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Essentials for Chemical Engineers

Abstract

In the present investigation transalkylation of cumene with toluene was carried over a series of zeolite containing rare earth metals such as lanthanum (La), cerium (Ce), and praseodymium (Pr). The modified zeolites were further characterized by EDS, XRD, BET and TPD. The surface area and acidities of the modified zeolite catalysts were reported. The transalkylation reactions were carried out varying different parameters such as metal loading (2–10 wt%), temperature (448–573 K), reactant ratio (1–15), and space-time (3.2–9.29 kg h/kmol). Praseodymium-modified X zeolite (PrX) showed the highest cumene conversion (60 wt%) and cymene selectivity (65.7 wt%) compared to the other zeolites. The maximum cumene conversion and cymene selectivity were obtained at 523 K, the toluene-to-cumene ratio of 9:1, and space-time of 9.29 kg h/kmol. Mass transfer resistances were studied in the said reaction conditions.

Abstract

The velocity field and concentration distribution of three radial and axial impellers were studied in miscible liquid blending in a stirred tank reactor. To obtain a better insight into the applicability of each impeller system, the influence of velocity profiles on the generated concentration profiles was studied in detail for each impeller. Particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF) methods were used as the measurement techniques. In the turbulent regime, the Rushton turbine provided a homogeneous concentration field throughout the reactor by generating high radial and axial velocities in the bottom and upper zones of the tank. Operation comparisons of the up and down-pumping pitched blade turbines illustrated that the up-pumping turbine had a better performance in overall because of producing high turbulence in the upper half of the reactor. In this region, the radial concentration profile approached the final homogenized value in a shorter time. In the laminar regime, all three impellers acted in a similar way and produced a radial flow throughout the reactor.

Abstract

Green synthesized nanoparticles from plant extracts are being used in various biomedical applications, particularly because of their bactericidal and cytotoxic activities. In this study, silver nanoparticles (AgNPs) were successfully synthesized from the Rosmarinus officinalis aqueous leaf extract. Different spectroscopic and microscopic analyses such as ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, and energy-dispersive X-ray spectroscopy were performed to verify the biosynthesized AgNPs in our sample. The formation of nanosilver particles was preliminarily confirmed by UV-vis spectroscopy at 400 nm. The presence of carboxylic or amide groups was confirmed by FTIR, for the reduction of the silver ion. Transmission electron microscopy confirmed a particle size of 12–22 nm. The prepared AgNPs showed good antibacterial activity against human pathogens and good cytotoxic activity against the human breast cancer cell line (MDA MB 231). The nanoparticles prepared from R. officinalis can be used for various biomedical applications.

Abstract

The rubber peptizer 2,2′-dibenzoylaminodiphenyl disulfide is typically synthesized from C7H5NS, NaOH, H2SO4, and H2O2, but these reactants were replaced with C6H4ClNO2, C2H6O, Na2S, S, and N2H4·H2O, and these raw materials effectively improved the synthesis yield, reduced the number of synthetic steps, and made the synthetic process greener. Although the catalyst is difficult to recover, it effectively avoids using ethanol as a volatile organic solvent. The Aspen Plus method was used to simulate the key processes in the synthesis in the experimental conditions as the boundary conditions. The simulation results show that the feed ratio of C7H5NS, H2O2, and C7H5ClO directly determines the yield of the reaction, and the equivalents of NaOH, H2SO4, and Na2CO3 indirectly affect the yield of the reaction by changing the reaction environment and controlling the formation of byproducts. The temperature of the ring-opening reaction and the acylation reaction should be maintained within 110–120°C to maximize the yield. The oxidation reaction temperature also directly affects the reaction yield and should be kept below 40°C. The simulation results are consistent with practical industrial production conditions. Based on the developed green synthesis process and the optimal process parameters obtained from the simulation, the industrial-scale production of 10,000 tons of 2,2′-di benzoyl amino diphenyl disulfide was carried out. Compared with that of o-nitrochlorobenzene, the yield of 2,2′-dibenzoylaminodiphenyl disulfide increased from approximately 72% to more than 90%. Using this method instead of the original synthesis method avoids the use of o-nitrochlorobenzene, which is neurotoxic; Raney nickel as the metal catalyst, which is difficult to recycle with existing environmental protection technologies; and ethanol as the organic solvent, which is associated with environmental problems. The amine tail gas that is easily generated in the original synthesis method is not generated in this system, and the drying step is eliminated.

