Levulinic acid as a platform for electrochemical synthesis: electrochemical conversion of levulinic acid and its primary products is presented as a promising alternative for the generation of renewable chemicals and biofuels and for energy storage.
Abstract:With the growth of aviation traffic and the demand for emission reduction, alternative fuels like the so-called electrofuels could comprise a sustainable solution. Electrofuels are understood as those that use renewable energy for fuel synthesis and that are carbon-neutral with respect to greenhouse gas emission. In this study, five potential electrofuels are discussed with respect to the potential application as aviation fuels, being n-octane, methanol, methane, hydrogen and ammonia, and compared to conventional Jet A-1 fuel. Three important aspects are illuminated. Firstly, the synthesis process of the electrofuel is described with its technological paths, its energy efficiency and the maturity or research need of the production. Secondly, the physico-chemical properties are compared with respect to specific energy, energy density, as well as those properties relevant to the combustion of the fuels, i.e., autoignition delay time, adiabatic flame temperature, laminar flame speed and extinction strain rate. Results show that the physical and combustion properties significantly differ from jet fuel, except for n-octane. The results describe how the different electrofuels perform with respect to important aspects such as fuel and air mass flow rates. In addition, the results help determine mixture properties of the exhaust gas for each electrofuel. Thirdly, a turbine configuration is investigated at a constant operating point to further analyze the drop-in potential of electrofuels in aircraft engines. It is found that electrofuels can generally substitute conventional kerosene-based fuels, but have some downsides in the form of higher structural loads and potentially lower efficiencies. Finally, a preliminary comparative evaluation matrix is developed. It contains specifically those fields for the different proposed electrofuels where special challenges and problematic points are seen that need more research for potential application. Synthetically-produced n-octane is seen as a potential candidate for a future electrofuel where even a drop-in capability is given. For the other fuels, more issues need further research to allow the application as electrofuels in aviation. Specifically interesting could be the combination of hydrogen with ammonia in the far future; however, the research is just at the beginning stage.
Here, we propose the use of hydroxyacetone, a dehydration product of glycerol, as a platform for the electrocatalytic synthesis of acetone, 1,2-propanediol, and 2-propanol. 11 non-noble metals were investigated as electrode materials in combination with three different electrolyte compositions toward the selectivity, Coulombic efficiency (CE), and reaction rates of the electrocatalytic hydrogenation (formation of 1,2-propanediol) and hydrodeoxygenation (formation of acetone and propanol) of hydroxyacetone. With a selectivity of 84.5 %, a reaction rate of 782 mmol h m and a CE of 32 % (for 0.09 m hydroxyacetone), iron electrodes, in a chloride electrolyte, yielded the best 1,2 propanediol formation. A further enhancement of the performance can be achieved upon increasing the educt concentration to 0.5 m, yielding a reaction rate of 2248.1 mmol h m and a CE of 64.5 %. Acetone formation was optimal at copper and lead electrodes in chloride solution, with lead showing the lowest tendency of side product formation. 2-propanol formation can be achieved using a consecutive oxidation of the formed acetone (at iron electrodes). 1-propanol formation was observed only in traces.
1,3-propanediol (1,3-PD) is a bulk chemical with myriad applications in polymers, lubricants, cosmetics, foods industries and in the synthesis of heterocyclic compounds. Current commercial production of 1,3-PD involves a thermocatalytic process using acrolein (DuPont) and ethylene oxide (Shell) as starting feedstock. These feedstocks are petroleum-based and there are many efforts at using glycerol as low cost biomass-derived feedstock for 1,3-PD production. A number of catalyst designs and bacterial & fungal strains are being explored for respective catalytic and fermentation routes to glycerol-to-1,3-PD.However, the electrochemical method received little attention for the purpose. In this work, in order to explore the possibility of using partly refined glycerol byproduct of biodiesel production as feedstock, we investigated conversion and 1,3-PD selectivity of glycerol electrolysis in chloride media. We demonstrated selective glycerol-to-1,3-PD conversion using Pt or RuO 2 -based dsa as anode and Zn or Pb as cathode in NaCl and KCl at pH 1. This electrochemical glycerol-to-1,3-PD conversion is not only green, it is a potential process network loop between biodiesel production and chlor-alkali industry.
An analyser for the simultaneous determination of carbon, hydrogen and nitrogen in organic compounds is described. The samples are burned in a static system in oxygen and the combustion products are determined using a self‐integrating thermal conductivity method. Up to 16 previously weighed samples of 0.5 ÷ 2.0 mg are analysed without any manual help and the results are presented in digital form. One determination takes between 7 and 13 minutes. At present the standard error of a single determination is 0.20, 0.08 and 0.30% (absolute) for carbon, hydrogen and nitrogen, respectively, but these figures may easily be improved by minor modifications.
Aiming toward a scalable continuous electrochemical production of valeric acid, the mutual insolubility of valeric acid with the aqueous reaction medium of levulinic acid and the aqueous electrolyte are investigated in order to assess the possibility for an integrated product separation based on the liquid-liquid equilibrium of the system. The influence of the electrolyte concentration in the mixture and the mixture temperature on the liquid-liquid equilibrium is studied. Based on these results, the possibility for a batch and a continuous product separation process is developed and discussed.
In this research, the electrochemical oxidation of thiophene at platinum and dimensionally stable anode (DSA) electrodes as low oxidation power anodes and at lead/lead oxide (Pb/PbOx) and boron-doped diamond (BDD) electrodes as high oxidation power anodes was comprehensively studied by determining the rate and degree of the electrochemical thiophene oxidation, the Coulombic efficiency (CE), and the selectivity of polar product formation [thiophene-2-one and 3hydroxythiophene-2(3H)-one (Thyox)]. The DSA showed the best performance among the low oxidation power electrodes, with a selectivity of 84.54% toward Thyox formation, a product formation rate of 224.51 mmol/(h m 2 ), a CE of 23.04%, and thiophene conversion of 97.96% in 0.5 M H 2 SO 4 solution for 3 h in ambient temperature. The conversion of thiophene was approximately the same using Pb/PbOx and BDD (about 92%), but Pb/PbOx yielded higher selectivity and product formation rate for Thyox formation [73.68% and 117.72 mmol/(h m 2 ), respectively]. However, CE of BDD (62%) was nearly 3 times greater than that of Pb/PbOx at lower potentials. The experimental results can provide a clear decision in the exploitation of oxidation processes at the industrial scale and could be easily extended to other thiophenic compounds.
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