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1.
In the fluid catalytic cracking reactor heavy gas oil is cracked into more valuable lighter hydrocarbon products. The reactor input is a mixture of hydrocarbons which makes the reaction kinetics very complicated due to the involved reactions. In this paper, a four-lump model is proposed to describe the process. This model is different from others mainly in that the deposition rate of coke on catalyst can be predicted from gas oil conversion and isolated from the C1–C4 gas yield. This is important since coke supplies heat required for endothermic reactions occurring in the reactor. By this model we can also conclude that the C1–C4 gas yield increases with increasing reactor temperature, while production of gasoline and coke decreases. 相似文献
2.
A continuous process is described whereby waste PTFE was converted into tetrafluoroethylene (C2F4, TFE), hexafluoroethane (C2F6, HFE), hexafluoropropylene (C3F6, HFP), and octafluorocyclobutane (c‐C4F8, OFCB). The waste PTFE was depolymerized inside a reactor that was heated by a radiofrequency induction generator. The reactor was capable of operating at various temperatures (600–900°C) as well as various reduced pressures (5–80 kPa). The depolymerization reaction conditions could be changed while the reactor was in operation in order to manipulate the reaction product composition. Under certain conditions, high yields of TFE (> 94%) and low concentrations of by‐products were formed. The PTFE was fed vertically downward from the hopper, with the screw feeder, into the reactor where the depolymerization process took place. The hot intermediate products were continuously evacuated through a self‐cleaning quench probe, where it was quenched to form the final products. The depolymerized products were analyzed with a gas chromatograph. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2752–2759, 2006 相似文献
3.
The kinetics experiments of fast reaction process of propylene chlorination at low temperature (30–90°C) and high temperature (420–480°C) are respectively conducted, and the corresponding reaction mechanisms and kinetics models are proposed. The radical mechanism at high temperature and the molecular mechanism at low temperature are found to be most likely with the experimental results. Specifically, the kinetics model, firstly considering the reversible reaction step of forming C3H6Cl · and direct hydrogen abstraction of forming C3H5 · , shows better agreement with the experimental data. Furthermore, the critical reaction temperature Tcritical is firstly proposed to determine the dominant reaction mechanism in different conditions, and correspondingly the combination method of the high-temperature and low-temperature kinetics models has been adopted for tubular reactor simulation, which can reasonably reflect the influence of wide variation range of temperature in the reactor and guide the industrial reactor design in the further work. 相似文献
4.
Diaminodiphenyl sulfone (DDS) cured tetraglycidyl-4,4'-diaminodiphenyl methane (TGDDM) epoxies, whose cure reactions are accelerated by BF3:amine catalysts, are the most common composite matrices utilized in aerospace high performance, fibrous composites. To process reproducible composites requires an understanding of the cure reactions and how these reactions are modified by the BF3:amine catalysts. In this article we report systematic differential scanning calorimetry (DSC) studies of (i) the constituents of BF3:NH2C2H5-catalyzed TGDDM–DDS epoxies and their mixtures, (ii) the effect of BF3:NH2C2H5 concentration on the cure reactions, (iii) the nature of the catalyzed cure reactions, and (iv) the environmental sensitivity of the catalyst. DSC studies are also reported on the cure reaction characteristics and environmental sensitivity of commercial C fiber–TGDDM–DDS epoxy prepregs. 相似文献
5.
《Fuel Processing Technology》1998,57(2):81-92
Pyrolysis of used sunflower oil was carried out in a reactor equipped with a fractionating packed column (in three different lengths of 180, 360 and 540 mm) at 400 and 420°C in the presence of sodium carbonate (1, 5, 10 and 20% based on oil weight) as a catalyst. The use of packed column increased the residence times of the primer pyrolysis products in the reactor and packed column by the fractionating of the products which caused the additional catalytic and thermal reactions in the reaction system and increased the content of liquid hydrocarbons in gasoline boiling range. The conversion of oil was high (42–83 wt.%) and the product distribution was depended strongly on the reaction temperature, packed column length and catalyst content. The pyrolysis products consisted of gas and liquid hydrocarbons, carboxylic acids, CO, CO2, H2 and water. Increase in the column length increased the amount of gas and coke–residual oil and decreased the amount of liquid hydrocarbon and acid phase. Also, increase of sodium carbonate content and the temperature increased the formation of liquid hydrocarbon and gas products and decreased the formation of aqueous phase, acid phase and coke–residual oil. The major hydrocarbons of the liquid hydrocarbon phase were C5–C11 hydrocarbons. The highest C5–C11 yields (36.4%) was obtained by using 10% Na2CO3 and a packed column of 180 mm at 420°C. The gas products included mostly C1–C3 hydrocarbons. 相似文献
6.
