Pyrolysis pressure, apparatus

Figure 1. Schematic setup of the pressure pyrolysis apparatus.

The pyrolysis apparatus consists of a vertical, electrically-heated Vycor tube (25 mm. I.D.) packed with 6-mm. lengths of Pyrex tubing (10 mm. O.D.) and mounted in an electric furnace about 45 cm. long (Notes 1 and 2). Attached to the top is a 100-ml. dropping funnel with a pressure-equalizing side arm that has an inlet for nitrogen (Note 3). A thermocouple well inside the tube holds a movable thermocouple and extends to the bottom of the heated section (Note 4). The bottom of the reactor is fitted to a 500-ml. side-arm flask packed in ice. The side arm leads to tw o traps in series cooled in ice and to a final trap cooled in a bath of dry ice and acetone (Note 5). 

The rigorously dried 2,4,6-triphenylpyridinium fluorides were heated in a pyrolysis apparatus (with a liquid N 2 cooled trap) at a pressure of 2 Torr or, for lower boiling fluorides, in a micro-Hickman apparatus at 760 Torr. 

A pyrolysis tube packed with Vycor Raschig rings was used in the standard pyrolysis apparatus, and 7.59 g 11-hydroxyhendecanoic acid lactone (41.2 mmol) was dropped through the pyrolysis tube at 520°C at a rate of 0.95 g/min to yield 6.87 g pale yellow liquid pyrolysate. A small amount of carbon was deposited in the pyrolysis tube. Titration at 0°C of a small portion of the pyrolysate dissolved in 95% ethanol indicated that the pyrolysate contained 86% of hendecenoic acid. The acid was separated from the lactone by 0.5 N sodium bicarbonate solution, then 0.5 N HCl and ether. The solvent was removed from the final ether extracts by distillation under reduced pressure, and the residue was dried in a vacuum desiccator to give 3.98 g 10-hendecenoic acid, in a yield of 58% (based on the weight of the pyrolysate), m.p. 17-19.6°C. 

Pyrolyses For reactions that require high temperatures but which take place at atmospheric pressure (e.g., acetate pyrolysis, ketene formation), it is usually convenient to use a pyrolysis apparatus (Fig. 1-5). An electrically heated cylindrical furnace (cfl. 70) fitted with a thermocouple is clamped in a vertical position. The pyrolysis tube, which is made of Pyrex (usable up to 600°), Vycor (to 1200°), or quartz (to 1300°), is inserted then an addition funnel, a three-necked flask, and a condenser are assembled as shown. It is usually advantageous to pack the pyrolysis tube with glass beads, glass helices, or porcelain chips to increase the surface area within the tube. 

Wentrup and co-workers also studied the flash vacuum pyrolysis of isopropylidene (monosubstituted amino)methylenemalonates (84JOC-2772). The pyrolysis of isopropylidene phenylaminomethylenemalonates (1223) between 400 and 600°C under a pressure of 10 5-10 3 torr afforded 4-hydroxyquinolines (1226) in 57-66% yields. The intermediates (1224 and 1225) of the pyrolysis of isopropylidene phenylaminomethylenemalonates (1223) could be isolated at - 196°C on KBr or BaF2 windows in a special apparatus allowing direct IR spectroscopic examination of the pyrolysates... 

The following is the specific procedure for the preparation of levoglucosenone (2) by the pyrolysis of 5 g of cellulose (l).8 To a 50-mL round-bottom flask fitted with a vacuum distillation apparatus was added phosphoric acid (25 mg, 0.5 wt %), cellulose (5 g) and vegetable oil (15 g). The slurry was stirred for about 5 min under reduced pressure (20-30 mm Hg), and then heated by an appropriate heating mantle for 7 min to 270°C, as indicated by the internal thermometer. The reaction mixture began to turn black and water distillate appeared at about 140°C. Yellow distillate containing water and levoglucosenone (2) appeared on the flask wall around 270°C, and the temperature in the distillation head reached around 110-120°C. The reaction... 

This procedure involves the pyrolysis of gas molecules with high content in carbon at elevated temperatures in the presence of catalyst [10, 25]. There are two basic protocols, in one of them, called supported growth process (the most used), the catalyst is prepared and deposited on a support medium, which is inserted into a flow apparatus (a tube at atmospheric pressure in a temperature controlled furnace) and exposed to elevated temperatures, usually 500-1100 °C for a given time. In the other protocol, called floating-catalyst growth, the catalyst and the... 

