Search

Several ternary oxides CuCeZrOy(CCZ) were synthesized by a facile grinding method followed by calcination at high temperatures, and used as catalysts for CO oxidation at low temperatures. The influences of calcination temperature (400–600 °C) on the physicochemical properties of the as-synthesized ternary oxides were investigated by thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman, inductively coupled plasma-optical emission spectrometry (ICP-OES), N2adsorption, H2-temperature programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS) characterizations. The results show that the increase in calcination temperature from 400 to 500 °C is conducive to the high dispersion of CuOxon catalyst surface and the incorporation of Cu species into the support to form the Cu–Ce–Zr–O solid solution. Further raising of calcination temperature from 500 to 600 °C, however, leads to the segregation of Cu species from the solid solution to aggregate on support surface and growth of highly dispersed CuOxnanoparticles. The highest catalytic activity is acquired over the CCZ calcined at 500 °C, which can be ascribed to the largest contents of Cu+species and oxygen vacancies owing to the formation of the maximum amount of Cu–Ce–Zr–O solid solution.

In this paper, the CuO–CeO2catalyst was prepared by a direct solvothermal method. The effects of different copper salt precursors (copper nitrate, copper acetate, copper sulfate) on the catalytic performance of the prepared catalyst for CO oxidation were investigated. The physical and chemical properties of the prepared catalysts were characterized by X-ray diffraction (XRD), Raman spectroscopy, N2physical adsorption, inductively coupled plasma-atomic emission spectrometry (ICP-AES), X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption analysis of CO (CO-TPD), in-situdiffuse reflectance infrared Fourier transform spectroscopy (DRIFTs), and temperature-programmed reduction with H2(H2-TPR). The results show that the CuO–CeO2catalyst prepared with copper acetate as precursor (CC-A) exhibits the best catalytic activity for CO oxidation at low temperatures, with T50and T90values of 62 and 78 °C respectively, which is mainly attributed to its large specific surface area, pore volume, CO adsorption capacity, and large amount and strong reactivity of surface oxygen. However, the CuO–CeO2catalyst prepared with copper nitrate as precursor (CC–N) displays better stability and resistance to water or CO2poisoning than CC-A.

Highly ordered microporous structures of UiO metal–organic frameworks (MOFs) with different cavity sizes and secondary building units were synthesized and selected as the host to prepare Rh–Mn bimetallic catalysts. The catalysts were investigated for the ethanol-based oxygenate synthesis via syngas conversion. Compared to RM@Ce-UiO-66, the Rh–Mn catalysts supported on Zr-UiO MOFs showed the better catalytic performance, while RM@UiO-67 achieved the highest yield of C2+oxygenates [322.0 g/(kg h)]. Characterization results revealed that the topology structures of the UiO MOFs were propitious to the fix of the confined ultrasmall bimetallic Rh–Mn nanoparticles and restricted the reduction of Rh–Mn particles. However, the unstable framework of Ce-UiO-66 in RM@Ce-UiO-66 would collapse after calcination and reduction, and the formed Rh/CeO2interfaces promoted the transformation of adsorbed CO into stable carbonate species, resulting in low CO conversion. Moreover, the best oxygenate synthesis performance over RM@UiO-67 should be mainly attributed to its highest ratio of Rh+/Rh0.

Two different Mn–Ce-Ox/TiO2catalysts were prepared by ordinary impregnation (denoted as MCT) and citric acid assisted impregnation (denoted as MCT-CA) methods, respectively. Excellent NOxremoval is achieved over MCT-CA for selective catalytic reduction with NH3(NH3-SCR), and 100% NOxconversion is obtained at 125 °C under weight hour space velocity (WHSV) of 80000 mL/(gcat·h). Particularly, 100% NOxis converted on MCT-CA in the presence of 10 vol% H2O at 175 °C. As H2O and SO2coexist in the reaction system for 9 h, NOxconversion can still be maintained >90%, much higher than that (22%) of MCT. A series of characterization results indicates that MCT-CA exhibits a larger BET specific surface area, pore volume, and pore size, which enhances the dispersion of Mn and Ce oxides and promotes the rapid adsorption of reactants and desorption of products. Additionally, MCT-CA possesses more Mn4+, Ce3+, chemisorbed oxygen species, and stronger reducibility, facilitating the conversion of NO to NO2. Specially, the amount of active NH3species and active nitrate species on MCT-CA is much more than that over MCT. The combined effect of the aforementioned factors devotes to the excellent low-temperature SCR performance and tolerance to H2O/SO2over MCT-CA.

