Combustion of toluene over cobalt-modified MFI zeolite dispersed on monolith produced using 3D printing technique

Recent Progress and Perspectives of Direct Ink Writing Applications for Mass Transfer Enhancement in Gas-Phase Adsorption and Catalysis

Conventional adsorbents and catalysts shaped by granulation or extrusion have high pressure drop and poor flexibility for chemical, energy, and environmental processes. Direct ink writing (DIW), a kind of 3D printing, has evolved into a crucial technique for manufacturing scalable configurations of adsorbents and catalysts with satisfactory programmable automation, highly optional materials, and reliable construction. Particularly, DIW can generate specific morphologies required for excellent mass transfer kinetics, which is essential in gas-phase adsorption and catalysis. Here, DIW methodologies for mass transfer enhancement in gas-phase adsorption and catalysis, covering the raw materials, fabrication process, auxiliary optimization methods, and practical applications are comprehensively summarized. The prospects and challenges of DIW methodology in realizing good mass transfer kinetics are discussed. Ideal components with a gradient porosity, multi-material structure, and hierarchical morphology are proposed for future investigations.

On the effect of metal loading on the performance of Co catalysts supported on mixed MgO-La2O3 oxides for ammonia synthesis

Synthesis of ammonia from nitrogen and hydrogen is one of the largest manmade chemical processes, with annual production reaching 170 million tons. The Haber-Bosch process is the main industrial method for producing ammonia, which proceeds at high temperatures (400-600 °C) and pressures (20-40 MPa) using an iron-based catalyst. It is thus highly desirable to develop new catalysts with sufficient activity and stability under mild conditions. In this work, we report cobalt catalysts supported on magnesium-lanthanum mixed oxide with different Co loading amounts synthesised via a simple wet impregnation method. We have found a clear relationship between the ammonia synthesis rate and the Co loading amount. Specifically, the NH₃ synthesis rate increased on increasing cobalt loading and reached a maximum at 40 wt% Co deposition. A further increase in Co loading did not change the activity significantly. Interestingly, the surface-specific activity (TOF) remained almost unchanged regardless of the Co loading amount in the catalysts. It revealed that the resultant ammonia synthesis rate over the studied catalysts did not depend on the size and structure of Co nanoparticles but strongly on the Co loading amount. Finally, it is believed that the use of this type of catalyst will be a starting point toward energy-efficient ammonia production.

Rational Design and Construction of Monolithic Ordered Mesoporous Co3O4@SiO2 Catalyst by a Novel 3D Printed Technology for Catalytic Oxidation of Toluene

Here, we report a novel 3D printed layered ordered mesoporous template that can encapsulate active Co-MOFs species in a confined way to achieve the goal of monolithic catalyst. The monolithic OM-Co₃O₄@SiO₂-S catalyst can maintain a macroscopic porous layered structure and a microscopic ordered mesoporous structure. This monolithic OM-Co₃O₄@SiO₂-S catalyst has excellent catalytic performance (T₉₀ = 236 °C), water resistance, and thermal stability in the catalytic combustion of toluene. The catalytic performance of the monolithic OM-Co₃O₄@SiO₂-S catalyst is much better than that of many monolithic catalysts reported in the former. Among them, the introduction of binder aluminum phosphate (AP) can effectively enhance the rheological properties of the printing ink, achieve the purpose of ink writing monolithic layered porous material, enrich the acidic point of the monolithic catalyst, and increase the number of reactive oxygen species. This work reveals a novel monolithic catalyst forming strategy that can combine the advantages of ordered mesoporous materials with active species to form macro-layered porous materials and provide ideas and an experimental basis for the elimination of VOCs in industrial applications.

Design of Co3O4@SiO2 Nanorattles for Catalytic Toluene Combustion Based on Bottom-Up Strategy Involving Spherical Poly(styrene-co-acrylic Acid) Template

Bearing in mind the need to develop optimal transition metal oxide-based catalysts for the combustion of volatile organic compounds (VOCs), yolk-shell materials were proposed. The constructed composites contained catalytically active Co3O4 nanoparticles, protected against aggregation and highly dispersed in a shell made of porous SiO2, forming a specific type of nanoreactor. The bottom-up synthesis started with obtaining spherical poly(styrene-co-acrylic acid) copolymer (PS30) cores, which were then covered with the SiO2 layer. The Co3O4 active phase was deposited by impregnation using the PS30@SiO2 composite as well as hollow SiO2 spheres with the removed copolymer core. Structure (XRD), morphology (SEM), chemical composition (XRF), state of the active phase (UV-Vis-DR and XPS) and reducibility (H2-TPR) of the obtained catalysts were studied. It was proven that the introduction of Co3O4 nanoparticles into the empty SiO2 spheres resulted in their loose distribution, which facilitated the access of reagents to active sites and, on the other hand, promoted the involvement of lattice oxygen in the catalytic process. As a result, the catalysts obtained in this way showed a very high activity in the combustion of toluene, which significantly exceeded that achieved over a standard silica gel supported Co3O4 catalyst.

3D Printing in Heterogeneous Catalysis-The State of the Art

This paper describes the process of additive manufacturing and a selection of three-dimensional (3D) printing methods which have applications in chemical synthesis, specifically for the production of monolithic catalysts. A review was conducted on reference literature for 3D printing applications in the field of catalysis. It was proven that 3D printing is a promising production method for catalysts.