Sustainable chlorine recycling via catalysed HCl oxidation: from fundamentals to implementation

Pérez‐Ramírez, Javier; Mondelli, Cecilia; Schmidt, Timm; Schlüter, Oliver F.-K.; Wolf, Aurel; Mleczko, Lesław; Dreier, Thorsten

doi:10.1039/c1ee02190g

“…To date, using numerous combinations of metals, high efficiency has been achieved by optimizing the adsorption energies [19][20][21] or increasing the electrical conductivity of the catalysts. [22][23][24] Multimetal systems have also been used to improve the stability of catalysts [25][26][27] or to reduce the precious metal content maintaining the catalytic activity, [25,28] as schematically illustrated in Figure 1. In this review, we present an overview of various design strategies for multimetal oxide OER catalysts along with recent understanding on the catalysis of multimetal oxides.…”

Section: Introductionmentioning

confidence: 99%

Recent Progress on Multimetal Oxide Catalysts for the Oxygen Evolution Reaction

Kim

¹

,

Kim

²

,

Kim

³

et al. 2018

Advanced Energy Materials

View full text Add to dashboard Cite

fossil fuels are being widely researched for the development of a sustainable energy system. Among the various candidates for green energy resources, hydrogen energy has been at the center of attention. [1,2] Hydrogen is both inexhaustible and environmentally friendly, because it can be produced from earth-abundant reactants such as water and methane and because no CO 2 or other toxic products are emitted during its conversion into other energy form such as electricity, respectively. Moreover, hydrogen can exhibit significantly larger energy density compared with other energy sources such as gasoline and coal. The most widely used method of hydrogen production today is steam reforming because of its low cost in the process. [3] Nevertheless, the release of carbon monoxide or carbon dioxide as byproducts in the steam reforming process diminishes the environmental merits of hydrogen energy. Thus, as a possible cleaner alternative, an electrolysis method that involves producing hydrogen by electrochemically splitting water has been extensively investigated. Using one of the most abundant resources, water, the production of hydrogen from it yields only oxygen as a byproduct.In the water electrolysis, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) occur simultaneously, as described by the following equationsIn order for the reaction to proceed, a voltage of 1.23 V is theoretically required between an anode and a cathode. However, an overpotential (represented by the symbol η) should be additionally applied to account for the potential loss resulting from kinetic limitations occurring during the electrochemical reaction. The use of electrocatalysts can lower the overpotential by kinetically facilitating the water-splitting reaction either in HER or OER. Due to the nature of four-electron involving OER, it is generally believed that the OER is much more sluggish than the HER; thus, the development of efficient OER Hydrogen is a promising alternative fuel for efficient energy production and storage, with water splitting considered one of the most clean, environmentally friendly, and sustainable approaches to generate hydrogen. However, to meet industrial demands with electrolysis-generated hydrogen, the development of a low-cost and efficient catalyst for the oxygen evolution reaction (OER) is critical, while conventional catalysts are mostly based on precious metals. Many studies have thus focused on exploring new efficient nonprecious-metal catalytic systems and improving the understandings on the OER mechanism, resulting in the design of catalysts with superior activity compared with that of conventional catalysts. In particular, the use of multimetal rather than single-metal catalysts is demonstrated to yield remarkable performance improvement, as the metal composition in these catalysts can be tailored to modify the intrinsic properties affecting the OER. Herein, recent progress and accomplishments of multimetal catalytic systems, including several important groups of catalysts: layered h...

show abstract

“…4,5,6,7,8 CeO 2 was recently identified as a cheaper potential alternative active phase in view of its remarkable stability, though it requires higher operating temperatures. 9 As revealed by XRD and XPS analyses, when using an appropriate over-stoichiometry of oxygen in the feed gas (O 2 :HCl > 0.75) the bulk of ceria was unaffected and only the surface got chlorinated under reaction condition.…”

Section: Introductionmentioning

confidence: 99%

Do observations on surface coverage-reactivity correlations always describe the true catalytic process? A case study on ceria

