Zeolitic adsorbent for the separation of hydrocarbon isomers
The present invention concerns a zeolitic adsorbent agglomerate comprising at least one zeolite of faujasite type comprising sodium and/or lithium and/or calcium, and/or barium and/or potassium, of porosity between 25% and 45%, and having a standard deviation σ of crystal size distribution in said agglomerate of less than 0.30 μm. The invention also concerns the use of the zeolitic adsorbent agglomerate to separate hydrocarbon mixtures, and the process to separate hydrocarbon mixtures using said zeolitic adsorbent agglomerate.
1. An agglomerated zeolitic adsorbent, comprising at least one faujasite zeolite of atomic ratio Si/Al higher than 1.50, wherein particle porosity of the adsorbent is between 25% and 45%, limits included, and wherein standard deviation o of crystal size distribution in the agglomerated zeolitic adsorbent is less than 0.30 μm.
2. The agglomerated zeolitic adsorbent according to claim 1 , wherein the adsorbent comprises zeolite crystals having a number-weighted mean diameter less than 1200 nm.
3. The agglomerated zeolitic adsorbent according to claim 1 , the adsorbent is in the form of beads of a mean diameter between 100 μm and 1000 μm, limits included.
4. The agglomerated zeolitic adsorbent according to claim 1 , wherein the at least one faujasite zeolite has a Si/Al atomic ratio of between 1.50 and 6.50, limits excluded.
5. The agglomerated zeolitic adsorbent according to claim 1 , comprising one or more cations.
6. The agglomerated zeolitic adsorbent according to claim 1 , wherein the adsorbent comprises sodium oxide (Na 2 O) in a content higher than 5% by weight relative to the total weight of the adsorbent.
7. The agglomerated zeolitic adsorbent according to claim 5 , wherein the total content of cations other than lithium, sodium, potassium, calcium and barium is less than 2%, this total content being expressed in weight of oxides of the cations relative to the total weight of the zeolitic adsorbent.
8. The agglomerated zeolitic adsorbent according to claim 1 , wherein no zeolitic structure other than the faujasite structure is detected by X-ray diffraction.
9. The agglomerated zeolitic adsorbent according to claim 1 , wherein the weight fraction of the at least one faujasite zeolite is higher than or equal to 80% relative to the total weight of the adsorbent.
10. A process for using an agglomerated zeolitic adsorbent according to claim 1 , where the process is chosen from the following:
separating C8 aromatic isomer fractions;
separating isomers of substituted toluene;
separating cresols;
separating polyhydric alcohols.
11. The process according to claim 10 , wherein meta-xylene is separated from aromatic isomer fractions having 8 carbon atoms.
12. A process for separating meta-xylene from aromatic isomer fractions having 8 carbon atoms, by contacting the aromatic isomer fractions with the agglomerated zeolitic adsorbent according to claim 1 , in a liquid phase or in a gas phase.
13. The process according to claim 12 , where the process takes place in a liquid phase via adsorption of the meta-xylene in the presence of a desorbent.
14. The process according to claim 12 , where the process is performed in a simulated moving bed type.