Catalysts Cost

Acid modifiers have been used to a limited extent to reduce acid consumption in the H2SO4 alkylation process (27). Increased catalyst costs will encourage the further development and appHcation of such acid modification techniques in the future. In addition, the development of new technology, such as two-step alkylation, may be accelerated based on the incentive to reduce catalyst consumption and increase product octane (28). 

Rhodium was about three times the price of gold through 1988—1989 until skyrocketing to 74/g ( 2300/troy oz) in early 1990. Thus precious metal catalyst costs requite an absolute minimum level of use and maximum number of catalyst recycle uses when batch processing is employed. Starting material contaminants may effect catalyst poisoning, though process routes to overcome this by feed stream pretreatment may be devised (37,60). 

Design considerations and costs of the catalyst, hardware, and a fume control system are direcdy proportional to the oven exhaust volume. The size of the catalyst bed often ranges from 1.0 m at 0°C and 101 kPa per 1000 m /min of exhaust, to 2 m for 1000 m /min of exhaust. Catalyst performance at a number of can plant installations has been enhanced by proper maintenance. Annual analytical measurements show reduction of solvent hydrocarbons to be in excess of 90% for 3—6 years, the equivalent of 12,000 to 30,000 operating hours. When propane was the only available fuel, the catalyst cost was recovered by fuel savings (vs thermal incineration prior to the catalyst retrofit) in two to three months. In numerous cases the fuel savings paid for the catalyst in 6 to 12 months. 

Syndiotactic polypropylene first became available in the 1990s (Fina, Mitsui Toastu, Sumitomo) and more recently has been marketed by Dow. Currently this polymer is more expensive than other polypropylenes both because of catalyst costs and the small scale of production. 

Determination of the actual cost of a hydrogenation process is difficult. Among the factors entering into the determination are catalyst cost, catalyst life, cost of materials, capital investment, actual yield, space-time yield, and purification costs, Considerable data are needed to make an accurate evaluation. 

The mistake is sometimes made of estimating catalyst cost based on the price of a small sample of catalyst. This price, which largely reflects the cost of handling, is very much higher than the price of bulk quantities. The price of bulk quantities can be obtained directly from manufacturers,... 

Space time yield refers to the quantity of product that can be produced in a reactor in a given time. It is a function of both selectivity and activity. Maximum efficiency is reached when this number is high, but if production schedules are not full, lower numbers may be tolerated. Acceptable catalyst life can be extended if space-time yield demands are not heavy. Catalyst cost thus becomes a function of the demands put upon it. 

The amount of fresh catalyst added is usually a balance between catalyst cost and desired activity. Most refiners monitor the MAT data from the catalyst vendor s equilibrium data sheet to adjust the fresh catalyst addition rate. It should be noted that MAT numbers are based on a fixed-bed reactor system and, therefore, do not truly reflect the dynamics of an FCC unit. A catalyst with a high MAT number may or may not produce the desired yields. An alternate method of measuring catalyst performance is dynamic activity. Dynamic activity is calculated as shown below ... 

A catalytic oxidation system may cost 150 per car, but the catalyst cost is estimated to be 30, less than 1% of the cost of an automobile (2). In a few years, the gross sale of automotive catalysts in dollars may exceed the combined sale of catalysts to the chemical and petroleum industries (3). On the other hand, if the emission laws are relaxed or if the automotive engineers succeed in developing a more economical and reliable non-catalytic solution to emission control, automotive catalysis may turn out to be a short boom. Automotive catalysis is still in its infancy, with tremendous potential for improvement. The innovations of catalytic scientists and engineers in the future will determine whether catalysis is the long term solution to automotive emissions. 

Product Product value ( /ton) Catalyst cost ( /ton product) Reference... 

Figure represents catalyst and auxiliary chemicals and therefore represents an upper limit for catalyst cost. 

Fig. 1. The field of catalysis. The numbers in circles are approximate annual catalyst cost for principal uses, in million. Total values Catalysts ca. 200,000,000. Products (excluding fuel) ca. 100-200,000 million.

Thus, the spread of catalyst cost is fairly even over the whole industry and about a third of the known metals are used in one way or another. Table III shows how catalyst costs vary in relation to product value. 

Although primary catalyst cost is not a major factor in the price of the product, the work of the catalyst chemist of course crucially affects a wide variety of process costs that are of far greater significance. What goes on in the reactor dictates feedstock requirements, capital charges, downtime for catalyst recharging, and strongly influences the purification problems... 

