Conversion of ethanol over transition metal oxide catalysts: Effect of tungsta addition on catalytic behaviour of titania and zirconia

Ethanol dehydration was investigated at atmospheric pressure with 1.43 h 121 WHSV in nitrogen, in the temperature range 423\u2013773K over titania and zirconia, as such and modified by addition of WO3. As for comparison, data on other WO3-free and WO3-containing catalysts are also discussed: a strong Lewis acid (alumina), a covalent oxide (silica) and a basic material (calcined hydrotalcite). The catalysts were characterized using FT-IR of adsorbed pyridine and of wolframate species, and by UV\u2013vis spectroscopy. The results presented here show that WO3/ZrO2 and WO3/TiO2 are excellent catalysts for ethanol dehydration. Their performances may compete with those of zeolites and alumina for conversion to diethyl ether and to ethylene. The addition of WO3 to both ZrO2 and TiO2 introduces strong Br\uf8nsted acid sites that are supposed to represent the active sites in the reaction, but also inhibits the formation of byproducts, i.e. acetaldehyde and higher hydrocarbons. This is attributed to the poisoning of basic sites and of reducible surface Ti and Zr centres, respectively

Conversion of Lignin to Chemical Intermediates:a Study of Pyrolysis of Kraft Lignin

Experiments of pyrolysis of commercial Kraft lignin have been realized in the 250-550 °C range. Product analyses have been performed by FTIR, GC-MS, EDX analyses. The main goal of the work is to optimize the experiments in terms of liquid yield, reduction of oxygen content in the resulting biochar, and removal of sulfur, found mainly in the gas phase. It has been concluded that the amount of the starting lignin charged in the reactor must be limited to be fully positioned in the heating chamber also during high temperature treatment. Sulfur may be partially removed in the gas phase as H2S and CH3SH mainly, by a pre-treatment at 250 °C. The maximum amount of liquid product, mainly constituted by methoxy- and alkyl-methoxy-phenols, and the maximum solid deoxygenation are both obtained at 550 °C

On the Role of Support in Metallic Heterogeneous Catalysis: A Study of Unsupported Nickel\u2013Cobalt Alloy Nanoparticles in Ethanol Steam Reforming

(Co, Ni) bimetallic nanoparticles have been prepared by reducing Ni and Co chloride solutions with sodium borohydride. The obtained materials have been characterized as cast and/or after annealing by means of XRD, magnetic measurements, IR spectroscopy, FE-SEM and TEM microscopies. The resulting nanomaterials, originally amorphous, crystallize into the cubic structure cF4-Cu as homogeneous (Co, Ni) solid solution alloy and with the additional presence of Boron containing phases due to the residual preparation impurities. The bimetallic nanoparticles are active in ethanol conversion in the presence of steam. For low Boron catalysts, the addition of Nickel to Cobalt nanoparticles improves the catalytic activity in ethanol steam reforming allowing yields as high as 87% at 773 K, at high space velocities (GHSV 324,000 h 121 ). The performances of the catalytic unsupported nanoparticles with a Ni/Co atomic ratio equal to 0.26 appear to be better than those of conventional supported catalysts. The state of Boron impurities affect catalytic activity of bimetallic (Co, Ni) NPs. Carbonaceous materials, such as carbon nanotubes and graphitic carbon, form on the catalyst surface upon reaction. Graphical Abstract: [Figure not available: see fulltext.]

Ethanol and diethyl ether catalytic conversion over commercial alumina and lanthanum-doped alumina: Reaction paths, catalyst structure and coking

Commercial high-pore-volume alumina and La-doped aluminas have been characterized and tested as catalysts for ethanol conversion to ethylene and diethyl ether and for diethyl ether cracking. In order to go deeper on reaction paths and mechanisms, steady state, TPSR and static experiments in an IR cell were performed. It is established that ethylene forms from ethanol by two parallel ways: i) cracking of ethoxy groups that occurs already at low temperature, and ii) the parallel synthesis and cracking of DEE at intermediate temperatures. Coordination of diethyl ether on Lewis sites represents the first step in its decomposition path. Lewis bonded DEE first cracks to ethoxy species and ethylene gas, while ethoxy species in part crack to a second step to another ethylene gas molecule and in part (only at low temperature) can desorb as gaseous ethanol. Commercial low loading lanthanum-doped alumina contain dispersed La3+-O2 12species mainly interacting with the most reactive defect, edge and corner sites of alumina nanocrystals. At higher loading (4 wt% La2O3) very small LaxOyclusters also appear. Lanthanum doping slightly reduces the number of active sites for ethanol dehydration as well as for DEE cracking, thus reducing catalytic activity, but does not modify significantly selectivities and ethylene yields at high temperature. However, it also considerably reduces the amount of carbonaceous residues formed upon both reactions over the catalyst. Thus, La-doping is proposed as a way to improve the alumina catalyst stability in the process. Catalytic cracking of DEE at 673 K does not represent a good way to remove odorous and dense DEE vapours from air, due to the coproduction of small amounts of acetaldehyde together with ethylene

