Packed reactors pretreatment

One of the great advantages of the FIA technology is the ease with which additional components can be added to the system to achieve a particular analytical objective. This is most notably exemplified by the incorporation of small packed reactors, which subject an injected sample to appropriate on-line pretreatment in order to facilitate the detection of analyte. Whatever the function, a packed reactor in a FIA system is therefore designed always to perform the same chemistry on each individual sample. This is in contrast to chromatography, where the purpose of the column is to separate each individual sample into several components. Besides, since the FIA apparatus is a low-pressure system, most often operated by sim-... 

The nested packed reactor (Fig. 5A0d) allows sample pretreatment prior to injection by means of solid oxidants, reductants, ion exchangers, immobilized enzymes, or suitable surface-active sorbents. The potential of this approach is largely unexploited, since so far such sample pretreatment has been used only to remove unwanted matrix, which is not retained on the column, for sample preconcentration, and for analyte conversion in connection with AAS and ICP (cf. Chapter 4.7). 

The reaction was carried out in a flow system using a fixed-bed reactor made of Pyrex (25 mm x 400 mm) provided with an internal thermocouple well. The catalyst was packed in the reactor and was pretreated in situ with hydrogen at 535°C for 2 hr. The mesh size used was 10-40. 

Santacesaria, E., Tesser, R., Di Serio, M., Guida, M., Gaetano, D., Garcia Agreda, A. 2007. Kinetics and mass transfer of free fatty acids esterification with methanol in a tubular packed bed reactor a key pretreatment in biodiesel production. Ind. Eng. Chem. Res., 46, 5113-5121. 

Hydrogenation of CO2 was conducted using a pressurized fixed-bed, flow-type micro-reactor. One gram of pre-reduced catalyst was packed in the reactor tube and was pretreated in-situ at 623 K for 0.5 h in an H2 flow of 200 cm /min. After cooling to room temperature, the gas was switched to H2 - CO2 premixed gas ( H2 / CO2 = 3 ) containing 1% of Ar as an internal standard for GC analysis, and the reaction was carried out under appropriate conditions. The effluent gas was analyzed by on-line gas chromatography with a PEG-1500 column ( 3 m, FID ) and a 2 wt% squalene/active carbon column ( 3 m, TCD ). The tubings from the catalyst bed to the GC were kept hot to avoid condensation of all products. 

Ethylene epoxidation reaction experiments over all studied catalysts were conducted in a differential flow reacfor, which was operafed at a constant pressure of 3.6 MPa and different reaction temperatures. The tubular reactor having 10-mm internal diameter was placed in a furnace equipped wifh a temperafure confroller. T)q)ically, 30 mg of a catalysf sample was placed inside the Pyrex tube reactor and secured with Pyrex glass wool plugs. The packed catalyst was initially pretreated... 

The activity tests of liquid-phase oxidation of aqueous phenol solution were conducted in a semibatch slurry reactor at operating conditions given in the caption of Figure 1. The experimental apparatus, the procedure of these measurements and the analysis of the reaction samples are described in detail in a preceding paper [6]. Additional kinetic and mechanistic investigations were carried out in an isothermal, differentially operated "liquid-saturated" fixed-bed reactor [8, 9] which was packed with a pretreated EX-1144.3 catalyst (Sfld-Chemie... 

The ARP experimental system employs a packed-bed column reactor through which the pretreatment liquid flows. Details of the reactor setup are described elsewhere [30]. ARP experiments were conducted under the following optimum set of conditions chosen for different feedstocks ... 

Different sample pretreatment operations include dilution, membrane-extraction (gas diffusion, dialysis), liquid-phase extraction techniques (liquid/liquid extraction, liquid-phase microextraction, single-drop microextraction) and solid reactors and packed columns aiming to facilitate online chemical derivatization, chromatographic separation of target species, removal of interfering matrix compounds, enzymatic assays, or determination of trace levels of analyte via sorptive preconcentration procedures (Marshall et al., 2003 Economou, 2005 Miro and Hansen, 2006 Theodoridis et al., 2007 McKelvie, 2008 Ruzicka, 2014). In this context, BIA and the LOV configurations are particularly useful. Acid-base titrations can also be automated using simple SIA manifolds and potentiometric (van Staden et al., 2002) or photometric (Kozak et al., 2011) detection. Typically, a zone of the sample to be titrated is sandwiched between two zones of titrant by aspiration. In the case of photometric detection, an additional zone of a suitable pH-sensitive colored indicator is aspirated. The stacked zones are delivered to the detector and the width of the peaks is monitored and related to the pH of the solution. 

The reactor (Fig. 11.8) was a vertical cylindrical vessel with a conical bottom, made of sheet stainless steel. The diameter of the cylindrical part was 480 mm, whereas the total height, 600 mm. The reactor had an outer insulation jacket. The reaction zone was packed with ceramic Raschig rings pretreated with a solution of potassium tetraborate. The gas—air mixture entered the tapered bottom of the reactor from below at a temperature of... 

---