Olefins paraffins

Fig. 1. Liquid—Hquid extraction selectivity 0> olefins , paraffins.

Olefin—Paraffin Separation. The catalytic dehydrogenation of / -paraffins offers a route to the commercial production of linear olefins. Because of limitations imposed by equiUbrium and side reactions, conversion is incomplete. Therefore, to obtain a concentrated olefin product, the olefins must be separated from the reactor effluent (81—85), and the unreacted / -paraffins must be recycled to the catalytic reactor for further conversion. 

Mobil MTG and MTO Process. Methanol from any source can be converted to gasoline range hydrocarbons using the Mobil MTG process. This process takes advantage of the shape selective activity of ZSM-5 zeoHte catalyst to limit the size of hydrocarbons in the product. The pore size and cavity dimensions favor the production of C-5—C-10 hydrocarbons. The first step in the conversion is the acid-catalyzed dehydration of methanol to form dimethyl ether. The ether subsequendy is converted to light olefins, then heavier olefins, paraffins, and aromatics. In practice the ether formation and hydrocarbon formation reactions may be performed in separate stages to faciHtate heat removal. 

Silver fluorocomplexes are also used ia the separation of olefin—paraffin mixtures (33), nitration (qv) of aromatic compounds (34), ia the synthesis of (9-bridged bicycHcs (35), pyrroles (36), cyclo-addition of vinylbromides to olefins (37), and ia the generation of thioben2oyl cations (38). 

FacilitatedTransport Process for Eow-Cost Olefin—Paraffin Separation, ATv2iacedTec m.o ogyPi.ogt.2im.E o. 70NANB4H1528 National Institute of Science and Technology, 1994. 

It is not feasible to model the reaction of each hydrocarbon species with oxides of nitrogen. Therefore, hydrocarbon species with similar reactivities are lumped together, e.g., into four groups of reactive hydrocarbons olefins, paraffins, aldehydes, and aromatics (32). 

Figure 10-2. Flame temperature of aromatics, olefins, paraffins, and alcohol [16].

Okamoto, K.,S. Kawamura, M. Yoshino, H. Kita, Y. Hirayama, N. Tanihara, and Y. Kusuki, Olefin/ paraffin separation through carbonized membranes derived from an asymmetric polyimide hollow fiber membrane, Ind. Eng. Chem. Res., 38, 4424,1999. 

Also, concerning the effect of the temperature on the reaction rates, different assumptions were made here with respect to our previous work.10 In that case, only the hydrogen and CO adsorption were regarded as activated steps, in order to describe the strong temperature effect on CO conversion. In contrast, due to the insensitivity of the ASF product distribution to temperature variations (see Section 16.3.1), other steps involved in the mechanism were considered as non-activated. In the present work, however, this simplification was removed in order to take into account the temperature effect on the olefin/paraffin ratio. For this reason, Equations 16.7 and 16.8 were considered as activated. 

Fig. 5 Olefin/paraffin ratio as a function of TOS for C2-C6 components for 12% Co/Si02. Step changes in olefin/paraffin ratio are due to increased GHSV at 23 h, as 20% water addition at 50 h, 33% water addition at 70 h and back to the dry feed at 95 h. H2/CO = 2.1, P - 20 bar, T = 483 K.19 Reprinted from Journal of Catalysis, Vol. 231, S. Storsaeter, 0. Borg, E. A. Blekkan and A. Holmen, Study of the effect of water on Fischer-Tropsch synthesis over supported cobalt catalysts, pp. 405 119. Copyright (2005), with permission from Elsevier. 

When CH3OH is adsorbed first, the strongly adsorbed CH OH is transformed into ethers, olefins, paraffins and aromatics, m a similar way, when it was the only reactant present (7) (A). C2H4 remains inactive below 623 K. At this temperature, it begins to react as it is shown by the NMR signals in the paraffinic region (B). It can be assumed that in such conditions, ethylene alkylates aromatics obtained from methanol. 

Non-aromatic hydrocarbons separation (e.g., olefin/paraffin, -paraffin/ non-n-paraffin) ... 

Padin, J. and Yang, R.T. (2000) New sorbents for olefin/paraffin separations by adsorption via tc-complexabon Synthesis and effects of substrates. Chem. Eng. Sd., 55, 2607. 

