Synthesis, Characterization and use of Nb2 O5 based Catalysts in Producing Biofuels by Transesterification, Esterification and Pyrolysis

Nb2O5/HX (X = HSO4-, H2PO4-, NO3-) compounds were obtained from the treatment of niobium acid (Nb2O5·xH2O) with sulfuric, phosphoric, and nitric acids as well as Nb2O5 and Nb2O5·xH2O have been investigated as catalysts for the transesterification, esterification and pyrolysis of vegetable oils. The compounds were characterized by thermal analysis (DTA-TGA), spectroscopy (DRX, FT-IR and FT-Raman), surface area (BET) and the acidity (Ho) determined by n-butylamine titration using the Hammet´s indicator method. It was observed that after the acid treatment both the surface area and the acidity decreased as compared to the starting Nb2O5·xH2O. The only exception was a higher acidity verified when nitric acid was used. Among the catalyst investigated, the Nb2O5/H3PO4 presented the highest activity in the alcoholysis of soybean oil with different mono-alcohols (methanol, ethanol, 2-propanol, n-butanol). All tested solids seemed to stabilize the carboxylic acids formed during the pyrolysis, yielding higher acid numbers for the obtained products. Finally, the use of Nb2O5/H3PO4 and Nb2O5/H2SO4 as catalysts for the esterification showed better activity than Nb2O5·xH2O and Nb2O5

Bio-based Thermosetting Polymers from Vegetable Oils

Vegetable oils are promising renewable resources for polymers, due to their low cost, ready availability, and versatile applications. Recently, increasing attention has been paid to vegetable oil-based polymeric materials due to both economic and environmental concerns. This review focuses on the latest developments in vegetable oil-based thermosets prepared by a variety of polymerization methods. The thermosets obtained exhibit a wide range of thermomechanical properties from soft and flexible rubbers to rigid and hard plastics. Some of the thermosets have properties comparable to petroleum-based analogs and show promise as replacements, providing possible solutions to environmental and energy concerns

Bio-Based Polymers with Potential for Biodegradability

A variety of renewable starting materials, such as sugars and polysaccharides, vegetable oils, lignin, pine resin derivatives, and proteins, have so far been investigated for the preparation of bio-based polymers. Among the various sources of bio-based feedstock, vegetable oils are one of the most widely used starting materials in the polymer industry due to their easy availability, low toxicity, and relative low cost. Another bio-based plastic of great interest is poly(lactic acid) (PLA), widely used in multiple commercial applications nowadays. There is an intrinsic expectation that bio-based polymers are also biodegradable, but in reality there is no guarantee that polymers prepared from biorenewable feedstock exhibit significant or relevant biodegradability. Biodegradability studies are therefore crucial in order to assess the long-term environmental impact of such materials. This review presents a brief overview of the different classes of bio-based polymers, with a strong focus on vegetable oil-derived resins and PLA. An entire section is dedicated to a discussion of the literature addressing the biodegradability of bio-based polymers

Emulsion Polymerization of Tung Oil-Based Latexes with Asolectin as a Biorenewable Surfactant

Bio-based vesicles, with potential application in drug delivery and/or catalyst encapsulation, have been prepared by the free radical emulsion co-polymerization of tung oil, divinylbenzene (DVB), n-butyl methacrylate (BMA), and asolectin in a xylene/water mixture. The free radical polymerization was initiated by di-tert-butyl peroxide (DTBP) at 100 °C in a convection oven. Molecular weights of approximately 11,000 Da were measured by Matrix-assisted Laser Desorption/Ionization-Time of Flight (Maldi-TOF) for tung oil-asolectin copolymers, verifying that significant polymerization occurs under the cure conditions employed. The cure of the co-monomer mixture employed in this work was monitored by Dielectric Analysis (DEA), while changes in the Raman spectrum of all co-monomers before and after the cure, along with differential scanning calorimetry (DSC) analysis, have been used to verify the need of a post-cure step and completion of the polymerization reaction. Scanning Transmission Electron Microscopy (STEM) images of the emulsion after polymerization indicate that vesicles were formed, and vesicle size distribution of samples prepared with different amounts of tung oil were determined using a Zetasizer

Experimental Study of Thermopower of SWCNTs and SiC Nanoparticles with B-P (Born-Phosphorus) Sol-Gel Diffusion

