Zeolites borosilicate

Various alkyl-substituted pyridine derivatives are formed from the condensation of butyraldehyde with ammonia at high temperatures. For example, cocondensation of -butyraldehyde with acrolein [107-02-8] and ammonia at 400°C over a borosilicate zeolite gives 3-ethylpyridine [536-78-7] in 70% yield... 

Elements such as B, Ga, P and Ge can substitute for Si and A1 in zeolitic frameworks. In naturally-occurring borosilicates B is usually present in trigonal coordination, but four-coordinated (tetrahedral) B is found in some minerals and in synthetic boro- and boroaluminosilicates. Boron can be incorporated into zeolitic frameworks during synthesis, provided that the concentration of aluminium species, favoured by the solid, is very low. (B,Si)-zeolites cannot be prepared from synthesis mixtures which are rich in aluminium. Protonic forms of borosilicate zeolites are less acidic than their aluminosilicate counterparts (1-4). but are active in catalyzing a variety of organic reactions, such as cracking, isomerization of xylene, dealkylation of arylbenzenes, alkylation and disproportionation of toluene and the conversion of methanol to hydrocarbons (5-11). It is now clear that the catalytic activity of borosilicates is actually due to traces of aluminium in the framework (6). However, controlled substitution of boron allows fine tuning of channel apertures and is useful for shape-selective sorption and catalysis. 

Reforming of FCC heavy gasoline and LCO with novel borosilicate zeolite catalysts... 

In this paper we report new methods for the lattice substitution of heteroatoms in large and extra-large pore borosilicate zeolites via post-synthetic treatment to prepare catalytically more active zeolites. Ga-SSZ-33, Al-SSZ-33 and Al-UTD-1 prepared from B-SSZ-33 and B-UTD-1, respectively, are discussed as examples. The materials are characterized with various physicochemical techniques and catalytic reactions. In particular, the advance of these methods is demonstrated by the exceptionally high activity of the resulting Al-SSZ-33 for acid-catalyzed hydrocarbon conversions. 

In the case of the borosilicate zeolite, the selectivity is lowered due to the formation of dimeric methyl isopropenyl ketone. The activity of the borosilicate zeolite can be increased and the side reaction... 

Using a Ce/Pd-doped borosilicate zeolite (Si02/B203... 

Aluminosilicate zeolite ([Al]ZSM-5), borosilicate zeolite ([B]ZSM-5), and iron silicate zeolite ([Fe]ZSM-5), doped with transition metal or rare-earth or noble metal were tested as the catalysts. Different modifications of the zeolite do not improve the olefin conversion. Neither isomorphous substitution of Al atom in the zeolite structure by B or Fe, nor doping the zeolite with metals influences notably the conversion of olefin into the acid compared with [Al]ZSM-5 (Table 23). 

The local structures of framework boron atoms in borosilicate zeolites B-p, B-SSZ-33 and B-SSZ-42 have been studied in the course of hydration/dehy-dration by employing solid-state NMR methods. In particular, characterisation of trigonal boron sites has been studied in great detail. B MAS NMR spectra showed that boron trigonally coordinated to the framework (B(OSi)3, denoted as B[3]) can be readily transformed to a defective trigonal boron site (B(OSi)2(OH), denoted as B[3]- I) as a result of hydration. The presence of B[3]-I sites was proven by utilising a number of different NMR methods including B MAS NMR at two different fields (11.7 and 19.6 T), B MQ MAS, B CP MAS, and B 2D HETCOR experiments. ... 

---