Commercial humic acid (HA) was anchored onto silica gel (SiAPTS) previously modified with 3-aminopropyltrimethoxysilane (APTS).
HA was anchored onto SiAPTS through two routes: adsorption and covalent chemical immobilization onto the surface. The adsorption
occurred by adding SiAPTS to HA in an aqueous solution, producing SiHA1, while chemical immobilization was performed by reacting
HA suspended in N,N-dimethylformamide with SiAPTS, to yield SiHA2. The infrared spectra confirm HA immobilization using both
procedures and the termogravimetric results showed that the anchored compounds have significantly thermal stability increased.
While natural HA presents a thermal stability up to 200C, the anchored compound presents a thermal stability near to 750C.
Authors:J. Sempere, R. Nomen, E. Serra, and J. Sales
A small scale (100 mL) calorimeter is developed. It includes a glass vessel submerged in a thermostatic bath, a compensation
electrical heater, and a control system. The typical operation mode consists on introducing the solvents and part of the reactants
into the vessel, to stabilise a temperature of the bath (Tj) some degrees below the desired process temperature (Tp) and to adjust the reaction mass temperature (Tr) to Tp using the electrical heater. An oscillating set point is established for Tr, which produces an oscillating response of the
applied compensation power (Qc). Finally, the rest of reactants are dosed to the vessel. A small deviation of Tr and Tp is observed. Even though it can be avoided improving the tuning of the controller, it can be useful for enhancing the calculation
of the heat capacity of the reaction mixture (CP). The signals of Tr, Qc and Tj are processed on-line using the FFT (Fast Fourier Transform) method as the mathematical tool used to analyse the data obtained,
producing accurate values of the heat evolved (Qc) by the process, the heat transfer coefficient (UA), and the heat capacity of the reaction mixture (CP).
Authors:R. Nomen, M. Bartra, J. Sempere, E. Serra, J. Sales, and X. Romero
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  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).