Structure–performance relations of molybdenum- and tungsten carbide catalysts for deoxygenation

Stellwagen, Daniel R.; Bitter, Johannes H.

doi:10.1039/c4gc01831a

Cited by 128 publications

(105 citation statements)

References 26 publications

(61 reference statements)

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“…Additionally, Mo2C was less sensitive to oxidation compared with W2C. The oxide phase was found to be responsible for dehydration reactions and thus producing unsaturated hydrocarbons (Stellwagen and Bitter, 2015). Hence, it seems that a tradeoff exists between catalytic activity and selectivity toward olefins.…”

Section: Transition Metal Carbides Nitrides and Phosphidesmentioning

confidence: 99%

“…The effect of time, particularly in batch and semi-batch reactors, is typically evaluated to obtain useful information about deoxygenation pathways as well as product evolution (Foraita et al, 2017). Reaction pathways are interesting because they enable scientists to rationally design new catalytic systems, while product evolution over time may indicate an opportunity to maximize the yield of some products (Stellwagen and Bitter, 2015). Although longer reaction times guarantee higher conversions and normally the production of saturated compounds under H2 atmosphere (Immer et …”

Section: Contact Timementioning

confidence: 99%

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A comprehensive review on biodiesel purification and upgrading

2017

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HIGHLIGHTS Various biodiesel purification methods, i.e., equilibrium-based, affinity-based, and reaction-based separation techniques along with membrane technology and solid-liquid separation processes were reviewed.Deoxygenating process via hydrodeoxygenation and decarboxylation/decarbonylation pathways is a common way to upgrade bio-based oils to produce biorenewable diesel with excellent fuel properties. Catalysts and operating conditions, i.e., pressure, temperature, and contact time, are the most important variables in biodiesel upgrading discussed herein. Serious environmental concerns regarding the use of fossil-based fuels have raised awareness regarding the necessity of alternative clean fuels and energy carriers. Biodiesel is considered a clean, biodegradable, and non-toxic diesel substitute produced via the transesterification of triglycerides with an alcohol in the presence of a proper catalyst. After initial separation of the by-product (glycerol), the crude biodiesel needs to be purified to meet the standard specifications prior to marketing. The presence of impurities in the biodiesel not only significantly affects its engine performance but also complicates its handling and storage. Therefore, biodiesel purification is an essential step prior to marketing. Biodiesel purification methods can be classified based on the nature of the process into equilibrium-based, affinity-based, membrane-based, reaction-based, and solid-liquid separation processes. The main adverse properties of biodiesel -namely moisture absorption, corrosiveness, and high viscosity -primarily arise from the presence of oxygen. To address these issues, several upgrading techniques have been proposed, among which catalytic (hydro)deoxygenation using conventional hydrotreating catalysts, supported metallic materials, and most recently transition metals in various forms appear promising. Nevertheless, catalyst deactivation (via coking) and/or inadequacy of product yields necessitate further research. This paper provides a comprehensive overview on the techniques and methods used for biodiesel purification and upgrading. ABSTRACT

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Section: Transition Metal Carbides Nitrides and Phosphidesmentioning

confidence: 99%

Section: Contact Timementioning

confidence: 99%

A comprehensive review on biodiesel purification and upgrading

2017

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“…Novel catalysts, such as metal carbides and nitrides, have also been investigated as potential hydrotreating catalysts over the past several decades [4][5][6], in part because of their noble metal-like catalytic properties [7][8][9][10]. Sajkowski and Oyama [11] reported that a Mo2C/Al2O3 catalyst had twice the HDS activity of a conventional MoS2 catalyst when measured at 633 K and 13.0 MPa H2 using a gas oil with 116 ppm S. The comparison was made based on the number of active sites as measured by CO uptake.…”

Section: Introductionmentioning

confidence: 99%

Preparation of Ni-Mo 2 C/carbon catalysts and their stability in the HDS of dibenzothiophene

Wang

Liu

Govindarajan

et al. 2017

Applied Catalysis A: General

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“…Carbon-based supports are particularly attractive given that the substrate is capable of acting as the carbon source in the synthesis of the catalyst, eliminating the need for carburization gases. Indeed, metal carbides supported on activated carbon (AC) [12,13], ordered mesoporous carbon (OMC) [14], carbon nanofibers (CNF) [2,[15][16][17] and carbon nanotubes (CNT) [18] have already shown promising activity and stability in the deoxygenation of biomass-derived molecules. The performance of these supported carbides is in most cases superior to that of the bulk molybdenum carbide as a result of improved active site accessibility through greater dispersion of carbide phases on the carbon supports [12].…”

Section: Introductionmentioning

confidence: 99%

Activated Carbon, Carbon Nanofiber and Carbon Nanotube Supported Molybdenum Carbide Catalysts for the Hydrodeoxygenation of Guaiacol

et al. 2015

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Abstract:Molybdenum carbide was supported on three types of carbon support-activated carbon; multi-walled carbon nanotubes; and carbon nanofibers-using ammonium molybdate and molybdic acid as Mo precursors. The use of activated carbon as support afforded an X-ray amorphous Mo phase, whereas crystalline molybdenum carbide phases were obtained on carbon nanofibers and, in some cases, on carbon nanotubes. When the resulting catalysts were tested in the hydrodeoxygenation (HDO) of guaiacol in dodecane, catechol and phenol were obtained as the main products, although in some instances significant amounts of cyclohexane were produced. The observation of catechol in all reaction mixtures suggests that guaiacol was converted into phenol via sequential demethylation and HDO, although the simultaneous occurrence of a direct demethoxylation pathway cannot be discounted. Catalysts based on carbon nanofibers generally afforded the highest yields of phenol; notably, the only crystalline phase detected in these samples was Mo2C or Mo2C-ζ, suggesting that crystalline Mo2C is particularly selective to phenol. At 350 °C, carbon nanofiber supported Mo2C afforded near quantitative guaiacol conversion, the selectivity to phenol approaching 50%. When guaiacol HDO was performed in the presence of acetic acid and furfural, guaiacol conversion decreased, although the selectivity to both catechol and phenol was increased. OPEN ACCESSCatalysts 2015, 5 425

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Structure–performance relations of molybdenum- and tungsten carbide catalysts for deoxygenation

Abstract: Tungsten- and molybdenum carbide catalysts of large particle size improve activity, stability and selectivity of the catalyst in (hydro)deoxygenation reactions.

Cited by 128 publications

References 26 publications

A comprehensive review on biodiesel purification and upgrading

A comprehensive review on biodiesel purification and upgrading

Preparation of Ni-Mo 2 C/carbon catalysts and their stability in the HDS of dibenzothiophene

Activated Carbon, Carbon Nanofiber and Carbon Nanotube Supported Molybdenum Carbide Catalysts for the Hydrodeoxygenation of Guaiacol

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