Thermal baseline

Data are also presented in this paper which describe the results of a solvent boiling range study when processing SRC-I. A run was also made to establish a thermal baseline wherein the SRC-I was processed over an inert 1/32 inch Shell catalyst support. 

Feed Blend Properties Solvent Study and Thermal Baseline Study... 

Thermal Baseline Study. PDU Run 2LCF-21 (Thermal Baseline) processed a 70/30 volume percent SRC-I/500°F IBP KC-Oil feed blend over an inert 1/32 inch Shell catalyst support. The inert support was the extrudate base for the modified Shell 324 catalyst and had been calcined at 1100-1150°C. The purpose of this run was to determine the extent of conversion and denitrogenation in the absence of an active catalyst ingredient - nickel and molybdenum (Ni/Mo). 

Thermal transitions can be studied by DSC. The crystallization transition is usually sharp with a good baseline. The melting transition is more complex and often not a single transition (Fig. 3.19)48 as it depends on the thermal history of the sample and the structural changes that can take place upon heating. In warming, solid-state transitions can take place in the unit cell, the lamellae can thicken, and secondary crystallization can also take place. The heats of crystallization and... 

This presents a problem since it is difficult to estimate the area of the peak. One cannot simply extend the baseline as in Case I. A much better solution is that shown in Case II, wherein the two very asymmetrical peaks, i.e.- the initial and final parts of the overall thermal reaction taking place, are delineated. This problem has not been satisfactorily answered as yet and represents a challenge to anyone using DCS methods to characterize a solid state reaction. 

A typical measurement was performed as follows. The feeder was lowered into the crucible and the sample solution (seawater) was allowed to flow under an inert atmosphere with the suction on. A constant current was applied for a predetermined time. When the pre-electrolysis was over, the flow was changed from the sample to the ammonium acetate washing solution, while the deposited metals were maintained under cathodic protection. Ammonium acetate was selected for its low decomposition temperature, and a 0.2 ml 1 1 concentration was used to ensure sufficient conductivity. At this point the feeder tip was raised to the highest position and the usual steps for an electrothermal atomic absorption spectrometry measurement were followed drying for 30 s at 900 C, ashing for 30 s at 700 °C, and atomization for 8 s at 1700 °C, with measurement at 283.3 nm. The baseline increases smoothly with time as a consequence of an upward lift of the crucible caused by thermal expansion of the material. 

Baseline Thermal cycled Irradiated and thermal cycled... 

The effect of radiation on the thermal expansion of this toughened composite (T300/CE 339) is shown (191 in Figure 24. The thermal strains measured during the cool-down portion of the first thermal cycle (cooling from RT to -150°C) are shown for the baseline composite (no radiation exposure) and for samples exposed to total doses as high as 10 0 rads. Radiation levels, as low as 10 rads... 

It can be concluded from equations 12.11 and 12.12 that the small deviation of the zero line relative to the isothermal baseline under the same scanning conditions is proportional to the heating rate and the difference in heat capacities of the two empty crucibles. This deviation can be positive (as in figure 12.4) or negative, depending on the magnitude of the intrinsic thermal asymmetry of the system under scanning conditions and the relative masses of the two crucibles. When the sample is introduced in the sample crucible,... 

W. E Hemminger, S. M. Sarge. The Baseline Construction and its Influence on the Measurement of Heat with Differential Scanning Calorimeters. J. Thermal Anal. 1991, 37, 1455-1477. 

Figure 13.1 Microcalorimetry scans displaying Tm values for interleukin-1 receptor (IL-1R type I). The inlay displays the unfolding of IL-1R (I) showing the ACp measured as the baseline difference between the native (N) and denatured (D) states for two independent scans. Thermal unfolding of IL-1R (I) is composed of three cooperative unfolding transitions, labeled 1, 2, and 3.

Figure 13.13 A plot showing the behavior of the thermal coefficient of expansion a (deg-1) for different amino acids, peptide, and water as a function of temperature measured by PPC. The dashed curve displays the estimated progress baseline for the pre- and posttransition region. (Permission to use the figure granted by MicroCal, LLC.)...

Thermal effects may also cause baseline disturbances and system peaks. These can be different from instrument to instrument as well. 

Figure 74. Improved thermal stability of an electrolyte by flame retardant HMPN (a, left) DSC traces for baseline electrolyte with (1.68%) and without HMPN in the presence of a fully lithiated graphite anode (Reproduced with permission from ref 523 (Figure 5). Copyright 2000 The Electrochemical Society.) (b, right) SHR of baseline electrolyte with (10.0%) and without HMPN in the presence of metallic lithium. (Reproduced with permission from ref 523 (Figure 6). Copyright 2000 The Electrochemical Society.)...

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