Enhancing the stability of the Rh/ZnO catalyst by the growth of ZIF-8 for the hydroformylation of higher olefins†

The hydroformylation of olefins is one of the most important homogeneously catalyzed processes in industry to produce bulk chemicals. Despite the high catalytic activities and selectivity’s using rhodium-based homogeneous hydroformylation catalysts, catalyst recovery and recycling from the reaction mixture remain a challenging topic on a process level. Therefore, technical solutions involving alternate approaches with heterogeneous catalysts for the conversion of olefins into aldehydes have been considered and research activities have addressed the synthesis and development of heterogeneous rhodium-based hydroformylation catalysts. Different strategies were pursued by different groups of authors, such as the deposition of molecular rhodium complexes, metallic rhodium nanoparticles and single-atom catalysts on a solid support as well as rhodium complexes present in supported liquids. An overview of the recent developments made in the area of the heterogenization of homogeneous rhodium catalysts and their application in the hydroformylation of short-chain olefins is given. A special focus is laid on the mechanistic understanding of the heterogeneously catalyzed reactions at a molecular level in order to provide a guide for the future design of rhodium-based heterogeneous hydroformylation catalysts.

Rhodium-catalyzed hydroformylation of olefins: Effect of [bis(2,4-di- tert-butyl) pentaerythritol] diphosphite (alkanox P-24) on the regioselectivity of the reaction

A novel selective palladium catalyst system based on bidentate 2,2'-heteroarylarylphosphines and p-TsOH has been developed for hydroformylation reactions (see scheme). By applying optimal conditions good to excellent regioselectivity is obtained for the hydroformylation of aliphatic and aromatic olefins. It is shown that a low acid concentration is crucial for obtaining high degrees of the linear isomer.The palladium-catalyzed hydroformylation of 1-octene has been studied in the presence of different phosphines and acid cocatalysts. The best results are achieved in the presence of in situ-generated palladium complexes with bidentate phosphines. It is demonstrated that the acid concentration is a crucial factor for obtaining high linear selectivity. A novel optimized catalyst based on an arylheteroarylphosphine has been applied for hydroformylation of different aliphatic and aromatic olefins. Good activity and excellent selectivity towards the linear aldehydes is achieved.

The hydroformylation of alkenes with CO and H2 to manufacture aldehydes is one of the most large-scale chemical reactions. However, an efficient and recyclable heterogeneous catalyst for alkene hydroformylation is extremely in demand in academia and industry. In this study, a sulfated carbon nitride supported rhodium particle catalyst (Rh/S-g-C3N4) was successfully synthesized via an impregnation-borohydride reduction method and applied in the hydroformylation of alkenes. The catalysts were characterized by XRD, FTIR, SEM, TEM, XPS, and nitrogen adsorption. The influence of the sulfate content, pressure of syngas, temperature, and reaction time, as well as the stability of Rh/S-g-C3N4, on the hydroformylation was examined in detail. The delocalized conjugated structure in g-C3N4 can lead to the formation of electron-deficient aromatic intermediates with alkenes. The sulphate g-C3N4 has a defected surface owing to the formation of oxygen vacancies, which increased the adsorption and dispersion of RhNPs on the surface of g-C3N4. Therefore, Rh/S-g-C3N4 exhibited an outstanding catalytic performance for styrene hydroformylation (TOF = 9000 h−1), the conversion of styrene could reach 99.9%, and the regioselectivity for the branched aldehyde was 52% under the optimized reaction conditions. The catalytic properties of Rh/S-g-C3N4 were also studied in the hydroformylation of various alkenes and displayed an excellent catalytic performance. Furthermore, the reuse of Rh/S-g-C3N4 was tested for five recycling processes, without an obvious decrease in the activity and selectivity under the optimum reaction conditions. These findings demonstrated that Rh/S-g-C3N4 is a potential catalyst for heterogeneous hydroformylation.

