Abstract
This paper investigates the oxidative dehydrogenation of ethane to produce ethylene at low temperatures (500 °C) in metallic structured substrates. To check this point, the FeCrAlloy® monoliths with different channel sizes (289–2360 cpsi) were prepared. The monoliths were coated with a Ni/Al2O3 catalyst (by washcoating of alumina and the latter nickel impregnation) and characterized by Scanning Electron Microscopy and Energy-Dispersive X-ray analysis (SEM-EDX), Temperature-Programmed Reduction (TPR), X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). The catalytic results showed that all monoliths coated with ~300 mg of catalyst presented similar ethane conversion (15%) at 450 °C. However, the lowest selectivity to ethylene was found for the monolith with the lower channel size and the higher geometric surface area, where a heterogeneous catalyst layer with Ni enriched islands was generated. Therefore, it can be said that the selectivity to ethylene is linked to the distribution of Ni species on the support (alumina). Nevertheless, in all cases the selectivity was high (above 70%). On the other hand, the stability in reaction tests of one of the coated monoliths was done. This structured catalyst proved to be more stable under reaction conditions than the powder catalyst, with an initial slight drop in the first 8 h but after that, constant activity for the 152 h left.
Highlights
Ethylene is one of the major building blocks in the petrochemical industries as it is mainly used for the synthesis of polyethylene and other compounds as acetaldehyde, ethanol, ethyl chloride, and ethylbenzene [1,2], which are important reactants for the synthesis of the everyday-life products.Between 2011 and 2016, ethylene world consumption grew at an average rate of about 3% per year, while its capacity increased at 2%, leading to higher utilization rates
A structured catalyst is composed of three parts: the substrate (FeCrAlloy® monolith in our case)
A structured catalyst(alumina), is composed of three parts: theexposes substrate the true catalytic support which is the one that the (FeCrAlloy high specific surface area, and case), the true catalytic support, which is the one that exposes the high surface the active phase (Ni) that is dispersed over the surface of the support, the alumina.specific
Summary
Between 2011 and 2016, ethylene world consumption grew at an average rate of about 3% per year, while its capacity increased at 2%, leading to higher utilization rates This olefin consumption is expected to grow at about 3–4% per year over the five years [3]. The production of ethylene consumes many energetic resources because it is produced by the steam cracking of ethane or naphtha and the thermal cracking of petrochemical feedstocks such as naphtha, propane, and gas oil. Both processes operate at temperatures over 800 ◦ C. These have important disadvantages as low olefin selectivity and raw material loss through coke formation, requiring shutdowns and maintenance [4,5]
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