Butane desorption

Fig. 10 shows the curves for the canister weight and the amount of vapor removed for the example canister during a purge event. In this case, the canister is being purged with an air stream flowing at a rate of about 22.6 liters per minute for a total of 15 minutes. The curves show that the n-butane desorption rate is initially quite rapid, and then it levels out at a lower rate. 

Fig. 3.2 Adsorption isotherms for argon and nitrogen at 78 K and for n-butane at 273 K on porous glass No. 3. Open symbols, adsorption solid symbols, desorption (courtesy Emmett and Cines). The uptake at saturation (calculate as volume of liquid) was as follows argon at 78 K, 00452 nitrogen at 78 K, 00455 butane at 273 K, 00434cm g .

Low-pressure hysteresis is not confined to Type I isotherms, however, and is frequently superimposed on the conventional hysteresis loop of the Type IV isotherm. In the region below the shoulder of the hysteresis loop the desorption branch runs parallel to the adsorption curve, as in Fig. 4.26, and in Fig. 4.2S(fi) and (d). It is usually found that the low-pressure hysteresis does not appear unless the desorption run commences from a relative pressure which is above some threshold value. In the study of butane adsorbed on powdered graphite referred to in Fig. 3.23, for example, the isotherm was reversible so long as the relative pressure was confined to the branch below the shoulder F. 

Fig. 5.5 Adsorption isotherms of butane at 0°C on Iceland Spar ground for 1000 h. Curve (i), the solid was outgassed at 25°C. Curve (ii), the solid was outgassed at 1S0°C. O, adsorption p Q, desorption.

Fig. 10. Purging (desorption) curves for the N-butane in a one liter canister...

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. 

Fig.9. Loading and breakthrough curves Fig. 10. Purging (desorption) curves for the in a one liter canister, 40 g/hr N-butane N-butane in a one liter canister feed rate...

Schulten, H.-R. Nibbeiing, N.M.M. An Emission-Controlled Field Desorption and Electron Impact Spectrometry Study of Some A-Substituted Propane and Butane... 

The increase in time resolution of advanced sorption uptake methods and the joint use of sorption and radio-spectroscopic techniques allow for a more detailed analysis of the so-called "non-Fickian" behaviour of sorbing species in the intracrystalline bulk phase [18,28,29,76]. Correspondingly, information on molecular dynamics has been obtained for n-butane and 2-but ne in NFI zeolites by means of the single step frequency response method and C n.m.r. line-shape analysis [29]. As can be seen from Figures 4 and 5, the ad- / desorption for both sorbates proceeds very quickly, but with a... 

We have tested the above hypothesis by investigating the activation of the C-H bonds of /z-butane and iso-butane and the C=C bonds of 1,3-butadiene, 1-butene and iso-butene on clean V(110) and on VC/V(110) surfaces by using HREELS and TDS.5 Figure 24.6 shows the TDS results following the reaction of/j-butane from clean and carbide-modified V(110) surfaces. For each set of TDS experiments, the clean and carbon-modified V(110) surfaces were exposed to identical exposures of /z-butane at 80 K. Desorption peaks from both parent molecules and the decomposition product (hydrogen) are compared. As shown in Figure 24.6, the adsorption of /z-butane on clean V(110) is completely reversible, as indicated by the absence of any H2 desorption peak. On the carbide-modified surfaces, the peak area of molecularly desorbed /z-butane decreases, which is accompanied by an increase in the peak area of H2 at approximately 500 K. Both observations indicate that the fraction of n-butane undergoing decomposition is increased on the carbide-modified surfaces. 

Figure 24.6 Comparison of TDS results following the reaction of n-butane on clean and carbide-modified V(110) surfaces. The left-panel shows the molecular desorption of n-butane (major cracking pattern at 43 amu) and the right-panel shows the desorption of H2 molecules.

Figure 3 shows a profile of the potential surface of the consecutive stages of (I). Let k be the rate constant of the reaction. Then, in conformity with the results obtained, km. It is clear, however, that the level 4 of the adsorbed butylene in the process of dehydrogenation of butane is the same as the level 6 of the butylene in the dehydrogenation of the latter. Hence, km = ka and consequently km km. Thus, in dehydrogenation the desorption rate constant of the initial substance is considerably larger than that of its dehydrogenation. 

The outlet gas composition is not constant and depends on the level of pressure. Desorption of the high-molecular weight hydrocarbons happens mainly for pressure lower than 1 MPa. Between 3.5 MPa and 1 MPa, the equilibrium conditions between the gas and the adsorbed phase entail values of the different ratios systematically lower than 1. This is especially pronounced for the /-butane and the / -pentane. 

BTT and BTN, butane-1,2,4-triol-trinitrate DNT, dinitrotoluene EGDN, ethylene glycol dinitrate HPLC, high-performance liquid chromatography LOD, limits of detection MDQ, minimum detectable quantities NB, nitrobenzene NG, nitroglycerine NN, nitronaphthalene NT, nitrotoluene PETN, pentaerythritol tetranitrate RDX, cyclotrimethylene trinitramine SFE, supercritical fluid extraction SGC, solvating gas chromatography TDM, thermal desorption modulator TNB, trinitrobenzene and TNT, trinitrotoluene. 

Reaction Products. No mercaptan or tetrahydrothiophene intermediates were found in the products of shot reactions over either catalyst. Instead thiophene reacted by rejecting its hydrocarbon portion either as a butadiene-butene mixture (from chromia) or a butene-butane mixture without butadiene (from cobalt molybdate). In both cases, the sulfur was left on the catalyst as adsorbed H2S. No H2S peak was observed following any such reaction and subsequent experiments with H2S showed that the rate of desorption of H2S was negligible until much higher concentrations on the catalyst surface had been reached. 

Further research (22-24) has shown that butene oxidation can produce many selective reaction products (furan, acetaldehyde, and methyl vinyl ketone), which are not detected during butane oxidation. It cannot be assumed that the oxidation of butane and of the unsaturated reactants proceed along the same pathway. The kinetics data must be viewed with this point in mind, although butane activation is widely accepted to be the rate-determining step. The intermediates are capable of desorbing from the surface (as observed in the TAP investigations), but they do not, indicating that the further reactions occur more readily than desorption. 

Figure 15.3 Desorption of butane and butene at room temperature in a flow of 2% Oj/kr from a 6% chromia/ aiumina cataiyst after butane dehydrogenation at 873 K.

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