Detectors catalytic reactions

Hall electrolytic emission Other Detectors Catalytic reaction to S, N, X 27... 

Although as yet seemingly restricted to above ca. 1500 cm 1 by the limited availability of tuneable infrared detectors, this technique also virtually eliminates gas-phase contributions to spectra. The pulsed lasers used also open up the possibilities of fast (nanosecond or less) kinetic studies of catalytic reactions. 

TPR of the samples in flowing He or H2 were performed in a Pyrex flow system which was also used for catalytic reactions. Acid properties of the samples were probed by TPD of NH3 preadsorbed at RT. The analysis of gaseous products was made by an on-line mass spectrometer or a thermal conductivity detector. Reactions of n-hexane in the presence of excess H2 were carried out at 623 K and atmospheric pressure. A saturator immersed in a constant temperature bath at 273 K was used to produce a reacting mixture of 6% n-hexane in H2. Reaction products were analyzed by an online gas chromatograph (HP-5890A) equipped with a flame ionization detector and an AT-1 (Alltech) capillary column. 

Catalytic reactions were carried out with 2 g catalyst placed in a fixed-bed continuous-flow reactor at the gas space velocity (F/W) of 1440 ml/g h under the reaction pressure of 200 KPa. The products were withdrawn periodically from the outlet of the reactor and analyzed by gas chromatography with a 4 m long squalane column and detected by a hydrogen flame ionization detector. The conversion and selectivity were calculated on the carbon number basis. 

The catalytic reaction was performed in a fixed bed flow glass reactor. A gas mixture of CO2 and H2 (1 4, volume ratio) was passed continuously on the catalyst with F/W = 5400 ml g- h-i, unless otherwise mentioned. After the reaction the gas mixture was analyzed using a Chrompac MicroGC CP2002 gas chromatograph equipped with a thermal conductivity detector. 

Vanadium molecular size distributions in residual oils are measured by size exclusion chromatography with an inductively coupled plasma detector (SEC-ICP). These distributions are then used as input for a reactor model which incorporates reaction and diffusion in cylindrical particles to calculate catalyst activity, product vanadium size distributions, and catalyst deactivation. Both catalytic and non-catalytic reactions are needed to explain the product size distribution of the vanadium-containing molecules. Metal distribution parameters calculated from the model compare well with experimental values determined by electron microprobe analysis, Modelling with feed molecular size distributions instead of an average molecular size results in predictions of shorter catalyst life at high conversion and longer catalyst life at low conversions. 

The catalytic reactions were carried out in a catalytic flow microreactor at atmosheric pressure and various temperatures. The catal ic bed (Ig) was covered by silica. TTie reaction conditions were the following the oil (40(wt%) in cyclohexane) was introduced with a flow of 0.12 mkmin l simultaneoulsy with hydrogen (flow = 20 mIxmin H. After evaporation of the solvant, the products were successively treated by sodium methoxide, methanol and sulfuric acid to obtain the free-esters before analysis. The final products were analysed by gas chromatography with a flame ionization detector and AT-FILAR (Altech) capillary column (30m, I.d = 0.32 pm, film thickness = 0.25 pm) at 140 C. 

Catalytic Reaction. A bead or wire is coated with a catalytic material so that it reacts with atarget gas. As the reaction on the catalyzed surface takes place, the bead or wire heats up, and changes its resistance. This resistance change can be proportionally related to the target gas concentration. An example of a catalytic bead detector is a sensor that consists oftwo beads placed in a wheatstone bridge circuit. One of the beads acts as a... 

The strategy which is employed in order to get the above mentioned features of catalysts active sites is the adsorption of appropriate gas phase probe, under the specific experimental conditions (that are chosen in a way to be similar to those applied in the particular catalytic reaction), followed by subsequent desorption, monitored with appropriate detector. One experiment, in which the characterisation of acid/base properties of solid material is performed, is designed as follows ... 

Catalytic activity for the selective oxidation of H2S was tested by a continuous flow reaction in a fixed-bed quartz tube reactor with 0.5 inch inside diameter. Gaseous H2S, O2, H2, CO, CO2 and N2 were used without further purification. Water vapor (H2O) was introduced by passing N2 through a saturator. Reaction test was conducted at a pressure of 101 kPa and in the temperature range of 150 to 300 °C on a 0.6 gram catalyst sample. Gas flow rates were controlled by a mass flow controller (Brooks, 5850 TR) and the gas compositions were analyzed by an on-line gas chromotograph equipped with a chromosil 310 coliunn and a thermal conductivity detector. 

The catalytic reforming of CH4 by CO2 was carried out in a conventional fixed bed reactor system. Flow rates of reactants were controlled by mass flow controllers [Bronkhorst HI-TEC Co.]. The reactor, with an inner diameter of 0.007 m, was heated in an electric furnace. The reaction temperatoe was controlled by a PID temperature controller and was monitored by a separated thermocouple placed in the catalyst bed. The effluent gases were analyzed by an online GC [Hewlett Packard Co., HP-6890 Series II] equipped with a thermal conductivity detector (TCD) and carbosphere column (0.0032 m O.D. and 2.5 m length, 80/100 meshes), and identified by a GC/MS [Hewlett Packard Co., 5890/5971] equipped with an HP-1 capillary column (0.0002 m O.D. and 50 m length). 

The cracking of diphenylmethane (DPM) was carried out in a continuous-flow tubular reactor. The liquid feed contained 29.5 wt.% of DPM (Fluka, >99%), 70% of n-dodecane (Aldrich, >99% solvent) and 0.5% of benzothiophene (Aldrich, 95% source of H2S, to keep the catalyst sulfided during the reaction). The temperature was 673 K and the total pressure 50 bar. The liquid feed flow rate was 16.5 ml.h and the H2 flow rate 24 l.h (STP). The catalytic bed consisted of 1.0 g of catalyst diluted with enough carborundum (Prolabo, 0.34 mm) to reach a final volume of 4 cm. The effluent of the reactor was condensed at high pressure. Liquid samples were taken at regular intervals and analyzed by gas chromatography, using an Intersmat IGC 120 FL, equipped with a flame ionization detector and a capillary column (Alltech CP-Sil-SCB). 

The catalytic experiments were performed at the stationnary state and at atmospheric pressure, in a gas flow microreactor. The gas composition (NO, CO, O2, C3H, CO2 and H2O diluted with He) is representative of the composition of exhaust gases. The analysis, performed by gas chromatography (TCD detector for CO2, N2O, O2, N2, CO and flame ionisation detector for C3H6) and by on line IR spectrometry (NO and NO2) has been previously described (1). A small amount of the sample (10 mg diluted with 40 mg of inactive a AI2O3 ) was used in order to prevent mass and heat transfer limitations, at least at low conversion. The hourly space velocity varied between 120 000 and 220 000 h T The reaction was studied at increasing and decreasing temperatures (2 K/min) between 423 and 773 K. The redox character of the feedstream is defined by the number "s" equal to 2[02]+[N0] / [C0]+9[C3H6]. ... 

The products resulting from the reaction were injeaed into a Varian 3400 gas phase chromatograph and analyzed with a flame ionization detector. The separation was made in a capillary column BPS (SGE). The catalytic activity of the catalyst was measured after a 5 hour reaction with CF3CH2CI (by the amount of chloroalkene formed CF2=CHC1, CFCl=CHCl(ZandE))... 

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