Catalyst Preparation Conditions Research Articles

Chemometric approaches on glycerol oxidation with H2O2 over supported gold nanoparticles

This paper reports a chemometric study of effects of the catalyst preparation method and reaction conditions on the efficiency of glycerol oxidation catalyzed by gold nanoparticles supported on activated carbon using H2O2 as oxidant. Factorial designs and principal component analysis were used for the evaluation of experimental conditions and reaction performance. Evaluating catalyst preparation conditions we found that larger Au nanoparticles are obtained using HAuCl4 in higher concentration. Glycerol conversion and production of glycerate and tartronate were higher using catalysts prepared with low polyvinyl alcohol (PVA) to Au ratio and low Au content. Higher HAuCl4 concentrations resulted in larger Au nanoparticles, which contributed to higher glycolate production. Evaluating reaction conditions we found that the influence of H2O2 to glycerol ratio was insignificant. Glycerol conversion and production of glycerate and tartronate were higher at lower temperature. Increasing H2O2 to glycerol ratio contributed to higher glycolate production. Glycerol to Au ratio has a smaller influence on the reaction course.

Catalytic Decomposition of CCl<sub>2</sub>F<sub>2</sub> over Solid Base Na<sub>2</sub>O/ZrO<sub>2</sub>

Catalytic decomposition of dichlorodifluoromethane (CCl2F2) in the presence of water vapor and oxygen was studied over a series of solid base that have different ZrO2 content using a fixed-bed reactor. CO2 and CClF3 were the main-products and no CO was detected as by-product. The decomposition activity depended on the calcination temperature and the Zr:Na. Calcined at 600 °C and Zr:Na=1:0.35 were the best catalyst preparation conditions. Adopting low concentration of oxygen and CCl2F2 and high concentration of water vapor is preferable to the achievement of high conversion of CCl2F2 and selectivity for CO2. The catalytic activity of Na2O/ZrO2 remained steady for 120 h on stream.

Research on Catalytic Degradation of Organic Wastewater Using CoFeMgO Non Homogeneous Fenton

Methyl orange stimulated wastewater was treated using non-homogeneous Fenton reaction. First the effect of catalyst composition on the treatment was investigated and then further investigation of the impact of reaction conditions on the degradation effect in the catalytic process was carried out. It showed the optimal conditions of treating methyl orange wastewater(100ml) of 10mg/L, The optimal conditions for catalyst preparation through experiments above were: proportion of the elements in the catalyst was Co0.5Fel.0(MgO)2.5, this article examined the impact of reaction conditions on the catalytic properties of the catalytic process. It turned out that on the condition that the amount of catalyst was 0.9g/L hydrogen peroxide concentration was 2.5ml/L, within the scope of application in a wide pH (4~14), catalyst degradation efficiency was significantly superior to conventional homogeneous Fenton system and methyl orange removal efficiency was above 95%.

Effect of catalyst preparation conditions on the performance of eggshell cobalt/SiO2 catalysts for Fischer–Tropsch synthesis

In this article, we examine the impact of solvent and calcination conditions, during catalyst preparation, on the performance of eggshell catalysts. Eggshell profile of silica supported cobalt catalysts provides a means to control selectivity in Fischer–Tropsch synthesis reactions. Solvents such as water and alcohol attach to the silanol groups on the silica gel surface and compete with metal salts during ion exchange and adsorption. The solution properties impact the metal dispersion and interaction with the metal support. The calcination conditions (static versus dynamic, oxidizing versus reducing atmosphere) also have an impact on metal dispersion and support interaction. Ethanol proved to be a better solvent for enhancing the dispersion due to its surface wetting pattern while direct reduction in dynamic hydrogen provided gradual decomposition of the cobalt precursor thus reducing agglomeration. The use of water as a solvent and a static air environment during calcination led to lower dispersion. Nitrogen physisorption experiments showed that under favorable conditions, synthesized eggshell catalyst retains most of the original support surface area. Surface elemental composition using XPS indicate that the effect of solvent was stronger than the calcination environment in determining catalyst dispersion. This result was also confirmed by hydrogen chemisorption studies. TPR results suggested that back reaction of calcination product (especially H2O) and the agglomeration were competing phenomena in a static oxidizing environment. However, hydrogen chemisorption indicated that metal agglomeration was far more significant than the back reaction in static air atmosphere. Catalyst activity and selectivity were tested in a fixed bed (FBR) reactor fitted with GC and FTIR analyzers. The eggshell catalyst demonstrated high activity as expected; however, selectivity of CO2 in our fixed bed catalytic reactor was higher than usual. The distribution of liquid hydrocarbon was in the narrow range of diesel and aviation fuel.

