Autothermal Reforming of Acetic Acid to Hydrogen and Syngas on Ni and Rh Catalysts

Lifita N Tande,Erik Resendiz-Mora,Valerie Dupont,Martyn V Twigg

doi:10.3390/catal11121504

Abstract

The autothermal reforming (ATR) of acetic acid (HAc) as a model bio-oil compound is examined via bench scale experiments and equilibrium modelling to produce hydrogen and syngas. This study compares the performance of nickel (Ni-Al, Ni-CaAl) vs. rhodium (Rh-Al) for particulate packed bed (PPB), and of Rh-Al in PPB vs. Rh with and without Ceria for honeycomb monolith (‘M’) catalysts (R-M and RC-M). All PPB and M catalysts used Al2O3 as main support or washcoat, and when not pre-reduced, exhibited good performance with more than 90% of the HAc converted to C1-gases. The maximum H2 yield (6.5 wt.% of feed HAc) was obtained with both the Rh-Al and Ni-CaAl catalysts used in PPB, compared to the equilibrium limit of 7.2 wt.%, although carbon deposition from Ni-CaAl at 13.9 mg gcat−1 h−1 was significantly larger than Rh-Al’s (5.5 mg gcat−1 h−1); close to maximum H2 yields of 6.2 and 6.3 wt.% were obtained for R-M and RC-M respectively. The overall better performance of the Ni-CaAl catalyst over that of the Ni-Al was attributed to the added CaO reducing the acidity of the Al2O3 support, which provided a superior resistance to persistent coke formation. Unlike Rh-Al, the R-M and RC-M exhibited low steam conversions to H2 and CH4, evidencing little activity in water gas shift and methanation. However, the monolith catalysts showed no significant loss of activity, unlike Ni-Al. Both catalytic PPB (small reactor volumes) and monolith structures (ease of flow, strength, and stability) offer different advantages, thus Rh and Ni catalysts with new supports and structures combining these advantages for their suitability to the scale of local biomass resources could help the future sustainable use of biomasses and their bio-oils as storage friendly and energy dense sources of green hydrogen.

Highlights

Autothermal reforming (ATR) of biofuels presents the possibility of using more compact designs than steam reforming, incurring lower capital cost [1]
To determine the reaction needed for optimum hydrogen production, andTo assess process of the experimental runs, equilibrium were determine theefficiencies reaction conditions needed for optimum hydrogen calculations production, and TM software
The results suggest that rather than being based on superior catalytic activity, the selection of a suitable catalyst for autothermal reforming (ATR) of have decided to choose acetic acid (HAc), will likely depend on cost versus longevity, mechanical integrity, ease of regeneration and recycling, sustainability of the materials and manufacture, scale of the process

Summary

Introduction

Autothermal reforming (ATR) of biofuels presents the possibility of using more compact designs than steam reforming, incurring lower capital cost [1]. Amongst the different biofuels that can be used for hydrogen production, pyrolysis oils or bio-oils have attracted significant attention [3,4,5] Due to their complex and varying chemical composition, any study involving the use of bio-oil depends to some degree on the pyrolysis method used to produce them and on the biomass feedstock. Previous studies showed that HAc is a prevalent component of fast pyrolysis of terrestrial biomass, often more than 20% of the total bio-oil composition [6,7] Even though this is a simple molecule and only represents a fraction of the family of compounds found in actual bio-oil samples, (some heavier and more prone to polymerisation and coking), its use in an autothermal reforming study will be able to contribute to the understanding of the overall performance of an actual bio-oil

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