Chemistry of inorganic compounds – Silicon or compound thereof – Oxygen containing
Reexamination Certificate
2002-04-23
2004-03-09
Sample, David (Department: 1755)
Chemistry of inorganic compounds
Silicon or compound thereof
Oxygen containing
C423S328200, C423S702000, C502S182000, C502S263000, C501S080000, C501S081000
Reexamination Certificate
active
06702993
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to mesoporous aluminosilicate compositions which have a unique structure which are stable at high temperatures and under hydrothermal conditions. In particular, the present invention relates to a process for producing the mesoporous aluminosilicate composition which uses a zeolite seed with a structure directing agent. Further still, the present invention relates to novel cracking catalysts for oil and other organic molecules. The present invention thus provides for the assembly of ultrastable mesoporous aluminosilicates with hexagonal, cubic and wormhole framework structures that do not suffer from the undesirable extensive de-alumination and steam instability of conventional aluminosilicate mesostructures.
(2) Description of Related Art
All previously reported aluminosilicate mesostructures, as prepared by either direct or post synthesis alumination, results in the extensive de-alumination of the framework upon calcination (Ryoo, R., et al., Chem. Commun. 2225 (1997); and Luan, Z. H., et al., J. Phys. Chem. 99 10590 (1995)). This undesired property has been attributed to the hydrolysis of the framework Al by steam generated in the calcination process (Corma, A., et al., J. Catal. 148 569 (1994); and Luan, Z. H., et al., J. Phys. Chem. 99 10590 (1995)). Regardless of the mechanism responsible for the de-alumination process, the acid catalytic properties of these materials for organic chemical conversions is greatly compromised. Moreover, all previously reported aluminosilicate mesostructures completely lose their framework mesoporosity when exposed to steam at the temperatures normally encountered in the processing of petroleum catalysts.
Soon after the discovery of mesoporous MCM-41 molecular sieves (Beck, J. S., et al., J. Am. Chem. Soc. 114 10834 (1992)), it was found that the incorporation of aluminum into the framework introduced mild acidic functionality, but the long range order and tetrahedral siting of the aluminum was compromised (Chen, C-Y., et al., Microporous Mater. 2 17 (1993); Borade, R. B., et al., Catal. Lett 31 267 (1994); Luan, Z. H., et al., J. Phys. Chem. 99 10590 (1995)), especially at intended aluminum loadings above about 8 mol %. Mild acidity and loss of structural integrity, together with poor steam stability under regeneration conditions made hexagonal Al-MCM-41 compositions unattractive candidates for the processing of high molecular weight petroleum fractions. More recently, important advances have been made in improving the structural integrity of Al-MCM-41 through direct assembly (Janicke, M. T., et al., Chem. Mater. 11 1342 (1999)) and post synthesis modification methods (Hamdan, H., et al., J. Chem. Soc. Faraday Trans 92 2311 (1996); Mokaya, R., et al., Chem. Commun. 2185 (1997); Ryoo, R., et al., J. Chem. Commun. 2225 (1997); and Ryoo, R., et al., Chem. Mater. 9 1607 (1998)). However, the low acidity and poor steam stability still limit potential applications in petroleum refining (Corma, A., Chem. Rev. 2373 (1997)).
There is thus a need for improved aluminosilicate compositions that are stable, particularly in the presence of steam. In particular, the present invention relates to aluminosilicates that have stable framework structures.
SUMMARY OF THE INVENTION
The present invention relates to a mesostructured aluminosilicate composition that comprises:
(a) a framework of linked tetrahedral SiO
4
and AlO
4
units, the framework defining mesopores having an onium ion surfactant in the mesopores, having an Si to Al molar ratio of between about 1000 to 1 and 1 to 1, and having at least one X-ray diffraction peak corresponding to a basal spacing between about 3.0 and 15.0 nm, and wherein the composition is derived from zeolite seeds.
