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The catalytic performance of iron-based nanodispersions in Fischer–Tropsch synthesis in two different slurry reactor types, specifically a continuous stirred-tank reactor (CSTR) and a slurry bubble column reactor (SBCR), was comparatively investigated. It was found that, at equal process temperatures, the CO conversion in the SBCR using a gas disperser with four equally spaced 1-mm holes was lower than that in the CSTR. However, this observation is inconsistent with other reports in the literature. Replacing this disperser with a plate with a single centered 2-mm hole enhanced the CO conversion up to values close to those obtained in the CSTR. The reaction rate constants were calculated for the different reactor types. [ABSTRACT FROM AUTHOR]

Under slurry reactor conditions, the products of condensation are generrally formed on strong Mg/HZSM-5 acid sites independently of the SiO2/Al2O3 molar ratio in the zeolite. The composition of condensation products remains virtually unchanged as the molar ratio grows and basically consists of trimethyl and tetramethyl benzenes, but their content falls as the volume of mesopores grows with increasing SiO2/Al2O3. This lowers the hindrances to diffusion and the contribution from secondary reactions to improve the removal of coke precursors from the zeolite's surface and favorably affect the catalyst's activity (DME conversion doubles). The composition of reaction products changes slightly with an increase in the SiO2/Al2O3 molar ratio, and the total selectivity toward lower olefins is ~70 wt %. A rapid loss in Mg/HZSM-5 activity upon extending the period of operation under slurry reactor conditions is not due to coking, but to the catalyst being clogged by dispersion medium (polydimethylsiloxane) decomposition products. [ABSTRACT FROM AUTHOR]

A thermodynamic simulation package is developed for the catalytic polymerization of olefins in autoclave slurry, loop slurry, gas‐phase, and autoclave solution reactors. The number of components in the reactors may vary from two to six. The simulator uses the Sanchez–Lacombe theory, one of the major thermodynamic models in the polymer industry. Step‐by‐step instructions on how to specify the system, derive and solve the resulting nonlinear equations, and estimate the required thermodynamic properties are given. The software is used to describe ethylene/1‐hexene copolymerizations with hydrogen in different reactors under industrial conditions. These simulations demonstrate why thermodynamic effects must be included in olefin polymerization models. [ABSTRACT FROM AUTHOR]

Due to the complexity of the structure–activity relationship of the CuAl2O4 spinel catalyst, optimization of the catalyst structure is a great challenge. In this paper, three different CuAl2O4 spinel catalysts were prepared by the solid-phase method using copper hydroxide, copper nitrate, and copper oxide as the copper source, respectively, to study the difference in the structure of CuAl2O4 spinel catalysts induced by the raw materials and the catalytic behavior for CO hydrogenation. The structure of CuAl2O4 spinel catalyst was characterized by XRD, BET, SEM, TEM, H2-TPR and XPS. The activity of CO hydrogenation over the CuAl2O4 spinel catalyst without pre-reduction was evaluated in the slurry reactor. The results demonstrated that different copper sources had obvious influence on the CuAl2O4 spinel texture properties, surface enrichment degree, as well as decomposition and reduction ability, which further regulated the ratio of Cu+/Cu0 and thus affected the catalytic performance, especially the alcohol distribution. The CuAl2O4 spinel, employing copper hydroxide as the copper source, showed better selectivity of C2+OH, which was assigned to a higher ratio of Cu+/Cu0, along with larger pore size and pore volume. Moreover, the synergistic effect between Cu0 and γ-Al2O3 improved the selectivity of dimethyl ether.

Slurry polymerization processes using Zeigler–Natta catalysts are most widely used for the production of polyethylene due to their several advantages over other processes. Optimal operating conditions are required to obtain the maximum productivity of the polymer at minimal cost while ensuring operational safety in the slurry phase ethylene polymerization reactors. The main focus of this multi-objective optimization study is to obtain the optimal operating conditions corresponding to the maximization of productivity and yield at a minimal operating cost. The tuned reactor model has been optimized. The single objective optimization (SOO) and multi-objective optimization (MOO) problems are solved using non-dominating sorting genetic algorithm-II (NSGA-II). A complete range of Pareto optimal solutions are obtained to obtain the maximum productivity and polymer yield at different input costs. [ABSTRACT FROM AUTHOR]

