Synthesis of Surface-Controlled CePO4 and Its Application for Catalyzed Decarbonylation of Lactic Acid to Acetaldehyde

摘要

abstract_textpCePO4 materials were prepared via reaction of cerous nitrate with phosphates such as Na3PO4, Na4P2O7, Na5P3O10 and (NH4)(x)H3-xPO4 (x=2, and 3) in aqueous solution, followed by calcination at 550(o)C under the air atmosphere. It was found that the uniform CePO4 indexed to JCPDS NO. 83-0650 was achieved no matter what the phosphates varied in the screened phosphate precursors. However, compared with relative intensity in the standard patterns with R(012)/(120) value of 0.715 (R(012)/(120), Intensity ratio between face (012) and face (120)), some samples obtained from Na4P2O7 and (NH4)(x)H3-xPO4 displayed an enhanced diffraction peak at 2 theta = 31.1(o), which ascribes to plane (012), while others obtained from Na3PO4 and Na5P3O10 were in good agreement with the standard sample (JCPDS NO. 83-0650, CePO4). Correlation between the crystal plane (012) and activity revealed that the enhanced crystal plane favored an enhancement of activity for decarbonylation of lactic acid to acetaldehyde. Effect of aqueous ammonia on catalytic performance of samples was also investigated. It was clearly seen that the sample obtained from Na4P2O7 offered an enhanced activity for decarbonylation of lactic acid as it was treated with aqueous ammonia while others almost remained unchanged or even decreased slightly. XRD patterns for the obtained sample from Na4P2O7 treated with aqueous ammonia disclosed that the diffraction peak at 2 theta = 31.1(o) increased, further demonstrating that crystal face (012) relates to activity of samples for decarbonylation of lactic acid. NH3 (CO2)-Temperature Programmed Desorption experiments suggested that the surface acid-base properties of catalysts related to the ratios of (012)/(120). Varying the catalyst preparation conditions such as calcination temperature and aqueous ammonia can control R(012)/(120) values, thus adjusting acid-base properties of catalysts. Stability experiments show that the catalyst has an acceptable durability, and the activity of the deactivated catalyst can be recovered by a simple calcination at 550 C-o in air./p/abstract_text