Potassium Catalyst Research Articles

Exploiting Ion-Pairing Interactions for Fast and Controlled Ring-Opening Polymerization of rac-β-Butyrolactone at Room Temperature with Dinuclear Sodium and Potassium Catalysts

Exploiting Ion-Pairing Interactions for Fast and Controlled Ring-Opening Polymerization of <i>rac</i>-β-Butyrolactone at Room Temperature with Dinuclear Sodium and Potassium Catalysts

Comparison of potassium catalysts on zeolite sodium A and X in transesterification of palm oil and active species specification

Heterogeneous catalysts consisting of potassium supported on zeolites are active for transesterification, but the effect of zeolite properties is not clearly understood. This work compares catalysts containing 12 wt.% potassium on zeolite sodium A and X (12K/NaA and 12K/NaX) in terms of performance and physicochemical properties. Both catalysts were prepared by ultrasound-assisted impregnation with potassium acetate buffer. 12K/NaA is a better catalyst in transesterification of palm oil, giving a higher biodiesel yield than 12K/NaX in the first run (99.1 ± 0.3 % and 77.9 ± 2.2 %, respectively). From characterization by CO2-TPD, XRD, FTIR, XPS, and SEM-EDS, both catalysts have similar basicity but different dispersion of carbonates and interaction on the zeolites. The 12K/NaA has those species on external surfaces and more monodentate carbonate than 12K/NaX. Ion exchange occurs between potassium ions from the precursor and sodium ions from the zeolite. Moreover, 12K/NaA is more stable, providing higher biodiesel yields in the second and third catalytic cycles.

A multi-layer membrane filter made of potassium catalyst and three-way catalyst for a passive after-treatment system

A multi-layer membrane has been fabricated to integrate a Three-Way Catalyst (TWC) and Gasoline Particulate Filter (GPF) into one device, called a four-way catalytic converter. The top layer, made of nano-scale potassium catalyst particles, traps Particulate Matter (PM) with almost 100% filtration efficiency at all times and oxidizes PM (mostly soot) with a significantly reduced temperature of 476°C at the oxidation peak. Moreover, the bottom layer catalyst is comprised of sub-micro TWC particles to combine NO reduction and CO oxidation capabilities. The effective temperature range for the simultaneous removal of all pollutants was between 420°C–500°C.

A clean route of biodiesel production using red mud-based potassium catalyst

In our work, a low-cost and high-efficiency red mud-based potassium composite (KRM) was successfully synthesized via solid-state method using red mud (RM) and potassium carbonate (K2CO3) as material, and then was applied to produce castor oil biodiesel through transesterification. The preparation conditions of red mud-based potassium composite were optimized. The synthesized catalysts were characterized by X-Ray diffractometer (XRD), Scanning electron microscopy (SEM), Hammett method and Brunauer-Emmett-Teller (BET). The maximum conversion from castor oil to biodiesel (94.52%) was acquired with methanol to oil molar ratio 18:1, catalyst dosage 5 wt%, reaction temperature 65 °C and reaction time 2.5 h. According to the thermo-kinetic results, the castor oil transesterification catalyzed by KRM catalyst was a first-order kinetics reaction and was not an exothermic and spontaneous reaction pathway. Particularly, the characterization results indicated that the brightly textural properties (small particle size, high basicity, high surface area and pore volume) were favorable factors for the high catalytic activity of KRM catalyst. The KRM catalyst showed excellent reusability after four cycles. Besides, turnover frequency (TOF), green parameter of transesterification process and cost analysis demonstrated that the transesterification process catalyzed by the high-efficiency KRM catalyst possessed green reaction pathway and the composite catalyst of KRM could effectively reduce the cost of biodiesel production.

Changes in the Physicochemical and Catalytic Properties of Iron–Potassium Catalysts under Operation in a Reactor of Ethylbenzene Dehydrogenation to Styrene at Nizhnekamskneftekhim

Changes in the Physicochemical and Catalytic Properties of Iron–Potassium Catalysts under Operation in a Reactor of Ethylbenzene Dehydrogenation to Styrene at Nizhnekamskneftekhim

Highly Dispersed Nickel Nanoparticles on Hierarchically Ordered Macroporous Al2O3 and Its Catalytic Performance for Steam Reforming of 1-Methyl Naphthalene