The development of CO 2 hydrogenation catalysts for hydrocarbon production is a challenging and relevant task as it can contribute to solving of the CO 2 emission problem. In the present work, we describe our journey in the development of catalysts for operating in a slurry reactor. The screening of the preparation methods and catalyst composition yielded an active and highly selective CO 2 hydrogenation catalyst with catalytic performances comparable to the best ones reported in the literature. The most perspective catalysts were successfully evaluated in CO 2 hydrogenation using a slurry reactor. The supported catalysts were found to have a lower ability to form higher hydrocarbons compared to bulk catalysts. This could be correlated with the particle sizes of the active component of the respective catalysts. This insight may be useful in preparing tailor-made Fe-based catalysts with high chain growth probability. The important issue of mechanical strength for slurry operation was highlighted. [Display omitted] • A screening strategy focusing on chain growth and less excess-methane is presented. • The obtained catalysts show good performance comparable to best literature data. • C 2+ hydrocarbon selectivity increases with the crystallite size of the active component. • Catalysts developed in fixed-bed were successfully evaluated in a slurry reactor. [ABSTRACT FROM AUTHOR]

The Sanchez–Lacombe model is used to investigate the multiphase and multicomponent thermodynamic equilibrium during ethylene polymerization and ethylene/1‐hexene copolymerization in slurry and gas‐phase reactors. The simulation study focuses on the interactions among ethylene, polyethylene, hydrogen, 1‐hexene, and n‐hexane under typical polymerization conditions. When used as a diluent, n‐hexane increases the concentrations of all reactants in the amorphous polymer phase due to the cosolubility effect. Moreover, n‐hexane significantly swells the amorphous polyethylene. This means that a polyethylene particle with the same degree of crystallinity has a larger amorphous phase fraction in slurry than in gas‐phase reactors. Consequently, if the gas phase concentration is the same in both modes of polymerization, the concentration of all reactive species in semi‐crystalline polyethylene particles will be higher in slurry reactors. The thermodynamic equilibrium simulations agree with the reported experimental results and can explain why supported catalysts behave differently in slurry and gas‐phase polymerizations. [ABSTRACT FROM AUTHOR]

The objective of this study was to characterize the zeolite MCM-22 support structure after static hydrothermal preparation, then to prepare a cobalt and ruthenium-based catalyst supported by MCM-22 zeolite via wet impregnation, and finally, to assess the performance of both catalysts in the Fischer–Tropsch reaction with regard to the production of long-chain (C8) hydrocarbons. Cobalt catalysts promoted with ruthenium and supported on MCM-22 were prepared using the co-impregnation method. The MCM-22 zeolite was prepared using a 150 °C hydrothermal treatment for two different lengths of time (9–10 days), under static conditions. The Co-Ru-MCM-22 catalyst was characterized by X-ray diffraction, X-ray energy dispersion spectroscopy, N2 adsorption–desorption, temperature-programmed reduction, scanning electron microscopy, and transmission electron microscopy. The Fischer–Tropsch synthesis was carried out in a slurry reactor using the following operating conditions: 240 °C, 10 and 20 bar, 1:1 CO:H2 molar ratio. X-ray diffractograms showed a well-defined MWW structure for MCM-22. Spherical particles were observed on the scanning electron micrographs. On transmission electron micrographs, it was possible to identity well-dispersed cobalt particles in the Co-MCM-22 catalyst having an average particle size of 33.89 nm. Both Co-Ru/MCM-22(9D) and Co-Ru/MCM-22(10D) were used in the improved FTS in order to study the influence of promoters on the production of hydrocarbons with higher commercial value (> C8). [ABSTRACT FROM AUTHOR]

This work was devoted to study the influence of well-known catalyst carriers (activated utilized in catalytic reactions carbon and silica) on the hydrodynamic parameters and mass transfer rate in a slurry reactor. The influence of silica and activated carbon particles concentration up to 20% v/v on regime transition, average gas holdup, mass transfer coefficient, and CO2 removal was studied in a semi- batch slurry bubble column reactor (SBC) with a porous gas sparger. The effects of hydrophobicity and surfactant were also investigated. It was concluded the gas holdup is reduced and the point of transition from laminar to turbulent regime is shifted to less gas velocity when the hydrophobic and hydrophilic particles concentration was larger than 3% (v/v). The Particle hydrophobicity, gas velocity, and electrolyte concentration have positive impacts on gas holdup while slurry concentration gave a different trend. Experimental results show that the optical fiber probe is valid to use in a slurry bubble column and can also generate useful data such as bubble rise velocity and bubble distribution. The optical fiber probe was proved to be good technique for estimation of volumetric mass transfer coefficient within an error of ±18%. Mass transfer experiments with gaseous CO2 showed a behavior of removal in the same trend of increasing gas holdup with gas velocity. A noticeable removal of gaseous pollutants was observed for non-wettable particles at solid loading of 3%v/v. Mathematical correlations were formulated for CO2 removal as function of studied operating variables with correlation factors of 0.95-0.98. The present study depicts the effect of catalyst carrier on the hydrodynamic characteristics and mass transfer in a slurry reactor

