Opportunities and challenges for the application of post-consumer plastic waste pyrolysis oils as steam cracker feedstocks: To decontaminate or not to decontaminate?

Thermochemical recycling of plastic waste to base chemicals via pyrolysis followed by a minimal amount of upgrading and steam cracking is expected to be the dominant chemical recycling technology in the coming decade. However, there are substantial safety and operational risks when using plastic waste pyrolysis oils instead of conventional fossil-based feedstocks. This is due to the fact that plastic waste pyrolysis oils contain a vast amount of contaminants which are the main drivers for corrosion, fouling and downstream catalyst poisoning in industrial steam cracking plants. Contaminants are therefore crucial to evaluate the steam cracking feasibility of these alternative feedstocks. Indeed, current plastic waste pyrolysis oils exceed typical feedstock specifications for numerous known contaminants, e.g. nitrogen (∼1650 vs. 100 ppm max.), oxygen (∼1250 vs. 100 ppm max.), chlorine (∼1460vs. 3 ppm max.), iron (∼33 vs. 0.001 ppm max.), sodium (∼0.8 vs. 0.125 ppm max.)and calcium (∼17vs. 0.5 ppm max.). Pyrolysis oils produced from post-consumer plastic waste can only meet the current specifications set for industrial steam cracker feedstocks if they are upgraded, with hydrogen based technologies being the most effective, in combination with an effective pre-treatment of the plastic waste such as dehalogenation. Moreover, steam crackers are reliant on a stable and predictable feedstock quality and quantity representing a challenge with plastic waste being largely influenced by consumer behavior, seasonal changes and local sorting efficiencies. Nevertheless, with standardization of sorting plants this is expected to become less problematic in the coming decade.

Quantitative on-line analysis of sulfur compounds in complex hydrocarbon matrices.

An improved method for on-line measurement of sulfur containing compounds in complex matrices is presented. The on-line system consists of a specifically designed sampling system connected to a comprehensive two-dimensional gas chromatograph (GC×GC) equipped with two capillary columns (Rtx®-1 PONA×SGE BPX50), a flame ionization detector (FID) and a sulfur chemiluminescence detector (SCD). The result is an unprecedented sensitivity down to ppm level (1 ppm-w) for various sulfur containing compounds in very complex hydrocarbon matrices. In addition to the GC×GC-SCD, the low molecular weight sulfur containing compounds such as hydrogen sulfide (H2S) and carbonyl sulfide (COS) can be analyzed using a thermal conductivity detector of a so-called refinery gas analyzer (RGA). The methodology was extensively tested on a continuous flow pilot plant for steam cracking, in which quantification of sulfur containing compounds in the reactor effluent was carried out using 3-chlorothiophene as internal standard. The GC×GC-FID/-SCD settings were optimized for ppm analysis of sulfur compounds in olefin-rich (ethylene- and propylene-rich) hydrocarbon matrices produced by steam cracking of petroleum feedstocks. Besides that is primarily used for analysis of the hydrocarbon matrix, FID of the GC×GC-FID/-SCD set-up serves to double check the amount of added sulfur internal standard which is crucial for a proper quantification of sulfur compounds. When vacuum gas oil containing 780 ppm-w of elemental sulfur in the form of benzothiophenes and dibenzothiophenes is subjected to steam cracking, the sulfur balance was closed, with 75% of the sulfur contained in the feed is converted to hydrogen sulfide, 13% to alkyl homologues of thiophene while the remaining 12% is present in the form of alkyl homologues of benzothiophenes. The methodology can be applied for many other conversion processes which use sulfur containing feeds such as hydrocracking, catalytic cracking, kerogen evolution, bio-waste pyrolysis, supercritical water treatment, etc.

On-line Analysis of Nitrogen Containing Compounds in Complex Hydrocarbon Matrixes.

