Benxian Shen

Effects of organic additives on crystallization process and the adsorption performances of zeolite A

The crystallization of zeolite A was monitored by measuring the adsorption capacities of synthetic products. The influences of organic additives on the crystallization process and adsorption performances of zeolite were investigated. SDS (sodium dodecyl sulphonate), TWEEN (Tween-80), and PEG (poly(ethylene glycol)) shorten the induction period by reducing the interfacial energy while SCMC (sodium carboxymethylcellulose) can prolong the induction period by increasing the interfacial energy. TEA (triethanolamine) can also suppress the nucleation through reducing the effective supply of aluminum. All the organic additives but SCMC diminish the rate of crystal growth. CTAB (cetyltrimethylammonium bromide) causes the destruction of crystal structure and reduce the concentration of OH− ions. As a result, the rate of crystal growth is significantly reduced. Meanwhile, PAM (poly(acrylamide)), SDS, TWEEN, HMTA (hexamethylenetetramine), and PEG increase the viscosities of synthesis systems, thus, diminish the growth rate. PAM restrains the transformation of zeolite A crystal into hydroxysodalite one, therefore, tremendously improves the stability of crystals of zeolite A. In addition, PAM can promote the rates of n-hexane adsorption on zeolite 5A because of the impact of PAM on the crystal-size distributions of zeolite 5A.

Oxidative regeneration of deactivated binderless 5A molecular sieves for the adsorption–separation of normal hydrocarbons

Abstract The deactivation of binderless 5A molecular sieves for the adsorption–separation of normal hydrocarbons was investigated on a fixed-bed adsorber. The deactivated molecular sieves were regenerated by removing the coke deposited through oxidation under various conditions. They showed lower surface area, smaller pore volume, and larger pore diameter than the fresh sample because certain passages of small pore in the molecular sieves were blocked by the coke deposited. With the increase of the coke content in the molecular sieves, the deactivation rate decreased gradually. With the increase of oxidation temperature from 582 K to 787 K, the coke removal efficiency was elevated from 64% to 100%. At 787 K, the coke deposited in the molecular sieves was completely removed and the adsorption activity of the molecular sieves was recovered; however, the surface area and pore volume of the regenerated molecular sieves could not be restored to the original values of the fresh samples. Under 685–884 K, the removal of coke from the binderless 5A molecular sieves by the oxidative treatment could be expressed with a macrokinetic formula: ln(C0/C) = 0.013exp(−28122.1/T) (po2)0.32t.

Adsorptive removal of dimethyl disulfide from methyl tert-butyl ether using an Ag-exchanged ZSM-5 zeolite

Ion-exchange modification can largely change the adsorption ability of various adsorbents of zeolite. A series of Ag-exchanged ZSM-5 zeolites were prepared using an ion-exchange method and used to remove dimethyl disulfide (DMDS) from methyl tert-butyl ether (MTBE). The structural properties and acidity of the modified zeolite were examined using X-ray diffraction, N2 adsorption, NH3-TPD and Py-IR. The effects of the ion-exchange level on DMDS adsorption were investigated. In addition, the adsorption isotherms and adsorption kinetic data were measured and interpreted. Introduction of Ag+ into ZSM-5 contributes to the adsorption ability and increases the adsorption capacity by 7.7 times through enhancing the interactions between DMDS and zeolite. Strong acidity and Lewis acid sites are considered favorable for DMDS adsorption. The adsorption isotherms and kinetics results reveal that DMDS adsorption onto AgZSM-5 was endothermic chemisorption having an activation energy of 7.4 kJ mol−1. The adsorbents can be regenerated at 300 °C in an air atmosphere.

Experimental study on coking, deactivation, and regeneration of binderless 5A zeolite during 1-hexene adsorption

Coking, deactivation, and regeneration of 5A zeolite during 1-hexene adsorption were studied on a fixed-bed adsorber and a themogravimetric analyzer. Adsorption activity measurement, scanning electron microscope (SEM) analysis, X-ray diffraction (XRD) analysis, FT-IR analysis, 1H NMR analysis, and porosity measurement were used to reveal the mechanism of coking and deactivation of 5A zeolite, and evaluate the influences of binder on them. There are distinct increases in both coke content and deactivation degree with increasing the adsorption temperature. Deactivation degrees of zeolite increase as coke contents rise, however, they display smaller increasing rate at higher coke content. The rates of coke formation and deactivation of 5A zeolite are significantly enhanced by the binder mainly due to the fact that the activity sites offered by the amorphous compounds contained in the binder catalyze the formation of coke precursors. As compared to the coke formed in zeolite with binder, the coke in binderless zeolite is more aromatic. The coke which consists of inflammable part and nonflammable part can be oxidatively removed completely while the temperature approaches 787 K. No destruction in 5A zeolite crystal structure was observed in the regenerated binderless sample. The formation of coke during 1-hexene adsorption on zeolite can be explained using the carbonization-cyclization reaction mechanism. Furthermore, the kinetics models for formation and removal of coke were developed.

