Influence of the addition of promoters to steam reforming catalysts

Iridium Catalysts for C-C and C-O Hydrogenolysis: Catalytic Consequences of Iridium Sites

“…13,14 Additionally, conversion of cyclohexane is typically used to probe the catalyst surface properties such as apparent dispersion (dehydrogenation to benzene) and surface structure (hydrogenolysis). [15][16][17][18][19][20] Several studies of cyclohexane conversion on Ir catalysts were performed to understand the dependence of cyclohexane hydrogenolysis activity and reaction mechanism on factors like dispersion, particle size and H 2 /cyclohexane ratio. 13,14,21 Locatelli et al 21 investigated cyclohexane hydrogenolysis over Ir/SiO 2 and proposed a reaction mechanism in which the key step is a concerted electronic transfer in a dimetallacyclopentane intermediate.…”

Hydrogen production from catalytic reforming of the aqueous fraction of pyrolysis bio-oil with modified Ni–Al catalysts

“…Promoters including alkaline and alkaline earth metals and others such as Ce, Zn have also been known to decrease the acidity of catalyst support, prohibiting cracking and polymerization reactions, which may lead to detrimental coke formation [33][34][35]. The improved stability of promoted Ni-Al catalyst was probably due to the enhanced steam absorption or the production of reactive carbon formed by the promoter [35,36]. Our previous studies have shown that adding metals such as Zn and Ca to Ni/Al 2 O 3 by co-precipitation are effective for biomass catalytic gasification, in relation to the reduction of coke deposition on the surface of the catalyst [6].…”

“…The benefit of Mg addition to the Ni-Al catalyst was suggested to block the active sites that were necessary for the coke formation on surface of catalyst [36]. Medrano and co-workers reported on the influence of the promoters, Mg and Ca, on Ni-Al catalysts in the catalytic steam reforming of pyrolysis liquids and reported that Ca showed poorer activity in relation to H 2 content and lower carbon conversion compared with Mg [8]; this is consistent with our results.…”

Tar Removal From Biomass Gasification Streams: Processes and Catalysts

“…51 Metais alcalinos e alcalino-terrosos são conhecidos como promotores da reação de gaseificação do carbono com vapor, reduzindo a relação molar vapor/carbono (V/C) necessária para a reação e promovendo a formação de coque mais facilmente removível. 52 O uso do potássio em catalisadores de reforma a vapor está relacionado à melhoria da redutibilidade dos catalisadores e associado à formação de coque do tipo filamentoso.…”

“…50,87 A presença desses compostos deve-se à ocorrência do craqueamento da carga em altas temperaturas, podendo levar à formação de produtos primários (>C5), hidrocarbonetos secundários (C1-C4), além de coque. 46 52,89 Adicionalmente, os estudos mostraram que a adição de 10 %m/m de naftaleno em solução de tolueno causou uma redução acentuada na conversão do tolueno, pois o naftaleno se adsorve mais fortemente que o tolueno, prejudicando a conversão deste último. 90 A Figura 4 ilustra o tipo de coque formado na reação de reforma a vapor de naftaleno/tolueno a 800 °C, com razão V/C = 1,5.…”