• Rh–Mn catalyst was supported on a Zr-based MOF with stability at high temperature. • The structure of UiO-66 can be beneficial to the high dispersion of supported metals. • The synergy of Rh and Mn can be influenced by the metal loading or Mn/Rh ratio. • Enhanced CO dissociation ability and weak Rh−CO band are advantage for oxygenates synthesis. A series of Zr-based metal-organic frameworks (UiO-66) supported Rh–Mn catalysts with various metal loadings were prepared by using a co-impregnation method, and the catalytic activities were investigated for the direct synthesis of ethanol-based C 2 + oxygenates from CO hydrogenation. The catalysts were comprehensively characterized by means of N 2 sorption, XRD, TEM, XPS, H 2 -TPR, and DRIFT. The structural and textural properties of the catalysts show clearly that the overall framework structure of UiO-66 can be beneficial to the high dispersion of supported metals, but the synergistic effect of Rh and Mn would be influenced by the metal loading or Mn/Rh ratio. When the loadings of Rh and Mn reached 3 wt.% and 3 wt.%, the catalyst has the best catalytic activity with the highest yield of C 2 + oxygenates of 200.1 g/(kg h), which can be attributed to the enhanced CO dissociation ability of Rh sites and weaker Rh−CO band strength. [ABSTRACT FROM AUTHOR]

A series of CuO/CeO2catalysts with different CuO loadings (0.5, 1, 3, and 5 wt%) were prepared by an impregnation method, and tested for the total oxidation of CO. The samples were characterized by various structural and textural detection techniques including XRD, N2sorption, TEM-EDS, H2-TPR, XPS, and in situDRIFTS. Unexpectedly, the low CuO loading (0.5–3 wt%) samples calcined at high temperature (800 °C) exhibited better catalytic performance than those calcined at 500 °C, and the catalytic activity gap between the catalysts calcined at 500 °C and 800 °C shrunk with the increase of copper content. In contrast, when the loading amount of CuO reached a normal value (5 wt%), the CuO/CeO2catalyst with low temperature calcination (500 °C) obtained a slightly better activity than that calcined at 800 °C. The results showed that, for the catalysts with low CuO content (0.5–3 wt%), the higher temperature calcination (800 °C) can promote the formation of the coordinatively unsaturated copper atoms and increase the content of active Cu species, resulting in a higher activity than those calcined at 500 °C. But this effect was suppressed when the CuO content reached 5 wt%. The coordinatively unsaturated copper atoms, as well as Cu+, were confirmed to be the main active sites of the CuO/CeO2catalysts.

CuO–CeO2catalysts with different CuO contents prepared viaa direct solvothermal method with superior activity as well as excellent water vapor resistance and good stability have been successfully developed for the catalytic oxidation of CO at low temperatures. The catalyst with a Cu/Ce ratio of 2 : 8 (mol/mol) delivers a high CO conversion of 90% at 86 °C, and particularly, is stable for at least 50 h even in the presence of water vapor without deactivation. By extensive characterization including ICP-AES, XRD, N2adsorption measurement, Raman, XPS, H2-TPR, CO-TPD, and in situDRIFTs, it was found that the presence of abundant oxygen vacancies and strong interaction between CuO and CeO2are responsible for the excellent catalytic performance of the CuO–CeO2catalysts for low-temperature CO oxidation.

