Manufacture Of Catalysts Research Articles

Diffusion in nanopores: inspecting the grounds

This paper provides a general overview of the phenomenon of guest diffusion in nanoporous materials. It introduces the different types of diffusion measurement that can be performed under both equilibrium and non-equilibrium conditions in either single- or multicomponent systems. In the technological application of nanoporous materials for mass separation and catalytic conversion diffusion often has a significant impact on the overall rate of the process and is quite commonly rate controlling. Diffusion enhancement is therefore often a major goal in the manufacture of catalysts and adsorbents.

Raman Spectroscopy as Molybdenum and Tungsten Content Analysis Tool for Mesoporous Silica and Beta Zeolite Catalysts.

Raman spectroscopy was used for the quantitative determination of Mo and W in Mo- and W-supported mesoporous silica (Mo/SBA-15 and W/SBA-15, respectively) and Mo-supported beta zeolite (Mo-BEA). Three Raman quantitative models were developed and optimized for the metal contents of Mo/SBA-15, W/SBA-15, and Mo/BEA. Subsequently, the models were characterized using the root mean square error of calibration (RMSEC), root mean square error of cross-validation (RMSECV), root mean square error of prediction (RMSEP), correlation coefficient, and predicted residual error sum of squares (PRESS) diagnostic function. The calibration range of the models were in the range of approximately 2–40 wt% for the SBA-15 support and 1–21 wt% for the BEA support because the BEA support presented lower Mo absorption than the SBA-15 support. The RMSEC, RMSECV, and RMSEP values were below 1.80% for all developed models. The highest and lowest correlation coefficients corresponded to the W/SBA-15 (0.9984) and Mo/BEA (0.9777) models, respectively. The change in catalyst support affected the mentioned chemometric parameters (Mo/SBA-15 vs. Mo/BEA). Subsequently, Raman spectroscopy combined with the temperature control stage was used to study the calcination of Mo/BEA, Mo/SBA-15, and W/SBA-15 using three-dimensional diagrams, in which the changes in catalyst structure were analyzed as functions of the temperature and time. Raman spectroscopy was determined to be a suitable analytical tool for the quantitative analysis of the metal contents of the catalyst and optimization of the calcination process. Therefore, Raman spectroscopy can be used during catalyst manufacturing.

Modified geopolymers as promising catalyst supports for abatement of dichloromethane

Geopolymers have not been extensively employed as catalytic materials despite of their zeolite-resembling Si–Al structure. Geopolymerization offers a novel way for preparation of catalysts and possibility to use waste or industrial side-stream derived raw material as a resource for catalyst manufacturing. This work concentrates on metakaolin-based geopolymer materials that were prepared, characterized and tested as alternative environmentally benign catalyst supports for the oxidation of dichloromethane. The geopolymers with the Si/Al ratio of 1.5 were modified with HCl to increase their specific surface area, which is important in catalytic applications. Significant increase in specific surface areas was achieved via leaching of Na and Al from the geopolymer structure. Highest specific surface areas achieved for calcined geopolymers were over 500 m2g-1. Use of acid concentrations higher than 1 M led to the dehydroxylation of the geopolymer. Dehydroxylation decreased the total acidity of geopolymer through the loss of the Brønsted acid sites, which are responsible for the adsorption of dichloromethane in the beginning of the catalytic reaction. Absence of Brønsted acid sites was observed by the formation of CH2O as the only reaction intermediate. The best result in the dichloromethane oxidation was found with the geopolymer treated with 1 M HCl. Without using any additional active sites, the maximum dichloromethane conversion of 90% was reached at 525 °C with the maximum HCl yield of 83%. This result indicates the good potential of modified geopolymers to be used as catalyst supports in environmental applications.

