Enhanced Charge Transfer via S-Scheme Heterojunction Interface Engineering of Supramolecular SubPc-Br/UiO-66 Arrays for Efficient Photocatalytic Oxidation.

Constructing heterojunction of supramolecular arrays self-assembled on metal-organic frameworks (MOFs) with elaborate charge transfer mechanisms is a promising strategy for the photocatalytic oxidation of organic pollutants. Herein, H12 SubPcB-Br (SubPc-Br) and UiO-66 are used to obtain the step-scheme (S-scheme) heterojunction SubPc-Br/UiO-66 for the first time, which is then applied in the photocatalytic oxidation of minocycline. Atomic-level B-O-Zr charge-transfer channels and van der Waals force connections synergistically accelerated the charge transfer at the interface of the SubPc-Br/UiO-66 heterojunction, while the establishment of the B-O-Zr bonds also led to the directional transfer of charge from SubPc-Br to UiO-66. The synergy is the key to improving the photocatalytic activity and stability of SubPc-Br/UiO-66, which is also verified by various characterization methods and theoretical calculations. The minocycline degradation efficiency of supramolecular SubPc-Br/UiO-66 arrays reach 90.9% within 30 min under visible light irradiation. The molecular dynamics simulations indicate that B-O-Zr bonds and van der Waals force contribute significantly to the stability of the SubPc-Br/UiO-66 heterojunction. This work reveals an approach for the rational design of semiconducting MOF-based heterojunctions with improved properties.

Comparative life cycle assessment of ammonia production by coke oven gas via single and coproduction processes.

As an abundant H2-rich byproduct from coking production, coke oven gas (COG) is a favorable feedstock for ammonia production. Recently, three COG-based ammonia processes have been applied, including single process, coproduction of ammonia with methanol, and coproduction of ammonia with liquefied natural gas (LNG). To systematically evaluate the environmental impacts of three COG routes, a comparative life cycle assessment was conducted with industrial data. Besides, the effects of ammonia synthesis pressure and electricity sources to the total LCA result were discussed. The results indicate that the environmental impacts of COG-based single ammonia route are mainly generated from ammonia production stage, accounting for 69.63 % of the overall normalized results, in which electricity and COG are the dominated contributors. Therefore, employing electricity from renewables like wind, solar, hydro and nuclear could dramatically mitigate the environmental impacts with a reduction of 36.3 %-70.7 % in most environmental indicators. Scenario analysis proves that reducing synthesis pressure from 31.4 MPa to 15 MPa does not show remarkable environmental benefits as expected since higher pressure is more conducive to ammonia synthesis. In comparison with coal based and natural gas-based ammonia routes, COG routes have obvious energy-saving benefit. In three COG-based ammonia routes, the two coproduction routes accounted for 49.1 % and 78.6 % of the energy depletion as single production due to highly efficient utilization of resources and energy. Coproduction of ammonia with methanol route exhibits better environmental performance than these in coproduction of ammonia with LNG route. Therefore, coproduction of ammonia with methanol route is more favorable in COG to ammonia processes. This study intends to provide a valuable reference for COG utilization and ammonia production options through the life cycle aspect.

Substitution Effects on the Reactivity and Thermostability of Five-Membered Ring Fluorides.

Recently, five-membered ring fluorides (c-C5Fs) have been significantly desirable in green chlorofluorocarbon substitutes due to their practically flexible application in various fields and environmental friendliness. Detailed knowledge regarding different substitution effects on their environmental properties and thermal stability is very limited due to their high-cost experiments. Here, comprehensive density functional theory and ab initio molecular dynamics calculations were performed to explore the relative electrophilic and nucleophilic reactivity and thermostability of c-C5F chemicals. The electronic properties induced by substitution effects of c-C5Fs were first explored. The environmental friendliness of c-C5Fs including 1,1,2,2,3,3-hexafluorocyclopentane (F6A), 1,1,2,2,3,3,4-heptafluorocyclopentane (F7A), cis-1,1,2,2,3,3,4,5-octafluorocyclopentane (F8A), 3,3,4,4,5,5-hexafluorocyclopentene (F6E), 1,3,3,4,4,5,5-heptafluorocyclopentene (F7E), octafluorocyclopentene (F8E), 1-chloro-3,3,4,4,5,5-hexafluorocyclopent-1-ene (F6-1), and 1-chloro-2,3,3,4,4,5,5-heptafluorocyclopent-1-ene (F7-1) was validly confirmed. Besides, their thermal stabilities at 600 K temperature were concluded due to their flexible carbon skeletons, where both in-plane stability and slight aromaticity of F6E were in peculiar found to contribute substantially. We also would like to stress the future application of F6-1 due to its significant out-plane stability. This study may pave the way for the development of chlorofluorocarbon substitutes.

