Catalytic Reforming Of Volatiles From Biomass Pyrolysis Over Limonite

In this paper, the structural evolution, i.e., the phase of evolution, the change of specific surface area and pore size, of natural limonite was studied by calcination at different temperatures. Catalytic reforming of volatiles from pyrolysis of biomass was conducted in a two-stage fixed-bed quartz reactor over limonite and Ni/Limonite to study the effects of catalyst, temperature, space velocity, Ni loadings and reuse times on gas yields and carbon distributions. At the same time, steam was introduced to study the activity for reforming of volatiles. Under inert atmosphere, the dehydroxylation of goethite leads to the form hematite when limonite was calcined above 200 oC. The specific surface area significantly increased to the maximum value of 183.1 m2/g when the temperature was increased to 400 oC, which should be ascribed to the formation of slit-shaped micropores during dehydroxylation process. The limonite ore can promote volatiles reforming and shows a certain activity for tar reforming. Compared with noncatalytic reforming, catalytic reforming over limonite at 650 oC give the maximum gas yield of 41.6 mmol/g-daf and a negligible carbon in water soluble tar yield of 0.7%. Steam introduced at 650-700 oC can not only promote the reforming of biomass volatiles significantly, but also suppress the coke deposition on the catalyst surface by the water-gas shift reactions. The addition of nickel caused the improvement of the activity of limonite for volatiles reforming. Most of the tarry material was cracked to from gas product over Ni/Limonite under inert atmosphere, and the Ni/Limonite with a Ni content of 9% was found to be the activate one. When the Ni/Limonite was reused four times, the total gas yield over the reused catalyst is about 77.1% of that obtained over fresh catalyst. The study revealed the mechanism and the possibility of using limonite and Ni/Limonite as an attractive alternative to the commercial precious metal catalysts for low-temperature catalytic reforming for volatiles from pyrolysis of biomass.