氮化物对柴油加氢脱硫影响的研究进展

分别从催化剂,工艺条件等方面介绍了氮化物对柴油加氢脱硫反应(HDS)影响的机理。介绍了氮化物对柴油HDS反应影响的动力学研究。结果表明:氮化物对柴油HDS反应具有抑制作用;在不同催化剂活性中心上和不同的工艺条件下氮化物对柴油HDS反应的影响存在差异且符合于拟一级反应动力学。氮化物对柴油HDS的影响研究,可以指导高活性催化剂的开发,寻求最优柴油HDS反应工艺。     

Catalytic process for decolorizing yellow plume

Yellow-colored exhaust gas streams from internal engines or gas turbines, frequently referred to as “yellow plume,” contain nitrogen dioxide (NO₂) at concentrations as low as 15 ppm. The process developed in this work for decolorizing the yellow plume is based on reduction of NO₂ to NO utilizing a combination of a Pt catalyst and a reducing agent. A stoichiometric excess of carbon monoxide, diesel oil, methanol or ethanol were used as reducing agents. Depending on the type of the reductant, the active temperature window of NO₂ reduction was varied with methanol and CO being active at lower temperatures and ethanol and diesel oil at higher temperatures. By changing the Pt loading of the catalysts the active temperature window of NO₂ reduction was also changed, higher loading Pt catalysts being active at lower temperatures. This scheme of NO₂ reduction process was verified in a pilot-scale test with the real exhaust gas from the gas turbine power plant, showing 96% of NO₂ reduction at the stack temperatures of 102–123 °C and at space velocities of 28,000–95,000 h⁻¹ with inherent CO in the exhaust gas as the reducing agent.     

DME as Reductant for Continuous Lean Reduction of NO x over ZSM-5 Catalysts

Dimethyl ether (DME) is an interesting alternative fuel to diesel, but is not an efficient reductant in lean NO _x conversion over typical diesel HC-SCR catalysts. Comparatively high deNO _x activity was found over H-ZSM-5 in the presence of water, giving reduction of 28% NO and 37% NO₂ respectively with a DME/NO _x -ratio of 4.     

Catalytic conversion of syngas into C2 oxygenates over Rh-based catalysts—Effect of carbon supports

Ethanol is considered as a potential alternative synthetic fuel to be used in automobiles or as a potential source of hydrogen for fuel cells. In this paper we first undertake a brief overview of the catalyst development for syngas conversion to C₂ oxygenates over Rh-based catalysts, mainly on the effects of various additives and supports on the activity and selectivity. Then we investigated the effects of carbon materials, which have been rarely studied as supports for Rh-based catalysts in this process. For example, rather well graphitized carbon black, very high surface area CMK-3 and activated carbon (AC) were compared to carbon nanotubes (CNTs), which exhibits a medium level surface area with well defined nanochannels. The CNT-supported catalyst shows a highest overall activity and yield of C₂ oxygenates compared to the other carbon-supported catalysts. The catalysts are characterized by N₂ adsorption–desorption, CO chemisorption, TEM, XRD and TPD. The graphitized structure combined with the tubular morphology of CNTs likely play an important role.     

Catalytic oxidative desulfurization of benzothiophene with hydrogen peroxide over Fe/AC in a biphasic model diesel-acetonitrile system

Catalytic oxidative desulfurization (Cat-ODS) of benzothiophene (BT) in n-octane has been investigated with hydrogen peroxide (H₂O₂) over catalysts of activated carbon (AC) supported iron oxide under mild conditions. The catalyst was characterized by N₂ adsorption, XRD, SEM/EDS, TPR and XPS. Under the best operating condition for the catalytic oxidative desulfurization—temperature 60 °C, atmospheric pressure, 0.15 g Fe/AC, 18 molar ratio of hydrogen peroxide to sulfur, using acetonitrile as extraction solvent for double extraction—the sulfur content in model diesel fuel (MDF) was reduced from 700 ppmw to 30 ppmw with 95.66% of total sulfur was removed.     

