Macroporous hollow silica microspheres-supported palladium catalyst for selective hydrogenation of nitrile butadiene rubber

Santos

et al. 2021

Reac Kinet Mech Cat

Redox phase unpromoted molybdenum catalysts with different Mo loadings (2.5% Mo/γ-Al 2 O 3 ; 5.0% Mo/γ-Al 2 O 3 ; 7.5% Mo/γ-Al 2 O 3 and 10.0% Mo/γ-Al 2 O 3 ) were prepared and characterized for the ammoxidation of glycerol to nitriles, such as acrylonitrile. The best catalyst (10.0% Mo/γ-Al 2 O 3 ) obtained a yield of 26% in nitriles. The increase in the molybdenum content and its oxidation states along with the amount of weak/moderate acid sites on the support surface are key points for the optimization of the catalysts.

Section: Introductionmentioning

confidence: 99%

Direct ammoxidation of glycerol to nitriles using Mo/alumina catalysts

Santos

et al. 2021

Reac Kinet Mech Cat

“…Nevertheless, those catalysts would be easily left in hydrogenated production, leading to high cost of separation and even the degradation of the HNBR latex. − Therefore, the heterogeneous catalysts are considered as alternative desired catalysts for an easy separation process. The most widely used heterogeneous catalysts in NBR hydrogenation are Rh/SiO 2 , Pd/SiO 2 , and Pd/Al 2 O 3 . With these catalysts, the hydrogenation degree (HD) of above 90% can be achieved.…”

Section: Introductionmentioning

confidence: 99%

“…12−14 Therefore, the heterogeneous catalysts are considered as alternative desired catalysts for an easy separation process. The most widely used heterogeneous catalysts in NBR hydrogenation are Rh/SiO 2 , 15 Pd/SiO 2 , 16 and Pd/Al 2 O 3 . 17 With these catalysts, the hydrogenation degree (HD) of above 90% can be achieved.…”

Section: Introductionmentioning

confidence: 99%

Nitrile Butadiene Rubber Hydrogenation over a Monolithic Pd/CNTs@Nickel Foam Catalysts: Tunable CNTs Morphology Effect on Catalytic Performance

Luo

Mao

et al. 2019

Ind. Eng. Chem. Res.

In heterogeneous catalyst systems, catalytic performance was often negatively influenced by mass transfer limitations in which macromolecular reactants cannot diffuse into the inner pores to attach active sites. Carbon nanotubes (CNTs) with no-porous structure were the promising supports to solve the problem. In this work,CNTs were directly prepared by the CVD (chemical vapor deposition) method on nickel foam (NF). The morphology of the assynthesized CNTs were effectively tailored by varying temperature for growing CNTs. The prepared CNTs composites (CNTs@NF) with good mechanical strength were employed as a palladium catalyst (Pd/CNTs@NF) for nitrile butadiene rubber (NBR) hydrogenation, where a high degree of hydrogenation (HD) was accomplished via Pd/CNTs@NF catalyst. The HD for fifth reuse was only slightly reduced, demonstrating its great recyclable activity. Remarkably, the structured Pd/CNTs@NF catalyst could be easily separated from the hydrogenated products, avoiding the necessity of filtration for industrialization.

“…The selective hydrogenation of the unsaturated olefin groups (CC) with the retention of nitrile groups (−CN) in nitrile butadiene rubber (NBR) is an effective method to obtain high-quality saturated NBR (HNBR) that exhibits improved thermal properties, and oil and chemical resistance over the original polymer. − With the growing demand for HNBR, the hydrogenation of NBR has attracted significant attention in industries. Generally, HNBR is produced by either homogeneous or heterogeneous catalytic hydrogenation of NBR .…”

Section: Introductionmentioning

confidence: 99%

“…The most widely explored supported catalysts have been developed by immobilizing Rh or Pd nanoparticles (NPs) on various supports, such as C, TiO 2 , SiO 2 , and carbon nanotubes, and the hydrogenation degree of 95% could be obtained. − ,− However, it was found that the supported Pd NPs on bare silica usually exhibited nonuniform distribution of Pd NPs and easily leached from the support during the reaction due to the poor adhesion on the surface, which eventually limited the catalytic activity and recyclability. − Recently, Yue and coauthors immobilized Rh onto the surface-functionalized SiO 2 or carbon nanotubes, and Ai’s group immobilized Pd onto the SiO 2 with [3-(Trimethoxysilyl)propyl]urea as a modifier through the chemical bonding to improve the adhesion of active metals on the support . We also modified the silica surface with N -propylethylendiamine to anchor the Pd particles by the chemical bonding with diamine and Pd, and which were useful for improving the adhesion and reducing the removal of Pd from the support .…”

Section: Introductionmentioning

confidence: 99%

A Surface-Cofunctionalized Silica Supported Palladium Catalyst for Selective Hydrogenation of Nitrile Butadiene Rubber with Enhanced Catalytic Activity and Recycling Performance

Chen

Liu

et al. 2019

Ind. Eng. Chem. Res.

A cofunctionalized silica-supported palladium catalyst has been successfully designed and controllably fabricated for the selective hydrogenation of nitrile butadiene rubber (NBR). The amino groups on the surface can anchor and stabilize Pd particles via the strong coordination with diamine ligands and methyl groups can enhance surface hydrophobicity, weakening the adhesion of NBR/hydrogenated NBR on catalyst and accelerating the desorption of product to re-expose the active sites. The cofunctionalized catalyst with small-sized and well-dispersed Pd particles exhibits an enhanced activity and stability, which can be easily recycled by filtration and reused without any treatment. It remains a high activity and 100% selectivity to CC after recycling five times, and only a slight loss of Pd is detected in products. Such catalyst with cofunctionalized surface is very efficient for NBR hydrogenation and also can be applied to other catalytic systems to tune their selectivity, activity, and reusability.