炭载体对Pt-C复合物非碱性条件下催化甘油氧化性能的影响

采用等量浸渍法制备了具有相似平均粒径的活性炭(AC)和碳纳米管(CNTs)负载的Pt催化剂,并比较研究了非碱性条件下两种催化剂催化甘油氧化反应的性能。结果表明,炭载体对Pt-C复合物催化甘油氧化反应的活性、选择性和稳定性有重要影响。相对于Pt/CNTs催化剂,Pt/AC催化剂中Pt 4f结合能较低,导致其表面氧的覆盖度相对较高,因而抑制了甘油的吸附,降低了甘油氧化反应的初始活性;Pt/AC催化剂会促进甘油醛进一步氧化成甘油酸以及C3产物的氧化断键;Pt/AC催化剂失活的主要原因是氧中毒和中间产物的吸附,而Pt/CNTs催化剂的失活主要是由于甘油酸的吸附堵塞Pt表面的活性位造成的。     

非碱性条件下磷酸镍钴分子筛对甘油催化氧化反应研究

采用水热合成法制备了磷酸镍钴分子筛(Co-VSB-1),将焙烧后的样品作为催化剂,在非碱性条件下以H2O2作为氧化剂用于甘油的催化氧化反应,考察了反应时间、温度以及H2O2和甘油摩尔比对甘油催化活性和选择性的影响。结果表明:Co-VSB-1作为催化剂对甘油酸和甲酸具有较高的选择性,当n(H2O2)∶n(甘油)=2∶1,反应时间为4 h,反应温度为70℃时,甘油的转化率为8.2%,甘油酸、甲酸和乙醇酸的选择性分别为45.1%,49.9%和5.0%。同时,通过催化性能实验,发现Co-VSB-1骨架中的钴离子作为催化活性中心对甘油的氧化起到了催化作用。     

新型载体对VOCs催化氧化反应性能的影响

综述了近些年来国内外科研工作者在VOCs催化氧化催化剂载体方面的创新性工作,包括金属氧化物载体、柱撑黏土载体(PILCs)、三维有序大孔材料(3DOM)载体、分子筛等载体用于VOCs催化氧化反应,并分析了载体结构特征、孔道结构、表面物理化学性质及活性组分的分散作用等对催化反应效果的影响,从而为高性能催化氧化催化剂载体的设计、研发及优化提供建议。     

新型载体对VOCs催化氧化反应性能的影响

综述了近些年来国内外科研工作者在VOCs催化氧化催化剂载体方面的创新性工作,包括金属氧化物载体、柱撑黏土载体(PILCs)、三维有序大孔材料(3DOM)载体、分子筛等载体用于VOCs催化氧化反应,并分析了载体结构特征、孔道结构、表面物理化学性质及活性组分的分散作用等对催化反应效果的影响,从而为高性能催化氧化催化剂载体的设计、研发及优化提供建议。     

制备条件对生物炭载铁催化剂催化破络Ni-EDTA性能及活性组分浸出的影响

为加强木质素高值化利用,以木质素和铁盐为原料,采用共热解法制备木质素生物炭载铁催化剂。考察铁源前体类型、铁负载量、升温速率和热解温度等制备条件对催化剂催化破络Ni-乙二胺四乙酸（EDTA）性能和铁活性组分浸出的影响,并结合不同热解温度下催化剂孔隙结构、表面元素及晶体结构等表征分析,系统阐述热解温度对催化剂性能的影响机制。结果表明,铁源前体类型直接决定催化剂表面元素组成、极性及Fe活性组分分布情况,以硝酸铁为铁源前体时催化剂性能最佳。负载铁活性物种有助于增加催化剂表面活性位点数量,升温速率可以改变生物炭孔隙结构,热解温度则决定生物炭碳质结构的形成及对Fe活性组分的固载能力。随着热解温度的升高,Fe活性组分逐渐向催化剂内部迁移,600℃时Fe浸出量始终低于1.0mg/L,催化氧化过程由均相Fenton反应为主向非均相反应转变;与此同时,催化剂表面O、N、S活性位点减少,其共同作用致使催化剂失活和Ni-EDTA破络效果降低。上述结果为以木质素生物炭为催化剂载体设计与制备提供了基础数据。     

不同载体的催化剂对臭氧催化氧化性能的影响

为考察不同载体的催化剂对臭氧非均相催化氧化处理煤化工废水的影响,选取了市面上常见的铝基和碳基载体催化剂,并对催化剂的比表面积和强度等理化指标进行表征测试.以废水的COD为考察指标,研究了不同载体催化剂的吸附性能及催化氧化性能.结果表明:铝基催化剂机械强度更高(最高为125.22 N),碳基催化剂比表面积较大,高达102...     

