Rubber HNBR

# We sell plastic and rubber raw material # Rubber HNBR

NBR Solution Hydrogenation

The solution hydrogenation of NBR is carried out in NBR solution with the precious metals palladium, calcium and rhodium as catalysts and hydrogen gas.The content of acrylonitrile on the molecular chain of NBR determines its oil resistance.When hydrogenating NBR, only the double bond of the diene unit is selectively hydrogenated and reduced to saturated bonds, and the side chain eyeball group -C≡N of the acrylonitrile unit is not hydrogenated. This hydrogenation method mainly uses Two types of catalysts are used for this hydrogenation method, namely, non-homogeneous carrier catalysts and homogeneous coordination catalysts. The first non-homogeneous carrier catalyst is Pd/C catalyst with carbon carrier, which has high selectivity and hydrogenation rate up to 95.6%, but in the hydrogenation reaction, the diene rubber affinity with carbon black is easily adsorbed on the surface of carbon black, and the carbon black is easily coagulated into lumps during stirring, which will have adverse effects on the vulcanization characteristics of Rubber HNBR. The Pd/SiO2 catalysts with SiO2 as the carrier have been industrialized by Ruion, Japan. When these two carrier catalysts are used for hydrogenation of NBR, the residues of NBR catalyst or the additives used in the polymerization reaction may adhere to the surface of the carrier or remain in the micro-pores, which will cause a sharp decrease in catalyst activity and affect the reuse.

There are three common homogeneous coordination catalysts: palladium catalyst, rhodium catalyst and iridium catalyst. Palladium type catalysts are stable to water and air, easy to store and transport, and can be recycled repeatedly, but the activity and selectivity are poor, and iridium type catalysts have very high activity and selectivity for hydrogenation of NBR, which has become one of the hot spots for Rubber HNBR development. Rhodium type catalyst has the highest activity and selectivity, RhH(PPh3)3 type hydrogenated rhodium catalyst can catalyze the hydrogenation of NBR in solution or emulsion, the solvent used in the reaction is benzene, the temperature is 80-160℃, the hydrogen pressure is 0.05-3MPa, and the time is 2-10 hours. In order to make the catalyst stable also need to add PPh3, the amount of catalyst and PPh3 are 0.05% ~ 20%, l% ~ 25% (based on NBR), the mass ratio of the two is 0.6/1 ~ 20/1. This catalytic system has high activity and selectivity, the minimum hydrogenation rate is 95%. However, rhodium resources are tight and expensive, and should be recycled for large-scale production. 81% of residual rhodium in HNBR has been absorbed with triaminosilane.

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