Infrared flow-reactor cell

Fig. 9. Infrared flow-reactor cell for in-situ measurements of, e.g., activation, reaction and diffusion [149,158]...

In this paper, we analyze these aspects in more detail combining data from flow reactor studies, infrared studies in a flow reactor cell and results obtained in a high-speed transient micrcu eactor coupled with a mass quadrupole detector (TAP - Temporal Analysis of Products - Reactor). Furthermore, we show and discuss how it is possible to limit and control these effects of deactivation by the addition of SO during Q-Cs alkane oxidation. 

In Table I the high-vacuum (HV) range means a pressure of 10 to 10 Torr entries designated by Torr mean pressures between 0.1 and 10 Torr flow refers to an unspecified steady-state flow pattern. It is apparent from Table I that there is a great diversity in the different oscillation conditions and catalytic systems. The pressures under which oscillations have been observed vary from 10 Torr for the CO/NO reaction on Pt(lOO) 141, 142) to atmospheric pressure for a large number of systems. The reactors used in these studies include ultrahigh-vacuum (UHV) systems, continuous stirred tank reactors (CSTRs), flow reactors, and reactors designed as infrared (IR) cells, calorimeters, and ellipsometric systems. 

Temporal analysis of products (TAP) and flow reactor catalytic measurements were done as reported elsewhere (2,4,8,121. Fourier-transform infrared (ET-IR) studies were carried out using a Perkin Elmer 1750 instrument and a flow reactor infnued cell connected to conventional vacuum... 

Reaction studies were carried out in a specially designed infrared cell which doubled as a flow reactor [10]. Before a given experiment, the catalyst was pressed into the form of a thin wafer, placed into the reactor cell, and reduced at 200-450°C for twenty hours. The catalyst was then run to steady-state in 3.4% CO and 0.8% NO for sixteen hours before any steady-state data were obtained. All data were obtained under differential reactor conditions and analysis of the feed and product gases was accomplished using an automated gas chromatographic system [11],... 

In-situ Infrared study of DMC, MPC and DMPD syntheses DMC, MPC and DMPD syntheses were studied in an in situ IR cell which was capable of operating up to 30 MPa. The solid catalyst sample was pressed into a self-support disk and placed between two Cap2 rods in the transmission IR cell. Table 1 lists reaction conditions for these synthesis reactions. Liquid reactant mixture (0.2 cm ) was brought into the IR cell by injection into a known amount of gaseous reactants flowing into the reactor cell. For the DMPD synthesis, the liquid reactant mixture was brought into IR cell via helium flow as a carrier. The... 

RTD experiments showed that the fixed-bed almost behaves like a plug-flow reactor and the infrared cell like a continuous stirred tank reactor. This fixed-bed is described by the tanks-in-series model, using 9 tanks for the catalyst compartment. The two kinetic models (Equations 1-6) are able to describe the stop-effect experiments at 180 and 200°C, and the considerations made in this work are valid for both temperatures. However, for the sake of clarity, only model discrimination at 180°C will be presented here. In the experimental conditions used here, both models can be simplified the first adsorption step is considered as irreversible, and instantaneous equilibrium is assumed for the second one. With these hypothesis the total number of kinetic parameters is reduced from five (ki, Li, k2, k.2 and ks) to three (ki, K2 and ks), and the models can be expressed as follows ... 

IR-spectroscopy was performed with Specord-JR-75. Infrared spectra were recorded after the CO adsorption (T=298K) and after CO+H2 reaction (P=0.1 MPa, T=200 C, experiment time is 30-120 minutes) over 10%Co-Pt/Al203 catalysts, using a conventional KBr cell combined with a flow reactor at room temperature in the wave number range of 1300-2400 cm. ... 

The experimental set-up is given in figure 6. A closed reactor-detector system was used to enable detection of small mole fluxes. The stirred cell reactor is 0.10 m in diameter and was filled before each experiment with 120 ml of charged 2.0 M DIPA solution. The gas phase in the system was circulated by means of a flexible tube pump over a flow-through cell in a Perkin Elmer model 257 Infrared Grating Spectrophotometer for CO2 detection. Although spectrophotometers are not exceptionally well-suited for quantitative measurements, we preferred this type of analysis compared to gas chromatography for example because it does not influence the gas phase. 

Transmission infrared spectra of pressed disks ( 14 mg) of Pt/SiOj were collected in situ and under operando conditions in an IR reactor-cell placed in an FTIR spectrometer (Mattson, Galaxy 6020) at a resolution of 2 cm" and 30 scans/spec-trum. The IR cell is equipped with NaCl windows, and it has connections for inlet and outlet flows, and thermocouples connected to a temperature controller to monitor and control its temperature. The spectra were obtained in absorbance mode after subtraction of the background spectrum of the catalyst s disk under He atmosphere at the corresponding temperature. The samples were pretreated at various conditions prior to study CO adsorption and reaction. During CO oxidation experiments, 10% O2 was added to the 1% CO-He feed. In most experiments, the heating rate was l°C/min with a total flow of 120 cc/min unless indicated otherwise. 

Although acetone was a major product, it was not observed by infrared spectroscopy. Flowing helium/acetone over the catalyst at room temperature gave a prominent carbonyl band at 1723 cm 1 (not show here). In this study, a DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) cell was placed in front of a fixed reactor DRIFTS only monitored the adsorbed and gaseous species in the front end of the catalyst bed. The absence of acetone s carbonyl IR band in Figure 3 and its presence in the reactor effluent suggest the following possibilities (i) acetone formation from partial oxidation is slower than epoxidation to form PO and/or (ii) acetone is produced from a secondary reaction of PO. 

Hydroformylation reaction. Styrene hydroformylation was carried out in an in situ high pressure infrared (IR) cell at a total pressure of 0.83 MPa. 0.1 g catalyst was pressed into a self-support disk and placed inside the IR cell. The reactor was heated up to the desired temperature and 0.2 ml styrene was injected slowly into the cell in the CO and H2 flow [CO/H2 (v/v) =1/1, total flow rate = 30 ml/min] to give a reactants molar ratio of CO H2 styrene = 1 1 1148. The reactor was pressurized to 0.83 MPa and the reaction was carried out in a batch mode. The IR spectra were collected during the entire course of reaction studies by a Nicolet MAGNA 550 Series II Fourier transform infrared spectrometer... 

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