Two other systems that produce high-temperature molecules should be mentioued shock waves and flames. Shock waves are typically formed by the rapid release of a high pressure of gas in a shock-tube apparatus. A shock wave is formed that can travel at several times the speed of sound temperatures as high as 20 000 K have been produced in shock tubes. Thus the method is ideal for monitoring pyrolysis and oxidation reactions. Flames are gaseous systems where a flow of gas combines with a self-supporting reaction to produce a steady-state situation. Again, oxidation reactions are amenable to this approach. In particular, short-hved intermediates in hydrocarbon oxidation, such as C2, OH, and CHO+, have been identified in flames. 

All pyrolysis experiments were carried out in the thermo-gravimetric apparatus (TGA) having a pressure capacity of up to 1000 psi. A schematic of the experimental unit is shown in Figure 1. It consists of the DuPont 1090 Thermal Analyzer and the microbalance reactor. The latter was enclosed inside a pressure vessel with a controlled temperature programmer and a computer data storage system. The pressure vessel was custom manufactured by Autoclave Engineers. A similar set-up was used previously by others.( )... 

The semi-continuous type of reactor with the large capacity was comprised of a pyrolysis chamber, a catalytic cracking chamber and a separation and purifying section. The feed plastic material was melted and decomposed in the pyrolysis chamber held at the ambient pressure and at the temperature 723-783 K, and fed to the catalytic cracking chamber. A reflux condenser was used to separate and purify the products formed in the chamber and individual factors were obtained using fractional distillation apparatus [26]. Different types of reactors are being utilized depending on the type of feed and the expected products from the pyrolysis. 

Figure 14.4 Schematic representation of an apparatus for FVP As with all high vacuum work, care must be taken. After all of the substrate has passed through the hot tube, turn off the furnace and allow to cool to room temperature (still under vacuum). Then turn off the pump and admit nitrogen to atmospheric pressure. Remove the traps to a fume cupboard and allow to warm to room temperature, and work up in the usual way. If the desired product is unstable towards air, water, or is simply very reactive, then a more sophisticated pyrolysis system might be required, and more elaborate work up procedures used.

A sample of 80 g was introduced into the batch retort. All the pyrolysis tests were performed at a temperature of 500°C, a total pressure of about 8 kPa and a heating rate of 12°C/min. The holding time of the solid residue after con Ietion of the test was one hour. Vapours formed in the reactor were removed and condensed in three traps connected in scries and maintained at -30°C, -78 C and -78 C, respectively. The non condensable gas was removed by the vacuum pump and stored in a vessel previously depressurized. A detailed description of the apparatus is available elsewhere [11]... 

Lagow et al. during these experiments in addition made the most important discovery, that polylithioalkanes prior to pyrolysis are stable in the gas phase for a short period of time. In this way for the first time mass spectra have been achieved of those compounds which have no observable vapor pressure below 650 °C even in the highest possible vacuum. A temperature of 1500 °C has been reached in less than three seconds by a special flash-vaporization apparatus, whereby e.g. dilithio-... 

The experimental setup consists of a gas dosing system and the DRIFT spectroscopy apparatus. For the pyrolysis experiments KBr was selected as matrix, different to the laser-induced decomposition experiments [141], where SiC was used. KBr was chosen because the emissivity did not increase drastically, as in the case of SiC, where it interfered with the measurements. The Kapton-KBr mixtures are placed in the sample holder of the DRIFT cell and packed using a pressure of 1 MPa as described elsewhere [288, 306]. The sample is heated in an inert gas atmosphere to the desired temperature using a heating rate of 10 K min-1. The spectrum of the Kapton-KBr mixture at a given temperature is collected and used as background spectrum. The following experiments were carried out. 

Pyrolysis of BaHg at atmospheric pressure by a filament heated to 240 °C produces a 25% yield of B10H14 after purification. The necessary apparatus is particularly simple. ... 

Apparatus. The experimental apparatus, an ion source coupled to an ESR spectrometer, has been described (7). However, with our first ion source we could not obtain enough electrons of energy lower than 15 e.v., and we could not operate at high pressure because pyrolysis of products on the hot filament gave spurious spectra and corroded the filament. 

Figure 8.2. Pyrolysis block and accessory apparatus as described by Rogers et al. 30)./. Pyrolysis chamber 2. nickel plug J. carrier gas inlet 4. carrier gas outlet 5. cartridge heater wells 12) 6, helical threads cut in inner body of block 7. outer shell of block 8, cooling jacket inlet 9, cooling jacket outlet. A. carrier gas supply B. pressure regulator C, flow-control needle valve D. reference thermal conductivity E. pyrolysis chamber F, combustion tube C. active cell H. manometer 1, pressure-control needle valve J. rotameter.

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