Hydrogenation Of Nitrile Butadiene Rubber Research Articles

Artificial Neural Network Modeling in the Presence of Uncertainty for Predicting Hydrogenation Degree in Continuous Nitrile Butadiene Rubber Processing

The transition from batch to continuous production in the catalytic hydrogenation of nitrile butadiene rubber (NBR) into hydrogenated NBR (HNBR) marks a significant advance for applications under demanding conditions. This study introduces a continuous process utilizing a static mixer (SM) reactor, which notably achieves a hydrogenation conversion rate exceeding 97%. We thoroughly review a mechanistic model of the SM reactor to elucidate the internal dynamics governing the hydrogenation process and address the inherent uncertainties in key parameters such as the Peclet number (Pe), dimensionless time (θτ), reaction coefficient (R), and flow rate coefficient (q). A comprehensive dataset generated from varied parameter values serves as the basis for training an artificial neural network (ANN), which is then compared against traditional models including linear regression, decision tree, and random forest in terms of efficacy. Our results clearly demonstrate the ANN’s superiority in predicting the degree of hydrogenation, achieving the lowest root mean squared error (RMSE) of 3.69 compared to 21.90 for linear regression, 4.94 for decision tree, and 7.51 for random forest. The ANN’s robust capability for modeling complex nonlinear relationships and dynamics significantly enhances decision-making, planning, and optimization of the reactor, reducing computational demands and operational costs. In other words, this approach allows users to rely on a single ML-based model instead of multiple mechanistic models for reflecting the effects of possible uncertainties. Additionally, a feature importance study validates the critical impact of time and element number on the hydrogenation process, further supporting the ANN’s predictive accuracy. These findings underscore the potential of ML-based models in streamlining and enhancing the efficiency of chemical production processes.

Hydrogenation of olefinic bonds in nitrile butadiene rubber on single-atom Pd1/CeO2−x catalysts with ultrahigh mass activity and stability

As pivotal high-performance elastomers, hydrogenated nitrile butadiene rubber (HNBR) was commonly manufactured by selective hydrogenation of nitrile butadiene rubber (NBR). Nevertheless, the high cost and poor stability of current noble metal-based catalysts seriously limit their large-scale applications. Herein, we report single-atom Pd supported by oxygen vacancies-rich CeO2−x nanorods (Pd1/CeO2−x) as a novel catalyst for selectively hydrogenating the NBR. As a result of strong interaction between single-atom Pd and CeO2−x support, the electrophilicity of Pd sites, and the nucleophilicity of olefinic bonds in NBR, the Pd1/CeO2−x show a very high hydrogenated degree of 97.6 %, an unprecedentedly high Pd mass activity of 93.9 gNBR gPd−1h−1, and outstanding cycling stability, which considerably outperform those for previously reported catalysts. Therefore, this work will promote the low-cost manufacture of HNBR and the exploration of single-atom catalysts for selective hydrogenation.

Enhanced catalytic performance of Pd-Pt bimetallic alloy nanocatalyst for hydrogenation of nitrile butadiene rubber

Nowadays, the rational design of high-performance catalysts with desirable resistance to metal leaching has become the principal challenge in the hydrogenation of nitrile butadiene rubber. In the present work, the Pd-Pt bimetallic alloy nanocatalyst exhibits an outstanding hydrogenation degree of 99.0%, obviously higher than that of the conventional monometallic Pd/SiO2 catalyst with the same Pd content (92.9%), accompanied by approximately 100% selectivity to C=C bonds. The results reveal that electron transfer from Pt to Pd confirms that the Pd species are in a rich-electron state, which boosts hydrogen activation and improves catalytic activity. Additionally, the incorporation of inactive Pt species promotes the formation of uniformly dispersed Pd-Pt alloy nanoparticles. The incorporation of inactive Pt species can enhance the metal-support interaction, reducing the residual metal content in hydrogenated nitrile butadiene rubber. The current research demonstrates a simple procedure for designing efficient bimetallic catalysts for the hydrogenation of unsaturated elastomer.

