Innovative Catalysis Program, Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 10084 (PR China).
ChemSusChem. 2014 Jun;7(6):1568-78. doi: 10.1002/cssc.201400134. Epub 2014 Jun 5.
Gas-phase dehydration of lactic acid (LA) to acrylic acid (AA) was investigated over alkali-exchanged β zeolite (M(x)Na(1-x)β, 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. K(x)Na(1-x)β of x=0.94 appeared to be the best performing catalyst whereas Li(x)Na(1-x)β 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.
考察了不同交换度（x）的碱交换β沸石（M(x)Na(1-x)β，M=Li(+)、K(+)、Rb(+)或Cs(+)）上乳酸（LA）气相脱水制丙烯酸（AA）的反应。在不同条件下进行了反应，以了解 AA 生产的催化剂选择性和副产物形成趋势。发现 M(+)的性质和交换度对于交换沸石的酸碱性质和催化性能至关重要。x=0.94 的 K(x)Na(1-x)β似乎是性能最佳的催化剂，而 Li(x)Na(1-x)β和 Naβ在 AA 选择性和产率方面表现最差。在最佳反应条件下，使用性能最佳的 K0.94Na0.06β，可在 8 小时内获得高达 61 mol%（选择性：64 mol%）的 AA 产率。通过吸附 NH3 和 CO2 的程序升温脱附（TPD）分别探测了催化剂的酸碱性，并与沸石中碱离子的静电势相关联，为讨论从 LA 可持续合成 AA 的酸碱催化提供了依据。
