Air purification by Ozone
Physical Chemistry of Fine Air Purification from Environmentally Hazardous Сhemicals by Ozonation on the Surface of Collector Catalysts for the Case of Diethyl Zinc
Tech Area / Field
- CHE-SYN/Basic and Synthetic Chemistry/Chemistry
3 Approved without Funding
VNIIEF, Russia, N. Novgorod reg., Sarov
- Nizhni Novgorod State University name after N.I. Lobachevsky, Russia, N. Novgorod reg., N. Novgorod
- Tohoku University / Graduate School of Life Sciences, Japan, Sendai
Project summaryChemicals that are widely used in various areas of industry and in everyday life constitute one of the leading factors in a variety of technogenic effects on the environment and human health. At the moment, more than 13 million chemicals are known, and more than 300 thousand chemical products are in circulation on the world trade market.
Because of the high price, labor and time requirements associated with toxicological studies, data on the critical ecological and toxicological properties needed for assessing their environmental and health risks are available only for 20 percent of potentially hazardous substances being produced or introduced into production.
In particular, there is lack of detailed data on the toxicity of the organometallic compound of diethyl zinc (Et2Zn) and its transformation products, which form at normal temperature and air humidity; the Russian Register of potentially hazardous chemical and biological substances contains no hygienic standards (MPC – maximum permissible concentration, SRLI – safe reference level of impact) for Et2Zn in workplace air.
Along with this, Et2Zn is known to have a wide range of applications:
- as a reagent and catalyst in the processes to produce chemicals of high practical value and materials on their basis;
- as a chemical compound applicable for centrifugal separation in the production of zinc depleted by 64Zn, which is used in reactor materials science in the USA, Japan and Germany.
Data on the kinetics, mechanism and composition of the products of oxidation by oxygen of diethyl cadmium and dimethyl cadmium, being the closest analogues to diethyl zinc, suggest that oxidation of diethyl zinc in the air will produce peroxide and non-peroxide derivatives: EtZnOOEt, (EtOO)2Zn, EtZnOEt, (EtO)2Zn, EtZnOH, EtOZnOH etc (studies by Project Scientific Leader Yu.A.Alexandrov). The properties of these compounds and their biological effects on human are unknown.
Along with this, it seems to be very costly, in terms of labor, financial expenses and time, to implement the whole scope of work necessary for assessing biological activity, toxicity and risks of the forming chemicals and for developing toxicological and hygienic regulations for the levels of Et2Zn and its transformation products in workplace air of enterprises that produce and use diethyl zinc and its derivatives.
In view of the above considerations, it is rather topical to expeditiously develop physicochemical fundamentals for an advanced way of air purification from diethyl zinc and products of its partial oxidation in order to prevent occupational poisoning and protect health of personnel. Complete topochemical oxidation of diethyl zinc by ozone-oxygen mixture on the surface of original synthetic porous ceramic collector catalysts to be fabricated based on the foam ceramics “CHIPEK” synthesized earlier (RF patent # 2091348, 1997; TU 57-59-010-10657190-97) was chosen a candidate way.
Ozone is widely used for sanitary treatment of residential-use water, and, in some cases, for air purification from environmentally hazardous substances, bacteria and viruses. However, “ozonation” has not become widely spread for a number of reasons, the major of which are as follows:
- because of the toxicity of ozone itself and necessity to prevent beyond-control reactions involving ozone (formation of ozonides etc), its production and application require high production culture to be maintained and safety precautions to be observed;
- low efficiency of “ozonation” by simple barbotage through water phase because of relatively low ozone solubility in water and, consequently, “overdosing” (unreasonably high consumption) of ozone at purifying water from environmentally hazardous chemicals characterized by low and very low MPC levels (pathogenic bacteria and viruses);
- relatively high price of ozone, with financial expenses by far increased by the “overdosing”.
At the same time, being a very strong oxidizer, which can be readily synthesized practically at any place of its use, ozone is considered to be a rather promising agent to solve the problems of environmental protection from environmentally hazardous chemicals and pathogenic bacteria and viruses.
The core of the Project is the idea to use original synthetic porous ceramic foams as sorbents (collectors) of ozone (without its breakdown) and oxidized substrate. Supposedly, for that purpose, there will be used hetero-packet sorbents (sorbents promoted with variable-valence metals). Decision on the sorbents will be determined by their ability to concentrate both ozone and oxidized substrate on their surface by sorption, and to catalyze complete oxidation of the substrate to environmentally safe or low-hazard products. Such an approach will implement the way of targeted ozone application in doses. This way is safe, economically favorable and has undoubted advantages as against other known methods, whose distinctive feature is promotion of ozone dilution in an “ozonized” medium (using membranes, accelerated barbotage etc).
