Nanoparticles for Catalytic Technologies
The Catalytic Technologies Based on Ensembles of Immobilized Nanoparticles
Tech Area / Field
- CHE-IND/Industrial Chemistry and Chemical Process Engineering/Chemistry
- CHE-THE/Physical and Theoretical Chemistry/Chemistry
8 Project completed
Senior Project Manager
Mitina L M
Moscow State University / Department of Chemistry, Russia, Moscow
- Russian Academy of Sciences / Physical Technical Institute, Russia, St Petersburg\nState Research Institute of Organic Chemistry and Technology, Russia, Moscow\nKarpov Institute of Physical Chemistry, Russia, Moscow
- Universität Hannover / Institute of Physical Chemistry and Electrochemistry, Germany, Hannover\nUniversity of Bremen / Institute of Applied and Physical Chemistry, Germany, Bremen
Project summaryThe aim of the project is a development of the technology of catalysts preparation based on ensembles of interacting nanoparticles. The technology proposed allows creating effective catalysts, which will exceed appreciably knowing ones in activity and contain less amount of noble metal. These catalysts, in their turn, create preconditions for the development of the new effective technology of catalytic hydrodechlorination of toxic halogen-containing organic compounds.
The novelty of the development is connected to discovered and theoretically proved by the authors phenomena of self-organization of the nanoparticle ensembles – the systems of interacting nanoclusters immobilized on the carrier surface, between which electron redistribution with formation of considerable amount of charged particles takes place. Directional formation of such systems is realized using the method of the laser electrodispersion evolved by the authors. The method developed allows creation of well-ordered nanocluster ensembles of almost identical form and size on a surface of supports. The unique properties of novel catalyst type are provided by the following factors:
- The small size of metal particles (2 to 5 nm depending on the metal);
- The narrow size and form distribution of particles (the difference of diameter of spherical particles does not exceed 20%);
- The amorphous state of metal;
- High coalescence and oxidative stability of nanoparticles in absence of additional stabilizers;
- Creation of interacting nanoparticles on the surface of a support, which are optimal for accumulation of charged nanoclusters on the carrier surface.
The dependence of activity and selectivity of nanosized catalysts on the size, the form and phase state of nanoparticles is well known. However, there was no literature discussion, before the authors’ publications, about the possibility to control catalytic properties of nanosized systems by changing the distances between nanoparticles and the character of their distribution on the surface. At the same time, it is clear that the transition from isolated nanoparticles to their ensembles and further to compact coatings when shortening the distance between particles should lead to drastic changes of physical-chemical and especially electrochemical and catalytic properties of the system. Theoretical estimations show the existence of some optimal distance between nanoparticles when the amount of surface charges in the nanocluster ensemble increases sharply due to electron tunneling between close particles. Since the majority of chemical reactions is sensible to the catalyst charge, there is a reason to propose the extremal dependence of catalytic activity on the mean distance between nanoparticles or on the density of the nanoclusters immobilized on a surface.
The increase of catalysis with nanocomposites at the certain density of metal particles is revealed experimentally by the authors of the project for series of processes of halogen-containing organic compounds conversion. This point to the possibility of creation the high-performance technologies of halogenated derivatives processing with the use of catalysts based on the ensembles of nanoclusters. At that, the consumption of noble metals, composing the active part of hydrodechlorination catalysts, could be lowered without loss of performance by an order and more as compared to known catalytic systems.
The processing of halogen-containing organic compounds, such as toxic wastes of chlorinated organics manufacturing, halogen-containing pesticides, polychlorobiphenyls (the main component of used transformer oils) etc. is the serious ecological problem. It becomes more acute due to specific peculiarities of halogenated compounds, which are able to produce dioxins and their analogues when keeping in contact with the atmosphere. The common method of chemical wastes destruction – incineration – is of little use in this case. The incineration of polyhalogenated organic compounds results in rejection of toxic products – hydrogen chloride, chlorine, phosgene and others – in the atmosphere. Moreover, when the temperature mode is broken, it leads to the formation of dioxins. Another technological and ecological problem is close connected to the considered one, it is the destruction of chemical weapon components. It is known that the overwhelming majority of military poison substances are halogen-containing organic compounds.
The most effective and ecologically clean method of toxic halogenated organic products processing is evidently the catalytic hydrodechlorination. The essence of the method is in the treatment of halogenated compounds by the hydrogen in the presence of heterogeneous catalysts. The palladium supported on carbon or oxides is considered the best one. Unfortunately, relatively low activity and short working time of these catalysts hinder the propagation of the method.
The new technology of catalyst production, providing formation of the ensembles of interacting nanoclusters on the surface of a support, is supposed to allow creation of effective hydrodechlorination catalysts exceeded essentially known ones in activity and containing less amount of noble metal. These catalysts, in their turn, create preconditions for the development of the new high-performance technology of catalytic hydrodechlorination of toxic halogen-containing organic compounds.
The realization of the project will resulted in creation of the model stand for the production of novel catalysts based on the ensembles of immobilized nanoparticles, and the pilot setup for hydrodechlorination of halogen-containing organic compounds. The demonstration test will carried out both with model substances and real technogenic compositions.
In the proposal the specialists of one of the leading defense enterprise – GosNIIOKhT, scientists from Chemical Department of Lomonosov MSU and leading scientific institutions of Russian Federation – NIFKhI Karpov and PTI will take part. Their qualification and experience in the given area will ensure the successful decision of the problems stated in the project.
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