Thermal behavior of oxidation of TiN and TiC nanoparticles

Titanium nitride and carbide oxidation have been studied using TG and DSC. Titanium nitride shows a oxidation behavior were both techniques detect a unique phenomenon. Titanium carbide shows a variable behavior depending on the heating rate and sample size. Low masses and heating rates provide similar results to titanium nitride. However, using moderate sample sizes and scanning rates a two-stage oxidation is observed. The first step is extremely fast and exothermic, consuming the oxygen trapped inside the nanoparticle bed. The second is controlled by the diffusion of the oxygen and CO₂ through the sample. Thermal safety conclusions are extracted from this observation. Energies of activation calculated using traditional kinetic models are lower than those found in the literature, being an indication of the influence of the specific surface of the material.     

Adiabatic Calorimetry Using Directly Agitated Test Cells

This paper explains why directly agitated test cells are sometimes required in order to obtain good adiabatic calorimetry data that can be used with confidence to predict large scale plant behaviour. Experiments for methyl methacrylate polymerisation are reported. Simple procedures are presented for calculating genuine thermo-kinetic parameters from data which includes energy dissipation from the stirrer drive system.This revised version was published online in November 2005 with corrections to the Cover Date.     

New synthesis of pyrido[2,3-d]pyrimidines. III. Nucleophilic substitution on 4-amino-2-halo and 2-amino-4-halo-5,6-dihydropyrido[2,3-d]pyrimidin-7(8H)-ones

As the third step of a new general synthesis of pyrido[2,3-d]pyrimidines, the substitution of the halogens by several nucleophiles has been carried out. Yields are between good and high in every case, even when 4-halogenated compounds have a neighbouring methyl group in C5.     

Progress in Non-parametric Kinetics

The non-parametric kinetics (NPK) method has been recently developed for the kinetic treatment of thermoanalytical data. The most significant feature of this method is its ability to provide information about the reaction kinetics without any assumptions either about the functionality of the reaction rate with the degree of conversion or the temperature. This paper presents the results of the application of the method to adiabatic calorimetry. Some data have been obtained by numerical simulation, but also the thermal decomposition of DTBP, a well known first order reaction, has been studied, being the obtained results in good agreement with literature. This revised version was published online in August 2006 with corrections to the Cover Date.     

Using sample qualification techniques to classify dsc records

The Similarity Match, Distance Match, Discriminant Analysis, Search Standards, and QC Compare Search techniques of statistical analysis are applied to DSC records in order to distinguish between two forms or classes of a new pharmaceutical active component. The classes are defined according to its therapeutic activity as 'positive' and 'negative'. Excellent results are obtained using the QC Compare Search Method. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Non-Parametric Kinetics A New Method for the Kinetic Study of Thermoanalytical Data

The application of the new method non-parametric kinetics for kinetic analysis is discussed. It is shown that this method is able to obtain all the kinetic information needed to reproduce accurately the experimental data. To validate this method a set of numerical simulations of the most commonly used kinetic models has been performed and analysed with the method. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of Activation Energies by Using Different Factors Φ in Adiabatic Calorimetry

Traditionally, the kinetic treatment of adiabatic calorimetry data has been based on the results of one or more experiments, but always with the assumption of the kinetic model that the reaction follows to calculate the kinetic parameters. In this paper a method for the determination of the activation energy that uses a set of adiabatic calorimetry data is developed. To check the method, the thermal decompositions of two peroxides were studied.This revised version was published online in November 2005 with corrections to the Cover Date.     

The estimation of reaction enthalpy for complex molecules using Benson groups</o:p>

Estimation methods developed over years by S. W. Benson and co-workers for calculation the thermodynamic properties of organic compounds in the gas phase are applied to a pharmaceutical real process with all type of non-idealities. The different strategies used to calculate the reaction enthalpy of a chemical process, in the absence of data for complex molecules, using the Benson group additivity method are presented and also compared with the experimental value of reaction enthalpy obtained using reaction calorimetry (Mettler-Toledo, RC1?). We demonstrate that there are some strategies that can be followed to obtain a good estimation of the reaction enthalpy in order to begin the safety assessment of a chemical reaction. This work is part of an industrial project [1] in which the main objective was the risk assessment of chemical real and complex processes using the commonly available tools for the SMEs (with limited resources).     

Production of macrocyclic lactones through catalytic oxidation of cyclohexanone

The aim of this work is basically centred in the improvement of the obtention of the peroxides precursors of macrocyclic lactones (C11 and C16) through the Story synthesis useful as raw materials for high performance linear polyesters. As a starting point, the yield has been increased respect to the classic synthesis using mild and intrinsically safer reactants. Concretely, a yield of 55% in triperoxide of cyclohexanone has been achieved using 35% hydrogen peroxide and phosphotungstic acid as catalyser. For this intention two factorial experimental designs, fractional and complete, have been carried out. The analytical method adequate for the reactive system studied (HPLC-UV-RI) has been chosen as well as the optimal operating conditions. A quantification of the risk on the first part of the reaction in calorimetric terms has been performed. This revised version was published online in July 2006 with corrections to the Cover Date.