Synthesis of hierarchical nanocrystalline ß zeolite as efficient catalyst for alkylation of benzene with benzyl alcohol.

To develop an efficient solid acid catalysts for the Friedel-Crafts alkylation reaction, especially for involving bulky molecules, the direct synthesis of hierarchical nanocrystalline ß zeolites were achieved by using amphiphilic organosilane ([(CH3O)3SiC3H6N(CH3)2C18H37]Cl, TPOAC) as collaborative structure-directing agent (SDA). The growth evolution of ß crystals and the influence of TPOAC/SiO2 molar ratio on the mesoporous structure, crystal size, and acidic properties of ß zeolites were investigated and discussed in detail. The characterization results reveal that intracrystalline mesopores and intercrystalline mesopores/macropores via the stacking of ß nanocrystals were generated over the hierarchical ß zeolites. Moreover, most of the strong acid sites were well remained compared with the conventional microporous ß zeolite. Consequently, the hierarchical nanocrystalline ß zeolite synthesized under the optimized synthesis conditions shows improved specific catalytic activity of acid sites (turnover number, TON) in alkylation of benzene with benzyl alcohol, which can be attributed to the integrated balance of considerable mesoporosity, accessibility of the acid sites, and well-remained strong acid sites in the hierarchical ß zeolite.

One-step direct conversion of methane to methanol with water in non-thermal plasma.

Achieving methane-to-methanol is challenging under mild conditions. In this study, methanol is synthesized by one-step direction conversion of CH4 with H2O at room temperature under atmospheric pressure in non-thermal plasma (NTP). This route is characterized by the use of methane and liquid water as the reactants, which enables the transfer of the methanol product to the liquid phase in time to inhibit its further decomposition and conversion. Therefore, the obtained product is free of carbon dioxide. The reaction products include gas and liquid-phase hydrocarbons, CO, CH3OH, and C2H5OH. The combination of plasma and semiconductor materials increases the production rate of methanol. In addition, the addition of Ar or He considerably increases the production rate and selectivity of methanol. The highest production rate of methanol and selectivity in liquid phase can reach 56.7 mmol gcat-1 h-1 and 93%, respectively. Compared with the absence of a catalyst and added gas, a more than 5-fold increase in the methanol production rate is achieved.

Controlled direct synthesis of single- to multiple-layer MWW zeolite.

The minimized diffusion limitation and completely exposed strong acid sites of the ultrathin zeolites make it an industrially important catalyst especially for converting bulky molecules. However, the structure-controlled and large-scale synthesis of the material is still a challenge. In this work, the direct synthesis of the single-layer MWW zeolite was demonstrated by using hexamethyleneimine and amphiphilic organosilane as structure-directing agents. Characterization results confirmed the formation of the single-layer MWW zeolite with high crystallinity and excellent thermal/hydrothermal stability. The formation mechanism was rigorously revealed as the balanced rates between the nucleation/growth of the MWW nanocrystals and the incorporation of the organosilane into the MWW unit cell, which is further supported by the formation of MWW nanosheets with tunable thickness via simply changing synthesis conditions. The commercially available reagents, well-controlled structure and the high catalytic stability for the alkylation of benzene with 1-dodecene make it an industrially important catalyst.

Synergistic Catalysis of the Synthesis of Ammonia with Co-Based Catalysts and Plasma: From Nanoparticles to a Single Atom.

