Hydrocracking of Vacuum Gasoil on NiMo/AAS-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts Prepared from Citric Acid: Effect of the Catalyst Heat Treatment Temperature

Ni-Mo bimetallic catalysts are prepared by impregnating a carrier containing amorphous aluminosilicate (AAS) and aluminum oxide using a solution with Ni, Mo, and citric acid. The temperature of the catalysts ranges from 120 to 550°С. The physicochemical properties of the catalysts are studied via XPS, TEM, and HCNS analysis, and they are tested in hydrocracking of vacuum gasoil. The particles of the sulfide active component (NiMoS phase) are localized predominantly on surfaces of aluminum oxide, and only some are on surfaces of AAS. When the temperature of catalyst calcination is raised, the average number of the layers in particles of the NiMoS phase grows as well, due to the removal of citric acid. This indicates strengthening of the interaction between the sulfide active component and aluminum oxide. The content of Ni-Mo massive sulfide particles also grows along with the temperature of calcination. The morphological characteristics of the sulfide active component affect the activity of the catalysts in hydrodesulfurization and hydrodenitrogenation, but not in hydrocracking. The optimum heat treatment temperature for NiMo/AAS-Al₂O₃ catalysts prepared with citric acid is 120°C. Recommendations are given for the heat treatment of catalysts under industrial conditions.     

Mechanochemical synthesis of β-NiMoO<Subscript>4</Subscript> as a precursor of bulk highly dispersed catalyst for the hydrocracking of oil fractions

The possibility of synthesizing bulk catalysts by means of mechanochemical activation (MCA), the basis for wasteless technologies for the production of catalysts with particle sizes less than 10 μm, is demonstrated. The precursors of Ni-Mo catalysts for hydrogenation processes are synthesized by MCA. The chemical and phase composition and specific surface area of mechanically activated composites with Ni: Mo atomic ratio = 1.0 and 1.4 are studied by DTA, XRD, TPR, and low-temperature adsorption. It is established that during the simultaneous MCA of Ni- and Mo-containing salts, solid-state reactions yield complex X-ray amorphous compounds that after calcination at 520°C form nickel molybdates composed almost entirely of highly active modified β-NiMoO₄, the sulfidation of which produces MoS₂ and Ni₃S₂ phases. Comparative testing of sulfide catalysts (i.e., bulk (Ni: Mo = 1.4) and industrial supported) in model reactions of the conversion of 1-methylnaphthalene and dibenzothiophene was performed at a temperature of 350°C, a pressure of 3.5 MPa, a feedstock hourly space velocity of 2 h⁻¹, and a hydrogen/feedstock ratio of 600. Based on the composition of the 1-methylnaphthalene and dibenzothiophene conversion products while using industrial and bulk catalysts, it is concluded that the bulk catalyst exhibits higher hydrogenating activity.     

Biodiesel Production from Soybean Oil Catalyzed by Li<Subscript>2</Subscript>CO<Subscript>3</Subscript>

In the present study, we synthesized biodiesel from soybean oil through a transesterification reaction catalyzed by lithium carbonate. Under the optimal reaction conditions of methanol/oil molar ratio 32:1, 12 % (wt/wt oil) catalyst amount, and a reaction temperature of 65 °C for 2 h, there was a 97.2 % conversion to biodiesel from soybean oil. The present study also evaluated the effects of methanol/oil ratio, catalyst amount, and reaction time on conversion. The catalytic activity of solid base catalysts was insensitive to exposure to air prior to use in the transesterification reaction. Results from ICP-OES exhibited non-significant leaching of the Li₂CO₃ active species into the reaction medium, and reusability of the catalyst was tested successfully in ten subsequent cycles. Free fatty acid in the feedstock for biodiesel production should not be higher than 0.12 % to afford a product that passes the EN biodiesel standard. Product quality, ester content, free glycerol, total glycerol, density, flash point, sulfur content, kinematic viscosity, copper corrosion, cetane number, iodine value, and acid value fulfilled ASTM and EN standards. Commercially available Li₂CO₃ is suitable for direct use in biodiesel production without further drying or thermal pretreatment, avoiding the usual solid catalyst need for activation at high temperature.     

