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Catalysts in Production of Clean Gasification Gas
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Catalysts in Production of Clean Gasification Gas

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Biomass Catalysis".

Deadline for manuscript submissions: closed (31 October 2022) | Viewed by 15614

Special Issue Editors

Dr. Pekka Simell

E-Mail Website
Guest Editor
VTT Technical Research Centre of Finland Ltd., P.O. Box 1000, FI-02044 Espoo, Finland
Interests: gasification, gas clean-up, reformer, catalysts, syngas, tars, filtration
Dr. Matti Reinikainen

E-Mail Website
Guest Editor
VTT Technical Research Centre of Finland Ltd., P.O. Box 1000, FI-02044 Espoo, Finland
Interests: FT-synthesis, catalysis, analytics

Special Issue Information

Dear Colleagues,

Catalysts play a key role in the development of technology to produce tar- and hydrocarbon-free synthesis gas from biomass and wastes. This Special Issue collects the developments done for gas clean-up for various synthesis applications. The developments have covered the most challenging and costly steps in biomass gasification-based processes: high-temperature gas filtration and reforming of hydrocarbon gases and tars. The tar content of product gas is one of the main factors defining the temperature window in which the hot-gas filtration can be used. Results from recent work on achieving higher and thus more economical operation temperatures are also included. Topics of great interest include the optimal operation of a catalytic reformer as well as novel reformer concepts.

Dr. Pekka Simell
Dr. Matti Reinikainen
Guest Editors

Manuscript Submission Information

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Keywords

  • gasification
  • gas cleanup
  • tar reforming
  • gas filtration
  • catalysts

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Published Papers (5 papers)