Pore-size dependent catalytic activity of supported Pd catalysts for selective hydrogenation of nitrile butadiene rubber

Pore diffusion effect plays a crucial role in heterogeneous hydrogenation of unsaturated polymers. However, how large pore size can eliminate the pore diffusion limitation remains a controversial issue. Herein, we prepared a series of Pd/SiO2 catalysts with graded pore sizes and investigated the effect of pore size on hydrogenation activity of nitrile butadiene rubber (NBR). It is found that when the catalyst pore size (Dcat) is 7 times of the diameter of NBR chains (DNBR), the Weisz modulus Φ can be reduced to < 0.3 thus the internal mass transfer limitation can be eliminated, making NBR easier to approach the active sites. Consequently, the catalysts with the Dcat/DNBR > 7 exhibit excellent catalytic activity (96.7%) and selectivity (100%) to C = C. This work emphasizes that the pore size of catalysts can regulate the pore transfer limitation and the accessibility of internal active sites, providing useful guidance for the design of efficient macromolecular hydrogenation catalysts.

Selective hydrogenation of nitrile butadiene rubber latex using Catmetium®RF 4 catalyst

Hydrogenation of nitrile butadiene rubber (NBR) latex is an important topic in the field of chemical modification of unsaturated diene-based polymers. At present, the main challenge that restricts the large-scale production of hydrogenated nitrile rubber (HNBR) via latex hydrogenation way is how to reduce or even eliminate the use of organic solvents and to achieve a high rate of hydrogenation combined with a low amount of catalyst. We found a high-efficiency catalyst, i.e., catMETium®RF 4, which can directly hydrogenate NBR latex. The effects of temperature, hydrogen pressure, concentration of [CC]0 and agitation speed on the rate of hydrogenation were fully investigated. It was found that by using catMETium®RF 4 catalyst to prepare HNBR, the rate of hydrogenation of NBR latex can be increased drastically to achieve a high CC conversion of 95 mol% with a very low catalyst level of 0.02 wt%, which greatly decrease the demand on the recovery of a homogeneous catalyst from HNBR matrix. In addition, the hydrogenation of HNBR latex by catMETium®RF 4 was completely free of organic solvents and no cross-linking was found.

Effects of precipitated size of water-soluble amide-containing polymers and pore size of filters on recovery of Pd nanoparticles dispersed in acetone solution including colloidal polymer

ABSTRACT When immobilized Pd nanoparticles (Pd NP) are used for the hydrogenation of nitrile butadiene rubber (NBR), some Pd NP leaks into the reaction medium. This Pd NP is expensive and must be recovered. In this study, Pd NP were recovered from an NBR acetone medium by precipitation with poly N-[2-(dimethylamino)ethyl] methacrylamide (poly(DAEMA)) and filtration. When poly(DAEMA) solution was added to the Pd NP NBR acetone solution, poly(DAEMA) interacted with Pd NP and formed a precipitate by dehydration. The poly(DAEMA) precipitate including trapped Pd NP was completely recovered by filtration through a filter with a pore size of 1 μm. Poly(acrylamide) solutions of different molecular weights were tested for Pd NP recovery, and those with high molecular weights formed large quantities of precipitates, resulting in low recovery percentages. The concentration and molecular weight of the polymer used for the recovery of Pd NP by nanoprecipitation and filtration must be chosen carefully for optimal recovery. Especially, 40 kDa of PAA and 1 μm filter pores were suitable for efficient Pd NP recovery.

Zirconium promoter effect on catalytic activity of Pd based catalysts for heterogeneous hydrogenation of nitrile butadiene rubber

Three PdZr bi-component catalysts supported on modified silica have been successfully synthesized via different Zr introduction methods and utilized for the hydrogenation of nitrile butadiene rubber (NBR) to produce high value-added hydrogenated NBR. It is demonstrated that the introduction of Zr can lead to the formation of small-sized and electron-rich Pd nanoparticles and the order of adding Zr can significantly affect the catalytic activity. In particular, the PdZr bi-component catalyst obtained by introducing Zr followed by adding Pd is found to be more stable on the silica support, which exhibits a high hydrogenation degree of 90.9% with 100% selectivity to CC bond, close to the single Pd catalyst with double Pd contents. The electronic structure and reaction mechanism analysis from density functional theory calculations further reveal that the addition of Zr component leads to negatively charged Pd species with lower energy barrier for the hydrogenation of CC bond. Our findings provide a useful guidance for the design of efficient and low-cost bi-component catalysts for the selective hydrogenation of unsaturated polymers.

