Catalytic Additives Research Articles

Catalytic hydrogenation of a three-component mixture of polyaromatic hydrocarbons in the presence of iron-containing additives

The results of the catalytic hydrogenation of a three-component anthracene-benzothiophene-biphenyl mixture in the presence of different catalytic additives are given. It was found that the conversion of the mixture of model substances was 85.9 or 85.0% with the use of FeS2 or Fe2O3 + S (1 : 1), respectively; in both cases, hydrocracking was the prevailing reaction path. A comparatively small difference was found in the products of hydrogenation and hydroisomerization, which was related to the hydrogenation of the structure of each particular component.

Real-time and in situ monitoring of mechanochemical milling reactions

Chemical and structural transformations have long been carried out by milling. Such mechanochemical steps are now ubiquitous in a number of industries (such as the pharmaceutical, chemical and metallurgical industries), and are emerging as excellent environmentally friendly alternatives to solution-based syntheses. However, mechanochemical transformations are typically difficult to monitor in real time, which leaves a large gap in the mechanistic understanding required for their development. We now report the real-time study of mechanochemical transformations in a ball mill by means of in situ diffraction of high-energy synchrotron X-rays. Focusing on the mechanosynthesis of metal-organic frameworks, we have directly monitored reaction profiles, the formation of intermediates, and interconversions of framework topologies. Our results reveal that mechanochemistry is highly dynamic, with reaction rates comparable to or greater than those in solution. The technique also enabled us to probe directly how catalytic additives recently introduced in the mechanosynthesis of metal-organic frameworks, such as organic liquids or ionic species, change the reactivity pathways and kinetics.

Effects of the degree of graphitization and the presence of Fe, Ni, Al, and Si on the reaction stability of carbon materials to the action of CO2

With the use of industrial cokes, synthetic graphite, and graphite foams as an example, it was shown that the reactivity and, correspondingly, the thermal stability of carbon in a reaction with CO2 can be regulated by increasing the fraction of graphite structures in the composition of a carbon material and by introducing the catalytic additives of 3d metals (iron and nickel) and also silicon or aluminum. The effect of the additives is explained by both a change in the degree of graphitization of the carbon material and the catalytic action on the course of reaction.

The effect of hydrothermal treatment of FCC catalysts and ZSM-5 additives in catalytic conversion of biomass

Fresh fluid catalytic cracking (FCC) catalysts and ZSM-5 additives were hydrothermally treated with 100% steam at 732°C (1350°F) and 788°C (1450°F) for 4h in a fluidized bed reactor. The catalytic pyrolysis of hybrid poplar wood with fresh and steam treated catalysts was conducted in a 50mm bench scale bubbling fluidized bed reactor at 475°C and a weight hourly space velocity (WHSV) of 2h−1. BET surface area measurements showed a reduction of 24% and 34% in the surface area of the FCC catalyst after steam treatment at 732°C and 788°C respectively. The non-phosphorus based ZSM-5 additive lost about 15% of its surface area after mild steaming at 732°C. However, the phosphorus impregnated ZSM-5 additive was not affected at both steaming conditions. The hydrothermal treatment of the catalysts influenced the catalytic product distribution and the quality of the bio-oil. The steamed FCC catalyst produced higher organic liquid and gas yields and lower formation of coke and water. The viscosity and the density of the bio-oils produced from the steamed FCC catalyst were lower than those produced with the fresh FCC catalyst. In the case of the ZSM-5 additives, the steam treatment affected only the organic liquid and gas yields. The organic liquid yield increased and the gas yield decreased. Steaming of the ZSM-5 additive did not show any effect on the char/coke yield as was seen with the FCC catalyst due to the lower tendency of ZSM-5 to form coke. The GC analysis of the product gases suggested that steam treatment influenced the catalyst selectivity in the formation of CO, CO2, H2, CH4 and C2C5 hydrocarbons. The 13C NMR analysis of the bio-oil showed generally that steaming of the FCC catalyst increased the selectivity for the production of aromatic hydrocarbons.

Effect of catalytic additives and aluminum particle size on the combustion of mixed compositions with a chlorine-free oxidizer

Experimental results on the stationary burning rate and solid content in the combustion products of mixed compositions with a chlorine-free oxidizer and an active fuel binder in the pressure range 0.025–6.0 MPa are presented. The effect of catalytic additives (silica and carbon black), the particle size of aluminum powder, and the method of preparing samples for combustion of the mixed compositions under consideration are analyzed.

