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We reported a bifunctional catalyst TiO2/Al2O3 and Pd/Cor for one-pot liquid-phase synthesis of MIBK from acetone in this paper. The characterizations of FT-IR, Raman spectra, TEM, XPS, CO2-TPD, NH3-TPD, Py-IR and TGA spectra revealed that the TiO2/Al2O3 could possess more acid sites and especially Lewis acid sites due to the coexistence of TiO2 an...
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Unexpected spiro cyclic products were obtained from the popular alkali catalyzed Claisen-Schmidt reaction of ketones with salicylaldehyde apart from the bis-chalcones. However, in the acid catalyzed reaction, we observe their transformation to a benzopyrylium salt. In the present study, we demonstrate this phenomenon for three ketones namely cyclop...
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... This is associated with more acidic sites on zeolites as indicated by NH 3 -TPD results. Moreover, there are both Bronsted and Lewis acid sites on zeolites, while only Lewis acid sites on ZrO 2 and TiO 2 [42,43]. The acid sites can promote the dehydration of cyclohexanol [23]. ...
Zeolites (Hβ, HZSM-5 and HM), TiO2 and ZrO2 supported NiCo alloy catalysts were tested for the hydrodeoxygenation of phenol in aqueous phase. It has been found that the catalyst acidity remarkably influences the catalyst activity and the product distribution. Zeolites supported catalysts give much higher yield of the deoxygenated products (mainly benzene and cyclohexane) than NiCo/TiO2 and NiCo/ZrO2, where cyclohexanol and cyclohexanone are dominating. Associated with NH3-TPD, we suggest that the catalyst acidity promotes the hydrodeoxygenation. Hβ zeolite supported NiCo alloy is more active than others, attributed to its higher metal dispersion and more acid sites. Therein, the Hβ zeolite calcined at 750 oC has moderate acidity, and its supported NiCo alloy catalyst (NiCo/HB-750) shows the best performance. Under a suitable reaction condition, the phenol conversion and the total yield of deoxygenated products reaches 96.8% and 94.5% on NiCo/HB-750, respectively.
... Using FT-IR spectroscopy, the surface of the samples obtained was studied (Fig. 9a). All samples are characterized by bands at 3450 cm −1 and at 1640 cm −1 , which can be assigned to the stretching modes and bending vibration of the adsorbed water [50,51]. The broad band in the region of 500-750 cm −1 for Ti/Al and samples calcined at 500 and 700 °C (Fig. 9, curves 1, 2, 5) is assigned to Ti-O-Ti bond of a titanium oxide and AlO 6 octahedra, whereas the shoulder at 890 cm −1 is assigned to AlO 4 tetrahedra [52,53]. ...
The creation of new nanomaterials with improved characteristics, as well as the development of new approaches to obtain such materials is an urgent task in science and technology. One of the promising directions in obtaining improved nanomaterials is the use of precursors in the form of multicomponent metal nanoparticles. Thermal oxidation of bimetallic Ti/Al nanoparticles obtained by electrical explosion of wires was investigated in this work. Ti/Al nanoparticles have been found to be completely oxidized with the formation of composite TiO2/Al2O3 nanoparticles after calcination at 900 °C. The formation of TiO2 phase with a rutile structure on heating to 500 °C, and the formation of TiO2 phases with a rutile and anatase structure, as well as α-Al2O3 on heating to 700 °C have been established, in addition to the residue of unoxidized metals. Complete oxidation of Ti/Al nanoparticles occurs when heated to 900 °C. The photochemical activity of TiO2/Al2O3 composite nanoparticles obtained at 900 °C was studied. The degradation of methyl orange dye reached 55% under UV irradiation for 120 min.
... high reaction pressure, low thermal stability of resin), seriously limited the practical application. In order to overcome these disadvantages, various catalyst systems including Pd-based [3,9,10], Pt-based [11], Ru-based [12], Ni-based [13], and Cu-based [14], have been developed during the recent decades, which improved the catalyst efficiency to a certain extent. But, research on the desirable support for improving the stability and activity of Pd-based catalysts was still an urgent matter. ...
