Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – And additional al or si containing component
Reexamination Certificate
2000-07-27
2003-12-23
Griffin, Walter D. (Department: 1764)
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
And additional al or si containing component
C502S074000, C502S077000, C502S060000, C502S063000, C502S064000, C502S071000, C502S439000, C208S120350
Reexamination Certificate
active
06667266
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for impregnating a Group VIII metal on a molecular sieve binder extrudate.
BACKGROUND OF THE INVENTION
PCT patent publication No. WO-A-9641849 describes an impregnation of platinum or palladium on a dealuminated silica-bound ZSM-5 with an aqueous solution of tetramine platinum hydroxide or tetramine palladium hydroxide. The impregnation of the silica-bound ZSM-5 was followed by drying for 2 hours at 120° C. and calcined for 2 hours at 300° C. Thereafter the catalyst was activated by reduction of the platinum or palladium.
A disadvantage of the impregnation method described in PCT patent publication No. WO-A-9641849 is the long drying time. The use of shorter drying times results in a less favourable distribution of the platinum or palladium on the silica-bound ZSM-5. It is generally known that a better distribution is possible when the molecular sieve is transformed before impregnation from its H-form to a NH
4
-form. By an “NH
4
-form” is understood that (part of) the H+ ions in the molecular sieve are exchanged for ammonium-ions.
An example of the transformation of a molecular sieve in a NH
4
-form before impregnation is described in US patent publication U.S. Pat. No. 5,397,454. This patent publication describes the impregnation of SSZ-32 zeolite powder with palladium. Before impregnation the zeolite was subjected to a sequence of 4 NH
4
NO
3
-ion exchanges. Hereafter it was slurried into an aqueous solution of NH
4
OH. Then a tetramine palladium nitrate solution, of which the pH was adjusted to 9.5 with NH
4
OH, was added slowly.
A disadvantage of this method is the long processing time for impregnation. It would be advantageous if the extrudate with the molecular sieve in its H-form could be used directly in the process of impregnating a molecular sieve-binder extrudate.
The object of the present invention is to provide a method for impregnating a Group VIII metal on a molecular sieve-binder extrudate, which allows a short drying time and results in a good distribution. Short drying times are desirable when a catalyst is prepared on a commercial scale.
SUMMARY OF THE INVENTION
This object has been achieved when the following steps are used for impregnating a Group VIII metal on a molecular sieve-binder extrudate wherein the binder comprises a low acidity refractory oxide binder material, which is essentially free of alumina. In particular it relates to a method for impregnating a Group VIII metal on such a molecular sieve-binder extrudate by ion exchange with an aqueous solution of a Group VIII metal salt. Such steps comprise:
a) contacting the molecular sieve-binder extrudate with an aqueous solution of a corresponding Group VIII metal nitrate salt having a pH of below 8, wherein the molar ratio between the Group VIII metal cations in the solution and the number of sorption sites present in the extrudate is equal to or larger than 1, and
b) drying the molecular sieve-binder extrudate obtained from step a).
DETAILED DESCRIPTION OF THE INVENTION
It has been found that with the process according to the invention a good group VIII metal distribution is obtained, while short drying times are possible. A further advantage is that the molecular sieve or molecular sieve-binder extrudate can be directly used in its H-form without the need to first transform the molecular sieve in a NH
4
-form.
