Desktop Molecular Modeling Help in Clarifying Odd Experimental Observations on Zeolites and Silica Gels

2012 Spring Symposium

Istvan Halasz
PQ Corporation

Abstract – Zeolites and amorphous silica gels are widely used in adsorption and catalysis. PQ commercializes silica based materials by tailoring them to specific customer needs worldwide. These modifications usually require series of material tests which mostly carried out at the company’s R&D Center where I have been assigned to investigate the porosity, acidity, sorption capacity, activity and other targeted properties of experimental and commercial products. Sometimes these experiments lead to unexpected, surprising, contradictory results which usually generate various speculative explanations. In this presentation I’ll illustrate through a few examples how molecular modeling can help in resolving conflicts between ideas and empirical findings. I intend to show that the commonly available computer power and modeling programs have developed so much during the past few years that even an experimentalist with limited resources and theoretical background can mimic various empirical data which is the basis to understanding material properties at the molecular level. It will be also shown how computer chemistry can lead to improved quantification of otherwise routinely measured molecular spectroscopic data. The presented examples will include model calculations based on force field related Monte Carlo algorithm, time dependent density functional theory, and a combination of quantum mechanical/molecular mechanical methods. Simulated experimental sorption isotherms and FTUV spectra of two hydrophobic zeolites will be presented to explain their unusual sorption properties and redox catalytic activities. Moreover, we compare the model and experimental FTIR and laser Raman spectra of some amorphous silicates and present the first experimental proof that silica gels obtained from aqueous alkaline silicate solutions or tetra-ethyl-orthosilicate at acidic or basic conditions can have distinct molecular structures which affect their final physical properties.

Speaker’s Biography – Istvan obtained a physics and chemistry teacher diploma from the Lajos Kossuth University, Hungary. Later he was awarded magna cum laude doctorate degree from the same university and a higher degree from the Hungarian Academy of Sciences, HAS. Following three years of teaching physical chemistry, he joined the Hungarian Hydrocarbon Institute, where he developed new, economic processes for pharmaceutical, fine chemical and petrochemical plants and studied the fundamentals of acid-base catalysis over metal oxides. As a young scientist he won several competitive awards and a research scholarship for the University of Technology in Vienna, Austria. After 12 years of industrial research, he moved to the Chemical Research Institute of HAS where his major research topics included shape selective catalysis on zeolites and synthesis of high temperature ceramic superconductors. Istvan also worked as postdoctoral researcher at Wayne State University and University of Iowa, focusing mainly on the catalytic abatement of automobile exhausts and industrial stack gases. He joined PQ nearly 14 years ago. He has been member of several scientific organizations and currently serves as president of NECZA (North East Corridor Zeolite Association). Istvan has authored and co-authored more than 180 publications.