Copper-containing catalytic slurries with different concentrations of active metal precursor solutions are synthesized by drop thermolysis in situ in the hydrocarbon medium of a slurry reactor. According to dynamic light scattering, the particle size of the catalytic slurry dispersion phase is 3–4.5 nm and it remains almost unchanged during the synthesis. Using FTIR spectroscopy it is shown that the structure of precursors of slurry active species depends on the concentration of solution, which may influence the phase composition of catalytically active fragments of the surface during the reduction and synthesis of alcohols. It is demonstrated that alcohols may be synthesized from CO and H2 in the slurry reactor in the presence of the formed nanosized slurries. It is revealed that the composition of alcohol phase products differs significantly with target product selectivity being comparable: at a low concentration of precursor solution a marked amount of methanol is contained in the mixture (up to 66%), while an increase in the concentration of precursor solution causes a rise in the proportion of higher molecular weight alcohols to 88%. [ABSTRACT FROM AUTHOR]

• New technology for high temperature three-phase Fischer-Tropsch synthesis. • Light liquid hydrocarbons enriched with α-olefins (up to 50% wt). • CO conversion of about 80% (per pass), selectivity toward liquid products of 85%, and C 5+ productivity of 600 g / h kg Me. TIPS RAS (Russia) has developed a new technology for high temperature three-phase Fischer-Tropsch synthesis. This technology is based on an original nanosized iron catalyst and a new reactor type. Producing light liquid hydrocarbons enriched with α-olefins (up to 50% wt) is the main distinction from industrial slurry-technologies. Yield of these products is about 140 g per 1 cubic meter of syngas. This technology is tested in a pilot plant with capacity of up to 2 liters of liquid hydrocarbons per day. Project indexes are CO conversion of about 80% (per pass), selectivity toward liquid products of 85%, and C 5+ productivity of 600 g / h kg Me. [ABSTRACT FROM AUTHOR]

The catalytic activity of zeolites of the FAU, MFI, and BEA framework types with different SiO2/Al2O3 ratios, which are dispersed in the reaction medium, has been studied in the liquid-phase cracking of n-alkanes at a temperature of 300–350°С and a hydrogen pressure of 7 atm. It has been found that a BEA zeolite catalyst with a SiO2/Al2O3 ratio of 75 exhibits the highest activity. It has been shown that the main factor determining the activity of zeolites under the above conditions is the specific surface area of the catalyst particles smaller than 200 nm. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate the continuous catalytic hydrotreating of sewage sludge-derived hydrothermal liquefaction oil on a versatile, pilot-scale testing unit, equipped with both a slurry and a fixed-bed reactor. Comparison of the two reactors shows that slurry hydrocracking is consistently more efficient in both heteroatom removal and cracking performance compared to the fixed-bed operation. The upgraded HTL oil from the slurry reactor contains 35% less nitrogen that the equivalent oil produced from the fixed-bed reactor at 350 °C and is lighter, consisting of 84 wt% molecules in the gasoline and diesel range, compared to 63 wt% in its counterpart. This is tentatively ascribed to the higher residence time and the lower mass-transfer limitations in the slurry reactor that enhance the hydrogenation and cracking reactions. Upgrading the HTL oil in a two-stage configuration improves only the nitrogen removal, which increases from 40‐55% in the one-stage process to 83%. Overall, slurry hydrocracking appears to be a promising strategy for the upgrading of bio-oils from renewable feedstocks, such as waste and biomass. Further research is required to study operability and stability issues for longer time-on-stream and investigate the process in the presence of dispersed liquid catalysts. • Slurry hydrocracking is as promising process for biocrude upgrading. • Demonstration of continuous catalytic upgrading of sewage sludge-derived HTL oil. • Slurry reactor more efficient in heteroatom removal and cracking compared to fixed-bed. • Complete sulfur and oxygen, and up to 83% nitrogen removal at 350 °C and 100 bar. • Further research required to study operability and stability for long reaction time. [ABSTRACT FROM AUTHOR]

