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Owing to the intrinsic nature of the uniformed topologies and ultrasmall Zr6 nodes of Zr-MOFs, herein, we employed Zr-MOFs (UiO-66 and UiO-67), as opposed to the support of traditional ZrO2, to prepare the Pd catalysts for toluene degradation. Compared with the catalysts of Pd/UiO-66 and Pd/ZrO2, Pd/UiO-67 catalyst boosted an excellence catalytic performance for toluene degradation, giving the lowest T90% value of 235 °C with long-term stability. With the assisting of the cavity confinement of Zr-MOFs, Pd nanoparticles are prone to be encapsulated in the 3D frameworks of Zr-MOFs, and the bigger micropores of UiO-67 are more conducive to the formation of larger Pd nanoparticles. The in situ FT-IR results further declared that although the active sites are partly sacrificed due to the larger Pd nanoparticles formed in UiO-67, the stable adsorbed toluene on Pd/UiO-67 boosted the quick degradation of toluene in the reaction interval even without undergoing intermediate processes of benzoate and benzaldehyde. UiO-66, UiO-67 and ZrO2 were employed to prepare the Pd catalysts for toluene degradation, Pd/UiO-67 catalyst boosted an excellence catalytic performance with long-term stability. [ABSTRACT FROM AUTHOR]

A series of highly ordered microporous Ce-based metal-organic frameworks (MOFs) were synthesized as the precursors for catalyst construction. The corresponding Ru catalysts were prepared by Ru impregnation on the derived CeO 2 by pyrolysis of Ce-MOF, and investigated for the CH 4 synthesis via CO 2 hydrogenation. Among the catalysts, Ru catalyst supported on the CeO 2 -B derived from Ce-BDC exhibited a highly competitive efficiency for CO 2 methanation, giving a CH 4 selectivity of 100% with a CO 2 conversion of 62% at 275 °C and 0.1 MPa, and the CH 4 productivity reached 0.49 mol/(mol Ru ·h). Characterization results revealed that more oxygen vacancies and corresponding surface oxygen species formed on the surface of CeO 2 -B derived from Ce-BDC caused to the stronger interaction between Ru and CeO 2 -B, which promoted the CO 2 adsorption and hydrogenation capacity of the catalyst, resulting in its better catalytic property. In situ diffuse reflectance infrared Fourier transform (DRIFT) studies further revealed that the route of HCOO* into CH 4 is a more competitive way of CO 2 hydrogenation to CH 4. [Display omitted] • CeO 2 supported Ru catalysts were constructed based on the heat-treatment strategy of Ce-MOFs. • Ru catalyst supported on CeO 2 -B exhibited a highly competitive efficacy for CO 2 methanation. • More oxygen vacancies and surface oxygen species were formed on CeO 2 -B surface. • The stronger interaction between Ru and CeO 2 -B promoted the CO 2 adsorption and hydrogenation. • The route of HCOO* into CH 4 is a more competitive way of CO 2 hydrogenation to CH 4. [ABSTRACT FROM AUTHOR]

Abstract Three CuO-ZnO-ZrO 2 -M x O y (CZZM, M = Cr, Mo and W) mixed oxides were prepared by a co-precipitation method and tested as catalysts for methanol synthesis from CO 2 hydrogenation. The catalysts were characterized by XRD, N 2 adsorption/desorption, XPS, reactive N 2 O adsorption, H 2 -TPR, and CO 2 -TPD techniques. The results indicated that the methanol selectivity and yield of the CuO-ZnO-ZrO 2 catalyst noticeably increased by the additions of MoO 3 and WO 3 , but slightly decreased by Cr 2 O 3 doping. Combining with the characterization results, the difference in methanol yield over the three catalysts can be attributed to the differences in their BET specific surface areas (S BET) and adsorption capacities for CO 2 , while the methanol selectivity is closely correlated to the ratio of surface contents of Zn to Cu, as well as the fraction of strong basic sites in the total basic sites of the investigated catalysts. Graphical abstract Image 1 Highlights • CuZnZrM (M = Cr/Mo/W) mixed oxides were used for methanol synthesis from CO 2 and H 2. • The CuO-ZnO-ZrO 2 -WO 3 catalyst shows the highest activity and methanol selectivity. • Methanol yield is related to the S BET and CO 2 adsorption capacity of the catalyst. • Methanol selectivity is closely related to the surface composition and basicity. [ABSTRACT FROM AUTHOR]

A series of WO 3 modified CuO-ZnO-ZrO 2 mixed oxides with different WO 3 contents (0–20 at.%) were prepared by co-precipitation method and used as catalyst for methanol synthesis from CO 2 hydrogenation. The effects of WO 3 content on the physicochemical and catalytic properties of the CuO-ZnO-ZrO 2 -WO 3 catalysts were investigated by X-ray diffraction, X-ray photoelectron spectra, temperature-programed reduction of hydrogen, temperature-programed desorption of CO 2 , N 2 adsorption and desorption, reactive N 2 O adsorption, and activity testing. The results indicated that both CO 2 conversion and methanol selectivity of the CuO-ZnO-ZrO 2 catalyst was enhanced by the addition of small amounts (2 and 5 at.%) of WO 3 . However, the activity was significantly decreased by the addition of excessive WO 3 (20 at.%). The activity was closely related to the specific surface area of metallic Cu ( S Cu ), amount of weak basic sites, and reducibility of the catalyst. [ABSTRACT FROM AUTHOR]

A series of CuO-ZnO-Al 2 O 3 -Li 2 O catalysts with various Al 2 O 3 /Li 2 O mass ratios were prepared by co-precipitation method and characterized by several techniques such as XRD, N 2 adsorption, SEM/EDX, reactive N 2 O adsorption, XPS/XAES, H 2 -TPR, H 2 -TPD, and CO-TPD. The results revealed that the specific surface area ( S BET ), dispersity of Cu species, metallic Cu surface area ( S Cu ) and adsorption capacity for reactants (H 2 and CO) were increased by the addition of suitable amount of Li 2 O to the CuO-ZnO-Al 2 O 3 catalyst, thus enhancing the catalytic activity of the hybrid catalyst composed of CuO-ZnO-Al 2 O 3 and HZSM-5 for the direct synthesis of dimethyl ether from biomass-derived gas. Furthermore, the addition of Li 2 O significantly improved the stability of CuO-ZnO-Al 2 O 3 catalyst due to the effective inhibition of the crystallization of Cu and ZnO. [ABSTRACT FROM AUTHOR]

