Process for preparing a spherical material with a hierarchical porosity comprising metallic particles trapped in a mesostructured matrix
A process is described for the preparation of an inorganic material with a hierarchical porosity in the micropore and mesopore domains. The material has at least two elementary spherical particles having a maximum diameter of 200 microns. The process comprises: a) preparing a solution containing zeolitic nanocrystals with a maximum nanometric dimension equal to 60 nm based on silicon and/or precursor elements of proto-zeolitic entities based on silicon; b) mixing, in solution, metallic particles or at least one metallic precursor of metallic particles, a surfactant and the solution obtained in accordance with a) such that the ratio of the volumes of inorganic and organic materials, V inorganic /V organic , is 0.29 to 0.50; c) aerosol atomization of the solution obtained in b) resulting in formation of spherical particles; d) drying the particles; g) eliminating any remaining precursor elements of proto-zeolitic entities based on silicon and the surfactant.
1. A process for the preparation of an inorganic material with a hierarchical porosity in the micropore and mesopore domains, said material being constituted by at least two elementary spherical particles having a maximum diameter of 200 microns, each of said spherical particles comprising metallic particles containing at least one or more metals selected from vanadium, niobium, tantalum, molybdenum, tungsten, iron, copper, zinc, cobalt and nickel, said metallic particles being present within a matrix, which is mesostructured, based on silicon oxide, having microporous walls with a thickness in the range 1 to 60 nm, said process comprising at least the following steps:
a) preparing a solution containing zeolitic nanocrystals with a maximum nanometric dimension equal to 60 nm based on silicon and/or precursor elements of proto-zeolitic entities based on silicon;
b) mixing, in solution, said metallic particles or at least one metallic precursor of said metallic particles, at least one surfactant and at least said solution obtained in accordance with a) such that the ratio of the volumes of inorganic and organic materials, V inorganic /V organic , is in the range 0.29 to 0.50;
c) aerosol atomization of said solution obtained in step b) in order to result in the formation of spherical particles;
d) drying said particles;
g) eliminating any remaining precursor elements of proto-zeolitic entities based on silicon and at least said surfactant;
h) regenerating said metallic particles to the form of a polyoxometallate which have decomposed during step g); and
i) drying the regenerated particles;
wherein said metallic particles are in the form of a polyoxometallate with formula (X x M m O y H h ) q− where H is a hydrogen atom, 0 is an oxygen atom, X is an element selected from phosphorus, silicon, boron, nickel and cobalt and M is one or more elements selected from vanadium, niobium, tantalum, molybdenum, tungsten, iron, copper, zinc, cobalt and nickel, x being equal to 0, 1, 2, or 4, m being equal to 5, 6, 7, 8, 9, 10, 11, 12 or 18, y being in the range 17 to 72, h being in the range 0 to 12 and q being in the range 1 to 20 and y, h and q being whole numbers.
2. A preparation process according to claim 1 , wherein following said step d), a step e) is carried out consisting of autoclaving the particles obtained from said step d) then carrying out a step f) consisting of drying said particles obtained at the end of said step e).
3. A preparation process according to claim 2 , in which said zeolitic nanocrystals comprise at least one zeolite selected from zeolites with structure type MFI, BEA, FAU and LTA and/or said proto-zeolitic entities comprise at least one species for initiating at least one zeolite selected from zeolites with structure type MFI, BEA, FAU and LTA.
4. A preparation process according to claim 1 , in which said metallic particles have at least one band with a wave number in the range 750 to 1050 cm −1 in Raman spectroscopy.
5. A preparation process according to claim 4 , in which said metallic particles are oxide nanoparticles comprising at least one metal selected from molybdenum, tungsten and a mixture of these two metals.
6. A preparation process according to claim 5 , in which at least one first monometallic precursor based on a metal selected from vanadium, niobium, tantalum, molybdenum and tungsten and at least one second monometallic precursor based on a metal from group VIII are dissolved to provide a solution prior to carrying out said step b), said solution then being introduced into the mixture in accordance with said step b).
7. A preparation process according to claim 1 , in which said metallic particles are heteropolyanions with formula P 2 Mo 5 O 23 H h (6−h)− , in which h=0, 1 or 2.
8. A preparation process according to claim 1 , in which said step a) consists of preparing a solution containing precursor elements of proto-zeolitic entities based on silicon and aluminium.
9. A preparation process according to claim 1 , in which said metallic particles are prepared by dissolving, prior to said step b), the metallic precursor(s) necessary for obtaining them in a solvent to provide a solution, said solution then being introduced into the mixture in accordance with said step b).
10. A preparation process according to claim 1 , in which at least one sulphur-containing compound is introduced into the mixture said step b) or when carrying out said step g).
11. A process for the transformation of a hydrocarbon feed, comprising 1) bringing an inorganic material obtained in accordance with the preparation process according to claim 1 into contact with a feed comprising at least one sulphur-containing compound, then 2) bringing said material obtained from said step 1) into contact with said hydrocarbon feed.