Direct Synthesis Reaction Research Articles

Plasma-Triggered CH4/NH3 Coupling Reaction for Direct Synthesis of Liquid Nitrogen-Containing Organic Chemicals.

Nitrogen-containing organic chemicals such as amines, amides, nitriles, and hydrazones are crucial in chemical and medical industries. This paper reports a direct synthesis of N,N-dimethyl cyanamide [(CH3)2NCN] and amino acetonitrile (NH2CH2CN) through a methane/ammonia (CH4/NH3) coupling reaction triggered by dielectric barrier discharge plasma, with by-products of hydrazine, amines, and hydrazones. The influence of CH4/NH3 molar ratio, feedstock residence time, and specific energy input on the CH4/NH3 plasma coupling reaction has been investigated and discussed. Under the optimized conditions, the productivities of (CH3)2NCN and NH2CH2CN reached 0.46 and 0.82 g·L–1·h–1, respectively, with 8.83% CH4 conversion. In addition, through combining the optical emission spectra diagnosis and the reaction results, a possible CH4/NH3 plasma coupling reaction mechanism has been proposed. This paper provides a potential fine application of CH4 and NH3 in green synthesis of liquid nitrogen-containing organic chemicals, such as nitriles, amines, amides, and hydrazones.

The enhancement of direct amide synthesis reaction rate over TiO 2 @SiO 2 @NiFe 2 O 4 magnetic catalysts in the continuous flow under radiofrequency heating

A series of TiO2@SiO2@NiFe2O4 composite magnetic catalyst with a core-double shell structure was synthesized by a sol-gel method. The morphology of the catalysts was studied by XRD, SEM, N2 physisorption and their magnetic properties were examined with magnetometry, and specific absorption rate measurements. The catalytic activity was determined in a direct amide synthesis reaction between aniline and phenylbutyric acid at 150 °C in a fixed bed flow reactor under radiofrequency heating. The intermediate silica layer of the catalyst increased the porosity of the outer titania layer and the specific absorbance rate of the catalyst. The initial reaction rate increased by 61% as compared to a similar core-shell TiO2@NiFe2O4 catalyst showing the detrimental effect of nickel ferrite on titania. The reaction rate was further increased by a factor of 3.5 after a sulfation treatment due to an optimum Lewis acid site strength. The highest specific reaction rate over TiO2@SiO2@NiFe2O4 was observed at a 7.5 wt% sulfate loading which was 2.6 times higher as compared to a mechanical mixture of the same composition. The initial reaction rate decreased by 36% after a period of 55 h on stream. The catalyst activity was restored after a treatment with a H2O2 solution.

Direct synthesis of liquefied petroleum gas from syngas over H-ZSM-5 enwrapped Pd-based zeolite capsule catalyst

A facile synthesis route, named dual-layer crystal growth method, was developed for preparing Pd-based zeolite capsule catalyst. The millimeter-sized zeolite capsule catalyst (Pd/SiO2-SZ) with a core-shell structure was prepared by a developed dual-layer crystal growth method: coating Silicalite-1 and H-ZSM-5 zeolite orderly as double shells encapsulating the Pd/SiO2 core catalyst. We employed the prepared Pd/SiO2-SZ zeolite capsule catalyst for the direct synthesis of liquefied petroleum gas (LPG) from syngas (CO+H2). In the reaction, the zeolite capsule catalyst showed excellent LPG selectivity than the single core catalyst of Pd/SiO2 and the physical mixture catalyst prepared by a simply mixing core and shell catalysts. The Pd/SiO2-SZ realized the highest LPG selectivity of 34.4% with CO conversion of 14.1%. Moreover, the optimal reaction temperature and pressure in the reaction for LPG direct synthesis from syngas over Pd/SiO2-SZ catalyst were 623K and 5.0MPa, respectively. The high performance of zeolite capsule catalyst Pd/SiO2-SZ was attributed to the enforced mass transfer diffusion from inside to outside of the catalyst.

