Efficient and stable Ru(III)-choline chloride catalyst system with low Ru content for non-mercury acetylene hydrochlorination

Encapsulated ruthenium sites in reaction microenvironment-regulated UiO-66 for stable acetylene hydrochlorination

Ruthenium (Ru)-based catalysts have been recognized as potential substitutes for mercury in the hydrochlorination of acetylene due to their high initial activity and low cost. However, rapid deactivation limits their industrial application and the agglomeration of active sites is considered as one of the main reasons for deactivation. To overcome this challenge, in this work, we introduced a thermally stable metal-organic framework to encapsulate Ru sites into regular channels successfully, thus enhancing the dispersion of Ru sites. To decrease the diffusion resistance caused by the channels, we partly substituted -H groups with -OH groups in the channels to change the reaction microenvironment. After characterization and simulation, we demonstrated that both the encapsulation strategy and channel regulation were beneficial for increasing the adsorption of reactants, thus obtaining 92.27% conversion of acetylene with a deactivation rate below 0.02% h-1 even when the gas hourly space velocity was at a high level (540 h-1). This work provides a new insight into inhibition of the deactivation of Ru-based catalysts in acetylene hydrochlorination via introducing skeleton materials with regular channels.

Metal-Organic Frameworks Encaged Ru Single Atoms for Rapid Acetylene Harvest and Activation in Hydrochlorination

Ruthenium (Ru)-based catalysts have been candidates in hydrochlorination for vinyl chloride monomer (VCM) production, yet they are limited by efficient acetylene (C₂H₂) utilization. The strong adsorption performance of HCl can deactivate Ru active sites which resulted in weak C₂H₂ adsorption and slow activation kinetics. Herein, we designed a channel that employed metal-organic framework (MOF)-encaged Ru single atoms to achieve rapid adsorption and activation of C₂H₂. Low-Ru (∼0.5 wt %) single-atom catalysts (named Ru-NC@MIL) were assembled by hydrogen-bonding nanotraps (the H-C≡C-H^δ+···O^δ- interactions between C₂H₂ and carboxylate groups/furan rings). Results confirmed that C₂H₂ could easily enter the encapsulation channels in an optimal mode perpendicular to the channel with a potential energy of 42.3 kJ/mol. The harvested C₂H₂ molecules can be quickly passed to Ru-N₄ active sites for activation by stretching the length of carbon-carbon triple bonds (C≡C) to 1.212 Å. Such a strategy guaranteed >99% C₂H₂ conversion efficiency and >99% VCM selectivity. Moreover, a stable long-term (>150 h) catalysis with high efficiency (∼0.85 kg_vcm/h/kg_cat.) and a low deactivation constant (0.001 h^-1) was also achieved. This work provides an innovative strategy for precise C₂H₂ adsorption and activation and guidance for designing multi-functional Ru-based catalysts.

The Pincer Ligand Supported Ruthenium Catalysts for Acetylene Hydrochlorination: Molecular Mechanisms from Theoretical Insights

Pincer ligand supported RuII chloride complexes may be used for acetylene hydrochlorination as non-mercury molecular catalysts. Based on theoretical calculations, the catalytic mechanism and the interaction between catalysts and reactants has been evaluated, indicating that the (pincer)RuIICl2 platform supports electrophilic proton-ruthenation of C2H2. Energy decomposition studies further illustrate the electron-rich property of the RuII center, which can increase the negative charge of C2H2 via 4d-electron backdonation. Thus, the electrophilic reaction mechanism is favored due to lower energetic barriers. By improving the electron-donating ability of ligands, this lowering of energetic barriers can be enhanced. Therefore, non-mercury catalysts for acetylene hydrochlorination with milder reaction conditions and higher catalytic activity can be designed.

Competing on the same stage: Ru-based catalysts modified by basic ligands and organic chlorine salts for acetylene hydrochlorination

To provide reference for the search of efficient ligands for acetylene hydrochlorination, various basic ligands with different alkaline gradients have been employed to modify Ru-based catalysts, and a rule is...

Ru supported on activated carbon and coated with a polydopamine layer for effective acetylene hydrochlorination

Ru/AC@PDA-T catalysts were synthesized by coating a protective layer of PDA derivatives on the Ru/AC catalyst. Significantly improved activity and stability provide directions for the development of environmentally friendly and economical catalysts.

A study on the rules of ligands in highly efficient Ru–amide/AC catalysts for acetylene hydrochlorination

The electron donor ability and steric hindrance of substituents on amide ligands jointly affect the modification effect of ligands on ruthenium based catalysts for acetylene hydrochlorination.

Waste cigarette butt-derived nitrogen-doped porous carbon as a non-mercury catalyst for acetylene hydrochlorination

The development of advanced carbon materials as metal-free catalysts holds great importance for mercury catalyst replacement in acetylene hydrochlorination.

Progress and Challenges of Mercury-Free Catalysis for Acetylene Hydrochlorination

Activated carbon-supported HgCl2 catalyst has been used widely in acetylene hydrochlorination in the chlor-alkali chemical industry. However, HgCl2 is an extremely toxic pollutant. It is not only harmful to human health but also pollutes the environment. Therefore, the design and synthesis of mercury-free and environmentally benign catalysts with high activity has become an urgent need for vinyl chloride monomer (VCM) production. This review summarizes research progress on the design and development of mercury-free catalysts for acetylene hydrochlorination. Three types of catalysts for acetylene hydrochlorination in the chlor-alkali chemical industry are discussed. These catalysts are a noble metal catalyst, non-noble metal catalyst, and non-metallic catalyst. This review serves as a guide in terms of the catalyst design, properties, and catalytic mechanism of mercury-free catalyst for the acetylene hydrochlorination of VCM. The key problems and issues are discussed, and future trends are envisioned.

Constructing and controlling ruthenium active phases for acetylene hydrochlorination

Ru-Based catalysts with distinct active phases from Ru0, to RuO2, RuCl3 and RuCl2N were synthesized and evaluated in acetylene hydrochlorination. RuCl2N is identified as the efficient active phase due to its co-activation of acetylene and hydrogen chloride. This discovery holds great potential to accelerate the large-scale application of Ru-based catalysts in industry.

Synthesis of a vinyl chloride monomer via acetylene hydrochlorination with a ruthenium-based N-heterocyclic carbene complex catalyst

Delocalisation and transfer of electrons in the formed IPr–(Ru) synergistically yields a significant improvement in activity with respect to its counterpart.

Gas–solid acetylene dimerization over copper-based catalysts

A gas–solid acetylene dimerization over copper-based catalysts, with high acetylene conversion and MVA selectivity and convenient operation, was reported.

Chlorocuprate(i) ionic liquid as an efficient and stable Cu-based catalyst for hydrochlorination of acetylene

Chlorocuprate(i) ionic liquids can be well-stabilized, low-cost, efficient and green non-mercury catalysts for hydrochlorination of acetylene.