Effect of size and oxidation state of size-controlled rhodium nanoparticles on the aqueous-phase hydrodechlorination of 4-chlorophenol

Unsupported size-controlled Rh nanoparticles of different size and oxidation state were tested as catalysts models in aqueous phase hydrodechlorination (303-318K, 1atm) using 4-chlorophenol (4-CP) as target compound. A chemical reduction method was employed for the synthesis of the nanoparticles using methanol and poly(N-vinyl-2-pyrrolidone) (PVP) as reducing and capping agent, respectively. The size of Rh nanoparticles was in a narrow range (1.9-4.9nm) whereas Rhn+/Rh0 ratio values were found within a wide range (0.56-3.89).High 4-CP conversion values (c.a. 100%) were achieved at low Rh concentration (2.45·10-3gL-1). Phenol, cyclohexanone, cyclohexanol and traces of cyclohexane were identified as reaction products. A wide range of activity values (1.7-29.4mmolg-1min-1) were obtained, being equivalent to the measured in a previous work with unsupported Pd nanoparticles, in spite of the fact that Rh supported catalysts have generally been reported as less active than Pd ones in liquid phase hydrodechlorination. As the size of Rh nanoparticles decreased the activity increased reaching a maximum at 2.8nm, lower size values leading to a significant decrease of activity. A remarkable dependence of activity on the Rhn+/Rh0 ratio was found, thus a higher activity corresponded to a higher relative amount of zero-valent Rh in the nanoparticles samples. Regression models were developed in order to address the significance of nanoparticles size and oxidation state for the prediction of selectivity to cyclohexanone and cyclohexanol at varying reaction times. A crossed effect of particle size and Rhn+/Rh0 ratio was identified as a significant factor influencing the selectivityWe greatly appreciate financial support from the Spanish MCYT (CTQ2009-09983 and CTQ2012-32821) and CAM (REMTAVARES S-2009/AMB-1588). J.A. Baeza thanks to the Spanish MICINN a research grant (BES-2010-030059

Activated carbon from grape seeds upon chemical activation with phosphoric acid: Application to the adsorption of diuron from water

The preparation of activated carbon from grape seeds was studied by chemical activation with phosphoric acid. Grape seeds were pretreated with sulfuric acid to improve wettability and impregnated at different grape seed to phosphoric acid ratios (1:1-1:4). The impregnated grape seeds were carbonized in a static horizontal furnace at temperatures between 350 and 550°C. Microporous activated carbons with some contribution of mesoporosity were obtained. The best results in terms of surface area (1139m2/g) and mesopore volume (0.24cm3/g) development were observed for a grape seeds to phosphoric acid ratio of 1:3 and a carbonization temperature of 500°C. The activated carbon prepared shows granular morphology and an egg shell structure that favors application in liquid phase. The activated carbon was tested in the adsorption of diuron from aqueous phase. The adsorption rate was measured within the temperature range of 15-45°C. First and second order rate equations and intraparticle diffusion model were checked to fit the kinetic dataWe greatly appreciate financial support from the Spanish MCYT (CTQ2009-09983 and CSD2006-44) and CAM (REMTAVARES S-2009/AMB-1588). M. Al Bahri thanks to the Spanish MICINN a research grant (CTQ2006-13512

Mechanistic understanding of the behavior of diuron in the adsorption from water onto activated carbon

The adsorption of diuron from aqueous phase by activated carbon has been analyzed from a molecular point of view thanks to a computational approach based on COSMO-RS methodology, with the aim of providing a mechanistic explanation of the experimental results. The adsorption experiments were carried out at different pH values (3-7) and temperatures (15-45 °C) using an activated carbon prepared by chemical activation of grape seeds. The most relevant characteristics of the adsorption of diuron were the increase of diuron uptake with temperature and the occurrence of multilayer adsorption at high equilibrium concentrations. Likewise, the contribution of cooperative adsorption was also found to increase with temperate, as shown by the change of the isotherm pattern from L-3 type (Giles classification) at 15 °C to S-3 at 45 °C. The formation of multilayer and the contribution of cooperative adsorption were not observed at the highest pH studied The results obtained from the computational approach were consistent with the trends shown by the experimental data. The molecular and thermodynamic properties of the solvent-adsorbate-adsorbent system were estimated using the quantum-chemical COSMO-RS method. Thus, the increase in diuron uptake at increasing temperature was ascribed to a higher population of diuron planar conformers, whose affinity for activated carbon is higher as evaluated in terms of the activated carbon/water partition coefficient. COSMO-RS simulations predicted strong interaction among diuron molecules due to the amphoteric character of the molecule. Likewise, the formation of clusters was found to be especially favored from a thermodynamic point of view in the case of planar conformers adsorbed on activated carbon, which supports the occurrence of cooperative adsorption and the formation of a multilayerWe greatly appreciate financial support from the Spanish MCYT (CTQ2009-09983 and CSD2006-44) and CAM (REMTAVARES S-2009/AMB-1588