The synthesis of light C2–C4 olefins from dimethyl ether (DME) in a three-phase system (slurry reactor) over nanosized MFI-type zeolites suspended in liquids with various chemical compositions (paraffins, hydrocarbon and silicone oils, and polyhydric alcohol esters) was studied. It was found that the target reaction can be accompanied by the catalytic decomposition of a dispersion liquid and its mechanical entrainment, which destabilizes the catalytic process. These negative factors can be minimized with the use of polydimethylsiloxane (Syltherm 800) as a dispersion liquid and MFI zeolite modified with magnesium as a catalyst. The rate of catalytic destruction of this oligomeric molecule in the presence of Mg–MFI was minimal at temperatures of 300°C or lower. The synthesis of olefins from DME at a temperature of 300°C over the Mg–MFI catalyst suspended in Syltherm 800 occurred in a stable way with high performance (70–90% conversion and 46–59% selectivity for the target products). The reaction carried out with the partial reflux of liquid reaction products after the dehydration of condensate excluded the loss of dispersion liquid in the course of the catalytic process due to its mechanical entrainment from the reactor. [ABSTRACT FROM AUTHOR]

In this study, photocatalytic activity of La loaded TiO 2 NPs was enhanced by engineering approach using monolithic honeycomb assisted photo-reactor system for dynamic hydrogen production. La/TiO 2 NPs loaded over monolithic honeycomb support were characterized by XRD, XPS, FESEM, RAMAN, HRTEM, BET, UV–Vis and PL-spectroscopy. The photocatalytic activity of La/TiO 2 NPs was enhanced by 1.8 folds higher than using pristine TiO 2 in a slurry photoreactor system. This enactment was due to larger surface area, faster charge carrier separation and decreased surface recombination centers due to the presence of oxygen vacancies. Moreover, using monolithic honeycomb support loaded with La/TiO 2 , H 2 generation rate of 165.5 ppm/h was obtained, 9.19 folds higher than using La/TiO 2 in a slurry phase. Moreover, apparent quantum yield and space yield of monolith photoreactor was 1.4 and 4.5 folds higher than the slurry phase photoreactor, respectively. The superior efficiency of monolith photoreactor was due to adaptable arrangement of reactor which permits most utilization of illuminated surface area and processing volume with effective mass transport which is restricted in a slurry phase photoreactor. Also, stability comparison of slurry and monolith photoreactor for hydrogen production reveals, reusability of La/TiO 2 loaded over monolithic support was 4.18% higher than the catalyst suspended in slurry phase photo-reactor. Therefore, enhanced efficiency of catalyst can be obtained using monolith photoreactor for photocatalytic H 2 production compared to suspended slurry system and can be employed for other energy applications. Unlabelled Image • Structured La/TiO 2 loaded over monolithic-support for photocatalytic H 2 production. • Performance comparison of slurry and monolith photoreactor for hydrogen production • H 2 yield over monolith coated La/TiO 2 was 9.19 folds higher than using slurry phase. • Quantum yield of monolithic catalyst was improved because of flexible configuration. • Space yield of monolith supported reactor was 4.5 folds higher than slurry phase. [ABSTRACT FROM AUTHOR]

Comparative analysis of deactivation of the catalyst SAPO-34 for methanol conversion to lower olefins was carried out in fixed-bed flow reactors, in fluidized-bed reactors, and slurry reactors with the catalyst dispersed in a polydimethylsiloxane (PDMS) medium. It has been found that the deactivation rate of the catalyst essentially depends on the reactor type. The uniform contact of methanol with the fluidized catalyst makes it possible to increase by one and a half the on-stream stability compared with the fixed bed catalyst. However, the reaction run in the PDMS medium in the slurry reactor leads to significant acceleration of deactivation, which is due to high solubility of olefins and methanol in PDMS and results in an increase in the contact time of the catalyst with the reactants and products. A method has been proposed for measuring the solubility of gases in liquid polymers at high temperatures using mass-spectroscopic detection of effluent gases. [ABSTRACT FROM AUTHOR]

