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Volatile organic compounds (VOCs) are a great threat to the health of human beings, and developing catalysts with prominent activity and stability to eliminate them are highly desired. In this work...

Directly using natural materials as supporting material and reducing agent to obtain supported catalysts is significance along with the research of green and sustainable technologies. Herein, diato...

This work reports the template-free synthesis of diverse Carbon, self-doped Zinc oxide (C-doped ZnOSPs) superstructures through synergy between Cinnamomum camphora leaf extract and NaOH assisted by freeze-drying and annealing at desired temperatures. The high-activity and cost-effective porous supports with improved reducibility and charge transport act as catalyst support for ultra fine Pd NPs in the gas-phase selective remediation of the volatile organic compounds (VOCs) benzene. Uv–vis spectroscopy, XRD, XPS, SEM and TEM and photoluminescence studies, were used to characterize and verify the nature of the ZnOSPs. XPS analyses reveal that C-doping is introduced into the lattice of the as-produced ZnOSPs and the extent varied with leaf extract amount used. FTIR-analysis and simulation experiments showed flavones, polyphenols, and proteins were responsible for the formation of the ZnOSPs. Moreover, ultrafine Pd NPs sizes 1˜3 nm can be anchored on the exterior surfaces of ZnOSPs to form diverse surface contact boundaries for enhanced low-temperature benzene oxidation. Pd/ZnOSP-3 catalyst with the least crystallite size 17.4 nm and largest surface contact boundary 3.2 nm presented the best performance. The superior activity of Pd/ZnOSPs over commercial Pd/ZnO-C is attributed to its carbon modification, the high porous framework; defects incorporation which causes smaller optical energy gap, improved reducibility, enhanced mechanical responses and high charge transport to promote the benzene oxidation reaction.

The search for efficient and durable catalysts for volatile organic compounds oxidation is essential for environmental remediation. Herein, porous coral-like cobalt–manganese oxide (CoMnOx) catalyst was synthesized through annealing Co–Mn–1,3-propanediol precursors at 300 °C in air and applied for the catalytic oxidation of benzene. The as-prepared CoMnOx exhibited uniform porous coral-like structure, with an improved benzene catalytic abatement performance as compared to those of Mn3O4 and Co3O4 samples prepared by the same method, respectively. According to BET, H2-TPR, O2-TPD, and XPS analysis, the as-obtained CoMnOx catalyst showed the highest BET surface area, better low-reducibility temperature, and high content of absorbed oxygen groups when compared to Mn3O4 and Co3O4, which makes significant contribution to its catalytic benzene oxidation activity. Moreover, a plausible surface reaction mechanism for benzene oxidation over CoMnOx catalyst was also proposed through the in situ DRIFTS study.

Highly dispersed Au catalysts supported on amorphous titanosilicate supports with three-dimensional wormhole-like mesoporosity were prepared by deposition–precipitation method, which show excellent performance in propylene epoxidation with H2 and O2. The best catalytic performance, propylene conversion of 12.8%, propylene oxide selectivity of 76.2% and PO space-time yield of 160.9 gpo/Kgcat/h, was obtained at the reaction temperature of 300 °C. The Ti/Si molar ratio of the supports and some experimental parameters, such as the urea amount, loading temperature and Au loading on the as-produced catalyst are optimized. In addition, with the assistance of in-situ Fourier transform infrared spectroscopy (In-situ FT-IR), adsorption and desorption of PO, propylene and the reaction mixture on the catalyst are conducted to further explore the deactivation mechanism. It suggests that propylene and PO can be irreversibly and strongly adsorbed on the catalyst surface and finally transform to carbonate adsorbed on the active sites Ti-OH, resulting in catalyst deactivation.

In this study, an efficient Bi6O6(OH)3(NO3)3·1.5H2O/BiOCl heterojunction was prepared by a facile hydrothermal method, Bi6O6(OH)3(NO)3·1.5H2O nanoparticles with an average size of approximately 10 nm were grown uniformly in situ on the plates of BiOCl. The modification of Bi6O6(OH)3(NO3)3·1.5H2O effectively improves the photocatalytic activity of BiOCl for the degradation of rhodamine B (RhB). The enhancement of the photocatalytic activity could be attributed to the increased light harvesting ability, decreased charge resistance, and suppressed recombination of photoinduced electron–hole pairs in Bi6O6(OH)3(NO3)3·1.5H2O/BiOCl heterojunction.

