Encapsulated nano-heat-sinks for thermal management of heterogeneous chemical reactions

Abstract

This paper describes a new way to control temperatures of heterogeneous exothermic reactions such as heterogeneous catalytic reaction and polymerization by using encapsulated nanoparticles of phase change materials as thermally functional additives. Silica-encapsulated indium nanoparticles and silica encapsulated paraffin nanoparticles are used to absorb heat released in catalytic reaction and to mitigate gel effect of polymerization, respectively. The local hot spots that are induced by nonhomogenous catalyst packing, reactant concentration fluctuation, and abrupt change of polymerization rate lead to solid to liquid phase change of nanoparticle cores so as to avoid thermal runaway by converting energies from exothermic reactions to latent heat of fusion. By quenching local hot spots at initial stage, reaction rates do not rise significantly because the thermal energy produced in reaction is isothermally removed. Nanoparticles of phase change materials will open a new dimension for thermal management of exothermic reactions to quench local hot spots, prevent thermal runaway of reaction, and change product distribution.

Indium@silica core–shell nanoparticles as plasmonic enhancers of molecular luminescence in the UV region

“…13 In conclusion, we reported the synthesis and characterisation of In@SiO2 core-shell nanoparticles for fluorescence enhancement in the UV region. While silica-coated indium cores have been reported before 17 , the preparation of such thin and uniform silica coatings over such relatively small indium cores remains, to the best of our knowledge, unprecedented. Our discrete nanoparticles were shown to enhance the intrinsic fluorescence of a commercial fluorophore, Carbostyril 124, and of tryptophan, a natural amino acid.…”

The micro‐/nano‐PCMs for thermal energy storage systems: A state of art review

“…Furthermore, the SiO 2 wall, acting as a heterogeneous nucleator, reduces the degree of supercooling to a minor extent, however, it is immense and unsuitable for actual life applications. Moreover organic and inorganic PCMs, metallic PCMs including indium, tin and alloys have also been confined by a SiO 2 shell . Higher crystallinity and thermal conductivity was reported in metallic PCMs.…”

Temperature stabilisation in Fischer–Tropsch reactors using phase change material (PCM)

“…These two scenarios depict the extremes of multiple stationary states that could be brought about by thermal instabilities. [7,[13][14].…”

“…This is especially true for heterogeneous reactions like the FTS, where chemical reactions occur on active catalyst sites [4,[13][14]. Micro-encapsulated PCM, with a phase transition temperature (ptt) lying between a nominal operating temperature and the onset temperature of carbon deposition or catalyst de-activation (whichever occurs first) can act as a rapid-responding, distributed temperature controller [4,[13][14].…”

“…It has been shown that a small reduction in the characteristic length of the PCM can have an exponential reduction in the melting time of the PCM, (2) encapsulated in an inert shell (e.g. SiO 2 ), in order to avoid agglomeration, leakage or contamination, (3) should form a homogeneous mixture with reactants or catalyst in order to quench local micro-sized hotspots [14][15].…”