Bimetallic Pt-Co Catalysts for the Liquid-Phase WGS

[EN] 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 kg·s/molCO), isothermal operation at 260 ºC 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 ºC) 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 ºC temperature range was 51.5 kJ/mol.This research was funded by Mineco (ENE2016-74850-R and PID2019-106692EB-I00) and FEDER. The APC was funded by ENE2016-74850-R. A.J.R. was supported by a PhD research fellowship provided by the University of the Basque Country UPV/EHU (PIF-17/319)

Bio‑hydrogen and valuable chemicals from industrial waste glycerol via catalytic aqueous-phase transformation

Waste glycerol obtained as by-product of biodiesel production has been submitted to a sequential physico-chemical treatment in order to make it suitable for continuous Aqueous-Phase Reforming (APR) in a tubular reactor. Special focus was given to the impact of impurities. APR was performed using 0.3%Pt/CoAl2O4 catalyst, at 260 °C and 50 bar within WHSV range 6–55 h−1 to cover whole conversion ranges. Glycerol conversion and yield to hydrogen reached 99.7% and 45.4%, respectively at WHSV = 6 h−1. The liquid product distribution strongly varied with glycerol conversion, maximum C-yield to 1,2-propylene glycol was attained in the 60–90% glycerol conversion range. APR of methanol and acetic acid aqueous feedstreams were investigated independently. It was concluded that acetic acid exerts a negative influence on catalyst stability since glycerol conversion decreased by 41% after 5 h TOS. Extensive characterization of fresh and exhausted catalysts revealed strong Co leaching, especially for acetic acid APR, oxidation of metals, and carbonaceous deposits. The basis for the regeneration of the spent catalyst, consisting of a reductive treatment at 500 °C, has been established. This work is expected to have significant implications for the development of APR technology for crude glycerol from biodiesel industry.This research was supported by grant PID2019-106692EB-I00 funded by MCIN/AEI/10.13039/501100011033. The authors thank for technical support provided by SGIker of UPV/EHU and European funding (ERDF and ESF)

Aqueous-phase reforming of glycerol over Pt-Co catalyst: Effect of process variables

This study examined the influence of process variables (glycerol concentration in feed, coupled temperature/pressure and space velocity) in the catalytic performance in the APR of glycerol over 0.3Pt/CoAl catalyst in a continuous fixed-bed reactor in order to maximize the production of H2. The effect of glycerol concentration in the feed was studied from 5 to 20 wt%, the coupled temperature/pressure varied from 225 °C/25 bar to 260 °C/50 bar and the spatial velocity was changed from 0.68 to 17 h-1. Our results reflected that H2 production was favored at higher reaction temperature/pressure (3.62 vs. 2.49 molH2/molGly-converted, at the most severe and mild conditions, respectively), lower WHSV (3.89 vs. 1.27 molH2/molGly-converted, at the lowest and highest space velocity, respectively) and more diluted feedstocks (3.95 vs. 1.44 molH2/molGly-converted, at the most diluted and concentrated freestreams, respectively). A threshold value at 10 wt% glycerol was found for the ratio of dehydrogenation to dehydration liquid products. The post-reaction catalyst was also characterized by several techniques, showing that Co leaching was the major drawback, especially at the mildest operation conditions, while carbonaceous deposits are negligible.Ministerio de Ciencia e Innovación, PID2019-106692RB-I0

Cobalt aluminate spinel-derived catalysts for glycerol aqueous phase reforming

Catalytic activity at mild (235 °C/3.5 MPa) and severe (260 °C/5.0 MPa) APR conditions was investigated over catalysts based on cobalt aluminate spinel synthetized by coprecipitation. Co/Al ratio was varied and physicochemical characteristics were assessed by N2 adsorption, H2 chemisorption, XRD, H2-TPR, DRS-UV, FTIR, CO2-TPD, NH3-TPD and XPS. Formation of cobalt aluminate produced strong Co-O-Al interaction in the catalyst precursor leading to improved Co dispersion upon activation. Co/Al ratio could be used to tune catalyst characteristics, thus selectivity towards the desired reaction pathway. Overall, Co/Al above the stoichiometric value produced smaller and more stable metallic Co, which allowed best APR performance. For instance, at 235 °C/3.5 MPa glycerol conversion and conversion to gas of 0.625CoAl (88% and 22%) were notably higher than those of bare Co3O4 (23% and 5%). At severe conditions, 0.625CoAl catalyst produced 231 μmolH2/gcat min (60% H2). Statistical analysis of data collected from long-term run was used to investigate reaction mechanism. Long-term run revealed that sintering and oxidation were main mechanisms for catalyst deactivation whereas some leaching of Co nanoparticles, and carbonaceous deposition was also detected.Ministerio de Economía y Competitividad, ENE2016-7450-

Hydrogen production by aqueous phase reforming of biomass-derived glycerol over cobalt-based catalysts

400 p.In the current context regarding the increase in energy demand and the need to decarbonize the global energy system to avoid even further deterioration of the on-going climate change crisis, hydrogen is a promising energy alternative. The use of hydrogen, produced from biomass, would drastically reduce CO2 emissions, contribute to reducing the current dependence on fossil fuels and, due to its greater availability, would improve the economic situation of many countries that are still plagued by energy poverty. Aqueous-phase reforming (APR) is a suitable and energy-efficient alternative process for hydrogen and other high value-added chemical production.This Doctoral Thesis aims to contribute to a development of new cobalt aluminate-based catalysts for glycerol valorisation through H2 production by APR establishing a structure-activity relationship. This research provides further insight into the aqueous-phase reforming of biomass-derived oxygenated compounds, the effect of operating conditions, the correlation with liquid-phase WGS reaction and the feasibility of crude bioglycerol as a feedstock

Hydrogen production by aqueous phase reforming of biomass-derived glycerol over cobalt-based catalysts

400 p.In the current context regarding the increase in energy demand and the need to decarbonize the global energy system to avoid even further deterioration of the on-going climate change crisis, hydrogen is a promising energy alternative. The use of hydrogen, produced from biomass, would drastically reduce CO2 emissions, contribute to reducing the current dependence on fossil fuels and, due to its greater availability, would improve the economic situation of many countries that are still plagued by energy poverty. Aqueous-phase reforming (APR) is a suitable and energy-efficient alternative process for hydrogen and other high value-added chemical production.This Doctoral Thesis aims to contribute to a development of new cobalt aluminate-based catalysts for glycerol valorisation through H2 production by APR establishing a structure-activity relationship. This research provides further insight into the aqueous-phase reforming of biomass-derived oxygenated compounds, the effect of operating conditions, the correlation with liquid-phase WGS reaction and the feasibility of crude bioglycerol as a feedstock