Experimental work on benzene oxidation over C, N doped-MnxOy species showed that the oscillation formation and utilization of sub-surface O2 species from the catalyst was the rate-determining factor for activity. The MnxOy species were synthesized using the biosynthesis method. Characterizations from XRD, XPS, H2-TPR, and In-situ DRIFT were employed to study their catalytic properties. The MnxOy@300 catalyst with low activation energy (Ea = 62 kJ/mol) and TOF of 0.035 h−1 showed the best performance. The kinetic and mathematical model was proposed based on the current results, and those from previous works. The Ea, heat of vaporization, and temperature included in the kinetic model, increased its efficiency. The parameters of the kinetic study were regressed and verified by experimental data and the oxidation route was simulated. The kinetic model was extended into a mathematical model to predict which parameters had the most effect on the C6H6 oxidation process.

We report the green synthesis of ZnO supported Ni-Pd alloy nanoparticles for the gas-phase selective hydrogenation of 1, 3- butadiene. The supported catalysts were synthesized through a simple bio-reduction route using Cinnamomum Camphora leaf extract. X-ray diffraction, scanning and transmission electron microscopy and energy dispersed X-ray were used to characterize and verify the nature of the catalysts. The results showed that the Ni-Pd alloy particles were 3.2 ± 0.7, 3.4 ± 0.3 and 3.8 ± 0.6 nm for Ni1Pd1, Ni1Pd3 and Ni3Pd1 respectively. FTIR analysis revealed that stretching vibration bands such as C-H,-C=C-, O-H, -C-O- O remained on the surface acting as stabilizer. The influence of some reaction variables, such as type of S-Pd bimetallic catalyst, type of metal oxide support and reaction temperature, on the hydrogenation activity and selectivity towards total butene (trans-2-butene, 1-butene and cis-2-butene) is investigated. The bioreduction supported catalysts showed excellent catalytic activity and selectivity to butene in the selective hydrogenation of 1,3 butadiene. The calculated total butene selectivity was above 80% for all supported S1-Pd1 catalyst compared to 46.92 % for monometallic Pd/ZnO catalyst. In addition, the Ni1-Pd1/ZnO catalyst presented the best butene yield 88.90 % which was 1.9 times that of Pd/ZnO catalyst. Moreover, it maintained stability over a 10 h durability experiment.

Microorganism-mediated, hexadecyltrimethylammonium chloride (CTAC)-directed (MCD) method was employed in this work to synthesize Pd nanoflowers (PdNFs). Proper Pichia pastoris cells (PPCs) dosage, ascorbic acid (AA), Pd(NO 3 ) 2 and CTAC concentrations were essential for the growth of the PdNFs. The size of the as-synthesized PdNFs could be tuned by adjusting the amount of Pd(NO 3 ) 2 solution and dosage of PPCs used. Characterization techniques such as X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy were used to verify the nature of the PdNFs. Finally the PdNF/PPC nanocomposites were immobilized onto TiO 2 supports to obtain bio-PdNF/TiO 2 catalysts which showed excellent catalytic activity for CO oxidation, obtaining 100% conversion at 100 °C and remaining stable over a period of 52 h of reaction time.

In this paper, we report a microwave-assisted biosynthesis method with Cinnamomum camphora (CC) leaf extract for the green and rapid synthesis of Ag nanoparticles (NPs). The as-produced Ag nanoparticles were immobilized onto CeO 2 as supported Ag/CeO 2 catalyst, which proved to be efficient for carbon monoxide (CO) oxidation. Active components in the plant extract were identified by FTIR analysis and later on validated through simulated experiments. The results revealed that polyphenols and proteins were the reducing and protecting agents, respectively. The optimum preparation conditions for the catalyst were irradiation time of 140 s, Ag loadings of 5 wt.%, CC extract concentration of 25 g L −1 and sintering temperature of 300 °C. Since biomolecules adsorbed over the surface of catalyst was detrimental to its catalytic activity, calcination to remove the biomolecules was critical to the enhanced activity. Considering the trade-off between particle size and biomass removal extent, the optimum calcination temperature was determined to be 300 °C.

Pt catalysts and Co doped Pt catalysts with TiO2 as the support were prepared by the sol immobilization method based on biological synthesis process, whereby Pt nanoparticles (PtNPs) were reduced from Na2PtCl4 using Cacumen Platycladi extract (CPE). The catalytic performance of the catalysts was studied using hydrogenation of cinnamaldehyde as the model reaction. For comparison, Co doped Pt/catalysts were also prepared by traditional impregnation method, TEM observation, and XRD measurement were carried out to characterize the catalysts. The effects of different Pt loadings and Co doping amounts were investigated. The results showed that the PtNPs could be well dispersed onto the TiO2 support with narrow size distribution between 4 and 6 nm. 1.0% was observed as the optimal Pt loading amount in our experiments showing a cinnamaldehyde conversion of 73.3% with 68.8% selectivity to cinnamyl alcohol. A proper Co doping amount was also essential to the catalytic performance of the prepared Pt/catalysts as wel...