Enhanced Direct Dimethyl Ether Synthesis from CO2-Rich Syngas with Cu/ZnO/ZrO2 Catalysts Prepared by Continuous Co-Precipitation

The manufacturing of technical catalysts generally involves a sequence of different process steps, of which co-precipitation is one of the most important. In this study, we investigate how continuous co-precipitation influences the properties of Cu/ZnO/ZrO2 (CZZ) catalysts and their application in the direct synthesis of dimethyl ether (DME) from CO2/CO/H2 feeds. We compare material characteristics investigated by means of XRF, XRD, N2 physisorption, H2-TPR, N2O-RFC, TEM and EDXS as well as the catalytic properties to those of CZZ catalysts prepared by a semi-batch co-precipitation method. Ultra-fast mixing in continuous co-precipitation results in high BET and copper surface areas as well as in improved metal dispersion. DME synthesis performed in combination with a ferrierite-type co-catalyst shows correspondingly improved productivity for CZZ catalysts prepared by the continuous co-precipitation method, using CO2-rich as well as CO-rich syngas feeds. Our continuous co-precipitation approach allows for improved material homogeneity due to faster and more homogeneous solid formation. The so-called “chemical memory” stamped during initial co-precipitation is kept through all process steps and is reflected in the final catalytic properties. Furthermore, our continuous co-precipitation approach may be easily scaled-up to industrial production rates by numbering-up. Hence, we believe that our approach represents a promising contribution to improve catalysts for direct DME synthesis.

Characterization and Reuse Investigation on Scrapped V2O5–WO3/TiO2 Catalysts Operated in Various Industrial Flue Gases for NH3-SCR Reactions

The three scrapped industrial V2O5–WO3/TiO2 catalysts, which had operated in three coal-fired power plants with various flue gas conditions in China, were collected and characterized by XRF, XRD, SEM, and XPS to analyze their deactivation mechanisms, with the complexities of various industrial flue gases from coal combustion considered. Then one scrapped industrial catalyst was selected as the carrier to prepare a new catalyst by adding Mn, Ce, and Cr species, for SCR reactions in flue gas with as well as without SO2 at much wider temperature range. Results showed that the content of TiO2 did not change and the structure kept still, further illustrating that the scrapped catalysts could be utilized as the carrier in the new catalyst manufacturing process. The SO2 in flue gas indeed increased the V4+/V5+ ratio on the catalyst surface, moreover, the alkaline earth metal oxides such as BaO and CaO contributed to more sulfates depositing on the catalyst surface, increased the ratios of S6+/S4+ and Oα/Oβ. For the new Mn–Ce–Cr catalyst carried on the scrapped industrial catalyst, it showed high SCR activities at a wider temperature range of 170 to 370 °C but low resistance for SO2 poisoning, indicating that it could be further developed and utilized for SCR process of boilers burning natural gas or biomass.

Conversion of delignified stem sorghum bicolor into levulinic acid using micro and mesoporous ZSM-5 catalysts

Sorghum bicolor stem is one of the biomass wastes that can be used as raw material for synthesizing platform chemicals. Levulinic acid is one of the chemicals that is currently a substance often synthesized or isolated. Levulinic acid can be catalytically synthesized from sorghum stem waste which is rich in cellulose. Cellulose in the sorghum stem is still bound to lignin and hemicellulose, therefore pretreatment is needed to reduce lignin. The method consists of pretreatment of biomass by delignification, manufacturing of micro and mesoporous ZSM-5 catalysts (double template method) and the reaction of the conversion of stem sorghum to levulinic acid is carried out in a mini reactor. Catalyst characterizations were conducted using FTIR, XRD, SEM EDX and product analysis by HPLC. The result of delignification is the cellulose content increased from 45.10 % to 76.66 %. The result of as-synthesized ZSM-5 showed the diffractogram patterns similar to the standard ZSM-5. SEM image showed a hexagonal coffin-like shape which is the characteristic of ZSM-5. The levulinic acid produced using meso-porous ZSM-5 catalyst was observed at the reaction time of 2–6 h, while the yield of levulinic acid using micro-porous ZSM-5 catalyst was observed at the end of the reaction time, i.e. 6–10 h. It can be concluded that the pore size of the catalyst and the duration of the conversion time influenced the yield of levulinic acid.

