Nanostructured catalytic films for multiphase microstructured reactors

The application of microstructured catalytic reactors for gas-liquid reactions requires the development of new techniques for the incorporation of highly active catalytic thin films onto their microstructured surfaces. These catalytic thin films may have open porosities even up to 50%. Their application limits the pressure drop over the microreactor in comparison to micro packed beds, it enhances the catalyst accessibility, and it may significantly reduce mass transfer limitations. In this PhD thesis, ordered mesoporous silica and titania films with a thickness of 100 to 400 nm were developed via an evaporation induced self assembly method on different substrates (glass, silicon, titanium). These polymer templated meso¬porous silica films have a narrow pore size distribution and were synthesized with a wide range of pore sizes (2 to 8 nm). A new calcination protocol was developed which allows the complete removal of the surfactant at mild conditions. The thermal and hydro¬thermal stability of the films that were obtained with an ionic surfactant was improved by pH adjust¬ment during hydrolysis and by Al incorporation. Microwave assisted hydro¬thermal synthesis of these ordered microporous films was also investigated in an attempt to reduce the synthesis time from several days to less than 10 hours. The obtained thin films have been loaded with polymetallic nanoparticles with a size of 1 to 3 nm to specifically activate a selected functionality of complex organic molecules. Methods for the deposition and the stabilization of bi-metallic and tri-metallic clusters by adsorption onto the mesoporous thin films have been investigated. A "one pot" sol-gel synthesis of the mesoporous films with embedded colloidal nano¬particles was developed which eliminates an additional impregnation step and produces a uniform distribution of the active components throughout the mesoporous films. Various experimental techniques such as ellipsometric porosimetry, XRD, 2D SAXS, XPS, SEM, and TEM have been applied to obtain insight in the physical and chemical phenomena that determine the performance as well as the stability of the thin films. The activity and the selectivity of the resulting catalytic thin films have been investigated in the batch and in the continuous mode in the hydrogenation of citral and phenylacetylene. The latter was done in a 10 m long micro capillary (i.d. 250 µm) with a catalytic thin film deposited onto its inner channel wall surface. It was shown that the selectivity towards the target product can be changed by varying the metal ratio in the bimetallic nanoparticles. The high stability of these catalytic thin films allows their further implementation in fine chemicals synthesis using microstructured reactors

Peculiarities of Glycerol Conversion to Chemicals Over Zeolite-Based Catalysts

Many countries have opted to produce biodiesel from vegetable oils for energy security and climate change concerns. Consequently, the availability of abundant glycerol, as a by-product in biodiesel production, is more obvious. Many institutions and companies have explored different routes to convert glycerol to highly-added chemical products and fuel additives. As the addition of the second reactant to glycerol may end up with worse exergy calculation, the conversion of glycerol over solid acid catalysts without the addition of the second reactant is preferred in this mini-review. Glycerol aromatization and glycerol dehydration over zeolite catalysts were focused with an emphasis on recent papers in the past 3 years. The role of acidity, hydrophilicity-hydrophobicity, zeolite frameworks are highlighted. The presence of water in the glycerol feed affected the stability of the catalysts. Low cost and naturally abundant zeolite and minerals are proposed. Numerous low-cost catalysts such as natural zeolites and natural clays are potentially used for this purpose

Perengkahan n-Butana Menggunakan Katalis Nanopartikel Zeolit Alam Klaten

 Increasing demand on olefins, high energy consumption of thermal cracking and oil depletion are the driving force to find new process to produce olefins. Catalytic cracking of n-butane is promising route to produce olefins. In this paper, we synthesized nanoparticle from natural zeolites by ball milling-recrystallization method and studied the effect of acid dealumination over the nanozeolites on the catalytic properties. Particle size was evaluated visually by using scanning electron microscope.  X-Ray Diffraction analysis was performed to study zeolites phase and its crystallinity. Acid dealumination effect over nanosized mordenite on the acidity were evaluated by ammonia TPD and pyridine FTIR. Textural properties of zeolites were characterized by nitrogen physisorption at -196 oC. The catalysts were tested in a fixed bed reactor for n-butane cracking to olefins product. Various temperature conditions were applied ranging from 350 oC to 650 oC for n-butane cracking in a fixed bed reactor. Conversions of n-butane were 15% and 90% at 350 oC and 650 oC, respectively. Selectivity to olefins was increase from 1% at 350 oC to 47% at 650 oC.  