Aqueous phase reforming of starch wastewater over Pt and Pt-based bimetallic catalysts for green hydrogen production

This work analyses the application of aqueous phase reforming (APR) for green hydrogen production from starch industry wastewater. This work reports for the first time on the direct conversion of a high molecular weight biomass polymer contained in wastewater in contrast to low molecular weight substrates mainly reported in the literature. The potential of this type of feedstock was evaluated by varying the starch source (rice, potato, sweet potato and cassava) and the type of catalyst (carbon supported Pt, PtRu, PtPd, PtRe and PtRh catalysts). In APR experiments at 220 °C with synthetic wastewater, PtRu/C and Pt/C catalysts achieved the highest H2 yield values, around 51 mmol H2 per g of organic carbon in the initial wastewater, close to 2.6 times higher than that reported in the literature of brewery wastewater, a promising substrate. The lack of free aldehyde or keto groups due to glycosidic bonds between glucose units in starch results in higher conversion to gas and H2 production compared to APR of glucose. This fact shows that APR has more feedstock flexibility than that previously reported for light compounds. In the experiments with real wastewaters, the organic matter removal was influenced largely by the starch source: the best APR performance (28.5 mmol H2 gTOCi−1) was obtained for rice processing wastewater, which is characterized by the highest starch concentration and the lowest protein content. Poor performance was observed in the APR of potato processing wastewater, probably due to catalyst deactivation caused by protein fractio

Development of porosity upon physical activation of grape seeds char by gas phase oxygen chemisorption–desorption cycles

Activation of grape seeds char upon cyclic oxygen chemisorption-desorption permits a controlled development of porosity versus burn-off using air as a cheap activation agent. In this work the influence of chemisorption and desorption temperature and the number of cycles is investigated. A fast increase of BET surface area (SBET) is obtained in the two first cycles; that increase becomes then lower although the SBET continues increasing upon the successive cycles. Regarding the Dubinin-Astakhov surface area (SDA) a slow increase was observed from cycle to cycle. The activation process led to the development of both micro and mesoporosity. Under the optimum conditions for surface area development, i.e. an oxidation temperature of 275°C and desorption temperatures between 850 and 950°C, values of 1129-1256 and 1339-1219m2/g were obtained for SBET and SDA, respectively. Porosity was found to increase mainly during the desorption stage, although chemisorption also led to some surface area development. SEM characterization showed that the activated carbon maintained the granular morphology of the seeds even after 10 cycles showing the egg-shell structure of the precursor with longer and deeper cracks at the outer surface. The activated carbons showed a good mechanical strength during attrition testsThe authors greatly appreciate financial support from the Spanish Ministerio de Ciencia e Innovación (CTQ2009-09983

Removal of chlorinated organic volatile compounds by gas phase adsorption with activated carbon

This paper discusses the removal of chlorinated volatile organic compounds (Cl-VOCs) from gas streams by means of fixed-bed adsorption with a commercial activated carbon (AC). Column experiments were performed at different conditions (inlet concentration, temperature, pressure, gas flow rate and bed length). A two-parameter model introduced by Yoon and Nelson was applied to predict the entire breakthrough curves for chloromethane adsorption. Complete regeneration of the exhausted AC was performed at mild conditions (atmospheric pressure and room temperature). In order to gain a better knowledge on the effect of the surface chemistry of AC on the adsorption of Cl-VOCs, the quantum-chemical COSMO-RS method was used to simulate the interactions between AC surface groups and different Cl-VOCs as monochloromethane, dichloromethane and trichloromethane. This information can be useful for tailoring the ACs with the objective of improving their adsorption capacities by further functionalization. To confirm this, the commercial AC tested was modified by means of different thermal and oxidative treatments (nitric acid and ammonium persulfate), being the surface chemistry and textural properties of the resulting materials characterized by different techniques. The modified ACs were then tested in column adsorption experiment with different Cl-VOCs. The uptake of these compounds increased with the basic character of the AC surfaceThe authors are grateful to the Spanish “Ministerio de Ciencia e Innovación (MICINN)” and “Comunidad de Madrid” for financial support (Projects CTQ2011-26758, CTQ2009-09983 and S2009/PPQ-1545

Influence of bicarbonate, other anions and carbon dioxide in the activity of Pd-Cu catalysts for nitrate reduction in drinking water

