Alternative hydrocarbon solvents for cottonseed extraction: Plant trials

Hexane has been used for decades to extract oil from cottonseed and is still the solvent of choice for the edible-oil industry. Due to increased regulations as a result of the 1990 Clean Air Act and potential health risks, the edible-oil extraction industry urgently needs an alternate hydrocarbon solvent to replace hexane. Based on laboratory-scale extraction tests, two hydrocarbon solvents, heptane and isohexane, were recommended as potential replacements for hexane. A cottonseed processing mill with a 270 MT/day (300 tons/day) capacity agreed to test both solvents with their expander-solvent process. Extraction efficiencies of isohexane and heptane, judged by extraction time and residual oil in meal, refined and bleached color of miscella refined oil, and solvent loss, were comparable to that of hexane. However, fewer problems were encountered with the lower-boiling isohexane than with the higher-boiling heptane. With isohexane, the daily throughput increased more than 20%, and natural gas consumption decreased more than 40% as compared to hexane.     

气相色谱法测定四甘醇样品甲苯和正庚烷含量

建立了测定四甘醇样品中甲苯、正庚烷含量的气相色谱分析法。采用峰面积归一化法进行定量 ,测得甲苯和正庚烷的回收率分别为 98 32 %～ 1 0 2 87%和 97 81 %～ 1 0 2 84% ,相对标准偏差不大于 1 5 0 %和 1 97%。该法快速 ,准确 ,精密度高 ,简单易行 ,具有一定的实用价值。     

NOx emissions in n-heptane/air partially premixed flames

NO_x emissions in n-heptane/air partially premixed flames (PPFs) in a counter-flow configuration have been investigated. The flame is computed using a detailed mechanism that combines the Held’s mechanism for n-heptane and the Li and Williams’ mechanism for NO_x. The combined mechanism contains 54 species and 327 reactions. Based on a detailed analysis, dominant mechanisms responsible for NOx formation and destruction in PPFs are found to be thermal, prompt, and reburn mechanisms. The dominant reactions associated with these mechanisms are also identified. The effects of strain rate (a_s) and equivalence ratio (φ) on NO_x emissions are characterized for conditions in which the flame contains two spatially separated reaction zones; a rich premixed zone on the fuel side and a non-premixed zone on the air side. For most conditions, except for relatively high level of partial premixing, the NO formation rate in the non-premixed zone is significantly higher than that in the rich premixed zone. Within the rich premixed zone, the contribution of thermal NO to total NO_x is higher than that of prompt NO, while in the non-premixed zone, the prompt NO is the major contributor. The behavior is related to the transport of acetylene from the rich premixed to the non-premixed zone, and higher concentrations of CH, O, and OH radicals in the latter zone. A notable result in this context is that the existence of CH does not automatically imply that prompt NO will form. The existence of O and OH is also necessary, in addition to CH, to form prompt NO. The relative contributions of thermal and prompt mechanisms to total NO_x are generally insensitive to variations in a_s, but show strong sensitivity to variations in φ. There is a NO_x destruction region sandwiched between the rich premixed and the non-premixed reaction zones. The NO_x destruction occurs mainly through the reburn mechanism. The NO_x emission index (EINOx) is computed as a function of φ and a_s. These results are qualitatively in accord with previous numerical and experimental results for methane-air PPFs.     

Steam reforming of heptane in a fluidized bed membrane reactor

n-Heptane served as a model compound to study steam reforming of naphtha as an alternative feedstock to natural gas for production of pure hydrogen in a fluidized bed membrane reactor. Selective removal of hydrogen using Pd₇₇Ag₂₃ membrane panels shifted the equilibrium-limited reactions to greater conversion of the hydrocarbons and lower yields of methane, an intermediate product. Experiments were conducted with no membranes, with one membrane panel, and with six panels along the height of the reactor to understand the performance improvement due to hydrogen removal in a reactor where catalyst particles were fluidized. Results indicate that a fluidized bed membrane reactor (FBMR) can provide a compact reformer for pure hydrogen production from a liquid hydrocarbon feedstock at moderate temperatures (475-550 °C). Under the experimental conditions investigated, the maximum achieved yield of pure hydrogen was 14.7 moles of pure hydrogen per mole of heptane fed.     

Synthesis and kinetics of microgel in inverse emulsion polymerization of acrylamide

The kinetic behavior is studied in inverse emulsion polymerization of acrylamide. The polymerization rate in a micelle is proportional to the monomer concentration and the effective average radical concentration. When concentrations of monomer and radical are too low to proceed the polymerization only, some finite final conversion is obtained. The micelles of various sizes have different effective average radical concentrations at the same monomer concentration. Therefore, the polymerization rate and the final conversion are different for various sized micelles. The minimum amounts of emulsifier required to get stable state during reaction is 10 and 7 wt% (based on oil phase) in toluene and n-heptane systems, respectively. Phase inversion is observed with the increase of viscosity during polymerization. The final latex coagulates obviously in the toluene system even with 10 wt% of emulsifier, however, it can be improved more in the n-heptane system with 10 wt% of emulsifier. The crosslinking agent which copolymerizes with the monomer was supposed to remain in the interface of micelles. Such interfacial copolymerization not only hardens particles but improves the stability of the system also, therefore avoiding coagulation among particles. An increase in the content of crosslinking agent leads to a more uniform size of final particles. The microgel added in the alkyd resin decreases the drying time. The greater the amount of microgel added, the shorter the drying time.     

