Ethane pyrolysis effect

It has also been shown that hydrogen sulphide has a strong inhibiting influence upon the pyrolysis of ethane (6, H,). This effect of hydrogen sulphide upon the formation of the major products of ethane pyrolysis has also been observed by Me LEAN and Me KENNEY in 1970 (U). 

DUNKLEMAN AND ALBRIGHT Surface Effects during Ethane Pyrolysis 243... 

DXJNKLEMAN AND ALBRIGHT Suffoce Effects duiing Ethane Pyrolysis 247... 

DUNKLEMAN AND ALBRIGHT Surfoce Effects duHng Ethane Pyrolysis 249... 

DUNKLEMAN AND ALBRIGHT Sutfoce Effects duHng Ethane Pyrolysis 253... 

If a mechanistic model is to be developed to represent the ethane pyrolysis data, then all Important reaction steps should be included. Clearly surface reactions often fall within this latter category. Since Insufficient data have as yet been obtained relative to rate constants and to the effect of surface reactions, it is currently impossible to develop such a model. If the experimeiital data can be corrected to eliminate the effect of surface reactions, then models using only gas-phase reaction steps could be tested. All corrected data at 750 to 900 C Including that shown In Figures 3,5,6, and 7 were tested In this way. 

The mechanistic model (of Table II of the previous chapter) was developed by successive approximations. First, only those reactions assumed to be most important were used in the model, and later secondary reaction steps were added until good predictions were obtained of the experimental results. In the previous chapter of the book, the parameters for the various reaction steps are reported. The major reactions for pyrolyses of both ethane and propane are grouped in Table II (1). When ethane is pyrolyzed, the propane reactions are. pf relatively minor importance and eliminating them from the model has little effect on the ethane pyrolysis predictions. When propane is pyrolyzed, however, significantly better predictions result when the ethane reactions are included and the entire set of reactions are employed. 

Reversed-phase hplc has been used to separate PPG into its components using evaporative light scattering and uv detection of their 3,5-dinitroben2oyl derivatives. Acetonitrile—water or methanol—water mixtures effected the separation (175). Polymer glycols in PUR elastomers have been identified (176) by pyrolysis-gc. The pyrolysis was carried out at 600°C and produced a small amount of ethane, CO2, propane, and mostiy propylene, CO, and CH4. The species responsible for a musty odor present in some PUR foam was separated and identified by gc (Supelco SP-2100 capillary column)... 

The pyrolysis of diethyl mercury has been studied using a nitrogen carrier flow system87 both in the presence and absence of toluene. The experimental conditions used were total pressure = 10+1 torr with 0.4 torr partial pressure of toluene, alkyl pressure 1-10 x 10 2 torr, decomposition 10-75 % and contact time 0.1-0.3 sec. The presence of toluene had no effect on the rate coefficient, the observed ethane/ethylene ratio ( 1) or the C4/C2 ratio ( 4). These ratios were essentially independent of temperature. 

Table 8.1 shows the stochastic model solution for the petrochemical system. The solution indicated the selection of 22 processes with a slightly different configuration and production capacities from the deterministic case, Table 4.2 in Chapter 4. For example, acetic acid was produced by direct oxidation of n-butylenes instead of the air oxidation of acetaldehyde. Furthermore, ethylene was produced by pyrolysis of ethane instead of steam cracking of ethane-propane (50-50 wt%). These changes, as well as the different production capacities obtained, illustrate the effect of the uncertainty in process yield, raw material and product prices, and lower product... 

H. R. Linden High temperature pyrolysis of coal with high energy sources seems to follow readily predictable paths similar to hydrocarbon pyrolysis. The effects of pressure, gas atmosphere, reaction time, and the volatile matter" content of the coal bear the same relationship to yields of methane, ethane, ethylene, acetylene, and hydrogen as for simple hydrocarbons. Effective reaction temperature, although not directly measurable, could be estimated by means of a suitable chemical thermometer, such as the C-. H-. -C. H4-H. system which approaches equilibrium very rapidly. As Dr. Given also noted, equating the volatile matter" to the reactive portion of the coal is an oversimplification but adequate for empirical purposes the C H ratio of the coal would probably be more suitable. 