A series of fluorinated nano-HZSM-5 zeolite catalysts were prepared by impregnating with NH 4 F solutions of various concentrations and applied to the selective conversion of bio-ethanol to propene at 500 °C, atmospheric pressure, and WHSV of 10 h − 1 . The characterizations by XRD, TEM, N 2 adsorption, ICP-OES, EDX, 27 Al MAS NMR, NH 3 -TPD, Py-IR, and TG techniques revealed that fluoride treatment had a major effect on the channel structure together with the acidic properties. The newly formed mesopores increased the coke tolerance capacity and reduced the probability of coke formation by facilitating mass transfer, and the weakened acidity suppressed the formation of coke. Hence, fluorine modification with suitable content (20 wt%) significantly enhanced the selectivity of propene as well as the catalytic stability. In addition to coke, elimination of aluminum in the zeolite framework was also an important reason for the deactivation of fluorinated nano-HZSM-5 zeolite catalyst. [ABSTRACT FROM AUTHOR]

• CuO-Ce x Zr 1-x O y are prepared via a facile surfactant-assisted grinding method. • CuO-Ce 0.7 Zr 0.3 O y exhibits the highest activity and moisture resistance. • Activity is related to contents of highly dispersed CuO and oxygen vacancies. • CO oxidation catalyzed by CuO-Ce x Zr 1-x O y mainly follows the L-H mechanism. • CuO-Ce 0.7 Zr 0.3 O y exhibits excellent stability and adaptability to space velocity. A series of CuO-Ce x Zr 1-x O y mixed oxides with different Ce contents were prepared via a facile surfactant-assisted grinding method, and their catalytic activity for CO oxidation under dry or moist atmosphere were investigated. The results indicate that the catalyst with a Ce content (x) of 0.7 in Ce x Zr 1-x O y (CuCe 0.7 Zr 0.3) exhibited the best activity under both dry and moist atmospheres, with the temperatures corresponding to CO conversion of 90 % (T 90) at a space velocity of 18000 mL/(g cat · h) being 90 and 120 °C, respectively. Combing with the physicochemical properties of the catalysts obtained by multiple characterization techniques such as ICP-OES, XRD, Raman, N 2 sorption, XPS, in situ DRIFTs, H 2 -TPR, O 2 -TPD and CO-TPD, the high activity of the CuCe 0.7 Zr 0.3 catalyst can be mainly attributed to the existence of large amounts of highly dispersed CuO x species and oxygen defect sites. [ABSTRACT FROM AUTHOR]

• Activation temperature exerts important effect on CuO-CeO 2 catalyst. • The catalyst activated at 550 °C exhibits superior activity and moisture resistance. • Activity is closely related to contents of Cu+ species and oxygen vacancies. • Dispersed CuO with strong interaction with CeO 2 exhibits good moisture resistance. • Bulk CuO with no or weak interaction with CeO 2 exhibits poor moisture resistance. Development of a highly efficient Cu-based catalyst for low-temperature CO oxidation under moisture condition remains a grand challenge. In this paper, effect of activation temperature (350–800 °C) on catalytic performance of CuO-CeO 2 , prepared by facile one-step solvothermal synthesis, in CO oxidation was investigated, and the catalysts' physicochemical properties were studied by TG-DSC, ICP-AES, N 2 sorption, XRD, TEM, Raman spectroscopy, XPS, in-situ DRIFTS, H 2 -TPR, CO-TPD, and O 2 -TPD. It was found that activation at 550 °C is beneficial for the interaction between CuO and CeO 2 , leading to the formation of more Cu+ species and oxygen vacancies advantageous for improving the catalytic activity. Activation at 800 °C, nevertheless, would weaken the interaction between CuO and CeO 2 due to the sintering of CuO and CeO 2 , thus decreasing the catalytic activity and moisture resistance. Interestingly, no deactivation was observed over the optimal catalyst (activated at 550 °C) after 50 h testing at a low temperature of 87 °C (at which 90% CO conversion was obtained), even when 4.2% water vapor was added into the feed gas. [ABSTRACT FROM AUTHOR]

It has been reported widely that Rh-Mn-Li/SiO 2 catalysts can exhibit high selectivity to C 2 + oxygenates during CO hydrogenation, with promoters of Mn and Li playing an important role in this behavior. In this study, a series catalysts of Rh-Mn-Li/SiO 2 with different amounts of Mn and Li were prepared, and the new insights into the effects of Mn and Li on the mechanistic pathway for C 2 + oxygenates synthesis from syngas were investigated. The XPS analysis showed that Rh existed mainly as metallic Rh after reduction, however partially positively charged Rh δ+ atoms appeared on the surface of Mn-containing catalyst due to the interaction of Rh-Mn. The results of H 2 -TPR indicated that both of Li and Mn can inhibit the reduction of Rh 2 O 3 . With the increase in the ratio of Mn/Rh, the most effective interaction, associated to the presence of two reduction centers of Rh 2 O 3 , was obtained when the ratio of Mn/Rh = 1. In situ -FTIR was used to probe the effects of Mn and Li on CO absorption and hydrogenation. With regards to the CO adsorption, the doping of Mn can enhance the CO adsorption ability of Rh and weaken the CO-Rh bond strength very effectively when the amount of Mn reached 1.5 wt.%. Improved capacity of CO adsorption is conducive to increase of CO conversion, while the weakening of CO-Rh bond is beneficial to the CO insertion reaction, thus contributing to the generation of C 2 + oxygenates. Moreover, the low amount of Li (≤0.075 wt.%) can also enhance the CO adsorption, resulting in the improvement of reactivity. On the other hand, Mn and Li promoted dissociation of H 2 , which is favorable to an increase in the rate of hydrogenation. But an opposite effect appeared at high content of Mn (>1.5 wt.%). As the optimized results, when Rh, Mn, Li content was 1.5 wt.%, 1.5 wt.% and 0.075 wt.%, the catalyst for CO hydrogenation of C 2 + oxygenates achieved the best performance of C 2 + oxygenates synthesis. [ABSTRACT FROM AUTHOR]

The effects of different impregnation sequences of copper and iron on the performance of Cu-Fe/SiO 2 catalysts for higher alcohols synthesis from syngas were investigated by N 2 adsorption, XRD, H 2 -TPR, CO-IR, XPS, and CO hydrogenation reaction. The results indicate that the catalyst prepared by impregnation of support first with Fe and then with Cu exhibits the highest selectivity (36.1%) and space time yield (153.3 g·kg cat − 1 ·h − 1 ) of alcohols. The CO conversion and alcohol selectivity of the catalysts was closely related to the content of surface Cu, and the ratio of surface contents of Cu to Fe, respectively. [ABSTRACT FROM AUTHOR]

CuO-ZnO-ZrO 2 /HZSM-5 bifunctional catalysts were prepared by a facile route of solid-state reaction and tested for one-step synthesis of dimethyl ether (DME) from CO 2 hydrogenation. The effects of calcination temperature (300–600 °C) on the physicochemical and catalytic properties of the bifunctional catalysts were investigated by XRD, N 2 adsorption, XPS, N 2 O chemisorption, SEM, H 2 -TPR, NH 3 -TPD, and CO 2 -TPD techniques. The results show that both the CO 2 conversion and DME selectivity of the bifunctional catalysts decrease with the increase in calcination temperature, which can mainly be attributed to the decrease of metallic copper surface area ( S Cu ), adsorption capacity of CO 2 , specific surface area, and reducibility of CuO. [ABSTRACT FROM AUTHOR]

