Ronghe Lin

Glycerol dehydration to acrolein over activated carbon-supported silicotungstic acids

Activated carbon (AC)-supported silicotungstic acid (H-4[SiW12O40] center dot nH(2)O, HSiW) catalysts were employed to produce acrolein from glycerol dehydration. The results indicated that catalysts with 10% HSiW loading exhibited the highest activity and selectivity. The space time yield of acrolein reached 68.5 mmol/(g.h), which is the best result ever reported in the literature. The properties of the catalysts were closely related to the HSiW dispersion and the relative quantities of strong acid sites.

Solvent Effect on Selective Dehydroxylation of Glycerol to 1,3-Propanediol over a Pt/WO3/ZrO2 Catalyst

Different solvents were studied for dehydroxylation of glycerol to1,3-propanediol over a Pt/WO3/ZrO2 catalyst. Protic solvents such as ethanol and water favored the formation of 1,3-propanediol from glycerol. Binary solvents containing a protic component showed a synergetic solvent effect on the selective dehydroxylation of glycerol to 1,3-propanediol. The protic component in the binary solvent influenced the performance of the Pt/WO3/ZrO2 catalyst.

Halogen-Mediated Conversion of Hydrocarbons to Commodities

Halogen chemistry plays a central role in the industrial manufacture of various important chemicals, pharmaceuticals, and polymers. It involves the reaction of halogens or halides with hydrocarbons, leading to intermediate compounds which are readily converted to valuable commodities. These transformations, predominantly mediated by heterogeneous catalysts, have long been successfully applied in the production of polymers. Recent discoveries of abundant conventional and unconventional natural gas reserves have revitalized strong interest in these processes as the most cost-effective gas-to-liquid technologies. This review provides an in-depth analysis of the fundamental understanding and applied relevance of halogen chemistry in polymer industries (polyvinyl chloride, polyurethanes, and polycarbonates) and in the activation of light hydrocarbons. The reactions of particular interest include halogenation and oxyhalogenation of alkanes and alkenes, dehydrogenation of alkanes, conversion of alkyl halides, and oxidation of hydrogen halides, with emphasis on the catalyst, reactor, and process design. Perspectives on the challenges and directions for future development in this exciting field are provided.

A Review on the Synthesis and Applications of Mesostructured Transition Metal Phosphates

Considerable efforts have been devoted to extending the range of the elemental composition of mesoporous materials since the pioneering work of the M41S family of ordered mesoporous silica by Mobil researchers. The synthesis of transition metal-containing mesostructured materials with large surface area and high porosity has drawn great attention for its potential applications in acid and redox catalysis, photocatalysis, proton conducting devices, environmental restoration and so on. Thus, various transition metals-containing mesoporous materials, including transition metal-substituted mesoporous silicates, mesostructured transition metal oxides and transition metal phosphates (TMP), have been documented in the literature. Among these, mesostructured TMP materials are less studied, but possess some unique features, partly because of the easy and facile functionalization of PO4 and/or P–OH groups, rendering them interesting functional materials. This review first introduced the general synthesis strategies for manufacturing mesostructured TMP materials, as well as advantages and disadvantages of the respective method; then, we surveyed the ongoing developments of fabrication and application of the TMP materials in three groups on the basis of their components and application fields. Future perspectives on existing problems related to the present synthesis routes and further modifying of the functional groups for the purpose of tailoring special physical-chemical properties to meet wide application requirements were also provided in the last part.

Effect of different synthetic routes on the performance of propylene hydroformylation over 3V-PPh3 polymer supported Rh catalysts

This article studied the difference between two 3V-PPh3 polymer (POL-PPh3) supported Rh catalysts synthesized via different synthetic strategies, one-pot and post-synthesis, respectively. The catalytic performance of the two catalysts was further evaluated for the hydroformylation of propylene on a fixed-bed reactor. The catalyst prepared through post-synthesis (Rh/POL-PPh3) showed better catalytic activity compared to the one-pot sample (Rh–POL-PPh3), and exhibited excellent long-term stability. N2 sorption, SEM, EXAFS and FT-IR characterization results suggested that the possible reasons for the different catalytic performance of two catalysts can be ascribed to the fact that part of Rh species was probably embedded into the framework of POL-PPh3 in the Rh–POL-PPh3 catalyst. Moreover, it might restrict the accessibility of reagents to Rh species and block the flexible coordination between Rh species and POL-PPh3. The Rh/POL-PPh3 catalyst synthesized via post-synthesis and the Rh species were uniformly distributed on the surface of POL-PPh3, which might have a positive effect on the improvement of the mass transfer and the flexible coordination of Rh species with POL-PPh3.

Europium Oxybromide Catalysts for Efficient Bromine Looping in Natural Gas Valorization

The industrialization of bromine-mediated natural gas upgrading is contingent on the ability to fully recycle hydrogen bromide (HBr), which is the end form of the halogen after the activation and coupling of the alkanes. Europium oxybromide (EuOBr) is introduced as a unique catalytic material to close the bromine loop via HBr oxidation, permitting low-temperature operation and long lifetimes with a stoichiometric feed (O2 :HBr=0.25)-conditions at which any catalyst reported to date severely deactivates because of excessive bromination. Besides, EuOBr exhibits unparalleled selectivity to methyl bromide in methane oxybromination, which is an alternative route for bromine looping. This novel active phase is finely dispersed on appropriate carriers and scaled up to technical extrudates, enhancing the utilization of the europium phase while preserving the performance. This catalytic system paves the way for sustainable valorization of stranded natural gas via bromine chemistry.