In this study, we investigate the effect of a hierarchically ordered macroporous structure of alumina support on the steam reforming of 1-methyl naphthalene with mesoporous alumina-supported nickel and potassium (xK/Ni–MeAl), and macroporous alumina-supported nickel and potassium (xK/Ni–MaAl) catalysts. Hierarchically ordered macroporosity in Al2O3 supports plays an important role in maintaining the high Ni dispersion through multiple interactions in Ni–K over AlO4 tetrahedra in alumina. This, in turn, improves the catalytic performance of steam reforming, including high gas yields, turnover frequency for hydrogen production, and 1-methyl naphthalene conversion. At high K content, the Ni active sites over xK/Ni–MeAl catalysts significantly decrease, resulting in almost zero steam reforming rate in the reaction test. Conversely, the potassium–alumina interaction in xK/Ni–MaAl catalysts not only diminishes the formation of the inactive nickel aluminate phase but also maintains the highly dispersed Ni active sites, resulting in a high steam reforming rate.

Sulfur Evolution and Capture Behavior by a Solid Waste of Red Mud during Chemical Looping Combustion of Petroleum Coke

The sulfur evolution behavior during the chemical looping combustion (CLC) process of petroleum coke was investigated in a fluidized bed reactor with a low-cost solid waste of red mud as the oxygen carrier. Effects of temperature, oxygen carrier, and potassium catalyst addition on sulfur release were investigated, and H2S oxidization kinetics with the red mud and the effect of elements in the red mud on sulfur conversion were evaluated in detail. The red mud oxygen carrier had a promoting effect on H2S generation and thus enhanced sulfur conversion. The addition of potassium remarkably accelerated carbon conversion due to its catalytic effect. Meanwhile, it promoted H2 generation and then enhanced the generation of H2S. The addition of potassium into the process could weaken the release of gaseous sulfur but had no obvious negative influence on the reactivity of the red mud oxygen carrier. The experiment H2S interaction with the red mud suggested that the conversion of H2S to SO2 decreased with increasing temperature. The red mud has a low ability to oxidize H2S to SO2 but a high reactivity to capture sulfur-containing gases. Solid sulfur-containing products such as CaSO4 and Fe3S4 as well as K2S2 in the case of K addition into the process were detected.

Catalytic gasification of rice hull by dielectric barrier discharge non-thermal plasma over potassium catalyst

Dielectric barrier discharge (DBD) non-thermal plasma was used for gasification of rice hull. And the gasification efficiency, gas production performance and gasification productions of rice hull were studied in the different atmosphere of the DBD gasification. The effect of the potassium metal on DBD gasification of rice hull was investigated and the catalytic mechanism of potassium was studied by density functional theory calculation. It was found that the gasification efficiency of rice hull by DBD in CO2 atmosphere is up to 87.14%, which is higher than that in the N2 atmosphere. The implantation of the potassium metal can also improve the DBD gasification efficiency, and promote the generation of H2 and CH4. The rice hull loaded with 3% potassium had the best gasification in the CO2 atmosphere. Almost no tar was found during the DBD gasification of rice hull. N2 adsorption and desorption, scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) were used to investigate the properties of the carbon materials, which was generated from the rice hull gasification. The carbon material which was produced by DBD gasification in CO2 atmosphere had large specific surface area and abundant functional groups. It can be used as catalyst carrier and other fields.

Potassium catalysts supported on γ-Al2O3 to produce biodiesel

&#x0D; Biodiesel production is carried out through homogeneous catalysis that forms complex reaction mixtures and has high operating costs. The aim of this work is to synthesize basic, active and selective heterogeneous catalysts for the transesterification reaction with vegetable oils employing g-alumina as support and potassium as active species. The catalysts were characterized by X-ray diffraction and infrared spectroscopy. The amount of catalyst used in the reaction was scanned in a range of 1-10% w, obtaining a maximum conversion of 85% at 55 °C with 6.5% w/w of catalyst with respect to the reagent load and with a methanol-oil molar ratio of 6: 1, reaching equilibrium conversion at six hours. The catalysts were tested at 40, 45, 50 and 55 °C in the transesterification reaction using refined sunflower oil and anhydrous methanol as reagents in a 6: 1 ratio. The 40% K catalyst obtained the best conversion at 55 °C with 85% and showed a selectivity of 45%.&#x0D;

Increase in processing flue gas flow rate while maintaining the fluidization state and filtration performance in a low-temperature continuous regeneration filter using a fluidized bed

