TiO2 Catalyst Research Articles

Low-pressure and Temperature Oxidation of 1,2-Dichlorobenzene Using Ozone and Metal-Loaded TiO2 Catalysts

AbstractAt low temperature and pressure (20 o C and 1 atm), the oxidation of 1,2-dichlorobenzene using ozone and metal (Mn, Ni, V, and Fe) supported on TiO2 catalysts was investigated in this study. The metal loaded on TiO2 catalysts were prepared using the wet impregnation method and characterized using FT-IR, XRD, SEM-EDX, BET, TEM, and ICP-OES techniques. 1,2-dichlorobenzene was oxidized for 24 h and the sample aliquots were collected after 3, 6, 9, 12, 15, 18, and 24 h of ozonation. The ozonation products were identified using GC-MS and FT-IR techniques and the identified products were 3,4-dichloro-2,5-furandione (DHF) and mucochloric acid (MCA). The 2.5% Fe/TiO2 was found to be the most active catalyst with a percentage conversion of 73% after 24 h of ozonation. Among the identified products, MCA recorded the highest percentage selectivity after 24 h of ozonation in all the metal-supported TiO2 catalyzed ozonation reactions. The highest percentage of selectivity towards the formation of the main product was 97%.

The Effect of CeO2 on the Catalytic Activity and SO2 Resistance of the V2O5-MoO3/TiO2 Catalyst Prepared Using the Ball Milling Method for the NH3-SCR of NO

The Effect of CeO2 on the Catalytic Activity and SO2 Resistance of the V2O5-MoO3/TiO2 Catalyst Prepared Using the Ball Milling Method for the NH3-SCR of NO

Surface self-modification of TiO2 for enhanced photocatalytic toluene oxidation via photothermal effect

Surface modification plays an important role in extending light absorption and enhancing the catalytic performance of semiconductor photocatalysts. However, most current studies focus on pre-modification of the semiconductors before reaction, while surface self-modification of catalyst during photocatalytic reaction process is often neglected. Here, we report the surface self-modification of TiO2 catalyst during photocatalytic oxidation of toluene under UV light irradiation, which changes the colour of TiO2 from white to yellow, and effectively extends its light absorption range into visible light region. The absorbed visible light is primarily released as thermal energy, significantly increasing the temperature of the catalytic system. Mechanistic studies reveal that the temperature elevation facilitates the separation of photogenerated charge carriers in TiO2 and promotes the generation of •O2−, consequently accelerating the surface redox reactions. The surface self-modified TiO2 exhibits an enhanced photothermal catalytic benzaldehyde generation of 4485 μmol g−1h−1 under UV–visible light irradiation, which surpasses the UV-driven activity of TiO2 by a factor of 1.9. This study offers new perspectives on the surface modification of semiconductor photocatalysts during organic transformations. It is anticipated to trigger increased research attention to this effect, ultimately advancing solar-to-chemical energy conversion.

Heterogeneous Catalytic Ozonation of Pharmaceuticals: Optimization of the Process by Response Surface Methodology.

Batch heterogeneous catalytic ozonation experiments were performed using commercial and synthesized nanoparticles as catalysts in aqueous ozone. The transferred ozone dose (TOD) ranged from 0 to 150 μM, and nanoparticles were added in concentrations between 0 and 1.5 g L-1, with all experiments conducted at 20 °C and a total volume of 240 mL. A Ce-doped TiO2 catalyst (1% molar ratio of Ce/Ti) was synthesized via the sol-gel method. Response surface methodology (RSM) was applied to identify the most significant factors affecting the removal of selected pharmaceuticals, with TOD emerging as the most critical variable. Higher TOD resulted in greater removal efficiencies. Furthermore, it was found that the commercially available metal oxides α-Al2O3, Mn2O3, TiO2, and CeO2, as well as the synthesized CeTiOx, did not increase the catalytic activity of ozone during the degradation of ibuprofen (IBF) and para-chlorobenzoic acid (pCBA). Carbamazepine (CBZ) and diclofenac (DCF) are compounds susceptible to ozone oxidation, thus their complete degradation at 150 μM transferred ozone dose was attained. The limited catalytic effect was attributed to the rapid consumption of ozone within the first minute of reaction, as well as the saturation of catalyst active sites by water molecules, which inhibited effective ozone adsorption and subsequent hydroxyl radical generation (●OH).