Influence of Preparation Conditions of the Solid Base Catalyst on the Performance of Synthesizing Polyglycerol

Different solid base catalysts used for the polymerization of glycerol were prepared by impregnation. Catalyst type and the preparation conditions were optimized on the base of polymerization degree. Results showed: the best catalyst was KF/Al2O3, and optimal condition for catalyst preparation was as follows: loading of 40% KF, calcinations temperature 600°C. The polymerization degree of 5.92 was obtained under the following reaction condition: the amount of catalyst 11.62,reaction temperature 250°C, reaction time 4 h.

Catalytic Application of H<sub>3</sub>PW<sub>6</sub>Mo<sub>6</sub>O<sub>40</sub>/SiO<sub>2</sub> in Synthesis of Acetals and Ketals

A novel catalyst, H3PW6Mo6O40/SiO2was prepared by a sol-gel technique and its catalytic application in synthesis of acetals and ketals were tested. The preparation conditions of catalyst were optimised by using the orthogonal experimental design. The optimum conditions are: the mass ratio of H3PW6Mo6O40 to SiO2is 0.4, calcination temperature is 150 °C and calcination time is 3 h. The steric properties of the reactants play an important role in the acetalization. The catalytic activity of the catalyst decreases when the size of the reactant increased. Although a decrease in catalytic activity was observed with its subsequent reuse, the catalyst could be reused at least four times without any other treatments. The results reveal that the H3PW6Mo6O40/SiO2catalysis generally results in good yields of acetals and ketals under mild reaction conditions.

Kinetic model of K–Ni/α-Al2O3 catalyst for oxidative reforming of methane determined by genetic algorithm

Effects of preparation conditions of a K–Ni/α-Al2O3 catalyst on the activity and selectivity of high-pressure reforming of methane was investigated. Catalyst preparation parameters such as calcination temperature of boehmite, the amount of NiO and the amount of K loading were designed by L9 orthogonal array, and the catalysts were prepared by an impregnation method. Each catalyst was used in an activity test where contact time was decreased by increasing the gas feed rate, and conversion was recorded until O2 conversion was below 30%. Both the conversions and syngas selectivity were used for fitting by Genetic algorithm. The algorithm was applied to determine the kinetic parameters of the reaction network of high-pressure reforming of methane. Then a support vector machine was trained using the nine dataset to correlate the catalyst preparation parameters and the kinetic parameters. After the training, we conducted grid searches to build response surfaces of the kinetic parameters. Thus, the all kinetic rate constants could be predicted as functions of the catalyst preparation conditions. The analysis of the kinetic model suggested that successive oxidation of the syngas was the most influential factor for low syngas selectivity. Whereas the amount of NiO loading influences on hydrogen oxidation, CO oxidation was not accelerated by NiO. High syngas selectivity was attained by using a less amount of diluent in the catalyst bed.

Kinetic study of NiMo/SBA-15 catalysts prepared with citric acid in hydrodesulfurization of dibenzothiophene

Abstract We performed a kinetic study of the effect of citric acid (CA) during the synthesis of NiMo catalysts supported on SBA-15 in hydrodesulfurization (HDS) of dibenzothiophene (DBT). The aim of this work is to get a deeper insight with respect to the thermal treatment and the pH of the impregnation solutions on the kinetic behavior of NiMoCA/ SBA-15 catalysts. NiMoCA/SBA-15 catalysts were characterized by N 2 physisorption, powder XRD, HRTEM and elemental analysis and tested in HDS of DBT in a Batch reactor at 300 °C for 8 h. The kinetic study of these catalysts showed changes by CA addition on hydrogenation and direct desulfurization reaction routes depending on catalyst preparation conditions.

