Ultrasonic-assisted preparation of ultrafine Pd nanocatalysts loaded on Cl−-intercalated MgAl layered double hydroxides for the catalytic dehydrogenation of dodecahydro-N-ethylcarbazole

N-ethylcarbazole/dodecahydro-N-ethylcarbazole (NEC/H12-NEC) is a promising LOHC, and the development of a catalyst with high activity and stability is the key to realizing its reversible hydrogen storage process. In this paper, ultrafine Pd nanocrystalline catalysts (Pd/LDHs-us) supported on Cl^--intercalated MgAl LDHs were prepared by a simple ultrasonic-assisted reduction method and applied in the dehydrogenation of 12H-NEC. In the process of ultrasonic-assisted reduction, the instantaneous high temperature generated by cavitation decomposed part of the CO₃^2– in LDHs interlayer, and promoted PdCl₄^2- to enter the interlayer and become new intercalated ions. At the same time, hydroxyl groups on the surface of LDHs were excited to generate hydrogen radicals (•H) with strong reducibility, which reduced PdCl₄^2- to Pd nanoparticles (PdNPs) in situ. The remaining Cl^- ions continued to exist in the interlayer as intercalated ions. The agglomeration of PdNPs was effectively inhibited, and the average particle size was 1.8 nm, which was uniformly dispersed on LDHs, which improved the catalytic activity of Pd/LDHs-us. The coordination between PdNPs and oxygen in the hydroxyl groups on the surface of LDHs improved its catalytic stability. Using Pd/LDHs-us catalyst, the conversion rate of H12-NEC was 100.0 %, and the dehydrogenation efficiency was 99.3 % at 180℃. When the reaction temperature drops to 170℃, the dehydrogenation efficiency can still reach 94.6 %, showing excellent catalytic performance. The study of dehydrogenation kinetics shows that the apparent activation energy of Pd/LDHs-us catalyst is only 90.97 kJ/mol. This provides a new method and idea for the preparation of efficient dehydrogenation catalysts in the future.     

Effect of Preparation Method on the SCR Activity of Fe-Doped CoCr Oxide Catalysts

Fe-doped CoCr oxide catalysts are prepared by solid-phase mixing method, coprecipitation method, mechanical mixing method, and citric acid method, respectively, and their catalytic activity in the selective catalytic reduction of nitrogen oxides with NH₃ (NH₃-SCR) is tested. The Fe_0.5CoCrO_x catalysts prepared by all preparation methods have good water resistance and sulfur resistance when the calcination temperature is 400 °C. Fe_0.5CoCrO_x prepared by coprecipitation method by calcination at 400 °C (CP-400) is shown to have the optimum catalyst activity. In addition, the catalysts are characterized by a series of characterizations. The characterization results show that CP-400 has the largest specific surface area, which makes the active and acidic sites highly dispersed on the surface of CP-400, resulting in stronger redox and acidity and improved SCR activity. The removal of NO by NH₃-SCR over CP-400 at 150 °C follows the Eley-Rideal (E R) and Langmuir-Hinshelwood (L H) mechanisms.     

CuCoMn-zeolite双功能催化剂转化生物质基合成气制取液态烃

选用四种不同的分子筛(SAPO-34, ZSM-5, Y, MCM-41)与CuCoMn(高醇合成组元)构成双功能催化剂,利用N₂吸脱附、H₂-TPR、XRD、NH₃-TPD等表征了催化剂的结构性质. 研究了催化剂在生物质基合成气一段法制取液态烃燃料的应用. 相比于CuCoMn催化剂,加入分子筛的双功能催化剂均不同程度地提高了液体烃燃料的选择性及收率,且收率按顺序递减呈CCM-ZSM-5>CCM-SAPO-34>CCM-Y>CCM-MCM-41. 同时,共沉淀法制备的CuCoMn-ZSM-5 (20wt%, Si/Al=100) 具有最佳的CO转化率(76%)及液体产物收率(30%). 相比于CuCoMn氧化物,双功能催化剂的比表面及孔容均得到提高. CCM-ZSM-5具有适中的微孔尺寸和中等强度的酸性,增加CCM-ZSM-5中ZSM-5含量或降低ZSM-5中的Si/Al比,均有利于提高酸性位的数量,主要是较弱的酸性位. 而共沉淀法制备的CCM-ZSM-5具有更好的金属分散性及还原性能.     

