The reaction pathway for hydrogenation of 2-butyne-1,4-diol involves parallel and consecutive isomerization as well as hydrogenation reactions forming other side products along with cis-2-butene-1,4-diol and butane-1,4-diol. Hence, achieving the highest selectivity to butene- and/or butanediol is critical from industrial point of view. Hydrogenation of butynediol is also of fundamental significance, due to its adsorption characteristics leading to the formation of active species and their role in determining the product distribution. Studies on designing various catalyst systems including colloidal as well supported palladium nanoparticles for the hydrogenation of butynediol, role of additives, catalyst pretreatment, kinetic studies carried out in our group has been presented in this review. Interestingly, almost complete selectivity to the intermediate olefinic diol was achieved with 1% Pd/CaCO3-NH3 catalyst system. This could be due to the competitive adsorption of ammonia on the palladium surface along with the substrate 2-butyne-1,4-diol. Studies on catalyst pretreatment and kinetics using palladium catalyst have also been presented here. Nanostructure palladium both colloidal as well as supported catalysts showed a very high catalytic activity (10-40 times more) in the hydrogenation 2-butyne-1,4-diol to cis-2-butene-1,4-diol compared with the corresponding conventional Pd catalysts. For platinum based catalysts, formation of side products was completely eliminated in the hydrogenation of butyne diol. The increase in the basic strength of alkali metal doped Pt catalysts measured by CO2-TPD, led to the increase in electron density of Pt hence, faster desorption and higher selectivity to butenediol. In the case of continuous hydrogenation, the selectivity pattern was completely different from that found in the case of batch slurry reactor and by varying the contact time, the selectivity to both butene- and butanediols could be varied over a wide range of conditions.
Minimal quantity lubrication (MQL) machining typically uses several tens of milliliters per hour of cutting fluid: a very small quantity compared with generally several tens of thousands of milliliters per hour in the conventional flood supply of cutting fluids. MQL machining can reduce considerably the consumption of cutting fluids, so is a representative and successful environmentally friendly manufacturing operation. Specific synthetic polyol esters with high biodegradability, excellent oxidation stability, and satisfactory cutting performance were evaluated as optimal cutting fluids for MQL machining. The esters are required to work as an effective lubricant in the cutting zone in very small amounts, so the tribological actions are particularly important to improve the cutting performance. A controlled atmosphere cutting apparatus was devised to investigate the relationship between the tribological action and the practical cutting performance of the esters in MQL machining. A model ester and oxygen showed mutually enhanced adsorption activities for machining of steel by the efficient formation of an adsorption film which provided the lubricating effect and improved the cutting performance. In contrast, the presence of oxygen resulted in unfavorable cutting situations for machining of aluminum.
The synthesis of inorganic materials was investigated in organic solvents at temperatures (200-300°C) higher than their boiling points (solvothermal method), and various inorganic materials were directly obtained. The solvothermal products had high surface areas, superior thermal stabilities, and characteristic morphologies as well as unique surface properties with high potential for catalytic applications. Here, two recent studies on catalytic applications of nanocrystalline mixed oxides synthesized by the solvothermal method are reviewed. First, the solvothermal synthesis of gamma-type Ga2O3-Al2O3 solid solutions and their activities for selective catalytic reduction of NO using methane as a reducing agent are described. Ga2O3-Al2O3 catalyst prepared in diethylenetriamine exhibited quite high activity for this reaction. The physicochemical properties of the catalysts as well as the active sites for this reaction are discussed. Second, the synthesis of nanocrystalline silica-modified titanias with large surface areas and high thermal stabilities by the glycothermal treatment of the mixture of titanium tetraisopropoxide and tetraethyl orthosilicate in 1,4-butanediol is described. The products were characterized by several techniques and the origin of the thermal stability of the products is discussed. The recovery of silica- modified titania particles as xerogels by flash evaporation of the reaction medium after the glycothermal reaction is described. Photocatalytic activities of the products under UV light irradiation and the visible light responsive photocatalytic activity of N-doped silica-modified titanias are also discussed.
