Recent membrane development for pervaporation processes

As primary feedstocks in the petrochemical industry, light olefins such as ethylene and propylene are mainly obtained from steam cracking of naphtha and short chain alkanes (ethane and propane). Due to their similar physical properties, the separations of olefins and paraffins-pivotal processes to meet the olefin purity requirement of downstream processing-are typically performed by highly energy-intensive cryogenic distillation at low temperatures and high pressures. To reduce the energy input and save costs, adsorptive olefin/paraffin separations have been proposed as promising techniques to complement or even replace cryogenic distillation, and growing efforts have been devoted to developing advanced adsorbents to fulfill this challenging task. In this Review, a holistic view of olefin/paraffin separations is first provided by summarizing how different processes have been established to leverage the differences between olefins and paraffins for effective separations. Subsequently, recent advances in the development of porous materials for adsorptive olefin/paraffin separations are highlighted with an emphasis on different separation mechanisms. Last, a perspective on possible directions to push the limit of the research in this field is presented.

Alternatives to Cryogenic Distillation: Advanced Porous Materials in Adsorptive Light Olefin/Paraffin Separations.

Tyrosinase is a natural enzyme and is often purified to only a low degree and it is involved in a variety of functions which mainly catalyse the o-hydroxylation of monophenols into their corresponding o-diphenols and the oxidation of o-diphenols to o-quinones using molecular oxygen, which then polymerizes to form brown or black pigments. The synthesis of o-diphenols is a potentially valuable catalytic ability and thus tyrosinase has attracted a lot of attention with respect to industrial applications. In environmental technology it is used for the detoxification of phenol-containing wastewaters and contaminated soils, as biosensors for phenol monitoring, and for the production of L-DOPA in pharmaceutical industries, and is also used in cosmetic and food industries as important catalytic enzyme. Melanin pigment synthesized by tyrosinase has found applications for protection against radiation cation exchangers, drug carriers, antioxidants, antiviral agents, or immunogen. The recombinant V. spinosum tryosinase protein can be used to produce tailor-made melanin and other polyphenolic materials using various phenols and catechols as starting materials. This review compiles the recent data on biochemical and molecular properties of microbial tyrosinases, underlining their importance in the industrial use of these enzymes. After that, their most promising applications in pharmaceutical, food processing, and environmental fields are presented.

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Microbial Tyrosinases: Promising Enzymes for Pharmaceutical, Food Bioprocessing, and Environmental Industry

Linde Type A (LTA) zeolite-based membranes have demonstrated excellent selectivity in pervaporation due to their unique structural framework and interaction with water. The development of LTA zeolite membranes for commercial application is limited by some parameters, particularly the complexity of the membrane preparation required to produce reproducible defect-free membranes and the high costs required for the membrane materials. In addition, the high content of Al in the zeolite framework makes the LTA zeolite membrane unsuitable for acidic conditions. A number of modification techniques have been proposed to produce a thin, defect-free, and high permselectivity LTA zeolite membrane with high reproducibility. Two major approaches are generally used to produce defect-free zeolite membranes, i.e. modifying either the seeding step or the synthesis process. Since the self-supported zeolite membrane has low mechanical stability, the LTA zeolite membrane is usually synthesized on an inorganic support to give better properties. Zeolite membrane costs can be reduced by several methods such as replacing the support, manufacturing a higher flux zeolite membrane, and fabricating a polymer–zeolite membrane. One should consider, however, that changing the support can dramatically influence and even reverse the obtained separation behavior. Despite various techniques used to prepare dense LTA zeolite membranes, a facile mass production technique with a highly reproducible result remains a significant challenge. To present a clear background for LTA zeolite and its performances in pervaporation, this paper includes a brief discussion on the recent trends related to LTA zeolite membranes. Some topics are discussed, including the features inherent to LTA zeolite, the transport phenomena in zeolite structures, preparation methods of LTA zeolite membranes, and the challenges associated with preparation. Furthermore, critical issues related to LTA zeolite membranes in pervaporation will be discussed to develop the topic further.

