Reactor intensification for CO2 utilization and related C1 chemistry

Francisco Vidal Vázquez

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

Carbon capture and utilization and Power-to-X technologies arise as synergetic solution for storing renewable energy and reducing CO2 emissions. Fuels and chemicals can be produced from CO2 as a carbon source instead of fossil-based raw materials. Synthesis reactions using CO2 and H2 are generally highly exothermic, which complicates a good control of reaction temperature. Reactor and process intensification can be used for good control of the reaction conditions and reducing the size and required equipment of a chemical plant. Reactor intensification was applied to the methanol steam reforming process. Control of the temperature in the catalyst bed proved to be a crucial aspect for obtaining reliable kinetic models. A heat exchanger reformer was designed and manufactured for material and thermal integration with a polymeric electrolyte membrane fuel cell stack. This reformer enabled good control of the catalyst temperature and homogeneous flow distribution of the heat transfer fluid. Production of CO from CO2 was investigated by studying the reverse Water-Gas shift (rWGS) reaction at high pressure and temperature. Ni-based catalysts showed the highest activity compared to a Rh-based catalyst. A kinetic model was obtained for the catalyst with 2 w-% of Ni, which displayed high selectivity towards CO formation. The two-step synthesis of linear hydrocarbons from CO2 and H2 was demonstrated in a container-sized unit. This process was formed by a rWGS reactor as a first step and a Fischer-Tropsch synthesis (FT) reactor as a second step. The experimental results revealed the limitations of this process concept for achieving high overall CO2 conversions. For this reason, an enhanced two-step synthesis concept was developed. This concept achieves almost complete CO2 conversion by combining rWGS and catalytic partial oxidation as a first step, high pressure operation and recirculation of the gaseous effluent from the FT reactor. Reactor intensification of CO2 methanation was investigated using Ni-based hydrotalcite (HT) catalyst coated on heat exchanger reactors. The lab-scale heat exchanger reactor allowed excellent control of reaction temperature in the catalyst layer. Kinetic modeling of coated catalyst using this reactor proved to be a reliable method. This was validated by comparison between experimental results and modeling results. A simulated plate type heat exchanger reactor with catalytically coated corrugated plates displayed good performance thanks to the high activity of the Ni-HT coated catalyst, homogeneous flow distribution and high surface area of the reactor. This proved that corrugated plates are a suitable alternative to microchannel plates.
Translated title of the contributionReactor intensification for CO2 utilization and related C1 chemistry
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Alopaeus, Ville, Supervising Professor
  • Simell, Pekka, Thesis Advisor
  • Lehtonen, Juha, Thesis Advisor
Publisher
Print ISBNs978-952-60-8307-0
Electronic ISBNs978-952-60-8308-7
Publication statusPublished - 2018
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • CO2 utilization
  • methanol steam reforming
  • reverse Water-Gas shift
  • Fischer-Tropsch synthesis
  • CO2 methanation
  • reactor intensification

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