Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By addition of entire unsaturated molecules – e.g.,...
Reexamination Certificate
2000-11-20
2002-01-08
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By addition of entire unsaturated molecules, e.g.,...
C585S510000, C585S520000, C585S530000, C585S532000
Reexamination Certificate
active
06337428
ABSTRACT:
CONVERSION OF HYDROCARBONS WITH A DEALUMINATED NU-86 ZEOLITE CATALYST
A process for the catalytic conversion of hydrocarbons, in particular for the oligomerisation of olefins wherein the catalyst comprises a zeolite which is at least partially in its acid form. The zeolite is a NU-86 zeolite comprising silicon and at least one element T selected from the group formed by aluminum, iron, gallium and boron, preferably aluminum, characterized in that element T has been extracted from the framework, and in that it has a global Si/T atomic ratio of more than about 20. Element T is extracted from the zeolitic framework (or network) by means of at least one heat treatment, optionally carried out in the presence of steam, followed by at least one acid attack using at least one solution of a mineral or organic acid, or by direct acid attack.
The synthesis of NU-86 zeolite has been described by ICI in European patent application EP-A2-0 463 768. NU-86 zeolite is generally synthesised in the presence of sodium cations and an organic structuring agent which is either octamethonium dibromide or nonamethonium dibromide.
The composition of the NU-86 zeolite samples prepared have Si/Al atomic ratios in the range 8.5 to 16 and generally have Na/Al ratios of more than 8%.
The structural type of this zeolite has not yet been officially attributed by the synthesis commission of the IZA (International Zeolite Association). However, following the work published at the 9
th
International Zeolite Conference by J. L. Casci, P. A. Box and M. D. Shannon (“Proceedings of the 9
th
International Zeolite Conference”. Montreal 1992, Eds R. Von Balimoos et al., 1993, Butterworth), it appears that:
NU-86 zeolite has a three-dimensional microporous system;
the three-dimensional microporous system is constituted by straight channels with a pore opening which is delimited by 11 T atoms (T being a tetrahedral atom principally selected from the group formed by Si, Al, Ga and Fe), straight channels which are alternately delimited by openings with 10 and with 12 T atoms, and sinusoidal channels which are also alternately delimited by openings with 10 and with 12 T atoms.
The term “pore openings with 10, 11 or 12 tetrahedral atoms (T)” means pores constituted by 10, 11 or 12 sides. Determination of the diameter of pores present in the NU-86 zeolite have given the following values: 4.8×5.8 for pores with 10 sides, 5.7×5.7 for pores with 12 sides and 5.5×6.2 for pores with 11 sides. With these pore diameters, NU-86 zeolite belongs in the category of medium pore diameter zeolites.
Of particular interest is an NU-86 zeolite in which element T has been extracted from the framework by at least one heat treatment, optionally in the presence of steam, followed by at least one acid attack using at least one solution of a mineral or organic acid, or by direct acid attack using at least one solution of a mineral or organic acid, also any catalyst comprising this zeolite for the conversion of hydrocarbons, in particular the oligomerisation of olefins.
When incorporated into a catalyst, the NU-86 zeolite (which is at least partially and preferably practically completely in its acid form and has a Si/T ratio of more than about 20), surprisingly exhibits improved catalytic performances for hydrocarbon conversion reactions over prior art catalysts, in particular as regards activities, stabilities and selectivities over the non dealuminated NU-86 zeolites described in EP-A2-0 463 768, as will be demonstrated in the Examples below.
The invention concerns a NU-86 zeolite comprising silicon and at least one element T selected from the group formed by aluminium, iron, gallium and boron, preferably aluminium, characterized in that element T has been extracted from the framework and in that it has a global Si/T atomic ratio of more than about 20, preferably more than about 22, and more preferably in the range about 22 to about 300.
The invention also concerns a catalyst comprising at least one NU-86 zeolite in which element T has been extracted from the framework and which is at least partially, preferably practically completely, in its acid form, comprising silicon and at least one element T selected from the group formed by aluminium, iron, gallium, and boron, preferably aluminium, and at least one matrix (or binder). The global atomic ratio Si/T of the dealuminated zeolite is preferably more than about 20, preferably more than about 22, and more preferably in the range about 22 to about 300. The catalyst also optionally comprises at least one element selected from the group formed by groups IB and VIII of the periodic table, preferably selected from the group formed by Ag, Ni, Pd and Pt, preferably Ni, Pd or Pt.
The matrix is generally selected from the group formed by clays (for example natural clays such as kaolin or bentonite), magnesia, aluminas, silicas, titanium oxide, boron oxide, zirconia, aluminium phosphates, titanium phosphates, zirconium phosphates, silica-aluminas and charcoal, preferably from elements of the group formed by aluminas and clays.
X ray diffraction diagrams of NU-86 zeolite are given in European patent application EP-A2-0 463 768. As is well known to the skilled person, a NU-86 zeolite possesses the principal X ray diffraction peaks of its structure, but the intensity of these peaks can vary depending on the form of the zeolite, without causing any doubt that that zeolite has that structure. Thus the NU-86 zeolite in which element T has been extracted from the framework possesses the principal peaks of its structure which are given in European patent application EP-A2-0 463 768, with a peak intensity which can be different to that shown in that patent.
When it is included in the catalyst of the invention, the NU-86 zeolite of the invention is at least partially, preferably practically completely, in its acid form, i.e., in its hydrogen (H
+
) form. The Na/T atomic ratio is generally less than 0.7%, preferably less than 0.6%, and more preferably less than 0.4%.
The catalyst of the invention generally contains 10% to 99%, preferably 20% to 95%, of NU-86 zeolite in which element T has been extracted from the framework, at least partially in its acid form. When the catalyst of the present invention contains at least one element selected from the group formed by groups IB and VIII of the periodic table, the weight content of said element(s) is generally in the range 0.01% to 10%, preferably 0.05% to 7%, more preferably 0.10% to 5%. The complement to 100% by weight generally consists of the matrix of the catalyst.
The global Si/T ratio of the zeolite and the chemical composition of the samples are determined by X ray fluorescence and atomic absorption.
For each sample, the total surface area of the signal over an angular range (2&thgr;) of 6° to 40° is measured from the X ray diffraction diagrams, then for the same zone, the surface area of the peaks as the number of pulses for a stepwise 3 second recording with a step size of 0.02° (2&thgr;) was measured. The ratio of these two values, surface area of peaks/total surface area, is characteristic of the quantity of crystalline material in the sample. This ratio or “peak ratio” is then compared for each sample with the peak ratio of a reference sample which is arbitrarily considered to be completely (100%) crystalline. The degree of crystallinity is then expressed as a percentage with respect to a reference, which must be carefully selected, as the relative intensity of the peaks varies depending on the nature, the proportion and position of the different atoms in the structure unit, in particular the cations and the structuring agent. For the examples of the present description, the reference selected is the form of NU-86 which had been calcined in dry air and exchanged three times in succession with an ammonium nitrate solution.
The microporous volume can also be estimated from the quantity of nitrogen adsorbed at 77 K for a partial pressure P/P
0
of 0.19, for example.
The invention also concerns the preparation of the NU-86 zeolite in whic
Benazzi Eric
Cauffriez Herve
Chouteau Nicolas
Griffin Walter D.
Institut Francais du Pe'trole
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