Catalytic Depolymerization Of Lignin In Supercritical Methanol Over PMOs Supported Catalysts

Lignin is widespread in nature, which is the second most organic compounds produced by plant generated through photosynthesis total, together with cellulose and hemicellulose form the main structure of plant. Lignin of the global annual output can reach 150 billion tons, most of which is directly emissed as papermaking waste.This not only wastes the resources, more to cause serious environmental pollution.Demand for oil and its derivatives in China is great, but at the same time China’s reserves of oil resource is very scarce, so looking for alternative oil of renewable energy to solve the energy problem faced by our country is of great significance.The molecular structure of the lignin is made up of oxygen generation propyl benzene and its derivatives, and contains a lot of alcohol, aldehyde group and carboxyl functional groups, can be generated by cracking a variety of important compounds, replace oil and become the important source of petroleum base chemicals.1. The study of depolymerization of lignin in supercritical methanol over Ni@PMOs catalystsHighly efficient depolymerization of lignin was performed in supercritical methanol over porous metal oxides supported Ni catalysts (Ni@PMOs). The hydrotalcite precursors, PMOs and Ni@PMOs were characterized using XRD and TEM. To explore the optimal reaction condition, an orthogonal test is performed to find the relationship between yield and reaction parameters. The depolymerization products were characterized mainly by GC-MS and elemental analysis. According to the experimental results, the three most effective parameters for transforming lignin to monomers and low-mass oligomers were reaction temperature, loading of nickel and amount of solvent. The optimal reaction condition for the highest conversion of 0.15 g lignin is to perform the conversion in 12 ml methanol, at 360℃ for 4 h, with 0.05 g 5 wt.% Ni@PMOs as catalyst. Under this optimal condition, the conversion efficiency of lignin can reach 76% with the proportion of 2-cyclopenten-l-one derivatives in the final product of 31.6%, which is never reported before.2. The study of depolymerization of lignin in supercritical methanol over different M@PMOs catalystsThe second experiment was designed based on the first experiment, to find the highest efficient and the best selectivity porous metal oxides carrier and the optimal load metal. The experiment can be divided into two parts.In the first part, we synthesized different types of hydrotalcite compound by replacing the Mg2+ with different M2+ metal ions. After calcinated under 500℃ for 8 h, porous metal oxides (POMs) could be obtained. The different porous metal oxides catalysts loaded with 5 wt.% Ni (5 wt.% Ni@PMOs) were prepared by impregnation-reduction method. Use these catalysts to catalysis depolymerize 0.15 g lignin with 12 ml methanol under 360℃. The products were analyzed to find the relationships between the productivity and different components of the PMOs.In the second part, we chose the highest efficient and selective PMOs as the carrier. Then prepared porous metal oxides catalysts loaded with 5 wt.% Ni,5 wt.% Pd,5 wt.% La, and 5 wt.% Fe by impregnation-reduction method. Use these catalysts to catalysis depolymerize 0.15 g lignin with 12 ml methanol under 360℃. The products were analyzed to find the relationships between the productivity and different loading metals.