Microemulsion Derived Titania Nanospheres: An Improved Pt Supported Catalyst for Glycerol Aqueous Phase Reforming

Glycerol aqueous phase reforming (APR) produces hydrogen and interesting compounds at relatively mild temperatures. Among APR catalysts investigated in literature, little attention has been given to Pt supported on TiO2. Therefore, herein we propose an innovative titania support which can be obtained through an optimized microemulsion technique. This procedure provided high surface area titania nanospheres, with a peculiar high density of weak acidic sites. The material was tested in the catalytic glycerol APR after Pt deposition. A mechanism hypothesis was drawn, which evidenced the pathways giving the main products. When compared with a commercial TiO2 support, the synthetized titania provided higher hydrogen selectivity and glycerol conversion thanks to improved catalytic activity and ability to prompt consecutive dehydrogenation reactions. This was correlated to an enhanced cooperation between Pt nanoparticles and the acid sites of the support.

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Cobalt-Based Metal Organic Frameworks as Solids Catalysts for Oxidation Reactions

Catalysts ◽

10.3390/catal11010095 ◽

2021 ◽

Vol 11 (1) ◽

pp. 95

Author(s):

Amarajothi Dhakshinamoorthy ◽

Eva Montero Lanzuela ◽

Sergio Navalon ◽

Hermenegildo Garcia

Keyword(s):

Aerobic Oxidation ◽

High Surface ◽

Metal Organic Frameworks ◽

High Surface Area ◽

Acid Sites ◽

Crystalline Lattice ◽

Oxidation Reactions ◽

Solid Catalysts ◽

Long Term Stability ◽

Metal Organic

Metal organic frameworks (MOFs) are porous crystalline solids whose frameworks are constituted by metal ions/nodes with rigid organic linkers leading to the formation of materials having high surface area and pore volume. One of the unique features of MOFs is the presence of coordinatively unsaturated metal sites in their crystalline lattice that can act as Lewis acid sites promoting organic transformations, including aerobic oxidation reactions of various substrates such as hydrocarbons, alcohols, and sulfides. This review article summarizes the existing Co-based MOFs for oxidation reactions organized according to the nature of substrates like hydrocarbon, alcohol, olefin, and water. Both aerobic conditions and peroxide oxidants are discussed. Emphasis is placed on comparing the advantages of using MOFs as solid catalysts with respect to homogeneous salts in terms of product selectivity and long-term stability. The final section provides our view on future developments in this field.

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Impact of Thermal Treatment of Nb2O5 on Its Performance in Glucose Dehydration to 5-Hydroxymethylfurfural in Water

Nanomaterials ◽

10.3390/nano10091685 ◽

2020 ◽

Vol 10 (9) ◽

pp. 1685

Author(s):

Katarzyna Morawa Eblagon ◽

Anna Malaika ◽

Karolina Ptaszynska ◽

Manuel Fernando R. Pereira ◽

José Luís Figueiredo

Keyword(s):

Thermal Treatment ◽

Surface Area ◽

Pure Water ◽

High Surface ◽

High Surface Area ◽

Acid Sites ◽

High Ratio ◽

Total Acidity ◽

One Pot ◽

Niobic Acid

The cascade dehydration of glucose to 5-hydroxymethylfurfural (HMF) was carried out in water over a series of Nb2O5 catalysts, which were derived from the thermal treatment of niobic acid at 300 and 550 °C, under air or inert atmosphere. Amorphous niobic acid showed high surface area (366 m2/g) and large acidity (2.35 mmol/g). With increasing the temperature of the thermal treatment up to 550 °C, the amorphous Nb2O5 was gradually transformed into a pseudohexagonal phase, resulting in a decrease in surface area (27–39 m2/g) and total acidity (0.05–0.19 mmol/g). The catalysts’ performance in cascade dehydration of glucose realized in pure water was strongly influenced by the total acidity of these materials. A remarkable yield of 37% HMF in one-pot reaction in water was achieved using mesoporous amorphous niobium oxide prepared by thermal treatment of niobic acid at 300 °C in air. The best-performing catalyst displayed a total acidity lower than niobic acid (1.69 mmol/g) which afforded a correct balance between a high glucose conversion and limited further conversion of the target product to numerous polymers and humins. On the other hand, the treatment of niobic acid at 550 °C, independently of the atmosphere used during the sample preparation (i.e., air or N2), resulted in Nb2O5 catalysts with a high ratio of Lewis to Brønsted acid sites and poor total acidity. These materials excelled at catalyzing the isomerization step in the tandem process.

