Kline, Matthew J.Karunarathne, Sampath A.Schwartz, Thomas J.Wheeler, M. Clayton...
9页
查看更多>>摘要：Nickel catalysts were synthesized by incipient wetness impregnation and coprecipitation and compared to a commercial Ni/kieselguhr catalyst for selective hydrogenation of 2-methylnaphthalene to yield methyldecalin. The catalysts were characterized using N-2 physisorption, TGA, XRD, and TEM. The apparent activation energy for hydrogenation depends on the support identity, with the highest value (87 kJ/mol) obtained for Ni/SiO2- Al2O3 and the lowest (30 kJ/mol) for Ni/kieselguhr. The selectivity to cis-/trans-methyldecalin varied as a function of both catalyst identity and reaction conditions, with high selectivity to cis-methyldecalin obtained using catalysts with higher Ni loadings and at lower reaction temperatures. The impregnation of a precious metal onto coprecipitated Ni catalysts also changed their selectivity, as catalysts containing ruthenium selectively formed cis-methyldecalin, whereas platinum catalysts produced mostly trans-methyldecalin. This research demonstrates that Ni catalysts can be useful for producing inexpensive catalysts for hydrogenation of polyaromatic-containing feedstocks.
查看更多>>摘要：The catalytic conversion of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), a renewably sourced substitution for petroleum-derived terephthalic acid, at a high concentration is highly demanding but challenging. Herein, the efficient conversion of HMF (10-25 wt%) in 1,4-dioxane/H2O was achieved, and a desirable FDCA yield of 98% was obtained from HMF (10 wt%) over commercial Ru/C (2 Equiv. NaHCO3, 4 MPa O-2, 3 h, and 140 ?). In addition, a two-step cascade reaction was developed for FDCA production, in which FDCA was employed as the acid catalyst to promote the dehydration of fructose (10 wt%) to HMF, followed by oxidation in 1,4-dioxane/H2O to FDCA over Ru/C. As compared to pure water or 1,4-dioxane, the better stability of HMF in 1,4-dioxane/H2O with a weak alkaline environment and the enhancement of superoxide radicals (center dot O-2(-)) in 1,4-dioxane/H2O could ensure high FDCA yield at high HMF concentration.
查看更多>>摘要：Conversion of lignin-derived molecules into value-added chemicals is critical for sustainable chemistry but still challenging. Herein, phosphorus-modified palladium catalyzed the degradation of lignin-derived 4-O-5 linkage to produce KA oil (cyclohexanone-cyclohexanol oil) was reported. The reaction proceeds via a restricted partial hydrogenation-hydrolysis pathway. Phosphorus-modified palladium catalyst suppressed the full hydrogenation of diary ether, which was the key point to produce KA oil selectively. Under the optimized conditions, the 4.5 nm Pd-P NPs could catalyze the conversion of 4-O-5 linkage into KA oil in 83% selectivity with a high production rate of 32.5 mmol.g(Pd)(-1).min(-1). This study represented an original method for KA oil production.
查看更多>>摘要：To comply with stricter regulations on particulate emissions, ceria based catalyst has been researched in developing diesel particulate filters. Here chemical reaction parameters are determined experimentally for CeO2-nanoparticle catalyzed soot oxidation for two representative environments: a bulk process with a catalyst/carbon mixture and individual carbon-nanoparticles attached to CeO2. The first task was carried out in simultaneous thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) experiments, while the second was performed with in-situ environmental scanning transmission electron microscopy (ESTEM). The TGA/DSC results suggested the role of gas diffusion through the porous sample was significant and slowed down the reaction rate. The ESTEM videos affirmed the catalyzed reaction resulted in a higher oxidation rate at the contact area between CeO2 and carbon, which caused the movement of carbon nanoparticles towards CeO2. Measured reaction kinetics data were compared to the Darcy's model and their discrepancies were elaborated.
查看更多>>摘要：Nanosized hierarchical titanosilicate-1 zeolites (nanoTS-1_D) with variable Ti doping content were synthesized by a simple and sequent two-step procedure consisting of microporous TS-1 nanocrystal synthesis through steamassisted dry-gel conversion and post alkali-etching treatment for mesopore formation. Comprehensive characterizations, e.g. XRD, N2 sorption isotherms, DLS, UV-Vis, SEM, TEM and water-droplet contact angle, indicated that the resultant nanoTS-1_D materials not only possess abundant intracrystal mesopores and high surface area, but importantly maintain the intrinsic surface hydrophobicity as those of microporous TS-1 zeolites. Consequently, they showed the expected superior catalytic performance in both bulky cyclohexene/cyclooctene epoxidation and phenol hydroxylation probe reactions, contrast to the microporous TS-1 and amorphous TiMCM-41 mesoporous counterparts. In the oxidative desulfurization of fuels, they exhibited 100% removal ability for thiophene and its bulky derivatives and excellent recyclability. In addition, a new Ti-dopant directed alkali-etching mechanism has been proposed to illustrate the synthesis of high-specific-surface-area nanoTS-1_D.