Ornidazole degradation based on peroxymonosulfate activation induced by oxygen vacancies (OV)-enriched Cu-Co-TiO2: Coexistence of free-radical and non-radical pathways

Employing transition-metal catalysts in peroxymonosulfate (PMS) activation reactions to facilitate combined free-radical and non-radical interactions is regarded as a proficient approach for decomposing organic contaminants. However, the creation of active catalysts faces significant challenges due to low activation efficiency, inadequate action sites, and instability of current activation materials. Here, we successfully prepared bimetallic Cu and Co co-doped TiO2 (Cu-Co-TiO2) catalyst using the sol-gel technique. Excellent ornidazole (ONZ) removal efficiency (0.628 min−1) was demonstrated by the Cu-Co-TiO2/PMS system, which was applicable across a broad pH range (4−10) and unaffected by different water matrices. Moreover, the coexistence of free-radical (SO4•-, •OH and O2•−) and non-radical (1O2) routes in the Cu-Co-TiO2/PMS system, where SO4•- and 1O2 are the predominant active substances, was confirmed by quenching experiments and electron paramagnetic resonance (EPR) study. The synergistic impact of Cu/Co bimetal may hasten the redox cycles of Cu+/Cu2+ and Co2+/Co3+, causing plenty of oxygen vacancies (OV) and improving PMS activation efficiency. The quantitative structure-activity relationship (QSAR) examination of the intermediates showed a decrease in toxicity, and the potential pathways of ONZ degradation were illustrated using Liquid Chromatography Mass Spectrometry (LC-MS) technology. This work not only demonstrated the effectiveness and stability of Cu-Co-TiO2 as a PMS activator, but it also offered fresh information on how to remove organic pollutants from wastewater by using PMS activation via the radical and non-radical oxidation pathway.

TiO2 Catalysts Co-Modified with Bi, F, SnO2, and SiO2 for Photocatalytic Degradation of Rhodamine B Under Simulated Sunlight

The organic pollutants discharged from industrial wastewater have caused serious harm to human health. The efficient photocatalytic degradation of organic pollutants under sunlight shows promise for industrial applications and energy utilization. In this study, a modified TiO2 photocatalyst doped with bismuth (Bi) and fluorine (F) and composited with SnO2 and SiO2 was prepared, and its performance for the degradation of Rhodamine B (RhB) under simulated sunlight was evaluated. Through the optimization of the doping levels of Bi and F, as well as the ratio of SnO2 and SiO2 to TiO2, the optimal catalyst reached degradation efficiency of 100% for RhB within 20 min under simulated sunlight, with a first-order reaction rate constant of 0.291 min−1. This value was 15, 41, 6.5, and 3.3 times higher than those of TiO2/SnO2, Bi/TiO2, Bi-TiO2/SnO2, and F/Bi-TiO2/SnO2, respectively. The active species detection showed that h+ was the most crucial active species in the process. The role of Bi and F addition and SnO2-SiO2 compositing was investigated by characterization. Bi formed a chemical bonding with TiO2 by doping into TiO2. The absorbance intensity in the UV and visible light regions was improved by SnO2 and F modification. Composite with SiO2 led to a larger surface area that allowed for more RhB adsorption sites. These beneficial modifications greatly enhanced the photocatalytic activity of the catalyst.