氧化硅载体对Ir-Re双金属的结构及其催化甘油氢解的影响

采用3 种氧化硅载体KIT-6、G-6 和FS 制备了Ir-Re 双金属催化剂,并应用于甘油选择性氢解制备1,3-丙二醇,采用TEM、XRD、H₂-TPR、CO-DRIFTS 和NH3-TPD 等手段详细表征了催化剂结构,并探讨其构效关系。研究结果表明: 3 种催化剂表面的Ir-Re 双金属催化剂均形成了Ir-Re 合金结构, 合金化程度为Ir-Re/KIT-6 > Ir-Re/FS > Ir-Re/G-6;载体表面羟基含量显著影响Ir-Re 纳米粒子的分散度及其与载体的相互作用。Ir-Re/FS 的金属分散度最高,甘油氢解的初始活性最高但稳定性最差;而具有良好合金结构的Ir-Re/KIT-6 在甘油氢解中表现出良好的氢解活性和最高的1,3-丙二醇选择性。     

甘油选择性氧化的催化体系研究进展

甘油是生物柴油生产过程中的副产物,甘油选择性氧化制备高值含氧衍生物开辟了从生物质到有机酸的生产路径,有效缓解了甘油大量过剩的困境并创造了潜在利用价值。论述了甘油高值转化为甘油酸和二羟基丙酮的催化体系研究进展,重点研究了Au基、Pd基、Pt基贵金属催化剂的催化性能,旨在提高甘油酸和二羟基丙酮的选择性,并介绍了催化剂的反应机理、催化剂失活的可能性以及相应的改进措施。     

过氧化氢催化氧化载体的研究进展

本文介绍有关过氧化氢的催化氧化反应,并重点介绍了其反应过程中的各种催化剂载体的研究进展,比如硅胶、分子筛、活性炭等载体。     

Promotional effect of hydroxyl on the aqueous phase oxidation of carbon monoxide and glycerol over supported Au catalysts

Gold particles supported on carbon and titania were explored as catalysts for oxidation of CO or glycerol by O₂ at room temperature in liquid-phase water. Although Au/carbon catalysts were not active for vapor phase CO oxidation at room temperature, a turnover frequency of 5 s⁻¹ could be achieved with comparable CO concentration in aqueous solution containing 1 M NaOH. The turnover frequency on Au/carbon was a strong function of pH, decreasing by about a factor of 50 when the pH decreased from 14 to 0.3. Evidently, a catalytic oxidation route that was not available in the vapor phase is enabled by operation in the liquid water at high pH. Since Au/titania is active for vapor phase CO oxidation, the role of water, and therefore hydroxyl concentration, is not as significant as that for Au/carbon. Hydrogen peroxide is also produced during CO oxidation over Au in liquid water and increasing the hydroxyl concentration enhances its formation rate. For glycerol oxidation to glyceric acid (C₃) and glycolic acid (C₂) with O₂ (1–10 atm) at 308–333 K over supported Au particles, high pH is required for catalysis to occur. Similar to CO oxidation in liquid water, H₂O₂ is also produced during glycerol oxidation at high pH. The formation of the C-C cleavage product glycolic acid is attributed to peroxide in the reaction.     

Zn(Al)O复合氧化物负载Au催化剂催化氧化甘油制备1,3-二羟基丙酮

以尿素为沉淀剂,采用均匀沉积沉淀法制备了Zn(Al)O复合氧化物负载Au催化剂,并用于无碱条件下催化氧化甘油制备1,3-二羟基丙酮（DHA）反应,值得注意的是随着载体中Zn/Al摩尔比的不同,负载Au催化剂的催化活性和产物DHA的选择性呈现明显差距。结合X射线衍射（XRD）、X射线光电子能谱（XPS）、透射电镜（TEM）、CO吸附傅里叶变换红外光谱（CO吸附FTIR）等表征手段,发现载体Zn(Al)O复合氧化物中Zn/Al摩尔比会影响表面氧物种的含量并进一步会影响催化剂的催化活性和选择性。当Zn/Al摩尔比为7∶1、反应温度为80℃、氧气压力为10bar、反应2h时获得最佳的甘油转化率（58.5%）和DHA的选择性（95.3%）。同时,还考察了反应温度、反应时间、反应压力及载体的焙烧温度对催化性能的影响,并发现反应条件对催化剂的催化活性和选择性均有不同程度的影响。此外,以Au/Zn(Al)O-7∶1催化剂为基准考察了催化剂的稳定性,并通过表征手段分析了催化剂失活的主要原因。     

Selective oxidation of glycerol over nitrogen-doped carbon nanotubes supported platinum catalyst in base-free solution

In this communication, N-doped multiwall carbon nanotube (N-MWCNT) supported Pt NPs (1.8 nm) were prepared via a facile routine under microwave irradiation and tested in the selective oxidation of glycerol in an aqueous base-free solution. Characterizations confirmed that N-MWCNTs could improve the dispersion of Pt through strengthened metal-support interactions and donate its electron to metallic Pt. This electron-enriched Pt NPs on the surface of N-MWCNTs is active and stable for the selective oxidation of glycerol.     

