Solvent free synthesis of chalcone and flavanone over zinc oxide supported metal oxide catalysts

Liquid phase Claisen–Schmidt condensation between 2′-hydroxyacetophenone and benzaldehyde to form 2′-hydroxychalcone, followed by intramolecular cyclisation to form flavanone was carried out over zinc oxide supported metal oxide catalysts under solvent free condition. The reaction was carried out over ZnO supported MgO, BaO, K₂O and Na₂O catalysts with 0.2 g of each catalyst at 140 °C for 3 h. Magnesium oxide impregnated zinc oxide was observed to offer higher conversion of 2′-hydroxyacetophenone than other catalysts. Further MgO impregnated with various other supports such as HZSM-5, Al₂O₃ and SiO₂ were also used for the reaction to assess the suitability of the support. The order of activity of the support is ZnO > SiO₂ > Al₂O₃ > HZSM-5. Various weight percentage of MgO was loaded on ZnO to optimize maximum efficiency of the catalyst system. The impregnation of MgO (wt%) in ZnO was optimized for better conversion of 2′-hydroxyacetophenone. The effect of temperature and catalyst loading was studied for the reaction.     

Selective gas-phase conversion of maleic anhydride to propionic acid on Pt-based catalysts

Pt-based catalysts, supported on Al₂O₃, SiO₂ and SiO₂–Al₂O₃, were prepared by incipient wetness impregnation and tested in the gas phase hydrogenation of maleic anhydride at atmospheric pressure and 240 °C. In these conditions, the hydrogenolytic activity pattern was: Pt/SiO₂ > Pt/Al₂O₃ > Pt/SiO₂–Al₂O₃, which is just the opposite of the support acidity trend. These metal Pt-based catalysts showed high selectivity to propionic acid, which was always higher than 80%. The selectivity pattern to this product was: Pt/Al₂O₃ > Pt/SiO₂ > Pt/SiO₂–Al₂O₃. Both activity and selectivity patterns may be explained on the basis of metal-support interaction and support acidity.     

Hydrodeoxygenation of phenol over Pd catalysts by in-situ generated hydrogen from aqueous reforming of formic acid

Hydrodeoxygenation of phenol, as model compound of bio-oil, was investigated over Pd catalysts, using formic acid as a hydrogen donor. The order of activity for deoxygenation of phenol with Pd catalysts was found to be: Pd/SiO₂ > Pd/MCM-41 > Pd/CA > Pd/Al₂O₃ > Pd/HY ≈ Pd/ZrO₂ ≈ Pd/CW > Pd/HSAPO-34 > Pd/HZSM-5. The good performance of Pd/SiO₂ is owing to its proper pore structure and large specific surface area. The high level of Brønsted acid sites in SiO₂ also favors the deoxygenation of phenol.     

Shape-selective amination of EO over HZSM-5 for MEA and DEA

Shape-selective amination of ethylene oxide over HZSM-5 was thoroughly investigated. TPD, FTIR and catalytic performance showed that HZSM-5 was more active than the sodium form. Relative selectivity of product was mainly controlled by the crystal size of ZSM-5. Surface modification such as silyation was effective for enhancing the shape selectivity. Among the catalysts tested in this study, HZSM-5 with SiO₂/Al₂O₃ ratio being 76.7 exhibited the best performance. At 353 K and total pressure of 8.0 MPa the total selectivity of MEA and DEA was 97.6%, the yield reached 96.6%, the best performance achieved so far among EO amination.     

Characterization and catalytic application of MnCl2 modified HZSM-5 zeolites in synthesis of aromatics from syngas via dimethyl ether

The conversion of syngas to aromatics via dimethyl ether was investigated over MnCl₂ modified HZSM-5 zeolites. The results demonstrated that 2%MnCl₂ modified HZSM-5 (SiO₂/Al₂O₃ = 38) exhibited higher p-xylene selectivity than other catalysts and further decreased 1,2,4,5-tetramethylbenzene selectivity. The CO conversion was obviously increased after 5%MnCl₂ modification to HZSM-5. The catalysts were characterized by XRD, BET, XPS, FT-IR, NH₃-TPD, SEM, element analysis and O₂-TPO. The loading amount of MnCl₂ affected the adsorption and reaction of DME molecules on zeolites. Appropriate amount of MnCl₂ introduction could adjust the acidity and pore volume of HZSM-5 to increase p-xylene selectivity and CO conversion.     

