Butanes, effect model

The temperature for methane and butane calculated with the isothermal model is a factor 1.4 times greater than the average temperature measured by Lihou and Maund (1982) in their small-scale tests, although higher local maximum temperatures were measured. In this model, combustion is stoichiometric, thus leading to very high fireball temperatures which, in turn, lead to high radiation emissions. Effective surface emissions measured experimentally were one-half the value calculated from this model, because combustion is not stoichiometric and emissivity is less than unity. 

Examine space-filling models for the two conformers and identify any likely unfavorable nonbonded interactions. Based on steric effects, which conformer would you anticipate would be the more stable Compare energies of anti-1,2-ethanediol and gauche-1,2-ethanediol to see if you are correct. Is this the same ordering of conformer energies as seen for n-butane (see Chapter 5, Problem 3)7... 

Butanes are chosen as the simplest models for the normal and branched isomers. Both branched and normal isomers contain a C-C bond (2 ) interacting with the terminal C-H bonds (2 and 2 ) (Scheme 26a). The cyclic -aj-a2 -a3 a2- interaction (Scheme 26b) occurs in the polarization of the middle C-C a-bond by the interactions with the antiperiplanar C-H a-bonds. The orbital phase is continuous in the branched isomer and discontinuous in the normal isomer (cf Scheme 4). The branched isomer is more stable. The basic rule of the branching effects on the stability of alkanes is ... 

The validity of the model is tested against the experiment. A ISOOcc canister, which is produced by UNICK Ltd. in Korea, is used for model validation experiment. In the case of adsorption, 2.4//min butane and 2.4//min N2 as a carrier gas simultaneously enter the canister and 2.1//min air flows into canister with a reverse direction during desorption. These are the same conditions as the products feasibility test of UNICK Ltd. The comparison between the simulation and experiment showed the validity of our model as in Fig. 5. The amount of fuel gas in the canister can be predicted with reasonable accuracy. Thus, the developed model is shown to be effective to simulate the behavior of adsorption/desorption of actual ORVR system. 

Muller et al. focused on polybead molecules in the united atom approximation as a test system these are chains formed by spherical methylene beads connected by rigid bonds of length 1.53 A. The angle between successive bonds of a chain is also fixed at 112°. The torsion angles around the chain backbone are restricted to three rotational isomeric states, the trans (t) and gauche states (g+ and g ). The three-fold torsional potential energy function introduced [142] in a study of butane was used to calculate the RIS correlation matrix. Second order interactions , reflected in the so-called pentane effect, which almost excludes the consecutive combination of g+g- states (and vice-versa) are taken into account. In analogy to the polyethylene molecule, a standard RIS-model [143] was used to account for the pentane effect. 

The y-gauche effect involving only C-H bonds has been recently investigated by means of a modified version of the INDO finite perturbation theory of 13C chemical shifts, using butane as a model. (41) While the expected geometrical dependence on the methyl chemical... 

Some other polymers of the same type with valence (I) were also prepared (Fig. 17). They exhibit almost the same structure, except that halides are replaced by diphosphine ligands (diphos) such as bis(diphenylphosphino) butane (dppb), bis(diphenylphosphino)pentane (dpppen), and bis(diphenyl-phosphino)hexane (dpph).36,40 Again a model complex, compound 25, was studied as reference (Fig. 17). The electronic spectra exhibit an absorption band near 480 nm. These coordination materials are not luminescent at room temperature but are luminescent in solution in butyronitrile at low temperature (i.e., 77 K). Density functional theory (DFT) calculations showed that luminescence arises from a da-da triplet excited state. In these polymers, the nature of the phosphine ligand has a crucial effect on absorption and emission bands. Such behavior is explained by the increase in electronic density on the... 

