Synthesis of liquid menthol by hydrogenation of dementholized peppermint oil over Ni catalysts

Hydrogenation of (-)-menthone and (+)-isomenthone was studied at 2.7 MPa and 100 ºC. The objective was to produce a liquid menthol mixture rich in (-)-menthol from dementholized peppermint oil. Ni-based catalysts were tested and compared for this reaction: a) 6 and 12% Ni dispersed into a nonstoichiometric magnesium aluminate (Ni-Mg-Al) with spinel structure; b) Ni-Raney catalyst. Both types of catalysts were active for (-)-menthone and (+)-isomenthone hydrogenation. Lower conversion but higher selectivity to (-)-menthol was obtained with Ni-Mg-Al catalysts. However, they rapidly lost their activity. Instead Ni-Raney catalysts kept its original activity even after several hydrogenation runs

Hidrogenación selectiva en fase liquida de 1-heptino sobre Ni/Al2O3. Efecto de la temperatura de reacción

In this work, it was studied the effect of reaction temperature during selective hydrogenation of 1-heptyne to 1- heptene. Supported nickel on ã -alumina was used as catalyst. Different operation temperatures (273, 303 and 323 K) were evaluated and the best behavior was found at the higher reaction temperature, showing high selectivity (c.a. 90 %). The prepared nickel catalyst can be seen as a cheaper alternative to industrial level compared to known palladium catalysts, not only due to the lower cost of metal, but also because of its small metal loading (3,6 % mass). The catalyst was characterized by X-Ray Diffraction, Temperature Programmed Reduction and X-Ray Photoelectron Spectroscopy. These different techniques indicated the presence of nickel oxide with support strong interactions at bulk level, and the presence of electron-deficient species of nickel at surface level, which were the active species during the hydrogenation of the terminal alkyne.En este trabajo fue evaluado el efecto de la temperatura de reaccion en la hidrogenacion selectiva de 1-heptino a 1-hepteno usando un catalizador de niquel soportado sobre �Á -alumina. Fueron estudiadas diferentes temperaturas operacionales (273, 303 y 323 K), obteniendose mayor conversion total del reactivo a la mayor temperatura, con una selectividad proxima al 90%. El catalizador de niquel preparado puede considerarse como una alternativa mas economica a nivel industrial frente a los ya conocidos catalizadores de paladio, no solo debido al bajo costo del metal sino tambien debido a su bajo contenido metalico (3,6% en masa). El catalizador fue caracterizado por Difraccion de Rayos X, Reduccion a Temperatura Programada y Espectroscopia Fotoelectronica de Rayos X. Estas indicaron la presencia de oxido de niquel a nivel masico con fuertes interacciones con el soporte y la existencia de especies electro-deficientes de niquel a nivel superficial quienes serian las especies activas durante la hidrogenacion del alquino terminal

Aprovechamiento de la glicerina obtenida durante la producción de biodiesel

Further uses of glycerin obtained during biodiesel production Limited oil resources as well as the need to reduce environmental pollution spurred the development of renewable fuels such as biodiesel. An increase in biodiesel production will lead to a surplus of non-commercial grade glycerin, a byproduct of the process. Thus, demand should be expanded within the legal framework already encompassing biodiesel use. At UCEL the authors have researched alternative uses of this byproduct to synthesize GTBE (glycerin tbutyl ether). The addition of this additive to fuels -whether oil or biodiesel- improves combustion efficiency and reduces emission of environmental pollutants.Las acotadas reservas de petróleo y la necesidad de disminuir la contaminación medioambiental intensificaron el desarrollo de combustibles renovables como el biodiesel. Debido a que su uso ha sido legislado en muchos países, el aumento en su producción provocará excedentes de la glicerina sin calidad comercial, obtenida como subproducto, si no se aumenta en la misma magnitud su demanda. En UCEL investigamos usos alternativos que permitan el aprovechamiento de este subproducto para sintetizar gliceriltert- butil-eter (GTBE), un aditivo que, incorporado al diesel de petróleo o biodiesel, mejora la eficiencia de la combustión y disminuye la emisión de contaminantes ambientales

H3PW12O40 (HPA), an efficient and reusable catalyst for biodiesel production related reactions: esterification of oleic acid and etherification of glycerol

