Preparation of Porous Alumina Monoliths Using Indirect 3D Printing

The synthesis of alumina monoliths is carried out by intrusion of an alumina precursor paste into the channels of a 3D‐printed template, followed by drying and calcination of the composite. To obtain durable monoliths, several approaches are applied: (a) conducting an additional phase transition to increase crystallite mobility; (b) slowing the composite drying rate by increasing the amount of slow‐boiling plasticizers in the paste and introducing isothermal exposure at low temperatures; and (c) introducing alumina additives with different porosity to reduce composite shrinkage. The first approach yields a strong alumina monolith with a monomodal pore size distribution. The other approaches produce coherent monoliths with multimodal pore size distribution, suitable for comparative catalytic tests in the hydroconversion of vacuum oil residue ( T  = 400 °C, p(H ₂ ) = 10 MPa, LHSV = 0.62 h ⁻¹ , H ₂ /Feed = 1000 L/L). The monolithic catalyst demonstrates greater activity as a guard catalyst than the reference pellets, as evidenced by a 9% reduction in product density and a 79‐fold reduction in kinematic viscosity (vs. 4% and 3‐fold for pellets, respectively). This difference is attributed to more efficient external mass transfer in the structured macrocapillary geometry.