. However, the Langmuir–Hinshelwood mechanism, as proposed by Voss et al. Experiments with acetone produced the smallest particle size (120.44 nm) and polydispersity (0.27). 1, 2, 3) suggest that CeZr is more active for the acetone generation compared with ZrO2 not only due to its acid properties, but also its reducibility and reactivity toward the H2O dissociation. The acetone synthesis from ethanol was studied employing Cu/ZnO/Al2O3, Ce0.75Zr0.25O2 and ZrO2. The E2 mechanism is related to the simultaneous abstraction of OH and β-H by a pair of acid and basic sites. In the case of the physical mixtures, the oxidant agent is mainly supplied by the dissociation of H2O on Cuo, which occurs equally for both mixtures. 25ml of 95% ethanol was added and the solution was allowed to come nearly to room temperature. Acidity, reducibility and the H2O dissociation activity are very relevant catalytic properties for the acetone synthesis from ethanol. Recently, Zonetti et al. The ethanol conversions of ZrO2 and CeZr are stable during 12 h (time on stream), whereas CZA exhibits a decrease of the conversion in the first 2 h and after that it remain stable (~10 h), (see Additional file 1: Figure S1). Thus, using physical mixtures it is possible to compare the catalytic behavior of ZrO2 and CeZr without the interference of their acid properties. The ZrO2 and CZA are commercial catalysts samples. Google Scholar, Carvalho DL, Borges LEP, Appel LG, De la Piscina PR, Homs N (2013) In situ infrared spectroscopic study of the reaction pathway of the direct synthesis of n-butanol from ethanol over MgAl mixed-oxide catalysts. The TPD-H2O were carried out using a micro reactor system coupled to a QMS200 Balzers mass quadrupole spectrometer. Working off-campus? According to Phatak et al. 4a). This catalyst shows very low selectivity to ethylene. & Appel, L.G. The mixed oxide is more active for the acetone generation when compared with ZrO2 not only due to its acid properties, but also due to its reducibility and reactivity towards the H2O dissociation. A silicone membrane was used to study butanol separation from model butanol solutions and fermentation broth. In relation to the oxides, these properties are associated with the presence of O vacancies. The TPSR results are very different from the CZA catalytic performance depicted in Table 1 and Fig. Thus, it can be inferred that these species are oxidized very fast. After that this compound reacts producing acetone and CO2 by the ketonization reaction. and you may need to create a new Wiley Online Library account. This adsorption might be the reason for the low selectivity to ethylene and high towards acetone as observed in the case of the physical mixtures when compared to CeZr and ZrO2. At this point, the surface might be more reduced than oxidized. Appl Catal A 363:109–114, Gaspar AB, Barbosa FG, Letichevsky S, Appel L (2010) The one-pot ethyl acetate syntheses: the role of the support in the oxidative and the dehydrogenative routes. The synthesis of acetone from ethanol is a good example of these processes. When CeO2 is previously reduced the same species were observed, i.e., at 1438 (symmetric carbonate), 1538 and 1345 cm−1 (bidentate carbonate). J Mol Catal A 139:73–80, Finocchio E, Daturi M, Binet C, Lavalley JC, Blanchard G (1999) Thermal evolution of the adsorbed methoxy species on CexZr1−xO2 solid solution samples: a FT-IR study. After that the wafers were submitted to high vacuum for 2 h, then to dry oxygen pulses for 1 h and exposed again to high vacuum for 30 min at 773 K. This procedure was repeated 3 times. It was verified (not shown) that the molecular desorption of H2O occurs from low to high temperatures, which is related to the recombination of hydroxyls species [35]. The authors declare that they have no competing interests. J Catal 302:20–30, Goguet A, Meunier FC, Tibiletti D, Breen JP, Burch R (2004) Spectrokinetic investigation of reverse water-gas-shift reaction intermediates over a Pt/CeO2 catalyst. The composition of the latter is the following: CuO (60 wt%), ZnO (29 wt%) and Al2O3 (11 wt%). The redox environment of the acetone synthesis from ethanol when employing CZA, CeZr and ZrO2 is exhibited by the TPSR followed by the IR-MS spectroscopy. Privacy Aiming at better describing the synthesis of acetone from ethanol, CeZr and CZA were analyzed by TPSR (temperature programmed surface reaction) of ethanol followed by IR and MS online analyses. [27] described the mechanism of the acetaldehyde synthesis on oxides according to the following steps: firstly, the