Effect of support morphology on the activity and reusability of Pd/SiO2 for NBR hydrogenation

Silica hollow microspheres with moonscape-like rough surface (RS) and macroporous surface (MS) have been controllably synthesized by a water–oil–water three-phase emulsion method, which are used as supports of the heterogeneous catalysts for the catalytic hydrogenation of nitrile-butadiene rubber (NBR). It is found that Pd can be uniformly dispersed on both amino-functionalized RS and MS supports and both the catalysts show high hydrogenation activity with 100% selectivity to C=C bonds. However, the reusability of Pd/N-RS is much better than that of Pd/N-MS, maintaining 92% of activity without any regeneration treatment after five times of recycling experiment. The high activity retention is because the moonscape-like surface of the RS support is favorable for the contact of NBR macromolecules with the active sites, and more importantly, the NBR macromolecules do not need to diffuse into the interior of the catalyst, leading to fast desorption of the hydrogenated NBR from the surface of catalyst and re-exposure of the active sites.

One-step Synthesis of End-Functionalized Hydrogenated Nitrile-Butadiene Rubber by Combining the Functional Metathesis with Hydrogenation.

End‐functionalized hydrogenated polymers obtained from nitrile‐butadiene rubber (NBR) yield new materials with suitable properties for a number of applications as sealing material and adhesives. We investigated the one‐step synthesis of ester end‐functionalized hydrogenated nitrile‐butadiene rubber (EF‐HNBR) by combining the functional metathesis with the hydrogenation of NBR in the presence of the 2nd generation Grubbs catalyst and a functionalized olefin as a chain transfer agent (CTA). We established the operating conditions for the effective production of saturated functional polymers with a high degree of hydrogenation, high chemo‐selectivity and moderate molecular weight. The structures of the products were confirmed by FT‐IR and 1H‐NMR spectroscopy, rubber molecular weight, and distribution determined by using gel permeation chromatography (GPC); their thermal properties were determined by thermo‐gravimetric analysis (TGA) and different scanning calorimetry (DSC).

Solvent Effect in Heterogeneous Catalytic Selective Hydrogenation of Nitrile Butadiene Rubber: Relationship between Reaction Activity and Solvents with Density Functional Theory Analysis

AbstractHerein, a systematical investigation is devoted to explore nitrile butadiene rubber (NBR) hydrogenation activity and selectivity in different organic solvents, and the dependence between reactivity and solvent is revealed with the assistance of the density functional theory (DFT). The results show that the electron‐pair donor solvents have better performance in NBR hydrogenation activity than the weak electron‐pair acceptor solvents, but they do not modify the selectivity to HNBR that always keeps up to 100 %. A direct correlation between reactivity and hydrogen bond acceptance ability (β) is discovered in both solvent families and the higher β, the better hydrogenation performance. The preferred solvent is cyclohexanone with hydrogenation degree of 91.4 % in 10 minutes and the highest conversion of 94.2 %. Our contribution is to provide useful information about solvent and solvent effect on the hydrogenation of NBR and gain new insight into NBR hydrogenation reaction process.

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

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...