Catalytic gasification of lignin with Ni/Al2O3–SiO2 in sub/supercritical water

Lignin has been gasified with a Ni/Al₂O₃–SiO₂ catalyst in sub/supercritical water (SCW) to produce gaseous fuels. XRD pattern at 6θ angle shows characteristic peaks of crystalline NiO, NiSi, and AlNi₃, suggesting that Al₂O₃–SiO₂ not only offers high surface area (122 m² g) for Ni, but also changes the crystal morphology of the metal. 9 mmol/g of H₂ and 3.5 mmol/g of CH₄ were produced at the conditions that 5.0 wt% alkaline lignin plus 1 g/g Ni/Al₂O₃–SiO₂ operating for 30 min at 550 °C. A kinetic model was also developed, and the activation energies of gas and char formation were calculated to be 36.68 ± 0.22 and 9.0 ± 2.4 kJ/mol, respectively. Although the loss of activity surface area during reuse caused slight activity reduction in Ni/Al₂O₃–SiO₂, the catalyst system still possessed high catalytic activity in generating H₂ and CH₄. It is noted that sulfur linkage could be hydrolyzed to hydrogen sulfide in the gasification process of alkaline lignin. The stable chemical states of Ni/Al₂O₃–SiO₂ grants its insensitivity to sulfur, suggesting that Ni/Al₂O₃–SiO₂ should be economically promising for sub/supercritical water gasification of biomass in the presence of sulfur.     

Phosphorus-containing activated carbon as acid support in a bifunctional Pt–Pd catalyst for tire oil hydrocracking

A bifunctional Pt–Pd catalyst supported on phosphorus-containing activated carbon has been prepared, characterized and tested in the hydrocracking of a hydrotreated tire pyrolysis oil. The product has a very interesting composition: 48–78 wt% naphtha and 19–42 wt% diesel fractions, with moderate amounts of aromatics (< 40 wt%) and sulfur (< 250 ppm). The challenge was to prepare a stable, porous, selective and acid carbonaceous catalyst from a waste (olive stone), which has been confirmed from the catalytic properties and product distribution point of view. In fact, phosphate groups in the activated carbon are stable hydrocracking sites, with comparable performance to that of the acid sites present in amorphous SiO₂–Al₂O₃.     

Analysis and removal of heteroatom containing species in coal liquid distillate over NiMo catalysts

Heteroatom containing molecules in South Banko coal liquid (SBCL) distillate were identified with a gas chromatograph equipped with an atomic emission detector (GC-AED). Thiophenes and benzothiophenes were found to be the major sulfur compounds. Pyridines, anilines, and phenols were the major nitrogen and oxygen compounds, respectively. Reactivities of heteroatom containing species in hydrotreatment over conventional NiMoS/Al₂O₃, NiMoS/Al₂O₃–SiO₂ catalysts were very different according to their cyclic structure as well as the kind of heteroatom in the species. The sulfur species were completely desulfurized over the catalysts examined in the present study by 60 min at 360 °C under initial hydrogen pressure of 5 MPa. However, hydrodenitrogenation was more difficult than hydrodesulfurization even at 450 °C. Anilines were found the most refractory ones among the nitrogen species. Hydrodeoxygenation of SBCL was also difficult in the hydrotreatment conditions examined in the present study. Dibenzofuran was the most refractory molecule among the oxygen species. A two-stage reaction configuration at 340 and 360 °C improved HDN and HDO reactivities, although the conversions were still insufficient. Increasing the acidity of the support as well as the loading of the metals on the NiMoS/Al₂O₃ catalysts improved very much the heteroatom reduction to achieve complete removal of nitrogen by two-stage reaction configuration at 340–360 °C and oxygen at 360 °C, respectively. The addition of H₂S in the reaction atmosphere inhibited the HDN reaction but increased markedly the HDO conversion. The acidic support increased the activity in hydrotreatment through enhancing the hydrogenation activity, while H₂S maintained the catalyst in a sufficiently sulfided state.     

