The MgAl layered hydrotalcites(MgAl-LDHs) precursors with submicron-scale were synthesized by introducing ethanol into hydrothermal synthesis method. The synthesis process parameters were optimized by orthogonal experiment, and then the composite metal oxide(MgAlOx) was obtained after the calcination process. The crystal phase, morphology and alkalinity of both hydrotalcite precursors and solid base oxides were characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM) and the temperature-programmed desorption of CO2(CO2-TPD), respecitively. Finally, the catalytic performance of MgAlOx was evaluated by the depolymerization test of calcium lignosulfonate. The products including solid, liquid, gas three phases, were analyzed by gel permeation chromatography(GPC), gas chromatography/mass spectrometry(GC-MS) and gas chromatography(GC). The results indicated that 140—230 nm of MgAl-LDHs were regulated by adding 15%(volume fraction) C2H5OH to the hydrothermal system, the optimal synthesis condition considered from relative crystallinity was n(Mg)/n(Al)=3, pH=12 and the temperature of 80 ℃ for 24 h. the MgAlOx obtained after the calcination of MgAl-LDHs at 600 ℃ for 6 h under air atmosphere. The optimal depolymerization of calcium lignosulfonate was 270 ℃, 4 h, the addition of 65%(volume fraction) C2H5OH and m(MgAlOx)/m(CLS)=1/2. The gas-liquid-solid three-phase yield distribution was 4.50%, 58.30% and 37.20% under the above condition, the liquid yields increased by 13.30% with the addition of MgAlOx, the main components of liquid products were phenolics, aromatics, esters and others. Moreover, the selectivity of oxy-containing compounds was 79.05%(phenolics of 66.06%, esters of 12.99%). Fortunately, MgAlOx would also keep high reactivity and stability even after four cycles of reactions.