H of the OH of ethanol is abstracted by a strong basic site generating ethoxide species, which are then adsorbed on acid sites. Appl Catal A 415–416:96–100, Article Manage cookies/Do not sell my data we use in the preference centre. Sufficient data were obtained to allow meaningful concentration distributions to be obtained for ammonia, acetone, isoprene and ethanol. IR spectroscopies (DRIFTS)—In situ IR studies were carried out using a Nicolet iS50 FT-IR spectrometer equipped with a MCT/B detector, diffuse reflectance assembly chamber (Harrick) and ZnSe window. However, it is worth mentioning that this catalyst, at high residence time (500 mg, 60 mL min−1, 673 K), shows high selectivity to acetone (50%) at high conversion. The selectivity to acetone of CZA is determined by its basicity and acidity. As it is well known, CeZr and ZrO2 show superficial vacancies. The H2 generation, which occurs during the TPSR, indicates the redox character of this synthesis. It can be observed that CZA generated a large peak of H2. Ethanol and H2O vapors were generated by passing N2 through two saturators, one at 278 K and the other at 325 K, respectively. Catal Today 253:20–32, Parrot SL, Rogers JW, White JM (1978) The decomposition of ethanol, propanol and acetic acid chemisorbed on magnesium oxide. The former does not promote the ketonization reaction and the latter does not keep the oxygenate species adsorbed. The IR spectra show that ethanol adsorbed is promptly oxidized to acetate species reducing the catalyst. Adding H2O, a very broad band at around 3500 cm−1 is observed exhibiting the hydroxylation of the catalytic surface during the TPSR (spectrum not shown). Nakajima et al. The samples were pretreated in situ under He flow at 403 K, then they were reduced under 40% H2/He flow up to 723 K for 1 h. The samples were cooled again at 298 K under He flow to remove H2 and the corresponding background spectra were taken. [23] studying ethanol reactions observed that Pd/CeO2 and CeO2 also synthesize acetone. 4. volume 11, Article number: 30 (2017) The CeZr catalyst was analyzed by Raman spectroscopy and XRD, which confirmed that the mixed oxide was synthesized, i.e., Zr is in the lattice of CeO2 [26]. At high residence time (see above), the readsorption of acetaldehyde might enhance the selectivity to acetone. Copyright © 2020 Elsevier B.V. or its licensors or contributors. The physical mixtures were composed of CZA + ZrO2 and CZA + CeZr. Considering the similarity between the redox step and the WGS reaction, it can be proposed that acetaldehyde, which is synthesized by these oxides according to the mechanism discussed above, is oxidized to carboxylate species by the O species of the lattice of these oxides, thus reducing them. Acetone is an important solvent and widely used in the synthesis of drugs and polymers. Copyright © 2013 Elsevier B.V. All rights reserved. The product was washed with cold ethanol … [17–19] worked with mixed oxides based on Fe–Zn and Zn–Ca, which showed high activities and selectivities to acetone. American Institute of Chemical Engineers 120 Wall St., 23rd floor New York, NY 10005 1-800-AIChemE (1-800-242-4363) (203) 702-7660 www.aiche.org. So yeah you wash with 50% ethanol to avoid dissolving your pretty crystals, but you still need some water to dissolve the non-precipitated alum. The following absorptions are observed at the ethanol adsorption and also at low temperature in the range of 1200–950 cm−1: 1152, 1117, 1098, 1062, 1052 cm−1 (Fig. It also exhibits the ratio between the oxygenate compounds syntheses and ethanol total consumption rates (Roxyg), the ratio between the ethylene formation and ethanol total consumption rates (Rolef), and, the ratio between the acetone generation and the oxygenate compounds syntheses rates (Racet). These results (Figs. The catalytic tests produced H2 and very small amounts of methane, CO and propylene as well. Venezuela 82/518, Saúde, Rio de Janeiro, RJ, CEP 21081-312, Brazil, Clarissa Perdomo Rodrigues, Priscila da Costa Zonetti & Lucia Gorenstin Appel, You can also search for this author in This work using catalyst physical mixtures and IR spectroscopy (DRIFTS) is consistent with the generation of acetone from ethanol by ketonization of carboxylates which are obtained by dehydrogenation of this alcohol followed by oxidation. Two of them commercial catalysts, (CuO/ZnO/Al2O3, CZA) and monoclinic ZrO2), as described in the methodology, and a third one was synthesized in the laboratory (Ce0.75Zr0.25O2, CeZr).
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