Azhagapillai Prabhu

Immobilization of enzymes on inorganic supports such as silica and carbon materials is an effective approach for chemical surface modification. In this work, hierarchical zeolite (HZ-SAPO's) materials were fabricated by a modified method, and mesoporous carbon (CMK-3) was synthesized using the SBA-15 mesoporous silica as a template. A variety of biocatalysts was prepared using HZ-SAPO with CMK to furnish the nanocomposite biocatalyst. The functionalization of amine group with APTES was done which was further immobilized by Soybean Peroxidase (SBP) enzyme. The material was subjected to a comprehensive characterization process utilizing numerous systematic methods, including X-ray diffraction, N₂ adsorption–desorption isotherms, Raman spectroscopy, scanning electron microscopy, high-resolution transmittance electron microscopy, and attenuated total reflectance Fourier transform infrared spectroscopy. The pH effect on the immobilized enzyme was examined and compared to that of SBP. Further, the assessment of repeated usability of immobilized SBP with successive cycles was carried out.

Biowaste utilization as a carbon source and its transformation into porous carbons have been of great interest to promote environmental remediation owing to biowaste's cost-effectiveness and useful physicochemical properties. In this work, crude glycerol (CG) residue from waste cooking oil transesterification was employed to fabricate mesoporous crude glycerol-based porous carbons (mCGPCs) using mesoporous silica (KIT-6) as a template. The obtained mCGPCs were characterized and compared to commercial activated carbon (AC) and CMK-8, a carbon material prepared using sucrose. The study aimed to evaluate the potential of mCGPC as a CO₂ adsorbent and demonstrated its superior adsorption capacity compared to AC and comparable to CMK-8. The X-ray diffraction (XRD) and Raman results clearly depicted the structure of carbon nature with (002) and (100) planes and defect (D) and graphitic (G) bands, respectively. The specific surface area, pore volume, and pore diameter values confirmed the mesoporosity of mCGPC materials. The transmission electron microscopy (TEM) images also clearly revealed the porous nature with the ordered mesopore structure. The mCGPCs, CMK-8, and AC materials were used as CO₂ adsorbents under optimized conditions. The mCGPC adsorption capacity (1.045 mmol/g) is superior to that of AC (0.689 mmol/g) and still comparable to that of CMK-8 (1.8 mmol/g). The thermodynamic analyses of the adsorption phenomena are also carried out. This work demonstrates the successful synthesis of a mesoporous carbon material using a biowaste (CG) and its application as a CO₂ adsorbent.

Zeolite-based molecular sieves are applied in industrial dehydration units for their high water uptake capacities and extremely low equilibrium pressure of water vapor. During their operational life, they tend to lose their water vapor adsorption capacity slowly. To optimize the usage of molecular sieves in dryer units, it is vital to understand the mechanism(s) leading to deactivation. In this work, the capacity loss was studied by exposing LTA- and FAU-type zeolites to methanol and heptane vapors under relatively harsh conditions using repetitive adsorption/regeneration cycles. A simple microflow unit was designed and used for the deactivation experiments. The water vapor adsorption capacity of the resulting samples was measured using a gravimetric analyzer. In addition, they were characterized by classic XRD, ¹³C NMR, and TGA techniques. The crystallinity of fresh and spent zeolite XRD patterns was not drastically affected even after exposure to the contaminants. It was found that methanol easily gave rise to a severe loss of water vapor adsorption capacity, much more so than heptane. Water vapor uptake in the methanol exposed samples is ∼50% lower than that for the fresh zeolites. This is attributed to nonvolatile, residual hydrocarbons.

Mesoporous Al‐SBA‐15 (Si/Al = 25) catalysts were synthesised by the ultrasonic (US) irradiation method at different time durations (1, 3, and 5 h) using the pluronic P123 triblock copolymer as a template. The synthesised catalysts were examined in detail by XRD, ICP‐AES, N₂ adsorption‐desorption, SEM, TEM, FT‐IR, and TGA characterization techniques. The characterization results reveal that the catalysts possess a well‐ordered hexagonal mesoporous structure. The catalytic activity of synthesised materials was investigated in the tert-butylation of ethylbenzene at different reaction conditions, and their identified products are para-tert‐butylethylbenzene (p-tert‐BEB) and meta-tert‐butylethylbenzene (m-tert‐BEB). It was found that high ethylbenzene conversion (69%) is achieved at 200°C with high selectivity towards p-tert‐butylethylbenzene (80%). The optimum feed ratio (ethylbenzene: t‐butyl alcohol) was 1 : 2, and the feed rate was 2 ml/h for high conversion and product selectivity. All these synthesised Al‐SBA‐15 (US) catalysts are compared with hydrothermally synthesised Al‐SBA‐15 (HT) at the same reaction conditions.

Benzene, toluene, and m-xylenes are some of the pollutants in the environment that may harm human health. These fugitive volatile organic compounds (VOC) emissions from the refineries and petrochemical industries are perennial, although at low concentrations in ppm levels. On similar grounds, the separation of benzene, toluene, and m-xylene compounds (BTX) from the feed gas of the sulfur recovery unit in natural gas processing industries is critical, as it is known to severely poison the catalyst in the Claus process. In this connection, a new hybrid material was synthesized using a precursor (metal-organic framework (MOF)) and silica aerogels (SA). The precursor (ZIF-8) proportion was varied to understand its effect, on the structural and adsorption characteristics. Various advanced analytical characterization was performed to understand the physicochemical characteristics of the synthesized material. Additionally, the synthesized materials were subjected to gas-phase adsorption of BTX to generate the adsorption isotherm at 25 °C. The hybrid material SA-ZIF-8 (20%) having a ZIF-8 proportion of 20% were found to have better adsorption capacity than the virgin ZIF-8 and silica aerogel adsorbents. The maximum adsorption capacity near the 90% saturation vapor pressure corresponds to 337 mg/g, 227 mg/g, and 263 mg/g at 25 °C for BTX, respectively.

Benzene is one of the aromatic hydrocarbons that are co‐absorbed with the acid gases during amine scrubbing and are carried over to the catalytic reactors in the sulfur recovery unit where they crack and deactivate the catalyst. As a solution, adsorption of benzene using porous adsorbents is being considered as a suitable process for removal. The present work considers carbon based porous adsorbents as potential adsorbents and attempts to screen the large pool of adsorbents. Preliminary screening was made using information in open literature and structural characteristics, before the adsorbents were subjected to gas phase benzene adsorption. The pool of porous carbons screened included highly acidic sulfonated carbons, ordered mesoporous carbons (OMCs) and various commercial activated carbons (ACs). Among the pool of porous carbons, mesoporous carbon identified as AC1, was found to possess the highest adsorption capacity for benzene with heat of adsorption capacity of 20–32 KJ/mol. It was found that it is possible to regenerate the benzene adsorption capacity of AC1 and a benzene adsorption capacity of about 14 mmol/g for the mesoporous carbon was found to be far superior to the adsorption capacities reported in literature. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S93–S99, 2019