Modeling of the van der Waals forces during the adhesion of capsule-shaped bacteria to flat surfaces

A novel model is developed to evaluate the van der Waals (vdW) interactions between a capsule shaped bacterium (P. putida) and flat minerals plates in different approach profiles: Vertically and horizontally. A comparison of the approaches to the well-developed spherical particle to mineral surface (semi-infinite wall and spherical) approach has been made in this investigation. The van der Waals (vdW) interaction potentials for a capsule-shaped bacterium are found using Hamaker’s microscopic approach of sphere to plate and cylinder to plate either vertically or horizontally to the flat surface. The numerical results show that a horizontal orientated capsule shaped bacterium to mineral surface interaction was more attractive compared to a capsule shaped bacterium approaching vertically. The orientation of the bacterial approaching a surface as well as the type and topology of the mineral influence the adhesion of a bacteria to that surface. Furthermore, the density difference among each type of bacteria shape (capsule, cylinder, and sphere) require different amounts of energy to adhere to hematite and quartz surfaces

Gas-phase hydrodeoxygenation of phenol over Zn/SiO2 catalysts:Effects of zinc load, temperature, weight hourly space velocity, and H 2 volumetric flow rate

The hydrodeoxygenation (HDO) of phenol catalyzed by Zn/SiO2 under atmospheric H2 pressure was investigated in a continuous fixed bed reactor. The effects of several process parameters (zinc load, reaction temperature, weight hourly space velocity (WHSV), and H2 volumetric flow rate) were evaluated to optimize process conditions. Phenol was selected as a stable model component for lignin degradation products in fast pyrolysis bio-oil. Silica-supported zinc catalysts were prepared with different loadings of the active metal (0.5%, 1%, 2%, 3%, and 4%) and assessed using characterization techniques such as XRD, ICP-OES, BET, H2-TPR/TPD, and FESEM–EDX. Reaction products including benzene, cyclohexene, and cyclohexane were identified through GC/FID analysis. Experimental results revealed that process yield increased with reaction temperature, metal loading, and WHSV. The selectivity percentages of the products were slightly changed by varying process parameters. Moreover, H2 volumetric flow rate exerted a negligible effect on product yield and selectivity

A review of the enzymatic hydroesterification process for biodiesel production

Enzymatic hydroesterification has recently attracted research interest because of the high-value products created during biodiesel production. The use of this process overcomes problems related to conventional methods for biodiesel production, such as slow reaction rate and soap formation. The method comprises two basic processes to produce fatty acid alkyl esters from triacylglycerols, namely, enzymatic hydrolysis and enzymatic esterification. Although enzymatic hydroesterification for biodiesel production has many advantages, such as lower energy consumption and converting low-quality feedstock, it has not been used on an industrial scale mainly because of some impediments, including enzyme cost and conversion efficiency. This review presents a comprehensive evaluation of recent investigations on enzymatic hydrolysis and enzymatic esterification to lower process costs and increase yields

Catalyst characteristics and performance of silica-supported zinc for hydrodeoxygenation of phenol

The present investigation aimed to study the physicochemical characteristics of supported catalysts comprising various percentages of zinc dispersed over SiO2. The physiochemical properties of these catalysts were surveyed by N2physisorption (BET), thermogravimetry analysis (TGA), H2temperature-programmed reduction, field-emission scanning electron microscopy (FESEM), inductively coupled plasma-optical emission spectrometry (ICP-OES), and NH3temperature-programmed desorption (NH3-TPD). In addition, to examine the activity and performance of the catalysts for the hydrodeoxygenation (HDO) of the bio-oil oxygenated compounds, the experimental reaction runs, as well as stability and durability tests, were performed using 3% Zn/SiO2as the catalyst. Characterization of silica-supported zinc catalysts revealed an even dispersion of the active site over the support in the various dopings of the zinc. The acidity of the calcinated catalysts elevated clearly up to 0.481 mmol/g. Moreover, characteristic outcomes indicate that elevating the doping of zinc metal led to interaction and substitution of proton sites on the SiO2surface that finally resulted in an increase in the desorption temperature peak. The experiments were performed at temperature 500 °C, pressure 1 atm; weight hourly space velocity (WHSV) 0.32 (h-1); feed flow rate 0.5 (mL/min); and hydrogen flow rate 150 (mL/min). Based on the results, it was revealed that among all the prepared catalysts, that with 3% of zinc had the highest conversion efficiency up to 80%. However, the selectivity of the major products, analyzed by gas chromatography flame-ionization detection (GC-FID), was not influenced by the variation in the active site doping