First, 0.0875 g of
lignin was suspended in DI water with the Ni–Fe cocatalysts
on magnesium silicate supports in a batch reactor. To study the effect
of temperature on the depolymerization of kraft lignin, the system
was studied at temperatures of 250, 300, and 350 °C. Catalysts
were further loaded at 0.0044 g into the reactor. Subsequently, the
reactor was sealed and purged with N2 to remove any reactive
air and achieve an inert atmosphere until reaching 10 bars of N2. The reactor was operated for 1 h with vertical shaking at
40 rpm.
After completing the reaction, the products were separated
by a centrifuge consisting of solid and liquid phases. The solid phase
was defined as char, while the liquid phase contained lignin-derived
products and residual lignin. Next, the liquid phase was acidified
to a pH of 2.00 with 1 M hydrochloric acid. In this step, the residual
lignin was precipitated out as solids by a centrifuge at 15 °C.
Next, the lignin-derived products were separated using ethyl acetate.
Finally, the samples were characterized and quantified by a gas chromatography
mass spectrometer.
The liquid fraction qualification was analyzed
on a GC–MS
instrument (Shimadzu) equipped with a capillary column (30 m ×
0.32 mm × 0.25 mm). The GC heating ramp was as follows: the oven
temperature program increased from 40 °C (held for 3 min) to
300 °C at a rate of 5 °C/min under a helium atmosphere.
The main products from the depolymerization of kraft lignin are anisole,
phenol, p-cresol, 4-ethylphenol, creosol, catechol,
guaiacol, mequinol, 4-ethylguaiacol, syringol, 4-hydroxybenzaldehyde,
vanillin, 4′-hydroxyacetophenone, 3,4-dimethoxyenzaldehyde,
and vanillic acid. These products were analyzed using the database
from the National Institute of Standards and Technology (NIST) for
comparison of the molecular weight. The yields of each product and
the kraft lignin conversion were calculated using the followingeqs 1 and 2 .
lignin was suspended in DI water with the Ni–Fe cocatalysts
on magnesium silicate supports in a batch reactor. To study the effect
of temperature on the depolymerization of kraft lignin, the system
was studied at temperatures of 250, 300, and 350 °C. Catalysts
were further loaded at 0.0044 g into the reactor. Subsequently, the
reactor was sealed and purged with N2 to remove any reactive
air and achieve an inert atmosphere until reaching 10 bars of N2. The reactor was operated for 1 h with vertical shaking at
40 rpm.
After completing the reaction, the products were separated
by a centrifuge consisting of solid and liquid phases. The solid phase
was defined as char, while the liquid phase contained lignin-derived
products and residual lignin. Next, the liquid phase was acidified
to a pH of 2.00 with 1 M hydrochloric acid. In this step, the residual
lignin was precipitated out as solids by a centrifuge at 15 °C.
Next, the lignin-derived products were separated using ethyl acetate.
Finally, the samples were characterized and quantified by a gas chromatography
mass spectrometer.
The liquid fraction qualification was analyzed
on a GC–MS
instrument (Shimadzu) equipped with a capillary column (30 m ×
0.32 mm × 0.25 mm). The GC heating ramp was as follows: the oven
temperature program increased from 40 °C (held for 3 min) to
300 °C at a rate of 5 °C/min under a helium atmosphere.
The main products from the depolymerization of kraft lignin are anisole,
phenol, p-cresol, 4-ethylphenol, creosol, catechol,
guaiacol, mequinol, 4-ethylguaiacol, syringol, 4-hydroxybenzaldehyde,
vanillin, 4′-hydroxyacetophenone, 3,4-dimethoxyenzaldehyde,
and vanillic acid. These products were analyzed using the database
from the National Institute of Standards and Technology (NIST) for
comparison of the molecular weight. The yields of each product and
the kraft lignin conversion were calculated using the following