Lead (Pb) is one of the heavy metal elements which have an obvious deactivation effect on catalysts for selective catalytic reduction (SCR) of NOxwith NH3. In this study, it was found that cobalt (Co) modification induced a significant enhancement of the Pb resistance of the Mn–Ce–Ox/TiO2catalyst. The fresh and Pb-poisoned catalysts were prepared by an impregnation method and characterized by ICP-OES, XRD, N2adsorption, XPS, H2-TPR, NH3- and NO-TPD, NO oxidation reaction, and in situDRIFTS. The results indicated that the introduction of Pb to the Mn–Ce–Ox/TiO2catalyst could promote the crystallization of MnO2and/or CeO2, reduce the catalyst specific surface area, and decrease the relative concentrations of Mn4+and Ce3+on the catalyst surface. In addition, the presence of Pb in the Mn–Ce–Ox/TiO2catalyst could result in the decrease of reducibility, adsorption capacities for NH3and NO, and oxidation ability for NO to NO2. However, modification of the Mn–Ce–Ox/TiO2catalyst with Co could greatly alleviate these negative effects resulting from Pb doping, thus markedly improving the Pb resistance of the Mn–Ce–Ox/TiO2catalyst.

A series of silica supported silver catalysts (Ag/SiO2) with Ag loading ranging from 5% to 15% were fabricated by the ammonia-evaporation deposition–precipitation method. The effect of Ag contents on the catalytic performance of the catalysts in the selective hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG) was investigated. The result indicates that the catalyst with a 10 wt% silver loading exhibits the best catalytic activity and excellent long-term stability of more than 150 h. Characteristic studies by N2adsorption, TPR, XRD, and XPS show that the Ag content has a significant impact on the physicochemical properties of the Ag/SiO2catalyst. Furthermore, the influence of some additives (B, Ni, La, Ce, and Mo) on the catalytic performance of the most active 10%Ag/SiO2catalyst in the DMO hydrogenation to MG was also studied.

The effects of TiO2phase composition on the catalytic and physico-chemical properties of supported Rh catalysts in the synthesis of C2oxygenates from syngas were studied. The catalysts supported on anatase containing TiO2were more active than those supported on rutile containing TiO2. Meanwhile, the catalyst supported on pure rutile TiO2exhibited a greatly higher C2oxygenate selectivity than that supported on anatase TiO2, and the TiO2with mixed phase composition could further improve the C2oxygenate selectivity compared with the pure phase TiO2. The results showed that the higher Rh dispersion and CO adsorption capacity at the reaction temperature were obtained on the anatase/anatase-rich TiO2supported Rh catalysts, resulting in their higher CO conversion compared with catalysts supported on rutile/rutile-rich TiO2. The chemical states of Rh sites can be affected by the different electron-donor properties of TiO2with different crystalline phases. The electropositivity of Rh+sites was weakened when using the rutile containing TiO2supports, which is conducive to transformation of Rh+(CO)2into Rh–CO species and weakens the Rh–CO bond strength, finally resulting in the increased CO insertion reaction, and accordingly the increase of C2oxygenate selectivity over the rutile containing catalysts. Moreover, the remarkably higher TOF of RM/TiO2-Ar can be attributed to the higher CO adsorption capacity and fast transformation of Rh+(CO)2into Rh–CO species.

A series of CuO–ZnO–ZrO2catalysts was prepared by a facile microwave‐assisted hydrothermal synthesis method and used for the direct synthesis of methanol by CO2hydrogenation in a fixed‐bed reactor at 240 °C, 3.0 MPa, CO2/H2=1:3 (v/v), and space velocity of 2400 mL gcat−1h−1. The effects of the hydrothermal synthesis temperature (80–150 °C) on the physicochemical properties and catalytic activity of the CuO–ZnO–ZrO2catalysts were investigated by using several techniques, including XRD, N2adsorption, reactive N2O adsorption, SEM with energy‐dispersive X‐ray spectroscopy, X‐ray photoelectron spectroscopy, temperature‐programmed reduction by H2, and the temperature‐programmed desorption of adsorbed CO2and H2. The catalyst prepared at 120 °C possessed a high surface area, a high dispersion of Cu species, a high adsorption capacity for CO2and H2, and thus exhibited a high CO2conversion and methanol selectivity. The surface area of metallic Cu (SCu) is the critical factor in determining the activity of the CuO–ZnO–ZrO2catalyst. Microwave catalyst: The performance of a CuO–ZnO–ZrO2catalyst prepared by microwave‐assisted hydrothermal synthesis is influenced greatly by the hydrothermal synthesis temperature. The catalyst prepared at 120 °C possesses a high surface area, high dispersion of Cu species, high adsorption capacity for CO2and H2, and thus a high CO2conversion and methanol selectivity.

