Process for preparing catalysts

Abstract

A process for manufacturing a catalyst composition comprises the steps of (i) precipitating one or more metal compounds from solution using an alkaline precipitant, preferably comprising an alkaline carbonate, optionally in the presence of a thermostabilising material, ii) ageing the precipitated composition, and (iii) recovering and drying the aged composition, wherein the ageing step is performed using a pulse-flow reactor.

What is claimed: 
     
         1 . A process for manufacturing a catalyst composition comprising the steps of
 (i) precipitating a composition comprising one or more metal compounds from solution using an alkaline carbonate precipitant,   (ii) ageing the precipitated composition with evolution of carbon dioxide, and   (iii) recovering and drying the aged composition,   wherein the ageing step is performed using a pulse-flow reactor having one or more inlets for introducing a slurry of the precipitated composition, one or more outlets for removing the aged composition, and one or more outlets for removing carbon dioxide.   
     
     
         2 . A process according to  claim 1  wherein the one or more metal compounds comprise one or more metals selected from the group consisting of Ca, Mg, Ti, V, Cr, Mn, Fe, Cr, Co, Ni, Cu, Zn, or Pb. 
     
     
         3 . A process according to  claim 1  wherein the one or more metal compounds comprise one or more metals selected from the group consisting of Co, Ni, Cu or Fe. 
     
     
         4 . A process according to  claim 1  wherein the one or more metal compounds comprise one or more metals selected from the group consisting of Cu, Zn and Mg. 
     
     
         5 . A process according to  claim 1  wherein a metal oxide thermostabilising material is present during the precipitation of the composition. 
     
     
         6 . A process according to  claim 1  wherein an alumina sol is present during the precipitation of the composition. 
     
     
         7 . A process according to  claim 1  wherein the alkaline carbonate precipitant is selected from the group consisting of sodium carbonate and potassium carbonate. 
     
     
         8 . A process according to  claim 1  wherein the pulse flow reactor comprises an elongate vessel and means for imposing on the slurry a pulsatile oscillatory motion in a direction substantially parallel to the direction of fluid flow in the elongate vessel, wherein
 (i) the one or more inlets for introducing the slurry of the precipitated composition is located at a first end or at any other point along the length of the elongate vessel, 
 (ii) the one or more outlets for removing the aged composition and carbon dioxide are located at a second end opposite to the first end or at any point along the length of the elongate vessel, and 
 (iii) a plurality of stationary baffles are mounted substantially traversely to the direction of fluid flow within the elongate vessel. 
 
     
     
         9 . A process according to  claim 1  wherein the pulse-flow reactor comprises a single straight section or a plurality of straight sections joined by U-bends. 
     
     
         10 . A process according to  claim 1  wherein the pulse-flow reactor is in a horizontal orientation or a vertical orientation. 
     
     
         11 . A process according to  claim 8  wherein the Internal cross-sectional area of the pulse-flow reactor taken up by each baffle is the same or different along the length of the reactor and is 20-80% of the total area. 
     
     
         12 . A process according to  claim 8  wherein when pulse-flow reactor is of circular cross-section, the baffles are discs having one central orifice through which the slurry may pass or comprise several orifices, or the discs are imperforate and have a smaller diameter than the internal diameter of the vessel thus leaving an annular space around their periphery. 
     
     
         13 . A process according to  claim 8  wherein 5 or more baffles are present in the pulse-flow reactor. 
     
     
         14 . A process according to  claim 8  wherein the pulsatile oscillatory motion is provided by continuously pumping the slurry along the elongate vessel using a centrifugal, diaphragm or gear pump and superimposing reciprocating oscillations by using a mechanism selected from the group consisting of a pump, valve, and a piston located so as to constitute an end wall of the pulse-flow reactor, or in hydraulic communication with an end of the reactor. 
     
     
         15 . A process according to  claim 8  wherein the pulsatile oscillatory motion has an oscillation frequency in the range 0.1-10 Hz. 
     
     
         16 . A process according to  claim 8  wherein the pulsatile oscillatory motion has an amplitude in the range 0.05-0.5 times the diameter of the reactor. 
     
     
         17 . A process according to  claim 1  wherein the ageing step is performed at a temperature in the range 0 to 100° C. 
     
     
         18 . A process according to  claim 1  further comprising a step of calcining the aged composition. 
     
     
         19 . A process according to  claim 3  further comprising a step of reducing the one or more metal compounds.