Liquid Phase Direct Synthesis of H2O2: Activity and Selectivity of Pd-Dispersed Phase on Acidic Niobia-Silica Supports

In this work, acidic niobia-silica (NbS, 4–14 wt % Nb) materials used as supports of dispersed Pd particles (1.0–2.0 wt % Pd) have been prepared from different Nb-precursors (niobium ethoxide, NBE, and ammonium niobium oxalate, ANBO) and techniques (coprecipitation and deposition), characterized, and tested in the direct synthesis of H2O2 in water and methanol solvents. In particular, on a typical NbS sample, the evolution of morphology (by N2-adsorption–desorption), crystalline-phase (by XRD), electronic structure (by UV–vis-DRS), and surface acidity with time/temperature of treatment (350–800 °C for 4–100 h) has been investigated. Surface acidity was measured by titrations with 2-phenylethylamine adsorption in various liquids: cyclohexane, for the intrinsic acidity, and water, methanol, and water–methanol mixtures for the effective acidities. Direct H2O2 synthesis reaction was performed in semibatch slurry reactor with continuous feeding of the gaseous mixture (H2, O2, and N2), under pressure (5 × 103 k...

From Surprising Solvothermal Reaction to Uncommon Zinc(II)-Catalyzed Aromatic C-H Activation Reaction for Direct Nitroquinoline Synthesis.

In this work, we first found a surprising solvothermal reaction for direct dinitration of quinoline derivative. To explore the application in direct nitroquinoline synthesis, this reaction was subsequently modified as an equivalent reaction in a Schlenk tube. More significantly, after a constant attempt, nitrated derivative was obtained in optimized condition with a zinc(II) sulfate catalyst, where some substrates with strong electron-withdrawing group were first nitrated by a directly catalyzed condition. This new zinc(II)-catalyzed aromatic C-H activation reaction is the first example of direct dinitration by a single catalyst, which will be a new facile and environmentally friendly strategy to access synthetically useful nitroquinoline derivative.

Selectivity control of H2/O2 plasma reaction for direct synthesis of high purity H2O2 with desired concentration

Low selectivity is one of the key problems which limit the application of plasma in chemical fields. High selectivity and concentration of H2O2 are critical in the direct synthesis of H2O2. Herein, we report that the selectivity of the H2/O2 plasma reaction can be controlled by specific energy input (SEI), i.e. low SEI leads to high H2O2 selectivity. When the SEI was fixed at 2.08J/ml, the H2O2 selectivity reached 91% with 17% O2 conversion, and a H2O2 solution with high concentration (90wt.%) was achieved. Plasma diagnostics and theoretical calculation results indicate that, low SEI results in low electron density, which leads to high H2O2 selectivity but low O2 conversion. Furthermore, the collision cross sections of H2 and O2 molecules with electrons indicate that the H2/O2 plasma, with average electron energy of 1–1.5eV, can synthesize H2O2 with high selectivity and high O2 conversion.

Colloidal lead halide perovskite nanocrystals: synthesis, optical properties and applications

Lead halide perovskite nanocrystals (NCs) are receiving a lot of attention nowadays, due to their exceptionally high photoluminescence quantum yields reaching almost 100% and tunability of their optical band gap over the entire visible spectral range by modifying composition or dimensionality/size. We review recent developments in the direct synthesis and ion exchange-based reactions, leading to hybrid organic–inorganic (CH3NH3PbX3) and all-inorganic (CsPbX3) lead halide (X=Cl, Br, I) perovskite NCs, and consider their optical properties related to quantum confinement effects, single emission spectroscopy and lasing. We summarize recent developments on perovskite NCs employed as an active material in several applications such as light-emitting devices, solar cells and photodetectors, and provide a critical outlook into the existing and future challenges. Although research into perovskite nanocrystals is still in its infancy, they are expected to be major players in future nanoscience. Lead halide perovskite nanocrystals are attracting much interest because their quantum yields for photoluminescence are approaching 100% and their optical band gap can be tuned over the entire visible wavelength region – properties that make them promising for use in lasers, light-emitting diodes (LEDs) and solar cells. Andrey Rogach of City University of Hong Kong and co-workers review the latest developments in the synthesis (of both hybrid organic-inorganic and all-inorganic nanocrystals), optical properties (quantum confinement effects, single particle emission and lasing studies) and applications (LEDs, solar cells and photodiodes) of these materials. They outline some of the many remaining challenges, but state their confidence that these should soon be overcome. This review summarizes recent developments in the direct synthesis and ion exchange-based reactions leading to hybrid organic–inorganic and all-inorganic lead halide perovskite nanocrystals. Optical properties related to quantum confinement effects, single emission spectroscopy and lasing are considered. Perovskite nanocrystals have been employed as an active material in several applications such as light-emitting devices, solar cells and photodetectors.

