Nano-Array Integrated Structured Catalysts: A New Paradigm upon Conventional Wash-Coated Monolithic Catalysts?

Abstract

Abstract:The monolithic catalyst, namely the structured catalyst, is one of the important categories of catalysts used in various fields, especially in catalytic exhaust after-treatment. Despite its successful application in conventional wash-coated catalysts in both mobile and stationary catalytic converters, washcoat-based technologies are facing multi-fold challenges, including: (1) high Pt-group metals (PGM) material loading being required, driving the market prices; (2) less-than ideal distribution of washcoats in typically square-shaped channels associated with pressure drop sacrifice; and (3) far from clear correlations between macroscopic washcoat structures and their catalytic performance. To tackle these challenges, the well-defined nanostructure array (nano-array)-integrated structured catalysts which we invented and developed recently have been proven to be a promising class of cost-effective and efficient devices that may complement or substitute wash-coated catalysts. This new type of structured catalysts is composed of honeycomb-structured monoliths, whose channel surfaces are grown in situ with a nano-array forest made of traditional binary transition metal oxide support such as Al 2 O 3 , CeO 2 , Co 3 O 4 , MnO 2 , TiO 2 , and ZnO, or newer support materials including perovskite-type ABO 3 structures, for example LaMnO 3 , LaCoO 3 , LaNiO, and LaFeO 3 . The integration strategy parts from the traditional washcoat technique. Instead, an in situ nanomaterial assembly method is utilized, such as a hydro (solva-) thermal synthesis approach, in order to create sound structure robustness, and increase ease and complex-shaped substrate adaptability. Specifically, the critical fabrication procedures for nano-array structured catalysts include deposition of seeding layer, in situ growth of nano-array, and loading of catalytic materials. The generic methodology utilization in both the magnetic stirring batch process and continuous flow reactor synthesis offers the nano-array catalysts with great potential to be scaled up readily and cost-effectively. The tunability of the structure and catalytic performance could be achieved through morphology and geometry adjustment and guest atoms and defect manipulation, as well as composite nano-array catalyst manufacture. Excellent stabilities under various conditions were also present compared to conventional wash-coated catalysts.

Rh/CeO2 Thin Catalytic Layer Deposition on Alumina Foams: Catalytic Performance and Controlling Regimes in Biogas Reforming Processes

“…These characteristics enhance the catalytic performance of reforming reactions, allowing operation at high space velocity simultaneously reducing the amount of catalytic material [27,28]. Thus, the research interest in structured catalysts development is constantly growing [4,27,[29][30][31][32][33][34][35][36].…”

“…However, the catalytic functionalization of the foam structures still remains one of the main critical issues. In fact, the catalytic coated layer needs to be highly active and stable, as well as resistant to thermal and mechanical stresses occurring during reforming reactions [4,29,42]. The conventional washcoating technique suffers from non-uniformity and exfoliation of coatings, as well as binder contamination.…”

Metal Nanotube/Nanowire-Based Unsupported Network Electrocatalysts

“…It is not surprising that a proper integration of nano-network catalysts into fuel cells, and the issues associated with aspects like catalyst attachment to the membrane, ionomer application, adaption of the water management, will require similar efforts on larger length scales [74]. Likewise, the assembly of nano-networks into flow reactors [142] and miniaturized devices [143], for which their free-standing superstructure is predestined, provides plentiful challenges and opportunities for catalysis research.…”

Scrap waste automotive converters as efficient catalysts for the continuous-flow hydrogenations of biomass derived chemicals

“…The honeycomb structure of SCATs is composed of four principal coats: the catalyst substrate, made of cordierite (2MgO•2Al 2 O 3 •5SiO 2 ), the wash coat (Al 2 O 3 , TiO 2 , SiO 2 or SiO 2 -Al 2 O 3 mixture), functioning as a carrier for the catalytic material, a coat made of CeO 2 or CeO 2 /ZrO 2 and a coat covered with noble metals in low loadings including platinum and palladium, and other metals, such as Fe, Mn, Ni and Ce. [8][9][10] Currently, SCATs are normally processed in order to extract and recover the noble metals (Platinum group metals -PGMs). However, these methodologies require the use of large amounts of highly toxic chemicals (i.e.…”

“…(T), pressure (p), flow rate, residence time (τ) §, concentration (c) and yields at stationary state conditions (after 15') for the hydrogenations of vanillin(7) to vanillyl alcohol(8).with commercial catalyst 1%Pd/C. This journal is © The Royal Society of Chemistry 20xx…”