Volume 14, Issue 4 - Special Issue: In Honour of Professor Serge Kaliaguine (Part II), Guest Editors: Benito Serrano Rosales and Ying Zheng

SBA15 supported transition metal phosphides Ni 2 P/SBA15 and WP/SBA15 have been identified as promising adsorbents especially for removing neutral nitrogen-containing compounds. Adsorption of model nitrogen- and sulfur-containing compounds as well as light cycled oil (LCO) was performed and applied for the evaluation of kinetics and isotherms. The pseudo second-order kinetic model was well fitted to both nitrogen and sulfur adsorption data. Molecular size of the adsorbates plays an important role in the adsorption. Despite of higher initial adsorption rates, the adsorption capacities for carbazole and DBT were lower than those for indole and quinoline due to their larger molecular size. Monolayer adsorption was observed for quinoline due to the acid-base interaction between the basic nitrogen adsorbate and the weak acidic support. The Freundlich model was suitable in describing the adsorption of nitrogen- and sulfur-containing compounds from LCO. Cooperative adsorption took place when replacing the model compound DBT by the sulfur-containing compounds in LCO.

This work reports the preparation of Cu-Zn and Au/TiO 2 catalysts on anodized aluminum monoliths (AAM). The structured catalysts were studied for the generation of H 2 by methanol steam reforming (MSR) and its purification by preferential oxidation of CO (CO-PrOx). Initially, it was possible to generate a surface with whiskers and larger surface area by hydrothermal treatment of the AAM. Subsequently, the structured catalysts were synthesized by incipient wetness impregnation (IWI) and hydrothermal synthesis (HS). IWI synthesis allowed for the deposition of a larger amount of catalytic material than HS, with very good adhesion. The TiO 2 -IWI structured catalyst presented a homogeneous catalytic coating, with the presence of agglomerated particles. On the other hand, Cu-Zn-IWI showed good dispersion of the deposited particles with a homogeneous surface coating. EDX analysis corroborated the presence of Ti, Cu and Zn in all the catalytic surfaces. The incorporation of Au over TiO 2 -IWI structured catalysts was successfully performed by IWI using a colloidal solution of gold nanoparticles. MSR was studied over the developed metallic monoliths functionalized with Cu-Zn by the IWI method. The samples showed promising results in terms of activity, selectivity, and stability. Both diluted and concentrated methanol + water feeds were assayed. Complete methanol conversion was achieved for the diluted feed. Maximum methanol conversions of 55 % with 60 % H 2 yield were measured when the concentrated feed was selected. Promising results were also achieved for the Au-based structured catalysts in the CO-PrOx in an H 2 -rich atmosphere. Although CO conversions of approximately 60 % were achieved, operating with higher catalyst loadings would be recommended to reach the high CO conversions required for PrOx catalysts.

The in-situ generation of hydrogen peroxide in the electro-Fenton process is paramount. For this reason, in this research the electrocatalytic activity of three carbon materials was evaluated in the reaction of oxygen reduction via two electrons. Furthermore, in order to eliminate the use of iron salts in solution (homogeneous process), the iron was electrodeposited on the surface of the carbon material and was applied in a heterogeneous electro-Fenton process for the degradation of methyl orange dye. The largest amount of generated H 2 O 2 was achieved with the Carbon Felt (CF) electrode (460 mg L −1 ) without iron after 60 minutes. The electrodes with electrodeposited iron were characterized by SEM and EDS, which showed that the surface of the Carbon Sponge (CS) electrode had the largest amount of iron (23.84 %). However, the CF electrode showed a greater and faster degradation of the dye (98 %) after 30 minutes of treatment. The CF material was the best and most-viable choice of material compared to the CS and Carbon Cloth (CC) for industrial application in electro-Fenton processes, due to its greater catalytic activity in the production of H 2 O 2 , uniform distribution of iron, more efficient TOC removal and lower cost per cm 2 of material.