Rh catalysts supported on knitting aryl network polymers for the hydroformylation of higher olefins

Rh catalysts supported on knitting aryl network polymers (Rh/KAPs) were prepared for the hydroformylation of higher olefins. Rh catalysts supported on triphenylphosphine-benzene-base polymers (Rh/KAPs-1) showed higher activity for the higher olefins than Rh/SiO2 catalysts. Fourier transform infrared spectroscopy, thermogravimetry, N-2 adsorption-desorption, X-ray diffraction, transmission electron microscopy, C-13 NMR, and P-31 NMR showed that the Rh/ICAPs-1 catalysts have high thermal stability, high surface area, hierarchical porosity, highly dispersed Rh nanoparticles, and in situ formed homogeneous active species during the reaction

Phase-controlled synthesis of iron phosphates: Via phosphation of β-FeOOH nanorods

Iron phosphates comprise an important class of materials with a wide range of applications. We have designed novel routes for the controlled synthesis of iron phosphate dihydrates of varying crystallographic phases (monoclinic and orthorhombic) and morphologies. Our approach comprises the phosphation of β-FeOOH nanorods with aqueous phosphoric acid solutions. Through a systematic parametric study coupled to an array of characterisation techniques, including XRD, TEM, HAADF-STEM, AAS, N2 sorption, TGA-MS, FTIR, UV-Vis, XPS, EXAFS, EPR, and 57Fe Mossbauer spectroscopy, we unravel the complex synthesis chemistry on both the macroscopic and microscopic levels. It is found that the formation of iron phosphates occurs exclusively under acidic conditions and in general involves the dissolution of β-FeOOH which, upon reaction with H3PO4, precipitates as FePO4·2H2O. The pH of the treatment solution determines the crystallographic phase of the resulting product by regulating the rate of β-FeOOH dissolution and of the precipitation of the iron phosphates, while the treatment time is decisive for the preservation of the morphology. The formation of the monoclinic phase entails a fast iron dissolution and subsequent precipitation in the solution. The generation of the orthorhombic analogue involves an interfacial reaction between H3PO4 and β-FeOOH, forming an amorphous layer of iron phosphate, which crystallises into a pure phase with increasing treatment time. The thermal transformation of hydrated to anhydrous iron phosphates is dependent on the phase and morphology of the precursors. The rod shape of iron-rich orthorhombic FePO4·2H2O can be preserved even after annealing at 923 K, with the formation of mesopores. These novel nanostructures may widen the applications of iron phosphates and the routes developed herein can be anticipated to guide the fabrication of other metal phosphates.

Model Iron Phosphate Catalysts for the Oxy-bromination of Methane

Three kinds of bulk iron phosphates were prepared via different methods and employed as model catalysts in the oxy-bromination of methane (OBM). Na3Fe2(PO4)3 was obtained via a fluoride route for the first time that showed even superior catalytic performance than FePO4. Phase evolution from Na3Fe2(PO4)3 to Na2Fe3(PO4)3 after the OBM was confirmed both by X-ray diffraction and 57Fe Mössbauer spectroscopy. Temperature-programmed reduction of hydrogen and desorption of CH3Br revealed that the redox capacity of iron phosphates were responsible for the generation of bromine radicals on catalyst surfaces while CH3Br-involved reactions likely belonged to gas-phase reactions.Graphical AbstractModel iron phosphate catalysts were synthesized by three different methods. It was found that the Na3Fe2(PO4)3 catalyst prepared by a fluoride route showed superior OBM performance than the other two catalysts both with the phase of FePO4, especially for producing higher CH3Br selectivity.

Comparative study on stability and coke deposition over supported Rh and FePO4 catalysts for oxy-bromination of methane

Rhodium- and iron phosphate-based catalysts are by far the most promising catalysts for oxy-bromination of methane (OBM) reaction. However, most literature reported either Rh- or FePO4-based catalysts, and the results were rarely studied in a uniform environmental condition. In this report, comparative study was conducted on silica- and silicon carbide-supported rhodium and iron phosphate catalysts with the main focuses on stability performance and coke deposition. The catalytic results demonstrated that the stability of both Rh- and FePO4-based catalysts was greatly influenced by the supports used, and silicon carbide-supported catalysts showed much better anti-coking ability as compared with silica-supported ones. Temperature-programmed oxidation over the used catalysts further indicated that the coke formation mechanisms were completely different between silica-supported rhodium and iron phosphate catalysts. While cokes might be caused by condensation of CH2Br2 over supported iron phosphate, methane decomposition might be the reason for coke formation over silica-supported rhodium catalyst. These findings might pave the way for designing highly efficient and stable catalysts of the OBM reaction.