Sulfur was typically regarded as a poison to precious metal complex catalysts in hydroformylation of olefins. However, the combination of sulfur and phosphine may present an intriguing interaction with heterogeneous mononuclear complex due to the difference of their electronegativities, and coordination capabilities. Herein, we report a novel sulfur-phosphine co-coordinated heterogeneous Rh mononuclear complex catalyst (Rh1/POPs-PPh3&S), which exhibits an unexpected 1.5-2.0 times catalytic activity for hydroformylation of olefins (C3=, C5=-C8=), in comparison with the solely phosphine-coordinated Rh mononuclear complex catalyst (Rh1/POPs-PPh3). In contrast, sulfur coordination alone leads to severe sulfur poisoning with significantly inhibited catalytic performance. Experimental and theoretical analyses reveal that phosphine coordination promotes catalytic activity via its strong electron-donating ability, while sulfur occupies a coordination site and reduces the electronic density of Rh ions. The synergistical coordination of sulfur and phosphine optimizes the electronic density of active Rh ions and decreases the energy barrier of the rate-determining step of olefin insertion, thus enhancing the hydroformylation activity, regioselectivity and stability of Rh1/POPs-PPh3&S.

Heterogeneous single-metal-site catalysts frequently encounter issues related to the poor stability of their coordination structures, hindering their industrial applications. Synthesizing bimetallic single-metal-site catalysts with two closely connected single sites may realize the full potential of single-site catalysts. Herein, we present a "top-down" dispersion process to prepare bimetallic single-metal-site catalysts from Pd-Ag alloy nanoparticles induced by CO and CH3I mixture, with the unique binuclear complex structure of Pd1-Ag1 established as PdI2(CO)-I2-AgI by combined characterization. The Pd1-Ag1/activated carbon (AC) catalyst showed a three times increase in conversion for acetylene dialkoxycarbonylation compared to Pd1/AC, owing to the promotive effect of the single-Ag-site via the binuclear complex configuration. Moreover, Pd1-Ag1/AC showed 98% selectivity for 1,4-unsaturated dicarboxylic acid esters over ten cycles without apparent decay, with the activated adsorption amount of acetylene doubled and the reduction of active Pd1 & ouml;+ species partially inhibited. According to density functional theory calculations, the Pd1-Ag1/AC catalyst exhibited a substantially lower reaction energy barrier of 0.45 eV for the rate-determining step compared with that of the Pd1/AC catalyst (1.06 eV). This study provides insight into the preparation and synergetic catalysis of bimetallic single-metal-site catalysts. Published by Elsevier B.V. All rights reserved.

Alcohols carbonylation is of great importance in industry but remains a challenge to abandon the usage of the halide additives and noble metals. Here we report the realization of direct alcohols heterogeneous carbonylation to carbonyl-containing chemicals, especially in methanol carbonylation, with a remarkable space-time-yield (STY) of 4.74 mol acetyl /kg cat. /h and a durable stability as long as 100 h on Ni@MoS 2 catalyst. Mechanistic analysis reveals that the Mo−Ni dual sites localized at edge sulfur vacancies of Ni@MoS 2 exhibit distinct charge density, which strongly activate CH 3 OH to break its C−O bond and non-dissociatively activate CO. Density functional theory calculations further suggest that the low charge density in Mo−Ni, the Ni site, could significantly lower the barrier for CO migration and nucleophilic attack of methoxy species, and finally leads to the rapid formation of acetyl products. Ni@MoS 2 catalyst could also effectively realize the carbonylation of ethanol, n-propanol and n-butanol to their acyl products, which may demonstrate its universal application for alcohols carbonylation.

The stability of heterogeneous single-metal-site catalysts (HSMSCs) is always a challenging issue. Deactivation of HSMSCs often occurred and draw much intention. The investigation of the single-metal-site evolution during the deactivation process is great significance to maintain the stability of HSMSCs. Herein, a fundamental understanding of the deactivation process of an initially efficient single-Pd-site catalyst (Pd-1/AC) for acetylene dialkoxycarbonylation was revealed from geometrical and electronic point of view via a series of characterizations. Synergistic effect of O-2 and iodine ligands contributed to the stability of Pd-1/AC catalyst to some extent. The valence of single Pd ions gradually changed from [Pd delta+] to [Pd-0], leading to the formation of Pd nanoparticles (Pd black). In addition, the blockage of support microspores also worsened the deactivation of Pd-1/AC. (C) 2022 Elsevier Inc. All rights reserved.

