Performance with Respect to Flue Gas Composition of a Combined Desulfurization／Denitration Process Using Powder-Particle Fluidized Bed

A new combined desulfarizatinn/denitraticon (DeSOx/DeNOx) procees was teeted in this study. The procees uses the so-called powder-partlcle fluidized bed (PPFB) as the major reactor in which a coarse DeNOx catalyst, several hundrsd micrometers in size, is fluidized by flue gas as the fluidization medium particles while a contlnuogsly supplied fine DeSOx sorbent, several to tens of micrometers in dianteter, is entrained with the flue gas. Ammonin for NOx reduction is fed to the bottom of the bed, thus, SOx and NOx are simultaneously removed in the single reactor.By adopting a model gas, SO2-NO-HaO-N2-air, to simulate actual flue gas in a laboratory-scale PPFB, simultaneous SO2 and NO removals were explored with respect to various gas components of flue gas. It was found that the vaxlations of SO2 removal with concentrations (fractions) of oxygen, water vapor, SO2 and NO in flue gas are little affected by the simultaneous NOx reduction. However,the dependencles of NO removal upon such gas components are clveely related to the inter-actions between DeSOx sorbent and DeNOx catalyst.     

γ-戊酮酸丁酯反应精馏过程的逐步优化方案设计

Butyl-levulinate has been identified as a promising fuel candidate with high oxygen content. Its combustion in diesel engines yields very low soot and NOx emissions. It can be produced by the esterification of butanol and levulinic acid, which themselves are platform chemicals in a biorenewables-based chemical supply chain. Since the equilibrium of esterification limits the conversion in a conventional reactor, reactive distillation can be applied to overcome this limitation. The presence of the high-boiling catalyst sulfuric acid requires a further separation step downstream of the reactive distillation column to recover the catalyst for recycle. Optimal design specifications and an optimal operating point are determined using rigorous flowsheet optimization. The challenging optimization problem is solved by a favorable initialization strategy and continuous reformulation. The design identified has the potential to produce a renewable transportation fuel at reasonable cost.     

Research progress in the SO2resistance of the catalysts for selective catalytic reduction of NOx

The selective catalytic reduction(SCR)of NOxwith NH3has been proven to be an efficient technology for NOx conversion to N2.However,the catalysts used for SCR usually suffer from the problem of sulfur poisoning which seriously limits their practical application.This review summarized sulfur poisoning mechanisms of various SCR deNOxcatalysts and strategies to reduce deactivation caused by SO2such as doping metals,control-ling the structures and morphologies of the catalysts,and selecting appropriate supports.The methods and procedures of catalysts preparation and the reaction conditions also have effect on SO2-resistance of the catalysts. Several novel catalyst systems that exhibited good SO2resistance are also introduced.This paper could provide guidance for the development of highly efficient sulfur-tolerant deNOxcatalysts.     

Desulfurization of liquid hydrocarbon fuels via Cu_2O catalyzed photooxidation coupled with liquid–liquid extraction

By combining the photochemical reaction and liquid–liquid extraction(PODS), we studied desulfurization of model fuel and FCC gasoline. The effects of air flow, illumination time, extractants, volume ratios of extractant/fuel, and catalyst amounts on the desulfurization process of PODS were analyzed in detail. Under the conditions with the air as oxidant(150 ml·min~(-1)), the mixture of DMF–water as extractant(the volume ratio of extractant/oil of 0.5) and photo-irradiation time of 2 h, the sulfur removal rate reached only 42.63% and 39.54% for the model and FCC gasoline, respectively. Under the same conditions, the sulfur removal rate increased significantly up to79% for gasoline in the presence of Cu_2O catalyst(2 g·L~(-1)). The results suggest that the PODS combined with a Cu_2O catalyst seems to be a promising alternative for sulfur removal of gasoline.     

Zn–Ca–Al mixed oxide as efficient catalyst for synthesis of propylene carbonate from urea and 1,2-propylene glycol

A series of Zn–Ca–Al oxides with different CaO and ZnO contents have been prepared and evaluated in the synthesis of propylene carbonate(PC) from 1,2-propylene glycol(PG) and urea in a batch reactor. The effect of catalyst composition, basicity and reaction process parameters such as temperature, catalyst dose, molar ratio of PG to urea, purge gas flow and reaction time has been studied to find suitable reaction conditions for the PC synthesis. The PC selectivity and yield under the desired conditions could reach 98.4% and 90.8%, respectively. The best performing catalyst also exhibited a good reusability without appreciable loss in the PC selectivity and yield after five consecutive reaction runs. In addition, a stepwise reaction pathway involving a 2-hydroxypropyl carbamate intermediate was proposed for the urea alcoholysis to PC in the presence of Zn–Ca–Al catalysts, according to the time dependences of reaction intermediates and products.     