The shift to heavy crude oils and the use of alternative fossil resources such as shale oil are a challenge for the petrochemical industry. The composition of heavy crude oils and shale oils varies substantially depending on the origin of the mixture. In particular they contain an increased amount of nitrogen containing compounds compared to the conventionally used sweet crude oils. As nitrogen compounds have an influence on the operation of thermal processes occurring in coker units and steam crackers, and as some species are considered as environmentally hazardous, a detailed analysis of the reactions involving nitrogen containing compounds under pyrolysis conditions provides valuable information. Therefore a novel method has been developed and validated with a feedstock containing a high nitrogen content, i.e., a shale oil. First, the feed was characterized offline by comprehensive two-dimensional gas chromatography (GC × GC) coupled with a nitrogen chemiluminescence detector (NCD). In a second step the on-line analysis method was developed and tested on a steam cracking pilot plant by feeding pyridine dissolved in heptane. The former being a representative compound for one of the most abundant classes of compounds present in shale oil. The composition of the reactor effluent was determined via an in-house developed automated sampling system followed by immediate injection of the sample on a GC × GC coupled with a time-of-flight mass spectrometer (TOF-MS), flame ionization detector (FID) and NCD. A novel method for quantitative analysis of nitrogen containing compounds using NCD and 2-chloropyridine as an internal standard has been developed and demonstrated.

[Impact of oxygen toxic action on the erythrocyte membrane and possibility of estimating central nervous system function disturbances].

UNLABELLED: BACKGROUND/AIM; Prolonged exposure to hyperbaric oxygen leads to changes of erythrocytes shape as a consequence of toxic effects of oxygen on the erythrocyte membrane. The aim of this study was to examine the association between occurance of pathological forms of erythrocytes at different time from the start of hyperbaric oxygenation and the moment of convulsions occurrence, an interrelationship of different pathological forms of erythrocytes during exposure to hyperbaric oxygenation, as well as the correlation between the presence of ruptured erythrocytes and function of central nervous system (CNS) after completion of hyperbaric treatment. METHODS: Sixty laboratory mice, Mus musculus, were exposed to the wholly-oxygen pressure of 3.5 absolute atmospheres (ATA). Blood was collected at the 32nd, 34th, 36th, 38th and 40th minutes after the exposure to oxygen. Pathological forms of erythrocytes were examined by electron microscopy. A moment of convulsions occurrence was registered in all animals. After decompression neurological examinations of experimental animals were perfomed. The Pearson's coefficient of correlation, and linear regression equations for the parameters outlined in the aim of the study were calculated. RESULTS: Hyperbaric oxygen caused damages of erythrocytes at the 34th minute after beginning of the treatment. Various forms of abnormal red blood cells occured, and immediately before the occurrence of irreversible changes (erythrocyte membrane rupture) echinocyte shape was dominated. A significant correlation between the number of damaged red blood cells at 34th minute and their number at the 36th, 38th and 40th minute was found. Convulsions were diagnosed significantly earlier in mice with a greater number of damaged red blood cells (p < 0.01). There was a negative correlation between the number of irreversiblly damaged red blood cells (ruptured) at the 40th minute and neurological score in the studied animals (p < 0.05). CONCLUSION: The analysis of altered erythrocytes during hyperbaric oxygenation could predict a moment of seizures occurrence, and therefore the duration of the therapy with hyperbaric oxygen. Ehinocytes indicate impending rupture of red blood cells and a possible occurrence of seizures. An increased number of ruptured red blood cells may also even indicate the potential burden of CNS after cessation of hyperbaric oxygenation.

Uptake of ingested uranium after low "acute intake".

