Investigation of carbon formation on Ni-based ceria zirconia catalysts in the autothermal steam reforming of acetic acid

Abstract

The acetic acid auto thermal steam reforming (ATR) was investigated over Ni/Ce75Zr25Ox catalyst via coke characterization along the catalyst bed. The ATR, partial oxidation (POX), and steam reforming (SR) of acetic acid were individually conducted to study gaseous products and carbon deposition using a continuous flow fixed-bed reactor. Each reaction was carried out at atmospheric pressure and a constant temperature of 650 ℃ under the following conditions: a total flow rate of 170 ml/min, steam-to-carbon molar ratio of 3:1, and oxygen-to-acetic acid molar ratio of 0.35:1 by varying contact times from 0.088 to 0.352 g·h·mol-1. Ce75Zr25Ox support was prepared via urea-hydrolysis followed by nickel (15 wt%) impregnation. It was apparent that a large amount of H2 production was obtainable for SR but unattainable for POX. However, H2 production under ATR conditions appears ca. 10 % lower than SR conditions. Besides, the products selectivity at the upper layer of the catalyst bed under ATR conditions behaved similar to the catalyst under POX conditions while its lower layer of the catalyst bed behaved similar to the catalyst under SR conditions. In addition, the results on coke characterization revealed that filamentous carbon was the main type of carbon deposited on spent catalyst for all processes whereas amorphous carbon was found in POX and only at the top portion of spent catalyst in ATR. This suggested that under ATR conditions, SR occurred when oxygen was completely consumed as well as the reaction zones were separately existed. Moreover, the advantage of ATR could be viable in lowering carbon formation compared with SR and POX operation.