Of propane/propylene mixture

Tphis work explores the important variables which must be considered - to design an extractive distillation process. The discussion identifies the economic effects of these variables and their possible interactions. Some of the design variables may have synergistic effects in terms of separation cost while others may not. As a result, the optimum design for an economic extractive distillation process must be a compromise set of values for the different process variables. These compromises are discussed and are illustrated for a particular case—i.e., separation of propane-propylene mixtures. For this commercially important separation fractional distillation is most often used, regardless of the low relative volatility (about 1.13-1.19 at 200 psia). 

Table 1. Typical results in pyrolysis of propane—propylene mixtures...

If this equation Is also valid In the pyrolysis of propane-propylene mixtures, the amount of propylene available for the copyrolysls Is defined as the sum of the propylene fed plus propylene produced from propane evaluated from Equation (23). However, the selectivity was small and could be negligible In the case of low propane to propylene ratio In feed (yCoHo 0.2). Methane yield from propane and propylene was larger chan that of ethylene as shown In Table 1. This result will be caused by hydrogenation and hydrogenolysis of each component. 

Determination of Rate Constant In the Pyrolysis of Propane-Propylene Mixtures... 

Figure 2. Arrhenius plots for propane decomposition rate in pyrolysis of propane-propylene mixtures...

HARAGucm ET AL. Pywlysk of Propane-Propylene Mixtures Table 4. Reaction model for pyrolysis of propane... 

An attempt was made to calculate the product distributions of propane pyrolysis on the basis of the reaction model considering both inhibition and acceleration effects observed in the pyrolysis of propane-propylene mixtures. The reaction model for propane pyrolysis used in this work is shown in Table 4. The rate constants given in Table 4 were measured in our previous works (3, 4). At the initial stage of propane pyrolysis, the formation of the primary products such as methane, ethylene and propylene is predominant but as the reaction proceeds, the consecutive decomposition of each product is also remarkable. Therefore, a reaction model was postulated which consisted of major stoichiometric reactions for propane (i) - (iv), for propylene (v), (vi) and... 

Using the experimental results of the pyrolysis of propane-propylene mixtures under the conditions of temperatures near 900 C, atmospheric pressure and hydrogen dilution, the relation between the decomposition rate constant of propane or propylene and the ratio of both reactants was obtained. It was found from the results that propylene had an inhibition effect on propane decomposition, and conversely, propane had an acceleration effect on propylene decomposition. 

The general guidelines for developing a gas separation process based on adsorption are reviewed. Two important industrial cases based on adsorption processes are selected the separation of propane/propylene mixtures and n/iso-paraffins mixtures. The 13X zeolite and Ag -Amberlyst were used as adsorbent for propane/propylene mixture taking into account information from the open literature. The 5A zeolite was selected for n/iso-paraffins system the adsorption equilibrium and diffusivity data were obtained from gravimetric and ZLC techniques respectively. A mathematical model for the bulk separation in fixed bed upon non-isothermal non-adiabatic conditions is formulated and solved numerically. The simulated results are compared with the available experimental breakthrough curves. Finally, a cyclic process based in the PSA-VSA and TSA concepts is proposed for these systems. 

In this article we report i) the measurement of sorption equilibrium data of nC,-, and nCy in 5A zeolite pellets on a flow microbalance ii) The measurement of intraparticle diffusivity of nCs and nCc on 5A zeolite pellets with crystals of different size by ZLC and gravimetry and iii) The development of a mathematical model in order to predict the behavior of fixed bed and cyclic adsorption processes, iv) The prediction of breakthrough curves of propane/propylene and n/iso-paraffins mixtures in a fixed-bed adsorber based on a model including parameters independently measured, iv) Study of cyclic adsorption processes as Pressure Swing Adsorption (PSA) / Vacuum Swing Adsorption (VSA) and Temperature Swing Adsorption (TSA) for the separation of propane /propylene mixtures and n/iso-paraffins mixtures. 

Huang, Y.H., et al.. Experimental study of binary equilibrium adsorption desorption of propane-propylene mixtures on 13X sieves by differential sorption bed system and investigation of their equilibrium expressions, Sep. Technol., 4(3), 156-166 (1994). 

The volumetric expansion parameter S may thus be taken as 0.9675. The product distribution will vary somewhat with temperature, but the stoichiometry indicated above is sufficient for preliminary design purposes. (We should also indicate that if one s primary goal is the production of ethylene, the obvious thing to do is to recycle the propylene and ethane and any unreacted propane after separation from the lighter components. In such cases the reactor feed would consist of a mixture of propane, propylene, and ethane, and the design analysis that we will present would have to be modified. For our purposes, however, the use of a mixed feed would involve significantly more computation without serving sufficient educational purpose.)... 

Synonyms/Trade Names Bottled gas, Compressed petroleum gas, Liquefied hydrocarbon gas. Liquefied petroleum gas, LPG [Note A fuel mixture of propane, propylene, butanes butylenes.]... 

In the present work, propane-propylene mixtures with various ratios were pyrolyzed at temperatures near 900°C and at an atmospheric pressure in an annular flow reactor. Hydrogen was used as a diluent. Under these experimental conditions, it was rather difficult to maintain an uniform temperature throughout the reactor since the reaction rate was high, and consequently, thermal effects due to the heat reaction were significant. In this work, therefore, experimental data at the initial stage of decomposition were analyzed using the effective temperature method to obtain kinetic rate parameters, activation energy and frequency factor, for propane and propylene decompositions. From the relations between... 

