Topic
Coke
About: Coke is a research topic. Over the lifetime, 26923 publications have been published within this topic receiving 240792 citations.
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TL;DR: In this article, the authors investigated the causes of deactivation of supported metal catalysts by carbon or coke formation, and found that deactivation can occur due to fouling of the metal surface, blockage of catalysts pores and voids, and actual physical disintegration of the catalyst support.
Abstract: Deactivation of supported metal catalysts by carbon or coke formation is a problem of serious magnitude in steam reforming, methanation, and other important catalytic processes. Its causes are generally threefold: (1) fouling of the metal surface, (2) blockage of catalysts pores and voids, and/or (3) actual physical disintegration of the catalyst support. Since loss of catalytic activity and physical destruction of the catalyst by carbon deposits can occur rapidly (within hours or days) under unfavorable conditions, understanding and control of these effects are of major technological and economical importance.
760 citations
TL;DR: In this article, a set of commercial and laboratory-synthesized catalysts were evaluated for their performance via pyrolysis/catalytic cracking via three types of biomass feedstocks; cellulose, lignin, and wood were pyroized (batch experiments) in quartz boats in physical contact with the catalysts at temperature ranging from 400°C to 600°C and catalyst-to-biomass ratios of 5-10 by weight.
723 citations
TL;DR: In this article, the modes of formation of carbonaceous deposits (coke) during the transformation of organic compounds over acid and over bifunctional noble metal-acid catalysts are described.
Abstract: The modes of formation of carbonaceous deposits (“coke”) during the transformation of organic compounds over acid and over bifunctional noble metal-acid catalysts are described. At low reaction temperatures, ( 350°C), the coke components are polyaromatic. Their formation involves hydrogen transfer (acid catalysts) and dehydrogenation (bifunctional catalysts) steps in addition to condensation and rearrangement steps. On microporous catalysts, the retention of coke molecules is due to their steric blockage within the micropores.
673 citations
TL;DR: In this article, the conversion of biomass compounds to aromatics by thermal decomposition in the presence of catalysts was investigated using a pyroprobe analytical pyrolyzer.
Abstract: The conversion of biomass compounds to aromatics by thermal decomposition in the presence of catalysts was investigated using a pyroprobe analytical pyrolyzer The first step in this process is the thermal decomposition of the biomass to smaller oxygenates that then enter the catalysts pores where they are converted to CO, CO2, water, coke and volatile aromatics The desired reaction is the conversion of biomass into aromatics, CO2 and water with the undesired products being coke and water Both the reaction conditions and catalyst properties are critical in maximizing the desired product selectivity High heating rates and high catalyst to feed ratio favor aromatic production over coke formation Aromatics with carbon yields in excess of 30 molar carbon% were obtained from glucose, xylitol, cellobiose, and cellulose with ZSM-5 (Si/Al = 60) at the optimal reactor conditions The aromatic yield for all the products was similar suggesting that all of these biomass-derived oxygenates go through a common intermediate At lower catalyst to feed ratios volatile oxygenates are formed including furan type compounds, acetic acid and hydroxyacetaldehyde The product selectivity is dependent on both the size of the catalyst pores and the nature of the active sites Five catalysts were tested including ZSM-5, silicalite, beta, Y-zeolite and silica–alumina ZSM-5 had the highest aromatic yields (30% carbon yield) and the least amount of coke
656 citations
TL;DR: The mechanism of coke formation is reviewed and different approaches to control coking are discussed in this paper, where an ensemble size control produced by adsorbing controlled amounts of sulphur on the nickel surface has been found to be very effective at controlling coking.
644 citations