Formation Energetics and Guest—Host Interactions of Molybdenum Carbide Confined in Zeolite Y
29 Sep 2021-Industrial & Engineering Chemistry Research (American Chemical Society (ACS))-Vol. 60, Iss: 38, pp 13991-14003
About: This article is published in Industrial & Engineering Chemistry Research.The article was published on 2021-09-29. It has received 3 citations till now.
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TL;DR: In this paper , a series of catalysts with metallic nickel (Ni) and molybdenum carbide (Mo2C) particles supported on zeolite Y (Ni-Mo 2C/FAU) in a methane steam reforming (MSR) reaction at 850 °C was presented.
Abstract: We report the synthesis and characterization, reaction kinetics, and deactivation mechanism of a series of catalysts with metallic nickel (Ni) and molybdenum carbide (Mo2C) particles supported on zeolite Y (Ni-Mo2C/FAU) in methane steam reforming (MSR) reaction at 850 °C. Despite a low Ni loading of 2.4 wt%, MSR on Ni-Mo2C/FAU exhibits high activity and stability, yet deactivation of Ni-FAU is significant. Further investigations elucidate that the catalyst deactivation is caused by Ni particle sintering via Ostwald ripening instead of coking, and steam induces hydroxylated Ni surface that accelerates sintering. Moreover, Mo2C boosts the activity and stability of Ni on zeolite Y by enhancing CH4 activation rather than activating H2O. The interplays among Mo2C and Ni particles dynamically balance the carbon formation and consumption rates, and inhibit Ni sintering. This study demonstrates that high MSR activity and stability can be achieved on transition metal carbide – Ni catalysts with systematically tuned compositional, structural, and interfacial factors.
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TL;DR: Tungsten carbide catalyzes the formation of water from hydrogen and oxygen at room temperature, the reduction of tungsten trioxide by hydrogen in the presence of water, and the isomerization of 2,2-dimethylpropane to 2-methylbutane.
Abstract: Tungsten carbide catalyzes the formation of water from hydrogen and oxygen at room temperature, the reduction of tungsten trioxide by hydrogen in the presence of water, and the isomerization of 2,2-dimethylpropane to 2-methylbutane. This catalytic behavior, which is typical of platinum, is not exhibited at all by tungsten. The surface electronic properties of the latter are therefore modified by carbon in such a way that they resemble those of platinum.
1,738 citations
TL;DR: Fluid catalytic cracking (FCC) is one of the major conversion technologies in the oil refinery industry, and the largest commercial catalytic process that uses zeolite materials.
Abstract: Fluid catalytic cracking (FCC) is one of the major conversion technologies in the oil refinery industry. FCC currently produces the majority of the world's gasoline, as well as an important fraction of propylene for the polymer industry. In this critical review, we give an overview of the latest trends in this field of research. These trends include ways to make it possible to process either very heavy or very light crude oil fractions as well as to co-process biomass-based oxygenates with regular crude oil fractions, and convert these more complex feedstocks in an increasing amount of propylene and diesel-range fuels. After providing some general background of the FCC process, including a short history as well as details on the process, reactor design, chemical reactions involved and catalyst material, we will discuss several trends in FCC catalysis research by focusing on ways to improve the zeolite structure stability, propylene selectivity and the overall catalyst accessibility by (a) the addition of rare earth elements and phosphorus, (b) constructing hierarchical pores systems and (c) the introduction of new zeolite structures. In addition, we present an overview of the state-of-the-art micro-spectroscopy methods for characterizing FCC catalysts at the single particle level. These new characterization tools are able to explain the influence of the harsh FCC processing conditions (e.g. steam) and the presence of various metal poisons (e.g. V, Fe and Ni) in the crude oil feedstocks on the 3-D structure and accessibility of FCC catalyst materials.
632 citations
TL;DR: The application of zeolites, equipped with a variety of active sites, in Brønsted acid, Lewis acid, or multifunctional catalysed reactions is discussed and generalised to provide a comprehensive overview.
Abstract: Increasing demand for sustainable chemicals and fuels has pushed academia and industry to search for alternative feedstocks replacing crude oil in traditional refineries. As a result, an immense academic attention has focused on the valorisation of biomass (components) and derived intermediates to generate valuable platform chemicals and fuels. Zeolite catalysis plays a distinct role in many of these biomass conversion routes. This contribution emphasizes the progress and potential in zeolite catalysed biomass conversions and relates these to concepts established in existing petrochemical processes. The application of zeolites, equipped with a variety of active sites, in Bronsted acid, Lewis acid, or multifunctional catalysed reactions is discussed and generalised to provide a comprehensive overview. In addition, the feedstock shift from crude oil to biomass involves new challenges in developing fields, like mesoporosity and pore interconnectivity of zeolites and stability of zeolites in liquid phase. Finally, the future challenges and perspectives of zeolites in the processing of biomass conversion are discussed.
568 citations
TL;DR: In this article, the authors review and discuss the developments that have taken place in the field of biomass conversion using zeolites and put emphasis on the conversion of lignocellulosic material to fuels using conventional zeolite as well as conversion of sugars using Lewis acidic zeolate to produce useful chemicals.
Abstract: Heterogeneous catalysts have been a central element in the efficient conversion of fossil resources to fuels and chemicals, but their role in biomass utilization is more ambiguous. Zeolites constitute a promising class of heterogeneous catalysts and developments in recent years have demonstrated their potential to find broad use in the conversion of biomass. In this perspective we review and discuss the developments that have taken place in the field of biomass conversion using zeolites. Emphasis is put on the conversion of lignocellulosic material to fuels using conventional zeolites as well as conversion of sugars using Lewis acidic zeolites to produce useful chemicals.
402 citations
TL;DR: The thermodynamics of this process, the catalysts used and the potential reactor configurations that can be applied are discussed, and carbon formation is inevitable, but the experimental findings show this can be kinetically limited by the use of H2 or oxidants in the feed, including CO2 or steam.
Abstract: Recent developments in natural gas production technology have led to lower prices for methane and renewed interest in converting methane to higher value products Processes such as those based on syngas from methane reforming are being investigated Another option is methane aromatization, which produces benzene and hydrogen: 6CH4(g) → C6H6(g) + 9H2(g) ΔGor = +433 kJ mol−1 ΔHor = +531 kJ mol−1 Thermodynamic calculations for this reaction show that benzene formation is insignificant below ∼600 °C, and that the formation of solid carbon [C(s)] is thermodynamically favored at temperatures above ∼300 °C Benzene formation is insignificant at all temperatures up to 1000 °C when C(s) is included in the calculation of equilibrium composition Interestingly, the thermodynamic limitation on benzene formation can be minimized by the addition of alkanes/alkenes to the methane feed By far the most widely studied catalysts for this reaction are Mo/HZSM-5 and Mo/MCM-22 Benzene selectivities are generally between 60 and 80% at methane conversions of ∼10%, corresponding to net benzene yields of less than 10% Major byproducts include lower molecular weight hydrocarbons and higher molecular weight substituted aromatics However, carbon formation is inevitable, but the experimental findings show this can be kinetically limited by the use of H2 or oxidants in the feed, including CO2 or steam A number of reactor configurations involving regeneration of the carbon-containing catalyst have been developed with the goal of minimizing the cost of regeneration of the catalyst once deactivated by carbon deposition In this tutorial review we discuss the thermodynamics of this process, the catalysts used and the potential reactor configurations that can be applied
319 citations