Highly Efficient Oxidation of Toluene to Benzoic Acid Catalyzed by Manganese Dioxide and <Emphasis Type="Italic">N</Emphasis>-Hydroxyphthalimide

Abstract  

Benzoic acid could be efficiently prepared from aerobic oxidation of toluene using manganese dioxide (MnO₂) and N-hydroxyphthalimide (NHPI) as catalysts. The conditions of oxidation, including temperature, amount of catalyst, dioxygen pressure and reaction time, were studied in details. Thus 94.4% conversion of toluene and 98.4% selectivity of benzoic acid could be obtained at 110 °C under 0.3 MPa for 3 h in the presence of 10 mol% NHPI and 4 mol% MnO₂.     

Aqueous-Phase Hydrogenolysis of Glycerol to 1,3-propanediol Over Pt-H<Subscript>4</Subscript>SiW<Subscript>12</Subscript>O<Subscript>40</Subscript>/SiO<Subscript>2</Subscript>

Abstract  

Hydrogenolysis of glycerol to 1,3-propanediol in aqueous-phase was investigated over Pt-H₄SiW₁₂O₄₀/SiO₂ bi-functional catalysts with different H₄SiW₁₂O₄₀ (HSiW) loading. Among them, Pt-15HSiW/SiO₂ showed superior performance due to the good dispersion of Pt and appropriate acidity. It is found that Br?nsted acid sites facilitate to produce 1,3-PDO selectively confirmed by Py-IR. The effects of weight hourly space velocity, reaction temperature and hydrogen pressure were also examined. The optimized Pt-HSiW/SiO₂ catalyst showed a 31.4% yield of 1,3-propanediol with glycerol conversion of 81.2% at 200 °C and 6 MPa.     

Liquefaction of giant fennel (Ferula orientalis L.) in supercritical organic solvents: Effects of liquefaction parameters on product yields and character

Ferula orientalis L. stalks were liquefied in an autoclave in supercritical organic solvents (methanol, ethanol, 2-propanol, acetone and 2-butanol) with (NaOH, Na₂CO₃, ZnCl₂) and without catalyst at five different temperatures ranging from 240 °C to 320 °C. The amounts of solid (unconverted raw material), liquid (bio-oil) and gas produced, as well as the composition of the resulting liquid phase, were determined. The effects of various parameters such as temperature, solvent, catalyst and ratio of catalyst on product yields were investigated. The results showed that conversion highly depends on the temperature and catalyst. The highest bio-oil yield (53.97%) was obtained using acetone with 10% zinc chloride at 300 °C. The liquid products were extracted with benzene and diethyl ether. Some of selected liquid products (bio-oils) were analyzed by elemental, FT-IR and GC–MS. 126 different compounds were identified by GC–MS in the liquid products obtained in ethanol at 300 °C.     

Influence of Reaction Conditions on Diacid Formation During Au-Catalyzed Oxidation of Glycerol and Hydroxymethylfurfural

The selective oxidation of glycerol and 5-hydroxymethylfurfural (HMF) to diacids over supported gold catalysts (Au/C and Au/TiO₂) in liquid water at mild temperatures was a strong function of the added base such as NaOH. Use of hydrotalcite as a solid base in place of NaOH in the HMF reaction medium facilitated the production of diacid over Au/TiO₂, but extensive leaching of magnesium suggested that hydrotalcite was consumed stoichiometrically in the reaction. Production of diacids from glycerol oxidation over supported Au catalysts was promoted by operating in a continuous flow reactor and by increasing the catalyst loading in a semi-batch reactor. Trace inhibitors formed by conversion of the product monoacid are proposed to account for the generally low selectivity to diacids over gold catalysts.     