Scale-Up Effects of Nanoparticle Production on the Burning Rate of Composite Propellant

The use of catalytic nanoparticle additives in composite solid propellant as burning rate modifiers has received much research attention in recent years, and as the widespread application of nanoparticles becomes more practical, scale-up processing and testing will be required. This article investigates the potential benefits of various additive processing methods and their effects on the burning rate of propellant consisting of ammonium perchlorate and hydroxyl terminated polybutadiene. Titania was investigated herein, but many of the results should apply to any metal oxide catalyst. Depending on how the additive was processed, it was seen to be both an effective and ineffective burning rate modifier. The ideal processing method was determined, leading to a better understanding of how the additive interacts with the propellant. The physical properties of the additive agglomerations were found to be a link between the additive processing and its effectiveness. Specifically, sintering of the additive agglomerates during heat treating limited the dispersion of the additives, ultimately hindering their ability to modify burning rate. This article presents one of the first studies that conclusively demonstrates the link between the processing of nanoparticles and their effectiveness in modifying propellant burning rate.

Study of a Renewable Biomass Powered SOFC

The objective of this work is to explore a solution to utilize biomass carbon by a tubular solid oxide fuel cell integrated with an "in-situ" steam gasification reactor. Non-catalyzed and catalyzed coconut shell carbons were employed as solid fuels, which were directly converted to gaseous fuels to feed the SOFC operated at 800°. Single cells showed variable electrochemical performances according to the catalytic additives. Sample without catalysts exhibited low power density, while those with catalysts such as Fe2O3 and K2CO3 showed higher performances. The enhanced cell performance with catalysts was considered to be the result of increased conversation rate of carbon and consequently high fuel concentration supplied to SOFC.

Promising applications of coals from the Moscow Basin

The results of an analysis of the current state of the Moscow Coal Basin and the development of science and technology for the multiple use and conversion of coal into refined energy carriers, products, and materials with new consumer properties are presented. It is demonstrated that a number of processes and facilities based on the coals and overburden rocks of the basin have been prepared for technical implementation, namely: the generation of heat and power at plants with in-cycle coal gasification; the fluidized-bed combustion of coal in low-power boiler units (50–60 MW); the manufacture of ballast-free humic plant growth stimulators and coagulants for the purification of wastewater and drinking water; and the use of coals and coal mining and benefication wastes as catalytic additives in the process of hydrogenation.

Effects of dual initiators and catalytic additives on atom transfer radical polymerization of styrene

The effect of two initiators, so-called dual initiators system on atom radical transfer polymerization (ATRP), were studied with dimethyl-2,6-dibromohepanedioate (DMDBHD) and ethyl-2-bromoisobutyrate (EBIB). Cu(I)Br as catalyst and N,N,N′,N′,N′-pentamethyl-diethylenetriamine as ligand were employed for styrene ATRP. Interestingly, bimodal MWD were shown for the dual initiator system, and one of the peaks had higher molecular weight (MW) and the other had lower MW compared to a one-initiator system. The lower MW peak in bimodal peaks seemed to be mainly resulting from EBIB and the higher MW peak from DMDBHD. Furthermore, methylaluminoxane (MAO) was fed into the ATRP reaction to observe the effect of it on ATRP. As the MAO/CuBr molar ratio in feed increased from 0 to 1, the molecular weight and conversion increased without a notable change in PDI and curve shape of GPC. The conversion in the presence of MAO was also increased with the increase in MAO/CuBr molar ratio. The effect of Cp*TiCl3 on the ATRP was opposite to that of MAO. As the Cp*TiCl3/CuBr molar ratio increased from 0 to 1, the conversion of polymerization was down from 56 to 35%. Furthermore, the molecular weight was drastically decreased from 10,000 to 5,500, but their PDI did not show a significant change. These results can elucidated by the retarding effect of Cp*TiCl3 on the propagation of polymerization.

