Gabriela M. Tonetto

A combined theoretical and experimental study of the effects of residual chlorine on the behavior of Pd/γ-Al2O3 catalysts for methane oxidation

Abstract Studies of the methane oxidation on Pd/γ-Al 2 O 3 catalysts with and without chloride were made. The reaction was investigated at temperatures in the range 20–500°C using stoichiometric reactant mixture. Dissociation of methane and oxygen and desorption of carbon dioxide and water on Pd catalysts have been investigated using a Molecular Orbital approach of the Extended Huckel type, including repulsion terms.

NO decomposition on PdMo/γ-Al2O3 catalysts

Abstract Studies of the NO decomposition reaction on Pd/γ-Al2O3, Mo/γ-Al2O3 and PdMo/γ-Al2O3 catalysts were made. The catalytic tests revealed that the binary catalyst has different behavior for the NO decomposition, being the principal differences a longer steady state activity and an increase of oxygen evolution at elevated temperatures. Characterization by TPR, hydrogen chemisorption and FT–IR of CO indicated that palladium physicochemical properties are altered by an effective interaction with molybdenum. The results would suggest a decoration effect of Mo over Pd particle. This interaction appears to be responsible for the observed modification in NO activity and selectivity.

Synthesis of biodiesel from soybean oil using zinc layered hydroxide salts as heterogeneous catalysts

In this work, the transesterification of soybean oil with methanol using layered heterogeneous catalysts to produce biodiesel was studied. The zinc hydroxy acetate salt Zn5(OH)8(CH3COO)2·4H2O (abbreviated Zn–Ac) and the zinc hydroxy nitrate salt Zn5(OH)8(NO3)2·2H2O (abbreviated Zn–Nit), which have a layered structure, were synthesized (chemical precipitation) and characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, particle size distribution measurements, specific surface area determination and thermogravimetric analysis. Zn–Ac and Zn–Nit were tested in the transesterification of soybean oil at 100 °C for 2 h. Zn–Nit presented 83.9% oil conversion with 51.5% FAME yield, and it was stable in three consecutive tests, showing good tolerance to aqueous content. Zn–Ac was not stable. The salts transformed into Zn glycerolate at 140 °C in the reaction medium.

Kinetics of the Hydrogenation of Sunflower Oil over Alumina Supported Palladium Catalyst

The present work studies the sunflower oil hydrogenation on supported palladium catalysts, by analyzing the surface kinetics and the mass transfer limitations of products and reactants. Initially, a simplified model was studied. This model took into account only the consecutive hydrogenation of linoleic acid (diene), to reach the production of oleic (monoene) and stearic (saturated) acids. Using the adjusted values of the kinetic constants and the activation energies of the hydrogenation obtained with this model, a new scheme was investigated considering the geometric isomerization reactions (cis-trans). The diene hydrogenation constant was larger than that of the monoene. This fact confirms the higher reaction rate of the diene hydrogenation in comparison with that of the monoene. With respect to the isomerization rates, these have an activation energy superior to that of the monoene hydrogenation, and slightly superior to the diene hydrogenation activation energy. This fact verifies the influence of temperature on the formation of trans-isomers.

Burkholderia cepacia lipase: A versatile catalyst in synthesis reactions

The lipase from Burkholderia cepacia, formerly known as Pseudomonas cepacia lipase, is a commercial enzyme in both soluble and immobilized forms widely recognized for its thermal resistance and tolerance to a large number of solvents and short‐chain alcohols. The main applications of this lipase are in transesterification reactions and in the synthesis of drugs (because of the properties mentioned above). This review intends to show the features of this enzyme and some of the most relevant aspects of its use in different synthesis reactions. Also, different immobilization techniques together with the effect of various compounds on lipase activity are presented. This lipase shows important advantages over other lipases, especially in reaction media including solvents or reactions involving short‐chain alcohols.

Overall Effectiveness Factor for Slab Geometry in a Three-Phase Reaction System

Abstract The overall effectiveness factor for slab geometry applicable to uniform washcoats on a monolith surface for three-phase reaction systems was studied in the present work. Analytical solutions for zero-order reactions and Langmuir–Hinshelwood and power law kinetics were reported. The analysis of the theoretical results showed that not considering the geometry of the monolithic system in a proper way lead to 14% errors in reactions parameters when operating under mixed control (kinetic-internal diffusion) and negligible external mass-transfer resistances.

Influence of the Preparation Method and Metal Precursor Compound on Alumina-Supported Pd Catalysts

Supported palladium catalysts were prepared by two different methods: wet impregnation and incipient-wetness impregnation. Commercial gamma-Al2O3 and sol-gel derived alumina were used as support. The synthesis of alumina xerogel was carried out by hydrolysis of aluminum isopropoxide (AIP) in 2-propanol solution. Organometallic -Pd(C5H7O2)2- and inorganic precursor -Pd(NH3)4Cl2.H2O- were used for the synthesis of the catalytic systems.Samples were characterized by BET surface area measurement, atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), temperature-programmed reduction (TPR), and hydrogen chemisorption. The activity of these catalysts was studied for the stoichiometric reduction of NO by methane. The decomposition of NO and methane oxidation were also used as a test reaction. Catalyst prepared by wet impregnation method using Pd(C5H7O2)2 and alumina xerogel presented the best performance for the studied reaction. The activity of Pd/alumina catalysts for NO-CH4 reaction is related to the facility for reduction/oxidation of the metal. This property is affected by the nature of the support as well as the metal precursor.

What Problems Arise When Enzymatic Synthesis of Structured Di- and Triglycerides Is Performed?

This chapter describes the batch and continuous reactors used in structured diglyceride and triglyceride (ST) synthesis, and analyzes and discusses the several problems found in the literature and in the practical settings for the production of STs, especially when scaling to industry is considered. The problems of adsorbent use, the reaction media composition, the relative adsorption of substrates and products, the secondary contamination due to protein leaching in some immobilized systems, the perturbations introduced by the adsorbents, the main problems of enzyme inhibition or inactivation due to glycerol/fatty acids and several others are discussed in this chapter.

What Is The Importance of Structured Triglycerides and Diglycerides

This chapter reviews several important aspects of structured triglycerides (STs) and diglycerides (SDs), with the most updated literature on the topic. STs and SDs are synthesized to achieve some specific metabolic effects or to enhance physical–chemical properties of fats and oils. They comprise cocoa butter equivalents, human milk fat substitutes, low-calorie fats and oils, health-beneficial fatty acid-rich fats/oils, or diglyceride oil, and margarines or other plastic fats. A review of the metabolic fate of triglycerides and the health and nutritional properties of structured tri and diglycerides is presented.

Literature Review: What Has Been Explored About Enzymatic Synthesis of ST and SD?

This chapter focuses on the enzymatic synthesis of triglycerides and diglycerides in one or more steps. It also discusses the attempts to introduce chemical steps to reduce relative costs. The main costs in practical, industrial environments are the solvent and the enzymes. The reactions are studied in either solvent or solvent-free media, especially in the last 5 years.