Nitric oxide reduction and carbon monoxide oxidation over carbon-supported copper-chromium catalysts

Carbon supported copper-chromium catalysts are shown to be very active for both the reduction of nitric oxide with carbon monoxide and the oxidation of carbon monoxide with oxygen. Mixed copper-chromium oxide active phases have good activity in the simultaneous removal of nitric oxide and carbon monoxide from exhaust gases. The influence of several catalyst variables has been investigated. The activity per volume of catalyst increases with increasing loading, while the intrinsic activity shows a maximum around C/M=100−50. An optimum catalyst for nitric oxide reduction and carbon monoxide oxidation has a copper/chromium ratio of 2/1. The apparent activation energy for the carbon monoxide oxidation over carbon supported copper-chromium catalysts is 77 kJ/mol, suggesting that the Cu---O bond rupture is the rate-limiting process. The reduction of nitric oxide takes place at higher temperatures. Since all catalysts have a low selectivity for molecular nitrogen formation at lower temperatures, the dissociation of nitric oxide is probably rate determining, resulting in a slightly reduced catalyst system. In an excess of carbon monoxide the reaction is first-order in nitric oxide and zero-order in carbon monoxide. Moisture inhibits the reaction by reversible competitive adsorption, whereas carbon dioxide does not. Oxygen completely inhibits the reduction of nitric oxide due to the more rapid reoxidation of the catalytic sites compared to nitric oxide. Therefore, the reduction of nitric oxide takes place only when all oxygen has been converted and, hence, is shifted to higher temperatures. As a possible consequence, the production of nitrous oxide is reduced. Nitric oxide and molecular oxygen react preferentially with carbon monoxide, so, in an excess of oxidizing component, gasification of the carbon support occurs at higher temperatures after carbon monoxide has been completely consumed.     

An experimental and theoretical study of glycerol oxidation to 1,3‐dihydroxyacetone over bimetallic Pt‐Bi catalysts

It is important to utilize glycerol, the main by‐product of biodiesel, to manufacture value‐added chemicals such as 1,3‐dihydroxyacetone (DHA). In the present work, the performance of five different catalysts (Pt‐Bi/AC, Pt‐Bi/ZSM‐5, Pt/MCM‐41, Pt‐Bi/MCM‐41, and Pt/Bi‐doped‐MCM‐41) was investigated experimentally, where Pt‐Bi/MCM‐41 was found to exhibit the highest DHA yield. To better understand the experimental results and to obtain insight into the reaction mechanism, density functional theory (DFT) computations were conducted to provide energy barriers of elementary steps. Both experimental and calculated results show that for high DHA selectivity, Bi should be located in an adatom‐like configuration Pt, rather than inside Pt. A favorable pathway and catalytic cycle of DHA formation were proposed based on the DFT results. A cooperative effect, between Pt as the primary component and Bi as a promoter, was identified for DHA formation. Both experimental and theoretical considerations demonstrate that Pt‐Bi is efficient to convert glycerol to DHA selectively. © 2016 American Institute of Chemical Engineers AIChE J, 63: 705–715, 2017     

甘油催化氧化合成二羟基丙酮研究进展

对甘油选择性催化氧化转化为二羟基丙酮的研究进行综述,介绍了负载型催化剂在不同条件下对产物选择性和反应物转化率的影响,以及催化剂的作用机理。阐述了甘油催化氧化存在的问题以及发展前景。从均相到非均相催化,从单金属到双金属负载催化,从金属到非金属催化,甘油氧化反应的研究不断在完善。研究发现用Bi改性的Pt负载催化剂可以有效地将甘油选择性催化氧化为二羟基丙酮,在最优条件下,可获得较高的甘油转化率和二羟基丙酮选择性,但催化剂稳定性较差,有待进一步提高。杂多酸催化剂以及非金属催化剂也存在稳定性差的问题。指出改善催化剂的稳定性将是未来研究的主要方向。