Metal-Organic Frameworks in Heterogeneous Catalysis: Recent Progress, New Trends, and Future Perspectives.

More than 95% (in volume) of all of today's chemical products are manufactured through catalytic processes, making research into more efficient catalytic materials a thrilling and very dynamic research field. In this regard, metal-organic frameworks (MOFs) offer great opportunities for the rational design of new catalytic solids, as highlighted by the unprecedented number of publications appearing over the past decade. In this review, the recent advances in the application of MOFs in heterogeneous catalysis are discussed. MOFs with intrinsic thermocatalytic activity, as hosts for the incorporation of metal nanoparticles, as precursors for the manufacture of composite catalysts and those active in photo- and electrocatalytic processes are critically reviewed. The review is wrapped up with our personal view on future research directions.

A novel nickel catalyst supported on activated coal fly ash for syngas production via biogas dry reforming

In this study, we prepared novel Ni catalysts via wet impregnation of a support formed of industrial solid waste. Raw, alkali-treated, and alkali/acid co-treated coal fly ash were used for the first time as support for biogas dry reforming catalysts. The proposed two-step activation approach was highly effective in improving the surface area and changing the elemental composition of supports, thus enhancing the activity of the Ni catalysts. All catalysts prepared in this study effectively catalyzed the biogas dry reforming reaction; the catalyst using alkali/acid co-treated coal fly ash as support exhibited the best catalytic activity, with CH4 and CO2 conversion rates exceeding 95%, and good stability during 12 h of biogas dry reforming at 850 °C. This catalyst is highly competitive in terms of both activity and stability compared with most current Ni catalysts formed using commercial SiO2 supports. This study provides a new method for high-value application of coal fly ash, facilitating the manufacture of promising catalysts for biogas dry reforming.

One-step hydrothermal synthesis of MnOx-CeO2/reduced graphene oxide composite aerogels for low temperature selective catalytic reduction of NOx

In response to the problem of air pollution caused by nitrogen oxides (NOx), we synthesized a three-dimensional (3D) MnOx-CeO2 nanoparticles/reduced graphene aerogel for low-temperature selective catalytic reduction (SCR) of NOx with NH3 by a facile one-step hydrothermal treatment. During the hydrothermal reaction, the graphene nanosheets and MnOx-CeO2 nanoparticles self-assembled into 3D interconnected networks, in which the nanoparticles MnOx-CeO2 with uniform size were densely anchored onto the graphene nanosheets. Besides, the MnOx-CeO2/reduced graphene oxide (RGA) exhibited unique properties such as high specific surface area, and numerous catalytically active sites in comparison with pure MnOx-CeO2 nanoparticles. Evidences have shown that the chemical bonding between MnOx-CeO2 and GO achieved high selective catalytic reduction efficiency. The MnOx-CeO2/RGA composites displayed highly enhanced catalytic activity in comparison to bare MnOx-CeO2 nanoparticles which achieved 99% NOx conversion at 220 °C. This work provided a versatile approach to induce the combination of reduced graphene oxide sheets and other oxide nanoparticles, which opened up new avenues for the design and manufacture of catalysts used for low temperature SCR of NOx with NH3.

Modification of CaO Catalyst with Impregnation Method Using KoH in Biodiesel Synthesis from Waste Cooking Oil

Chicken eggshells can be used as raw material in the manufacture of CaO catalysts. Increased CaO catalyst activity can be done by the impregnation method. The purpose of this study was to determine the effect of %K on the wet impregnation of CaO catalyst using KOH and to find out the impregnation catalyst (CaO / K2O) on the biodiesel yield. Prepared chicken egg shells were calcined at 900oC for 3 hours. Then the CaO obtained was impregnated using KOH with a variation of % K (5%, 7%, 9% and 12% (w / w)) while heated at 85oC. The impregnation product was calcined at 600oC for 5 hours. The impregnation catalyst (CaO K2O) was applied to the biodiesel synthesis through a transesterification reaction with a mole ratio of 1:12 waste cooking oil: methanol, the amount of catalyst was 1.5% at a reaction temperature of 70°C for 2.5 hours. Based on the results of SEM-EDS analysis, the highest K2O at 7% K was 21.99%), while the highest CaO content was at 9% K by 81.53%. For the highest surface area analysis at 7% K with a surface area of 71.22 m2 / g, alkalinity was 2.59 mmol / g. The best biodiesel was obtained with a yield of 87.17%, kinematic viscosity of 2.89 cSt, water content of 0.032%, density of 0.819 g/ml, methyl ester level of 99.39%.