The synthesis of C2 oxygenates including ethanol directly from coal-derived syngas is significant from both academic and practical points of view and SiO2 supported Rh-based catalysts are very effective for this conversion. However, the high price of Rh requires the improvement of its dispersion to maximize Rh efficiency. The adjustment of impregnation solution pH value can modify effectively the metal dispersion over the support. Herein, we reported the pH effect on catalytic performance of Rh-Mn-Li/SiO2 for CO hydrogenation to C2 oxygenates for the first time. A series of catalysts were prepared from different pH values of impregnation solutions, and were characterized by various techniques. With the increasing of solution pH value above zero point of charge (ZPC) of silica, Rh particle sizes increased with much wider size distribution and reduction of Rh species was restrained over the prepared catalysts owing to the stronger interaction between Rh and support. As a result, the active sites for CO insertion, especially for CO or H2 dissociation was lowered, leading to the depletion of the activity for the formation of C2 oxygenates from CO hydrogenation, and larger Rh particle size with wider size distribution favors the production of long chain hydrocarbons. On the contrary, when the catalyst was prepared using solution with pH below ZPC of silica, the dispersion and the reduction of Rh were promoted due to suitable Rh-support interaction, and in the CO hydrogenation reaction, the space time yield and selectivity of C2 oxygenates reached 679.4 g/kg-cat/h and 73.3%, respectively. The pH value of impregnating solution regulate the metal-support interaction and thus Rh particle sizes and its reduction, which effects strongly CO hydrogenation activity and selectivity.

Silica is a traditional carrier for Rh-based catalyst for CO hydrogenation to C-2 oxygenates, and its pretreatment with various organic solvents under specified conditions usually affects the surface and textural properties of silica and thus the catalytic performance of Rh-based catalyst. In this paper, silica samples were hydrothermally treated with different concentrations of ammonia and were used to support Rh-based catalysts. The as-made supports and the respective catalysts were characterized by N-2 adsorption-desorption, TEM, XRD, FT-IR, H-2-TPR, CO chemisorption, CO-TPD, and temperature-programmed surface reaction (TPSR). The results showed that the hydrothermal treatment enlarged the pore size of silica gradually from 8.1 nm on parent sample to 26.5 nm on that treated by 10% ammonia. Smaller pore size usually with higher surface area of silica was beneficial to the formation of highly dispersed Rh species; however, the mean Rh particle sizes here were within the optimal range of 2-4 nm. It was also demonstrated that, with the increasing of pore size of silica, the CO insertion ability weakened, while the CO dissociation capability strengthened relatively; meanwhile, the diffusion limitation of CO could be eliminated gradually, leading to a decrease of the local H-2/CO ratio during CO hydrogenation reaction. This could restrain the hydrogenation ability but facilitate the CO dissociation or insertion. Consequently, carbon chain propagation was much promoted to give more C-2(+) hydrocarbons, while the hydrogenation of C-2 oxygenate precursors was prohibited to yield much less ethanol. Moreover, Rh-based catalysts supported on larger pore sizes of silica were more stable than that on the untreated one. This finding provides a useful strategy to effectively adjust the catalytic performance of Rh-based catalyst through controlling internal diffusion by selecting a support with the proper pore size.

It is of great significance to produce C-2 oxygenated compounds such as ethanol directly from CO hydrogenation via coal, natural gas or biomass that can replace the traditional oil and food routes. The supported promoted Rh is the most effective catalyst to realize this transformation. The Rh-promoter (support) contact interfaces are the active sites for the formation of C-2 oxygenates from syngas, thus the contact interface areas directly determines the performance of the catalyst. Therefore, recently many researchers have been working on various physical or chemical methods to improve the preparation process of Rh-based catalysts to maximize the metal-promoter interfaces. In this paper, the principle, process, advantages and disadvantages of these methods (coating, formation of composite oxide or alloy, strong electrostatic adsorption, controlled surface reaction method and atomic layer deposition) are briefly introduced and reviewed. Through the combination of the above synthesis methods, it is possible to prepare the catalysts with uniform distribution of well-defined active sites at the interface.