Synthetic and commercial drinking waters with different composition were studied as reaction media to study the influence of salts in NO3- catalytic reduction using a Pd-Cu catalyst supported on a carbon black. As a general trend, a decrease in NO3- conversion and an increase in NH4+ selectivity were observed for high HCO3- concentration media in mixed salts waters. Literature has commonly ascribed HCO3- effect to competitive adsorption with NO3-. However, in the current work, the mechanism for effect HCO3- is reconsidered basis on HCO2- formation during NO3- catalytic reduction, here reported for the first time. HCO2- formation indicates that hydrogenation of HCO3- occurs in addition to adsorption. Likewise, decomposition of HCO2- on the catalysts surface releases hydrogen leading to increased spill-over and relevant hydrogenation of NO3- to NH4+. The presence of SO42-, Cl- reduces NH4+ selectivity due to competition for active sites and lower HCO2- generation. Furthermore, it was observed that the use of CO2 as buffer also contribute to the hydrogenation of NO3- to NH4+ through HCO2- routeThe authors greatly appreciate the support from Spanish Agencia Estatal de Investigacion ´ RTI2018-098431-B-I00 (MCIU/AEI/FEDER, UE). Dydia Tanisha Gonzalez ´ thanks the Regional Government of Madrid a research grant (PEJ-2020-AI/AMB-17551

Effect of structural ordering of the carbon support on the behavior of Pd catalysts in aqueous-phase hydrodechlorination

Catalysts consisting of Pd supported on virgin and heat-treated carbon blacks (homemade and commercial), graphites (natural and synthetic) and commercial carbon nanofibers were prepared and tested in the aqueous phase hydrodechlorinaton (HDC) of 4-chlorophenol (4-CP) under near ambient conditions (30 °C, 1 atm) in order to explore the effect of the support on the catalytic behavior. The homemade graphitized supports were prepared from commercial carbon black (CB) and from a carbon black-like material (CBPE) obtained from pyrolysis of low-density polyethylene. All the catalysts prepared yielded complete 4-CP conversion, although a wide range of activity was observed (10.7–173.5 mmol gPd−1 min−1). The graphitized carbon black provided the most active catalysts, showing Pd nanoparticles around 3 nm in size and a well-balanced contribution of Pd species (Pdn+/Pd0 = 0.9). Substantial differences of activity were found between the graphitized and not graphitized supports, even for catalysts with similar Pd nanoparticle size. The higher activity of the catalysts with graphitized supports can be partly associated to a more balanced initial Pdn+ to Pd0 ratio. Moreover, higher selectivity to hydrogenation products (cyclohexanone) was also achieved with those catalysts due to a higher contribution of the Pd0 speciesThe authors greatly appreciate financial support from the Spanish MINECO (CTQ2012-32821

Subsea Compression Applications ,

TutorialTutorial 22: The use of Subsea gas compression technology for subsea re-injection and/or gas transport boosting represents a new and exciting application for rotating equipment, which will allow new gas/condensate field production opportunities, enhanced recovery of existing gas/condensate fields and cost effective production from marginal gas fields. This panel session includes short presentations on the benefits of subsea compression, an overview of currently ongoing projects, and recent advances and technologies that are available and/or under development for subsea gas compression. The panel session includes presentations from SIEMENS ENERGY, MAN DIESEL & TURBO, GE OIL & GAS, and DRESSER-RAND and. The respective presentation titles are: 1. Subsea Electrical Distribution – Siemens Energy, 2. HOFIMTM Type Compressors for Subsea Applications – MAN Diesel & Turbo, 3. GE Oil & Gas Experience in Subsea Gas Compression– GE Oil & Gas, and 4. DATUM I Compressor for Subsea Applications: Update on Qualification Efforts- Dresser-Ran

Testing of Gas-Liquid Centrifugal Separation and Compression Technology at Demanding Operating Conditions

LectureThis paper describes experimental testing of a Rotating Centrifugal Separator (RCS) integrated within the casing of a centrifugal compressor. This unique combination of rotary gasliquid separation and centrifugal compression technologies represents a new class of turbomachinery and leads to increased system compactness by eliminating the need for large external gravity based separation/scrubbing vessels often used on traditional compressor trains. The OEM’s closed-loop, multiphase flow test facility was used for measuring aero/thermodynamic and liquid separation performance of the system. The test loop utilized inert gas as the vapor phase component and a commercially available, stabilized liquid hydrocarbon based solvent as the liquid phase component. The phase of the test program discussed in the paper extends the separation performance data previously obtained for the RCS stage to more challenging separation conditions. The paper also discusses the application of this technology in two production type machines, and illustrates the intimate relationship that can exist between the processing side and the rotating equipment side of the oil and gas business