Environmentally friendly processes

Abstract

Environmental concerns have raised public awareness of environmental issues and are driving forces for regulation. The impact of regulation on the cost of production is expected to become important in determining the international competitiveness of the US chemical industry. In response to cost pressures, industry has launched a number of initiatives aimed at improving efficiency and reducing environmental impact. Some of these environmental success stories are receiving increased national attention due to programs such as the Presidential Green Chemistry Challenge Awards Program. In addition to traditional metrics for evaluating process performance, such as productivity, environmental considerations increasingly are important in process development. Chemical processes evolve through life cycle phases, beginning with research, and then moving to process engineering, plant operation, and eventually, decommissioning. The number of technology options available for reducing environmental impact are highest early on in the life cycle and then decrease drastically. In contrast, costs associated with resolving an environmental problem typically increase exponentially as the process matures and the scale of equipment gets larger. There is, therefore, a considerable incentive to address and resolve environmental issues early in the life cycle. Chemical reactions responsible for producing high value-added products are, in most cases, also responsible for generating by-products and pollutants. New chemical and biochemical approaches are providing new reaction concepts. As in the development of traditional chemical and petrochemical processes, reaction engineering, broadly defined as the field that quantifies the engineering aspects of chemically reactive systems, is providing enabling tools that accelerate the development of environmentally friendly processes. Core reaction engineering methods are being utilized for kinetic modeling, reactor selection, scale-up, and design. Meanwhile, the research frontiers are providing new reaction engineering tools, from computational chemistry to probe the nature of catalytic active sites to computational fluid dynamics modeling for designing the internals of reaction-separation systems. The long-term goal is to develop processes having 100% raw materials utilization, or zero waste. The near-term strategy for controlling emissions is to institute pollution prevention programs and install cost-effective end-of-pipe technologies. These technologies typically control generic classes of air pollutant emissions such as carbon monoxide, volatile organic compounds (VOCs), nitrogen oxides (NO x ) and sulfur oxides (SO x ). Technologies for treating wastewater are also available. Over time, a shift in focus is expected, from mere compliance to a point where environmentalism, like safety, is fully integrated into the corporate culture. The present paper discusses the role of reaction engineering in the development of environmentally-friendly processes. Select examples of processes, from the author’s experience, that benefit from reaction engineering will be presented.