In this study, a series of Co nanoparticles (NPs) with different sizes and Co single-atom catalysts (SACs) with different cobalt-nitrogen coordination numbers (Co-N2, Co-N3, and Co-N4) were synthesized and applied to the synthesis of ammonia catalyzed by plasma at low temperatures and atmospheric pressures. Under the same reaction conditions, the yield of nitrogen obtained from the reduction to ammonia over a series of Co NP catalysts varies with the Co particle size. The smaller the size of the Co NPs, the greater the number of exposed active centers, and the catalytic activity is higher. Among the Co SACs, the best catalyst was Co-N2 with two coordinated nitrogen atoms, and the ammonia yield was 181 mg·h-1·gcat-1. The experimental and theoretical calculations were consistent in that a low Co-N coordination number was beneficial to the adsorption and dissociation of N2, thereby enhancing the reduction activity of N2 and promoting the increase of ammonia production.

CFD Analysis of a Water Vaporization Process in a Three-Dimensional Spouted Bed for Flue Gas Desulfurization.

In this work, the gas-solid flow and water vaporization process are simulated by the method of Euler-Eulerian two-fluid model in a three-dimensional spouted bed, which have a significant influence on the desulfurization efficiency. The results of simulation indicate that the change trends of the particle volume fraction are similar under superficial gas velocities of 0.7 and 0.8 m/s. The degree of particle pulsation is the highest at the bottom of the spout area, and the degree of gas pulsation is the highest at the junction of the annulus area and spout area. The temperatures of gas, liquid, and particles are also analyzed. The results demonstrate that in the spout area, the gas temperature is much higher than that of the liquid and particles, but the three phases are uniformly mixed and have similar temperatures in other areas. Moreover, water vaporization mainly occurs at the junction of the annulus area and the spout area, a small amount of liquid is vaporized at the center of the spout area, and basically no vaporization reaction occurs in the outer radius of the annulus area. With the increase in gas velocity, gas temperature, and liquid temperature and the decrease in gas humidity, water vaporization reaction is promoted.

Catalytic Conversion of a ≥ 200 °C Fraction Separated from Low-Temperature Coal Tar into Light Aromatic Hydrocarbons.

A ≥ 200 °C fraction (CT200F) of low-temperature coal tar was prepared by a rotary film evaporator. The catalytic conversion experiments of CT200F and six model compounds were conducted on the pyrolysis gas chromatography-mass spectrometer. The yields of catalytic conversion products benzene, toluene, xylene, and naphthalene (BTXN) were analyzed by semi-quantitative analysis according to the chromatographic peak areas. Additionally, the possible formation pathways and mechanisms of the target products BTXN generated over different catalysts were investigated. The results show that the yield of aromatic hydrocarbons increases and the yield of acid compounds decreases during CT200F pyrolysis over ZSM-5, HY, USY, and ß-zeolite compared with that of its non-catalytic pyrolysis, especially the yields of BTXN obtained over USY and ß-zeolite increase by 128 and 108%, respectively. The pore structure of ZSM-5 is suitable to produce BTX, while the suitable acidity and pore structure of USY, HY, and ß-zeolite are more beneficial for the selective preparation of naphthalene than that of ZSM-5. The conversion pathways of six model compounds into BTXN over zeolites were obtained, and the following conclusions can be drawn: The dehydroxylation effect of zeolites shows the order of ZSM-5 > HY > USY > ß-zeolite. The catalytic effect of zeolites on the cracking and ring opening of PAHs in CT200F shows the order of ß-zeolite > USY > HY > ZSM-5. The catalytic effect of catalysts on the cracking and aromatization of aliphatic compounds shows the order of ZSM-5 > ß-zeolite > USY > HY. ß-zeolite has an outstanding catalytic performance in the conversion of PAHs into naphthalene. ZSM-5 and HY can effectively remove phenolic hydroxyl groups in phenol and naphthol. During the catalytic conversion processes of the coal tar fraction and model compounds, the catalytic effect of the pore constructions of zeolites is more important than their acidities, which determines whether large molecules can enter and whether acid sites in non-micropores can be effectively utilized.

Hydrodynamic Behavior of Particles in a 3D Integral Multi-Jet Spout-Fluidized Bed.

