Nanocomposites and nanomaterials

Bulk and supported nanocatalysts for hydrogenation of CO2:  improvement or degradation? 
Dyachenko А.G.2,3, Ischenko O.V.1, Lisnyak V.V.1, Goncharuk O.V.2, Borysenko M.V.2
1Taras Shevchenko National University of Kyiv, 64/13 Volodymyrs’ka Str, Kyiv, 01601, Ukraine
2O.O. Chuiko Institute of Surface Chemistry National Academy of Science of Ukraine, 17 General Naumov Str, Kyiv, 03164, Ukraine
3Institute of Physical Chemistry of Polish Academy of Sciences, 44/52 Kaspzaka, 01-224 Warsaw, Poland.
E-mail: dyachenko.alla@yahoo.com

The highly effective heterometallic catalysts were investigated in the reaction of CO2 hydrogenation. The bulk NiCo, NiFe and CoFe catalysts synthesized by the coprecipitation method demonstrate high catalytic efficiency in the methane production by the reaction of CO2 + H2 compared with monometallic ones. The optimal ratio of the components of the presented bimetallic compositions is obtained for achieving maximum and selective conversion of CO2 to methane.
The most effective bimetallic compositions were applied onto the surface of different carriers (carbon nanotubes, ultradispersed nanodiamonds, graphite nanoplatelets and inert oxides such as silica and alumina) by the method of wet impregnation with inorganic salt solutions of the appropriate metals. The amount of applied actives was 5-20 wt%. The activity of nanocomposite catalysts compared to their bulk counterparts varied depending on the composition of the active mass. Obviously, the application of NiFe and NiCo on the carrier leads to an increase in catalytic activity, and for CoFe the opposite effect of the carrier influence on the efficiency of bimetallic nanoparticles was found.
The data of CO2 conversion (X (CO2)) and CH4 yield (Y (CH4)) at the 300 °C over the bulk and some deposited catalysts are presented in the table below.
Catalyst	X (CO2), %	Y (CH4), %	Catalyst	X (CO2), %	Y (CH4), %	
Ni	40	34	Co(80)Ni(20)/Al2O3	100	100	
Co	55	52	Co(80)Ni(20)/SiO2	90	64	
Fe	10	0	Ni(80)Fe(20)/Al2O3	100	100	
Co(80)Ni(20)	62	60	Ni(80)Fe(20)/SiO2	95	68	
Ni(80)Fe(20)	67	64	Co(93)Fe(07)/Al2O3	90	69	
Co(93)Fe(07)	100	100	Co(93)Fe(07)/SiO2	70	49