Steam reforming of phenol-ethanol to produce hydrogen over bimetallic Ni[sbnd]Cu catalysts supported on sepiolite

Abstract

A series of NiCu bimetallic catalysts supported on sepiolite (NixCuy/SEP) were prepared by co-precipitation method. The all as-prepared catalysts were characterized by using XRD, FT-IR, H2-TPR, and TEM. The results shown the NiCu alloys were successfully synthesized in bimetallic catalysts, and the addition of Cu promoter decreased the particles size, improved the redox ability and metal dispersion of bimetallic catalysts. Specially, the Ni1Cu0.25/SEP catalyst exhibited the smallest particles (10.2 nm) and highest metal dispersion (8.2%). In addition, the catalytic performance of prepared catalysts was evaluated during the mixture of phenol and ethanol steam reforming (PESR) reaction under the following conditions: steam to carbon ratio (S/C) = 1, WHSV = 3.2 h−1 and different temperatures (550 °C and 650 °C). The experimental results shown the high temperature was positive for increasing carbon conversion and H2 yield. Moreover, the Ni1Cu0.25/SEP catalyst exhibited the highest carbon conversion (83.5%) and H2 yield (67.5%) with relating to the lowest CH4 selectivity (8.8%), which was attributed to the formation of NiCu alloy and the smallest particle size in Ni1Cu0.25/SEP catalyst, leading to inhibit methanation reaction and enhance the steam reforming (SR) of methane. Additionally, the effect of steam S/C ratios (1, 5, 8) on the carbon conversion and H2 yield over Ni1Cu0.25/SEP was also tested at 650 °C, it shown that the carbon conversion was increased with the increase of S/C. Meanwhile, the test of stability was carried out over different catalysts at 650 °C. It found that the Ni1Cu0.25/SEP catalyst exhibited the outstanding stability during 24 h on steam, while the Ni1Cu0/SEP and Ni0Cu1/SEP shown rapidly deactivation after 10 h on steam. In order to illuminate the deactivation mechanism, the spent catalysts after 24 h of reaction were also characterized by XRD, TEM and TGA. The results shown Ni1Cu0.25/SEP catalyst exhibited smaller amount of carbon deposition in comparison with Ni1Cu0/SEP and Ni0Cu1/SEP catalysts, suggesting that the formation of NiCu alloy plays an important role in resisting to coke formation.