| Summary: | 碩士 === 東海大學 === 應用化學系 === 84 === Abstract
one-step synthesis of methyl isobutyl ketone (MIBK)
from acetone and hydrogen over metal modified solid base
catalysts has been studied at atmospheric pressure and
175~250℃by using a fixed-bed , integral-flow reactor . Two
types of catalysts have been used : (1) metal oxides modified
with sodium and palladium (Pd/Na/MgO , Pd/Na/NaOH/γ-
Al2O3) ; (2) zeolites modified with palladium (Pd/KZSM-5 ,
Pd/Kβ) . The catalyst properties , i.e., the composition , the
basicity , the surface area and the structure are characterized
by the methods of atomic absorption , temperature-
programmed desorption , surface adsorption and scanning
electron microscopy . Sodium vapor deposition on magnesia
followed by impregnation with tetraamine palladium(Π)
chloride apparently enhances the catalyst basicity as
compared with that of magnesia supported palladium ;
Pd/0.47wt.-%Na/MgO exhibits the largest base amount . For
catalysts of different supports , the base amount decreases in
the order of Pd/Na/MgO > Pd/Na/NaOH/γ-Al2O3 >
Pd/KZSM-5 > Pd/Kβ , in accordance with the catalyst
activities . As the amount of palladium in Pd/Na/MgO
increases , both acetone conversion and MIBK selectivity
also increase but then decrease . Better acetone conversion
and MIBK selectivity are obtained at higher pretreating
temperature of hydrogen . The catalyst activity of
Pd/Na/MgO increases with the reaction temperature but the
decay rate also increases . The acetone/hydrogen molar ratio
of 1 gives the highest acetone conversion . Increasing contact
time causes an increase in the selectivity of diisobutyl ketone
due to further reaction of MIBK with acetone and hydrogen .
Based on the above results , the optimum reaction conditions
are 0.5wt.-%Pd/0.47wt.-%Na/MgO , reaction temperature
200℃ , acetone /hydrogen molar ratio 1, W/FA 6g.h/mol and
the pretreatment temperature of hydrogen 400℃ . According
to the FT-IR results of acetone adsorption on Pd/Na/MgO ,
the following reaction mechanism is proposed : self
condensation of acetone on catalyst base sites followed by
dehydration on acid sites and then hydrogenation to yield
MIBK .
|
|---|
