Ki-Young Yoon, Jinkyung Noh, Quan Gan, Julian P Edwards, Robert Tuba, Tae-Lim Choi, Robert H. Grubbs
2022. 09. 26. Nature Chemistry
Abstract
Cyclic polymers are topologically interesting and envisioned as a lubricant material. However, scalable synthesis of pure cyclic polymers remains elusive. The most straightforward way is to recover a used catalyst after the synthesis of cyclic polymers and reuse it. Unfortunately, this is demanding because of the catalyst’s vulnerability and inseparability from polymers, which reduce the practicality of the process. Here we develop a continuous circular process, where polymerization, polymer separation and catalyst recovery happen in situ, to dispense a pure cyclic polymer after bulk ring-expansion metathesis polymerization of cyclopentene. It is enabled by introducing silica-supported ruthenium catalysts and newly designed glassware. Different depolymerization kinetics of the cyclic polymer from its linear analogue are also discussed. This process minimizes manual labour, maximizes the security of vulnerable …
Márton Nagyházi, Ádám Lukács, Gábor Turczel, Jenő Hancsók, József Valyon, Attila Bényei, Sándor Kéki, Róbert Tuba
2022. 04. 14. Angewandte Chemie International Edition
Abstract
One of the most exciting scientific challenges today is the catalytic degradation of non‐biodegradable polymers into value‐added chemical feedstocks. The mild pyrolysis of polyolefins, including high‐density polyethylene (HDPE), results in pyrolysis oils containing long‐chain olefins as major products. In this paper, novel bicyclic (alkyl)(amino)carbene ruthenium (BICAAC−Ru) temperature‐activated latent olefin metathesis catalysts, which can be used for catalytic decomposition of long‐chain olefins to propylene are reported. These thermally stable catalysts show significantly higher selectivity to propylene at a reaction temperature of 75 °C compared to second generation Hoveyda–Grubbs or CAAC−Ru catalysts under ethenolysis conditions. The conversion of long‐chain olefins (e.g., 1‐octadecene or methyl oleate) to propylene via isomerization‐metathesis is performed by using a (RuHCl)(CO)(PPh3)3 …
Vajk Farkas, Pascal Albrecht, Ádám Erdélyi, Márton Nagyházi, Beatrix Csutorás, Gábor Turczel, Norbert Miskolczi, Janka Bobek-Nagy, Ole Osterthun, Jürgen Klankermayer, Robert Tuba
2024. 08. 16. Green Chemistry
Abstract
As a model of a chemical upcycling process, we have developed a single-metal homogeneous catalytic system to break down persistent polyethylene waste into valuable chemical intermediates. This could ultimately be used to produce important chemical products, including environmentally friendly, biodegradable plastics. In the first step, a slow pyrolysis of polyolefin waste yields oils, containing long-chain olefins as the major components. Then, for the next transformation step, tailored bicyclic (alkyl)(amino)carbene (BICAAC)-Ru olefin metathesis catalysts were used in combination with an alkene isomerization catalyst (RuHCl(CO)(PPh3)3) for the transformation of the pyrolysis oil to propylene via isomerization-metathesis (ISOMET) reaction in ethylene atmosphere. Eventually, translation of the highly efficient single-metal catalyst system enabled ISOMET reaction to a 900 mL reactor setup and repetitive batch …
Ádám Erdélyi, Vajk Farkas, Gábor Turczel, Márton Nagyházi, Attila Bényei, Merell Lystra Ledesma Recta, Tibor Nagy, Sándor Kéki, Ole Osterthun, Jürgen Klankermayer, Róbert Tuba
2024. 05. 23. Chemistry–A European Journal
Abstract
A series of a novel CAAC ligands featuring a spiro‐fluorene group have been synthesized and complexed with ruthenium alkylidenes, yielding the corresponding Hoveyda‐type derivatives as a new family of olefin metathesis catalysts. The novel complexes have been characterized by XRD, HRMS and NMR measurements. The synthetized complexes were tested in catalysis and showed good activity in olefin metathesis, as demonstrated on diethyl diallylmalonate and allyl acetate substrates. The unique backbone in the ligand system with the large, yet inflexible condensed system renders interesting properties to the catalyst, exemplified by the good catalytic performance and improved Z‑selectivity. In addition, the complex can also serve as a hydrogenation catalyst in a consecutive (one‐pot) reaction. The latter reaction can convert allyl acetate to butane‑1,4‑diol, a valuable chemical intermediate for biodegradable …
Vajk Farkas, Dániel Csókás, Ádám Erdélyi, Gábor Turczel, Attila Bényei, Tibor Nagy, Sándor Kéki, Imre Pápai, Róbert Tuba
2024. 05. 01. Advanced Science
Abstract
Isomerization Metathesis (ISOMET) reaction is an emerging tool for “open loop” chemical recycling of polyethylene to propylene. Novel, latent N‐Alkyl substituted Cyclic(Alkyl)(Amino)Carbene (CAAC)–ruthenium catalysts (5a‐Ru, 3b‐Ru – 6c‐Ru) are developed rendering “inverted” chemical structure while showing enhanced ISOMET activity in combination with (RuHCl)(CO)(PPh3)3 (RuH) double bond isomerization co‐catalyst. Systematic investigations reveal that the steric hindrance of the substituents on nitrogen and carbon atom adjacent to carbene moiety in the CAAC ligand have significantly improved the catalytic activity and robustness. In contrast to the NHC‐Ru and CAAC‐Ru catalyst systems known so far, these systems show higher isomerization metathesis (ISOMET) activity (TON: 7400) on the model compound 1‐octadecene at as low as 3.0 bar optimized pressure, using technical grade (3.0) ethylene …