Facile decolorization of methylene blue by morphology-dependence δ-MnO2 nanosheets -modified diatomite

In this work, coscinodiscus-diatomite and melosira-diatomite have been decorated by ultrathin birnessite MnO₂ (δ-MnO₂) nanosheets through a one-pot hydrothermal method without using any surfactants. The δ-MnO₂ nanosheets are observed to grow vertically on the purified melosira-diatomite as well as coscinodiscus-diatomite. Moreover, the two composites exhibit high efficiency for decomposing methylene blue (MB) in the presence of H₂O₂. The coscinodiscus-diatmite@MnO₂ achieves a removal rate of 81.8% (2 h), and yet melosira-diatomite@MnO₂ reaches a higher degradation rate of 91.3% in 2 h. Additionally, the effects of catalyst amount, catalysis reaction temperature, preparing time have also been investigated. In principle, the diverse diatomite@MnO₂ nanostructures not only present an environmentally friendly and low cost with a good cycling stability, but also offer a simple way for the catalytic degradation of dye waste water in practical applications.     

Cucurbit[n]urils/CdS-MoS2的表征及可见光催化性能

为了降低CdS光生电子-空穴的复合对其光催化性能的影响,利用窄带隙半导体MoS₂和有机大分子瓜环(cucurbit[n]uril,Q[n])对CdS进行改性研究. 本文采用水热法合成了Q[n]/CdS-MoS₂\\(n=6,7,8)复合光催化剂. 利用FT-IR、XRD、XPS、SEM、UV-Vis和PL等手段对产物结构、形貌和光学等性质进行表征,并考察Q[n]/CdS-MoS₂复合催化剂对次甲基蓝、罗丹明B和结晶紫溶液的催化降解性能. 结果表明,瓜环对CdS-MoS₂颗粒生长结晶起到了调控作用,Q[n]/CdS-MoS₂(n=6,7,8)形成了具有花瓣状叶片的花团,催化剂表面积增大,活性位点增加,禁帯宽度减小,电子-空穴对得到了更好的分离和迁移. Q[6]/CdS-MoS₂和Q[7]/CdS-MoS₂对亚甲基蓝具有良好的光催化活性,催化过程为羟基自由基原理.     

High-efficiency degradation catalytic performance of a novel Angelica sinensis polysaccharide-silver nanomaterial for dyes by ultrasonic cavitation

Currently, the polluted wastewater discharged by industry accounts for the major part of polluted bodies of water. As one of the industrial wastewaters, dye wastewater is characterized by high toxicity, wide pollution, and difficulty in decolorization degradation. In this paper, a novel composite nanomaterial catalyst of silver was prepared by using Angelica sinensis polysaccharide (ASP) as a reducing and stabilizing agent. And the optimum reaction conditions explored are V_AgNO3 = 5 mL (300 mM) and v_ASP = 7% (w/v) for 6 h at 90 °C. In addition, the ASP-Ag nanocatalyst was characterized by several techniques. The results demonstrated that ASP-Ag nanoparticles were successfully synthesized. Degradation rate, which provides a numerical visualization of the percentage reduction in pollutant concentration. With the wrapping of ASP, the ultrasonic catalytic degradation rates of different organic dyes including rhodamine B (RB), methylene blue (MB), and methyl orange (MO) were from 88.2%, 88.7%, and 85.2% to 96.1%, 95.2% and 93.5% at room temperature, respectively. After the experiments, when c_dyes = 10 mg/L, the highest degradation rate can be observed under c_APS-AgNPs = 10 mg/L with the most powerful cavitation frequency f = 59 kHz. The effect of ultrasonic frequency on the acoustic pressure distribution in the reactor was investigated by using COMSOL Multiphysis^@ software to propose the mechanism of ultrasonic degradation and the mechanism was confirmed by OH radical trapping experiments. It indicates that OH produced by the ultrasonic cavitation effect plays a determinant role in the degradation. And then, the intermediate products of the dye degradation process were analyzed by gas chromatography and mass spectrometry (GC–MS), and the possible degradation processes of dyes were proposed. The resulting products of degradation are SO₄²⁻, NH₄⁺, NO₃⁻, N₂, CO₂ and H₂O. Finally, the recycling degradation experiments showed that catalyst maintains a high degradation rate within reusing 5 cycles. Thus, this catalyst is highly efficient and recyclable.     

