Edible oils are one of the renewable sources that enable the possibility of producing biodiesel sustainably. The transesterification of canola oil with methanol using cesium-modified phosphotungstic acid (Cs2.5H0.5PW12O40) as a heterogeneous catalyst was studied. Reaction conditions, specifically reaction time, catalyst loading, and the ratio of methanol to canola oil, were systematically explored. The canola oil conversion reached 55% at room temperature after 24 h. The reusability tests showed that the conversion of canola oil to biodiesel was maintained.

A series of nickel- and iron-modified titanium dioxide (Ni-Fe/TiO2) are studied for the dry reforming of methane (DRM) at 550 °C. Temperature-programmed surface reactions using CH4 and CO2 as probe molecules, as well as activity results, confirmed that both CO2 and CH4 conversion decreased with the addition of Fe. The XPS results obtained from reduced and used catalysts suggested changes in the surface nickel and iron species. Characterizations, particularly thermogravimetric analysis (TGA) and Raman spectroscopy over used catalysts, revealed that the addition of Fe can greatly inhibit the coke formation. In situ DRIFTS further identified that the addition of Fe favored the formation of carbonate species, which can facilitate the removal of coke deposited on the surface.

A high-power ultraviolet light-emitting diode (UV-LED) array is promising for dye decolorization. However, its practical application is limited by the heat dissipation efficiency of UV-LED. Hence, a coupling system combined with heat management of UV-LED arrays and great photocatalytic activity was proposed. In this work, multilayer wall-type active heat dissipation was first designed and compared from UV-LED beads irradiance, heat dissipation, and AR26 decolorization performance. Simulation and light intensity tests show that uniform arrangement, quincunX arrangement, and one-typed/rectangular arrangement are optimal for one, two, and three-layers system, respectively. Among these arrangements, the two-layer system shows the best performance compared with others, which owns the lower junction temperature (44 degrees C) and highest rate constant kapp (0.027 min-1). The effect of sewage temperature on photocatalytic performance under a two-layer system was further probed, and sewage with 20 to 40 degrees C is most beneficial to dye removal due to the trade-off relationship between light intensity and photocatalytic reaction rate. The life test verified the long-term stability of the coupling system, and only 15% luminous attenuation was reached after 85-day tests under high power conditions, which is much lower than that with conventional air cooling (35% reduction after 40-day tests). Our study paves the way to effectively use high-power UV-LED in dye wastewater treatments.

Copper‑titanium dioxide (Cu-TiO2) catalysts are pretreated with hydrogen‑helium and oxygen‑helium before evaluation of the carbon monoxide oxidation. Pre-reduced Cu-TiO2 catalysts showed higher initial and overall activity than pre-oxidized Cu-TiO2 catalysts. H2-TPR results revealed that copper species are dispersed differently after pre-reduction and pre-oxidation treatments. XPS results confirmed that Cu+ and Cu2+ species exist for both treatments. Meanwhile, IR results suggested Cu+ species promote the absorption of CO, leading to increased reaction rates.

Copper supported on nitrogen modified titanium dioxide (Cu-N-TiO2) was studied for the oxidation reaction of carbon monoxide. The interstitial nitrogen is identified as the dominant nitrogen species, which facilitates copper dispersion on the surface. Therefore, the reaction rate is improved comparatively to that of Cu-TiO2. Cu(+)is beneficial to the carbon monoxide oxidation reaction. Importantly, the value of ([Cu+]/[O](sur)) is positively proportional to the reaction rates.

We present how to calculate the weight fraction of anatase in the physical anatase-rutile mixture based on the analysis of Raman spectra. Raman-based correlation is also applicable to characterize quantitively the weight fraction of anatase from chemically synthesized anatase-rutile titanium dioxide mixtures.