The effects of alkaline, phosphorous and dual alkaline-phosphorous modifications on the selective conversion of bio-ethanol to propylene over HZSM-5 zeolite catalysts were investigated. The results demonstrate that the doubly modified HZSM-5 zeolite catalyst offers higher propylene selectivity and remarkably improved catalytic stability than the parent and singly modified counterparts, which can be contributed to the formation of new mesoporous and decreased amount of strong acid sites induced by the alkaline treatment and phosphorous modification, respectively. The deactivation of the phosphorous and dual alkaline-phosphorous modified HZSM-5 zeolite catalysts was caused by carbon deposition but not by dealumination, which can be attributed to the enhanced hydrothermal stability of the framework aluminum by the modification of ZSM-5 zeolite with phosphorus. [ABSTRACT FROM AUTHOR]

The influence of TiO 2 , ZrO 2 , and TiO 2 –ZrO 2 mixed oxide on the catalytic performance of CuO–ZnO catalyst in the methanol synthesis from CO 2 hydrogenation was studied. The catalysts were prepared by oxalate co-precipitation method and characterized by TGA, N 2 adsorption, XRD, reactive N 2 O adsorption, XPS, H 2 -TPR, H 2 -TPD, and CO 2 -TPD techniques. Characterization results reveal that all the additives improve the CuO dispersion in the catalyst body and increase the Cu surface area and adsorption capacities of CO 2 and H 2 . The results of catalytic test reveal that the additives increase both the CO 2 conversion and methanol selectivity, and TiO 2 –ZrO 2 mixed oxide is more effective than single components of TiO 2 or ZrO 2 . Moreover, the activity of methanol synthesis is correlated directly with CO 2 adsorption capacity over the catalysts. [ABSTRACT FROM AUTHOR]

A series of CuO–ZnO–ZrO 2 catalysts are synthesized by a surfactant-assisted co-precipitation method and tested for the synthesis of methanol from CO 2 hydrogenation. The effects of calcination temperature on the physicochemical properties of as-prepared catalysts are investigated extensively by TG-DSC, N 2 adsorption/desorption, XRD, N 2 O chemisorption, SEM/TEM, EDX, XPS, TPR, H 2 -TPD and CO 2 -TPD techniques. The results show that the size of copper particles increases with the increase in calcination temperature, leading to the decrease in turnover frequency (TOF) for methanol formation. Moreover, compared with the counterparts prepared by the conventional co-precipitation method, the CuO–ZnO–ZrO 2 catalysts prepared by this novel method show significantly high methanol selectivity. The superior property of the prepared CuO–ZnO–ZrO 2 catalyst can be attributed to the formation of more amounts of Cu–ZnO x and/or Cu–ZrO x species resulted from the homogeneous element distribution, intimate interface contact of Cu species with ZnO and/or ZrO 2 , and to porous structure with larger pore size. [ABSTRACT FROM AUTHOR]

Abstract: The effects of different impregnation sequences for the precursors of iron and other metals (Rh, Mn, Li) on the catalytic properties of Fe-promoted Rh–Mn–Li/SiO2 catalysts for the synthesis of C2 + oxygenates were investigated. The means of N2 adsorption–desorption, XRD, H2-TPR, in-situ FT-IR, and TPSR were used to characterize the physics-chemical properties of the catalysts. The results showed that when the iron was impregnated and calcined first followed by Rh–Mn–Li impregnation, it would availably inhibit the reduction of Rh and Mn oxides; however, if the iron was impregnated second onto a calcined Rh–Mn–Li/SiO2 catalyst, it was more conducive to the dissociation and spillover of hydrogen, which could partly promote the reduction of Rh and Mn oxides. Based on the IR description and catalytic performance of the catalysts for CO hydrogenation, it is conceivable that the facile transformation of dicarbonyl Rh+(CO)2 into H–Rh–CO and Rh–CO–Fe is responsible for the higher selectivity of C2 + oxygenates over the catalyst, in which Fe was impregnated and calcined first followed by Rh–Mn–Li impregnation. [Copyright &y& Elsevier]

Abstract: Rh-Mn-Li catalysts supported on SiO2, ZrO2 and SiO2-ZrO2 mixed oxides with various molar ratios of Si/Zr were prepared and tested for the synthesis of C2-oxygenates from syngas. Compared with pure SiO2 and ZrO2 supported catalysts, catalysts supported on SiO2-ZrO2 mixed oxides showed higher activity and C2-oxygenates selectivity, in which Rh-Mn-Li/SiO2-ZrO2 (molar ratio of Si/Zr=1:3) exhibited the best yield of C2-oxygenates. The effect of the support on the performance of the Rh-based catalysts was investigated comprehensively by XRD, N2 adsorption-desorption, H2 and CO uptakes, FT-IR, XPS, H2-TPR, TPSR and CO-TPD techniques. The results indicated that the chemical state of Rh, CO adsorption species, dispersion of Rh and the ability of CO hydrogenation varied over catalysts supported on SiO2, ZrO2 and SiO2-ZrO2 mixed oxides, which led to the diverse catalytic activity toward C2-oxygenates synthesis. [Copyright &y& Elsevier]

Abstract: A series of Rh–Mn–Li catalysts supported on SiO2 prepared by different methods were tested for the synthesis of C2+ oxygenates via CO hydrogenation. The catalysts were comprehensively characterized by N2 adsorption–desorption, XRD, in situ FT-IR, CO-TPD, TPSR, and H2-TPR. It was found that the Rh–Mn–Li catalyst supported on the SiO2 synthesized by the Stöber method exhibited the highest CO conversion and selectivity toward C2+ oxygenates compared with other catalysts. The investigation based on the catalytic performance and characterizations of the catalysts suggests that the hydroxyl–metal interaction over the catalysts supported on different SiO2 results in different desorption behavior of the adsorbed CO. The specific interaction between the active components and weakly H-bonded hydroxyls on the SiO2 prepared by the Stöber method promoted the transformation from Rh+(CO)2 to Rh–CO and facilitated the desorption/reactivity of adsorbed CO as a function of temperature in the presence of hydrogen, which were proposed to be the crucial factors for obtaining higher CO conversion and C2+ oxygenates selectivity. [Copyright &y& Elsevier]

Abstract: The effect of calcination temperature of the monodispersed SiO2 synthesized by the Stöber method on the catalytic performance of Rhph name="sbnd" />Li/SiO2 for CO hydrogenation to C2 oxygenates was investigated. The means of N2 adsorption-desorption, in-situ FT-IR, H2-TPD, H2-TPR, CO-TPD, and TPSR were used to characterize the physico-chemical properties of SiO2 supports and the corresponding Rhph name="sbnd" />Li/SiO2 catalysts. The results showed that the amount of surface Si-OH groups on SiO2 affects the Rh dispersion and Rhction. The increase in the number of Si on the SiO2 was favorable for the Rh dispersion and CO adsorption, further enhanced the activity of the catalyst. In addition, an appropriate amount of surface Si on the SiO2 calcined at 350°C can gain a moderate Rhction. This interaction is conducive to achieve the right hydrogenation ability, which is favorable for the CO insertion into metal-CHx band, and ultimately increases the selectivity of C2 oxygenates. [Copyright &y& Elsevier]

