Graphene that had nanomeshes, only one to two graphene layers, and specific surface areas of up to 1654 m(2) g(-1) was produced on gram-scale by template growth on porous MgO layers. Its unique porous structure gave excellent electrochemical capacitance (up to 255 F g(-1)), cycle stability and rate performance.
Catalytic cracking experiments in which various blend levels of coker gas oil (CGO) in fluidized catalytic cracking (FCC) feedstock were reacted over two kinds of commercial equilibrium catalysts (RGD-1 and LBO-16) demonstrate that the blending ratio affects the potential ability of a FCC unit treating CGO obviously. The limits of the blending ratio for Daqing CGO and Dagang CGO are 30 and 20 wt %, respectively, to obtain a desirable product distribution at a relatively high feed conversion. The operating condition of a high catalyst/ oil ratio in combination with a short residence time (or high weight hourly space velocity) and moderate reaction temperature is the optimal operating condition for catalytic cracking of CGO and its mixture. A FCC catalyst, such as RGD-1, which has proper acidities and high accessibility, is suitable for dealing with CGO effectively, which leads to an obvious improvement over conversion and product distribution. The analysis and contrast catalytic cracking experiments of narrow cuts of Daqing CGO show that the fraction of Daqing CGO is accumulated largely in the range of 300-450 °C and there exists high content of basic nitrogen and polycyclic aromatics. The lowest crackability of the cut from 400 to 450 °C constrains total CGO cracking performance, which is caused by a preferential chemisorption of the polycyclic aromatic molecules, and basic nitrogen compounds take place prior to the desirable adsorption of the other hydrocarbons, which is necessary for the cracking reaction to occur.
The basic nitrogen compounds in coker gas oil (CGO) narrow fractions were enriched, and their influences on hydrocarbons during fluid catalytic cracking (FCC) were investigated. The results show that the content of basic nitrogen compounds has influence on hydrocarbons cracking during CGO FCC reaction, but it is not as obvious as reported before. Furthermore, the compositional and structural identification of basic extracts by positive-ion electrospray Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) shows that basic nitrogen compounds in CGO include N, N 2 , NO, N 2 O 1 , and NS class species. The N 1 class species centered at 9 < DBE < 13 with a carbon number ranging from 20 to 24 is the most abundant, and it is a key for CGO's retarding performance. The effect of structure and composition of basic nitrogen compounds is much more obvious than that of content, and it is stronger with the increase of their rings plus double bond equivalence (DBE).
An experimental and computational study is presented on the hydrodynamic characteristics of FCC particles in a turbulent fluidized bed. Based on the Eulerian/Eulerian model, a computational fluid dynamics (CFD) model incorporating a modified gassolid drag model has been presented, and the model parameters are examined by using a commercial CFD software package (FLUENT 6.2.16). Relative to other drag models, the modified one gives a reasonable hydrodynamic prediction in comparison with experimental data. The hydrodynamics show more sensitive to the coefficient of restitution than to the flow models and kinetics theories. Experimental and numerical results indicate that there exist two different coexisting regions in the turbulent fluidized bed: a bottom dense, bubbling region and a dilute, dispersed flow region. At low-gas velocity, solid-volume fractions show high near the wall region, and low in the center of the bed. Increasing gas velocity aggravates the turbulent disorder in the turbulent fluidized bed, resulting in an irregularity of the radial particle concentration profile.
Reactive adsorption desulfurization of FCC gasoline over a Ni/ZnO-SiO 2 -Al 2 O 3 adsorbent was carried out in a fixed-fluidized bed reactor at low pressures in the presence of hydrogen. The results show that high temperature, high pressure, high molar ratios of hydrogen-to-oil, and low weight hourly space velocity are favorable to improve the desulfurization ability of adsorbent but not conducive to maintaining the octane number of FCC gasoline throughout the condition range examined. Under optimal operating conditions, ultralow sulfur gasoline can be produced, and the RON loss is only 1 unit. Furthermore, the effect of prereduction and adsorbent characterization data (SEM/EDX, N 2 adsorption) reveal that reduction increases the interaction between Ni and S compounds and improves the pore structure of adsorbent, leading to a significant improvement in the desulfurization capability of adsorbent. Take 3-methylthiophene for example, after adsorbing on an active Ni atom via the S-Ni bond, the sulfur of 3-methylthiophene is removed by direct hydrogenolysis of the C-S bond, resulting in the formation of NiS x and 2-methyl-1,3-butadiene in hydrogen atmosphere. The latter is mainly hydrogenated to 2-methyl-2-butene and 2-methylbutane. ZnO acts as a sulfur-acceptor, which can regenerate the active Ni in situ in hydrogen atmosphere. The complete sulfidation of adsorbent particles takes place by ion diffusion.
Pretreating inferior residues to provide feedstock with trace metals and a few asphaltenes for downstream processes is important for refineries to process heavier crude oils. Toward this end, the upgrading of vacuum residue (VR) over special catalysts designed for decarbonization and demetalization was investigated in a fluidized-bed reactor. The effects of operating parameters such as reaction temperature, catalyst-to-oil ratio, and weight hourly space velocity on product distribution and removals of contaminants were determined. The experimental results demonstrate that low cracking severity is favorable for obtaining the maximum liquid yield, giving rates of removal for metals, Conradson carbon residue, and asphaltenes for residue of more than 98%, 85%, and 97% respectively. In addition, a seven-lump kinetic model with a detailed product distribution was developed to describe reaction behaviors of VR upgrading. Rate constants and apparent activation energies were estimated with the improved Marquardt method. The effect tests show that the kinetic model can predict the product yields very well.
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