Hexane combustion

Figure 3 Effects of addition of other VOCs on hexane combustion over bimetallic Pt-Pd catalyst at GHSV= 50,000 h in the range 250-450°C (total VOC concentration = 1,200 ppm, VOC mixture of hexane, benzene, ethyl acetate, methyl ethyl ketone and iso-propanol) data adapted from [5] x hexane u hexane in mixture...

G. Picasso, 2007, Preparation and characterization of Ce-Zr and Ce-Mn based oxides for n-hexane combustion Application to catalytic membrane reactors. Chemical Engineering Journal, 126,119-130. 

Santamaria and coworkers (Aguado cf a/.,2005) preparedPt/ZSM-5 membrane reactors for the combustion of n-hexane present at a low concentration in the air. Experimental results showed that n-hexane combustion was achieved at 210°C. A comparison of the conversion of the hexane obtained using the membrane reactor and the fixed bed reactor evidenced the better performance of the membrane reactor with a light-off temperature lower (about 70°C) than that obtained in the fixed bed reactor as illustrated in Fig. 6.5. Another example of the successful application of a Pt/ZSM-5 membrane in the catalytic combustion of volatile organic compounds (VOCs) (Bottino et al, 2001) showed that a high removal efficiency of toluene can be obtained and that the zeolite membrane with a relatively thick layer (40 pm) is clearly affected by mass transfer limitations. 

Their heats of combustion (Table 3 2) reveal that trans 1 4 dimethylcyclohexane is 7 kJ/mol (17 kcal/mol) more stable than the cis stereoisomer It is unrealistic to believe that van der Waals strain between cis substituents is responsible because the methyl groups are too far away from each other To understand why trans 1 4 dimethylcyclo hexane is more stable than cis 1 4 dimethylcyclohexane we need to examine each stereoisomer m its most stable conformation... 

Write and balance the chemical equation for the combustion of hexane, GfcH14, to gaseous carbon dioxide gas and gaseous water. 

This chapter reports about an investigation on the catalytic gas-phase armnoxidation of u-hexane aimed at the production of 1,6-Ce dinitriles, precursors for the synthesis of hexamethylenediamine. Catalysts tested were those also active and selective in the ammoxidation of propane to aciylonitrile mtile-type V/Sb and SnA /Nb/Sb mixed oxides. Several A-containing compounds formed however, the selectivity to cyano-containing aliphatic linear Ce compounds was low, due to the relevant contribution of side reactions such as combustion, cracking and formation of heavy compounds. 

Due to the narrow safe area in the hydrocarbon-lean zone, operation in the n-hexane-rich zone was preferred. In the latter case, however, feed compositions having high hydrocarbon concentration had to be avoided, in order to hmit the contribution of radical-chain reactions, favoured at high temperature under aerobic conditions. Therefore, operation with a diluted feed was preferred the ballast used for the reaction was helium, in order to allow evaluation of the amount of N2 produced by ammonia combustion. 

Hydrocarbon-rich conditions imply that oxygen is the limiting reactant, due to the high oxygen-to-hydrocarbon stoichiometric ratio in n-hexane ammoxidation. Therefore, the conversion of the hydrocarbon is low this should favour, in principle, the selectivity to products of partial (amm)oxidation instead of that to combustion products. 

A room 3mx4mx 3m high with an opening in a wall 2 m x 2 m contains hexane fuel, which can burn in pools on the floor. The ambient temperature is 25 °C. The heat of combustion for hexane is 43.8 kJ/g. The construction material of the room is an insulator which responds quickly, and thus has a constant effective heat loss coefficient, hk — 0.015 kW/m2K. Use this to compute the overall heat loss to the room. 

CHETAH uses the negative values of the decomposition/combustion enthalpies 1 = hexane... 

They are sensitive to all flammable gases, and they give approximately the same response to the presence of the lower explosive limit (LEL) concentrations of all the common hydrocarbon gases and vapors. However it should be remembered that gas detectors do not respond equally to different combustible gases. The milli-volt signal output of a typical catalytic detector for hexane or xylene is roughly one half the signal output for methane. 

Hexane may be expected to comprise around 2% of the VOCs in urban air polluted with hydrocarbons from automobile emissions or other combustion byproducts (Barrefors and Petersson 1993). The -hexane concentrations in urban air will typically be approximately 60% of the concentrations of benzene (Daisey et al. 1994). Close proximity to the exhaust systems of cars or other gasoline-powered vehicles can lead to exposures to increased concentrations of -hexane. Under rush-hour conditions, the concentrations in the interior air of buses will tend to be lower (55 g/m3 or 19.8 ppbv) than the interior levels in cars (69 g/m3 or 24.9 ppbv) or the air around persons riding motorcycles (106 g/m3 or... 

