过渡金属改性的Pt／n-Al2O3在肉桂醛加氢反应中的催化性能

用NaBH4作还原剂,制备了中性氧化铝（n-Al2O3）负载的Pt-M（M=Fe,Co,Ni,Cu,Mn,Sn）双金属催化剂。考察了过渡金属及反应条件对Pt-M／n·Al2O3催化肉桂醛加氢制肉桂醇的影响。结果表明,Fe改性的Pt／n-Al2O3对催化肉桂醛加氢制肉桂醇具有较好的催化性能,当Pt-Fe／n—Al2O3（中性）催化剂中Pt、Fe的含量均为0．3％时,在70℃,2MPa氢气条件下反应1．5h,肉桂醛的转化率为100％,肉桂醇选择性高达84．8％。     

掺杂Co对CNTs负载Pt催化剂上肉桂醛选择性催化加氢性能的影响

研究了Co的掺杂对Pt/CNTs催化剂催化加氢肉桂醛反应性能的影响。结果发现, Co的掺杂对Pt/CNTs催化剂催化加氢活性起到明显促进作用, 并有利于C＝O基团的选择性加氢。Pt-0.17% Co/CNTs催化剂显示了较高的肉桂醇加氢选择性, 在反应条件为70℃、2 MPa和1.5 h时, 肉桂醛的加氢转化率达到97.1％,生成肉桂醇的选择性达到93.6％。同时, 初步研究了该催化剂上肉桂醛催化加氢反应动力学, 催化反应的活化能为26.5 kJ•mol^-1。     

Pt/Fe_3O_4@C磁响应核壳催化剂上肉桂醛选择性加氢性能

采用溶剂热法合成了Pt/Fe3O4@C磁响应核壳催化剂,以扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)和超导量子干涉磁强计(SQUID)对催化剂的结构和磁性质进行了表征。研究发现Pt颗粒均匀地分散在碳层上,Pt/Fe3O4@C催化剂显示了良好的超顺磁性。研究了Pt/Fe3O4@C磁响应催化剂上肉桂醛(CAL)的选择性加氢反应,结果显示催化剂具有良好的C=O加氢活性,在考察的条件下,肉桂醛转化率在60%左右时,肉桂醇选择性可达96%以上。催化剂在外加磁场作用下可以高效地从液相反应体系中分离,经多次循环使用后仍具有良好的催化性能。     

共沉淀法制备氧化铝负载铜催化剂及其在肉桂醛选择性加氢反应中的应用

采用共沉淀法制备了Al2O3负载Cu催化剂,表征了其晶相、孔结构、表面形貌,考察了制备条件对催化肉桂醛加氢性能的影响. 结果表明,与浸渍法所制催化剂相比,共沉淀法所制催化剂具有更高的肉桂醛加氢活性;随焙烧温度升高,催化剂活性组分粒径增大,肉桂醛的转化率先升高后下降,873 K还原的催化剂的活性最高;随反应温度升高,反应速率迅速上升,肉桂醇的选择性则下降. 在2 MPa和363 K条件下,反应4 h后肉桂醛的转化率为14.7%,肉桂醇的选择性为56.5%.     

氧-氮等离子体表面改性石墨烯用于α,β-不饱和醛水相加氢反应

使用冷等离子体表面改性技术在石墨烯表面引入适量含氮基团,通过优化等离子体气源、等离子体放电功率、放电时间和工作气压等工艺条件,高效制备具有两亲表面的氮掺杂石墨烯(NDGR)。采用傅里叶变换红外光谱(FT-IR)、拉曼光谱仪(Raman)、有机元素分析(OEA)、透射电子显微镜(TEM)和水接触角(WCA)等方法对其进行表征。接着以NDGR为载体,制备铂纳米催化剂Pt/NDGR,用于肉桂醛和巴豆醛水相加氢反应。结果表明,采用等离子体两步接枝工艺,即先以氧气(O2)为等离子体气源活化石墨烯表面,再以氨(NH3)为等离子体气源在石墨烯表面接枝含氮基团得到的氮掺杂石墨烯NDGR(O2-NH3)具有最佳的表面性质。与原始石墨烯负载Pt催化剂(Pt/GR)相比,最佳条件 (放电功率140 W, 工作气压200 Pa,放电时间6 min) 下制备的NDGR(O2-NH3)负载Pt催化剂Pt/NDGR(O2-NH3)在肉桂醛(CAL)和巴豆醛(CRAL)水相加氢反应中显示出优良的催化性能。反应条件为80 ℃,3 MPa下,Pt/NDGR(O2-NH3)在4 h内催化肉桂醛的转化率达98%,对不饱和醇肉桂醇(COL)保持高选择性(约84%);而在巴豆醛水相加氢反应中,Pt/NDGR(O-NH)的表观速率常数kapp达0.53 h-1,远高于Pt/GR (0.37 h-1)。接近完全反应时,Pt/NDGR(O-NH3)亦对巴豆醇(CROL)保持了高选择性(约40%)。Pt/NPGR(O2-NH3)的高催化性能得益于石墨烯表面接枝少量含氮基团后表面性质的增强,包括Pt纳米粒子锚定位点的增加、对底物的高吸附性能以及金属-载体间协同作用。     