A Pd/Al2O3–CeO2 nanosheets catalyst was fabricated successfully via coprecipitation strategy for the one-pot conversion of acetone to methyl isobutyl ketone (MIBK). Compared with Pd/Al2O3 or Pd/CeO2, Pd/Al2O3–CeO2 exhibited the highest catalytic activity (xACE = 46%) and selectivity (SMIBK = 85%), thereby indicating the excellent synergistic effect between Al2O3 and CeO2. The DFT calculation results indicated that the adsorbed acetone in Pd/Al2O3–CeO2 possessed a stronger orbital energy level than acetone, demonstrating that Pd/Al2O3–CeO2 could increase electron activity of acetone and thus activate acetone hydrogenation process. Meanwhile, more electrons were transferred from CeO2 to Al2O3 and reactants (i.e. acetone, diacetone alcohol, mesityl oxide). When reactants were adsorbed in the catalyst model, some chemical bonds (i.e. C = O, C–H, C–O and C = C) were extended accordingly, indicating that Pd/Al2O3–CeO2 could reduce the reaction barrier and accelerate acetone hydrogenation.
Graphical Abstract
The Pd/Al2O3–CeO2 nanosheets exhibited the highest catalytic activity (xACE = 46%, SMIBK = 85%) due to the unique synergistic effect between Al2O3 and CeO2.
Titanium and its alloys are known to allow the straightforward laser-based manufacturing of ordered surface nanostructures, so-called high spatial frequency laser-induced periodic surface structures (HSFL). These structures exhibit sub-100 nm spatial periods – far below the optical diffraction limit. However, the resulting surface functionalities are usually enabled by both, topographic and chemical alterations of the nanostructured surfaces. For exploring these effects, multi-method characterizations were performed here for HSFL processed on Ti-6Al-4V alloy upon irradiation with near-infrared ps-laser pulses (1030 nm, ∽1 ps pulse duration, 1–400 kHz) under different laser scan processing conditions, i.e., by systematically varying the pulse repetition frequency and the number of laser irradiation passes. The sample characterization involved morphological and topographical investigations by scanning electron microscopy, atomic force microscopy, tactile stylus profilometry, as well as near-surface chemical analyses hard X-ray photoelectron spectroscopy and depth-profiling time-of-flight secondary ion mass spectrometry. This provides a quantification of the laser ablation depth, the geometrical HSFL characteristics and enables new detailed insights into the depth extent and the nature of the non-ablative laser-induced near-surface oxidation accompanying these nanostructures. This allows to answer the questions how the processing of HSFL can be industrially scaled up, and whether the latter is limited by heat-accumulation effects.
A series of TiO2/Al2O3 catalysts for cyclohexanone condensation have been prepared by impregnation method. Various characterization techniques, including XRD, BET, SEM, FT-IR, NH3-TPD, and Py-IR were applied to characterize their physical properties and chemical structures. The results show that the acidity of the TiO2/Al2O3 catalysts are all come from L-acid. In addition, the effects of reaction parameters such as TiO2 loading dosage, amount of cyclohexane, catalyst dosage, particle mesh, agitation rate, temperature and time were examined. The optimal reaction conditions were 40 ~ 60 particle mesh, 8% catalyst dosage, 393.15 K reaction temperature, 300 r/min agitation rate for 120 min with the conversion of cyclohexanone is 29.11% and close to 100% ultrahigh selectivity. Five cycles of reaction suggested the activity and selectivity of the catalyst did not change obviously and had potential industrial application value. Finally, the reaction kinetics was evaluated in cyclohexane under the reaction conditions of particle mesh 40 ~ 60 and 8% catalyst dosage and absence removing water produced, indicating the cyclohexanone self-condensation reaction was a second-order reaction.