A safe and efficient process for the preparation of difluoromethane in continuous flow

Difluoromethane is typically produced vialiquid-phase fluorination as performed in a batch reactor. However,this process suffers from some problems, e.g., severe corrosion of the reactor, high safety risk, and the regeneration of the catalyst. In this paper, a flow process as performed in the tubular reactor was designed. The optimum conditions for continuous synthesis of difluoromethane were obtained as follows: the reaction temperature was 100℃, the molar ratio of dichloromethane to hydrogen fluoride was 1.6:1 and the reaction time was 300 s. The operation of the cyclic process was stable for 24 h with the conversion per pass of hydrogen fluoride up to 16.2%.The unreacted raw materials were easily reused. The deactivation of the common catalyst, antimony pentachloride, was investigated by catalyst concentration curve and XPS analysis. The approach proposed in this work is proven to be safe, efficient and low amount of catalyst.     

Functionalized metal–organic frameworks with strong acidity and hydrophobicity as an efficient catalyst for the production of 5-hydroxymethylfurfural

In the dehydration of fructose to 5-hydroxymethyl furfural(HMF), in situ produced water weakens the acid strength of the catalyst and causes the rehydration of HMF, causing unsatisfactory catalytic activity and selectivity. In this work, a class of benzenesulfonic acid-grafted metal–organic frameworks with strong acidity and hydrophobicity is obtained by the direct sulfonation method using 4-chlorobenzenesulfonic acid as sulfonating agent. The resultant MOFs have a specific surface area of greater than 250 m~2·g~(-1), acid density above 1.0 mmol·g~(-1), and water contact angle up to 129°. The hydrophobic MOF-Ph SO_3 H exhibits both higher catalytic activity and selectivity than MOF-SO_3 H in the HMF synthesis due to its better hydrophobicity and olephilicity. Moreover, the catalyst has a high recycled stability. At last, fructose is completely converted, and 98.0% yield of HMF is obtained under 120 °C in a DMSO solvent system. The successful preparation of the hydrophobic acidic MOF provides a novel hydrophobic catalyst for the synthesis of HMF.     

Kinetic Study of Co-b-Zeolite for Selective Catalytic Reduction

The effects of grain size, space velocity, temperature and reactant concentration on the kinetics of NOx reduction with propane over Co-b-zeolite catalyst were investigated. The external mass transfer phenomenon was examined by varying the space velocity. The results show that the transfer can be negligible when the space velocity is greater than 60000 h-1 in low temperature range. However, the transfer exists at high temperatures even when the space velocity reaches a high level. Variation of the catalyst grain size from 0.05 to 0.125 mm does not change the conversion rate of NOx. The concentrations of components, NOx, C3H8 and O2, were also investigated to have a better understanding of mechanism. Based on the experimental data, the selectivity formula was proposed. The results shows that lower temperature is helpful to get higher selectivity as the activation energy of hydrocarbon oxidation, Ea,2, is greater than that of NOx reduction, Ea,1, (Ea,2>Ea,1). High NOx concentration and low C3H8 concentration are beneficial to high selectivity. However in order to maintain high activity simultaneously, the temperature and C3H8 concentration should be high enough to promote NOx reduction. 10%(j) H2O and 75′10-6(j) SO2 were introduced into the reaction system, and Co-b-zeolite shows strong resistance to water and SO2.     

高岭土微球原位合成SAPO-34分子筛及其在流化床甲醇/二甲醚制烯烃过程中的应用(英文)

SAPO-34 zeolite is considered to be an effective catalyst for methanol or dimethyl ether conversion to olefins. In this study, we developed the in situ synthesis technology to prepare SAPO-34 zeolite in kaolin microspheres as a catalyst for fluidized methanol or dimethyl ether to olefins process. The silicoaluminophosphate zeolite was first time reported to be synthesized in kaolin microspheres. The SAPO-34 content of synthesized catalyst was about 22% as measured by three different quantitative methods (micropore area, X-ray fluorescence and energy dispersive spectroscopy element analysis). Most of the SAPO-34 zeolites were in nanoscale size and distributed uniformly inside the spheres. The catalytic performance was evaluated in fixed bed and fluidized bed reactors. Compared with the conventional spray-dry catalyst, SAPO/kaolin catalyst showed superior catalytic activities, better olefin selectivities (up to 94%, exclusive coke), and very good hydrothermal stability. The in situ synthesis of SAPO-34 in kaolin microspheres is a facile and economically feasible way to prepare more effective catalyst for fluidized MTO/DTO (methanol to olefins/dimethyl ether to olefins) process.     

