Preparation Of Supported Superbase And Nickeland Their Catalyzed Hydrocracking Of Sawdust

Biomass resources have attracted increasing attention due to their great benefits for climate, health and economy. The methodologies used for the degradation of biomass are based on thermochemical and biochemical techniques. However, inferiorities such as high energy consumption, high cost, high residue, harsh production conditions, waste of precious components and environmental pollution are rising to restrict the application in the development of biomass. Therefore, new methods for the further development of utilization of biomass are necessary.C–O bind is the primary joining method in the structure of biomass. Selectively cleaving the C–O bonds is of great importance for biomass conversion to liquid fuel and fine chemicals. Selective hydrogenolysis of aromatic Car–Oalk bonds is always a challenge because of the strength and high stability of the linkages. Most processes for converting biomass to liquid fuel significantly depended on the major chemical changes that occur when biomass is heated above 350–400 °C. Such conversions at high temperatures lead to severe increase in the yields of both gases and complex products with huge energy consumption. The complex products usually contain 20–30% of water and up to 60% of organic oxygen. Hydro–liquification is an efficient measure for selective cleavage of Car–Oalk bridged bonds. The key problem of this process is to select a suitable and active catalyst.Sawdust has been a high–volume byproduct of the paper and other industry since the beginning of the commercial operation. There has been a great deal of interest in the potential use of sawdust, that is, as a renewable source of energy and chemicals. Sawdust hydrocracking was used as a model reaction to evaluate the process of hydro–liquification for carbon–oxygen bond cleavage under mild conditions. Catalytic hydrocracking of biomass is a crucial subject for using biomass resources, and center on highly active catalysts, which usually contain solid base and nickel as the main catalytic active substance. In this paper two highly dispersive supported nickel catalysts and a novel magnetic solid super–base catalyst was prepared, specific, the main results were listed as follows:(1) Supported nickel catalysts: Ni(CO)4(NTC) was used as the precursor for nickel. NTC can directly decomposes to highly dispersive nickel when elevated temperature, and then it was dissolved into diethyl ether mixed with microfiber attapulgite(MFA) in an stainless steel autoclave. After in situ decomposition of NTC at low temperature. The catalyst Ni/MFA was prepared easily and efficiently.(2) A novel linear core–shell structured mesoporous silica coated microfiber attapulgite(MPSCMFA) was prepared. MPSCMFA–supported nickel catalyst was subsequently prepared by thermally decomposing NTC on MPSCMFA. The results indicating a higher catalytic efficiency of Ni/MPSCMFA than Ni/MFA, this could be due to the specific surface area of MPSCMFA increase after coated mesoporous silica.(3) By using Fe SO4·7H2O as a single iron source, a novel cubic magnetite nanoparticles Fe3O4 and high quality coated with mesoporous silica was successfully prepared. In order to produce core/shell–structured magnetic silica nanoparticles, a sol–gel approach based on the hydrolysis and condensation of TEOS was used to generate and deposit silica on the surface of magnetic microspheres, and subsequently highly active solid super–bases Mg2 Si was immersion into the mesoporous magnetic core(MMC), finally a novel magnetic supported super–base(MSSB) catalyst was prepared.(4) A series of related model compounds were used to evaluate the catalytic activity. Sawdust was selected as a analysis sample in the catalytic hydrocracking reactions with catalysts under different conditions. Compare with the conventional catalysts prepared by impregnation reduction, the Ni/MFA showed a higher activity to catalyze arenes hydrogenation. Catalyzed by the Ni/MFA, many model cmpounds were all hydrogenated completely, such as toluene, benzyloxybenzene, benzyl ether naphthalene, 1–methoxynaphthalene(MON), anthracene, phenanthrene, 9–phenylanthracene, etc. The catalyst could be recycled for several times. the Ni/MPSCMFA catalyst indicating a higher catalytic efficiency than Ni/MFA catalyst. Because of the MPSCMFA support has larger precific surface area than MFA, and the Ni particles on MPSCMFA support shows much uniform particle size and without obvious aggregation. Those two catalysts exhibits a high activity for hydrocracking the C–O bond. Becaues metal catalytic the chemical reaction of the hydrogen free radical. Based on a lot of experiments, it is proposed that the Ni/MPSCMFA catalyst enhanced biatomic hydrogen transfer at low temperature, while selectively promoted monatomic hydrogen transfer at high temperature. Compare with the Ni/MPSCMFA. Examine the MSSB–catalyzed alkanolysis of model compounds, in which oxygen–containing bridged bonds(OCBBs) are contained between aromatic rings; to reveal the mechanisms for the MSSB–catalyzed cleavage of the OCBBs; to successively destroy different OCBBs in biomass by hrdrocracking in methanol or cyclohexane over the MSSB at lower temperatures to 340 °C, and to comprehensively and deeply understand the OCBB types and the structures of aromatic rings which are connected by the OCBBs by subsequent analyses. These investigations will provide important scientific basis for biomass directional conversions. The reactions of model compounds show that MSSB catalyst has high selectivity to cleavage of Car–Oalk bond, and the reaction reactivity depend on resonance energy value(RE) of corresponding bond and the super delocalization energy(Sr). Strong electron donating abilities and strong alkalinity of the MSSB facilitates heterolytical splitting of H2 to an immobile H+ adhered to the MSSB surface and a mobile H–. The mobile H– which added to the ipso–position of arylalkoxys to lead the cleavage of Car–Oalk bond. Hydrocracking of di(1–naphthyl)methane(DNM) shows that MSSB also has highly active to promote the cleavage of Car–Calk bridge bonds. The generation of H– is the significant step and add the H– to the ipso–position is the key step for hydrocracking reactions.According to multiple characterizations, i.e. Scanning electron microscopy(SEM), High resolution transmission electron microscopy(HRTEM) with Energy dispersive spectroscopy(EDS), X–ray diffraction(XRD), CO2 temperature programmed desorption(CO2–TPD), H2 temperature programmed reduction(H2–TPR), X–ray photoelectron spectroscopy(XPS), BET method(BET) and superconducting quantum interference device magnetometer(SQUID). The coercive force of MMC was zero, and MMC showed paramagnetic property. A little lower than those uncoated Fe3O4, that well keeps the magnetic property. The desorption CO2 of at high temperature can be attributed to the unusually strongly basic sites.