Optimal catalyst composition

Single-reaction-step processes have been studied. However, higher selectivity is possible by optimizing catalyst composition and reaction conditions for each of these two steps (40,41). This more efficient utilization of raw material has led to two separate oxidation stages in all commercial faciUties. A two-step continuous process without isolation of the intermediate acrolein was first described by the Toyo Soda Company (42). A mixture of propylene, air, and steam is converted to acrolein in the first reactor. The effluent from the first reactor is then passed directiy to the second reactor where the acrolein is oxidized to acryUc acid. The products are absorbed in water to give about 30—60% aqueous acryUc acid in about 80—85% yield based on propylene. 

Previously, we performed single- and multi-response optimization works in order to address optimal catalyst composition (%CaO and %MnO) and optimal operating conditions (temperature and CO2/CH4 feed ratio [3]. The maximum C2 selectivity and yield of 76.6% and 3.7%, respectively were achieved in multi-responses optimization over the 12.8% CaO-6.4% Mn0/Ce02 catalyst corresponding to the optimum reactor temperature being 1127 K and CO2/CH4 ratio being 2 [3]. The recent contribution on the catalyst technology of CO2 OCM was... 

The results of primary screening data are used to determine the design of a more focused electrocatalyst library, thereby beginning the next cycle of the primary workflow. In each subsequent cycle, the examined experimental variables become more and more limited as the experimental results move toward an optimized set of process parameters or an optimized catalyst composition. There are several strategies as to how best design the next cycle of catalyst libraries to maximize the... 

Primary thin film hits , i.e., optimized catalyst compositions determined during one or more primary screening cycles as represented in Fig. 11.8, are examined in... 

It is impossible to define an optimal catalyst composition, because the composition which is most effective for one set of synthesis conditions will be far from optimal for other conditions. Thus Telegin, Sidorov, and Shpulenko (6) have shown that the amount of AI2O3 necessary to stabilize a catalyst for work at 450° and 1 atm. is far from sufficient to give it stable activity at 500° and 300 atm. The difference may be so great that if 0.1 % AI2O3 is sufficient in the former case, up to 5% AI2O3 may be required in the latter. This is not only a problem of stability of the catalysts it is also a question of activity. A series of catalysts do not... 

As is seen from Fig. 6, the increase in basicity leads to the important decrease in O-methylation rate (R2) without significant changing in the rate of 3-methyl catechol formation (R3) until 7.5 at.% of Mg ". At higher magnesium concentration the rate R3 goes down more rapidly, than for guaiacol formation. It results in the observed maximum for 3-methyl catechol selectivity at 7.5 at.% Mg V Y-AI2O3, reported as an optimal catalyst composition [4]. 

For catalyst optimization using high-throughput experimentation, evolutionary strategies have been shown to be very effective if vast parameter spaces (many nominal catalyst components) have to be searched for the optimal catalyst composition. The concept of the algorithm has been described in detail by Wolf et al. [21], some application examples are discussed by Rodemerck et al. [22] and Holena [23]. 

For high-throughput preparation of solid catalytic materials, automated robots equipped with synthesis control protocols are used. These robots carry out the various synthesis steps at high speed and in parallel or consecutively. The steps require high accuracy and reproducibiUty, without which no reliable data on optimal catalyst composition and best performance can be obtained. Moreover, the steps have to be performed in such a way, which is transferable to pilot- and technical-scale plant operation. For illustration, an automated sjmthesis robot is presented in Figure 2.3. 

The NH3-SCR activities of a series of extmded and calcined V0x/Zr02-S04 - sepiolite catalysts were determined. The pore stmctures were heavily influenced by the clay content with macropore sizes ranging from 50 to >1000 mn. Mechanical strength and SCR activity measurements snggested that 25% w/w sepiolite is the optimal catalyst composition. 

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