Catalytic Hydrogenation Of Hydrogenated Nitrile Butadiene Rubber Under The Action Of Carbon Dioxide

In recent years,there has been a high interest in the application of CO₂ in the selective hydrogenation of various substrates,but it is more often applied in the hydrogenation reactions of small molecule olefins.The synthesis and production of HNBR has become an important topic for the defense industry,and the hydrogen transfer of the aqueous phase in the emulsion method has been a huge problem in the industry.Sc CO₂ as a green co-solvent with high transfer efficiency,we explore the role of sc CO₂in the selective hydrogenation of NBR and its effect on the performance of HNBR.We explored the role of sc CO₂ in the selective hydrogenation of NBR and its effect on the performance of HNBR.We firstly used sc CO₂ to swell the nitrile latex and used ruthenium-based catalyst emulsion to hydrogenate the NBR emulsion.Firstly,we explored the acid and alkaline conditions of nitrile latex in CO₂,and solved the problem of blocked hydrogenation of nitrile latex after CO₂ expansion,and then explored the effect of type and amount of plasticizer,type and amount of solvent,temperature.After that,we investigated the effects of the type and amount of plasticizer,type and amount of solvent,temperature,speed and other conditions on the particle size in the swelling action,and determined the optimal sc CO₂ swelling conditions for the effective hydrogenation of the NBR latex after the swelling of the rubber particles.This method has not been reported so far.The produced HNBR raw gels showed higher meniscus viscosity and GPC tests compared to the CH-02 series prepared by Therban 3406,so we characterized their gels and microgels and found that microgels may be an important factor affecting the meniscus viscosity of HNBR when the difference in HNBR gel content is not significant.For this reason,we analyzed the vulcanization characteristics,mechanical properties,oil resistance and aging resistance of CH-02,Zetpol 2000 and Therban 3406,and found that the high microgel did not affect the performance of HNBR products,and the comprehensive performance of CH-02,which was synthesized by sc CO₂ swelling method,was comparable to the imported mainstream products,and even better than the commercial products in terms of resilience and oil resistance.It is even better than commercial products in terms of resilience and oil resistance.CXL is a green swelling fluid widely studied at home and abroad.Since solution hydrogenation has relatively better mass transfer efficiency than emulsion hydrogenation,we use CXL to investigate the role of CO₂ in solution,which is simpler to operate and easier to achieve.We optimized the effect of solvent type,CO₂ pressure,expansion temperature,H₂ pressure and catalyst dosage on the hydrogenation of NBR solution under CXL and compared it with the unexpanded reaction system.The results showed that the degree of hydrogenation was significantly higher in the CXL system,which was attributed to the improved H₂ solubility and mass transfer.The obtained results also indicate that hydrogenation of NBR solution under CXL can be performed at lower H₂ pressure and catalyst dosage to achieve efficient conversion.Furthermore,the results show that in the CXL system with a catalyst/NBR mass ratio of 0.02 wt%and a lower H₂ pressure of 800 psi,we achieved an efficient hydrogenation of 88 mol%for5 h,which is comparable to the results of the unexpanded system with 1100 psi H₂reaction for 5 h.It is fully demonstrated that the CXL system can effectively improve the mass transfer and H₂ solubility,thus serving to partially replace H₂ for efficient hydrogenation.FT-IR and 1H NMR tests showed that this method can effectively selectively reduce the carbon-carbon double bond（-C=C-）bond while retaining the integrity of cyano（-CN）.We also investigated the co-soluble hydrogenation of acetone solution of NBR by sc CO₂,and found that sc CO₂ also has good effect on the hydrogenation of NBR,but due to its high reaction pressure and insignificant advantage over CXL,we believe that CXL is a more efficient and environmentally friendly mass transfer medium for the hydrogenation of NBR solution.