以类水滑石为前体的铜基催化剂催化甘油氢解反应

以Cu-Zn-Al和Cu-Mg-Al类水滑石为前体经焙烧、还原制备了铜基催化剂,采用XRD、H2-TPR、N2吸附、H2-TPD、NH3-TPD、CO2-TPD及活性评价等方法,研究了M2+离子(M2+=Zn2+或Mg2+)及n(M2+)/n(Al3+)比对催化剂结构和甘油氢解反应性能的影响。结果表明,经450℃焙烧后,类水滑石转变为由尖晶石和/或氧化物组成的氧化态前驱体,再经270℃还原后制得高分散Cu催化剂。随氧化铝含量提高,催化剂比表面及酸量增加。Cu-Zn-Al催化剂表面氢吸附量大于CuMg-Al。Cu-Mg-Al催化剂碱性强于Cu-Zn-Al。Cu-Zn-Al[n(Cu)∶n(Zn)∶n(Al)=1∶1∶4]催化剂具有较佳甘油氢解活性及1,2-丙二醇选择性,这与其具有较多表面铜中心、较大酸量及Zn物种参与氢吸附有关。此外,Cu-Mg-Al催化剂表面铜中心和碱中心可能存在协同作用促进甘油氢解反应。     

Glycerol Hydrogenolysis to 1,2-Propanediol by Cu/ZnO/Al2O3 Catalysts

The effect of preparation methods on the Cu/ZnO/Al₂O₃ catalyst structure and catalytic activity on liquid glycerol hydrogenolysis to 1,2-propanediol has been investigated. The physicochemical properties of the catalysts were characterized by BET, XRD, TG/DTA, NH₃-TPD and TPR. The experimental results showed that the catalyst prepared by an oxalate gel–coprecipitation had the highest activity. At 200 °C and 400 psi hydrogen pressure, the glycerol conversion and 1,2-propanediol selectivity catalyzed by the Cu/ZnO/Al₂O₃ catalyst prepared via oxalate gel–coprecipitation were 92.3 and 94.5 % respectively. It was found that the 1,2-propanediol selectivity was dependent on hydrogen pressure and the un-desired by-products were mainly due to the side reactions caused by the presence of the intermediate acetol.     

Glycerol Hydrogenolysis to 1,2-Propanediol by Cu/ZnO/Al2O3 Catalysts

The effect of preparation methods on the Cu/ZnO/Al₂O₃ catalyst structure and catalytic activity on liquid glycerol hydrogenolysis to 1,2-propanediol has been investigated. The physicochemical properties of the catalysts were characterized by BET, XRD, TG/DTA, NH₃-TPD and TPR. The experimental results showed that the catalyst prepared by an oxalate gel–coprecipitation had the highest activity. At 200 °C and 400 psi hydrogen pressure, the glycerol conversion and 1,2-propanediol selectivity catalyzed by the Cu/ZnO/Al₂O₃ catalyst prepared via oxalate gel–coprecipitation were 92.3 and 94.5 % respectively. It was found that the 1,2-propanediol selectivity was dependent on hydrogen pressure and the un-desired by-products were mainly due to the side reactions caused by the presence of the intermediate acetol.

     

硼改性Cu/Al_2O_3催化甘油氢解反应合成1,2-丙二醇

采用分步浸渍法制备了硼改性Cu/Al2O3催化剂,利用XRD、FTIR、UV-Vis、N2吸附、H2-TPR、NH3-TPD和N2O解离吸附等方法对其结构进行了表征,研究了硼改性对催化剂结构及其催化甘油氢解反应性能的影响。结果表明,先浸渍硼再浸渍Cu时,随硼含量提高,催化剂酸量和Cu分散度增加,Cu与硼物种的相互作用增强。先浸渍Cu后浸渍硼时,催化剂的酸量提高、Cu物种分散程度变化不明显。先浸渍硼明显提高了Cu/Al2O3活性及1,2-丙二醇选择性。在220℃、3 MPa、质量空速2.0 h-1及H2/甘油比为20的条件下,随硼含量提高,甘油转化率及1,2-丙二醇选择性呈现增大趋势,其中硼含量为2%的催化剂上甘油转化率及1,2-丙二醇选择性分别达到99.9%和96.2%。硼改性对Cu/Al2O3催化性能的促进作用与催化剂酸性提高及Cu与B之间的相互作用有关。     

