Method For Preparing A Sorbent

Abstract

A sorbent precursor is described comprising agglomerates of an inert particulate support material, the agglomerates being bound together with a binder comprising cement and/or clay, said binder being characterized as an agglomerate binder, wherein (a) the agglomerates are coated with a surface layer coating comprising a particulate copper compound and one or more coating binders, and (b) the surface layer has a thickness in a range of from 1 to 1000 μm. The sorbent precursor may be sulphided to prepare a sorbent for removing heavy metals from fluid streams.

1 . A sorbent precursor comprising agglomerates of an inert particulate support material, the agglomerates being bound together with a binder comprising cement and/or clay, said binder being characterized as an agglomerate binder, wherein:
 (a) the agglomerates are coated with a surface layer coating comprising a particulate copper compound and one or more binders, said one or more binders being characterized as coating binders; and   (b) the surface layer has a thickness in a range of from 1 to 1000 μm.   
     
     
         2 . The sorbent precursor of  claim 1  wherein the inert particulate support material is alumina, metal-aluminate, silicon carbide, silica, titania, zirconia, zinc oxide, aluminosilicates, zeolites, metal carbonate, carbon, or a mixture thereof. 
     
     
         3 . The sorbent precursor of  claim 1 , wherein the inert particulate support material is an alumina or hydrated alumina. 
     
     
         4 . The sorbent precursor of  claim 1 , wherein the inert particulate support material is in the form of a powder with a D 50  particle size in the range of from 1 to 100 μm. 
     
     
         5 . The sorbent precursor of  claim 1 , wherein the inert particulate support material is in the form of a powder with a D 50  particle size in the range of from 5 to 20 μm. 
     
     
         6 . The sorbent precursor of  claim 1 , wherein the agglomerate binder used to prepare the agglomerates is a combination of a cement and a clay. 
     
     
         7 . The sorbent precursor of  claim 6 , wherein the relative weights of the cement agglomerate binder and clay agglomerate binder is in the range 1:1 to 3:1 (first to second binder). 
     
     
         8 . The sorbent precursor of  claim 1 , wherein the total amount of the agglomerate binder in the agglomerate is in the range of from 5 to 30% by weight. 
     
     
         9 . The sorbent precursor of  claim 1  wherein the agglomerates have a diameter in the range of from 1 to 15 mm. 
     
     
         10 . The sorbent precursor of  claim 1 , wherein the particulate copper compound is one or more of copper oxide, basic copper carbonate, or a precipitated material comprising copper basic carbonate and zinc basic carbonate. 
     
     
         11 . The sorbent precursor of  claim 1 , wherein the particulate copper compound is in the form of a powder with an average particle size, [D 50 ], in the range of from 5 to 100 μm. 
     
     
         12 . The sorbent precursor of  claim 1 , wherein the particulate copper compound is in the form of a powder with an average particle size, [D 50 ], in the range of from 10 to 50 μm. 
     
     
         13 . The sorbent precursor of  claim 1 , wherein the copper content of the sorbent precursor is in the range of from 0.5 to 30% by weight, based on the total weight of the sorbent precursor. 
     
     
         14 . The sorbent precursor of  claim 1 , wherein the total coating binder content of the surface layer coating is in the range of from 5 to 20% by weight. 
     
     
         15 . The sorbent precursor of  claim 1 , wherein the surface layer coating comprises a particulate copper compound and a clay binder as the sole coating binder. 
     
     
         16 . The sorbent precursor of  claim 1 , wherein the thickness of the surface layer coating of particulate copper compound in the sorbent precursor is in the range of from 1 to 500 μm. 
     
     
         17 . The sorbent precursor of  claim 1 , wherein the sorbent precursor comprises a mixture of a particulate basic copper carbonate and a clay coating binder, as a surface layer of 1 to 1000 μm thickness coated on the surface of agglomerates formed from a particulate hydrated alumina support material, which is bound together in the agglomerates with an agglomerate binder comprising cement and a clay. 
     
     
         18 . The sorbent of  claim 1 , wherein the sorbent precursor comprises granulated agglomerates. 
     
     
         19 . A method for preparing the sorbent precursor of  claim 1 , comprising the steps of: (i) mixing together the inert particulate support material and the one or more agglomerate binders to form a support mixture, (ii) shaping the support mixture by granulation using a liquid in a granulator to form the agglomerates, (iii) coating the agglomerates with a coating mixture powder comprising the particulate copper compound and the one or more coating binders to form a coated agglomerate, and (iv) drying the coated agglomerate to form a dried sorbent precursor; wherein the agglomerates are coated in step (iii) by adding the coating mixture powder to the agglomerates in the granulator. 
     
     
         20 . The method of  claim 19 , wherein the sorbent precursor comprises granulated agglomerates. 
     
     
         21 . A sorbent prepared from the sorbent precursor of  claim 1 , wherein the sorbent precursor has been subjected to a sulphiding step to convert the particulate copper compound to copper sulphide. 
     
     
         22 . A process for removing a heavy metal from a fluid stream comprising contacting the fluid stream with a sorbent according to  claim 21 .