Materials and methods for the removal of sulfur compounds from feedstock
View Patent ↗A composite material having utility for removing sulfur from a feedstock comprises a ceramic matrix having a relatively low melting point metal such as tin, zinc, lead or bismuth nanodispersed therein. The material may be prepared from a mixture of particles of a precursor of the ceramic matrix and precursor of the metal. The precursors are selected such that the melting point of the precursor of the ceramic is less than the melting point of the precursor of the metal. The mixture of precursor materials is heated to a temperature sufficient to melt the precursor of the ceramic material so as to coat it onto the precursor of the metal. The ceramic precursor is then reacted so as to convert it to a ceramic. Thereafter, the precursor of the metal is converted to a free metal which is retained within the ceramic matrix so as to prevent agglomeration.
1. A multi-step method for preparing a composite material which comprises a ceramic matrix having a metal nanodispersed therein, said method including the steps of:
providing a precursor of the ceramic matrix;
providing a precursor of the metal, said precursor of the metal having a melting point which is greater than the melting point of the precursor of the ceramic matrix;
mixing said precursor of the ceramic matrix and the precursor of the metal so as to produce a mixture comprised of particles of the precursor of the ceramic matrix and particles of the precursor of the metal;
heating said mixture to a first temperature which is greater than the melting point of the precursor of the ceramic matrix and less than the melting point of the precursor of the metal, under conditions which will not convert said precursor of said ceramic matrix to said ceramic matrix and said precursor of said metal to said metal, whereby the particles of the precursor of the metal are at least partially coated with the precursor of the ceramic matrix;
carrying out a conversion reaction which converts the precursor of the ceramic matrix into said ceramic matrix wherein said ceramic matrix is porous, said reaction being carried out in a carburizing atmosphere, and at a second temperature which is less than the melting point of the precursor of the metal; and
carrying out a conversion reaction which converts the precursor of the metal to said metal, said reaction being carried out in a reducing atmosphere, and at a third temperature which is greater than said second temperature, so as to produce said composite material.
2. The method of claim 1 , wherein the precursor of the ceramic matrix is a vanadium-oxygen material, and the reaction which converts the precursor of the ceramic matrix is a carburizing reaction which converts the vanadium oxide precursor to a vanadium carbide ceramic.
3. The method of claim 2 , wherein the vanadium-oxygen material is selected from the group consisting of an oxide of vanadium, ammonium vanadate, and combinations thereof.
4. The method of claim 1 , wherein said metal is selected from the group consisting of tin, zinc, lead, bismuth, and combinations thereof.
5. The method of claim 1 , wherein said precursor of said metal is an oxide or a sulfide of said metal.
6. The method of claim 1 , including the further steps of:
providing an agglomeration inhibitor; and
mixing said agglomeration inhibitor with said precursor of the ceramic matrix and said precursor of the metal.
7. The method of claim 6 , wherein said agglomeration inhibitor is silica.
8. The method of claim 1 , wherein amounts of said precursor of the ceramic matrix and said precursor of the metal are selected so that the weight percentage of metal present in the composite material is in the range of 60-70%.
9. The method of claim 1 , wherein said carburizing atmosphere includes a hydrocarbon gas.
10. The method of claim 1 , wherein said reducing atmosphere includes hydrogen.