Hydroformylation of alkenes using heterogeneous catalyst prepared by intercalation of HRh(CO)(TPPTS) 3 complex in hydrotalcite

The hydroformylation of alkenes is a cornerstone transformation for the chemical industry, central for both functionalizing and extending the carbon backbone of an alkene. In this study, silica‐supported crystalline rhodium sulfide nanoparticles are explored as heterogeneous catalysts in hydroformylation reactions, and it is found that RhxSy systems (x = 17, y = 15 or x = 2, y = 3 with 1 wt% Rh on SiO2) greatly outperform metallic Rh nanoparticles. These systems prove to be exceptionally competitive when benchmarked against other cutting‐edge catalysts in terms of activity, with Rh17S15/SiO2 being the superior catalyst candidate. By employing local environment descriptors, unsupervised machine learning and density functional theory, the structure‐performance relationships are examined. The results highlight that the presence of S in close proximity to the catalytic site unlocks the tunability of the surface catalytic properties. This allows for the substrate affinity to be modulated, in particular for Rh17S15, with adsorption energies rivalling those of pristine Rh and improved spatial resolution.

Development of a continuous process for the hydroformylation of long-chain olefins in aqueous multiphase systems

Green chemistry and catalysis

Hydroformylation of olefins catalyzed by single-atom Co(II) sites in zirconium phosphate

Continuously operated miniplant for the rhodium catalyzed hydroformylation of 1-dodecene in a thermomorphic multicomponent solvent system (TMS)

Hydroformylation of olefins with H2 and CO is an important industrial process for aldehyde production, and developing Earth-abundant catalysts with high catalytic activity and stability remains challenging. Here, we synthesize a rhodium-like high-efficiency single-atom cobalt catalyst over β-Mo2C toward olefin hydroformylation. During the hydroformylation of propene, the single atomic cobalt catalyst achieves a turnover number of 3,834 and a turnover frequency of 749 h−1, which to our knowledge surpasses all the reported heterogeneous cobalt-based catalysts and approaches the performance of rhodium catalysts. Moreover, the catalyst can be reused five times without an obvious activity decline, confirming the excellent stability of single-atom Co supported on β-Mo2C. We demonstrate that a Co1-MoxCy motif forms on the carbide surface with electronic metal-support interaction (EMSI). Such an EMSI effect plays a pivotal role in optimizing the charge density, reducing the reaction barrier, and stabilizing the active site.

Poly(propylene)s prepared using MgCl2-supported catalysts containing different electron donors have been characterized using temperature rising elution fractionation (TREF), gel permeation chromatography (GPC) and 13C NMR analysis. In addition, the regio- and stereochemical composition of oligomeric fractions present in selected polymers has been determined. The results indicate that catalysts in which the internal donor is a diether have a relatively narrow distribution of active species, for which the effects of regioselectivity on chain transfer with hydrogen are particularly prominent. The regio- and stereoselectivity of active species in catalysts in which the internal donor is diisobutyl phthalate is dependent on the nature of the alkoxysilane external donor used in polymerization. The effects of different alkoxysilanes on polymer tacticity and molecular weight distribution are interpreted in terms of lability of donor coordination in the vicinity of active species, a labile as opposed to a stable donor coordination giving rise to a higher proportion of defect-rich sequences in the polymer chain. Such species will also give relatively low molecular weight as a result of an increased probability of chain transfer with decreasing regio- and stereoselectivity. A broad tacticity and molecular weight distribution in poly(propylene) prepared using monoesters as internal and external donors indicates that these systems may contain not only a significant proportion of labile active species, but also species that do not require the presence of an electron donor in their immediate vicinity for high selectivity.

Biphasic hydroformylation of olefins using a novel water soluble rhodium polyethylene glycolate catalyst

A new dirhodium(I) bisimidazolium-carbene complex has been obtained and fully characterized by means of NMR spectroscopy and single-crystal X-ray diffraction. The complex has been used as catalyst in hydroformylation reactions, showing selectivity on the branched aldehyde. High-pressure NMR spectroscopy provides evidence that the dinuclear unit is maintained under catalytic conditions.

Application of heterogeneous catalysts in olefin hydroformylation