Abstract: Different amounts of Fe promoted Rh–Mn–Li/SiO2 catalysts were prepared and investigated for the synthesis of C2 oxygenates from syngas. The results showed that the low amount of Fe (≤0.1wt.%) improved the reactivity and yield of C2 + oxygenates, but an opposite effect appeared at high content of Fe (>0.1wt.%). Diffuse reflectance infrared Fourier transform spectroscopy was used to probe the effects of Fe on CO adsorption and hydrogenation, and two opposing effects were evidenced. Moreover, it is proposed that the facile transformation of dicarbonyl Rh+(CO)2 into H–Rh–CO is responsible for high selectivity of C2 + oxygenates. [Copyright &y& Elsevier]

Abstract: A novel SiO2 synthesized by the Stöber method was studied as the support for Rh–Mn–Li catalyst, and better performance for C2 oxygenate synthesis via CO hydrogenation was achieved compared with the counterpart using commercial SiO2 as the support. The investigation based on the catalytic performance and characterizations of the catalysts suggests that the hydroxyl–metal interaction over the catalyst supported on SiO2 prepared by the Stöber method results in a change in the CO adsorption on Rh particles, which promotes the CO dissociation and CO insertion, leading to higher CO conversion and C2 oxygenate selectivity. [Copyright &y& Elsevier]

Abstract: SiO2, TiO2 and SiO2–TiO2 mixed oxide were synthesized by sol–gel method and used as supports for Rh-based catalysts. The effect of support on the performance of Rh-based catalysts for C2-oxygenates synthesis from syngas was investigated by XRD, N2 adsorption-desorption, FT-IR, H2-TPD, H2-TPR and TPSR techniques. The results indicated that SiO2–TiO2 supported catalyst had higher dispersion of Rh and thus more Rh+ sites, better capability for CO adsorption and dissociation, and moderate ability for hydrogenation. As a result, SiO2–TiO2 supported Rh-based catalyst exhibited higher activity and C2 oxygenates selectivity compared with counterparts supported on TiO2 and SiO2. [Copyright &y& Elsevier]

Abstract: Three ZSM-5 zeolites with different crystal sizes were prepared and characterized by SEM, XRD, adsorption/desorption of N2, NH3-TPD, Py-IR and TG-DTA techniques. The results show that the acidic properties of HZSM-5 catalysts are very similar, but their textual properties are strongly influenced by crystal size. Their catalytic performances for the ethanol conversion to propylene were investigated in a continuous flow fixed-bed micro-reactor. In comparison with the large-sized HZSM-5, the small-sized HZSM-5 shows higher propylene selectivity and better stability, which reveals that decreasing the crystal size of zeolite is of benefit to ethanol conversion to propylene. [Copyright &y& Elsevier]

Abstract: A series of Cu/ZrO2 catalysts with various La loadings for methanol synthesis from CO2 hydrogenation were prepared by a urea–nitrate combustion method. The catalysts were characterized with N2 adsorption, XRD, reactive N2O adsorption, XPS, TPR, H2-TPD and CO2-TPD techniques, and tested for methanol synthesis from CO2 hydrogenation. With increasing La loading, the Cu surface area increases first and then decreases, whereas the amount of basic site over catalysts increases continuously. The results of catalytic test reveal that a linear relationship exists between the conversion of CO2 and the Cu surface area. Moreover, it is found for the first time that the selectivity to methanol is related to the distribution of basic site on the catalyst surface. The presence of La favors the production of methanol, and the optimum catalytic activity is obtained when the amount of La doping is 5% of the total amount of Cu2+ and Zr4+. [Copyright &y& Elsevier]

Abstract: Cu/ZnO/ZrO2 catalysts were prepared by a route of solid-state reaction and tested for the synthesis of methanol from CO2 hydrogenation. The effects of calcination temperature on the physicochemical properties of as-prepared catalysts were investigated by N2 adsorption, XRD, TEM, N2O titration and H2-TPR techniques. The results show that the dispersion of copper species decreases with the increase in calcination temperature. Meanwhile, the phase transformation of zirconia from tetragonal to monoclinic was observed. The highest activity was achieved over the catalyst calcined at 400°C. This method is a promising alternative for the preparation of highly efficient Cu/ZnO/ZrO2 catalysts. [Copyright &y& Elsevier]

Abstract: A series of HZSM-5 zeolites modified with various contents of antimony oxide (0–30wt.%) were prepared by solid state ion reaction at 500°C, and the acidities of the resulted materials were characterized by temperature-programmed desorption of NH3. The direct synthesis of dimethyl ether (DME) from syngas was carried out over the admixed catalysts of an industrial CuO–ZnO–Al2O3 methanol synthesis catalyst and the parent and antimony oxide modified HZSM-5 zeolites under pressurized fixed-bed continuous flow conditions. The results indicated that modification of HZSM-5 with suitable amount of antimony oxide significantly decreased the selectivity for undesired byproducts like hydrocarbons and carbon dioxide from 9.3% and 32.4% to less than 1% and 28%, respectively, so the selectivity for DME was enhanced greatly from 55% to 69% under temperature of 260°C, pressure of 4MPa and gas hourly space velocity of 1500mLh−1 . The decrease in the formation of hydrocarbons and carbon dioxide can be attributed to the significant decline in the amount of strong acid sites of the HZSM-5 zeolite induced by antimony oxide modification. Additionally, the influences of the operating parameters on the performance of the most efficient catalyst were also investigated. The results showed that high reaction temperature and high gas hourly space velocity resulted in both lower carbon monoxide conversion and lower dimethyl ether selectivity, so they should be no higher than 280°C and 3000mLh−1 , respectively. [Copyright &y& Elsevier]

Abstract: A series of CuO–ZnO–ZrO2 (CZZ) catalysts were synthesized by a glycine–nitrate combustion method and characterized by XRD, BET, N2O chemisorption, SEM and TPR techniques. The results show that the physicochemical properties of the catalysts are strongly influenced by the fuel content used in the combustion process. The dispersion of CuO exhibits an inverse-volcano variation trend with an increase in the glycine amount from 50% to 150% of the stoichiometry. The relationship between physiochemical properties and the fuel content is discussed in detail in terms of combustion temperature. The catalytic performance for the synthesis of methanol from CO2 hydrogenation was examined. The CZZ catalyst exhibits an optimum catalytic activity when 50% of stoichiometric amount of glycine was used. The turnover frequency has been calculated for various CZZ catalysts, and it reveals that the catalytic activities depend not only on the surface area of metallic copper but also on the phase state of ZrO2. [Copyright &y& Elsevier]

