Investigating the effect of metal oxide additives on the properties of Cu/ZnO/Al2O3 catalysts in methanol synthesis from syngas using factorial experimental design

The Cu/ZnO/Al₂O₃ catalysts, prepared by co-precipitation method, have been modified by adding small amount of Mn, Mg, Zr, Cr, Ba, W and Ce oxides using design of experiments (1/16 full factorial design). The structure and morphology of catalysts were studied by X-ray diffraction (XRD) and BET. Performance of the prepared catalysts for CO/CO₂ hydrogenation to methanol was evaluated by using a stainless steel fixed-bed reactor at 5 MPa and 513 K. The oxide additives were found to influence the catalytic activity, dispersion of Cu, Cu crystallite size, surface composition of catalyst and stability of catalysts during their operations. The results showed that the Mn and Zr promoted catalysts have high performance for methanol synthesis from syngas.     

Characteristics of the Pd-only three-way catalysts prepared by sol–gel method

Pd-only three-way catalysts prepared by the sol–gel method were investigated by the three-way catalytic performance test with a simulated exhaust gas in a continuous U-tube quartz reactor at a gas hourly space velocity of 72 000 h⁻¹. The catalysts were characterized with XRD, XPS, BET surface area and pore volume. The activity and thermal stability of the Pd–Al₂O₃ catalyst prepared at pH 10 were superior to those at pH 4 during hydrolysis and condensation, which could be explained by the anchoring effect. Zr and V were found to be good promoters for the enhancement of the thermal stability and SO₂ resistance, respectively. Optimally formulated catalyst, Pd(1)–V(2)–Zr(10)–Al₂O₃, was thermally stable up to 900^oC and showed a much more improved low-temperature activity and excellent SO₂ resistance.     

Partial oxidation of alkanes to oxygenates in supercritical carbon dioxide

The catalytic partial oxidation of propane in supercritical carbon dioxide has been investigated in a stirred batch reactor. Various metals (oxides) have been used as supported catalysts with respect to their activity and selectivity for the formation of oxygenates. The reactions run with a 1:2.3–2.9:68–108 molar ratio of propane:synthetic air:CO₂ at 453–573 K and 80–100 bar. Using a precipitated 2.4 wt.% Co₃O₄–SiO₂ catalyst at 573 K, a total oxygenate (i.e. acetic acid, acetone, acetaldehyde, methanol) selectivity of 59% and a propene selectivity of 21% were obtained at a propane conversion of 12 mol%. The same catalyst has been used to investigate the influence of the supercritical conditions and initial feed composition on the reaction, varying the density of CO₂ and the concentration of synthetic air, respectively.     

A structured Co–B catalyst for hydrogen extraction from NaBH4 solution

A structured Co–B catalyst has been developed to produce hydrogen from an alkaline NaBH₄ solution. The catalyst was prepared by chemical reduction of Co precursors coated on a Ni foam support. The effects of catalyst preparation conditions on activity of the catalyst were investigated. The active catalyst was amorphous in structure and contains boron with a Co/B molar ratio of 1.5–2.8. With increasing the heat treatment temperature, the catalyst showed a maximum activity to hydrogen generation at approximately 250 °C. Adhesion of the catalyst to the support was also enhanced by heat treatment at 300–400 °C. The catalysts were successfully applied in both a batch reactor and a flow reactor for continuous generation of hydrogen.     

Low-temperature methanol synthesis in catalytic systems composed of nickel compounds and alkali alkoxides in liquid phases

Catalysts prepared from NaH, tert-amyl alcohol and nickel acetate were tested for CO hydrogenation in organic solvents in the range of 353–433 K and 1.0–5.0 MPa. Methanol was produced selectively under the studied conditions. Higher temperatures and higher pressures enhanced methanol productivity; a maximum space–time yield of 0.95 kg MeOH l⁻¹ h⁻¹, higher than that of the conventional methanol production process, was obtained at 433 K and 5.0 MPa. The addition of methanol to the catalyst did not significantly affect the product yields, but such addition did eliminate the induction period that was observed during the run in the absence of methanol addition to the catalyst. This suggested that methanol promoted the formation of a catalytically active species and/or that a certain amount of methanol was required to run a catalytic reaction cycle smoothly, in which methanol would be a reactant. The catalysts exhibited a catalytic decline over a short period due to the consumption of the alkoxide component.     

