Biofuel Production from Chinese Tallow Tree Seeds Using Microwave Technology

In-situ transesterification (simultaneous extraction and transesterification) of Chinese tallow tree seeds into methyl esters using two microwave systems were investigated in this study. In the first part, utilizing a batch system, parameters tested were catalyst concentration (1-4 wt.%), solvent ratio (2-6 v/w), reaction time (15-60 min) and temperature (50-70°C). A high degree of oil extraction and efficient conversion of oil to biodiesel were found in the proposed range. The process was further optimized in terms of product yields and conversion rates using Dohlert optimization methodology. Based on the experimental results and statistical analysis, the optimal production yield conditions for this process were determined as: catalyst concentration of 1.74 wt.%, solvent ratio about 3 (v/w), reaction time of 20 min and temperature of 58.1°C. GC and H-NMR were used to profile the fatty acid methyl esters and reaction conversion, respectively. All methyl esters produced using this method met ASTM biodiesel quality specifications. For the second part, a continuous In-situ transesterification of the seeds using a microwave-assisted CSTR system was investigated with determination of kinetic parameters. A high production yield of 90.02% with 97.53% conversion rate was obtained in 24 min CSTR residence time at a methanol/hexane/CTT seed ratio of 3:3:1 (v/v/w), a microwave heating power of 290 W and 14 sec exposure time, reaction temperature of 60°C and sodium hydroxide catalyst loading of 4% wt. of oil. The experimental data fits the first order reaction kinetics. The values of rate constants at different temperatures and the corresponding activation energy were found out to be 0.083-0.087 min -1 and 1987.82 J/mol, respectively. The thermodynamic parameters values such as Gibbs free energy (ÄG), enthalpy (ÄH) and entropy of activation (ÄS) were also determined. The positive values of ÄG and small negative value of ÄH indicated that the reaction has an unspontaneous/endergonic nature and is slightly exothermic

Primary Homogeneous Pathways of Lignin Depolymerization in Gas Phase

The unique decomposition pathways of hydrolytic lignin (HL) dissolved in acetone/water mixture and dispersed into gas phase has been investigated using two unique reactors. The first one is a non-isothermal continuous wave-IR CO2 Laser Powered Homogeneous Pyrolysis (LPHP) and the second one is an isothermal Continuous Droplet Evaporation (CDE) reactor. Both of these reactors operated using atmospheric N2 carrier gas. A temperature region of 400 – 550°C, and various residence time of 0.12-2 sec were chosen for CDE reactor. The temperature distribution in the LPHP reactor was evaluated via thermocouple measurements and validated by the method of “chemical thermometer” and COMSOL Multiphysics simulations. The pyrolysis results validate the fact that dispersion of the lignin into gas phase, as a way to decrease the sample size which also minimizes the char area to avoid catalytic contact of molecular products/radicals with the char surface, may open new perspectives to understand the chemistry of depolymerization of lignin. Delivery of HL into gas phase and subsequent pyrolysis, in both reactors, at very low mass delivery rates and conversion (less than 20%) revealed the primary processes of depolymerization; MALDI-TOF-MS analysis confirmed break down of HL macromolecules into oligomer-fragments after pyrolysis in a Continuous Atomization reactor (CA) reactor, with negligible amounts of phenolics detected. Surprisingly, the expected phenolic compounds after pyrolysis were in trace amounts at less than 15% conversion of lignin. The hypothesis about a largely disputed key question on lignin pyrolysis, as to whether the phenolic compounds or oligomers (dimers, trimers, etc.) are the primary products is discussed. Additionally, a focus on free radical mechanism of depolymerization of solid lignin by formation of free intermediate radicals from initial lignin macromolecule as well as from inherent, low molecular weight oligomer molecules is developed based on Low Temperature Matrix Isolation (LTMI) EPR technique

Interobserver repeatability of measurements on computed tomography images of lax canine hip joints from youth to maturity