Vapor phase oxidation of dimethyl sulfide with ozone over V2O5/TiO2 catalyst

The removal of volatile and odorous emissions from pulp and paper industrial processes usually generates secondary pollution which is treated further by scrubbing, adsorption, and catalytic incineration. Studies using a flow reactor packed with 10% vanadia/titania (V₂O₅/TiO₂) catalyst showed complete conversion of dimethyl sulfide (DMS) in the presence of ozone. The molar yields of partial oxidation products were only 10–20%. Small amounts of partial oxidation products, such as and dimethyl sulfone (DMSO₂), dimethyl disulfide (DMDS), and dimethyl sulfoxide (DMSO), were also formed. The results of the oxidation of DMS using ozone only, ozone plus catalyst, and oxygen plus catalyst suggest that the combined use of O₃ with catalyst is essential for the complete destruction of DMS to CO₂ and SO₂. A Box-Behnken design was used to determine the factors that have a significant effect on the conversion and selectivity of the products. It was concluded that product selectivity is strongly influenced by temperature, gas hourly space velocity (GHSV), and ozone concentration. The catalysts were characterized using XRD, surface area measurements, and SEM techniques. Time-on-stream studies carried out in a 500 ppmv gas stream held at 150 °C for 6 h, using 2 g of the catalyst, an ozone-to-DMS molar ratio of 0.9, and a GHSV of 37,000 h⁻¹, yielded 99.9% conversion of DMS. A plausible reaction mechanism has been proposed for the oxidation of DMS based on reaction product distribution and possible intermediates formed.     

Selective Allylic oxidation of Cyclohexene by a Magnetically Recoverable Cobalt Oxide Catalyst

Abstract  

In this work, we prepared a new magnetically recoverable CoO catalyst through the deposition of the catalytic active metal nanoparticles of 2–3 nm on silica-coated magnetite nanoparticles to facilitate the solid separation from liquid media. The catalyst was fully characterized and presented interesting properties in the oxidation of cyclohexene, as for example, selectivity to the allylic oxidation product. It was also observed that CoO is the most active species when compared to Co²⁺, Co₃O₄ and Fe₃O₄ in the catalytic conditions studied.     

Vapor phase oxidation of dimethyl sulfide with ozone over V2O5/TiO2 catalyst

The removal of volatile and odorous emissions from pulp and paper industrial processes usually generates secondary pollution which is treated further by scrubbing, adsorption, and catalytic incineration. Studies using a flow reactor packed with 10% vanadia/titania (V₂O₅/TiO₂) catalyst showed complete conversion of dimethyl sulfide (DMS) in the presence of ozone. The molar yields of partial oxidation products were only 10–20%. Small amounts of partial oxidation products, such as and dimethyl sulfone (DMSO₂), dimethyl disulfide (DMDS), and dimethyl sulfoxide (DMSO), were also formed. The results of the oxidation of DMS using ozone only, ozone plus catalyst, and oxygen plus catalyst suggest that the combined use of O₃ with catalyst is essential for the complete destruction of DMS to CO₂ and SO₂. A Box-Behnken design was used to determine the factors that have a significant effect on the conversion and selectivity of the products. It was concluded that product selectivity is strongly influenced by temperature, gas hourly space velocity (GHSV), and ozone concentration. The catalysts were characterized using XRD, surface area measurements, and SEM techniques. Time-on-stream studies carried out in a 500 ppmv gas stream held at 150 °C for 6 h, using 2 g of the catalyst, an ozone-to-DMS molar ratio of 0.9, and a GHSV of 37,000 h⁻¹, yielded 99.9% conversion of DMS. A plausible reaction mechanism has been proposed for the oxidation of DMS based on reaction product distribution and possible intermediates formed.     

Oxidation of 5-hydroxymethylfurfural over supported Pt, Pd and Au catalysts

Supported Pt, Pd, and Au catalysts were evaluated in the aqueous-phase oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) at 295 K and high pH in a semibatch reactor. The intermediate reaction product 5-hydroxymethyl-2-furancarboxylic acid (HFCA) was formed in high yield over Au/C and Au/TiO₂ at 690 kPa O₂, 0.15 M HMF and 0.3 M NaOH, but did not continue to react substantially to FDCA at the specified O₂ pressure and base concentration. In contrast, the final reaction product FDCA was formed over Pt/C and Pd/C under identical conditions. The initial turnover frequency of HMF conversion was an order of magnitude greater on Au catalysts compared to either Pt or Pd. Increasing the O₂ pressure and NaOH concentration facilitated the conversion of HFCA to FDCA over the supported Au. The significant influence of base concentration on the product distribution indicates an important role of OH⁻ in the activation, oxidation and degradation of HMF.     

