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- Bernardini, A., et al.
(author)
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Direct synthesis of H2O2 over Pd supported on rare earths promoted zirconia
- 2015
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In: Catalysis Today. - : Elsevier BV. - 0920-5861 .- 1873-4308. ; 256, s. 294-301
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Journal article (peer-reviewed)abstract
- In this work Pd (0.3 or 0.6 wt.%) was supported on both ZrxM1-xO2 (M = La, Y, Ce) and on mechanical mixtures of CeO2 and ZrO2. The synthesized catalysts were characterized by XRD, TPR, AAS and CO chemisorption and tested for the direct synthesis of hydrogen peroxide in a high pressure semibatch apparatus. The reactants conversion was limited in order to avoid mass-transfer limitations. No selectivity enhancers of any kind were used and the all the materials were halide free. Small metal particles were obtained (1-2.6 nm). Supports with smaller pore diameters leaded to larger Pd particles, which in turn were found to preferentially support the formation of the peroxide. Moreover, supports with higher reducibility favored the production of H2O2, probably due to an easier reduction of the active metal, essential to achieve high selectivity. Notwithstanding the absence of enhancers, the specific activity and selectivity recorded were very high.
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| 3. |
- Konwar, Lakhya Jyoti, et al.
(author)
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Reaction kinetics with catalyst deactivation in simultaneous esterification and transesterification of acid oils to biodiesel (FAME) over a mesoporous sulphonated carbon catalyst
- 2016
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In: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 166, s. 1-11
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Journal article (peer-reviewed)abstract
- In this work, a careful analysis of the reaction kinetics upon simultaneous esterification and transesterification of acidic oils over a mesoporous sulphonated carbon catalyst is discussed. A batch reactor system was used and the synthesized carbon catalyst were characterized by N2-physisorption, transmission electron microscopy, elemental analysis and NH3-TPD. A second order pseudo-homogeneous kinetic model was proposed which explained the experimental results obtained for three different feedstock oils with ⩾98% accuracy. The rate constants (k), activation energies (Ea) and equilibrium constants (Keq) of the individual reactions were determined by regression analysis which confirmed that the reaction steps were kinetically controlled and not limited by inter-particle diffusion or external mass transfer limitations (Ea > 25 kJ mol−1). Furthermore, the composition feedstock was found to have a distinct effect on the solubility of methanol and oil phase which influenced k, Keq and Ea values, eventually determining the final biodiesel (FAME) yield. To account for the loss of activity upon catalyst reuse, a deactivation model was also proposed which explained our results with ∼94% accuracy. In fact, the loss of activity was accounted for by incorporating a concentration-independent ‘deactivation constant’ kd in the reaction rate equations. Moreover, under optimized reaction conditions (120 °C and 20:1 methanol-to-FFA molar ratio), FAME yields up to 79–91 wt% could be obtained in one step process from oils containing 21–41 wt% FFA.
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| 4. |
- Riittonen, T., et al.
(author)
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Direct Synthesis of 1-Butanol from Ethanol in a Plug Flow Reactor : Reactor and Reaction Kinetics Modeling
- 2014
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In: Topics in catalysis. - : Springer Science and Business Media LLC. - 1022-5528 .- 1572-9028. ; 57:17-20, s. 1425-1429
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Journal article (peer-reviewed)abstract
- Bio-ethanol is well known for its use as a gasoline additive. However, it can be blended in low portions to traditional gasoline although it has a corrosive nature. By taking advantage of modern continuous reactor technology and heterogeneous alumina catalysts, ethanol can be upgraded to 1-butanol in fixed beds. Butanol has more feasible properties as fuel component in comparison to ethanol. Mathematical modeling of reaction kinetics revealed a simple kinetic model could be used to describe the complex reaction process on a Cu/alumina catalyst. The reaction kinetics model is based on five parallel reactions in which ethanol reacts to 1-butanol, acetealdehyde, ethyl acetate, diethyl ether and diethoxyethane, respectively.
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| 5. |
- Rogne, Per, et al.
(author)
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Real-time 31P NMR investigation on the catalytic behavior of the enzyme Adenylate kinase in the matrix of a switchable ionic liquid
- 2015
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In: ChemSusChem. - : John Wiley & Sons. - 1864-5631 .- 1864-564X. ; 8:2, s. 3764-3768
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Journal article (peer-reviewed)abstract
- The integration of highly efficient enzymatic catalysis with the solvation properties of ionic liquids for an environmentally friendly and efficient use of raw materials such as wood requires fundamental knowledge about the influence of relevant ionic liquids on enzymes. Switchable ionic liquids (SIL) are promising candidates for implementation of enzymatic treatments of raw materials. One industrially interesting SIL is constituted by monoethanol amine (MEA) and 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) formed with sulfur dioxide (SO2) as the coupling media (DBU-SO2-MEASIL). It has the ability to solubilize the matrix of lignocellulosic biomass while leaving the cellulose backbone intact. Using a novel 31P NMR-based real-time assay we show that this SIL is compatible with enzymatic catalysis because a model enzyme, adenylate kinase, retains its activity in up to at least 25 wt % of DBU-SO2-MEASIL. Thus this SIL appears suitable for, for example, enzymatic degradation of hemicellulose.
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