Zeolite T membranes

Cui Y, Kita H, and Okamoto KI. Zeolite T membrane Preparation, characterization, pervaporation of water/organic liquid mixtures and acid stability. J Membr Sci 2004 236 17-27. 

Tanaka K, Yoshikawa R, Ying V, Kita H, and Okamoto K. Application of zeolite T membrane to vapor-permeation-aided esterification of lactic acid with ethanol. Chem Eng Sci 2002 57 1577-1584. 

NaA/polyelectrolyte multilayer-pervaporation membrane showing a greater stability under acidic conditions in comparison with a pure zeolite A membrane and maintaining a high selectivity for water over alcohols. For the same purpose, Kita et al. [181-183] proposed a zeolite T membrane, prepared by ex situ crystallization, for the per-vaporation-aided or vapor-permeation-aided esterification of acetic acid with ethanol. This membrane has a higher acid resistance and can be directly immersed in the liquid-phase reaction mixture. The conversions achieved exceed the equilibrium limit and reached to almost 100% after a stabilization period of 8 h. 

Zeolite T membranes are hydrophilic and also acid resistant and they would be preferred for the pervaporation dehydration in the presence of organic acid, such as the esterification hybrid process. However, there are fewer reports about the zeolite T membranes preparation. Cui et reported the... 

Figure 17.9 Feed composition dependence on permeance of each component and CO2/N2 (closed symbol) and CO2/CH4 (open symbol) separation factors at 35 °C and a feed pressure of 100 kPa. Reprinted from Y. Cui, H. Kita and K. Okamoto, Preparation and gas separation properties of zeolite T membranes, Chemical Communications, 2154—2155, 2003, with permission from RSC.

Tanaka et al. (2001) used zeolite T membranes in an ISU membrane reactor (at 343 K). Almost complete conversion was reached. The reaction time courses were well described by a model based on two assumptions (1) the reaction obeyed to a second-order kinetic and (2) the permeation flux of each component was proportional to its concentration. 

Some small-pore zeolite and molecular sieve membranes, such as zeolite T (0.41 nm pore diameter), DDR (0.36 x 0.44nm) and SAPO-34 (0.38nm), have been prepared recenhy [15-21]. These membranes possess pores that are similar in size to CH4 but larger than CO2 and have high CO2/CH4 selechvihes due to a molecular sieving mechanism. For example, a DDR-type zeolite membrane shows much higher CO2 permeability and CO2/CH4 selechvity compared to polymer membranes [15-17]. SAPO-34 molecular sieve membranes show improved selechvity for separation of certain gas mixtures, including mixtures of CO2 and CH4 [18-21]. 

Kyotani, T., Mizuno, T., Katakura, Y., Kakui, S., Shimotsuma, N., Saito, )., and Nakane, T. (2007) Characterization of mbular zeolite NaA membranes prepared from dear solutions by ETIR-ATR, GIXRD and EIB-TEM-SEM.J. Membr. Sci., 296,162-170. 

For a zeolite T (OFF stmcture, 0.68 nm XRD pore diameter), Tanaka et al. [131], observed that the separation factor of a water/acetic acid (50/50 wt%) measured at 75°C decreased monotonically after the immersion of the membrane into the acetic acid mixmre. Initially, the separation factor and water flux were 182 and 1.46 kg/m h, respectively, and after 32 h these values changed to 86 and 1.77 kg/m h, showing a deterioration of the membrane. Cui et al. [130] also smdied the stability of crystals and membranes of zeolite T in acid medium. The powders were immersed in a 50/50 wt% water/acetic acid mixture for 7 days at 75°C and also in HCl solutions 0.5 and 1 M for 1 h at 50°C. The analysis of the samples after the treatment by ICP and XRD indicated that the sample treated in the acetic acid solution maintained its original Si/Al ratio equal to 4 however, the hydrochloridric acid treatment with the 1 M solution destroyed the zeolite stmcmre and the 0.5 M solution dealuminated the zeolite to a Si/Al equal to 8.9 and the XRD analysis corresponded to zeolite T. The membrane performance, after being used for 1 week at different water/acetic acid concentrations, remains almost unchanged and the separation factor of the membrane treated in HCl dramatically decreased as was expected. 

Masuda T, Asanuma T, Shouji M, Mukai SR, Kawase M, and Hashimoto K. Methanol to olefins using ZSM-5 zeolite catalyst membrane reactor. Chem Eng Sci 2003 58 649-656. 

Yamamura T, Kondo M, Abe J, Kita H, and Okamoto K. The vapor permeation module using zeolite NaA membrane for producing absolute ethanol from biomass ethanol. Proceedings of the Eight International Conference on Inorganic Membranes, Cincinnati, OH, July 18-22, 2004, pp. 599-603. 

For a zeolite T (OFF structure, 0.68 nm XRD pore diameter), Tanaka et al. [183] observed that the separation factor of a water/acetic acid (50/50 wt.%) measured at 75°C decreased monotonically after the immersion of the membrane into the acetic acid mixture. Initially, the separation factor and water flux were 182 and 1.46 kg/(m h), respectively, and after 32 h, these values changed to 86 and 1.77 kg/(m h), showing a deterioration of the membrane. Cui et al. [182] also studied the stability of crystals and membranes of zeolite T in an... 