Sonochemical synthesis of amide-functionalized metal-organic framework/graphene oxide nanocomposite for the adsorption of methylene blue from aqueous solution

Graphene oxide-[Zn₂(oba)₂(bpfb)]·(DMF)₅ metal-organic framework nanocomposite (GO-TMU-23; H₂oba = 4,4′-oxybisbenzoic acid, bpfb = N,N′-bis-(4-pyridylformamide)-1,4-benzenediamine, DMF = N,N-dimethylformamide) is prepared through a simple and large-scale sonochemical preparation method at room temperature. The obtained nanocomposite is characterized by Field Emission Scanning Electron Microscopy (FE-SEM), powder X-ray diffraction (PXRD) and FT-IR spectroscopy. Additionally, the absorption ability of GO-TMU-23 nanocomposite toward cationic dye methylene blue was also performed. Significantly, GO-TMU-23 nanocomposite exhibits remarkably accelerated adsorption kinetics for methylene blue in comparison with the parent materials. The adsorption process shows that 90% of the dye has been removed and the equilibrium status has been reached in 2 min by using the nanocomposites as the adsorbent.     

Enhanced sonocatalytic degradation of organic dyes from aqueous solutions by novel synthesis of mesoporous Fe3O4-graphene/ZnO@SiO2 nanocomposites

Fe₃O₄-graphene/ZnO@mesoporous-SiO₂ (MGZ@SiO₂) nanocomposites was synthesized via a simple one pot hydrothermal method. The as-obtained samples were investigated using various techniques, as follows: scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and specific surface area (BET) vibrating sample magnetometer (VSM), among others. The sonocatalytic activities of the catalysts were tested according to the oxidation for the removal of methylene blue (MB), methyl orange (MO), and rhodamine B (RhB) under ultrasonic irradiation. The optimal conditions including the irradiation time, pH, dye concentration, catalyst dosage, and ultrasonic intensity are 60 min, 11, 50 mg/L, 1.00 g/L, and 40 W/m², respectively. The MGZ@SiO₂ showed the higher enhanced sonocatalytic degradation from among the three dyes; furthermore, the sonocatalytic-degradation mechanism is discussed. This study shows that the MGZ@SiO₂ can be applied as a novel-design catalyst for the removal of organic pollutants from aqueous solutions.     

Surface modification of HMS material with silica sol leading to a remarkable enhanced catalytic performance of Cu/SiO2

Cu/SiO₂ catalysts with different bimodal pore structures adjusted by the ratio of HMS and silica sol were prepared via modified impregnation method. Structure evolutions of the catalyst were systematically characterized by N₂-physisorption, X-ray diffraction, H₂ temperature-programmed reduction, N₂O titration and X-ray photoelectron spectroscopy. The results show that the composite silica supported copper catalysts showed remarkably enhanced catalytic performance in the selective hydrogenation of dimethyl oxalate to ethylene glycol compared to the individual silica supported ones obtained by the same method. The dimethyl oxalate conversion and the ethylene glycol selectivity can reach 100% and 98% at 473 K with 2.5 MPa H₂ pressure and 1.5 h⁻¹ liquid hour space velocity of dimethyl oxalate over the optimized Cu/SiO₂ catalyst. The remarkably enhanced catalytic performance of Cu/SiO₂ catalysts might be attributed to the homogeneous dispersion and uniformity of the active copper species and to the larger copper surface areas attained on the HMS supports with large pore diameters and surface areas.     