Highly effective CuZn0.3MgxAlOy(x= 0–0.2) catalysts for the synthesis of chiral l-phenylalaninol derived from Cu-rich hydrotalcite-like precursors were prepared by a co-precipitation method with Na2CO3as the precipitant, and their physicochemical and catalytic properties were characterized. The results show that the presence of Mg2+ions can promote the formation of hydrotalcite-like (htl) precursors, and the Mg2+content would affect the phase purity of the prepared htl precursors. The BET surface area, exposed copper surface area and amount of acid sites of the samples decreased with the increase in the molar ratio of Mg2+/Al3+. Also, the dense layered htl precursors are beneficial to the atomically uniform distribution of the corresponding metal oxides in the prepared catalysts, promoting the stronger interaction between Cu0and Al2O3after the catalysts were reduced (SMSI effect). The activity of the CuZn0.3MgxAlOycatalysts is greatly dependent on not only the metallic copper surface area, but also the SMSI effect and the acidity of the catalysts. When Mg2+/Al3+= 0.1 (mol), a phase-pure htl precursor could be obtained, and after calcination, the prepared CZA-0.1 catalyst exhibited very excellent catalytic performance for the hydrogenation of l-phenylalanine methyl ester to chiral l-phenylalaninol. After 5 h of reaction at 110 °C and 4 MPa H2, 100% conversion of l-phenylalanine methyl ester and 91.1% yield of l-phenylalaninol with an ee value of ~100% were achieved. After recycling 13 times, the l-phenylalaninol selectivity of the CZA-0.1 catalyst only decreased by 7.2%.

A modified CuO/CeO2catalyst was prepared by surfactant-assisted impregnation method and showed better catalytic activity for low temperature CO oxidation than that from conventional impregnation method. The physicochemical properties of different CuO/CeO2catalysts were characterized by thermogravimetric and differential scanning calorimetric measurements (TG-DSC), X-ray diffraction (XRD), N2adsorption-desorption, Raman spectroscopy, H2temperature-programmed reduction (H2-TPR), temperature-programmed desorption of O2(O2-TPD), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results suggested that the addition of hexadecyl trimethyl ammonium bromide (CTAB) into the impregnation solution could improve the dispersion of CuO species, which could facilitate Cu2+incorporating into CeO2lattice and strengthened the synergistic effects between CuO and CeO2, making the lattice oxygen more active, and eventually resulting in enhanced activity for CO oxidation.

CuO-CeO 2 -ZrO 2 catalysts were prepared via facile dry oxalate-precursor synthesis and tested for CO oxidation. The effect of Cu contents was investigated by N 2 adsorption, TEM, XRD, XPS, H 2 -TPR, CO-TPD and Raman techniques. The results show that CuO dispersion, S BET and adsorbed CO amount exhibit a volcano trend with increasing the Cu content. The highest activity was achieved over the catalyst with 18 mol% Cu with the CO conversion being 99% at 85 °C. The superior performance of the catalyst prepared by this method is attributed to the finely dispersed CuO species and the strong interaction of CuO with ceria-zirconia phase. [ABSTRACT FROM AUTHOR]

Mesoporous CuO synthesized by the hydrothermal method was used as a catalyst for the oxidation of vanillymandelic acid to vanillin with molecular oxygen as the terminal oxidant for the first time. The effects of reaction conditions on the catalytic performances have been investigated in detail, almost 100 % conversion of vanillymandelic acid and 88.3 % yield of goal product were achieved under the best conditions of reaction time 6 h, oxygen pressure 0.45 MPa, 85 °C and pH 12.5. In addition, the mesoporous CuO revealed outstanding recyclability and exhibited several pivotal advantages, including mild reaction conditions, environmentally friendly oxidant, as well as greatly reduced the amount of catalyst. A plausible mechanism for the liquid-phase oxidation of vanillymandelic acid on CuO was proposed.

