US 4,301,037 AGranted

Extruded alumina catalyst support having controlled distribution of pore sizes

AssigneeW. R. Grace & Co.

InventorsMoises G. Sanchez, Jose E. Herrera

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Abstract

A thermally stable, pure transition alumina extrudate suitable for use as a catalyst support has a uniquely defined bimodal pore size distribution and very good mechanical properties. Most of the surface area is in a micropore region having pores of less than 500 Angstrom units, a pore volume of 0.60 to 0.80 cm..sup.3 /g., a narrowly defined effective pore volume distribution within this region and a median pore diameter which can be controlled within the range of 90-210 Angstrom units. The macropore region made of pores having diameters of 1,000- 10,000 Angstrom units has a pore volume of at least 0.10 cm..sup.3 /g. These two pore volumes are essentially connected directly to each other. The extrudates can be strengthened by acidic additives and given increased thermal stability by adding rare earth oxides.

Claims55

Dependent claims

A thermally stable, bimodal extrudate consisting essentially of a pure transition alumina suitable for use as a catalyst support having a substantial first micropore volume made of relatively small pores having a pore diameter of less than 500 Angstrom units, a second macropore volume made of relatively large pores with a pore diameter in the range of 1,000 to 10,000 Angstrom units, and with very little intermediate pore volume made of pores with a pore diameter in the range of 500 to 1,000 Angstrom units, said alumina extrudate having

a first micropore volume, as measured by mercury porosimetry, having pore diameters of 500 Angstrom units or less, of about 0.60 to about 0.85 cm..sup.3 /g.;
a second macropore volume, as measured by mercury porosimetry having pore diameters in the range of 1,000 to 10,000 Angstrom units, of about 0.10 to less than 0.30 cm..sup.3 /g.;
an intermediate pore volume, as measured by mercury porosimetry, having pore diameters in the range of 500 to 1,000 Angstrom units, of less than about 0.05 cm..sup.3 /g.;
said micropore volume having a median pore diameter of 90-210 Angstrom units and having a relatively narrow effective pore size distribution about the median pore diameter with a value of greater than 0.55 for the uniformity factor, U, given by the formula ##EQU6## where D.sub.50 is the micropore volume median diameter,
D.sub.95 is the smallest pore diameter of that fraction of the largest micropores which constitutes 5 percent of the micropore volume, and
D.sub.5 is the largest pore diameter of that fraction of the smallest micropores which constitutes 5 percent of the micropore volume;
the surface area within said micropore volume being greater than 95 percent of the total surface area measured by nitrogen adsorption;
an average crush strength given by the formula
ACS>kdD.sup.2 L
where
ACS is the average crush strength in pounds force,
d is the compacted bulk density of the extrudates in pounds per cubic foot,
D is the average extrudate diameter in inches,
L is the average extrudate length in inches, and
k is a factor with a value of at least 90;
and
an attrition loss of less than 7 percent.

14 more elements

A method of producing a bimodal thermally stable, pure transition alumina extrudate suitable for use as a catalyst support having a substantial first micropore volume made of relatively small pores having a pore diameter of less than 500 Angstrom units, a second macropore volume made of relatively large pores with a pore diameter in the range of 1,000 to 10,000 Angstrom units, and with very little intermediate pore volume made of pores with a pore diameter in the range of 500 to 1,000 Angstrom units, said method comprising the steps of

(a) forming an aqueous mixture of a microcrystalline alpha alumina monohydrate which is an intermediate between boehmite and pseudoboehmite having a solids content in the range of 32-42 weight percent;
(b) mixing the material of step (a) to form a paste for 15 to 300 minutes which renders the paste extrudable;
(c) extruding the paste of step (b) to form extrudates having a length to diameter ratio of about 1 to 1 to about 8 to 1;
(d) drying the extrudates;
and
(e) calcining the extrudates at a temperature in the range of 800.degree.-2,000.degree. F. to obtain an alumina extrudate having
a first micropore volume, as measured by mercury porosimetry, having pore diameters of 500 Angstrom units or less, of about 0.60 to 0.85 cm..sup.3 /g.;
a second macropore volume, as measured by mercury porosimetry having pore diameters in the range of 1,000 to 10,000 Angstrom units, of about 0.10 to less than 0.30 cm..sup.3 /g.;
an intermediate pore volume, as measured by mercury porosimetry, having pore diameters in the range of 500 to 1,000 Angstrom units, of less than 0.05 cm..sup.3 /g.;
and
a median micropore diameter, of 90-210 Angstrom units.

8 more elements

Dependencies are inferred from the claim text.