Catalytic upgrading of biorefinery oil from micro-algae

Micro-algae are seen as one of the major future fuel sources. Culture and growth of oil rich micro-algae and catalytic process for the conversion of their crude oils or biomass is reviewed here. While there is a significant literature on growth and extraction of oil from the resultant biomass the literature on the problems of refining these oils is diverse and needs collation. It is clear that previous work has been focused on the two green algae Botryococcus braunii and Chlorella protothecoides containing terpenoid hydrocarbons and glyceryl lipids as their major crude oils, respectively, both of which will need different refinery technology for upgrading. Studies show a number of conventional catalysts in the petroleum refining industry including transition metals, zeolites, acid and base catalysts can be used with variable effect. These have been employed for cracking, hydrocracking, liquefaction, pyrolysis and transesterification processes to produce diesel, jet fuel and petrol (gasoline). However there is strong evidence that new nano-scale materials containing a high number of active sites and high surface areas may offer more potential.     

Optimization of soy-biodiesel combustion in a modern diesel engine

As global petroleum demand continues to increase, alternative fuel vehicles are becoming the focus of increasing attention. Biodiesel has emerged as an attractive alternative fuel option due to its domestic availability from renewable sources, its relative physical and chemical similarities to conventional diesel fuel, and its miscibility with conventional diesel. Biodiesel combustion in modern diesel engines does, however, generally result in higher fuel consumption and nitrogen oxide (NO_x) emissions compared to diesel combustion due to fuel property differences including calorific value and oxygen content. The purpose of this study is to determine the optimal engine decision-making for 100% soy-based biodiesel to accommodate fuel property differences via modulation of air-fuel ratio (AFR), exhaust gas recirculation (EGR) fraction, fuel rail pressure, and start of main fuel injection pulse at over 150 different random combinations, each at four very different operating locations. Applying the nominal diesel settings to biodiesel combustion resulted in increases in NO_x at three of the four locations (up to 44%) and fuel consumption (11-20%) over the nominal diesel levels accompanied by substantial reductions in particulate matter (over 80%). The biodiesel optimal settings were defined as the parameter settings that produced comparable or lower NO_x, particulate matter (PM), and peak rate of change of in-cylinder pressure (peak dP/dt, a metric for noise) with respect to nominal diesel levels, while minimizing brake specific fuel consumption (BSFC). At most of the operating locations, the optimal engine decision-making was clearly shifted to lower AFRs and higher EGR fractions in order to reduce the observed increases in NO_x at the nominal settings, and to more advanced timings in order to mitigate the observed increases in fuel consumption at the nominal settings. These optimal parameter combinations for biodiesel were able to reduce NO_x and noise levels below nominal diesel levels while largely maintaining the substantial PM reductions. These parameter combinations, however, had little (maximum 4% reduction) or no net impact on reducing the biodiesel fuel consumption penalty.     

Catalytic ammonia decomposition: COx-free hydrogen production for fuel cell applications

Catalytic decomposition of ammonia has been investigated as a method to produce hydrogen for fuel cell applications. The absence of any undesirable by-products (unlike, e.g., CO_x, formed during reforming of hydrocarbons and alcohols) makes this process an ideal source of hydrogen for fuel cells. In this study a variety of supported metal catalysts have been studied. Supported Ru catalysts were found to be the most active, whereas supported Ni catalysts were the least active. The supports were found to play a profound role in the ammonia decomposition process. The activation energies for the ammonia decomposition process varied from 17 to 22 kcal/mol depending upon the catalyst employed. The activation energies of the supported Ir catalysts were found to be in excellent agreement with our recent studies addressing ammonia decomposition on single crystal Ir.     

Catalytic hydrodenitrogenation of basic and non-basic nitrogen compounds in Athabasca bitumen distillates

The denitrogenation of distillates derived from Athabasca bitumen over several unpromoted and promoted molybdenum oxide/alumina catalysts has been studied. The removals of both the basic and non-basic nitrogen compounds are compared for a heavy gas oil and a coker kerosene distillate. The addition of MoO₃ to alumina had a much more pronounced effect on the removal of non-basic nitrogen compounds than of basic ones. Comparison of several nickel- and cobalt-promoted catalysts showed that the denitrogenation activity of catalysts increased with the promoter/molybdenum ratio up to an atomic ratio of about 0.6. Any further increase in the atomic ratio did not change the denitrogenation activity. As this trend was observed with catalysts made with different supports, as well as with varying MoO₃ concentrations, it is believed to be independent of physical properties such as surface area. Basic nitrogen removal also followed similar trends with increasing promoter/ molybdenum ratio.     

