Hydrogen production from biomass wastes by reforming in hot compressed water: studies with model oxygenates in the quest for finding an optimal catalyst

Anna Kaisa Kristiina Vikla

Research output: ThesisPhD Thesis - Research UT, graduation UTAcademic

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Abstract

This thesis focuses on a catalyst development for Aqueous Phase Reforming (APR). APR operates at high temperatures and at elevated pressures with a target to convert dilute biomass feeds to hydrogen/syngas. Due to the operation conditions and complex feedstocks used, the catalyst stability and selectivity to hydrogen is a challenge.

The objective of this thesis is to understand issues that affect catalyst stability and effect of catalyst properties for maximized hydrogen yields using model feedstock molecules. Furthermore, understanding formation of side products and they role in deactivation/stability of the catalyst is essential. With this in mind, APR studies are carried out with low feed concentrations 2.5-5wt% of reactant (ethylene glycol, EG and hydroxyacetone, HYDA) and at conditions of 225-270 °C/ 35-90 bar.

Starting with catalyst stability, it is well-known that γ-Al2O3 suffers from phase transformation to AlO(OH) under APR. Therefore, we prepared Pt on AlO(OH) and compared its activity to Pt/γ-Al2O3. Pt/AlO(OH) catalyst is stable for APR of EG and interestingly, it has improved H2-selectivity compared to Pt/γ-Al2O3.

As biomass feeds are complex, we continued further to study stability of Pt/AlO(OH), Pt/C (mesoporous) and Pt/ZrO2 for APR of HYDA, a ketone present in biomass feeds in appreciable amounts. The results showed that the oxide supported materials suffered from carbon deposits on the catalysts and deactivated rapidly. Carbon, however, was stable and had a good gasification activity. This showed good promise for further development of this catalyst.

Therefore, we studied Pt/C in more detail by preparing it in different ways to achieve variable Pt size and distribution on the support. The results indicated that catalysts with higher Pt size and more egg-shell type distribution of metal showed higher H2 production rate in APR of EG. This suggested that APR of EG has a structure sensitivity.

Further, possible diffusion limitations of Pt/C catalysts were studied by varying catalysts grain size and reaction conditions under APR of HYDA. The experimental results are discussed in comparison with transport criteria.

Pt/C is stable and active for gasification of the studied model compounds, further development requires improving Water-Gas-Shift activity to increase H2-selectivity.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • University of Twente
Supervisors/Advisors
  • Seshan, K., Supervisor
Award date11 Jan 2019
Place of PublicationEnschede
Publisher
Print ISBNs978-90-365-4668-3
DOIs
Publication statusPublished - 11 Jan 2019

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Reforming reactions
Hydrogen production
Biomass
Catalysts
Water
Hydrogen
Gasification
Feedstocks
Carbon
Water gas shift
Ethylene Glycol
Catalyst selectivity
Ketones
Catalyst supports
Oxides
Deposits
Phase transitions
Metals

Cite this

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title = "Hydrogen production from biomass wastes by reforming in hot compressed water: studies with model oxygenates in the quest for finding an optimal catalyst",
abstract = "This thesis focuses on a catalyst development for Aqueous Phase Reforming (APR). APR operates at high temperatures and at elevated pressures with a target to convert dilute biomass feeds to hydrogen/syngas. Due to the operation conditions and complex feedstocks used, the catalyst stability and selectivity to hydrogen is a challenge. The objective of this thesis is to understand issues that affect catalyst stability and effect of catalyst properties for maximized hydrogen yields using model feedstock molecules. Furthermore, understanding formation of side products and they role in deactivation/stability of the catalyst is essential. With this in mind, APR studies are carried out with low feed concentrations 2.5-5wt{\%} of reactant (ethylene glycol, EG and hydroxyacetone, HYDA) and at conditions of 225-270 °C/ 35-90 bar. Starting with catalyst stability, it is well-known that γ-Al2O3 suffers from phase transformation to AlO(OH) under APR. Therefore, we prepared Pt on AlO(OH) and compared its activity to Pt/γ-Al2O3. Pt/AlO(OH) catalyst is stable for APR of EG and interestingly, it has improved H2-selectivity compared to Pt/γ-Al2O3.As biomass feeds are complex, we continued further to study stability of Pt/AlO(OH), Pt/C (mesoporous) and Pt/ZrO2 for APR of HYDA, a ketone present in biomass feeds in appreciable amounts. The results showed that the oxide supported materials suffered from carbon deposits on the catalysts and deactivated rapidly. Carbon, however, was stable and had a good gasification activity. This showed good promise for further development of this catalyst.Therefore, we studied Pt/C in more detail by preparing it in different ways to achieve variable Pt size and distribution on the support. The results indicated that catalysts with higher Pt size and more egg-shell type distribution of metal showed higher H2 production rate in APR of EG. This suggested that APR of EG has a structure sensitivity. Further, possible diffusion limitations of Pt/C catalysts were studied by varying catalysts grain size and reaction conditions under APR of HYDA. The experimental results are discussed in comparison with transport criteria. Pt/C is stable and active for gasification of the studied model compounds, further development requires improving Water-Gas-Shift activity to increase H2-selectivity.",
author = "Vikla, {Anna Kaisa Kristiina}",
year = "2019",
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day = "11",
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language = "English",
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publisher = "University of Twente",
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Hydrogen production from biomass wastes by reforming in hot compressed water : studies with model oxygenates in the quest for finding an optimal catalyst. / Vikla, Anna Kaisa Kristiina.

