26 February 2016
Valerii Bukhtiyarov, director of Boreskov Institute of Catalysis (Novosibirsk), reported on the prospects of using the renewable vegetable stock in the fuel and petrochemical complex of Tatarstan
We develop methods for preparation of monolithic of unique chemical composition and in a series of special geometry. For this purpose we have all nesessary laboratory scale equipment: mixer for the preparation of extrusion masses, laboratory extruder, desiccator and ovens for the monolith thermal treatment (up to 1600oC). For the preparation of monolith supports with standard dimensions (diameter - 10, 20 and 45 mm) several dies were designed and manufactured.
|Type 1||Type 2||Type 3|
|Diameter||10 mm||20 mm||45 mm|
|Channel size||1x1 mm||1x1 mm||2x2 mm|
|Wall thickness||0.25 mm||0.5 mm||0.5 mm|
The elements of die for the monolith structure preparation
with diameter of 20 mm extrusion are presented.
At present more than five types of monolithic supports with the optimal physicochemical properties are prepared and tested both in BIC and other laboratories in frame
of our co-operation projects.
|SBET m2/g||Phase composition
|Mech. Strength, kg/cm2||Pore volume
|TiO2 / 700oC||86||TiO2(anatase) + Al2O3*SiO2||8||0.36|
|TiO2 + ZrO2 / 700oC||69||TiO2(anatase) + ZrO2(cub.) + Al2O3*SiO2||13||0.36|
|Alumosilicate / 700oC||33||Al2O3*SiO2 + α-SiO2||19.5||0.12|
|Al2O3 / 600oC||190||γ-Al2O3||28||0.34|
|H-ZSM-5 / 600oC||350||H-ZSM-5 + Al2O3*SiO2||20||0.4|
The monoliths based on TiO2, ZrO2, and Al2O3 still possess relatively high surface area and acceptable mechanical strength that allows their application as supports for monolith catalysts.
Washcoated monolith supports
Shematic presentaion of monolith
channel with supported washcoating layer.
Micrograph of cross-section view of washcoating layer on monolith surface with different enlargement.
Monolithic honeycomb supports and catalysts
Technologies are Adopted on Pilot Scale:
Technologies for preparing honeycomb monolithic supports and catalysts are covered by the Russian patents.
Methods of synthesis of multi-layer compositions for simultaneous realization of both membrane and catalytic processes are developed.
The main advantages of highly porous reticulated ceramic & metal foam (RF)
Specially designed porosity and, accordingly structural and frame properties of the ceramic and metal reticulated foam, provide favourable conditions for heat and mass transfer for catalytic processes. These advantages allow the use of the catalysts under conditions of high space velocities and heating up to 1000-1100оС.
Samples of washcoated foam supports
Samples of new Foam structure catalyst supportes prepared by method of Self popogating high temperature Synthesis (SHS). (in cooperation with Department of Structure microkinetics, Tomsk, Russia).
Catalytic heat exchangers - catalytic fixed bed reactors for fuel (methane) combustion with improved heat-utilization and heat-transfer characteristics have been elaborated.
The heat-exchanging reactor comprises a fuel combustion catalytic layer supported on metallic carrier (sintered metal or metal foam) on one side of the reactor wall providing high heat transfer for the endothermic process proceeding on the other side of the wall.
Catalytic methane combustion combined with methane
steam/dry reforming in catalytic heat-exchangers.
The new technology for the production of metal supported catalysts and tubular catalytic heat-exchangers has been developed. Metal tubes with 2.5 mm outside metal foam coating (Ni, Ni-Cr) are fabricated by sintering in vacuum at high temperatures. The plasma spray method is applied to deposit the 100 µm adhesive, mechanically and thermally stable alumina layer on the metal support. Noble metal (Pd-Ce) and perovskite (La-Mn) containing active component are deposited on the plasma sprayed gradient layer. The methane reforming Ni-based catalyst supported on Ni foam is loaded directly inside the tube.
Catalytic heat-exchanging reactor with metal foam deposited
on the internal and external surfaces of a metal tube.
Catalytic heat exchangers have been successfully tested in methane combustion combined with methane steam/dry reforming (syngas production) reactions. Complete methane combustion stoichiometric methane/air mixtures is attained at 5000-20000 h-1, and the temperature of combustion catalysts does not exceed 1000oC. The activity of perovskite catalysts supported on metal foams has been shown to be close to that of a noble metal catalyst on a similar support. No cracking or active component sintering was observed after series of thermal shocks from room temperature to 1000oC.
Plasma spraying is very promising for synthesis of materials with improved or modified catalytic properties. During last five years Laboratory of Environmental Catalysis and Institute of Applied and Theoretical Physics perform the joint comprehensive study on the development of different types of catalysts by plasma technique.
Multipurpose plasmotron constructed at the Institute of Applied and Theoretical Physics and providing the variation of the regime of a jet outflow (laminar, transient, turbulent) is used for the preparation of catalysts.
Laminar (a) and turbulent (b) plasma jet outflow.
The technique of deposition of active coatings on metal and ceramic supports has been worked out. The procedure developed allows to synthesize composite materials consisting of various combinations of plasma sprayed gradient and active layers. Alumina, titania, zirconia are used to deposit plasma sprayed gradient layer on the surface of supports of different geometry (plates, tubes, foam materials). Active components (perovskites, hexaaluminates, noble metals) are deposited on the plasma sprayed gradient layer by chemical methods. Catalysts developed are successfully used in the catalytic heat exchangers.
A systematic investigation of the regularities of the formation of the phase composition and porous structure of different types of alumina treated in a plasma jet outflow is carried out. Based on the results obtained the technique of the preparation of spherical γ-alumina encapsulated in α-alumina is worked out. The procedure developed gives wide possibilities to synthesize different spherical catalysts for the application in energy saving processes. Encapsulation of the active core in thermostable α-alumina shell will allow to protect the catalysts against high temperature exposure and attrition process and as a result will improve the exploitation characteristics of the catalysts.
Micrograph of a cross-section view of (a) initial and (b) encapsulated γ-Al2O3 particles.
Gas-tight perovskite membranes with mixed oxygen ionic and electronic conductivity for oxygen separation and membrane catalysis processes are of considerable interest. Catalytic reactors built from these membranes have potential applications in industrial oxidation processes such as syngas production. However, application of mixed conductive membranes is limited by specific disadvantages, such as low mechanical strength and phase stability during long term operation. Development of supported gas-tight ceramic membranes can overcome these problems:
Schematic overview of supported gas-tight perovskite membrane.
Gas-tight perovskite membranes deposited on ZrO2-Y2O3 supports for partial oxidation of methane are being worked out:
Supported gas-tight perovskite membranes and ZrO2-Y2O3 plates.
Micrographs of cross section view of supported gas-tight perovskite membrane.
Gas-tight perovskite layer.