Hydrogen production from water splitting via photocatalytic reactions can be an alternative clean energy of fossil fuels in the future. Graphitic carbon nitride (g-C 3 N 4 ) is one of the active photocatalysts in the visible light region that can be combined with other semiconductors in order to increase its photocatalytic efficiency. TiO 2 is one of the most appropriate choices to combine with g-C 3 N 4 because of its conduction band edge and variety forms of nanostructures. In this work, nanosheets of g-C 3 N 4 were mixed with the nanoparticles of titanate in order to enhance charge separation and photocatalytic efficiency. Consequently, the hydrogen evolution of this novel nanocomposite produced almost double hydrogen in comparison with g-C 3 N 4 .

In this work, the selective hydrogenation of C 3 -cut in the liquid phase has been investigated. A realistic model has been developed to simulate the selective transformation of methylacetylene (MA) and propadiene (PD) into propylene in an industrial-scale reactor. The reaction rates have been determined for the gas phase hydrogenation process and adapted for the liquid phase by considering several changes including the catalyst activity and the concentration of reactive components. In the last part of this work, a three-phase hydrodynamic model was developed and the kinetic and hydrodynamic models were then combined in order to achieve the global reactor model. In addition, the results obtained from the model were compared to those from an industrial reactor. It was found that there is a good agreement between the simulation predictions and the output of the real industrial reactor.

Inorganic membranes can be made of different materials. However, there have been only few reports on membrane evaluation to convert lab-scale membranes into a prototype for industrial applications. In order to fill this significant gap, new approaches for the development and optimization of membrane products are required. This work focuses on the different aspects related to the performance assessment of membranes used for gas separation and membrane reactors. This approach can be visualized as an algorithm consisting of three specific loops involving different aspects of the overall membrane evaluation. Several factors that have an impact on membrane performance are discussed. These factors are divided into two categories: directly affecting the measurements (setup leakage, concentration polarization, repeatability, pressure gradient) and related to the intrinsic characteristics of permeation flux across the membrane (single and mixture permeation, transport modeling, defect flux, microstructure flexibility). This evaluation protocol includes a literature review with the most recent breakthroughs in this research area.

The comprehensive study involving uptake and kinetics behaviour of methane and ethane was carried out on a commercial carbon molecular sieve. The gravimetric technique was applied to measure the adsorption isotherms at different temperatures. The kinetic behaviours of methane and ethane were investigated by extracting the uptake data from isotherms at different pressure steps. Considering CMS as a homogenous microporous adsorbent, only two main resistances: surface barrier (at the pore mouth) and diffusion resistance (inside the pores) were considered in analysing the kinetic data. The kinetic analysis showed dominance of surface barrier resistance at all temperatures and pressures investigated in this study. Modified Darken equation was used to calculate the sorbates’ activation energies for adsorption in CMS pores. Compared to Darken equation, the modified Darken model predicted the concentration dependency of the surface rate constants more accurately, especially at higher sorbates’ concentrations. The activation energy of methane and ethane was greater than the heat of adsorption demonstrating a large impedance and barrier at the pore surface to the methane and ethane molecules. The kinetic selectivity of methane over ethane was calculated from the combined surface barrier/diffusion model parametric analysis. The results generally showed a greater selectivity to methane over ethane, i. e., the higher mass transfer rates.

Unsaturated fatty acids can be converted into mono and dicarboxylic acids, which are applicably valuable materials, through oxidative cleavage reaction in the presence of a highly efficient catalyst/oxidant system. In this work, two types of advanced heterogeneous catalysts have been developed; (i) high surface area mesoporous tungsten oxide/γ-alumina mixed metal oxide, and (ii) surfactant-capped tungsten oxide nanoparticles. Various technique including N 2 adsorption/desorption isotherms, XRD, SEM, EDS, TGA and catalytic test were used to monitor the physicochemical and catalytic properties of these materials. The characterization results revealed that type (i) materials exhibit high surface area and narrow particle size distribution, and the used surfactant could quantitatively enough cap the surface of type (ii) materials. The catalytic activities of these materials in the oxidative cleavage of oleic acid with H 2 O 2 as oxidant were investigated. GC-MS was used to determine the produced amounts of desired products, azelaic and pelargonic acids. The catalytic test results showed more than 90 % conversion for type (ii) catalyst in 5 h reaction at 120 °C with acceptable production yields for azelaic and pelargonic acids. The significantly higher activity of this catalyst compared to type (i) arises from the interesting surface properties of tungsten oxides nanoparticles, which make them able to exploit the good features of homogeneous and heterogeneous catalysts.

