Cu/MoO_3-TiO_2光催化CO_2与C_3H_6反应合成甲基丙烯酸的性能

Photocatalytic Synthesis of Methacrylic Acid from CO_2 and C_3H_6 on Cu/MoO_3-TiO_2

研究了Cu/MoO3 TiO2 上CO2 和C3 H6的吸附特性及其光催化CO2 与C3 H6反应合成甲基丙烯酸 (MAA)的性能 .结果表明 ,在Cu/MoO3 TiO2 催化剂表面存在金属Cu位、Lewis酸位Mo6+ 和Ti4+ 以及Lewis碱位Mo-O -Ti的桥氧和Mo=O的端氧三类活性中心 .在金属Cu位和Lewis酸位Ti4+ (Mo6+ )的协同作用下 ,CO2 形成活性较高的卧式吸附态Cu- (CO) -O→Ti4+ (Mo6+ ) ,C3 H6的 β H和 β C分别吸附在Lewis碱位 Mo=O与金属Cu位上形成Cu -C(CH2 ) (CH3 ) -H→O =Mo吸附态 .Cu/MoO3 TiO2 催化剂吸收阈值蓝移和光吸收量的提高均有利于其催化活性的提高 ,Cu/ 10 %MoO3 TiO2 光催化剂的催化活性优于其它MoO3 含量的催化剂 ,光量子产率达 2 2 8% ,在 110℃ ,0 1MPa ,空速 2 0 0h-1和 12 5W紫外灯辐照下 ,C3 H6转化率为 8 4 % ,MAA选择性超过 95 % .提出了催化剂光促表面催化CO2 与C3 H6合成MAA的反应机理 .

Photocatalytic synthesis of hydrocarbon oxygenates from CO 2 and hydrocarbons is of great importance to environmental protection, utilization of carbon resources and synthetic chemistry. The adsorption property of CO 2 and C 3H 6 and the photo-stimulated surface reaction to synthesize methacrylic acid (MAA) from CO 2 and C 3H 6 on the Cu/MoO 3-TiO 2 catalyst were studied. The experimental results pointed out that there existed three kinds of active sites on the surface of Cu/MoO 3-TiO 2 catalyst: metallic site Cu, Lewis acid sites Mo 6+ and Ti 4+, Lewis base sites bridge O in Mo-O-Ti and terminal O in Mo=O. Chemisorbed CO 2 on the surface of Cu/MoO 3-TiO 2 catalyst formed high active horizontal state Cu-(CO)-O→Ti 4+(Mo 6+) by the synergic action of metallic site Cu and Lewis acid sites Ti 4+ (Mo 6+), while dual-sites adsorption of β-H and β-C of C 3H 6, which formed state Cu-C(CH 2)(CH 3)-H→ O=Mo, had been found mainly on the Lewis base site Mo=O and the metallic site Cu, respectively. The blue-shift of band edge of absorption spectra and the increase of luminous absorption capacity on Cu/MoO 3-TiO 2 catalyst improved the catalytic activity of Cu/MoO 3-TiO 2. Photo-quantum efficiency of the surface reaction of CO 2 and C 3H 6 on Cu/10%MoO 3-TiO 2 was the highest, which reached 22 8%, and the selectivity for MAA was over 95% under the proper reaction conditions (p=0 1 MPa, SV=200 h -1, T=383 K and power=125 W). Based on the experimental results, a possible mechanism was proposed for the photo-stimulated surface reaction of CO 2 and C 3H 6 to synthesize MAA on Cu/MoO 3-TiO 2 catalyst.