation of Alkenes and Alkanes

Reaction Mechanism of Tetrahydrofurfuryl Alcohol Hydrogenolysis on Ru/SiO₂ Studied by In‐Situ FTIR Spectroscopy