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High purity hydrogen production via aqueous phase reforming of xylose over small Pt nanoparticles on a γ-Al2O3 support

International Journal of Hydrogen Energy ◽

10.1016/j.ijhydene.2020.03.014 ◽

2020 ◽

Vol 45 (27) ◽

pp. 13848-13861 ◽

Cited By ~ 2

Author(s):

Yoondo Kim ◽

Minkyeong Kim ◽

Hyangsoo Jeong ◽

Yongmin Kim ◽

Sun Hee Choi ◽

...

Keyword(s):

Hydrogen Production ◽

Aqueous Phase ◽

High Purity ◽

Pt Nanoparticles ◽

Aqueous Phase Reforming ◽

Al2o3 Support ◽

High Purity Hydrogen

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Promoting Li/MgO Catalyst with Molybdenum Oxide for Oxidative Conversion of n-Hexane

Catalysts ◽

10.3390/catal10030354 ◽

2020 ◽

Vol 10 (3) ◽

pp. 354 ◽

Cited By ~ 1

Author(s):

Cassia Boyadjian ◽

Leon Lefferts

Keyword(s):

Raman Spectroscopy ◽

High Surface ◽

High Surface Area ◽

Deep Oxidation ◽

Oxidative Conversion ◽

X Ray Diffraction ◽

X Ray ◽

Anionic Species ◽

Dehydrogenation Reactions ◽

Lithium Molybdate

In this work, molybdena-promoted Li/MgO is studied as a catalyst for the oxidative conversion of n-hexane. The structure of the catalysts is investigated with X-ray Diffraction (XRD) and Raman spectroscopy. The MoO3/Li/MgO catalyst contains three types of molybdena-containing species, the presence of which depend on molybdena loading. At low Mo/Li ratios (i) isolated dispersed [MoO4]2− anionic species are observed. At high Mo/Li ratios, the formation of crystalline lithium molybdate phases such as (ii) monomeric Li2MoO4 and tentatively (iii) polymeric Li2Mo4O13 are concluded. The presence of these lithium molybdates diminishes the formation of Li2CO3 in the catalyst. Subsequently, the catalyst maintains high surface area and stability with time-on-stream during oxidative conversion. Molybdena loading as low as 0.5 wt % is sufficient to induce these improvements, maintaining the non-redox characteristics of the catalyst, whereas higher loadings enhance deep oxidation and oxidative dehydrogenation reactions. Promoting a Li/MgO catalyst with 0.5 wt % MoO3 is thus efficient for selective conversion of n-hexane to alkenes, giving alkene yield up to 24% as well as good stability.

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Oriented Pt Nanoparticles Supported on Few-Layers Graphene as Highly Active Catalyst for Aqueous-Phase Reforming of Ethylene Glycol

ACS Applied Materials & Interfaces ◽

10.1021/acsami.6b11904 ◽

2016 ◽

Vol 8 (49) ◽

pp. 33690-33696 ◽

Cited By ~ 10

Author(s):

Iván Esteve-Adell ◽

Nadia Bakker ◽

Ana Primo ◽

Emiel Hensen ◽

Hermenegildo García

Keyword(s):

Ethylene Glycol ◽

Aqueous Phase ◽

Active Catalyst ◽

Pt Nanoparticles ◽

Aqueous Phase Reforming ◽

Highly Active

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Structure-dependent selective hydrogenation of cinnamaldehyde over high-surface-area CeO 2 -ZrO 2 composites supported Pt nanoparticles

Chemical Engineering Journal ◽

10.1016/j.cej.2017.04.026 ◽

2017 ◽

Vol 322 ◽

pp. 234-245 ◽

Cited By ~ 31

Author(s):