The catalytic activity of zeolites of three types—Y, ZSM-5, and Beta—in the cracking of С20–С35n-alkanes in a three-phase reactor has been studied under the following conditions: a temperature of 300–380°C, a hydrogen pressure of 7 atm, and a catalyst content of 1 wt %. It has been shown that the activity of zeolite Beta in cracking reactions is several times higher than the activity of zeolites of the other types. This finding can be apparently attributed to a large mesopore volume in the Beta structure. [ABSTRACT FROM AUTHOR]

Highlights • Sodium borohydride is a strong and very selective reducing agent used in chemical and pharmaceutical industry. • Precise kinetic data for the synthesis of sodium borohydride were reported. • A multphase reactor model for a semibatch reactor was developed. • A new mathematical model was developed for the sodium borohydride synthesis. • The model can be used for process design and optimization. Abstract A mathematical model for the synthesis of sodium borohydride (NaBH 4) from finely dispersed solid sodium hydride (NaH) and dissolved trimethyl borate (B(OH) 3) in inert mineral oil was developed. The model is based on a plausible reaction mechanism of dissolved and adsorbed trimethyl borate on the surface of sodium hydride, where the reaction is presumed to take place. The surface reaction between sodium hydride and trimethyl borate leads to the formation of main (NaBH 4) and side products (methoxy borohydrides), which was verified by chemical analysis of sodium borohydride and methanol in the water extract of the oil phase. Extensive kinetic experiments in a laboratory-scale isothermal and isobaric slurry reactor enabled a detailed kinetic analysis of the data, including the derivation of a mathematical model for the formation of sodium borohydride in a semibatch slurry reactor. The kinetic model was verified with experimental information and can be used as an element for process design. [ABSTRACT FROM AUTHOR]

Highlights • The radiation distribution in a slurry reactor is studied. • The absorption coefficient is related to the local catalyst loading. • There exists an optimal inlet catalyst loading for the photocatalytic reaction. Abstract The multiphase flow leads a non-uniform distribution of catalyst particles in a slurry reactor. The previous studies used the inlet catalyst loading to compute the absorption coefficient and the scattering coefficient in the slurry reactor, which did not consider the non-uniform distribution of catalyst particle. The present study numerically studies the effect of multiphase flow on the radiation distribution in a slurry reactor. Herein, the absorption coefficient and the scattering coefficient are related to the local volume fraction of catalyst. The volume fraction of catalyst is obtained using the Eulerian-Eulerian method. The radiative transfer equation is solved using the DO model. Results show that the local catalyst loading are non-uniform in the slurry reactor. The reactor-averaged catalyst loading is always less than the inlet catalyst loading. It may leads to the underestimation of the incident radiation as well as UV disinfection and the overestimation of LVREA and as well as photocatalytic reaction rate. It is more reasonable to compute the absorption coefficient and the scattering coefficient using the local catalyst loading. A large diameter and a large inlet catalyst loading can lead to a large catalyst loading in the reactor, the large absorption coefficient and scattering coefficient, meaning a low radiation intensity in the reactor. There exists an optimal inlet catalyst loading for the photocatalytic reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Innovative use of g-C 3 N 4 as suspension catalyst in PEC degradation of PhACs. • PEC degradation of diclofenac surpasses photocatalytic and electrocatalytic oxidation. • Parameter optimisation: electrode distance, cathode material and electrolyte medium. • Reutilization cycles prove durability and potential of g-C 3 N 4 for PEC applications. • Efficient PEC removal of pharmaceuticals from spiked urban wastewater. Graphitic carbon nitride (g-C 3 N 4) recently emerged as a remarkable photoelectrocatalyst for water treatment. Advanced oxidation processes (AOPs) consisting of photoelectrocatalytic (PEC) systems are being researched towards the development of sustainable strategies for the complete removal of refractory contaminants from effluents of urban wastewater treatment plants (WWTPs). This work consists of the optimisation of a PEC system, composed of a boron-doped diamond (BDD) anode, titanium cathode, and a suspended g-C 3 N 4 photoelectrocatalyst, for the treatment of both synthetic and real urban waste waters spiked with pharmaceutical active compounds (PhACs). Different working parameters were considered and optimised to improve degradation and mineralisation rates, such as the cathode material, anode-to-cathode distance, electrolyte resistivity, and matrix composition. The optimal conditions allowed removals of 100 % diclofenac, 88 % fluoxetine and 77 % ibuprofen in the complex wastewater matrix. Moreover, it was observed that the presence of other refractory organic molecules offered a greater impediment to PEC treatment than residual co-existing substances. The main oxidative agents were investigated by scavenging experiments, showing that generated holes and reactive oxy-species, i.e. hydroxyl and superoxide radicals, take a major role in the degradation of PhACs. The recyclability of the g-C 3 N 4 suspension as photoelectrocatalyst in the PEC process provides a promising perspective for the development of wastewater treatment units. [ABSTRACT FROM AUTHOR]

