Zeolites general strategies

Using appropriate problem solving strategies, the system should be able to reason on this theoretical and conceptual knowledge to answer more general questions such as what is the most suitable zeolite catalyst for the synthesis of p-cymene . It should suggest a zeolite, or at least its required catalytic functions such as pore system, acidity, modification,. .., and propose a general mechanism, even if this reaction was not yet recorded in the system. 

Zeolite materials are used commercially as shape/ size selective catalysts in the petrochemical and petroleum refining industry, and as molecular sieving separation media for gases and hydrocarbons. For both applications, zeolites are used in powder composite form such as pellets and granules. In this entry, we focus on zeolite membranes. We define zeolite membranes as a continuous phase of zeolite-based materials (pure zeolite or composite) that separate two spaces. Zeolite membranes are generally uniform thin films attached to a porous or a nonporous substrate. They can also be self-standing without a substrate. Note that we have included zeolite films and layers on nonporous substrate in this entry because we believe many of the synthesis strategies and applications reported for those nonporous substrates are easily transferred to a porous substrate to prepare a zeolite membrane. 

However, there are at least two additional important structure-direction factors interplaying with that of fluoride in the synthesis of pure-silica zeolites by the fluoride route the OSDA and the degree of dilution of the synthesis gel. Villaescusa and Camblor have shown that the general concepts outlined above regarding structure-direction by OSD As can be successfully used in the search for new pure-silica materials, as shown for instance by the synthesis strategies that finally lead to the three-dimensional large pore zeolite ITQ-7. Nonetheless, we would like to point out at least one peculiarity, in this respect, of the fluoride route small cations may show by this route a rather specific structure-direction effect (like 1,3,5-trimethylimidazolium, which has a (C- -N)/N ratio of 8 but shows a rather large specificity towards zeolite ITQ-12 in fluoride aqueous medium). 

The various strategies for preparation of zeolite encapsulated phthalocyanine complexes have largely involved the condensation of dicyanobenzene (DCB) around an intrazeolite metal ion to form the MPc complex. The efficiency of this template synthesis depends on the nature and location of the intrazeolite metal ion to be complexed. For example, metals have been introduced to the zeolite by ion exchange (7-13), metal carbonyls (14-19) and metallocene complexes (2-5,19-21) prior to reaction with DCB. Some of the advantages and disadvantages of these methods have been detailed by Jacobs (2). However, there are several problems that are inherent to the template synthesis in general. Often there is incomplete... 

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