Mathematical analysis of physicochemical phenomena in the catalyst during hydrogenating depolymerization of coal extract benzene insoluble fraction

Efficiency and selectivity of hydrogenating depolymerization of the coal extract benzene-insoluble part over the heterogeneous Co–Mo/Al₂O₃ catalystwere assessed using a mathematical model. The analytical equations of the mathematical modelwere generated based onmaterial balance incorporating the physico-chemical phenomena (reaction and diffusion) both in the autoclave and the catalyst grain. The equations offer the possibility for predicting changes of the reactants in the autoclave during the process and for determining the distribution of reactant concentrations in the grain as a function of its radius. The analytical equations of the model serve as the basis of the algorithm for assessing the influence of restrictive diffusion on the effectiveness and selectivity of the catalyst, and also for defining the optimal radii of the catalyst's pores to enable free transport of reactants in the grain interior.     

CARBON DEPOSITION AND CATALYST DEACTIVATION OF Sb-Fe OXIDE CATALYST IN THE AMMOXIDATION OF PROPYLENE

Carbon deposition and catalyst deactivation of Sb-Fe oxide catalyst in the ammoxidation of propylenewere investigated by means of a fluidized-bed reactor.The reactivity,surface acidity,specific surfacearea,average pore radius,and electron spin resonance spectrum data were obtained from the catalysts ofincreasing carbon deposition.Chemisorption of oxygen and propylene and thermal programmed desorptionof propylene were carried out on the Sb-Fe oxide catalyst as well as a commercial one,Mo-Bi.Isotopicexperiment using acrylonitrile-2-~(14)C as tracer was also accomplished.It was found that carbon deposition due to intermediates and acrylonitrile on selective oxidation sitescould be the primary reason for catalyst deactivation,and that because of the Sb-Fe oxide catalytspossessing a property of easy reduction and difficult reoxidation,the structure of the FeSbO_4 would bedecomposed under the oxygen-lean condition into Sb_2O_3 and Fe_2O_3 which form the deep oxidation catalystcomponent.According to the above investigation a suggestion for improving catalyst properties has been proposed.     

Simulation of Catalytic Combustion of Methane in a Monolith Honeycomb Reactor

1 INTRODUCTION Monolith honeycomb reactor plays an important role in catalytic combustion[1] such as combustion chambers for gas turbines used in power generation where methane is the main reactant. It contains hun-dreds of parallel channels that are often of the order of 1—2mm in diameter. The catalyst may be dispersed within a washcoat that is coated onto the surface of the channels[2] where catalytic combustion occurs. Com-pared to conventional gas-phase combustion, catalytic combusti…     

Study on the growth of platinum nanowires as cathode catalysts in proton exchange membrane fuel cells

The platinum nanowires have been verified to be a promising catalyst to promote the performance of proton exchange membrane fuel cells.In this paper,accurately controlled growth of nanowires in a carbon matrix is achieved for reducing Pt loading.The effects of formic acid concentration and reaction temperature on the morphology and size of the Pt nanowires,as well as their electrochemical performances in a single cell,are investigated.The results showed that the increase in the formic acid concentration results in a volcano trend with the length of Pt nanowires.With increasing reduction temperature,the diameter of Pt nanowires increases while Pt particles evolve from one-dimensional to zero-dimensional up to 40°C.A mechanism of the Pt nanowires growth is proposed.The optimized Pt nanowires electrode exhibits a power density(based on electrochemical active surface area)79%higher than conventional Pt/C one.The control strategy obtained contributes to the design and control of novel nanostructures in nano-synthesis and catalyst applications.     

Research progress in ionic liquids catalyzed isobutane/butene alkylation

The complicated reaction mechanism and the character of competitive reactions lead to a stringent requirement for the catalyst of C4 alkylation process. Due to their unique properties, ionic liquids (ILs) are thought to be new potential acid catalysts for C4 alkylation. An analysis of the regular and modified chloroaluminate ILs, novel Br?nsted ILs and composite ILs used in isobutane/butene alkylation shows that the use of either ILs or ILs coupled with mineral acid as homogeneous catalysts can help to greatly adjust the acid strength. By modifying the struc-tural parameters of the cations and anions of the ILs, the solubility of the reactants could also be adjusted, which in turn displays a positive effect on improving the activity of ILs. Immobilization of ILs is an effective way to mod-ulate the surface adsorption/desorption properties and acid strength distribution of the solid acid catalysts. Such a process has a tremendous potential to reduce the deactivation of catalyst and enhance the activity of the solid acid catalyst. The development of novel acid catalysts for C4 alkylation is a comprehensive consideration of acid strength and its distribution, interfacial properties and transport characteristics.     