Laser-engraved defects in TiO2 support: Enhancing reducibility and redox capability of Pt/TiO2 catalyst for reactive and selective hydrogenation

Titanium dioxide (TiO2) has been studied as catalyst or catalyst support in catalysis. Its synthesis or modification approach controls the structural, optical, and electronic properties. Here we applied laser engraving to the anatase TiO2 and studied the consequent changes in its structure and property as well as the properties of TiO2 supported platinum (i.e., Pt/TiO2) catalyst. The laser engraving enlarged the particle size, formed rutile phase and created defects (i.e., oxygen vacancy (Ov) and Ti3+) in anatase TiO2. This induced band gap change and enhanced visible light absorption. The defects created by laser engraving are stable and more reducible than those existed in the pristine TiO2. The defective TiO2 is structurally stable and has great redox properties. The metal-support interaction in the Pt/defective TiO2 catalyst is stronger than that of the pristine Pt/TiO2 catalyst, which enabled higher reactivity and selectivity in hydrogenation of 3-nitrostyrene and furfuryl alcohol. Laser-engraved TiO2 has been rarely studied for thermal catalysis. This work provides basic understanding of material properties and catalysis application of laser-engraved catalyst supports and catalysts in field of thermal catalysis.

Novel framework-confined Cu@ 13X catalyst with excellent resistance to toxic SO2 as an eco-friendly substitute for hazardous V-based NH3-SCR catalyst

V2O5-WO3/TiO2 (VWTi) catalyst has long been utilized in fixed source flue gases to purify harmful NO gas. However, VWTi is classified as a hazardous material because of its harm to human health and environment. To address this issue, a low-cost green Cu-based zeolite catalyst (Cu@13X) with a wide temperature range was synthesized using an in-situ hydrothermal method. This method is intended to control the adsorption capacity of toxic SO2 by regulating the location of Cu species. UV-Vis DRS and EXAFS analyses revealed that a significant amount of Cu was encapsulated within the 12-membered ring pores of the 13X molecular sieve. SO2-TPD and DFT calculations further indicated that Cu@ 13X exhibits reduced SO2 chemical adsorption capacity. Consequently, this green catalyst demonstrated superior catalytic performance, maintaining superior NOx conversion for over 70 h in the mixture gas containing 250 ppm SO2; while the Cu/13X catalyst lacked NH3-SCR catalytic activity under the same conditions. Moreover, Cu@ 13X catalyst also has excellent NH3-SCR catalytic performance in low temperature flue gas below 250 °C, which is significantly better than the hazardous VWTi catalyst. Characterization techniques such as NH3-TPD, H2-TPR, and XPS confirmed that the Cu@ 13X catalyst possesses excellent acidity, robust redox capabilities, and abundant surface defects. In-situ DRIFT spectra further illustrated that the NH3-SCR reaction on the catalyst surface adheres to the Eley-Rideal mechanism both before and after the introduction of toxic SO2. This study offers a fresh perspective on the development of framework-confined NH3-SCR catalysts and elucidates the mechanism behind the sulfur resistance of these catalysts. And the green Cu@ 13X catalyst is anticipated to serve as an effective alternative to the hazardous VWTi catalyst.

Reduction of N2 to NH3 using FeP(101)/TiO2 catalysts: A First-principles study

The electrochemical nitrogen reduction reaction offers an eco-friendly and sustainable way for synthesizing ammonia at room temperature, in contrast to the energy-intensive Haber-Bosch process. In this study, we demonstrate that FeP (101) is stabilized by anatase TiO2(101), resulting in the formation of a FeP/TiO2 composite. This composite shows promising potential as a catalyst for N2 electroreduction. All hydrogenation reactions are feasible and occur spontaneously, with the ∗N2-∗N2H step serving as the potential determining step (PDS) with a value of 0.59 V. In comparison to the Ru (0001) surface (1.08 V), which exhibits superior catalytic activity in nitrogen reduction reactions (NRR), the obtained value is significantly lower. FeP/TiO2 exhibits ∼100% selectivity towards ammonia synthesis as compared to the competitive hydrogen evolution process (HER). This study demonstrates that the correlation between N2 activation and the electronic structure will aid in the fundamental comprehension, design, and alteration of NRR catalysts.