Shaoping Wei ◽

Yitong Zhao ◽

Guoli Fan ◽

Lan Yang ◽

Feng Li

Keyword(s):

Surface Area ◽

Selective Hydrogenation ◽

High Surface ◽

High Surface Area ◽

Pt Nanoparticles

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High Surface Area VOx/TiO2/SBA-15 Model Catalysts for Ammonia SCR Prepared by Atomic Layer Deposition

Catalysts ◽

10.3390/catal10121386 ◽

2020 ◽

Vol 10 (12) ◽

pp. 1386

Author(s):

Jun Shen ◽

Christian Hess

Keyword(s):

Atomic Layer Deposition ◽

Lewis Acid ◽

High Surface ◽

High Surface Area ◽

Atomic Layer ◽

Acid Sites ◽

Lewis Acid Sites ◽

X Ray ◽

Nox Conversion ◽

Layer Deposition

The mode of operation of titania-supported vanadia (VOx) catalysts for NOx abatement using ammonia selective catalytic reduction (NH3-SCR) is still vigorously debated. We introduce a new high surface area VOx/TiO2/SBA-15 model catalyst system based on mesoporous silica SBA-15 making use of atomic layer deposition (ALD) for controlled synthesis of titania and vanadia multilayers. The bulk and surface structure is characterized by X-ray diffraction (XRD), UV-vis and Raman spectroscopy, as well as X-ray photoelectron spectroscopy (XPS), revealing the presence of dispersed surface VOx species on amorphous TiO2 domains on SBA-15, forming hybrid Si–O–V and Ti–O–V linkages. Temperature-dependent analysis of the ammonia SCR catalytic activity reveals NOx conversion levels of up to ~60%. In situ and operando diffuse reflection IR Fourier transform (DRIFT) spectroscopy shows N–Hstretching modes, representing adsorbed ammonia and -NH2 and -NH intermediate structures on Bronsted and Lewis acid sites. Partial Lewis acid sites with adjacent redox sites are proposed as the active sites and desorption of product molecules as the rate-determining step at low temperature. The high NOx conversion is attributed to the presence of highly dispersed VOx species and the moderate acidity of VOx supported on TiO2/SBA-15.

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A simple aqueous phase synthesis of high surface area aluminum fluoride and its bulk and surface structure

Inorganica Chimica Acta ◽

10.1016/j.ica.2006.07.105 ◽

2006 ◽

Vol 359 (15) ◽

pp. 4851-4854 ◽

Cited By ~ 20

Author(s):

Wolfgang Kleist ◽

Carmen Haeßner ◽

Oksana Storcheva ◽

Klaus Köhler

Keyword(s):

Surface Structure ◽

Surface Area ◽

Aqueous Phase ◽

High Surface ◽

High Surface Area ◽

Aluminum Fluoride ◽

Phase Synthesis

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TEM study of supported catalyst clusters

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100089469 ◽

1991 ◽

Vol 49 ◽

pp. 1030-1031

Author(s):

M. H. Yao ◽

David J. Smith ◽

I. E. Wachs

Keyword(s):

Metal Oxide ◽

High Surface ◽

High Surface Area ◽

Supported Catalyst ◽

High Resolution Electron Microscopy ◽

Support Materials ◽

Direct Observations ◽

Resolution Electron ◽

Oxide Substrate ◽

Surface Metal

In the present work we have studied two-dimensional metal oxide overlayers (Re2O7, WO3, etc) deposited on a second high-surface-area metal oxide substrate (TiO2, Al2O3, etc). The molecular structure of these surface metal oxide species has been extensively studied in the past decade by Raman spectroscopy and EXAFS because of their importance in catalytic applications. However, direct observations of these overlayers are still needed in order to better understand the basic properties of the overlayer species. High resolution electron microscopy(HREM) is one of the most commonly used methods for direct characterization of small catalyst particles. It can provide particle size distributions and information about particle disposition over the support materials. But it is generally believed that bright field imaging is only well suited for particles sizes larger than about 10 Å. For smaller metal particles on typical supports, HAADF in STEM has been proposed as a better choice.

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