Abstract: Various CuO–ZnO–ZrO2 (CZZ) catalysts have been synthesized by urea–nitrate combustion method and their performances for methanol synthesis from CO2 hydrogenation have been investigated. The effects of urea/nitrate ratio on physicochemical and catalytic properties were studied by XRD, BET, H2-TPR and reactive N2O adsorption techniques. The results show that when 50% of stoichiometric amount of urea was used, the CZZ catalyst exhibited an optimum catalytic behavior. The combustion method was found to be a simple, fast and valuable route for the preparation of CZZ catalyst for methanol synthesis from CO2 hydrogenation. [Copyright &y& Elsevier]

Abstract: A series of CuO–TiO2–ZrO2 catalysts with various Ti and Zr molar ratios were prepared by co-precipitation method and characterized by N2 physisorption, X-ray diffraction (XRD) and temperature-programmed reduction of hydrogen (H2-TPR). The prepared CuO–TiO2–ZrO2 samples were mixed physically with HZSM-5 zeolite to synthesize dimethyl ether (DME) via CO2 hydrogenation. The results indicated that CuO–TiO2–ZrO2/HZSM-5 had higher CO2 conversion and DME yield compared to CuO–TiO2/HZSM-5 and CuO–ZrO2/HZSM-5 catalyst, in which the catalyst with equimole of Ti and Zr got the best performance. The activities of CuO–TiO2–ZrO2/HZSM-5 catalysts were well correlated to the reduction properties of CuO–TiO2–ZrO2 samples. [Copyright &y& Elsevier]

Abstract: Pure HMCM-22 zeolites with different SiO2/Al2O3 ratios were synthesized and characterized by XRD, N2 adsoption, 27Al MAS NMR, pyridine-FT-IR and NH3–TPD. The HMCM-22 samples were mechanically mixed with a methanol synthesis catalyst and then applied in the one-step synthesis of dimethyl ether from syngas (STD process). The results indicated that with the increase of SiO2/Al2O3 ratio of zeolites HMCM-22, selectivity to dimethyl ether increased and the selectivities of by-products decreased due to the weakening of their acidities. It is concluded that the high-silica HMCM-22 zeolite is an effective dehydration component of the hybrid catalyst for the STD process. [Copyright &y& Elsevier]

Abstract: The effect of B2O3 addition on the crystallization of amorphous TiO2–ZrO2 mixed oxide was investigated by X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG/DTA). TiO2–ZrO2 mixed oxide was prepared by co-precipitation method with aqueous ammonia as the precipitation reagent. Boric acid was used as a source of boria, and boria contents varied from 2 to 20wt%. The results indicate that the addition of small amount of boria (<8wt%) hinders the crystallization of amorphous TiO2–ZrO2 into a crystalline ZrTiO4 compound, while a larger amount of boria (⩾8wt%) promotes the crystallization process. FT-IR spectroscopy and 11B MAS NMR results show that tetrahedral borate species predominate at low boria loading, and trigonal borate species increase with increasing boria loading. Thus it is concluded that highly dispersed tetrahedral BO4 units delay, while a build-up of trigonal BO3 promote, the crystallization of amorphous TiO2–ZrO2 to form ZrTiO4 crystals. [Copyright &y& Elsevier]

Abstract: Fluorination by NH4F solution was used to modify the acidity of alumina. The textural and acidic properties of the parent alumina and modified alumina were studied by N2 adsorption and NH3-TPD. It was disclosed that both surface area and acidity of alumina are enhanced by the treatment with 0.1mol/l NH4F solution, while modification with more concentrated NH4F solutions leads to the decrease in surface area of alumina and thereby weakens its acidity. The catalytic properties of these alumina samples were subsequently investigated in the production of DME. Sample AF1, treated by 0.1mol/l NH4F solution, performed best in both methanol dehydration and the STD process (syngas to dimethyl ether) because of its strongest acidity. [Copyright &y& Elsevier]

Abstract: A series of γ-Al2O3 samples modified with various contents of sulfate (0–15wt.%) and calcined at different temperatures (350–750°C) were prepared by an impregnation method and physically admixed with CuO–ZnO–Al2O3 methanol synthesis catalyst to form hybrid catalysts. The direct synthesis of dimethyl ether (DME) from syngas was carried out over the prepared hybrid catalysts under pressurized fixed-bed continuous flow conditions. The results revealed that the catalytic activity of SO4 2−/γ-Al2O3 for methanol dehydration increased significantly when the content of sulfate increased to 10wt.%, resulting in the increase in both DME selectivity and CO conversion. However, when the content of sulfate of SO4 2−/γ-Al2O3 was further increased to 15wt.%, the activity for methanol dehydration was increased, and the selectivity for DME decreased slightly as reflected in the increased formation of byproducts like hydrocarbons and CO2. On the other hand, when the calcination temperature of SO4 2−/γ-Al2O3 increased from 350°C to 550°C, both the CO conversion and the DME selectivity increased gradually, accompanied with the decreased formation of CO2. Nevertheless, a further increase in calcination temperature to 750°C remarkably decreased the catalytic activity of SO4 2−/γ-Al2O3 for methanol dehydration, resulting in the significant decline in both DME selectivity and CO conversion. The hybrid catalyst containing the SO4 2−/γ-Al2O3 with 10wt.% sulfate and calcined at 550°C exhibited the highest selectivity and yield for the synthesis of DME. [Copyright &y& Elsevier]

Abstract: A series of MCM-22 zeolites were prepared by hydrothermal synthesis and subsequent dealumination by oxalic/citric acid leaching and steaming. The structural and acidic properties of the prepared samples were characterized by methods of XRD, ICP-AES, 27Al MAS NMR, pyridine-adsorbed IR and NH3-TPD. The results indicated that the sample treated by oxalic acid (MCM-22O) has the lowest aluminum content while the samples treated by steam have little change of the aluminum content. Unusually, sample MCM-22O possessed the strongest acidity among the dealuminated samples in spite of its lowest content of aluminum. It may be due to its least content of extraframework aluminum, which may lead to the weakening of acidity. Additionally, the prepared zeolites were mixed with a methanol synthesis catalyst and then applied in the process of syngas to dimethyl ether. Citric acid treated sample performed best with the least generation of byproducts, which have been well related to its structural and acidic properties. [Copyright &y& Elsevier]

Abstract: The deactivation and regeneration of B2O3/TiO2-ZrO2 catalyst for the vapor phase Beckmann rearrangement of cyclohexanone oxime to ɛ-caprolactam were studied. The fresh, deactivated and regenerated catalysts were characterized by using adsorption of nitrogen, X-ray diffraction (XRD), thermogravimetry (TG) and NH3-temperature-programmed desorption (NH3-TPD) techniques. The crystal structure and pore size distribution of the catalyst were retained after reaction, but the number of acid sites decreased significantly. There was a relationship between the amount of coke deposited on the catalyst and the decline in catalytic activity. These results suggest that the coke deposition on the surface of catalyst is mainly responsible for the catalyst deactivation. The catalytic activity can be recovered completely after calcining the deactivated catalyst in air flow at 600°C for 8h. [Copyright &y& Elsevier]