The effect of support pretreatment with ammonia on the performance of Cu Fe/SiO 2 catalyst for higher alcohols synthesis from syngas was studied by CO hydrogenation, X-ray diffraction, N 2 adsorption–desorption, temperature-programmed reduction of H 2 , Fourier transform infrared spectroscopy, N 2 O chemisorption and temperature-programmed desorption of adsorbed CO. The results indicated that the pretreatment of SiO 2 with ammonia resulted in the formation of more active sites of Cu and higher dispersion of Fe species on the catalyst surface and enhanced the synergistic effect between the copper and iron species. As a result, the CO conversion and the space time yield of alcohols of the Cu Fe/SiO 2 catalyst increased from 14.8% and 89.0 g kg −1 h −1 to 17.4% and 107.0 g kg −1 h −1 , respectively. [ABSTRACT FROM AUTHOR]

CuO/CeO2catalysts for CO oxidation were prepared by impregnation using different Cu precursors (acetate, nitrate, chloride, and sulfate) and calcined at 500 or 800 °C. Their physicochemical properties were characterized by TG-DSC, XRD, TEM, N2adsorption, Raman, XPS, H2-TPR, CO-TPD, and DRIFTS. The results show that CuO is the dominant Cu species in all cases except for copper sulfate calcined at 500 °C, under which temperature some Cu2(OH)3Cl are also obtained from copper chloride. CuO/CeO2prepared from copper acetate and calcined at 500 °C shows the best activity for CO oxidation, due to the presence of more finely dispersed CuO and stronger synergistic effects. The synergistic effects can induce the formation of Cu+(the better CO adsorption sites) and activate the lattice oxygen, thus exerting a crucial role in the catalytic process. However, the residual Cl−and SO42−have a negative effect on the synergistic effects, resulting in low activity in CO oxidation.

The Pd–Cu–Clx/Al2O3catalysts (PCC) were prepared by a two-step impregnation (TI) method in organic solvent, wet impregnation (WI) method and NH3coordination-impregnation (CI) method. The PCC-TI catalyst prepared by the two-step impregnation method (TI) exhibited much higher activity and stability for CO oxidation than the other catalysts, resulting from the smaller size of Cu2Cl(OH)3and fewer carbonates deposited on the surface of PCC-TI catalyst. Using the PCC-TI catalyst, the complete conversion temperature of CO was 10 °C in the presence of 3.1% H2O. Among the three catalysts, the activation energy (Ea) of PCC-TI/ethanol was the lowest (27.1 kJ mol−1). The PCC-TI/ethanol prepared in ethanol solvent showed a higher activity compared with PCC-TI/methanol, due to much stronger interactions between the copper and palladium species. High concentrations of moisture and CO had a negative effect on the CO conversion. The former is due to excessive numbers of –OH groups (from H2O dissociation) which occupy the active sites of Pd and Cu, though –OH groups can work as part of the catalytic cycle, and the latter may originate from competitive adsorption and the presence of carbonates on the surface. We used DFT calculations to study the adsorption of H2O and CO on the surface, and the catalytic cycle of CO oxidation on the Pd species, revealing the possible routes for the formation of common species observed in the in situDRIFTS spectra.

CeO2-ZrO2mixed oxide (Ce0.6Zr0.4O2) prepared by microwave-assisted heating co-precipitation was used as a support to prepare a series of CuO/Ce0.6Zr0.4O2catalysts with various CuO contents (0 wt.%–15 wt.%) via the method of incipient-wetness impregnation. The obtained CuO/Ce0.6Zr0.4O2samples were characterized by N2adsorption, XRD, Raman, TEM and H2-TPR technologies, and their catalytic activities for CO oxidation were investigated. The results showed that the activity of CuO/Ce0.6Zr0.4O2catalyst was strongly influenced by the content of CuO, and the catalyst with 10 wt.% CuO exhibited the best catalytic activity in CO oxidation, which could be attributed to the high dispersion and reducibility of CuO, and high oxygen vacancy concentration in the catalyst.

