Isomerization of Oleic Acid over Acid Zeolites: Design of Experiments and Proposal of a Novel Kinetic Mechanism

Abstract

Three acid zeolites (H-ZSM-5, H-Beta, and H-FER) were evaluated in the oleic acid isomerization to branched-chain fatty acids (bc-FA). Understanding its kinetic behavior is essential to develop new technologies regarding biofuels, lubricants, and cosmetics. The catalysts were characterized through XRD, N2 physisorption, and NH3-TPD. Preliminary reactions demonstrated that Ferrierite shows better yields in the reaction, which is associated with its higher Brønsted acidity. Optimal reaction pressure and time were 10 bar and 10 h, respectively. A full factorial design of experiments was used to evaluate the reaction temperature and the use of the cocatalysts, water and triphenylphosphine (TPP). The maximum yield (59%) was achieved using 8% of water and 10% of TPP at 300 °C. A reaction mechanism in which the oleic acid turns into its trans isomer before bc-FA formation was proposed, and the kinetic modeling of the process was carried out with reproducible results.

Green Synthesis and Property Analysis of Biolubricants Based on Structural Variations

“…The kinematic viscosity of HOSuO and G-OA is found to be almost identical as expected (Table ). However, in G-IO and T-IO, the FA chains are in trans -form as in the skeletal isomerization reaction, and OA transforms into trans -IOA. , The linearity of the FA chains (no steric hindrance) and the CC double bond (no free rotation around the double bond) make G-IO and T-IO free moving, i.e., less viscous.…”

Modulating acid site spatial location of Zn/ZSM‐5 catalyst to boost the stable aromatization of hexane

“…To clarify the acidic site spatial location directly, the Zn/ZSM‐5 and Zn/ZSM‐5‐ x Si catalysts were treated by triphenylphosphine oxide to poison the outer surface acidity 28,29 . Table S3 shows that the total acid content of the Zn/ZSM‐5 catalyst decreases significantly from 1.10 to 0.35 mmol/g, while the total acid content of the Zn/ZSM‐5‐Si, Zn/ZSM‐5‐4Si, and Zn/ZSM‐5‐6Si catalysts changes little before and after poisoning.…”

“…The sample was heated to 1000 C at a rate of 10 C/min. 29 Si MAS NMR spectra and 27 Al MAS NMR spectra were conducted on Bruker 400 M Nuclear Magnetic Resonance Spectrometer (Bruker Corp., Switzerland) to analyze the loading form of metal on catalysts. The acidity and acid strength of the materials were estimated by the ammonia temperatureprogrammed desorption (NH 3 -TPD) using the Micromeritics Autochem 2920 II.…”

“…and Zn/ZSM-5-xSi catalysts were treated by triphenylphosphine oxide to poison the outer surface acidity. 28,29 Table S3 shows that the total acid content of the Zn/ZSM-5 catalyst decreases significantly from 1.10 to 0.35 mmol/g, while the total acid content of the Zn/ZSM-5-Si, Zn/ZSM-5-4Si, and Zn/ZSM-5-6Si catalysts changes little before and after poisoning. Notably, the total acid amount of the Zn/ZSM-5 catalyst after poisoning is 0.35 mmol/g, which is close to the acid amount of the Zn/ZSM-5-Si catalyst without poisoning (0.37 mmol/g).…”

“…The characterization of the spent Zn/ZSM-5 and Zn/ZSM-5-Si catalysts in FigureS8shows that the crystallinity of the spent Zn/ZSM-5-Si catalyst decreases significantly while that of the spent Zn/ZSM-5-Si catalyst decreases slightly. Meanwhile, the content of Si (O Si) 2 of the spent Zn/ZSM-5 catalyst increases from 2.2% to 12.1% in the29 Si MAS-NMR, and the peak position of Al in the27 Al-NMR increased. These indicate that the skeleton structure of the spent Zn/ZSM-5 catalyst collapses more seriously compared with the spent Zn/ZSM-5-Si catalyst.…”