Glycerol to solketal for fuel additive: Recent progress in heterogeneous catalysts

© 2019 by the authors. Biodiesel has been successfully commercialized in numerous countries. Glycerol, as a byproduct in biodiesel production plant, has been explored recently for fuel additive production. One of the most prospective fuel additives is solketal, which is produced from glycerol and acetone via an acetalization reaction. This manuscript reviewed recent progress on heterogeneous catalysts used in the exploratory stage of glycerol conversion to solketal. The effects of acidity strength, hydrophobicity, confinement effect, and others are discussed to find the most critical parameters to design better catalysts for solketal production. Among the heterogeneous catalysts, resins, hierarchical zeolites, mesoporous silica materials, and clays have been explored as effective catalysts for acetalization of glycerol. Challenges with each popular catalytic material are elaborated. Future works on glycerol to solketal will be improved by considering the stability of the catalysts in the presence of water as a byproduct. The presence of water and salt in the feed is certainly destructive to the activity and the stability of the catalysts

Film properties and in-situ optical analysis of TiO2 layers synthesized by remote plasma ALD

TiO2 is a widely studied material due to its optical and photocatalytic properties and its hydrophilic nature after prolonged UV exposure. When synthesized by atomic layer deposition (ALD) the TiO2 can be deposited with ultimate growth control with a high conformality on demanding topologies and even at room temperature when e.g. using a plasma based process. We report on the deposition of TiO2 films using remote plasma ALD with titanium (IV) isopropoxide as precursor and O2 plasma as oxidant. Stochiometric TiO2 films with carbon and hydrogen levels below the detection limit of Rutherford backscattering/elastic recoil detection (<2 at.%) have been deposited within the temperature range of 25°C to 300°C. Depending on the ALD conditions and film thickness amorphous films turn anatase for temperatures higher than 200°C as revealed by X-ray diffraction. It is demonstrated that this change in crystal phase can also be observed by spectroscopic ellipsometry revealing an increase in growth rate per cycle (from typically 0.45 Å/cycle to 0.7 Å/cycle) and change in bandgap (from 3.4 eV to 3.7 eV) when the TiO2 becomes anatase. An accompanying change in surface topology is clearly observed by atomic force microscopy. The hydrophilicity of low temperature TiO2 films is studied by contact angle measurements for adhesion purposes revealing that the amorphous films are super-hydrophilic after UV exposure

Citral hydrogenation over Pt loaded micro- and mesoporous supports : the interplay between steric limitations and acidity

The effect of pore morphology and acidity on the selectivity in the hydrogenation of citral was investigated on a series of bifunctional catalysts: Pt-H-SAPO-5, Pt-H-Y zeolite, and Pt-H-MCM-41. The reaction was studied in a batch reactor at 70oC with 10 bar total pressure. The highest selectivity to the unsaturated alcohols of 57% was obtained on the Pt-H-SAPO-5 catalyst at a conversion of 46%. The interplay among a monodimensional pore channel of the H-SAPO-5 support, weak Br?nsted acidity of this silicoaluminophosphate, and large platinum nanoparticles contributed to a high selectivity. The corresponding turn over frequency was 0.036 s-1. Pt-H-MCM-41 showed the highest selectivity to menthol as by product, while Pt-H-Y zeolite demonstrated the highest dehydration rate

Spent Bleaching Earth Supported CeFeO3 Perovskite for Visible Light Photocatalytic Oxidation of Methylene Blue

