Dynamic Simulation of Sorption Enhanced Reaction Processes for Biodiesel Production

Abstract

The objective of this work was to establish fixed bed sorption enhanced reactors (SER) and simulated moving bed reactors (SMBR) for the production of high purity biodiesel (fatty acid methyl ester, FAME) using esterification reactions between fatty acids (FA) in used oils and methanol. This study has demonstrated that these processes have tremendous potential in terms of overcoming the low conversion and separation difficulties that are faced in conventional biodiesel production processes. Additionally, the SMBR process operating conditions can be optimized to produce FAME at a desired purity in a continuous mode. The novelty of this work lays in the development of generic and comprehensive dynamic simulation and systematic parametric analysis frameworks. These were used to deduce the following operating conditions for achieving more than 90% conversion of FA and 80% purity of FAME, from an SMBR process: switching time of 900 s, length of 0.25 m, and feed, raffinate, and eluent flow rate ratios of 0.41, 0.49, and 0.75, for a given velocity of 2.4 × 10−4 m/s in the reaction zone.

Comment on the “Dynamic Simulation of Sorption Enhanced Reaction Processes for Biodiesel Production”

“…In eq 3 in the Kapil et al work, 1 is not it missing a stoichiometric coefficient? (2) The next step in Kapil et al's methodology is the section, "Modeling of SMBR".…”

“…(2) The next step in Kapil et al's methodology is the section, "Modeling of SMBR". 1 (a) The authors argue that adsorbent (cationic resin) characteristics are based in Yu et al, 5 considering a linear adsorption isotherm type for all components (methanol, palmitic acid, FAME, and water). However, the work of Yu et al 5 involves the esterification of acetic acid with methanol to produce methyl acetate.…”

“…Only water and methanol are common species to the biodiesel process. The acetic acid and methyl acetate adsorption constants from Yu et al 5 were used in the Kapil et al 1 work as palmitic acid and FAME, respectively. This approach, which is completely misleading, was not even commented by the authors.…”

“…This approach, which is completely misleading, was not even commented by the authors. (b) Regarding the resins, Kapil et al 1 seem to use a mixture of catalyst/adsorbent: (i) the silica-supported Nafion resin (SAC-13) from Ni and Meunier 4 was used as a catalyst, and (ii) the Amberlyst 15 resin from Yu et al 5 was used as an adsorbent. These are both cationic exchange resins, and, thus, one expects that they will both catalyze the esterification as they selectively adsorb the various species, but not to the same extent.…”

“…In addition, the units in the SMBR model do not match: (i) the adsorbed concentration given in eq 5 is presented in units of mol/L, while in the bulk mass balance (eq 7), should be expressed in mol/kg, and (ii) the rate of reaction given by eq 3 is expressed in units of mol/(L s), which is consistent with eq 2 and the kinetic parameter presented in Table 1, but does not match that used in eq 7, where the rate of reaction is expressed in units of mol/(kg s). (3) The remarks in the "Results and Discussion" section of Kapil et al 1 are not conclusive at all, because they are based on simulations performed for a single-cycle time period (just the four initial switching times). The type of observations that the authors try to address are only acceptable if the SMBR process analysis is carried out at the cyclic steady state (CSS), as in most of the state-of-the-art literature.…”