Enhanced Desorption and Absorption Properties of Eutectic LiBH4–Ca(BH4)2 Infiltrated into Mesoporous Carbon

We present enhanced hydrogen storage properties of the eutectic LiBH4–Ca(BH4)2 composite confined inside a mesoporous carbon scaffold via melt infiltration. The eutectic composition was examined by analyzing the enthalpy of fusion as a function of the LiBH4-to-Ca(BH4)2 ratio. Elemental analysis by energy dispersive X-ray spectroscopy and phase analysis by X-ray diffraction patterns provided both direct and indirect evidence for the infiltration of the LiBH4–Ca(BH4)2 composite into the mesoporous channels of the carbon. The major dehydrogenation event occurred at ∼300 °C, which is lower compared with the same composite without carbon or previously reported pure LiBH4 confined in mesoporous carbons. Without additional catalytic additives, almost half of the initial hydrogen capacity was recovered after one cycling. This improved performance is a synergistic effect of the nanoconfinement and the mutual destabilization between LiBH4 and Ca(BH4)2, and it also indicates that the eutectic melting phenomenon can be exploited as an effective way of coinfiltration of reactive hydride composites.

Development of a technology for coal conversion in the presence of coal tar

A new process for the hydrogenation of coal in the presence of wide-cut coal tar was proposed; it involves cavitation treatment, mixing with catalytic additives, and heating the resulting mixture at an elevated pressure in an atmosphere of hydrogen. The yields of hydrocarbon fractions to 300°C and gas condensate were evaluated.

Hydrogenation of a model mixture of anthracene with benzothiophene

The reactivity of an anthracene-benzothiophene mixture in the presence of various catalytic additives was studied. The efficiency of the catalytic additives was evaluated from various standpoints.

Autoclave leaching of molybdenite concentrates with catalytic additives of nitric acid

The scientific theoretical prerequisites for the use of small additives of nitric acid for the intensification of the autoclave oxidative leaching (AOL) of sulfide concentrates are checked in order to increase the degree of extraction of the base metal with a simultaneous decrease in the cost of the process. The technological parameters of the AOL conditions applied to molybdenite are also refined, and recommendations for a practical application of the apparatus of the process and for a decrease in its cost are made.

The Effects of Cryogenic Milling and Catalytic Additives on the Hydrogen Desorption Behaviour of Nanostructured MgH<sub>2</sub>

It is well known that catalytic additives and mechanical milling are effective in improving hydrogen desorption kinetics of MgH2. In this study, the effect of catalytic additives including BaCa1-xNdxO3-δ (BCN) on the desorption behavior of MgH2 was investigated. It was found that BCN can improve the desorption kinetics, but not as effective as other known additives such as Nb2O5. The effect of milling temperature was also studied. It was found that the cryogenic milling is not as effective as room temperature milling primarily due to the inhomogeneous particle size distribution.

Determination of acetone and ethanol vapors using semiconductor sensors

Sensors with gas-sensing layers based on tin dioxide with nanosized catalytic additives of palladium, platinum, antimony, and lanthanum have been used to determine ethanol and acetone vapors in air. The use of nonstationary temperature modes, allowed us to reach record-breaking low detection limits for acetone (∼0.1 ppm). For the first time ethanol and acetone have been selectively determined with a single sensor.

Metal oxide semiconductors based on tin dioxide: Gas-sensitivity to methane in a wide range of temperatures, concentrations and humidities of the gas phase

The response of metal oxide semiconductors (MOSs) made by the thick-film technology on the basis of SnO2 with various catalytic additives was studied in dry gaseous media containing 200 ppm CH4 in the temperature range 100–600° C. Concentration dependence was studied for four sensors (on the basis of pure SnO2 and with three catalytic additives, 3% Pd, 1% Sb2O5 + 3% La2O3, and 1% Pt + 3% Pd) in the concentration range 1–20600 ppm CH4 at the humidity of the gas phase varied from 0 to 100%. It was found out that, in the strength of all performance and technical characteristics, the structure SnO2 + 1% Pt + 3% Pd working at 400°C and consuming ∼180 mW was the best for recording CH4.