Aquathermolysis of polyolefin plastic wastes over a MOF-derived TiO2 anatase catalyst: Enhancing C–N bond cleavage and coke suppression

Plastics are ubiquitous in modern society owing to their cost-effectiveness, low weight, and durability. However, the disposal and recycling of plastic waste remain significant challenges. Aquathermolysis has emerged as a promising strategy for converting contaminant-rich polyolefin plastic waste into value-added liquid fuels. This study investigates the plastic-waste aquathermolysis potential of a TiO2 catalyst derived from the sacrificial precursor Ti-containing MIL-125 via a MOF-mediated synthesis pathway combined with calcination. The TiO2 catalyst retained its mesoporous properties and predominantly anatase phase on calcination at 450 ℃. The aquathermolysis catalysis and stability of the newly synthesized catalyst for plastic-waste conversion were evaluated and compared with those of other catalytic systems. Additionally, the role of water in the N removal efficiency and coke suppression properties of the catalyst were analyzed. Water significantly improved the removal of N and S impurities, with a N reduction of 80–95% at the optimal water content (20–40 wt%). The robustness of the as-synthesized catalyst was confirmed by deconvoluted X-ray photoelectron spectroscopy patterns, which indicated the persistence of the TiO2 phase, even after prolonged catalysis in aqueous environments, and transmission electron microscopy results, which showed that the anatase phase remained well-dispersed under aquathermolysis conditions with a significant reduction in the C/Ti ratio and a corresponding increment in the N/C ratio. The results of this study could guide future research on the development of catalysts, similar to the MIL-125-derived TiO2 catalyst investigated here, with high potential for efficient plastic-waste conversion and impurity removal in aqueous environments.

The role of TiO2 and gC3N4 bimetallic catalysts in boosting antibiotic resistance gene removal through photocatalyst assisted peroxone process

Antibiotics are extensively used in human medicine, aquaculture, and animal husbandry, leading to the release of antimicrobial resistance into the environment. This contributes to the rapid spread of antibiotic-resistant genes (ARGs), posing a significant threat to human health and aquatic ecosystems. Conventional wastewater treatment methods often fail to eliminate ARGs, prompting the adoption of advanced oxidation processes (AOPs) to address this growing risk. The study investigates the efficacy of visible light-driven photocatalytic systems utilizing two catalyst types (TiO2-Pd/Cu and g-C3N4-Pd/Cu), with a particular emphasis on their effectiveness in eliminating blaTEM, ermB, qnrS, tetM. intl1, 16 S rDNA and 23 S rDNA through photocatalytic ozonation and peroxone processes. Incorporating O3 into photocatalytic processes significantly enhances target removal efficiency, with the photocatalyst-assisted peroxone process emerging as the most effective AOP. The reemergence of targeted contaminants following treatment highlights the pivotal importance of AOPs and the meticulous selection of catalysts in ensuring sustained treatment efficacy. Furthermore, Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) analysis reveals challenges in eradicating GC-rich bacteria with TiO2 and g-C3N4 processes, while slight differences in Cu/Pd loadings suggest g-C3N4-based ozonation improved antibacterial effectiveness. Terminal Restriction Fragment Length Polymorphism analysis highlights the efficacy of the photocatalyst-assisted peroxone process in treating diverse samples.

Core-shell structured composite high-efficiency catalyst Co@Pd/TiO2 with a compressed-strain Pd shell for the direct synthesis of H2O2

Direct synthesis of H2O2 from H2 and O2 still faces the dilemma of low selectivity and productivity due to the O-O bond dissociation. To expedite the resolution of this issue, we introduce a core–shell structured catalyst Co@Pd/TiO2 with a compressed-strain Pd shell. The Co@Pd/TiO2 catalyst demonstrates a superior H2O2 productivity of 6.95 × 103 mmol·gPd-1·h−1 and H2O2 selectivity of 98.1 %, with enhancements of over 192 % and 139 %, respectively, when compared to Pd/TiO2. The construction of the compressed-strain Pd shell on the Co@Pd/TiO2 catalyst induces a winder width (wd) and a lower center (εd) of the Pd d-band, allowing the Co@Pd/TiO2 catalyst to achieve the following benefits for improving H2O2 selectivity and productivity: (1) Reducing the degree of electron back-donation to O2* (* denotes adsorbed state, the same below), thus inhibiting the cleavage of the O-O bond in O2*; (2) Showing a weaker Pd-O bond strength, which stabilizes the OOH* species and suppresses the breakage of the O-O bond therein; (3) Weakening the interaction between the catalyst and chemical substances, thereby restraining H2O2 degradation.