甘油氢解合成1,2-丙二醇铜锌铝催化剂的性能

采用共沉淀法制备了铜锌铝类水滑石前驱体,经焙烧和还原后制得铜基催化剂。采用XRD、H₂-TPR、H₂-TPD、NH₃-TPD和CO₂-TPD等表征手段并结合甘油氢解反应评价,研究了类水滑石前驱体的老化对催化剂结构和性能的影响,考察了反应条件对催化剂甘油氢解反应性能的影响。结果表明,老化有利于形成结构更为完整的类水滑石前驱体,但对铜物种的还原性能未造成显著影响。与由未老化前驱体制备的催化剂相比,由老化前驱体制备的铜锌铝催化剂具有较大Cu表面及较大酸量,但表面碱中心数量较低,从而该催化剂具有较好的甘油氢解活性及稳定性。在220 ℃、H₂压力3.0 MPa、n(H₂)/n(甘油)为18.9、甘油重时空速1.26 h^-1及质量分数为60%甘油水溶液的条件下,经老化前驱体制备的铜锌铝催化剂上甘油转化率接近100%、1, 2-丙二醇选择性约为96%。     

甘油氢解制1,2-丙二醇Cu/ZrO_2催化剂的稀土改性

用等体积浸渍法制备了稀土改性的Zr O2负载铜催化剂,考察其在质量分数40%甘油水溶液进料时气相氢解制1,2-丙二醇反应的性能,并用比表面积及孔径分析仪(BET)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)和氢气程序升温还原(H2-TPR)表征了催化剂的孔结构、形貌、晶相和还原性。典型的氢解反应条件为220℃、1MPa、氢与甘油的摩尔比值为100,液时空速为0.25 g甘油/(g催化剂·h)。首先在预实验中对Al2O3、Si O2和Zr O23种载体进行对比实验,发现未改性的负载铜催化剂均不稳定。浸渍Ce改性的Cu/Si O2催化剂稳定性有较大改善,但只维持700 h左右。接着考察用共沉淀法在Zr O2载体中添加稀土元素铈(Ce)、镧(La)和钇(Y)的改性效果,发现均能显著提高催化活性和选择性,而加Y稳定的氧化锆(YSZ)载体性能最佳。最后浸渍Ce对Cu/YSZ催化剂进行改性,并对Ce的含量进行了优化,结果证明,18%Cu~4%Ce O2/YSZ(均为质量分数)催化剂活性和选择性最佳,1,2-丙二醇得率超过93%。该催化剂具有开放性孔结构,比表面积达到107 m2/g,前躯体中Cu O晶粒最小,还原温度最低。对最优条件下制备的催化剂进行了长运转考察,稳定运行超过1 600 h,1,2-丙二醇收率维持在94%以上。     

甘油催化氢解制1,2-丙二醇的研究进展

综述了甘油催化氢解制1,2-丙二醇的研究进展。除了Ru、Cu等催化剂,Ag和Co催化剂也对甘油氢解反应有催化活性。载体、制备方法以及使用环境等都对催化剂性能有一定影响。其中,Cu催化剂价格相对低廉,对1,2-丙二醇选择性较高,可回收利用,满足工业化需求。最后对原位氢解机理和直接氢解机理进行解释说明。     

Resin-Based Catalysts for the Hydrogenolysis of Glycerol to Propylene Glycol

Three alkysulfonic resins were obtained by co-polymerization of 2-acrylamido-2-methyl-propansulfonic acid with N,N-dimethylacrylamide and ethylene dimethacrylate (the cross-linker), with respectively 4, 20 and 40 mol% cross-linking degree (DAE26-4, DAE26-20, DAE26-40). These resins were employed as acidic components in physical mixtures with Ru/C (5 %, w/w) or as supports for bifunctional ruthenium and copper catalysts, to be used in the hydrogenolysis of glycerol (20 %, w/w, in water). The physical mixtures were more efficient than the bifunctional catalysts, but temperatures as high as 200 °C are required to obtain an appreciable activity. However, in view of their relatively high thermal stability in comparison with the sulfonated polystyrene-divinylbenzene ion-exchange catalysts employed so far they can withstand this temperature, while Amberlyst 70 cannot be employed above 180–190 °C. Interestingly, the catalytic systems based on physical mixtures of DAE with Ru/C resins at 200 °C are much more selective towards propylene glycol than those containing A70 are at 180 °C.     

Glycerol Hydrogenolysis over Co Catalysts Derived from a Layered Double Hydroxide Precursor

Abstract  

Co catalysts, obtained from a layered double Co–Zn–Al hydroxide, are highly active and stable towards the hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO) in aqueous media. The Co-673 catalyst, containing a CoO species, provided a glycerol conversion of 67.7% and a 1,2-PDO selectivity of 50.5%. The Co-873 catalyst comprising 16 nm Co nanoparticles gave a glycerol conversion of 70.6% and a 1,2-PDO selectivity of 57.8%. It was revealed that the CoO species in the Co-673 catalyst was readily converted to 50 nm Co particles under the glycerol hydrogenolysis conditions. The Co catalysts maintained a stable size and phase in recycling tests.     

