Jianmin Chang

Thermogravimetric investigation on the degradation properties and combustion performance of bio-oils

The degradation properties and combustion performance of raw bio-oil, aged bio-oil, and bio-oil from torrefied wood were investigated through thermogravimetric analysis. A three-stage process was observed for the degradation of bio-oils, including devolatilization of the aqueous fraction and light compounds, transition of the heavy faction to solid, and combustion of carbonaceous residues. Pyrolysis kinetics parameters were calculated via the reaction order model and 3D-diffusion model, and combustion indexes were used to qualitatively evaluate the thermal profiles of tested bio-oils for comparison with commercial oils such as fuel oils. It was found that aged bio-oil was more thermally instable and produced more combustion-detrimental carbonaceous solid. Raw bio-oil and bio-oil from torrefied wood had comparable combustion performance to fuel oils. It was considered that bio-oil has a potential to be mixed with or totally replace the fuel oils in boilers.

On the Cure Acceleration of Oil-Phenol-Formaldehyde Resins with Different Catalysts

Oil-phenol-formaldehyde (Oil-PF) resins containing 50 wt% replacement of petroleum phenol with bio-oil were prepared and different catalysts [sodium carbonate (Na2CO3), urea, and magnesium oxide (MgO)] were added in the synthesis process of resins to accelerate the cure. The cure-acceleration effects of catalysts on cure characteristics of oil-PF resins were investigated by using differential scanning calorimetry (DSC), gel time, and a plywood panels test. The results indicated that catalysts presented different accelerating effects on the cure of the oil-PF resin. Both Na2CO3 and MgO can accelerate the oil-PF resin cure at a low temperature; however, urea seemed to have no significant effect on the cure of the resin. The application of Na2CO3- and MgO-accelerated oil-PF resins reduced hot pressing time for the manufacture of three-layer plywood panels. Compared with MgO, Na2CO3 had more significant accelerating effect on the cure of the oil-PF resin.

Cure properties and adhesive performances of cure-accelerated phenol-urea-formaldehyde resins

The cure properties of cure-accelerated phenol-urea-formaldehyde (PUF) resins with different catalysts [calcium oxide (CaO), sodium carbonate (Na2CO3), zinc oxide (ZnO), and magnesium oxide (MgO)] were investigated by gelation test and differential scanning calorimetry (DSC) analysis. The results indicated that catalysts such as Na2CO3, ZnO, and MgO were capable of increasing the curing rate and decreasing the curing temperature of PUF resins, however, the CaO inhibited the cure reaction. The formation of methylene bridges was considered to be the main reaction during curing. For the ZnO- and MgO-accelerated PUF resins, the addition reaction of formaldehyde with free phenolic site may act as subsidiary reaction. The activation energies (Ea) of cure-accelerated PUF resins other than CaO-acceleration were much lower than the control resin. The effects of catalysts and hot press temperature on adhesive performances of PUF resins were also discussed by plywood test. The PUF resins with Na2CO3, ZnO, and MgO had higher wet shear strength than the control resin. Hot press temperature had a strong influence on the wet shear strength as well as the catalysts. Among the catalysts, MgO had more significant improving effect on both the curing process and the wet shear strength of PUF resin.ZusammenfassungMittels Geliertest und Differentialrasterkalorimetrie (DSC) wurden die Aushärtungseigenschaften von Phenol-Harnstoff-Formaldehydharzen (PUF), denen verschiedene Katalysatoren (Calciumoxid (CaO), Natriumcarbonat (Na2CO3), Zinkoxid (ZnO) und Magnesiumoxid (MgO)) als Härtungsbeschleuniger zugesetzt wurden, untersucht. Die Ergebnisse zeigten, dass die Katalysatoren Na2CO3, ZnO und MgO in der Lage sind, die Aushärtungsgeschwindigkeit zu erhöhen und die Aushärtungstemperatur von PUF Harzen zu senken, wohingegen CaO die Aushärtungsreaktion hemmte. Die Bildung von Methylenbrücken wurde als Hauptreaktion bei der Aushärtung angesehen. Bei den mit ZnO- und MgO beschleunigten PUF-Harzen kann die Anlagerung von Formaldehyd an die freien phenolischen OH-Gruppen eine Nebenreaktion darstellen. Die Aktivierungsenergien (Ea) von mit Härtungsbeschleunigern versetzen PUF-Harzen waren, außer bei CaO, viel niedriger als die des Kontrollharzes. Der Einfluss der Katalysatoren und der Heißpresstemperatur auf das Klebstoffverhalten von PUF-Harzen wurde auch an Sperrholz geprüft. PUF-Harze mit zugesetztem Na2CO3, ZnO und MgO wiesen eine höhere Nassscherfestigkeit als das Kontrollharz auf. Die Heißpresstemperatur hatte ebenfalls einen starken Einfluss auf die Nassscherfestigkeit. Unter allen Katalysatoren hatte MgO den größten positiven Einfluss auf sowohl das Aushärten als auch die Nassscherfestigkeit des PUF-Harzes.