To increase the processing gas flow rate in a fluidized bed filter, the effects of superficial velocity and fluidization state on PM filtration and combustion were examined by experiments using large bed particles (710 μm). The fluidization state at 710 μm was measured by image analysis and recurrence plot, and the superficial velocities as experimental conditions were determined to obtain almost the same fluidization state and filtration efficiency as those for small bed particles (420 μm) in previous studies. The BET-surface area of 710 μm is slightly larger than that of 420 μm, and the amount of potassium catalyst doped on large bed particles is comparable to that at 420 μm. The gas phase velocity is increased by increasing the processing gas flow rate, and the contact probability between PM and oxidizer increases. The PM combustion reaction is significantly promoted owing to the effects of the potassium catalyst and the increase in the gas phase velocity, and the minimum continuous regeneration temperature is 30 °C lower than that at 420 μm. As a result, fluidized bed filters using large bed particles can be operated in continuous regeneration mode at a bed temperature of 320 °C while maintaining a filtration efficiency of 100%.

Effect of pre-treatment on catalytic coal gasification characteristics of sub-bituminous coal

Sintering or agglomeration is formed in the process of the gasification of coal when fluxing K2CO3, which leading to the entire bed defluidization. In order to study the catalytic coal gasification reactivity and agglomeration properties in pressurized fluidized bed, Wangjiata raw coal, demineralized coal with HCl-HF treatment, and raw coal with different amounts of clay mineral addition were selected. The catalytic coal gasification reactivity, the agglomeration and sintering properties were studied. As well as water-soluble catalyst recovery from the gasification residue was also determined. The results show that for potassium-catalyzed steam gasification, not only coal ash content but also composition affected the gasification reactivity, agglomeration, and catalyst recovery. The carbon conversion increased varying degrees with increasing K2CO3 loadings, K2CO3 impregnated coal showed a high degree of agglomeration, and agglomeration increased with increasing K2CO3 amount. Demineralized coal couldn't improve the agglomeration property. The addition of Clay mineral, was found to be very efficient in anti-sintering. However, compared with demineralized coal, the carbon conversion and water washing catalyst recoveries decreased obviously for those samples with the addition of clay minerals. The test verifies that part of potassium catalyst irreversibly reacted with coal ash to form relatively water-insoluble potassium compounds such as kaliophilite and sanidine.

Effects of potassium additives on the combustion characteristics of graphite as a heating source of heat-not-burn tobacco.

“Heat-not-burn” tobacco with an external heating source is a cleaner alternative to conventional cigarettes due to its lower emission of nicotine, CO and tar in the smoke, and graphite is a promising carbon heating source for a “heat-not-burn” tobacco product yet is not easy to be fired. This work aims to improve the combustion properties of graphite using potassium catalysts. Thermal gravimetric analysis is performed to investigate the combustion properties, and a first-order kinetic model is applied to describe the combustion process. Scanning electron microscopy is used to observe the surface morphology, and the mineral and elemental composition are investigated by powder X-ray diffraction and energy dispersive spectrometry, respectively. The results indicate that the potassium additives can significantly decrease the ignition temperature of the graphite samples by 51–124 °C, and the promotion effects are closely related to the potassium and oxygen content of the additives. Further kinetic analysis implies that K and O can decrease the activation energy required for the oxidation reactions by 45.1% from 194.5 to 106.8 kJ mol−1, thereby improving the graphite combustion. Moreover, potassium can play the role of “O2 transfer”, which can transfer atmospheric oxygen to support graphite combustion. K2CO3 is a suitable catalyst for graphite combustion, and the suggested addition amount is 0.88% in weight.

The evolution of catalytically active calcium catalyst during steam gasification of lignite char

Coal or coal char/pyrocarbon gasification is a viable way to produce cheaper hydrogen. The gasification of three different lignites and their pretreated samples showed that either the intrinsic calcium in lignite or the extrinsic calcium added by ion exchange had high catalytic activity. It was proven that most of the calcium in the lignite was organically associated, which was mainly bound to carboxyl groups and highly dispersed at an atomic level. Furthermore, Yuxi lignite was demineralized to investigate the catalytic characteristics of calcium and potassium catalysts on steam gasification. The changes of gasification rate, gas compositions and oxygen chemisorption capacity with carbon conversion hinted that the catalytic mechanism of calcium was different from that of potassium. X-ray absorption near edge structure (XANES) analysis revealed that carboxyl-bound calcium was the active form of the catalyst, and the deactivation of the calcium catalyst in the gasification process was due to the transformation of carboxyl-bound calcium to other chemical forms. The organically bound calcium also led to the porous char structures at the early gasification stage, which improved the catalytic activity.

