Chemistry of inorganic compounds – Zeolite – Organic compound used to form zeolite
Reexamination Certificate
2000-12-14
2003-05-06
Sample, David (Department: 1755)
Chemistry of inorganic compounds
Zeolite
Organic compound used to form zeolite
C423S705000, C423S706000, C423S707000, C423SDIG002, C502S064000, C502S066000, C502S068000, C502S074000, C208S046000, C208S111010, C208S111300, C208S111350, C208S120010, C208S120300, C208S120350
Reexamination Certificate
active
06558647
ABSTRACT:
This invention relates to an acidic solid that contains organized micropores and mesopores, a process for preparation and its use for the conversion of hydrocarbon feedstocks and in particular hydrocracking.
In the field of refining and petrochemistry, and in particular hydrocracking, two main types of materials constitute the acidic active phase of the catalysts, on the one hand the silica-aluminas, on the other hand the zeolites. The silica-aluminas generally have diameters with pores of between 4 and 50 nm and SiO
2
contents of between 1 and 90% by weight. One of their main defects resides in the fact that they have a very low acidity. Conversely, the zeolites and more particularly the aluminosilicate-type molecular sieves have an acidity that is 1,000 to 10,000 times more significant than the standard silica-aluminas. The zeolites, however, are microporous solids with pore openings that do not exceed 0.8 nm, which can constitute a handicap when it is desired to treat the feedstocks that comprise relatively voluminous molecules. As a result, when the zeolite is used in hydrocracking, it should first be dealuminified, which imparts to it both a suitable acidity and the mesoporosity that facilitates the diffusion of voluminous molecules.
The works achieved to date for obtaining microporous solids with a larger pore opening led to, for example, the synthesis of AlPO
4
-8 (0.79×0.87 nm) in 1990, VPI-5 in 1988 (1.21 nm) and cloverite (1.32 nm) in 1991. To date, it was still possible to prepare these molecular sieves only in the AI-P or Ga-P systems for the cloverite, which does not impart acidity to them.
More recently, several types of solids with organized mesoporosity were described, the first in 1992 by Mobil (MCM-41). The MCM-41-type solids have a uniform and periodic mesoporous system with a diameter of between 1.5 and 10 nm.
Recent works had as a goal obtaining by synthesis a solid that comprises a microporous phase and a mesoporous phase. Lujano et al. (EP 0811423, 1997) describes obtaining a solid with microporous crystalline walls that are accessible via mesoporous channels. The X-ray diffraction spectrum that is obtained in these materials corresponds to that of the X zeolite. It does not show organized mesoporosity.
The research efforts of the applicant focused on the preparation of organized solids that have pores of a size greater than 0.8 nm, with a narrow pore size distribution and an acidity that can be adjusted.
The works of the applicant made it possible to achieve the preparation of silicoaluminate solids that comprise a well-organized mesoporosity, mean diameters of mesopores of between 2 and 20 nm, a zeolitic microporous phase and an acidity that is higher than those of silica-aluminas or standard mesoporous compounds and closer to that of zeolites, and that lead in hydrocarbon conversion to mean conversions that are close to those observed in zeolites, and therefore much higher than those observed in silica-aluminas or in standard mesoporous compounds.
This invention therefore makes it possible to avoid the drawbacks of standard silica-aluminas, namely their low acidity and their low activity, as well as the drawbacks of zeolites that do not make it possible to convert voluminous molecules because of their pore sizes that are limited to several nm.
More specifically, the invention relates to a solid that comprises organized micropores and mesopores and that has:
an SiO
2
/Al
2
O
3
molar ratio of between 5-250
by X-diffraction at least one line at an interrecticular distance of between 20-200 Å that represents an organized mesoporosity
by infrared spectroscopy at least one band between 400-1600 cm
−1
that is characteristic of the Si—O framework bonds of a zeolitic microporous phase
by infrared analysis, after high-temperature vacuum treatment then pyridine chemisorption to saturation, the area of the band at about 1545 cm
−1
, representative of the acidity, is at least equal to 50 per 1 g of dry solid (expressed by absorbance unit×wave number).
