Catalysts catalyst: clay ratio

Bakke et al. (1982) have shown how montmorillonite catalyses chlorination and nitration of toluene nitration leads to 56 % para and 41 % ortho derivative compared to approximately 40 % para and 60 % ortho derivatives in the absence of the catalyst. Montmorillonite clays have an acidity comparable to nitric acid / sulphuric acid mixtures and the use of iron-exchanged material (Clayfen) gives a remarkable improvement in the para, ortho ratio in the nitration of phenols. The nitration of estrones, which is relevant in making various estrogenic drugs, can be improved in a remarkable way by using molecular engineered layer structures (MELS), while a reduction in the cost by a factor of six has been indicated. With a Clayfen type catalyst, it seems possible to manipulate the para, ortho ratio drastically for a variety of substrates and this should be useful in the manufacture of fine chemicals. In principle, such catalysts may approach biomimetic chemistry our ability to predict selectivity is very limited. 

The compatibilization of clay with LDPE and HDFE is accomplished by the in situ polymerization of MAH or its precursor maleic acid, in the presence of a radical catalyst. The latter must be capable of initiating the homopolymerization of MAH, i.e. it must be present in high concentration and/or have a half-life of less than 30 min at the reaction temperature, e.g. t-butyl per-benzoate (tBFB) at 150°C. In a one-step process, the clay and PE are mixed with MAH-tBPB in the desired PE/clay ratio. In the preferred two-step process, a 70/30-90/10 clay/PE concentrate is prepared initially in the presence of MAH-tBPB and then blended with additional PE to the desired clay loading. The compatibil-ized or coupled PE-MAH-clay composites have better physical properties, including higher impact strengths, than unfilled PE or PE-clay mixtures prepared in the absence of MAH-tBPB. 

Catalytic evaluation of the different pillared clays was performed using a microactivity test (MAT) and conditions described in detail elsewhere (5). The weight hourly space velocity (WHSV) was 14-15 the reactor temperature was 510 C. A catalyst-to-oil ratio of 3.5-3.8 was used. The chargestock s slurry oil (S.O., b.p. >354 C), light cycle oil (LCGO, 232 C < b.p. <354 C) and gasoline content were 62.7 vol%, 33.1 vol% and 4.2 vol% respectively. Conversions were on a vol% fresh feed (FF) basis and were defined as [VfVp/V ] x 100, where is the volume of feed... 

The BET surface areas, pore volumes and pore size distributions for all catalysts investigated are summarized in Table 1. S-lOTi sample showed high specific surface area. But, according to the increase of Ti/clay ratio, the surface area was decreased. This result indicates that the higher Ti/clay ratio leads to a progressive plugging of the internal structure of the clay. 

The A1 content fixed by the pillared clay increases with the pH and with the Al/clay ratio. According to the preparation process, the whole amount of the pillaring Al-species is not always completely fixed in the interlayer space. For some samples, it may be suspected that another Al-species is precipitated to a greater or lesser extent on the layer surface. The best stability of Al-pillared saponite is obtained under the following experimental conditions clay concentration < 5 g.l Al/clay < 5 mmol.g and pH values between 4.8 and 6.0. A very carefull thermal treatment is required up to SOOX (36 /h heating rate) to transform the intercalated species into oxide pillars. At 750 C, the surface areas are about 150- 250 m. g and the basal spacings dpoi about 17.3 A. According to these values, Al-pillared saponites may be used as catalysts of 7-8 A pore space. 

Table 1 shows chemical compositions of clay catalysts measured by XRF analysis. Si02 and AI2O3 are main components of the three clay catalysts with minor amount of Na20, Fc203 and others. The Si/Al ratio increased from HH [Pg.434]

Finally, PILC, REY-PILC, and a commercial equilibrium catalyst were evaluated at near constant conversion using a heavier feed, hydrotreated resid. The product yields are shown in Table III. Steam deactivated (D), REY-PILC, produced the same gasoline selectivity, LCO/HCO ratio, and coke yield as calcined PILC. The equilibrium catalyst which represents a more severely deactivated (E) sample had higher gasoline selectivity, lower coke yield, and lower HCO/LCO ratio. The higher coke yield of REY-PILC could be due to occlusion of high molecular weight hydrocarbons in the microstructure of the pillared clay. 

We varied the gel-forming parameters, the content of Kaolin clay, the crystal size, and the thickness-to-diameter ratio in a series of experiments. A dual structure began to appear at about 35-40% Kaolin. If the clay content was increased to too high a level, the microspheres became too weak and began to have poor attrition resistance. The cost of the various grades also affected our choice. Figure 9 shows a comparison of pore volume distribution for a typical synthetic versus a clay modified catalyst. 

The REHY catalyst employed was a commercial Quantum 2000 sample with a rare earth content of 1.27 wt%. The ZSM-5 catalyst was prepared on a pilot plant spray dryer from 25% wt% zeolite, 25% wt% silica sol, and 50 wt% kaolin clay. The ZSM-5 sample used in this study analysed at 30 1 silica-alumina ratio. 

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