This work aimed to contrast the performance of quicklime and CaO reagent grade as heterogeneous catalysts for the safflower oil transesterification reaction. Quicklime was characterized by TGA analysis, XRD, atomic absorption, nitrogen physisorption and by Hammett method. In the safflower transesterification reaction, four main variables were studied: addition reagents order, reagents dosage, type of catalyst and methanol-oil molar ratio. The addition reagents order was not found to be determinant on time for reaching equilibrium or maximum methyl esters yield. On the contrary, reagents dosage was found to negatively affect reaction rate and methyl esters yield. It was found that quicklime performs better than CaO and this was ascribed to an increased basicity found in the former. From the results can also be inferred that the use of quicklime as catalyst of the transesterification reaction allows the decrease of the process cost by reducing both, the reaction time and the required amount of alcohol.

Hexagonal mesoporous type silica SBA-15 with pore sizes in the range 5.0–8.3 nm was synthesized using non-ionic triblock copolymer and characterized by Accelerated Surface Area Porosimetry (ASAP), FT-IR spectroscopy, X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Different lipases were immobilized in glutaraldehyde activated mesoporous SBA-15 support. The resulting supported enzymes were shown to be active and stable catalysts for esterification of glycerol with oleic acid to produce monoglyceride (MG) which is commonly used in food industry. Various parameters were studied systematically to study kinetics. MG Synthesis using enzymatic process is an environmentally friendly approach. Enzyme immobilized on SBA-15 showed the best stability and catalytic activity in organic solvents. Out of various lipases studied penicillium camembertii (Lipase G) produced MG efficiently at low temperature. Reusability was studied on immobilized enzymes. Immobilized lipase maintained 90 % of its esterification activity in non-aqueous media even after 4 cycles of use. The selectivity of Lipase G is found to be 98 % for monoacylglyceride.

The kinetics of the transesterification of safflower oil and methanol catalyzed by K 2 O/NaX was studied and modeled. The influence of the oil-methanol initial molar ratio and amount of catalyst were investigated to achieve a maximum triglycerides conversion (99 %) and a final methyl esters content of 94 % ±1. A kinetic model based on an Eley–Rideal mechanism was found to best fit the experimental data when assuming methanol adsorption as determining step. Other models derived from Langmuir – Hinshelwood – Hougen –Watson (LHHW) mechanisms were rejected based on statistical analysis, mechanistic considerations and physicochemical interpretation of the estimated parameters.

The aim of this work was to assess the whole cell bioconversion of (+)-valencene to (+)-nootkatone in 100 % organic phase (orange essential oil) using a stirred tank bioreactor. Yarrowia lipolytica 2.2ab was used to perform bioconversion experiments; 600 mL of orange essential oil was inoculated with 50 cm 3 of cell paste containing 13.5 g of biomass previously permeabilized with 0.2 % (w/v) of cetyl trimethylammonium bromide (CTAB) and enriched with 2.0 mM niacin. Experiments were conducted at 200 rpm, 0.5 vvm and 30 °C. The highest (+)-nootkatone yield was ca. 773 mg L −1 after 4 days of conversion. Bioconversion percent and volumetric productivity increased to 82.3 % and 8.06 mg L −1 h −1 compared to those reported previously using a three-phase partitioning bioreactor. The absence of free water in the system did not affect the performance of Y. lipolytica 2.2ab.