Performance of a micro engine with heptane as working fluid

A micro Newcomen engine is proposed. To overcome the problems of friction and leakage of the micro mechanical parts during engine’s operation, we use a flexible ripple tube to integrate piston and cylinder into one monolithic part. Heptane is used as the working fluid, and it works in the two-phase condition for higher energy output density per thermodynamic cycle. In the experiment, the prototype engine is tested under different operational conditions. It works continuously and generates the net mechanical work of 0.833 J per cycle with an efficiency of 2.77% in the maximum. The experimental results prove its feasibility. However, the prototype engine still requires further improvement and optimization for better performance.     

Rehydrogenation performance of an MgH2–Nb2O5 system modified by heptane and acetone

An MgH₂ + 1 mol% Nb₂O₅ system was modified by heptane and acetone through a high-energy ball milling process, and their rehydrogenation performances were investigated. XRD results indicated that except MgH₂ and Nb₂O₅ phases Mg and MgO phases existed after ball milling. The rehydrogenation results showed that after modification by heptane the capacity increased from 3.0 wt% and 4.2 wt% to 5.0 wt% and 5.5 wt% within 110 s at 523 K and 573 K, respectively. The hydriding rate increased from 0.08 wt%/s after 20 s to 0.22 wt%/s after 10 s at 523 K. However, after modification by acetone it only absorbed 1.8 wt% and 2.0 wt% of hydrogen even within 8000 s at 523 K and 573 K, respectively. Rietveld refinement results indicated that after modification by the heptane the content of MgO was reduced from 6.8 wt% to 4.2 wt%, while after the modification by the acetone the content of MgO was significantly increased from 6.8 wt% to 23.8 wt%. The difference in the rehydrogenation performance was believed to be attributed to the different contents of the MgO phase, which led to the difference in the contents of the MgH₂ phase. It implied that the heptane acted as a solvent without oxygen element in it to prevent the MgH₂ + Nb₂O₅ system from aggregation, crystallization and oxidation. It suggested heptane was suitable for the improvement of the rehydrogenation performance of MgH₂ system.     

Analysis of heptane autothermal reformer to generate hydrogen for fuel cell applications

In this paper, reaction engineering principles are utilized to analyze process conditions for producing sufficient hydrogen in a heptane autothermal reformer for generating 1 kW of power in a fuel cell. It is shown that operating the reformer adiabatically results in a sharp decrease in temperature due to endothermic reactions, which results in low conversion of heptane. For this reason, a heating jacket is added to the reformer where heptane is combusted to provide heat for the endothermic reactions. It is observed that when the reactor is operated non-isothermally, it is possible to get complete conversion of heptane and produce sufficient hydrogen to generate 1 kW of power via a fuel cell.     

An experimental and modeling study of surrogate mixtures of n-propyl- and n-butylbenzene in n-heptane to simulate n-decylbenzene ignition

This paper presents experimental data for the oxidation of two surrogates for the large alkylbenzene class of compounds contained in diesel fuels, namely n-decylbenzene. A 57:43 molar% mixture of n-propylbenzene:n  -heptane in air (21% _O2${\mathrm{O}}_2$, 79% _N2${\mathrm{N}}_2$) was used in addition to a 64:36 molar% mixture of n-butylbenzene:36% n-heptane in air. These mixtures were designed to contain a similar carbon/hydrogen ratio, molecular weight and aromatic/alkane ratio when compared to n-decylbenzene. Nominal equivalence ratios of 0.3, 0.5, 1.0 and 2.0 were used. Ignition times were measured at 1 atm in the shock tube and at pressures of 10, 30 and 50 atm in both the shock tube and in the rapid compression machine. The temperature range studied was from approximately 650–1700 K. The effects of reflected shock pressure and equivalence ratio on ignition delay time were determined and common trends highlighted. It was noted that both mixtures showed similar reactivity throughout the temperature range studied. A reaction mechanism published previously was used to simulate this data. Overall the reaction mechanism captures the experimental data reasonably successfully with a variation of approximately a factor of 2 for mixtures at 10 atm and fuel-rich and stoichiometric conditions.     

SEPARATION OF AROMATIC AND ALIPHATIC HYDROCARBONS WITH IONIC LIQUIDS

Naphtha cracker feeds may contain 10–25 wt% aromatic compounds. Removal of these aromatic compounds from the feed to the cracker would offer several advantages: higher capacity, higher thermal efficiency, and less coke formation. In this work, we investigated the separation of toluene from heptane by extraction with ionic liquids.