The hydrodynamic behavior of particles in a 3D integral multi-jet spout-fluidized bed has been studied experimentally by particle image velocimetry method. In the cross section of the spouted bed, especially in the annulus, it was found that particle movement can be effectively promoted by adding the integral multi-jet, thus enhancing the radial movement of particles in the annulus and effectively eliminating the dead zone of particle flow in the annulus region. With the decrease of particle handling capacity, the fluidization effect of multi-jets was improved. When the static bed depth was 0.165 m, the enhancement effect of multi-jets on the movement of particles in the spouted bed would be optimal. When the particle diameter was overly small, the fluidization effect of the side jet would be relatively low, while excessive particle diameter would weaken the fluidization effect of the side jet due to the rise in the inertia force of particles. The analysis of the average turbulent kinetic energy and radial velocity of the particles revealed that when the particle diameter is equal to 0.72 mm, the strengthening factor of movement of particles (η) reaches the peak, the turbulence fluctuation of particles in the annulus region reaches the highest, and the fluidization effect of side jets on the particles is the best.

Synthesis, Characterization and Optoelectronic Property of Axial-Substituted Subphthalocyanines.

Two novel substituted subphthalocyanines have been prepared introducing m-hydroxybenzoic acid and m-hydroxyphenylacetic acid into the axial position of bromo-subphthalocyanine. The compounds have been characterized by Fourier transform infrared (FT-IR), Nuclear Magnetic Resonance (NMR) and single-crystal X-rays diffraction (XRD) methods. Their photophysical properties show that the axial substitution results into a relatively higher fluorescence quantum efficiency (ΦF=5.74 for m-hydroxybenzoic acid and 9.09 % for m-hydroxyphenylacetic acid) in comparison with that of the prototype compound, despite the almost negligible influence on the maximum absorption or the emission position. Moreover, the electrochemical behaviors show that the axial-substituted subphthalocyanines also exhibit enhanced specific capacitances of 395 F/g (m-hydroxybenzoic acid) and 362 F/g (m-hydroxyphenylacetic acid) compared with 342 F/g (the prototype) to the largest capacitance at the scan rate of 5 mV/s, and the significantly larger capacitance retentions of 83.6 % and 82.1 % versus 37.3 % upon density up to 3 A/g. These results show the potential of these axial-substituted subphthalocyanines in the use as organic photovoltaics and supercapacitors.

Eulerian-Eulerian Numerical Study of the Flue Gas Desulfurization Process in a Semidry Spouted Bed Reactor.

The Eulerian-Eulerian two-fluid model (TFM) in conjunction with kinetic theory of granular flows (KTGF) was used for analyzing water vaporization and the semidry flue gas desulfurization process in a two-dimensional powder-particle spouted bed (PPSB). In an environment with high-temperature gas, desulfurization slurry is wrapped on the surface of moving particles and evaporated, along with the application of the user defined function (UDF) method to accomplish water heat and mass transfer by considering evaporation in the simulation process. The simulation results revealed that the best mass- and heat-transfer effect of each phase can be found in the outer annulus and the near spout region, both of which are also the main areas where water vaporization occurs. The rate of desulfurization products decreases with the increase in inlet gas temperature as the water vaporization rate increases. The volume fraction of desulfurization reaction products decreases with the increase in inlet flue gas temperature. Compared with other working conditions, the highest desulfurization efficiency reaches 84% when the inlet flue gas temperature is 480 K. The change of the desulfurization product rate with the radial distance is the same under different superficial gas velocities, with the peak desulfurization efficiency appearing in the annulus. The optimal operating parameter for the desulfurization process is available in PPSB, and the desulfurization efficiency and gas handling capacity reach the best result when the superficial gas velocity equals 1.2 Ums.

Numerical Study on the Gas-Solid Flow in a Spouted Bed Installed with a Controllable Nozzle and a Swirling Flow Generator.

