Applied Chemical Engineering (Transferred)

Abstract

In order to obtain better electrocatalytic hydrogen evolution performance, Fe₃S₄ with different morphologies was synthesized by controlling the reaction conditions. During that progress, the ferric oleate as an iron source, and the sulfur powder dissolved in oleylamine as a sulfur source. Fe₃S₄ with particle morphology proved to have the best electrochemical catalytic activity after adding 40% carbon black. In dehydrogenation, the overpotential was 234 mV and the Tafel slope was 213 mV/dec at a current density of 10 mA/cm². Meanwhile, Fe₃S₄ with a particle morphology exhibited superior electrochemical stability. Therefore, the controllably fabricated Fe₃S₄ with a particle morphology is a promising electrocatalyst for dehydrogenation.

Abstract

The surface modification of nano-TiO₂ was carried out with lanthanide-acetylacetonate complexes by adsorption method. The effects of lanthanide complexes content, lanthanide  element type, adsorption temperature, solvent dosage, adsorption time and other conditions on the photodegradation activity of methyl orange by the modified catalyst were studied, and suitable modification conditions were obtained. The results show that the photocatalytic activity of the modified nano-TiO₂ is much higher than that of the unmodified pure TiO₂, and the lanthanide-acetylacetonate complexes is an excellent surface modifier.

Abstract Graphene/MoS₂ hybrid material was prepared by the hydrothermal method. The hybrid material was characterized by X-ray diffraction spectrum, Raman spectra, transmission electron microscope and UV-vis-NIRS. It was used as a near-infrared photocatalyst to catalyze and degrade Rhodamine B (RhB). The results showed that when the concentration of the RhB solution was 50.0 mg·L^–1, the pH value of the solution was 7, the volume of the solution was 50.0 mL, the amount of G/MoS₂ catalyst was 0.05 g and near-infrared radiation was carried out for 3 h, the degradation rate of RhB in the 50 mL solution reached 96.5%. When MoS₂ was used as the photocatalyst, the degradation rate of RhB was only 75.5%. After 5 times of recycling, the catalytic efficiency of the hybrid photocatalyst was still more than 90%, indicating that the catalyst is very stable.

Abstract

The in-situ reaction process was used to prepare composite materials loaded with cadmium sulfide, which were respectively loaded by carbon nanotubes, activated carbon, and carbon nanotube/activated carbon composites for the study of photocatalytic degradation of methyl orange. The results show that when carbon nanotubes and activated carbon are used as carriers, the photocatalytic degradation reaction rate constants are 3.6 times and 8.8 times higher than those without a carrier. The photocatalytic performance of the carbon nanotube/activated carbon composite carrier with a mass ratio of 20: 80 to support cadmium sulfide is significantly higher than that of cadmium sulfide supported by carbon nanotubes and activated carbon respectively, and its photocatalytic degradation reaction rate constant is 30% – 40% higher than that under the condition of activated carbon alone as carrier. It shows that when the modified activated carbon is used as a photocatalyst carrier, carbon nanotubes have a significant effect in improving the efficiency of degrading organic matter.

Abstract

This paper presents a brief history of catalysis, as well as the processes of selective oxidation of hydrocarbons. On the other hand, the basic concepts involved in heterogeneous catalysis are mentioned, emphasizing the role of catalytic materials in chemical oxidation processes and posing a series of guiding questions to be followed when approaching a process catalyzed by solid materials. In the same way, the methods of synthesis of catalysts known in the literature as sol-gel and impregnation are shown, identifying the influence of each stage of preparation with the physical and chemical properties of the materials. Finally, a case study applied to the selective catalytic oxidation of methane and methanol using iron, molybdenum, and vanadium catalytic materials synthesized by the sol-gel method is presented.

Abstract

A novel dinuclear gadolinium(III) complex of an amide linked bispolyazatricarboxylate macrocycle (DO3VA) having 2-bromoisovaleric acid pendant arm is reported. The molecular longitudinal relaxivity of the dinuclear complex [Gd2{acamidoet(DO3VA)2}(H2O)2] is 13.23mM–1s–1 which corresponds to a “per Gd” relaxivity of 6.62 mM–1 s–1 (20 MHz, 37 ± 0.1 °C, pH 7). The “per Gd” r1p value is higher than the relaxivity of the clinically approved CAs. The transverse relaxivity (r2p) of [Gd2{acamidoet(DO3VA)2}(H2O)2] is 14.34 mM–1 s–1. The r2p/r1p values of 1.08 indicate that the complex is T1-weighted CAs. The 2-bromoisovaleric acid seems to be an excellent pendant arm for holding Gd(III) metal ion at any pH. The remarkable stability of the complex at various pH and in presence of protein shows that the ligand can be used as functionality in making new CAs for MRI and the amide core is a versatile core molecule for the creation of polynuclear gadolinium(III) chelates and dendrimeric CAs.

