This work presents a novel chemical vapor deposition (CVD) approach that enables the deposition of ultrathin and conformal SiO2 layers on TiO2 anatase nanoparticles at room temperature using SiCl4 and air containing water without the use of a catalyst. The morphology of the CVD-grown SiO2 layers was found to be strongly dependent on the initial surface states of the TiO2 nanopowders, which could be altered by applying a simple heat pretreatment. The deposition on untreated TiO2 resulted in granular films, whereas on preheated TiO2 highly uniform and conformal SiO2 layers were obtained. By varying the SiCl4 precursor dosing time and the number of CVD cycles, the thickness of the SiO2 could be controlled at the nanometer level, which allowed us to investigate the influence of film thickness on the photocatalytic suppression ability. We found that a conformal SiO2 layer with a thickness of 3 nm could sufficiently suppress the photocatalytic activity of anatase TiO2 nanoparticles, which was demonstrated by the photodegradation of Rhodamine B. Our approach offers a simple, fast, feasible and low-temperature deposition method which can be directly applied to SiO2 coating on nanoparticles in pigments and other fields, particularly heat-sensitive materials, and further developed for large-scale production.

Surface-fluorinated TiO2 (F-TiO2) particles was synthesized by a simple fluorosilanization method to serve as a visible-light photocatalyst for rapid degradation of Rhodamine B (RhB) dyes. The fluroalkylsilane (FAS-17) was covalently immobilized on the TiO2 particles via robust Si–O bonds. The changes in surface properties of the F-TiO2 particles were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) and zeta potential measurements. The optical property of the F-TiO2 particles was determined by UV-visible spectroscopy. Upon the fluorination modification, the zeta potential of TiO2 particles switched from positive to negative, whilst the optical property of bulk TiO2 particles remained almost unchanged. Photodegradation experimental results demonstrated that zwitterionic RhB dyes were more favorably adsorbed on F-TiO2 rather than on the Ti(IV) sites of the pristine TiO2, and that the photodegradation reaction of RhB on F-TiO2 proceeded much faster than that on the pristine TiO2. However, the adsorption and photodegradation rate of anionic methyl orange (MO) dyes did not show an obvious change on F-TiO2. These results suggested that the molecular structure of dyes played a key role in visible-light photodegradation reactions on F-TiO2 particles. Positive-charged diethylamine groups of RhB molecular structures were postulated to promote the adsorption of RhB dyes on the surface of F-TiO2 particles, thus leading to easy electron injection and induction of rapid photodegradation under visible-light illumination.

This paper describes a kinetic study on the sulfidation and regeneration of Mn/Al2O3 sorbent for high temperature H2S removal. The influence of the reactant gas compositions and temperatures on the sulfidation and regeneration behavior was systematically investigated in a thermogravimetric apparatus. The results show that the shrinking core model can be used to correlate with the experimental data. The sulfidation is mainly dominated by diffusion. Through the regressions of the initial sulfidation reaction data, the chemical reaction order, activation energy, and pre-exponential factor are 1, 37.42 kJ/mol, and 4.16 × 10–2 m/s, respectively, and the diffusion activation energy and pre-exponential factor are 57.23 kJ/mol and 6.41 × 10–5 m2/s, respectively. O2 regeneration has the same situation as sulfidation; the chemical reaction order, activation energy, and pre-exponential factor are 1, 24.62 kJ/mol, and 0.17 m/s, respectively, and the diffusion activation energy and pre-exponential factor are 122.44 kJ/mol and 8.51 × 10–4 m2/s, respectively. For SO2 regeneration, the regeneration rate is controlled by the chemical reaction in the early stage, and then it is controlled by the diffusion in the latter stage; the chemical reaction order, activation energy, and pre-exponential factor are 1, 124.82 kJ/mol, and l.62 × 102 m/s, respectively, and the diffusion activation energy and pre-exponential factor are 224.83 kJ/mol and 2.33 × 10–6 m–2/s, respectively.

