Sustainable bio-based phenol-formaldehyde resoles using hydrolytically depolymerized kraft lignin

© 2017 by the authors. In this study bio-based bio-phenol-formaldehyde (BPF) resoles were prepared using hydrolytically depolymerized Kraft lignin (DKL) as bio-phenol to partially substitute phenol. The effects of phenol substitution ratio, weight-average molecular weight (Mw) of DKL and formaldehyde-to-phenol (F/P) ratio were also investigated to find the optimum curing temperature for BPF resoles. The results indicated that DKL with Mw ∼1200 g/mol provides a curing temperature of less than 180°C for any substitution level, provided that F/P ratios are controlled. Incorporation of lignin reduced the curing temperature of the resin, however, higher Mw DKL negatively affected the curing process. For any level of lignin Mw, the curing temperature was found to increase with lower F/P ratios at lower phenol substitution levels. At 25% and 50% phenol substitution, increasing the F/P ratio allows for synthesis of resoles with lower curing temperatures. Increasing the phenol substitution from 50% to 75% allows for a broader range of lignin Mw to attain low curing temperatures

Catalytic isomerization of glucose to fructose using heterogeneous solid Base catalysts in a continuous-flow tubular reactor: Catalyst screening study

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.cattod.2018.03.056 © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Isomerization reactions of glucose into fructose in aqueous media were studied in a continuous-flow tubular reactor using different heterogeneous solid base catalysts, including calcined-rehydrated hydrotalcite, magnesium oxide, Amberlyst A21 ion exchange resin and two commercial hydrotalcite catalysts. The catalysts were characterized and their activities for glucose isomerization were compared. The most active catalyst was found to be magnesium oxide, which showed the highest glucose conversion (36.3%) and highest fructose yield (22.8%) at 100 °C. Among all catalysts, the calcined-rehydrated hydrotalcite showed the highest selectivity towards fructose, reaching 78% at 100 °C. It was also found that increasing the reaction temperature had positive effects on glucose conversion and fructose yield for both activated hydrotalcite and MgO catalysts. The fructose yield at 120 °C attained 19.5% and 25.1% with the activated hydrotalcite and MgO catalysts, respectively. The catalytic activity of hydrotalcite calcined at 450 °C for glucose isomerization reaction was found to be greater that calcined at 350 °C. The hyrdotalcite and magnesium oxide catalysts were observed to be stable in the four hours of continuous tests on stream. TGA analyses of the used catalysts proved the formation of undesired insoluble by-products, mainly humins, on the surface of the used catalysts.NSERC Discovery Program, Ontario governmen

Low-temperature thermal pre-treatment of municipal wastewater sludge: process optimization and effects on solubilization and anaerobic degradation

The present study examines the relationship between the degree of solubilization and biodegradability of wastewater sludge in anaerobic digestion as a result of low-temperature thermal pre-treatment. The main effect of thermal pre-treatment is the disintegration of cell membranes and thus solubilization of organic compounds. There is an established correlation between chemical oxygen demand (COD) solubilization and temperature of thermal pre-treatment, but results of thermal pre-treatment in terms of biodegradability are not well understood. Aiming to determine the impact of low temperature treatments on biogas production, the thermal pre-treatment process was first optimized based on an experimental design study on waste activated sludge in batch mode. The optimum temperature, reaction time and pH of the process were determined to be 80\ua0°C, 5\ua0h and pH 10, respectively. All three factors had a strong individual effect (p\ua

Stability Mechanism and Control Factors on Equipment Removal Area under “Goaf-Roof-Coal” Structure

One of the main difficulties in longwall mining (LM) is the movement of mining equipment from one panel to the next panel during mining process. The shields of the LM face may be damaged by the collapse of the roof in shallow coal seam under the “Goaf-Roof-Coal” (GRC) structure, especially when moving the shields from the current panel to the next panel. In order to solve this problem, the stability mechanism and its control factors during the LM equipment removal were investigated by using comprehensive methods including theoretical analysis, numerical simulation, and field validation based on the working conditions of Panel 31102 in Liangshuijing Coal Mine. The numerical simulations demonstrate that four different failure zones, shear failure zone, tension failure zone, partly elastic zone, and plastic failure zone, appear around the area due to the position of rock and the arrangements of the supports. The shear failure zone, which is controlled by shield working resistance and roof supporting strength, is the main cause of the failure in the removal area. To minimize the shear failure zone, several measures such as optimizing the end position for LM face, decreasing the width of removal area, and increasing the amount of cable support were taken to ensure the stability of surrounding rock in removal area, which have successfully controlled the damage of roof and equipment in Panel 31102. The field observation confirms that the proposed stability mechanism and control measures are effective under GRC structure

