Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F7/00—Compounds of aluminium
  • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
  • C01F7/30—Preparation of aluminium oxide or hydroxide by thermal decomposition or by hydrolysis or oxidation of aluminium compounds
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F7/00—Compounds of aluminium
  • C01F7/78—Compounds containing aluminium and two or more other elements, with the exception of oxygen and hydrogen
  • C01F7/782—Compounds containing aluminium and two or more other elements, with the exception of oxygen and hydrogen containing carbonate ions, e.g. dawsonite
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/12—Surface area

Definitions

• This invention relates to a process for produc ⁇ ing a high surface area alumina that is useful in alumina- base catalysts.
• Catalysts are employed in many chemical indus ⁇ tries to facilitate chemical reactions which would other ⁇ wise require unduly stringent reaction conditions.
• Many catalysts are based on alumina, used either alone (such as
• Typical hydrorefining catalysts comprise a Group VIII metal (typically nickel or cobalt) and a Group VIB metal (typically molybdenum or tungsten) sup ⁇ ported on an alumina base. The preparation of such a
• catalyst may be exemplified by U.S. Patent No. 4,113,661 to Tamm, the disclosure of which is incorporated herein by reference.
• the alumina present in such catalysts is typically ⁇ -alumina, though some catalysts prepared by higher-temperature calcination contain ⁇ - or ⁇ -alumina.
• the catalysts are typically particulate, with sizes rang ⁇ ing from 0.8 mm diameter cylinders to 5-10 mm diameter cylinders, and more complex shapes such as ovals, tri- lobes, rings, etc. being common.
• 35 lyst is dependent in part on the surface area of that catalyst, it would be desirable to have an alumina that has a high surface area so that it could be used in such a catalyst.
• This invention provides a process for the pro- duction of such a high surface area alumina.
• this invention provides a process which comprises:
• alumina-base catalyst means a catalyst the base (i.e., the non-catalytic support, unless the support itself is catalytic) of which comprises alumina.
• the term refers to a catalyst base comprising at least 50%, usually at least 80%, and preferably at least 90% by weiqht of alumina.
• the non-alumina components may be, for example, silica or other refractory oxides, aluminosili- cates such as clays or zeolites, etc.
• aluminum salt particles are treated with an aqueous solu- tion of ammonium hydroxide and ammonium carbonate to cause a reaction converting at least a substantial proportion of the aluminum salt to an ammonium aluminum hydroxycarbo ⁇ nate, which is then heated slowly to between 150° and 400, ⁇ > C for a period of at least 2 hours to cause its decom- position to said alumina.
• the alumina should have a BET surface area of at least 300 m /g, preferably at least 450 m * Vg, more prefer- ably at least 800 m /g. It is often desirable to have a catalyst of very high surface area with corresponding small pores—less than 50 Angstroms. Such catalysts would be used in processes not limited by diffusion control or size exclusion of the reacting molecule. In these cases, reaction rates would be directly proportional to surface area.
• aluminum salt particles are treated with an aqueous solution of ammonium hydroxide and ammonium carbonate to cause a reaction converting at least a substantial proportion of the aluminum salt to an ammo ⁇ nium aluminum hydroxycarbonate.
• the aluminum salt is preferably either aluminum sulfate, aluminum chloride, or aluminum nitrate. More preferably, the aluminum salt is aluminum sulfate, because of its low cost. However when aluminum sulfate is used, the resulting alumina should be washed with water at a temperature of at least 50°C to remove a substantial part of the sulfur, ammonia, and other residuals from the alu ⁇ mina.
• the reaction pH of the first step is between 9 and 12, preferably between* 10 and 11.
• a typical solution contains ammonium hydroxide and ammonium carbonate.
• a typical reaction in this case may be:
• the ammonium aluminum hydroxycarbonate is heated slowly to between 150° and 400°C for a period of at least two hours to cause its decomposition to said alumina.
• the heating temperature is about 200°C, for at that temperature, decomposition will occur slowly which is important in obtaining the highest surface area.
• an alumina having a BET surface area of at least 800 irr/g is produced by treating aluminum sulfate particles with an aqueous solution of ammonium hydroxide and ammonium carbonate at a pH of 10 to 11 to cause a reaction converting at least a substantial proportion of the aluminum sulfate to NH 4 Al(OH) 2 C0 3 * H 2 0, heating said NH 4 A1(0H) 2 C0 3 * H 2 0 to about 200°C for a period of at least 2 hours to cause its decomposition to alumina; and washing the alumina with water at a temperature of at least 50°C to remove a substantial part of the sulfur, ammonia, and other residuals from the alumina.
• Example 1 An ammonium aluminum hydroxycarbonate was prepared by adding 318 grams of Al 2 (S0 4 ) 3 *16H 2 0 to 1 liter of solution containing 3M NH3 and 1.5 M (NH3) 2 C0 . The mixture was reacted for one hour at 70°C and filtered, then the precipitate was dried in a vacuum oven overnight at 150°C. A similar preparation was made by adding dissolved aluminum sulfate to the same ammonical solution.
• Example 2 A large preparation was made by adding solid aluminum sulfate as in the previous example. In this case, 704 grams of hydroxycarbonate were decomposed at 250°C for eight hours. As in the previous example, the large mass of material resulted in a relatively slow heating rate. The BET surface area was 700 /g.
• Example 3 This example shows the adverse effect that rapid : heat-up has on surface area. A hydroxycarbonate prepared as in previous examples was decomposed at various tempera ⁇ tures for three hours. The important variable in this example was the rapid heating rate. Rapid heating resulted from placing only about 8 grams of hydroxycarbon- ' ate into a preheated oven. Table I shows that rapid decomposition even at low temperatures reduced the surface area significantly from the very high values seen previously.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Inorganic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
• Catalysts (AREA)

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• 1985
  • 1985-08-27 NL NL8520271A patent/NL8520271A/nl not_active Application Discontinuation
  • 1985-08-27 JP JP60503915A patent/JPS63500794A/ja active Pending
  • 1985-08-27 DE DE19853590012 patent/DE3590012T1/de not_active Withdrawn
  • 1985-08-27 WO PCT/US1985/001649 patent/WO1987001365A1/en not_active Application Discontinuation
  • 1985-08-27 EP EP19850904387 patent/EP0235126A4/en not_active Withdrawn

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