Programmable Furnaces

Slow pyrolysis is generally produced using either a programmable furnace or 

Programmable fnmaces may be interfaced to a gas chromatograph, generally with some sort of intermediate trapping, bnt are rarely interfaced directly to spectroscopic techniqnes. Thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy (TGA-FT-IR) is an important exception, since many thermal units are capable of heating samples to pyrolysis temperatnres, with the resnlting pyrolysate swept directly into the cell of the FT-IR.  

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All subsequent green coke operations were made in a second coker, which was fashioned from steel pipe approximately 18 cm in diameter and 25 cm in length. A metal plate was welded to one end and a metal collar was welded to the other end such that a steel lid could be bolted to the system. Typically, about 250 to 500 g of pitch were sealed imder nitrogen in the coker reactor and the system placed in a large temperature-programmable furnace. The heat treatment process was as follows. The temperature was raised 5°C/min to 350 °C and then l°C/min to 425°C and the temperature held at 425°C for 90 minutes. Finally the temperature was raised further at 3°C/min to between 500 and 600°C, and held there for 3 hours. The coker was cooled to room temperature and the material recovered to determine green coke yield. 

In TA the mass loss versus increasing temperature of the sample is recorded. The basic instrumental requirements are simple a precision balance, a programmable furnace, and a recorder (Figure 1). Modem instruments, however, tend to be automated and include software for data reduction. In addition, provisions are made for surrounding the sample with an air, nitrogen, or an oxygen atmosphere. 

In a DSC experiment the difference in energy input to a sample and a reference material is measured while the sample and reference are subjected to a controlled temperature program. DSC requires two cells equipped with thermocouples in addition to a programmable furnace, recorder, and gas controller. Automation is even more extensive than in TA due to the more complicated nature of the instrumentation and calculations. 

A schematic of a commercial TMA instrument is shown in Fig. 16.33. The instrument consists of a dimensionally stable (with ternperamre) sample holder and measuring probe, a programmable furnace, a linear variable displacement transducer (LVDT) to measure the change in length, a means of applying force (load) to the sample via the probe (core rod, push rod), and a temperature sensor (usually a thermocouple). 

Except for TG, programmable furnaces are rarely interfaced directly to spectroscopic techniques. Davidson [835] has indicated several data processing schemes to extract information about composition and overlapping thermal decomposition reactions of evolved gaseous reaction products of polymers subjected to linear temperature-programmed pyrolysis-infrared spectroscopy. 

The cell was a vitreous carbon crucible placed in a cylindrical vessel made of refractory steel and closed by a stainless steel lid cooled by circulating water. The description of this cell has been detailed in previous work [6]. The experiments were performed under an inert argon atmosphere (Linde). The cell was heated using a programmable furnace and the temperature was measured using a chromel-alumel thermocouple. 

First, 0.064 g (2.00 mmol) of S powder, 0.052 g (0.25 mmol) of Bi, and 0.078 g (1.00 mmol) of Na2S are weighed and mixed thoroughly and then transferred to a Pyrex tube (6 mL in volume) inside a Nj-filled glovebox. The tube is then flame-sealed under vacuum at the pressure of 10 torn The reaction tube is placed in a programmable furnace, and the reaction temperature is... 

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