Methyl isobutyl ketone (MIBK) is a highly valuable product in the chemical industry. It is wide-ly used as an extracting agent for heavy metals, antibiotics, and lubricating oils. Generally, MIBK can be produced by three-step and one-step liquid-phase methods. These methods are ex-pensive and energy-demanding due to the high pressure and low conversion of acetone. A novel nano-Pd/nano-ZnCr2O4 catalyst was developed to produce MIBK with high conversion and se-lectivity of 77.3% and 72.1%, respectively, at 350 °C and ambient pressure, eliminating the need for high pressure in conventional MIBK processes. This study is the first that proposes a newly developed process of methyl isobutyl ketone (MIBK) production using the low-pressure one-step gas-phase selective hydrogenation of acetone. In this work, a novel process flow di-agram has been developed for the production of MIBK using the developed nano-catalyst. The process was heat integrated, resulting in a 26% and a 19.5% reduction in the heating and cooling utilities, respectively, leading to a 12.6% reduction in the total energy demand. An economic analysis was performed to determine the economic feasibility of the developed process, which shows that the process is highly profitable, in which it reduced both the capital and operating costs of MIBK synthesis and showed a return on investment (ROI) of 29.6% with a payback peri-od of 2.2 years. It was found that the ROI could be increased by 18% when the reactor tempera-ture is increased to 350 °C. In addition, the economic sensitivity analysis showed that the process is highly sensitive to product prices and least sensitive to utility prices, which is due to the ver-satility of the process that requires only a low amount of energy.
Two pilot scale experiments investigating the one-step synthesis of methyl isobutyl ketone (MIBK) from acetone and hydrogen were conducted via catalytic distillation (CD) utilizing a Pd/Nb2O5/SiO2 catalyst at a reaction temperature of 160°C and system pressure of about 1.4 MPa. Moisture analysis of liquid samples extracted about the major axis of the CD column revealed that when the reactor was initially operated at 100% reflux as suggested in the patent of Lawson and Nkosi, water had accumulated in the top half of the reactor as evidenced by water concentrations of 9.4 and 21.0 wt% in the reactive and rectification sections respectively, resulting in the suppression of the DAA dehydration reaction and consequently a relatively low MIBK productivity. However, operation of the CD column at 83 to 97% reflux enabled the rapid in situ separation of water from the reactive section via the overhead distillate stream, which directly resulted in increases in the MIBK productivity and the hydrogen uptake efficiency by factors of about 20. This result demonstrates a unique advantage of CD technology, whereby a substantial kinetic enhancement may be realized from the selective in situ separation of a kinetically relevant inhibiting substrate from the reactant mixture. MIBK in excess of 50 wt% was observed in the reboiler product during this mode of operation, which is significant since state of the art processes for MIBK production typically yield less than 30 wt% MIBK in the reactor effluent. The reboiler product was found to be essentially moisture free, which is also significant since MIBK and water are known to produce azeotropic mixtures resulting in difficult and costly downstream separations. An experiment was conducted to study the effects of the hydrogen and reflux flow rates on the MIBK yield. The CD process for MIBK synthesis was found to be controlled by the rate of external mass transfer of hydrogen. The results indicate that the catalyst wetting efficiency affects the catalytic hydrogenation as evidenced by an increase in mesityl oxide conversion with decreasing reflux flow rate. This suggests the catalyst wetting efficiency is an important design criterion for this process.
Developing multifunctional catalyst for cascade reactions such as one-pot synthesis of methyl isobutyl ketone (MIBK) from acetone and hydrogen is critical for practical applications. Here, we adjusted the acid-base property by doping phosphor into h-BN and used it as support for Pd. Experiments and characterizations indicated that the phosphor-doped h-BN could catalyze the aldol condensation and dehydration by modulating the ratio of BNH2, N2P=O and N3P-OH groups thereon. An acetone conversion of 58.24% and MIBK selectivity of 68.39% were achieved over Pd/BN(H)P-E-0.07, providing a new avenue for metal-free materials utilized in the cascade reactions.
