Volume 21, Issue 4 - Special issue dedicated to the International Energy Conference, IEC 2021: Sustainable energy as a platform for post-pandemic economic; Guest Editors: Margarita González-Brambila and Carlos O. Castillo-Araiza

In this work, the influence of pressure and temperature experimentally applied on reactive distillation (RD) under lower conditions than conventional hydrotreating (HDT) processes, the hydrodesulfurization (HDS) reaction of 4,6–dimethyldibenzothiophene (4,6–DMDBT) molecule and the experimental performance of a down-flow micro trickle bed reactor (micro-TBR) with n–dodecane and decalin were studied. Thermodynamic analyses to evaluate hydrogen solubility in liquid hydrocarbons and evaporation for n–dodecane and decalin as lineal and cyclic representative solvents, respectively, were considered. It was possible to define experimental conditions, producing a small deviation of the plug flow model (PFM) and diminished the gas–liquid (G–L) mass transfer limitation as determined from a reactor model at 2.5 MPa. The axial dispersion model (ADM) and PFM models adjust the experimental data at 2.5 MPa operational pressure and the 4,6–DMDBT conversion obtained was ca. 20–50% using n–dodecane; 1.5 times higher when decalin was using. This behavior was due to the liquid hydrogen fraction of n–dodecane was two times higher than for decalin for all operational pressures. In this sense, the use of n–dodecane as a solvent decreased the mass transfer resistance at the G–L and liquid–solid (L–S) interphases. The internal mass transfer resistance in the G–L interphase not only depends on the diffusivity of the solvent, but it also depends on both, the temperature and hydrogen pressure, finding that the RD conditions with n–dodecane are viable in the treatment of sterically impaired molecules in HDS processes.

Notwithstanding the benefits that oil provides as a source of energy, society also recognizes the environmental problems caused by its use. We evaluated eight coastal sites in the central area of the Gulf of Mexico. At these sites, 14 hydrocarbons were detected which belong to compounds formed by carbons ranging from C9 to C27. The hydrocarbons with the highest concentrations were n-nonane (3.07 ± 1.60 mg L −1 ), carbazole (0.93 ± 0.12 mg L −1 ) and benzo [a] pyrene (1.33 ± 0.71 mg L −1 ). The hydrocarbons found belong mostly to medium fraction hydrocarbons, which are mostly found in fuels such as diesel. Therefore, this fuel was used as a carbon source or substrate in bubble column bioreactors. The capacity of non-genetically modified organisms to degrade microbial hydrocarbons was evaluated using a mineral medium for a period of 14 days. Suspended solids increased from 0.8 to 2.94 g L −1 . Diesel consumption was achieved in 12 days of operation.

Cellulose can be used to produce biofuels and many other products like pharmaceutical goods, food supplements, cosmetics, bio-plastics, etc. Lignocellulosic materials, like O . ficus indica residuals, are a heterogeneous biopolymer formed mainly by lignin, hemicellulose and cellulose. Lignin provides protection to the plants against chemical and microbial degradation, but it can be degraded by white rot fungi species, like Pycnoporus cinnabarinus . Since cellulose molecules are arranged in regular bundles enveloped by hemicellulose and lignin molecules, it is necessary to brake lignin and hemicellulose molecules to recover cellulose for its use in bioprocess. In this work, a biotechnological process for cellulose recovery from cactus waste through depolymerization of lignin by P . cinnabarinus , is presented. The delignification is carried out by aerobic culture in batch stirred bioreactors, with a liquid culture medium enriched with nutrients and minerals with O . ficus indica residuals as the unique carbon source, during eight-day span under continuous feeding of oxygen. A factorial design of experiments (DOE) for eight sets of factor values was selected for this study. The factors were: particle size, pH level, and process temperature. For each experiment, biomass, total reducing carbohydrates (TRC) and dissolved oxygen (DO) concentrations were measured every 24 h. At the end of each experiment, the percentage of delignification, and cellulose recovery was measured by Infrared (IR) spectroscopy. Up to 67% of delignification and 22% of cellulose recovery were obtained by the process. These results were analyzed by a factorial DOE in order to maximize each response individually and to optimize both responses together. The delignification of Opuntia ficus indica thorns has not been previously reported to our knowledge.

