A simple plug-flow model was developed to study the deactivation mechanisms of hydroprocessing catalysts in atmospheric residue desulfurization (ARDS) units. The three stages of catalyst deactivationsat the start of the run, middle of the run, and end of the runsare considered. The catalyst deactivation is mainly due to metal and coke deposition. The model parameters considered are the unit temperature, fluid velocity, reaction rate constant, catalyst combination, catalyst bed length, and feed concentration of sulfur, metals, and asphaltenes. The simulated results compared very well with our laboratory data for a long catalyst life test operated under constanttemperature mode. The model is further applied to a parametric study that examines the effects of space velocity, unit temperature, and maximum metal capacity on the performance of catalyst systems. A constant-sulfur-mode simulation is also given.

Polypropylene (PP) is a commodity material that has been increasingly used in different industries in the past two decades due to its versatile properties when enhanced with additives. Homo polypropylene, in general, has weak mechanical properties and limited chemical resistance; thus, using a different type of fillers to adjust such properties to fit the required applications opened a large market for this commodity. Understanding the interface constituent between the polymer matrix and the added filler and the nucleation behavior is a key to fine control of the enhancement of PP properties. In this study, PP was incorporated with nano calcium carbonate (CaCO3) at 2 and 5 wt% in the presence of maleic anhydride (MAH) to overcome the weak interface due to low polymer polarity. The mix was compounded in a twin screws extruder at a temperature range of 180–200 °C ; then, the prepared samples were left to dry for 24 h at 25 °C. Nuclear Magnetic Resonance (NMR) was used to study the interface adhesion of the nanofiller and the curved revealed that at 2% of nano CaCO3 PP structure remained the same and the nano experienced good adhesion to the polymer matrix. The mechanical impact resistance results showed a real enhancement to the polymer matrix of the nanocomposite by 37%. Moreover, DSC results showed a faster crystallinity rate due to the nanofiller acting as a nucleating agent and rheology tests indicated that low content of nano additive (2%) has better processability behavior, with suitable viscosity complex values at high frequencies.

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Soil contamination by hydrocarbons due to oil spills has become a global concern and it has more implications in oil producing regions. Biostimulation is considered as one of the promising remediation techniques that can be adopted to enhance the rate of degradation of crude oil. The soil microbial consortia play a critical role in governing the biodegradation of total petroleum hydrocarbons (TPHs), in particular polycyclic aromatic hydrocarbons (PAHs). In this study, the degradation pattern of TPHs and PAHs of Kuwait soil biopiles was measured at three-month intervals. Then, the microbial consortium associated with oil degradation at each interval was revealed through 16S rRNA based next generation sequencing. Rapid degradation of TPHs and most of the PAHs was noticed at the first 3 months of biostimulation with a degradation rate of pyrene significantly higher compared to other PAHs counterparts. The taxonomic profiling of individual stages of remediation revealed that, biostimulation of the investigated soil favored the growth of Proteobacteria, Alphaprotobacteria, Chloroflexi, Chlorobi, and Acidobacteria groups. These findings provide a key step towards the restoration of oil-contaminated lands in the arid environment.

Soil contamination by polycyclic aromatic hydrocarbons (PAHs) and heavy metals is a major concern affecting soil quality. Bioremediation is an efficient approach to decontaminate these pollutants while posing the lowest risk to the environment. This technique is based on identifying microorganisms with the metabolic potential to degrade the pollutants. In this study, the physiochemical properties of oil-contaminated soils in Kuwait were investigated. The soil had alkaline pH (8.36) with a salinity of 0.08% and PAHs compounds were detected at high concentrations (pyrene, 1212 mg/kg), (phenanthrene, 710 mg/kg) and (fluorene 326 mg/kg). Heavy metals such as iron, aluminum, sodium, magnesium, vanadium, copper, etc., were also detected in the soil samples. Then, selective screening for PAH degraders was performed and assessed by colony forming units (CFU) and 16S rDNA gene sequences to determine their growth profiles and taxonomical identification. In total, 21 strains were selected for their resistance to PAHs, which include Pseudomonas (9), Burkholderia (6), Bacillus (2), Bordetella (1), Microbacterium (1), Micrococcus (1), and Kocuria (1). Among all, the growth by Burkholderia sp. P14, in the presence of phenanthrene and fluorene, has maintained a stationary phase from day 5 to 8 with a 6 log CFU/ml bacterial count. The draft genome of the Burkholderia contaminans P14 strain comprised 68 contigs with 8,584,157bp, 66% GC content, 4 rRNA and 75 tRNA. A total of 80 genes were involved in the degradation of the benzoate, naphthalene, and PAH . Genes that encode the PAH degradation were clustered into four distinct groups, including pcaHG, pcaB, pcaIJ, and pcaKFR and were found to be in contigs 5, 11, 8 and 13 of B. contaminans P14, respectively. KEGG analysis suggested that PAHs were degraded in P14 via the protocatechuate and catechol branches of the β-ketoadipate protocatechuate degradation pathway. The genomic island regions in P14 differed from those in the reference genome of B. contaminans M14, indicating the novelty and genomic recombination of the strain. Genomic information on P14 has helped clarify the molecular mechanisms involved in PAH catabolism. Burkholderia contaminans P14 strain will enhance the bioremediation of oil-contaminated soils.