Zeolite in detergents

A few practical examples provide some indication of the large number of uses for zeolites in research and industry, especially as catalysts and sorbents. The total annual zeolite consumption by industry is over 550,000 metric tons, of which more than 100,000 tons are used as catalysts, 375,000 tons are zeolites in detergent, and 40,000 tons are used as sorbents. 

The expected evolution over 5 years (up to the year 2003) is on average a moderate global growth in the order of 1 to 1.5 % per year approximately for catalysis, from 1 to 2 % for adsorbents and desiccators and, for detergents, a slight decrease on average (-1-2 % per year) in the major developed countries (lower queintities of zeolite in detergents). 

Detergents Tonnage wise, the use of zeolites in detergent formulations is a large market with even far larger potential. Zeolite A nearly exclusively serves here as a sequestering agent to substitute phosphates. 

Practically all industrial ion exchange appHcations, except the use of zeolites in detergency, involve column operations (e.g. the removal of radionuclides from nuclear waste effluents). However, basic studies of ion exchange equilibria are usually carried out using the batch method. 

It may be noted that the ion exchange capacity is directly connected with the Al-content (each Al provides one negative charge). The zeolite used in detergent formulations (over 10 t/a) is NaA with Si/Al = 1, so with maximum exchange abi ity. 

Zeolites form a unique class of oxides, consisting of microporous, crystalline aluminosilicates that can either be found in nature or synthesized artificially [J.M. Thomas, R.G. Bell and C.R.A. Catlow in Handbook of Heterogeneous Catalysis (Ed. G. Ertl, H. Knbzinger and J. Weitkamp) (1997), Vol. 1, p. 206, VCH, Weinheim.]. The zeolite framework is very open and contains channels and cages where cations, water and adsorbed molecules may reside and react. The specific absorption properties of zeolites are used in detergents, toothpaste, and desiccants, whereas their acidity makes them attractive catalysts. 

Contrary to the commodity chemical business, the key to win in the specialty products market does not lie in squeezing out profits by means of economies of scale or process optimization. Rather, it lies in the ability for fast new product launches in order to capture the largest market share as soon as possible. Since superior product quality and performance is what really differentiates one specialty product from another, the product properties need to be adjusted as required by business needs. For example, the ability to manipulate functional chemicals in detergent products such as enzymes and zeolites, as well as backbone chemicals like surfactants, is often the key to success for both the detergent manufacturers and chemical suppliers [3], This trend has created an urgent need for an efficient and effective product and process development for these products. 

Choose a builder and its amount depending on the aqueous solubility of the builder in the product besides its chelating power. For instance, do not use insoluble zeolites in unstructured liquid detergents. 

In 1962 Mobil Oil introduced the use of synthetic zeolite X as a hydrocarbon cracking catalyst In 1969 Grace described the first modification chemistry based on steaming zeolite Y to form an ultrastable Y. In 1967-1969 Mobil Oil reported the synthesis of the high silica zeolites beta and ZSM-5. In 1974 Henkel introduced zeolite A in detergents as a replacement for the environmentally suspect phosphates. By 2008 industry-wide approximately 367 0001 of zeolite Y were in use in catalytic cracking [22]. In 1977 Union Carbide introduced zeolites for ion-exchange separations. 

The price of zeolites varies considerably depending on the apphcation. The typical price of catalysts in the United States varies from about US 3 /kg for FCC to about US 20/kg for specialty catalysts, adsorbents from about US 5-9/ kg, up to tens of dollars per kilogram for specialty adsorbents and about US 2/ kg for detergents. Natural zeolites in bulk applications sell for US 0.04—0.25/kg and in industrial adsorbent applications for US 1.50-3.50/kg [22]. 

Zeolites have an enormous impact on our daily lives, both directly and indirectly. For example, upstream hydrocarbons such as aromatics and olefins are produced using zeolite catalysts. The aromatics or olefins are then separated from the reaction mixtures using zeolite adsorbents. The purified components produced by these zeolite-based methods are then used in downstream processes to produce products that we use daily, such as clothes, furniture, foods, construchon materials and materials to build roads, automobile parts, fuels, gasoline, etc. In addihon to the indirect impacts mentioned above, zeolites also have a direct impact on our daily lives. For example, zeolites are used as builders in detergent formulations. 

Tomlinson, AAG. Modern zeolites structure and function in detergents and petrochemicals. Zurieh Trans Teeh Publications 1998. 

Alternatively, finely powdered zeolites may be used in detergent powders as a builder since zeolite particles smaller than 10 pm do not stick to clothing. Formerly, sodium polyphosphates (Section 7.7) were used extensively as detergent builders to tie up the Ca2+ and Mg2+ in hard water as soluble complexes (or as a precipitate that washes away). However, many communities ban phosphate detergents because of pollution problems (Sections 7.7 and 9.6), thus creating a major new market for zeolites. 

Interest in detergent products derived from renewable resources and with better biodegradability has driven evaluation of oxidized sugars and starches as builders or co-builders in detergents.113 Builders and co-builders complex calcium and magnesium ions in hard water to prevent sealing or deposits due to precipitation of insoluble carbonate salts. In current powder detergents, the builders are usually zeolites used in combination with polycarboxylate polymers derived from synthetic acrylic-maleic acid copolymers.114... 

However, the major use of ionic exchange in zeolites today is the application of the synthetic zeolite A in detergents for the softening of laundry water. 

Ion-exchange in detergents, A zeolites replacing the polluting polyphosphates (1974)... 

In the case of these three major areas of applications, the zeolite crystallite size has to be small generally 1 /jm for adsorption and catalysis, the optimal size for ion exchange in detergents being 3-4 /jm. This illustrates the advantage of synthetic zeolites since the precise engineering of their properties (crystal size, composition, polarity...) is now possible in contrast to their natural counterparts. 

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