Applying chemical additives (molecule inhibitors or dispersants) is a common way to control asphaltene agglomeration and precipitation. Until now, it has not been clear why under some conditions the flocculation inhibitors do not inhibit (and may also promote) the asphaltene agglomeration, and why increasing the additive concentration may lead to the diminishing of their efficacy. To clarify this issue, we performed a set of vapor pressure osmometry experiments investigating the asphaltene agglomeration inhibition by commercial and new inhibitor molecules in toluene and o-diclorobenzene. Monte Carlo computer modeling was carried out to interpret some unexpected trends of the averaged molar mass of the Puerto Ceiba asphaltene clusters at different concentrations of inhibitor, assuming that inhibitor efficiency is directly related to their adsorption on the surface of asphaltene. It is shown that the self-assembly of inhibitor molecules, induced by relative lyophilic or lyophobic interactions with a solvent, may be a reason for the inhibitor efficacy declining.

Asymptotic behavior correlations (ABCs) based on the properties of pure n-paraffins are used to predict the bulk properties of liquid mixtures derived from the Fischer-Tropsch synthesis. Comparisons are made with literature data for congealing point, density, specific heat, viscosity, thermal conductivity, and surface tension. Mixture property predictions are based on appropriate average carbon numbers and on a general property mixing rule. Both ideal and nonideal solution behavior are exhibited. For the nonideal properties, viscosity and surface tension, mixing rules are proposed and parameters regressed to obtain reasonable agreement with mixture data. Property estimates based on the appropriate average carbon number are probably sufficient for most engineering applications. Methods are outlined for estimating different carbon-number averages based on congealing- and melting-point, density, and the Anderson-Schulz-Flory distribution when the carbon number distribution of the mixture is not available. The presence of other Fischer-Tropsch byproducts appears to have little effect on the accuracy of predictions made for high molecular weight mixtures.

Abstract A large number of experimental data points obtained in our laboratory as well as from the literature, covering wide ranges of reactor geometry (column diameter, gas distributor type/open area), physicochemical properties (liquid and gas densities and molecular weights, liquid viscosity and surface tension, gas diffusivity, solid particles size/density), and operating variables (superficial gas velocity, temperature and pressure, solid loading, impurities concentration, mixtures) were used to develop empirical as well as Back-Propagation Neural Network (BPNN) correlations in order to predict the hydrodynamic and mass transfer parameters in bubble column reactors (BCRs) and slurry bubble column reactors (SBCRs). The empirical and BPNN correlations developed were incorporated in an algorithm for predicting gas holdups (εG, εG-Small, εG-Large); volumetric liquid-side mass transfer coefficients (kLa, kLa-Small, kLa-Large); Sauter mean bubble diameters (dS, dS-Small, dS-Large); gas–liquid interfacial areas (a, aSmall, aLarge); and liquid-side mass transfer coefficients (kL, kL-Large, kL-Small) for total, small and large gas bubbles in BCRs and SBCRs. The developed algorithm was used to predict the effects of reactor diameter and solid (alumina) loading on the hydrodynamic and mass transfer parameters in the Fisher–Tropsch (F–T) synthesis for the hydrogenation of carbon monoxide in a SBCR, and to predict the effects of presence of organic impurities (which decrease the liquid surface tension) and air superficial mass velocity in the Loprox process for the wet air oxidation of organic pollutants in a BCR. In the F–T process, the predictions showed that increasing the reactor diameter from 0.1 to 7.0 m and/or increasing the alumina loading from 25 to 50 wt.% significantly decreased εG, kLaH2 and kLaCO and increased dS. The decrease of the total gas holdup was found to be controlled by the holdup of small gas bubbles. The increase of the Sauter mean bubble diameter increased both kLH2 and kLCO, however, the decrease of the total gas holdup coupled with the increase of dS resulted in a dramatic decrease of the gas–liquid interfacial area, a, and subsequently kLaH2 and kLaCO. Thus, in the churn-turbulent flow regime, the hydrodynamic and mass transfer behaviors of the F–T SBCR were controlled by the holdup and the gas–liquid interfacial area of small bubbles. In the Loprox process, the predictions showed that increasing the liquid surface tension (removal of organic impurities from water) significantly increased dS and decreased both εG and kLaO2. The decrease of the total gas holdup with increasing liquid-phase surface tension was due mainly to the decrease of the liquid-phase foamability which led to the decrease of the holdup of small gas bubbles. The increase of the Sauter mean bubble diameter and the decrease of the total gas holdup resulted in a strong decrease of the gas–liquid interfacial area, and subsequently kLaO2. Increasing the air superficial mass velocity increased εG, dS, a, kL-O2 and kLaO2. Within the conditions used in the Loprox BCR, the hydrodynamics and mass transfer parameter behaviors of the process appeared also to be controlled by the gas holdup of small gas bubbles; and the gas–liquid interfacial area.