Optimization of nickel and ceria catalyst content for synthetic natural gas production through CO2 methanation

Manufacturing of catalysts with high reaction rates at mild conditions is important for an efficient production of synthetic natural gas through the CO2 methanation process. In this work, the design of a technical catalyst based on an optimal content of Ni as active phase, CeO2 as promoter and γ-Al2O3 micro-spheres as support (dp = 400–500 μm) is evaluated. The systematic optimization of Ni, CeO2 and γ-Al2O3 content revealed that a proper balance of the positive effects that each component provided individually, was found at 25 wt% Ni, 20 wt% CeO2 and 55 wt% γ-Al2O3 content. This catalyst was stable for 120 h at 300 °C. The high loading of CeO2 is far from the classical definition of promoter and it covers the gap between the addition in a low amount as promoter and its uncompetitive use as bulk support. The highest catalytic activity was attributed to high metallic surface area (5 m2·g−1), high nickel reducibility (79% at 500 °C) and the formation of moderate basic sites that can adsorb CO2 (−65 kJ·molCO2−1). In comparison with similar research catalysts and a commercial reference, the optimum formation showed higher activity for synthetic natural gas production. Therefore, the micro-catalyst can be implemented in the micro-structured reactors that are available in the market.

Use of Surfactants in Manufacture of Catalysts for Conversion of Methane

Effects are compared of various surfactants on the properties of an impregnating solution of nickel and aluminum nitrates in the condensate, used in manufacture of supported catalysts for conversion of methane. It was shown that use of synthanols (oxyethylated alcohols, which are nonionogenic surfactants) makes it possible to significantly (by three orders of magnitude) reduce the necessary content of surfactants in solution, which is confirmed by many years of industrial experience. Results are presented of quantum-chemical calculations of the interaction of synthanol molecules with nickel ions. The use of synthanol can substantially reduce the probability of carbonization of the catalyst surface and the possible carryover of a part of metal ions with the impregnating solution and also diminish the toxicity and the explosion hazard in the production area.

Fine tuning H-transfer and β-scission reactions in VGO FCC using metal promoted dual functional ZSM-5

Recently the importance of Petroleum Refining Industries has gradually shifted from a supplier of nonrenewable fuels to a supplier of petrochemical feed stocks such as olefins and aromatics (BTX). Zeolite ZSM-5 still remains a zeolite of tremendous importance due to its application as a FCC additive among other applications. New cracking technologies such as deep catalytic cracking, which also use ZSM-5 catalyst to increase gas yields, are also being developed and commercialized. ZSM-5 increases the yields of gaseous fractions at the expense of gasoline and is a good source of Ethylene, Propylene, Butenes and Pentenes because of high alkene/alkane ratios in the gas fraction.Conventionally catalyst manufacturers have independently marketed propylene maximization and olefin reduction additives for the benefit of petroleum refiners. In this article, the use of metal promoted ZSM-5 based FCC additives for the increase of propylene yields along with simultaneous reduction of olefins in gasoline fraction is elaborated. A Dual Functional Index was proposed to compare the effectiveness of additives towards this objective. The effect of metal modification in same proportions on cracking ratios and product distribution over additives was analyzed and it was demonstrated that the extent of H-transfer, β-scission, protolytic cracking and dehydrogenation reactions could be fine-tuned by metal modifications. It was observed that an excess of H-transfer reactions led to high aromatics and high coke deposit on the additive whereas a balance between β-scission reactions and H-transfer reactions lead to high propylene yields along with a great reduction in cracked naphtha olefin content and minimum carbon loss as dry gas.

