On-line analysis of complex hydrocarbon mixtures using comprehensive two-dimensional gas chromatography

This paper discusses the first setup for on-line qualitative and quantitative comprehensive two-dimensional gas chromatography (GC × GC) of complex hydrocarbon mixtures. A built-in 4-port 2-way valve allows switching between flame ionization detection (FID) and time-of-flight mass spectrometry (TOF-MS) between runs, without the need to cool down and vent the MS. Proper selection of GC carrier gas flow rates enables maximal agreement between the obtained chromatograms in both configurations. For on-line analysis of reactor effluents, a dedicated sampling system allows automatic sampling of the hot reactor effluent gases and immediate injection of the sample on the GC × GC. To determine a complete effluent composition in a single run of the GC × GC, a subzero oven starting temperature was employed. Modulation is started when the oven temperature reaches 40 °C, thus dividing the chromatogram in a conventional 1D and a comprehensive 2D part. This work illustrates the mature and robust character of GC × GC, extending its capabilities from mere laboratory use to on-line routine analysis for industrial processes in the (petro-)chemical industry.     

Kinetic treatment of unsegmented flow systems : Part 2. Detailed Treatment of Flow-Injection Systems with Gradient Chamber

A kinetic model is utilized for a detailed mathematical treatment and experimental evaluation of single-channel and dual-channel flow injection systems that include a gradient chamber. The kinetic model includes three distinct stages in the process, namely clearing reactant from the gradient chamber by first portions of sample, continued entry of sample into the gradient chamber, and decrease of determinant concentration in the gradient chamber via dilution and reaction with reagent. Equations predict entirely different behavioral patterns for different conditions and these predictions are verified experimentally for a wide range of conditions. The data show that the variable-time kinetic model is superior to the titration models previously utilized to describe these flow systems. The principal limitation of the kinetic equations involves an assumption of plug flow that is not completely valid. The extent of deviations from ideal behavior depend on conditions, but are negligible at low concentrations (0–50 mmol l^-1) and can be 10% or larger at higher concentrations (100 mmol l^-1). While equations are not exact, they are useful in predicting performance characteristics for a variety of conditions and experimental approaches.     

Alcohols as petrochemicals

Efficient processes have been developed in recent years for the large-scale manufacture of alcohols from petrochemicals. These allow production of aliphatic alcohols both with short and with long alkyl groups more economically than was previously possible by fermentation. In this paper the most important principles and the technical execution of the hydration of olefins, the air oxidation of paraffins, and especially the synthesis reactions (e.g. the catalytic hydroformylation of olefins with carbon monoxide and hydrogen according to Roelen, the Reppe synthesis, and the Ziegler growth reaction with ethylene and triethylaluminum) are described.     

Robust flow-batch coulometric/biamperometric titration system: determination of bromine index and bromine number of petrochemicals

A flow–batch system was constructed and evaluated to perform coulometric titrations with biamperometric end point detection. The flow section of the system is employed for sampling by injecting a sample volume (50–300 μL) in a flow injection-like system. About 1.5 mL of a suitable carrier solution is delivered by a peristaltic pump in order to quantitatively transfer the sample to the system titration cell (2.0 mL total inner volume). The carrier contains the coulometric precursor for the titrant species. The cell contains two pairs of platinum electrodes used for coulometric generation of reagent and biamperometric detection and is actively stirred. The titrant species is generated and the titration is performed by the usual batch procedure with the excess of titrant being detected by biamperometry following the analysis of the titration curve. System operation is computer controlled and all operations are automated, including titration curve analysis and cell cleaning after the titration is ended. The system is characterized by its robustness because its operation does not depend on flow rates, and the work using coulometric methods which generate gases at the counter-electrode is not troublesome. The flow–batch system has been evaluated for determination of bromine index and bromine number (relative to the total reactive olefin content) in petrochemicals according to an ASTM procedure. Typical precision (R.S.D.) is between 0.5 and 6% for different petrochemicals whose bromine number/index vary from 1000 to 10 mg of bromine per 100 g of sample, respectively. Recoveries for standard additions are between 92 and 123% for 10 mg of Br₂ per 100 g increments and 98 to 101% for 100 mg per 100 g increments. Accuracy of the proposed system was evaluated against results obtained by the standard ASTM with no significant difference detected at 95% confidence level.     

Kinetic treatment of unsegmented flow systems : Part 1. Subjective and semiquantitative evaluations of flow-injection systems with gradient chamber

A variable-time kinetic model is used to evaluate a single-channel flow-injection system with gradient chamber that has been identified as a continuous-flow titration. A physical model, mathematical equations, computed concentration vs. time profiles, experimental data, and formal definitions are used to identify qualitative and quantitative features of the method that have not been apparent from the titration model for the system. It is shown that determinations can be performed with and without reactant in the flow stream and when reactant is in the flow stream, with and without reactant in the gradient chamber when the sample is introduced. It is shown that lowest concentrations with shortest cycle times can be achieved when determinations are performed without reagent in the gradient chamber initially. Characteristics unique to each of three different data processing options are used to evaluate the validity of equations presented. It is suggested that some methods previously identified as continuous-flow titrations are most accurately identified as variable-time kinetic methods, and it is shown that this semantic differentiation can provide improved insight into the methods and can expand the scope of the methods by suggesting new experimental approaches with potential advantages relative to previously described procedures.     

Polymer and its effect on environment

This is an era where plastic pollution is increasing hazardously. Plastics are spreading all over the environment due to this it's a big threat to the equilibrium of the environment and health of the human beings. Its not due to their properties but it is also a strong carrier of pesticides, poly aromatic hydrocarbons, diphenyl, pharmaceutical products etc. Majorly plastics are being used everywhere like in packaging, water bottles etc. We have about to reach the stage where we require to produce biodegradable or recyclable plastic. It reduces the usage of oil, CO₂ emission and reduces the quantity of waste to be disposed. Phthalates, BPA and others should be banned in plastic products which are in direct contact with food, children and bio-degradable plastics should be more used. Our study focused on varieties of plastics, its hazardous impact on the environment especially on the environment, its recycling strategies and use of biodegradable materials.