Diana Mier Ana G. Gayubo Andres T. Aguayo Martin Olazar Javier Bilbao 《American Institute of Chemical Engineers》2011,57(10):2841-2853
The joint transformation of methanol and n‐butane fed into a fixed‐bed reactor on a HZSM‐5 zeolite catalyst has been studied under energy neutral conditions (methanol/n‐butane molar ratio of 3/1). The kinetic scheme of lumps proposed integrates the reaction steps corresponding to the individual reactions (cracking of n‐butane and MTO process at high‐temperature) and takes into account the synergies between the steps of both reactions. The deactivation by coke deposition has been quantified by an expression dependent on the concentration of the components in the reaction medium, which is evidence that oxygenates are the main coke precursors. The concentration of the components in the reaction medium (methanol, dimethyl ether, n‐butane, C2? C4 paraffins, C2? C4 olefins, C5? C10 lump, and methane) is satisfactorily calculated in a wide range of conditions (between 400 and 550°C, up to 9.5 (g of catalyst) h (mol CH2)?1 and with a time on stream of 5 h) by combining the equation of deactivation with the kinetic model of the main integrated process. © 2010 American Institute of Chemical Engineers AIChE J, 2011 相似文献
7.
Yanyong Liu Toshiaki Hanaoka Tomohisa Miyazawa Kazuhisa Murata Kiyomi Okabe Kinya Sakanishi 《Fuel Processing Technology》2009,90(7-8):901-908
Fischer–Tropsch (F–T) synthesis was carried out in a gas-flowed slurry-phase reaction system over Mn- and Zr-modified Co/SiO2 catalysts. A 0.5 L stirred tank slurry reactor (STSR) was used for catalyst screening and a 12.5 L slurry bubble column reactor (SBCR) was used for trial pilot operation. While using the 0.5 L reactor for catalyst screening, Co supported on the SiO2 with an average pore size of 10 nm showed a high catalytic performance for the F–T synthesis due to the suitable Co particle size in the catalyst. Zr promoter improved the activity and Mn promoter improved the stability of Co/SiO2 catalyst for the F–T synthesis. H2-TPR profiles indicated that Zr and Mn promoters improved the reduction degree of Co3O4 particles (on SiO2 surface) to Co0 active species in H2 flow at low temperature. While using the 12.5 L reactor for trial pilot operation over Mn–Zr–Co/SiO2 catalyst, the space-time yield (STY) of C5+ hydrocarbons (liquid fuel) showed almost the same values when various solvents (n-C16H34, n-C14H30, diesel from petrol station, F–T crude oil) were used. Diesel and F–T crude oil are suitable for using in a large-scaled F–T synthesis plant owing to the low prices. Mn–Zr–Co/SiO2 catalyst achieved a STY of C5+ hydrocarbons larger than 1000 g-C5+ kg-cat? 1 h? 1 in the 12.5 L reactor. The production capacity of liquid fuel from the 12.5 L reactor reached to 15.6 L per day (assumed for 24 h continuous operation). The stirring was very important for the F–T synthesis both reaction in the 0.5 L reactor and reaction in the 12.5 L reactor. The shape of slurry reactor also influenced the CO conversion for the F–T synthesis: reaction in the 12.5 L SBCR gave a higher CO conversion than that of reaction in the 0.5 L STSR (at the same W/F value under the same stirring speed) because the slender column reactor (SBCR) extended the residue time of reaction gas in the slurry-phase containing catalyst. 相似文献
8.