Copper-Titanium Dioxide (Cu-TiO2) catalysts have been widely used to catalyze small molecules through photo and thermal-catalytic approaches. We report nitrogen doped titanium oxide (N-TiO2) improved catalytic performance of Cu-TiO2 in the carbon monoxide oxidation reaction. Anatase TiO2 and rutile TiO2 are chosen to investigate the effect of the TiO2 phase for nitrogen modification. XPS and DFT results showed both interstitial nitrogen and substitutional nitrogen exists over nitrogen doped anatase TiO2, N-TiO2 (A). Only substitutional nitrogen exists over nitrogen doped rutile TiO2, N-TiO2 (R). Compared with copper over titanium dioxide (CuTiO2) catalysts, copper over nitrogen doped titanium dioxide catalysts (Cu-N-TiO2) showed enhanced redox properties based on analysis of temperature programmed reactions including H-2-TPR and CO-TPSR. IR studies using CO as a probe molecule as well as copper XPS results showed that surface copper concentration distributed differently with the addition of nitrogen. Therefore, correlation between the ratio of [Cu+]/[O-surf.] and the reaction rate is suggested, because this ratio represents contributions from both active and spectator species in the carbon monoxide oxidation reaction.

Gold supported on cerium oxide has been studied over the past two decades as a potential alternative to platinum metals for low-temperature CO oxidation and the water–gas shift (WGS) reaction because of its higher intrinsic activity, and as an alternative to copper catalysts for methanol steam reforming because of its better resistance to deactivation in fuel cell system operation. The literature on the subject is briefly reviewed in this chapter. The evolution of our understanding of how to make this type of robust catalyst is described with specific cases drawn from our own work and that of others. Properly prepared ceria at the nanoscale with and without dopants can stabilize a large amount of atomically bound Au–Ox species which are the active sites for the WGS and the methanol steam reforming reactions operating through different mechanisms on these sites. Design principles for this and other metals atomically dispersed on ceria can be drawn from this review.

Less is More: Atomically dispersed gold species catalyze the decomposition of formic acid through the dehydrogenation pathway at near-ambient temperatures. Gold on ceria is demonstrated to be an effective and stable catalyst. By using this catalyst, mechanistic insights are obtained that can lead to the use of trace amounts of gold to achieve robust and cost-effective catalysts.

We have investigated the structure sensitivity of the water-gas shift (WGS) reaction on Cu–CeO2 catalysts prepared at the nanoscale by different techniques. On the surface of ceria, different CuOx structures exist. We show here that only the strongly bound Cu–[Ox]–Ce species, probably associated with the surface oxygen vacancies of ceria, are active for catalyzing the low-temperature WGS reaction. Weakly bound CuOx clusters and CuO nanoparticles are spectator species in the reaction. Isolated Cu2+ ions doping the ceria surface are not active themselves, but they are important in that they create oxygen vacancies and can be used as a reservoir of copper to replenish surface Cu removed by leaching or sintering. Accordingly, synthesis techniques such as coprecipitation that allow for extensive solubility of Cu in ceria should be preferred over impregnation, deposition–precipitation, ion exchange or another two-step method whereby the copper precursor is added to already made ceria nanocrystals. For the synthesis of different structures, we have used two methods: a homogeneous coprecipitation (CP), involving hexamethylenetetramine as the precipitating agent and the pH buffer; and a deposition–precipitation (DP) technique. In the latter case, the ceria supports were first synthesized at the nanoscale with different shapes (rods, cubes) to investigate any potential shape effect on the reaction. Cu–CeO2 catalysts with different copper contents up to ca. 20 at.% were prepared. An indirect shape effect of CeO2, manifested by the propensity to form oxygen vacancies and strongly bind copper in the active form, was established; i.e. the water-gas shift reaction is not structure-sensitive. The apparent activation energy of the reaction on all samples was similar, 50 ± 10 kJ/mol, in a product-free (2% CO–10% H2O) gas mixture.