The Effects of Different Preparation Conditions of IR Catalyst on the Simultaneous Removal of Soot and NOx in the Presence of Rich Oxygen and H<sub>2</sub>O as Well as SO<sub>2</sub>

A series of Ir-supported catalysts were prepared by incipient impregnation method. The activity of Ir catalyst for the simultaneous removal of soot and NOx in the presence of rich-oxygen and H2O as well as SO2 has been studied, and the effects of calcination temperature, calcination time, calcination atmosphere, loading, carrier and precursor on its catalytic performance has also been investigated. Ir catalyst exhibits a high activity. With the calcination temperature increasing, Ir catalytic activity increases firstly and then decreases, and the optimal calcination temperature is 900°C. With the calcination time prolonged, Ir catalytic activity also increases firstly and then decreases, and the optimal calcination time is 3h. The optimal calcination atmosphere is 1.5vol.% H2/N2. Support material and precursor have a little effect on the catalytic activity, and the order is Ir/TiO2 > Ir/ZrO2 > Ir/SiO2 > Ir/Al2O3 > Ir/ZSM-5 and IrCl (CO)[P(C6H5)3]2/ZrO2 > H2IrCl6·6H2O/ZrO2 > IrCl4·4H2O/ZrO2.

Growth Characteristics of Carbon Nanotubes on Oxidized Catalyst under Low-Pressure Condition

Low-pressure alcohol catalytic chemical vapor deposition (LP-ACCVD), which is an ACCVD method at a lower pressure (<1 Pa) than that in the conventional method, has been attracting much interest because it enables the low-temperature growth of single-wall carbon nanotubes (CNTs). However, the growth rate of CNTs by LP-ACCVD is markedly low owing to its low growth pressure. To alleviate this problem, we have examined the influence of the catalyst preparation and CVD conditions on the properties of CNTs grown by LP-ACCVD. It has been found that the oxidation of catalyst enhances the growth of CNTs by LP-ACCVD. Furthermore, the low flow rate of the ethanol enhances the growth yield of CNTs at lower growth temperature, which is understood to be the result of sufficient gas heating on the substrate.

Growth Characteristics of Carbon Nanotubes on Oxidized Catalyst under Low-Pressure Condition

Low-pressure alcohol catalytic chemical vapor deposition (LP-ACCVD), which is an ACCVD method at a lower pressure (<1 Pa) than that in the conventional method, has been attracting much interest because it enables the low-temperature growth of single-wall carbon nanotubes (CNTs). However, the growth rate of CNTs by LP-ACCVD is markedly low owing to its low growth pressure. To alleviate this problem, we have examined the influence of the catalyst preparation and CVD conditions on the properties of CNTs grown by LP-ACCVD. It has been found that the oxidation of catalyst enhances the growth of CNTs by LP-ACCVD. Furthermore, the low flow rate of the ethanol enhances the growth yield of CNTs at lower growth temperature, which is understood to be the result of sufficient gas heating on the substrate.

Preparation and Application on High-Efficiency Catalyst for Catalytic Wet Oxidation

The Catalytic Wet Oxidation (CWO) method was investigated to treat phenol cleaning wastewater from chemical container which is difficult dispose with traditional biological methods. In this paper, high-efficiency catalysts were prepared, two methods were used to prepare the catalyst: impregnating, sol-gel. Effects of metal salts concentration, calcination temperature and calcination time on each catalysts performance were explored and optimal catalyst preparation condition was optimized. The results show that the optimum sol-gel condition: Cu / Mn / Ce ratio of 2:2:2, the calcination temperature is 700 °C, calcination time is 5h.; the optimum impregnating condition: Cu / Mn / Ce ratio of 2:2:2, impregnated carrier (AC) of 0.9g/L mixture, the calcination temperature is 300 °C, calcination time is 4h; the sol-gel catalyst has longer service life, the samples prepared by impregnating technique were more active than the samples prepared by sol-gel technique at given reaction conditions.

Study on SO 42−/ZrO 2-MoO 3 in the integrative transformation of cottonseed oil deodorizing distillate

With the integrative transformation of non α-tocopherols, glycerides, free fatty acids, and methyl alcohol in cottonseed oil deodorizing distillate as the target reaction, we prepared highly catalytic SO 4 2−/ZrO 2-MoO 3 solid acid catalyst by precipitation–wet impregnation. The optimal conditions for catalyst preparation were then determined by varying sulfuric acid concentration, MoO 3 loading factor, calcination temperature, and calcination time. The structure of SO 4 2−/ZrO 2-MoO 3 solid acid catalyst was then examined by X-ray diffraction (XRD), Brunauer–Emmett–Teller measurements, scanning electron microscopy, and other methods. Results show that the MoO 3 loading factor (percentage weight ratio of MoO 3 to ZrO 2), impregnation concentration of sulfuric acid, and calcination temperature were the most important factors that influenced catalytic activity. The optimal conditions for catalyst preparation were an MoO 3 loading factor of 20%, a sulfuric acid impregnation concentration of 0.75 mol/L, a calcination temperature of 550 °C, and a calcination time of 6 h. The obtained catalyst exhibited the highest catalytic activity under these conditions.