Catalytic activity of copper (II) oxide prepared via ultrasound assisted Fenton-like reaction

Copper (II) oxide nanoparticles were synthesized in an ultrasound assisted Fenton-like aqueous reaction between copper (II) cations and hydrogen peroxide. The reactions were initiated with the degradation of hydrogen peroxide by ultrasound induced cavitations at 0 °C or 5 °C and subsequent generation of the OH radical. The radical was converted into hydroxide anion in Fenton-like reactions and copper hydroxides were readily converted to oxides without the need of post annealing or aging of the samples. The products were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) surface area analysis. Catalytic activity of the nanoparticles for the hydrogen peroxide assisted degradation of polycyclic aromatic hydrocarbons in the dark was tested by UV–visible spectroscopy with methylene blue as the model compound. The rate of the reaction was first order, however the rate constants changed after the initial hour. Initial rate constants as high as 0.030 min⁻¹ were associated with the high values of surface area, i.e. 70 m²/g. Annealing of the products at 150 °C under vacuum resulted in the decrease of the catalytic activity, underlying the significance of the cavitation induced surface defects in the catalytic process.     

Preparation and characterization of Cobalt Sulfophthalocyanine/TiO2/fly-ash cenospheres photocatalyst and study on degradation activity under visible light

Cobalt Sulfophthalocyanine (CoSPc) sensitized TiO₂ sol samples were prepared through a Sol-Gel method using Cobalt Sulfophthalocyanine as a sensitizer. Loading and modified floating photocatalyst was prepared by hydrothermal method using fly-ash cenospheres as a carrier. The properties of the samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and UV-vis diffuse reflectance spectrum (DRS). Photocatalytic activity was studied by degrading wastewater of methylene blue under visible light. The results indicate that the fly-ash cenospheres are covered by modified TiO₂ film which composed of the anatase, brookite and rutile misch crystal phase. CoSPc/TiO₂/fly-ash cenospheres samples have good catalytic activity under visible light, and have strong absorbency during 600-700 nm. The sensitization of CoSPc can enhance visible light catalytic activity of TiO₂/fly-ash cenospheres. The degradation rate of methylene blue reaches 73.36% in 180 min under the visible light illumination. But too much CoSPc can decrease its catalytic activity.     

A versatile sonication-assisted deposition–reduction method for preparing supported metal catalysts for catalytic applications

This work aims to develop a rapid and efficient strategy for preparing supported metal catalysts for catalytic applications. The sonication-assisted reduction–precipitation method was employed to prepare the heterogeneous mono- and bi-metallic catalysts for photocatalytic degradation of methyl orange (MO) and preferential oxidation (PROX) of CO in H₂-rich gas. In general, there are three advantages for the sonication-assisted method as compared with the conventional methods, including high dispersion of metal nanoparticles on the catalyst support, the much higher deposition efficiency (DE) than those of the deposition–precipitation (DP) and co-precipitation (CP) methods, and the very fast preparation, which only lasts 10–20 s for the deposition. In the AuPd/TiO₂ catalysts series, the AuPd(3:1)/TiO₂ catalyst is the most active for MO photocatalytic degradation; while for PROX reaction, Ru/TiO₂, Au–Cu/SBA-15 and Pt/γ-Al₂O₃ catalysts are very active, and the last one showed high stability in the lifetime test. The structural characterization revealed that in the AuPd(3:1)/TiO₂ catalyst, Au–Pd alloy particles were formed and a high percentage of Au atoms was located at the surface. Therefore, this sonication-assisted method is efficient and rapid in the preparation of supported metal catalysts with obvious structural characteristics for various catalytic applications.     

Characteristics and heterostructure of metal-doped TiO2/ZnO nanocatalysts

In this study, Ag or Al-doped TiO₂/ZnO heterostructure nanocatalysts were prepared using a sol-gel method for photocatalysis to evaluate the degradability. The photocatalytic behavior was evaluated by the degradation of methylene blue (MB) under ultraviolet (UV) light irradiation. Photocatalytic studies suggested that 1 mol% Ag-doped TiO₂/ZnO (TiO₂/ZnO = 0.75/0.25) heterostructure nanocatalysts showed higher photocatalytic activity, and that the degradation efficiency can reach 83% in 4 h, 14% higher than that for pure TiO₂. Finally, the photocatalysis mechanism for the Ag-doped TiO₂/ZnO heterostructure nanocatalysts is discussed.     