Formaldehyde is emitted from building and furnishing materials and consumer products, and is known to cause irritation of eyes and respiratory tract, headache, pneumonia, and even cancer. It is a dominant indoor air pollutant, especially in developing countries, and significant efforts have gone into indoor HCHO purification to meet environmental regulations and human health needs. Removal of HCHO by adsorbents has been investigated extensively using potassium permanganate, activated carbon, aluminum oxide, and some ceramic materials. Sorbent effectiveness is typically limited by low adsorption capacities. Catalytic oxidation is the most effective technology for volatile organic compound (VOC) abatement because VOCs can be oxidized to CO2 over certain catalysts at much lower temperatures than in thermal oxidation. Supported noble metal catalysts (Pt, Pd, Rh, Au, Ag) or metal oxide catalysts (Ni, Cu, Cr, Mn) have been used for the catalytic oxidation of VOCs. Complete oxidation of HCHO over catalysts occurs above 150 8C on clean and oxidized films of Ni, Pd, and Al and over silver–cerium composite oxide, above 100 8C over Ag/MnOx-CeO2 [18] and Au/CeO2, [19] and above 85 8C over Pd-Mn/Al2O3 [17] and Au/FeOx. As catalytic oxidation at even lower temperatures is desirable for indoor air purification, the development of a catalyst for total HCHOoxidation at room temperature is of great interest. In our recent study, 1% Pt/TiO2 catalyst was shown to be effective for HCHO oxidation at room temperature, achieving 100% conversion of d= 100 ppm HCHO to CO2 and H2O at a gas hourly space velocity (GHSV) of 50000 h . However, we also observed that this type catalyst is not as active as needed for practical applications, and deactivates with time-on-stream. Herein, we report a novel alkali-metal-promoted Pt/TiO2 catalyst for the ambient destruction of HCHO. We show that the addition of alkali-metal ions (such as Li, Na, and K) to Pt/TiO2 catalyst stabilized an atomically dispersed PtO(OH)x–alkali-metal species on the catalyst surface and also opened a new low-temperature reaction pathway, significantly promoting the activity for the HCHO oxidation by activating H2O and catalyzing the facile reaction between surface OH and formate species to total oxidation products. Figure 1a shows the HCHO conversion to CO2 as a function of temperature over the x% Na-1% Pt/TiO2 (x= 0, 1, and 2) samples at a GHSVof 120000 h 1 andHCHO inlet of d= 600 ppm. All gas streams were humidified to a RH of around 50%. Before each activity test, the samples were reduced in H2 at 300 8C for 30 min. The sodium-free catalyst had low activity for the HCHO oxidation reaction, with HCHO conversion being only about 19% at 15 8C. With 1% Na addition, the HCHO conversion reached 96% at 15 8C and 100% at 40 8C. With 2% Na addition, 100% HCHO conversion to CO2 and H2O was measured at 15 8C. The effect of Na addition on the surface reducibility was examined by H2 temperature-programmed reduction (TPR; Figure 1b). The amounts of H2 consumption were about the same over all the samples, but the addition of Na shifted the reduction peak to lower temperatures, that is, from 2 8C for 1% Pt/TiO2 to 6 8C for 1% Na-1% Pt/TiO2 and 11 8C for 2% Na-1% Pt/ TiO2. Thus, the sample reducibility correlates with the sample activity. The most active 2% Na-promoted sample had excellent stability as checked by long isothermal tests. For example, at a GHSV of 300000 h 1 and with the same other reaction conditions, approximately 80% HCHO conversion was maintained over a 72 h-long test (Figure 1a, inset). Li and K were equally effective promoters to Na and imparted the same high activity and stability to the Pt species (Supporting Information, Figure S1). Water vapor and oxygen effects on the activity of Na-Pt/TiO2 are important (Supporting Information, Figures S2,S3). Deionized-water washing of the samples was performed to check the alkali-metal and Pt interaction.While most of the Na was removed from the Nacontaining catalysts, a residual amount remained (Supporting Information, Table S1). Activity test results (Supporting Information, Figure S1) showed that the washed catalyst had identical activity for HCHO [*] C. Zhang, F. Liu, Y. Liu, Prof. H. He Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Shuangqing Road 18, Beijing, 100085 (China) E-mail: honghe@rcees.ac.cn

We report the activity of shape-controlled metal oxide (CeO2, ZnO and Fe3O4) supported gold catalysts for the steam reforming of methanol (SRM) and the water gas shift (WGS) reactions. Metal oxide nanoshapes, prepared by controlled hydrolysis and thermolysis methods, expose different crystal surfaces, and consequently disperse and stabilize gold differently. We observe that similar to gold supported on CeO2 shapes exposing the {110} and {111} surfaces, gold supported on the oxygen-rich ZnO {0001} and Fe3O4 {111} surfaces shows higher activity for the SRM and WGS reactions. While the reaction rates vary among the Au-CeO2, Au-ZnO and Au-Fe3O4 shapes, the apparent activation energies are similar, indicating a common active site. TPR data further indicate that the reaction lightoff coincides with the activation of Au-O-M species on the surface of all three oxide supports evaluated here. Different shapes contain a different number of binding sites for the gold, imparting different overall activity.