There are three liquid-phase adsorption Sorbex technology-based separation processes for the production of olefins. The first two are the UOP C4 Olex and UOP Sorbutene processes and the third is the detergent Olex process(Cio i,5) [25, 26]. The three olefin separation processes share many similarities. The first similarity between the three olefin separation processes is that each one utilizes a proprietary adsorbent whose empirical formula is represented by Cation,([(A102)),(Si02)2] [27]. The cation type imparts the desired selectivity for the particular separation. This zeolite has a three-dimensional pore structure with pores running perpendicular to each other in the x, y and z planes [28]. The second similarity between the three olefin separation processes is the use of a mixed olefin/paraffin desorbent. The specifics of each desorbent composition are discussed in their corresponding sections. The third similarity is the fact that all three utilize the standard Sorbex bed allotment that enables them to achieve product purities in excess of 98%. The following sechons review each process in detail. 

The C4 Olex process is designed with the full allotment of Sorbex beds in addition to the four basic Sorbex zones. The C4 Olex process employs sufficient operating temperature to overcome diffusion limitations with a corresponding operating pressure to maintain liquid-phase operation. The C4 Olex process utilizes a mixed paraffin/olefin heavy desorbent. In this case it is an olefin/paraffin mix consisting of n-hexene isomers and -hexane. A rerun column is needed to remove heavy feed components such as Cs/C because they would contaminate or dilute the hexene/hexane desorbent. Table 8.5 contains the typical feed and product distributions. 

Light hydrocarbons (Ci to C4) and aromatics (mainly Ce to Ce) were produced by ZSM-5 due to the the conversion of olefins and paraffins. Thus,these results provide evidence for cracking of olefins, paraffins and cyclization of olefins by ZSM-5 at 500 C. The steam deactivated ZSM-5 catalyst exhibited reduced olefin conversion and negligible paraffin conversion activity. 

The scheme implies that in the presence of a metal which establishes the olefin-paraffin equilibrium, the carbonium ion concentration on the surface depends on the hydrogen partial pressure. The stabilizing effect of a given metal load will depend on its dispersion and distribution and on the prevailing hydrogen pressure. Similar experiments show that for zeolite Y based catalysts the reaction mechanism is identical with that discussed above for mordenite. 

Respect to olefins/parafFins ratio, it can be mentioned that the it electron bonds present in the unsaturated hydrocarbons can interact with the surface electrons of the carbon microdomains these surface electrons act as hydrogenation catalyst in the same way that Platinum surface electrons act in conventional catalytic hydrogenation processes The observed values of olefins/paraffins ratio decrease from CON to C-155, and practically olefins are not present as a product when C-155 is used, suggesting for the new developed materials the presence of high electronic densities surrounding the carbon microdomains. 

The comparison of the reaction rates of 03, H02, and CH302 with olefin, paraffin, and NO reveals that the predominant reactions of these reactive species are the oxidations of NO [(V1II-18), (VI11-21 a), and (VI11-24)]. The major destruction processes of olefin are the reactions with 03 and with OH. (The rate of olefin destruction is proportional to the rate constant times the concentration of the active species.) The destruction process of olefins by H02 is less important and those by O atoms and CH302 radicals are also minor. 

Steigelmann and Hughes develop olefin/paraffin facilitated transport membrane demonstrate process at the Peinemann demonstrates pilot scale - 1980-1982 dispersed solid Ag + salts can facilitate olefins -1992... 

The best hope for olefin/paraffin facilitated membrane separations seems to be the solid polymer electrolyte membranes discussed earlier, the results of which are shown in Figures 11.21 and 11.22. If stable membranes with these properties can be produced on an industrial scale, significant applications could develop in treating gases from steam crackers that manufacture ethylene and from polyolefin plants. 

I. Pinnau and L.G. Toy, Solid Polymer Electrolyte Composite Membranes for Olefin/ Paraffin Separation, 7. Membr. Sci. 184, 39 (2001). 

A. Morisato, Z. He, I. Pinnau and T.C. Merkel, Transport Properties of PA12-PTMO/ AgBF4 Solid Polymer Electrolyte Membranes for Olefin/Paraffin Separation, Desalination 145, 347 (2002). 

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