P-type zeolites

Li and coworkers (2001a,b,c, 2002) used silicate-1, ZSM-5, ZSM-11, mordenite, and X-, Y-, and p-type zeolite membranes to remove 1-3-propanediol from glycerol... 

The search for sodium tripolyphosphate substitutes in the 1970s resulted in other candidate builder systems besides zeolite A. One of these is zeolite P, which is also known as zeolite MAP (it is a P-type zeolite having maximum aluminium content) and zeolite A24. It was not before the early 1990s that it became commercially available under the brand name Doucil 24 [66,143]. 

The basic principles of P-type zeolite production are not unlike those of zeolite A, which are well known. It has been reported that zeolite P production is currently accomplished on converted zeolite A4 manufacturing plants. 

The application of a seeding process may be advantageous. Thus, a slurry of P-type zeolite may be recirculated to the hydrogel precipitation vessel via the stream of recycled filtrate and mother liquor. As a result, a higher product yield can be realized [169,172]. 

Zeolite A is the largest volume zeolitic builder produced today. The new P-type zeolite and zeolite AX have different properties and aim at novel applications fields. Nevertheless, they have to prove their ability for world-scale commercialization. 

Brosius, R., Bazin, P., Thibault-Starzyk, F. et al., (2005) Operando FTIR study of reaction pathways of selective catalytic reduction of NOx with decane in the presence of water on iron-exchanged MFI-type zeolite, J. Catal., 234, 191. 

Maher, P.K. and Scherzer, J. (1970) Method of preparing microcrystalline faujasite-type zeolite. US Patent 3,516,786. 

Materials. An H-ZSM-5 type zeolite (overall Si/Al = 33.5) was provided by DEGUSSA, Wolfgang, F.R.G. The well-shaped crystallites had an average size of 8.8 p x 5.2 p x 3.2 y. Pyridine, benzene and ethylbenzene were from MERCK, Darmstadt, F.R.G., spectroscopic grade, purified by distillation as well as repeated freeze-pump-thaw cycles and finally stored over highly activated 3A molecular sieve pellets. 

Selective hydroxylation of phenol with hydrogen peroxide was reported on acid zeolite catalysts [91-92]. Peroxonium ions, formed by H2O2 protonation, are the oxidizing species. When the reaction is carried out on a faujasite catalyst, a mixture of hydroxybenzenes and tars is obtained [91]. In the presence of H-ZSM-5 on the other hand, no tar formation was mentioned (which does not necessarily mean that it was absent) and p-selectivities close to 100% were reported for the hydroxylation [92]. These superior selectivities reflect the shape selective properties of ZSM type zeolites. 

A different variation in size for water adsorption is observed for the faujasite-type zeolites (Figure 5). These zeolites at first contract, reaching a limit of 0.3-0.45 % at 0 = 0.7-0.8, and then they expand. Except for zeolite CaY, their sizes, even at p/ps 0.85, remain below their initial values. The maximum contraction is observed for zeolite NaY, and the minimum for NaX. 

Carbon dioxide adsorption causes changes in the sizes of all the zeolites studied similar to the variation observed for faujasite-type zeolites after water adsorption (Figure 6). For all zeolites, an increase in the adsorption of carbon dioxide leads to contraction this reached a minimum in the adsorption range 3-5.5 mM/gram. The final length of the pellets is below the initial value up to a relative pressure of p/ps 0.7 for zeolites CaA, CaY, and NaY while for NaA and NaX the contraction passes to an expansion, reaching 0.11% of the initial length at p/ps = 0.66 for NaX and 0.32 for NaA. 

