Processes cleaner

The use of more efficient technologies or process changes can reduce PIC emissions. Advanced coal combustion technologies such as coal gasification and fiuidized-bed combustion are examples of cleaner processes that may lower PICs by approximately 10%. Enclosed coal crushers and grinders emit lower PM. 

There are several problems with these standards for older coal-fired plants that limit a sensible NO,-reduction policy. First, they are relatively lenient. Because they require only that low-NO, burners be used at coal-fired plants, relatively inexpensive NO,-reduction technologies are not being used, because the plants already meet the minimum standards. Second, standards are established on a technology-by-technology basis, and have resulted in more lenient requirements for dirtier technologies. This has created little or no incentive to switch to cleaner processes in the past decade. Thirdly, these standards are input-based, which means they provide no incentive for efficiency within any technology category. 

The first stable carbonylmetal-l//-azepine complex 25 (R = Et) was obtained by irradiating a mixture of ethyl 1 //-azepine-l-carboxylate (24, R = Et) and pentacarbonyliron(O) in tetrahy-drofuran (Method A).220 Hydrolysis of the complex with sodium methoxide gave azepine)tricarbonyliron(O) (26). Subsequently, the reaction of 24 with nonacarbonyldiiron(O) in warm benzene is reported to be a simpler and cleaner process.61 Both procedures fail, however, with alkyl-substituted l/Z-azepine-l-carboxylates. 

A final option for dealing with the bromide effluent problem is to recover the bromine for re-use giving a more environmentally acceptable effluent. The alternative approaches will be discussed in detail later, but H2O2 offers particular attractions in terms of giving a cleaner process. 

In-house process control. This comprises the achievement of optimum efficiency in relation to production and processing methods including the introduction, where feasible, of cleaner processes (alternative technology) or processing methods (substitute materials and/or reformulations, process modifications, and equipment redesign). 

Being microwave-transparent, the reaction vessels will be no hotter than their contents. As mentioned above, they usually are made from insulating polymeric materials like polytetrafluoroethylene (PTFE), which have inherent advantages for cleaner processing. In contrast with other materials, PTFE is resistant to attack by strong bases or HF and is not corroded by halide ions. 

Increasing environmental concerns and dwindling supplies of raw materials and energy sources mean that there is now a significant pressure to introduce cleaner processing in the chemical and pharmaceutical industries. 

Green chemistry offers cleaner processes for energy abatement. Some of these energy conversion processes are ... 

There are several ways to make burning coal a cleaner process. The coal can be purified before it is burned, pollutants can be filtered out after combustion, or the combustion process can be modified so that it is more efficient and fewer pollutants are produced. 

These advantages are all significant to green and sustainable chemistry as they have the potential to increase efficiency, to enhance safety in several different ways and to eliminate or avoid waste generation through cleaner processing. 

The subject of catalytic oxidation with hydrogen peroxide is an area in which many exciting new developments are taking place. The driving force behind these investigations is the need for cleaner processes, particularly in fine chemical manufacture, and shorter routes with higher product selectivity. In... 

Catalyst technologies have been and will continue to be a key part of achieving these objectives. These new technologies offer exciting areas of research to both academic and industrial researchers and the impact of their research will contribute to a better environment through cleaner processes and less damaging products. 

As with oxide CMP (Chapter 5), metal CMP may enhance yields by virtue of reduced defect densities. In addition to a reduction in nonplanarity induced defects (Section 5.24), CMP is a cleaner process than the relatively dirty RIE etch back processes. Figure 6.5 shows a 3X reduction in particles using CMP vs. RIE. The result is a decrease in metal-to-metal shorts on the subsequent interconnection level (Figure 6.6). As with oxide CMP, increased die yields is one of the major driving forces for acceptance of metal CMP processes for tungsten stud formation. ... 

The industrial chemistry of oils and fats is a mature technology, with decades of experience and rehnement behind current practices. It is not, however, static. Environmental pressures demand cleaner processes, and there is a market for new products. Current developments are in three areas green chemistry, using cleaner processes, less energy, and renewable resources enzyme catalyzed reactions, used both as environmentally friendly processes and to produce tailor-made products and novel chemistry to functionalize the carbon chain, leading to new... 

A major challenge for chemists is to develop new products that achieve economic objectives. At one time this was carried out with little or no thought of the impact that production had on the environment, but two of the greatest challenges to chemists today are the replacement of existing technology with cleaner processes and the development of new products that are kinder to the environment.1 This requires a new approach, which sets out to reduce the materials and energy used in manufacture, minimize or ideally eliminate the dispersion of chemicals in the environment, maximize the use of resources, and extend the durability and recyclability of products. 

The use of ionic liquids in combination with CO2 has the potential to produce cleaner processes with improved selectivity. The negligible miscibility of the ionic liquid in CO2 compared with appreciable amounts of CO2 that can be found in the liquid phase make the use of CO2 as a green solvent attractive for continuous reaction processes. Sellin, Webb, and Cole-Hamilton conducted a hydroformylation of hex-l-ene and 1-octene catalyzed by rhodium based catalyst in l-butyl-3-methylimidazolium hexafluoro-phosphate (BMIMHF) in contact with CO2. Improved n iso product selectivity was obtained, compared with that using toluene with similar selectivity, but substantially lower yield (40% compared to >99%). Using 1-octene as a substrate and [Rh2(OAc)4]/[1-propyl-3-methylimidazolium] [PhP(C6H4S03)2] as catalyst, over 20 hr of continuous operation was achieved with minimal catalyst leaching at 373 K. 

There are basically two options in the purification, that is, the water washing process and adsorbent treatment process (water-free process). In the water washing process the main drawbacks are the amount of wastewater produced and the energy costs to evaporate and recover water for re-use. In the adsorbent treatment process the problems are the high cost of adsorbent (e.g., Mg-silicate) and the disposal of the spent adsorbents. A potential cleaner process should thus eliminate the catalyst cleanup step and simplify biodiesel and glycerol purification. The options are (i) the use of heterogeneous solid catalysts, (ii) the use of an enzymatic transesterification processes and (iii) a catalyst-free process, using, for example, supercritical methanol. 

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