Selective oxidation of HMF to DFF using Ru/γ-alumina catalyst in moderate boiling solvents toward industrial production

Selective oxidation of 5-hydroxymethyl-2-furfural (HMF) to 2,5-diformylfuran (DFF) toward industrial production was studied over Ru supported γ-alumina catalyst using molecular oxygen as an oxidant. From the solvents screening, considering recyclability after reaction, toluene was found to be the best solvent and gave maximum conversion of 99% with 97% DFF selectivity at 130 °C and 40 psi O₂ pressure. Catalyst was washed with NaOH solution of pH = 12 to remove the adsorbed polymer impurities and then reused up to 5 cycles. The product could be purified by simple evaporation of the solvent, which could add advantage for industrial process.     

An integrated catalytic approach for the production of hydrogen by glycerol reforming coupled with water-gas shift

Reaction kinetics measurements of glycerol conversion on carbon-supported Pt-based bimetallic catalysts at temperatures from 548 to 623 K show that the addition of Ru, Re and Os to platinum significantly increases the catalyst activity for the production of synthesis gas (H₂/CO mixtures) at low temperatures (548–573 K). Based on this finding, we demonstrate a gas phase catalytic process for glycerol reforming, based on the use of two catalyst beds that can be tuned to yield hydrogen (and CO₂) or synthesis gas at 573 K and a pressure of 1 atm. The first bed consists of a carbon-supported bimetallic platinum-based catalyst to achieve conversion of glycerol to a H₂/CO gas mixture, followed by a second bed comprised of a catalyst that is effective for water-gas shift, such as 1.0% Pt/CeO₂/ZrO₂. This integrated catalytic system displayed 100% carbon conversion of concentrated glycerol solutions (30–80 wt.%) into CO₂ and CO, with a hydrogen yield equal to 80% of the amount that would ideally be obtained from the stoichiometric conversion of glycerol to H₂ and CO followed by equilibrated water-gas shift with the water present in the feed.     

Biodiesel Preparation from Soybean Oil by Using a Heterogeneous Ca<Subscript>x</Subscript>Mg<Subscript>2−x</Subscript>O<Subscript>2</Subscript> Catalyst

Abstract  

An effective heterogeneous catalyst, Ca_xMg_2−xO₂, was prepared and tested for soybean oil transesterification with methanol. The catalysts were characterized by using X-ray diffraction , Fourier transform infrared spectra, thermo gravimetric and differential thermal analysis , and Hammett indicator method. The catalyst with Ca/Mg ratio of 1.0 and calcined at 800 °C exhibited high catalytic activities. Under the suitable transesterification conditions (methanol/oil ratio 12:1, catalyst loading 6 wt%, reaction time 5 h, at reflux of methanol), the oil conversion of 91.3% could be achieved. The catalyst can be easily recovered and reused without significant deactivation.     

Steam Reforming of Glycerin Using Ni-based Catalysts Loaded on CaO–ZrO2 Solid Solution

Abstract  

Steam reforming of glycerin on Ni-loaded catalyst was performed using a ZrO₂-based support material. The addition of CaO to ZrO₂ improved the catalyst performance, and NiO/CaO–ZrO₂ afforded glycerin conversion of 88.9% with an H₂ yield of 75.3% at 600 °C. Carbon formation decreased from 4.2 to 2.0% with CaO-added catalyst. Solid solution was formed with the addition of CaO to ZrO₂, and it exhibited basic characteristics. Further reduction of carbon formation during the reforming reaction was achieved by using a quaternary complex oxide catalyst NiO–CeO₂/CaO–ZrO₂, where glycerin conversion of 96.1% and a H₂ yield of 83.7% were achieved with carbon formation of 0.7% at 600 °C.     