Combined pre-reforming-desulfurization of high-sulfur fuels for distributed hydrogen applications

A major challenge facing the future Hydrogen Economy is the issue of hydrogen fuel delivery and distribution. In the near term, it may be necessary to deliver high-density hydrocarbon fuels (e.g., diesel fuel) directly to the end-user (e.g., a fueling station) wherein it is reformed to hydrogen, on demand. This approach has the advantages of utilizing the existing fuel delivery infrastructure, and the fact that more energy can be delivered per trip when the tanker is filled with diesel instead of liquefied or compressed hydrogen gas. Reforming high-sulfur hydrocarbon fuels (e.g., diesel, JP-8, etc.) is particularly challenging due to rapid deactivation of conventional reforming catalysts by sulfurous compounds. A new on-demand hydrogen production technology for distributed hydrogen production is reported. In this process, first, the diesel fuel is catalytically pre-reformed to shorter chain hydrocarbons (C₁-C₆) before being fed to the steam reformer, where it is converted to syngas and further to high-purity hydrogen gas. In the pre-reformer, most sulfurous species present in the fuel are converted to H₂S. Desulfurization of the pre-reformate gas is carried out in a special regenerative redox system, which includes an iron-based scrubber coupled with an electrolyzer. The integrated pre-reformer and sulfur-scrubbing unit operated successfully for 100 h at desulfurization efficiency of greater than 95%.     

Computer Modeling System of the Industrial Diesel Fuel Catalytic Dewaxing Process

An unsteady mathematical model and a computer modeling system of the diesel fuel catalytic dewaxing process (mild hydrocracking) were developed. The modeling system allows for calculating the optimal technological mode to produce low‐freezing diesel fuel with the required cold filter plugging point taking into account the feedstock composition and catalyst activity. The modeling system consists of the main blocks: database, knowledge base, unsteady mathematical model of the diesel fuel catalytic dewaxing process, and application program package. Using the developed computer modeling system, the influence of the feedstock composition and flow rate as well as of the catalyst activity on the cold filter plugging point and the yield of diesel fuel is demonstrated.     

Catalytic wall-flow filters for the abatement of diesel particulate: regeneration parameters study

A 1% Pt on CeO₂-promoted PrCrO₃ perovskite catalyst has been synthesized over a wall-flow monolith by the in situ solution combustion synthesis (SCS) method. The role of the catalyst, highly active towards diesel particulate combustion, has been studied during the regeneration phase as a function of three different operating parameters: the inlet trap temperature at which the regeneration is induced, the residual oxygen concentration in the exhaust gases and the load of particulate at the start of the regeneration. The final aim of this study is to improve the knowledge on the catalytic regeneration process in order to derive information suitable for designing an optimized catalytic soot trap entailing minimal fuel penalties.     

Heterogeneous Catalytic Aziridination of Styrene Using Transition-Metal-Exchanged Zeolite Y

Hydrogen for fuel cells can be produced by reforming hydrocarbons. The H₂-rich reformate typically contains about 1 mol% CO which will poison the anode of polymer electrolyte fuel cells. The CO concentration can be reduced by preferential oxidation (PROX) using near-stoichiometric amounts of O₂. The conversion of CO should be over 99% while minimizing oxidation of H₂. Supported Pt catalysts with and without promotion by Ce were compared for the catalytic oxidation of CO by O₂ in a H₂ stream. With unsupported Pt catalysts, selectivity (to CO₂ as opposed to H₂O) was highest at low temperatures and low O₂/CO ratios, however conversion was low. Addition of Ce significantly improved CO conversion under these conditions.     

A New <Emphasis Type="Italic">n</Emphasis>-Alkane Hydroisomerization Catalyst Modified with Nanosized Molybdenum Carbides and Its Catalytic Properties in Diesel Fraction Hydroisomerization. Part III: Comparison of the Catalytic Properties of Bifunctional SAPO-31 and SAPO-11 Based Catalysts