Abstract: A series of HZSM-5 zeolites modified with various contents of magnesium oxide (0–10 wt%) were prepared with an incipient impregnation technique and characterized by X-ray diffraction, N2 adsorption, temperature-programmed desorption of NH3 and CO2, 27Al MAS NMR, and FT-IR. The modified HZSM-5 zeolites were mixed physically with methanol synthesis components (CuO–ZnO–Al2O3) to perform the direct synthesis of dimethyl ether (DME) from syngas under pressurized fixed-bed continuous-flow conditions. The results indicated that modification of HZSM-5 with a suitable amount of MgO significantly decreased the selectivities for undesired by-products like hydrocarbons and CO2 from 9.3 and 37.1% to less than 0.4 and 31%, respectively, through the removal of unselective strong Brønsted acid sites and hence enhanced the selectivity for DME from 49% to more than 64%, whereas the conversion of carbon monoxide was scarcely affected. However, when the MgO contents were equal to or higher than 5 wt%, both the conversion of CO and selectivity for DME decreased markedly because of the decreased activity for methanol dehydration. A mechanism for methanol dehydration to DME involving both acidic and basic sites on the HZSM-5 zeolites modified with MgO has been proposed based on the results obtained. [Copyright &y& Elsevier]

Abstract: The effect of calcination temperature (500–700°C) on the performance of B2O3/TiO2–ZrO2 catalyst for vapor-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam was investigated. Catalysts were characterized by adsorption of nitrogen, X-ray diffraction and ammonia temperature-programmed desorption. The results indicated that the percent of acid sites of medium strength within the total acid sites and the pore size both increased with calcination temperature. Such increases led to increases of the oxime conversion and caprolactam selectivity. However, a large amount of crystalline B2O3 appeared after calcination at 700°C and caused the decrease of the total amount of acid sites, which resulted in remarkable decrease in the activity of the catalyst. Another part of this work focused on the effect of solvent on the catalytic performance of B2O3/TiO2–ZrO2. Solvents with various polarities were investigated for the reaction. It was found that acetonitrile, which has the highest polarity for solvents examined here, was the most effective for the formation of caprolactam. The solvent with high polarity increases the desorption rate of produced caprolactam from catalyst surface, resulting in a high selectivity to caprolactam and low catalyst deactivation rate. FT-IR measurements confirmed the efficient desorption of caprolactam induced by the attack of the acetonitrile molecule. [Copyright &y& Elsevier]

The effects of calcination temperature and preparation method of TiO2–ZrO2 mixed oxide on catalytic performance of B2O3/TiO2–ZrO2 catalysts were investigated. TiO2–ZrO2 mixed oxides with the same molar ratio of 1:1 were prepared by co-precipitation method, homogeneous precipitation method, sol–gel method and physical mixing method; each oxide was calcined at a temperature between 110 and 700 °C. Catalytic synthesis of #x03B5;-caprolactam from cyclohexanone oxime was evaluated in a fixed-bed flow microreactor at 300 °C and atmosphere pressure. Characterization of catalysts was carried out using adsorption of nitrogen, X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR) and temperature-programmed desorption of ammonia (NH3-TPD) techniques. The experimental results reveal that the calcination temperature in the range of 110–500 °C had only a slight effect on the catalytic performance, but after calcination at 700 °C, the ZrTiO4 crystallite was formed and accounted for the decrease of acidity and catalytic performance. The co-precipitation method provided the catalyst with the highest reactivity while the physical mixing method resulted in the worst catalyst. Catalytic performance of the B2O3/TiO2–ZrO2 catalyst was closely related to its acid strength distributions and pore size. [Copyright &y& Elsevier]

Pure TiO2, ZrO2 and TiO2-ZrO2 mixed oxides with various compositions were prepared by the co-precipitation method. Catalysts containing 12 wt.% boria were prepared using these oxides and their catalytic performance for vapor-phase Beckmann rearrangement of cyclohexanone oxime to &epsiv;-caprolactam was determined. With increasing zirconia content in the mixed oxide, the specific surface area and the temperature of the phase transformation increased; maximum values were obtained for a mixed oxide having a Ti and Zr molar ratio of 1/1. XRD results indicated that TiO2-ZrO2 became amorphous after calcination at 500 °C if neither the content of TiO2 nor that of ZrO2 was less than 25%. The yield of lactam increased with increasing zirconia content in mixed oxide and reached a maximum value for the B2O3/TiO2-ZrO2 (1/1) catalyst. With further increase in zirconia content, the lactam yield decreased; the lowest value was observed for the pure ZrO2-supported catalyst. The acidic property and the pore characteristics of the catalyst were key factors that affected its performance. The influences of the operating parameters on the performance of B2O3/TiO2-ZrO2 (1/1) catalyst were also investigated. [Copyright &y& Elsevier]

H3PW12O40-modified MnOx catalysts (denoted as Mn-HPW) were used for NOx elimination with co-fed NH3. The optimal Mn-HPW0.02 catalyst exhibited over 90% NOx conversion at 90–270 °C. The incorporation of HPW increased the amount of Lewis acid sites of the catalyst for adsorbing NH3, and accelerated the reaction between the adsorbed NH3 species and gas-phase NOx, thus, increasing the low-temperature catalytic activity. The oxidation ability of the Mn catalyst was decreased due to the addition of HPW, thus, mitigating the overoxidation of the adsorbed NH3 species and improving the de-NOx activity and N2 selectivity in the high-temperature region. DRIFT results revealed that the NH3 species on Lewis and Brønsted acid sites, bridged nitrate, and bidentate nitrate were important species/intermediates for the reaction. NH3-SCR over the Mn and Mn-HPW0.02 catalysts obeyed the Eley–Rideal and Langmuir–Hinshelwood mechanisms, simultaneously, at 120 °C. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe and Na were found to be the most efficient promotors of Rh/CeO 2 catalyst for CO 2 hydrogenation to ethanol. • The optimized catalyst of 2Rh0.5Fe0.5Na/CeO 2 obtains a high ethanol selectivity of 29.8 % with a CO 2 conversion of 13.0 %. • The modification of Fe and Na promote the formation of Rh+ species, enhancing capacities of CO 2 adsorption and dissociation. • The Rh active sites synergized with Fe and Na can stabilize the adsorbed species of m-CO 3 2− and CO 3 H−. • The generation of HCOO*, CH 3 O* and CH 3 CH 2 O* intermediates promotes the ethanol formation. Rh catalyst is investigated as a strong candidate for CO 2 hydrogenation to ethanol, but it is still challenging because of the poor conversion efficiency. Here, by screening the promotors systematically and varying the amounts of components simultaneously, the optimized catalyst of 2Rh0.5Fe0.5Na/CeO 2 was found to highly efficient catalytic CO 2 hydrogenation to ethanol, giving a high ethanol selectivity of 29.8 % with a superior CO 2 conversion of 13.0 % at 250 °C, 3 MPa, and the ethanol productivity reached 116.7 mmol·g Rh −1·h−1. Characterization results revealed that the modification of Fe and Na, can promote the dispersion of Rh and the formation of Rh+ species, enhancing the capacities of CO 2 adsorption and dissociation. In situ DRIFT experiment illuminated that the Rh active sites synergized with Fe and Na can stabilize the adsorbed species of m-CO 3 2− and CO 3 H−, and promote the generation of HCOO* and CO* intermediates, which can be provided to couple with the CH x species, resulting in the high efficacy for ethanol synthesis from CO 2 hydrogenation. [ABSTRACT FROM AUTHOR]

