Abstract
Nieuwland catalyst is a key step in the dimerization of acetylene. Various zirconium metal additives incorporating Nieuwland catalysts were prepared, and their catalytic performances were assessed in acetylene dimerization. Different characterization techniques (i.e., thermogravimetric analysis, temperature-programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy, hydrogen ion concentration measurement and transmission electron microscopy) were employed in this study. The best catalytic performance was obtained over zirconium-acetylacetonate-incorporated Nieuwland catalysts, with an acetylene conversion of 53.3% and a monovinylacetylene selectivity of 87.4%. Based on these results, the zirconium acetylacetonate additive could reduce the types of transition state complexes, and it could also change the morphology of the catalyst. In addition, the additives could significantly inhibit the occurrence of trimerization products and polymers. Hence, the conversion of acetylene, monovinylacetylene selectivity, and stability of the Nieuwland catalysts were enhanced.
Highlights
Chloroprene rubber (CR), which possesses excellent physical and chemical properties, is one of the five engineering plastics and is widely used in various applications, such as industrial applications, agricultural activities, and daily life [1,2,3,4]
The Nieuwland catalyst used as a control was labeled NC, and the catalysts containing ZrX additive were denoted as ZrX/NC, where X denotes the different kinds of anions added
The catalysts were tested in a self-designed bubble column reactor that was made of glass, which was used for the acetylene dimerization reaction
Summary
Chloroprene rubber (CR), which possesses excellent physical and chemical properties, is one of the five engineering plastics and is widely used in various applications, such as industrial applications, agricultural activities, and daily life [1,2,3,4]. The poor contact between acetylene and the catalyst is further aggravated by the presence of by-products, which can cover the surfaces of the active components of the catalyst To mitigate this issue, Cu+ can catalyze the dimerization reaction, hydrochlorination, and acetaldehyde reaction, which allows the continual dimerization of acetylene to MVA. The reaction system has been continuously optimized by numerous researchers Various strategies, such as adding a second metal to develop a synergistic catalyst, ligand modification, catalytic mechanism, and process strengthening, have been proposed, with encouraging results reported. Side-reactions of acetylene hydration and acetylene dimerization often occur in the Nieuwland catalyst, which results in a low selectivity of MVA These studies found that the addition of a second metal can significantly improve the selectivity of MVA (90%) and the stability of the catalyst in the acetylene dimerization reaction, the conversion rate of acetylene was reduced significantly (10–15%). Deionized water was prepared in the laboratory using a standard reagent-type ultrapure water machine (FBZ1002-SUP, Qingdao Flom Technology Co., Ltd., Qingdao, China)
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