A series of Fe–Mn-based sorbents with different Fe/Mn mole ratios was prepared via coprecipitation for the high-temperature removal of H2S. Performance tests were carried out at 1123 K in a fixed-bed reactor, indicating that metallic Fe and MnO were the active components of the Fe–Mn-based sorbents in the hot gas. Single Fe-based sorbents exhibited a low desulfurization efficiency and effective sulfur capacity. The addition of manganese (Fe/Mn mole ratios less than 8:2) considerably improved the desulfurization efficiency and effective sulfur capacity of the Fe-based sorbents. In the first sulfidation test, effective sulfur capacities of 20.71, 20.72, and 20.14 g S/(100 g sorbent) were obtained for Mn7Fe3, Mn5Fe5, and Mn3Fe7, respectively. During five sulfidation–regeneration cycles, Mn7Fe3, Mn5Fe5, and Mn3Fe7 were stable, maintaining high activities and sulfur capacities, and reduced the amount of H2S to a few ppmv. After sulfidation, the sulfided sorbents could easily be regenerated with 2% O2 in N2 at 1123 K to obtain SO2 and S2. The elemental sulfur recovery rate increased with the decrease of manganese content. Characterization with XRD, SEM, and BET showed that Fe–Mn-based sorbents kept stable structures during successive sulfidation–regeneration cycles.

Ca–Al–O regenerable sorbents with various calcium contents have been prepared by co-precipitation method for H2S removal at 850 °C. For the sorbent with a calcium content of 52.5 wt%, its sulfur capacity reached 36 g S/100 g sorbent. The saturated S/Ca molar ratios of the sulfided sorbents changed from 0.82 to 0.88, depending on the Ca content of sorbent. They are much higher than the case of pure CaO. Regeneration by diluted air, a cyclic oxidation/reduction process, or water vapor was applied for the regeneration of sulfided sorbents. The sulfided sorbent cannot be regenerated completely in the diluted air regeneration operation. It was completely regenerated in the oxidation/reduction process, in which the oxidation used 3% O2 and the reduction used 10% H2. Repeating the oxidation/reduction 4 times, CaS was completely converted to CaO. Under such regeneration conditions, the sorbent performance was stable during 5 sulfidation–regeneration cycles. Sintering was observed in high O2 concentration regeneration due to the strong exothermic reaction, which resulted in activity drop. During 6 cycles of steam regeneration with 81% H2O at 850 °C, the sulfur capacities of the regenerated sorbents with an initial calcium content of 61.2 wt% remained stable at 36 g S/100 g sorbent.

We report an alternative technology for the mineralization of CO2 and production of soluble potash fertilizer via thermal activation of the insoluble K-feldspar with industrial waste of CaCl2 with lower energy consumption since the activation temperature was about 800–900 °C compared with the conventional temperature of 1300 °C. A remarkable K-extraction and CO2 mineralization ratio could be obtained at an appropriate activation temperature and content of additive CaCl2, which possessed the exchange of skeletal K+ with dissociative Ca2+ to form soluble K+ species, the collapse of K-feldspar framework, and the formation of intermediates (e.g., anorthite, pseudowollastonite, and wollastonite) to react with CO2. Characterization results (e.g., XRD, EDS, and SEM) indicated that pseudowollastonite and wollastonite were the major species to fix CO2. Moreover, the reaction principles of the K-extraction and CO2 mineralization were discussed, and a possible mechanism was proposed.

This article describes a novel CO2 mineralization approach using natural insoluble K-feldspar and phosphogypsum for the emission of CO2, reduction of phosphogypsum waste, and production of soluble potash. K-feldspar was activated with CaSO4 at high temperature and then mineralized with CO2 to extract potassium under hydrothermal conditions. Activation and mineralization conditions (e.g., ore/CaSO4 mass ratio, calcination and mineralization temperatures, initial pressure of CO2) were systematically investigated with an optical potassium extraction ratio of ∼87% and a CO2 mineralization ratio of ∼7.7%. A reaction mechanism was proposed based on the experimental results and the characterizations, such as polarized light microscopy, X-ray diffraction, and thermogravimetric and differential thermal analyses. This new methodology is a promising process and has the potential to reduce emissions of CO2 and phosphogypsum from a practical point of view.