Continuous H2O2 direct synthesis process: an analysis of the process conditions that make the difference

Abstract A trickle bed reactor (TBR) was used to study different process parameters upon hydrogen peroxide direct synthesis. The catalysts used were commercial palladium on active carbon. The influence of pressure (1.75–25 barg), temperature (5–60°C), liquid flow rate (2–13.8 ml·min-1), gas flow rate (3.4–58.5 ml·min-1), catalyst amount (90–540 mg), Pd percentage on the support (5% wt., 10% wt. and 30% wt. Pd/C) as well as promoter concentrations (0.0005–0.001 m) were all varied as process parameters to better understand the behaviour of the system. By contrast, the gas phase molar composition of the feed (4:20:76=H2:O2:CO2) was kept constant. The strong influence between liquid flow rate, gas flow rate and catalyst amount were identified as the key parameters to tune the reaction, and related to the activity of the catalyst. In essence, these parameters must be carefully tuned to control the hydrogen consumption. The maximum productivity (289 μmol H2O2·min-1) and yield (83.8%) were obtained when a diluted bed of 30% Pd/C was applied. The H2O2 hydrogenation was studied in order to understand its role in the H2O2 direct synthesis reaction network. The hydrogenation reaction mechanism and the role of NaBr were identified thanks to the experiment proposed in the present work. Consequently, understanding the whole reaction mechanism from the process conditions studied led to a deeper understanding of all of the phenomena involved in the H2O2 direct synthesis.

A new multicomponent reaction for direct synthesis of primary γ-nitroamides

The multicomponent synthesis of γ-nitroamides were achieved by the use of ammonium carbonate as reagent and catalyst.

Effect of bed characters on the direct synthesis of dimethyldichlorosilane in fluidized bed reactor.

This paper presents the numerical investigation of the effects of the general bed characteristics such as superficial gas velocities, bed temperature, bed heights and particle size, on the direct synthesis in a 3D fluidized bed reactor. A 3D model for the gas flow, heat transfer, and mass transfer was coupled to the direct synthesis reaction mechanism verified in the literature. The model was verified by comparing the simulated reaction rate and dimethyldichlorosilane (M2) selectivity with the experimental data in the open literature and real production data. Computed results indicate that superficial gas velocities, bed temperature, bed heights, and particle size have vital effect on the reaction rates and/or M2 selectivity.

Direct Synthesis of Hydrogen Peroxide over Au‐Pd Catalyst—The Effect of Co‐Solvent Addition

AbstractDirect synthesis represents a green alternative, an environmentally benign process for the production of hydrogen peroxide. This is a three‐phase reaction, a solid catalyst with gas reactants and a liquid phase, which collects hydrogen peroxide formed from the catalyst surface. The choice of solvent and/or addition of promoters has a significant effect on the reaction rates observed, as well as selectivity towards peroxide. In addition to non‐toxic water, short chain alcohols are very attractive, due to good solubility of reacting gases. Here we report an extensive study on the influence of different groups of solvents on the direct synthesis reaction when either applied alone or as co‐solvent under non‐explosive and conventionally explosive reaction conditions.

Direct synthesis of hydrogen peroxide in a wall-coated microchannel reactor over Au–Pd catalyst: A performance study

The direct synthesis of hydrogen peroxide out of hydrogen and oxygen has been studied in a wall-coated microchannel. A silica wash-coat layer embedded with Au–Pd colloidal nanoparticles served as an active catalyst for the direct synthesis reaction. The influence of different reaction variables has been evaluated in order to identify optimal process conditions and to maximize the concentration of peroxide produced in the liquid phase. The gas mixture used in this study contained hydrogen and oxygen concentrations that would be considered explosive in conventional reactors. The results presented here show that combining the active Au–Pd catalyst with microchannel technology can lead up to 5wt% peroxide solutions at hydrogen conversions as high as 80%.

A three dimensional CFD simulation and optimization of direct DME synthesis in a fixed bed reactor

