Production of porous alpha-alumina supports from boehmitic derived aluminas
A porous alpha-alumina catalyst support is prepared by (i) preparing a precursor material comprising a boehmitic-derived alumina having a pore volume of at least 0.6 mL/g, wherein the boehmitic-derived alumina is obtained by thermal decomposition of a boehmitic starting material and the boehmitic starting material consists predominantly of block-shaped crystals, and optionally an inorganic bond material; (ii) forming the precursor material into shaped bodies; (iii) calcining the shaped bodies to obtain the porous alpha-alumina catalyst support. The support structure has a high overall pore volume, while keeping its surface area sufficiently large so as to provide optimal dispersion of catalytically active species, in particular metal species. The support is useful for a catalyst for producing ethylene oxide by gas-phase oxidation of ethylene.
1 . A process for producing a porous alpha-alumina catalyst support, comprising
i) preparing a precursor material comprising a boehmitic-derived alumina having a pore volume of at least 0.6 mL/g as determined by nitrogen sorption, wherein the boehmitic-derived alumina is obtained by thermal decomposition of a boehmitic starting material and the boehmitic starting material predominantly comprises block-shaped crystals, and optionally an inorganic bond material;
ii) forming the precursor material into shaped bodies; and
iii) calcining the shaped bodies to obtain the porous alpha-alumina catalyst support.
2 . The process according to claim 1 , wherein the block-shaped crystals have an aspect ratio of at most 3.0, wherein the aspect ratio is defined as the ratio of the largest crystal dimension to the smallest crystal dimension.
3 . The process according to claim 1 , wherein the boehmitic starting material comprises at least 60 wt. % of block-shaped crystals, relative to the total weight of crystals constituting the boehmitic starting material.
4 . The process according to claim 1 , wherein the boehmitic starting material comprises boehmite and/or pseudoboehmite.
5 . The process according to claim 1 , wherein the precursor material comprises, based on inorganic solids content, at least 50 wt. % wt. % of the boehmitic-derived alumina.
6 . The process according to claim 1 , wherein the boehmitic-derived alumina comprises alpha-alumina, a transition alumina, or a mixture thereof.
7 . The process according to claim 6 , wherein the transition alumina comprises at least 50 wt. % of a transition alumina having an average particle size of 10 to 100 μm, based on the total weight of transition alumina.
8 . The process according to claim 1 , wherein the boehmitic-derived alumina has a loose bulk density in the range of 50 to 600 g/L, a pore volume of 0.6 to 2.0 mL/g, as determined by nitrogen sorption, and a median pore diameter of at least 15 nm, as determined by nitrogen sorption.
9 . The process according to claim 1 , wherein the boehmitic-derived alumina has a total content of alkali metals of at most 1500 ppm.
10 . The process according to claim 1 , wherein the precursor material comprises, based on inorganic solids content, 1 to 30 wt.-% of the inorganic bond material.
11 . The process according to claim 1 , wherein the precursor material is formed into shaped bodies via extrusion, tableting, granulation casting, molding, or micro-extrusion.
12 . The process according to claim 1 , wherein calcining is performed at a temperature of at least 1300° C.