Co-Fe/硅藻土催化剂上肉桂醛的选择加氢——反应性能的研究

在固定床反应器中对肉桂醛选择加氢制肉桂醇的反应性能进行了研究。考察了Co-Fe催化剂的活性和选择性;Co负载量、助剂Fe对催化剂选择加氢性能的影响;考察了反应温度、压力、H2的空速等对肉桂醛在催化剂上加氢性能的影响。结果表明,钴/硅藻土催化剂的最佳钴负载量为12%,助催化剂和主催化剂的最佳比为Fe/Co=0.20(mol/mol)。最佳反应温度为423 K,反应的压力越高越有利于催化反应,但压力大于4 MPa后,肉桂醛的转化率和肉桂醇的选择性提高幅度不大,宜控制在4 MPa左右。空速对肉桂醇的选择性影响不大,但空速越高肉桂醛的转化率越低,催化反应中宜控制较低的氢气空速为佳。     

PtSn-丝光沸石催化剂的制备及其肉桂醛加氢性能的研究

利用微乳液法制备了一系列Fe和Sn改性的Pt基催化剂,并将其应用于肉桂醛选择性加氢反应中。通过XRD、TEM、FT-IR、BET、XPS等对催化剂的结构和性质进行表征。结果表明,丝光沸石分子筛可以较好地分散活性组分,双组分负载的催化材料仍保持较好的介孔结构,适量Sn组分的加入提高了Pt物种的分散度,并使Pt物种处于富电子状态。在3.0MPa、80℃条件下,Pt-1Sn-2/H-丝光沸石催化剂的最优催化性能为:肉桂醛转化率为74.0%,肉桂醇选择性为77.0%。催化剂的重复循环反应测试结果表明,催化剂活性组分基本没有流失,催化剂稳定性较好。     

肉桂醛选择性加氢Co-Fe/硅藻土催化剂稳定性考察

通过肉桂醛在高压微反固定床上24 h的催化加氢反应,考察了肉桂醛选择加氢的催化剂Co-Fe/硅藻土稳定性。结果表明,肉桂醛选择加氢催化剂Co-Fe/硅藻土在反应初期存在反应的诱导期,诱导期后,肉桂醛转化率70%,肉桂醇选择性80%,肉桂醇收率可达60%以上,且催化性能趋于平稳,表现出良好的催化性能和稳定性。利用XRD、SEM、TG-DSC对反应前后催化剂结构进行表征,发现催化剂经24 h反应,结构不变,表面颗粒分布更细化,无积炭迹象。     

Mucor sp.JX23发酵液生物催化肉桂醛选择加氢制肉桂醇

研究了Mucor sp. JX23发酵液直接生物催化肉桂醛选择加氢制肉桂醇的反应,并考察了肉桂醛质量浓度、反应pH值、温度、时间等因素对反应转化率和选择性的影响。结果表明,Mucor sp. JX23发酵液的最适催化条件为：肉桂醛质量浓度3 g/L,反应体系的初始pH = 6.0,28℃反应70h。在此条件下,肉桂醛的转化率为82.9%,肉桂醇的选择性为90.4%。     

Co—Fe催藻土催化剂上肉桂醛的选择加氢——反应性能的研究

在固定床反应器中对肉桂醛选择加氢制肉桂醇的反应性能进行了研究。考察了Co-Fe催化剂的活性和选择性;Co负载量、助剂Fe对催化剂选择加氢性能的影响;考察了反应温度、压力、H2的空速等对肉桂醛在催化剂上加氢性能的影响。结果表明,钴／硅藻土催化剂的最佳钴负载量为12％,助催化剂和主催化剂的最佳比为Fe／Co=0．20（mol／mol）。最佳反应温度为423K,反应的压力越高越有利于催化反应,但压力大于4MVa后,肉桂醛的转化率和肉桂醇的选择性提高幅度不大,宜控制在4MVa左右。空速对肉桂醇的选择性影响不大,但空速越高肉桂醛的转化率越低,催化反应中宜控制较低的氢气空速为佳。     

Selective Hydrogenation of Cinnamaldehyde over Pt/ZrO2 Catalyst Modified by Cr, Mn, Fe, Co and Ni