Shailesh J. Patil 《Chemical Engineering Communications》2019,206(5):605-618
Jatropha oil is a promising nonedible feedstock for producing renewable diesel. In this work, the hydrotreatment processing of jatropha oil was investigated. Instead of using conventional alumina-supported Co–Mo, Ni–Mo, and Ni–W catalysts that need sulfidation pretreatment, noble metals such as Pd and Ru were chosen. Trials were performed in an isothermal trickle-bed reactor and the reaction conditions were as follows: temperature 603–663?K, weight hourly space velocity (WHSV) 1 to 4/h, pressure 1.5–3?MPa, and H2/oil ratio 200–800 (v/v). Yield of n-C15 to n-C18 hydrocarbons was maximized (70.3 and 43.8% for Pd/Al2O3 and Ru/Al2O3, respectively) at the following conditions: T?=?663 K, WHSV?=?2/h, P?=?3?MPa, and H2/oil ratio?=?600 (v/v). Since Ru favored cracking reactions to a larger extent than Pd, the yield of C15 to C18 hydrocarbons over Ru/Al2O3 was lowered. Using simple first-order plots for oil conversion, activation energies for the hydrotreating process over Pd/Al2O3 and Ru/Al2O3 were found and they were equal to 109 and 121?kJ/mol, correspondingly. 相似文献
9.
《Diamond and Related Materials》1999,8(2-5):242-245
The chemkin suite of computer programs has been used to model the concentration profiles of different hydrocarbon species present within a hot filament CVD reactor during diamond growth, and the calculated values are compared with those obtained by direct measurements using an in situ molecular beam mass spectrometer. Different hydrocarbon gases (CH4, C2H2, C2H4 and C2H6) were used as the carbon source in the input gas mixture, ensuring that the ratio of C:H2 remained constant at 1%. Calculations for when C2H6 is used as the precursor gas, after reaction and thermal equilibrium is realised, yield similar CH4:C2H2 mole fraction ratios in the reactor under growth conditions to those obtained using CH4, and to those measured experimentally. However, simulations using C2H4 or C2H2 as input gases do not reproduce the experimentally observed ratio of CH4:C2H2 mole fractions. This suggests that the conversion of unsaturated C2 species to C1 species is not a straightforward gas phase process, and there must be one or more reactions occurring within the chamber that are not present in the standard models for hydrocarbon reactions. We suggest that these neglected reaction(s) probably involve surface-catalysed hydrogenation, which in this case, is most likely occurring on the surface of the filament. 相似文献
10.
《Chemical engineering science》2003,58(3-6):1053-1061
The Liapunov–Schmidt technique of classical bifurcation theory is used to spatially average the convection–diffusion–reaction (CDR) equations over smaller time/length scales to obtain low-dimensional two-mode models for describing mixing effects due to local diffusion, velocity gradients and reactions. For the cases of isothermal homogeneous tubular, loop/recycle and tank reactors, the two-mode models are described by a pair of coupled balance equations for the mixing-cup (Cm) and spatial average (〈C〉) concentrations. The global equation describes the variation of Cm with residence time (or position) in the reactor, while the local equation expresses the coupling between local diffusion, velocity gradients and reaction at the local scales, in terms of the difference between Cm and 〈C〉. It is shown that the two-mode models have many similarities with the classical two-phase models of heterogeneous catalytic reactors with the concept of transfer between phases being replaced by that of exchange between the two-modes. It is also shown that when the local Damköhler number (ratio of local diffusion to reaction time) is small, the solution of two-mode models approaches the exact solution of full CDR equations, while for fast reactions the two-mode models retain all the qualitative features of the latter. Examples are provided to illustrate the usefulness of these two-mode models in predicting micromixing effects on homogeneous reactions. 相似文献
11.