Heterogeneous catalysts, in the general sense of catalysts placed in a phase different from that of the reagents and products, present clear advantages from a practical point of view, including ease of recovery and potential recycling and reuse. The latter point is especially important when the catalyst cost is high, as is the case for chiral catalysts [1]. 

Both sulfided and unsulfided Pt catalysts were more active for the reaction between cyclohexanone and aniline to yield N-cyclohexylaniline compared to acetone as the ketone. Again, BS2 was significantly more active but as selective as BSl catalyst. No cyclohexanol was observed with sulfided Pt catalysts, while only a trace amount was found with the B1 catalyst. The sulfided Pd catalyst, AS2 had activity and selectivity similar to that of unsulfided Pt catalyst. This suggests that if catalyst cost is of higher importance than productivity in the commercial process, an optimally sulfided Pd catalyst may be an acceptable alternative to a sulfided Pt catalyst. 

Catalyst cost constitutes 15-20% of the capital cost of an SCR unit therefore, it is essential to operate at temperatures as high as possible to maximize space velocity and thus minimize catalyst volume. At the same time, it is necessary to minimize the rate of oxidation of S02 to S03, which is more temperature sensitive than the SCR reaction. The optimum operating temperature for the SCR process using titanium and vanadium oxide catalysts is about 38CM180oC. Most installations use an economizer bypass to provide flue gas to the reactors at the desired temperature during periods when flue gas temperatures are low, such as low-load operation. 

Precious metal catalysts have shown to be effective for the desulfurization of the steri-cally hindered compounds. One example is given with a commercial catalyst using both, palladium and platinum [23]. The high activity of these metals towards hydrogenation would result in aromatic saturation reactions, and consequently an increase in operating costs (not only for the catalyst cost but also for the increase in hydrogen uptake). 

The mantiosdcctivity, expressed as enantiomeric excess (ee, %) of a catalyst should be >99% for pharmaceuticals if no purification is possible. This case is quite rare, and ee-values >90% are often acceptable. Chemosdectivity (or functional group tolerance) will be very important when multifunctional substrates are involved. The catalyst productivity, given as turnover number (TON mol product per mol catalyst) or as substrate catalyst ratio (SCR), determines catalyst costs. For hydrogenation reactions, TONs should be >1000 for high-value products and >50000 for large-scale or less-expensive products (catalyst re-use increases the productivity). 

The catalyst activity, given as average turnover frequency (TOF mol product per mol catalyst per reaction time units h-1), affects the production capacity. For hydrogenations, TOFs should be >200h 1 for small-scale products, and >10000 IT1 for large-scale products. Due to lower catalyst costs and often higher added values, lower TON and TOF values are acceptable for enantioselective oxidation and C-C bond-forming reactions. 

Clearly, when considering chemicals and/or catalyst cost alone there is an economic optimum design that is a hybrid process involving catalytic treatment for the high... 

Hence the dimension ("the order") of the reaction is different, even in the simplest case, and hence a comparison of the two rate constants has little meaning. Comparisons of rates are meaningful only if the catalysts follow the same mechanism and if the product formation can be expressed by the same rate equation. In this instance we can talk about rate enhancements of catalysts relative to another. If an uncatalysed reaction and a catalysed one occur simultaneously in a system we may determine what part of the product is made via the catalytic route and what part isn t. In enzyme catalysis and enzyme mimics one often compares the k, of the uncatalysed reaction with k2 of the catalysed reaction if the mechanisms of the two reactions are the same this may be a useful comparison. A practical yardstick of catalyst performance in industry is the space-time-yield mentioned above, that is to say the yield of kg of product per reactor volume per unit of time (e.g. kg product/m3.h), assuming that other factors such as catalyst costs, including recycling, and work-up costs remain the same. 

In Phases 2 and 3, it is not only the results of the catalyst tests (selectivity, activity, productivity, catalyst costs, etc.) but also the total product costs that decide whether the catalytic route will be further developed, or abandoned. 

The catalyst costs will only be important later, when the costs of goods of the desired product are compared. For homogeneous catalysts, the (chiral) ligand often is the most expensive component (typical prices for the most important chiral phosphines are 100 to 500 g for laboratory quantities and 5000 to >40000 kg on a larger scale). 

Catalyst Cost. Catalyst replacement cost represents a large operating expenditure, in addition to the effect that catalyst performance (good or bad) can have on yield and associated profit. Therefore, in addition to all the other objectives, we continually evaluated catalyst composition and method of manufacture as they impacted on catalyst cost. Catalyst manufacturing modifications as they impacted cost were always carefully reviewed and such review was a key part of the catalyst development program. 

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