Production of middle distillate through hydrocracking of paraffin wax over NiMo/TiO<Subscript>2</Subscript>-SiO<Subscript>2</Subscript> catalysts

Titania-silica (TS(X), X=19, 26, 55, 70, and 79) supports with different titania content (X, wt%) were prepared by a precipitation method. NiMo/TS(X) catalysts prepared by an incipient wetness method were then applied to the production of middle distillate through hydrocracking of paraffin wax. Successful formation of NiMo/TS(X) (X=19, 26, 55, 70, and 79) catalysts was confirmed by ICP-AES and XRD measurements. NH₃-TPD experiments were conducted to measure the acid property of NiMo/TS(X) (X=19, 26, 55, 70, and 79) catalysts. It was revealed that acidity of the catalyst played an important role in determining the catalytic performance in the hydrocracking of paraffin wax. Conversion of paraffin wax increased with increasing acidity of the catalyst, while yield for middle distillate showed a volcano-shaped curve with respect to acidity of the catalyst. Among the catalysts tested, NiMo/TS(26) retaining moderate acidity showed the highest yield for middle distillate.     

Dibenzothiophene hydrodesulfurization over MoP/SiO<Subscript>2</Subscript> catalyst prepared with sol-gel method

Silica-supported molybdenum phosphide, MoP/SiO₂ catalysts with different Mo weight loadings were prepared by temperature programmed reduction of the oxidic catalyst precursors, which were prepared via sol-gel technique using ethyl silicate-40 as silica source. Samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface area measurements, and their catalytic activity in hydrodesulfurization (HDS) was tested with dibenzothiophene (DBT) as model compound. XRD analysis revealed the amorphous nature of the catalyst up to 10 wt% Mo loading and the formation of crystalline MoP phase on amorphous silica support with higher Mo loading. BET surface area showed high surface area for catalysts prepared by sol-gel technique with lower Mo content, and the surface area decreased with increasing in Mo loading. The HDS results showed that prepared MoP/SiO₂ exhibited high HDS activity and stability toward the catalytic test. Among the series of catalysts prepared, MoP/SiO₂ containing 20 wt% Mo was found to be the most active catalyst. And the effects of reaction temperature and hydrogen pressure on conversion and product selectivity were investigated.     

Cu/ZnO/AlOOH catalyst for methanol synthesis through CO<Subscript>2</Subscript> hydrogenation

Catalytic conversion of CO₂ to methanol is gaining attention as a promising route to using carbon dioxide as a new carbon feedstock. AlOOH supported copper-based methanol synthesis catalyst was investigated for direct hydrogenation of CO₂ to methanol. The bare AlOOH catalyst support was found to have increased adsorption capacity of CO₂ compared to conventional Al₂O₃ support by CO₂ temperature-programmed desorption (TPD) and FT-IR analysis. The catalytic activity measurement was carried out in a fixed bed reactor at 523 K, 30 atm and GHSV 6,000 hr^?1 with the feed gas of CO₂/H₂ ratio of 1/3. The surface basicity of the AlOOH supported Cu-based catalysts increased linearly according to the amount of AlOOH. The optimum catalyst composition was found to be Cu : Zn : Al=40 : 30 : 30 at%. A decrease of methanol productivity was observed by further increasing the amount of AlOOH due to the limitation of hydrogenation rate on Cu sites. The AlOOH supported catalyst with optimum catalyst compositions was slightly more active than the conventional Al₂O₃ supported Cu-based catalyst.     