查看更多>>摘要：Fe-zeolites are widely applied in petrochemical, fine chemical, environmental protection, and other catalytic fields because of the zeolitic properties as well as the redox properties endowed by the introduction of Fe species. After being introduced into the zeolitic framework, the poor properties of traditional aluminosilicate zeolites, i. e., lack of active sites, low catalytic activity, poor anti-coking performance, etc., could be effectively improved. The state of Fe species in zeolite, which significantly affects the properties (stability, acidity, redox properties, etc.) of Fe-zeolite, was determined by both the introduction methods/conditions and the properties (porosity / acidity, etc.) of zeolite. From this point of view, a clear understanding of the structure-activity relationship of Fezeolite is an important prerequisite for designing functional materials as necessary. Therefore, in this review, recent developments on the synthesis, properties as well as the application of Fe-based zeolites were briefly summarized. In detail, the factors affecting the recognition of types as well as the distribution of Fe species in Fezeolites and the effects of the introduction of Fe on the physicochemical properties & catalytic performance of zeolites are systematically clarified. Then, the applications of Fe-zeolite in chemical industry and environmental engineering were reviewed and outlooked. This review is expected to provide theoretical reference for the structural design and application of Fe-based zeolites in the future.
Silva, ManojBaltrus, John P.Williams, ClintonKnopf, Allan...
13页
查看更多>>摘要：A facile thermal decomposition method was utilized to synthesize mesoporous Cu-doped MgO nanoparticles. These Cu-MgO nanoparticles were shown to be efficient photo-Fenton-like catalysts for degrading emerging pharmaceutical contaminants in wastewater and completely oxidized salicylic acid within 1 h under optimized conditions. Tetracycline was shown to be converted to other intermediates with a large portion of it undergoing full mineralization. Batch experiments were conducted to demonstrate the effects of Cu loading on MgO, overall catalyst loading, and H2O2 concentration on the salicylic acid and tetracycline conversion and rate constants. Quenching experiments revealed that both center dot OH radicals or HO2 center dot/center dot O-2-radicals were involved in the reaction, with the latter showing a higher contribution. The surface dissolution of MgO was shown to increase solution pH which completely prevented Cu from leaching out while retaining high activity. The catalyst reusability was shown to be satisfactory with high activity and conversion being preserved over five cycles.
查看更多>>摘要：Oxygen mobility contributes to HCHO oxidation at room temperature. In this work, oxygen mobilities of the Pt/CeO2 catalysts were controlled by changing ceria shapes to nanorods (CeO2-R), nanocubes (CeO2-C) and nanoparticles (CeO2-P) for HCHO elimination. The smallest ceria crystallite size, the strongest metal-support interaction and the most oxygen vacancy in the Pt/CeO2-R catalyst than those in the Pt/CeO2-C and Pt/CeO2-P catalysts resulted in the greatest redox of surface lattice oxygen and the most oxygen molecules activation at oxygen vacancy sites. These contributed to the most active mobile oxygen and therefore the highest HCHO oxidation performance. In-situ diffused reflectance infrared Fourier-transform spectra (DRIFT) indicated the fastest decomposition of formate at Pt-CeO2 & nbsp;interface on the Pt/CeO2-R catalyst because of its highest oxygen mobility. This work illustrated importance of oxygen mobility for efficient HCHO oxidation.
Gabriel, RafaelaDe Carvalho, Sandra H. V.Duarte, Jose Leandro da SilvaOliveira, Leonardo M. T. M....
17页
查看更多>>摘要：Demand for energy has increased globally due to population growth and socioeconomic development stemming from rapid industrialization and urbanization. This scenario worsens the dependence on energy resources and highlights the question regarding their availability, showing the fragility of non-renewable fossil fuels. In order to supply the growing world demand for energy and respond to environmental concerns, biodiesel was adopted as a mitigating solution to the problems arising from the burning of fossil fuels as it has a biodegradable, renewable and non-toxic character. Recently, many studies have given attention to the heterogeneous catalysts for the production of biodiesel, since some economic and technological problems were recognized in the production via homogeneous reaction. Among the studied catalysts, layered double hydroxides (LDH) have stood out for presenting adjustable properties according to the composition and methods of synthesis, which are directly associated with the structural, morphological and catalytic aspects of their oxides. This review article aims to elucidate the relationship between the structure, basicity, composition and catalytic activity of metal mixed oxides (MMOs) from LDHs. In addition, a comprehensive description is made of the advantages of using MMOs/ LDH-based catalysts, of the reaction optimization parameters and of the regeneration and reuse processes of these minerals.
查看更多>>摘要：A 0.33 wt% Pd/BN catalyst has been proved highly active for the liquid-phase selective hydrogenation of maleic anhydride (MA) to succinic anhydride (SA) at room temperature and highly selective to SA within a wide temperature range, far beyond the Pd/Al2O3 and Pd/MgO catalysts. An SA productivity of 6000 KgSA Kg(Pd)(-1) h(-1) and a high TOF value of 9.0 s(-1) can be achieved at room temperature on the Pd/BN, and the high SA selectivity over 99.7% can be retained at the reaction temperature up to 150 ?. Detailed structural characterizations and reactant-adsorption/desorption tests have demonstrated that the support effect on MA hydrogenation is related not only to the adsorption configurations of MA on Pd, which exhibits the indirect effect of the support via the electronic interaction with Pd, but also to the direct adsorption of MA on the support itself. In particular, for our catalysts with the low Pd loading, the difference of metal centers is largely masked by the adsorption of the support itself. For the Pd/BN, the predominant MA adsorption on Pd through a di-sigma mode, the weak MA adsorption with a small amount on BN, and a high H-spillover ability are responsible for its high activity and selectivity. Moreover, it has been also revealed that the catalyst prereduction temperature can change the catalytic performance of the Pd/BN through an integrated effect including the removal of residual chlorine on Pd and the growth of Pd particles.
NSTL
Elsevier