Zhangfeng Qin

Graphene-supported Au-Pd bimetallic nanoparticles with excellent catalytic performance in selective oxidation of methanol to methyl formate.

Graphene supported Au-Pd bimetallic nanoparticles exhibit high catalytic activity in methanol selective oxidation, with a methanol conversion of 90.2% and selectivity of 100%, to methyl formate at 70 °C, owing to the synergism of Au and Pd particles as well as the strong interaction between graphene and Au-Pd nanoparticles.

A New Molybdenum Nitride Catalyst with Rhombohedral MoS2 Structure for Hydrogenation Applications

Nitrogen-rich transition-metal nitrides hold great promise to be the next-generation catalysts for clean and renewable energy applications. However, incorporation of nitrogen into the crystalline lattices of transition metals is thermodynamically unfavorable at atmospheric pressure; most of the known transition metal nitrides are nitrogen-deficient with molar ratios of N:metal less than a unity. In this work, we have formulated a high-pressure route for the synthesis of a nitrogen-rich molybdenum nitride through a solid-state ion-exchange reaction. The newly discovered nitride, 3R-MoN2, adopts a rhombohedral R3m structure, isotypic with MoS2. This new nitride exhibits catalytic activities that are three times more active than the traditional catalyst MoS2 for the hydrodesulfurization of dibenzothiophene and more than twice as high in the selectivity to hydrogenation. The nitride is also catalytically active in sour methanation of syngas with >80% CO and H2 conversion at 723 K. Our formulated route for the synthesis of 3R-MoN2 is at a moderate pressure of 3.5 GPa and, thus, is feasible for industrial-scale catalyst production.

Synthesis of polyoxymethylene dimethyl ethers from methanol and trioxymethylene with molecular sieves as catalysts

Abstract Polyoxymethylene dimethyl ethers (PODE n or DMM n ) were synthesized by the condensation of methanol and trioxymethylene over the catalysts of several molecular sieves like HY, HZSM-5, Hβ, and HMCM-22; the effect of their acidic properties on product distribution was investigated. The results indicated that the acidic molecular sieves, especially HMCM-22, are catalytically active for the condensation of methanol and trioxymethylene to form DMM n . Over HY, the main product is dimethoxymethane (DMM), with a selectivity of 92.87%. Over HZSM-5 and Hβ, the main products turn out to be DMM 1-3 and the yields of DMM 3-8 , which are ideal additives for diesel fuel, reach 6.40% and 13.78%, respectively. With HMCM-22 as the catalyst, the formation of long chain DMM n products is further enhanced and the yield of DMM 3-8 attains 29.39%. The results of NH 3 -TPD demonstrated that the product distribution is related to the surface acidic properties of the catalyst used; short chain DMM may be primarily formed on weak acidic sites, while the acidic sites of medium strength can enhance the formation of diesel fuel additive components DMM 3-8 .

High Si/Al ratio HZSM-5 zeolite: an efficient catalyst for the synthesis of polyoxymethylene dimethyl ethers from dimethoxymethane and trioxymethylene

The catalytic performance of HZSM-5 zeolite in the synthesis of polyoxymethylene dimethyl ethers (PODEn) from dimethoxymethane (DMM) and trioxymethylene (TOM) is closely related to its Si/Al ratio; HZSM-5 with a high Si/Al ratio exhibits high PODE2–8 yield and excellent stability and reusability.

Methane formation mechanism in the initial methanol-to-olefins process catalyzed by SAPO-34

A clear understanding of the methane formation mechanism in the initial MTO process is beneficial for the illustration of the initial C–H bond activation mechanism and the first C–C bond formation route. Thus, attempts are made here to unravel the methane formation pathway in the initial MTO process by elaborately designing experiments. It is shown that methane is generated together with formaldehyde or methoxymethyl cation by attacking the C–H bond of methanol or dimethyl ether (DME) with surface methoxy species (SMS). The reaction of DME and SMS provides strong evidence for the occurrence of C–H bond cleavage and the “methoxymethyl cation mechanism” in the initial MTO process.

Theoretical and Experimental Study on Reaction Coupling： Dehydrogenation of Ethylbenzene in the Presence of Carbon Dioxide

Abstract Dehydrogenation of ethylbenzene (EB) to styrene (ST) in the presence of CO2, in which EB dehydrogenation is coupled with the reverse water-gas shift (RWGS), was investigated extensively through both theoretical analysis and experimental characterization. The reaction coupling proved to be superior to the single dehydrogenation in several respects. Thermodynamic analysis suggests that equilibrium conversion of EB can be improved greatly by reaction coupling due to the simultaneous elimination of the hydrogen produced from dehydrogenation. Catalytic tests proved that iron and vanadium supported on activated carbon or Al2O3 with certain promoters are potential catalysts for this coupling process. The catalysts of iron and vanadium are different in the reaction mechanism, although ST yield is always associated with CO2 conversion over various catalysts. The two-step pathway plays an important role in the coupling process over Fe/Al2O3 while the one-step pathway dominates the reaction over V/Al2O3. Coke deposition and deep reduction of active components are the major causes of catalyst deactivation. CO2 can alleviate the catalyst deactivation effectively through preserving the active species at high valence in the coupling process, though it can not suppress the coke deposition.