In-situ transesterification (simultaneous extraction and transesterification) of Chinese tallow tree seeds into methyl esters using a batch microwave system was investigated in this study. A high degree of oil extraction and efficient conversion of oil to biodiesel were found in the proposed range. The process was further optimized in terms of product yields and conversion rates using Doehlert optimization methodology. Based on the experimental results and statistical analysis, the optimal production yield conditions for this process were determined as: catalyst concentration of 1.74wt.%, solvent ratio about 3 (v/w), reaction time of 20min and temperature of 58.1°C. H(+)NMR was used to calculate reaction conversion. All methyl esters produced using this method met ASTM biodiesel quality specifications

Peculiarities of Pyrolysis of Hydrolytic Lignin in Dispersed Gas Phase and in Solid State

The unique decomposition pathways of hydrolytic lignin (HL) dissolved in an acetone/water mixture (9:1) and dispersed by a droplet evaporation technique under nitrogen gas flow has been investigated in a conventional reactor at atmospheric condition, a temperature region of 400–550 °C, and a residence time of 0.12 s. The results validate the fact that dispersion of the lignin into the gas phase by decreasing the sample size (as well as “minimizing the char area to avoid catalytic contact” of molecular products/radicals with the surface) may open new perspectives in understanding the chemistry of the depolymerization of lignin. Using Laser Desorption Ionization-Time of Flight-Mass Spectrometry (LDI-TOF-MS) the intrinsic ion <i>m</i>/<i>z</i> = 550, as the major MS peak from fresh HL dissolved in an acetone/water mixture before pyrolysis, was detected. Surprisingly, the expected phenolic compounds after pyrolysis were in trace amounts at less than 15% conversion of lignin. Instead, oligomeric intermediate substances with low (<550 Da) and high molecular weight (>550 Da) containing lignin-substructures (trapped on quartz wool located at the end of the reactor at ∼300 °C) were detected as major products using LDI-TOF-MS. The hypothesis about a largely disputed key question on lignin pyrolysis as to whether the phenolic compounds or oligomers (dimers, trimers, etc.) are the primary products is discussed. Additionally, a focus on the free-radical mechanism of depolymerization of solid lignin by formation of free intermediate radicals from initial lignin macromolecules as well as from inherent, low molecular weight oligomer molecules is developed based on the Low Temperature Matrix Isolation (LTMI) EPR technique

Methylcellulose based thermally reversible hydrogel system for tissue engineering applications

To assess contribution of the radicals formed from biomass burning, our recent findings toward the formation of resonantly stabilized persistent radicals from hydrolytic lignin pyrolysis in a metal-free environment are presented in detail. Such radicals have particularly been identified during fast pyrolysis of lignin dispersed into the gas phase in a flow reactor. The trapped radicals were analyzed by X-band electron paramagnetic resonance (EPR) and high-frequency (HF) EPR spectroscopy. To conceptualize available data, the metal-free biogenic bulky stable radicals with extended conjugated backbones are suggested to categorize as a new type of metal-free environmentally persistent free radicals (EPFRs) (bio-EPFRs). They can be originated not only from lignin/biomass pyrolysis but also during various thermal processes in combustion reactors and media, including tobacco smoke, anthropogenic sources and wildfires (forest/bushfires), and so on. The persistency of bio-EPFRs from lignin gas-phase pyrolysis was outlined with the evaluated lifetime of two groups of radicals being 33 and 143 h, respectively. The experimental results from pyrolysis of coniferyl alcohol as a model compound of lignin in the same fast flow reactor, along with our detailed potential energy surface analyses using high-level DFT and ab initio methods toward decomposition of a few other model compounds reported earlier, provide a mechanistic view on the formation of C- and O-centered radicals during lignin pyrolysis. The preliminary measurements using HF-EPR spectroscopy also support the existence of O-centered radicals in the radical mixtures from pyrolysis of lignin possessing a high value (2.0048)