Jiezhen Liang

Subcritical carbon dioxide-water hydrolysis of sugarcane bagasse pith for reducing sugars production

The aim of present study was to obtain total reducing sugars (TRS) by hydrolysis in subcritical CO2-water from sugarcane bagasse pith (SCBP), the fibrous residue remaining after papermaking from sugarcane bagasse. The optimum hydrolysis conditions were evaluated by L16(45) orthogonal experiments. The TRS yield achieved 45.8% at the optimal conditions: 200°C, 40min, 500rmin-1, CO2 initial pressure of 1MPa and liquid-to-solid ratio of 50:1. Fourier transform infrared spectrometry and two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance were used to characterize hydrolysis liquor, treated and untreated SCBP, resulting in the removal of hemicelluloses to mainly produce xylose, glucose and arabinose during hydrolysis. The severity factors had no correlation to TRS yield, indicating that the simple kinetic processes of biomass solubilisation cannot perfectly describe the SCBP hydrolysis. The first-order kinetic model based on consecutive reaction was used to obtain rate constants, activation energies and pre-exponential factors.

Hydrolysis behaviors of sugarcane bagasse pith in subcritical carbon dioxide–water

The aim of this study was to describe the hydrolysis behavior of sugarcane bagasse pith (SCBP) in subcritical CO2–water. The hydrolysis was carried out in a batch reactor using different temperatures (160 to 260 °C), liquid to solid ratios (20:1 to 100:1), CO2 pressures (0 to 7.3 MPa), stirring speeds (0 to 500 rpm) and reaction times (0 to 40 min). The highest total reducing sugar yield (43.6%) was obtained at 200 °C, liquid to solid ratio 30:1, 2 MPa CO2, 500 rpm and 50 min. Two-dimensional heteronuclear single quantum coherence (2D HSQC) nuclear magnetic resonance (NMR), scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FT-IR) were used to help elucidate the physical and chemical characteristics of the raw material and residual solid particles, with results consistent with the removal of hemicellulose during hydrolysis. The changes in the concentration of products with time were analyzed to understand product distribution through high-performance liquid chromatography (HPLC) and to infer the reaction mechanism.

Thermal Decomposition Kinetics of Abietic Acid in Static Air

Abstract The thermal decomposition of abietic acid in air was investigated under non-isothermal condition using thermogravimetric analysis-differential thermal analysis (TGA-DTA) technique with heating rates of 5, 10, 15 and 25 K·min−1. The non-isothermal kinetic parameters were obtained via the analysis of the thermogravimetric and differential thermogravimetric (TG-DTG) curves by using Flynn-Wall-Ozawa method and Kissinger method. The thermal decomposition mechanism of abietic acid was studied with four integral methods (Satava-Sestak, MacCallum-Tanner, ordinary integral and Agrawal). The results show that the thermal decomposition mechanism is nucleation and growth, and the mechanism function is Avrami-Erofeev equation with n equates 1/2. The activation energy and the pre-exponential factor are 64.04 kJ·mol−1 and 5.89×105 s−1, respectively.

A novel acid catalyst based on super/subcritical CO2-enriched water for the efficient esterification of rosin

Rosin esters are widely applied as masticatory substances and beverage stabilizers, while classical acid-catalysed processes will lead to metal residue or environmental issues. Super/subcritical CO2–enriched high temperature liquid water (HTLW) as a green acid catalyst in the esterification reaction of rosin with glycerol was investigated. The pH of CO2–H2O binary system, as calculated based on gas–liquid equilibrium, charge balance and chemical equilibrium equations, ranged from 3.49 to 3.70 depending on the reaction conditions, indicating effective acid catalysis. Response surface methodology experiments showed the optimum conditions were 3.5 h, 3.9 MPa CO2 pressure, a rosin-to-glycerol molar ratio of 1.32 and 269°C, and an enhanced esterification yield of 94.74% was achieved, which was superior to that obtained using a ZnO catalyst. It was found that the esterification kinetics was a pseudo first-order reaction, and the enthalpy and entropy of activation were calculated using the Arrhenius–Polanyi equation. The presence of super/subcritical CO2-enriched HTLW catalyst can decrease the activation energy and significantly accelerate the reaction rate.