The cooperation effect of Ni and Pt in the hydrogenation of acetic acid

The catalytic hydrogenation of carboxylic acid to alcohols is one of the important strategies for the conversion of biomass.Herein,a series of Ni-doped PtSn catalysts were prepared,characterized and studied in the hydrogenation of acetic acid.The Ni dopant has a strong interaction with Pt,which promotes the hydrogen adsorption,providing an activated hydrogen-rich environment for the hydrogenation.Meanwhile,the presence of Ni also improves the Pt dispersion,giving more accessible active sites for hydrogen activation.The cooperation of Pt and Ni significantly promotes the catalytic activity of the hydrogenation of acetic acid to ethanol.As a result,the catalyst with 0.1%Ni exhibits the best reaction activity,and its space time yield is twice as that of the PtSn/SiO2 catalyst.It provides a meaningful instruction on the catalyst design for the carboxylic acid hydrogenation.     

Kinetics of Sawdust Hydrolysis with Dilute Hydrochloric Acid and Ferrous Chloride

With dilute hydrochloric acid as catalyst and promoted by ferrous chloride, hydrolysis of waste sawdust to produce monosaccharides was conducted by using an one-step method in a batch-wise operation reactor. Based on the model of first order consecutive irreversible reactions, the kinetics equation incorporating the term of catalyst concentration was obtained that is suitable for describing the hydrolysis of sawdust. Activation energies were calculated for hydrolysis of sawdust and decomposition of monosaccharides.     

Effects of iron precursors on the structure and catalytic performance of iron molybdate prepared by mechanochemical route for methanol to formaldehyde

Mechanochemical synthesis has been applied for many novel material preparations and gained more and more attention due to green and high-efficiency recently. In order to explore the influences of iron precursors on structure and performance of iron molybdate catalyst prepared by mechanochemical route, three typical and cheap iron precursors have been used in preparation of iron molybdate catalyst. Many characterization methods have been employed to obtain the physical and chemical properties of iron molybdate catalyst. Results indicate that iron precursors have the significant impact on the phase composition, crystal morphology and catalytic performance in the conversion of methanol to formaldehyde. It is hard to regulate the phase composition by changing Mo/Fe mole ratios for Fe_2(SO_4)_3 as iron precursor. In addition, as for Fe_2(SO_4)_3, the formaldehyde yield is lower than that from iron molybdate catalyst prepared with Fe(NO_3)_3·9H_2O due to the reduction in Fe_2(MoO_4)_3 phase as active phase. Based on mechanochemical and coprecipitation method, the solvent water could be a key factor for the formation of MoO_3 and Fe_2(MoO_4) for FeCl_3·6H_2O and Fe_2(SO_4)_3 as precursors. Iron molybdate catalyst prepared with Fe(NO_3)_3·9H_2O by mechanochemical route, shows the best methanol conversion and formaldehyde yield in this reaction.     

水滑石高效催化缺电子烯与胺类的共轭加成反应

The novel efficient procedure has been developed for the conjugate addition of amines to electron deficient alkenes. A series of hydrotalcite-like materials were synthesized as catalyst for the conjugate addition of amines and alkenes. After optimizing the reaction conditions, ZnAl-LDHs (3︰1) was chosen as the best catalyst for the reaction. The results showed that the catalyst worked very well for the conjugate addition of amines to electron deficient alkenes with the excellent yields in several minutes. Operational simplicity, no solvent, low cost of the catalyst, high yields, reusability, excellent chemoselectivity, wide applicability are the key features of this method.     

Study on Optimal Strategy of Grade Transition in Industrial Fluidized Bed Gas-Phase Polyethylene Production Process

A model of grade transition is presented for a commercialized fluidized bed gas-phase polyethylene production process. The quantity of off-specification product and the time of grade transition can be minimized by the optimization of operating variables, such as polymerization temperature, the ratio of hydrogen to ethylene, the ratio of co-monomer to ethylene, feed rate of catalyst, and bed level. A new performance index, the ratio of melt flow (MFR), is included in the objective function, for restraining the sharp adjustment of operation variables and narrowing the distribution of molecular weight of the resin. It is recommended that catalyst feed rate and bed level are decreased in order to reduce the grade transition time and the quantity of off-specification product. This optimization problem is solved by an algorithm of sequential quadratic programming (SQP) in MATLAB. There is considerable difference between the forward transition and reverse transition of grade with regard to the operating variab     

Ni-mediated Liquid Phase Reduction of Carbonyl Compounds in the Presence of Atmospheric Hydrogen

An efficient reduction system of benzaldehyde with hydrogen under ambient pressure was developed using facile NiO catalyst. The non-aromatic solvents such as cyclohexane, tetrahydrofuran （THF） and n-hexane, and the additive with strong basicity e.g. KOH, were necessary for smooth conversion of the substrate. That the catalyst can be recovered and reused for nine times without loss of catalytic activity indicates that this catalyst is a recyclable one for benzaldehyde reduction.