Gas-phase epoxidation of butadiene: Effect of the concentration and distribution of cesium on the properties of the Ag/α-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst

Using the well-known patent methods, we have synthesized 1,3-butadiene epoxidation α-Al₂O₃ supported catalysts containing 15 wt % of Ag and 250–1500 ppm of Cs (Johnson Matthey, H16P07). The physicochemical properties of samples are systematically studied by varying the dispersion of supported silver, the amount of an introduced promoter, and its distribution over the surface of a catalyst. Catalytic tests of samples show that the optimum amount of a promoter depends directly on the surface of a catalyst. With optimum promotion, the steady-state activity of catalysts is determined by the dispersion of supported silver. In the course of catalytic tests, it is established that the shape of kinetic curves is governed by the excess or lack of Cs in a catalyst, thus providing a method for optimizing the concentration of the promoter. An analysis of the energy dispersion spectra (EDS) is applied for the first time to study the distribution of Cs over the surface of promoted catalysts. It is shown that thermal treatment favors the uniform distribution of a promoter over the surface of a catalyst and shortens the time required to attain its steady-state activity in catalytic tests. In our work, the steady-state productivity of catalysts reaches 0.5 g of 3,4-epoxy-1-butene per gram of the catalyst per hour, thus exceeding the claimed patent values.     

Properties of unsupported MoS<Subscript>2</Subscript> species produced in the preparation of MoS<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> using a sonochemical method

Unsupported MoS₂ particles, which were produced in the preparation of MoS₂/Al₂O₃ using a sonochemical method, were successfully separated from the prepared sample catalyst by adding oleylamine as an agent for dispersing the unsupported particles. The fraction of the unsupported MoS₂, which was estimated based on Mo balance, varied between 0.03 and 0.4, independent of the Mo loading levels investigated (6–54 wt% of Mo). The activity of the unsupported MoS₂ for the hydrodesulfurization of dibenzothiophene was nearly the same as that of the Al₂O₃-supported MoS₂, indicating that the activity of the prepared catalyst was not affected by the presence of the unsupported MoS₂ particles.     

Effects of La<Subscript>2</Subscript>O<Subscript>3</Subscript> on ZrO<Subscript>2</Subscript> supported Ni catalysts for autothermal reforming of CH<Subscript>4</Subscript>

The effect of La₂O₃ content in Ni-La-Zr catalyst was investigated for the autothermal reforming (ATR) of CH₄. The catalysts were prepared by the coprecipitation method and had a mesoporous structure. Temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) indicated that a strong interaction developed between Ni species and the support with the addition of La₂O₃. Thermogravimetric analysis (TGA) and H₂-pulse chemisorption showed that the addition of La₂O₃ led to well dispersed NiO molecules on the support. Ni-La-Zr catalysts gave much higher CH₄ conversion than Ni-Zr catalyst. The Ni-La-Zr containing 3.2 wt% La₂O₃ showed the highest activity. The optimum conditions for maximal CH₄ conversion and H₂ yield were H₂O/CH₄=1.00, O₂/CH₄=0.75. Under these conditions, CH₄ conversion of 83% was achieved at 700 °C. In excess O₂ (O₂/CH₄>0.88), the catalytic activity was decreased due to sintering of the catalyst.     

Ternary Pt<Subscript>45</Subscript>Ru<Subscript>45</Subscript>M<Subscript>10</Subscript>/C (M=Mn,Mo and W) catalysts for methanol and ethanol electro-oxidation

Ternary Pt₄₅Ru₄₅Mn₁₀/C, Pt₄₅Ru₄₅Mo₁₀/C and Pt₄₅Ru₄₅W₁₀/C catalysts were synthesized and physical and electrochemical properties were characterized. Particle sizes of the catalysts were determined by X-ray diffraction to be 3.9, 4.8 and 4.6 nm for the Mn, Mo and W incorporated catalysts, respectively. Electrochemically active surface areas were calculated from CO stripping results, which were 17.7, 17.2 and 15.7 m²/g _catal for the Pt₄₅Ru₄₅Mn₁₀/C, Pt₄₅Ru₄₅Mo₁₀/C and Pt₄₅Ru₄₅W₁₀/C catalysts, respectively. In methanol electro-oxidation, the Pt₄₅Ru₄₅W₁₀/C catalyst showed highest mass and specific activities of 2.78 A/g _cat. and 177 mA/m², respectively, which were 22 and 100% higher than those of commercial PtRu/C. In the case of ethanol electro-oxidation, the Pt₄₅Ru₄₅Mo₁₀/C catalyst exhibited highest mass and specific activities of 4.8 A/g _catal and 280 mA/m², respectively. Specific activity of the Pt₄₅Ru₄₅Mo₁₀/C catalyst was 56% higher than that of the commercial PtRu/C.     

