Xianguo Hu

Hydrothermal liquefaction of Chlorella pyrenoidosa for bio-oil production over Ce/HZSM-5.

This paper investigated a novel hydrothermal liquefaction process of Chlorella pyrenoidosa catalyzed by Ce/HZSM-5. The chemical groups and components of the residues of C. pyrenoidosa were analyzed by Fourier transform infrared spectrometry and Gas Chromatograph-Mass Spectrometer. The crystal structure and micro surface topography of C. pyrenoidosa before and after catalytic liquefaction were characterized by X-ray diffraction and Scanning electron microscopy, respectively. The experimental results showed that the catalytic cracking effects of Ce/HZSM-5 were superior to that of HZSM-5 as a liquefaction catalyst of C. pyrenoidosa. Compared with HZSM-5, Ce/HZSM-5 has a significantly enhanced Lewis acid active center, smaller particle size, larger specific surface, and highly dispersed Ce4O7 with trivalent and tetravalent cerium in the zeolite skeleton channel that accelerate the catalytic liquefaction of C. pyrenoidosa. The rare earth modified zeolite Ce/HZSM-5 exhibits good potential and a beneficial nature for the preparation of bio-oil from microalgae with high efficiency.

Hydro-abrasive erosion of steel-fibre reinforced hydraulic concrete

In this paper, hydro-abrasive erosion tests on plain concrete (PC) and on steel-fibre reinforced concrete (FRC) are performed, and the erosion behaviour of the materials for different erosion conditions is investigated. Effects of suspension velocity, impact angle and solid content have been studied in detail. Two major erosion modes are identified. When the impact angle is shallow (15°), the damage is caused mainly by cutting the cement matrix and exposing the aggregates. However, at orthogonal impact, the formation and development of fatigue cracks in the concrete is the main cause of erosion. The addition of steel fibres provides a reinforcement to improve the erosion resistance of hydraulic concrete at shallow impact angles (15°) only. For low suspension velocities (ca. 60 m/s), fibre reinforcement and solid abrasive content do not influence the erosion rate favourably. For higher suspension velocities, abrasive content becomes important.

Tribological behaviour of modified polyacetal against MC nylon without lubrication

Compared with other polymers, polyacetal or polyoxymethylene (POM) which is widely used as bearing, guide, gear and other sliding parts, has high strength and stiffness, excellent chemical resistance and superior antifriction and wear resistance. To improve the toughness and self‐lubrication capacity of POM due to its higher crystallizability, other components, which include toughening phase and solid lubricants, are often added to the POM matrix. This paper deals with the friction and wear behaviours of POM which was modified by the toughening phase polyurethane (PU) and filled with polytetrafluoroethylene (PTFE) and silicone oil, during rubbing against MC nylon without liquid lubrication. Friction and wear tests show the tribological performance of the modified POM (M‐POM) with 10 wt% PU is better than those of pure POM and POM blended with PTFE under dry friction. The frictional coefficient of the M‐POM decreases with increasing nominal load. The sliding velocity has a more obvious effect on the tribological properties of the M‐POM than the nominal load. The higher sliding velocity leads to thermal degradation and melting of the experimental polymers because of the frictional heat.

Study on Mechanical and Tribological Property of Nanometer ZrO2-filled Polyoxymethylene Composites

The polyoxymethylene (POM) matrix composites with different contents of nano-ZrO2 particles were prepared. The effect of ZrO2 on the crystallization and thermal property of POM were investigated through polarizing microscopy (PLM) and differential scanning calorimetry (DSC). The surface hardness and the tribological performance were measured by Rockwell sclerometer and ring-on-block tribometer, respectively. The surface morphology of the wear scar were observed by scanning electron microscope (SEM). The results show that the nano-ZrO2 acted as the nucleation agent in POM and decreased the crystallite size of POM, increased the crystal growth rate. The wear resistance was enhanced and the friction coefficient was changed a little.

Bio-oil Production from Algae via Thermochemical Catalytic Liquefaction

A bio-oil was prepared from planktonic algal biomass via thermochemical liquefaction with a NaOH catalyst. The effects of reaction conditions, including temperature, time, and the ratio of biomass to solvent, on the liquefaction yield were investigated. The liquefaction yield initially increased and then decreased with increasing temperature and reaction time. The maximum yield (61.6%) was observed after liquefaction at 300°C for 30 min with 0.2 mol/L NaOH as a catalyst and a biomass to solvent ratio of 1:10. The chemical components of the obtained bio-oil were analyzed via gas chromatography/mass spectrometry, with results indicating that the algal bio-oil was composed of furan, phenol, acid, and ester derivatives.