The sweetening units are the most important in natural gas processing. Packed bed absorption columns are widely used in the sweetening process; however, their operation and control are not simple due to their highly non-linear behavior derived from their distributed nature and interaction between multiple physical phenomena. In this work, two robust model-based control schemes are implemented to regulate the CO 2 concentration at the outlet of a packed bed absorption column in the gas sweetening process. The model of an industrial-scale absorption column and the structure of the controllers, i) control based on modeling error compensation (MEC) ideas, and ii) nonlinear model predictive control (NMPC) are described. Numerical results show that the proposed robust model-based controllers can regulate the controlled variable to the desired reference despite external disturbances, set-point changes, and uncertainties in the absorption column model.

Chromium Cr(VI) is a highly toxic environmental contaminant for any organism, its presence in the environment is mainly due to anthropogenic activities. The use of biotechnology has been implemented for the treatment of effluents contaminated with Cr(VI).Our working group has isolated several fungi and bacteria capable of removing Cr(VI) from the culture medium. Aspergillus niger var tubingensis Ed8 is a strain that can produce metabolites which reduce Cr (VI) to Cr (III). The objective of this work was to determine the effect of sodium salicylate on the growth of this strain and on the Cr(VI) reduction system, as well as to identify the metabolites that are produced from sodium salicylate. Our results show that the Culture medium containing sodium salicylate (20 mM) inhibits strain growth compared to the control condition (0 mM). However, it increases the specific reduction capacity of Cr (VI) red/mg Biomass in order of magnitude. Analysis of the culture medium corresponding to 48 h of incubation shows the presence of catechol and salicylate diminution. In addition, as a product of the enzymatic activity of a cell-free cellular extract, after 24 h of incubation, the consumption of salicylate is detected, as well as the presence of peaks corresponding to resorcinol and catechol. Our results show that it is possible to increase the Cr(VI) reducing capacity of the Ed8 strain, depending on the composition of the culture medium.

We obtain the clean semi-analytical solutions with method of directly defining inverse mapping (MDDiM) to the system of nonlinear equations arising in the magnetohydrodynamic (MHD) convection motion of Molybdenum disulfide (MoS 2 ) engine-oil intrinsic nanofluid in a circumnavigatethe structure is considered for analysis. Finding the solutions by using MDDiM is a novel idea and first time solving for the system of nonlinear partial differential equations. We have chosen inverse linear mapping for the five-term solution and it emphasizes by residual error and this gives the low error (10 −2 to 10 −17 ) and can easily derive deformation terms by spending very low CPU time. Based on the proposed method, the convergence rate, accuracy, and efficiency of the governing equations are demonstrated, and result outputs shown in tabular and graphically, which exhibit meaningful structures and advantages in science and engineering.

Single-doped TiO 2 /FTO and co-doped TiO 2 -VO 2 /FTO thin films were prepared by sonochemistry and spray pyrolysis deposition on FTO substrates. The co-deposition of TiO 2 -VO 2 on FTO significantly changed the morphological, structural, optical, and photocatalytical properties compared to the single-deposition. X-ray diffraction and HRTEM results showed polycrystalline film structures composed of SnO 2 -tetragonal from FTO, anatase-TiO 2 , rutile-TiO 2 , and monoclinic-VO 2 phases. The co-deposition technique increases the particle size distribution by approximately two times compared to simple deposition. The single-doped TiO 2 /FTO thin film had a 15% higher bandgap than the co-doped TiO 2 -VO 2 /FTO thin film, and the electrical resistivity calculated from the van der Pauw method was 55.3 MΩ sq −1 for the TiO 2 -VO 2 /FTO co-doped thin film, 2.7 times lower than that obtained for the TiO 2 /FTO thin film. Single-doped TiO 2 /FTO and co-doped TiO 2 -VO 2 /FTO thin films presented pseudo-first-order reactions at pH 6.5, with kinetic constants of 0.026 and 0.015 min −1 , respectively. This behavior is related to the production of inactive or less active aggregates by the addition of vanadium during the co-doping process, which led to lattice contraction, which encouraged the formation of the rutile phase rather than the anatase phase. However, the co-doped thin film can modify the metal-insulator transition compared to the single-doped TiO 2 /FTO thin film. Furthermore, co-deposition decreased the bandgap value by 16% compared to single-deposition thin film. In this sense, co-doped TiO 2 -VO 2 /FTO thin films inhibited the recombination of photogenerated carriers and the formation of reactive oxygen species involved in the photocatalytic degradation of naproxen.

