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摘要: 采用连续流动固定床反应装置，Ni/AC作为催化剂，在533 K、1.5 MPa、CO/CH3OH/CH3I摩尔比20/19/1、7.5 gcat·h·mol－1下考察了催化剂的稳定性，并通过XPS、ICP和XRD等技术对甲醇气相羰基化反应前后Ni/AC催化剂进行了表征。结果表明，长时间运转催化剂表面形成NiI2，使具有催化活性的Ni0活性中心数量减少，活性降低。XPS结果显示羰基化活性中心Ni不断迁移并在催化剂表面富集，导致积炭效应，堵塞催化剂孔道，使催化剂失活。进一步对积炭类型研究，发现形成的碳物种主要是石墨型碳。Ni向催化剂表面迁移富集，并与CO形成可挥发的Ni(CO)4，造成金属镍的大量流失由ICP所证实。Abstract: Deactivated causes of Ni/AC catalyst for vapor phase carbonylation of methanol were investigated. The carbonylation reaction was carried out in a fixed bed reactor at pressurized condition in the presence of methyl iodide as the promoter. Several characterization techniques (XRD, XPS and ICP) were used to study catalyst change before and after reaction. The characterization results showed that the number of Ni0 active center decreased with the formation of NiI2, and that carbonylation active center Ni migrated continuously and accumulated on the surface of the catalyst forming the active center of carbon deposition, resulting in catalyst deactivation. Species and structure of carbon deposition on the catalyst were also investigated. Results showed that graphite carbon deposited on Ni/AC catalyst after reaction. The loss of Ni on the surface of support induced by the formation of Ni(CO)4 was confirmed by ICP-AES.
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Key words:
- methanol /
- carbonylation /
- acetic acid /
- XPS /
- deactivation
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