Evaluation of alumina-supported Mo carbide produced via propane carburization for the Fischer–Tropsch synthesis

CO hydrogenation over alumina-supported Mo carbide catalyst synthesized by temperature-programmed carburization of the impregnated MoO3 utilizing H2/C3H8 feed has been investigated. Samples were prepared following a 23-factorial design with temperature, hydrocarbon composition and reaction time as the carburization factors. Catalysts were characterized using N2 physisorption, NH3 temperature-programmed desorption and solid total organic carbon (TOC) analysis. Solid-state carburization kinetics was studied in a thermogravimetric analyzer at different heating rates. Statistical analysis revealed that carburization temperature was a strong determinant of key physicochemical properties (BET, pore volume, acid site strength and concentration). Increasing the H2:C3H8 ratio in the carburizing gas reduced the acid site strength and concentration but improved overall hydrocarbon synthesis rate, olefin-to-paraffin ratio and specific activity. All catalysts possessed Lewis acid centers. The carburizing temperature was also a statistically significant factor in the determination of the FT reaction metrics. A two-stage process involving the transformation of Mo oxide to the MoC1−x carbide via an intermediate oxycarbide phase was observed. The solid-state kinetics was captured by a contracting volume model and Arrhenius treatment implicated the occurrence of a ‘compensation effect’ for the carbothermal synthesis. Although the rate-composition envelope exhibited qualitatively similar features for the entire Mo carbide class, the optimum feed composition for maximum hydrocarbon formation rate varied between 0.67 and 0.75 depending on the catalyst preparation conditions and the carbon number. The olefin-to-paraffin ratio has a reciprocal relationship to the H2 partial pressure but experienced an exponential decay with carbon number. Catalyst with 15wt.% Mo loading produced the highest hydrocarbon synthesis rate and chain growth probability.

The Preparation Conditions of Catalyst for Steam Reforming of Fast Pyrolysis Bio-Oil

Catalytic steam reforming of bio-oil is an economically feasible route producing renewable hydrogen. Ni/MgO-La2O3-Al2O3 catalyst was prepared with Ni as active agent, Al2O3 as support and MgO, La2O3 as promoters. The experiments were carried out in a fixed-bed reactor. The content of Ni, calcination temperature, and calcinations time, were investigated with hydrogen yield as index. The optimal preparation conditions were concluded as follows: the Ni content 18%, the calcination temperature 8500C and the calcinations time 6 h.

Synthesis of Methyl Isopropyl Ketone and Diethyl Ketone over Ni-Na/ZrO 2-MnO 2-ZnO Catalyst

ZrO 2-MnO 2-ZnO supports were prepared by the co-precipitation method, and then Ni-Na/ZrO 2-MnO 2-ZnO catalysts were prepared by the impregnation method. In this paper, the reactions to synthesize methyl isopropyl ketone and diethyl ketone by the one-step synthesis method over this catalyst were studied, and meanwhile, the impact of the catalyst preparation conditions and the reaction conditions on catalyst performance was also investigated. It was observed that under the conditions when Ni loading was 25%, calcination temperature was 400 °C and reduction temperature was 410 °C, this catalyst had good catalytic performance on the reaction. The suitable reaction conditions were achieved: reaction temperature was 400 °C; reaction at atmospheric pressure; liquid hourly space velocity of raw material of 0.5 h −1; and the molar ratio of (methanol)/(methyl ethyl ketone)/(water) was equal to 1/1/1. Under such conditions, the conversion of methyl ethyl ketone could achieve 41.7%, and the overall selectivity of methyl isopropyl ketone and diethyl ketone could achieve 83.3%, which was comparable to the conversion of 38.1% and the selectivity of 82.2% achieved by using palladium as the active material. The good stability made this catalyst have good prospects for industrial application.

