Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – And additional al or si containing component
Reexamination Certificate
2000-12-08
2003-10-14
Dunn, Tom (Department: 1725)
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
And additional al or si containing component
C502S079000, C502S400000, C502S411000
Reexamination Certificate
active
06632766
ABSTRACT:
FIELD OF THE INVENTION
This application relates to an adsorbent which comprises a zeolite, an alumina component and a metal component e.g. sodium in an amount at least 10% of the zeolite's ion exchange capacity. This new adsorbent is used to remove contaminants from hydrocarbon streams, e.g. removing CO
2
, CO
3
, H
2
S, AsH
3
, methanol, mercaptans and other S- or O-containing organic compounds from ethylene, propylene, C
3
-C
4
hydrocarbon products and other lights hydrocarbon streams.
BACKGROUND OF THE INVENTION
Solid adsorbents are commonly used to remove contaminants from hydrocarbon streams such as olefins, natural gas and light hydrocarbon fractions. Since these streams can contain different contaminants, more than one adsorbent or adsorbent bed are needed to sufficiently purify the stream so that it can be used in the desired process. Contaminants which can be present in these streams include H
2
O, CO, O
2
, CO
2
, COS, H
2
S, NH
3
, AsH
3
, PH
3
, Hg, methanol, mercaptans and other S- or O-containing organic compounds.
However, while various adsorbents can remove one or more contaminant, they can also remove and/or promote reactions of the desired hydrocarbon. For example, faujasite type zeolites, e.g. zeolite 13X, are good adsorbents for sulfur and oxygenate compounds but they are also good adsorbents for olefins which results in high temperature rise that can cause run-away reactions. Additionally, owing to the zeolite's residual surface reactivity reactions such as oligomerization and polymerization can occur during regeneration. This leads to fouling and performance deterioration.
In attempts to remedy this problem, there are reports in the art where zeolites have been mixed with alumina. U.S. Pat. No. 4,762,537 discloses the use of an adsorbent comprising zeolite Y and alumina to remove HCl from a hydrogen stream. In U.S. Pat. Nos. 4,686,198 and 4,717,483 it is disclosed that a mixture of alumina and sodium Y zeolite can remove ammonia sulfides and organic impurities from waste water. The sodium Y zeolite contains at least 12.7 wt. % Na
2
O. The same adsorbent is also used to reduce the acidity and moisture content of used organophosphate functional fluids, see U.S. Pat. No. 4,751,211. The use of alumina with alkali or alkaline earth metal for removing HCl and other contaminants is disclosed in U.S. Pat. No. 6,013,600.
Applicant has developed an improved adsorbent which can remove multiple contaminants from various hydrocarbon streams. Surprisingly these contaminants can be removed with only a small temperature rise and the adsorbent has increased stability upon multiple regenerations. This adsorbent comprises a zeolite, alumina and a metal component (Madd) which is present in an amount of at least 10 mole % of the stoichiometric amount of metal (expressed as the oxide) needed to compensate for the negative charge of the zeolite lattice.
SUMMARY OF THE INVENTION
This invention relates to a solid shaped adsorbent, a process for preparing the adsorbent and a process for removing contaminants from a hydrocarbon stream using the adsorbent. Accordingly, one embodiment of the invention is a solid shaped adsorbent for purifying hydrocarbon streams comprising an alumina component, a zeolite component and a metal component selected from the group consisting of alkali metals, alkaline earth metals and mixtures thereof, the metal component present in an amount of at least 10 mole % of the stoichiometric amount of metal needed to compensate for the negative charge of the zeolite lattice, expressed as the oxide.
Another embodiment of the invention is a process for preparing a solid shaped adsorbent for purifying hydrocarbon streams comprising an alumina component, a zeolite component and a metal component selected from the group consisting of alkali metals, alkaline earth metals and mixtures thereof, the metal component present in an amount of at least 10 mole % of the stoichiometric amount of metal needed to compensate for the negative charge of the zeolite lattice, expressed as the oxide.
The process comprises forming a shaped article by combining an alumina component, a zeolite component and a metal component precursor in any order to form a shaped article, curing the shaped article at curing conditions to give a cured shaped article and activating the cured article at activation conditions to give the solid shaped adsorbent.
Yet another embodiment of the invention is a process for removing contaminants from hydrocarbon streams comprising contacting the stream with the solid shaped adsorbent described above at adsorption conditions to remove at least a portion of at least one contaminant.
These and other objects and embodiments will become clearer after a detailed description of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Applicant's invention comprises a solid shaped adsorbent, a process for preparing the adsorbent and purification processes using the adsorbent. With regard to the solid shaped adsorbent, one necessary component is an activated alumina. Activated aluminas include aluminas having a surface area usually greater than 100 m
2
/g and typically in the range of 100 to 400 m
2
/g. Further, the activated alumina powder is preferably obtained by rapid dehydration of aluminum hydroxides, e.g., alumina trihydrate of hydrargillite in a stream of hot gasses or solid heat carrier. Dehydration may be accomplished in any suitable apparatus using the stream of hot gases or solid heat carrier. Generally, the time for heating or contacting with the hot gases is a very short period of time, typically from a fraction of a second to 4 or 5 seconds. Normally, the temperature of the gases varies between 400° and 1000° C. The process is commonly referred to as flash calcination and is disclosed, for example in U.S. Pat. No. 2,915,365, incorporated herein by reference. However, other methods of calcination may be employed.
The activated aluminas suitable for use in the present invention have a median particle size in the range of 0.1 to 300 microns, preferably 1 to 100 microns and typically 1 to 20 microns. In certain instances, it may be desirable to use aluminas with a median particle size of 1 to 10 microns. The alumina may be ground to the desired particle size before or after activation. The activated alumina typically has an LOI (loss on ignition) in the range of about 5 to 12% at a temperature of 200° to 1000° C.
One source of activated alumina is gibbsite which is one form of alumina hydrate derived from bauxite using the Bayer process. However, alpha alumina monohydrate, pseudoboehmite or the alumina trihydrate may be used if sufficiently calcined. Other sources of alumina may also be utilized including clays and alumina alkoxides.
Another necessary component of the present invention is a zeolite. Zeolites are crystalline aluminosilicate compositions which are microporous and which have a three-dimensional oxide framework formed from corner sharing AlO
2
and SiO
2
tetrahedra. Zeolites are characterized by having pore openings of uniform dimensions, having a significant ion exchange capacity, and being capable of reversibly desorbing an adsorbed phase which is dispersed throughout the internal voids of the crystal without significantly displacing any atoms which make up the permanent zeolite crystal structure. The zeolites which can be used in the present invention are those which have a pore opening of about 5 to about 10 Å.
In general, the zeolites have a composition represented by the empirical formula:
M
2
O:Al
2
O
3
:bSiO
2
M is a cation having a valence of “n” and “b” has a value of about 2 to about 500. Preferred zeolites are those that have a SiO
2
/Al
2
O
3
ratio of about 2:1 to about 6:1 and/or those having the crystal structure of zeolite X, faujasite, zeolite Y, zeolite A, mordenite, beta and ferrierite. Especially preferred zeolites are zeolites X, Y and A.
Preparation of these zeolites is well known in the art and involves forming a reaction mixture composed of reactive sources of the components which mixture is then hydrot
Dunn Tom
Ildebrando Christina
Molinaro Frank S.
Tolomei John G.
UOP LLC
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