Abstract The effect of zinc sulfate and ferric sulfate on the pyrolysis process of lignin was studied at three different heating rates by using the thermogravimetric analysis technique. It was found that the pyrolysis of pure lignin is barely affected with the change of heating rates between 10 to 100 °C/min, which is unexpected because of the kinetic nature of pyrolysis. The pyrolysis kinetics of this major component of biomass was studied by using three fitting methods: the differential method with reaction order model n, the isoconversional method, and the distribution of activation energies model, DAEM. The best fit, which allowed calculating acceptable kinetic parameters, was obtained using the last method. The results show the influence of the catalysts and the heating rate on the lignin pyrolysis processes in the presence of the sulfates under study, which is confirmed by obtaining different kinetic parameters. The results suggest that zinc sulfate and ferric sulfate change the kinetic mechanism of lignin pyrolysis.

Abstract

Cobalt molybdenum carbide supported on activated carbon was synthesized and the effect of sulfiding on the catalytic activity of the glycerol trioleate deoxygenation process (DOX) was evaluated. Prior to the glycerol trioleate deoxygenation reactions, the catalyst was reduced and sulfided with CS2/H2. The CoMo/CA carbide was characterized by specific area (B.E.T), X-ray diffraction (XRD), elemental analysis (CHON-S), potentiometric titration with n-butylamine and X-ray photoelectron spectroscopy (XPS). The specific area of the CoMo/CA carbide and the support were 246 m2/g and 881 m2/g, respectively. XRD analysis proved the presence of Co6Mo6C2 and metallic cobalt. XPS showed the presence on the surface of signals assignable to Moδ+, Mo4+, Mo6+, Co2+, S2– and SO42–. Sulfided CoMo/CA carbide showed higher activad to glycerol trioleate esoxygenation than unsulfided CoMo/CA carbide. The highest yield was obtained at 310 °C, 900 psi H2 and 2 h of reaction (100% conversion) and a higher selectivity towards heptadecane (55%) and octadecane (45%) favoring decarboxylation (HDCX) and decarbonylation (HDCn) than hydrodeoxygenation (HDO).

Abstract

In this study, the degradation kinetics and degradation mechanism of 23 trace organic pollutants (TrOCs) in the secondary effluent of sewage by the combined membrane-UV/chlorine process were investigated, and the halogenated disinfection by-products (X-DBPs) in the combined process were investigated and its generation potential (X-DBPsFP), and the cytotoxicity and genotoxicity of the treated water samples were also evaluated. The results showed that membrane pretreatment could effectively promote the degradation of TrOCs in UV/chlorine system, and nanofiltration (NF) was more effective than ultrafiltration (UF). Compared with UF, NF intercepts more dissolved organic matter (DOM), thus weakening the light shielding effect, chlorine consumption and radical quenching to a greater extent. It is found that the degradation mechanism of TrOCs can be divided into the following four categories: Ho˙ dominated, RHS dominated, chlorine and RHS jointly dominated and chlorine dominated. Membrane pretreatment can well reduce the formation of X-DBPs, among which UF and NF reduce the formation of haloacetamide (HAMs) and trihalomethanes (THMs) most significantly, while NF reduces the formation of X-DBPs and X-DBPsFP and the toxicity of water samples much stronger than UF. In addition, NF UV/chlorine can significantly remove the precursors of X-DBPs, so as to effectively control the enhancement of cytotoxicity and genotoxicity of water samples in the post chlorination process. The research results promote the development of advanced sewage treatment technology and provide theoretical guidance for related research.

Abstract

Polyoxometalate (POM) is an eco-friendly solid acid. It is a polyatomic anion containing transition metal (group Ⅴ or group Ⅵ) oxyanions, which are connected by common oxygen atoms. In addition to the advantages of other photocatalysts, such as non-toxic, no secondary pollution, convenient, fast and efficient, it also has the characteristics of high oxygen rich surface, and because there are a large number of metal centers in its structure, it can show rapid reversible and multi electron redox transformation. Its band gap is narrow, and the spectral response range is wide. It has excellent photocatalytic degradation performance, and has been widely used in photocatalytic degradation of wastewater containing organic pollutants. In this paper, the types of polyoxometalates photocatalysts, the modification methods of polyoxometalates and the application of polyoxometalates and its compounds in the degradation of organic pollutants are reviewed. The prominent problems and corresponding solutions of polyoxometalates photocatalytic degradation technology at present are pointed out, and its future development direction is prospected.