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Research

21 pages, 5029 KiB  
Article
Carbon Formation in the Reforming of Simulated Biomass Gasification Gas on Nickel and Rhodium Catalysts
by Johanna Kihlman and Pekka Simell
Catalysts 2022, 12(4), 410; https://doi.org/10.3390/catal12040410 - 7 Apr 2022
Cited by 4 | Viewed by 2637
Abstract
Biomass gasification gas contains hydrocarbons that must be converted to CO and H2 prior to the utilization of the gas in a synthesis unit. Autothermal or steam reforming operating with a nickel or noble metal catalyst is a feasible option to treat [...] Read more.
Biomass gasification gas contains hydrocarbons that must be converted to CO and H2 prior to the utilization of the gas in a synthesis unit. Autothermal or steam reforming operating with a nickel or noble metal catalyst is a feasible option to treat the gas, but the harsh reaction conditions may lead to the formation of solid carbon. This study discusses the effects of pressure, time-on-stream, and ethylene content on the carbon formation on nickel and rhodium catalysts. The experiments were carried out with laboratory-scale equipment using reaction conditions that were closely simulated after a pilot-scale biomass gasifier. The results indicated that ethylene content above 20,000 vol-ppm and the increased pressure would increase the carbon formation, although there were differences between the rhodium and nickel catalysts. However, carbon formation was significantly more pronounced on the nickel catalyst when the reaction time was increased from 5 h to 144 h. The type of carbon was found to be primarily encapsulating and graphitic. The formation of whisker carbons (also known as carbon nanotubes) was not observed, which is consistent with the literature as the feed gas contained H2S. It was concluded that utilizing a noble metal catalyst as the front layer of the catalyst bed could lower the risk for carbon formation sufficiently to provide stable long-term operation. Full article
(This article belongs to the Special Issue Catalysts in Production of Clean Gasification Gas)
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17 pages, 4960 KiB  
Article
Mapping the Effects of Potassium on Fuel Conversion in Industrial-Scale Fluidized Bed Gasifiers and Combustors
by Teresa Berdugo Vilches, Jelena Maric, Henrik Thunman and Martin Seemann
Catalysts 2021, 11(11), 1380; https://doi.org/10.3390/catal11111380 - 16 Nov 2021
Cited by 3 | Viewed by 2345
Abstract
Potassium (K) is a notorious villain among the ash components found in the biomass, being the cause of bed agglomeration and contributing to fouling and corrosion. At the same time, K is known to have catalytic properties towards fuel conversion in combustion and [...] Read more.
Potassium (K) is a notorious villain among the ash components found in the biomass, being the cause of bed agglomeration and contributing to fouling and corrosion. At the same time, K is known to have catalytic properties towards fuel conversion in combustion and gasification environments. Olivine (MgFe silicate) used as gasifier bed material has a higher propensity to form catalytically active K species than traditional silica sand beds, which tend to react with K to form stable and inactive silicates. In a dual fluidized bed (DFB) gasifier, many of those catalytic effects are expected to be relevant, given that the bed material becomes naturally enriched with ash elements from the fuel. However, a comprehensive overview of how enrichment of the bed with alkali affects fuel conversion in both parts of the DFB system is lacking. In this work, the effects of ash-enriched olivine on fuel conversion in the gasification and combustion parts of the process are mapped. The work is based on a dedicated experimental campaign in a Chalmers DFB gasifier, wherein enrichment of the bed material with K is promoted by the addition of a reaction partner, i.e., sulfur, which ensures K retention in the bed in forms other than inactive silicates. The choice of sulfur is based on its affinity for K under combustion conditions. The addition of sulfur proved to be an efficient strategy for capturing catalytic K in olivine particles. In the gasification part, K-loaded olivine enhanced the char gasification rate, decreased the tar concentration, and promoted the WGS equilibrium. In the combustion part, K prevented full oxidation of CO, which could be mitigated by the addition of sulfur to the cyclone outlet. Full article
(This article belongs to the Special Issue Catalysts in Production of Clean Gasification Gas)
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29 pages, 11709 KiB  
Article
Catalytic Tar Conversion in Two Different Hot Syngas Cleaning Systems
by Grazyna Straczewski, Robert Mai, Uta Gerhards, Krassimir Garbev and Hans Leibold
Catalysts 2021, 11(10), 1231; https://doi.org/10.3390/catal11101231 - 13 Oct 2021
Cited by 3 | Viewed by 3743
Abstract
Tar in the product gas of biomass gasifiers reduces the efficiency of gasification processes and causes fouling of system components and pipework. Therefore, an efficient tar conversion in the product gas is a key step of effective and reliable syngas production. One of [...] Read more.
Tar in the product gas of biomass gasifiers reduces the efficiency of gasification processes and causes fouling of system components and pipework. Therefore, an efficient tar conversion in the product gas is a key step of effective and reliable syngas production. One of the most promising approaches is the catalytic decomposition of the tar species combined with hot syngas cleaning. The catalyst must be able to convert tar components in the synthesis gas at temperatures of around 700 °C downstream of the gasifier without preheating. A Ni-based doped catalyst with high activity in tar conversion was developed and characterized in detail. An appropriate composition of transition metals was applied to minimize catalyst coking. Precious metals (Pt, Pd, Rh, or a combination of two of them) were added to the catalyst in small quantities. Depending on the hot gas cleaning system used, both transition metals and precious metals were co-impregnated on pellets or on a ceramic filter material. In the case of a pelletized-type catalyst, the hot gas cleaning system revealed a conversion above 80% for 70 and 110 h. The catalyst composed of Ni, Fe, and Cr oxides, promoted with Pt and impregnated on a ceramic fiber filter composed of Al2O3(44%)/SiO2(56%), was the most active catalyst for a compact cleaning system. This catalyst was catalytically active with a naphthalene conversion of around 93% over 95 h without catalyst deactivation. Full article
(This article belongs to the Special Issue Catalysts in Production of Clean Gasification Gas)
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16 pages, 4046 KiB  
Article
Solid-State Redox Kinetics of CeO2 in Two-Step Solar CH4 Partial Oxidation and Thermochemical CO2 Conversion
by Mahesh Muraleedharan Nair and Stéphane Abanades
Catalysts 2021, 11(6), 723; https://doi.org/10.3390/catal11060723 - 10 Jun 2021
Cited by 7 | Viewed by 2772
Abstract
The CeO2/CeO2−δ redox system occupies a unique position as an oxygen carrier in chemical looping processes for producing solar fuels, using concentrated solar energy. The two-step thermochemical ceria-based cycle for the production of synthesis gas from methane and solar energy, [...] Read more.
The CeO2/CeO2−δ redox system occupies a unique position as an oxygen carrier in chemical looping processes for producing solar fuels, using concentrated solar energy. The two-step thermochemical ceria-based cycle for the production of synthesis gas from methane and solar energy, followed by CO2 splitting, was considered in this work. This topic concerns one of the emerging and most promising processes for the recycling and valorization of anthropogenic greenhouse gas emissions. The development of redox-active catalysts with enhanced efficiency for solar thermochemical fuel production and CO2 conversion is a highly demanding and challenging topic. The determination of redox reaction kinetics is crucial for process design and optimization. In this study, the solid-state redox kinetics of CeO2 in the two-step process with CH4 as the reducing agent and CO2 as the oxidizing agent was investigated in an original prototype solar thermogravimetric reactor equipped with a parabolic dish solar concentrator. In particular, the ceria reduction and re-oxidation reactions were carried out under isothermal conditions. Several solid-state kinetic models based on reaction order, nucleation, shrinking core, and diffusion were utilized for deducing the reaction mechanisms. It was observed that both ceria reduction with CH4 and re-oxidation with CO2 were best represented by a 2D nucleation and nuclei growth model under the applied conditions. The kinetic models exhibiting the best agreement with the experimental reaction data were used to estimate the kinetic parameters. The values of apparent activation energies (~80 kJ·mol−1 for reduction and ~10 kJ·mol−1 for re-oxidation) and pre-exponential factors (~2–9 s−1 for reduction and ~123–253 s−1 for re-oxidation) were obtained from the Arrhenius plots. Full article
(This article belongs to the Special Issue Catalysts in Production of Clean Gasification Gas)
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15 pages, 3985 KiB  
Article
Atomic Layer Deposition Coated Filters in Catalytic Filtration of Gasification Gas
by Tyko Viertiö, Viivi Kivelä, Matti Putkonen, Johanna Kihlman and Pekka Simell
Catalysts 2021, 11(6), 688; https://doi.org/10.3390/catal11060688 - 29 May 2021
Cited by 1 | Viewed by 2822
Abstract
Steel filter discs were catalytically activated by ALD, using a coating of supporting Al2O3 layer and an active NiO layer for gas cleaning. Prepared discs were tested for model biomass gasification and gas catalytic filtration to reduce or eliminate the [...] Read more.
Steel filter discs were catalytically activated by ALD, using a coating of supporting Al2O3 layer and an active NiO layer for gas cleaning. Prepared discs were tested for model biomass gasification and gas catalytic filtration to reduce or eliminate the need for a separate reforming unit for gasification gas tars and lighter hydrocarbons. Two different coating methods were tested. The method utilizing the stop-flow setting was shown to be the most suitable for the preparation of active and durable catalytic filters, which significantly decreases the amount of tar compounds in gasification gas. A pressure of 5 bar and temperatures of over 850 °C are required for efficient tar reforming. In optimal conditions, applying catalytic coating to the filter resulted in a seven-fold naphthalene conversion increase from 7% to 49%. Full article
(This article belongs to the Special Issue Catalysts in Production of Clean Gasification Gas)
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