Abstract
Bimetallic Pt-Co catalysts derived from cobalt aluminate spinel were investigated in the liquid-phase water–gas shift (WGS) reaction and CO hydrogenation. Liquid-phase WGS is a key reaction in the aqueous-phase reforming (APR) of polyols; thus, WGS activity is essential to formulate good APR catalysts. In this work, catalysts with different Pt/Co molar ratios were synthesized together with a reference Pt/alumina. All the synthesized catalysts were characterized by various techniques in order to gain knowledge on their structural and surface characteristics. WGS activity was tested with a feedstream of CO/H2O = 1/15 (space-time of 76.8 kgcat·s/molCO), isothermal operation at 260 °C and 50 bar, for 10 TOS. Bimetallic Pt-Co catalysts showed improved activity in liquid-phase WGS in comparison to bare Co or Pt catalysts, which was ascribed to the synergistic effect. Despite being subjected to an increased hydrogen concentration in the feedstream (H2/CO between 0 and 12/3), these catalysts maintained a preferential selectivity towards WGS activity. In addition, the effect of temperature (220–260 °C) and pressure (25–50 bar) was investigated over a catalyst with 0.3Pt/CoAl. CO conversion and CO2 yield were more sensitive to temperature, while a higher pressure favored methane production. The measured activation energy in the 220–260 °C temperature range was 51.5 kJ/mol.
Highlights
The water–gas shift (WGS) reaction, first observed by Felice Fontana in 1780 [1], is related to the production of hydrogen and carbon dioxide from a mixture of carbon monoxide and steam
WGS is a key element in mature technologies devoted to hydrogen production by the steam reforming of natural gas in industrial applications such as ammonia synthesis or synthesis gas plants
In view of all this, we studied the WGS reaction under similar operation conditions to those previously used to investigate aqueous-phase reforming (APR) on bimetallic Pt-Co catalysts derived from cobalt aluminate precursor [24]
Summary
The water–gas shift (WGS) reaction, first observed by Felice Fontana in 1780 [1], is related to the production of hydrogen and carbon dioxide from a mixture of carbon monoxide and steam. Due to the growing concerns about environmental issues and the challenge of implementing the hydrogen economy, research on new catalysts for the WGS reaction has been notably boosted [2]. This renewed interest in WGS has been motivated by the search for renewable feedstocks as alternatives to fossil fuels, which are to blame for environmental problems such as global warming. To overcome the equilibrium limitations, industrially, WGS is carried out in two consecutive stages, with intermediate cooling. A sorption-enhanced WGS reaction can be used to intensify the process by the in-situ removal of CO2 to shift the equilibrium towards hydrogen production [4]. Supported ionic liquids (SILP), prepared via the Catalysts 2020, 10, 830; doi:10.3390/catal10080830 www.mdpi.com/journal/catalysts
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