Farra

¹

,

Eichelbaum

²

,

Schlögl

³

et al. 2013

Journal of Catalysis

Self Cite

View full text Add to dashboard Cite

In situ (operando) investigations aim at establishing structure-function and/or coverage-reactivity correlations. Herein, we investigated the HCl oxidation reaction (4HCl + O 2 → 2Cl 2 + 2H 2 O) over ceria. In spite of its remarkable performance, under low oxygen over-stoichiometry this oxide is prone to a certain extent to subsurface/bulk chlorination, which leads to deactivation. In situ Prompt Gamma Activation Analysis (PGAA) studies evidenced that the chlorination rate is independent of the pre-chlorination degree but increases at lower oxygen over-stoichiometry, while dechlorination is effective in oxygen-rich feeds and its rate is higher for a more extensively pre-chlorinated ceria. Even bulk CeCl 3 could be transformed into CeO 2 under oxygen excess. Electron Paramagnetic Resonance experiments strongly suggested that oxygen activation is inhibited by a high surface chlorination degree.The coverages of most abundant surface intermediates, OH and Cl, were monitored by in situ infrared spectroscopy and PGAA under various conditions. Higher temperature and p(O 2 ) led to enhanced OH coverage, reduced Cl coverage, and increasing reactivity. Variation of p(HCl) gave rise to opposite correlations, while raising p(Cl 2 ) did not induce any measurable increase in the Cl coverage despite the strong inhibition of the reaction rate. The results indicate that only a small fraction of surface sites are actively involved in the reaction and most of the surface species probed in the in situ observation are spectator. Therefore, when performing in situ steady-state experiments, a large set of variables should be considered to obtain accurate conclusions.

show abstract

“…For this reason, and since HCl is also available as a byproduct in several processes using Cl 2 , such as phosgene-based isocyanate production, processes have also been developed to oxidize HCl back to chlorine [11]. However, such processes amount to at most 5% of the total world capacity for chlorine.…”

Section: Chlorine Derivativesmentioning

confidence: 98%

Oxidation

Teles

¹

,

Hermans

²

,

Franz³

et al. 2015

Ullmann's Encyclopedia of Industrial Chemistry

View full text Add to dashboard Cite

The article contains sections titled: 1. Introduction 2. Overview of industrial oxidation processes 2.1. Inorganic chemicals 2.1.1. Sulfur derivatives 2.1.2. Carbon derivatives 2.1.3. Nitrogen derivatives 2.1.4. Chlorine derivatives 2.2. Organic chemicals 2.2.1. Olefins and alkynes 2.2.2. Epoxides 2.2.3. Hydroperoxides 2.2.4. Alcohols 2.2.5. Aldehydes 2.2.6. Ketones 2.2.7. Phenols and derivatives 2.2.8. Carboxylic acids, saturated 2.2.9. Carboxylic acids and anhydrides, unsaturated 2.2.10. Carboxylic acids and anhydrides, aromatic 2.2.11. Esters, lactones and carbonates 2.2.12. Nitriles 2.2.13. Oxidized nitrogen compounds 2.2.14. Chlorinated compounds 2.2.15. Sulfur compounds 3. Thermodynamics; Stability of Hydrocarbons 4. Reaction Types 5. Homolytic Oxidation 5.1. Historical Development; Reaction Mechanism; Radical Reactivity 5.2. Kinetics of Autoxidation 5.3. Differences between Liquid‐ and Gas‐Phase Autoxidations 5.4. Homolytic Oxidation in the Liquid Phase 5.4.1. Secondary Reactions of Radicals, Peroxides, and other Intermediates 5.4.2. Metal Catalysis in Homolytic Liquid‐Phase Oxidation 5.4.3. Inhibitors of Homolytic Liquid‐Phase Oxidation 5.4.4. Special Cases of Homolytic Oxidation 5.4.5. Process Technology of Homolytic Liquid‐Phase Oxidation 5.5. Homolytic Gas‐Phase Oxidation 5.6. Gas Explosions and Safety Data 6. Heterolytic Oxidation 6.1. Heterolytic Oxidation in the Liquid Phase 6.2. Heterogeneously Catalyzed Gas‐Phase Oxidation 6.2.1. Oxidation Catalysts 6.2.2. Process Technology of Heterogeneously Catalyzed Oxidations

show abstract

Sustainable chlorine recycling via catalysed HCl oxidation: from fundamentals to implementation

Cited by 195 publications

References 29 publications

Recent Progress on Multimetal Oxide Catalysts for the Oxygen Evolution Reaction

Recent Progress on Multimetal Oxide Catalysts for the Oxygen Evolution Reaction

Do observations on surface coverage-reactivity correlations always describe the true catalytic process? A case study on ceria

Oxidation

Contact Info

Product

Resources

About