负载型磷化钼的原位还原制备及其加氢脱硫反应活性

PREPARATION OF THE SUPPORTED MoP BY IN SITU REDUCTION AND ITS PERFORMANCE IN HYDRODESULFURIZATION

以SiO2为载体,用钼酸铵和磷酸氢二铵作钼源和磷源,采用共浸渍法制备了负载型磷化钼氧化态前体;在固定床反应器上,用H2原位还原制备了MoP/SiO2催化剂。在温度360℃、压力5.0 MPa和液时空速21 h-1的条件下,用二苯并噻吩的加氢脱硫反应(HDS)对所制备的磷化钼催化剂进行了活性评价;考察了活性组分担载量和原位还原反应条件对催化剂活性的影响。结果表明,MoP的最佳担载量为25%(质量分数),适宜的原位还原反应条件为:升温速率r≤5℃/min,H2流量F≥80 ml/min,总压p≥1.0 MPa,还原终温0θ≥600℃。XRD表征结果表明,催化剂的活性相为MoP。原位还原法制备的MoP/SiO2催化剂的加氢脱硫活性高于传统的还原-钝化-还原法制备的催化剂。

Silica supported molybdenum phosphides were prepared in a fixed bed reactor by an in situ reduction method from their oxidic precursors. The precursors were obtained by impregation of silica in an aqueous solution of ammonium heptamolybdate tetrahydrate [（NH4）6MoTO24.4H2O] and diammonium hydrogen phosphate [（NH4 ）2 HPO4], followed by drying at 120℃ and calcining at 500℃ in air. The performance of the prepared molybdenum phospide catalyst in hydrodesulfurization （HDS） was evaluated in the same fixed bed reactor with 0. 8% （mass fraction） dibenzothiophene in decalin as the feed at temperature 360℃, pressure 5.0 MPa and MHSV 21 h^-1. It was shown that both the total loading of the active species and the in situ reduction condition had great influence on the HDS performance of the prepared catalysts. Highest performance was observed at a total loading of 25% （mass fraction）. The favorable conditions of the in situ reduction were as follows： heating rate r≤5℃/min, H2 flow rate F≥80 ml/min, total pressure p≥ 1.0 MPa and reduction temperature θ0）600℃. XRD characterization revealed that the active phase in HDS was MoP crystals. The activity of supported MoP catalysts prepared by the in situ reduction method was superior to that by the conventional reduction-passivation-reduction method in HDS of DBT.