This research aims to assess the presence of four antibiotic compounds detected in the influent and effluent of wastewater treatment plants (WWTPs) in the POCTEFA territory (north of Spain and south of France) during the period of 2018–2019, and to relate the removal of antibiotic compounds with the processes used in the WWTPs. The performance of a photocatalytic TiO2/UV-VIS pilot-scale plant was then evaluated for the degradation of selected antibiotics previously detected in urban treated effluent. The main results reflect that azithromycin had the highest mass loadings (11.3 g/day per 1000 inhabitants) in the influent of one of the selected WWTPs. The results also show considerable differences in the extent of antibiotics removal in WWTPs ranging from 100% for sulfadiazine to practically 0% for trimethoprim. Finally, the photocatalytic TiO2/UV-VIS pilot-scale plant achieved the removal of the four antibiotics after 240 min of treatment from 78%–80% for trimethoprim and enrofloxacin, up to 100% for amoxicillin, sulfadiazine and azithromycin. The catalyst recovery via mechanical coagulation–flocculation–decantation was almost total. The Ti concentration in the effluent of the TiO2/UV-VIS pilot-scale plant was lower than 0.1% (w/w), and its release into the environment was subsequently minimized.

Effect of mode parameters, such as the feed gas flow rate, its content of dimethyl ether, and content of a catalyst in the suspension, on the main parameters of the dimethyl ether conversion into light C2-C4 olefins in a three-phase system (slurry reactor) in the presence of a catalytic suspension based on a nanosize zeolite Mg-MFI dispersed in silicone oil was examined. The values of the parameters, at which the conversion of dimethyl ether occurs in the steady state mode under favorable hydrodynamic conditions at a relative chemical stability of the dispersion medium and its minimum mechanical entrainment from the reactor, were found. Irrespective of the dimethyl ether concentration in the operating gas, the reaction was shown to occur with conversion of up to ~80% at selectivity of ~50%, and ethylene is the main reaction product (up to 30 wt %). [ABSTRACT FROM AUTHOR]

The textural, acidic and catalytic properties of nanosized samples of commercial MFI zeolites with SiO2/Al2O3 molar ratios of 30, 50 and 80 supplied by Zeolyst Co. and some synthesized nanocrystallites of MFI zeolites with a SiO2/Al2O3 molar ratio of 55 and 80 were compared. It was shown that the SiO2/Al2O3 ratio had no impact on catalyst deactivation in the slurry reactor as in the conventional fixed-bed reactor. Irreversible deactivation was observed only for the samples with an extremely high external surface Brønsted acidity indicating that near-surface secondary processes are responsible in catalyst deactivation. It was shown that the reaction temperature influenced the product selectivity due to change in the contribution of both hydrogen transfer reaction and arene/alkene circles and can be considered to be an efficient tool of selectivity control for DME conversion in the slurry reactor. [ABSTRACT FROM AUTHOR]

Abstract: A stable CuZnAl slurry catalyst for the synthesis of ethanol from syngas has been developed by adjusting the heat treatment conditions of the complete liquid-phase method. The activity evaluation results showed that the CuZnAl catalyst, when heat-treated under a high pressure and temperature, was a stable catalyst for the synthesis of ethanol. The selectivity of ethanol using the CuZnAl slurry catalyst, which was heat-treated at 553 K under 4.0 MPa, increased continuously with time and was stable at approximately 26.00% after 144 h. The characterization results indicated that the CuZnAl slurry catalyst heat-treated under high pressure conditions could facilitate the formation of a more perfect structure with a larger specific surface area. The prepared catalyst contained a balance of strong and weak acid sites, an appropriate form of Cu2O and a high Cu/Zn atomic ratio at the catalyst surface, providing its stability in ethanol synthesis from syngas. [ABSTRACT FROM AUTHOR]