Róbert Tuba, Róbert Kurdi, Gyula Pályi
2024. 01. 27. Journal of Organometallic ChemistryAbstract
The almost centennary history of alkyl- and acylcobalt carbonyls started with preparative and structural interest in these particular compounds, but the attention also soon included important industrial problems. These two driving forces induced intense research toward this compound class, which produced useful experimental details for the petrochemical industry and led to unexpected new application possibilities at the dawn of the 3rd millennium. In this review, an attempt is made to deduce the most characteristic features of the history of these compounds, to collect interesting, unexpected discoveries from related research and to list the newest possible discoveries offered by the most recent results. This paper does not intend to provide a complete literature list; only those reports will be mentioned, which are regarded as important steps forward, with special attention given to the results obtained by the László …
Vajk Farkas, Márton Nagyházi, Paul T Anastas, Jürgen Klankermayer, Róbert Tuba
2023. 08. 07. ChemSusChemAbstract
The vastness of the scale of the plastic waste problem will require a variety of strategies and technologies to move toward sustainable and circular materials. One of these strategies to address the challenge of persistent fossil‐based plastics is new catalytic processes that are being developed to convert recalcitrant waste such as polyethylene to produce propylene, which can be an important precursor of high‐performance polymers that can be designed to biodegrade or to degrade on demand. Remarkably, this process also enables the production of biodegradable polymers using renewable raw materials. In this Perspective, current catalyst systems and strategies that enable the catalytic degradation of polyethylene to propylene are presented. In addition, concepts for using “green” propylene as a raw material to produce compostable polymers is also discussed.
Áron Balla, Márton Nagyházi, Gábor Turczel, Hanna E Solt, Magdolna R Mihályi, Jenő Hancsók, József Valyon, Tibor Nagy, Sándor Kéki, Paul T Anastas, Róbert Tuba
2022. 07. 25. New Journal of ChemistryAbstract
Cyclic alkyl amino mono- and bis-carbene ruthenium (CAAC–Ru) complexes were immobilized on mesoporous Y zeolite (catalysts 3 and 4) and showed high activity and stability in ammonia borane (AB) hydrolytic dehydrogenation. Both catalysts have a Ru content as low as 0.1 wt%. Catalysts 3 and 4 provide a reasonable activity even at a loading of 10 ppm (0.001 mol%) giving a turnover number (TON) of 79 000 molH2 molcat−1. The optimal loading, however, was found to be slightly higher for catalyst 4, at around 50 ppm (0.005 mol%), giving a turnover frequency (TOF) of 8500 molH2 molcat−1 h−1 and a TON of 49 375 molH2 molcat−1 whilst retaining a high nH2/nAB ratio (2.51). This value is higher than those observed for its homogeneous analogue 2 (TOF, 7500 molH2 molcat−1 h−1; TON, 43 600 molH2 molcat−1; released nH2/nAB ratio, 2.18). Interestingly, it was found that the zeolite-supported catalyst …
Márton Nagyházi, Balázs Almási, Ádám Lukács, Attila Bényei, Tibor Nagy, Sándor Kéki, Róbert Tuba
2022. 05. 15. Journal of Molecular StructureAbstract
A series of bicyclic alkylamino carbenes (BICAAC) (where N-aryl = dipp, mes, 2,6-dimethyl-4-(dimethylamino)phenyl, 5a–d) and their novel air- and moisture-resistant pyridine (pyridine, 4-dimethylaminopyridine) containing palladium Pd(II) complexes (6a–e) were synthetized and characterized. As novel examples of the PEPPSI (“pyridine enhanced precatalyst preparation stabilization and initiation”)-Pd compounds, the reported complexes have shown high activity in Mizoroki–Heck coupling reaction even at as low as 100 ppm loading (TON up to 10000). Kinetic studies revealed that reactions carried out in the presence of elemental mercury resulted decrease in activity. It indicates that the coupling reaction may have both molecular and Pd(0)-mediated catalytic paths.
Anvar Mirzaei, Gábor Turczel, Márton Nagyházi, Vajk Farkas, Áron Balla, Hai Dang Vu, Robert Tuba
2021. 01. 22. European Journal of Organic ChemistryAbstract
Since the first discovery by Huigsen and co‐workers fifty years ago, a wide range of organic reactions have taken place through the intermediary of the dipolar/zwitterionic species produced by the combination of a neutral nucleophile and an unsaturated electrophile. Nucleophilic initiators including heterocycles may react or play a mediating role based on their nucleophilic nature and reaction conditions. This review highlights the recent developments of the cyclization chemistry of heterocycles using multicomponent reactions (MCRs) – including unusual dearomatizative examples. Heterocycles as very common structural units can often be found in natural and pharmaceutical products. MCRs are environmentally benign and highly atom economic reactions. Their application in the synthesis of biologically active molecules may provide alternatives for the greener synthesis of drugs lowering the carbon footprint of …