In esterification of oleic acid with methanol at 25 °C HPA displayed the highest activity. Moreover the HPA could be reused after being transformed into its cesium salt. In the reaction of etherification of glycerol HPA and Amberlyst 35W showed similar initial activity levels. The results of acid properties demonstrate that HPA is a strong protonic acid and that both surface and bulk protons contribute to the acidity. Because of its strong affinity for polar compounds, HPA is also seemingly dissolved in both oleic acid and methanol. The reaction in this case proceeds with the catalyst in the homogenous phase

Isomerization-cracking of n-octane on catalysts based on heteropolyacid H3Pw12O40 and heteropolyacid supported on zirconia and promoted with Pt and Cs

Isomerization - cracking of n-octane was studied using H3PW12O40 (HPA) and HPA supported on zirconia and promoted with Pt and Cs. The addition of Pt and Cs to the supported HPA did not modify the Keggin structure. The Pt addition to the supported HPA did not substantially modify the total acidity; however, the Brönsted acidity increased significantly. Cs increased the total acidity and Brönsted acidity. A linear relation was observed between the n-C8 total conversion and Brönsted acidity. The most adequate catalysts for performing isomerization and cracking to yield high research octane number (RON) are those with higher values of Brönsted acidity

Poisoning and regeneration of Pt-Pd/WO3-ZrO2 short paraffin isomerization catalysts

WO3-ZrO2 catalysts promoted with Pt and Pd were tested as paraffin isomerization catalysts using n-hexane as model compound. Sulfur and amine poisoning and regeneration tests were used to assess the impact of the addition of Pt and Pd on the deactivation resistance and regenerability. Pt and PtPd catalysts were the most active for n-hexane isomerization. The low activity of the Pd catalyst was attributed to poor Pd metal properties when supported over WO3-ZrO2 and to a decrease of the number of BrQnsted acid sites. PtPd was the only catalyst capable of full regeneration after S poisoning. Amine poisoning completely supressed the isomerization activity and the original activity could only be restored by calcination and reduction

NANOPARTICLES OF TUNGSTEN AS LOW-COST MONOMETALLIC CATALYST FOR SELECTIVE HYDROGENATION OF 3-HEXYNE

Low-cost tungsten monometallic catalysts containing variable amounts of metal (4.5, 7.1 and 8.5%W) were prepared by impregnating alumina with ammonium metatungstate as an inexpensive precursor. The catalysts were characterized using ICP, XPS, XRD, TPR and hydrogen chemisorption. These techniques revealed mainly WO3-Al2O3 (W6+) species on the surface. The effects of the content of W nanoparticles and reaction temperature on activity and selectivity for the partial hydrogenation of 3-hexyne, a non-terminal alkyne, were assessed under moderate conditions of temperature and pressure. The monometallic catalysts prepared were found to be active and stereoselective for the production of (Z )-3-hexene, had the following order: 7.1WN/A > 8.5 WN/A ≥ 4.5 WN/A. Additionally, the performance of the synthesized xWN/A catalysts exhibited high sensitivity to temperature variation. In all cases, the maximum 3-hexyne total conversion and selectivity was achieved at 323 K. The performance of the catalysts was considered to be a consequence of two phenomena: a) the electronic effects, related to the high charge of W (+6), causing an intensive dipole moment in the hydrogen molecule (van der Waals forces) and leading to heterolytic bond rupture; the H+ and H- species generated approach a 3-hexyne adsorbate molecule and cause heterolytic rupture of the C≡C bond into C- = C+; and b) steric effects related to the high concentration of WO3 on 8.5WN/A that block the Al2O3 support. Catalyst deactivation was detected, starting at about 50 min of reaction time. Electrodeficient W6+ species are responsible for the formation of green oil at the surface level, blocking pores and active sites of the catalyst, particularly at low reaction temperatures (293 and 303 K). The resulting best catalyst, 7.1WN/A, has low fabrication cost and high selectivity for (Z )-3-hexene (94%) at 323 K. This selectivity is comparable to that of the classical and more expensive industrial Lindlar catalyst (5 wt% Pd). The alumina supported tungsten catalysts are low-cost potential replacements for the Lindlar industrial catalyst. These catalysts could also be used for preparing bimetallic W-Pd catalysts for selective hydrogenation of terminal and non-terminal alkynes.The financial support of UNL, CONICET and ANPCyT are greatly acknowledged