Yang-Soo Won 《Korean Journal of Chemical Engineering》2009,26(1):36-41
The thermal reaction of trichloroethylene (TCE: C2HCl3) has been conducted in an isothermal tubular flow reactor at 1 atm total pressure in order to investigate characteristics
of chlorinated hydrocarbons decomposition and pyrolytic reaction pathways for formation of product under excess hydrogen reaction
environment. The reactions were studied over the temperature range 650 to 900 °C with reaction times of 0.3–2.0 s. A constant
feed molar ratio C2HCl3: H2 of 4: 96 was maintained through the whole experiments. Complete decay (99%) of the parent reagent, C2HCl3 was observed at temperature near 800 °C with 1 s reaction time. The maximum concentration (28%) of C2H2Cl2 as the primary intermediate product was found at temperature 700 °C where up to 68% decay of C2HCl3 occurred. The C2H3Cl as highest concentration (19%) of secondary products was detected at 750 °C. The one less chlorinated methane than parent
increased with temperature rise subsequently. The number of qualitative and qualitative chlorinated products decreased with
increasing temperature. HCl and dechlorinated hydrocarbons such as C2H4, C2H6, CH4 and C2H2 were the final products at above 800 °C. The almost 95% carbon material balance was given over a wide range of temperatures,
and trace amounts of C6H6, C4H6 and C2HCl were observed above 800 °C. The decay of reactant, C2HCl3 and the hydrodechlorination of intermediate products, resulted from H atom cyclic chain reaction via abstraction and addition
replacement reactions. The important pyrolytic reaction pathways to describe the important features of reagent decay, intermediate
product distributions and carbon mass balances, based upon thermochemical and kinetic principles, were suggested. The main
reaction pathways for formation of major products along with preliminary activation energies and rate constants were given. 相似文献
12.
The cure reactions, chemical structure, and network topography of diaminodiphenyl sulfone (DDS)-cured tetraglycidyl 4,4′diaminodiphenyl methane (TGDDM) epoxies are reported. Systematic Fourier transform infrared (FTIR) spectroscopy studies of the cure and degradation reactions of TGDDM-DDS epoxies in the 100–300°C temperature range as a function of DDS and boron trifluoride monoethylamine, BF3: NH2C2H5 catalyst concentrations are presented. FTIR studies indicate TGDDM epoxide homopolymerizes in the 175–250°C range via epoxide-hydroxyl (E-OH) chain extension reactions. The hydroxyl groups are initially present as α-glycol impurities or are formed by epoxide isomerization and/or oxidation. Three principal cure reactions occur at 177°C for TGDDM-DDS epoxies, namely primary amine-epoxide (PA-E), secondary amine-epoxide (SA-E) and E-OH reaction with the PA-E reaction being an order of magnitude faster than the other two cure reactions. The PA-E reaction dominates the early stages of cure and, hence, composite processing conditions. The three cure reactions are catalyzed to similar extents by BF3: NH2C2H5. FTIR and molecular modeling studies indicate that the E-OH and SA-E reactions can occur intermolecularly to form crosslinks or intramolecularly to form non-cross-linked internal rings. The complex degradation reactions of TGDDM-DDS epoxies in the 177–300°C range are reported. The principal degradation reactions involve (1) dehydration and/or oxidation to form ether crosslinks and (2) decomposition of the EOH cure reaction products to form propenal. Based on a knowledge of the cure reactions, together with molecular modeling, the chemical structure and network topography of TGDDM-DDS epoxies are reported. 相似文献
13.
Yun-Jo Lee Jo-Yong Park Ki-Won Jun Jong Wook Bae Nagabhatla Viswanadham 《Catalysis Letters》2008,126(1-2):149-154
An attempt made for the selective production of C2–C4 olefins directly from the synthesis gas (CO + H2) has led to the development of a dual catalyst system having a Fischer–Tropsch (K/Fe–Cu/AlOx) catalyst and cracking (H-ZSM-5) catalyst operate in consecutive dual reactors. The flow rate (space velocity) and H2/CO molar ratio of the feed have been optimized for achieving higher CO conversions and olefin selectivities. The selectivity to C2–C4 olefins is further enhanced by optimizing the reaction temperature in the second reactor (cracking), where the product exhibited 51% selectivity to C2–C4 hydrocarbons rich in olefins (77%) with a stable time-on-stream performance in a studied period of 100 h. 相似文献
14.
Metal cation (metal = Cu, In and La) ion exchanged ZSM-5 zeolites as catalysts for the NO selective reduction by propane and propene in excess oxygen. The surface reactions of HC-SCR over catalysts were investigated through in situ DRIFTS method. For C3H8-SCR, adsorbed nitrate species (–NO3) were observed as main reaction intermediates and they could react with gaseous propane to produce N2, H2O and CO2. While for C3H6-SCR, adsorbed amine species (–NH2) were observed as main reaction intermediates and they could react with NO or NO2 to produce the final products. The different reaction pathways for C3H8-SCR and C3H6-SCR over catalysts were proposed based on the DRIFTS results and the main factors controlling the activities of catalysts were discussed in details. The competing adsorption between NO–O2 and HC–O2 on the Brønsted acid sites of catalysts was responsible for the different reaction pathways in HC-SCR. 相似文献
15.