On the role of triethylene glycol in the preparation of highly active Ni-Mo/Al2O3 hydrodesulfurization catalysts: A spectroscopic study

The interaction of triethylene glycol (TEG) with alumina and its role in preparing improved NiMo/Al2O3 hydrodesulfurization catalysts was investigated by spectroscopic methods. The FT-IR study shows that TEG is mainly adsorbed on the corners and edges of the alumina microcrystals where the strongest Lewis sites and the higher OH frequency hydroxyl groups are mainly located. It is also observed that the Mo O stretching vibration of surface molybdenyl groups in the oxide catalyst precursor is shifted down in the presence of TEG, indicating a lower interaction with the alumina surface. The IR spectra of CO adsorbed on the reduced/sulfided NiMo/Al2O3 catalysts confirm that the amount of promoted phase (NiMoS sites) increases in the samples prepared with TEG. Accordingly, the activity measurements in the HDS of 4,6-dimethyldibenzothiophene show that the catalyst prepared with TEG is more active than the one prepared without it. It is proposed that TEG and its decomposition products, formed upon heating (mainly acetates) occupy preferably the strongly interacting edge and corner sites of the alumina crystals, forcing the Mo and Ni species to migrate mainly to the less reactive plane faces. This weakens the metalsupport interaction allowing a better sulfidation and, at the same time, favoring the Ni\u2013Mo interaction and the formation of the promoted NiMoS phase

Deoxygenation of non-edible vegetable oil to produce hydrocarbons over Mg-Al mixed oxides

none7noopenRomero, Max; Pizzi, Andrea; Toscano, Giuseppe; Casazza, Alessandro Alberto; Busca, Guido; Bosio, Barbara; Arato, ElisabettaRomero, Max; Pizzi, Andrea; Toscano, Giuseppe; Casazza, Alessandro Alberto; Busca, Guido; Bosio, Barbara; Arato, Elisabett

A study of Ni/La-Al 2 O 3 catalysts: A competitive system for CO 2 methanation

Ni/La-\u3b3-Al 2 O 3 samples containing 13.6 wt.% Ni and a variable amount of lanthana (0, 4, 14 and 37 wt.%) were prepared by incipient wetness impregnation, using silica-free \u3b3-Al 2 O 3 support. The materials were characterized, as such or after reaction, with XRD, H 2 -TPR, IR, UV\u2013vis-NIR, XPS and FE-SEM techniques. They were tested as catalysts for CO 2 methanation at atmospheric pressure at GHSV 55000 h 121 . The reaction is under kinetic control at T < 650\u2013673 K, while the product mixture is under thermodynamic control above this temperature range. Lanthanum addition strongly increases the activity of Ni/\u3b3-Al 2 O 3 for CO 2 methanation. Methane selectivity is increased to nearly 100% at low temperatures (T < 650 K). The CO 2 methanation reaction on La-doped Ni/\u3b3-Al 2 O 3 occurs with similar activation energies (80 kJ/mol), and with slightly higher reaction order for hydrogen and lower reaction order for CO 2 than those observed for undoped Ni/\u3b3-Al 2 O 3 . Lanthanum acts as a promoter because of the stronger basicity of the lanthana-alumina support allowing stronger adsorption of CO 2 as surface carbonates that can be act as \u201creactant reservoirs\u201d. The Ni/La-alumina catalysts studied here are similarly effective as Ru/alumina catalysts for the selective CO 2 methanation at low temperature and atmospheric pressure

Removal of VOCs by catalytic process. A study of MnZnO composites synthesized from waste alkaline and Zn/C batteries

Spent alkaline and zinc-carbon batteries were subjected to a biohydrometallurgy process, in order to recover manganese and mixed manganese zinc oxides. Two solids were synthesized, one of them prepared by reaction of MnSO4 and KMnO4 (MnOx) and the other obtained by chemical precipitation with NaOH (ZnMnO). The characterization by XRD, TPR, FTIR and XPS revealed the presence of Mn3+ and Mn4+ cations in both samples, and the presence of ZnO and Mn-Zn spinels in ZnMnO. The samples were evaluated in the oxidation reaction of ethanol and toluene. The results in the flow reactor showed that ethanol conversion on both catalysts, MnOx and ZnMnO, is rather similar, but toluene conversion is markedly higher on MnOx, due to a greater Mn/Zn ratio and to the absence of a crystallized ZnO phase. The FTIR study demonstrated that ethanol is oxidized to acetaldehyde at low temperature, and to CO2 and CO at 400 C. Traces of CH4 in the gas phase are also detected at high temperature. The formation of ethoxy and acetate groups is observed at the catalyst surface. With respect to toluene oxidation, CO2 is detected at 300 C and when the temperature is increased, CO is also observed in the gas phase. The results showed that: (i) the alkaline and Zn-carbon batteries can be recycled as catalysts and (ii) the solids can be used in the catalytic process for VOCs control.Centro de Investigación y Desarrollo en Ciencias Aplicada

