Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – Faujasite type
Reexamination Certificate
2001-07-03
2003-11-18
Elve, M. Alexandra (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
Faujasite type
C502S064000, C502S065000, C502S066000, C502S073000, C502S074000
Reexamination Certificate
active
06649556
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a process for the preparation of agglomerated zeolites of X type, a portion of the exchangeable cationic sites of which is occupied by lithium ions.
BACKGROUND OF THE INVENTION
The term “zeolite of X type” is understood to mean, throughout the following, zeolites X with an Si/Al atomic ratio=1.5 and more particularly zeolites LSX (Low Silica X), i.e. the Si/Al ratio of which is in the region of 1.
Zeolites X exchanged with lithium (that is to say, those for which at least a portion of the cationic exchangeable sites is occupied by lithium ions) have numerous industrial applications and are widely used for the separation of nitrogen from other gases, such as, for example, oxygen, argon and hydrogen, according to techniques for the selective adsorption of the gases to be separated. The zeolites employed can be provided in various forms and the exact form which they adopt can determine their usefulness in industrial adsorption processes. When zeolites are used in industrial adsorbers, it is generally preferred to agglomerate them (for example by converting them to granules) in order not to risk compacting the pulverulent zeolite in an adsorption column of industrial size, thus blocking or at the very least greatly reducing the flow through the column.
According to U.S. Pat. No. 3,140,933, a zeolite of X type having base ions replaced by lithium ions can be efficiently used to separate nitrogen from oxygen at temperatures ranging up to 30° C. Because the exchange of ions is not total and because the zeolites X have been synthesized in a sodium medium, the adsorbent used is a mixed sodium/lithium zeolite.
U.S. Pat. No. 4,859,217 discloses that very good separation of nitrogen from oxygen can be obtained by adsorption at temperatures of 15 to 70° C. using a zeolite of X type which has more than 88% of its ions in the form of lithium ions, in particular when a zeolite is used with an Si/Al atomic ratio of between 1 and 1.25.
U.S. Pat. No. 5,179,979 maintains that lithium/alkaline earth metal zeolites of X type having lithium/alkaline earth metal molar ratios of the order of 95/5 to 50/50 approximately have a higher thermal stability than that of the corresponding zeolites with pure lithium and good adsorption selectivities and capacities.
U.S. Pat. No. 5,152,813 discloses the adsorption of nitrogen from gas mixtures which uses crystalline zeolites X having an Si/Al zeolite ratio≦1.5 in which the exchangeable sites are occupied by at least 2 ions: between 5 and 95% of lithium ion and between 5 and 95% of a second ion chosen from calcium, strontium and mixtures of these, the total (lithium and second exchangeable ion) being at least 60%.
U.S. Pat. No. 5,464,467 provides a zeolite of X type, the cations of which comprise, referred to as equivalents, from approximately 50 to approximately 95% of lithium, from approximately 4 to approximately 50% of trivalent ions chosen from aluminium, scandium, gallium, iron(III), chromium(III), indium, yttrium, lanthanides alone, mixtures of two lanthanides or more, and mixtures of these, and from 0 to approximately 15% of residual ions chosen from sodium, potassium, ammonium, hydronium, calcium, strontium, magnesium, barium, zinc, copper(II) and mixtures of these, which is prepared by exchange of the exchangeable cations of the zeolite, preagglomerated with a binder, first with lithium and then with the trivalent cation or cations.
U.S. Pat. No. 5,932,509 provides for the preparation of these same zeolites according to a process which consists first in exchanging the exchangeable cations of the powdered zeolite X with trivalent cations, in then agglomerating with a binder and finally in carrying out the lithium exchange on the agglomerated zeolite. This process requires drying and intermediate activation of the zeolite material. However, it has the advantage of only carrying out the final Li exchange on a product which has been pregraded by particle separation, thus limiting the losses of finished product, which is expensive because of its lithium content.
Due to the high costs of lithium salts, it is essential to have a process for lithium exchange which is as selective as possible in order to avoid losses of lithium.
EP 863 109 discloses a continuous countercurrentwise process for exchanging the ions of a zeolite, preferably in granular form, characterized in that the solution for exchanging ions, in particular lithium ions, is passed into at least two receptacles in series, arranged so as to be able to be swapped around cyclically and filled with the zeolite to be exchanged, the exchanging solution being transferred, on each occasion, from a first receptacle in the series to the following receptacle and, when the desired level of ion exchange is obtained, the receptacle comprising the zeolite at the desired degree of exchange is taken out of the series and the exchanging solution is separated from the zeolite, which is washed, isolated and replaced by a fresh charge of zeolite to be exchanged. This process makes it possible to obtain zeolites which have been highly exchanged with lithium, that is to say for which the level of exchange with regard to lithium (corresponding to the Li/Li+Na molar ratio of the Li and Na ions in the zeolite) is high, but with a very poor output with regard to lithium, namely at most 12%; such a process cannot be transferred to the industrial scale insofar as the solution recovered at the outlet of the receptacle comprising the lithium-exchange zeolite comprises not only lithium but also the ions which were exchanged, typically sodium and/or potassium, and this solution is difficult to recover in value industrially insofar as it requires a cumbersome reprocessing treatment before possibly being able to be discharged as it is to the environment.
DESCRIPTION OF THE INVENTION
The present invention provides a process for the preparation of agglomerated zeolites X, at least a portion of the exchangeable sites of which is occupied by lithium ions, which does not exhibit the disadvantages of the processes of the prior art detailed above.
The abovementioned zeolites prepared according to the process which is a subject-matter of the invention are zeolites of X type having an Si/Al atomic ratio of less than or equal to 1.5 and preferably of between 0.9 and 1.1, the exchangeable cations of which comprise, referred to as equivalents;
from approximately 50 to approximately 99% of lithium ions and preferably at least 96%,
from approximately 4 to approximately 50% of trivalent ions chosen from aluminium, scandium, gallium, iron(III), chromium(III), indium, yttrium, lanthanides or rare earth metals, alone or as mixtures, and/or of divalent ions chosen from calcium, strontium, zinc, copper, chromium(II), iron(II), manganese, nickel or cobalt, alone or as a mixture,
0 to approximately 15% of residual ions chosen from sodium, potassium, ammonium or hydronium, alone or as a mixture, agglomerated with a binder.
The process according to the invention results not only in a final level of lithium exchange of at least 96% but it is also characterized by a greatly improved output with respect to that of EP 863 109, i.e. greater than or equal to 45%, with easy treatment of the lithium-comprising effluents for the purpose of their recovery in value, indeed even, in a particularly preferred optimized embodiment, makes it possible to achieve a lithium output of greater than or equal to 80%,
the level of exchange being defined as the Li/Li+Na+K ratio, where Li, Na and K are the respective concentrations of Li, Na and K in the zeolite obtained,
and the lithium output as the ratio of the amount of lithium fixed to the zeolite to the amount of lithium entering.
Agglomeration
The first stage of the process developed by the Applicant Company consists of a stage of agglomeration of the starting zeolite with an inert binder. Use is conventionally made, as starting zeolite, of powdered zeolites X, the exchangeable sites of which are predominantly occupied by sodium and/or potassium ions
Masini Jean-Jacques
Plee Dominique
Sacleux Jean-Claude
Vidal Jean-Louis
CECA S.A.
Elve M. Alexandra
Ildebrando Christina
Smith , Gambrell & Russell, LLP
LandOfFree
Process for the preparation of agglomerated zeolites X and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the preparation of agglomerated zeolites X and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the preparation of agglomerated zeolites X and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3144973