The relation between morphology of (Co)MoS2 phases and selective hydrodesulfurization for CoMo catalysts

A series of CoMo catalysts were prepared by various methods with three different supports (Al₂O₃-1 of γ phase, Al₂O₃-2 containing γ and δ mixed phases, SiO₂). And the effect of morphology of (Co)MoS₂ phases on selective hydrodesulfurization was studied systematically. The TEM images showed, in general, the average slab length, the stacking number and the ratio of edge/corner of the sulfided catalysts increase remarkably in the order: SiO₂ > Al₂O₃-2 > Al₂O₃-1, with the extent of metal–support interaction decreasing in the order: SiO₂ < Al₂O₃-2 < Al₂O₃-1. And the hydrodesulfurization selectivity correlates linearly with the slab length (or the ratio of edge/corner) of (Co)MoS₂ phases, the longer average slab length, the higher ratio of edge/corner, and then the better hydrodesulfurization selectivity. Among all the catalysts, sulfided CoMo/SiO₂ of the longest average slab length and the highest edge/corner ratio exhibits the best hydrodesulfurization selectivity.     

Zr/HZSM-5 catalyst for NO reduction by C2H2 in lean-burn conditions

Zr-based zeolite catalysts were investigated for the first time in selective catalytic reduction of NO by hydrocarbon (HC-SCR). Highly dispersed zirconium species, especially the amorphous ultrafine zirconium oxide in the catalyst, considerably enhanced the activity for selective catalytic reduction of NO by acetylene (C₂H₂-SCR), both by accelerating the NO oxidation to NO₂ and enlarging the NO₂ adsorption capacity of the catalyst under the reaction conditions. Thus a durable and active Zr/HZSM-5 catalyst giving 89% of NO conversion to N₂ at 350 °C in 1600 ppm NO, 800 ppm C₂H₂, and 9.95% O₂ in helium was obtained. For the C₂H₂-SCR of NO, it was suggested that acidic sites with strong acidity on the Zr-based HZSM-5 catalysts are indispensable to initiate the aimed reaction via the route of NO oxidation to NO₂, which explains the higher activity for the reaction obtained over the Zr/HZSM-5 catalyst sample with lower SiO₂/Al₂O₃ ratio. The zirconium species could only functioned in the presence of protons in the C₂H₂-SCR of NO, so a synergistic effect between the zirconium species and protons of the Zr/HZSM-5 catalyst was proposed.     

Synthesizing carbon nanotubes and carbon nanofibers over supported-nickel oxide catalysts via catalytic decomposition of methane

Supported-NiO catalysts were tested in the synthesis of carbon nanotubes and carbon nanofibers by catalytic decomposition of methane at 550 °C and 700 °C. Catalytic activity was characterized by the conversion levels of methane and the amount of carbons accumulated on the catalysts. Selectivity of carbon nanotubes and carbon nanofiber formation were determined using transmission electron microscopy (TEM). The catalytic performance of the supported-NiO catalysts and the types of filamentous carbons produced were discussed based on the X-ray diffraction (XRD) results and the TEM images of the used catalysts. The experimental results show that the catalytic performance of supported-NiO catalysts decreased in the order of NiO/SiO₂ > NiO/HZSM-5 > NiO/CeO₂ > NiO/Al₂O₃ at both reaction temperatures. The structures of the carbons formed by decomposition of methane were dependent on the types of catalyst supports used and the reaction temperatures conducted. It was found that Al₂O₃ was crucial to the dispersion of smaller NiO crystallites, which gave rise to the formation of multi-walled carbon nanotubes at the reaction temperature of 550 °C and a mixture of multi-walled carbon nanotubes and single-walled carbon nanotubes at 700 °C. Other than NiO/Al₂O₃ catalyst, all the tested supported-NiO catalysts formed carbon nanofibers at 550 °C and multi-walled carbon nanotubes at 700 °C except for NiO/HZSM-5 catalyst, which grew carbon nanofibers at both 550 °C and 700 °C.     

Catalytic conversion of glucose to 5-hydroxymethylfurfural over nano-sized mesoporous Al2O3–B2O3 solid acids

A series of nano-sized mesoporous Al₂O₃–B₂O₃ catalysts with different molar ratios of Al/B were prepared from aluminum isopropoxide and boric acid through an evaporation-induced self-assembly (EISA) process, and were characterized by ICP-AES, FTIR (pyridine adsorption), XRD, NH₃-TPD, SEM, TEM, and N₂ adsorption–desorption. These catalysts were further used as solid acids in the catalytic conversion of glucose to 5-hydroxymethylfurfural (HMF). An optimized HMF yield of 41.4% was obtained within 120 min at 140 °C over Al₂O₃–B₂O₃ (Al/B = 5:5). It was demonstrated that catalysts with the presence of Lewis acid sites were more favorable for the formation of HMF.     