Seebeck coefficients of randomly distributed single-walled carbon nanotubes (SWCNTs) combined with Silicon Carbide (SiC) nanoparticles were experimentally determined. The Seebeck coefficients of pristine SiC/SWCNT samples were compared with those ofSiC/SWCNT samples doped with P-type (Boron) and N-type (Phosphorous) sol–gel dopants. Pristine SiC/SWCNT samples were prepared by depositing SiC nanoparticles and SWCNTs on a non-conductive glass substrate. Doped SiC/SWCNT samples were prepared by coating each half of the samples alternately with B and P sol–gel dopants. Thermoelectric circuits were prepared by creating hot and cold junctions on the P and N-doped ends of the SiC/SWCNT samples with conductive Silver epoxy and Alumel (Ni–Al) wire. Voltage, current and resistance were measured across the samples against temperature difference. The SWCNTs used were approximately 60% semiconducting and 40% metallic. The Seebeck coefficient for pristine SWCNTs was 0.10 ± 0.006 mV per degree Celsius. When diffused with B–P, the Seebeck coefficient increased to 0.308 mV per degree Celsius. Pristine SiC nanoparticles showed no presence of thermoelectric (TE) effect, but substantial TE effects were observed upon inclusion of SWCNTs. Although the samples with various SWCNT compositions showed similar Seebeck coefficients, the current, resistance and power factor (PF) changed accordingly. Resistance of the pristine SWCNTs slightly decreased with increase in temperature. Structure–property relations were determined using scanning electron microscopy (SEM) and Raman spectroscopy. It was revealed that fibre-like SWCNTs created randomly distributed networks with nano-contact junctions inside the SiC matrix. Diffusion of dopants into CNTs in the doped samples increased the charged carrier concentration enhancing the thermopower of SWCNTs. Analysis of the Raman spectra showed an upshift in the tangential vibrational G-band modes of SWCNTs when doped with an electron-acceptor dopant (Boron), and a downshift in the case of an electron-donor dopant (Phosphorus). Incorporation of the dopant materials in the SWCNT structure was also evidenced by the presence of disorder induced D-band peaks in the doped SWCNTs

Effect of Microwave Cure on the Thermo-Mechanical Properties of Tung Oil-Based/Carbon Nanotube Composites

Tung oil is uniquely reactive among plant-based natural oils due to the series ofconjugated carbon-carbon double bonds in its fatty acid chains. These conjugatedcarbon-carbon double bonds impart a high reactivity towards cationic polymerization in thepresence of other reactive co-monomers, such as divinylbenzene and styrene. An impressivedecrease in the cure time of tung oil-based thermosets has been achieved when the resinsinvestigated were microwaved in the presence of carbon nanotubes (CNTs). However, thefast cure compromised the overall thermo-mechanical properties of the materialsinvestigated. Microwave power, exposure time, and CNT loading effects have been assessedby means of dielectric analysis (DEA), thermogravimetric analysis (TGA), differentialscanning calorimetry (DSC), dynamic mechanical analysis (DMA), and proton nuclearmagnetic resonance (1H NMR) spectroscopy of extracts obtained by Soxhlet extraction.Possible reasons were proposed to explain the overall inferior properties observed wheneverfaster cure rates were achieved

Synthesis and Thermomechanical Properties of Polyurethanes and Biocomposites Derived from Macauba Oil and Coconut Husk Fibers

This work reports on a very effective route to produce bio-based polyurethanes (PUs) and composites with high content of renewable carbon sources. The PUs are prepared with polyols synthesized from macauba oil (Acrocomia aculeata) and methylene diphenyl diisocyanate, at different [NCO]/[OH] molar ratios. Later, biocomposites are prepared with the as-obtained PUs reinforced with coconut husk fibers. The successful synthesis of natural oil-based polyols is ascribed to the hydroxylation and consumption of carbon-carbon double bonds in the fatty acid chains of the original starting oil as attested by FTIR spectroscopy. According to different thermal analysis techniques (TG, DTG, and DTA), the increase in the [NCO]/[OH] molar ratio improves the thermal stability of PUs, likely due to an increase of crosslinks. Dynamic mechanical analysis evidences the reinforcement effect of coconut husk fibers in bio-based PUs. The present PUs and composites are of low-cost and environmentally friendly materials for structural applications