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Cetane Number (cetane + number)
Selected AbstractsBiodiesel production by direct methanolysis of oleaginous microbial biomassJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2007Bo Liu Abstract Biodiesel is a renewable fuel conventionally prepared by transesterification of pre-extracted vegetable oils and animal fats of all resources with methanol, catalyzed by strong acids or bases. This paper reports on a novel biodiesel production method that features acid-promoted direct methanolysis of cellular biomass of oleaginous yeasts and filamentous fungi. The process was optimized for tuning operation parameters, such as methanol dosage, catalyst concentration, reaction temperature and time. Up to 98% yield was reached with reaction conditions of 70 °C, under ambient pressure for 20 h and a dried biomass to methanol ratio 1:20 (w/v) catalyzed by either 0.2 mol L,1 H2SO4 or 0.4 mol L,1 HCl. Cetane numbers for these products were estimated to range from 56 to 59. This integrated method is thus effective and technically attractive, as dried microbial biomass as feedstocks omits otherwise tedious and time-consuming oil extraction processes. Copyright © 2007 Society of Chemical Industry [source] A hybrid density functional theory study of the low-temperature dimethyl ether combustion pathways.ISRAEL JOURNAL OF CHEMISTRY, Issue 2-3 2002I: Chain-propagation Dimethyl ether (DME) has been proposed to be a promising alternative to conventional diesel fuel because of its favorable compression ignition property (high cetane number) and its soot-free combustion. A radical chain mechanism for hydrocarbon autoignition has been proposed for DME at low temperatures. In this mechanism, the chain initiation step consists of DME undergoing hydrogen abstraction by a highly reactive species (typically ·OH). The CH3O·H2 created in the initiation step then combines with O2; the subsequent CH3OCH2OO· radical is involved in a Lindemann-type mechanism, which can lead to the production of formaldehyde (CH2 = O) and ·OH. This concludes the chain-propagating step: the one ·OH produced then sustains the chain-reaction by creating another CH3O·H2. A relatively stable intermediate (·CH2OCH2OOH), formed via isomerization of CH3OCH2OO· in the chain-propagation step, can combine with a second O2 to produce a radical (·OOCH2OCH2OOH) that can potentially decompose into two ·OH radical (and other products). This path leads to chain-branching and an exponential increase in the rate of DME oxidation. We have used spin-polarized density functional theory with the Becke-3-parameter Lee,Parr,Yang exchange-correlation functional to calculate the structures and energies of key reactants, intermediates, and products involved in (and competing with) the chain-propagating and chain-branching steps of low-temperature DME oxidation. In this article, Part I, we consider only the chain-propagation mechanism and its competing mechanisms for DME combustion. Here, we show that only certain conformers can undergo the isomerization to ·CH2OCH2OOH. A new transition state has been discovered for the disproportionation reaction ·CH2OCH2OOH , 2CH2O + ·OH in the chain-propagating step of DME autoignition that is much lower than previous barriers. The key to making this decomposition pathway facile is initial cleavage of the O,O rather than the C,O bond. This renders all transition states along the chain-propagation potential energy surface below the CH3O·H2 + O2 reactants. In contrast with the more well-studied CH3·H2 (ethyl radical) + O2 system, the H-transfer isomerization of CH3OCH2OO· to ·CH2OCH2OOH in low-temperature DME oxidation has a much lower activation energy. This is most likely due to the larger ring strain of the analogous transition state in ethane oxidation, which is a five-membered ring opposed to a six-membered ring in dimethyl ether oxidation. Thus low-temperature ethane oxidation is much less likely to form the ·ROOH (where R is a generic group) radicals necessary for chain-branching, which leads to autoignition. Three competing reactions are considered: CH3O·H2 , CH2O + ·CH3; ·CH2OCH2OOH , 1,3-dioxetane + ·OH; and ·CH2OCH2OOH , ethylene oxide + HOO·. The reaction barriers of all these competing paths are much higher in energy (7,10 kcal/mol) than the reactants CH3O·H2 + O2 and, therefore, are unlikely low-temperature paths. Interestingly, an analysis of the highest occupied molecular orbital along the CH3O·H2 decomposition path shows that electronically excited (1A2 or 3A2) CH2O can form; this can also be shown for ·CH2OCH2OOH, which forms two formaldehyde molecules. This may explain the luminosity of DME's low-temperature flames. [source] Light FCC gasoline olefin oligomerization over a magnetic NiSo4/,-Al2o3 catalyst in a magnetically stabilized bedAICHE JOURNAL, Issue 3 2009Ying Peng Abstract Magnetic NiSO4/,-Al2O3 catalysts were prepared by impregnating NiSO4 solutions onto the ,-Al2O3 support containing a magnetic material of Fe3O4. Characterization by XRD, NH3 -TPD, and thermal analysis showed that the magnetic NiSO4/,-Al2O3 catalyst with a nickel content of 7.0% by weight had a monolayer dispersion of NiSO4 and the largest number of moderate strength acid sites, and a high specific saturation magnetization. The magnetic catalyst was evaluated for light FCC gasoline olefin oligomerization in both fixed-bed and magnetically stabilized bed (MSB) reactors. Comparing with that in the fixed-bed reactor, the optimal reaction temperature in the MSB lowered to 443 K, and its space velocity ranged broadly from 2.0 to 6.0 h,1. The sulfur-free diesel distillate produced by operation of the MSB for 100 h had higher cetane number and good low-temperature flow property, which illuminates a promising application of the MSB to manufacture clean diesel fuels with high productivity and flexibility. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] The gas-phase oxidation of n -hexadecaneINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2001R. Fournet Since n -hexadecane or cetane is a reference fuel for the estimation of cetane numbers in diesel engines, a detailed chemical model of its gas-phase oxidation and combustion will help to enhance diesel performance and reduce the emission of pollutants at their outlet. However, until recently the gas-phase reactions of n -hexadecane had not been experimentally studied, prohibiting a validation of oxidation models which could be written. This paper presents a modeling study of the oxidation of n -hexadecane based on experiments performed in a jet-stirred reactor, at temperatures ranging from 1000 to 1250 K, 1-atm pressure, a constant mean residence time of 0.07 s, and high degree of nitrogen dilution (0.03 mol% of fuel) for equivalence ratios equal to 0.5, 1, and 1.5. A detailed kinetic mechanism was automatically generated by using the computer package (EXGAS) developed in Nancy. The long linear chain of this alkane necessitates the use of a detailed secondary mechanism for the consumption of the alkenes formed as a result of primary parent fuel decomposition. This high-temperature mechanism includes 1787 reactions and 265 species, featuring satisfactory agreement for both the consumption of reactants and the formation of products. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 574,586, 2001 [source] | ||||||||||