The solid according to the invention has as its characteristics:
the silica/alumina (SiO
2
/Al
2
O
3
) molar ratio is between 5 and 250, preferably between 10 and 200, even more preferably between 10 and 100,
the X-ray diffraction spectrum has at least one line at an interrecticular distance of between 20 and 100 Å, preferably at least one line around 40±5 Å, representative of an organized mesoporous solid,
the X-ray diffraction spectrum has lines that are characteristic of a microporous zeolitic compound,
said solid preferably has a mesoporous volume that is determined by the BJH method (ASTM Standard D4641-93) that is at least equal to 0.13 cm
3
/g, preferably with a mesopore size distribution that is centered at a value of between 1.5 and 10 nm, preferably between 2 and 4 nm, such that the width at mid-height is less than 2 nm, preferably less than 1 nm,
said solid preferably has a microporous volume that is determined by the t-plot method (ASTM Standard D4365-85) of between 0.01 and 0.18 cm
3
/g, preferably between 0.01 and 0.15 cm
3
/g
by infrared spectroscopy, said solid has at least one band (in general several) in the wavelength domain of between 400 and 1600 cm
−1
characteristic of Si—O framework bonds of a zeolitic phase,
the acidity is such that by infrared analysis, after high-temperature vacuum treatment then pyridine chemisorption to saturation, the area of the band that corresponds to the wave number at 1545 cm
−1
and attributed to the pyridinium ion, therefore to the Brönsted acidity, expressed by absorbance unit multiplied by a wave number (in cm
−1
) and measured relative to the tangent to the peak, is at least equal to 50 per 1 g of dry solid, preferably at least equal to 80 per 1 g of dry solid.
This invention also relates to a process for preparation of said solid and its use for hydrocarbon conversion.
More specifically, the preparation process comprises:
(a) mixing in aqueous solution of at least one aluminum source, at least one silicon source and at least one structuring agent R of the zeolitic phase, whereby said mixture has the composition (in mol/mol):
Al
/
Si
=
0.005
–0
.6
R
/
Si
=
0.1
–1
.5
H
2
O
/
Si
=
10
–100
(b) autoclaving of the homogenized mixture at 80-200° C. for 1 hour to 5 days to obtain a crystal suspension whose size remains smaller than 300 nm
(c) at least one surfactant S is added to said cooled suspension that is optionally diluted with water and at least one aluminum source and/or at least one silicon source to obtain at pH=8-12 the composition (in mol/mol):
Al
/
Si
=
0.005
–1
R
/
Si
=
0.1
–1
.5
S
/
Si
=
0.1
–1
H
2
O
/
S
=
100
–1000
H
2
O
/
Si
=
20
–200
OH
-
/
Si
=
0.1
–0
.4
(d) autoclaving at 20-160° C. for 15 minutes to 5 days
(e) the autoclaved solid is cooled, washed, and calcined.
The preparation of the aluminosilicate according to the invention preferably comprises the following stages:
A first reaction mixture is formed in aqueous solution that comprises in particular water, at least one source of the element aluminum, at least one source of the element silicon, and at least one source of an organic or mineral compound that acts as a structuring agent of the zeolitic phase and denoted R. Said mixture has a composition in terms of molar ratio that is included in the intervals of the following values:
Al/Si
0.005-0.6, preferably 0.01-0.1
R/Si
0.1-1.5, preferably 0.2 to 1
H
2
O/Si
10-100, preferably 10-50.
The mixture is stirred at ambient temperature until homogenization takes place, for example, for one hour, then transferred into an autoclave that is coated with polytetrafluoroethylene and placed in a drying oven that is kept at a temperature of between 80 and 200° C. for a period that can vary from 1 hour to 5 days under static conditions or while being stirred. The autoclaving period is selected such that a sampling of the centrifuged mixture that is then washed, for example by redispersion in water and
Benazzi Eric
Caullet Philippe
Jouve Alexandre
Kessler Henri
Lacombe Sylvie
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
Sample David
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