Sustainable Production of Acrylic Acid: Alkali-Ion Exchanged Beta Zeolite for Gas-Phase Dehydration of Lactic Acid

Authors

  • Bo Yan,

    1. Innovative Catalysis Program, Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 10084 (PR China)
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  • Li-Zhi Tao,

    1. Innovative Catalysis Program, Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 10084 (PR China)
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  • Yu Liang,

    1. Innovative Catalysis Program, Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 10084 (PR China)
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  • Prof. Dr. Bo-Qing Xu

    Corresponding author
    1. Innovative Catalysis Program, Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 10084 (PR China)
    • Innovative Catalysis Program, Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 10084 (PR China)===

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Abstract

Gas-phase dehydration of lactic acid (LA) to acrylic acid (AA) was investigated over alkali-exchanged β zeolite (MxNa1−xβ, M=Li+, K+, Rb+, or Cs+) of different exchange degrees (x). The reaction was conducted under varying conditions to understand the catalyst selectivity for AA production and trends of byproduct formation. The nature and exchange degree of M+ were found to be critical for the acid–base properties and catalytic performance of the exchanged zeolite. KxNa1−xβ of x=0.94 appeared to be the best performing catalyst whereas LixNa1−xβ and Naβ were the poorest in terms of AA selectivity and yield. The AA yield as high as 61 mol % (selectivity: 64 mol %) could be obtained under optimized reaction conditions for up to 8 h over the best performing K0.94Na0.06β. The acid and base properties of the catalysts were probed, respectively by temperature-programmed desorption (TPD) of adsorbed NH3 and CO2, and were related to the electrostatic potentials of the alkali ions in the zeolite, which provided a basis for the discussion of the acid–base catalysis for sustainable AA formation from LA.

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