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Due to the demands of oxygenated derivatives of hydrocarbons for the industry, the methane (CH4) to methanol (MeOH) conversion through solid-state catalysis is a current topic, with definite questions and specific challenges. This work shows a statistical model that predicts the quantity of methanol produced through a batch conversion process employing copper-exchanged mordenite in accordance with a full factorial experimental design. Synthesis was performed through solid-state ion exchange from Cu(acac)2 and NH4-Mordenite, obtaining weight percentages (%Cu) of 1%, 3%, and 5%, which was followed by activation through calcination at a range of temperatures (Tcal) between 300-500 °C, as well as a reaction with methane under 2-10 bar pressure (P) in static conditions employing a batch reactor. The quantities of MeOH produced, and their yields were determined through a gas chromatography and mass spectrometry analysis of the reaction samples. Finally, the role and contribution of each of the variables considered in the conversion process were analyzed. By using a nonlinear model, a quadratic dependence with %Cu and P in the studied range of the variables was found, as well as a linear dependence with Tcal. Finally, for this experiment, the highest yields (μmol/g) were obtained with the following conditions: %Cu = 3 %, P = 6 bar, and Tcal = 400 °C. RESUMEN Debido a la demanda de derivados oxigenados de hidrocarburos para la industria, la conversión de metano (CH4) a metanol (CH3OH) por medio de catálisis en estado sólido es una cuestión de actualidad, precisa y con retos específicos. Este trabajo muestra un modelo estadístico que predice la cantidad de metanol producido por un proceso de conversión por lotes empleando mordenitas intercambiadas con cobre de acuerdo con un diseño experimental factorial. La síntesis fue realizada por intercambio iónico en estado sólido a partir de Cu(acac)2 y NH4-Mordenita, obteniendo porcentajes de intercambio en peso de Cobre (%Cu) de 1 %, 3 % y 5 %, seguido de una activación por calcinación en el rango de temperaturas (Tcal) de 300-500 °C, así como una reacción con metano en el rango de presiones de 2-10 bar (P) bajo condiciones estáticas con un reactor por lotes. Las cantidades de MeOH producidas y sus rendimientos fueron determinados usando análisis de cromatografía de gases y espectrometría de masas de las muestras de la reacción. Finalmente se analizaron el papel y la contribución de cada una de las variables consideradas en el proceso de conversión. Usando un modelo no lineal, se encontró una dependencia cuadrática del %Cu y P en el rango estudiado de cada variable, así como una dependencia lineal con Tcal. Finalmente, para este experimento, los mayores rendimientos (μmol/gr) se obtuvieron con las siguientes condiciones: %Cu=3 %, P = 6 bar y Tcal = 400 °C.

Reducing the particle size to improve the electrochemical properties of LiMn2O4 has been a common practice along the last years claiming that, by doing this, the Jahn-Teller (JT) distortion in its 3 V region is reduced. However, only a few papers have proved actual links between the mitigation of the JT effect and particle size; therefore, the JT effect is often entangled with mechanical and kinetic improvements, which are also associated to diminishing the particle size. Regardless that, there is a consensus that reducing particle size positively impacts Li+ insertion into LiMn2O4, particularly in its 3 V plateau. On the other hand, defects have emerged as factors determining the electrochemical behaviours of LiMn2O4. Several works pointed out that certain defects such as Mnitet, F and V colour centres, dislocations or voids, could improve the 3 V performance of the LiMn2O4 by decreasing the JT distortion. Nevertheless, the preponderant defect causing this enhancement has not yet been established. The present paper aims to determine, among Mnitet, F and V centres as well as dislocations, which defect impacts the most on the JT transition, specific capacity and stability of nanometric LiMn2O4. The aforementioned defects were detected by HRTEM, XRD, UV–Vis as well as magnetic measurements. Their implications on the potential drop caused by the JT effect, specific capacity and stability were recorded by potentiometric and galvanostatic charge/discharge measurements. The results indicate that only Mnitet-related defect reduces the JT distortion, increasing the stability and capacity within the 3 V region, especially when particle are small.

Methane has been widely employed as a feedstock for numerous chemical and electrochemical processes. However, methane activation poses a challenge due to the molecule’s relative inertness, lack of significant polarity and because its bond energy is the highest among all hydrocarbons. Consequently, the ability to activate methane (CH4), or access the C atom to form new bonds is a difficult endeavor [1]. Furthermore, CH4 gas emission has long been ignored and regarded as a trivial matter [2], even though its effect as a greenhouse gas is over 30 times more potent than that of CO2 [3]. In this regard, the oxidation and conversion of CH4 to liquid alcohols is an economical and energy efficient alternative with academic and industry interest. The present study shows the synthesis and characterization of Fe, Co, Cu oxides/ZrO2 nanocomposites used as bifunctional electrocatalyst for the electrochemical activation of methane, which in conventional alkaline electrochemical systems is always performed at room temperature. Fe, Co, Cu oxides/ZrO2 nanocomposites were synthesized using an aqueous-phase precipitation technique and their structural, spectroscopic, magnetic and electrochemical characteristics were evaluated. Methane was electrochemically activated over the three functional electrocatalysts here synthesized. Carbonate anions were used as an oxygen donator to facilitate methane activation while ZrO2 adsorbed and donated carbonate anions to active sites on Fe, Co and Cu oxides where methane was adsorbed and activated. Products formed were studied by gas chromatography. References: [1] R. Bergman, Nature, 446, 391 (2007). [2] A. R. Brandt, G. A. Heath, E. A. Kort, F. O. Sullivan, G. Petron, S. M. Jordaan, P. Tans, J. Wilcox, A. M. Gopstein, D. Arent, S. Wofsy, N. J. Brown, R. Bradley, G. D. Stucky, D. Eardley, R. Harriss, Science, 343, 733 (2014). [3] D. T. Shindell, G. Faluvegi, D. M. Koch, G. A. Schmidt, N. Unger, S. E. Bauer, Science, 326, 716 (2009). [4] Neil Spinner and William E. Mustain, Journal of The Electrochemical Society, 160 (11) F1275-F1281 (2013).