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LTA zeolite membranes: current progress and challenges in pervaporation

Separation of thiophene/n-heptane mixtures using PEBAX/PVDF-composited membranes via pervaporation

Desulfurization of gasoline has gained growing importance because of tighter limits of less than 10 ppm sulfur in gasoline in recent regulations. On the other hand, preserving octane rating in gasoline is the most concern subject of the manufacturers. This review focuses on the desulfurization of gasoline by means of pervaporation (PV) process. The process as a new technology has drawn increasing attention and provided an efficient approach for eco-friend sulfur removal in petrochemical industries due to its high selectivity, feasible economics, and safety. Theoretical aspects in selection of materials for the applied membranes and their modifications are investigated. The various parameters including the type and concentrations of sulfur and hydrocarbon species, feed temperature, feed flow rate, and permeate pressure, which influence the performance of PV are discussed.

https://www.tpbin.com/Uploads/Subjects/c801e5d5-0bbb-46d9-9e25-1e3b9f3ad95e.pdf

A review on removal of sulfur components from gasoline by pervaporation

Partial purification of plant peroxidase from turnip (Brassica rapa) was optimized. Aqueous two phase system and precipitation by ammonium sulfate (as two parallel purification methods) were used. Polyethylene glycol/ammonium sulfate/NaCl (25:7:3%, w/v) system followed by gel-filtration chromatography gave a purification factor of about 36 fold. On the other hand, ammonium sulfate precipitation (60−80% deg) followed by gel filtration gave only about 13 purification fold. Hence, the aqueous two-phase system was more efficient and useful method as a primary purification step since it was less laborious, less time-consuming, and led to more purification factor. The partially purified turnip enzyme was stable at a pH range 2.6−6.0 and had an optimum pH at 4.0. The enzyme was stable up to 55 °C with an optimum activity at 35 °C.

Turnip (Brassica rapa) Peroxidase: Purification and Characterization

Experimental kinetic analysis of ethylene absorption in ionic liquid [Bmim]NO3 with dissolved AgNO3 by a semi-continuous process

Ethylene absorption from an ethylene–ethane gaseous mixture in the silver nitrate solution is studied at different temperatures and concentrations. Unlike the previous studies, in which the absorption was studied by batch processes, a semi-continuous process is applied in the present research. The results show that increase in temperature reduces the amount of absorbed ethylene and absorption time. The amount of absorbed ethylene is increased in solutions with higher concentrations of AgNO3, whereas the mole ratio of absorbed ethylene per silver nitrate is decreased by increasing the AgNO3 concentration. Total absorption is modelled as a function of the temperature and concentration of absorbing solution. The estimated values from the model are in good agreement with the experimental data.



L'absorption du melange gazeux de l'ethylene-ethane dans une solution de nitrate d'argent est etudiee a differentes temperatures et concentrations. Contrairement aux etudes anterieures lors desquelles l'absorption etait etudiee par procedes en lots, un procede semi-continu a servi pour la recherche actuelle. Les resultats indiquent qu'une hausse de temperature reduit la quantite d'ethylene absorbee et le temps d'absorption. La quantite d'ethylene absorbee est augmentee dans les solutions ayant des concentrations de AgNO3 plus elevees alors que le ratio de moles d'ethylene absorbes par nitrate d'argent est diminue en augmentant la concentration de AgNO3. L'absorption totale est modelisee en tant que fonction de la temperature et de la concentration de la solution absorbante. Les valeurs estimees a partir du modele appuient les donnees experimentales.

Absorption of ethylene from ethylene‐ethane gaseous mixture by AgNO3 solution in a semi‐continuous process

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F. Ghaemmaghami

Papers

A review on removal of sulfur components from gasoline by pervaporation

Turnip (Brassica rapa) Peroxidase: Purification and Characterization

Experimental kinetic analysis of ethylene absorption in ionic liquid [Bmim]NO3 with dissolved AgNO3 by a semi-continuous process

Absorption of ethylene from ethylene‐ethane gaseous mixture by AgNO3 solution in a semi‐continuous process

A Method for Recovery of N-methyl 2-pyrrolidone from Wastes of Solvent Regeneration Unit in 1,3-Butadiene Extraction Plant