Gas‐Phase Hydrogenolysis of Glycerol Catalyzed by Cu/MOx Catalysts

The catalytic activities of Cu/MO_x (MO_x = Al₂O₃, TiO₂, and ZnO) catalysts in the gas‐phase hydrogenolysis of glycerol were studied at 180–300 °C under 0.1 MPa of H₂. Cu/MO_x (MO_x = Al₂O₃, TiO₂, and ZnO) catalysts were prepared by the incipient wetness impregnation method. After reduction, CuO species were converted to metallic copper (Cu⁰). Cu/Al₂O₃ catalysts with high acidity, high specific surface areas and small metallic copper size favored the formation of 1,2‐propanediol with a maximum selectivity of 87.9 % at complete conversion of glycerol and a low reaction temperature of 180 °C, and favored the formation of ethylene glycol and monohydric alcohols at high reaction temperature of 300 °C. Cu/TiO₂ and Cu/ZnO catalysts exhibited high catalytic activity toward the formation of hydroxyacetone with a selectivity of approx. 90 % in a wide range of reaction temperature.     

The Selective Oxidation of 1,2-Propanediol by Supported Gold-Based Nanoparticulate Catalysts

The oxidation of 1,2-propanediol to form lactic acid and hydroxyacetone has been investigated using supported metal nanoparticles. A series of supported gold, palladium, platinum and combinations of these metals have been investigated. In the presence of base the major product formed is lactate, often in excellent yields as, under these conditions the terminal hydroxyl group is oxidised. In the absence of base, more vigorous conditions are required to elicit high conversions; surprisingly, a major product from such reactions is a mono-oxidation product hydroxyacetone, along with lactate.     

Ni-Cu双金属催化剂上甘油催化转移氢解制备1,2-丙二醇

采用等体积浸渍法制备了一系列Ni-Cu/γ-Al2O3双金属催化剂.考察了Ni/Cu质量比、金属负载量和不同供氢体等因素对甘油催化转移氢解制备丙二醇反应的影响.结果表明:当Ni/Cu质量比为3∶2时,催化剂表现出最好的催化活性.当催化剂Ni-Cu总负载量为25％(15Ni-10Cu/γ-Al2O3)时,在甲酸和甲醇两种供氢体条件下均具有最佳催化效果,尤其以甲酸为供氢体时效果更好,在220℃下反应16h,甘油转化率达85.2％,1,2-丙二醇的选择性为80.4％.     

甘油氢解制二元醇的研究进展

近年来,随着国内外生物柴油产业的快速发展,生成大量副产物甘油,合理利用过剩的甘油将有助于整个生物柴油产业的经济效益。本文针对以甘油为底物,催化氢解合成高附加值二元醇的研究进行了综述,介绍了甘油催化氢解成二元醇的反应机理和研究现状,并对发展前景作了展望。     

微生物转化甘油生产1,3-丙二醇的研究进展

甘油是油裂解和生物柴油生产过程中的主要副产物,生物柴油市场的蓬勃发展将会造成甘油价格的下降。这些甘油-水混合物不用再次处理就可以直接用于微生物发酵。在众多甘油的利用当中,附加值最高的应该是1,3-丙二醇(PDO),利用甘油在厌氧条件下发酵生产PDO与传统工艺相比产物浓度从70～80g/L提高到了100g/L,而且如果用固定化细胞发酵,产率可以从2g/(L·h)提高到30g/(L·h)。综述了微生物转化甘油为1,3-丙二醇的研究进展。     

甘油生物歧化为1,3-丙二醇过程的优化控制

An iterative optimization strategy is proposed and applied to the steady state optimizing control of the bio-dissimilation process of glycerol to 1,3-propanediol in the presence of model-plant mismatch and input con-straints. The scheme is based on the Augmented Integrated System Optimization and Parameter Estimation (AI-SOPE) technique, but a linearization of some performance function in the modified model-based optimization problem of AISOPE is introduced to overcome the difficulty of determining an appropriate penalty parameter.When carrying out the iterative optimization, the penalty coefficient is set to a larger value at the current iteration than at the previous iteration, which can promote the evolution rate of the iterative optimization. Simulation studies illustrate the potential of the approach presented for the optimizing control of the bio-dissimilation process of glyc-erol to 1,3-propanediol. The effects of measurement noise, measured and unmeasured disturbances on the proposed algorithm are also investigated.     

Hydrogenolysis of Glycerol to Propanediol Over Ru: Polyoxometalate Bifunctional Catalyst

Ruthenium-doped (5 wt%) acidic heteropoly salt Cs_2.5H_0.5[PW₁₂O₄₀] (CsPW) is an active bifunctional catalyst for the one-pot hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO) in liquid phase, providing 96% selectivity to 1,2-PDO at 21% glycerol conversion at 150 °C and an unprecedented low hydrogen pressure of 5 bar. Rhodium catalyst, 5%Rh/CsPW, although less active, shows considerable selectivity to 1,3-PDO (7.1%), with 1,2-PDO being the main product (65%).