Xiao Long Zhou

Crumb Rubber–Modified Asphalt: Microwave Treatment Effects

Abstract Crumb rubber pretreatment by microwave irradiation before blending with an asphalt matrix improves the properties of rubber–asphalt blends. This treatment cleft the surface vulcanization network, resulting in higher surface activity of the crumb rubber and improved compatibility with asphalt. This new rubber blend exhibited minor temperature susceptibility behaviors and high ductility at 5°C and an improved viscoelastic nature and storage stability. Characterization has also been performed to elucidate the mechanism for this improvement using a microwave treatment technique.

Removal of dibenzothiophene in diesel oil by oxidation over a promoted activated carbon catalyst

Oxidative removal of dibenzothiophene (DBT) in n-octane solution by H2O2 on a promoted activated carbon (AC) catalyst was studied. DBT adsorption and catalytic behaviors on AC were examined. Effects of pH in aqueous phase, amounts of AC and formic acid (HCOOH) for promotion as well as initial molar H2O2/S ratio were investigated. Experimental results led to conclusion that DBT was readily oxidized by H2O2 over an AC catalyst promoted by HCOOH. Suitable amount of AC can improve the activity of H2O2 resulting in a deeper extent of sulfur removal. A 100% conversion of DBT in an octane solution by H2O2 oxidation was attained on the HCOOH-H2O2/AC catalyst at 80°C for a reaction time of 30 min.

Adsorption of Dibenzothiophene on Transition Metals Loaded Activated Carbon

Transition metal-modified carbon-based adsorbents were prepared by impregnating activated carbon with solutions of copper, cobalt or nickel chloride or nitrate. The mixtures were dried and then calcined under nitrogen stream. The surface metal species were analyzed by XRD technique and the surface oxygen-containing groups were characterized by FTIR. Their adsorption capacities for dibenzothiophene (DBT) were measured by using DBT-containing n-octane solution as model oil. Experimental results show that the metal species on the carbon surface could be controlled by the calcination process under nitrogen atmosphere. Both the transition metal precursors and kinds of metal species on the carbon surface have significant effects on DBT adsorption capacity.

Simulation of Delayed Coking Reaction in Coke Drum

Abstract The effect of basic operating variables and technologies on reaction behaviors during the whole coking half cycle of an empty coke drum in three industrial delayed coking units was examined. It was observed that the temperature of the liquid streams and yields for gasoline and diesel oil in the coke drum were all stable after a few hours. Since then it was demonstrated that the coke drum was operated like a steady-state flow-type stirred-tank reactor (STR). These results will pave the way for the theoretical calculation of the coke drum for simulation and prediction.

Adsorptive Removal of Dibenzothiophene in Diesel Fuel on an Adsorbent from Rice Hull Activated by Phosphoric Acid

Rice hull (designated with RH) was activated by phosphoric acid to prepare an adsorbent for the removal of sulfur-containing compounds from diesel fuel. Adsorption tests for both, a 300 µg.g-1 dibenzothiophene (DBT)-containing n-octane solution using as model oil and a commercial hydro-treated diesel fuel, were performed to elucidate the effect of varying phosphoric acid to RH ratio, treating temperature and the removal of silica from the adsorbent on the combination of the textural structure, surface chemical property and adsorption capacity. It was indicated that high surface area and micro-pore volume of the adsorbent favored the adsorption of DBT and its derivatives. Richening of oxygen-containing compounds on the adsorbent surface was advantageous to the adsorption and removal of DBTs. At a phosphoric acid and RH weight ratio of 3:1 by using a two-step treatment, a satisfactory adsorbent with an adsorption capacity of 28.89 mg S/g was successfully prepared. If the silica in the adsorbent was further removed, the product exhibited the highest performance, reaching 30.43 mg S/g for the model oil and 21.79 mg S/g for the commercial diesel fuel. Both the textural structure and the surface chemical property like acidic groups of a RH-based adsorbent play important roles in its adsorption behaviors, and the formation of donor-acceptor complexes between surface acidic groups and DBT may probably benefit DBT adsorption capacity.