Microwave-Assisted Hydrothermal Preparation of Corn Straw Hydrochar as Supercapacitor Electrode Materials.

In this work, we propose the microwave-assisted hydrothermal activation method to synthesize supercapacitor electrode materials from corn straw under a small amount of the potassium catalyst (30 wt %), which can meet the environmental protection and low-cost requirement. With the extension of radiation time from 40 to 100 min, the pore structure of hydrochar expands from the micropore to hierarchical pore, and the microstructure evolves from an amorphous structure to graphene-like sheets. Microwave-assisted hydrothermal activation can control the synergistic development of hierarchical pore and graphene-like sheets of hydrochar under the condition of using a lesser amount of the catalyst. The as-obtained HTC-40/70/100 shows an excellent graphitization degree and the developed hierarchical pores. By comparing the electrochemical performance of the symmetrical capacitor devices composed of corn straw hydrochar and pyrochar in organic electrolytes, we have found that the hydrochar is suitable for organic system symmetric capacitance, and the pore structure and graphitization degree are closely related to the transmission of ions and electrons in the electrolyte. Therefore, HTC-100 with a high specific surface area (1781 m2/g) and highly ordered microstructure has the best electrochemical performance.

Iron–Potassium on Single-Walled Carbon Nanotubes as Efficient Catalyst for CO2 Hydrogenation to Heavy Olefins

The iron–potassium catalysts supported on single- and multiwalled carbon nanotubes, FeK/SWNTs and FeK/MWNTs, were fabricated, characterized, and evaluated in CO2 hydrogenation. The FeK/SWNTs cataly...

Operando potassium K-edge X-ray absorption spectroscopy: investigating potassium catalysts during soot oxidation.

The chemical and structural nature of potassium compounds involved in catalytic soot oxidation have been studied by a combination of temperature programmed oxidation and operando potassium K-edge X-ray absorption spectroscopy experiments. These experiments are the first known operando studies using tender X-rays (∼3.6 keV) under high temperature oxidation reaction conditions. X-ray absorption near edge structure analysis of K2CO3/Al2O3 catalysts during heating shows that, at temperatures between 100 and 200 °C, potassium species undergo a structural change from an initial hydrated K2CO3·xH2O and KHCO3 mixture to well-defined K2CO3. As the catalyst is heated from 200 °C to 600 °C, a feature associated with multiple scattering shifts to lower energy, indicating increased K2CO3 dispersion, due to its mobility at high reaction temperature. This shift was noted to be greater in samples containing soot than in control experiments without soot and can be attributed to enhanced mobility of the K2CO3, due to the interaction between soot and potassium species. No potassium species except K2CO3 could be defined during reactions, which excludes a potential reaction mechanism in which carbonate ions are the active soot-oxidising species. Simulations of K-edge absorption near edge structures were performed to rationalise the observed changes seen. Findings showed that cluster size, unit cell distortions and variation in the distribution of potassium crystallographic sites influenced the simulated spectra of K2CO3. While further simulation studies are required for a more complete understanding, the current results support the hypothesis that changes in the local structure on dispersion can influence the observed spectra. Ex situ characterisation was carried out on the fresh and used catalyst, by X-ray diffraction and X-ray photoelectron spectroscopy, which indicated changes to the carbonate species, in line with the X-ray absorption spectroscopy experiments.

Biodiesel and Crude Glycerol from Waste Frying Oil: Production, Characterization and Evaluation of Biodiesel Oxidative Stability with Diesel Blends