A series of sorbents with different manganese contents have been prepared by co-precipitation method for 850 °C regenerative H2S removal. The sulfur capacity increased linearly with the increase of manganese content. The performance of sorbents prepared by co-precipitation of Mn nitrate and Al nitrate appears to be stable over five sulfidation–regeneration cycles. Al2O3 plays an important role in the performance of sorbents and the recovery of elemental sulfur in O2 regeneration. With increasing Mn content in the sorbent, increasing O2 concentration in the regeneration gas or increasing total regeneration gas flow rate, the recovery of elemental sulfur decreased. Elemental sulfur is the only product with SO2 regeneration. The sorbents cannot be completely regenerated with SO2 under the conditions used. The sorbents, however, can be completely regenerated by steam. The main product for steam regeneration is H2S. Steam regeneration results in less sintering than O2 regeneration.Highlights• Co-precipitation method was used to prepare Mn/Al sorbents for 850 °C H2S removal. • Regeneration of sulfided sorbents with diluted air, SO2 or steam was studied. • Elemental S can be obtained as a regeneration product with diluted air. • A two step regeneration with 50% SO2 followed with 3% O2 at 850 °C can provide elemental sulfur and complete regeneration. • Steam was another way for complete regeneration.

Kerosene-in-water emulsions were de-emulsified by narrow plate-type microchannels. The emulsions with different Sauter diameters of 5 or 10 μm were formed by high-shear homogenization method and passed through microchannels with clearances of 100 to 200 μm. The de-emulsification efficiency was from 10% to 30% in a single pass through the channel. By repeatedly passing through the microchannels, up to 90% de-emulsification efficiency can be achieved. The results showed that the de-emulsification efficiency was influenced by the flow rate, Sauter diameter, microchannel size, and wall materials. Hydrophobic surface of the microchannel improved the de-emulsification efficiency. A coupled two-step mechanism was proposed to illustrate the de-emulsification process. Specially, polytetrafluoroethylene−stainless steel (PTFE-SS) plate combination of the microchannel induced different velocities of the continuous phase close to the wall surface and helped the droplets of the emulsion move toward the PTFE wall and be captured.

In this work, the vapor−liquid equilibrium (VLE) data for binary systems of cyclohexane + cyclohexanone and cyclohexane + cyclohexanol were measured using a static-analytical apparatus at temperatures from (414.0 to 433.7) K. To avoid the disturbance of pressure drop during the sampling process, a stopcock was designed inside the autoclave to block out a part of vapor-phase space quickly before sampling. The measured VLE data were correlated by the Soave−Redlich−Kwong state equation (SRK) and Wilson activity coefficient models. The Redlich−Kwong (RK) and Hayden−O’Connell (HOC) equations were used to modify the vapor ideality in the Wilson models. The fitted Wilson model with the HOC equation (Wilson-HOC) was also compared against predictive universal functional activity coefficient (UNIFAC) models (standard UNIFAC and Dortmund modified UNIFAC). By error analysis, the Wilson-HOC model gave the best fit.

The size of initial bubbles is an important factor to the developed bubble size distribution in a gas-liquid contactor. A liquid cross-flow over a sparger can produce smaller bubbles, and hereby enhance the performance of contactor. A one stage model by balancing the forces acting on a growing bubble was developed to describe the formation of the bubble from an orifice exposed to liquid cross-flow. The prediction with this model agrees with the experimental data available in the literatures, and show that orifice size strongly affects the bubble size. It is showed that the shear-lift force, inertia force, surface tension force and buoyancy force are major forces, and a simplified mathematical model was developed, and the detachment bubble diameter can be predicted with accuracy of <±21%.

In many gas-liquid processes, the initial bubble size is determined by a series of operation parameters along with the sparger design and gas-liquid flow pattern. Bubble formation models for variant gas-liquid flow patterns have been developed based on force balance. The effects of the orientation of gas-liquid flow, gas velocity, liquid velocity and orifice diameter on the initial bubble size have been clarified. In ambient air-water system, the suitable gas-liquid flow pattern is important to obtain smaller bubbles under the low velocity liquid cross-flow conditions with stainless steel spargers. Among the four types of gas-liquid flow patterns discussed, the horizontal orifice in a vertically upward liquid flow produces the smallest initial bubbles. However the orientation effects of gas and liquid flow are found to be insignificant when liquid velocity is higher than 3.2 m·s−1 or the orifice diameter is small enough.