Effective Utilization of the Catalytically Active Phase: NH<Subscript>3</Subscript> Oxidation Over Unsupported and Supported Co<Subscript>3</Subscript>O<Subscript>4</Subscript>

Abstract  

The performance of pellets of unsupported and silica-supported Co₃O₄ in the ammonia oxidation was investigated as a function of the particle size to investigate the utilization of the catalytically active phase in these materials. The obtained activity in terms of ammonia conversion over the silica-supported Co₃O₄ is higher compared to the conversion over the unsupported Co₃O₄, despite a lower cobalt oxide loading and more severe diffusional limitations. The effectiveness factor for the silica-supported catalyst is slightly lower than the effectiveness factor for the unsupported catalyst in the form of pellets of similar size. However, the effective utilization of cobalt within the catalyst is higher for the silica-supported catalyst, mainly due to the higher dispersion of the catalytically active phase.     

Efficient Conversion of Glycerol into High Value-Added Chemicals by Partial Oxidation

Glycerol can be effectively converted to glyceric acid, a high value-added pharmaceutical raw material, through its partial oxidation over an Au/Al₂O₃ catalyst under strongly basic conditions. The factors important for the highly selective production of glyceric acid were investigated experimentally. It was clarified that NaOH was involved in the glycerol activation step to a glycerol alkoxide intermediate (2, 3-dihydroxypropoxide) in the liquid phase, then glyceric acid was formed by OOH species derived from O₂ on an Au catalyst in the partial oxidation step. We have newly discovered the concerted effect of NaOH and O₂ in different reaction steps.     

Effects of Reaction Variables on Fischer–Tropsch Synthesis with Co-Precipitated K/FeCuAlO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Catalysts

Abstract  

The effects of reduction temperature and reaction temperature, pressure and space velocity on iron-based K/FeCuAlO _x Fischer–Tropsch catalysts prepared by co-precipitation were investigated. The catalyst reduced at 150 °C deactivated quickly due to an abundance of unreduced iron species. With increasing reduction temperature, the iron oxide’s phase transformed from hematite (α-Fe₂O₃) to magnetite (Fe₃O₄) and finally to metallic iron (α-Fe). The induction period to reach steady-state catalytic activity was reduced at increased reduction temperatures due to in situ reduction by syngas during reaction. CO conversion increased with increasing reaction temperature, and selectivity to C₅+ decreased with increasing reaction pressure and space velocity. At reaction temperatures up to of 300 °C, CO₂ formation by the water–gas shift reaction was linearly correlated with the extent of CO conversion, and CO₂ formation was slightly suppressed at ≥350 °C by a reverse water–gas shift reaction.     

Glycerol Hydrogenolysis to 1,2-Propanediol by Cu/ZnO/Al2O3 Catalysts

The effect of preparation methods on the Cu/ZnO/Al₂O₃ catalyst structure and catalytic activity on liquid glycerol hydrogenolysis to 1,2-propanediol has been investigated. The physicochemical properties of the catalysts were characterized by BET, XRD, TG/DTA, NH₃-TPD and TPR. The experimental results showed that the catalyst prepared by an oxalate gel–coprecipitation had the highest activity. At 200 °C and 400 psi hydrogen pressure, the glycerol conversion and 1,2-propanediol selectivity catalyzed by the Cu/ZnO/Al₂O₃ catalyst prepared via oxalate gel–coprecipitation were 92.3 and 94.5 % respectively. It was found that the 1,2-propanediol selectivity was dependent on hydrogen pressure and the un-desired by-products were mainly due to the side reactions caused by the presence of the intermediate acetol.     

Glycerol Hydrogenolysis over Co Catalysts Derived from a Layered Double Hydroxide Precursor

Abstract  

Co catalysts, obtained from a layered double Co–Zn–Al hydroxide, are highly active and stable towards the hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO) in aqueous media. The Co-673 catalyst, containing a CoO species, provided a glycerol conversion of 67.7% and a 1,2-PDO selectivity of 50.5%. The Co-873 catalyst comprising 16 nm Co nanoparticles gave a glycerol conversion of 70.6% and a 1,2-PDO selectivity of 57.8%. It was revealed that the CoO species in the Co-673 catalyst was readily converted to 50 nm Co particles under the glycerol hydrogenolysis conditions. The Co catalysts maintained a stable size and phase in recycling tests.     