Effect of crystalline TiO2 on V2O5WO3/TiO2 as tunable low-temperature shift De-NOx catalyst

Based on the crystalline size of anatase TiO2, a series of tunable low-temperature shift V2O5-WO3/TiO2 (VW/Ti) catalysts for NH3 selective catalytic reduction (NH3-SCR) of NOx were prepared by impregnation process. These catalysts contained a loading amount of 2 wt% WO3 and either 2 or 5 wt% V2O5. The tunable low-temperature shift De-NOx performance of the VW/Ti catalysts was significantly enhanced and dramatically decreased after heat treatment of TiO2 from 100 °C to 700 °C (Ti100 ∼ Ti700). Nearly 100 % De-NOx efficiency was achieved at a gas hourly space velocity (GHSV) of 60,000 h−1. A notable shift from higher to lower temperatures was observed from V2W2/Ti100 to V2W2/Ti600; however, the activity was lost for V2W2/Ti650 to V2W2/Ti700. When the V2O5 loading increased from 2 wt% to 5 wt%, the V5W2/Ti600 showed the highest De-NOx efficiency at 225 °C, demonstrating a remarkable synergistic effect compared to the V2W2/Ti100 catalyst, which achieved maximum efficiency at 375 °C. The De-NOx performance and low-temperature shift effect of these catalysts were elucidated by considering TiO2 crystalline size, the synergistic effect between V2O5 content and TiO2, and the V4+/V5+ oxidation state of V2O5 in the catalyst. Additionally, the high crystalline TiO2-based V2W2/Ti600 catalyst prepared in this study is expected to effectively decompose NOx at low temperatures, in contrast to the low crystalline TiO2-based V2W2/Ti100 catalyst.

Simultaneous removal of E1, E2, EE2 and levonorgestrel from water using TiO2 catalyst anchored on activated carbon: Processes optimization, materials characterization, and assessment of the estrogenicity reduction

Removal of estrogen hormones from water matrices is crucial owing to its adverse effects on aquatic ecosystems and human health. The present investigation applies an advanced approach to assess the effectiveness of combined processes (adsorption and visible-light-driven photo-degradation) for simultaneous removal of estrone (E1), 17β-estradiol (E2), 17α-ethinylestradiol (EE2), and levonorgestrel (LEVO) in water, applying TiO2-activated carbon composite selected through design of experiment (DoE) for process optimization. Based on a central composite rotatable design (CCRD), composites were synthesized with percentages of activated carbon (AC) ranging from 2.93% to 17.07% (wt.) and calcination temperatures between 259 and 541 °C. The composite with the best performance TiO2-AC15%-541 (15% wt. AC, calcined at 541 °C), achieved a total removal of 98.3 ± 1.15% for E1, 99.0 ± 1% for E2, 99.3 ± 1.15% for EE2, and 96.0 ± 2.65% for LEVO at the initial concentration of 100 μg L−1 under simulated solar irradiation. Further optimization using once more CCRD involved three independent variables: pH; hormone concentration/TiO2-AC15%-541 loading ratio; and the intensity of simulated solar irradiation. Under optimized conditions (pH 2.64, hormone concentration/TiO2-AC15%-541 loading ratio of 3.8 mg g−1, and irradiation intensity of 41 W m−2 UV-A), the TiO2-AC15%-541 composite removed 99.8% of E1, 99.8% of E2, 99.0% of EE2, and 92.1% of LEVO. Furthermore, the process achieved a 99.9% reduction in estrogenic activity, assessed with yeast estrogen screen (YES) assay. These results demonstrate that TiO2-AC15%-541 is an efficient and cost-effective remediation agent for treating mixed estrogen compounds in water, with significant potential for commercial applications.