Dyes substances from the textile industry wastewater are internationally classified as poisonous substances, and they cause a severe threat to humans being and other living things, even at low concentrations. Therefore, this waste has to be treated before discharge to the environment. One of the most effective processes for degrading dyes is photocatalytic oxidation. Two different pretreatments of Spent bleaching earth (SBE) from palm oil refinery plant were applied to produce catalyst supports. The SBEe support was prepared by extraction using n-hexane, SBEc by calcination at 500 oC, and then used as a support for CeFeO3/SBEe and CeFeO3/SBEc perovskite catalyst. Both catalysts were tested for the degradation of methylene blue (MB) using photocatalytic oxidation. The properties of catalysts were characterized using some characterization methods, such as thermogravimetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with Dispersive Energy X-ray Spectroscopy (EDS), specific surface area (BET) and pore size analysis. CeFeO3/SBEe catalyst was found more efficient in photocatalytic oxidation for MB compared with the CeFeO3/SBEc catalyst. CeFeO3/SBEe catalyst could degrade 99.5% of MB during 120 min, at the condition of 25 mg/L MB, 1.0 g/L catalyst, and pH 7. The effect of pH on the performance of the catalyst followed the order of pH 7 > pH 9 > pH 5. Moreover, the CeFeO3/SBEe catalyst demonstrated excellent activity in the degradation of MB, displaying that CeFeO3/SBEe is a favorable catalyst for water purification

LaMnO3 Perovskite Activation of Peroxymonosulfate for Catalytic Palm Oil Mill Secondary Effluent Degradation

The LaMnO3 perovskite catalyst was successfully synthesized using a simple solid-state reaction method. This catalyst is used to activate PMS in the organic content's degradation process in the secondary effluent palm oil mill (POMSE). The organic content in POMSE is equivalent to the COD value; thus the COD value is used as a parameter for the process's success. The catalyst performance test shows that the catalyst effectively reduces COD, and the waste meets the maximum threshold allowed by government regulations. The variables that affect the catalyst's effectiveness were the calcination temperature of the catalyst, catalyst loading, PMS concentration, and temperature. The temperature of calcination affects the perovskite crystal formation; the higher the temperature, the more active catalyst obtained. The catalyst loading and PMS concentration variables affect the degradation process of organic levels in POMSE; at low levels, the higher the catalyst loading and PMS concentrations will increase the effectiveness of the degradation process, but at certain levels, the addition of catalysts and PMS reduces the effectiveness of the process. LaMnO3-800oC catalyst presents the highest activity of 92.7% and met the allowable threshold of COD < 300 mg/L. The sequence for removal of COD among the three catalysts with an order of LaMnO3-800oC > LaMnO3-700oC > LaMnO3-600 oC. The pseudo-second-order kinetics equation fits the experimental data. The effect of temperature on the kinetics constant follows the Arrhenius equation. Furthermore, the catalyst obtained was stable, with no significant decrease in catalysts activity up to three runs

Stability Assessment of Regenerated Hierarchical ZSM-48 Zeolite Designed by Post-Synthesis Treatment for Catalytic Cracking of Light Naphtha

Hierarchical ZSM-48, a one-dimensional pore system zeolite with the presence of mesopores, was obtained by post-synthesis alkaline and acid treatments. Hierarchical ZSM-48 exhibited excellent hexane cracking activity compared to parent ZSM-48, which can be attributed to better diffusion as a result of the created mesoporosity. Moreover, the post-synthesis treatment allowed for manipulation of the distribution of active sites. Consequently, better stability and higher propylene selectivity were accomplished. The spent catalyst was regenerated by removing the deposited coke from the pores, and the regenerated catalyst was characterized again to investigate the recyclability of the hierarchical structure achieved. Parent ZSM-48 showed the same textural and acidic properties after regeneration, while the structure of the post-treated sample suffered from serious defects. The defects severely decreased the number of active sites as measured by pyridine Fourier transform infrared spectroscopy and caused major structural collapse as observed by scanning electron microscopy and transmission electron microscopy