Propane pressure

Figure B-19. Propane pressure-enthalpy diagram. (From Edmister and Lee, Apftfifd IfyJrot arbon Thermodynamics, Voi. I. Second Edition, Gulf Publishing Company, Houston, TX, 1984.)...

Aquilante and Volpi indicate (2) that propanium ions formed by proton transfer from H3 + are not collisionally stabilized at propane pressures as great as 0.3 mm. and that they decompose by elimination of hydrogen or a smaller saturated hydrocarbon to form an alkyl carbonium ion. Others (16, 19) have proposed one or the other of these fates for unstabilized propanium ions. Our observations can be rationalized within this framework by the following mechanisms ... 

Experiments of propane pyrolysis were carried out using a thin tubular CVD reactor as shown in Fig. 1 [4]. The inner diameter and heating length of the tube were 4.8 mm and 30 cm, respectively. Temperature was around 1000°C. Propane pressure was 0.1-6.7 kPa. Total pressure was 6.7 kPa. Helium was used as carrier gas. The product gas was analyzed by gas chromatography and the carbon deposition rate was calculated from the film thickness measured by electron microscopy. The effects of the residence time and the temperature... 

Methane Produced in the Photolysis of Isotopic Propanes Propane pressure, mm. Percentage... 

At lower propane pressures (cf. Table IV) Pprsn increases more rapidly than Rco, suggesting that Eu > Ez. In fact, from the series at Pc,h, = 150 torr, a value of 1.0 0.2 kcal./mole was obtained for Eu — Ez. 

Propane Pressurized flow reactor 600-900 K 1.0 and 1.5 MPa. Oxidation through the NTC region... 

Nucleophilic capture of the spirooctadienyl cation opens the 3-member ring. This behavior characterizes many reactions of many other cyclopropane-containing carbocations, as well, y-radiolysis of perdeuterated propane forms CsD ions, most of which either transfer D or form isopropyl adducts. As the propane pressure is raised from 1000 mbar to 2000 mbar, however, the isopropyl/ -propyl adduct ratio falls from 30 1 to about 5.5 1. This implies the formation of corner-protonated cyclopropane, which reacts with nucleophiles as though it were an -propyl cation. With increased pressure, vibrationally excited protonated cyclopropane experiences more frequent nonreactive collisions, which deactivate it and slow down its rate of unimolecular isomerization to isopropyl cation. 

Fig. 3.20. Adsorption isotherms of propane and butane mixtuK on activated carbon amount adsorbed of propane and butane for propane pressures 0.76, 114 and 228Torr.

Carroll et al. (1992) conducted a comprehensive study of phase equilibria in the system propane-3M MDEA solution including vapor-liquid, liquid-liquid, and vapor-liquid-liquid equilibria. Data on propane solubility in the amine solution are of particular interest because dissolved hydrocarbons represent a loss of valuable product, and, when stripped from solution with the acid gases, can affect peifonnance of a downstream sulfur conversion unit The study showed that the solubili of propane in 3M MDEA is low, but more than twice its solubility in pure water under Ae same conditions. For example, at 100°F (37.8°C) and a propane pressure of 10,000 kPa (1.450 psia), the mole fraction propane in Ae 3M MDEA solution was found to be about 0.0006. This compares to a mole fraction of propane in pure water of about 0.00025 under Ae same conAtions. 

This sketch also shows an alternate arrangement sometimes used to get a constant gas density for an air-gas mixing valve. The thermostatic valve will maintain a constant gas-off temperature and a constant propane pressure in the vaporizer. 

The Reid vapor pressure is generally barely different from the true vapor pressure at 37.8°C if the light gas content —methane, ethane, propane, and butane— of the sample is small, which is usually the case with petroleum products. The differences are greater for those products containing large quantities of dissolved gases such as the crude oils shown in Table 4.13. 

LPG is divided into two types of products commercial propane and commercial butane, each stored as liquid at ambient temperature and corresponding vapor pressure. 

Commercial butane comprises mainly C4 hydrocarbons, with propane and propylene content being less than 19 volume %. The density should be equal to or greater than 0.559 kg/1 at 15°C (0.513 kg/1 at 50°C). The maximum vapor pressure should be 6.9 bar at 50°C and the end point less than or equal to 1°C. 

Solvent deasphalting. This is an extraction of the heaviest fractions of a vacuum residue or heavy distillate. The extract is used to produce the bitumen. The separation is based on the precipitation of asphaltenes and the dissolution of the oil in an alkane solvent. The solvents employed are butane or propane or a butane-propane mixture. By selecting the proper feedstock and by controlling the deasphalting parameters, notably temperature and pressure, it is possible to obtain different grades of bitumen by this process. 

Under standard conditions of temperature and pressure (STP), the first four members of the alkane series (methane, ethane, propane, and butane) are gases. As length of the carbon increases the density of the compound increases (pentane) to C yHgg are liquids, and from C.,gH3g, the compounds exist as wax-like solids at STP. 