Application of TiO2 Photocatalyst for Improving Ozone Generation Efficiency

ABSTRACT With a strong oxidizing capability, ozone (O3) is widely used in industry. However, ozone generators on the market are expensive and require a lot of energy to operate, which remains the bottleneck for the wide applications. In this study, a novel and energy-efficient ozone generation system is developed via the combination of black-TiO2 photocatalyst and plasma system. Black-TiO2 catalyst is prepared by calcining commercial TiO2 catalyst at 550 °C under a nitrogen atmosphere to extend the absorption spectrum to visible light range to improve catalytic activity. The experimental results show that ozone generation efficiency can be greatly increased to 415 g O3/kWh via combined black-TiO2 catalyst and plasma with O2 as the feeding gas. This can be attributed to the fact that black-TiO2 catalyst with a smaller energy gap is more efficiently activated to form electron–hole pairs in plasma, which can enhance ozone generation. On the other hand, black-TiO2 catalyst can provide abundant active sites for active O atoms and O2 molecules to promote O3 generation. Black-TiO2 catalyst prepared in this study reveals good stability. Overall, combination of black-TiO2 catalyst with plasma reveals good ozone generation efficiency and has a good potential for practical applications.

Hydrothermal synthesis of bare TiO2 nanowires and polystyrene (PS)-TiO2 nanowires used for selective photocatalytic oxidation of 3-pyridinemethanol in water and PS photodegradation in solid state

In the present work, nanowire (NW) structured TiO2 nanoparticles were prepared using the hydrothermal method and characterized by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), and BET specific surface area techniques. They were obtained in the anatase phase and presented a high surface area (ca. 300 m2/g). A commercial TiO2 (anatase, Merck) was used for comparison. The TiO2 catalysts were tested for photocatalytic oxidation of 3-pyridinemethanol to 3-pyridinemethanal and vitamin B3 in water under UVA irradiation. The effects of acid treatment and subsequent calcination for TiO2 catalysts after the hydrothermal synthesis were also investigated. The sample, subjected to acid treatment and calcined at 300 °C (NW-HCl-300), showed the highest photocatalytic activity and selectivity towards the products. Consequently, this sample and Merck TiO2 were used to prepare polystyrene (PS)/TiO2 composites using the hydrothermal method. They were characterized by XRD, SEM–EDX, Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), UV–Vis, Gel Permeation Chromatography (GPC), and contact angle measurements and tested for PS (present in the composite) photodegradation. The results indicated that NW-HCl-300 had a high surface area, and was highly hydroxylated, favouring a good distribution of PS in the composite. The composite presented high thermal stability, but under UVA irradiation the polymer underwent solid-state photocatalytic degradation due to the contact with TiO2. The composite photodegradation was investigated using gravimetric, GPC, FT-IR, UV–Vis, and SEM techniques.

Facile synthesis of spherical-shaped CeC2–TiO2 nanocomposite electrocatalyst with boosted alkaline OER

Developing noble metal-free multifunctional electrocatalysts to catalyze water oxidation is vital for future renewable energy systems. Herein, through several defect modifications, the CeC2–TiO2 nanocomposite on the strength of enriched oxygen vacancies was successfully fabricated by facile hydrothermal method on SS (stainless steel) substrate, attributed to the conductive ability for fast electron transportation. A well-defined phase growth, vibrational bonding of metal atoms, morphological determination, and elemental composition for synthesized heterostructured electrocatalysts were revealed by XRD, FTIR, TEM, and EDX, respectively. XPS has complied to understand the moderate binding energies of CeC2–TiO2 for OER intermediates, which signifies the strong interactions between electronic states of Ce, C, Ti, and O atoms. With the plentiful catalytic active sites, the resultant CeC2–TiO2 entails low overpotentials of only 169 mV and 108.8 mV/dec Tafel slope to afford 10 mA cm−2 for OER in 1.0 M KOH are tested through cyclic and linear sweep voltammogram measurements, thereby exhibit promising activity in alkaline water electrolysis. EIS measurements revealed a decreased polarization resistance for the composite dominated by the small semicircle diameter, corresponding to the adsorption of intermediates. Finally, observed results strongly recommended that the CeC2–TiO2 catalyst exhibited superior OER performance due to excellent electrical chemical coupling between CeC2 and TiO2.

