Deactivation Pattern of a “Model” Ni/MgO Catalyst in the Pre-Reforming of n-Hexane

Abstract

Abstract:The deactivation pattern of a "model" Ni/MgO catalyst in the pre-reforming of n-hexane with steam (T, 450 °C; P, 5-15 bar) is reviewed. The influence of the steam-to-carbon ratio (S/C, 1.5-3.5) on the rate of catalyst fouling by coking is ascertained. Catalyst fouling leads to an exponential decay in activity, denoting 1 st -order dependence of the coking process on active sites availability. Hydrogen hinders the coking process, though slight activity decay is due to sintering of the active Ni phase. Deactivation by thiophene causes a sharp, almost linear, drop to nearly zero activity within only 6 h; this deactivation is likely due to dissociative adsorption of thiophene with subsequent strong, irreversible chemical adsorption of S-atoms on active Ni sites, i.e., irreversible poisoning. Modeling of activity decay curves (α, a t /a 0 ) by proper kinetic equations allows assessing the effects of temperature, pressure, S/C, H 2 and thiophene feed on the deactivation pattern of the model Ni/MgO catalyst by coking, sintering, and poisoning phenomena.

Advances in Catalyst Deactivation and Regeneration

“…Trunfio and Arena [8] studied deactivation of a model Ni/MgO catalyst in the pre-reforming of n-hexane at 450 °C and 5-15 bar at steam-to-carbon (S/C) ratios of 1.5-3.5. Fouling of the catalyst by coke causes a first-order, exponential decay in activity.…”

“…It consists of a comprehensive review of catalyst deactivation and regeneration [3]; two topical reviews of deactivation and regeneration in Fischer-Tropsch synthesis (FTS) [4,5]; a review of Pd catalyst deactivation in emissions control converters for natural gas vehicles [6]; and four focused, topical studies of deactivation in hydrogen production in ethanol steam-reforming [7], pre-reforming of hexane [8], liquid-phase alcohol oxidation [9], and photocatalytic oxidative dehydrogenation of cyclohexane [10]. Computational studies predict that Pt or Ru impede Co activity decay caused by carbon deposits on the Co surface by increasing the energy barrier for carbon-carbon coupling reactions.…”

Influence of metal cation doping on Ru/CeO2/Al2O3 catalyst for steam reforming of desulfurized kerosene

“…Catalyst developments for pre-reformers have been also reported in steam reforming of liquefied petroleum gas (LPG) [23,24]. The pre-reforming is a well-established process in modern syngas production, and can convert higher hydrocarbon feedstocks by steam reforming reactions in the low temperature range around 773 K with several practical advantages as follows; an increased production capacity, a higher feedstock flexibility enhancement of catalyst lifetime of steam reformers and lowering of the energy consumption and investment costs [25]. Compared to natural gas and LPG, the components of desulfurized kerosene are much higher and complex.…”

First principles study of the electronic properties of MgO under pressure

“…MgO can be widely used in industry. For example, MgO also is an excellent insulator [4] and carrier of catalyst [5]. MgO can also be used as expansive cement and concrete [6].…”