Influence of phosphorous addition on Bi<Subscript>3</Subscript>Mo<Subscript>2</Subscript>Fe<Subscript>1</Subscript> oxide catalysts for the oxidative dehydrogenation of 1-butene

Bi₃Mo₂Fe₁P _x oxide catalysts were prepared by a co-precipitation method and the influence of phosphorous content on the catalytic performance in the oxidative dehydrogenation of 1-butene was investigated. The addition of phosphorous up to 0.4mole ratio to Bi₃Mo₂Fe₁ oxide catalyst led to an increase in the catalytic performance; however, a higher phosphorous content (above P=0.4) led to a decrease of conversion. Of the tested catalysts, Bi₃Mo₂Fe₁P_0.4 oxide catalyst exhibited the highest catalytic performance. Characterization results showed that the catalytic performance was related to the quantity of a π-allylic intermediate, facile desorption behavior of adsorbed intermediates and ability for re-oxidation of catalysts.     

Single-step polyol synthesis of alloy Pt<Subscript>7</Subscript>Sn<Subscript>3</Subscript> versus bi-phase Pt/SnO<Subscript>x</Subscript> nano-catalysts of controlled size for ethanol electro-oxidation

Disordered alloy and bi-phase PtSn nanoparticles of nominal Pt:Sn ratio of 70:30 atomic % with controlled size and narrow size distribution were synthesized using a single-step polyol method. By adjusting the solution pH it was possible to obtain Pt₇Sn₃ nanoparticles of various sizes from 2.8 to 6.5 nm. We found that the presence of NaOH in the synthesis solution not only influenced the nanoparticle size, but as it was revealed by XRD, it apparently also dictated the degree of Pt and Sn alloying. Three catalysts prepared at lower NaOH concentrations (C_NaOH < 0.15 M) showed disordered alloy structure of the nominal composition, while the other three catalysts synthesized at higher NaOH concentrations (C_NaOH > 0.15 M) consisted of bi-phase nanoparticles comprising a crystalline phase close to that of pure Pt together with an amorphous Sn phase. These observations are plausibly due to the phase separation and formation of monometallic Pt and amorphous SnO_x phases. A proposed reaction mechanism of Pt₇Sn₃ nanoparticle formation is presented to explain these observations along with the catalytic activities measured for the six synthesized carbon-supported Pt₇Sn₃ catalysts. The highest catalytic activity towards ethanol electro-oxidation was found for the carbon-supported bi-phase catalyst that formed the largest Pt (6.5 nm) nanoparticles and SnO_x phase. The second best catalyst was a disordered alloy Pt₇Sn₃ catalyst with the second largest nanoparticle size (5 nm), while catalysts of smaller size (4.5–4.6 nm) but different structure (disordered alloy vs. bi-phase) showed similar catalytic performance inferior to that of the 5 nm disordered alloy Pt₇Sn₃ catalyst. This work demonstrated the importance of producing bi-metallic PtSn catalysts with large Pt surfaces in order to efficiently electro-oxidize ethanol.     

Co<Subscript>x</Subscript>P<Subscript>y</Subscript> Catalysts in HDO of Phenol and Dibenzofuran: Effect of P content

Cobalt phosphide catalysts supporting on SiO₂ presenting different Co_xP_y stoichiometry were proved in hydrodeoxygenation (HDO) of two different model molecules present in biomass derived bio-oil such as phenol (Ph) and dibenzofuran (DBF). To investigate composition effects a series of cobalt phosphide catalysts presenting different initial P/Co atomic ratio were prepared. The catalysts were characterized by a range of techniques (N₂ physisorption, XRD, TEM, NH₃-TPD and XPS) and tested for DBF and Ph HDO activity and selectivity. Characterization results evidenced good textural properties, high dispersion of the active phase, as well as the presence of acid sites after P and Co incorporation. The highest activity was observed for catalysts containing an intermediate P/Co content were the CoP phase was the predominat one. Those catalyst containing Co₂P or CoP₂ phases were less active in these reactions.     