Children, like adults, are subject to low level -hexane background exposures associated with emissions from the combustion of motor fuels or heating oil or other uses of petroleum products. Some products used in the home, such as rubber cement, contain -hexane and could pose exposure risks to children from inhalation. In addition to inhalation exposures through the normal use of such products in poorly... 

Example 2 Combustion of n-hexane (C6H14, 150 Ib/hr) occurs at ambient conditions (77 F, 1 atm). 

Reid vapor pressure is measured at 100°F (37.8°C) and is used to help ensure that gasoline will vaporize adequately and ignite within the combustion chamber of an engine. Vapor pressure is provided by volatile gasoline components such as dissolved butane gas and the presence of pentanes, hexanes, heptanes, and benzene. 

The gaseous oxidation of n-alkanes can, in suitable circumstances, yield substantial amounts of O-heterocycles of the same carbon number as the initial hydrocarbon. A comparative study has been carried out of the formation of O-heterocyclic products during the combustion of n-butane, n-pentane, and n-hexane. The way in which the yields of such compounds vary with reaction conditions has been investigated. As a result of the optimization of the amounts of O-heterocycles it has been possible to obtain maximum yields of these compounds of up to 30% from n-pentane but only about 10% from n-butane and n-hexane. An attempt is made to account for the observed differences in the amounts and nature of the O-heterocyclic products formed from the three n-alkanes. 

In the present work, therefore, a comparative study of the production of O-heterocycles during the cool-flame combustion of three consecutive n-alkanes—viz., n-butane, n-pentane, and n-hexane—was carried out under a wide range of reaction conditions in a static system. The importance of carbon chain length, mixture composition, pressure, temperature, and time of reaction was assessed. In addition, the optimum conditions for the formation of O-heterocycles and the maximum yields of these products were determined. The results are discussed in the light of currently accepted oxidation mechanisms. 

The halogen compounds used were methylene dichloride, chloroform, carbon tetrachloride, ethylene dichloride, ethyl bromide, ethylene dibromide, bromoform, methyl iodide, and ethyl iodide. The hydrocarbons selected for their interesting combustion properties were hexane, 2-methylpentane, 2,2-dimethylbutane, hex-l-ene, heptane, methylcyclo-hexane, isooctane, diisobutylene, benzene, toluene, m-xylene, and ethylbenzene. 

It was the late Professor Callender (12), who as an outcome of experiments upon the slow combustion of hexane which resulted in the formation of valeraldenyde, acetaldehyde, and fonnaldehyde without any detectable initial hexyl alcohol, CeHi3OH, first suggested that the initial oxidation of a hydrocarbon in air more probably involves the formation of an alkyl peroxide by the direct incorporation of the oxygen molecule in the hydrocarbon molecule after the collision which subsequently decomposes into aldehydes and water thus... 

Barusch and Payne (6), in 1951, were successful in stabilizing a cool flame in a straight tube, and used this device to investigate the relationship between the octane number of the fuel and its tendency to form cool flames. Using a similar device Ober-dorfer (30), working in the author s laboratory was able to study the cool flames of the isomeric hexanes. In this manner, n-hexane, 2-methyl pentane, 3-methylpentane, and 2,2-dimethylbutane were readily brought to cool-flame combustion. The fuel-air ratio... 

Formaldehyde, acetaldehyde, acetone, and carbon monoxide were common combustion products of the four hexanes. Propionaldehyde, n-butyraldehyde, acrylic aldehyde, crotonic aldehyde, and methyl ethyl ketone were all found as intermediates in the combustion of n-hcxane. Acetaldehyde and acetone were prominent and propionaldehyde and acrylic aldehyde were present among the intermediates from 2-methylpentane. Acetaldehyde and methyl ethyl ketone were peculiarly characteristic of 3-methyl-pentane and acetaldehyde, acetone, and pivalic aldehyde were characteristic of 2,2-dimethylbutane. In other words, the intermediate monocarbonyl combustion products... 

The analytical data on monocarbonyls, olefins, and oxides of carbon were then used to strike a carbon balance for the purpose of finding what part of the cool-flame combustion products had been accounted for. The balance for n-hexane proved to be nearly quantitative. For the more highly branched isohexanes the carbon balance was much less complete. 

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