Heatable cell

The infrared absorbance spectra were recorded at room temperature on a Fourier transform spectrophotometer (Biucker I.F.S. 110) with a resolution of 4 cm To compare the integrated adsorbances of the various samples the weight of the pellet and the Pd content were considered. The samples were placed in a heatable cell where the catalysts were treated "in situ". Different kinds of experiments were carried out ... 

Figure 6.8-1 Heatable cell for recording IR spectra of vapors and gases up to 250 °C. The cell can also be used to record spectra of compounds which are liquid or solid at ambient temperature.

Powder DR data were collected with a Harrick DRA-2CI attachment and a HVC-DRP heatable cell, evacuable below 0.1 Pa. To collect spectra below 4000 cm-1, the silica powder was generally mixed with potassium bromide, without any pressure, so that there was no close interaction between KBr and the silica surface. 

Figure 5 Schematic illustration of the heatable cell used to shufy small molecule ingress into high molecular weight polymers (reproduced from reference [18]).

According to Hummel et al. [854], who described linear temperature-programmed pyrolysis of several thermo-resistant polymers (Twaron, Kapton and Py-rolin PI-2555) using FTIR with a heatable cell and LVEIMS (18 eV) for evolved gas analysis, FTIR is superior for the analysis of light fragments, whereas EIMS is more sensitive than FTIR. PyFTIR has mainly been used in the 80s and now appears to be declining. 

There are other varieties of accessories available, mostly for special techniques. In the latter category are heatable cells (and the necessary controls), cryostats, horizontal cells, high-pressure cells, etc. One item, however, deserves more than just mention, as it is a very useful and versatile accessory this is the beam attenuator. There are several types of attenuators available commercially that are continuously variable. (It is also possible to use wire screens for the variation.) The attenuator is used in the reference beam in combination with many of the acces-... 

Finally, cells developed for special purposes have been suggested, such as windowless cells equipped with acoustic baffles to reduce the influence of the ambient noise or heatable cells for studying liquid samples with low volatility. 

Heat is the most widely used means of sterilization, which can be employed for both liquid medium and heatable solid objects. It can be applied as dry or moist heat (steam). The moist heat is more effective than the dry heat, because the intrinsic heat resistance of vegetative bacterial cells is greatly increased in a completely dry state. As a result the death rate is much lower for the dry cells than for moist ones. The heat conduction in dry air is also less rapid than in steam. Therefore, dry heat is used only for the sterilization of glassware or heatable solid materials. By pressurizing a vessel, the steam temperature can be increased significantly above the boiling point of water. Laboratory autoclaves are commonly operated at a steam pressure of about 30 psia, which corresponds to 121°C. Even bacterial spores are rapidly killed at 121 °C. 

Hoffmann and Knozinger17 have performed a detailed study of the free hydroxyl vibration, using high resolution (0.25 cm 1) FTIR, equipped with a heatable vacuum cell. They observed a (very small) peak shift as a function of temperature, but also a significant peak narrowing (table 5.2). 

FTIR methods which use heatable gas cells, e.g., fast thermolysis FTIR [111], the on-the-spot TG-FTIR technique, which avoids transfer lines, monitors the gaseous atmosphere directly above the sample pan spectral information is obtained which is directly correlated to the recorded mass change as a function of time and temperature. At the end of a TG... 

The model molecules which are solid at room temperature (except for benzene), were evaporated from a source consisted of a borosilicate glass container with a small opening, like the design of a Knudsen cell. The source was mounted inside a heatable and coolable copper shaft, that could be inserted to the vaccum system through a load-lock arrangement. Upon heating, the pressure was... 

Thermostated sample cells for all physical states are commercially available. To obtain vapor phase spectra of materials with low vapor pressure, heatable gas cells with a standard length or multiple reflection cells are needed. 

IR spectra were recorded with a Bruker spectrometer IFS 113v at room temperature coadding 300 scans which was equipped with a heatable vacuum cell. The samples were pressed into 7.5 mg cm disks. Before measmement of the unloaded sample and CDjCN dosage the samples were activated for 1 h at 723 (In-Sil at 673 K) in high vacuum. 

In-situ oxidation experiments were conducted in a heatable IR flow cell of... 

The gas analysis system consisted of an FT-IR spectrometer (Bruker IFS-66) with a heatable gas cell (100 cm volume) and a quadrupole mass spectrometer (Balzers GAM 400). NO, NO2, N2O, NH3, CH4, C3H6, C3H8, CO, CO2, and H2O were analysed by FT-IR spectroscopy and O2 and H2 by mass spectrometry. The analytical system permitted the quantitative analysis with a resolution of up to 15 measurements per second. 

Olefin reactions were, among other reactions, also studied in situ by DRIFT spectroscopy as described in an review article by Maroni et al. [883], where a cell was used similar to that mentioned in Sect. 4.2 (cf. [176]). Salzer et al. [884] described in-situ DRIFT experiments of activation of zeolite catalysts, for instance, NH4-erionite, where they also employed the commercially available, heatable DRIFT cell mentioned in Sect. 4.2. 

Liquid samples are easily studied with the aid of a wide variety of liquid cells, including heatable. flow through, and variable path length cells. These cells are constructed of two infrared transparent windows with a spacer between them, thereby forming a cavity for the sample. As the samples are often strong infrared absorbers, for this spectral range the liquid transmission cell must be constructed with short optical path lengths (0.025 -1 mm). 

The spin casting process can be carried out in a heatable centrifuge using a spinning cell of the desired sample dimensions. It is advisable to cover the inner wall of the cell with a strip of poly(tetrafluoroethylene) foil (Teflon) in order to avoid adherence between the casted elastomer film and the wall and allow for easy removal. The ends of the strip should not overlap and they should be marked so that they can be recognized easily after synthesis. 

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