Aluminophosphates AlPO synthesis

There is limited patent literature available on manufacturing techniques for aluminophosphates. Although many patents describe AlPO synthesis, most described examples are small-scale preparations. The fact that at least two catalytic applications have been commercialized for SAPO molecular sieves indicates that they have been scaled-up to large quantities [55, 56]. A large-scale preparation of SAPO-34 is described in a recent patent [57]. 

Besides the conventional zeolites, several novel zeolite analogues such as the ALPOs (aluminophosphates), MeALPOs (divalent-metal (Me) substituted aluminophos-phates), SAPOs (silicon substituted aluminophosphates) and so on have been synthesized (Davis Lobo, 1992). Wilson et al. (1982) first reported the synthesis of microporous ALPOs. ALPO synthesis differs from zeolite synthesis in that it involves acidic or mildly basic conditions and no alkali metal ions. Some members in the ALPO... 

The same periodic structures can also be formed from alternating AIO4 and PO4 tetrahedra the resulting aluminophosphates are not called zeolites but AlPOs. Zeolites are made by hydrothermal synthesis under pressure in autoclaves, in the presence of template molecules such as tetramethylammonium, which act as structure directing agents. 

Heat-up rate effects have been investigated with respect to microwave synthesis of AlPO phases, however there are few publications concerning the heat-up effects in conventional heating [58]. There has also been at least one study of pH and H2O level on aluminophosphate crystallization [59]. A recent paper attempts to study the unique crystallization process of several aluminophosphate molecular sieve compositions [60]. 

Recently, we also focused attention on the synthesis of aluminoarsenates and galloarsenates with open framework structures (refs. 12—14). While the aluminophosphates are labeled as AlPO s, the gallophosphates, aluminoarsenates and galloarsenates can be designated as AlPO s, AlAsO s and GaAsO s respectively. 

The synthesis of the first members of a new family of aluminophosphate molecular sieves (the ALPOs) was disclosed by Union Carbide scientists in the early 1980s (Wilson et al., 1982a,b). The zeotype frameworks of the ALPO structures can be pictured as alternating [AlOJ and [P02]+ units and so are electrically neutral with both Al and P occupying adjoining T-sites. 

The amount of water present during the synthesis of large AFI-type aluminophosphate crystals was found to be of significant importance. However, yield of AlPO -5 and crystal size were countercurrently influenced. It follows tnat at least with tripropyl amine, either few large crystals or maximum conversions into small particle AlP04-5 is possible. 

Predicting the Templating Ability of Organic Amines for the Synthesis of Aluminophosphates with an Open Framework Analogous to AlPO-HDA... 

Aluminophosphates (denoted as ALPO s) are porous crystalline molecular sieves, consisting of AlO g Since the first synthesis of these materials,... 

Aluminophosphates denoted as AlPO-n (n means the framework structure) are a new family of molecular sieves with unique zeolitic pore structure. Since the first report on the synthesis of AlPO-n by Wilson et al., synthesis of various types of AlPO-n as well as the isomorphous substitution of metal cation into the AlPO-n structure have been reported. At present, more than 50 different crystal structures of AlPO-n have been reported, which is comparable to that of aluminosilicate zeolites, making the aluminophosphates an important class of microporous crystals." ... 

Later, the synthesis of the family of crystalline silicoaluminophosphate (SAPO- ) was reported. Some of them have structures topologically related to zeolites or AlPOs-n, some having novel structures. SAPO-n composition can be considered in terms of silicon substitution into a hypothetical aluminophosphate framework, the predominant substitution mechanism being silicon substitution for phosphorus. 

Usually, the synthesis of zeolite materials requires an excess amount of reactant reagents. After the resultant products are filtered from the reaction mixture, the filtrate (mother-liquor) containing abundant nutrients is discarded as a waste solution. With the concept of green chemistry, Yu and coworkers attempted a mother-liquor-reused route to synthesize cobalt aluminophosphate zeolites CoAPO-CJ51 (GIS) and CoAPO-CJ52 (LAU) by introducing Co + cations into the filtrated mother liquors of two layered aluminophosphates Mu-4 and AlPO-IM, respectively [47]. The mother-liquor-reused route provides a low-cost way for the synthesis of zeolite materials. 

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