Oxidative Removal of Dibenzothiophene by H2O2 over Activated Carbon-Supported Phosphotungstic Acid Catalysts

Phosphotungstic acid (HPW) supported on activated carbon (AC) combined with hydrogen peroxide formed an oxidative desulfurizaiton (ODS) system to oxidize sulfur-containing compounds in diesel fuel. Dibenzothiophene (DBT) dissolved in n-octane was selected as a model feedstock for studying this new ODS system. The HPW/AC catalysts were characterized with XRD, FTIR and N2 adsorption-desorption measurements. HPW was highly dispersed on the surface of carbon support. It was found that the DBT adsorption capacity decreased from 42 mg S/g to 33.13 mg S/g as HPW loading amount increased from 0 to 15 wt.%. Oxidative removal of DBT in the model oil significantly increased with increasing HPW loadings on the support from 0 to 10 wt.%. 100 % DBT was removed by using the catalysts with HPW content higher than 10 wt. %. At 80 °C, oxidative removal of DBT reached 100 % after 40 min of reaction when O/S molar ratio ranged from 4 to 10.

Performance of different zeolites as adsorbents for methane

ABSTRACT The adsorption behavior of methane in simulated coal-bed gas on several micropore zeolites is studied. Alkali and steaming treatments of ZSM-5 are carried out in order to adjust the pore structure and to further elucidate the effect of pore structures on methane adsorption behavior. Further, the effect of adsorbed water on ZSM-5 zeolite is also considered. Textural properties of material are characterized by nitrogen adsorption-desorption at 77 K. The results indicate that pore structures of zeolite adsorbent have a more important effect on the adsorption performance, compared with the specific surface area. The presence of adsorbed water on micropore zeolite is unfavorable to the methane adsorption.

Normal Hexane Hydroisomerization Over an Alumina and Yttria Promoted Pt/SO4 2−/ZrO2 Catalyst

Sulfated zirconia was promoted with alumina and yttria in order to improve catalyst isomerization behaviors. The n-hexane hydroisomerization reaction was carried out in a continuous flow fixed-bed reactor for 80 h on stream to evaluate catalyst reaction stability. The catalyst was characterized by XRD, TGA, H2-TPR, and NH3-TPD technologies in order to investigate the crystalline structure, sulfur content, reduction behavior, and acidity of the catalyst. It was proved that the addition of alumina and yttria obviously increased the sulfur content on the fresh catalyst and also markedly stabilized the sulfur species on the used catalysts. Thus, the modified catalyst possessed the better stable activity and selectivity although the addition of promoter could not enhance the isomerization activity. The crystalline structure of sulfated zirconia, acidity, and sulfur content only showed a limited influence on the isomerization activity of the catalyst. This work would have potential use to prepare an ideal catalyst for a commercial alkane hydroisomerization unit.

Normal Hexane Hydroisomerization Over Alumina Modified Pt/SO4 2−/ZrO2 Catalyst

Pt/SO4 2−/ZrO2-Al2O3 (PSZA) catalysts were prepared by extruding sulfated hydroxide zirconium with SB powder. The n-hexane hydroisomerization reaction was performed in a continuous flow fixed-bed reactor. Isomerization activities under varying pretreatment parameters (including catalyst storage time before use, activating temperature, and reduction temperature) and reaction conditions (including reaction temperature, space velocity, and the molar ratio of hydrogen to n-hexane) were investigated. The results indicated the optimum pretreatment conditions for the PSZA catalyst is as follows: five days of storage, 350°C of the activation temperature, and 250°C of the reduction temperature. In addition, the optimum reaction conditions contained the reaction temperature ranging from 200 to 210°C, space velocity of 1 hr−1, and hydrogen to hexane mole ratio of 5.

Synthesis of Si-Based Mesoporous Materials with Different Structural Regularity

Two types of mesoporous Si-MCM-41 materials were synthesized via a cationic surfactant template method using different Si-precursors. The materials obtained were characterized by FTIR, XRD, BET, TEM and 29Si MAS-NMR techniques. When fumed silica was used as Si precursor, a Si-MCM-41-I solid with wormhole-like pore topologies was obtained. However, when tetraethylorthosilicate (TEOS) was used as Si precursor, a mesoporous Si-MCM-41-II solid with hexagonal arranges and a long-range ordered structure could be obtained. These two kinds of mesoporous materials had a uniform pore size distribution with an average pore diameter within 2.3-2.8 nm. Rather weak Lewis acid sites were formed on both the Si-MCM-41 samples prepared by the two methods.