Unexpected Support Effect in Hydrotreating: Evidence of a Metallic Character for ReS<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and ReS<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> Catalysts

Abstract  

Rhenium sulfide based catalysts were prepared by the incipient wetness impregnation method over alumina and silica supports and evaluated for 4,6-dimethyldibenzothiophene hydrodesulfurization in a high-pressure stirred-tank reactor. The catalyst prepared over silica was about six times more active for hydrodesulfurization than the corresponding catalyst prepared over alumina and a NiMo/Al₂O₃ industrial reference catalyst. This surprising and positive SiO₂ support effect was explained by a metallic character of the supported sulfide, which was demonstrated using a kinetic approach of competitive hydrogenations and by XPS characterization.     

Performance of Ni catalyst supported on La-hexaaluminate in CO<Subscript>2</Subscript> reforming of CH<Subscript>4</Subscript>

CO₂ reforming of CH₄ was performed using Ni catalyst supported on La-hexaaluminate which has been an well-known material for high-temperature combustion. La-hexaaluminate was synthesized by sol-gel method at various conditions where different amount of Ni (5–20 wt%) was loaded. Ni/La-hexaaluminate experienced 72 h reaction and its catalytic activity was compared with that of Ni/Al₂O₃, Ni/La-hexaaluminate shows higher reforming activity and resistance to coke deposition compared to the Ni/Al₂O₃ model catalyst. Coke deposition increases proportionally to Ni content. Consequently, Ni(5)/La-hexaaluminate(700) is the most efficient catalyst among various Ni/La-hexaaluminate catalysts regarding the cost of Ni in Ni(X)/La-hexaaluminate catalysts. BET surface area, XRD, EA, TGA and TPO were performed for surface characterization. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Hierarchical ordered meso/macroporous H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript>/SiO<Subscript>2</Subscript> catalysts with superior oxidative desulfurization activity

A series of phosphotungstic acid (HPW)/SiO₂ materials with hierarchical meso/macroporous structure were synthesized by evaporation-induced self-assembly method (EISA), using nonionic surfactant (P123) and polystyrene (PS) spheres as templates. SEM images displayed uniform macropores with an average pore size of 210 nm. TEM, small-angle XRD and N₂ adsorption–desorption isotherms confirmed the existence of the ordered mesoporous structures, embedded in the wall of macropores. The wild-angle XRD and FT-IR spectra proved Keggin-type HPW dispersed homogeneously in the silica framework. With the amount of added PS spheres, the density of the macropores increased, the hierarchically ordered porous HPW/SiO₂ possessed two-dimensional (2D) hexagonal (p6mm) mesostructures and uniform periodic macropores. The ODS catalytic activity of these samples were tested, the result showed that the meso/macroporous HPW/SiO₂ catalyst with proper PS beads usage displayed much higher catalytic activity than other catalysts. In addition, the reusability of the meso/macroporous HPW/SiO₂ catalyst was investigated, the activity of catalyst has not obviously decreased even after eight times.     

Catalytic hydrocracking of bitumen at mild experimental condition

Mo-containing catalysts were prepared by impregnation method using silica-based porous supports and their physical properties were characterized by BET, XRD and TEM. Catalytic hydrocracking of bitumen extracted from oil sand was carried out in a high pressure reactor using Athabasca oil sand over 5 wt% Mo containing catalyst supported on SiO₂, MCF(Meso Cellular Foam) and SBA-15, respectively, under the conditions of 200 °C, 20 h and 10 atm of H₂ gas. Catalytic hydrocracking activity was estimated by analyzing H/C mole ratio based on EA data, and TGA was employed to compare the thermal behavior of bitumen before and after reaction. Upon hydrocracking over Mo/MCF catalyst, H/C was increased from 1.50 (bitumen itself) to 1.66.     

