加压下Ni/MgO催化剂催化CO_2重整CH_4反应的特性

Catalytic Feature of Ni/MgO Catalyst for CO_2 Reforming of Methane under Pressurized Condition

以在流动N2中热处理的Mg(OH)2醇凝胶制得的纳米氧化镁(MgO AN)为载体,制备了Ni/MgO AN催化剂.这种催化剂在常压下的CO2重整CH4反应中表现出了高活性和稳定性,而在加压反应中的催化活性随着反应压力的升高而降低,并呈现出自稳定特性.采用TG,XRD和TPH技术对催化剂进行了表征.结果表明,常压反应中催化剂表面的积炭量很少,而在加压反应中催化剂表面有明显的积炭,且积炭量随着反应的进行逐渐增加,并在12h左右达到一个稳定值.催化剂的活性组分金属Ni在常压CO2重整CH4反应中不发生烧结长大,而在加压反应中发生明显的烧结.常压反应中催化剂表面只形成一种积炭物种,而在加压反应中形成两种积炭物种.因此,Ni/MgO AN在加压反应中的催化行为与常压反应中的有明显区别.

The Ni/MgO-AN catalyst, prepared by loading of Ni onto nano-magnesia (MgO-AN) obtained from thermal processing of a Mg(OH)(2) alcogel, Was used for CO) reforming of methane under different pressures (0. 1 similar to 2. 0 MPa). The catalyst exhibited high and stable activity under atmospheric pressure. However, the catalyst activity declined with increasing reaction pressure. Thermogravimetry, X-ray diffraction and temperature- programmed hydrogenation (TPH) characterization results showed that carbon deposition was very little on the catalyst reacted under atmospheric pressure. In contrast, serious carbon deposition was found on the catalyst reacted under 1. 0 similar to 2. 0 MPa. The amount of carbon deposits increased with the reaction time up to 12 h when it became stabilized, indicating a self -stabilization feature of the working catalyst at the high pressures. No significant sintering of metallic nickel was detected on the used catalyst in the reaction under atmospheric pressure whereas marked sintering happened in the high-pressure reaction. The carbon deposits on the catalyst used in the atmospheric pressure reaction appeared as a single peak on the TPH profile, but two peaks were observed for the samples used in the high-pressure reaction. These results demonstrate that the catalytic performance of Ni/MgO-AN was different under atmospheric and high pressures.