Part III of this work continues the study of the catalytic properties of new molybdenum carbide based hydroisomerization catalysts, which are resistant to sulfur compounds and allow the synthesis of waxy diesel fuels with the same quality characteristics as those of platinum-containing catalysts. The catalytic properties of such bifunctional catalysts as 7%Mo₂C/SAPO-31 (LCCH-2) and 7%Mo₂C/SAPO-11 (LCCH-2-2) in diesel fraction hydroisomerization in the temperature range of 320–400°C are compared. It is shown that LCCH-2 ensures a higher yield of the hydroisomerized diesel fraction with a lower freezing point as compared to LCCH-2-2 at temperatures above 320°C. The ratio between mono- and di-isomers in reaction products is analyzed. It is concluded that SAPO-31 based catalyst is more selective to the formation of terminal monosubstituted alkanes than SAPO-11 based catalyst. The resistance of both catalysts to deactivation with coke deposits (tests over 100 h at 320 and 360°C in hydroisomerization) is studied. It is established that LCCH-2-2 is less resistant to deactivation than LCCH-2. These findings are due to differences in acidity, the degree of uniformity in the distribution of acidic hydrogenating/dehydrogenating sites in the catalysts, and the structural type of their acidic supports.     

Simultaneous abatement of diesel soot and NOX emissions by effective catalysts at low temperature: An overview

The diesel engine generally achieves the highest fuel, energy, and thermal efficiency due to its very high compression/expansion ratio (14:1 to 25:1). Diesel engines can have a thermal efficiency that exceeds 50%. The main problem is that they emit more pollution like fine black soot particulates (C₈H to C₁₀H) and nitrogen oxides (NO_X). These pollutants have been causing serious problems for human health and the global environment and also impacts on the engine. There are many types of catalysts investigated for simultaneous control of these two pollutants, i.e., platinum group metals (PGM; Pt, Pd, Rh, and Ir) based, spinel-type oxides, hydrotalcite, rare earth metal oxides, mixed transient metal oxides, etc. The high raw material cost of PGM catalysts has become a significant issue, so developing non-PGM catalysts are one of the promising challenges. There are no extra reductants required because soot catalytically oxidizes itself in the presence of NO_X at a faster rate than molecular oxygen and simultaneously NO_X is reduced to nitrogen. The order of oxidation potential of NO_X to oxidized soot in comparison to molecular oxygen is as follows: NO₂ > NO > O₂. To meet the very strict EPA US 2010 and Euro VI regulations of particulate matter (PM) and NO_X for heavy-duty and light-duty vehicular stringent emission, it is very important to apply the integrated catalytic systems to significantly remove PM and NO_X simultaneously. Many papers related to simultaneous control of soot and NO_X over different catalysts have been published but till now some of effective catalysts showing high conversion at low temperatures (possibly within the range typical of diesel exhaust: 150–450°C) have not been reviewed. Thus, this article provides a summary of published information regarding the effective catalysts, their preparation methods, properties, and application for simultaneous control of diesel soot and NO_X.     

Study of oxygenated biomass fuel blends on a diesel engine

Vegetable methyl ester was added in ethanol–diesel fuel to prevent separation of ethanol from diesel in this study. The ethanol blend proportion can be increased to 30% in volume by adding the vegetable methyl ester. Engine performance and emissions characteristics of the fuel blends were investigated on a diesel engine and compared with those of diesel fuel. Experimental results show that the torque of the engine is decreased by 6%–7% for every 10% (by volume) ethanol added to the diesel fuel without modification on the engine. Brake specific fuel consumption (BSFC) increases with the addition of oxygen from ethanol but equivalent brake specific fuel consumption (EBSFC) of oxygenated fuels is at the same level of that of diesel. Smoke and particulate matter (PM) emissions decrease significantly with the increase of oxygen content in the fuel. However, PM reduction is less significant than smoke reduction. In addition, PM components are affected by the oxygenated fuel. When blended fuels are used, nitrogen oxides (NO_x) emissions are almost the same as or slightly higher than the NO_x emissions when diesel fuel is used. Hydrocarbon (HC) is apparently decreased when the engine was fueled with ethanol–ester–diesel blends. Fuelling the engine with oxygenated diesel fuels showed increased carbon monoxide (CO) emissions at low and medium loads, but reduced CO emissions at high and full loads, when compared to pure diesel fuel.     

