Microporous crystalline silico-alumino-phosphate...

Chemistry of inorganic compounds – Zeolite – Structure defined x-ray diffraction pattern

Reexamination Certificate

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C423S305000, C423S306000, C423SDIG003, C502S214000, C585S639000, C585S640000

Reexamination Certificate

active

06334994

ABSTRACT:

The invention concerns catalysts for converting methanol to olefins comprising silico-alumino-phosphate (SAPO) materials with AEI/CHA-mixed phase composition.
From Norwegian Patent No. 169 380 (corresponds to U.S. Pat. No. 4,440,871) microporous crystalline silico-alumino-phosphates and a procedure for synthesising such products. These products are known have a three-dimensional space lattice built up from PO
2
+, AlO
2
—and SiO
2
tetrahedral units, whose most important chemical composition on a water-free basis is:
mR:(Si
x
Al
y
P
z
)O
2
where “R” represents at least one organic template material which is present in the intracrystalline pore system; “m” is the number of moles of “R” present per mole of (Si
x
Al
y
P
z
)O
2
and m has a value between 0 and 0.3, the maximum value in each case being dependent on the molecular dimensions of the template material and the available pore volume in the silico-alumino-phosphate structure in question; “x”, “y” and “z” are molar fractions of silicon, aluminium and phosphorus respectively, present as tetrahedral oxides. The minimum value of “x”, “y” and “z” is 0.01, and the maximum value of “x” is 0.98, of “y” 0.6 and of “z” 0.52. The minimum value of “m” in the formula above is 0.02.
The reaction mixture is achieved by combining at least one part each of the aluminium and phosphorus sources in the absence of the silicon source. Then the resultant mixture is reacted with the remaining components to get the total reaction mixture.
The reaction mixture is placed in a pressure vessel for shaking and then heating under autogenic pressure to a temperature of at least 100° C., and preferably between 100 and 260° C., until a crystalline silico-alumino-phosphate is obtained. The product is extracted in any appropriate way, for example by centrifuging or filtering.
From our own Norwegian Patent No. 174341 an improved method of producing silico-alumino-phosphate catalysts for the conversion of methanol into light olefins such as ethylene and propylene (the MTO reaction) is known. The improved method of synthesis can be used to control chemical composition of the silico-alumino-phosphates, especially the silicon content. In particular, it was found that catalysts that are more stable towards deactivation by “coking” can be synthesised, which is very important for the design of an MTO process based on the synthesised silico-alumino-phosphates.
From our own Norwegian Patent Application No. 932915 a microporous crystalline silico-alumino-phosphate with theoretical composition on a water-free basis after synthesis and calcination:
H
x
Si
x
Al
y
P
z
O
2
where x has a value between 0.005 and 0.1 and y and z are values between 0.4 and 0.6, is known. The product has AEI-structure and has acidic properties. The product is useful as sorbent and as catalyst for olefin production from methanol.
A problem related to all the catalysts known from the above mentioned prior art is that the lifetime of the catalysts is limited.
Thus, a main object of the invention is to produce a catalyst with prolonged life compared to those belonging to the prior art.
This object and other objects of the invention are achieved as defined in the patent claims listed at the end of this application.
The present invention concerns a crystalline silico-alumino-phosphate microporous material containing at least the two phases AEI and CHA, the theoretical, average chemical composition of which, on a water-free base after synthesis and calcination, is:
H
x
Si
x
Al
y
P
z
O
2
where x has a value between 0.005 and 0.1 and y and z are values between 0.4 and 0.6, and “x”, “y” and “z” are mol fractions of silicon, aluminium and phosphorous respectively, present as tetrahedric oxides. The present invention further concerns the use of said material for the production of light olefins from methanol, for which said material surprisingly has been found to be superior to materials of the same chemical composition with either pure AEI or pure CHA phase, as illustrated in examples below.
The manufactured catalytic material, called RUW-19, consists of small, irregularly shaped particles which, after calcination in air at 550° C. for 4 hours, produce a characteristic x-ray diffractogram which at least includes the reflections stated in Table 1, all of which are reflections characteristic of either the AEI-phase, the CHA-phase or both phases, and from which the reflection between 2 theta=9.3 and 9.5 is always the strongest.
TABLE 1
2&thgr;
d(Å)
9.3-9.5
9.3-9.4
10.4-10.6
8.3-8.5
12.7-12.9
6.8-7.0
13.8-14.0
6.3-6.4
15.9-16.1
5.5-5.6
16.7-16.9
5.2-5.3
18.9-19.0
4.6-4.7
20.5-20.7
4.3-4.4
21.0-21.3
4.1-4.3
23.7-24.0
3.7-3.8
25.7-26.0
3.4-3.5
30.9-31.1
2.8-2.9
The product has acidic properties as demonstrated by the fact that>0.05 mmoles NH
3
/g material sorbed at 100° C. is desorbed at temperatures>300° C. when it is heated in flowing helium at a ramp rate of 10° C./min.
The content of Si in the calcined product is in the range between 0.2 and 3% weight, preferably between 0.4 and 1.2. The manufactured product has pore openings and channels of 4-5 Å diameter, and cavities, the smallest size of which is>5 Å, as found for both the AEI- and the CHA-structures.
RUW-19 is manufactured from a mixture of reactive sources of SiO
2
, Al
2
O
3
and P
2
O
5
and an organic template material. Said mixture is manufactured by combining at least one portion of the Al-source and the P-source with water, the Si-source and the organic template material. The reagents can be added in different orders and quantities, and from different sources, but Al-isopropoxide, phosphoric acid, colloidal silica and tetraethylammonium hydroxide have proved to be particularly useful sources of Al, P, Si and organic template material, respectively. It has further proved convenient to mix the Al-source with the P-source and water first, and thereafter adding either the Si-source or the organic template material and finally the remaining reagent. The Si-source may also be dissolved in the organic template solution prior to blending with the other reagents. It is convenient to stir or shake the mixture between each addition, but this is not necessary. All the reagents may well be added before stirring or shaking starts. After so preparing the precursor gel it is put into a steel autoclave and after a short or long ageing period at room temperature the autoclave is heated to a maximum temperature between 180 and 260° C., for at least 1 hour, and preferably for more than 2 hours. It is important that the autoclave is either shaken, stirred or rotated during the entire process of ageing and crystallisation.
RUW-19 comprises as major constituents at least the two silico-alumino-phosphate phases with AEI- and CHA-structures, and the material is not well defined regarding the ratios between the different phases. Any silico-alumino-phosphate prepared in one batch crystallisation exhibiting x-ray-reflections characteristic of both phases AEI and CHA are defined as RUW-19 catalytic material. This means in practice that the ratio between the two phases are always between 0.1 and 10, because otherwise the identification of the minor constituent becomes uncertain. Physical mixtures of the two phases AEI and CHA prepared by mixing samples of the two pure materials are not defined as RUW-19.
Typically, RUW-19 is obtained as a product in preparations where some of the critical parameters of a SAPO-34-synthesis (see comparative example 5) are combined with some critical parameters of a SAPO-18-synthesis (see comparative example 4). This does not imply however that RUW-19 is always obtained in such preparations. RUW-19 is obtained only when certain critical parameters of a typical SAPO-34-preparation are combined with certain critical parameters of a typical SAPO-18-preparation, as described and exemplified below. In addition to this there are also some features characteristic of a typical RUW-19 preparation which are not found in typical preparations of SAPO-34 nor of SAPO-18, such as relatively short synthesis times and rela

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