Synergistic lubrication of MoS2 particles with different morphologies in liquid paraffin

Purpose – The purpose of this paper is to explore the synergistic lubrication of MoS2 particles with different morphologies.Design/methodology/approach – The synergistic lubrication of MoS2 particles with different morphologies is evaluated using a four‐fall tribometer in liquid paraffin.Findings – Results show that the morphology of MoS2 has an influence on the tribological properties of MoS2. Both MoS2 nano‐balls and nano‐platelets function as lubrication additives in liquid paraffin better than MoS2 micro‐platelets do. It is also found that there is a synergistic lubrication between two different morphologies of MoS2. The composite MoS2 additives with different morphologies can improve the wear resistance and friction reduction of liquid paraffin more than each of them singly does. The synergistic lubrication between two different MoS2 morphologies results from the cooperation of their different lubrication mechanism.Originality/value – The paper reveals a synergistic lubrication between two different ...

Friction-Induced Transformation from Graphite Dispersed in Esterified Bio-Oil to Graphene

Fabricating high-quality graphene with simple methods has aroused considerable interests in recent years. In this paper, graphite was dispersed in esterified bio-oil as a lubricant for steel/gray cast iron friction pairs, and the shear-induced transformation from graphite to graphene was observed. The tribological behavior during this process, including the influence of the normal load and sliding velocity, was investigated. The products formed after sliding were confirmed by Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The results showed that friction induces exfoliation, accounting for the transformation from graphite into graphene, and the frictional conditions influence the products. It was also found that high loads and low sliding velocities facilitate the formation of high-quality single-layer graphene during sliding, and high loads and low sliding velocities also contributed to obtaining excellent tribological performance for friction pairs. Friction-induced transformation demonstrates a potentially new strategy for in situ graphene preparation.

Hydrothermal catalytic liquefaction mechanisms of agal biomass to bio-oil

ABSTRACT The liquefaction mechanisms of the algal biomass to bio-oil were investigated by using Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy, respectively. It was found that NaOH was a satisfactory catalyst and contributed to helping the liquefaction of algal biomass. The bio-oil from algal biomass was composed of many compounds, including carbohydrates, alcohol, hydroxybenzene, carboxylic acid, alkene, ester, and others. The mechanism of hydrothermal catalytic liquefaction was discussed. It was found that, comparing with the husk bio-fuel, the algal bio-oil as a promising alternative fuel was more close to the traditional diesel fuel in physicochemical properties. The novel research outcomes contribute to improving the yield of bio-oil from microalgae, reducing the cost of the bio-oil and accelerating the commercial application of the algal bio-oil in the near future.

On the thermal oxidation stability of pyrolysis biomass oil.

The rice husk-based biomass-oil is composed of complex organic compounds and water, and its oxidation stability has a direct influence on its physico-chemical property and application. The advanced oxidation experiments were carried out through the flowing of air and oxygen respectively. The influences of four factors, including gas flux, oxidation time, temperature and copper foil, on the oxidation process of rice husk-based biomass-oil, by measuring the pH value variation and the weight of deposit before and after oxidation were studied. The results showed that the pH value of biomass-oil decreased slowly with the increases of the gas flux and operation time. The presence of copper in the oil made the sediment weight increase after oxidation. Based on the GC-MS analyses of the compositions of biomass-oil before and after oxidation, it was found that the acetic acid was the main component in the oxidised biomass-oil, which was attributed to the pH value decrease of biomass-oil after oxidation. At the same time the content of phenolic compound was also increased compared with that before oxidation. It was also proposed a chain-reaction-based mechanism for the biomass oxidation.

Preliminary Study on Tribological Performance of Straw Based Bio-Fuel

More and more attention has been paid to alternative fuel in internal combustion engine. One of alternative fuels is to convert straw biomass to biomass fuel. Various methods and apparatuses used for converting straw biomass to bio-fuel were invented and developed. However, alternative fuel from biomass can not be used well in internal combustion engine. The reason is complicated and relative with the separation technology of bio-fuel and corrosion, wear, lubrication and combustion chemical reaction between bio-fuel and the surface of combustion room. It is necessary to study the tribological properties of bio-fuel in order to instead the current gasoline or diesel oil in internal combustion engine in the future. In the present study, the straw based bio-oil obtained by liquidizing process was chosen to evaluate its lubrication by MQ-800 fourball tribometer, in which extreme pressure and friction coefficient and wear resistance were measured respectively. The experimental results showed that the extreme pressure of the bio-fuel was up to 392 N, and the extreme pressure of diesel oil was 333 N. The frictional coefficient of bio-fuel varies between 0.08 and 0.11. The wear scar diameter increased with load slowly in 30min. SEM images indicate that lots of thin and dense belt-like ploughs were presented on the rubbed ball surface. The chemical compositions of the worn zone on the ball surface were analyzed by XPS, the thermal property and variation of chemical compositions of bio-fuel before and after friction and wear tests were studied by TGA and GC-MS, respectively. It was shown that the rubbing surface film was composed of FeS, FeSO4 and organic compounds with C-C, −COH and −COOH groups.Copyright