High-Throughput Operando Raman–Quadrupole Mass Spectrometer (QMS) System to Screen Catalytic Systems Manuel Garcı ´a-Casado, a * Jose ´ Prieto, a,b Emilio Vico-Ruiz, Enrique Lozano-Diz, Consuelo Goberna-Selma, a,b Miguel A. Ban ˜ ares a * a Instituto de Cata ´lisis y Petroleoquı´mica, CSIC, Marie Curie, 2; E-28049-Madrid, Spain b PID Eng. & Tech. Plomo, 15-Pol.Ind.Sur; E-28770 Colmenar Viejo-Madrid, Spain This paper describes the design and setup of a high-throughput Raman system for an array of eight parallel catalytic reactors during reaction conditions. The ‘‘operando’’ methodology com- bines in situ spectroscopy during catalytic reaction with a simultaneous activity measurement. The high-throughput operan- do Raman system, multi-operando, is a device that automates this operando methodology for several catalyst samples at the same time, all samples being in the same reaction conditions. We describe how the system is made, how Raman system positions and acquires spectra, and how each reactor outlet gas is selected and analyzed. Index Headings: Raman; Catalysis; In situ; Operando; High through- put; Supported oxides; Vanadia; Alkali dopant. INTRODUCTION Developments in the chemical industry stand on catalysis. Ninety percent of industrial chemical process- es involve a catalyst. Finding a catalyst for a particular reaction is a challenge. Some decades ago, catalysts were discovered by trial-and-error processes. Catalysts have traditionally been studied before (fresh) or after (aged) reaction. The structure of catalysts may not be the same after chemical reaction than before; the catalyti- cally relevant structure is the one during reactions. Several spectroscopic techniques can be used to characterize a catalyst, depending on the impinging photons and whether this is a single-photon event or a two-photon event. Raman, ultraviolet-visible (UV-Vis), infrared (IR), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and synchrotron-based methodolo- gies are used for in situ studies. Spectroscopic studies may approach reactive and catalytic reality at several levels: (a) in situ studies— the use of spectroscopy when the catalyst is under controlled conditions provides information about the state of the catalyst and that of adsorbed molecules at given temperatures and pressures; (b) Variable-condi- tions in situ studies—in these, a parameter is changed (gas composition, pH, temperature, pressure), and spectroscopy monitors changes on the material and of the adsorbed molecules. An added value of these studies is that online techniques may analyze the effluents from the cell to assess the reactive properties of the material. This is particularly interesting, among other, for the temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), or tempera- ture-programmed decomposition (TPD) of adsorbed probe molecules. For an accurate online analysis, it is critical that the sample characteristics (e.g. powder, pressed wafer, shaped, gauze or microreactor, config- uration, particle size) and reactor characteristics (no void volume, no temperature or pressure gradient, among others) are such that the activity reading is meaningful. A final extrapolation of reactive environ- ments is for (c) operando studies, in which the sample is analyzed while working. ‘‘Operando’’ is Latin for ‘‘work- ing.’’ In such a methodology, it is critical to acquire reliable catalytic data (e.g. conversion, selectivity, or activation energies). Therefore, if we make sure that the in situ cell is designed to meet not only spectroscopic requirements but also those of a catalytic reactor, we have an operando cell. 1–7 The operando technique allows broadening knowledge in the molecular struc- ture-activity relationships. 8–23 High-throughput combinatorial methodologies have delivered new catalyst formulations. 24–26 These produce libraries of catalysts for their chemical reactions that have been obtained by methods such as resonance- enhanced multi-photon ionization (REMPI), 27 infrared thermography (IRT), or mass-spectra sampling, but these methods do not allow for the individual monitoring of each catalyst, since all samples are under the same atmosphere. The above-mentioned operando method allows studying of a catalyst sample at each time separately. The significant progress of catalytic perfor- mance screening has its reflection in spectroscopic studies. The increasing growth in the use of parallel screening in microstructured reactors is the prelude to the development of high-throughput multi-operando systems, which would permit a knowledge-based dis- covery of catalysts. There has been major progress in the area of X-ray absorption; Sankar et al. 28 published the design of a microstructured reactor cell for X-ray absorption fine structure (XAFS), which was fabricated by photolithography. The design consisted of a single 8 mm-deep and 120 mm-wide microchannel. The catalyst was a silver film coated on the reaction channel, and the reactor was sealed with a glass cover with inlet and outlet holes. It was used for an extended X-ray absorption fine structure (EXAFS) study of the Ag K- edge during methanol oxidation to formaldehyde. Grun- waldt et al. 29 combined a microreactor array with an X- ray camera to record the XAFS spectra of ten catalysts simultaneously. Thus, operando techniques may be Received 11 July 2013; accepted 3 October 2013. * Authors to whom correspondence should be sent. E-mail: mgac@icp. csic.es, miguel.banares@csic.es. DOI: 10.1366/13-07212 Volume 68, Number 1, 2014 APPLIED SPECTROSCOPY 69 0003-7028/14/6801-0069/0 Q 2014 Society for Applied Spectroscopy