In the present study we have found that gold supported on CeO2 and ZnO with well-defined crystal structures or shapes is an excellent catalyst for the low-temperature (175-225 degrees C) steam reforming of methanol (SRM). We have compared the active nature of gold dispersed on {0001} surfaces of ZnO nanorods and polyhedra to our previous work, which demonstrates that TEM-invisible gold dispersed on the {110} surfaces of CeO2 catalyzes the SRM reaction in a cooperative mechanism with CeO2. Similar to Au-CeO2, we have found that Au-O bonds are essential species for SRM over Au-ZnO and the same apparent activation energy (110-120 kJ . mol(-1)) of the reaction was calculated for both catalysts. On the basis of temperature-programmed surface reaction/mass spectrometry analysis, we determined that the SRM reaction on both Au-ZnO and Au-CeO2 involves methanol dehydrogenation, methyl formate hydrolysis, and formic acid decomposition steps to produce CO2 and H-2. Better than 95% catalyst selectivity to CO2 was found over the temperature range from 175 to 250 degrees C for both catalysts. In the presence of methanol, the water-gas shift reaction is suppressed and is not part of the mechanism at temperatures below 250 degrees C. The SRM stability of the Au-ZnO and Au-CeO2 systems is good for practical application of this type catalyst.

We report that a small amount (<1 at%) of gold on ceria single crystals prepared as nanorods (10 ± 2.8 by 50–200 nm) of {110} and {100} crystal surfaces shows excellent catalytic activity in both the steam reforming of methanol (SRM) and the water gas shift (WGS) reactions at low temperatures (<250 °C). The ceria nanorods bind and stabilize gold as atoms and clusters (<1 nm, TEM invisible). On the other hand, gold nanoparticles (∼3 nm) are found on the {100} surfaces of ceria nanocubes. Very low rates of SRM and WGS were measured on the Au–ceria {100} cubes, while the rates on Au–ceria {110} rods were at least an order of magnitude higher. However, the apparent activation energies did not depend on the shape of ceria. Strong bonded Aun–O–Ce species are the active sites and these are present only in negligible concentrations on the {100} surfaces. Thus, both reactions are structure-insensitive on Au–ceria. SRM proceeds through the methyl formate route. The Au–ceria {110} catalyst shows both high SRM activity and high selectivity to CO2 at temperatures below 250 °C.

In this work we have found that a small amount (∼1at.%) of gold deposited on ceria nanorods exhibits excellent catalytic activity for the low-temperature steam reforming of methanol (SRM). Gold clusters (<1nm, TEM invisible) dispersed on the {110} faces of ceria nanorods catalyze the reaction in a cooperative mechanism with ceria. Gold nanoparticles (∼3nm) on the {100} surfaces of ceria nanocubes are inactive. The apparent activation energy of the SRM reaction on Au-ceria is ∼110kJmol−1. On the basis of TPSR/MS analysis, we determined that the SRM reaction on Au-ceria involves methanol dehydrogenation, methyl formate hydrolysis and formic acid decomposition steps to produce CO2 and H2. Better than 97% catalyst selectivity to CO2 was found over the temperature range from 175 to 250°C. In the presence of methanol, the water–gas shift (WGS) reaction is suppressed and is not part of the mechanism at temperatures below 250°C. The SRM stability of the Au-ceria system is good for practical application of this type catalyst.

We compare the activity and relevant gold species of nanostructured gold–cerium oxide and gold–iron oxide catalysts for the CO oxidation by dioxygen and water. Well dispersed gold nanoparticles in reduced form provide the active sites for the CO oxidation reaction on both oxide supports. On the other hand, oxidized gold species, strongly bound on the support catalyze the water-gas shift reaction. Gold species weakly bound to ceria (doped with lanthana) or iron oxide can be removed by sodium cyanide at pH ≥12. Both parent and leached catalysts were investigated. The activity of the leached gold–iron oxide catalyst in CO oxidation is approximately two orders of magnitude lower than that of the parent material. However, after exposure to H 2 up to 400 °C gold diffuses out and is in reduced form on the surface, a process accompanied by a dramatic enhancement of the CO oxidation activity. Similar results were found with the gold–ceria catalysts. On the other hand, pre-reduction of the calcined leached catalyst samples did not promote their water-gas shift activity. UV–Vis, XANES and XPS were used to probe the oxidation state of the catalysts after various treatments.