α–Pinene Isomerization Catalyzed by a Nanometer Solid Superacid

Nanometer composite S2O82-/SnO2-TiO2, a novel solid superacid, was prepared by the sol-gel method and its structure was characterized by XRD, TEM, FT-IR and nitrogen adsorption. Results indicated that the composite S2O82-/SnO2-TiO2 had a narrow particle size distribution with an average particle diameter about 15~20nm. S2O82- combined with SnO2-TiO2 resulted in formation of strong acid sites on the surfaces. The surface area of catalysts obviously increased after incorporating SnO2. Nanometer S2O82-/ SnO2-TiO2 composite was used as a catalyst for a-pinene isomerization and the influence of catalyst preparation conditions on its performances were investigated. The optimum condition for superacid catalyst preparation was found to be with 2:1 Sn/Ti mole ratio, S2O82- 1 mol · L-1 of impregnation consideration and toasting temperature of 773K. With 3% of S2O82-/SnO2- TiO2 catalyst dosage at a reaction temperature at 403K for 2 h, the conversion of a-pinene was 98 % and the selectivity to camphene was 62 %.

Chromia-alumina catalysts for the dehydrogenation of propane prepared by a modified method of codeposition

A method for preparing chromia-alumina catalysts for the dehydrogenation of propane, enabling us to increase the activity and thermal stability of a catalyst relative to currently known catalysts, is proposed. Chromia-alumina catalysts were prepared for the first time using a modified method of codeposition, in which a suspension of chromium and aluminum hydroxides was subjected to a high-temperature treatment (550°C). The proposed method is simple and allows us to reduce the number of stages in the preparation of the catalyst. The phase composition and texture of the catalyst, and the formation and properties of surface-active forms in dependence on the conditions of catalyst preparation, were studied using a set of physicochemical methods. The selected conditions of catalyst preparation ensured high specific surface area and a stable bond between the surface forms of chromium and the support, hindering the formation of the catalytically low-activity form α-Cr2O3 during calcination. In this work, we synthesized and studied laboratory samples of a chromia-alumina catalyst with different contents of chromium (2.8–11.3 wt %). With respect to the main parameters (conversion of propane, selectivity to propylene, and resistance to coke formation), the catalyst was as good as more active samples known from the literature and exhibited high activity at low chromium contents (2.8–5.5 wt %). This method of catalyst preparation is protected by a patent of the Russian Federation and recommended for improving industrial technology.

Activity Monitoring for a Polymerization Catalyst System

AbstractSummary: Catalyst systems for polymerization often exhibit variable and poorly controllable activity because of strong influences of trace components and catalyst preparation conditions. In cationic polymerizations in particular, determining catalytic activity and hence the amount of catalyst to be used is challenging. The assessment of a given initiator system typically requires testing it in polymerization reactions. Determining catalytic activity before using the initiator in a polymerization reaction is a desirable approach. This contribution describes the development of such an activity monitoring tool. In the first part, results from a fundamental characterization of the system diethylaluminum chloride/ethylaluminum dichloride/water by different NMR measurements and elemental analysis are reported. Structures characteristic of catalytically active systems are presented. The second part describes the application of transmission IR to the characterization of this system and the correlation of IR results to catalytic activity in dimerization and polymerization reactions. Implementation of the IR analysis as an on‐line measurement is demonstrated.

Effects of Catalyst Precursor Type and Preparation Conditions, and Solvent Type on Activity and Selectivity of Pt/SiO2 Catalyst in Citral Hydrogenation

In this study, citral hydrogenation reaction in liquid phase over silica gel supported Pt catalysts was investigated. It was desired to hydrogenate carbonyl group selectively to produce valuable unsaturated alcohols, namely geraniol and nerol. Pt/SiO2 catalysts were prepared by impregnation method. The effects of parameters investigated in the present study included Pt precursor type (hexachloroplatinic acid (HCLPA), platinum II acetylacetonate (PAA)), catalyst activation temperature (350°C and 450°C), catalyst activation without calcination, catalyst washing with 0.1 M NaOH and solvent type (ethanol, 2-pentanol). The catalysts activities and selectivities were affected by the type of precursor and activation temperature. The maximum citral conversion (89.50 percent) was achieved at lower activation temperature (350°C) with PAA precursor based catalyst. It was observed that higher activation temperature provided lower citral conversion but higher selectivity to unsaturated alcohols; increasing the activation temperature to 450°C decreased citral conversion to 26.10 percent. But selectivity to unsaturated alcohols, geraniol and nerol, increased from 7.06 to 54.60 percent. Catalyst washing and 2-pentanol prevented acetal formation. Catalyst activation without calcination gave lower citral conversion (20.84 percent) and selectivity to unsaturated alcohols (30.00 percent).