The classical fixed bed C3–C4 paraffin dehydrogenation process is a cyclic operation in which the reactor alternates between reaction and reheat cycles. During the reheat cycle, the necessary energy for the dehydrogenation reaction is stored in the fixed bed by passing hot air through it. In this established technology, both the hydrocarbon reactant and the reheat hot air are fed into the fixed bed from the same end (top) of the reactor. This is termed parallel flow (cocurrent) operation. An alternative feeding fixed bed has the hydrocarbon reactant and the reheat air entering from the opposite ends of the reactor. This is termed reverse flow (countercurrent) operation. This alternate creates an ideal temperature profile for an equilibrium limited endothermic reaction (rising temperature profile along the reactor). The transient flow behavior of both parallel and reverse flow reactors has been modelled and the dynamics of temperature profile development for both concepts have been analyzed. Based upon the model predictions, the characteristics as well as the reactor stability of the both concepts have been discussed. 相似文献
16.
Yanis Caro Fabrice Turon Pierre Villeneuve Michel Pina Jean Graille 《European Journal of Lipid Science and Technology》2004,106(8):503-512
We have examined the possibility of producing analogs of medium‐chain triglycerides (MCT) from copra oil, i.e. a triacylglycerol mixture with a high content of medium‐chain fatty acid moieties (C6–C10). A two‐step enzymatic process was used in which copra triacylglycerols were first split with papain lipase by alcoholysis with an alkyl alcohol and then subjected to interesterification with the alkyl esters recovered using papain lipase. Effects of temperature, water activity content, substrate ratio, biocatalyst amount, and alcohol chain length were also investigated. On the one hand, the sn‐3 stereoselectivity of the lipase in the alcoholysis of copra oil with butanol has permitted a direct enrichment of caproic, caprylic and capric moieties in the synthesized butyl esters. Thus, in the batch reactor, the reaction led to about 31% conversion of the oil after 24 h, and the content of C6–C10 acids in the synthesized esters increased from about 16% in the starting oil to almost 42%. A similar enzymatic alcoholysis in a packed‐bed column bioreactor gave 31% conversion of the oil after 120 min of reactor residence time. The reaction was also very selective because the C6–C10 fatty acyl groups represented about half of the newly formed butyl esters, whereas they accounted for only 16% of total fatty acids in the starting oil. On the other hand, the transesterification of the alkyl esters recovered (highly enriched in C6–C10 fatty acyl groups) with native copra oil directly led to an increase in the content of MCT in the oil, from 18 mol‐% at the beginning of the reaction to 61 mol‐% of MCT after a time period of 72 h in the batch reactor. 相似文献
17.
Epoxidation of ethylene, propylene, 2‐methylpropene, trans‐2‐butene, 2‐methyl‐2‐butene, and 2,3‐dimethyl‐2‐butene were carried out in a flow‐through reactor in the homogeneous gas phase at pressures of 0.25–1.0 bar in the temperature range of 250–375 °C. Residence times in the reactor varied from 8.3 to 38 ms. The oxidizing agent needed in the feed gas is ozone. The O3 efficiency (reacted olefin/initial O3) was found to be strongly dependent on the reactivity of the olefin used. For C4–C6 olefins, the O3 efficiency was better than 75 % in each case. For 2‐methyl‐2‐butene and 2,3‐dimethyl‐2‐butene, the O3 efficiency exceeded the theoretical value of 100 % considerably. The selectivity to epoxide was about 90 % independent of the olefin used. Under conditions of nearly total olefin conversion, the high selectivity to the epoxide has been retained as unchanged. There were no indications for consecutive reactions of the epoxides. 相似文献
18.
