Zeolites starting materials

Hybrid catalysts consisting of a zeolite (ZSM-5 or Beta) and bentonite as a binder were prepared and characterized by XRD, pyridine FTIR and nitrogen adsorption. The hybrid catalysts exhibited similar properties as the combined starting materials. Catalytic pyrolysis over pure ZSM-5 and Beta as well as hybrid catalysts has been successfully carried out in a dual-fluidized bed reactor. De-oxygenation of the produced bio-oil over the different zeolitic materials was increased compared to non-catalytic pyrolysis over quartz sand. 

A commercial zeolite NaZSM-5 (Zeocat, Si/Al = 26) is used as a starting material. The HZSM-5 zeolite form is prepared by three aqueous exchanges at 80°C for 24h with a HNO3 solution (0.1M). 

HZSM-5 was used, the starting material (12) was recovered in 69% yield, a result most probably attributable to its more confined-pore structure. However, the highest regioselectivity for the furanoside/pyranoside form (14 1) was obtained with this medium-pore zeolite. It could also be concluded that the external surface area of the zeolites and the Lewis acid sites (Table II), do not have any effect on yield/ regioselectivity of this reaction. 

Tri-iron dodecacarbonyl zeolites adducts. The adducts Fe3(C0)12-HY and Fe3(CO) 2-NaY were used as starting materials. 

Bi s(cyclopentadi enyldi c arbonyliron)-zeolit es adduct s. The adducts CpFe(CO)2 2 HYand CpFe(CO)2 2 NaY were used as starting materials. They are not decomposed before the catalytic run. Infrared spectra of these materials show that the integrity of the molecular complex is retained it is expected that owing to its size, which is smaller than that of Fe3(C0)- 2,... 

Dicobalt octacarbony1-NaY zeolite adducts.Only the adducts Co2(C0)g-NaY were used as starting materials. No decomposition trough thermal treatment was attempted before the catalytic runs. 

Fischer-Tropsch synthesis could be "tailored by the use of iron, cobalt and ruthenium carbonyl complexes deposited on faujasite Y-type zeolite as starting materials for the preparation of catalysts. Short chain hydrocarbons, i.e. in the C-j-Cq range are obtained. It appears that the formation and the stabilization of small metallic aggregates into the zeolite supercage are the prerequisite to induce a chain length limitation in the hydrocondensation of carbon monoxide. However, the control of this selectivity through either a definite particle size of the metal or a shape selectivity of the zeolite is still a matter of speculation. Further work is needed to solve this dilemna. 

In a more general context, metal carbonyls on zeolites can be a unique way to prepare highly dispersed metal catalysts. In the present work, this is especially the case for iron as no other mild methods are operative. It is expected that the method could be applied to the preparation of bi- and polymetallic catalysts even though the starting material are not bi- or polymetallic clusters, but more conveniently homometallic clusters. 

When a gaseous flow of cyclopropylcarbinyl chloride is passed over NaY zeolite at room temperature, formation of cyclobutyl chloride and allylcarbinyl chloride was observed (scheme 4), as well as cyclopropylcarbinyl chloride (product and unreacted starting material). These data are consistent with formation of the C4H7+ cation with internal return of the chloride ion. 

Another opportunity to combine two reaction steps towards a one pot synthesis is the epoxidation of a-pinene and the isomerization of the epoxide to campho-lenic aldehyde (Scheme 5.6). Zeolite Ti-Beta seems adequate to deal with both steps as a catalyst [24]. Campholenic aldehyde is the starting material for several sandalwood fragrances. 

The large demand for benzene is due to its use as a starting material in the production of polystyrene, acrylonitrile styrene butadiene rubber, nylons, polycarbonates and linear alkyl benzene detergent. All of these final chemical products that are suitable to form into consumer goods have multiple chemical transformations in various industrial processes to obtain them from benzene. Because the production of benzene does not involve a liquid adsorptive process on a zeolite, these processes are not described here but can be found in other sources. However, it is important to note that benzene is typically a large byproduct from an aromatics... 

Owing to the possibility of tuning (1) their acidic and basic properties, (2) their surface hydrophilicity, and (3) their adsorption and shape-selectivity properties, catalytic activity of zeolites was investigated in the production of HMF from carbohydrates. Whatever the hexose used as starting material, acidic pillared montmorillonites and faujasite were poorly selective towards HMF, yielding levu-linic and formic acids as the main products [81-83]. 

The starting material, especially the silica source, and the stirring condition during crystallization were found to affect not only the rate of crystallization but also the crystallization area of high silica zeolites, while water content in a reactant mixture was found not to be critical. 

The preparation of silicon-rich zeolites, such as zeolite Y, can be achieved by varying the composition of the starting materials but can also be done by subsequent removal of aluminium from a synthesized aluminosilicate framework using a chemical treatment. Several different methods are available, including extraction of the aluminium by mineral acid, and extraction using complexing agents. 

Xylenes. Because of the practical significance of xylenes, isomerization of xylenes over zeolites is frequently studied.348 The aim is to modify zeolite properties to enhance shape selectivity, that is, to increase the selectivity of the formation of the para isomer, which is the starting material to produce terephthalic acid. In addition, m-xylene isomerization is used as a probe reaction to characterize acidic zeolites.349,350... 

Zeolite formation depends on reaction conditions 2-4). It is generally believed that most zeolites are formed as metastable phases. According to Barrer (3), the course of the synthesis, beginning with the type of starting material, determines the structure of the zeolite formed. The studies of Zhdanov 2, 5) on the composition of liquid and solid phases of hydrogels indicate that the kind and composition of the zeolite formed depend on the hydrogel composition and that the results of crystallization of aluminosilicate gels obtained in the same way are reproducible. 

Materials. The zeolites studied are summarized in Table I. The unit cells of the starting materials contain, in the dehydrated form ... 

Influence of Temperature. Data concerning the thermal stability of the catalytic activity are given in Figure 2 and Table I. The thermal stability of the starting materials Na-8.7 and D.Na-5.4 is discussed first. The limit of stability of the Na-8.7 sample appears to be higher than for the NaHY zeolites studied previously (3, 6, 27, 28). Nevertheless, this sample cannot be considered ultrastable since neither its structural data nor the thermal stability of its OH groups are characteristic of ultrastable zeolites (17). This increase in the stability may be explained by dry air heating and subsequent rehydration. 

Taking the crystallinity parameter QA (external standard [6]) as a measure for content of crystallized zeolite. Starting Si02/Al203-ratio in the reaction mixture was 69. The QAi-values of about 1 are representing a tranformation of 100% into the zeolitic material. 

Each step in the substitution reaction, taking zeolite Na-Y with an Si/Al ratio of y/x as starting material can be written... 

Develii]ied in the eurly I lHOs. tohcrinoriies have selectivity properties intermediate between those of clay minerals and zeolites. They have been considered in catalysis and nuclear and hazardous waste disposal. Tobermorilc. Ca Si H () s 4HiO. occurs naturally as a hydrous calcium silicate in calc-silicate rock. Tobermorilex have layer structures similar to those of 2 1 clay minerals, but the structure varies with the chemical composition as well as with Ihe nature of their synthesis. They have heen synthesized from a number of starting materials. 

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