A series of Au/TiO2 catalysts for CO oxidation with same Au loading but different Au nanoparticles (NPs) sizes were prepared by varying the calcination temperatures and biomass concentration via a biosynthetic approach. The resulting catalysts were characterized by DRUV–vis, TEM, and TG techniques. The experimental results showed that the activity of the gold catalysts for CO oxidation was very sensitive to the particle size. Among the tested catalysts, the one with mean size of 3.8 nm was the most active. As determined by TEM, the contact boundary between the Au NPs and the TiO2 support was related to the size of the Au NPs. For the most active catalyst, hemispherical Au NPs (3.8 ± 0.6 nm) had the best contact boundary with the TiO2 support, yielding the longest perimeter interface, suggesting that the contact boundary was the most critical factor for the CO oxidation. The in-situ FTIR study of CO adsorption on the catalysts showed that CO was not adsorbed on the Au surface. This might be due to the modi...

Au/TS-1 catalysts prepared by an eco-friendly and economical bioreduction method were used for the liquid phase epoxidation of styrene to styrene oxide (SO) using aqueous hydrogen peroxide (H2O2) as oxidant. The catalysts were characterized by a variety of techniques including FT-IR, DRUV–Vis, UV–Vis, N2 physisorption, XRD, XPS, TG–DTG and TEM. The influence of various parameters (Au loading, calcination, solvents, oxidants, reaction temperature, reaction time and catalyst amount) on the catalytic performance was systematically investigated. The results showed that both the conversion of styrene and selectivity to SO were improved and enhanced when catalyzed by biosynthesized gold nanoparticles (GNPs) supported on TS-1. However, decomposing the Cacumen Platycladi (CP) biomass properly through calcinations can enhance the catalytic performance though it acted as reductant and protective agents during the catalysts preparation. Besides, the optimum catalytic activity and stability of bioreduction Au/TS-1 catalysts were obtained under operational conditions of Au loading of 1.0 wt.%, CP extract (10 g L−1) as reductant, calcined at 723 K for 2 h, reaction time of 10 h, reaction temperature of 333 K, catalyst amount of 500 mg, aqueous H2O2 (30 wt.%) as oxidant and N,N-dimethylformamide as solvent. Under the optimal condition, styrene conversion of 92.7% and SO selectivity of 90.4% was achieved, which were comparable or even superior to those reported in the literatures. The catalyst was reused five times, without significant decrease in both the styrene conversion and SO selectivity.

The activity of supported Pd catalyst as a result of metal oxide support (zinc, titanium, copper and manganese) is explored in the abatement of C6H6 in the gas-phase. The high-activity and cost-effective catalysts were synthesized utilizing impregnation assisted biosynthesis (IB) method. NH3-TPD, XRD, H2-TPR, TEM, XPS, O2 and Benzene-TPD, SEM and in situ DRIFT were done to probe their physicochemical characteristics and predict the plausible oxidation mechanism. Pd particle size and dispersion, and support active acid sites were the determining factors for activity. These factors markedly affected the catalyst ability to generate surface active O2 species from the metal oxides lattice station and controlled the benzene absorption/desorption rates. The as-synthesized Pd/Mn3O4-O with small crystallite size, good Pd dispersion, improved acid sites, and low activation energy (Ea = 45.3 kJ/mol) showed commendable O2 transportability and activity as low as 140 °C, GHSV of 120,000 mLg−1 h−1. Its T100 at 240 °C was similar to Pd supported on TiO2 but was 20, 40 and 60 °C better than Pd/Mn3O4-C, Pd/ZnO and Pd/CuO. In situ DRIFT studies showed that the main intermediate species benzoquinone are oxidized to CO2 and H2O through the alkoxide and acid sites. Moreover, it was stable and highly resistant to H2O vapor.

Based on rapid adsorption and incomplete reduction in Pd (II) ions by yeast, Pichia pastoris (P. pastoris) GS115, the effects of pretreatment on adsorption and reduction of Pd (II) ions and the catalytic properties of Pd NP/P. pastoris catalysts were studied. Interestingly, the results showed that the adsorption ability of the cells for Pd (II) ions was greatly enhanced after they were pretreated with aqueous HCl, aqueous NaOH and methylation of amino group. For the reduction in the adsorbed Pd (II) ions, more slow reduction rates by pretreated P. pastoris cells were displayed compared with the cells without pretreatment. Using the reduction of 4-nitrophenol as a model reaction, the Pd NP/P. pastoris catalysts based on the cells after pretreatment with aqueous HCl, aqueous NaOH and methylation of amino group exhibited higher stability than the unpretreated cells. The enhanced stability of the Pd catalysts can be attributed to smaller Pd NPs, better dispersion of the Pd NPs, and stronger binding forces of the pretreated P. pastoris for preparing the Pd NPs. This work exemplifies enhancing the stability of Pd catalysts through pretreatments.