The silica (S0) was pretreated with slightly acidic (S1) or basic (S2) aqueous solutions of ammonium salts before using as a support to prepare Rh–Mn–Li catalyst for CO hydrogenation to C2 oxygenates. The results showed that the weak acidity of the modified silica stem from silanol groups where the number of free silanol groups increased as S0 < S1 < S2. This evolution could tune the interactions among support, Rh, and Mn components, and results in the variation of dispersion and chemical states of Rh species. Therefore, Rh/S1 catalyst with smaller Rh particle sizes and more Rh0 sites for CO dissociation exhibited higher CO hydrogenation activity, giving higher space time yield of C2 oxygenates of 766.1 g/kg/h than the untreated Rh/S0 catalyst (674.3 g/kg/h). Meanwhile, Rh/S1 catalyst has improved ethanol selectivity (19.3%) comparing with Rh/S0 (15.7%). Though Rh/S2 catalyst showed similar catalytic performance to Rh/S0 catalyst, it further increases the ethanol selectivity to 19.9%. The H2–TPD results suggested that the catalyst with high fraction of free silanol groups improved the migration of activated hydrogen spillover from metal Rh centers, where C2 oxygenates precursors adsorbed on the support could be hydrogenated into ethanol.

The mode of contact between Rh and Cr is different to that between Rh and Fe.

β-SiC was used as a support for a 0.5% Rh-based catalyst for CO hydrogenation to C2 oxygenates for the first time. The β-SiC was acid etched and/or calcined at high temperature before use. The results show that the pretreatments had little effect on the textural and crystal properties of SiC, but calcination markedly increased the number of surface oxygen-containing groups. The pretreatment significantly increased the catalytic activities of SiC-supported RhMnLi/SiC catalysts in CO hydrogenation. An Rh efficiency of 97.2g/g-Rh/h was achieved, the highest value reported in the literature to date. Possible reasons for this enhancement are suggested.

Rh, Mn and Li were supported on SBA-15 samples that had been calcined at 550, 700, 800, and 900 degrees C, using an incipient co-impregnation technique. The catalytic performances of these materials were subsequently evaluated for the hydrogenation of carbon monoxide. The catalysts were characterized by means of N-2 adsorption-desorption, X-ray diffraction, transmission electron microscopy, H-2 chemisorption, and Fourier transform infrared spectroscopy. The structure of the SBA-15 support remained unchanged even after its calcination at 900 degrees C. However, the specific surface area, pore size, and total pore volume of SBA-15 decreased from 842.6 m(2). g(-1), 9.57 nm, and 1.18 cm(3).g(-1) to 246.4 m(2). g(-1) 5.62 nm, and 0.34 cm(3).g(-1), respectively, when the calcination temperature increased from 550 to 900 C. In addition, the Rh particle size increased in the range of 1.5-4.0 nm with increasing calcination temperature. Furthermore, the Rh particles showed a greater tendency towards the mesopores of support when they were calcined at high temperatures, which could be attributed to the reduced number of micropores. These changes therefore made it easier for H2 and CO to interact with the Rh particles immobilized on the supports calcined at high temperatures. High levels of activity and selectivity towards C2+ oxygenates were therefore obtained on the Rh-Mn-Li/SBA-15 prepared using the SBA-15 calcined at 900 degrees C.

There is great significance to produce C-2-oxygenates such as ethanol via syngas from coal, natural gas or biomass from practical and academy of view; and supported Rh-based catalysts are the most effective for this conversion. The choice of promoter is critical for obtaining high-performance catalysts, of which Fe, Mn, and Li are most widely used. The effects of promoters have been studied extensively and comprehensively, but their roles remain the subject of much debate. We review the progress on the promotion nature of Fe, Mn, and Li. The roles of these promoters depend on the catalyst system and preparation procedures empolyed, which affect directly the interaction between Rh and promoter(s). This interaction determines the displayed structures and properties of the promoters, which behaves different effects on the elemental steps of CO hydrogenation reaction. This review is expected to deeply aid our understanding of the effects of these promoters.