A Novel Carbon Dioxide Phase Transition Rock Breaking Technology: Theory and Application of Non-Explosive Blasting

As a non-explosive low-disturbance rock breaking technology, carbon dioxide phase transition blasting (CDPTB) is widely used in rock breaking projects such as pressure relief and permeability enhancement in coal mines, open-pit mining, road subgrade excavation, foundation pit excavation, etc. In this paper, the principle and equipment of CDPTB are systematically analyzed, and the characteristics of a reusable fracturing tube and disposable fracturing tube are determined. Different energy calculation methods are analyzed to determine the magnitude or equivalent explosive equivalent of CDPTB. According to the characteristics of impact stress wave and high-pressure gas, the cracking mechanism of CDPTB is proposed. Under the action of medium-impact stress, rock mass will produce multi-point cracking, and high-pressure gas will produce a gas wedge effect in the initial fracture, which determines the comprehensive action path of the stress wave and high-pressure gas. In terms of fracture characteristics, the fractal method is used to evaluate the macroscopic crack and fragment, microscopic fracture and pore characteristics. In terms of vibration characteristics, the attenuation law of CDPTB vibration with distance is statistically analyzed, and the Hilbert–Huang transform method is used to analyze the time–frequency characteristics of CDPTB. This rock breaking technology can be widely used in different projects, and the existing problems and future challenges are put forward

Selective Hydrogenolysis of Glycerol and Crude Glycerol (a By-Product or Waste Stream from the Biodiesel Industry) to 1,2-Propanediol over B2O3 Promoted Cu/Al2O3 Catalysts

The performance of boron oxide (B2O3)-promoted Cu/Al2O3 catalyst in the selective hydrogenolysis of glycerol and crude glycerol (a by-product or waste stream from the biodiesel industry) to produce 1,2-propanediol (1,2-PDO) was investigated. The catalysts were characterized using N2-adsorption-desorption isotherm, Inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), ammonia temperature programmed desorption (NH3-TPD), thermogravimetric analysis (TGA), temperature programmed reduction (TPR), and transmission electron microscopy (TEM). Incorporation of B2O3 to Cu/Al2O3 was found to enhance the catalytic activity. At the optimum condition (250 °C, 6 MPa H2 pressure, 0.1 h−1 WHSV (weight hourly space velocity), and 5Cu-B/Al2O3 catalyst), 10 wt% aqueous solution of glycerol was converted into 1,2-PDO at 98 ± 2% glycerol conversion and 98 ± 2% selectivity. The effects of temperature, pressure, boron addition amount, and liquid hourly space velocity were studied. Different grades of glycerol (pharmaceutical, technical, or crude glycerol) were used in the process to investigate the stability and resistance to deactivation of the selected 5Cu-B/Al2O3 catalyst

Study of the Stability Control of Rock Surrounding Longwall Recovery Roadways in Shallow Seams

The rock pressure appearance of longwall faces in shallow seams is generally violent, and roofs and supports are susceptible to damage during equipment extraction. Stability control of the rock surrounding longwall recovery roadways allows safe and rapid equipment extraction. Herein, via theoretical analysis, numerical simulations, and field observations, the stability control of the rock surrounding recovery roadways is studied to ensure the release of the accumulated rock pressure on the roof, the working resistance of the supports and the reasonableness of the recovery roadway support design. Pressure-relief technology is introduced to release the accumulated rock pressure before equipment extraction, and a discriminative approach is proposed to determine the breaking and articulated forms of key strata and broken blocks, respectively. On this basis, mechanical models of roof instability are established based on four key stratum structures in the overburden of shallow seams. Methods for calculating a reasonable working resistance for supports are discussed. Finally, Liangshuijing Coal Mine and Fengjiata Coal Mine are taken as research objects to evaluate the roof stability of recovery roadways based on observations of weighting characteristics. The support working resistances and reasonable recovery roadway widths under three key stratum structures are determined. Considering the time effect of plastic zone development, the support design of recovery roadways is optimized. FLAC2D software simulates the surrounding rock control effect of two support designs, and roof subsidence curves are obtained. The results show that the key to equipment extraction in shallow seams is to ensure that supports have reasonable working resistances and to improve the support of recovery roadways. The results provide a reference for the selection and extraction of supports in shallow seam faces