In this study, a comprehensive three-dimensional dynamic model was developed for simulating the flow behavior and catalytic coupling reactions for direct synthesis of dimethyl ether (DME) from syngas including CO2 in a fixed bed reactor at commercial scale under both adiabatic and isothermal conditions. For this purpose, a computational fluid dynamic (CFD) simulation was carried out through which the standard k-ɛ model with 10% turbulence tolerations was implemented. At first, an adiabatic fixed bed reactor was simulated and the obtained results were compared with those of an equivalent commercial slurry reactor. Then the concentration and temperature profiles along the reactor were predicted. Consequently, the optimum temperature, pressure, hydrogen to carbon monoxide ratio in the feedstock and the reactor height under different operation conditions were determined. Finally, the results obtained from this three-dimensional dynamic model under appropriate industrial boundary conditions were compared with those of others available in literature to verify the model. Next, through changing the boundary conditions, the simulation was performed for an isothermal fixed bed reactor. Furthermore, it was revealed that, under isothermal conditions, the performed equilibrium simulations were done for a single phase system. Considering the simultaneous effects of temperature and pressure, the optimum operation conditions for the isothermal and adiabatic fixed bed reactors were investigated. The results of the H2+CO conversions indicated that, under isothermal condition, higher conversion could be achieved, in compared with that under adiabatic conditions. Then, the effects of various operating parameters, including the pressure and temperature, of the reactor on the DME production were examined. Ultimately the CFD modeling results generated in the present work showed reasonable agreement with previously obtained data available in the literature.

A Bi-component Cu Catalyst for the Direct Synthesis of Methylchlorosilane from Silicon and Methyl Chloride

A bi-component catalyst comprising CuCl and metallic copper was used in the direct synthesis of methylchlorosilane to study the catalytic synergy between the different copper sources. The catalyst exhibited high activity and high selectivity of dimethyldichlorosilane (M2) in the stirred bed reactor. The effect of the proportion of CuCl used was studied and 10%-30% CuCl gave the best yield of M2. The use of CuCl decreased the induction period of reaction, improved the selectivity in the induction stage, and gave a longer stable stage. These results suggest that bi-component catalyst has advantages in the direct synthesis reaction.

Reactivity Aspects of SBA15-Based Doped Supported Catalysts: H2O2 Direct Synthesis and Disproportionation Reactions

Pd and PdAu catalysts supported on SBA15 and SiO2 were prepared and investigated for H2O2 direct synthesis in a batch autoclave (10 °C and 17.5 bar) and in the absence of halides and acids. The SiO2 supported catalysts exhibited inferior performances compared to the mesoporous ordered SBA15. A good control of both the catalysts dispersion and nanoparticle stability was achieved using SBA15. Catalysts were doped with bromine, a promoter in the H2O2 direct synthesis. Productivity and selectivity decreased when bromine was incorporated in the catalysts, thus indicating a possible poisoning due to the grafting process. A synergetic effect between Pd and Au was observed both in presence and absence of bromopropylsilane grafting on the catalyst surface. Three modifiers of the SBA15 support (Al, CeO2 and Ti) were chosen to elucidate the influence of the surface properties on metal dispersion and catalytic performance. Higher productivity and selectivity were achieved incorporating Al into the SBA15 framework, whereas neither Ti nor CeO2 improved H2O2 yields. The enhanced performance observed for the Prau/Al–SBA15 catalysts was attributed to the increased number of Bronsted acid sites. A modification of this catalyst with bromine was confirmed to impair both productivity and selectivity, possibly due to the broader particle size distribution and the poor stability of the metal nanoparticles, as demonstrate by transmission electron microscopy (TEM) images. H2O2 disproportionation was also investigated. A much slower reaction rate was observed compared to the H2O2 production, suggesting that the major contributor in the process of H2O2 destruction must be connected to the hydrogenation reaction.

Boosted CO2 reaction with methanol to yield dimethyl carbonate over Mg–Al hydrotalcite-silica lyogels

Nonimmobilized and immobilized Mg-Al hydrotalcite-like materials on silica lyogels were prepared and activated by calcination to be tested as catalysts in the direct carboxylation reaction of methanol. The HTs supported on silica lyogels showed an important improvement and high stability in the direct synthesis reaction of DMC from CO2 and MeOH.

Research on Mineral Formation Mechanism of Pulverized Coal Combustion Boiler Co-Generating Q-Phase Cement Clinker

Conduct test of 2CaO•Al2O3•SiO2 transformed into Q-phase mineral with analytical reagent CaO, SiO2, Al2O3 and MgO in library high-temperature furnace. And carry out experimental investigation on the mineral formation rule of co-generation Q-phase cement clinker on two-section multiphase reaction test stand simulating pulverized coal combustion boiler based on the test. It was found that: 2CaO•Al2O3•SiO2 may generate Q-phase mineral with hydration activity together with appreciated amount of CaO and MgO; experimental coal sort in reasonable ratio may co-generate cement clinker with main mineral sort of 2CaO•SiO2 and Q-phase mineral. Thermodynamic analysis on mineral formation reaction shows that, in Yanzhou coal co-generating Q-phase cement clinker, the most probably occurring is the direct synthesis reaction of 2CaO•Al2O3•SiO2, followed by 2CaO•SiO2 direct synthesis reaction and the Q-phase indirect synthesis reaction comes last according to chemical composition of clinkers.

