Ruilin Feng,Yanlong Qi,Shijun Liu,Long Cui,Quanquan Dai,Chenxi Bai
1,3-Pentadiene plays an extremely important role in the production of polymers and fine chemicals. Herein, the LaPO 4 catalyst exhibits excellent catalytic performance for the dehydration production of 1,3-pentadiene with 2,3-pentanediol, a C5 diol platform compound that can be easily obtained by hydrogenation of bio-based 2,3-pentanedione. The relationships of catalyst structure-acid/base properties-catalytic performance was established, and an acid-base synergy effect was disclosed for the on-purpose synthesis of 1,3-pentadiene. Thus, a balance between acid and base sites was required, and an optimized LaPO 4 with acid/base ratio of 2.63 afforded a yield of 1,3-pentadiene as high as 61.5% at atmospheric pressure. Notably, the Brønsted acid sites with weak or medium in LaPO 4 catalyst can inhibit the occurrence of pinacol rearrangement, resulting in higher 1,3-pentadiene production. In addition, the investigation on reaction pathways demonstrated that the E2 mechanism was dominant in this dehydration reaction, accompanied by the assistance of E1 and E1cb.
Tongyun Zhang,Chengping Zhang,Xiaoxun Ma,Hengdao Quan
3,3,3-trifluoropropyne (HFY-2223tz) is a novel refrigerant with great physicochemical properties. Though preparation of HFY-2223tz from halogenated olefins is theoretically effective, it remains great challenges for dehydrohalogenation from halogenated olefins, limiting the detailed knowledge. Here, we established a facile investigation to explore the gas-phase dehydrochlorination reaction of 2‑chloro-3,3,3-trifluoropropene (HCFO-1233xf) over various halides (Na, K, Rb, Cs) supported active carbon (AC) catalysts. The CsF was concluded as the optimal active component with best dehydrochlorination selectivity and conversion of HCFO-1233xf. The CO 2 -TPD results illustrated that dehydrochlorination of HCFO-1233xf proceeded through E1cB mechanism. Mechanism study revealed the evolution of side-products including ( Z / E )-1,3,3,3-tetrafluoropropylene, 2,3,3,3-tetrafluoropropylene, ( Z / E )-1‑chloro‑3,3,3-trifluoroproene, and 3,3,3-trifluoroprop-1-ene, etc. However, observable deactivation of CsF catalyst was noticed, which, according to combined XRD and XPS results and density functional theory (DFT) calculations, was attributed to the F/Cl exchange between HCFO-1233xf and catalyst, leading to rapid fluorine consumption. This work thus provides basic knowledge about heterogeneous catalytic synthesis of HFY-2223tz from dehydrohalogenation of halogenated olefins.
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