Investigation of gas-sensitivity of sensor structures to hydrogen in a wide range of temperature, concentration and humidity of gas medium

Response to H2 of seven sensor structures of SnO2 with various catalytic additives, made by thick-film technology, was investigated in a dry gas medium at a concentration of 200 ppm H2 in a temperature range of 100–600 °C. Concentration dependence of six sensors (pure SnO2 and doped with five catalytic additives: 3% Pd, 3% La2O3, 1% Pt + 3% Pd, 1% Sb2O5 + 3% La2O3 and 3% Pd with a support layer from Al2O3) was investigated in a range of 1–19,700 ppm H2 of different relative humidity (RH) in a range of 0–100% RH at two operating temperatures. The resistance and response of the sensors weakly depended on the humidity of the gas medium at RH ≥ 0 or 10%. Arithmetic mean values of response and resistance in the range of 0 (10)–100% RH were approximated by linear functions of log(Sma − 1) = B + n log C and log Rma = A + k log C, respectively. Based on the comparative analysis of experimental data (response to H2, reproducibility of indications, influence of humidity on the resistance and response, response threshold and a resistance drift in pure air), the best for H2 detection were the two sensor structures of pure SnO2 and SnO2 + 3% La2O3, working at temperatures 500 °C and 450 °C, respectively. Formulas for resistance and response of these sensors were presented, which allowed estimation of H2 concentration in air based on the measured parameters. Reproducibility of indications in the range of 1–19,700 ppm H2 was within 4–10%. The response threshold was 0.08 ± 0.006 ppm H2 in the mentioned range of humidity at the response equal to 1.1. The interpretation was given for the mechanism of interaction of H2 with the catalytic surface of semiconductive sensors. The present sensors can be recommended as the primary transducer of H2 concentration in air for the gas control devices.

The effect of graphitization catalyst on the structure and porosity of SiC derived carbons

A number of carbide-derived carbon (CDC) samples were synthesized through the reaction between α-SiC and gaseous chlorine at temperatures 900, 1000 and 1100 °C and by varying the amount of catalyst. The chlorides of Co(II), Ni(II) and Fe(III) were used as catalytic additives in a range of concentration of 0.1–5 wt%. The structural differences of the obtained carbons were studied by low-temperature nitrogen adsorption, X-ray diffraction and Raman spectroscopy. Results showed that porosity, specific surface area and graphitization degree of the CDC materials is a function of chlorination temperature and catalyst concentration, which agrees with previous results. It was shown that the catalytic graphitization only weakly influences the L a value of the crystallites, which according to the Raman scattering is ∼4–5 nm in both the highly disordered SiC derived carbons and in fully graphitic carbons made from SiC containing 15 wt% of surface-contacted Co–Ni–Fe catalyst. The surface area of the CDC materials can be controlled in the range of 300–1350 m 2 g −1, depending on the amount of catalysts used.

Development of Modified Wood Products Based on Furan Chemistry

The first processes for “furfurylation” of wood (wood modification with furfuryl alcohol) were developed several decades ago. Furfuryl alcohol is a renewable chemical since it is derived from furfural, produced from hydrolysed biomass waste. Over the last decade modernised processes for furfurylation of wood have been developed. These new processes are based on completely new catalytic systems and process additives. The properties of furfurylated wood depend on the retention of grafted/polymerised furfuryl alcohol (PFA) in the wood. At high modification levels (high retention of PFA) the enhancement of a wide variety of properties are achieved: an exceptional hardness increase, exceptional resistance to microbial decay and insect attack, high resistance to chemical degradation, increase in MOR and MOE, and high dimensional stability. At lower modification levels many property enhancements also occur, however to slightly lower extent. Notable are resistance to microbial decay and insect attack, increase in MOR and MOE, and relatively high dimensional stability. Two main processes for production of furfurylated wood have been developed for Kebony ASA (Former Wood Polymer Technology ASA) by the authors. Kebony TM for hardwood modification and VisorWood TM for soft wood modification, where the name reflects the colour of the material produced by the process. Commercial production according to the Kebony process has been running since October 2003, mainly for flooring. A small Kebony production plant is now in operation in Lithuania. A Kebony/VisorWood production plant was started during of 2003 in Porsgrunn, Norway. There are now planed for an expansion of this plant, and plans for a large Visorwood plant is ongoing. Further commercialisation of the technology will be done through licences issued by Kebony ASA.

Control over m-nitrotoluene concentration in products of heterogeneous mononitration of toluene

Heterogeneous mononitration of toluene with sulfuric-nitric acid mixtures, occurring in the charged interfacial monolayer with high para selectivity, was studied. Ways to suppress the meta substitution in the toluene mononitration stage by controlling the nitrating mixture composition, process parameters, and catalytic additives were found.