Enhanced photothermal dehydration of methanol over W_(18)O_(49)/Au/SAPO-34 catalysts with broadened light absorption

Methanol-to-olefins(MTO)process is one of the most critical pathways to produce low carbon olefins.Typically,the reaction is driven by thermal catalysis,which inevitably needs to consume large amounts of fossil fuel.Developing a new technique to substitute for the fuel burning is urgent for MTO process to improve the industry prospects and sustainability.Herein,we report a novel W_(18)O_(49)/Au/SAPO-34(W/Au/S),a multifunctional photothermal catalyst for the MTO reaction.A high methanol conversion was achieved under xenonum(Xe)lamp irradiation,yielding methyl ether(ME)and ethylene as the main products.The optimized W/Au/S catalysts showed ethylene yield as high as 250μmol in 60 min,which was 2.5 times higher than that of Au/SAPO-34.The physiochemical characterization revealed that the SAPO-34 molecular sieves were surrounded by Au and W_(18)O_(49)nanoparticles,which exhibited a strong localized surface plasmon resonance excitation around 540 nm and light absorption beyond 500 nm.The multifunctional catalysts showed a strong photothermal effect,arising from the broadened light absorption of Au and W_(18)O_(49)nanoparticles,leading to a temperature as high as 250℃on the surface of the catalysts.Mechanism study showed that the superior ethylene selectivity of W/Au/S catalysts was attributed to the moderating acidic sites of W_(18)O_(49)for methanol dehydration to ethylene.This research may provide new insight for designing heterostructures to improve photo-to-chemical conversion performance and is expected to accelerate progress toward the excellent multifunctional photothermal catalysts with broad light absorption for methanol activation and C-C bond formation.

Separation of arsenic and antimony from dust with high content of arsenic by a selective sulfidation roasting process using sulfur

The separation of arsenic and antimony from dust with high content of arsenic was conducted via a selective sulfidation roasting process.The factors such as roasting temperature,roasting time,sulfur content and nitrogen flow rate were investigated using XRD,EPMA and SEM-EDS.In a certain range,the sulfur addition has an active effect on the arsenic volatilization because the solid solution phase（（Sb,As）2O3）in the dust can be destroyed after the Sb component in it being vulcanized to Sb2S3 and this generated As2O3 continues to volatile.In addition,an amorphization reaction between As2O（3 ）and Sb2O（3 ）is hindered through the sulfidation of Sb2O3,which is also beneficial to increasing arsenic volatilization rate.The results show that volatilization rates of arsenic and antimony reach 95.36%and only 9.07%,respectively,under the optimum condition of roasting temperature of 350℃,roasting time of 90 min,sulfur content of 22%and N2 flow rate of 70 m L/min.In addition,the antimony in the residues can be reclaimed through a reverberatory process.

Morphology and activity relationships of macroporous CuO-ZnO-ZrO_2 catalysts for methanol synthesis from CO_2 hydrogenation

A series of macroporous CuO-ZnO-ZrO2 （CZZ） catalysts with different Zn/Zr ratios were successfully prepared by template method and characterized by X-ray diffraction （XRD）, N2 adsorption, reactive N2O adsorption, scanning electron microscopy （SEM）, H2 temperature-pro- grammed reduction （H2-TPR）, and transmission electron microscopy （TEM）. The activity of the catalysts was tested for methanol synthesis from CO2 hydrogenation. It is found that the increase in the Zn/Zr ratio could lead to the sintering of the catalysts, destroying the macroporous structure integrity. The macroporous CZZ catalysts own lower Zn/Zr ratio, exhibiting a better morphology and activity. For comparison, the conventional nonporous CZZ catalysts were also investigated. The results show that the CZZ catalysts with macroporous structure own smaller particles, higher CO2 conversion, and CH3OH yield. It reveals that the macroporous structure could inhibit the growth of the par- ticle size, and the special porous structure is favorable for diffusion and penetration of CO2, which could improve the catalytic activities.

Selective oxidation of methane and carbon deposition over Fe_2O_3/Ce_(1-x)Zr_xO_2 oxides

A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2（x = 0.1–0.4） oxides was prepared and their physicochemical features were investigated by X-ray diffraction（XRD）, transmission electron microscope（TEM）, and H2-temperature-programmed reduction（H2-TPR） techniques. The gas–solid reactions between these oxides and methane for syngas generation as well as the catalytic performance for selective oxidation of carbon deposition in O2-enriched atmosphere were investigated in detail. The results show that the samples with the presence of Fe2O3show much higher activity for methane oxidation compared with the Ce0.7Zr0.3O2solid solution,while the CeO2-contained samples represent higher CO selectively in methane oxidation than the Fe2O3/Al2O3sample. This suggests that the iron species should be the active sites for methane activation, and the cerium oxides provide the oxygen source for the selective oxidation of the activated methane to syngas during the reaction between methane and Fe2O3/Ce0.7Zr0.3O2. For the oxidation process of the carbon deposition, the CeO2-containing samples show much higher CO selectivity than the Fe2O3/Al2O3sample, which indicates that the cerium species should play a very important role in catalyzing the carbon selective oxidation to CO. The presence of the Ce–Zr–O solid solution could induce the growth direction of the carbonfilament, resulting in a loose contact between the carbon filament and the catalyst. This results in abundant exposed active sites for catalyzing carbon oxidation, strongly improving the oxidation rate of the carbon deposition over this sample. In addition, the Fe2O3/Ce0.7Zr0.3O2also represents much higher selectivity（ca. 97 %） for the conversion of carbon to CO than the Fe2O3/CeO2sample, which can be attributed to the higher concentration of reduced cerium sites on this sample. The increase of the Zr content in the Fe2O3/Ce1-xZrxO2samples could improve the reactivity of the materials for methane oxidation, but it also reduces the selectivity for CO formation.