Kinetics of wet oxidation of black liquor over a Pt–Pd–Ce/alumina catalyst

The catalytic oxidation of industrial wastewater from paper and pulp mills has been investigated in a slurry reactor at a temperature range 433–463 K and at pressures from 1.5 to 2.2 MPa. Adding Ce on alumina support promotes the catalytic activity for oxidation of black liquor. Pt–Pd–Ce/alumina catalyst shows a promising activity for wet catalytic oxidation of black liquor. The oxidation reaction over a Pt–Pd–Ce catalyst is characterized by an initial fast reaction step followed by a slow reaction step. The rate of total organic carbon (TOC) reduction was described by first-order kinetics with respect to TOC concentration in black liquor for both initial and later reaction steps. The activation energies were determined to be 54.53 and 50.13 kJ/mol for the initial and later oxidation steps, respectively. Comparison of the data with the generalized kinetic model was also presented.     

Influence of preparation method on performance of Cu(Zn)(Zr)-alumina catalysts for the hydrogen production via steam reforming of methanol

The selective production of hydrogen via steam reforming of methanol (SRM) was performed using prepared catalysts at atmospheric pressure over a temperature range 200–260^∘C. Reverse water gas shift reaction and methanol decomposition reactions also take place simultaneously with the steam reforming reaction producing carbon monoxide which is highly poisonous to the platinum anode of PEM fuel cell, therefore the detailed study of effect of catalyst preparation method and of different promoters on SRM has been carried out for the minimization of carbon monoxide formation and maximization of hydrogen production. Wet impregnation and co-precipitation methods have been comparatively examined for the preparation of precursors to Cu(Zn)(Al₂O₃) and Cu(Zn)(Zr)(Al₂O₃). The catalyst preparation method affected the methanol conversion, hydrogen yield and carbon monoxide formation significantly. Incorporation of zirconia in Cu(Zn)(Al₂O₃) catalyst enhanced the catalytic activity, hydrogen selectivity and also lower the CO formation. Catalyst Cu(Zn)(Zr)(Al₂O₃) with composition Cu/Zn/Zr/Al:12/4/4/80 prepared by co-precipitation method was the most active catalyst giving methanol conversion up to 97% and CO concentration up to 400 ppm. Catalysts were characterized by atomic absorption spectroscopy (AAS), Brunauer-Emett-Teller (BET) surface area, pore volume, pore size and X-ray powder diffraction (XRPD). The XRPD patterns revealed that the addition of zirconia improves the dispersion of copper which resulted in the better catalytic performance of Cu(Zn)(Zr)(Al₂O₃). The time-on-stream (TOS) catalysts stability test was also conducted for which the Cu(Zn)(Zr)(Al₂O₃) catalyst gave the consistent performance for a long time compared to other catalysts.     

Complete conversion of brown coal into distillate

The conditions for complete conversion of Victorian brown coal were investigated with an iron–sulfur catalyst in a continuous reactor system consisting of three stirred tank reactors in series. The coal was found to be completely converted into distillate (b.p.<420°C) when the gas flow rate (GFR) through the reactors was increased and the slurry-feed rate was reduced at a temperature of 450°C and a pressure of 18.6 MPa. An analysis of the composition of the liquid in the reactors under liquefaction conditions confirmed that the increase in GFR markedly enhanced the stripping of the solvent fraction in the feed slurry and the lighter fraction derived from the coal, resulting in marked increases in the actual residence time (θ_RT) of the liquid consisting of the concentrated catalyst and heavy fraction. The stripping effect markedly enhanced liquefaction reactions, thus providing a higher distillate yield. However, the GFR effect was gradually saturated as the liquid remaining in the reactors (reactor liquid) became heavier with the increase in the GFR. The extension of nominal residence time (defined by the ratio of slurry-feed rate to reactor volume, θ_NT) from reduction of the slurry feed rate was found to be effective in extending the GFR effects under a high GFR condition, resulting in the complete conversion of the coal. In addition, the stripping of the solvent by the increased GFR was also found to be more enhanced at 18.6 MPa than that at 14.7 MPa although its vaporization was suppressed at a higher pressure. This is due to the heavy fraction in the reactor liquid being more hydrogenated over the concentrated catalyst at a higher hydrogen pressure. However, the dependencies of the conversion rate of the heavy fraction on θ_RT were almost the same for both 14.7 and 18.6 MPa. These results suggested that a complete conversion of the coal could be achieved at 14.7 MPa by using a heavier solvent.     

