Temperature ramp

There are two main applications for such real-time analysis. The first is the detemiination of the chemical reaction kinetics. Wlien the sample temperature is ramped linearly with time, the data of thickness of fomied phase together with ramped temperature allows calculation of the complete reaction kinetics (that is, both the activation energy and tlie pre-exponential factor) from a single sample [6], instead of having to perfomi many different temperature ramps as is the usual case in differential themial analysis [7, 8, 9, 10 and H]. The second application is in detemiining the... 

Thenual desorption spectroscopy (TDS) or temperature progranuned desorption (TPD), as it is also called, is a simple and very popular teclmique in surface science. A sample covered with one or more adsorbate(s) is heated at a constant rate and the desorbing gases are detected with a mass spectrometer. If a reaction takes place diirmg the temperature ramp, one speaks of temperature programmed reaction spectroscopy (TPRS). 

During the temperature ramp period, pressure is applied. How much pressure is applied depends on the adhesive and the type of assembly. Honeycomb assemblies are limited by the compression strength of the honeycomb core, so cure pressure is typically limited to 50 psi for aluminum core of standard density. Metal to metal assemblies can withstand higher pressures and usually have fewer bondline voids when cured at higher pressures. Metal-to-metal assemblies bonded with standard modified epoxies are cured at 90 psi. 

Temperature-programmed reduction TPR was used to determine the reduction behaviors of the catalyst samples. It was carried out using 50 mg of a sample and a temperature ramp from 35 to 800°C at 5°C/min. The carrier gas was 5% H2 in Ar. A cold trap was placed before the detector to remove water produced during the reaction. 

Figure 2 shows the results of heating a model system consisting of a 30 X platinum film on oxidized titanium. A linear temperature ramp was applied until the foil reached 760 K, after which the temp-... 

Figure 2. A decomposition example for a spectrum taken during an XAS/TPS experiment on Co20 /Si02-923 in 1 atmosphere of flowing 2% H2S/H2. The temperature ramp was 5 C/minute.

Figure 3. XAS/TPR results for CO3O4, 00304/3102-62 and CO304/Si02 923 in 1 atmosphere of flowing Hj The temperature ramp was S C/minute.

Thermal desorption spectroscopy and temperature programmed reaction experiments have provided significant insight into the chemistry of a wide variety of reactions on well characterized surfaces. In such experiments, characterized, adsorbate covered, surfaces are heated at rates of 10-100 K/sec and molecular species which desorb are monitored by mass spectrometry. Typically, several masses are monitored in each experiment by computer multiplexing techniques. Often, in such experiments, the species desorbed are the result of a surface reaction during the temperature ramp. 

Hgure 2. 6600 ppm NO was preadsorbed for 40 min. at room temperai ire and desorbed in He. during temperature ramp. 

Hgure4. 6000ppmNOwaspfeadsorbedfQr20inin at room temperature, and maintaiAed over the catalyst during temperature ramp. 

Rgurc 6. 3800 ppm NO + 5.4% Oj was passed over the catalyst for 20 min at room icmpcraiure, before beginning temperature ramp-... 

Thermally stable AI2O3 was synthesized as in ref. 5, by hydrolysis of A1 isopropoxide (99.99+% Aldrich Chemicals) dissolved in 2-methylpentane-2,4-diol. The resulting solid was filtered, washed in 2-propanol, and dried in air at 373 K. Then, it was calcined in flowing dry air, while the temperature was raised at 1 K/min to 733 K, when 2.4% HjO was introduced to the flowing air. Afterwards, the temperature ramp was continued to 973 K. The sample was kept at 973 K for 2 h in 7% water. The isoelectric point of the resulting y-Al Oj was pH 8. The BET surface areas were 205 to 235 mVg, and the average pore size radius was around 8.3 nm... 

By an industrial investigation of a gas-phase reaction, the chlorination of alkanes, thermal management (faster temperature ramping, avoidance of overshoots) was improved and, hence, control over radical formation was exerted. As a result, a significant increase in space-time yield to about 430 g h 1 was achieved using a hybrid micro-reactor plant compared with the conventional performance of 240 g h [127, 161]. 

To use the DCI probe, 1-2 xL of the sample (in solution) are applied to the probe tip, composed of a small platinum coil, and after the solvent has been allowed to evaporate at room temperature, the probe is inserted into the source. DCI probes have the capability of very fast temperature ramping from 20 to 700 °C over several seconds, in order to volatilise the sample before it thermally decomposes. With slower temperature gradients, samples containing a mixture of components can be fractionally desorbed. The temperature ramp can be reproduced accurately. It is important to use as volatile a solvent as possible, so as to minimise the time required to wait for solvent evaporation, which leaves a thin layer of sample covering the coil. The observed spectrum is likely to be the superposition of various phenomena evaporation of the sample with rapid ionisation direct ionisation on the filament surface direct desorption of ions and, at higher temperature, pyrolysis followed by ionisation. 

DIP-ToFMS is theoretically another option for the separation of additives from polymer in dissolutions using a probe temperature ramp. However, the technique also allows direct handling of solid substrate material, which is even more convenient. The technique has profitably been used for the analysis of non-UV cured ink, revealing diluent, photo-initiator and polymer [54]. 

The strength of the Bronsted (BAS) and Lewis (LAS) acid sites of the pure and synthesized materials was measured by Fourier transformed infrared spectroscopy (ATI Mattson FTIR) by using pyridine as a probe molecule. Spectral bands at 1545 cm 1 and 1450 cm 1 were used to indentify BAS and LAS, respectively. Quantitative determination of BAS and LAS was calculated with the coefficients reported by Emeis [5], The measurements were performed by pressing the catalyst into self supported wafers. Thereafter, the cell with the catalyst wafer was outgassed and heated to 450°C for lh. Background spectra were recorded at 100°C. Pyridine was then adsorbed onto the catalyst for 30 min followed by desorption at 250, 350 and 450°C. Spectra were recorded at 100°C in between every temperature ramp. 

GC/MS separation of mixtures of the compounds are usually performed on capillary columns with low and mid polarity and a length in the range of 30 50 m, with a total separation time of20 40 min, and temperature ramping from 40 to 300 °C. Total ion current (TIC) profiles are often obtained using ion trap or quadrupole analysers. Quantification is performed by selected-ion monitoring (SIM) detection using calibration curves. 

Fig. 3.5. OptiMelt MPA100—Automated Melting Point System. This instrument has automatic and visual determination of melting points. There is PID-controlled temperature ramping and a digital movie is taken of each melt.

Figure 4.18 shows the results of a cyclic DSC evaluation of a sample of the aqueous IV formulation. The sample was analyzed in an open aluminum pan, being cooled and then heated (under nitrogen purge) through a series of three and a half freeze/thaw cycles at a temperature ramp of 10°C per min over the range of -50 to +25°C. This range was... 

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