Nora Comelli

Liquid Phase Isomerization of α-Pinene. Study of the Reaction on Sulfated ZrO2

The α-pinene isomerization reaction was studied on sulfated zirconium oxide catalyst for different experimental conditions. The catalysts are active for producing camphene when they present Brönsted acidity and when zirconium oxide crystallizes in the tetragonal phase. The α-pinene conversion and its selectivity to camphene can be optimised by proper selection of operating conditions such as temperature, catalyst concentration and reaction time. The use of this catalyst in the appropriate conditions can result in selectivity to camphene of about 70%.

OBTENTION OF CAMPHENE WITH H3PW12O40 CATALYSTS SUPPORTED ON TiO2, SiO2 AND ZrO2nH2O

The -pinene isomerization reaction was studied on catalysts based on H3PW12O40 (HPW) supported on TiO2, SiO2 and ZrO2nH2O. Catalysts with a 40% nominal charge of phosphotungstic acid (HPW) were prepared by impregnation of supports with a HPW solution. The study of the isomerization reaction was carried out in liquid phase by using a discontinuous reactor, magnetically stirred and maintaining a constant temperature. The catalyst supported on SiO2 resulted to be the most active while the one supported on ZrO2nH2O was the less active. This behavior correlated with the number and strength of the acid sites. XRD studies revealed the formation of HPW crystals when it was supported on SiO2.

ACIDITY OF H3PW12O40/SiO2 AND CATALYTIC ACTIVITY OF a -PINENE

The isomerization reaction in liquid phase of a -pinene in camphene catalyzed by tungstophosphoric acid supported on silica is studied. The catalyst is characterized with FT-IR and XRD to establish if the tungstophosphoric acid maintains the Keggin structure after being supported. The catalyst acidity exposed to different thermal treatments was determined by using FT-IR and TPD techniques of ammonia adsorbed. Two types of sites are distinguished, weak acid sites and strong acid sites. The weak acid sites concentration increases with the thermal treatment and can be responsible for the selectivity decrease in camphene by formation of products of higher molecular weight, while the strong acid sites concentration remains almost constant affecting in a lesser degree the obtention of monocyclic compounds

HYDRATION AND ACETYLATION OF LIMONENE: SUPPORTED HETEROPOLYACIDS

The limonene hydration and acetylation in liquid phase catalyzed by phosphotungstic and phosphomolybdic acid bulk and supported on silica and titanium dioxide were studied. The reaction was performed in a batch reactor in acetic acid at 40oC, with magnetic stirring of the reaction mixture. Reaction products were analyzed by gaseous chromatography with FID detector using a capillary column for separation of products. The identification of compounds was made with pattern terpenes and by gaseous chromatography with mass spectrometry. All catalysts tested result to be active in the hydration and acetylation reaction of limonene. Catalysts based on phophotungstic acid (HPW) produce larger amount of hydration and acetylation products than phosphomolybdic acid (HPMo) catalyst. Hydration products increase faster than isomerization products when the reaction time is increased. The structure of heteropolyacids and the presence of acid sites Bronsted and Lewis were determined by FTIR. Keyword: Hydration, acetylation, limonene, heteropolyacids, α-terpineol

Catalyst Deactivation during α-Pinene Isomerization. Fe-Mn-Promoted Sulfated Zirconium Oxide

This works studies the deactivation of zirconium oxide, promoted by iron and manganese catalysts (SZFM), during the α-pinene isomerization. Experiments were done in liquid phase by using a batch reactor, and the solid crystalline structure was studied by XRD while the acidity by FTIR. The deactivated catalyst exhibited coke deposits and lost its Brönsted acidity, though it still kept its crystalline structure. The nature of the coke deposit formed was analyzed by infrared spectroscopy (FTIR) as well as by Temperature Programmed Oxidation (TPO). Regeneration was done in air flow, where the temperature required to restore Brönsted acidity and to totally eliminate the coke deposits was of about 873 K.

ISOMERIZACION DE alfa-PINENO. INFLUENCIA DE LA CONCENTRACION DE HIERRO EN OXIDO DE CIRCONIO SULFATADO

Catalizadores de oxido de circonio sulfatado (SZ) conteniendo una cantidad constante de manganeso fueron promovidos con cantidades variables de hierro (SFMZ). Esos materiales se ensayaron para la obtencion de canfeno a partir de a-pineno y se caracterizaron mediante tecnicasde difraccion de rayos X (DRX), medidas de area superficial (BET), espectroscopia de infrarrojo con amoniaco adsorbido(FTIR) y la reaccion de transformacion de 2-propanol para caracterizar los sitios acidos. La adicion de Fe en la preparacion de los catalizadores, incrementa la actividad para la transformacion de a-pineno, en el rango de baja concentracion de hierro. Los resultados de la reaccion de deshidratacion de 2-propanol revelan que la acidez disminuye con el incremento en el contenido de hierro. Estos resultados indicarian que el cambio de actividad esta asociada con la acidez de los catalizadores

Dimerization of α-pinene, Using Phosphotungstic Acid Supported on SiO 2 as Catalyst

Fil: Merino, Nora Andrea. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico San Luis. Instituto de Investigaciones En Tecnologia Quimica; Argentina