The swirling flow technology is adopted on a nozzle of the spouted bed in order to enhance the radial movement of the particles. The hydrodynamic characteristics in a spouted bed with a swirling flow generator installed on the nozzle are numerically investigated based on the two-fluid model (TFM). The traditional spouted bed and spouted bed with an integral swirling blade nozzle (ISBN) are simulated and analyzed. Numerical results show that the dead zone at the cone region of the annulus can be effectively eliminated by using the ISBN. The maximum decrease in particle concentration near the cone region is 72%, and the ISBN structure can significantly improve the comprehensive fluidization degree of the spouted bed when γ equals 86°. The turbulent kinetic energy of gas can be significantly increased by the swirling flow along the radial direction in the spouted bed, especially in the spout region. Also, the swirling flow can promote the radial velocity and granular temperature of the particles in the spouted bed, which is helpful to the radial mixing of particles and gas phase between the central spout and the annulus in the spouted bed. There exists a value of ξ (equals 0.526), which brings the greatest elimination effect of the flow dead zone in the annulus of the limited spouted bed space, and the overall fluidization of the spouted bed has the best performance when ξ = 0.316.

Iridium-catalyzed ortho-selective carbon-hydrogen amidation of benzamides with sulfonyl azides in ionic liquid.

An efficient and convenient iridium(iii) catalyzed ortho-C-H bond amidation of weakly coordinating benzamides treated with readily available sulfonyl azides as the amino source has been described. In this transformation, ionic liquids represents an ideal reaction medium, giving rise to a broad range of amidation products under mild conditions in the open air. This protocol offers moderate to excellent chemical yields, exclusive regioselectivities, and good functional group tolerance.

Synergistic conversion of coal char and methane for syngas and carbon-based supercapacitor electrodes.

A facile one-pot process for synergistic conversion of coal char and methane is conducted by employing K2CO3 as the catalyst. Besides syngas production, valuable carbon products are obtained and used to serve for supercapacitor electrodes. Effect of the operating parameters (including the catalyst dosage, gas feed flow rate, reaction temperature and time) is evaluated on electrochemical performance of the as-prepared carbon. The appropriate surface and structural properties enable the prepared carbon electrode to have a remarkable capacitive performance, along with a specific capacitance up to 125 F/g at a scan rate of 5 mV/s and 133 F/g at a current density of 1 A/g. According to the potential capacitive contribution of the carbon species, the high capacitive performance is mainly attributed to formation and growth of abundant carbon fibers in the one-pot process.

Experimental Study on Gas-Solid Flow in the Spouted Bed under Longitudinal Vortex Effect.

To strengthen the particles radial movement and mixing, the longitudinal vortex generator of a sphere was adopted in the spouted bed in this study. To find the influence of the longitudinal vortex and particle properties on axial and radial velocities of particles in a 152 mm-diametered spouted bed, particle image velocimetry (PIV) was employed. The experimental results show that the addition of the longitudinal vortex generator caused the vortex movement of high-speed gas and induced a considerable secondary fine vortex in the cross section of the spouted bed, and the existence of longitudinal vortex significantly improved the radial velocity of particles, compared with that of the conventional spouted bed. Due to the effect of longitudinal vortex on particles, the phenomenon of early dropping of particles was increasingly obvious with the rise in bed height, and the value of axial velocity of particle phase was negative. With the decrease in the particle diameter, the longitudinal vortex effect of gas-driven particle movement would be enhanced. The longitudinal vortex could enhance particle velocity under a wide range of particle diameters, and the enhancement factor η decreased with the rise in the particle diameter and gradually approaches to 1.

CFD Simulation and Optimization of Mixing Behaviors in a Spouted Bed with a Longitudinal Vortex.

The radial mixing characteristics of gas and solid phases in a cylindrical spouted bed with a pair of longitudinal vortex generators (LVGs) are numerically studied by a two-fluid model. The influence of the distance between the centers of two spheres (L) and the shape of LVGs on hydrodynamics in a spouted bed are discussed. The results show that the value of the coefficient of variation (CV) of the particle concentration can be significantly reduced by the longitudinal vortex produced in spouted beds. The particle concentration near the spout decreases first and then increases with the increase of L. When the shape of LVGs is cylindrical, a maximum increase of 188 % for particle volume fraction is found near the spout region of the spouted bed. The strengthening effect on particles' velocity achieves the best in annulus of the spouted bed, and CV of the particle concentration in the spouted bed reaches its minimum value with a pair of cylindrical LVGs.