Metal valorization from the waste produced in the manufacturing of Co/Mo catalysts: leaching and selective precipitation

Two different strategies have been designed for the acid and alkaline leaching steps of hydrodesulphurization catalysts. Tests have been performed on out-of-range catalysts issued from catalyst manufacturing process. Experimental conditions have been screened for these different processes considering the effects of concentration, temperature, solid/liquid ratio, etc. The best conditions have been used for producing two leachates that were treated by precipitation for recovery of valuable metals such as cobalt and molybdenum. Post-treatments have also been designed for the selective separation of Co from Mo: X-ray diffraction analyses on selective precipitates (as sulfide) confirm the purity of produced materials. Two flow sheets are proposed that allow selectively recovering more than 95% of the valuable metals.

Biotransformation of lanthanum by Aspergillus niger

Lanthanum is an important rare earth element and has many applications in modern electronics and catalyst manufacturing. However, there exist several obstacles in the recovery and cycling of this element due to a low average grade in exploitable deposits and low recovery rates by energy-intensive extraction procedures. In this work, a novel method to transform and recover La has been proposed using the geoactive properties of Aspergillus niger. La-containing crystals were formed and collected after A. niger was grown on Czapek-Dox agar medium amended with LaCl3. Energy-dispersive X-ray analysis (EDXA) showed the crystals contained C, O, and La; scanning electron microscopy revealed that the crystals were of a tabular structure with terraced surfaces. X-ray diffraction identified the mineral phase of the sample as La2(C2O4)3·10H2O. Thermogravimetric analysis transformed the oxalate crystals into La2O3 with the kinetics of thermal decomposition corresponding well with theoretical calculations. Geochemical modelling further confirmed that the crystals were lanthanum decahydrate and identified optimal conditions for their precipitation. To quantify crystal production, biomass-free fungal culture supernatants were used to precipitate La. The results showed that the precipitated lanthanum decahydrate achieved optimal yields when the concentration of La was above 15 mM and that 100% La was removed from the system at 5 mM La. Our findings provide a new aspect in the biotransformation and biorecovery of rare earth elements from solution using biomass-free fungal culture systems.

Estimating Precommercial Heterogeneous Catalyst Price: A Simple Step-Based Method

Developers of novel catalysts often have limited access to information on the costs of their catalytic materials. The R&D and commercialization decisions made by these researchers would benefit from cost estimates that are accurate and directly comparable to the prices of incumbent catalytic materials, but developing such estimates requires detailed knowledge of industrial synthesis methods and their costs. In order to address one critical part of this need for cost information, namely, the capital and operating costs of using catalyst manufacturing process equipment, a simple and researcher-accessible “step method” is described herein. This method is based on the estimating techniques that contract manufacturers of industrial catalysts use to develop price quotes for their services. It allows the development of an estimate of catalyst synthesis costs by selection of individual processing steps from a list. Data and methods to allow estimation of processing cost via the step method are provided for synthe...

Overcoming the Engineering Constraints for Scaling-Up the State-of-the-Art Catalyst for Tail-Gas N2O Decomposition

An efficient process is reported for preparing a state-of-the-art Fe-ferrierite catalyst for N2O decomposition under industrial tail-gas conditions. In the synthesis procedure, we evaluate the very demanding constraints for scale-up; i.e. large reactor volumes are typically needed, and long processing times and considerable amounts of wastewater are generated. The proposed synthesis minimizes the amount of water used, and therefore, the amount of produced wastewater is minimal; in this approach there is no liquid residual water stream that would need intensive processing. This has remarkable benefits in terms of process design, since the volume of equipment is reduced and the energy-intensive filtration is eliminated. This route exemplifies the concept of process intensification, with the ambition to re-engineer an existing process to make the industrial catalyst manufacture more sustainable. The so-obtained catalyst is active, selective, and very stable under tail-gas conditions containing H2O, NO, and O2, together with N2O, keeping a high conversion during 70 h time on stream at 700 K, with a decay of 0.01%/h, while the standard reference catalyst decays at 0.06%/h; hence, it deactivates 6 times more slowly, with ∼5% absolute points of higher conversion. The excellent catalytic performance is preliminarily ascribed to the differential speciation.