Effect of calcination atmospheres on the catalytic performance of nano-CeO<Subscript>2</Subscript> in direct synthesis of DMC from methanol and CO<Subscript>2</Subscript>

Nano-CeO₂ was prepared through the calcination of Ce(OH)₃ precursor in different atmospheres (H₂, Ar, air, O₂), which was prepared by a hydrothermal method, and then used as catalysts in the direct synthesis of dimethyl carbonate (DMC) from methanol and CO₂. The results indicated that the catalyst calcined in O₂ (CeO₂-O₂) showed an optimum catalytic performance, and the yield of DMC reached to 1.304 mmol/mmol_cat. In addition, reaction temperature and weight of catalyst were optimized. Based on characterizations of the catalysts, the ratio of Ce(IV)/Ce(III) and Lewis acid-base property of nano-CeO₂ catalyst could be adjusted through different calcination atmosphere treatment. It was determined that the higher activity of CeO₂-O₂ catalyst is mainly attributed to its higher ratio of Ce(IV)/Ce(III) as well as abundant and moderate intensity Lewis acid base sites.     

Synthesis of nickel catalysts supported on Zr-doped ordered mesoporous Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and their catalytic performance for low-temperature CO<Subscript>2</Subscript> reforming of CH<Subscript>4</Subscript>

A series of Zr-doped ordered mesoporous Al₂O₃ with various Zr contents were synthesized by evaporation-induced self-assembly strategy and the Ni-based catalysts supported on these Al₂O₃ materials were prepared by impregnation method. These catalysts with large specific surface area, big pore volume, uniform pore size possess excellent catalytic performance for the low-temperature carbon dioxide reforming of methane. The activities of these catalysts were tested in carbon dioxide reforming of methane reaction with temperature increasing from 500 to 650?°C and the stabilities of these catalysts were evaluated for long time reaction at 650?°C. It was found that when Zr/(Zr?+?Al) molar ratio?=?0.5%, the Ni/0.5ZrO₂–Al₂O₃ catalyst showed the highest activity, and exhibited superior stabilization compared to the Ni-based catalyst supported on traditional ordered mesoporous Al₂O₃. The “confinement effect” from mesoporous channels of alumina matrix is helpful to stabilize the Ni nanoparticles. As a promoter, Zr could stabilize the ordered mesoporous framework by reacting with Al₂O₃ to form ZrO₂–Al₂O₃ solid solution. Since ZrO₂ enhances the dissociation of carbon dioxide, more oxygen intermediates are given to remove the carbon formed during the reaction.     

Synthesis of Phytosteryl Esters by Using Alumina-Supported Zinc Oxide (ZnO/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>) from Esterification Production of Phytosterol with Fatty Acid

The feasibility of zinc oxide-catalyzed esterification of natural phytosterols with oleic acid was investigated well by a chemical process. The influences of various reaction parameters were evaluated. Basic solid zinc oxide is the most desirable catalyst due to its high selectivity (more than 90%), reusability, activity and less corrosivity, whereas sterol selectivity with other catalysts, such as H₂SO₄, NaHSO₄ and NaOMe, did not exceed 80%. Further results showed that during zinc oxide-catalyzed synthesis, the nature of the acyl donor was of paramount importance with direct esterification with fatty acids, which gives better results with higher conversion rate selectivity and more mild reaction conditions than transesterification with methyl esters. The substrate molar ratio of 2:1 (oleic acid/phytosterol) was optimal. Other parameters such as optimal catalyst load (0.5%) and temperature (170 °C) showed a maximum production of steryl esters close to 98% after 8 h. It was also found that the amount of trans fatty acid formed in esterification was low, and the trans fatty acid content (%) in the phytosterol oleate ester fraction (3.26%) was much lower than that in free oleic oil (7.35%), which suggested that fatty acids in esters were more stable than free fatty acids regarding the combination with sterol. Immobilized ZnO could be a promising catalyst for replacing homogeneous and corrosive catalysts for esterification reactions of sterol.