Performance and operating limits of a sorbent-catalyst system for sorption-enhanced reforming (SER) in a fluidized bed reactor

Abstract

The combined performance of a synthetic CaO-Ca12Al14O33 sorbent and an Ni-MgAl2O4 reforming catalyst was tested in a fluidized bed reactor under relevant operating conditions for the sorption-enhanced reforming (SER) process. The effect of CH4 space velocity (i.e. kgCH4/h•kgcat), steam-to-carbon (S/C) ratio and superficial gas velocity on product gas composition was assessed, as well as the effect of regeneration conditions on material performance. Moreover, a bi-functional material prepared by mechanical mixing of the separate materials was also tested in the reactor under consecutive SER/regeneration cycles. H2 contents as high as 96 vol% (N2 free, dry basis) were achieved under SER operation, using the separated materials working with an Ni content of 3.75 wt% in the solid bed at 650 ºC with S/C ratios of 3 and 4. This solid system is able to process up to 0.63 kgCH4/h•kgcat at 0.1 m/s superficial gas velocity and with an S/C ratio of 4, although the CH4 input has to be reduced to 0.33 kgCH4/h•kgcat when working with a lower S/C ratio. Similar H2 contents to those found in the separated materials were obtained with the combined sorbent-catalyst material working with 0.33 kgCH4/h•kgcat at 0.1 m/s superficial gas velocity and S/C ratios of 3 and 4. The CO2 sorption capacity of the combined material produced the same as that of the separate sorbent particles (i.e. around 0.25 gCO2/g calcined sorbent), while remaining stable throughout the SER/regeneration cycles.

Sorption enhanced steam methane reforming by Ni/CaO/mayenite combined systems: Overview of experimental results from European research project ASCENT

“…This emphasized the need for a stable catalytic phase when the long lifetime of CSCM must be ensured for usage in industrially relevant conditions. As a confirmation of this, the most promising CSCM produced by ASCENT WP4 was a mechanical agglomerate of CaOmayenite sorbent and commercial Ni-based catalyst for reforming, [53][54][55][56][57] which took advantage of industrial know-how on the issue of catalyst stability.…”

“…[11] In light of these observations, several synthesis methods were investigated by WP4 to obtain Ni/CaObased CSCMs that fulfil ASCENT requirements, and a high-shear agglomeration of a hydrothermal CaOmayenite sorbent (30 wt% of CaO) and a commercial Nibased reforming catalyst was chosen as their best option. [53][54][55][56][57] Nonetheless, other intriguing production paths and materials emerged as potentially applicable.…”

Modelling of Sorption-Enhanced Steam Reforming (Se-Sr) Process in Fluidised Bed Reactors for Low-Carbon Hydrogen Production: A Review

“…Martínez et al [55] compared the performance of a synthetic CaObased sorbent and reforming catalyst compared with a combined sorbent catalyst material (CSCM) under relevant operating conditions. An SE-SR experiment was conducted in a batch fluidised bed reactor of length -853 mm, internal diameter -53.1 mm and distributor plate located 586 mm from top reactor.…”

Ni Alumina-Based Catalyst for Sorption Enhanced Reforming - Effect of Calcination Temperature

“…The presence of oxygen leads to partial oxidation of the catalyst, and consequently, the material is exposed to reduction-oxidation cycles, which also leads to sintering. One option for reducing the effect of regeneration gas atmosphere on catalyst performance is to add a small amount of H 2 during regeneration [16]. Furthermore, a high thermodynamic potential for coke formation during reforming reaction can occur [17], thus covering the Ni surface or leading to the formation of carbon nanotubes, which will eventually lift the Ni particle from the support surface and thereby break the anchoring bonds between Ni and the support.…”