Catalytic methyl esterification of colophony over ZnO/SFCCR with subcritical CO 2 : catalytic performance, reaction pathway and kinetics

A heterogeneous catalyst (ZnO/SFCCR) composed of ZnO supported on spent fluid cracking catalyst by wet impregnation was synthesized and applied to the esterification of colophony acids with methanol under subcritical CO2 conditions. The catalyst was characterized by SEM-EDS, BET, ICP, FTIR, XRD and Py-IR. An experimental set-up involving a new injection technique was designed to promote the heterogeneous methyl esterification, and the subcritical CO2 played a role in auxiliary acid catalysis (a pH range of 3.54–3.91), increasing the lifespan of ZnO/SFCCR, reducing the viscosity of the system to promote gas–liquid mass transfer. A maximum conversion rate of 97.01% was obtained in a relatively short time of 5 h. Kinetic experiments were performed from 190 to 220°C using a special high-temperature sampling device and analysing aliquots with high-performance liquid chromatography. A new reaction pathway, involving methyl abietate, methyl dehydroabietate, methyl neoabietate and methyl palustrate along with other kinds of colophony acids, was developed. The kinetic parameters were obtained using the Levenberg–Marquardt nonlinear least-squares method, and the activation energies for the isomerizations of neoabietic and palustric acids and for the methyl esterification of neoabietic, abietic, palustric and dehydroabietic acids were found to be 107.09, 113.95, 68.99, 49.85, 75.43 and 59.20 kJ mol−1, respectively. The results from the kinetic model were in good agreement with experimental values.

A Ni-based catalyst with polyvinyl pyrrolidone as a dispersant supported in a pretreated fluid catalytic cracking catalyst residue for C9 petroleum resin (C9 PR) hydrogenation

A Ni-based catalyst (Ni-PVP/PFC3R) with polyvinyl pyrrolidone (PVP) as a dispersant supported in a pretreated fluid catalytic cracking catalyst residue (PFC3R) was synthesized and applied to C9 petroleum resin (C9 PR) hydrogenation. For comparison, a Ni catalyst without PVP (Ni/PFC3R) was prepared in the same way. Ni-PVP/PFC3R exhibited higher activity and better stability. The catalysts were characterized by X-ray diffraction, scanning electron microscope, H2-temperature programmed reduction/temperature programmed desorption, Fourier transform infrared spectroscopy and the Brunauer–Emmett–Teller method. The catalysts had a smaller crystallite size and stronger interactions between the Ni species and the PFC3R support in the presence of PVP. The effects of nickel loading, H2 pressure, temperature and reaction time for C9 PR hydrogenation over Ni-PVP/PFC3R were investigated. The bromine number was reduced to 1.25 under the following conditions: nickel content of 12 wt%, PVP amount of 1.5 wt%, temperature of 270°C, H2 pressure of 8 MPa and reaction time of 240 min.

A small eggshell Ni/SFC3R catalyst for C5 petroleum resin hydrogenation: preparation and characterization

A small eggshell Ni-based catalyst, supported in a fluid catalytic cracking catalyst residue (SFC3R) with distinct outer shell regions, was synthesized by incipient wetness impregnation using n-heptane and nickel nitrate solution and was applied to C5 petroleum resin hydrogenation. For comparison, a uniform Ni/SFC3R catalyst was prepared by conventional impregnation. The eggshell Ni/SFC3R catalyst exhibited higher activity and better stability than the uniform Ni/SFC3R catalyst for C5 petroleum resin hydrogenation because of its nickel component distribution in the outer region of the particles, small NiO particles, and interaction of NiO–SFC3R. The morphology and microstructure of the micron-sized Ni/SFC3R particles were determined through a FIB (focused ion beam)-cutting technique combined with SEM-EDX. The results showed that the eggshell thickness was approximately 1.8 μm.