The uptake of uranium, ingested as a soluble compound, was studied by monitoring the uranium level in urine by inductively coupled plasma mass spectrometry and through measurement of an isotopic tracer. The high sensitivity of this method allows measurement of uranium levels in urine samples from each voiding, therefore more detailed biokinetic studies are possible. To simulate low "acute intake," five volunteers with "normal" levels (5-15 ng L(-1)) of uranium in urine ingested a grapefruit drink spiked with 100 microg of uranium (235U/238U = 0.245%) as uranyl nitrate, and the level of uranium in their urine after ingestion was monitored. Two techniques were applied to estimate the extent of exposure: a) uranium levels above the normal level for each volunteer; and b) the deviation from natural isotopic ratio. Results were normalized relative to the creatinine concentration, which served as an indicator of urine dilution, to reduce effects due to diurnal changes. The results clearly indicate that currently accepted bio-kinetic models overestimate the time between ingestion of dissolved uranium and its excretion in urine, the maximum of which was found to be around 6-10 h. The uptake fraction was in agreement with recent studies, i.e., 0.1-0.5% of the ingested uranium for four of the subjects but above 1.5% for the fifth, and well below the 5% reported in International Commission on Radiation Protection Publication 54. Finally, partial results from the isotope dilution study indicate that uranium absorbed through the intestine interchanges with uranium retained in body organs. The time scale of this process is quite short, and the acute exposure led to a minimum in the isotopic ratio within hours, while recovery back to natural abundance due to low chronic exposure takes several days.

Uranium in urine--normalization to creatinine.

"Spot samples" of urine are routinely used to monitor occupational exposure to uranium and other toxic heavy metals, such as mercury, lead, and cadmium. In the present work, it was shown that diurnal variations in the uranium concentration in different urine samples from the same individual could be quite large. However, these variations were in correlation to the creatinine level of the same samples, with values of R = 0.72-0.99, for the five subjects studied here. Thus, it is proposed here that uranium concentrations in "spot" urine samples be expressed in terms of ng uranium g(-1) creatinine rather than ng uranium L(-1). Once the 24-h creatinine level is estimated for the individual based on weight, height and age, the adjusted values can be used for determination of the internal dose of uranium.

Inductively coupled plasma mass spectrometry as a simple, rapid, and inexpensive method for determination of uranium in urine and fresh water: comparison with LIF.

A simple method, based on inductively coupled plasma mass spectrometry, for determination of uranium in urine at levels that indicate occupational exposure, is presented. Sample preparation involves a fifty-fold dilution of the urine by nitric acid (2% HNO3) and no other chemical treatment or separation. The analysis itself is completed in under 3 min. The analytical procedure is fully automated so that a technician may perform over 100 analyses per day. With proper control of the blank contribution, a lower limit of detection of 3 ng L(-1) in the original urine sample was achieved. Uranium concentrations in the range 6-30 ng L(-1) were found in urine samples of people that are not occupationally exposed. The validity of the results was demonstrated through measurement of standards, controlled uranium addition experiments and, at higher concentrations, by comparison with results obtained by an independent method based on laser induced fluorescence. The laser induced fluorescence technique was found to be sufficient for detection of occupational exposure at an action level of 1.5 microg L(-1). Use of internal standards, indium, and thallium, improved quantification by about 10%, but was not deemed necessary for routine analysis. The inductively coupled plasma mass spectrometry is also ideally suited for monitoring uranium in fresh water and drinking water, as no sample dilution is required and the lower limit of detection is below 0.15 ng L(-1).

[Electrophysiologic research on the anti-arrhythmia properties of bonnecor--a new dibenzazepine derivative]. / Elektrofiziologicheskoe issledovanie antiaritmicheskikh svoistv bonnekora--novogo proizvodnogo dibenzazepina.

A new dibenzepin derivative, bonnecor, showed marked antiarrhythmic and antifibrillation properties in anesthetized cats. One and 2 mg/kg doses of the drug reduce cardiac assimilation of imposed ventricular electric stimuli, increase ventricular fibrillation threshold with a strong and lasting effect and prevent arrhythmias and fibrillation due to 10-minute occlusion and subsequent reperfusion of the anterior descending branch of the left coronary artery. Experimental holding of atrial trabecular membrane potential in a frog, in conditions of a double saccharose bridge, showed bonnecor, in 5 X 10(-7) and 1 X 10(-6) g/ml concentrations, to inhibit rapid sodium inflow and slow calcium inflow. It is expected that bonnecor can be used clinically to control critical arrhythmias and prevent sudden cardiac death.