Experiment study of oxygenates impact on n-heptane flames with tunable synchrotron vacuum UV photoionization

In order to determine the effects of oxygenates on the fuel combustion, the experiments reported here investigated the premixed n-heptane flame chemistry. Heptane typifies the large alkanes that comprise the bulk of most hydrocarbon fuels. The specific flames were low-pressure (25 Torr), laminar, premixed flames of n-heptane/oxygen/argon and n-heptane/oxygenate/oxygen/argon at an equivalence ratio of 1.0. Two different fuel oxygenates (i.e. MTBE and ethanol) were tested, these are the main oxygenates used to improve motor vehicle fuel properties. The experiment was performed with tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam sampling mass spectrometry. Major species on the centerline of each flame were identified by measurements of the photoionization mass spectrum and photoionization efficiency (PIE) spectra. Mole fraction profiles of these species were derived at the selected photon energies near the ionization thresholds. A large amount of oxygenated intermediates was detected in the oxygenate containing flames. The species measurements indicated that MTBE and ethanol enhanced the heptane oxidation via different routes, and reduced the mole fractions of aromatics and cycloalkenes in varying degrees. The results are a useful databases for testing detailed chemical kinetic mechanism of fuel decomposition.     

Simulation d'une machine frigorifique à absorption fonctionnant avec des mélanges d'alcanes

We propose in this article an absorption chiller operating with binary alkane mixtures as an alternative to compression machines. It is an installation using low-level energy at a temperature below 150 °C (waste heat or solar energy) and operating with environmentally friendly fluids. Ten mixtures are considered and compared with two cooling mediums of the condenser and the absorber: the ambient air at 35 °C and the water at 25 °C. For an air-cooled chiller, the COP reaches 0.37 for the n-butane/octane system. This value remains 27% lower than that of an ammonia/water installation operating under the same conditions. For a water-cooling chiller, the n-butane/octane and propane/octane systems give a COP of about 0.63, which is comparable to that of the ammonia/water system. When n-butane is used as refrigerant, the machine works at a pressure under 5 bars, which is an advantage compared with machines working with ammonia/water mixtures.     

Catalytic behavior of Pt nanoparticles dealuminated Y-zeolite for some n-alkane hydroisomerization

Dealuminated zeolite Y-supported platinum was prepared adopting two dealumination methods, viz. fast (1, 3 and 6 h) and slow method (18 h). The content of Pt was constant at 0.5 wt% in all investigated catalysts. The prepared samples were characterized using TGA/DSC, XRD, FTIR techniques, nitrogen adsorption at −196 °C and TEM-connected with energy dispersive spectroscopy (EDS). Surface acidity was investigated via pyridine adsorption using FT-IR spectroscopy. The parent and dealuminated Y-zeolite samples were characterized by their microporous system. By increasing the dealumination time to 6 h, the increased specific surface area and total pore volume indicated a sort of pore opening taking place with an increase in the accessibility of nitrogen molecules. DSC confirmed the thermal stability of the dealuminated zeolite samples up to 800 °C. The prepared catalysts were tested through hydroisomerization reactions of n-hexane and n-heptane using a micro-catalytic pulse technique. Different catalytic behaviors could be distinguished for the dealuminated samples based on competitive reactions; hydro-isomerization, hydrocracking and cyclization. Slow dealumination leads to the most selective catalysts for hydroisomerization. n-Heptane was converted to higher extent than n-hexane; cracking process was more evident when the former was fed to the reactor.     

典型海相油和典型煤成油轻烃组成特征及地球化学意义

通过对塔里木盆地塔中隆起典型海相原油和吐哈盆地典型煤成油的轻烃组分、Mango参数和成熟度等分析后发现:2类原油轻烃组分含量差异明显，塔中隆起海相油富含正庚烷,吐哈盆地煤成油则富含甲基环己烷;塔中隆起海相油Mango参数K₁值分布在0.97~1.19之间，与Mango所报道的结果相一致，而吐哈盆地煤成油的K₁值却异常高（1.35~1.66）；塔中隆起海相油成熟度参数庚烷值(32.3%~45.4%)和异庚烷值(1.9~3.7)高于煤成油，已处于高成熟阶段，塔中隆起典型海相油的形成温度要明显高于吐哈盆地煤成油。