Adding nickel formate in alkali lignin to increase contents of alkylphenols and aromatics during fast pyrolysis

The composition of pyrolysis vapors obtained from alkali lignin pyrolysis with the additive of nickel formate was examined using the pyrolysis gas chromatography-mass spectrometry (Py-GC/MS). Characterization of bio-chars was performed using X-ray diffraction (XRD). Results showed that the nickel formate significantly increased liquid yield, simplified the types of alkali lignin pyrolysis products and increased individual component contents. The additive of nickel formate increased contents of alkylphenols and aromatics from alkali lignin pyrolysis. With an increase in temperature, a greater amount of the relative contents can be achieved. The nickel formate was thermally decomposed to form hydrogen, resulting in hydrodeoxygenation of alkali lignin during pyrolysis. It was also found that Ni is in favor of producing alkylphenols. The analysis based on the experimental result provided evidences used to propose reaction mechanism for pyrolysis of nickel formate-assisted alkali lignin.

Py–GC–MS examination of intermediates in the vapor from rapid pyrolysis of larch wood and its model components

Py–GC–MS was used to examine the components of vapor from rapid pyrolysis of larch wood and its model components, i.e. example cellulose, xylan, and lignin, and their mixture in accordance with the proportion of the components in larch wood. In this study, a total of 97 compounds in 12 categories were identified in the pyrolysis vapor and were compared. It was found that the most abundant chemical species in these five types of pyrolysis vapor were different. Saccharides and ketones were the major compounds in the pyrolysis vapor from microcrystalline cellulose and xylan, respectively, whereas the most abundant compounds in the pyrolysis vapor from alkaline lignin were sulfur compounds and phenols. Saccharides and ketones were major components of the pyrolysis vapor from MMC, whereas the main compounds in the pyrolysis vapor from larch wood were ketones, phenols, aldehydes, and saccharides. The different composition of the pyrolysis vapor from larch wood and its model mixture was explained on the basis of their different structural frameworks and the non-structural components of larch wood. It was also concluded that the presence of non-structural components, including extractives and ash, affect the pyrolysis reaction of larch wood. Nevertheless, the detailed patterns of this process must be further studied.

Aging Properties of Phenol-Formaldehyde Resin Modified by Bio-Oil Using UV Weathering

The aging properties of phenol-formaldehyde resin modified by bio-oil (BPF) were analyzed using ultraviolet (UV) weathering. The variations on bonding strength of BPF were measured, and the changes on microstructure, atomic composition and chemical structure of BPF were characterized by using a scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance (NMR), respectively. With the increase of aging time, the bonding strength decreased gradually, the resin surface became rougher and the O/C radio of resin surface increased. However, the loss rate of bonding strength of BPFs was 9.6–23.0% lower than that of phenol-formaldehyde resin (PF) after aging 960 h. The aging degree of BPF surfaces was smaller in comparison to PF at the same aging time. These results showed that the bio-oil had a positive effect on the anti-aging property. Analytical results revealed that with increasing the aging time, the XPS peak area of C–C/C–H decreased, while that of C=O and O–C=O increased. The intensity of methylene and ether bridges in NMR analysis decreased along with increasing the intensity of aldehydes, ketones, acids and esters. These results indicated that the aging mechanism of BPF was a process of the breakage of molecular chains and formation of oxygen-containing compounds.