载体对其负载的Cu-Co双金属催化剂上5-羟甲基糠醛氢解选择性生成2,5-二甲基呋喃的影响

碳-氧键氢解是生物质呋喃基化合物制备交通燃料常见的模型反应,其中5-羟甲基糠醛(HMF)转化为汽油添加剂2,5-二甲基呋喃(DMF)尤为引人关注.本文采用CeO2,ZrO2和Al2O3负载的Cu-Co双金属催化剂用于HMF选择性氢解制DMF的反应中.采用X射线衍射、N2吸附-脱附、投射电镜、H2-程序升温还原、氨-程序升温脱附和元素分析表征了新鲜的和使用过催化剂的结构,并将其与催化活性相关联.Cu-Co/CeO2催化剂通过在大的Cu颗粒上还原C=O键生成了最多的2,5双(羟甲基呋喃)(BHMF).但Cu-Co/Al2O3催化剂具有高度分散的Cu,Cu-Co复合氧化物和大量的弱酸位,因而生成DMF的选择性最高.Cu-Co/ZrO2催化剂则由于存在强酸位,DMF选择性较低,生成了各种过度氢解产物,如2,5而甲基四氢呋喃和5,5-二(亚甲基)双(2-甲基呋喃).因此,考察了Cu-Co/Al2O3催化剂上的反应路径,以及温度、氢气压力和时间等操作条件的影响,使其具有较优的HMF转化率和DMF选择性.

Influence of supports for selective production of 2,5-dimethylfuran via bimetallic copper-cobalt catalyzed 5-hydroxymethylfurfural hydrogenolysis

The hydrogenolysis of carbon-oxygen bonds is an important model reaction in upgrading biomass-derived furanic compounds to transportation fuels.One of these model reactions,namely conversion of 5-hydroxymethylfurfural (HMF) to the gasoline additive 2,5-dimethylfuran (DMF),is especially attractive.In this study,bimetallic Cu-Co catalysts supported on CeO2,ZrO2,and Al203 were used for the selective hydrogenolysis of HMF to DMF.The structures of the fresh and used catalysts were studied using X-ray diffraction,the Brunauer-Emmett-Teller method,transmission electron microscopy,temperature-programmed reduction by H2,temperature-programmed desorption of NH3,and CHNS analysis.The structures were correlated with the catalytic activities.The Cu-Co/CeO2 catalyst produced mainly 2,5-bis(hydroxymethyl)furan via reduction of C=O bonds on large Cu particles.The Cu-Co/Al2O3 catalyst gave the best selectivity for DMF,as a result of a combination of highly dispersed Cu,mixed copper-cobalt oxides,and suitable weak acidic sites.Cu-Co/ZrO2 had low selectivity for DMF and produced a combination of various over-hydrogenolysis products,including 2,5-dimethyltetrahydrofuran and 5,5-oxybis(methylene)-bis(2-methylfuran),because of the presence of strong acidic sites.The reaction pathways and effects of various operating parameters,namely temperature,H2 pressure,and time,were studied to enable optimization of the selective conversion of HMF to DMF over the Cu-Co/Al2O3 catalyst.