MF1 type zeolites are known to show enhanced selectivity to p-substituted products in alkylation and isomerization of aromatic molecules [e.g. 1,2,3,4]. This shape selectivity is more pronounced with larger zeolite crystals and can be further enhanced by modification of the parent zeolites through post-synthesis treatments like impregnation with basic oxides, metal salts or the deposition of silica or coke [3,5,6,7]. The gain in selectivity is, however, usually accompanied with loss in catalytic activity and in some cases more rapid deactivation [8,9]. Despite the large number of patents and reports in open literature, the reasons for the enhancement of shape selectivity of MFI zeolites by post-synthesis treatment and the limits of the severity of this treatment are not unequivocally explained to date. 

HFI-type ZEOLITES. A large number of HFI-type zeolitea could be obtained in F" media (2-4. 12-15) according to the described route (1) with Prx NH+( 4 x) (Pr = n-propyl, x = 1 to 4) templatea and for the T elements quoted above. P N is the best template (Table III). 

PURELY SILICEOUS HFI-tvoe ZEOLITES. Among the templating cations which were uaed, P R proved to be the moat efficient for easy and fast crystallization. In Table IT are given the crystallographic oharacteriatica of the obtained siliceous HFI-type zeolites (16) aa a function of the template. 

E. de Vos Burchart, B. E. van der Linden, H. van Bekkum, and B. van de Graaf, Collect. Czech. Chem. Commun., 57, 675 (1992). Molecular Mechanics Studies on MFl Type Zeolites. 1. Effect of p-Xylene Adsorption on the Zeolite Structure. 

Apparently, in both zeolite structures the pore deformation that has to be achieved to adsorb guest molecules is caused by the collisions of these molecules with the pore entrances. In the case of the MFI-type zeolite, p-xylene as well as naphthalene were loaded to the maximum population, which is 8 and 4 molecules/u.c., respectively, in the pores. 

Y.-C. Long, X. Chen, Z.-H. Ping, S.-K. Fu, and Y.-J. Sun, MFI-type zeolite filled silicone rubber membranes Preparation, composition, and performance. Zeolites and related microporous materials State of the art 1994 Part B. Proc. lOth Int. Zeol. Conf., Garmisch-Panenkirchen (J. Weitkamp, H.G. Karge, H. Pfeifer, and W. Holderich, eds.), Elsevier, Amsterdam, 1994, p. 1083. 

The air-induced oxidation of trimethylphosphine has been followed in Y-type zeolites using solid state P n.m.r. techniques.The known chiral triphosphines (76) have been transformed into their monoxides and monosulphides via protection of the diphosphinoethane moiety by coordination.- A more detailed study of the reactivity of 1,3,5-triaza-7-phospha-adamantane (77) has revealed that whereas protonation and... 

Vilaseca M, Mateo E, Palacio L, Pradanos P, Hernandez A, Paniagua A, Coronas J, and Santamaria J. AFM characterization of the growth of MFI-type zeolite films on alumina substrates. Micropor Mesopor Mater 2004 71 33-37. 

C. P. Herrero, /. Phys. Chem., 97, 3338 (1993). Monte Carlo Simulation of the Si, A1 Distribution in A-Type Zeolites. 

In the synthesis of faujasite type zeolite, the sequence of the phase evolution amorphous faujasite "P", is well known. Dwyer and Chu( l demonstrated that when TMA ions was added to the initial synthesis mixture a new sequence amorphous faujasite —> ZSM-4, prevailed. In the present work, we utilised a nucleation gel, usually used for directing faujasite phase( ), to the new synthesis system for omega zeolite. Here, we report the effects of nucleation gel on the crystallization processes. 

Onaka and coworkers have reported highly selective V-monoalkylation of aniline and its derivatives over alkali cation exchanged X- and Y-type zeolites. The intrinsic pore structures of X and Y zeolites are assumed to be responsible for the high selectivity. Linde 3A zeolites cannot promote the alkylation of aniline because of their smaller pore structure (Scheme 3). Aniline derivatives having strong electron-withdrawing substituents, such as p-nitroaniline, which is otherwise hardly alkylated even in the presence of KOH, can be successfully alkylated in benzene. Celite coated with KF is also effective for the alkylation of amines. - ... 

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