Yufu Xu

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.

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

Tribological Behavior of Self-Lubrication Bearing Materials of Steel-Copper-Polyoxymethylene Containing MoS2-IC Nanoparticles

Intercalation compound of polyoxymethylene into molybdenum disulfide nanoparticles (POM/MoS2 -IC) were prepared from trioxane, dioxolane and restacked exfoliated-MoS2 . The so prepared nanocomposite was used as the plastic layer of self-lubrication bearing materials of steel-copper-POM. Pure POM was also selected as a comparative sample. Tribological behaviors of the obtained samples were studied on an end-face tribometer. Wear scar surfaces of the two plastic layers were characterized by a field emission scanning electron microscope. The elements of the counterpart steel surface were investigated by X-ray photoelectron spectroscopy. Results showed the wear surface of steel-copper-pure polyoxymethylene consisted of deep furrows, large-area scars and obvious flow marks. However, self-lubrication bearing materials of steel-copper-polyoxymethylene containing MoS2 -IC nanoparticles presented excellent friction reduction and wear resistance especially under high loads. POM/MoS2 -IC nanoparticles and its tribochemical resultants restrained the plowing effect of the counterpart steel on the plastic layer through forming a transferred film on the counterpart friction surface.Copyright

Characterization of the Tribological Behavior of the Textured Steel Surfaces Fabricated by Photolithographic Etching

A photolithography etching technique was used to fabricate textured surfaces on steel samples. The friction and wear behavior of the textured surfaces were studied with surface contact sliding. The influence of the diameter and the density of the dimples were investigated. The results show that the textured surfaces with appropriate diameters and densities had excellent friction reducing and antiwear properties. Large-diameter dimples can destroy the integrity of the lubricating film, and low- or high-density dimples produce more iron sulfates and fewer ferrous sulfides on the rubbing surfaces due to the tribo-reactions, which resulted in higher friction coefficients. The tribo-chemical films, oil micro-reservoir and wear debris-containing roles of the dimples together help the textured surfaces to provide improved antiwear properties.

Cavitation erosion and wear behaviour of a boron cast iron cylinder liner under bio-fuel conditions

The use of renewable bio-fuel in internal combustion engines is the trend for the near future. However, it is easy to affect the cylinder liner due to the cavitation of the fuels. This study shows definite evidence that the cavitation erosion affects the tribological behaviour of the boron cast iron cylinder liner. The results indicate that the amount of both adsorbed lubricating film and tribo-film on the worn surfaces of the boron cast iron decreased with an increase in cavitation time, which is the direct reason for the increase of the friction coefficient and wear loss of the cylinder liner.