Co3O4catalysts supported on TiO2with different crystalline structures (anatase (A), rutile (R) and P25 (Degussa)) were prepared by a deposition–precipitation method, and characterized by nitrogen adsorption/desorption, XRD, HR-TEM, EPR, Raman spectroscopy, XPS and H2-TPR techniques. The results show that Co3O4/TiO2(A) exhibited the highest activity among the three Co3O4/TiO2catalysts: CO can be completely oxidized to CO2at −43 °C. When rutile TiO2or P25 were used as the support, its catalytic activity was decreased obviously, because the TiO2crystal structure has an influence on the physicochemical and catalytic properties of the Co3O4catalysts. The results show that the Co3O4/TiO2(A) catalyst contains Ti3+species, which is in an unstable state and can affect the properties of Co3O4by the interaction between the deposited Co3O4and anatase TiO2support. The Co3O4/TiO2(A) catalyst exhibits highly defective structure and good oxygen adsorption ability. The reducibility of Co3O4is improved by the anatase TiO2support, resulting in Co3O4/TiO2(A) possessing the better redox property than the other Co3O4/TiO2catalysts, which is an important factor for its high catalytic activity.

The effects of the preparation method on the properties of Cu/ZnO/Al2O3catalysts for l-phenylalanine methyl ester hydrogenation to l-phenylalaninol were investigated in detail, including the precipitation method and conditions (the aging time, calcination temperature and so on), with the help of ICP-OES, N2and N2O adsorption, XRD, H2-TPR and TEM techniques. The results show that physicochemical properties of the catalysts are greatly affected by the preparation method and conditions. The uniform size distribution of CuO species can be obtained by fractional co-precipitation. The appropriate aging time is 2 h, and the catalyst aged for 2 h has the largest metallic copper surface area (SCu) and surface copper amount and the smallest CuO crystallites. The lower calcination temperature is favorable for increasing the surface area and metallic copper surface area of the catalyst. The spinel structure CuAl2O4phase can form after calcination at 550 °C. The turnover frequency (TOF) values of l-phenylalaninol formed using different catalysts indicate the structurally sensitive character of the title reaction, and SCuis not the sole cause affecting the catalytic activities of the catalysts. B-TOF on the basis of the active sites (Cu0) in the boundary between CuO and ZnO or Al2O3was proposed; the relationships of B-TOF with dCuO(particle size of CuO) and SCuwere established. Using the Cu/ZnO/Al2O3catalyst prepared by fractional co-precipitation with aging at 70 °C for 2 h and calcination at 450 °C for 4 h, 83.6% selectivity to l-phenylalaninol without racemization was achieved.

Abstract: The effect of Fe promoter on the catalytic properties of Rh–Mn–Li/SiO2 catalyst for CO hydrogenation was investigated. The catalysts were comprehensively characterized by means of X-ray diffraction (XRD), N2 adsorption–desorption, temperature programmed reduction (TPR), temperature programmed desorption (TPD), temperature programmed surface reaction (TPSR), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Activity testing results showed that low loading of Fe (≤0.1wt%) improved the reactivity and yield of C2 + oxygenates; however, the opposite effect appeared at the high values of Fe (>0.1wt%). Characterization results suggested that the addition of Fe strengthened the Rh–Mn interaction and increased the desorption/transformation rate of adsorbed CO, which could be responsible for the increase of CO conversion. But on the other hand, the existence of Fe might deposit over the Rh surface, and decreased the number of active sites, resulting in the decrease of CO conversion when the Fe amount was excessive. The selectivity to C2 + oxygenates varied inversely with the reducibility of Rh oxide species. Moreover, it is proposed that the transformation of dicarbonyl Rh+(CO)2 into H–Rh–CO is favorable for the formation of C2 + oxygenates, and the hydrogenation ability of Fe can increase the hydrogenation of acetaldehyde to ethanol. [Copyright &y& Elsevier]

The Cu/ZnO/Al2O3catalyst for hydrogenation of l-phenylalaninate to l-phenylalaninol was prepared by a co-precipitation method, and characterized by XRD, low-temperature N2adsorption, H2-TPR, N2O chemisorption and ICP-AES. The results show that the physicochemical properties of the catalyst are greatly affected by the ZnO amount, and that the exposed copper surface area, dispersion of CuO and BET surface area of the Cu/ZnO/Al2O3catalyst (Cu/Zn/Al = 1.0 : 0.3 : 1.0) reach the largest. The chemoselectivity of l-phenylalaninol is changed with ZnO amount in the Cu/ZnO/Al2O3catalyst, and when Cu/Zn/Al = 1.0 : 0.3 : 1.0, the catalyst exhibits higher catalytic performance and chemoselectivity to l-phenylalaninol. Furthermore, the effect of temperature, pressure, reaction time and the molar ratio of catalyst to ester on the catalytic hydrogenation of l-phenylalaninate were investigated. When the catalytic hydrogenation of l-phenylalaninate was operated at 110 °C and 4 MPa of H2for 5 h, the yield of l-phenylalaninol can reach 69.2 %, and its eeselectivity is 99.84 %.