Calculations are presented here for model molecules which resemble ethane (or ethyl radical) and butane (or butyl radical). The models are not identical with the real molecules, since our principal purpose is to vary certain energetic, structural, and frequency parameters in order to display their effects on the reaction rate and its characteristics. Thus, the results have a more general connotation than the special reactions of ethane, ethyl, butane, and butyl but, at the same time, certain cases correlate quite directly with the latter, although such connections have not been optimized. 

There have been some molecular dynamics simulations with anisotropic atom-atom potentials, the earliest being simulations with chlorine poten-tials. " Those simulations demonstrated that the computer time requirements were quite reasonable, and the results were effective compared with the inclusion of additional isotropic sites. The technique has also been extended to butane by means of a four-site anisotropic carbon model. A general DMA based potential model is being implemented into the new CCP5 molecular simulation program DL POLY. Monte Carlo simulations can use anisotropic atom-atom potentials readily, " since the calculations require the evaluation of only the energy. 

The more complex selective 1,3-butadiene (BD) hydrogenation was also examined [56, 57]. Butadiene hydrogenation produces 1-butene, tranx-2-butene, cti-2-butene, and n-butane, with 1-butene as the desired product. Pd-Al Oj model catalysts with mean particle diameters of 2-8 nm were applied to examine size effects. The abihty to accurately determine the relative abundance of specific surface sites (such as terrace, edge, interface atoms, etc. cf. surface site statistics in Table 1, 2 of [51]) is a tremendous advantage of model catalysts. Knowledge of the exact number and type of available surface sites allows the calculation of more accurate turnover frequencies. 

Thomke has used model alcohols very effectively in his studies of dehydration mechanisms. For several oxides including thoria a number of deuteriated butanols were employed including d,l erthro(threo)-[3- Y i -butan-2-ol(a), [l,l,l,2,3,3- H6]butan-2-ol (b), and [2- Hi]butan-2-ol (c). 

Blue et al. have studied the dehydrogenation of butane at atmospheric pressure, using a chromia-alumina catalyst at 530°C. For a spherical catalyst size of dp = 0.32 cm the experimental data suggest a first-order rate constant of about 0.94 cm /(sec)(g catalyst). The pore radius is given as 110 A. Assuming Knudsen diffusivity at this low pressure and estimating the pore volume as 0.35 cm /g, predict an effectiveness factor for the catalyst. Use the parallel-pore model with a tortuosity factor of 2.0. 

Figure 69. Effect of platinum, palladium and rhodium at an equimolar loading on the temperature needed to reach 50% conversion of butene and butane, as a function of the exhaust gas oxygen current (monolith catalyst with 62 cells cm y-Al203 washcoat fresh precious metal loading 8.8 mmol 1" model gas light-off test at a space velocity of 60000N11 h model gas composition is stoichiometric at 1.0 vol % O2). Reprinted with permission from ref [30], (g) 1994 Society of Automotive Engineers, Inc.

Kinzl, M. et al., SAFT modeling of inert-gas effects on the cloud-point pressures in ethylene copolymerization systems poly(ethylene-co-vinyl acetate)- -vinyl acetate-i-ethylene and poly(ethylene-co-hexene-l)-thexene-l-tethylene with carbon dioxide, nitrogen or -butane, Ind. Eng. Ghent. Res., 39, 541-546, 2000. 

A, and for B3LYP calculations 1.0985 0.0008 A, 1.0995 0.0008 A, 1.1010 0.0008 A for propane, trans butane, and cis 1-butene respectively. These bond lengths get progressively longer by 0.001 A from propane to butane to 1-butene. They are also remarkable consistent across the different basis sets and the inclusion or exclusion of polarization functions has little effect except for the MP2 model as indicated by the values. 

The kinetics of the ODH of n-butane has been investigated for unpromoted and cesium promoted a-NiMoOa catalysts. The reaction rates of dehydrogenation products as functions of the butane and oxygen partial pressures are described by a kinetic model based on the Mars and van Krevelen mechanism. The effects of Cs on the kinetic parameters can be interpreted on the basis of recently published results concerning the properties of those catalysts. 

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