The Project is expected to include:
- Experiments on the synthesis of porous ceramics having a combination of desired properties: high chemical stability when exposed to ozone-oxygen gas environment, absence or minor catalysis of undesired breakdown of ozone at its sorption, effective sorption of both ozone and diethyl zinc and products of partial oxidation of the latter.
- Determination of the basic formal kinetic features of Et2Zn oxidation by ozone-oxygen mixture, with the focus on the dependence of reaction rate on the nature of sorbent catalyst, concentration of reagents, temperature etc, in order to optimize conditions for fine air purification from Et2Zn and products of its partial oxidative transformation: EtZnOOEt, (EtOO)2Zn, EtZnOEt, (EtO)2Zn, EtZnOH, EtOZnOH, EtOOZnOH etc.
- Determination of the basic physico-chemical features of ozone and diethyl zinc sorption on the surface of the chosen (optimal) collector catalysts.
- Determination of the basic chemical and physico-chemical properties of the optimal collector catalysts: density, porosity, thermal stability, resistance to hydrolysis, mechanical strength, physical and chemical adsorption capacity for the case of “model” compounds.
- Development of draft Specifications for the process of fine air purification from diethyl zinc and products of its partial transformation by their oxidation by ozone on the surface of collector catalysts.
- Development of recommendations for the setting up of the pilot production of the collector catalysts developed.
- Preparation of documents, such as descriptions of anticipated intellectual property objects, to assess their patentability (foreign patenting included), for: synthesis method and composition of the task-specific collector catalyst; method for ozone stabilization in condensed phase; novel technologies to purify air from environmentally hazardous chemicals (for the case of diethyl zinc).
This Project is in full compliance with the objectives and goals of the ISTC:
- Examining the processes of complete diethyl zinc oxidation on the surface of original synthetic porous ceramic collector catalysts (SPCCC) to purify air from environmentally hazardous products is of great significance, because it addresses a fundamentally new approach to environmental protection from environmentally hazardous products of human activity, pathogenic bacteria and viruses, namely a method for sorptive concentration of ozone and oxidized substrate and catalysis of their interaction on the surface of SPCCC;
- Gaining more profound knowledge about the character, mechanism, kinetics of primary reactions depending on the nature of the environment, intermediate products and their transformations seems to be necessary both for the development of theoretical chemistry and for solving many applied problems;
- Project results will be offered for the development of sanitary and hygienic practices to provide safe occupational environment at enterprises that produce or use diethyl zinc;
- Economic benefits from implementation of the proposals based on the Project outcome are determined by precluding adverse health effects from hazardous chemicals and consuming the oxidizer in an economical manner;
- Experience of RFNC-VNIIEF and NNSU specialists in the fields of synthesis and chemical kinetics, catalysis, topochemistry, thermodynamics etc., combined with the knowledge of SPF CHICOMA experts in the area of synthesis of porous ceramics with high sorption capacity and catalytic activity in the processes of oxidation of organic and organometallic compounds, will be effectively used at working on the tasks specified.
Confidence in the successful implementation of project proposals rests upon the wide experience gained in the area of making synthetic ceramics with controlled properties: thermal stability, resistance to hydrolysis, mechanical strength, density, sorption capacity etc (RF patent # 2091348, 1997; TU 5759-010-10657190-97). Based on this knowledge, there have already been developed effective sorbent catalysts for the processes of oxidation of CO, joint CO oxidation/ NOx reduction, pyrolysis of propane-butane gas mixture to ethylene at a temperature of 700-750оC without “coking” etc. Under the guidance of Professor Yu.A.Alexandrov, in 1993, there was established production of a composition for “cold” phosphatation of steel-3 parts and a polymeric composition to prevent corrosion of steel-3 under permanent contact with hot domestic water. Customers: enterprises of Teploenergo (heat and power suppliers). In 1995 he established a pilot production of stiff heat insulation ceramics CHIPEK. Customers: enterprises of heat and power engineering, chemical industry etc. Samples of CHIPEK were demonstrated at the Techno Pia’99 trade show at Intex Osaka on May 19-22, 1999. More than 50 companies from Japan expressed interest to CHIPEK. Currently, a joint project with “Nizhegorodteplostroy” (N.Novgorod Heat and Construction Enterprise) is under development to establish production of one of CHIPEK modifications, CHIPEK-04, with a working temperature of 1300-1500оC. Under development are the projects for establishing pilot production of another CHIPEK modification, CHIPEK-3, (jointly with SIBURNEFTEKHIM Public Corp.).
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