Study on the adsorption behavior of glycerin from fatty acid methyl esters by a tertiary amine-type anion exchange resin.

A weakly basic anion exchange resin with hydroxylated tertiary amine groups was successfully synthesized and used for the first time in an adsorption study for glycerin in fatty acid methyl esters (FAME). A kinetic study of glycerin adsorption on the resin demonstrated that the resin exhibited a rapid initial adsorption behavior, and the correlation coefficients (r22) of the pseudo-second order reaction model were all greater than 0.98, which indicated the existence of hydrogen bonds through sharing electrons between glycerin and active sites on the resin. The whole process of glycerin adsorption onto the resin was a combination mechanism involving hydrogen bond sorption and intraparticle diffusion. The thermodynamic experiments showed that the glycerin adsorption onto the resin was a spontaneous exothermic process accompanied with a gradual decrease in entropy. In addition to intraparticle diffusion, the adsorption behaviors of the resin for glycerin also involved hydrogen bond forces between the OH in the glycerin molecule and N atom in the N(CH3)2 group, glycerin intermolecular hydrogen bond attraction, the dipole bond forces between glycerin and the N(CH3)2 group (90.96%) in the resin, and the dipole bond forces between glycerin and several of the N(CH3)3+ groups (9.04%) in the resin.

Effect of template removal using plasma treatment on the structure and catalytic performance of MCM-22.

To investigate the effect of template removal methods on the structure, properties and catalytic performance of the MCM-22 zeolite, dielectric-barrier discharge (DBD) plasma treatment and thermal calcination have been comparatively studied for the removal of hexamethyleneimine (HMI) from the two-dimensional layered precursor of MCM-22 (MCM-22(P)). The materials were characterized using FT-IR, TG, XRD, N2 adsorption at low temperature, NH3-TPD, and 27Al and 29Si MAS NMR. The results revealed that the seven-membered heterocyclic compound HMI can be effectively removed from the MCM-22 zeolite, and the condensation of silanol groups on the neighboring surface of MWW nanosheets can be induced by DBD treatment. Compared with calcination, DBD treatment could preserve the structure well and decrease the formation of extra-framework aluminum. Consequently, the concentration of acidic sites over MCM-22 treated by DBD (MCM-22(DBD)) is higher than that over calcined MCM-22 (MCM-22(C)). Moreover, MCM-22(DBD) possesses a certain amount of external surface area derived from the intercrystal pores due to the inhibiting effect of the condensation of the silanol groups on the external surface of the MCM-22 crystals. The activity and product selectivity of the Fischer-Tropsch (FT) synthesis was investigated over cobalt supported on the obtained MCM-22 zeolites. Compared with Co/MCM-22(C), Co/MCM-22(DBD) shows a higher catalytic activity in the FT synthesis reaction. Moreover, Co/MCM-22(DBD) can effectively decrease CH4 selectivity and increase C5-C20 liquid fuel selectivity.

Purification and Preparation of Rebaudioside A from Steviol Glycosides Using One-Dimensional Hydrophilic Interaction Chromatography.

A method for purifying and preparing rebaudioside A (RA) from steviol glycosides at preparative scale was developed with resin based on hydrophilic interaction liquid chromatography (HILIC). In pure water and acetone-water system, the adsorption capacity and selectivity of five anion resins for RA, rebaudioside C (RC) and stevioside (ST) were examined and discussed. Strongly basic IRA458 with the quaternary amine group was chosen as the resin used for separating and preparing RA. The hydroxide form of IRA458 (IRA458-OH) showed the best results in terms of the adsorption behaviors for RA, RC and ST. The retentions of RA, RC and ST on IRA458-OH resin at high concentration of acetone solution followed HILIC mode, in which retention is probably based on surface adsorption of the resin. Under optimized chromatographic conditions, the pooled purity and yield of RA were up to 98.18 and 98.62%, the relative standard deviations (n = 3) for these two parameters were 1.2 and 5.7%, respectively. The present method has the characteristics of simple, low cost, high purity and high yield. The study will be a promising tool for RA industrialized production and also provides a possible mode for purifying and preparing polar components from their analogs.