Partial oxidation of propane in compressed carbon dioxide using CoOx/SiO2 catalysts

The application of compressed carbon dioxide as an alternative reaction medium was investigated for the heterogeneously catalysed partial oxidation of propane. The catalytic tests were performed in a stirred batch as well as in a continuous flow reactor at 553–623 K, 2.6–11.3 MPa and a CO₂:synthetic air:propane molar ratio of 94–124:4–7:1 using precipitated CoO_x/SiO₂ (2.4–3.7 wt.% Co) catalysts. In addition, the critical temperature and pressure of the reaction mixture were determined by the opalescence method in a high-pressure optical cell. The catalytic experiments revealed a significantly higher cumulative oxygenate selectivity (i.e. acetic acid, methanol, acrolein, acetone) with increasing pressure. It is supposed that the formed oxygenates were removed more easily from the catalyst surface without being totally oxidised due to the higher solvent power of the dense CO₂ in the supercritical phase.     

苯酚气相甲基化催化剂单管放大及再生试验研究

本文叙述了苯酚与甲醇气相催化甲基化合成邻甲酚和2,6-二甲酚催化剂V₂0₅-Fe₂O₃的单管放大研究,选取反应管内径Φ32mm,装填催化剂2kg,装填高度2500mm,在催化剂负荷90g-Ph/kg-cat·h,原料配比PhOH∶MeOH∶H₂O＝1∶₄∶3(mol)条件下,催化剂连续运转2400小时,催化剂共进行了4次再生,苯酚单程转化率为62.21%,邻甲酚选择性80.47%,邻甲酚单程摩尔收率50.06%。     

Catalytic combustion over platinum group catalysts: fuel-lean versus fuel-rich operation

Performance data are presented for methane oxidation on alumina-supported Pd, Pt, and Rh catalysts under both fuel-rich and fuel-lean conditions. Catalyst activity was measured in a micro-scale isothermal reactor at temperatures between 300 and 800 °C. Non-isothermal (near adiabatic) temperature and reaction data were obtained in a full-length (non-differential) sub-scale reactor operating at high pressure (0.9 MPa) and constant inlet temperature, simulating actual reactor operation in catalytic combustion applications.

Under fuel-lean conditions, Pd catalyst was the most active, although deactivation occurred above 650 °C, with reactivation upon cooling. Rh catalyst also deactivated above 750 °C, but did not reactivate. Pt catalyst was active above 600 °C. Fuel-lean reaction products were CO₂ and H₂O for all three catalysts.

The same catalysts tested under fuel-rich conditions demonstrated much higher activity. In addition, a ‘lightoff’ temperature was found (between 450 and 600 °C), where a stepwise increase in reaction rate was observed. Following ‘lightoff’ partial oxidation products (CO, H₂) appeared in the mixture, and their concentration increased with increasing temperature. All three catalysts exhibited this behavior.

High-pressure (0.9 MPa) sub-scale reactor and combustor data are shown, demonstrating the benefits of fuel-rich operation over the catalyst for ultra-low emissions combustion.     

Selective hydrogenation of benzene to cyclohexene using a suspended Ru catalyst in a mechanically agitated tetraphase reactor

The reactivity on unsupported Ru based catalyst in benzene selective hydrogenation to cyclohexene has been studied. The reaction has been carried out in a tetraphase slurry reactor at 423 K, at 5 MPa, in the presence of two liquid phases: benzene and an aqueous solution of ZnSO₄ 0.6 mol l⁻¹. A detailed study of the influence of the transport phenomena on the reactivity of the catalyst has been carried out. No correlation has been found between the characteristic numbers of Weeler–Weisz and of Carberry mass transport at external liquid/solid interface or into the catalyst pores for both benzene and hydrogen and the selectivity of the catalyst. The main features of the catalysts are the strong dependence between the catalysts preparation procedure and their activity and selectivity. In particular the influence of the alkaline or the earth alkaline hydroxide, employed in the precipitation of the Ru precursor, on the selectivity, has been studied. Hydrogen chemisorption measurements indicate that the amount of weakly adsorbed hydrogen depends on the nature of the base employed in the precipitation step.     