Enschede : University of Twente, 2019. 167 p.

Research output: ThesisPhD Thesis - Research UT, graduation UTAcademic

TY - THES

T1 - Hydrogen production from biomass wastes by reforming in hot compressed water

T2 - studies with model oxygenates in the quest for finding an optimal catalyst

AU - Vikla, Anna Kaisa Kristiina

PY - 2019/1/11

Y1 - 2019/1/11

N2 - This thesis focuses on a catalyst development for Aqueous Phase Reforming (APR). APR operates at high temperatures and at elevated pressures with a target to convert dilute biomass feeds to hydrogen/syngas. Due to the operation conditions and complex feedstocks used, the catalyst stability and selectivity to hydrogen is a challenge. The objective of this thesis is to understand issues that affect catalyst stability and effect of catalyst properties for maximized hydrogen yields using model feedstock molecules. Furthermore, understanding formation of side products and they role in deactivation/stability of the catalyst is essential. With this in mind, APR studies are carried out with low feed concentrations 2.5-5wt% of reactant (ethylene glycol, EG and hydroxyacetone, HYDA) and at conditions of 225-270 °C/ 35-90 bar. Starting with catalyst stability, it is well-known that γ-Al2O3 suffers from phase transformation to AlO(OH) under APR. Therefore, we prepared Pt on AlO(OH) and compared its activity to Pt/γ-Al2O3. Pt/AlO(OH) catalyst is stable for APR of EG and interestingly, it has improved H2-selectivity compared to Pt/γ-Al2O3.As biomass feeds are complex, we continued further to study stability of Pt/AlO(OH), Pt/C (mesoporous) and Pt/ZrO2 for APR of HYDA, a ketone present in biomass feeds in appreciable amounts. The results showed that the oxide supported materials suffered from carbon deposits on the catalysts and deactivated rapidly. Carbon, however, was stable and had a good gasification activity. This showed good promise for further development of this catalyst.Therefore, we studied Pt/C in more detail by preparing it in different ways to achieve variable Pt size and distribution on the support. The results indicated that catalysts with higher Pt size and more egg-shell type distribution of metal showed higher H2 production rate in APR of EG. This suggested that APR of EG has a structure sensitivity. Further, possible diffusion limitations of Pt/C catalysts were studied by varying catalysts grain size and reaction conditions under APR of HYDA. The experimental results are discussed in comparison with transport criteria. Pt/C is stable and active for gasification of the studied model compounds, further development requires improving Water-Gas-Shift activity to increase H2-selectivity.

AB - This thesis focuses on a catalyst development for Aqueous Phase Reforming (APR). APR operates at high temperatures and at elevated pressures with a target to convert dilute biomass feeds to hydrogen/syngas. Due to the operation conditions and complex feedstocks used, the catalyst stability and selectivity to hydrogen is a challenge. The objective of this thesis is to understand issues that affect catalyst stability and effect of catalyst properties for maximized hydrogen yields using model feedstock molecules. Furthermore, understanding formation of side products and they role in deactivation/stability of the catalyst is essential. With this in mind, APR studies are carried out with low feed concentrations 2.5-5wt% of reactant (ethylene glycol, EG and hydroxyacetone, HYDA) and at conditions of 225-270 °C/ 35-90 bar. Starting with catalyst stability, it is well-known that γ-Al2O3 suffers from phase transformation to AlO(OH) under APR. Therefore, we prepared Pt on AlO(OH) and compared its activity to Pt/γ-Al2O3. Pt/AlO(OH) catalyst is stable for APR of EG and interestingly, it has improved H2-selectivity compared to Pt/γ-Al2O3.As biomass feeds are complex, we continued further to study stability of Pt/AlO(OH), Pt/C (mesoporous) and Pt/ZrO2 for APR of HYDA, a ketone present in biomass feeds in appreciable amounts. The results showed that the oxide supported materials suffered from carbon deposits on the catalysts and deactivated rapidly. Carbon, however, was stable and had a good gasification activity. This showed good promise for further development of this catalyst.Therefore, we studied Pt/C in more detail by preparing it in different ways to achieve variable Pt size and distribution on the support. The results indicated that catalysts with higher Pt size and more egg-shell type distribution of metal showed higher H2 production rate in APR of EG. This suggested that APR of EG has a structure sensitivity. Further, possible diffusion limitations of Pt/C catalysts were studied by varying catalysts grain size and reaction conditions under APR of HYDA. The experimental results are discussed in comparison with transport criteria. Pt/C is stable and active for gasification of the studied model compounds, further development requires improving Water-Gas-Shift activity to increase H2-selectivity.

U2 - 10.3990/1.9789036546683

DO - 10.3990/1.9789036546683

M3 - PhD Thesis - Research UT, graduation UT

SN - 978-90-365-4668-3

PB - University of Twente

CY - Enschede

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