Study On Preparation Of Carbon-based Palladium Or Nickel Catalyst And Their Catalytic Hydrogenation Of ?-pinene Or Rosin

Turpentine oil and rosin are important renewable natural resources.Their hydrogenated products,namely pinane and hydrogenated rosin,can be used in the fields of electronics,food,medicine and functional materials et al.,which possess high economic value.In this paper,from the perspective of environmental friendliness,high activity,easy separation of products and high stability catalysis,melamine or dicyandiamide is selected as carbon source and nitrogen source,palladium chloride or nickel acetate tetrahydrate as the source of palladium or nickel,the carbon-based carriers containing nitrogen heterocycle are prepared,which make it better to stabilize the metallic active component.Furthermore,the as-prepared carbon-based Pd/Ni catalysts are applied in catalytic hydrogenation of?-pinene?the main component of turpentine oil?or rosin to prepare cis-pinane or hydrogenated rosin.By using SiO₂ and dicyandiamide as raw materials,trithiocyanuric acid,phosphonitrilic chloride trimer and ammonia borane as the source of S,P and B respectively,the hetero-atom-doped mesoporous graphite phase nitride carbon X-mp-C₃N₄?X stands for B,S,P?was prepared through high-temperature calcination and NH₄HF₂ etching,and the surface acidity of the carriers was analyzed by NH₃-TPD method.With palladium chloride as palladium source and sodium borohydride as reductant,X-mp-C₃N₄ supported Pd catalysts?Pd/X-mp-C₃N₄?were synthesized and applied in catalytic hydrogenation of?-pinene.The better carrier was selected as B-mp-C₃N₄-0.15?0.15 represents that the mass of ammonia borane added per 3.00 g dicyandiamide is 0.15 g?.By means of XRD,FT-IR,N₂ adsorption-desorption,XPS and ICP-AES techniques,the phase structure,structural composition,specific surface area and pore diameter of Pd/B-mp-C₃N₄-0.15,as well as the valence state distribution and content of Pd were investigated.TEM,FESEM-EDS and TG analysis were used to investigate the morphology,elemental distribution and thermal stability of Pd/B-mp-C₃N₄-0.15.The optimized hydrogenation process of?-pinene was:0.0532 g Pd/B-mp-C₃N₄-0.15,Pd loading 4.00%,2.40 g?-pinene,90?,2.0 MPa H₂,3 h,and the conversion of?-pinene was 97.5%,the selectivity for cis-pinane was 74.9%.Under the optimal process,the catalyst has good stability.After 7 cycles,?-pinene conversion remained at 96.4%and the selectivity was almost unchanged.Ni-N-C catalyst was designed and synthesized by using tripyridine and dicyandiamide as the source of carbon and nitrogen,nickel acetate tetrahydrate as nickel source,MgO as templating agent,H₂SO₄ as etchant and absolute ethanol as solvent.The phase structure,structural composition,the specific surface area and pore diameter of Ni-N-C as well as the valence distribution and content of Ni were investigated by XRD,FT-IR,N₂ adsorption-desorption XPS and ICP-AES.The morphology,elemental distribution and thermal stability of Ni-N-C were investigated by TEM,FESEM-EDS and TG analysis.Ni-N-C was applied in the catalytic hydrogenation of?-pinene.The optimized hydrogenation process was as follows:0.0243 g Ni-N-C,2.00 g?-pinene,5.0MPa H₂,170?,5 h.The conversion of?-pineneand the selectivity for cis-pinane were75.2%and 73.7%,respectively.The catalyst showed good stability.After 5 cycles,neither activity nor selectivity changed obviously.Mesoporous graphite phase carbon nitride?mpg-C₃N₄?was prepared through high-temperature calcination method by using SiO₂ and melamine as raw materials.,mpg-C₃N₄ supported Pd catalysts?Pd/mpg-C₃N₄?were synthesized with palladium chloride as palladium source and sodium borohydride as reductant.The phase structure,structural composition,the specific surface area and pore diameter of Pd/mpg-C₃N₄ as well as the valence distribution and content of Pd were investigated by XRD,FT-IR,N₂ adsorption-desorption XPS and ICP-AES.The morphology and thermal stability of Pd/mpg-C₃N₄were investigated by TEM and TG analysis.Pd/mpg-C₃N₄ was applied in the catalytic hydrogenation of rosin.The optimized hydrogenation process was as follows:0.600 g rosin,0.030 g Pd/mpg-C₃N₄,7.96%Pd loading,5.0 MPa H₂,150?,4 h.The conversion of abietic acid was 99.8%,the selectivity for tetrahydroabietic acid was37.2%,the selectivity for dihydroabietic acid was 56.8%,and the content of dehydroabietic acid was 6.0%.After 4 cycles,the selectivity for tetrahydroabietic acid decreased to 26.4%,the selectivity for dihydroabietic acid increased to 63.2%,and the content of dehydroabietic acid increased to 10.4%.Hollow mesoporous carbon spheres coated with carbon nitride?SiO₂@SiO₂/C@g-C₃N₄?were obtained through high-temperature calcination by using ethyl orthosilicate?TEOS?and propyl orthosilicate?TPOS?as silicon source,the polycondensate of resorcinol and formaldehyde as carbon source,and melamine as carbon and nitrogen source.The phase structure,structural composition,the specific surface area and pore diameter and light absorption intensity of SiO₂@SiO₂/C as well as the valence distribution and content of Ni were investigated by XRD,FT-IR,N₂ adsorption-desorption and UV-Vis methods.The morphological changes of SiO₂@SiO₂/C@g-C₃N₄in each preparation stage were explored through TEM and SEM analysis.With palladium chloride as palladium source and sodium borohydride as reductant,SiO₂@SiO₂/C@g-C₃N₄ supported Pd catalysts were synthesized and preliminarily applied in catalytic hydrogenation of rosin.When they react at 5.0 MPa H₂,150?for4 h,The conversion of abietic acid was 93.8%,the selectivity for dihydroabietic acid was67.5%,the selectivity for tetrahydroabietic acid was 29.9%and the content of dehydroabietic acid was 2.60%.The above four carbon-based metal-type catalysts system designed and prepared with carbon nitrogen heterocycles as the framework exhibited better activity,selectivity,stability and easy seperation from products for both the hydrogenation of?-pinene and that of rosin,which can be attributed to the large?bond originated from delocalization of the electrons of the carbon nitrogen heterocycles and the relatively strong metal coordination ability.Our research also provides a reference for catalytic hydrogenation of other natural products.