Acetylene, mixing ratios

Furthermore, acetylene concentrations decayed faster than expected from removal by OH and Cl, indicating the presence of bromine atoms with mixing ratios of l-2pmolmol . The corresponding BrO mixing ratios in the range of several tens of pmol moP should cause loss of ozone by —90% per day by the BrO-BrO reaction cycle. Estimated concentrations of chlorine atoms were —1,000 times smaller than those of bromine (Jobson et al., 1994). There are some tentative indications of substantial concentrations of CIO radicals, similar to those of BrO, 21 12 pmol mol , at a detection limit of 20pmolmol per individual measurement. 

Table 6-8. Average Mixing Ratios (ppbv) of Several Alkenes, Acetylene, and Some Aromatic Compounds in the Continental Boundary Layer at Rural Measurement Sites...

FIG. 6a, b IR sj tra of plasmapolymerized acetylene using (a) acetylene/argon with a mixing ratio of 15 seem/15 seem and (b) acetylen/air with a mixing ratio of 5 sccm/15 seem... 

Thermal energy in flame atomization is provided by the combustion of a fuel-oxidant mixture. Common fuels and oxidants and their normal temperature ranges are listed in Table 10.9. Of these, the air-acetylene and nitrous oxide-acetylene flames are used most frequently. Normally, the fuel and oxidant are mixed in an approximately stoichiometric ratio however, a fuel-rich mixture may be desirable for atoms that are easily oxidized. The most common design for the burner is the slot burner shown in Figure 10.38. This burner provides a long path length for monitoring absorbance and a stable flame. 

The unit Kureha operated at Nakoso to process 120,000 metric tons per year of naphtha produces a mix of acetylene and ethylene at a 1 1 ratio. Kureha s development work was directed toward producing ethylene from cmde oil. Their work showed that at extreme operating conditions, 2000°C and short residence time, appreciable acetylene production was possible. In the process, cmde oil or naphtha is sprayed with superheated steam into the specially designed reactor. The steam is superheated to 2000°C in refractory lined, pebble bed regenerative-type heaters. A pair of the heaters are used with countercurrent flows of combustion gas and steam to alternately heat the refractory and produce the superheated steam. In addition to the acetylene and ethylene products, the process produces a variety of by-products including pitch, tars, and oils rich in naphthalene. One of the important attributes of this type of reactor is its abiUty to produce variable quantities of ethylene as a coproduct by dropping the reaction temperature (20—22). 

The cathode mix is a compressed mixture of electrolytic Mn02 (EMD) and synthetic graphite or acetylene black to provide electronic conductivity, in a ratio of 4—5 1, wetted with electrolyte. The cathode current collector is generally the external steel can, which may be nickel-plated or coated with conductive carbon. Reduction of Mn02 in alkaline conditions is a complex process and follows a number of steps which can be written formally as... 

The purity of the gas is tested by explosion analysis (J. C. S., 84, 555) the ratio, contraction on explosion to absorption by baryta water after explosion, should lie between 0-73 and 0-77 (theoretical 0,75). Great care must be taken that this preparation is carried out in the absence of flame, and that neither the apparatus nor the collected gas is exposed to direct sunlight, which decomposes acetylene. Also the cupric chloride solution employed for washing should be kept acid if it becomes alkaline the explosive copper aeetylide is precipitated. Should this occur the solution is mixed with much water and poured away. 

In direct aspiration FLAA, a sample in the aerosol form is aspirated into a flame fueled with acetylene. An oxidant (air or nitrous oxide) is mixed with the acetylene fuel to create the necessary temperature conditions. Depending on the fuel/oxidant ratio, the temperature of the flame may range from 2400 to 2800°C. Precise temperature control is critical in FLAA analysis, as the concentrations of ionized and unionized species of a vaporized element are sensitive to the temperature of the flame. 

Chloroprene is of high industrial importance for manufacture of synthetic rubbers. For a long time the synthesis was based on acetylene. More recent processes are based on butadiene as a feedstock, which is substantially cheaper [29]. The initial step is a gas-phase free-radical chlorination at 250 °C and temperature control is ensured by use of excess butadiene (molar ratio of Cl2 to butadiene 1 5 to 1 50) [44]. To limit side reactions, short contact time reactors operating at higher temperatures and residence times below one second are also known [45], Good mix-... 

The problems involved in the measurement of acidities or relative acidities of weak acids are illustrated by the widely different estimates which have been given for the acidity of substituted acetylenes. Two different approaches have been used for measuring the equilibrium acidity of carbon acids which do not ionize in the pH range. In one approach, the ionization of a carbon acid is studied in mixed solvents containing base. Some of these solutions are more basic than aqueous solutions and by varying the solvent mixture the ionization of acids with pK values in the range 12—25 can be studied. Values at the low end of the pK range are directly compared with aqueous p/iC values. It is assumed that ratios of the activity coefficients (f) for the ionized (S-) and unionized acids (SH) are the same for all the acids studied and an acidity function (86)... 

The process is fed with three streams ethane, ethylene, and chlorine. The ethane and ethylene streams have the same molar flow rate, and the ratio of chlorine to ethane plus ethylene is 1.5. The ethane/ethylene stream also contains 1.5 percent acetylene and carbon dioxide. (For this problem, just use 1.5 percent carbon dioxide.) The feed streams are mixed with an ethylene recycle stream and go to the first reactor (chlorination reactor) where the ethane reacts with chlorine with a 95 percent conversion per pass. The product stream is cooled and ethyl chloride is condensed and separated. Assume that all the ethane and ethyl chloride go out in the condensate stream. The gases go to another reactor (hydrochlorination reactor) where the reaction with ethylene takes place with a 50 percent conversion per pass. The product stream is cooled to condense the ethyl chloride, and the gases (predominately ethylene and chlorine) are recycled. A purge or bleed stream takes off a fraction of the recycle stream (use 1 percent). Complete the mass balance for this process. 

The industrial process does not yield a pure product. Acetylene-derived carbon black is degassed at 1200°C, mixed with TiOg (mole ratio 1 2), and the mixture placed in a silicon carbide or molybdenum boat it is calcined for three hours at 1250°C in a stream of Ng. The product contains 98% nitride the remainder is lower Ti oxides. 

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