Chimiométrie

La chimiométrie est l'application d'outils mathématiques, en particulier statistiques, pour obtenir le maximum d'informations à partir de données chimiques. La chimiométrie est une discipline très appliquée. Son objectif est d'améliorer le contrôle et l'optimisation des procédés ainsi que la qualité des produits fabriqués. Son développement a été fortement accéléré par celui de la spectrométrie proche infrarouge dans les laboratoires de chimie analytique. La chimiométrie se distingue des statistiques par le fait que :

les statistiques requièrent que des hypothèses soient vérifiées a priori. Par exemple on vérifie l’indépendance et la distribution des variables avant de réaliser une régression linéaire ;
la chimiométrie néglige ces précautions, car elles sont irréalisables sur les données qu’elle traite, mais procède à des vérifications a posteriori, sur la qualité des structures construites ou sur les performances des modèles.

La chimiométrie regroupe notamment :

les méthode

Analysis and Removal of Product Gas Contaminants Present in Gasification Processes

Sven Philip Edinger

Energy demand and economic development are intrinsically linked. Earlier economic development came at the price of serious environmental pollution, posing a risk to life on earth. Thus, a transition from fossil to renewable energy is needed. Among the renewable energy technologies, gasification of biomass promises high process efficiency and flexibility concerning the feedstock and products. In such a process, gas contaminants have to be removed to protect downstream equipment and the environment. Finding an optimal configuration of process steps in gas cleanup chains, offering reliability, availability and high efficiency at low operating and capital costs is still a challenge and one of the major hurdles for commercial deployment of biomass gasification processes. This thesis aimed to investigate the gas cleanup chain as part of gasification processes. Two aspects, the analysis of gas contaminants and their elimination, were examined. At first, three analytical methods, aimed at the detection of sulphur containing hydrocarbons, tars and trace elements, were developed. In the next step, these analytical tools were employed to investigate the performance of gas cleanup units, intended for the removal of the sulphur containing hydrocarbon thiophene, tars and the trace element Se. The removal of thiophene by activated carbons (AC) was explored experimentally and theoretically. Experiments were performed in a packed bed column between 100-200°C. The adsorption process was described by a 1D approach, including mass transfer phenomena and axial dispersion. Experimental validation showed good agreement between measured and predicted breakthrough times and capacities. A global sensitivity analysis (GSA) was performed to rank the importance of model input factors and gain further process insight. The work showed that ACs are a promising option for thiophene removal and provided a generic approach for the application of GSA to adsorption models. In this context, the analysis demonstrated that the selection of common model assumptions deserves as much attention as the model parameters. Further work chapter aimed at understanding the effect of H2O, H2 and H2S on the decomposition of thiophene over CaO. Experiments were performed in a fixed bed reactor at 810°C. The factors were varied as part of a full factorial design at two levels. Results were fitted to a linear model with interactions. Analysis showed that H2O and H2S had a major effect on thiophene conversion, while that of H2 was less pronounced. Interactions between varied factors were found to be negligible. A UV-Vis method was developed to obtain online information on tar compound concentrations in real process gases in the low ppmv region. Spectra were analysed for their tar composition by two chemometric approaches. Applied to two case studies, the developed tool proved to be a rapid, sensitive tool, applicable to qualitative process monitoring with the added benefit of quantification in gases with a limited number of tar compounds. An ICP-MS was employed as a tool for the online detection of trace elements. The low detection limits (< 2 ppbv for H2Se, PH3; < 0.1 ppbv for AsH3; < 0.01 ppbv for Hg) and the high temporal resolution render this method a quick and robust tool for the performance evaluation of sorbent materials. A case study investigated the capture of H2Se by a Zn/Al2O3 sorbent between 150-350°C.

EPFL2017

A thorough investigation of photo-catalytic degradation of ortho and para-nitro phenols in binary mixtures: new insights into evaluating degradation progress using chemometrics approaches

Sayyed Hashem Sajjadi

In this study, photocatalytic degradation of 2-nitrophenol and 4-nitrophenol were carried out efficiently using ZnO nanoparticles photo-catalyst under simulated solar irradiation. The photo-decomposition processes were optimized simultaneously by employing central composite design and multivariate curve resolution alternating least squares. The effective factors were as follows: the amount of the nano-photo-catalyst, the concentration of 2-NP and 4-NP, the volume of H2O2 and temperature. Since both analytes have acid-base properties, the pH-dependency of the kinetic processes were investigated by conducting each experiment under both acidic and basic conditions, where only the protonated or deprotonated forms of the analytes were present in the solution. Each experiment was monitored spectrophotometrically and then suitable chemometrics approaches were applied to the data to discover underlying photo-decomposition reactions. A new and simple criterion based on the standard deviation of a kinetic profile was proposed as a degradation index for quantifying the progress of nitrophenols decomposition processes and considered as a response in the experimental design analysis. The results revealed that acidic and basic forms of both nitrophenols were involved in three-step consecutive reactions during degradations, but the kinetic rate constants of the processes were really different, a fact, which resulted in different optimal conditions for acid and basic media.

ROYAL SOC CHEMISTRY2021

Analysis and Removal of Product Gas Contaminants Present in Gasification Processes

Sven Philip Edinger

EPFL2017

Analysis and Removal of Product Gas Contaminants Present in Gasification Processes

On the Number of Observable Species, Observable Reactions and Observable Fluxes in Chemometric Studies and the Role of Multichannel Integration

A thorough investigation of photo-catalytic degradation of ortho and para-nitro phenols in binary mixtures: new insights into evaluating degradation progress using chemometrics approaches

On the Number of Observable Species, Observable Reactions and Observable Fluxes in Chemometric Studies and the Role of Multichannel Integration

A thorough investigation of photo-catalytic degradation of ortho and para-nitro phenols in binary mixtures: new insights into evaluating degradation progress using chemometrics approaches

Analysis and Removal of Product Gas Contaminants Present in Gasification Processes