Estudio de FTIR de la adsorción y reacción de cloroformo sobre óxidos de Mn-Zn

A partir de una solución de MnSO4 y ZnSO4 obtenida mediante un proceso de tratamiento de pilas alcalinas agotadas, se sintetizaron dos sólidos: OMR, mediante precipitación con KMnO4 y OMI, mediante impregnación del sólido OMR con solución de Zn2+ proveniente del ánodo de pilas alcalinas. La relación Mn/Zn fue de 2,6 y 1,2 para OMR y OMI, respectivamente. Por DRX se detectaron diferentes fases en función del contenido de Zn. El estudio de la atmósfera gaseosa en la oxidación de CHCl3 en presencia de H2O y aire mediante espectroscopia FTIR sobre los óxidos, permitió detectar HCl, CO2 y CO además de algunos subproductos clorados, tales como C2H3Cl3, CCl4 y CH2Cl2. Por otro lado se observó fosgeno en el sólido OMI, señalando la complejidad del mecanismo de reacción. El estudio de la superficie de los sólidos por FTIR, en presencia de CHCl3/H2O/aire, muestra la participación de las especies SO42- en el proceso de adsorción de cloroformo.Two solids were synthesized from a MnSO4 and ZnSO4 solution obtained by a recycling treatment of spent alkaline batteries: OMR, by precipitation with KMnO4 and OMI, by impregnation of the solid OMR with Zn2+ solution obtained by dissolving the anode of alkaline batteries. The Mn/Zn ratio was 2.6 and 1.2 for OMR and IMO, respectively. Different phases were detected by DRX as a function of the Zn content. The study of the gaseous atmosphere in the oxidation of CHCl3 in the presence of H2O and air over the oxides by FTIR spectroscopy, allowed us to detect HCl, CO2 and CO besides some chlorinated byproducts, such as C2H3Cl3, CCl4 and CH2Cl2. On the other hand phosgene was observed in the OMI solid, indicating the complexity of the reaction mechanism. The study of the surface of the solids by FTIR, in the presence of CHCl3 / H2O / air, shows the participation of SO42- species in the chloroform adsorption process.Trabajo publicado en Álvarez, María E., Sandra G. Casuscelli, Mónica E. Crivello y Griselda A. Eimer (eds.). Actas del XX Congreso Argentino de Catálisis. Universidad Tecnológica Nacional, Facultad Regional Córdoba, Buenos Aires, 2017.Facultad de Ciencias Exacta

Estudio de FTIR de la adsorción y reacción de cloroformo sobre óxidos de Mn-Zn

A partir de una solución de MnSO4 y ZnSO4 obtenida mediante un proceso de tratamiento de pilas alcalinas agotadas, se sintetizaron dos sólidos: OMR, mediante precipitación con KMnO4 y OMI, mediante impregnación del sólido OMR con solución de Zn2+ proveniente del ánodo de pilas alcalinas. La relación Mn/Zn fue de 2,6 y 1,2 para OMR y OMI, respectivamente. Por DRX se detectaron diferentes fases en función del contenido de Zn. El estudio de la atmósfera gaseosa en la oxidación de CHCl3 en presencia de H2O y aire mediante espectroscopia FTIR sobre los óxidos, permitió detectar HCl, CO2 y CO además de algunos subproductos clorados, tales como C2H3Cl3, CCl4 y CH2Cl2. Por otro lado se observó fosgeno en el sólido OMI, señalando la complejidad del mecanismo de reacción. El estudio de la superficie de los sólidos por FTIR, en presencia de CHCl3/H2O/aire, muestra la participación de las especies SO42- en el proceso de adsorción de cloroformo.Two solids were synthesized from a MnSO4 and ZnSO4 solution obtained by a recycling treatment of spent alkaline batteries: OMR, by precipitation with KMnO4 and OMI, by impregnation of the solid OMR with Zn2+ solution obtained by dissolving the anode of alkaline batteries. The Mn/Zn ratio was 2.6 and 1.2 for OMR and IMO, respectively. Different phases were detected by DRX as a function of the Zn content. The study of the gaseous atmosphere in the oxidation of CHCl3 in the presence of H2O and air over the oxides by FTIR spectroscopy, allowed us to detect HCl, CO2 and CO besides some chlorinated byproducts, such as C2H3Cl3, CCl4 and CH2Cl2. On the other hand phosgene was observed in the OMI solid, indicating the complexity of the reaction mechanism. The study of the surface of the solids by FTIR, in the presence of CHCl3 / H2O / air, shows the participation of SO42- species in the chloroform adsorption process.Trabajo publicado en Álvarez, María E., Sandra G. Casuscelli, Mónica E. Crivello y Griselda A. Eimer (eds.). Actas del XX Congreso Argentino de Catálisis. Universidad Tecnológica Nacional, Facultad Regional Córdoba, Buenos Aires, 2017.Facultad de Ciencias Exacta