A series of Rh–Mn–Li/SiO2 catalysts were prepared by the impregnation of a silica support with solutions containing metal precursors with different amounts of urea. Catalyst performance was investigated by the hydrogenation of carbon monoxide. The catalysts were characterized by X-ray diffraction, transmission electron microscopy, hydrogen chemisorption, diffuse reflectance ultraviolet–visible (DR UV–Vis) spectroscopy, and thermogravimetric analysis. The results revealed that the amount of urea had a significant effect on the particle size of Rh, which increased from approximately 2–5 nm with the increase in urea loading from 0 to 2.0 wt%. DR UV–Vis spectra indicated that the increase in the Rh particle size with increasing urea loading might be attributed to the coordination of Rh3+ with urea or its derivatives during calcination. At a urea loading of 1.0 wt%, the particle size of Rh was 3.7 nm, and the space time yield of C2+ oxygenates reached a maximum of 560.0 g kg−1 h−1.

Silica was treated with trimethylchlorosilane before using as the supports for Rh-Mn-Li catalysts in CO hydrogenation to C2 oxygenates. The catalysts were characterized by infrared spectroscopy, N2 adsorption-desorption, C content measurements, transmission electron microscopy, H2 temperature programmed reduction, and temperature programmed surface reaction. The results showed that the silanization degree has little effect on the textural properties of silica. The mean Rh particle size ( about 3 nm ) , CO adsorption state on Rh and reducibility of Rh supported on silica remain unchanged by the silanization of silica support. However, with an increase of the silanization degree of silica, the ability of Rh to dissociate CO is improved, which can enhance the catalytic activity of Rh-Mn-Li/SiO2 in CO hydrogenation but has little influence on the selectivity towards C2 oxygenates.

以活性炭（AC）为载体,采用浸渍法制备了Ru/AC催化剂,并应用于邻苯二胺（o-PDA）催化加氢制1,2-环己二胺的反应。考察了Ru负载量、溶剂种类、反应温度、添加剂Na NO2用量、水用量等反应条件对加氢性能的影响。实验结果表明,适宜的反应条件为:温度170℃,压力8.0 MPa,o-PDA 16.0 g,异丙醇75 m L,Na NO2 0.50 g,水4.0 m L,5%（w）Ru/AC催化剂3.0 g;在此条件下,o-PDA的转化率为99.5%,1,2-环己二胺的收率为86.3%。5%（w）Ru/AC催化剂循环使用5次后,o-PDA的转化率由99.5%降至85.7%,1,2-环己二胺的选择性维持在85%以上。循环使用5次后的催化剂经洗涤、干燥和还原活化后,活性恢复,可重复使用。

SiO2- and Al2O3-supported Co2C catalysts were prepared by carburizing supported Co precursors with CO. The catalysts were characterized by N2 physisorption, X-ray diffraction and H2 temperature-programmed reduction techniques, and evaluated by the Fischer-Tropsch (F-T) reaction. The results showed that SiO2- and Al2O3-supported Co2C catalysts could be successfully obtained but sufficient carburization time was required. All of the as-prepared supported Co2C catalysts exhibited activity and selectivity towards alcohols. It is considered that surface metallic Co species contributed to the activity, surface Co2C species were responsible for the formation of alcohols, and bulk Co2C species were inert during the F-T reaction.

Supported Rh-based catalysts are one of the most efficient catalysts for CO hydrogen to C2-oxygenates,such as ethanol from coal or biomass via syngas,however,the selection of support is vitally important for the design and preparation of the catalyst. Herein,the catalytic performances and the research progresses of silica,Al2O3,TiO2,porous carbon materials,zeolites,and mixed oxides supported Rh-based catalysts were reviewed. The effects of support properties,such as the impurities, pore structures,acid-base properties,the reactivity of surface groups,and reducibility,on the chemical-physical properties and thus catalytic performance of Rh-based catalysts were compared and summarized. The results showed that the key point to understand the support effect was to investigate the interactions between metal (promoters) and support. Accordingly,novel support with proper pore structures , weakly basic , moderate surface reactivity and reducibility should be designed and synthesized , which could modify the interaction between support and Rh combing with the optimization of preparation and activation conditions. This ensures more active sites for syngas conversion and thus makes the maximum use of Rh,pushing the commercialization of this process.