Novel Two-Step Process for the Production of Renewable Aromatic Hydrocarbons from Triacylglycerides

A two-step process was developed for the production of aromatic hydrocarbons from triglyceride (TG) oils. In the first reaction step, TG (soybean) oil was noncatalytically cracked and purified by distillation to produce an organic liquid product (OLP). The resulting OLP was then converted into aromatic compounds in a second reaction using a zeolite catalyst, HZSM-5. In this second reaction, three main factors were found to influence the yield of aromatic hydrocarbons: the SiO₂:Al₂O₃ ratio in the HZSM-5, the reaction temperature and the OLP-to-catalyst ratio. Upon cursory optimization, up to 58 w/w% aromatics were obtained. Detailed analyses revealed that most of the alkenes and carboxylic acids, and even many of the unidentified/unresolved compounds, which are characteristic products of noncatalytic TG cracking, were reformed into aromatic hydrocarbons. Instead of BTEX compounds, which are the common products of C₂–C₈ alkene and other feedstock reforming with HZSM-5, longer-chain alkylbenzenes dominated the reformate (along with medium-size <i>n-</i>alkanes). Another novel feature of the two-step process was a sizable (up to 13 w/w%) concentration of alicyclic hydrocarbons, both cyclohexanes and cyclopentanes. Thus, this novel two-step process may provide a new route for the production of renewable aromatic hydrocarbons as an important coproduct with transportation fuel products

Thermal Carbon Analysis Enabling Comprehensive Characterization of Lignin and Its Degradation Products

We have developed a novel thermal carbon analysis (TCA) method that provides both carbon mass balance and thermal fractionation profiles. Though not providing chemical structural information, this method enables a comprehensive characterization of both lignin and its degradation products, potential renewable and sustainable feedstocks. TCA is essential as a complement to a qualitative chemical speciation by thermal desorption–pyrolysis gas chromatography–mass spectrometry (TD–Py–GC–MS). Mono- and diaromatic oxygenated compounds were used as model compounds to optimize the method. The influence of various parameters such as solvents, amounts of sample loaded, and temperature ramp configuration, were investigated. A multistep temperature program with TD and pyrolytic temperatures with and without oxygen was employed for analysis of untreated lignin, where up to 55 wt % evolved in the presence of oxygen only, this fraction being unaccounted for by currently used methods. The TCA results were supported by thermogravimetric analysis with a matching heating ramp resulting in a similar mass distribution; however, TCA has the advantage of being selective for carbon. For lignin degradation products, the TD steps of TCA yielded similar recoveries as a solvent extraction followed by GC–MS. Thus, TCA may be used for screening significant product fractions to quantify the previously uncharacterized oligomer/polymer and char fractions

Selective Synthesis of Phenolic Compounds from Alkali Lignin in a Mixture of Sub- and Supercritical Fluids: Catalysis by CO₂

A successful selective liquefaction of lignin has been demonstrated in the presence of a H₂O–CO₂ mixture at 300 °C, yielding 40–50 wt % organic phenolic phase. The effect of the temperature at a constant pressure and short residence time on the selectivity and yield of phenolic products from the hydrothermal reforming of alkali lignin in a mixture of sub- and supercritical fluids (H₂O mixed with CO₂ or N₂) has been investigated. Dependent upon the processing conditions, the lignin samples produced a homologous series of phenols, such as guaiacol, homovanillic acid, quaiacyl carbonyls, guaiacyl dimers, phenol, and cresol. Gas chromatography–mass spectrometry (GC–MS), total organic carbon (TOC), and pyrolysis–GC–MS (Py–GC–MS) were used for chemical analysis of the organic liquid and solid phases. The results from GC–MS analysis of the liquid organic phases demonstrated the trend of increasing the amounts of major guaiacol products with the temperature. The thermal carbon analysis (TCA) showed a significant increase of the readily volatile organic carbon in the liquid fractions resulting from the treatments at 300 and 400 °C at the expense of less volatile organic carbon and recalcitrant pyrolyzed carbon. Evaluated for the first time, a significant effect of CO₂ versus N₂ was demonstrated, providing both a higher yield of volatile products and more selective synthesis of guaiacols

High Strength Magnetic/Temperature Dual-Response Hydrogels for Applications as Actuators

Anisotropically structured magnetic/temperature dual-response hydrogels have great application prospects as actuators because they can exhibit controlled, complex behaviors. However, one key issue hindering the application of such hydrogels is the imbalance of the mechanical and response properties. This study used a combination of flexible chain polymers such as poly(N-isopropylacrylamide) (PNIPAM), poly(vinyl alcohol) (PVA), and polyacrylamide (PAM) to build a multinetwork structure. The introduction of TEMPO-oxidized cellulose nanofibrils (TOCNF) as a nanofiber reinforcement agent led to a key improvement to ensure a high mechanical strength by creating additional hydrogen bonding. The cross-linking density was further increased through a salting out treatment to obtain a greater mechanical strength while improving the dissipation of energy applied by external sources. The obtained temperature responsive layer featured a high tensile strength (1.97 MPa) while the magnetically responsive layer showed a high magnetization (6.1 emu/g) with a good tensile strength (0.47 MPa). The main idea of this study was in combining two hydrogel layers with different polymer network structures, with magnetic nanoparticles being dispersed within one layer, whereas the other layer was designed as temperature-sensitive. The obtained bilayer hydrogel had suitable mechanical properties (the tensile strength reaching 0.81 MPa) coupled with strong dissipation of the applied external energy and could rapidly and reversibly undergo bending deformations upon a temperature change within a narrow range, 25–37 °C (bending angle up to 160° within 5 min). With high magnetization characteristics for the magnetically responsive layer, the bilayer hydrogel could easily be driven by an external magnetic field to transport a target object, which was “grabbed” due to the gel bending. It also showed good biocompatibility, thus enabling applications in the field of invasive medical actuators