Chemicals case study
Scientists at the Dow Chemical Company in collaboration with the University of Utrecht in the
Netherlands and the Technical University of Munich in Germany studied the properties and
activity of the lanthanum-based catalysts: La2O3, LaOCl, LaCl3, and lanthanum phases with an
intermediate extent of chlorination. These materials are used as components in the formulation
of commercial catalysts or studied as potential catalysts for such processes as oxidative
methane coupling, oxidative dehydrogenation of ethane, oxidative chlorination of methane,
decomposition of chloromethane and conversion of ethane and ethylene to vinyl chloride. The
work illustrates how experimental and computational results complement each other; how
computation can provide results that are inaccessible to experiment; and ultimately provides
information on reaction mechanisms that can be used to design improved commercial catalysts.
Reporting in the scientific literature,1,2,3 the researchers studied the decomposition
of chloromethanes, such as CCl4, to carbon oxides over the lanthanum materials. This
reaction can proceed non-catalytically with a gradual conversion of La2O3 to LaOCl and,
eventually, to LaCl3 through diffusion of oxygen atoms from the bulk into the surface
together with the reverse diffusion of chlorine atoms. The reported results suggest that
the reaction can be run catalytically, i.e., a catalytic cycle can be constructed if the surface
of the lanthanum materials is dechlorinated with steam.
Spectroscopic measurements were used for evaluating the surface composition at various
stages of the reaction and also for characterizing acid and base surface sites using multiple
probe molecules, including CO and CO2. The scientists used Materials Studio’s density
functional theory (DFT) code DMol3 to evaluate the modes of adsorption for CO and CO2.
on the different surfaces (some representative examples are shown in Figure 1). Theoretical
frequencies for optimized CO, CO2 and OH surface structu