Hydrocarbons quenching

Problems with solvent flameout, hydrocarbon quenching structure-response variations for different sulfur-phosphorus-containing compounds can be partially solved by using dual-flame burner. Figure 3.14 (177-179). The lower flame... 

The Influence of DNA Structure and Environment on the Intercalation of Hydrocarbon Metabolites and Metabolite Model Compounds. The physical binding of hydrocarbon metabolites to DNA is very sensitive to DNA structure and environment. This is demonstrated by the data in Figures 4 and 5, which show how heat denaturation of DNA inhibits hydrocarbon quenching. These results are consistent with early studies which indicate that the ability of native DNA to solubilize pyrene and BP is much greater than that of denatured DNA (40). 

Hydrocarbon quenching can result from high levels of C02 in the flame... 

In hydrocracking of HVGO alone the reason for decreased gas formation over Co-AC catalyst (compared with a thermal run) may be the fact that the activated carbon leads to the formation of more H or HS which terminates the radical degradation pathy-ways. However, in the case of a blend, in the absence of catalytic activity, hydrocarbon quenching (with radicals from derivated plastics) may be more pronounced than hydrogen quenching (with H ). 

In the presence of SbFs, inorganic halides such as NaCl and NaBr can serve as electrophilic halogenating agents [21b,28]. The halogenation of alkanes with dichloro- or dibromomethane has been achieved in the presence of SbFs (Eq. 13) [29], In this reaction, halonium ions are initially formed these in turn abstract hydride from hydrocarbons. Quenching of the resulting carbocations with halides leads to the desired haloalkanes. 

Problems with solvent flameout, hydrocarbon quenching and structure-response variations for different sulfur- and phosphorus-containing compounds with the single flame detector can be partially overcome using a dual-flame configuration. Figure 3.23... 

A linear dependence between detector response and the amount of sample entering the detector is expected for phosphorus. The response for sulfur is inherently nonlinear and is described by 1(82) = A [S]", where 1(82 ) is the detector response, A an experimental constant, [8] the mass flow rate of sulfur atoms, and n an exponential factor. The theoretical value for n is 2, but in practice, values between 1.6 and 2.2 are frequently observed for the single flame FPD. Non-optimized flame conditions, compound-dependent decomposition, hydrocarbon quenching, and competing flame reactions that lead to de-excitation all contribute to this deviation. Decoupling the... 

Difficulties in its use and non-uniformity of results has led to frustration in the application of the FPD to sulfur compound detection (24). Most often dted problems with the FPD (23-25) are its non-linear response, reduced response with co-eluting hydrocarbons (quenching), and inconsistent selectivity and srasitivity. 

Flame photometric 2 X 10 g of sulfur 1 X 10 for sulfur 10 to 1 by mass Hydrocarbon quenching can result from high levels of COj... 

Flame photometric detector (FPD) 2 X 10 g of sulfur compounds, 9 X 10 g of phosphorous compounds 1 X 10 for sulfur compounds lx 10 for phosphorous compounds 10 to 1 by mass selectivity of S or P over carbon Hydrocarbon quenching can result from high levels of CO in the flame Self-quenching of S and P analytes can occur with large samples Gas flows are critical to optimization Response is temperature dependent Condensed water can be a source of window fogging and corrosion... 

Polymerizations are typically quenched with water, alcohol, or base. The resulting polymerizates are then distilled and steam and/or vacuum stripped to yield hard resin. Hydrocarbon resins may also be precipitated by the addition of the quenched reaction mixture to an excess of an appropriate poor solvent. As an example, aUphatic C-5 resins are readily precipitated in acetone, while a more polar solvent such as methanol is better suited for aromatic C-9 resins. 

Hydrocarbon, typically natural gas, is fed into the reactor to intersect with an electric arc stmck between a graphite cathode and a metal (copper) anode. The arc temperatures are in the vicinity of 20,000 K inducing a net reaction temperature of about 1500°C. Residence time is a few milliseconds before the reaction temperature is drastically reduced by quenching with water. Just under 11 kWh of energy is required per kg of acetylene produced. Low reactor pressure favors acetylene yield and the geometry of the anode tube affects the stabiUty of the arc. The maximum theoretical concentration of acetylene in the cracked gas is 25% (75% hydrogen). The optimum obtained under laboratory conditions was 18.5 vol % with an energy expenditure of 13.5 kWh/kg (4). 

The cracked gas contains the products produced in the arc from the feedstock as well as the products obtained from the quench hydrocarbons. The Hquid quench feed amounts to 120 kg/1000 kWh and is composed of 25 kg C Hg, 60 kg and 35 kg iso-C H Q. 

Taking into account the purification losses, the following operating requirements are necessary in order to obtain 100 kg of purified acetylene 200 kg hydrocarbons (feedstock plus quench), 1030 kWh electric energy for the arc, 250 kWh electric energy for the separation unit, and 150 kg steam. 

Hoechst WHP Process. The Hoechst WLP process uses an electric arc-heated hydrogen plasma at 3500—4000 K it was developed to industrial scale by Farbwerke Hoechst AG (8). Naphtha, or other Hquid hydrocarbon, is injected axially into the hot plasma and 60% of the feedstock is converted to acetylene, ethylene, hydrogen, soot, and other by-products in a residence time of 2—3 milliseconds Additional ethylene may be produced by a secondary injection of naphtha (Table 7, Case A), or by means of radial injection of the naphtha feed (Case B). The oil quenching also removes soot. 

The carbon black (soot) produced in the partial combustion and electrical discharge processes is of rather small particle si2e and contains substantial amounts of higher (mostly aromatic) hydrocarbons which may render it hydrophobic, sticky, and difficult to remove by filtration. Electrostatic units, combined with water scmbbers, moving coke beds, and bag filters, are used for the removal of soot. The recovery is illustrated by the BASF separation and purification system (23). The bulk of the carbon in the reactor effluent is removed by a water scmbber (quencher). Residual carbon clean-up is by electrostatic filtering in the case of methane feedstock, and by coke particles if the feed is naphtha. Carbon in the quench water is concentrated by flotation, then burned. 

There are two approaches to estimation of AG fThe first is an empirical approach (36) based on dynamics of fluorescence quenching of aromatic hydrocarbons ia acetonitrile solution. Accordingly,... 

A typical reactor operates at 600—900°C with no catalyst and a residence time of 10—12 s. It produces a 92—93% yield of carbon tetrachloride and tetrachloroethylene, based on the chlorine input. The principal steps in the process include (/) chlorination of the hydrocarbon (2) quenching of reactor effluents 3) separation of hydrogen chloride and chlorine (4) recycling of chlorine to the reactor and (i) distillation to separate reaction products from the hydrogen chloride by-product. Advantages of this process include the use of cheap raw materials, flexibiUty of the ratios of carbon tetrachloride and tetrachloroethylene produced, and utilization of waste chlorinated residues that are used as a feedstock to the reactor. The hydrogen chloride by-product can be recycled to an oxychlorination unit (30) or sold as anhydrous or aqueous hydrogen chloride. 

Fig. 3. Quenching distance as function of equivalence ratio for hydrocarbon mixtures with air (1), where x = methane, = propane, A = propylene, and...

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