Preparation and evaluation of 30# hard grade asphalt

ABSTRACT The preparation and evaluation of 30# hard grade asphalt by blending softening point hard deoil asphalt with several soft components were investigated. The results showed that the properties and proportions of blending soft components had a great influence on the properties of 30# asphalt. Chunfeng 70# asphalt and Maoming deoil asphalt were more suitable as blending soft components and their blended asphalt met the technical requirements of GB/T 15180-2010 when the proportion of hard deoil asphalt were 6–12% and 8–16%, respectively. PG grade results indicated that dynamic modulus of 30# asphalts at high temperature increased significantly, and antirutting ability was also improved notably, while the bending resistant ability at low temperature was slightly inferior to the high-grade asphalt. The results of mix performance tests showed that 30# hard grade asphalt had excellent anti–high-temperature deformation ability and preferable water stability compared with high-grade asphalts.

Characterization of hard-grade asphalt using entropy analysis

ABSTRACT By adopting different technologies and raw materials, several kinds of hard-grade asphalts were prepared, and the correlation between performances and chemical compositions for these hard-grade asphalts was investigated based on grey relation entropy analysis. Results indicated that nine types of hard-grade asphalts were in accordance with GB/T 15180-2010 standard for 30# asphalt, although they have obvious differences in the performances. The main factors influencing high temperature performances were the presence of aromatics and resins and molecular weight distribution, while the main factors influencing temperature susceptibility were the presence of saturates and asphaltenes and the unstability of colloids. While there has been slight difference in Er(Xi) for ductility (10°C and 15°C), the remarkable factors influencing the crack resistance at low temperature (stiffness and m value) were the presence of aromatics and resins and molecular weight distribution, in accordance with high temperature performances.

Reduction of NOx in fluid catalytic cracking flue gas over Mg-Al spinel modified with transition metal oxides

ABSTRACT Mg-Al spinel modification with transition metal oxides of CuO, Mn2O3, and Fe2O3 was prepared to catalyze the NO+CO reaction for the DeNOx of fluid catalytic cracking flue gas. Mg-Al spinel modification with CuO showed the best catalytic performance for the easy adsorption of CO on CuO. The Cu+ in amorphous state of the catalyst surface was contributed for the main adsorption site of CO from the characterization results by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy technology. The additive amount of CuO was optimized to 4%, and the excess CuO sintered and converted to crystal phase.

A kinetic model for in situ coking denitrification of heavy oil with high nitrogen content based on starch using a structure-oriented lumping method

In this study, in situ coking denitrification technology was utilized to simplify the entire process by adding an appropriate quantity of denitrification agents to the delayed-coking tower without any further follow-up denitrification process. The effect of starch as the denitrification agent in the in situ coking denitrification process was studied. The distribution of oil products was characterized by GC of simulated distillation. The results indicated that the nitrogen compounds present in heavy oil transformed to coke via in situ coking conversion by reacting with starch. A molecular-level process model for the coking process was developed. Product distribution on the complex reaction network could be described accurately by the model.

Blending modification of Tahe vacuum residuum using Chunfeng vacuum residuum

Abstract Utilization of vacuum residue resources has been receiving extensive research interests in order to maximize the economic benefits of refineries. In present work, Tahe vacuum residuum (THVR) was blended with Chunfeng vacuum residue (CFVR). The influences of addition of CFVR on properties of THVR were investigated and the average molecular structures of SARA (referring to saturates, aromatics, resins and asphaltenes) of base and modified THVR were determined by using experimental and simulation methods. The results show that CFVR has better low-temperature performance but worse temperature susceptibility as compared with THVR. The blending TH-CF-40 sample containing 40% CFVR can meet the standard of 60# road petroleum asphalt. The saturate of TH-CF-40 has the L of 14.44, which is smaller than that of THVR. Moreover, the aromatic, resin and asphaltene have fA of 0.29, 0.42 and 0.46, RA/RN of 1.24, 2.65 and 2.93, and L of 6.78, 6.09 and 5.40. CFVR shows the similar molecular structure to THVR, therefore, contributes to the improved low-temperature ductility of blending TH-CF-40. Present results can provide theoretical guidance on the optimization utilization of vacuum residue resources.

Optimization of vacuum resid solvent deasphalting to produce bright stock and hard asphalt

ABSTRACT To prepare bright stock (BS) and 30# hard asphalt simultaneously, propane solvent deasphalting (SDA) of Oman vacuum residue was optimized. Result showed the optimal process conditions were as follows: extraction tower top temperature of 64°C, settling tower top temperature of 74°C, extraction pressure of 3.35 MPa, solvent ratio of 5. Compared with SDA of Oman VR to prepare bright stock and 70# asphalt, the yields of light deasphalted oil (LDAO) and heavy deasphalted oil (HDAO) were 26.8% and 24.7%, and increased by 1.7% and 5.2% respectively; carbon residue of LDAO was less than 1.2%, conformed to the feed requirement of furfural refining to produce bright stock. The yield of DOA was 48.5%, and DOA could be directly used to produce 30# hard asphalt. The PG grade of 30# asphalt was PG 76–22 and the 30# asphalt mixture had high rut dynamic stability and water resistant stability. HDAO could be used as feedstock of catalytic cracking and light yield oil (gasoline and diesel) was 65.99%.