Efrén Aguilar-Garnica

A robust monitoring tool for distributed parameter plug flow reactors

This paper deals with the design of an interval observer for plug flow reactors that are modeled by first-order hyperbolic partial differential equations. This model is considered to obtain the dynamics of an auxiliary variable that are further represented by a set of ordinary differential equations by means of the method of characteristics. Regarding these equations, the structure of the interval observer is deduced. This proposed estimation scheme is valid at a certain fixed specific axial point, is robust in the face of both uncertain parameters and load disturbances and is successfully implemented through simulations on an isothermal plug flow reactor within which a consecutive reaction is taking place and on a nonisothermal plug flow reactor with lateral feed where an irreversible reaction is carried out.

Analysis of recycled poly (styrene-co-butadiene) sulfonation: a new approach in solid catalysts for biodiesel production

The disposal of solid waste is a serious problem worldwide that is made worse in developing countries due to inadequate planning and unsustainable solid waste management. In Mexico, only 2% of total urban solid waste is recycled. One non-recyclable material is poly (styrene-co-butadiene), which is commonly used in consumer products (like components of appliances and toys), in the automotive industry (in instrument panels) and in food services (e.g. hot and cold drinking cups and glasses). In this paper, a lab-scale strategy is proposed for recycling poly (styrene-co-butadiene) waste by sulfonation with fuming sulfuric acid. Tests of the sulfonation strategy were carried out at various reaction conditions. The results show that 75°C and 2.5 h are the operating conditions that maximize the sulfonation level expressed as number of acid sites. The modified resin is tested as a heterogeneous catalyst in the first step (known as esterification) of biodiesel production from a mixture containing tallow fat and canola oil with 59% of free fatty acids. The preliminary results show that esterification can reach 91% conversion in the presence of the sulfonated polymeric catalyst compared with 67% conversion when the reaction is performed without catalyst.

Optimization of Lignin-Based Biocatalyst Production from Pine Sawdust and Wheat Straw

Pine sawdust and wheat straw are abundant lignocellulosic wastes that have been recently converted into bioethanol under a biochemical platform scheme whose main waste is lignin. Lignin can be transformed into a wide variety of high added-value products, including its functionalization as a catalyst. A key step in the synthesis of a lignin-based catalyst is the sulfonation reaction, whose operating conditions, namely, H2SO4 to lignin ratio (mL/g), temperature and time, have been arbitrarily chosen. In this contribution, an optimization methodology (i.e., Box-Behnken) is applied in order to found the operating conditions during the sulfonation reaction that maximizes the total acid sites density of lignin-based catalysts from pine sawdust and wheat straw. The optimization results show that the time in sulfonation reactions can be significantly reduced, compared to those previously reported, without affecting the performance of both catalysts in esterification reactions. These results could be further considered for energy and costs reduction purposes during the conceptual design engineering of the sulfonation reaction.

Software sensors design and selection for the production of biodiesel from grease trap wastes

Abstract In this paper, a couple of software sensors were designed for CSTR processes and they were tested in the esterification of grease trap wastes which is a low-cost feedstock for biodiesel production. Both software sensors were designed for the estimation of the concentration of Free Fatty Acids (FFAs) from discrete CSTR’s temperature measurements. One of these software sensors, called asymptotic observer, is recognized for its capacity to provide estimates without the knowledge of the process kinetics. It has been also designed an estimation algorithm known as reset fuzzy observer. This approach has been recently proposed and is able to update the estimated states at each instant when discrete measurements are available. Both observers were built regarding the structure of a validated dynamical model for the esterification of grease trap wastes and they were tested considering experimental data. The results show that the asymptotic observer offers a very poor performance when some process’s disturbances (e.g. input concentration of FFAs, jacket temperature) are carried out, whereas the reset fuzzy observer is able to reconstruct satisfactorily the concentration of FFAs in the presence of such disturbances. Therefore, this fuzzy observer can be selected as reliable monitoring approach that could be further used as a key part of robust control schemes conceived for this specific biodiesel production process.