纳米催化剂在碳氢燃料和生物柴油领域中的应用

纳米材料因独特的结构特征而拥有了高效的催化性能,已被广泛应用于石油化工、能源、化学合成、生物和环保等多个领域。笔者聚焦于燃料领域,重点介绍了纳米催化剂在碳氢燃料的催化裂解及燃烧、新燃料的合成、生物柴油的制备和催化燃烧方面的应用进展,剖析了目前纳米催化剂研究中面临的问题,提出了理论结合实验推动纳米催化剂研究发展的观点。     

Au nanoparticles decorated on magnetic nanocomposite (GO-Fe3O4/Dop/Au) as a recoverable catalyst for degradation of methylene blue and methyl orange in water

In the present research, magnetically recyclable graphene oxide (GO)/dopamine hydrochloride/AuNPs nanocatalyst are prepared by a green path with Acorus calamus seeds extract as a stabilizing and reducing agent and its catalytic efficiency was used for the reduction of methylene blue (MB) and methyl orange (MO) in the presence of NaBH₄ as a reducing agent in the aqueous medium in the ambient conditions. The prepared nanocatalyst was characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), Fourier transformed infrared (FT-IR) spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and UV–Vis spectroscopy. The prepared nanocatalyst has good catalytic activity and can be regain by an external magnet and recycled several times without considerable loss of its catalytic activity in the process of reduction of organic dyes.     

Structural/texture evolution of CaO/MCM‐41 nanocatalyst by doping various amounts of cerium for active and stable catalyst: Biodiesel production from waste vegetable cooking oil

In present work, the aim of producing biodiesel from waste cooking oil was pursued by doping the cerium element into the MCM‐41 framework as catalyst with various Si/Ce molar ratio (5, 10, 25, 50, and Ce = 0). The catalytic performance and stability improved by employing the ultrasound irradiation in active phase loading step of catalyst preparation. The physicochemical characteristics of synthesized samples were investigated using various techniques as follows: Brunauer‐Emmett‐Teller (BET), X‐ray powder diffraction (XRD), Fourier transfer infrared (FTIR), energy‐dispersive X‐ray spectroscopy (EDX), transmission electron microscopy (TEM), and field emission scanning electron microscope (FESEM). The XRD patterns along with the results of FTIR and BET analysis revealed the MCM‐41 framework destruction while increasing the Ce content. The FESEM images of the nanocatalysts illustrated a well distribution and uniform morphology for the Ca/CeM (Si/Ce = 25). The particle size and size distribution of the Ca/CeM (Si/Ce = 25) were subsequently determined by TEM and FESEM images. The activity of fabricated nanocatalysts was evaluated by measuring the free acid methyl ester (FAME) content of produced biodiesel. The tests were carried out at constant operational conditions: T = 60°C, catalyst loading = 5 wt%, methanol/oil molar ratio = 9, and 6‐hour reaction time. A superior activity was observed for Ca/CeM (Si/Ce = 25) among other nanocatalysts with 96.8% conversion of triglycerides to biodiesel. The mentioned sample was utilized in five reaction cycles, and at the end of the fifth cycle, the conversion reached to 91.5% which demonstrated its significant stability.     

Hydrogen liberation from the dehydrocoupling of dimethylamine–borane at room temperature by using novel and highly monodispersed RuPtNi nanocatalysts decorated with graphene oxide

Addressed herein, we reported the fabrication of the graphene oxide (GO) supported monodispersed ruthenium–platinum–nickel (RuPtNi) nanomaterials (3.40 ± 0.32 nm) to be utilized as a catalyst in the process of dimethylamine borane (DMAB) dehydrogenation. The nanoparticles were fabricated through the ultrasonication method by co-reducing the Ru³⁺, Pt²⁺ and Ni²⁺ cations and then the nanomaterials were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), inductively coupled plasma optical emission spectrometry (ICP-OES), and X-ray photoelectron spectroscopy (XPS). The fabricated nanomaterials showed outstanding efficiency and remarkable reusability in addition to their record catalytic activity at low temperatures and with extreme low concentrations. They had a significantly high turnover frequency (TOF) (727 h^?1) and low activation energy (E_a) (49.43 ± 2 kJ mol^?1) for DMAB dehydrocoupling. To the best of our knowledge, RuPtNi@GO NPs become a very promising candidate as the best catalyst ever.     

Hierarchical porous metal-organic frameworks/polymer microparticles for enhanced catalytic degradation of organic contaminants

This work reports on a simple microfluidic strategy to controllably fabricate uniform polymeric microparticles containing hierarchical porous structures integrated with highly accessible catalytic metal organic frameworks for efficient degradation of organic contaminants. Monodisperse (W1/O)/W2 emulsion droplets generated from microfluidics are used as templates for the microparticle synthesis. The emulsion droplets contain tiny water microdroplets from homogenization and water nanodroplets from diffusion-induced swollen micelles as the dual pore-forming templates, and Fe-based metal-organic framework nanorods as the nanocatalysts. The obtained microparticles possess interconnected hierarchical porous structures decorated with highly accessible Fe-based metal-organic framework nanorods for enhanced degradation of organic contaminants via a heterogeneous Fenton-like reaction. Such a degradation performance is highlighted by using these microparticles for efficient degradation of rhodamine B in hydrogen peroxide solution. This work provides a simple and general strategy to flexibly combine hierarchical porous structures and catalytic metal-organic frameworks to engineer advanced microparticles for water decontamination.     