The choice of molecular sieve is not essential for obtaining the advantages of the invention, namely good distribution and short drying times. Examples of molecular sieves include metallosilicates, metallophosphates and silica metallophosphates. Possible metallo components in the framework of these molecular sieves include metals such as Al, Fe, B, Ga or Ti or combinations of these metals. Preferred molecular sieves are aluminosilicates, alumino phosphates and silica aluminium phosphates, such as SAPO-11, SAPO-31 and SAPO-41. Especially preferred molecular sieves are aluminosilicates, further referred to as zeolites. Examples of suitable zeolites include ZSM-4 (Omega), ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-50, Beta, X,Y and L as well as ferrierite and mordenite and isotypic framework structures thereof. When the catalyst, resulting after impregnation of the molecular sieve-binder extrudate, is to be used for catalytic dewaxing purposes, the preferred zeolite crystallites suitably have pores with a maximum diameter in the range of from 0.35 to 0.80 nm. Preferred zeolite crystallites include MFI-type zeolites having pores with diameters of 0.55 and 0.56 nm, such as ZSM-5 and silicalite, offretite having pores with diameters of approximately 0.68 nm and zeolites of the ferrierite group having pores with diameter of 0.54 nm, such as ZSM-35 and ferrierite. Another preferred class of zeolite crystallites include TON-type zeolites. Examples of TON-type zeolite crystallites are ZSM-22, Theta-1 and Nu-10 as described in U.S. Pat. No. 5,336,478, EP-A-57049 and EP-A-65400. A further preferred class of zeolite crystallites are of the MTW-type. Examples of molecular sieve crystallites having the MTW-type topology are ZSM-12, Nu-13, TEA-silicate, TPZ-3, TPZ-12, VS-12 and Theta-3 as for example described in U.S. Pat. No. 3,832,449, EP-A-513118, EP-A-59059 and EP-A-162719. A next preferred class of zeolite crystallites are of the MTT-type. Examples of zeolite crystallites having the MTT-type topology are ZSM-23, SSZ-32, ISI-4, KZ-1, EU-1, EU-4 and EU-13 as for example described U.S. Pat. Nos. 4,076,842, 4,619,820, EP-A-522196, EP-A-108486 and EP-A-42226.
The primary crystallite size of the molecular sieve can vary within a wide range of 0.001 mm to 5 mm. For catalytic dewaxing purposes the crystallite size of the zeolite may suitably be as high as 100 micron. Preferably small crystallites are used in order to achieve an optimum catalytic activity. Preferably crystallites smaller than 10 micron and more preferably smaller than 1 micron are used.
The binder of the molecular sieve-binder extrudate comprises a low acidity refractory oxide binder material, which is essentially free of alumina. Suitable binder materials, then, include low acidity refractory oxides such as silica, zirconia, titanium dioxide, germanium dioxide, boria and mixtures of two or more of these. The most preferred binder, however, is silica. The binder may occur naturally or may be in the form of gelatinous precipitates, sols or gels. The binder may also be present as a mixture of those. Preferred extrudates are those prepared by the method described in U.S. Pat. No. 5,053,374.
The weight ratio of the molecular sieve and the binder can be anywhere between 5:95 and 95:5. Lower molecular sieve content may in some cases be advantageous for achieving a higher selectivity and higher molecular sieve content is to be preferred when a higher activity is desired.
After extrusion the molecular sieve-binder extrudate is dried for a time in the range of 15 minutes to 24 hours, more preferably from 1 to 3 hours, at a temperature in the range from 10 to 350° C., more preferably from 120 to 150° C. Thereafter the catalyst composition is subjected to calcining under normal conditions, suitably at a temperature of between 400 to 900° C. by heating in air for 1 to 48, preferably 1 to 10 hours.
Step a) of the method of the invention comprises contacting the molecular sieve-binder extrudate with an aqueous solution of a corresponding Group VIII metal nitrate salt having a pH of below 8, wherein the molar ratio between the Group VIII metal cations in the solution and the number of sorption sites present in the extrudate is equal to or larger than 1. Preferably the molar ratio between the Group VIII metal cations and the number of sorption sites is between 1 and 20. A sorption site is a site where theoretically one Group VIII cation can be adsorbed. Calculation of the number of sorption sites per gram extrudate can be done as follows. An extrudate has a fixed value of moles H+ per gram extrudate. The number of moles H+ per gram extrudate is determined by means of NH
3
Remans Thomas Joris
Van Vegchel Ingrid Maria
Arnold Jr. James
Griffin Walter D.
Shell Oil Company
LandOfFree
Method for impregnation of molecular sieve-binder extrudates does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for impregnation of molecular sieve-binder extrudates, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for impregnation of molecular sieve-binder extrudates will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3179136