Other zeolite membranes such as zeolite T, DD3R and SAPO-34 have been studied for these gaseous separations, since they give the possibility of separating small species on the basis of molecular sieving mechanism due to their small pore size. 

Van den Berg, A.W.C., Gora, L., Jansen, J.C., Makkee, M. and Maschmeyer, T. 2003. Zeolite A membranes synthesized on UV-irradiated TiOj coated metal support The high pervaporation performance. P Memh Sa. 224 29—37. 

C. Kong, T. Shintani, T. Tsuru, Pre-seeding -assisted synthesis of a high performance polyamide-zeolite nanocomposite membrane for water purification, New Journal of Chemistry 34 (2010) 2101-2104. 

Sawamoto, S., Ohya, H., Yanase K., Semenova, S., Aihara, M., Takeuchi, T., and Negishi, Y. (2000). Nanotechnological method to control pore diameter of organic-inorganic composite membrane. Part 2. Molecular-wise vapor polymerization./. Membr. Sci. 174 131-139. Kumakiri, I., Yamaguchi, T., and Nakao, S. (2000). Application of a zeolite A membrane to reverse osmosis process./. Chem. Eng.Jpn. 33 333-336. 

Using a hydrophilic zeolite membrane such as LTA and zeolite T to remove the water from the reaction system by sweep gas or vacuum (pervaporation), the esterification reaction would drive toward the product side with the result of enhanced yields. Beneficial aspects of PVMRs also include low energy consumption and the possibility of carrying out esterification at a selected temperature. 

In all cases, if the cost of the octane number was low (3.1 euros/RON point/ t), addition of a MFI zeolite-based membrane separation unit was not financially justified. Under these conditions, in fact, either the energy consumption related to the vaporization of the feed weighed too heavily on the operating costs (membrane temperature 300 °C), or the margin cleared by the gain in octane number was not sufficient to make the construction of the membrane separation unit profitable, since it was too large (area > 10 000 m ). 

Nakayama, K., Suzuki, K., Yoshida, M., Yajima, K., and Tomita, T. (2006) Method for preparing DDR type zeolite membrane, DDR type zeolite membrane, and composite DDR type zeolite membrane, and method for preparation thereof US Patent 7,014,680. 

For single-component gas permeation through a microporous membrane, the flux (J) can be described by Eq. (10.1), where p is the density of the membrane, ris the thermodynamic correction factor which describes the equilibrium relationship between the concentration in the membrane and partial pressure of the permeating gas (adsorption isotherm), q is the concentration of the permeating species in zeolite and x is the position in the permeating direction in the membrane. Dc is the diffusivity corrected for the interaction between the transporting species and the membrane and is described by Eq. (10.2), where Ed is the diffusion activation energy, R is the ideal gas constant and T is the absolute temperature. 

Tsuru, T., Takata, Y., Kondo, H., Hirano, F., Yoshioka, T., and Asaeda, M. (2003) Characterization of sol-gel derived membranes and zeolite membranes by nanopermporometry. Separ. Purif. Technol., 32, 23-27. 

Gardner, T.Q., Martinek, ).G., Falconer, J.L., and Noble, R.D. (2007) Enhanced flux through double-sided zeolite membranes. J. Membr. Sci., 304,... 

Tomita, T., Nakayama, K., and Sakai, H. (2004) Gas separation characteristics of DDR type zeolite membrane. Micropor. Mesopor. Mater., 68, 71-75. 

Li, Y., Chung, T.S., Cao, C., and Kulprathipanja, S. (2005) The effects of polymer chain rigidification, zeolite pore size and pore blockage on polyethersul-fone (PES)-zeolite A mixed matrix membranes./. Memhr. Sci., 260, 45-55. 

Pechar, T.W., Tspatsis, M., Marand, E., and Davis, R. (2002) Preparation and characterization of a glassy fluorinated polyimide zeolite mixed matrix membrane. Desalination, 146, 3-9. 

Buttal, T., Bac, N., and Yilmaz, L. (1995) Effect of feed composition on the performance of polymer-zeolite mixed matrix gas separation membranes. Sep. Sci. Technol, 30 (11), 2365-2384. 

This abstract definition will be explained with the actual example of gaseous permeation through a zeolite/alumina composite membrane. Here, we must investigate the effect of the five following factors on the rate of permeation the temperature (T) when the domain is between 200 and 400 °C, the trans-membrane pressure (Ap) when the domain is between 40 and 80 bar, the membrane porosity (s) ranging from 0.08 to 0.18 m /m, the zeolite concentration within the porous structure (c ) from 0.01 to 0.08 kg/kg and the molecular weight of the permeated gas (M) which is between 16 and 48 kg/kmol. With respect to the first... 

Many reactions over zeolites don t seem to require strong acidity. They are probably utilizing the polarity of the crystal lattice, and taking advantage of the tremendous reactant-concentrating effect of the vast, membrane-like internal surface area of the zeolite. Perhaps we even can look at zeolites as rugged, primitive proto-enzymes. Of course, they... 

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