Mo-Bi-V-Al 복합 산화물 촉매의 제조와 메탄 부분산화에 의한 메탄올 합성반응에 응용

본 연구는 메탄 부분산화에 의한 메탄올 직접 합성을 위한 촉매 개발을 목표로 수행되었다. 이를 위하여 Mo-Bi-V-Al 복합 산화물 촉매를 제조하였으며, 제조 방법에 따른 촉매 물성을 비교하고, 제조한 촉매를 이용하여 메탄올 합성반응을 수행하여 그 결과를 검토하여 보았다. 졸-겔법으로 제조한 촉매가 공침법으로 제조한 촉매보다 비표면적이 훨씬 컸다. 입자가 작고 표면적이 클수록 부분산화반응보다는 완전산화반응이나 메탄올 산화반응이 더 잘 진행되어 메탄올의 선택도는 낮아지고 이산화탄소의 선택도는 증가하였다. 졸-겔법으로 제조한 촉매가 공침법으로 제조한 촉매보다 약 <TEX>$20^{\circ}C$</TEX> 정도 더 낮은 온도에서 더 높은 메탄올 선택도(13%)를 보였다. 두 방법으로 제조한 촉매의 XRD 분석 결과 두 촉매의 결정 구조가 서로 달랐다. 본 반응에서 압력이 증가할수록 완전산화 반응이 억제되고 부분산화 반응이 일어나서 메탄올의 선택도는 증가하였고 이산화탄소의 선택도는 감소하였다. This study was aimed at the development of catalysts for the direct methanol synthesis by partial oxidation of methane. Mo-Bi-V-Al mixed oxide catalysts were prepared and characterized and used in the direct methanol synthesis reaction. The catalysts prepared by the sol-gel method had much larger surface areas than those prepared by the co-precipitation method. The larger the surface area was, the less the methanol selectivity was. The catalysts having larger surface area facilitate the complete oxidation of methane, decreasing the selectivity of methanol. The catalysts prepared by the sol-gel method showed higher methanol selectivity of 13% at <TEX>$20^{\circ}C$</TEX> lower temperature than those prepared by the co-precipitation method. Through XRD analysis, it was revealed that the structures of the catalysts prepared by the two methods were different. In the reaction, methanol selectivity increased and carbon dioxide selectivity decreased with pressure due to the suppression of complete oxidation reaction at a high pressure.

Experiment and Thermodynamic Analysis on Mineral Formation of Cement Clinker Cogeneration from Coal in Pulverized Coal Combustion Boiler

Take Changguang high-sulfur coal as experimental coal type; carry out the experiment of mineral formation rule of co-generation cement clicker on two-section multiphase reaction test stand and conduct XRD, SEM and EDS analyses on the mineral composition of the obtained co-generation clicker sample. It can be found from the experimental results that the mineral composition of co-generation clinker presents great difference with the temperature change in the furnace on the test stand; when the temperature in the furnace reaches to 1,330°C, the main mineral species in co-generation clinker sample are 2CaO•SiO2, Q phase and 3CaO•3Al2O3•CaSO4with excellent hydration activity. Conducted thermodynamic calculation on the mineral formation reaction probably occurring in the chemical compositions of Q-phase cement clinker co-generated from Changguang coal. It is shown in the findings of computational analyses that, according to the chemical composition of clinker, the direct synthesis reaction of 2CaO•Al2O3•SiO2firstly occurs, followed by the direct synthesis reaction of 2CaO•SiO2, the next is the indirect synthesis reaction of Q-phase mineral, and the last is the indirect synthetic reaction of 3CaO•3Al2O3•CaSO4; the final main mineral compositions of co-generation clinker should be 2CaO•SiO2, Q phase and 3CaO•3Al2O3•CaSO4. The conclusion of thermodynamic analyses on co-generation clicker mineral formation reaction basically conforms to the mineral composition in experiment of Changguang coal co-generating Q-phase cement clinker.

ChemInform Abstract: Iodine Catalyzed One‐Pot Five‐Component Reactions for Direct Synthesis of Densely Functionalized Piperidines.

AbstractThe reaction of 1,3‐dicarbonyl compounds (I) or (V) with 2 molecules of an aromatic or aliphatic amine and two molecules of a benzaldehyde affords the piperidines.