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Oxides of sulfur and nitrogen are the main air pollutants that are also responsible for acid rain. Excessive sulfur content in petroleum fractions such as naphtha, in addition to causing air pollutants, can corrode tanks, reactors, pipes and fittings. Currently desulfurization is carried out using desulphurization catalysts adjacent to hydrogen; thus at a certain temperature and pressure, as well as a specific proportion of hydrogen, sulfur atoms convert to hydrogen sulfide. Catalysts based on γ–alumina are commonly used for desulphurization. Alumina has various applications including ceramic membranes, paints, refinery and chemical catalysts, pollution control and base catalyst. The mesoporous γ–alumina with pore diameter in the range of 2 to 50 nm due to its high specific surface area, high porosity, good thermal stability and suitable pore distribution is used as the most common base catalyst in desulphurization.
Refinery and chemical catalysts
Pollution control
Mesoporous materials have a large surface area-to-volume ratio compared with bulk materials. The large specific surface area of nanopores generated in the catalyst increases the catalytic activity.
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Structural lightweight concrete has an in-place density on the order of 1400 to 1900 kg/m3 compared to normal-weight concrete with a density in the in the range of 2000 to 2400 kg/m3. For structural applications, the concrete strength should be greater than 17 MPa. The concrete mixture is made with lightweight coarse aggregate. In some cases, a portion or the entire fine aggregate may be a lightweight product. Lightweight aggregates used in structural lightweight concrete are typically expanded shale, clay or slate materials that have been fired in a rotary kiln to develop a porous structure.
Concrete is unique in construction and it is only an exclusive product for trading; so it involves a significant share of research and development, and income in the industry to itself. Concrete, a multi-phase, complex and nanostructured material, is a composite structure mainly composed of cement and water. Nanoscience and nanoengineering of concrete are phrases which describe two essential approaches regarding the application of nanotechnology in concrete. Up to now, concrete has been primarily known as a structural material. Nanotechnology is capable of making a multi-functional material from concrete. Concrete can be nanoengineered by incorporating nanoscale building blocks, nanoparticles, nanotubes, etc.
More efficient heat transfer systems are increasingly preferred because of the accelerating miniaturization, on the one hand, and the ever-increasing heat flux, on the other hand. The poor heat transfer properties of the common fluids like water compared to most solids is a primary obstacle to the high compactness and effectiveness of heat exchangers. Passive enhancement methods such as enhanced surfaces are often employed in thermo-fluid systems. Therefore, the development of advanced heat transfer fluids with higher thermal conductivity and improved heat transfer is in strong demand. Nanofluids are heat transfer liquids with dispersed nanoparticles. The effectiveness of heat transfer enhancement has been found to be dependent on the amount of dispersed particle, material type, particle shape, etc.
Rainwater pipes are used to transfer the rain and snow water from roof of the buildings. Polyvinyl chloride (PVC) is kind of useful plastics in construction and buildings. By adding lubricants, this material will become softer and more flexible than plastics. If no lubricant and plasticizer is added, UPVC is obtained. Chemical resistance of this polymer makes it interesting for a variety of industries especially pipe industry. Usage of UPVC includes sewer pipelines, water mains and potable water services, power and telecommunication cables. These pipes are supposed to have chemical and corrosion resistance, high elasticity module and toughness, long term tensile strength and abrasion resistance, but they may become brittle exposed to cold atmosphere. In addition, they tend to deform and lose their strength in high temperature conditions. These pipes have been given better properties by addition of nanoparticles.
Air filters are used to prevent damage to power plant equipment through dust particles, contaminants and other harmful particles in the air. The main goal is the maximum absorption of dust particles from the air. Nanofibers with lower thickness and higher specific surface area than that of conventional fibers have many applications in filtration and electrospinning is the most efficient process for production of continuous fibers from synthetic or natural polymers. Electrospinning is used to improve the performance and efficiency of the filter. This technology while increases the efficiency of dust absorption, avoid high pressure drop. Fibers produced by electrospinning have a diameter of less than 100 nm and cover the surface of the filter paper uniformly.
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