Recent advance in catalysis for solving energy and environmental problems

Recent advances in catalysis for solving the energy and environmental problems are summarized. For these purposes, rapid conversion and selective reaction even under conditions deviating extremely from reaction stoichiometry must be indispensable requisites. In order to realize these requisites, changes in the state of catalyst surface during the reaction were studied, and the catalyst structures on which the optimum reaction performance occurs were determined. An ultra-rapid reforming of methane to syngas with a space–time yield (STY) of 25 000 mol/l h was achieved by using a Rh-modified Ni–Ce₂O₃–Pt catalyst in which the Rh played the role of portholes for hydrogen spillover and prevents coke deposition on the catalyst surface. As a result, a stable state of the catalyst and the high reaction rate were exhibited. A new catalyst composed of Cu–Zn–Cr–Al–Ga oxides modified with supported Pd exerted a high activity with a high STY of methanol, 6700 g/l h. The catalyst components, Pd and Ga, controlled the reduction state of the catalyst surface by their role on normal and inverse spillover of hydrogen, respectively. The methanol thus produced was then totally converted selectively on a metallosilicate catalyst containing Ga or Fe into an aromatics-lean gasoline using an STY of 1860 g/l h. Finally, non-linear reaction mechanism is used to explain the elimination of NO on metallosilicate catalysts under O₂-excess conditions.     

Transesterification of edible and non-edible oils over basic solid Mg/Zr catalysts

A series of Mg–Zr catalysts with varying Mg to Zr ratios was prepared by co-precipitation method. These catalysts were characterized by BET surface area, X-ray diffraction, X-ray photo electron spectroscopy and temperature programmed desorption of CO₂. The catalytic activity of these catalysts was evaluated for the room temperature transesterification of both edible and non-edible oils to their corresponding fatty acid methyl esters. The catalyst with Mg/Zr (2:1 wt./wt.%) exhibited exceptional activity towards transesterification reaction within short reaction time. The effects of different reaction parameters such as catalyst to oil mass ratio, reaction temperature, reaction time and methanol to oil molar ratio were studied to optimize the reaction conditions. The reasons for the observed activity of these catalysts are discussed in terms of their basicity and other physico-chemical properties.     

Selective oxidation of methanol to formaldehyde over V–Mg–O catalysts

The results of a complex investigation of V–Mg–O catalysts for oxidative dehydrogenation (ODH) of methanol are presented. The efficiency of vanadium–magnesium oxide catalysts in production of formaldehyde has been evaluated. Strong dependence of the formaldehyde yield and selectivity upon vanadium oxide loading and the conditions of heat treatment of the catalyst were observed. The parameters of the preparation mode for the efficient catalyst were identified. In optimised reaction conditions the V–Mg–O catalysts at the temperature approximate 450 °C ensured the formation of formaldehyde with the yield of 94% at the selectivity of 97%.

No visible changes in the performance of the catalyst (methanol conversion, formaldehyde yield and selectivity) were detected during the 60 h of operation in prolonged runs. Characterization of the catalyst by XRD, IR, and UV methods suggests the formation of species of the pyrovanadate type (Mg₂V₂O₇) with irregular structure on the surface of a V–Mg–O catalyst. These species make the catalyst efficient for methanol ODH.     

CoMo/MgO–Al2O3 supported catalysts: An alternative approach to prepare HDS catalysts

Three different supports were prepared with distinct magnesia–alumina ratio x = MgO/(MgO + Al₂O₃) = 0.01, 0.1 and 0.5. Synthesized supports were impregnated with Co and Mo salts by the incipient wetness method along with 1,2-cyclohexanediamine-N,N,N′,N′-tetraacetic acid (CyDTA) as chelating agent. Catalysts were characterized by BET surface area, Raman spectroscopy, SEM-EDX and HRTEM (STEM) spectroscopy techniques. The catalysts were evaluated for the thiophene hydrodesulfurization reaction and its activity results are discussed in terms of using chelating agent during the preparation of catalyst. A comparison of the activity between uncalcined and calcined catalysts was made and a higher activity was obtained with calcined MgO–Al₂O₃ supported catalysts. Two different MgO containing calcined catalysts were tested at micro-plant with industrial feedstocks of heavy Maya crude oil. The effect of support composition was observed for hydrodesulfurization (HDS), hydrodemetallization (HDM), hydrodeasphaltenization (HDAs) and hydrodenitrogenation (HDN) reactions, which were reported at temperature of 380 °C, pressure of 7 MPa and space-velocity of 1.0 h⁻¹ during 204 h of time-on-stream (TOS).     