Eisenberg and Bliss and Palmer et al have studied the time-course of the methane pyrolysis there is an initial acceleration followed by retardation. Both studies show that ethane accelerates the reaction. The work of Palmer et indicates that there is a deposition of vitreous carbon on the walls of the vessel, that the reaction is inhibited by carbon, and that the rate is not appreciably affected by the surface volume ratio. They also find that the reaction is strongly accelerated by added naphthalene, which tends to produce carbon nuclei very rapidly. They conclude that the formation of nuclei has a strong effect on the rate of decomposition. The inhibition by hydrogen may then be due to its removal of nuclei. The accelerating effect of added ethane is attributed to its more rapid decomposition, with accompanying formation of nuclei aside from this, ethane is a good source of free radicals. 

A typical determination is that of Lossing and Tickner for the methyl radical. Methyl radicals were produced by the pyrolysis of mercury dimethyl diluted by helium, and the mass spectrum showed that only CH3, mercury, ethane and a trace of methane were formed. Sensitivity calibrations were obtained in the usual way for the stable substances, and then the net peak at mass 15, after subtraction of the contributions from mercury dimethyl, ethane and methane, was determined. At high temperatures of pyrolysis, where the methyl radicals were most abundant, the sensitivity for the mass 15 peak of the methyl radical could then be calculated on the basis of 100 % carbon balance. As discussed earlier, wall reactions may lead to appreciable disappearance of the radical under observation, and such effects must be taken into account when calculating the sensitivity of the apparatus. Corrections of these kinds were applied to the experiments described above when Ingold and Lossing discovered that part of the methane observed was produced by reaction in the ionization chamber. The smallest relative concentration of radicals which can be determined accurately i.e. where several species give rise to the... 

When a reaction has many reactive species (which may be the case even for apparently simple processes such as pyrolysis of ethane or synthesis of methanol), a factorial or sequential experimental design should be developed and the data can be subjected to a response surface analysis (Box, Hunter, and Hunter, Statistics for Experimenters, 2d ed., Wiley Interscience, 2005 Davies, Design ana Analysis of Industrial Experiments, Oliver Boyd, 1954). This can result in a black box correlation or statistical model, such as a quadratic (limited to first- and second-order effects) for the variables Xi, x2, and X3 ... 

Effect of pretreatment of a steel reactor surface (Sandvik 15Re10) on the product gas composition during pyrolysis of ethane and ethylene at 750 C with a constant feed rate = 0.58 1/min. Dimensions of the reactor tube length = 88 cm and inside diameter = 0.92 cm. The reactoj tube was filled with pieces of the reactor material 3.92 g or approximately 130 cm. ... 

Dunkleman, J.J. Albright, L.F. "Surface Effects During Pyrolysis of Ethane in Tubular Flow Reactors". ACS Symp. Ser. 1976. 32, 241. 

Table III shows the effect of shifting furnace operation from propane fresh feed to ethane. Data are from Schutt and Zdonik (54). The reduction of propylene yield from ethane to negligible levels in favor of increased ethylene production cannot be done if a plant has propylene commitments. Because propylene requirements cannot be satisfied with ethane feed, Ericsson (14) has concluded that propane will continue to be the preferred feedstock to make ethylene. Actually, 85% of the U.S. ethylene plants are located in the Gulf Coast area so that they can obtain and operate on economical ethane and propane feeds. The need for propane pyrolysis has resulted in a renewal of experimental interest in this area, and in-depth studies have been made by Crynes and Albright (17) and by Buekens and Froment (7).

Similar to the pyrolysis of ethane (10-5), effective plasma catalysis takes place in the direct plasma decomposition of methane with the production of soot and lydrogen ... 

Plasma Catalysis of Hydrogen Production by Direct Decomposition (Pyrolysis) of Ethane. Interpreting the plasma-catalytic effect of ethane decomposition and hydrogen production illustrated in Fig. 10-10, explain why the application of thermal plasma results in an increase of gas temperature, while application of non-equilibrium plasma results in gas cooling and additional hydrogen production. Compare the thermodynamics of these systems with that of refrigerators and heat pumps. 

The cracked gases are compressed to 30 to 40 bar, freed from carbon dioxide and hydrogen sulfide and dried. Low temperature distillation at temperatures of — 30 to 140 °C effects separation into ethylene, ethane, propylene, propane, mixtures of C4- and Cs-hydrocarbons and light pyrolysis gasoline. This refining pro-... 

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