A series of ZnO/ZrO2 catalysts were synthesized by the precipitation method. The effect of different precipitation modes on the physicochemical properties of the ZnO/ZrO2 catalysts for CO2 hydrogenation to methanol was investigated. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption, transmission electron microscopy (TEM), temperature programmed desorption of CO2 (CO2-TPD), temperature programmed reduction of H2 (H2-TPR), and X-ray photoelectron spectroscopy (XPS). The results showed that the catalyst of ZnO/ZrO2 prepared by the concurrent precipitation method had more CO2 adsorption sites, resulting in its higher CO2 conversion. While the stepwise precipitation mode increased the surface oxygen content of ZnO/ZrO2, which enhanced the methanol selectivity. Overall, the ZnO/ZrO2 prepared by the concurrent precipitation mode exhibited a highly competitive efficacy for CO2 hydrogenation, giving a methanol selectivity of 81.4% with a CO2 conversion of 5.1% at 280 ℃ and 3 MPa, and the methanol yield reached 4.2%. The effect of different precipitation modes on the physicochemical properties of the ZnO/ZrO2 catalysts for CO2 hydrogenation to methanol was investigated, and the ZnO/ZrO2 prepared by the concurrent precipitation mode exhibited a highly competitive efficacy for CO2 hydrogenation. [ABSTRACT FROM AUTHOR]

A series of Mn3Co16Ox composite oxides catalysts were fabricated via a solid-phase synthesis using different manganese precursors (namely manganese acetate (A), nitrate (N), and sulfate (S)). It has been demonstrated that the obtained catalysts presented variable catalytic activities for CO oxidation and remarkable diversity of physicochemical properties closely depending on the manganese precursors. In detail, the catalytic activity and catalytic durability for CO oxidation under humid conditions generally followed a descending order of Mn3Co16Ox-A > Mn3Co16Ox-N > Mn3Co16Ox-S. The optimum catalytic performance of Mn3Co16Ox-A was predominantly attributed to its larger specific surface area, significantly higher low-temperature reducibility and lattice oxygen mobility, and more plentiful oxygen vacancies. [ABSTRACT FROM AUTHOR]

A series of Cu-ZnO-ZrO2 (CCZ) catalysts were prepared by the solvothermal method with different solvothermal times (1 h, 3 h, 6 h, and 12 h). The physicochemical properties of these catalysts and the catalytic performance for CO2 hydrogenation to methanol were studied. The highest methanol yield was achieved when the solvothermal time was 6 h (CCZ-6). Furthermore, we found that the copper surface area (SCu) increases and then decreases with an increase in the solvothermal time and that there is a strong correlation between the methanol yield and the SCu. This research highlights the crucial influence of the solvothermal time on the structure and catalytic behavior of Cu-ZnO-ZrO2 catalysts, providing a valuable reference for the development of efficient catalysts. [ABSTRACT FROM AUTHOR]

Maintaining high conversion under the premise of high oxygenates selectivity in syngas conversion is important but a formidable challenge in Rh catalysis. Monometallic Rh catalysts provide poor oxygenate conversion efficiency, and efforts have been focused on constructing adjacent polymetallic sites; however, the one‐pass yields of C2+ oxygenates over the reported Rh‐based catalysts were mostly <20 %. In this study, we constructed a monometallic Rh catalyst encapsulated in UiO‐67 (Rh/UiO‐67) with enhanced proximity to dual‐site Rh1,2‐Rhn ensembles. Unexpectedly, this catalyst exhibited high efficacy for oxygenate synthesis from syngas, giving a high oxygenate selectivity of 72.0 % with a remarkable CO conversion of 50.4 %, and the one‐pass yield of C2+ oxygenates exceeded 25 %. The state‐of‐the‐art characterizations further revealed the spontaneous formation of an ensemble of Rh single atoms/dimers (Rh1,2) in the proximity of ultrasmall Rh clusters (Rhn) confined within the nanocavity of UiO‐67, providing adjacent Rh+‐Rh0 dual sites dynamically during the reaction that promote the relay of the undissociated CHO species to the CHx species. Thus, our results open a new route for designing highly efficient Rh catalysts for the conversion of syngas to oxygenates by precisely tuning the ensemble and proximity of the dual active sites in a confined space. [ABSTRACT FROM AUTHOR]

Maintaining high conversion under the premise of high oxygenates selectivity in syngas conversion is important but a formidable challenge in Rh catalysis. Monometallic Rh catalysts provide poor oxygenate conversion efficiency, and efforts have been focused on constructing adjacent polymetallic sites; however, the one‐pass yields of C2+ oxygenates over the reported Rh‐based catalysts were mostly <20 %. In this study, we constructed a monometallic Rh catalyst encapsulated in UiO‐67 (Rh/UiO‐67) with enhanced proximity to dual‐site Rh1,2‐Rhn ensembles. Unexpectedly, this catalyst exhibited high efficacy for oxygenate synthesis from syngas, giving a high oxygenate selectivity of 72.0 % with a remarkable CO conversion of 50.4 %, and the one‐pass yield of C2+ oxygenates exceeded 25 %. The state‐of‐the‐art characterizations further revealed the spontaneous formation of an ensemble of Rh single atoms/dimers (Rh1,2) in the proximity of ultrasmall Rh clusters (Rhn) confined within the nanocavity of UiO‐67, providing adjacent Rh+‐Rh0 dual sites dynamically during the reaction that promote the relay of the undissociated CHO species to the CHx species. Thus, our results open a new route for designing highly efficient Rh catalysts for the conversion of syngas to oxygenates by precisely tuning the ensemble and proximity of the dual active sites in a confined space. [ABSTRACT FROM AUTHOR]