One-step chemically vapor deposited hybrid 1T-MoS2/2H-MoS2 heterostructures towards methylene blue photodegradation

The photocatalytic degradation of methylene blue is a straightforward and cost-effective solution for water decontamination. Although many materials have been reported so far for this purpose, the proposed solutions inflicted high fabrication costs and low efficiencies. Here, we report on the synthesis of tetragonal (1T) and hexagonal (2H) mixed molybdenum disulfide (MoS₂) heterostructures for an improved photocatalytic degradation efficiency by means of a single-step chemical vapor deposition (CVD) technique. We demonstrate that the 1T-MoS₂/2H-MoS₂ heterostructures exhibited a narrow bandgap ∼ 1.7 eV, and a very low reflectance (<5%) under visible-light, owing to their particular vertical micro-flower-like structure. We exfoliated the CVD-synthesised 1T-MoS₂/2H-MoS₂ films to assess their photodegradation properties towards the standard methylene blue dye. Our results showed that the photo-degradation rate-constant of the 1T-MoS₂/2H-MoS₂ heterostructures is much greater under UV excitation (i.e., 12.5 × 10⁻³ min⁻¹) than under visible light illumination (i.e., 9.2 × 10⁻³ min⁻¹). Our findings suggested that the intermixing of the conductive 1T-MoS₂ with the semi-conducting 2H-MoS₂ phases favors the photogeneration of electron-hole pairs. More importantly, it promotes a higher efficient charge transfer, which accelerates the methylene blue photodegradation process.     

Preparation of nanocomposite PbO·CuO/CNTs via microemulsion process and its catalysis on thermal decomposition of RDX

Mixture of carbon black, copper and lead was used as catalyst of high-content RDX-composite-modified double base propellant. To enhance the catalytic effect and improve the flaring performance, metal oxide deposited on carbon nanotubes (CNTs) are replaced with afore-mentioned catalyst. A new type of nano-combustion catalyst is synthesized with microemulsion process. In present work, ternary diagram was adopted to analyze the essential factors which affect microemulsion, including temperature, surfactant or cosurfactant and concentration of solution in order to find the best technical parameters and thus to control the core formation and growth of oxides on the nano-template. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) are applied to characterize the products. Through observation of microstructures and analysis of crystal structure, it is confirmed that nano-oxides are deposited on the surface of carbon nanotubes. Its particle size is below 50 nm. According to propellant components, a certain amount of combustion catalyst and RDX will be mixed. PbO·CuO/CNTs can catalyze thermal decomposition of RDX by thermal analysis. The results show that the new catalysts obviously accelerate the decomposition of RDX, and the peak temperature of decomposition reduce by 14.1 °C. The catalytic effect of nano-catalyst is better than original catalyst.     

Binary-surfactant (Brij 35 + Tween 20) assisted preparation of highly dispersed Pt nanoparticles on carbon

Pt nanoparticles supported on Vulcan XC-72R, synthesized by a surfactant-stabilized colloidal method, exhibited excellent properties as anode catalyst for low-temperature fuel cell. The Pt/C catalyst prepared with binary-surfactant (Brij 35 + Tween 20) at 10 times CMC had an average particle size of 2.8 nm with quite a narrow distribution between 2 and 4 nm. Our preparation method resulted in complete reduction of Pt and full loading of Pt nanoparticles on the carbon. The home-made Pt/C catalyst showed higher EAS and better catalytic activity than a commercial Pt/C catalyst. The method used in this study provided an easy and reproducible procedure for the preparation of Pt nanoparticles supported on carbon.     

Biodiesel production from non-edible Silybum marianum oil using heterogeneous solid base catalyst under ultrasonication

The aim of this study is to investigate modified TiO₂ doped with C₄H₄O₆HK as heterogeneous solid base catalyst for transesterification of non-edible, Silybum marianum oil to biodiesel using methanol under ultrasonication. Upon screening the catalytic performance of modified TiO₂ doped with different K-compounds, 0.7 C₄H₄O₆HK doped on TiO₂ was selected. The preparation of the catalyst was done using incipient wetness impregnation method. Having doped modified TiO₂ with C₄H₄O₆HK, followed by impregnation, drying and calcination at 600 °C for 6 h, the catalyst was characterized by XRD, FTIR, SEM, BET, TGA, UV and the Hammett indicators. The yield of the biodiesel was proportional to the catalyst basicity. The catalyst had granular and porous structures with high basicity and superior performance. Combined conditions of 16:1 molar ratio of methanol to oil, 5 wt.% catalyst amount, 60 °C reaction temperature and 30 min reaction time was enough for maximum yield of 90.1%. The catalyst maintained sustained activity after five cycles of use. The oxidative stability which was the main problem of the biodiesel was improved from 2.0 h to 3.2 h after 30 days using ascorbic acid as antioxidant. The other properties including the flash point, cetane number and the cold flow ones were however, comparable to international standards. The study indicated that Ti-0.7-600-6 is an efficient, economical and environmentally, friendly catalyst under ultrasonication for producing biodiesel from S. marianum oil with a substantial yield.     