Optimal Layout Methods for Deep Chamber to Separate Coal and Gangue Based on the Weak Stratum Horizon

Aiming at the optimal layout of a deep chamber for coal–gangue separation (DCCS) based on the weak stratum horizon, an in-depth study was carried out by combining field investigations, model tests, and numerical simulations. Firstly, the main structural characteristics of DCCS were summarized. Then, the deformation and failure law for rocks surrounding DCCS were revealed under different horizons in the weak stratum. Finally, the optimal layout methods of DCCS based on the thickness and horizon in the weak stratum were determined in different in situ stresses, using the proposed comprehensive evaluation method for surrounding-rock stability. The results show that if the thickness of the weak stratum was small, the side near the roof of DCCS should be arranged along the weak stratum when the lateral pressure coefficient was λ λ > 1. The side near the floor of DCCS was arranged along the weak stratum when 0.6 ≤ λ ≤ 1 and the surrounding-rock stability was the best. If the thickness of the weak stratum was large, the side of DCCS should be arranged along the weak stratum when λ λ > 1. The floor of DCCS was arranged along the weak stratum when 0.6 ≤ λ ≤ 1, which was most favorable for the surrounding-rock control. The research results have important guiding significance for the spatial layout and support design of DCCS

Effects of Process Parameters on Hydrolytic Treatment of Black Liquor for the Production of Low-Molecular-Weight Depolymerized Kraft Lignin

The present research work aimed at hydrolytic treatment of kraft black liquor (KBL) at 200–300 °C for the production of low-molecular-weight depolymerized kraft lignin (DKL). Various process conditions such as reaction temperature, reaction time, initial kraft lignin (KL) substrate concentration, presence of a catalyst (NaOH), capping agent (phenol) or co-solvent (methanol) were evaluated. The research demonstrated effective depolymerization of KL in KBL at 250–300 °C with NaOH as a catalyst at a NaOH/lignin ratio of about 0.3 (w/w) using diluted KBL (with 9 wt. % KL). Treatment of the diluted KBL at 250 °C for 2 h with 5% addition of methanol co-solvent produced DKL with a weight-average molecular weight (Mw) of 2340 Da, at approx. 45 wt. % yield, and a solid residue at a yield of ≤1 wt. %. A longer reaction time favored the process by reducing the Mw of the DKL products. Adding a capping agent (phenol) helped reduce repolymerization/condensation reactions thereby reducing the Mw of the DKL products, enhancing DKL yield and increasing the hydroxyl group content of the lignin. For the treatment of diluted KBL (with 9 wt. % KL) at 250 °C for 2 h, with 5% addition of methanol co-solvent in the presence of NaOH/lignin ≈ 0.3 (w/w), followed by acidification to recover the DKL, the overall mass balances for C, Na and S were measured to be approx. 74%, 90% and 77%, respectively. These results represent an important step towards developing a cost-effective approach for valorization of KBL for chemicals

Mild Hydrothermal Liquefaction of High Water Content Agricultural Residue for Bio-Crude Oil Production: A Parametric Study

Depleting petroleum reserves together with the associated environmental concerns have intensified the exploration of alternatives to petroleum. Wet food processing wastes present promising bioresources for liquid fuel production via hydrothermal liquefaction (HTL) followed by additional upgrading. In this study, tomato plant waste (TPW) was utilized as a feedstock for the production of bio-crude oils via HTL at medium-temperature (220⁻280 °C) in water or a water⁻ethanol (17/3, v/v) medium in a 600 mL autoclave reactor. Effects of various operating parameters, such as catalysts (H2SO4 or KOH), reaction time (15⁻60 min) and reaction temperature (220⁻280 °C) on product yields were investigated. This study showed that a high yield (45.1 wt%) of bio-crude oil was achieved from HTL of TPW in water⁻ethanol medium at 250 °C in the presence of acid catalyst H2SO4. The oil, gas and solid residue (SR) products were analyzed for their chemical and structural properties