The present thesis focuses on the development of key catalyst in the production of valuable commodity chemicals from bio-glycerol through hydrogenolysis.Works are put on the correlation of catalyst preparation,structure and performance.Herein the crystallized Ni-Co-B and Ni-Fe-B catalysts were prepared by chemical reduction in aqueous solution and then by H2-reduction in gas-phase at elevated temperatures.The effect of bimetal atomic ratio and reduction temperature on the catalytic performance of Ni-Co-B and Ni-Fe-B catalysts was investigated by controlled experimental conditions.The samples were characterized by N2-adsorption/desorption,X-ray diffraction,NH3-TPD,H2-TPD and XPS so as to correlate between structure and performance.The reaction mechanism was also disussed on the basis of characterization results.The crystallized Ni-Co-B and Ni-Fe-B catalysts exhibited excellent activities and good selectivities to 1,2-propanediol（1,2-PDO） and ethylene glycol（EG） in the glycerol hydrogenolysis under relatively mild conditions.The bimetal atomic ratio and reduction temperature showed a considerable influence on the glycerol conversion.As for Ni-Co-B catalyst,the hydrogenolysis of a 20wt%glycerol aqueous solution with an optimized Ni/Co atomic ratio at 1/7 could give a glycerol conversion higher than 95%with combined selectivity to 1,2-PDO and EG above 70%when the reaction was run at 473 K and 2.0 MPa for 12 h.The conversion tended to decrease when the Co amount was increased in the crystallized Ni-Co-B catalyst with almost retention of the selectivities to 1,2-PDO and EG.As for Ni-Fe-B catalyst,the glycerol conversion reached a maximum of 82.9%with an optimized Ni/Fe atomic ratio at 4/1. The conversion tended to decrease at higher content of Fe in the crystallized Ni-Fe-B catalyst,but the selectivity to 1,2-PDO kept increasing gradually.In addition,the glycerol conversion tended to decrease when both catalysts were reduced at higher temperatures,but the selectivities to 1,2-PDO and EG kept unchanged essentially. Besides,it was worthy noting that acetol was detected with different degrees in all products of glycerol hydrogenolysis over the Ni-Co-B and Ni-Fe-B catalysts. The XRD results indicated that the phase transition occurred to the amorphous Ni-Co-B and Ni-Fe-B precursors by reduction at 523 K in 5%H2-N2.The diffraction lines became more intensive after the glycerol hydrogenolysis.As for Ni-Co-B catalyst,the incorporation of Ni into Co-B could bring about changes in the BET surface area.The sample with Ni/Co molar ratio at 1/7 gave a maximal surface area of 59.4 m2 g-1.As for Ni-Fe-B catalyst,the sample with Ni/Fe molar ratio at 1/1 gave a maximal surface area by 87.1 m2 g-1.Moreover,there was an obvious drop in the surface area of both Ni-Co-B and Ni-Fe-B catalysts reduced at higher temperatures. The NH3-TPD and H2-TPD results indicated that there existed both acid-sites and hydrogenation-sites on the crystallized Ni-Co-B and Ni-Fe-B surfaces.Moreover,the desorption amount of hydrogen increased with increasing the Ni amount in the crystallized Ni-Co-B and Ni-Fe-B samples.Therefore,the concurrence of acid and hydrogenation sites in the catalysts might be beneficial for the reactivity towards glycerol hydrogenolysis.Glycerol was believed to be dehydrated to form an acetol intermediate-acetol over the acid sites,which was then hydrogenated to produce 1,2-PDO.On the other hand,glycerol could also be dehydrogenated to form glyceraldehydes,followed by dehydration to 2-hydroxylacrolein,and then by hydrogenation to 1,2-PDO.Nevertheless,the glyceraldehyde molecule could also undergo C-C bond cleavage through a reverse aldolization reaction to give 2-hydroxyacetaldehyde,subsequently giving EG by catalytic hydrogenation.
Post about "EG"
T Polyvinyl alcohol(PVA) has been widely applied in many fields and has a great future. Howerer, it has a low limiting oxygen index(LOI) value and is flammable. The fateful drawback of PVA restricts its wider application. Therefore, how to improve its flame retardancy is very important.In this paper, we have used halogen-free flame retardants for PVA and studied theirs highly flame-retardant efficiency. In the experiment,flame-retardant polyvinyl alcohol composites.is prepared by solution blending, whill water-soluble PVA plastic film as a carrier. At the same time, we have studied on PVA thermal stability, flame resistance and the applied property. To obtain excellent flame retardant properties of halogen-free flame-retardant plastic film.Detailed analysis results are as follows:1、The impact of different sizes of expanded graphite on the PVA/EG composite flame-retardant properties were different. Add the same amount of fire retardant, the 50 mesh is better than 80 mesh.2、When EG is used alone, flame retardant is ineffective. In the combustion process, the expansion carbon layer is not thick enough, and “worm-like” carbon layer is too loose, it is easy to fall off.3、We compound EG and APP, Through LOI, and UL-94 test for a large number of formulations of, eventually make good flame retardant properties:When the add-on of flame-retardant additives reaches 15%, the proportion between Eg and APP is 1:2, the LOI of the complex material increases to 36.7 and UL-94reachesV-0 grade. Experimental results show that between the two flame-retardant exists certain synergy.4、Results show that added EG and APP could improve of polyvinyl alcohol to a great extend respectively. EG help to promote the formation of carbon layer, while the addition of APP to the combustion of PVA has a certain viscosity, increasing the adhesion of carbon layer. The results showed that the thermal stability and flame retardant have been a good improvement.5、Preparation of PVA material of this study is simple and technology is mature, easy to control.In summary, under experimental conditions, through the flame retardant synergistic effect, more effectively improve the stability of the carbon layer, the density and heat resistance, and thus greatly improve the flame retardancy of PVA.
Research on the Preparation and Flame-Retarding Performance of Epoxy Modified with Expandable Graphite
In this paper, we research on the preparation and flame-retarding performance of Epoxy modified with expandable graphite. Flammabilities and thermal behaviors of added different usage of EG, added different size of the EG and added EG-APP of the cured resins were investigated by Limit Oxygen Index (LOI), Vertical Burning Test, Thermogravimetric Analysis (TGA).The flame-retardant mechanism of EG for epoxy resins was investigated by Scanning electron microscope (SEM).Results show that added EG of the cured resins, added EG-APP of the cured resins could improve of epoxy resins to a great extent respectively. When the add-on of EG(80mwsh) reaches 15wt%, the LOI of the cured resins increases from 20.2 to 29.4. When the add-on of EG(50mesh) reaches 15wt%, the LOI of the cured resins increases to 30.6. When the add-on of 7.5wt% EG(50mesh)-7.5wt%APP reaches 15wt%, the LOI of the cured resins increases to 37.2 and UL-94 reaches V-0 grade. EG(50mesh) have higher expansion ratio than EG(80mesh), when they are heated, EG(50mesh) can produce more compact and thick coal bed, so the retardant effectiveness will be better. In addition, with the addition of APP, the viscosity and compactness of the coal bed will be increased. The LOI value increases obviously, thermal decomposition rate is lowered and the thermo stability is enhanced, which suggests that EG/APP has synergistic flame-retarding function of compact, stable expandable charcoal layer.