Crystallisation of amorphous spray-dried precursors in the Al2O3–SiO2 system

The crystallisation of amorphous precursors has been studied in the whole range of composition in the Al₂O₃–SiO₂ system. The amorphous precursors have been obtained by hydrolysing TEOS directly in a diluted aqueous solution of aluminium nitrate, spray drying the clear solution and heating the resulting powder. Up to 70 mol % Al₂O₃, only mullite crystallises around 980–1000 °C; between 70 and 80 mol % Al₂O₃ mullite and spinel crystallise together; and for more than 80 mol % Al₂O₃ only spinel is formed. In the 70–80 mol % Al₂O₃ range of composition, when both mullite and spinel crystallise, low heating favours the crystallisation of mullite and it is nearly possible to crystallise only mullite from a 75 mol % Al₂O₃ sample. By rapid heating it is also possible to crystallise only spinel from the same 75 mol % Al₂O₃ precursor. The enthalpy and the activation energy for crystallisation are maximum for 60–80 mol % Al₂O₃. Heating the samples up to 1700 °C for 1 h, the phase equilibrium is not reached, particularly when both mullite and spinel crystallise together, and θ-Al₂O₃ is still present.     

Two-step process for synthesis of a single phase Na–A zeolite from coal fly ash by dialysis

Using the amorphous aluminosilicate in coal fly ash (FA), a single phase Na–A zeolite was synthesized from FA by dialysis. The FA and NaOH solution added into the tube made by semipermeable membrane were pretreated in the same NaOH solution at 85 °C for 24 h. After the pretreatment, the tube was removed and NaOH–NaAlO₂ solution was added into the residual solution to control SiO₂/Al₂O₃ molar ratio of the solutions from 0.9 to 4.3. The precipitates thus formed were aged for 24 h at 85 °C. The amorphous aluminosilicate in FA was dissolved during the pretreatment. When the NaOH–NaAlO₂ solution was added into the solution after the pretreatment and then aged, white precipitates were yielded over the whole SiO₂/Al₂O₃ range. At SiO₂/Al₂O₃=0.9, the material formed was identified as a single phase Na–A zeolite. The Na–X zeolite was slightly produced at SiO₂/Al₂O₃≥1.7.     

A new and economic approach to fabricate resistant porous membrane supports using kaolin and CaCO3

This new and economic approach to fabricate resistant porous membrane supports consists of Algerian kaolin and calcite (CaCO₃) instead of Al₂O₃. The porous mullite (3Al₂O₃·2SiO₂) and anorthite (CaO·Al₂O₃·2SiO₂) based ceramics were obtained by solid state reaction. Different calcite amounts (10–28 wt%) have been added into kaolin halloysite type (Al₂O₃·2SiO₂·4H₂O) in order to control pores forming with appropriate distribution and sizes. Based on a pore distribution and formed phases, a kaolin + 15 wt% calcite (K15C) mixture was selected for flat and tubular configurations. A porosity of 45–52% was also obtained when K15C compacts were sintered at 1100–1250 °C. For example, porosity, average pore size (APS) and 3 point flexural strength were 49%, 3 μm and 87 MPa (same as Al₂O₃ value), respectively when K15C compacts were sintered at 1250 °C for 1 h. Finally, a correlation between microstructure and mechanical properties of elaborated supports has been discussed.     

Dielectric properties of composition spread SiO2–Al2O3 mixed phase thin films deposited at room temperature by off-axis RF magnetron sputtering

The dielectric properties of composition spread SiO₂–Al₂O₃ thin films deposited by off-axis radio-frequency magnetron sputtering at room temperature were explored to obtain optimized compositions, which have low dielectric constants and losses. The specific points (compositions) showing superior dielectric properties of low dielectric constants (8.13 and 9.12) and losses (tanδ ～0.02) at 1 MHz were found in area of the distance of 25.0 mm (Al₂Si₃O₈) and 42 mm (Al_2.4Si₃O₈) apart from SiO₂ target side in 75 mm × 25 mm sized Pt/Ti/SiO₂/Si(1 0 0) substrates, respectively. The specific thin films were amorphous phase and the compositions were Al₂Si₃O₈ (k ～8.13) and Al_2.4Si₃O₈ (k ～9.12).     