Assessing the performance of an industrial SBCR for Fischer–Tropsch synthesis: Experimental and modeling
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Laurent Sehabiague Omar M. Basha Yemin Hong Badie Morsi Zhansheng Shi Haolin Jia Li Weng Zhuowu Men Ke Liu Yi Cheng 《American Institute of Chemical Engineers》2015,61(11):3838-3857
The main objective of this study is to predict the performance of an industrial‐scale (ID = 5.8 m) slurry bubble column reactor (SBCR) operating with iron‐based catalyst for Fischer–Tropsch (FT) synthesis, with emphasis on catalyst deactivation. To achieve this objective, a comprehensive reactor model, incorporating the hydrodynamic and mass‐transfer parameters (gas holdup, εG, Sauter‐mean diameter of gas bubbles, d32, and volumetric liquid‐side mass‐transfer coefficients, kLa), and FT as well as water gas shift reaction kinetics, was developed. The hydrodynamic and mass‐transfer parameters for He/N2 gaseous mixtures, as surrogates for H2/CO, were obtained in an actual molten FT reactor wax produced from the same reactor. The data were measured in a pilot‐scale (0.29 m) SBCR under different pressures (4–31 bar), temperatures (380–500 K), superficial gas velocities (0.1–0.3 m/s), and iron‐based catalyst concentrations (0–45 wt %). The data were modeled and predictive correlations were incorporated into the reactor model. The reactor model was then used to study the effects of catalyst concentration and reactor length‐to‐diameter ratio (L/D) on the water partial pressure, which is mainly responsible for iron catalyst deactivation, the H2 and CO conversions and the C5+ product yields. The modeling results of the industrial SBCR investigated in this study showed that (1) the water partial pressure should be maintained under 3 bars to minimize deactivation of the iron‐based catalyst used; (2) the catalyst concentration has much more impact on the gas holdup and reactor performance than the reactor height; and (3) the reactor should be operated in the kinetically controlled regime with an L/D of 4.48 and a catalyst concentration of 22 wt % to maximize C5+ products yield, while minimizing the iron catalyst deactivation. Under such conditions, the H2 and CO conversions were 49.4% and 69.3%, respectively, and the C5+ products yield was 435.6 ton/day. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3838–3857, 2015 相似文献
19.
A. A. Vostrikov O. N. Fedyaeva S. A. Psarov D. Yu. Dubov M. Ya. Sokol 《Solid Fuel Chemistry》2007,41(5):280-289
A test bench was developed and the conversion of the organic matter of coal (OMC) in supercritical water (SCW) was studied under conditions of a continuous supply of a water-coal suspension to a vertical flow reactor at 390–760°C and a pressure of 30 MPa. From 44 to 63% OMC was released as liquid and gaseous products from coal particles (from the water-coal supension) during the time of fall to the reactor. This stage was referred to as the dynamic conversion of coal. The particles passed through the stage of the dynamic conversion of coal did not agglomerate in the reactor in the subsequent process of batch conversion in a coal layer at T = 550–760°C. The volatile products of the overall process of the dynamic and batch conversion of coal included saturated hydrocarbons (CH4 and C2H6), aromatic hydrocarbons (C6H6, C7H8, and C8H10), synthesis gas (H2 and CO), and CO2. At T < 600°C, CO2 and CO were the degradation products of oxygen-containing OMC fragments, whereas they also resulted from the decomposition of water molecules at higher temperatures in accordance with the reaction (C) + H2O = CO + H2. The mechanisms were considered, and the parameters responsible for the dynamic conversion of coal were calculated. 相似文献
20.
Gencun Wang Kan Zhang Ping Liu Haitao Hui Yisheng Tan 《Journal of Industrial and Engineering Chemistry》2013,19(3):961-965
Fe–Mn–V–K catalysts for the synthesis of light olefins from CO hydrogenation were prepared by a specially controlled degradation method. The effect of the V content on the structure and the catalytic performance of the catalysts were investigated in a continuously stirred tank slurry reactor. Mössbauer spectra (MES) results show that the incorporation of V with appropriate contents can improve the dispersion of the α-Fe2O3 phase. CO hydrogenation results indicate that a small addition of V can improve the product distribution. The addition can also increase the selectivity to light olefins by inhibiting the secondary hydrogenation reaction of the initial olefin. The best catalytic performance was obtained at the Fe/Mn/V molar ratio of 3/1/0.2. The total C2–C4 content in all hydrocarbons and O/P in the C2–C4 fraction were 49.15 wt% and 3.95, respectively. 相似文献