MoO3/TiO2纳米复合催化剂的合成及催化脱氢性能

采用溶胶-凝胶法合成MoO3/TiO2、K2O-MoO3/TiO2、V2O5-MoO3/TiO2、Al2O3-MoO3/TiO2、K2O-V2O5-MoO3/TiO2系列纳米催化剂。借助TEM、XRD、IR等技术对催化剂进行了表征,并利用环己烷催化氧化脱氢成环己烯的反应进行活性测试。结果表明,MoO3在载体TiO2呈单层和多层分布,单层分布时发生了Mo与O—Ti的键合作用,同时使TiO2表面水分子发生解离反应,活化时脱去—OH产生Mo6+和Mo—O-活性中心;多层分布时以Mo[FY=,1]O、Mo—O-活性物种为主。脱氢中心和供氧中心之间存在协同作用,K、Al、V均能影响其协同作用。     

In situ upgrading of bitumen and heavy oils via nanocatalysis

Thermal in situ bitumen production has introduced a different engineering approach compared to conventional oil exploitation. Steam injection for example, allows the development of a relatively confined liquid and gas chamber surrounding and along the length of the production wells. This heated place can be converted into a reactor for upgrading processes founding expectations of extensive reservoir upgrading of unconventional oils reducing the total energy currently required to both exploit the reservoir and surface upgrade the produced bitumen. These could also selectively transform contaminants into harmless products remaining in the reservoir. This article highlights the nanocatalytic in situ upgrading paths that may result in economical and environmentally efficient oil sands exploitation. © 2012 Canadian Society for Chemical Engineering     

Preparation and characterization of a PtRu/C nanocatalyst for direct methanol fuel cells

PtRu/C nanocatalysts were prepared by changing the molar ratio of citric acid to platinum and ruthenium metal salts (CA:PtRu) from 1:1, 2:1, 3:1 to 4:1 using sodium borohydride as a reducing agent. Transmission electron microscopy analysis indicated that well-dispersed smaller PtRu particles (2.6 nm) were obtained when the molar ratio was maintained at 1:1. X-ray diffraction analysis confirmed the formation of PtRu alloy; the atomic percentage of the alloy analyzed by the energy dispersive X-ray spectrum indicated an enrichment of Pt in the nanocatalyst. X-ray photoelectron spectroscopy measurements revealed that 83.34% of Pt and 79.54% of Ru were present in their metallic states. Both the linear sweep voltammetry and chronoamperometric results demonstrated that the 1:1 molar ratio catalyst exhibited a higher methanol oxidation current and a lower poisoning rate among all the other molar ratios catalysts. The CO stripping voltammetry studies showed that the E-TEK catalyst had a relatively higher CO oxidation current than did the 1:1 molar ratio catalyst. Testing of the PtRu/C catalysts at the anode of a direct methanol fuel cell (DMFC) indicated that the in-house PtRu/C nanocatalyst gave a slightly higher performance than did the E-TEK catalyst.     

An Efficient,Stable and Reusable Palladium Nanocatalyst: Chemoselective Reduction of Aldehydes with Molecular Hydrogen in Water

Palladium nanoparticles (Pd‐BNP) stabilized by a binaphthyl‐backbone can be efficiently used for the chemoselective reduction of aldehydes in the presence of hydrogen at room temperature in water. The Pd‐BNP catalyst is easily recovered and reused for five catalytic cycles.

     

Facile Synthesis of 7-Aryl-benzo[h]tetrazolo[5,1-b]quinazoline-5,6-dione Fused Polycyclic Compounds by Using a Novel Magnetic Polyurethane Catalyst

Novel Brönsted acid functionalized magnetic polymeric nanocomposite, Ba_0.5Sr_0.5Fe₁₂O₁₉@PU-SO₃H, has been successfully synthesized and characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) techniques. The catalytic activity of the nanocomposite was tested in the regioselective synthesis of 7-aryl-benzo[h]tetrazolo [5,1-b] quinazoline-5,6-diones in an eco-friendly and recyclable media, deep eutectic solvent (DES), based on choline chloride and urea. This novel method offers several advantages, such as high yields, short reaction time, environmentally friendly reaction media, easy isolation of the product, and also offers an easy method for the synthesis of nanocatalysts. The catalyst was readily recycled by the use of an external magnetic field and could be reused 6 times without significant loss of activity or mass. DES as one of the most promising environmentally benign and cost-effective alternatives to conventional ionic liquids and volatile organic solvents was recovered from the aqueous filtrate by evaporating the water under vacuum. The recycled DES was used up to 4 runs without any loss in activity.