[Display omitted] • Poisoning effects of different K-salts on Mn-HPW are investigated and compared. • De-NO x activities on KN/Mn-HPW and KS/Mn-HPW are inhibited only at <210 °C. • The deactivation can be observed on KC/Mn-HPW at 90–300 °C. • K species decreases the quantity and reactivity of active intermediates. • Cl− aggravates deactivation due to the inhibitory effect on active intermediates. The inevitable presence of various K species in real flue gas may deactivate catalysts used for NH 3 -SCR of NO x. Herein, the poisoning effects of several K salts (KNO 3 , K 2 SO 4 , KCl) on catalytic performance of phosphotungstic acid-modified MnO x (Mn-HPW) were studied. The extent of deactivation follows the sequence of KC/Mn-HPW > KN/Mn-HPW ≈ KS/Mn-HPW. Especially, KCl decreases significantly SCR activity of Mn-HPW at 90–300 °C, whereas K 2 O or K 2 SO 4 exerts the negative effect only below 210 °C. The characterization results show that the presence of K species leads to worse reducibility as well as fewer amounts of Mn4+, Mn3+, and chemisorbed oxygen of the Mn-HPW catalyst. The decrease in the quantity and reactivity of active NH 3 -Lewis and active bridged nitrate is another critical reason for inhibiting NO x elimination at low temperatures on poisoned catalysts. Especially, SO 4 2− in KS/Mn-HPW acts as the spectators in the reaction between active NH 3 -Lewis with NO x or between active bridged nitrate with NH 3 , so de-NO x activity of KS/Mn-HPW is comparable to that of KN/Mn-HPW. For KCl/Mn-HPW, the reducibility and relative concentrations of active sites as well as chemisorbed oxygen are the worst. Furthermore, Cl− further restrains the adsorption of active NH 3 -Lewis, undermining the NO x removal by E-R route; Cl− also hinders the formation of active bridged nitrate, cutting off the reaction through the L-H route. Therefore, KCl exerts the most serious deactivation of Mn-HPW. [ABSTRACT FROM AUTHOR]

A series of CuO-ZnO–ZrO2 (CZZ) catalysts were synthesized via a solvothermal method. The effects of four saturated monohydric alcohols (methanol, ethanol, n-propanol, and n-butanol) as solvents on the physicochemical properties and catalytic performance for the direct synthesis of methanol from CO2 hydrogenation of the prepared catalysts were investigated. N2 physical adsorption, X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray (EDX) spectroscopy mapping, reactive N2O adsorption, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction by H2 (H2-TPR), and temperature programmed desorption (H2-TPD, CO2-TPD) techniques were used to characterize the catalysts. The results indicate that the catalyst prepared with methanol as solvent (CZZ-M) has the smallest Cu crystallites and the largest metallic Cu surface area, thus exhibiting the highest methanol yield of 7.4% at 240 °C, 3.0 MPa, H2:CO2 of 3 (v/v), and GHSV of 2400 mL/(gcat·h). [ABSTRACT FROM AUTHOR]

[Display omitted] • Zn exerts an unusual promotion effect on SCR performance over Mn-HPW at > 180 °C. • Introducing HPW protects effectively acid sites on Mn from Zn poisoning. • Moderate decrease in redox performance of Zn/Mn-HPW alleviates NH 3 over-oxidation. • Both E-R and L-H mechanisms are applicative to Zn/Mn and Zn/Mn-HPW at 120 °C. • Only E-R route is involved in the reaction for Zn/Mn and Zn/Mn-HPW at 210 °C. MnO x -based catalysts are highly efficient for selective catalytic reduction (SCR) of NO x with NH 3 at low temperatures, but Zn contained in industrial flue gas may poison conventional SCR catalysts, and MnO x -based catalysts usually have low Zn tolerance. Herein, phosphotungstic acid-modified MnO x (denoted as Mn-HPW) was prepared to study the Zn tolerance. It was found that the deposition of Zn on Mn-HPW decreases the SCR activity at < 180 °C, but both NO x conversion and N 2 selectivity are enhanced at 180–300 °C, and > 95% NO x conversion can be achieved on Zn/Mn-HPW. Relevant catalysts were characterized and the results reveal that the decline in the activity at < 180 °C is related to the decrease in the quantities of Mn4+, Mn3+, and chemisorbed oxygen as well as the decreased capacities for adsorbing and activating NH 3 and NO x. The unusual improvement of SCR performance on Zn/Mn-HPW at 180–300 °C is mainly attributed to two aspects: (i) HPW can protect effectively the surface acid sites from Zn poisoning; (ii) The decrease in oxidation properties alleviates the over-oxidation of NH 3 , promoting the participation of more NH 3 in SCR. [ABSTRACT FROM AUTHOR]

A series of M 3 Co 16 O x (M = Cr, Ti, Zr, Fe, Mn) oxide catalysts wrapped by polymer nanofilm were developed by the solid-phase method, and the catalytic activities were investigated for low temperature oxidation of carbon monoxide under moisture-rich condition. The catalysts were characterized by HR-TEM, FT-IR, XRD, N 2 adsorption-desorption, H 2 -TPR, CO-TPD and XPS techniques. The results reveal that the M 3 Co 16 O x composite oxides are high-dispersive mesoporous materials coated by polymer nanofilm with an average thickness in the scope of 4–7 nm. The percentages of surface oxygen vacancy and lattice oxygen on the catalysts decrease in the following order: Mn 3 Co 16 O x > Fe 3 Co 16 O x > Zr 3 Co 16 O x > Ti 3 Co 16 O x > Cr 3 Co 16 O x , which is consistent with their catalytic performances. Among all the prepared catalysts, the polymer nanofilm wrapped Mn 3 Co 16 O x nanoparticles possess the highest Co 3+ /Co 2+ ratio (1.56), the highest percentage of surface oxygen vacancy (17.5%) and lattice oxygen (62.2%), resulting in the best catalytic activity, such as, 100% conversion at 55 °C under moisture-rich condition (∼0.6 vol.%). Moreover, the Mn 3 Co 16 O x catalyst also exhibits long-term catalytic stability (>one month) even at a very high water vapor level (3.1 vol.%) and considerably low temperature (85 °C). [ABSTRACT FROM AUTHOR]

A series of CuO-ZnO-MO x (M = Zr, Al, Cr, Ti) catalysts were prepared by co-precipitation method and characterized by ICP-OES, XRD, N 2 adsorption, N 2 O titration, H 2 -TPR, and XPS. The CuO-ZnO-ZrO 2 catalyst exhibits the highest BET surface area and Cu surface area. For all the CuO-ZnO-MO x catalysts, Cu 0 was the predominant copper species detectable on the surface of both reduced and spent samples. As-prepared CuO-ZnO-MO x catalysts were mixed physically with HZSM-5 zeolite to synthesize dimethyl ether (DME) via biomass-derived syngas. The highest CO conversion and DME yield were obtained over a CuO-ZnO-ZrO 2 /HZSM-5 hybrid catalyst. The CO conversion increases with the increase in the Cu surface area, but the relationship between them is not linear. Due to the H 2 -deficient characteristic of biomass-derived syngas, the water-gas shift reaction, by which H 2 can be produced in-situ for the hydrogenation of CO, plays an important role in the direct DME synthesis. [ABSTRACT FROM AUTHOR]