Waste oils are becoming increasingly more important as feedstock for the production of fuels and glycerol as byproduc. Optimization of homogeneous transesterification of waste frying oil (WFO) to biodiesel over hydroxide potassium (KOH) catalyst have been investigated. In this respect, response surface methodology (RSM) was applied to determine the relationships between methanol and WFO molar ratio (3:1–12:1), KOH concentration (0.5%–2%) and temperature (25–65 °C) on the conversion yield. Transesterification of WFO produced 96.33% maximum methyl ester yield at the optimum methanol/WFO molar ratio 7.3:1, KOH loading 0.5 wt. % and the reaction temperature was 58.30 °C. The physicochemical properties of optimized biodiesel met the requirements of the European Norm 14214, such as kinematic viscosity at 40 °C 4.57 mm/s2, the sulfur content 0.005 wt. %, and the density at 15 °C 889.3 kg/m3. This study also examined the accelerated oxidation of biodiesel and biodiesel/diesel blends under combined temperature and air effect at different periods of time while measuring their acidity. Results have shown that total acid number increased proportionally to the biodiesel content of the biodiesel/diesel blends from 0.5 mgKOH/g for B7 (7% (v/v) biodiesel and 93% (v/v) diesel) up to 2.8 mg KOH/g for B100 (100% biodiesel). The synthesized trans-esterified oil can be a potential alternative to petrodiesel, hence its application at an industrial scale. This work also reports some properties of crude glycerol (CG) derived from biodiesel from WFO. The glycerol yield (%), pH, water content (wt. %), density at 15 °C (g/cm3), and kinematic viscosity at 40 °C (mm2/s) was analyzed according to standard test methods.

Formation of carbon nanotubes from potassium catalyzed pyrolysis of bituminous coal

In the present work, a novel method has been proposed, which can be used for generating carbon nanotubes (CNTs) using coal as the raw material and potassium hydroxide as the catalyst precursor. The results of Fourier Transform Infrared (FTIR) spectroscopy indicated that the groups of CH3, CH2 contained in the coal gradually disappeared during the potassium catalyzed pyrolysis. Raman analysis showed that the graphitization degree of catalytic pyrolysis products of raw coal was high, and the ratio of the intensities of G and D peaks (IG/ID) was 3.0. The results of Scanning Electron Microscope (SEM) showed that there were many CNTs in the product. The Transmission Electron Microscopy (TEM) showed that these CNTs had different shapes (linear or curved) and have good graphite crystal structure with a wall number of 18–65 layers and a diameter of 20–155 nm. The potassium catalyst has the dual function of catalyzing the formation of CNTs and etching large molecular structure to generate carbon source. The formation process of CNTs is as follows: coal takes pyrolysis to produce small carbon-containing molecules such as CH4, and the small carbon-containing molecules formed CNTs through catalytic cracking under the action of catalyst. A “stepwise growth” model of CNTs was established.

Gaseous and particulate emissions from a chimneyless biomass cookstove equipped with a potassium catalyst

Approximately three billion people cook with solid fuels, mostly wood, on open fires or rudimentary stoves. These traditional cooking methods produce particulate matter and carbon monoxide known to cause significant respiratory health problems, especially among women and children, who often have the highest exposure. In this work, an inexpensive potassium-based catalyst was incorporated in a chimneyless biomass cookstove to reduce harmful emissions through catalytic oxidation. Potassium titanate was identified as an effective and stable oxidation catalyst capable of oxidizing particulate matter and carbon monoxide. Using a cordierite monolith to incorporate potassium titanate within a bespoke, rocket-style, improved cookstove led to a 36% reduction in particulate matter emissions relative to a baseline stove with a blank monolith and a 26% reduction relative to a stove with no monolith. Additionally, the catalytic stove reduced particulate matter emissions by 82%, reduced carbon monoxide emissions by 70%, and improved efficiency by 100% compared to a carefully tended, three-stone fire. Potassium titanate was also shown to oxidize carbon monoxide at temperatures as low as 500 °C, or as low as 300 °C when doped with copper or cobalt.

Electronic-Structure-Dependent Performance of Single-Site Potassium Catalysts for Formaldehyde Emission Control

Depending on the dispersion degree and electronic states, alkali metals such as potassium can function as either promoters or inhibitors in catalytic reactions, but the underlying reasons for that are still obscure. Herein, we fabricated two kinds of single-site potassium catalysts (K1/HMO and K1/HWO) by using hollandite-type manganese oxide (HMO) and hexagonal tungsten oxide (HWO) as supports. K1/HMO with the partially charged single K ions efficiently enhances the ability to activate both surface lattice oxygen and molecular oxygen, thereby leading to a higher catalytic activity for HCHO oxidation. In contrast, K1/HWO is less active than HWO due to the electron-lean K ions. This work provides a feasible explanation for the functions played by alkali metals in catalytic oxidation, and thus assists the design of efficient catalysts promoted by alkali metals.