A series of novel bimetallic copper/zirconia carbon nanofibers supported catalysts with different Cu contents (5–25 wt%) were synthesized via deposition precipitation method. The physicochemical characterization of the calcined catalysts was carried out by X-ray diffraction, inductively coupled plasma optical emission spectroscopy, N 2 adsorption–desorption, N 2 O chemisorption, temperature programmed reduction, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy and temperature programmed CO 2 desorption. Structure-reactivity correlation for catalytic hydrogenation of CO 2 to methanol was discussed in details. Reaction studies revealed 15 wt% as optimum Cu concentration for CO 2 conversion to methanol with CO 2 /H 2 feed volume ratio of 1:3. Cu surface area was found to play a vital role in methanol synthesis rate. CO 2 conversion was observed to be directly proportional to the number of total basic sites. A comparative study of this novel catalyst with the recently reported data revealed the better CO 2 conversion at relatively low reaction temperature. [ABSTRACT FROM AUTHOR]

Nanodispersed suspensions that are effective in DME conversion and stable in the reaction zone in a three-phase system (slurry reactor) are obtained from MFI zeolite commercial samples (TsVM, IK-17- 1, and CBV) in liquid media via ultrasonic treatment (UST). It is found that the dispersion medium, in which ultrasound affects zeolite commercial sample, has a large influence on particle size in the suspension. UST in the aqueous medium produces zeolite nanoparticles smaller than 50 nm, while larger particles of MFI zeolite samples form in silicone or hydrocarbon oils. Spectral and adsorption data show that when zeolites undergo UST in an aqueous medium, the acid sites are redistributed on the zeolite surface and the specific surface area of the mesopores increases. Preliminary UST in aqueous media of zeolite commercial samples (TsVM, IK-17-1 and CBV) affects the catalytic properties of MFI zeolite nanodispersed suspensions. The selectivity of samples when paraffins and olefins form is largely due to superacid sites consisting of OH groups of hydroxonium ion H3O+. [ABSTRACT FROM AUTHOR]

Cobalt- and iron-containing dispersions that can be used as active catalysts for Fischer-Tropsch (FT) synthesis in slurry reactors and a new modification of this process based on the use of nanoheterogeneous catalysis approaches have been discussed. Synthesis procedures for the catalytic dispersions and specific features of occurrence of FT synthesis in the presence of these catalysts have been described. [ABSTRACT FROM AUTHOR]

The efficiency of three photocatalytic reactor configurations for the degradation of the micropollutant clofibric acid in water was assessed. The following reaction systems were tested: (i) a slurry reactor with suspended TiO 2 particles; (ii) a fixed-film reactor with TiO 2 immobilized onto the reactor window; and (iii) a fixed-bed reactor filled with TiO 2 -coated glass rings. The influence of the catalyst concentration in the suspended system and the number of the catalyst coatings in the immobilized systems were evaluated. The performances of the reactors, under the experimental condition of highest reaction rate for each configuration, were compared with the aid of two parameters: (i) the photonic efficiency ( η ), which is the ratio of the reaction rate to the rate of incident photons; and (ii) the quantum efficiency ( η Rxn ), which is the ratio of the reaction rate to the photon absorption rate. The obtained values of η Rxn were 4.59, 2.96 and 2.02% for the slurry reactor, the fixed-bed reactor and the fixed-film reactor, respectively. Although the slurry reactor was the most efficient configuration, the fixed-bed reactor rendered a value of quantum efficiency only one third lower than the suspended system, making this configuration very convenient for photocatalytic reactions. The analysis of the reaction rate, the photon absorption rate and the quantum efficiency are essential to rationally improve the design, configuration and experimental conditions of photocatalytic reactors. [ABSTRACT FROM AUTHOR]