Hydrogenation properties of cinnamaldehyde (CMA) have been studied over Pt/ZrO₂ and PtM/ZrO₂ catalysts (M = Cr, Mn, Fe, Co and Ni) in ethanol at 343 K and 2.0 MPa. The effect of different content of Ni and base has also been investigated over PtNi/ZrO₂ catalyst. With introduction of transition metals to Pt/ZrO₂ catalyst shows a significant influence on the catalytic properties. PtCo/ZrO₂ catalysts show the best yield of cinnamyl alcohol (CMO), and PtNi/ZrO₂ catalyst shows good yield of hydrocinnamaldehyde (HCMA). In the presence of base solution, rate of the hydrogenation of CMA over PtNi/ZrO₂(0.4 wt%) catalyst increases significantly and side reaction is remarkably inhibited. More bare metal atoms situated remote from the interface region on PtNi/ZrO₂ catalyst surface are the reason of good selectivity of HCMA for PtNi/ZrO₂ catalyst.     

Influence of Preparation Modes on Pt–Ni/CNTs Catalysts Used in the Selective Hydrogenation of Cinnamaldehyde to Hydrocinnamaldehyde

Pt–Ni/CNTs catalysts are prepared by different impregnation techniques and different reduction methods (H₂, HCHO, and KBH₄) for the selective hydrogenation of cinnamaldehyde (CMA) to hydrocinnamaldehyde (HCMA) and investigated by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and temperature programmed reduction (H₂-TPR) techniques. The results show that the catalytic selectivity and activity of the Pt–Ni/CNTs catalysts would significantly be improved by using KBH₄ as a reducing agent, due to the electronic synergetic effect of Pt–Ni–B, and 96% for conversion of CMA and 88% for selectivity of HCMA are obtained over Pt–Ni/CNTs catalyst reduced by KBH₄. Furthermore, the hydrogenation rate of CMA and selectivity of CMA to HCMA over Pt–Ni/CNTs catalyst are significantly improved in the presence of trace base or acid promoters again. The best result (92% for conversion of CMA and 96% for selectivity of HCMA) is obtained when NaOAc is used as base promoter.     

镍基纳米SiC-Al2O3复合电刷镀层的组织及性能

在45#钢基体上制备了n-Al2O3/Ni和n-SiC–Al2O3/Ni复合刷镀层,采用能谱仪(EDS)、X射线衍射仪(XRD)、扫描电镜(SEM)和T-11球盘式磨损试验机等设备对比研究了2种复合刷镀层的组织及性能。EDS分析结果表明,n–Al2O3/Ni复合刷镀层中纳米颗粒特征元素Al的质量分数为5.65%,n-SiC–Al2O3/Ni复合刷镀层中纳米颗粒特征元素Al的质量分数为5.63%,Si元素的质量分数为4.86%。SEM分析结果表明,与n-Al2O3/Ni复合刷镀层相比,n-SiC–Al2O3/Ni复合刷镀层的表面更加平整,组织更加细化。n-SiC–Al2O3/Ni和n-Al2O3/Ni复合刷镀层的显微硬度分别为587HV和555HV,n-SiC–Al2O3/Ni复合刷镀层的耐磨性是n-Al2O3/Ni复合刷镀层的1.7倍。     

Selective hydrogenation of (E)-2-hexenal to (E)-2-hexen-1-ol over Co-based bimetallic catalysts

Hydrogenation of (E)-2-hexenal was carried out in a liquid phase using Co-based bimetallic catalysts (M–Co/Al₂O₃, M=Pd, Pt, Ru, Rh, Sn, Fe, or Cu). Pd–Co/Al₂O₃ showed the highest activity among the catalysts tested and catalyzed the hydrogenation of CC bond predominantly to produce hexanal and 1-hexanol. Pt–Co/Al₂O₃ was more active than monometallic Co/Al₂O₃ for the hydrogenation of CO bond. The excellent result, 92% selectivity to (E)-2-hexen-1-ol formation at 90% conversion, was obtained by the hydrogenation over Pt–Co/Al₂O₃ bimetallic catalyst. No improved activities were observed for the other bimetallic catalysts.     

Synthesis and Catalytic Performance of Highly Ordered Ru-Containing Mesoporous Carbons for Hydrogenation of Cinnamaldehyde

Highly ordered Ru-containing mesoporous carbons (Ru-OMC) were for the first time synthesized by a one-pot method. Comparing with our previously reported Ir-OMC, the Ru precursor must be added after the formaldehyde was consumed by polycondensation with resorcinol to obtain a small particle size. The resultant Ru-OMC samples with different Ru contents were characterized with X-ray diffraction (XRD), N₂ adsorption-desorption, and Transmission electron microscopy (TEM). The results evidenced the formation of highly ordered mesostructure, in which Ru particles were imbedded. The new carbon materials were further evaluated in the selective hydrogenation of cinnamaldehyde (CMA). By comparison with the traditional Ru/AC catalyst, our Ru-OMC samples exhibited much higher activity (2–14-fold) and up to 60% of selectivity to cinnamyl alcohol (CMO).