Next Article in Journal
Solvent-Free Lipase-Catalyzed Synthesis of Technical-Grade Sugar Esters and Evaluation of Their Physicochemical and Bioactive Properties
Previous Article in Journal
Role of Conformational Motions in Enzyme Function: Selected Methodologies and Case Studies
Article Menu

Export Article

Open AccessArticle
Catalysts 2016, 6(6), 80; doi:10.3390/catal6060080

Co-Assembled Supported Catalysts: Synthesis of Nano-Structured Supported Catalysts with Hierarchic Pores through Combined Flow and Radiation Induced Co-Assembled Nano-Reactors

1
Faculty of Science and Arts, Canik Basari University, 55080 Samsun, Turkey
2
Department of Chemical Engineering and Advanced Materials, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
Academic Editor: Keith Hohn
Received: 9 March 2016 / Revised: 4 May 2016 / Accepted: 9 May 2016 / Published: 28 May 2016

Abstract

A novel generic method of silica supported catalyst system generation from a fluid state is presented. The technique is based on the combined flow and radiation (such as microwave, thermal or UV) induced co-assembly of the support and catalyst precursors forming nano-reactors, followed by catalyst precursor decomposition. The transformation from the precursor to supported catalyst oxide state can be controlled from a few seconds to several minutes. The resulting nano-structured micro-porous silica supported catalyst system has a surface area approaching 300 m2/g and X-ray Diffraction (XRD)-based catalyst size controlled in the range of 1–10 nm in which the catalyst structure appears as lamellar sheets sandwiched between the catalyst support. These catalyst characteristics are dependent primarily on the processing history as well as the catalyst (Fe, Co and Ni studied) when the catalyst/support molar ratio is typically 0.1–2. In addition, Ca, Mn and Cu were used as co-catalysts with Fe and Co in the evaluation of the mechanism of catalyst generation. Based on extensive XRD, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) studies, the micro- and nano-structure of the catalyst system were evaluated. It was found that the catalyst and silica support form extensive 0.6–2 nm thick lamellar sheets of 10–100 nm planar dimensions. In these lamellae, the alternate silica support and catalyst layer appear in the form of a bar-code structure. When these lamellae structures pack, they form the walls of a micro-porous catalyst system which typically has a density of 0.2 g/cm3. A tentative mechanism of catalyst nano-structure formation is provided based on the rheology and fluid mechanics of the catalyst/support precursor fluid as well as co-assembly nano-reactor formation during processing. In order to achieve these structures and characteristics, catalyst support must be in the form of silane coated silica nano-particles dispersed in water which also contains the catalyst precursor nitrate salt. This support-catalyst precursor fluid must have a sufficiently low viscosity but high elastic modulus (high extensional viscosity) to form films and bubbles when exposed to processing energy sources such as microwave, thermal, ultra-sound or UV-radiation or their combination. The micro-to-nano structures of the catalyst system are essentially formed at an early stage of energy input. It is shown that the primary particles of silica are transformed to a proto-silica particle state and form lamellar structures with the catalyst precursor. While the nano-structure is forming, water is evaporated leaving a highly porous solid support-catalyst precursor which then undergoes decomposition to form a silica-catalyst oxide system. The final catalyst system is obtained after catalyst oxide reduction. Although the XRD-based catalyst size changes slightly during the subsequent heat treatments, the nano-structure of the catalyst system remains substantially unaltered as evaluated through TEM images. However, if the catalyst preparation is carried out without film formation, the XRD-based catalyst size increases substantially by a factor of 2–8, with no significant alteration in surface area. View Full-Text
Keywords: catalyst synthesis; catalysts with hierarchic pores; co-assembled catalysts; co-assembly; co-assembled nano-reactors; flow induced assembly; heterogeneous catalysis; nano-reactors; nano-structured catalysts; process intensification; radiation induced assembly; self-assembly; silica supported catalysts; supported catalysts catalyst synthesis; catalysts with hierarchic pores; co-assembled catalysts; co-assembly; co-assembled nano-reactors; flow induced assembly; heterogeneous catalysis; nano-reactors; nano-structured catalysts; process intensification; radiation induced assembly; self-assembly; silica supported catalysts; supported catalysts
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

Scifeed alert for new publications

Never miss any articles matching your research from any publisher
  • Get alerts for new papers matching your research
  • Find out the new papers from selected authors
  • Updated daily for 49'000+ journals and 6000+ publishers
  • Define your Scifeed now

SciFeed Share & Cite This Article

MDPI and ACS Style

Akay, G. Co-Assembled Supported Catalysts: Synthesis of Nano-Structured Supported Catalysts with Hierarchic Pores through Combined Flow and Radiation Induced Co-Assembled Nano-Reactors. Catalysts 2016, 6, 80.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Catalysts EISSN 2073-4344 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top