Research On Antioxygenic Properies And Hydrogen Of Lignosulphonates Based On Catalyst With Cerium

Lignin is a kind of important biological resources that have not been highly utilized,and the lignin sulfonate(LS)is mainly from the sulfite paper industry.The chemical structure and morphological characteristics of the activated lignin were characterized by infrared spectroscopy(FTIR),ultraviolet spectrophotometer(UV),nuclear magnetic hydrogen spectrum(1HNMR),nuclear magnetic carbon spectrum(13CNMR),two-dimensional nuclear magnetic(2D-HSQC),scanning thermogravimetric analysis(TG)and hydroxyl functional group.The hydroxyl content analysis,the methoxy content analysis,and the anti-oxidation performance,the clearance of the activated lignin material to the 1,1-diphenyl-2-trinitrobenzene(DPPH ·)free radical is detected,The clearance of 2,2-N-bis(3-ethyl-benzo-1-6-sulfonic acid)disalt(ABTS·)free radicals and the evaluation of the reduction ability.Firstly,the rare earth oxide of the rare earth system is doped into the oxidizing agent and directly used as a carrier,the single-load(CexZr(1-X)O2 and Pd/CexZr(1-X)O2)and the double-load(S2O82-/Pd/CexZr(1-X)O2 and Pd/CeO2)contain sulfate ions and metal ionsan ammonia program temperature-raising adsorption method(NH3-TPD),a hydrogen program temperature-raising adsorption method(H2-TPD)and an X-ray-ray diffraction(XRD)are adopted.The series of catalysts were characterized by X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM),transmission electron microscopy(TEM)and the like.The ZrO2 series supports of mixed La、Nd and Ce were prepared with SO42-/ZrO2 as reference,and the solid acid catalysts with better performance were obtained by loading S2O82-ions.The strength range of solid acid and acid was determined by Hammett method,and the sulfur content was determined by BaSO4 gravimetric method and XPS method.SO42-/ZrO2 solid acid catalyst was optimized from two aspects of support and acid support.CexZr(1-X)O2,Pd/CexZr(1-X)O2,bifunctional S2O82-/Pd/CexZr(1-X)O2 and Pd/CeO2 catalysts were prepared by doping.The acid strength range of solid acid was determined,and the surface morphology of the catalyst was observed by scanning electron microscope(SEM).The results show that the amorphous structure of Ce element is formed by doping ZrO2,which is increased to the specific surface area of 75.16 m2·g-1 carrier.The specific surface area of bifunctional S2O82-/Pd/CexZr(1-X)O2 catalyst was 67.91 m2·g-1,the contents of phenolic hydroxyl group and alcohol hydroxyl group were 4.10%and 24.99%,and the methoxyl content decreased by 13.02%,respectively.Pd/CeO2 catalyst carrier could reach nanometer level,and the specific surface area of CeO2 carrier was 94.90 m2·g-1.The average hole width with microporous structure is 4.68 nm.The phenolic hydroxyl content,total hydroxyl group and methoxyl content of lignin sulfonic acid hydrogenation activation product increased by 17.71%,14.75%and 16.69%,respectively.The chemical structure of lignin after hydrogenation was analyzed by measuring the hydroxyl content of lignin and 1HNMR.the chemical structure of lignin LS after hydrogenation was analyzed by 13CNMR and 2D-HSQC,and the possible chemical reaction was discussed.In nuclear magnetic carbon spectrum,181.80 ppm comes from aliphatic carboxy structure.In hydrogenated lignin LS,aliphatic carbonyl absorption signal weakens and some carbonyl groups are reduced to hydroxyl group,which is consistent with the improvement data of alcohol hydroxyl group in product LS.The C-4 etherification of the guaiacol propane unit(G),the absorption signal of the non-etherified structure and the structure of the lilac propane unit(S)and the connection structure signal present in the p-hydroxyphenylpropane unit(H)signal,2D-HSQC side chain region(δc/δH50.0-90.0/2.5-5.5 ppm),indicating that the reaction mainly occurs in the side chain region.It is most likely to be hydrogenated and hydrolyzed on the β-β’structure Cβ and ether bonds of methoxy MeO and Bβ.Furthermore,with BHT as a reference,the scavenging rate of DPPH·free radicals can be rapidly increased to a higher level,and the scavenging mechanism is coordinated by the scavenging mechanism of HAT and ET.Lignosulfonate has low scavenging efficiency on ABTS·radical,but the scavenging effect of catalytic activated sample on ABTS·radical is improved to some extent.It was found that in the range of sample concentration 0.10mg·mL-1-0.80mg·mL-1,the reduction ability of LS increased with the increase of sample concentration.The antioxidant capacity of LS mainly came from hydroxyl structure,and the scavenging efficiency was mainly affected by phenolic hydroxyl content,which was a useful functional group in the utilization of lignosulfonate resources.This paper provides basic data and technical support for hydrogenation and reduction of lignin catalyzed by Ce catalyst.