Siris Laursen

Geometric and electronic characteristics of active sites on TiO2-supported Au nano-catalysts: insights from first principles.

Quantum chemical and ab initio thermodynamic calculations were used to investigate the mechanism of CO oxidation on Au/TiO(2) and the geometric and electronic character of active sites. We show that CO oxidation over Au/TiO(2) might proceed via a two site mechanism with oxygen adsorbing and dissociating at the Au/oxide interface or the perimeter of Au particles and CO adsorbing on Au sites away from the interface. The electronic fingerprint of active Au is a function of external conditions, and it is likely that most Au atoms are populated by CO and electronically neutral. Under highly oxidizing conditions, the Au/oxide interface can accommodate oxygen adsorbates, and these Au atoms will have a cationic fingerprint due to their interaction with oxygen. The choice of precursors used to synthesize catalysts as well as the catalyst preparation and pretreatment procedures significantly affect the electronic characteristics and catalytic activity of Au nano-structures. Based on our first-principles analysis we propose a hypothesis that might help us understand these experimental observations.

Dynamic hybrid neural network model of an industrial fed-batch fermentation process to produce foreign protein

An industrial pharmaceutical company has provided industrial pilot scale fed-batch data from a biological process used to produce a foreign protein from fed-batch fermentation. This process had proven difficult to control due to the complex behavior of the bacteria after induction. Because of the difficulty of modeling the process fundamentally, neural networks are an attractive alternative. To capture dynamic systems a gray box model approach of parameter function neural networks was used. The parameter function neural network approach has been able to capture well this pilot scale fed-batch fermentation process. In order to obtain accurate training data, the data sets were fit and smoothed using smoothing cubic spline functions. Neural networks were found for the five critical parameter functions of growth rate, glucose consumption rate, oxygen consumption rate, acetate production rate, and protein production rate. Relatively simple networks were used in order to capture process behavior and not the significant noise in the industrial scale pilot data. Simulations using the neural network parameters predicted dynamic response data well.

First‐Principles Design of Highly Active and Selective Catalysts for Phosgene‐Free Synthesis of Aromatic Polyurethanes

We thank the Generalitat Valenciana (GV/2009/063 and PROM-ETEO 2088/130) and the Spanish MICINN (MAT2011-28009, and Consolider Ingenio 2010-MULTICAT: CSD2009-00050) for financial support. We thank Red Espanola de Supercomputacion (RES) for computational resources. D.C. thanks Spanish MICINN for a postgraduate scholarship, and S.L. thanks ITQ for a post-doctoral fellowship.

Photo- and Electro-Catalysis: CO2 Mitigation Technologies

Abstract The replacement of fossil fuels by clean and renewable energy sources is one of the major challenges for modern human civilization. The photo- and electro-catalytic conversion of CO 2 to value-added chemicals and fuels is an attractive processes to address both energy and environmental issues. Here we present an overview of photo- and electro-catalytic conversion of CO 2 to useful chemicals. We aim to provide a comprehensive picture of the scientific and technological challenges inherent to the transformation of CO 2 . Specifically, we focus on the difficulty in activating the thermochemically stable CO 2 molecule, complex reaction mechanisms that involve multiple electron transfer steps, catalyst stability, high overpotential and efficiency losses encountered in electrocatalytic processes, low conversion rates, and many other topics.The replacement of fossil fuels by clean and renewable energy sources is one of the major challenges for modern human civilization. The photo- and electro-catalytic conversion of CO2 to value-added chemicals and fuels is an attractive processes to address both energy and environmental issues. Here we present an overview of photo- and electro-catalytic conversion of CO2 to useful chemicals. We aim to provide a comprehensive picture of the scientific and technological challenges inherent to the transformation of CO2. Specifically, we focus on the difficulty in activating the thermochemically stable CO2 molecule, complex reaction mechanisms that involve multiple electron transfer steps, catalyst stability, high overpotential and efficiency losses encountered in electrocatalytic processes, low conversion rates, and many other topics.