Pure TiO 2and La-doped TiO 2were prepared by the sol-gel method. Au was supported on TiO 2by the deposition-precipitation (DP) method, and its catalytic activity for CO oxidation was tested. The results showed that doping La in Au/TiO 2could improve its catalytic activity obviously for CO oxidation. The analyses of X-ray diffraction (XRD), temperature-programmed desorption (TPD), and Brunauer-Emmett-Teller (BET) surface area further showed that the presence of La in TiO 2not only increased its surface area and restrained the growth of TiO 2crystallites, but could also enhance the microstrain of TiO 2. In terms of O 2-TPD, a new adsorbed species O −appeared on the surface of La-doped TiO 2. The results of in-situFourier transform-infrared (FT-IR) spectroscopy illustrated that the high activity of Au/La 2O 3-TiO 2was attributed to the presence of La promoting the reactivity of CO adsorbed on the Au site and the formation of the second active site on the surface of TiO 2

A series of boria catalysts supported on titania–zirconia mixed oxide (B2O3/TiO2–ZrO2) with different boria loadings (8–20 wt%) were prepared and characterized by X-ray diffraction, adsorption of nitrogen, 11B magic angle spinning (MAS) NMR measurements and temperature-programmed desorption (TPD) of ammonia. The catalytic performance of B2O3/TiO2–ZrO2for vapor-phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam was studied at 300°C. It was found that the lactam selectivity increased with increasing of boria loading, whereas a maximum oxime conversion was obtained at the boria loading of 12 wt%. The acid sites of medium strength on the surface of the catalyst play an important role in the selective formation of lactam.

A series of TiO2–Al2O3composites with Al/Ti molar ratios of 0.1, 0.2, and 0.4 were synthesized by a co-precipitation method and used as supports to prepare supported MnCeOxcatalysts by an impregnation method. The physico-chemical properties of the samples were extensively characterized by N2physisorption, X-ray diffraction, Raman spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy element mapping, X-ray photoelectron spectroscopy,H2-temperature programmed reduction, ammonia temperature programmed desorption, and in-situdiffuse reflectance infrared fourier transform spectroscopy. The catalytic activity and resistance to water vapor and SO2of the as-prepared catalysts for the SCR of NOxwith NH3were evaluated at 50–250 °C and GHSV of 80000 mL/(gcat∙h). The results reveal that MnCeOx/TiO2–Al2O3exhibits higher activity and better SO2tolerance than MnCeOx/TiO2. Combining with the characterization results, the enhanced activity and SO2tolerance of MnCeOx/TiO2–Al2O3can be mainly attributed to higher relative concentrations of Mn4+and chemisorbed oxygen species, stronger reducibility, and larger adsorption capacity for NH3and NO, which originate from the larger specific surface area and pore volume, higher dispersion of Mn and Ce species compared with MnCeOx/TiO2. Moreover, in situDRIFTS was used to investigate the reaction mechanism, and the results indicate that the NH3-SCR reaction over MnCeOx/TiO2and MnCeOx/TiO2–Al2O3takes place by both the E–R and L–H mechanisms.

This paper presents a novel modification of highly siliceous MFI zeolites with hydrofluoric acid treatment: Silicalite-1 undergone such treatment exhibited remarkable improvements in stability and selectivity for Beckmann rearrangement of cyclohexanone oxime, which are even much better than those obtained by basic modification.

The HMCM-49 zeolites before and after steam treatment were commingled with methanol synthesis catalyst to perform the single-step syngas-to-dimethyl ether process. The high temperature steam treatment meliorated the acidity of HMCM-49 zeolite, and consequently enhanced the selectivity to dimethyl ether significantly by reducing the formation of by-products like carbon dioxide and hydrocarbons.