This article describes the synthesis of methanol by the direct hydrogenation of CO 2 over Cu/ZrO 2 catalyst at different ZrO 2 concentrations (5, 10, 15, 20 and 25 wt.%) in a three-phase phase reactor. The techniques of N 2 adsorption/desorption, x-ray diffraction, x-ray photoelectron spectroscopy, transmission electron microscopy, temperature-programmed desorption by CO 2 , N 2 O chemisorption and inductively coupled plasma optical emission spectrometry were employed for catalyst characterization. At a reaction temperature of 180 °C, pressure of 3.0 MP and 0.020 g/mL of the catalyst, the conversion of CO 2 and the yield of methanol were 10% and 25 g/kg.h, respectively. Surface area of the metallic copper was increased from 8.1 to 9.5 m 2 /g with the presence of ZrO 2 from 5 to 15 wt.%. The methanol turnover frequency exhibited a linear relationship with ZrO 2 concentration. Methanol synthesis rate was progressively increased with increasing fraction of dispersed copper. A comparative study with the literature revealed better activity of this novel catalyst at relatively low reaction conditions. [ABSTRACT FROM AUTHOR]

The world market of dimethyl ether (DME) is rapidly gaining in strength. The review addresses prospects for using the slurry technology in the large-scale world production of DME. The literature and patent data pertaining to the manufacture of dimethyl ether in slurry reactors using finely divided heterogeneous catalysts suspended in inert liquids are generalized. Variants of the slurry technology used in the one-step DME synthesis from syngas and in the two-step DME synthesis (at the stage of dimethyl ether manufacturing via methanol dehydration) are considered. Advantages of the slurry technology over the conventional gas-phase methods of DME production are highlighted. [ABSTRACT FROM AUTHOR]

Unsupported nickel-molybdenum and cobalt-molybdenum sulfide catalysts are synthesized via the in situ decomposition of water-soluble bimetallic precursors in a hydrocarbon feedstock using nickel-molybdenum and cobalt-molybdenum complexes with citric, oxalic, succinic, glutaric, and tartaric acids as precursors. The sulfide catalysts are characterized by means of transmission electron microscopy and X-ray photoelectron spectroscopy. The catalyst activity in the hydrogenation of bicyclic aromatic hydrocarbons and the hydrodesulfurization of dibenzothiophene is studied. The effect the composition of the precursor solution in the hydrocarbon feedstock emulsion has on the activity of the resulting catalyst is determined. It is shown that the activity reaches high values even after 1 h of reaction. The hydrogenation of mono-, di-, and trimethylnaphthalenes and ethylnaphthalene is studied. The optimum promoter-to-molybdenum ratio (0.25: 1) is found. It is shown that the catalyst activity does not fall during recycling, due to the elimination of the negative effect of water contained in the emulsion, which results in oxidation of the catalyst surface. After the second reaction cycle, the catalyst particles are longer and have a greater number of MoS layers than the respective parameters of the catalyst particles after the first cycle. XPS shows that the content of oxygen on the catalyst's surface falls during recycling, while the fraction of metals in the sulfide environment and the sulfur in the sulfide state grows. [ABSTRACT FROM AUTHOR]

Technological aspects of the reductive amination of benzaldehyde with ammonia in the absence of solvents are discussed. The reaction kinetics in a slurry reactor was experimentally studied in order to maximize the yield of benzylamine. Effects of reaction conditions and type of solid catalyst on the content of undesirable by-products were investigated. In particular, benzyl alcohol and trimers of benzylimine, namely, hydrobenzamide and 2,4,5-triphenyl-4,5-dihydro-1 H-imidazole, were found as significant by-products. The formation of poorly soluble high-boiling trimers of benzylimine was minimized by semi-batch arrangement of the process with continuous addition of benzaldehyde into the load of benzylamine, ammonia, and Raney-Ni catalyst. Some important features of benzaldehyde amination, which make it less advantageous for benzylamine production compared to the benzonitrile hydrogenation, are described. [ABSTRACT FROM AUTHOR]

Fischer-Tropsch synthesis in the presence of nanosized cobalt-containing catalysts suspended in a mixture of long-chain alkanes has been studied. It has been found that the molecular-mass distribution of the products differs substantially from the typical Anderson-Schulz-Flory distribution. The most evident cause of this phenomenon is the intense hydrogenolysis of long-chain alkanes of the liquid medium which occurs during catalyst activation; this process may proceed to a sufficient extent during Fischer-Tropsch synthesis. The molecular-mass distribution of hydrogenolysis products shows a number of specific features that differ appreciably from those for both classical hydrogenolysis (cracking) in the presence of zeolites and terminal methanolysis, which is frequently observed in the presence of group VIII metals. Problems encountered during the construction of models for the observed distribution are discussed. [ABSTRACT FROM AUTHOR]