Several ionic liquids are suitable for extraction of toluene from toluene/heptane mixtures. The selectivities for the aromatic/aliphatic hydrocarbon separation with all ionic liquids tested increase with decreasing aromatic content in the feed. The toluene/heptane selectivities at 10% toluene in the feed at T = 40°C and 75°C with several ionic liquids ([emim]HSO₄, [mmim] methylsulfate, [emim] ethylsulfate, [bmim]BF₄, [emim] tosylate, [mebupy]BF₄, and [mebupy] methylsulfate) are a factor of 1.5–2.5 higher than those obtained with sulfolane, which is a conventional solvent for the extraction of aromatic hydrocarbons from a mixed aromatic/aliphatic hydrocarbon stream. The three most suitable ionic liquids from the ionic liquids tested for the separation of aromatic and aliphatic hydrocarbons are [mebupy]BF₄, [mebupy]CH₃SO₄, and [bmim]BF₄ and at 75°C also [emim] tosylate. The ionic liquid [mebupy]BF₄ is selected for further testing in our extraction pilot plant.

Because ionic liquids have a negligible vapor pressure, evaporating the extracted hydrocarbons from the ionic liquid phase could achieve the recovery of the ionic liquid. A conceptual process scheme for the extraction has been set up. Preliminary calculations show that both the investment costs and the energy costs will be considerably lower with ionic liquids than with sulfolane as the solvent.     

Tributylamine as an initiator for cracking of heptane

Tributylamine (TBA) was found to be effective in promoting the cracking of heptane. The conversion of heptane and the yield of gas product are both distinctly accelerated. The selectivity of propylene is remarkably promoted compared with that by cracking pure heptane at 550 °C, while at the higher temperature of 600 °C, the selectivity of all gas products changes very little. The cause to this effect could be that the butyl radical and its derivatives derived from TBA capture hydrogen from the heptane.     

Clay minerals in nonaqueous extraction of bitumen from Alberta oil sands: Part 1. Nonaqueous extraction procedure

A non-aqueous bitumen extraction process was studied where only toluene and heptane, with no water additions, were used to extract bitumen from two Alberta oil sands ore samples. One sample had a high bitumen (13.5 wt.%) and low fines (5.3 wt.% < 45 μm) contents, while the other sample had an intermediate bitumen (10.5 wt.%) and high fines (23.3 wt.%) contents. Bitumen recovery and product quality were measured under different process conditions such as the ratio of toluene to heptane and settling time. The Dean Stark procedure was used to determine the solids, bitumen and water contents of the extraction products. In addition, the water content was determined by the Karl Fischer titration method. High bitumen recovery was obtained for both oil sands ore samples although the high fines ore sample was more sensitive to the extraction conditions, especially the toluene to heptane ratio. A product with high purity, containing more than 99.5 wt.% bitumen on a solvent-free basis, was produced at room temperature under the optimum extraction conditions tested. The optimum settling time to achieve a pure product was less than 10 min, based on solids and water contents in the supernatant.     

Thermodynamic feasibility study of absorption diffusion machine working with hydrocarbons

We propose in this work a thermodynamic feasibility study of absorptiondiffusion refrigerating machine working with hydrocarbon mixtures. We used a machine of low power (300 W) that operates with generator temperatures lower than 150 °C (fossil energy or solar energy can be used) and where the condenser and absorber temperatures are taken equal to 42 °C. The inert gas used is helium and the total functioning pressure is about 17.5 bars. A modeling on suitable software was made to simulate the machine functioning for four binary mixtures which are: propylene/hexane, propylene/heptane, propylene/octane and propylene/nonane. The validation of our model was made by comparison with the results taken from literature and the optimal operating conditions are determined.     

气相色谱法测定工业纯苯中微量正庚烷含量

选用合适的色谱柱,重新建立气相色谱分析方法,准确测定工业纯苯中微量正庚烷含量,满足公司原料分析计划的检测要求。通过选择色谱柱型号,改变柱温、载气流速等参数,优化气相色谱条件,使杂质组分达到最佳分离。采用色谱柱为CP7773毛细管柱,氮气为载气,分流比为20∶1,运用程序升温模式,外标法测定正庚烷含量。得到线性回归方程为y=1.011x+0.666,相关系数r=0.999,标准偏差小于0.4(n=8),平均回收率为99.80%~101.20%。