Olefins zeolite membranes

This cost differential can be tolerated only in applications in which polymeric membranes completely fail in the separation [78]. Demanding separation applications, where zeolite membranes could be justified, due to the high temperatures involved or the added value of the components, and have been tested at laboratory scale, are the following separation of isomers (i.e., butane isomers, xylene isomers), organic vapor separations, carbon dioxide from methane, LNG (liquefied natural gas) removal, olefines/paraffins and H2 from mixtures. In most cases, the separation is based on selective diffusion, selective adsorption, pore-blocking effects, molecular sieving, or combinations thereof. The performance or efficiency of a membrane in a mixture is determined by two parameters the separation selectivity and the permeation flux through the membrane. 

Using a similar approach, Masuda et al. [219] employed a ZSM-5 zeolite membrane in a flow-through configuration for the methanol-to-olefins process. As in the previous work, permeating molecules would ideally have a uniform residence time... 

Kobayashi. Y. Koyama, T. Pervaporation of concentrated aeetie aeid solution and reaction of membrane of inethanol to olefin using eylindrical MFT-type zeolite membranes without any pin holes. Catal. Catal. 1998. 40. 348. 

Several studies concerning the separation of propylene from propane base on faujasite (FAU zeolite) membranes or titanosilicate ETS have been published recently. The olefin/paraffin selectivity of all those materials was comparable to glassy polymers and always below 10. 

A zeolite membrane having MFI topology was also used to test the reaction of methanol to olefins (Masuda et al, 2003). The authors produced olefins with a high selectivity (80-90%) and high conversion (60-98%) by adjusting the diffusion and chemical reaction rates of the molecular species in the zeolite layer of the membrane. 

As documented in Chapter 5, zeolites are very powerful adsorbents used to separate many products from industrial process steams. In many cases, adsorption is the only separation tool when other conventional separation techniques such as distillation, extraction, membranes, crystallization and absorption are not applicable. For example, adsorption is the only process that can separate a mixture of C10-C14 olefins from a mixture of C10-C14 hydrocarbons. It has also been found that in certain processes, adsorption has many technological and economical advantages over conventional processes. This was seen, for example, when the separation of m-xylene from other Cg-aromatics by the HF-BF3 extraction process was replaced by adsorption using the UOP MX Sorbex process. Although zeolite separations have many advantages, there are some disadvantages such as complexity in the separation chemistry and the need to recover and recycle desorbents. 

M., Mukai, S.R., Kawase, M., and Hashimoto, K. (2003) Methanol to olefins using ZSM-5 zeolite catalyst membrane reactor. Chem. Eng. Sci.,... 

Another example for microreactor-controlled selectivity in the reaction of olefin with x02 can be found in the photosensitized oxidation of DPB in ZSM zeolite [160], Nafion membranes [161], and vesicles [163], In homogeneous solution, ZSM zeolite, and Nafion membranes, the oxidation of DPB with 02 yielded the [2 + 4] reaction product, endoperoxide 6, as the unique product (Figs. 15 and 18). In sharp contrast, in vesicle medium, the oxidation produced the aldehydes 1 and 2 ([2 + 2] reaction) in quantitative yield as described in Section III.B.l (Fig. 

The preceding discussions illustrate that membranes have shown great potential as an alternative for olefin/paraffin separation, yet the performance of current membranes is insufficient for commercial deployment of this technology. Advanced material development is highly desired to improve the membrane properties and reduce cost. Another possible approach involves hybrid membranes with zeolites or CMS incorporated in a continuous polymer phase. More discussion in this regard will be covered later in this chapter. 

Torres, M., Lopez, L., Dominguez, J. M., Mantilla, A., Ferrat, G., Gutierrez, M. and Maubert, M. Olefins catalytic oligomerization on new composites of beta-zeolite films supported on a-Al203 membranes. Chem. Eng. J., 2003, 92, 1-6. 

In Parton et al., a new type of heterogeneous catalyst was proposed consisting of a solid catalyst (iron phthalocyanine zeolite Y) dispersed in a dense PDMS (polydimethylsiloxane) polymer matrix.[l] The system resulted in strongly increased catalytic activities in the oxidation of cyclohexane.[2] Other systems, such as Mn(bipy)2-Y (mangtuiese bipyridine zeolite Y) were also proven to benefit from such incorporation.[3,4] The results presented here using Ti-MCM-41 confirm this for the epoxidation of olefins, an important route for the production of fine chemicals.[5] The influence of the polymer on the reaction activity and selectivity is shown by using different oxidants and solvent conditions in the epoxidation of 1-octene. It will enable the deduction of the advantages and limitations of the reported membrane occluded catalyst system. 

Rattanawong, W., Osuwam, S., Risksomboen, T., and Kulprathipanja, S. (2001). Zeolite-cellulose acetate mixed-matrix membrane for olefin/patafiin separation. Am. Chem. Soc. Div. Petrochem. 46, 166. 

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