Over 40% of global energy-related CO 2 emissions are due to the combustion of fossil fuels for electric energy generation. Albeit CO 2 capture and storage have been identified as promissory actions to mitigate its emissions, the problem separating N 2 and CO 2 remains. A very effective solution for the former problem is to obtain the combustion CO 2 as a pure molecule, which is possible using the Chemical Looping Combustion (CLC) technology, which uses a solid oxygen carrier to transport the oxygen from an oxidating media (regeneration reactor) to a reducing media (combustion reactor). One of the key issues to apply CLC is to find or develop some material, suitable from the kinetic and thermodynamic points of view, for the reduction-oxidation cycles taking place inside combustion and regenerator reactors. The evaluation of “oxygen carrier” candidates for CLC is based on reactivity (rates and conversions), resistance to carbon accumulation, and “regenerability”, which means the ability of the material for cyclic reduction and oxidation. Another challenging issue to use CLC processes is the loss of oxygen carrier; this problem involves the use of supported metals on materials, such as zirconia, Al 2 O 3 , etc. Preparation of this kind of supported carriers requires time, money, and equipment. Meanwhile, the natural mineral ore named ilmenite, which consists of a mixture of iron and titanium oxides, and do not need to be supported, has been seen as promising to increase CLC efficiency as oxygen carrier. In this work, the performance of ilmenite is compared with some other oxygen carriers used in CLC.

Microalgae are used to produce renewable biofuels and high-value components and in bioremediation and CO 2 sequestration tasks. These increasing applications, in conjunction with a desirable constant large-scale productivity, motivate the development and application of practical controllers. This paper addresses the application of robust control schemes for microalgae cultivation in continuous photobioreactors. Due to the model uncertainties and external perturbations, robust control designs are required to guarantee the desired microalgae productivity. Furthermore, simple controller designs are desirable for practical implementation purposes. Therefore, two robust control designs are applied and evaluated in this paper for two relevant case studies of microalgae cultivation in photobioreactors. The first control design is based on an enhanced simple-input output model with uncertain estimation. The second control design is the robust nonlinear model predictive control considering different uncertain scenarios. Numerical simulations of two case studies aimed at lipid production and CO 2 capture under different conditions are presented to evaluate the robust closed-loop performance.

The purpose of this work is to evaluate the performance of a rough-textured evaporator applied to a single-stage absorption heat transformer for water desalination (SAHT-WD). The stainless-steel evaporator was subjected to an abrasive material release treatment (sandblast texture) to provide a texture that fosters phase change heat transfer compared to a smooth surface. To determine the performance of the evaporator, the evaluation has been divided into an experimental and a theoretical analysis. The experimental analysis focused on determining the operating conditions that favor the performance of the evaporator and the SAHT-WD. For the theoretical analysis, a mathematical model was developed to predict the wetting efficiency and the heat-transfer coefficients of the evaporator. To quantify the improvement in the performance of the rough-surface evaporator, the experimental results were compared with those reported in a reference work. The results indicate that the sandblasted texture improved the performance of the evaporator as well as that of the SAHT-WD. The results of the mathematical model suggest that the rough tube improved the wetting efficiency of the evaporator.

Microalgae oil has great potential to address the growing energy demand and dependence on fossil fuels. However, the multilayered cell walls of microalgae hinder efficient extraction and enhanced lipid recovery. In this study, we develop a novel protocol based on near infrared-assisted extraction (NIRAE) technology to extract efficiently total lipids from Scenedesmus obliquus . Under a greener solvent extraction approach, the effect of nine non-polar/polar solvent systems in various ratios on lipid yield was tested, and the results were compared with Soxhlet, Folch, and Bligh–Dyer methods. The highest oil yields were NIRAE 15.43%, and Soxhlet 22.24%, using AcoEt/MeOH (1:2 v/v). For Folch and Bligh–Dyer, 9.11 and 10%, respectively. The optimized NIRAE conditions obtained using response surface methodology (RSM): 43.8 min, solvent/biomass 129.90:1 (m/v), and AcOEt/MeOH 0.57:2.43 (v/v) increased the oil yield significantly to 24.20%. In contrast to conventional methods, the overall optimized NIRAE process satisfied the requirements of a green extraction because of the simple and safe operation, less solvent toxicity, lower extraction time, and solvent and energy consumption.