Catalyst treatment could boost exhaust cleanup

The catalysts that clean up automotive emissions typically consist of particles of platinum and other precious metals anchored on oxides. Because only the metal atoms at the particle surfaces come in contact with reactants and catalyze reactions, catalyst manufacturers strive to make these particles as tiny as possible. But these supported catalysts come with trade-offs. Dispersing the precious metal as finely as possible can go too far, and the catalysts can become unstable: The metal particles diffuse, coalesce, and lose their catalytic oomph. And the catalysts are often inactive when the temperature of the exhaust is low, which is the case when today’s engines start on a cold morning and will regularly be the case with future energy-efficient engines. A new study on automobile exhaust cleanup describes a way to bypass those problems in a catalytic two-for-one deal. Researchers have shown that a simple procedure can stabilize a platinum-based automotive

Nano-Array Integrated Structured Catalysts: A New Paradigm upon Conventional Wash-Coated Monolithic Catalysts?

The monolithic catalyst, namely the structured catalyst, is one of the important categories of catalysts used in various fields, especially in catalytic exhaust after-treatment. Despite its successful application in conventional wash-coated catalysts in both mobile and stationary catalytic converters, washcoat-based technologies are facing multi-fold challenges, including: (1) high Pt-group metals (PGM) material loading being required, driving the market prices; (2) less-than ideal distribution of washcoats in typically square-shaped channels associated with pressure drop sacrifice; and (3) far from clear correlations between macroscopic washcoat structures and their catalytic performance. To tackle these challenges, the well-defined nanostructure array (nano-array)-integrated structured catalysts which we invented and developed recently have been proven to be a promising class of cost-effective and efficient devices that may complement or substitute wash-coated catalysts. This new type of structured catalysts is composed of honeycomb-structured monoliths, whose channel surfaces are grown in situ with a nano-array forest made of traditional binary transition metal oxide support such as Al2O3, CeO2, Co3O4, MnO2, TiO2, and ZnO, or newer support materials including perovskite-type ABO3 structures, for example LaMnO3, LaCoO3, LaNiO, and LaFeO3. The integration strategy parts from the traditional washcoat technique. Instead, an in situ nanomaterial assembly method is utilized, such as a hydro (solva-) thermal synthesis approach, in order to create sound structure robustness, and increase ease and complex-shaped substrate adaptability. Specifically, the critical fabrication procedures for nano-array structured catalysts include deposition of seeding layer, in situ growth of nano-array, and loading of catalytic materials. The generic methodology utilization in both the magnetic stirring batch process and continuous flow reactor synthesis offers the nano-array catalysts with great potential to be scaled up readily and cost-effectively. The tunability of the structure and catalytic performance could be achieved through morphology and geometry adjustment and guest atoms and defect manipulation, as well as composite nano-array catalyst manufacture. Excellent stabilities under various conditions were also present compared to conventional wash-coated catalysts.

Mechanochemical synthesis of highly dispersed iron oxide from metallic powders in manufacture of catalysts

X-ray phase, X-ray diffraction, and synchronous thermal analyses, Mossbauer and IR spectroscopy, and scanning electron microscopy were used to study processes occurring in the stages of mechanochemical oxidation and thermal treatment of coarsely dispersed iron and cast iron powders in a dispersion medium of water and oxalic acid solutions. The optimal mechanochemical-synthesis conditions were determined and it was found that the preparation method affects the phase composition, structure, and properties of the resulting oxides. It was experimentally confirmed that the mechanochemical oxidation method makes it possible to obtain oxides by the zero-sewage technology with a specific surface area 1.5–12 times larger that that in oxides produced by the conventional precipitation technique. An analysis of the reactivity of the samples in the model reaction of carbon monoxide conversion by steam demonstrated their high catalytic activity.