ZnO doped with Co2+ has been prepared by a Pechini process and investigated in terms of crystallographic structure and UV-visible properties. We emphasize for the first time a splitting of the ZnO band gap in two "sub-band gaps" (never clearly mentioned until now) which is fully interpreted basing on the iono-covalent nature of the O-Zn bonds. An anticipative approach of the potential structure relaxations was discussed from exchanged effective charge per bond calculated with the purely ionic Brown and Altermatt model. --------------------------------------------------------------------------------

A novel motionless mixer named Ramond supermixer (RSM) was used to disperse nanoparticle suspensions under the various process conditions. Commercially available nanoparticles, fumed silica (SiO2) of primary particle diameter (d0) ranging from 7 to 30 nm, zirconia (ZrO2) of d0 = 12 nm, and titanium oxide (TiO2) of d0 = 21 nm, were dispersed either in an ion-exchanged water or in aqueous ethylene glycol solutions. The smaller the d0, the harder it is to disperse the aggregates. Zeta potential was largely dependent on d0 and became independent of process variables and, hence, of aggregate diameter. By evaluation of energy barrier values, the aggregation during disruption was found to be negligible. Aggregate disruption was predominant at the viscous subrange. By balancing mechanical energy with turbulent disruptive energy, a mechanistic model was developed for aggregate disruption. The analysis of fractal dimension showed that nanoaggregates are made up by orthokinetic cluster-cluster collision. Fractal dimensions are invariant throughout the disruption process. The rheological measurements further confirmed the evaluated fractal dimensionality. --------------------------------------------------------------------------------

Aggregation and disruption of nanoparticle suspensions under the various process conditions were studied in a stirred vessel with a Ramond stirrer. Commercially available nanoparticles, fumed silica (SiO2) of primary particle diameter (d0) ranging from 7 to 30 nm, zirconia (ZrO2) of d0 = 12 nm, and titanium oxide (TiO2) of d0 = 21 nm, were dispersed either in an ion-exchanged water or in aqueous ethylene glycol solutions. A kinetic model for simultaneous aggregation and disruption was developed theoretically for both inertia and viscous subranges and was fitted to the experimental data. At the initial stage, aggregation becomes predominant, and as the time proceeds, disruption becomes evident. The energy barrier was evaluated by taking van der Waals attractive forces, electrostatic repulsive forces, and dispersive forces into consideration, and also the aggregation rates were measured. Fractal dimensions were obtained experimentally by ultra-small-angle X-ray scattering. Correlations were obtained for aggregate diameter at equilibrium stage, with process variables. The initial aggregation rate was modeled with process variables. --------------------------------------------------------------------------------

Glycerol hydrogenolysis was catalyzed by Pt/WO3/ZrO2 to give 1,3-propanediol (1,3-PD) in the yields up to 24 %. The catalytic activities and the selectivity toward 1,3-PD were remarkably affected by the type of support, the type of loaded noble metal (NM) and the preparation/impregnation procedure. Controlled experiments show that the active site of catalyst for the formation of 1,3-PD may be the Pt over WO3 supported on ZrO2. Glycerol hydrogenolysis was catalyzed by Pt/WO3/ZrO2 to give 1,3-PD in high yields up to 24 %. The other noble metals tested for this catalysis were much less effective for the formation of 1,3-PD than Pt. Furthermore, a sequential impregnation of WO3 and then Pt on ZrO2 is necessary to make effective catalysts. These facts together with the others suggest that the active site for the hydrogenolysis of glycerol to 1,3-PD may be Pt on WO3 supported on ZrO2.