Patent GB-1113703-A (GB)
Title: Production of nitric oxide
IPC: C01B21/26
Filed: 1966-02-23
Abstract: In the catalytic oxidation of NH3, the catalyst is a Pt group metal supported on a unitary crystalline refractory structure having a thermal coefficient of expansion of less than 6 x 10-6 per  DEG  C. between 30 DEG  and 700 DEG  C. and having a plurality of preferably parallel channels in the direction of gas flow, with pores greater than 2000 <\>r in diameter in their walls. The structure may contain 100-2500 channels per square inch with walls 2-10 mils. thick, and have a pore volume (excluding channels) greater than 0.01 c.c./g. and a total surface area of 0.1 to 3 m.2/gm.  It may occupy the whole reaction zone, or a plurality of blocks may be used. Before depositing the Pt metal, a layer of activated metal oxide, e.g. g -Al2O3, BeO, ZrO2, MgO, SiO2, B2O3-Al2O3, o SiO2-Al2O3, may be deposited on the support, in amount 1-50% by weight or 15-150 g/l. of the support, of thickness 0.0004-0.001 inch, and of surface area greater than 25 m.2/g., by dipping the support in a solution or 10-70% suspension of the metal salt and calcining at 15-800 DEG  C. in air, O2, N2, H2, flue gas, or vacuum. The Pt metal is applied by immersing the support (\sB oxide) in an aqueous solution of an inorganic Pt metal salt, precipitating the metal as oxide, and reducing in H2 at 100-1100 DEG  C. The metal may be Pt, Rh, Ir, or alloys, e.g. Pt with 2-40% Rh, Ir or Pd.  It is present as a thin layer on the surfaces of the channels and pores, in amount 1-50% by weight of the final catalyst.  Suitable support materials are listed. The process is operated by mixing NH3 with air or O2 e.g. in excess, at gas space velocities of 100-1,000,000 cubic feet/cubic foot of catalyst/hour, temperatures of 650-1000 DEG  C., and pressures of atmospheric to 110 p.s.i.g.  The mixture of NO with some NO2, H2O vapour and N2 is cooled and introduced into the bottom of a packed or baffled absorber zone together with air, in countercurrent to water, to produce HNO3.ALSO:A catalyst for the oxidation of NH3 comprises a Pt group metal supported on a unitary crystalline refractory structure having a thermal coefficient of expansion of less than 6x10-6 per  DEG C between 30 and 700 DEG C and having a plurality of preferably parallel channels in the direction of gas flow, with pores greater than 2,000 DEG A in diameter in their walls.  The structure may contain 100-2500 channels per sq. in. with walls 2-10 mils thick, and have a pore volume (excluding channels) greater than .01 cc/g and a total surface area of .1 to 3 m2/gm.  It may occupy the whole reaction zone, or a plurality of blocks may be used.  Before depositing the Pt metal, a layer of activated metal oxide, e.g. g -Al2O3, BeO, ZrO2, MgO, SiO2, B2O3-Al2O3, or SiO2-Al2O3, may be deposited on the support, in amount 1-50% by weight or 15-150 g/l of the support, of thickness .004-.001 in., and of surface area greater than 25 m2/g, by dipping the support in a solution or 10-70% suspension of the metal salt and calcining at 150-800 DEG C in air, O2, N2, H2, flue gas, or vacuum.  The Pt metal is applied by immersing the support (\sB oxide) in an aqueous solution of an inorganic Pt metal salt, precipitating the metal as oxide, and reducing in H2 at 100-1100 DEG C.  The metal may be Pt, Rh, Ir, or alloys, e.g. Pt with 2-40% Rh, Ir or Pd.  It is present as a thin layer on the surfaces of the channels and pores, in amount 1-50% by weight of the final catalyst.  Suitable support materials are listed.