Paramagnetic detectors

Before performing TPO, the wet catalyst was dried under N2 flowing 10 Fh at 120°C for a period of 17 h before being slowly cooled to 20°C. Once the catalyst was stabilized at 20°C the pure N2 was switched to a 4 vol.% O2 in N2 mixture flowing at 10 1/h while the catalyst s temperature was ramped to 800°C at the rate of 8°/min. The O2 content of the gas mixture leaving the catalyst bed was measured by an Oxynos 100 paramagnetic detector and plotted with respect to either time or temperature. The plot of the vol.% O2 with respect to time was used to determine the O2 consumption of the catalyst. 

Nondispersive infrared analyzer, on-line Paramagnetic detector, on-line... 

On-line analysis was perfonned for the hydrocarbons by a flame ioniziation detector, for CO, N2O and CO2 by NDIR-detectors, for NO, NO2 and NOx by a chemuluminescence detector and for O2 by a paramagnetic detector. Except for the O2 detector, all sample lines were heated to > 120°C to avoid condensation of the exhaust gas components. The amount of N2 formed by the reaction was calculated from the mass balance. A detailed list of the on-line analyzers used is given in Table 3. 

The Scatchard formalism can of course be applied to the binding of any small molecule to any biomacromolecule, such as the binding of a substrate or inhibitor to an enzyme, or the binding of a metal ion to an apoprotein. In receptor research, the determination of Kd typically requires labeling of the substrate by radioactivity or by fluorescence. However, we might just as well choose paramagnetism as the label, and this then makes the EPR spectrometer the detector for the determination of binding equilibria. The Scatchard plot in Equation 13.4 has two experimental observables [L] and [RL], and so we must find ways to determine these quantities from EPR spectra. 

Several methods have been developed to estimate the exposure to such emissions. Most methods are based on either ambient air quality surveys or emission modeling. Exposure to other components of diesel emissions, such as PAHs, is also higher in occupational settings than it is in ambient environments. The principles of the techniques most often used in exhaust gas analysis include infrared (NDIR and FTIR), chemiluminescence, flame ionization detector (FID and fast FID), and paramagnetic methods. 

Gas analysers 02-paramagnetic, C02-Non-dispersive infra-red (NDIR), CO-NDIR, SO2-NDIR, CxHy-Flame Ionization Detector (FID), and NOx-Chemiluminescence. 

In the analysis section, CH4, CO and CO2 concentrations are monitored with an online NDIR multiple analyzer (Advance Optima, Uras 14). For the analysis of O2 a continuous paramagnetic analyzer (Advance Optima, Magnos 106) is employed H2 is analyzed with a thermal conductivity detector (Advance Optima, Caldos 17). An analog-digital board (National Instruments, AT-M lO 64E) allows... 

As a special feature the PAS detector can be combined with a magneto-acoustic detector (MA) for the measurement of oxygen (02). Oxygen does not absorb IR light but it is paramagnetic. This means that if a switched magnetic field is applied... 

As was shown in Figure 3.159, cryogenic temperatures can be detected by integrated circuit diodes types K, T, and E thermocouples (TCs) class A and B resistance temperature detectors (RTDs) acoustic and ultrasonic thermometers germanium and carbon resistors and paramagnetic salts. As TCs and RTDs will be discussed in separate subsections, here the focus will be on the other sensors. 

Materials with very narrow ESR lines (AHpp < 20 mG) can be used as small-volume and low-power magnetic sensors of great sensitivity. Such devices would have applications as submarine mine detectors, local terrestrial magnetic field detectors [65,66], and for the identification of objects with an added suitable paramagnetic substance [67]. 

The concentrations of 2, CO2, CO, NO and NO and THC were measured in two positions in the boiler, 0.1 m upstream and 1.5 m downstream of the catalyst. Oxygen was measured with a paramagnetic instrument (M C PMA25), CO and CO2 with IR (Leybold-Heraeus Binos 1,2 and Rosemount NGA 2000), NO and NO2 with UV/IR (Rosemount NGA 2000) and THC using a FID (Flame Ionisation Detector, Rosemount Termo-FID). The FID was calibrated using methane. 

Note Key CL = chemiluminescent EC = electro-chemical FID = flame ionization detector GC = gas chromatograph HC = hydrocarbons IR = nondispersive infrared LA = line absorption Para. = paramagnetic RS = Raman spectroscopy. 

There are a few common methods of measuring oxygen concentration in the gas phase. Electrochemical sensors and paramagnetic sensors are typically used to measure oxygen concentration on a wet and dry basis, respectively. Carbon monoxide (CO) is most commonly measured using a nondispersive infrared technique. A gas sample flows between an infrared radiation source and an infrared detector. Carbon monoxide absorbs infrared radiation, hence the difference in intensity proportional to the concentration of CO in the gas sample. 

A typical gas arriving at the catalyst face contained 2.5% CO, 1000 ppm HC, 500 ppm NO, 3% 02, and 0.48 g Pb/hr (as tetraethyllead). Catalyst inlet and exit gas samples were monitored for HC by flame ionization detector, for CO by nondispersive IR analyzer, and for 02 by paramagnetic analyzer. The effect of the TEL poison on catalyst activity was monitored by measuring the decrease in CO and HC conversion levels. 

Catalyst activity was usually measured in a bench test assembly (Figure 1). The reactor included a preheat section containing tabular alumina just above (upstream from) the 30 cm3 of catalyst in the center of the reactor. Water was pumped by a minipump (Milton-Roy) to the steam generator. From a three-temperature profile around the catalyst bed, it was determined that the midpoint data were most useful and reliable. The analytical equipment consisted of an infrared device (Mine Safety Appliances) for carbon monoxide, a flame ionization detector (Beckman) for hydrocarbons, and a paramagnetic oxygen analyzer (Beckman). The entire assembly except for Telex printer and computer is pictured in Figure 2. 

For analysis, CO, HC and CO2 were measured using infrared detectors, NO by chemihuninescence, and O2 by paramagnetism. 

A zeolite with MFI structure was synthesised with 3 different amounts of niobium ammonium complex (NAC) in the reaction mixture. The samples obtained were characterised by scanning electron microscopy (SEM) using secondary electron detector and energy dispersive spectrum (EDS) detector, X-ray diffraction (XRD), differential thermal analysis (DTA), and electron paramagnetic resonance (EPR). The increase of NAC in the reaction mixture results in the decrease of the crystal size of the zeolite. The characterisation shows evidence that the niobium was incorporated into MFI structure. 

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