Alcohol Oxidation at Platinum–Gas and Platinum–Liquid Interfaces: The Effect of Platinum Nanoparticle Size, Water Coadsorption, and Alcohol Concentration

Abstract

Platinum nanoparticles size range from 1 to 8 nm deposited on mesoporous silica MCF-17 catalyzed alcohol oxidations were studied in the gas and liquid phases. Among methanol, ethanol, 2-propanol and 2-butanol reactions, the turnover frequency increased with Pt nanoparticle size for all the alcohols utilized. The activation energies for the oxidations were 1 almost same among all alcohol species, but higher in the gas phase than those in the liquid phase.Water coadsorption poisoned the reaction in the gas phase, while it increased the reaction turnover rates in the liquid phase. Sum frequency generation (SFG) vibrational spectroscopy studies and DFT calculations revealed that the alcohol molecules pack horizontally on the metal surface in low concentrations and stand up in high concentrations, which affect the dissociation of β-hydrogen of the alcohols as the critical step in alcohol oxidations.

Tuning the Activity and Selectivity of Phenylacetylene Hydrosilylation with Triethylsilane in the Liquid Phase over Size Controlled Pt Nanoparticles

“…Hence, the synthesis as well as the catalytic activity and selectivity of size controlled metallic nanoparticles have been extensively studied [20][21][22][23][24][25]. For instance, in the gas phase, Rh nanoparticles with smaller sizes showed higher activity in CO oxidation [26].…”

Molecular Orientations Change Reaction Kinetics and Mechanism: A Review on Catalytic Alcohol Oxidation in Gas Phase and Liquid Phase on Size-Controlled Pt Nanoparticles

“…These results suggest that the reaction rates of catalytic alcohol oxidation heavily depended on the reaction phase (gas phase versus liquid phase), and the intrinsic root cause for such discrepancy should be understood at the molecular level. [9,[19][20][21][22], respectively).…”

“…Catalytic partial oxidation and complete oxidation of alcohols over platinum group metals (PGM) or metal oxide catalysts are fundamental processes not only in energy conversion, such as in fuel cells [1,2], but also in fine chemical synthesis and the pharmaceutical industry [3][4][5][6][7]. Usually, the production of aldehydes and ketones is performed through alcohol oxidation in the gas phase at high temperatures, while the production of fine chemicals and pharmaceutical intermediates is performed in the liquid phase at low temperatures [8,9]. Many researchers have focused on the synthesis of novel, highly efficient, poisoning-resistant, or low-cost catalysts to improve productivity and selectivity, as well as to lower environmental impact [6,[10][11][12][13][14][15][16][17][18].…”

“…This review paper systematically summarizes our previous work in the catalytic alcohol oxidation area, in both gas phase and liquid phase over size-controlled Pt nanoparticles [9,[19][20][21][22]. The studied alcohols included C1-C4 molecules, i.e., methanol (MeOH), ethanol (EtOH), 1-propanol (1-PrOH), 2-propanol (2-PrOH), and 2-butanol (2-BuOH).…”

Eletro-Oxidação de Etanol em Meio Alcalino: Cinética Complexa e Eletrocatálise

“…Quanto maior a energia de hidratação do cátion, o maior a cobertura do cluster cátion−OHad, explicando por que o valor da TOF diminui na sequência: K + > Na + > Li + . Os valores da TOF, encontrados na literatura, para o estado estacionário da oxidação catalítica do etanol na interface sólido-líquido em nanopartículas de Pt, à temperatura ambiente, está entre 0,03 e 0,09 molécula sítio −1 s −1 para 0,26 mol L −1 de etanol [97] e 0,027 molécula sítio −1 s −1 para 0,016 mol L −1 de etanol[89,90] (tendo em conta o efeito da temperatura descrito pelo Equação de Arrhenius). Estes valores possuem uma magnitude menor do que os resultados obtidos para a TOF do estado estacionário, calculada a partir dos dados eletroquímicos apresentados neste capítulo, que fica entre 0,374 e 0,472 molécula sítio −1 s −1 (para um fator de decaimento abaixo de 0,05 para cada meio).Ponderando todos os fatores, podemos listar duas possíveis razões para os maiores valores de TOF encontrados na eletrocatálise da ROE: (a) a adsorção de etanol pode resultar na remoção de venenos superficiais e b) a dessorção de acetaldeído é auxiliada pelo OHads produzindo ácido acético/acetato como o principal produto final em eletrocatálise, enquanto que, em catálise, a Pt é mais de 98% seletiva para acetaldeído solúvel[90], resultante da cinética de dessorção do acetaldeído.Finalmente, os valores da TOF intrínsecas (x = 1) para ROE em diferentes meios são propostas.…”