Beyond propane, it is possible to arrange the carbon atoms in branched chains while maintaining the same number of hydrogen atoms. These alternative arrangements are called isomers, and display slightly different physical properties (e.g. boiling point, density, critical temperature and pressure). Some examples are shown below ... 

Under certain conditions of temperature and pressure, and in the presence of free water, hydrocarbon gases can form hydrates, which are a solid formed by the combination of water molecules and the methane, ethane, propane or butane. Hydrates look like compacted snow, and can form blockages in pipelines and other vessels. Process engineers use correlation techniques and process simulation to predict the possibility of hydrate formation, and prevent its formation by either drying the gas or adding a chemical (such as tri-ethylene glycol), or a combination of both. This is further discussed in SectionlO.1. 

Ethyl propane-1 1 3 3-tetracarboxylate. Cool a mixture of 320 g. (302 ml.) of redistilled diethyl malonate and 80 g. of 40 per cent, formaldehyde solution ( formalin ) contained in a 1-htre round-bottomed flask to 5° by immersion in ice, and add 5 g. (7 ml.) of diethylamine. Keep the mixture at room temperature for 15 hours and then heat under a reflux condenser on a boiling water bath for 6 hours. Separate the aqueous layer, dry the organic layer with anhydrous magnesium sulphate, and distil under reduced pressure. Collect the ethyl 1 1 3 3-tetracarboxylate at 200-215°/20 mm. The yield is 250 g. 

The locations of the tietriangle and biaodal curves ia the phase diagram depead oa the molecular stmctures of the amphiphile and oil, on the concentration of cosurfactant and/or electrolyte if either of these components is added, and on the temperature (and, especially for compressible oils such as propane or carbon dioxide, on the pressure (29,30)). Unfortunately for the laboratory worker, only by measuriag (or correcdy estimatiag) the compositions of T, Af, and B can one be certain whether a certain pair of Hquid layers are a microemulsion and conjugate aqueous phase, a microemulsion and oleic phase, or simply a pair of aqueous and oleic phases. 

Hydroca.rbons. Hydrocarbonsn such as propane, butane, and isobutane, which find use as propellants, are assigned numbers based upon their vapor pressure in psia at 21°C. For example, as shown in Table 2, aerosol-grade propane is known as A-108, / -butane as A-17. Blends of hydrocarbons, eg, A-46, and blends of hydrocarbons and hydrochlorocarbons orHCFCs are also used. The chief problem associated with hydrocarbon propellants is their flammabihty. 

Fig. 4. Plot of maximum rate of pressure change for propane VPO showing NTC region 5.33 kPa propane, 13.33 kPa O2. Courtesy of Blackwell Scientific...

Table 1. Products from the Reaction of a Propane Air Mixture at Various Pressures, %...

Cool Flames. An intriguing phenomenon known as "cool" flames or oscillations appears to be intimately associated with NTC relationships. A cool flame occurs in static systems at certain compositions of hydrocarbon and oxygen mixtures over certain ranges of temperature and pressure. After an induction period of a few minutes, a pale blue flame may propagate slowly outward from the center of the reaction vessel. Depending on conditions, several such flames may be seen in succession. As many as five have been reported for propane (75) and for methyl ethyl ketone (76) six have been reported for butane (77). As many as 10 cool flames have been reported for some alkanes (60). The relationships of cool flames to other VPO domains are depicted in Figure 6. 

Propane. The VPO of propane [74-98-6] is the classic case (66,89,131—137). The low temperature oxidation (beginning at ca 300°C) readily produces oxygenated products. A prominent NTC region is encountered on raising the temperature (see Fig. 4) and cool flames and oscillations are extensively reported as compHcated functions of composition, pressure, and temperature (see Fig. 6) (96,128,138—140). There can be a marked induction period. Product distributions for propane oxidation are given in Table 1. 

Commercial VPO of propane—butane mixtures was in operation at Celanese Chemical Co. plants in Texas and/or Canada from the 1940s to the 1970s. The principal primary products were acetaldehyde, formaldehyde, methanol, and acetone. The process was mn at low hydrocarbon conversion (3—10%) and a pressure in excess of 790 kPa (7.8 atm). These operations were discontinued because of various economic factors, mainly the energy-intensive purification system required to separate the complex product streams. 

Propane. Propane is difficult to oxidize in LPO because of its volatility and lack of reactivity. It can, however, be oxidized with a suitable solvent and sufficiently high pressures and temperatures (211). The principal products are acetone and isopropyl alcohol. 

In the paraffin series, methane, CH, to / -butane, C H q, are gases at ambient conditions. Propane, C Hg, and butanes are sometimes considered in a special category because they can be fiquefied at reasonable pressures. These compounds are commonly referred to as fiquefied petroleum gases (qv) (LPG). The pentanes, to pentadecane [629-62-9], fiquids, commonly called distillates, which include gasoline [8006-61-9], kerosene... 

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