Preparation of mesoporous carbon from commercial activated carbon with steam activation in the presence of cerium oxide

Mesoporous carbon was prepared from the commercial activated carbon by steam activation with cerium oxide as catalyst. Steam activation with a catalyst loading of 0.5-2.0 wt% at 680-870 degrees C was examined. The surface area and pore size were evaluated by nitrogen adsorption at 77 K, and the structure of cerium oxide was characterized by XRD, XPS, and TEM. The results showed that the catalyst promoted the development of a mesopore at lower temperature (680-740 degrees C), and the mesopore was concentrated around 4-10 nm. The noncatalytic activation was advantageous in mesopore development and the catalyst would restrict the formation of mesopores at high temperature (800-870 degrees C). Higher loading of cerium oxide and higher activation temperature caused the aggregation of cerium oxide and then resulted in scattered pore size distribution.

Degradable polymers from ring-opening polymerization of α-angelica lactone, a five-membered unsaturated lactone

A degradable polymer was prepared from α-angelica lactone, a five-membered unsaturated lactone, by ring-opening polymerization (ROP). The polymerizability of α-angelica lactone was explained by a DFT calculation. The degradability of the resultant polymer and the reaction kinetics of α-angelica lactone ROP were also considered. Owing to the presence of a CC bond in α-angelica lactone, the ROP of five-membered cyclic lactone becomes feasible under moderate conditions and the resultant polyester exhibits good degradability under light or acidic/basic circumstances. Since α-angelica lactone can be easily obtained from the commercially available green bio-platform chemical levulinic acid, its ROP may provide a potential route to produce functionalized aliphatic polyesters from renewable resources.

V2O5/Ce0.6Zr0.4O2-Al2O3 as an efficient catalyst for the oxidative dehydrogenation of ethylbenzene with carbon dioxide.

Vanadium has been widely used in catalysis because metaloxide-supported vanadia can catalyze many industrially important reactions, such as oxidation reactions. 2] The activity of the supported vanadia is highly dependent on the specific oxide support as a result of the so-called strong metal oxide–support effect. Although many researchers have attempted to gain insight into the catalytic mechanism, by using theoretic calculations and various characterization techniques, it is not yet fully understood. Thus, the design of a high-performance supported vanadia catalyst, especially one with a high degree of stability, is still a challenge. The oxidative dehydrogenation of hydrocarbons (ODH) to alkenes is industrially important for various large-volume synthetic polymers. Because ODH with molecular oxygen as oxidant is a promising solution, many efforts have been reported. Based on the concepts of dehydrogenation and selective catalytic oxidation of hydrogen, the commercial SMART process for the oxidative dehydrogenation of ethylbenzene was developed. This process co-feeds oxygen and steam in seriesreactor system. b] To overcome safety problems that result from mixing oxygen and light hydrocarbons, a novel idea to remove the dehydrogenation product of hydrogen by using reducible lattice oxygen was proposed, and a high-performance catalyst for the selective combustion of hydrogen in the presence of light hydrocarbons has been developed. Alternatively, ODH using CO2, being a soft oxidant without the problem of deep oxidation, is very attractive because it may open up new directions for oxidation reactions, and create a new route for ODH. Thus, oxidative dehydrogenation of ethylbenzene with CO2 (CO2-ODEB) has been extensively investigated as an efficient, energy-saving, and environmentally benign process. 7] Although the supported vanadia catalyst shows high activity towards CO2-ODEB, [7a–f] which proceeds via the Mars–van Krevelen redox mechanism, 2] it still suffers from severe catalyst deactivation. Being an excellent redox material, ceria stabilized with zirconia has found widespread use as catalyst or catalyst support. 8] Moreover, defect-site-enriched ceria (with the nature of the defects determined by the applied preparation method) has been reported to promote ODEB with N2O. [9] Thus, the combination of CeZrO2 with vanadia may create a unique ODH catalyst, provided that a very well dispersed oxide can be achieved. In this case, CO2-ODEB may proceed according to the redox cycle illustrated in Scheme 1. The oxidation of Ce to Ce by CO2 and the reduction of V 5+ to lower oxidation states (possibly V) by ethylbenzene are directly involved in CO2ODEB. Subsequently, V is oxidized to V with the reduction of Ce to Ce to complete the full cycle.

Reaction Coupling of Ethylbenzene Dehydrogenation with Nitrobenzene Hydrogenation

The chemical equilibrium for the coupling of ethylbenzene dehydrogenation with nitrobenzene hydrogenation, to produce styrene and aniline simultaneously, has been calculated on the basis of the Soave–Redlich–Kwong equation of state. The dehydrogenation of ethylbenzene in the presence of nitrobenzene over the catalysts γ-Al2O3, ZSM-5, activated carbon and platinum supported on activated carbon has been carried out at 400 °C. The effects of Pt loading and the pretreatment of the catalysts have been investigated. It has been revealed that the conversion of ethylbenzene can be greatly improved by the reaction coupling due to the elimination of the hydrogen produced in the reaction by the hydrogenation of nitrobenzene. Platinum supported on the activated carbon has been suggested as a suitable catalyst. The best results with ethylbenzene conversion of 33.8% and styrene selectivity of 99.2% were obtained over Pt(0.02 wt%)/AC at 400 °C. Moreover, such process is also energetically favored since the necessary process heat to drive the ethylbenzene dehydrogenation can be provided by the coupling with the exothermic nitrobenzene hydrogenation reaction.