Enhanced Separation Capability of Rhodium Ionic Catalyst Encapsulated by Propionation-Terminated Poly(propylene imine) Dendrimer

The second generation of poly(propylene imine) dendrimer peripherally terminated by propionation (G2-P) was synthesized. The structure and composition of G2-P were characterized by Fourier transform infrared (FTIR) spectrometer, 1H nuclear magnetic resonance spectroscopy (NMR), 13C NMR, matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) and elemental analysis. The encapsulated catalyst (G2-P(Rh3+)) was prepared by the coordination between G2-P and RhCl3·3H2O, and applied to the hydrogenation of nitrile-butadiene rubber (NBR) and styrene-butadiene rubber (SBR). G2-P(Rh3+) displayed excellent catalytic activity and selectivity for NBR and SBR hydrogenation, and Rh residue contents for hydrogenated NBR (HNBR) and hydrogenated SBR were only 80 ppm and 35 ppm respectively without any post treatment, which decreased 69.8% and 80.9% respectively compared with those of RhCl(PPh3)3. Open image in new window

Stable and recyclable Pd catalyst supported on modified silica hollow microspheres with macroporous shells for enhanced catalytic hydrogenation of NBR

In this work, a stable and recyclable Pd catalyst supported on N-containing silane coupling agent modified silica hollow microspheres with macroporous shells (Pd/N-SHMs) was successfully prepared and used for the selective hydrogenation of nitrile-butadiene rubber (NBR) with enhanced catalytic performance. The results showed that Pd/N-SHMs possessed small-sized and well-dispersed Pd nanoparticles (NPs) and the macroporous shells were beneficial for the diffusion of macromolecular NBR, and thus with such a catalyst, the reaction could occur under mild conditions and high hydrogenation degree (96.6%) with 100% selectivity to C=C was obtained. The prepared catalyst could be easily recycled and reused with a high efficiency. More importantly, because of the strong coordination between Pd and diamine ligands, Pd NPs could be anchored steadily over the support and only 5.0 ppm Pd residues was detected in products. This reaction was considered as pseudo-first order at high H2 pressures, and the reaction activation energy was calculated to be as low as 18.1 kJ/mol. Our contribution is to provide an efficient and recyclable supported Pd catalyst, which may promote the development of heterogeneous catalytic systems for unsaturated macromolecular hydrogenation.

Synthesis of Pd/SiO2 Catalysts in Various HCl Concentrations for Selective NBR Hydrogenation: Effects of H+ and Cl- Concentrations and Electrostatic Interactions.

A series of silica supported Pd (Pd/SiO2) catalysts were prepared in various HCl concentrations (CHCl) of the impregnation solution with different electrostatic interactions between Pd precursor and support, and their catalytic properties were evaluated by the selective hydrogenation of nitrile butadiene rubber (NBR). The results show that with the CHCl increasing from 0.1 to 5 M, the particle size of Pd nanoparticles dramatically decreases from 24.2 to 5.1 nm and stabilizes at ∼5 nm when CHCl is higher than 2 M. Using the catalysts prepared with a high CHCl (>2 M), an excellent hydrogenation degree (HD) of ∼94% with 100% selectivity to C=C can be acquired under mild conditions. Interestingly, the HD could be remarkably increased from 65 to 92% by increasing only CCl– from 0.1 to 2 M with the addition of NaCl while keeping CH+ at 0.1 M. This is because PdCl42– is the predominant existing form of precursor at high CCl–, which has a strong electrostatic attraction with the positively charged support favorable for the formation of small-sized Pd nanoparticles over silica. Notably, Pd leaching behavior during the hydrogenation reaction is closely related to CH+, and the higher the CH+, the less Pd residues are detected in the hydrogenated NBR. Our contribution is to provide a facile strategy to synthesize effective and stable Pd/SiO2 catalysts via adjusting the electrostatic interaction, which exhibits a high activity and selectivity for NBR hydrogenation.

Ureido-modified macroporous hollow silica microspheres for recovery of Wilkinson's catalyst in hydrogenated nitrile butadiene rubber

Hydrogenated nitrile butadiene rubber (H-NBR), which is obtained by the selective hydrogenation of nitrile butadiene rubber (NBR), has attracted great interests in many industrial fields. However, the recovery of the catalyst remains a challenge in the homogeneous catalytic hydrogenation of NBR, restricting its industrial production. In the present work, 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 loading, 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.

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

Abstract 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 present work. Compared with the Pd nanoparticles supported on macroporous hollow silica (Pd/MHS) via conversional incipient wetness impregnation with different free chelating reagents (HCl or EDTA) catalysts, the Pd nanoparticles supported on the modified macroporous hollow silica (Pd/M-MHS) catalyst showed better distribution of Pd nanoparticles and catalytic performance. High hydrogenation degree (HD) toward the –CH CH– group of 97% was achieved in acetone solution at 70 °C with H 2 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.

