Zeolite ITQ-5

Details Zeolite ITQ-5 Zeolite ITQ-5

2000-06-19

2002-06-25

Sample, David (Department: 1755)

Chemistry of inorganic compounds

Zeolite

Organic compound used to form zeolite

C423S713000, C423S718000, C423SDIG002, C585S467000, C585S722000, C208S109000, C208S135000, C208S120010

Reexamination Certificate

active

06409986

ABSTRACT:

FIELD OF THE ART
Micro-porous crystalline materials
STATE OF THE ART
Zeolites are micro-porous crystalline materials of variable composition characterised by a crystalline network of TO
4
tetrahedrons (where T normally represents Si and Al, but it can also represent Ti, Ge, B, Ga, . . . ) that share all their vertices giving rise to a three-dimensional structure that contains channels and/or cavities of molecular, dimensions. When some of the T atoms are present in an oxidation state less than +4, the crystalline network formed is negatively charged. This charge is compensated for by the presence of organic or inorganic cations in the channels or cavities, organic molecules, salts and H
2
O can also occupy these channels and cavities. Thus, in general terms, the chemical composition of the zeolites can be represented by the following empirical formula:
X(M
1/2
XO
2
):YYO
2
:zR:wH
2
O
where M is one or several organic or inorganic cations with a +n charge; X is one or several trivalent elements; Y is one or several tetravalent elements; and R is one or several organic substances or a salt. Although the nature of M, X, Y and R and the values of x, y, z and w can, in general, be changed by post-synthesis treatments, the chemical composition of a zeolite material (as it is synthesised or after roasting) has a range that is characteristic of each zeolite and of their method of production.
On the other hand, a zeolite material is also characterised by its crystalline structure that defines its channel and cavity system and gives rise to a specific X-ray diffraction pattern. Thus, zeolites can be differentiated from each other by their chemical composition range and their X-ray diffraction pattern. The intensity of the diffraction lines, with suitable reference to a standard sample, can be used as an indication of the “crystallinity”. This concept can refer both to the quantity of material of a crystalline phase in a solid that also contains other phases (for example, an amorphous solid) or to the structural “perfection” of the solid. Both the more or less perfect crystalline structure and the chemical structure also determine the physico-chemical properties of each zeolite or zeotype and their applicability in different industrial processes. Other characteristics of the zeolite that can have a large influence on its applicability include the crystal size and the presence of reticular flaws. Both these properties and the chemical composition of the material can be highly dependent on the preparation method and/or posterior treatments.
The Beta zeolite (U.S. Pat No. 28,341) is a micro-porous crystalline material characterised by its crystalline structure, which gives rise to a specific X-ray diffraction pattern and a unique system of channels, and by its chemical composition, which can be represented by the empirical formula
[xNa,(1−x)TEA]AlO
2
.ySiO
2
.wH
2
O
where x<1, y=5-100, w is up to around 4 and TEA represents the tetraethylammonium cation. In general, the Beta zeolite is synthesised in the presence of alkali cations and the crystalline product normally shows a crystal size between 0.1 and 1 &mgr;m. For the zeolite to attain its adsorption properties it is necessary to roast the material synthesised to decompose the tetraethylammonium cation and free the empty intrazeolite volume. Typically, this roasting process is accompanied by a large loss in crystallinity and a de-aluminising effect. The loss of crystallinity may be due to a partial process making the material more amorphous, leading to a loss of the specific properties of the zeolite in catalytic processes. It can also be due to a large increase in the concentration of reticular defects (Si—OH type), which affects the physico-chemical properties of the material and its stability in subsequent thermal processes (such as those that require regeneration of the catalyst in various processes of hydrocarbon transformation, such as catalytic hydrocarbon cracking). The de-aluminising process involves the loss of Al from the network, and therefore the loss of the corresponding Bronsted acid centres, giving rise to Aluminium species outside the network. These species can be very varied and this may have important consequences for the activity of the material. If the synthesis is carried out in the presence of alkali cations it is necessary to effect a cation exchange to obtain the acid form active in catalytic processes that transform hydrocarbons.
An zeotype isomorphous with the Beta zeolite can also be synthesised using Ti atoms in the network, in accordance with the Spanish patent 2,037,596. In this case, the zeotype can be used as a catalyst in processes of selective oxidation of organic products using H
2
O
2
or hydroperoxides or organic peroxides as the oxidant. In this case, the chemical composition of the material in its anhydrous and roasted state can be represented by the formula
x(HXO
2
):yTiO
2
:SiO
2
where X is a trivalent cation (Al, Ga, B, . . . ) and y can take values between 0 and 0.1.
DESCRIPTION OF THE INVENTION
The present invention relates to a new zeolitic material, denominated ITQ-5, and to a method for preparation thereof, characterised by the relatively low pH of the synthesis medium and the use of F anions as mineralising agent. The material in roasted form has the empirical formula
x(HXO
2
):TO
2
where T is one or several tetravalent elements, X is a trivalent element (Al, Ga, Fe, B, Cr, . . . ), and x has a value less than 0.5, this being able to be 0. Also claimed is the use of the materials obtained in catalytic processes of hydrocarbon and functionalised hydrocarbon transformation. When the material contains Ti, V or some other element with oxidative catalytic capacity (Ti-ITQ-5, V-ITQ-5, etc.) the material is also claimed in processes of selective oxidation of organic compounds using H
2
O
2
or peroxides or organic hydroperoxides.
A more specific zeolitic material is one which has the empirical formula in the roasted and anhydrous form of:
x(HXO
2
):gGeO
2
:SiO
2
where the ratio Si/Ge is greater than 2, X is a trivalent cation as stated above and (Si+Ge)/X is greater than 5. A further specific material is one having the empirical formula in the roasted and anhydrous form of:
X(HXO
2
):gGeO
2
:tTiO
2
:SiO
2
where the ratio of Si/Ge is greater than 2, X is a trivalent cation as stated above, the ratio (Si+Ge)/X is greater than 5 and the ratio (Si+Ge)/Ti is in the range 10 to 10,000. A final specific zeolitic material of this invention is represented by the empirical formula in the roasted and anhydrous form of:
x(HXO
2
):gGeO
2
:tTO
2
:SiO
2
where the ratio Si/Ge is greater than 2, X is trivalent cation, the ratio (Si+Ge)/X is greater than 5, T is a tetravalent cation different from Si and Ge and the ratio (Si+Ge)/T is in the range 10 to 10,000.
The preparation method is based on heating a reaction mixture that contains a silicon source (amorphous silica, colloidal silica, silica gel, tetraalkylorthosilicate, etc., preferably amorphous silica or tetraethylorthosilicate), a source of germanium (germanium oxide, germanium alkoxide, . . . ), optionally a source of aluminium (aluminium oxide or hydroxide, another aluminium salt, aluminate of an organic cation or metallic aluminium, preferably metallic aluminium or aluminium hydroxide) or other trivalent elements (Cr, Ga, B, Fe, . . . ), optionally a source of Ti (titanium alkoxide 5 or halide, preferably titanium tetraethoxide, tetrapropoxide or tetrabutoxide), V (such as vanadium sulphate for example) or another tetravalent element, an organic cation as a structure director (preferably tetraethylammonium), optionally H
2
O
2
, a source of F anions and water, avoiding the presence of alkali cations, to temperatures of 363-473 K, preferably to 403-423 K. The sources of F anions and of organic cations are chosen in such a way that the final pH, after crystallisation, lies in the range 6 to 12, preferably in the range 8-9.5. The composition of the synthesis mixture is characterised by the foll

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