Abstract

Stabilization of zero-valent CuNi nanoparticles (NPs) supported on Cicer arietenum (CP) is reported here for the reduction and removal of persistent organic pollutants. The functional groups and interactions of NPs with the CP were determined by ATR-FTIR. The crystallinity, morphology, and the elemental composition of the samples were determined through powder XRD, FESEM, and EDS techniques, respectively. The XRD spectrum displayed a sharp crystalline peak at 43.9 for CuNi. The Cu and Ni zero-valent NPs displayed a peak at almost the same region, and thus, both the peaks are merged and appeared as a single peak. The chemical reduction/degradation of eight model pollutants, viz., 2-nitrophenol (ONP), 3-nitrophenol (MNP), 4-nitrophenol (PNP), 2,4-dinitrophenol (DNP), methyl orange (MO), congo red (CR), methylene blue (MB), and rhodamine B (RB) were carried out in the presence of NaBH4. The k app value of 0.1 mM 4NP was highest which was 1.8 × 10−1 min−1 while the slowest rate was observed for CR and RB with k app 5.5 × 10−3 and 5.4 × 10−3 min−1 respectively. This article helps in the removal of toxic organic pollutants through green supported NPs.

Abstract

Bioreactors are used in many biochemical industries to produce commercial life products such as medicines, enzymes, perfumes, paints and antibiotics. In the presented study, a specially shaped bioreactor has been designed, built and operated to increase the mass transfer coefficient. The constructed bioreactor, according to type of microorganisms, can provide high amounts of oxygen or carbon dioxide. Moreover, the manuscript was aimed at investigating the hydrodynamic properties of the bioreactor. The bioreactor was constructed from three parts including shower in upper part, middle section for mass transfer and bottom section as a reservoir. Liquid flow rate, shower holes diameter, aeration velocity and the middle part height of the bioreactor have been studied as factors influencing the hydrodynamics. The results showed that the highest mass transfer coefficient was 30.1 1/h which was achieved when the liquid flow rate, the shower holes diameter, aeration velocity and middle part height of the bioreactor were 280 mL/min, 2 mm, 0.03 vvm and 60 cm, respectively.

Abstract

Present study deals with the treatment of coking waste water (CWW) for the reduction of pollutants COD, phenol and cyanide using catalytic thermolysis (CT). For screening of catalyst and optimization of pH the CT was performed at 100 °C, pH = 3–11 using catalyst mass loading Cw = 3 g/L. In this study Cu (NO3)2 gave best performance. Further, CT was carried out using Cu (NO3)2 catalyst in high pressure reactor (HPR). The investigated parameters range were initial pH (pHi) = 3–11, Cw = 1–5 g/L, temperature (T) = 100–160 °C and treatment time (tR) = 6 h. The maximum percentage reduction for COD, phenol and cyanide were 83.33, 80.57 and 97.61%, respectively at pH = 9, Cw = 4 g/L, T = 140 °C and tR = 6 h. The CT did not give complete reduction of pollutant; therefore it was further treated using adsorption process as second stage treatment. The initial value of COD = 610 mg/L, phenol = 70.58 mg/L and cyanide = 0.45 mg/L were further reduced to 98.85, 100.00 and 55.55%, respectively, when adsorption process was performed at pH = 9, adsorbents dose Aw = 4 g/L, tR = 2 h. The response surface methodology (RSM) was performed through central composite design (CCD) for the designing of experiments and optimization of both the process. The kinetics studies of CT at HPR showed first order with respect to COD and phenol, and 0.24–0.608 order with respect to CW.

Abstract

Ultrasonic-assisted extraction (UAE) was performed to extract the total phenolic compounds from avocado (Persea americana Mill. var. Drymifolia; Lauraceae) leaves with different electric powers (UAE 0%, UAE 60%, and UAE 100%) and extraction times. Ultrasonic extraction parameters were optimized by using a mathematical model made by stepwise regression (SWR) for the determination of the maximum total phenolic content (TPC) and their antioxidant activity. Moreover, TPC extraction was modeled applying heterogeneous models to elucidate the involved mechanisms phenomena that determine the extraction rates. Optimization results found that the maximum value of TPC reached 48,732 mg GAE/100 g D.M. at 84.5% electric power and 29.7 min of extraction, which was superior to 0% electric power UAE. It was also found that the ultrasound causes the degradation of phenolic compounds, whereas the final extraction yield of TPC increases and their antioxidant activity decreased with the increase of ultrasound electric power. Proposed models gave a satisfactory quality of fit data using a second-order reaction for the degradation kinetics of TPC under ultrasound application. The estimated effective diffusivity values were in a range from 1.3889 × 10−11 m2/s to 2.2128 × 10−11 m2/s for the UAE 0% and UAE 100%, respectively. UAE significantly increased the extraction yield through the enhancement of the effective diffusivity, demonstrating that it is a promising technology to extract phenolic substances from avocado leaves.