Effect of Al2O3 content on BaO–Al2O3–B2O3–SiO2 glass sealant for solid oxide fuel cell

The glass structure, wetting behavior and crystallization of BaO–Al₂O₃–B₂O₃–SiO₂ system glass containing 2–10 mol% Al₂O₃ were investigated. The introduction of Al₂O₃ caused the conversion of [BO₃] units and [BO₄] units to each other and it played as glass network former when the content was up to 10 mol%, accompanied by [BO₄] → [BO₃]. The stability of the glass improved first and then decreased as Al₂O₃ increased from 2 to 10 mol%, the glass with 5 mol% Al₂O₃ being the most stable one. The wetting behavior of the glasses indicates that excess Al₂O₃ leads to high sealing temperature. The glass containing 5 mol% Al₂O₃ characterized by a lower sealing temperature is suitable for SOFC sealing. Al₂O₃ improves the crystallization temperature of the glass. The crystal phases in the reheated glasses are mainly composed of Ba₂Si₃O₈, BaSiO₃, BaB₂O₄ and BaAl₂Si₂O₈. Al₂O₃ helps the crystallization of BaSiO₃ and BaAl₂Si₂O₈.     

Identification of the coke accumulation and deactivation sites of Mo2C/HZSM-5 catalyst in CH4 dehydroaromatization

Identifying the preferentially coking sites of Mo₂C/HZSM-5 catalyst in the CH₄ dehydroaromatization at non-oxidative conditions was attempted by employing a physically separable Mo₂C/α-Al₂O₃ + HZSM-5 mixture instead of Mo₂C/HZSM-5 as catalyst. Photographic observation on the spent Mo₂C/α-Al₂O₃ and HZSM-5 components separated from the deactivated mixture and their thermogravimetric analysis clearly revealed that coke accumulation occurred predominantly on the HZSM-5. Then, the comparative activity tests with the physical blends of the deactivated Mo₂C/α-Al₂O₃ + HZSM-5 mixture sample with fresh Mo₂C/α-Al₂O₃ or HZSM-5 further confirmed that the coked HZSM-5 component in the deactivated mixture definitely deactivated while that un-coked Mo₂C constituent remained highly active.     

Utilization of recycled paper processing residues and clay of different sources for the production of porous anorthite ceramics

Production of porous anorthite ceramics from mixtures of paper processing residues and three different clays are investigated. Suitability of three different clays such as enriched clay, commercial clay and fireclay for manufacturing of anorthite based lightweight refractory bricks was studied. Porous character to the ceramic was provided by addition of paper processing residues (PPR). Samples with 30–40 wt% PPR fired at 1200–1400 °C contained anorthite (CaO·Al₂O₃·2SiO₂) as major phase and some minor secondary phases such as mullite (3Al₂O₃·2SiO₂) or gehlenite (2CaO·Al₂O₃·SiO₂), depending on the calcite to clay ratio. Anorthite formation for all clay types was quite successful in samples with 30–40 wt% of paper residues fired at 1300 °C. A higher firing temperature of 1400 °C was needed for the fireclay added samples to produce a well sintered product with large pores. Gehlenite phase occurred mostly at lower temperatures and in samples containing higher amount of calcium (50 wt% PPR). Compressive strength of compacted and fired pellets consisting of mainly anorthite ranged from 8 to 43 MPa.     

Esterification of octanoic acid using SiO2 doped sulfated aluminum-based solid acid as catalyst

In this paper, SO₄^2 −/Al₂O₃-SiO₂ (SAS) was prepared and used for the esterification of octanoic acid with methanol. The effect of introduction of SiO₂ was characterized by nitrogen sorption, ICP-AES, XRD, NH₃-TPD, TG, FTIR and FTIR-pyridine adsorption. The results demonstrated that the doping of SiO₂ resulted in the increase of BET surface areas and amount of surface sulfur species which led to an increase of acid sites especially Brönsted acid sites, which consequently boosted the catalytic esterification activity. In addition, the introduction of SiO₂ can also increase the thermal stability of SO₄^2 − and its interaction with Al₂O₃ support which resulted in the alleviation of catalyst deactivation.