Abstract
In this research, catalytic steam reforming of acetic acid derived from the aqueous portion of bio-oil for hydrogen production was investigated using different Ni/ATC (Attapulgite Clay) catalysts prepared by precipitation, impregnation and mechanical blending methods. The fresh and reduced catalysts were characterized by XRD, N2 adsorption–desorption, TEM and temperature program reduction (H2-TPR). The comprehensive results demonstrated that the interaction between active metallic Ni and ATC carrier was significantly improved in Ni/ATC catalyst prepared by precipitation method, from which the mean of Ni particle size was the smallest (~13 nm), resulting in the highest metal dispersion (7.5%). The catalytic performance of the catalysts was evaluated by the process of steam reforming of acetic acid in a fixed-bed reactor under atmospheric pressure at two different temperatures: 550 °C and 650 °C. The test results showed the Ni/ATC prepared by way of precipitation method (PM-Ni/ATC) achieved the highest H2 yield of ~82% and a little lower acetic acid conversion efficiency of ~85% than that of Ni/ATC prepared by way of impregnation method (IM-Ni/ATC) (~95%). In addition, the deactivation catalysts after reaction for 4 h were analyzed by XRD, TGA-DTG and TEM, which demonstrated the catalyst deactivation was not caused by the amount of carbon deposition, but owed to the significant agglomeration and sintering of Ni particles in the carrier.
Highlights
In the past decades, environmental pollution and energy consumption have increased rapidly all over the world, in populous nations such as China and India
It can be found that the peaks at 2θ of 19.8◦, 20.8◦ 24.2◦, 26.7◦, 33.6◦ and 35.3◦ in attapulgite clay (ATC) and all fresh catalysts exhibit good consistence with palygorskite (JCPDS PDF# 31-0783), and the peaks at 30.8◦, 37.3◦, 41.2◦, 45.0◦, 51.2◦, 59.9◦, 63.5◦ and 67.4◦ may belong to dolomite (JCPDS PDF# 99-0046) or ankerite (JCPDS PDF# 99-0011)
It is worth noting that the peaks attributed to crystal structure of dolomite or ankerite disappear after reduction and reaction, which shows that dolomite or ankerite is reduced to some amorphous species and the ATC structure has been partly destroyed
Summary
Environmental pollution and energy consumption have increased rapidly all over the world, in populous nations such as China and India. In order to relieve these situations, clean and renewable energies with high energy density and environment-friendly nature have attracted significant attention at present [1,2,3]. Hydrogen energy has long been known as a clean energy and an important alternative for fossil fuel. The conventional hydrogen production method is steam reforming (SR) of non-renewable fossil fuels, such as coal, nature gas and naphtha. These processes produce a large amount of CO2 causing the global warming phenomenon, accompanied by the depletion of fossil fuel reserves. It is profitable to study the exploitation of hydrogen generation technology from renewable energy sources, i.e., biomass that is carbon neutral [4]
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