Temperature programming cool-down rates

Dynamic control of programmed temperature profiles, starting and ending temperatures, rate of temperature increase with one or more limc-controlled segments or isothermal temperature, and cooling-down cycle. 

Temperature programmed desorption (TPD) of NH3 was performed in a quartz micro-reactor. 0.10 g of sample was firstly heated in helium at 600°C for 2 h. NH3 was introduced to the sample after it was cooled down to room temperature. To remove the weakly adsorbed NH3, the sample was swept using helium at 100°C for 1 h. The TPD experiments were then carried out with a carrier-gas flow rate of 40 ml/min helium from 100 to 600°C using a linear heating rate of 10°C/min. The desorption of NH3 was detected by Shimadzu GC-8A equipped with a TCD detector. 

Temperature programmed reduction (TPR) was performed in situ in a stream of 25 cm /min of 10 % H2/Ar and a heating rate of 10 K/min. A thermal conductivity cell was used to follow H2 consumption. In the case of fresh samples, they were previously dried at 423 K under flow of N2 and cooled down to room temperature before ruiming the TPR experiment. 

Temperature programmed reduction experiments were performed using an apparatus described by Robertson et al. [9]. The reduction was carried out with a purified hydrogen-argon mixture (10 vol.% hydrogen) at a heating rate P = 10 K min up to 1048 K. The TPR reactor was charged with 0.25 g of calcined (fresh) catalyst. Before the reduction, the catalyst was oxidized in a O2 flow to 1048 K for 1 h, and then cooled down to 300 K in Ar. This reduction-oxidation cycle was repeated several times. 

The temperature programmed reduction (TPR) experiments were performed in a SETARAM TGDTA 92 microbalance. After evacuation of the sample to 10 mbar, the sample was equilibrated at room temperature with a 65 ml/min pure argon flow. The temperature was then raised with rate of 10 K/min up to 823 K and kept at this temperature for 1 h. Then the sample was cooled down to 360 K and 50 ral/min of the argon flow was replaced by the equal amount of hydrogen (80 kPa Hz in the total flow). Finally the sample was purged in hydrogen at 360 K for 15 min and TPR was performed at a scan rate 10 K/min up to 1073 K. 

An analytical TREF system was first described by Wild and Ryle [8], Their system (Fig. 8) used components taken from a Waters model 200 size exclusion chromatograph. The solvent reservoir, degasser and pump from the Waters unit was used as was the refractive index detector system. In place of the SEC oven a temperature programmed oil bath provided the temperature gradients. A 0.2 g polymer sample was loaded in a hot trichlorobenzene solution into a small column packed with 40-60 mesh Chromosorb P. Crystallization was achieved by slow-cooling the polymer solution (0.2 g in 5 ml) in the packed column at a rate of 1.5 K/hour down to room temperature. The temperature rising elution was carried out at a flow rate of 6 ml/min and a rate of temperature rise of 8 K/hour. The refractive index response and the separation temperature were recorded continuously on a two-pen recorder. A calibration curve of methyl content vs. elution... 

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