Reactivation of an industrial batch of CoMo/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst for the deep hydrotreatment of oil fractions

The results from industrial tests of technology developed earlier for the reactivation of CoMo/Al₂O₃ catalyst for the deep hydrotreating of diesel fuel, including the oxidative regeneration of the catalyst with subsequent treatment using organic complexing agents, are presented. Samples of the catalyst, fresh and at different stages of its reactivation, are investigated using a set of analytical and physicochemical methods. The chemical composition, textural characteristics, mechanical strength, structure of the active sulfide component (TEM, XPS) are determined. Catalytic tests are performed that include lifetime tests (360 h) in the hydrotreatment of a straight-run diesel fraction. The restoration of the physicochemical and catalytic properties is observed for a sample subjected to oxidative regeneration with subsequent treatment using organic complexing agents. An industrial batch of deep hydrotreatment catalyst reactivated by this technology is loaded into an L-24-6 industrial plant facility and ensures stable purification of straight-run diesel fuel containing up to 10% of light catalytic cracking gas oil to a residual sulfur content of less than 10 ppm. Comparison of the obtained results and data on the industrial operation of fresh catalysts shows that the technology developed by the Institute of Catalysis and PAO Gazprom Neft ensures almost complete restoration of the properties of the deactivated catalysts.     

The production of fatty acid isopropyl esters and their use as a diesel engine fuel

Biodiesel is an alternative fuel for diesel engines that consists of the monoalkyl esters of vegetable oils or animal fats. Currently, most biodiesel consists of methyl esters, which have poor cold-flow properties. Methyl esters of soybean oil will crystallize and plug fuel filters and lines at about 0°C. However, isopropyl esters have better cold-flow properties than methyl esters. This paper describes the production of isopropyl esters and their evaluation in a diesel engine. The effects of the alcohol amount, the catalyst amount, and two different catalysts on producing quality biodiesel were studied. Both sodium isopropoxide and potassium isopropoxide were found to be suitable for use in the transesterification process. A 20∶1 alcohol/TG molar ratio and a catalyst amount equal to 1% by weight (based on the TG amount) of sodium metal was the most cost-effective way to produce biodiesel fuel. The emissions from a diesel engine running on isopropyl esters made from soybean oil and yellow grease were investigated by comparing them with No. 2 diesel fuel and methyl esters. For nitrogen oxide emission, the difference between the biodiesel produced from soybean oil and yellow grease was greater than the difference between the methyl and isopropyl esters of both feedstocks. The other emissions from using isopropyl esters were about 50% lower in hydrocarbons, 10–20% lower in carbon monoxide, and 40% lower in smoke number when compared with No. 2 diesel fuel.     

V-Mo based catalysts for oxidative desulfurization of diesel fuel

Catalytic oxidative desulfurization (ODS) of a Mexican diesel fuel on a spent HDS catalyst, deactivated by metal deposits, was carried out during several reactive-batch cycles in order to study the catalytic performance to obtain low sulfur diesel. To explain catalytic activity results, Mo and/or V oxides supported on alumina pellets were prepared and evaluated in the ODS of a model diesel using tert-butyl hydroperoxide (TBHP) or H₂O₂ as oxidant. The catalytic results show that V-Mo based catalysts are more active during several ODS cycles using TBHP. The performance of the catalysts was discussed in terms of reduced species of vanadium oxide, prevailing on the catalysts, which increase the sulfone yield of refractory HDS compounds (DBT, 4-MDBT and 4,6-DMDBT).     

Ultra-deep oxidative desulfurization of diesel fuel by the Mo/Al2O3-H2O2 system: The effect of system parameters on catalytic activity

This work presents the results obtained in the development of Mo/γ-Al₂O₃ catalysts and their evaluation in the oxidative desulfurization (OD) process of diesel fuel using hydrogen peroxide as the oxidizing reagent. The catalysts were prepared by equilibrium adsorption using several molybdenum precursors and aluminas with different acidity values. They were characterized by Raman spectroscopy. The effect of the reaction time, reaction temperature, nature of solvent, concentration of solvent and hydrogen peroxide, content of molybdenum and phosphate in the catalysts were investigated. The results showed that the activity for sulfur elimination depends mainly on the presence of hepta- and octamolybdates species on the catalyst support and the use of a polar aprotic solvent. Likewise, the presence of phosphate markedly increases the sulfur elimination. In this way, it is possible to reduce sulfur level in diesel fuel from about 320 to less than 10 ppmw at 333 K and atmospheric pressure. Additionally, on the basis of the results obtained a mechanistic proposal for this reaction is described, as an oxidation mechanism by nucleophilic attack of the sulfur atom on peroxo species of hepta- and octamolybdates, but a mechanism involving the singlet oxygen presence can be discarded.