Propane-propylene mixtures were pyrolyzed in a flow reactor near 900 C and atmospheric pressure with a large amount of hydrogen dilution. Under these e erlmental conditions, the temperature distributions in the reactor axis were highly nonuniform. 

Methodology of gas adsorption process design. Separation of propane/propylene and n/iso-paraffins mixtures... 

In the chlorohydrin reactor, gaseous propylene and chlorine (equimolar amount) are mixed with an excess of water. Propylene chlorohydrin is formed at 35-50 °C and 2-3 bar. The water plays an important role in this reaction step. The reaction products remain in aqueous solution and water, acting as diluent, minimizes the formation of by-products. Water is also a reactant [Eq. (6.12.8)] and direct cooling medium. In the separator the vent gas (mixture of propane, propylene, CI2, O2, N2, H2, and CO2) is removed from the propylene chlorohydrin solution and sent to the... 

Van Damme,P.So, SoNarayanan and G.F.Froment. "Thermal Cracking of Propane and Propane-Propylene Mixtures, Pilot Plant versus Industrial Data". AIChE.J. v21 (1975) 1065-1073. 

Van Damme, P.S., Narayanan, S. and Froment, G.F. (1975) Thermal cracking of propane and propane-propylene mixtures pilot plant versus industrial data , AIChE J., 21, 6, 1065-1073. 

Figure 9 Experimental breakthrough curves for the adsorption of equimolar (a) ethane/ethylene and (b) propane/propylene mixtures flowing through a 1.5-mL bed of FeMOF-74 at 318 K with a total gas flow of 2 mL min at atmospheric pressure. After breakthrough of the olefln and return to an equimolar mixture composition, a nitrogen purge was applied, leading to desorption of the olefin, (c) The first coordination spheres for the iron centers in the solid-state structures obtained on dosing FeMOF-74 with acetylene, ethylene, ethane, propylene, and propane (From Ref. 81. Reprinted with permission from AAAS.)...

Figure 6 Single component gas adsorption isotherms for (a) methane, ethane, ethylene, and acetylene and (b) propane and propene at 318 K in Fe2(dobdc). The filled and open circles represent adsorption and desorption data, respectively, (c) and (d) represent experimental breakthrough curves for the adsorption of equimolar ethane/ethylene and propane/propylene mixtures. (Reproduced with permission from Ref 50. Copyright 2012 American Association of Advancement of Science.)...

Some small amount of byproduct formation occurs. The principal byproduct is di-isopropyl ether. The reactor product is cooled, and a phase separation of the resulting vapor-liquid mixture produces a vapor containing predominantly propylene and propane and a liquid containing predominantly the other components. Unreacted propylene is recycled to the reactor, and a purge prevents the buildup of propane. The first distillation in Fig. 10.3a (column Cl) removes... 

Many simple systems that could be expected to form ideal Hquid mixtures are reasonably predicted by extending pure-species adsorption equiUbrium data to a multicomponent equation. The potential theory has been extended to binary mixtures of several hydrocarbons on activated carbon by assuming an ideal mixture (99) and to hydrocarbons on activated carbon and carbon molecular sieves, and to O2 and N2 on 5A and lOX zeoHtes (100). Mixture isotherms predicted by lAST agree with experimental data for methane + ethane and for ethylene + CO2 on activated carbon, and for CO + O2 and for propane + propylene on siUca gel (36). A statistical thermodynamic model has been successfully appHed to equiUbrium isotherms of several nonpolar species on 5A zeoHte, to predict multicomponent sorption equiUbria from the Henry constants for the pure components (26). A set of equations that incorporate surface heterogeneity into the lAST model provides a means for predicting multicomponent equiUbria, but the agreement is only good up to 50% surface saturation (9). 

The noncatalytic oxidation of propane in the vapor phase is nonselec-tive and produces a mixture of oxygenated products. Oxidation at temperatures below 400°C produces a mixture of aldehydes (acetaldehyde and formaldehyde) and alcohols (methyl and ethyl alcohols). At higher temperatures, propylene and ethylene are obtained in addition to hydrogen peroxide. Due to the nonselectivity of this reaction, separation of the products is complex, and the process is not industrially attractive. 

In the vapor-phase process, the reaction temperature and pressure are approximately 250°C and 40 atmospheres. Phosphoric acid on Kieselguhr is a commonly used catalyst. To limit polyalkylation, a mixture of propene-propane feed is used. Propylene can be as low as 40% of the feed mixture. A high benzene/propylene ratio is also used to decrease polyalkylation. A selectivity of about 97% based on benzene can be obtained. 

The first stage of the process is a hydroformylation (oxo) reaction from which the main product is n-butyraldehyde. The feeds to this reactor are synthesis gas (CO/H2 mixture) and propylene in the molar ratio 2 1, and the recycled products of isobutyraldehyde cracking. The reactor operates at 130°C and 350 bar, using cobalt carbonyl as catalyst in solution. The main reaction products are n- and isobutyraldehyde in the ratio of 4 1, the former being the required product for subsequent conversion to 2-ethylhexanol. In addition, 3 per cent of the propylene feed is converted to propane whilst some does not react. 

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