Fluidized-bed OCM reaction: A promising Mn2O3-Na2WO4/TiO2 catalyst and a numerical study

The fluidized-bed reactor with excellent heat and mass transfer features has great appeal for application in the oxidative coupling of methane (FB-OCM), whereas qualified fluid catalysts represent a grand challenge. Herein, we report a high-performance Mn2O3-Na2WO4/TiO2 fluid catalyst (5.4 wt% Mn2O3 and 2 wt% Na2WO4), which was obtained by the incipient-wetness impregnation method and examined in the OCM reaction in an electric-heating quartz fluidized-bed reactor (i.d., 2 cm). The standard normalization method on the basis of carbon atom was used for calculating the CH4 conversion and C2-C3 selectivity. This catalyst achieves 35.5 % CH4 conversion, 66 % C2-C3 selectivity and particularly 15.1 % single-pass yield of C2H4 for a feed of CH4/O2/H2O=3/1/1 with a catalyst dosage of 20 mL at 700 °C and a total GHSV of 7200 h−1. Such catalyst is stable for at least 50 h without signs of deactivation and agglomeration/defluidization. The catalyst particle size is crucial for the FB-OCM reaction with respect to the reaction light-off and catalyst fluidization. The catalyst with preferable particle size of 450–600 μm can not only trigger the OCM reaction at a relatively low temperature of 630 °C but also warrant active bubbling fluidization. Furthermore, thanks to the low amount of Na2WO4 and interpenetrating structure of TiO2-nanorod, such catalyst achieves good anti-aggregation and robust mechanical strength (with a low attrition index of 1.9 %). The effects of water-adding amount in feedstock and catalyst particle size distribution on the hydrodynamics behaviour were investigated in a laboratory-scale fluidized-bed OCM reactor by using numerical simulation method.

Green hydrogen and acetaldehyde production via photo-induced thermal dehydrogenation of bioethanol over a highly dispersed CuS/ TiO2 catalyst

The emergence of global warming issues has triggered the interest in producing carbon-neutral energy sources and fossil-based chemicals from affordable and renewable feedstocks (e.g., bio-ethanol). Herein, the synthesis of highly dispersed CuS/TiO2 photothermal catalysts is reported for simultaneously converting ethanol into hydrogen and acetaldehyde under simulated sunlight. The catalyst achieved a hydrogen evolution rate of 51.61 mmol g−1 h−1 and an acetaldehyde production rate of 48.63 mmol g−1 h−1, with a maximal acetaldehyde selectivity of 97% among carbon-containing products. Compared to pristine TiO2, the introduction of plasmonic CuS largely extended the light adsorption range and enhanced the photothermal performance, whilst the formation of heterojunction structure improved the charge transfer and separation efficiency. The density functional theory calculation results demonstrate that CuS/TiO2 composite interfaces could significantly lower the activation energy of ethanol dehydrogenation reaction and improve hydrogen evolution reaction ability. This study provides deep insight into understanding and optimizing hot carrier dynamics in photothermal catalytic systems.

Evaporation-induced self-assembly Al doped black TiO2 for the degradation of tetracycline hydrochloride under visible light

Light absorption range, recycling stability and charge transfer efficiency are key to the performance of photocatalytic material. Based on these targets, a Al doped TiO2 catalyst was synthesized by the evaporation-induced process, after processed by NaBH4 reduction, the black TiO2 doped with Al was finally prepared. Uv-vis DRS, EPR and XPS analyses confirm the expanded light absorption window (300 nm - 1000 nm) and the introduction of abundant oxygen vacancy after the reduction process. The final product BTiO2/Al-0.5 has a degradation rate of about 84 % over the tetracycline hydrochloride within 60 minutes, the reaction rate constant (k) is 10.6 times higher than the unreduced sample. The dramatic change of photocatalytic ability can be assigned to the broadened visible light absorption, increased charge separation efficiency, narrowed band gap and defect-enriched oxygen vacancy. This work offers insights into the fabrication of TiO2 catalyst and the introduction of oxygen defect.