Method of making molecular sieve catalyst

Details Method of making molecular sieve catalyst Method of making molecular sieve catalyst

2002-01-17

2004-03-23

Wood, Elizabeth D. (Department: 1755)

Catalyst, solid sorbent, or support therefor: product or process

Catalyst or precursor therefor

Phosphorus or compound containing same

C502S060000, C502S063000, C502S064000, C502S068000

Reexamination Certificate

active

06710008

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a method of making molecular sieve catalyst. In particular, this invention relates to a method of making molecular sieve catalyst from dried molecular sieve catalyst particles.
BACKGROUND OF THE INVENTION
A molecular sieve is generally a microporous structure composed of either crystalline aluminosilicate, belonging to a class of materials known as zeolites, or crystalline aluminophosphates, or crystalline silicoaluminophosphates. Molecular sieves can be made by hydrothermal crystallization from a reaction mixture comprising reactive sources of silicon and/or aluminum and/or phosphorous containing compounds, usually in the presence of one or several organic amine or quaternary ammonium salt as structure directing agent, also known as template.
Molecular sieve catalysts are compositions made of molecular sieve particles bound together to form particles larger than the molecular sieve components. The molecular sieve catalyst particles can also include other components such as binders, fillers, like clay, and optionally other catalytically active agents such as rare earth metal oxides, transition metal oxides, or noble metal components.
Conventional methods of making molecular sieve catalyst particles include mixing together molecular sieve and binder, as well as other optional components such as fillers and other catalytic components. The mixture is typically stirred in solution to form a slurry, and the slurry is dried to form molecular sieve catalyst particles. Following drying, the particles are calcined to harden, as well as activate, the catalyst particles.
For example, WO 99/21651 describes a method for making molecular sieve catalyst. The method includes the steps of mixing together a molecular sieve and an alumina sol, the alumina sol being made in solution and maintained at a pH of 2 to 10. The mixture is then spray dried and calcined. The calcined product is reported to be relatively hard, i.e., attrition resistant.
U.S. Pat. No. 6,153,552 describes another method for making molecular sieve catalyst. The catalyst is made by mixing together a silicon containing oxide sol as a binder material and a molecular sieve material. The pH of the mixture is adjusted prior to spray drying. Following spray drying, the catalyst material is calcined to form a finished catalyst product, which is reported to be relatively hard, i.e., attrition resistant.
During the manufacture of molecular sieve catalyst, catalyst particles can be made which have undesirable properties such as undesirable attrition resistance properties or undesirable particle size properties. Rather than discarding such catalyst particles, it would be beneficial to find a method that allows for the catalyst particles to be remanufactured or recycled so as to provide properties which are acceptable to the user or manufacturer.
SUMMARY OF THE INVENTION
This invention provides a method for making molecular sieve catalyst particles from catalyst particles which have certain undesirable properties. In essence, this invention provides for the remanufacturing or recycling or re-working of molecular sieve catalyst to provide properties which are acceptable to the user or manufacturer.
In one embodiment, there is provided a method of making molecular sieve catalyst particles, comprising
a) providing a first dried molecular sieve catalyst;
b) combining the first dried molecular sieve catalyst with water to form a water-catalyst composition;
c) mixing the water-catalyst composition to form a slurry; and
d) drying the slurry to form particles of a second dried molecular sieve catalyst.
In another embodiment, there is provided a method of recycling molecular sieve catalyst particles having undesired properties, comprising
(i) mixing a composition comprising molecular sieve, binder and water;
(ii) drying the composition to form a first dried molecular sieve catalyst;
(iii) combining at least a portion of the first dried molecular sieve catalyst with water to form a water-catalyst composition;
(iv) mixing the water-catalyst composition to form a slurry;
(v) drying the slurry to form particles of a second dried molecular sieve catalyst.
In yet another embodiment, there is provided a method of making a molecular sieve catalyst composition, comprising: providing first dried molecular sieve catalyst particles, wherein the first dried molecular sieve catalyst particles yield, upon calcining, a calcined molecular sieve composition having greater than 5 wt % catalyst particles having an average particle diameter greater than or equal to 250 microns; combining the dried molecular sieve catalyst particles with water to form a slurry; and drying the slurry to form the molecular sieve catalyst composition.
In all embodiments of the invention, it is preferred that the water combined with the first dried molecular sieve catalyst comprises at least 95 wt % water and/or is substantially free of any molecular sieve particle. Preferably, the water is at a substantially neutral pH prior to combining with the dried molecular sieve catalyst particles.
The first dried molecular sieve catalyst may be uncalcined and may thus contain template material. Preferably, the template material is selected from the group consisting of triethylamine, cyclohexylamine, piperidine, dipropylamine, pyridine, isopropylamine, tetraethyl ammonium salts, and mixtures thereof.
It is preferred that the first dried molecular sieve catalyst and water be mixed so to break apart the particles of the first dried molecular sieve catalyst.
A slurry is formed, preferably having a viscosity of from 100 cP to 9,000 cP measured using a Brookfield LV-DVE viscometer with a No. 3 spindle at 10 rpm, and a solids content of from 10 wt % to 75 wt %.
The slurry is then dried to form particles of a second dried molecular sieve catalyst. Preferably drying is by spray drying.
The particles of the second dried molecular sieve catalyst may be submitted to calcination. Preferably, the molecular sieve catalyst particles obtained in e) have an EMARI of not greater than 1 wt %/hr, preferably not greater than 0.7 wt %/hr, most preferably not greater than 0.3 wt %/hr, and/or have a particle size such that 50% of the particles have a diameter larger than 30 &mgr;m and smaller than 150 &mgr;m.
The first dried molecular sieve catalyst preferably comprises a silicoaluminophosphate molecular sieve, more preferably selected from the group consisting of SAPO-18, SAPO-34, SAPO-35, SAPO-44, SAPO-56, ALPO-18 and ALPO-34, metal containing molecular sieves thereof, and mixtures thereof, even more preferably selected from the group consisting of SAPO-18, SAPO-34, ALPO-34 and ALPO-18, metal containing molecular sieves thereof, and mixtures thereof. In another embodiment, the first dried molecular sieve catalyst is selected from the group consisting of silicoaluminphosphate molecular sieves having CHA, AEI or a combination of CHA and AEI framework type.
The first dried molecular sieve catalyst may also comprise a binder selected from the group consisting of hydrated alumina, silicas, and/or other inorganic oxide sol and/or a filler selected from the group consisting of clays, clay-type compositions and mixtures thereof.
The present invention also relates to a calcined molecular sieve catalyst composition comprising catalyst particles, wherein the catalyst particles, after being submitted to calcination, have an EMARI of equal or less than 0.7 wt %/hr, preferably less than 0.3 wt %/hr.
The molecular sieve catalysts prepared by the method of the present invention are useful catalysts for the conversion of feedstocks comprising at least one oxygenate into olefins.
DETAILED DESCRIPTION OF THE INVENTION
This invention provides a method for making molecular sieve catalyst particles. The method is accomplished by combining a first dried molecular sieve catalyst with water to make a water-catalyst composition, making a slurry from the water-catalyst composition, and drying the slurry to produce a second dried molecular sieve catalyst. The method particularly provides for the re-

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