Olefin Metathesis Reaction And Catalytic Hydrogenation Of Nitrile Rubber

The dissertation is the result of a project from Lanzhou Petrochemical Research Center. The chapter 1 summarizes the NBR olefin metathesis technique and the research progress of hydrogenation technology.Chapter 2 mainly concern selectively catalytic hydrogenation of NBR with a Grubbs catalyst. Hydrogenated nitrile-butadiene rubber (H-NBR) is a high-performance elastomer with important applications in the automobile industry and petroleum field.Selectively catalytic hydrogenation of nitrile-butadiene rubber (NBR) with a typical olefin metathesis catalyst, Grubbs II, has been developed in the present work. The catalytic selectivity for the hydrogenation of -C=C- instead of -C?N was supported by FT-IR and NMR analysis. The effects of the reaction conditions, such as reaction time,temperature, pressure, catalyst amount, and solvent, on the hydrogenation degree (HD)and relative molecular weight and distribution of the hydrogenated products have been investigated in detail. Under the optimized condition, 6 mg catalyst per 1.0 g NBR in 100 mL toluene solution and H2 pressure of 5.0 MPa at 55 ? for 3 h, a hydrogenation degree of 75% was obtained. In the case, the degradation of polymer chains might provide a solution for the challenge of high Mooney viscosity of H-NBR,strongly restricting its processability in many applications.In the chapter 3, olefin cross metathesis was used to degrade XNBR with acrylonitrile(AN) as chain transfer agent for the first time, to solve the solubility problem. After degradation under the optimized condition, with 2% AN and 0.2% catalyst at 60 ?for 30 min, the weight-average molecular weight (Mw) of the product decreased to 0.98 × 104 with distribution (Mw/Mn) of 3.83. Such product was easy to be dissolved,so the carboxyl content in XNBR could be determined with the routine titrimetric analysis methods.A potential high durable heterogeneous catalyst for the industrial selective hydrogenation of nitrile butadiene rubber (NBR) has been established by immobilizing palladium (Pd) nanoparticles on macroporous hollow silica (MHS)microspheres in the chapter 4. By comparing the distribution of Pd nanoparticles in the resultant catalysts and their catalytic performance of the Pd nanoparticles supported on macroporous hollow silica (Pd/IHS) catalysts via conversional incipient wetness impregnation with different free chelating reagents (HCl or EDTA)or modified chelating group, the Pd nanoparticles supported on modified macroporous hollow silica (Pd/M-MHS) catalyst was selected as an optimal one. The hydrogenation degree (HD) towards the -CH2=CH2- group of 97% was achieved in acetone solution at 70 0C with H2 pressure of 4.5 MPa for 6 h, while the nitrile (-C?N)group had not been hydrogenated in the reaction. And there was no obvious change in the relative molecular weight and polydispersion index of the product in comparison with the raw NBR. The HD for the 5th reuse was 90.5%, remaining more than 93% of its HD for the original time, demonstrating its high durable activity.Hydrogenated nitrile-butadiene rubber (H-NBR) is a high-performance elastomer with important applications in the automobile industry and petroleum field. Selectively catalytic hydrogenation of nitrile-butadiene rubber (NBR) with a typical olefin metathesis catalyst, Grubbs II, has been developed in the chapter 5. The catalytic selectivity for the hydrogenation of -C=C- instead of -C=N was supported by FT-IR and NMR analysis. The effects of the reaction conditions, such as reaction time,temperature, pressure, catalyst amount, and solvent, on the hydrogenation degree (HD)and relative molecular weight and distribution of the hydrogenated products have been investigated in detail. Under the optimized condition, 6 mg catalyst per 1.0 g NBR in 100 mL toluene solution and H2 pressure of 5.0 MPa at 55 ? for 3 h, a hydrogenation degree of 75% was obtained. In the case, the degradation of polymer chains might provide a solution for the challenge of high Mooney viscosity of H-NBR,strongly restricting its processability in many applications.However, the recovery of the catalyst remains a challenge in the homogeneous catalytic hydrogenation of NBR, restricting its industrial production. In the chapter 6,ureido-modified macroporous hollow silica microspheres were designed for the recovery of the Rh-based catalyst, with Wilkinson's catalyst (RhCl(P(C6H5)3)3) as an example, in the homogeneous catalytic hydrogenation of NBR. After the effects of the adsorbent dosage, adsorption parameters (temperature, agitating speed and time), and separation condition (centrifugal speed and time) on the Rh recovery rate were optimized in detail, a maximum Rh recovery rate of 92.2% was achieved.