| 摘要 |
1,212,889. Catalyst comprising support material coated with alumina. E.I. DU PONT DE NEMOURS & CO. 4 June, 1968 [8 June, 1967], No. 26621/68. Heading B1E. A catalyst in the form of catalyst support material which carries a uniform coating of material having a high surface area is prepared by a process which comprises (i) preparing an aqueous composition comprising colloidal bochmite (i.e. alumina monohydrate) and particles of alumina having a size of from 8 to 60 microns, preferably of from 30 to 40 microns, and a surface area of from 50 to 600 m<SP>2</SP>/g, preferably of from 180 to 250m<SP>2</SP>/g, (ii) applying such composition (for example by dipping, brushing or spraying) to catalyst support material thereby to form a coating thereon and (iii) calcining the coated support material, for example at a temperature of from 400‹C to 500‹C. The support material may be porous but preferably and advantageously has a smooth surface (i.e. is substantially non- porous) and has a low surface area; support materials exemplified are glass, metals (none specified), fused alumina, fused silica, mullite, beryl, zirconia, zircon, porcelain, dense sintered alumina, chromia, spinel, magnesia, fused magnesia and titania. A preferred support material is a mullite honeycomb which has been prepared by the in situ oxidation of aluminium coated with a fluxing agent and with silicon carbide. The alumina particles preferably have been acid washed, for example with acetic, hydrochloric, nitric or sulphuric acid, so that the mixture of colloidal bochmite and particulate alumina will have a pH preferably of from 3.0 to 4.5, more preferably of from 3.5 to 4.0, thereby to prevent settling or gelation. Examples of suitable and commercially available bochmite and alumina are given in the specification. After calcining, the coating on the catalyst support material may be impregnated with catalytic material; alternatively and preferably, catalytic material may be incorporated in the coating by including catalytic material in the coating composition comprising colloidal bochmite particulate alumina. The catalytic material may comprise at least one member selected from the oxides, heat-decomposable oxide precursors (for example hydroxides, carbonates, nitrates, ammonium salts and organic salts), cerates, chromates, chromites, manganates, manganites, molybdates, tungstates, stannates, ferrites and vanadates of the metals calcium, chromium, manganese, iron, cobalt, nickel, copper, zinc, molybdenum, ruthenium, rhodium, palladium, silver, cadmium, tin, barium, tungsten, iridium, platinum, mercury and lead and of the rare earth metals; elemental ruthenium, rhodium, palladium and platinum; and heteropoly acids. A catalyst comprising catalytic material may, if desired and/or required, be calcined and/or reduced. The coating also may include at least one promoter and/or fluxing agent. Promoters exemplified are compounds, for example oxides and mineral salts, of the rare earth metals and of the transition metals, for example magganese, iron, cobalt, nickel, ruthenium, rhodium, palladium and platinum; fluxing agents exemplified are salts of the alkali metals, for example lithium, sodium and potassium. The coating preferably is continuous and has a thickness preferably of between 0.1 mil and 1/16 inch, more preferably of between 1 and 25 mils; preferred relative proportions of the support material, coating and components of the coating are given in the specification. |