Catalytic-oxidative/adsorptive denitrogenation of model hydrocarbon fuels under ultrasonic field using magnetic reduced graphene oxide-based phosphomolybdic acid (PMo-Fe3O4/rGO)

In this work, the effect of ultrasound irradiation on the catalytic oxidative/adsorptive denitrogenation (COADN) of model hydrocarbon fuels (composed of pyrrole or indole as an organonitrogen compounds dissolved in n-nonane) has been investigated using magnetic reduced graphene oxide supported with phosphomolybdic acid (PMo-Fe₃O₄/rGO) as a heterogeneous catalyst/adsorbent and hydrogen peroxide as an oxidant. The synthesized PMo-Fe₃O₄/rGO nanocomposite was characterized by XRD, FE-SEM, VSM and BET surface area analysis methods. Moreover, different experimental variables including catalyst dose, initial pyrrole/indole concentration, H₂O₂ to pyrrole/indole molar ratio, ultrasound power and sonication time have been studied on the COADN process. The regeneration/recyclability of PMo-Fe₃O₄/rGO catalyst was also examined. Experimental results revealed that, the ultrasound treatment significantly improved the adsorption process of organonitrogen compounds from model fuels (q_e increased by 50.3% for pyrrole and 18% for indole). Furthermore, high ultrasound-aided catalytic oxidative denitrogenation efficiency (85.6% for pyrrole and 90% for indole) has been attained under optimal conditions (ultrasonic power = 200 W, sonication time = 240 min, catalyst dose = 2 g/L, and H₂O₂:pyrrole/indole molar ratio = 5). The recyclability of catalyst displayed that the prepared catalyst can be reused five times without any significant reduction in its performance.     

Distinguishing the impact of temperature on iron catalyst during the catalytic-pyrolysis of waste polypropylene

The catalytic pyrolysis of waste plastics with iron-based catalyst can produce H₂ rich gas, liquid oil and carbon nanotube (CNTs) together. While the catalytic pyrolysis mechanism is still unclear, in this study, the catalytic pyrolysis of polypropylene (PP) was explored in depth, and the influence of catalyst and temperature was distinguished. The results indicated that a lower temperature led to the generation of waxes, while a higher temperature promoted the formation of aromatic hydrocarbons when plastic pyrolysis was performed without a catalyst. In addition, a large number of carbon deposits, mainly in the form of spheres, were collected when the temperature was over 800 ℃. These carbon spheres originated from the agglomeration of aromatic hydrocarbons. Once catalysts were introduced, a large amount of liquid oil was transferred into carbon deposits at both lower and higher catalytic temperatures, simultaneously, leading to more light gases releasing, like hydrogen. At a lower temperature (≤ 800 ℃), it was mainly CNTs while carbon spheres are the main solid product at higher temperatures (> 800 ℃). In addition, two different mechanisms of CNTs formation were also concluded that the base-growth model dominated the of generation CNTs at 600 °C whereas the CNTs followed the tip-growth model at 800 ℃. The results show that the optimized temperature for the catalytic process should be around 800 ^o℃ where approximately 35 mmol/g_plastic hydrogen, 50% hydrogen efficiency and over 320 mg/g_plastic carbon nanotubes (CNTs) were obtained.     

抗坏血酸—钼酸铵体系催人工法测痕量铜的研究

Ammonium molybdate was reduced to molybdenum blue by ascorbic acid in the medium of phosphorous acid in the presence of copper catalyst. A new method for catalytic spectrophotometric determination of trace copper has been developed. The linear range was 0-0.024 microgram.25 mL-1. The limit of detection was 1.54 x 10(-11) g.mL-1. The method has been used to determine trace copper in human hair with satisfactory results.