Synthesis of dimethyl carbonate from propylene carbonate and methanol using CaO–ZrO2 solid solutions as highly stable catalysts

CaO–ZrO₂ catalysts were prepared by coprecipitation and their catalytic performances were evaluated in the synthesis of dimethyl carbonate from propylene carbonate and methanol. The characterization by XRD, N₂ adsorption, XPS and CO₂–TPD indicated that Ca²⁺ ion substituted for Zr⁴⁺ ions in the host lattice to form homogeneous CaO–ZrO₂ solid solution when Ca/(Ca + Zr) ratio changed from 0.1 to 0.3, and CaO segregated at grain boundaries with Ca/(Ca + Zr) ratio from 0.4 to 0.5. As a result, the catalysts showed different activity and stability towards the transesterification of propylene carbonate and methanol into dimethyl carbonate. The activity of catalysts was improved with increase in Ca content, whereas high stability was shown with Ca/(Ca + Zr) ratio below 0.3. The formation of homogeneous CaO–ZrO₂ solid solution was responsible for the stability of catalysts.     

Influence of preparation method on performance of Cu(Zn)(Zr)-alumina catalysts for the hydrogen production via steam reforming of methanol

The selective production of hydrogen via steam reforming of methanol (SRM) was performed using prepared catalysts at atmospheric pressure over a temperature range 200–260^°C. Reverse water gas shift reaction and methanol decomposition reactions also take place simultaneously with the steam reforming reaction producing carbon monoxide which is highly poisonous to the platinum anode of PEM fuel cell, therefore the detailed study of effect of catalyst preparation method and of different promoters on SRM has been carried out for the minimization of carbon monoxide formation and maximization of hydrogen production. Wet impregnation and co-precipitation methods have been comparatively examined for the preparation of precursors to Cu(Zn)(Al₂O₃) and Cu(Zn)(Zr)(Al₂O₃). The catalyst preparation method affected the methanol conversion, hydrogen yield and carbon monoxide formation significantly. Incorporation of zirconia in Cu(Zn)(Al₂O₃) catalyst enhanced the catalytic activity, hydrogen selectivity and also lower the CO formation. Catalyst Cu(Zn)(Zr)(Al₂O₃) with composition Cu/Zn/Zr/Al:12/4/4/80 prepared by co-precipitation method was the most active catalyst giving methanol conversion up to 97% and CO concentration up to 400 ppm. Catalysts were characterized by atomic absorption spectroscopy (AAS), Brunauer-Emett-Teller (BET) surface area, pore volume, pore size and X-ray powder diffraction (XRPD). The XRPD patterns revealed that the addition of zirconia improves the dispersion of copper which resulted in the better catalytic performance of Cu(Zn)(Zr)(Al₂O₃). The time-on-stream (TOS) catalysts stability test was also conducted for which the Cu(Zn)(Zr)(Al₂O₃) catalyst gave the consistent performance for a long time compared to other catalysts.     

Syngas production from methane reforming with CO2/H2O and O2 over NiO–MgO solid solution catalyst in fluidized bed reactors

Catalyst performance of NiO–MgO solid solution catalysts for methane reforming with CO₂ and H₂O in the presence of oxygen using fluidized and fixed bed reactors under atmospheric and pressurized conditions was investigated. Especially, methane and CO₂ conversion in the fluidized bed reactor in methane reforming with CO₂ and O₂ was higher than those in the fixed bed reactor over Ni_0.15Mg_0.85O catalyst under 1.0 MPa. In contrast, conversion levels in the fluidized and fixed bed reactor were almost the same over MgO-supported Ni and Pt catalysts. It is suggested that the promoting effect of catalyst fluidization on the activity is related to the catalyst reducibility. On a catalyst with suitable reducibility, the oxidized and deactivated catalyst can be reduced with the produced syngas and the reforming activity regenerates in the fluidized bed reactor during the catalyst fluidization. In addition, the catalyst fluidization inhibited the carbon deposition.     

Thioreduction of cyclopentanone and hydrodesulfurization of dibenzothiophene over sulfided nickel or cobalt-promoted molybdenum on alumina catalysts

Two series of sulfided Ni or Co promoted Mo/alumina catalysts, having different Ni or Co loadings, were characterized by their activities for the transformation of cyclopentanone into cyclopentanethiol (flow reactor, 220°C, atmospheric pressure) and for the hydrodesulfurization of dibenzothiophene (flow reactor, 340°C, 3 MPa hydrogen pressure). The addition of the promoter increased significantly the activity of the Mo/alumina catalyst for both reactions, up to a maximum obtained with the catalysts having a (promoter)/(promoter+Mo) molar ratio equal to 0.3–0.4. This increase in activity was due in part to an increase in the hydrogenating properties of the Mo/alumina catalyst. However, an additional modification of the catalyst (basic and nucleophilic properties) must be considered to account for the spectacular effect of the promoter on the rate of the dibenzothiophene direct desulfurization reaction.