Abstract: The synthesis of methacrylic acid from biomass-derived itaconic acid is a green route, for it can get rid of the dependence on fossil resource. In order to solve the problems on this route such as use of a preciousmetal catalyst and a corrosive homogeneous alkali, we prepared a series of hydroxyapatite catalysts by an ionic liquid-assisted hydrothermal method and evaluated their catalytic performance. The results showed that the ionic liquid [Bmim]BF₄ can affect the crystal growth of hydroxyapatite, provide fluoride ion for fluorination of hydroxyapatite, and adjust the surface acidity and basicity, morphology, textural properties, crystallinity, and composition of hydroxyapatite. The [Bmim]BF₄ dosage and hydrothermal temperature can affect the fluoride ion concentration in the hydrothermal system, thus changing the degree of fluoridation of hydroxyapatite. High fluoride-ion concentration can lead to the formation of CaF₂ and thus significantly decrease the catalytic performance of hydroxyapatite. The hydrothermal time mainly affects the growth of hydroxyapatite crystals on the c axis, leading to different catalytic performance. The suitable conditions for the preparation of this fluoridized hydroxyapatite are as follows: a mass ratio of [Bmim]BF₄ to calcium salt =≥0.2:1, a hydrothermal time of 12 h, and a hydrothermal temperature of 130℃. A maximal methacrylic acid yield of 54.7% was obtained using the fluoridized hydroxyapatite under relatively mild reaction conditions (250℃ and 2 MPa of N₂) in the absence of a precious-metal catalyst and a corrosive homogeneous alkali.

Key words: Ionic liquid, Hydroxyapatite, Itaconic acid, Methacrylic, Decarboxylation reaction

摘要： The synthesis of methacrylic acid from biomass-derived itaconic acid is a green route, for it can get rid of the dependence on fossil resource. In order to solve the problems on this route such as use of a preciousmetal catalyst and a corrosive homogeneous alkali, we prepared a series of hydroxyapatite catalysts by an ionic liquid-assisted hydrothermal method and evaluated their catalytic performance. The results showed that the ionic liquid [Bmim]BF₄ can affect the crystal growth of hydroxyapatite, provide fluoride ion for fluorination of hydroxyapatite, and adjust the surface acidity and basicity, morphology, textural properties, crystallinity, and composition of hydroxyapatite. The [Bmim]BF₄ dosage and hydrothermal temperature can affect the fluoride ion concentration in the hydrothermal system, thus changing the degree of fluoridation of hydroxyapatite. High fluoride-ion concentration can lead to the formation of CaF₂ and thus significantly decrease the catalytic performance of hydroxyapatite. The hydrothermal time mainly affects the growth of hydroxyapatite crystals on the c axis, leading to different catalytic performance. The suitable conditions for the preparation of this fluoridized hydroxyapatite are as follows: a mass ratio of [Bmim]BF₄ to calcium salt =≥0.2:1, a hydrothermal time of 12 h, and a hydrothermal temperature of 130℃. A maximal methacrylic acid yield of 54.7% was obtained using the fluoridized hydroxyapatite under relatively mild reaction conditions (250℃ and 2 MPa of N₂) in the absence of a precious-metal catalyst and a corrosive homogeneous alkali.

关键词: Ionic liquid, Hydroxyapatite, Itaconic acid, Methacrylic, Decarboxylation reaction