The present invention also relates to a mesoporous aluminosilicate composition that comprises: a framework of tetrahedral linked SiO
4
and AlO
4
units, the framework defining mesopores having an Si to Al molar ratio of between about 1000 to 1 and 1 to 1, and having at least one X-ray diffraction peak corresponding to a basal spacing between about 3.0 and 15.0 nm, wherein the composition is derived from zeolite seeds, wherein a BET surface area is between 400 and 1300 m
2
per gram, wherein an average pore size of the framework is between about 2.0 and 10.0 nm, and wherein a pore volume of the framework is between about 0.30 and 1.3 cm
3
per gram. The framework can contain 0.01 to 10% by weight carbon.
The present invention relates to a mesostructured aluminosilicate composition which comprises: framework of linked tetrahedral SiO
4
and AlO
4
units, the framework defining mesopores having an onium ion surfactant in the mesopores, having an Si to Al molar ratio of between about 1000 and 1 and 1 to 1, and having at least one X-ray diffraction peak corresponding to a basal spacing between about 3.0 and 15.0 nm, and wherein the tetrahedral AlO
4
in the framework exhibit a
27
Al MAS-NMR resonance with a chemical shift between about 57 and 65 ppm relative to a 1.0 M aluminum nitrate solution as an external chemical shift reference.
The present invention also relates to a mesoporous aluminosilicate composition which comprises framework of a linked tetrahedral SiO
4
and AlO
4
units, having an Si to Al molar ratio of between about 1000 to 1 and 1 to 1, and having at least one X-ray diffraction peak corresponding to a basal spacing between about 3.0 and 15.0 nm, wherein the tetrahedral AlO
4
units exhibit a
27
Al MAS-NMR resonance with a chemical shift between about 57 and 65 ppm relative to a 1.0 M aluminum nitrate solution as an external chemical shift reference, wherein a BET surface area is between 400 and 1300 m
2
per gram, wherein an average pore size of the framework is between about 2.0 and 10.0 nm, and wherein a pore volume of the framework is between about 0.1 and 1.9 cm
3
per gram.
The present invention also relates to a hybrid mesoporous aluminosilicate-carbon composition which comprises framework of linked tetrahedral SiO
4
and AlO
4
units, the framework defining mesopores having a Si to Al molar ratio of between about 1000 to 1 and 1 to 1 and between 0.01 and 10 wt % carbon embedded in the mesopores, and having at least one X-ray diffraction peak corresponding to a basal spacing between about 3.0 and 15.0 nm, wherein the tetrahedral AlO
4
units in the framework exhibit a
27
Al MAS-NMR resonance with a chemical shift between about 57 and 65 ppm relative to a 1.0 M aluminum nitrate solution as an external chemical shift reference, wherein a BET surface area is between 400 and 1300 m
2
per gram, wherein an average pore size of the framework is between about 2.0 and 10.0 nm, and wherein a pore volume of the framework is between about 0.1 and 1.9 cm
3
per gram.
The present invention further relates to a method for forming the mesoporous aluminosilicate composition that comprises:
(a) reacting a sodium silicate solution at basic pH with a sodium aluminate solution at an aluminum to silicon ratio between about 1000 to 1 and 1 to 1 and aging the mixture at 25 to 200° C. for periods of up to 48 hours to form zeolite seeds;
(b) diluting the reaction mixture from (a) with water and reacting the resultant mixture with a surfactant containing an onium ion;
(c) acidifying the mixture obtained from (b) with a protonic acid to obtain a mixture with an OH
31
/(Si+Al) ratio in the range of 0.10 to 1.0;
(d) aging the mixture from step (c) at a temperature between 80 and 200° C. to obtain a precipitate of the composition; and
(e) separating the composition from mixture of step (d).
The present invention also relates to a method for forming the mesoporous aluminosilicate composition which comprises:
(a) providing an aqueous solution of zeolite seeds;
(b) reacting the zeolite seeds in the aqueous solution with a surfactant containing an onium ion wherein the solution has an OH
−
/(Si+Al) ratio in the range of 0.5 to 5.0;
(c) aging the mixture from step (b) at a temperature between 80 and 200° C. to obtain a precipit
Liu Yu
Pinnavaia Thomas J.
Zhang Wenzhong
Board of Trustees of Michigan State University
McLeod Ian C.
Sample David
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