Vapor-phase hydrogenolysis of glycerol to 1,2-propanediol using a chromium-free Ni-Cu-SiO2 nanocomposite catalyst

A Ni-Cu-SiO₂ nanocomposite was studied as a catalyst for vapor-phase glycerol hydrogenation to produce 1,2-propanediol (1,2-PDO). Substitution of a small amount (3 wt%) of Ni for Cu is beneficial for decreasing the Cu particle size, which would be advantageous for attaining higher 1,2-PDO selectivity and higher glycerol conversion. 92% 1,2-PDO selectivity and 100% glycerol conversion were obtained at 220 °C, 30 bar, and a weight hourly space velocity of 0.5 h^− 1 over Ni(3)-Cu(77)-SiO_2, which were nearly identical to those obtained with the conventional copper chromite (CuO-Cr₂O₃) catalyst. Therefore, the present Ni(3)-Cu(77)-SiO₂ nanocomposite is regarded as a green and efficient catalyst for glycerol conversion into more valuable 1,2-PDO.     

Benzylation of benzene to diphenylmethane using zeolite catalysts

The catalytic liquid phase benzylation of benzene to diphenylmethane (DPM) with benzyl chloride (BC) is investigated over a number of zeolite catalysts at 358 K and under atmospheric pressure. Conventional homogeneous Lewis acid catalyst, AlCl₃, is also included for comparison. Zeolite H-β is found to be more selective but less active compared to HY and H-ZSM-5 zeolites in the benzylation of benzene. The conversion of BC, rate of BC conversion and selectivity to DPM over H-β after 6 h of reaction time are 33.3 wt%, 4.7 × 10⁻³ mmol g⁻¹ h⁻¹ and 89.1 wt%, respectively. For comparison, the conversion of BC, rate of BC conversion and selectivity to DPM over AlCl₃, under identical reaction condition, are found to be 100 wt%, 170 × 10⁻³ mmol g⁻¹ h⁻¹ and 58 wt%, respectively. Higher amounts of consecutive products are obtained over AlCl₃ due to its non shape selectivity. The acidity of the zeolite catalysts is measured by temperature programmed desorption method. The effect of the duration of the run, SiO₂/Al₂O₃ ratio of H-β, catalyst concentration, reaction temperature and benzene to BC molar ratio on the catalyst performance is also investigated in order to optimize the conversion of BC and selectivity for DPM. The conversion of BC using H-β is increased with the increase in the reaction time, catalyst concentration, reaction temperature and molar ratios whereas it decreases with the increase in SiO₂/Al₂O₃ molar ratio of H-β. H-β is recycled two times and a slight decrease in BC conversion is observed after each cycle, which is related to the minor dealumination of the zeolite catalyst by HCl, which is produced during the reaction as by product. The formation of DPM is explained by an electrophilic attack of the benzyl cation (C₆H₅CH₂⁺) on the benzene ring, which is produced by the polarization of BC over acidic sites of the zeolite catalysts.     

Bio <Emphasis Type="Italic">n</Emphasis>-Butanol Partial Oxidation to Butyraldehyde in Gas Phase on Supported Ru and Cu Catalysts

Abstract  

Ceria, titania, and zirconia supported ruthenium and copper catalysts were tested in the butyraldehyde production by gas phase n-butanol partial oxidation. These catalysts were characterized by means of N₂ adsorption–desorption isotherms, temperature-programmed reduction and X-ray photoelectron spectroscopy techniques. The activity tests were performed in a fixed bed reactor at 0.1 MPa and 623 K using air and n-butanol mixture as reactants (in stoichiometric proportion n-butanol/O₂) to generate butyraldehyde. For n-butanol partial oxidation, the ruthenium catalysts showed higher activity and stability than the copper ones. The n-butanol conversion was almost similar for all the ruthenium catalysts, but the different supports modified the metal dispersion and, as a result, the product distribution was modified. The catalysts supported on ZrO₂ and CeO₂ allowed the highest butyraldehyde yields. The copper doping of the ruthenium catalyst also improved the selectivity toward butyraldehyde.