Preparation of facile separable homogeneous Rhodium catalyst and its application for the catalytic hydrogenation of nitrile butadiene rubber and styrene-butadiene rubber

Poly(propylene imine) dendrimer (G2-PPI) terminated by nitrogen-containing triolefinic macrocycle on the periphery (G2-M) was synthesized by a nucleophilic substitution reaction. The structure and composition of G2-M were characterized by FT-IR, 1H-NMR and elemental analysis. The Rh3+ dendrimer-stabilized catalyst (G2-M(Rh3+)) was prepared by utilizing G2-M as stabilizer and analyzed by UV–Vis spectroscopy, 1H-NMR spectrometry, XPS and XRD. G2-M(Rh3+) demonstrates excellent catalytic activity and selectivity for the hydrogenation of nitrile-butadiene rubber (NBR) and styrene-butadiene rubber (SBR), and Rh residue contents for HNBR and HSBR are only 35 and 13 ppm, respectively, without any post treatment.

Preparation and catalytic application of Rh3+/Ru3+ bimetallic catalyst stabilized by triolefinic macrocycle-terminated poly(propylene imine) dendrimer

The novel homogeneous bimetallic Rh3+/Ru3+ catalyst (G2-M(Rh3+xRu3+10-x)) was prepared within a second-generation poly(propylene imine) dendrimer terminated by nitrogen-containing triolefinic macrocycle (G2-M) by a co-complexation route. The G2-M(Rh3+x Ru3+10-x) catalyst was analyzed by 1H NMR (nuclear magnetic resonance), XPS (X-ray photoelectron spectroscopy), and XRD (X-ray diffraction). As a novel catalyst system, The bimetallic ions of Rh3+ and Ru3+ influenced on the catalytic activity for the hydrogenation of nitrile-butadiene rubber (NBR), which can be related to electron-deficiency effect resulting from the electron density shift from the Rh3+ to the Ru3+. The G2-M (Rh3+10) and G2-M(Rh3+7Ru3+3) displayed more excellent activity and favorable separation capability for the hydrogenation of NBR than the Rh nanoparticle catalyst stabilized by G2-M (G2-M(Rh10)).

Preparation of a novel homogeneous bimetallic Rhodium/Palladium ionic catalyst and its application for the catalytic hydrogenation of nitrile butadiene rubber

A new hybrid second-generation poly (propylene imine) dendrimer terminated by nitrogen-containing triolefinic macrocycle on the periphery (G2-M) was synthesized. The bimetallic Rhodium (III)/Palladium (II) (Rh3+/Pd2+) dendrimer-stabilized catalysts (G2-M(Rh3+xPd2+10-x)) were prepared by a co-complexation route within G2-M and analyzed by 1H NMR, XRD and XPS. The catalytic activity, selectivity and separation capability for the hydrogenation of nitrile-butadiene rubber (NBR) catalyzed by the G2-M(Rh3+xPd2+10−x) have been researched. As a novel catalyst system, the bimetallic ions of Rh3+ and Pd2+ have influenced on the catalytic activity for the hydrogenation of NBR, which can be related to electron-deficiency effect of Rh3+ resulting from the interaction of Rh3+ and Pd2+ within G2-M.

Selective hydrogenation of nitrile butadiene rubber (NBR) with rhodium nanoparticles supported on carbon nanotubes at room temperature

Carbon-nanotubes (CNTs)-supported rhodium (Rh) nanoparticle catalysts were prepared by sequential sonication-assisted liquid phase exfoliation of multi-walled CNTs (MWCNTs) in the presence of polyvinylpyrrolidone (PVP), followed by microwave-assisted hydrothermal reduction of the supported Rh. The as-prepared Rh-PVP-MWCNT catalysts were applied in the selective hydrogenation of nitrile butadiene rubber. The catalyst had excellent activity even at room temperature and can be easily separated from the product.