Steam reforming of dimethyl ether, DME, over Cu/ZnO/ZrO2 and γ-Al2O3 mixed catalysts prepared by the extrusion technique was investigated. The catalysts were characterized by BET, pore-size distribution measurements, N2O chemisorption, powder X-ray diffraction, and SEM-EDX analysis. The effect of reaction temperature on catalyst life time was investigated. Steam reforming of DME over the extruded catalyst proceeded above 623 K. The major reaction products were H2 and CO2 with relatively small amounts of CO and CH4. DME steam reforming was not restricted by the equilibrium limitation of DME hydration to CH3OH, suggesting that CH3OH produced was subsequently reformed into H2 and CO2 over the catalyst. The catalyst suffered from thermal deactivation at higher temperatures; mainly caused by a reduction in Cu dispersion in the Cu/ZnO/ZrO2 catalyst. Incorporation of ZrO2 into Cu/ZnO may stabilize Cu dispersion and increase the stability of the extruded catalyst for long-term operation.
Synthetic crude oils (SCOs) derived from oil shale, coal, and oil sands contain relatively large amounts of heteroatoms such as nitrogen and sulfur, and severe hydrorefining conditions are necessary to convert SCOs into substitute transport fuels. In this study, extraction of nitrogen compounds from SCOs by complex formation with CuCl2.2H2O was carried out and the denitrogenated oils were hydrotreated to explore the effect of nitrogen pre-removal on hydrodenitrogenation (HDN) and hydrodesulfurization (HDS). Light gas oil fractions derived from shale oil, coal-derived liquid, and pyrolysis product of Athabasca bitumen were used as feedstocks. Hydrotreatment tests were carried out using a batch-type autoclave and commercial NiMo/Al2O3 catalyst at 350°C for 2-4 h under H2 initial pressure of 5 MPa. The results showed that basic and heterocyclic nitrogen compounds could be separated efficiently from SCO by complex formation. The pre-removal of nitrogen compounds greatly enhanced the HDN reaction rates and greatly reduced the residual nitrogen content. The recovery of CuCl2.2H2O was also possible by simply washing CH2Cl2 solution containing the complex with water. The proposed method is another option for the conversion of SCO to a high quality feedstock suitable for production of clean diesel fuels.
Bacteria were screened to identify strains that could degrade carbazole, a model compound for the N-containing compounds present in fossil fuels which could be removed by biodenitrogenation instead of hydrotreatment. Enrichment cultures from 6 different habitats were examined with carbazole as a source of nitrogen. Bacterium strain NIY3 was isolated, which efficiently metabolized very low concentrations of carbazole. Strain NIY3 is a bright yellow Gram-negative immotile bacterium with a rod shape (0.7×0.7-1.0 μm). DNA base sequence analysis revealed that strain NIY3 belongs to genus Novosphingobium sp., most closely related to Novosphingobium subarcticum (98.3% similarity). Novosphingobium sp. strain NIY3 could degrade 95% of 100 ppm of carbazole in a culture within 3 days.
The effects of sound-wave irradiation were investigated on the decomposition of carbon dioxide in a discharge plasma. Discharge plasma supplies high local energy levels, as charged medium particles, so chemical reactions ungoverned by thermodynamics can occur. However, the discharge space is extremely confined, which restricts the conversion rate. This study investigated the combination of plasma and sound-wave irradiation, which increases the vibration motion of the medium. A streamer was observed to expand into a fan shape on irradiation of sound waves. The expansion of the discharge space was positively correlated with the magnitude of the sound. Accordingly, the effects of sound-wave irradiation on the direct decomposition of carbon dioxide were evaluated. The decomposition rate of carbon dioxide (rCO2) increased with sound pressure at the closed end of the sound tube, and rCO2 at 1.8 kPa approximately increased to approximately twice that for no sound-wave irradiation. This increase in rCO2 resulted from the improvement in the reaction probability due to expansion of the discharge space and increased vibration of the charged particles.
Ozonolysis of triacylglycerol was carried out over heterogeneous catalysts. The triacylglycerol was decomposed to some compounds with low boiling points containing hydrocarbons, aldehydes, ketones, fatty acids and lactones over H-Y zeolite catalyst at 353-423 K. The amounts of products were strongly dependent on the properties of catalysts and reaction conditions.