Hollow spherical catalyst for fixed bed with internal fluidization of particles, and method for preparing same

A method for preparing a hollow spherical catalyst for a fixed bed with internal fluidization of particles, comprising:

• A. preparing an aluminum oxide molding solution
• fully mixing an aluminum sol and a hexamethylenetetramine aqueous solution at a mass ratio of 2.0-6.0:1 in an ice water bath to get aluminum oxide molding solution;
• preparing the aluminum sol:
• weighing aluminum powder with a purity greater than 99.6%, dissolving the aluminum powder in dilute hydrochloric acid at a concentration of 5-20% or an aluminum chloride crystal solution at a concentration of 10-25% at 95-105° C. to obtain the transparent and stable aluminum sol, wherein the aluminum content is 6-20%, and the Al/Cl mass ratio is 0.3-3.0;
• and
• preparing the hexamethylenetetramine solution:
• adding hexamethylenetetramine into deionized water to prepare the hexamethylenetetramine aqueous solution at a concentration of 20-40%, and then adding a viscosity regulator therein to obtain the hexamethylenetetramine solution;
• wherein the viscosity regulator is 10-30% acrylamide and/or hydroxymethylacrylamide, and the amount added is 1-10% of a mass of the hexamethylenetetramine aqueous solution;
• B. preparing an internal oil phase suspension
• fully dispersing powder of precious metal X in an oily substance at a mass fraction of 0.1-5.0% to obtain a suspension, i.e., the internal oil phase suspension;
• wherein the powder of the precious metal X is one of Pd, Pt, Au, or Ag nanopowder with a size of 200-500 nm;
• and the oily substance is one of liquid paraffin, white oil No. 2, white oil No. 3, or white oil No. 7;
• C. preparing oil-in-water alumina gel balls
• preparation using a coaxial dual-dropper forming apparatus comprising steps of:
• transferring the aluminum oxide molding solution in a material tank 2, switching on the delivery pump;
• adding the internal oil phase suspension into the material tank for pumping into an inner tube 6 of the coaxial dropper through the delivery pump at a flow rate of 6-20 mL/h;
• simultaneously loading the aluminum oxide molding solution into another material tank for pumping into an outer tube of the coaxial dropper through another delivery pump at a flow rate of 8-25 mL/h, and controlling the flow rate in the outer tube to be 2-5 mL/h faster than that in the inner tube;
• oil-in-water sol balls will be formed at the outlet of the dropper;
• dropwise adding the sol balls into a hot oil column at 70-95° C., then adding the sol balls into forming oil at 70-95° C. present in an aging reactor, heating the forming oil to 130-160° C. for aging for 4-6 h, cooling the mixture to room temperature, taking out the mixture, washing and drying. In this way, oil-in-water alumina gel balls with a diameter of 1.5-5.0 mm can be obtained;
• wherein the forming oil is one of vacuum pump oil, dimethicone, or white oil No. 15;
• and
• a mass fraction of the precious metal X in each catalyst particle is controlled by regulating the feed liquid flow rates in the outer tube and the inner tube;
• and
• D. preparing an X@ Al2O3 catalyst
• heating dry alumina gel balls in a muffle furnace to 400-500° C. at a rate of 1-5° C./min, and keeping the gel balls at the temperature for 2-4 h, to remove oily substances in the internal oil phase suspension;
• then heating the mixture to 550-1,000° C. at a rate of 5-10° C./min for calcination for 2-4 h, to obtain different crystal forms of aluminum oxide;
• air cooling the aluminum oxide to room temperature, transferring the aluminum oxide to an atmosphere furnace, and heating the aluminum oxide in a reduction atmosphere to 200-450° C. at a rate of 2-10° C./min for reduction for 1-4 h, to obtain the X@Al2O3 catalyst;
• wherein the reduction atmosphere is one of 5-40% H2/N2 or 5-40% CO/N2 at a gas flow rate of 20-100 mL/min.