Nickel-contaminated particles

Sediment nickel concentrations are grossly elevated near the nickel-copper smelter at Sudbury, Ontario, and downstream from steel manufacturing plants. Sediments from nickel-contaminated sites have between 20 and 5000 mg Ni/kg DW these values are at least 100 times lower at comparable uncontaminated sites (Chau and Kulikovsky-Cordeiro 1995). A decrease in the pH of water caused by acid rain may release some of the nickel in sediments to the water column (NRCC 1981). Transfer of nickel from water column to sediments is greatest when sediment particle size is comparatively small and sediments contain high concentrations of clays or organics (Bubb and Lester 1996). 

To show the effect of having zeolite present in the contaminated particles, a REY commercial cracking catalyst with a matrix surface area of ca. 85 m /g was also contaminated with nickel and vanadium, and steamed (1450 F, 4 hrs, 90% steam, 10% air) to age the metals. Its select vities were compared to the non-zeolitic additive having the same surface area and chemical composition blended with sufficient metals-free active cracking component to give the same conversion. 

Hydrocarbon adsorption experiments show significant differences between the nickel contaminated zeolitic and non-zeolitic particles at metals levels comparable to those of the catalytic experiments. Neither hexane nor 1-hexene showed any interaction with nickel on the low surface area, non-zeolitic particles (the unpromoted material of Table I) at temperatures up to 425 C. Additionally, no interaction between hexene and the nickel on the zeolitic particles was observed over the temperature range studied. However, the nickel on the zeolitic component did cause significant retention of hexane at temperatures as low as 200 C with generation of what appeared to be higher molecular weight products. No cracking products were observed. With the uncontaminated zeolitic particles, hexane retention only occurred at temperatures above 300°C. Thus, the lower temperature retention for the contaminated particles appears to be due to the presence of nickel. 

The second of these hypotheses (more facile reduction of nickel on zeolitic particles) is contradicted by the results of our TPR experiments. In fact, the TPR results on both nickel contaminated zeolitic and non-zeolitic particles suggest that none of the nickel on these materials is reduced under normal MAT testing conditions, since the onset temperature of nickel reduction (1100-1150°F) is considerably higher than the operating temperature of the MAT (910op). 

Our third hypothesis, i.e., that the activity enhancement involves the proximity of the zeolite s acid sites, appears to be consistent with the hydrocarbon adsorption experiments, but may also be due to differences in the nickel dispersion arising from surface area differences between the two types of particles. Clearly, the adsorption of hexane at lower temperature on the nickel contaminated zeolitic particles suggests a significantly altered environment from both the uncontaminated and the non-zeolitic materials. 

The ability of the working surface to become wetted with water also affects the value of the coefficient of friction. Since hydrophobic surfaces hold contaminating particles relatively poorly (see 27), the operation of the machines should be improved by hy-drophobization. The hydrophobization of steel is effected by the addition of chromium and nickel, by chromium plating the surface, and also by treatment with silico-organic compounds [472]. Chromium-nickel steels also have a high value of hardness and suffer less severe wear than ordinary steel parts. 

Variation of the content of impurities in the different CNT preparations [21] offers additional challenges in the accurate and consistent assessment of CNT toxicity. As-produced CNTs generally contain high amounts of catalytic metal particles, such as iron and nickel, used as precursors in their synthesis. The cytotoxicity of high concentrations of these metals is well known [35, 36], mainly due to oxidative stress and induction of inflammatory processes generated by catalytic reactions at the metal particle surface [37]. Another very important contaminant is amorphous carbon, which exhibits comparable biological effects to carbon black or relevant ambient air particles. 

Figure 2. Temperature Programmed Reduction of Ni contaminated catalyst components a) non-zeolitic particles with 10,100 ppm Ni b) zeolitic particles with 10,860 ppm Ni. These materials were impregnated using nickel naphthenate and then steamed (1450°F, 4 hrs, 90% steam, 10% air) prior to running the TPR. The Ni on the non-zeolitic particles reduced at a lower temperature than that on the zeolitic particles.

The results of this work suggest that the greatest contaminant metals effects are due not only to the most recently deposited metals, but to those recently deposited metals which are present on the most recently added zeolitic particles (i.e., those containing the most zeolite). At constant metals aging then, the contaminant selectivities due to nickel and vanadium are in a large part determined by 1) the presence or absence of zeolite in the particle 2) the non-zeolitic surface area of the particle and 3) the chemical composition of the particle. 

On non-zeolitic particles in the absence of a vanadium passivator, vanadium (when present at the 0.4 wt% level) makes a greater contribution to contaminant coke and hydrogen yields than nickel at constant surface area and metals loading. Incorporation of a vanadium passivator into the catalyst matrix can greatly alter the selectivity effects of vanadium, and can essentially negate its effect on non-zeolitic particles as in the case of magnesium. 

Morphin is often contaminated with narcotic, which may be entirely removed by ether, or the impure mass may be treated with very dilute acetic add which dissolves the former, leaving the latter untouched. To determine the purity—from nareotin—of any sample of morphin, it may be dissolved in hydrochloric acid, and treated with caustic potassa in excess, in which the morphia will entirely dissolve, while any narcotin present remains untouched. If a very small portion of morphia is placed in a watch-glass with, a little pure sulphuric aoid and au equal quantity of water, and if a particle of bichromate of potassa be added, a nickel green color appears, which changes, first to a copper green, and finally, to a dark dirty green. 

The characterization of petroleum cracking catalysts, with which a third of the world s crude oil is processed, presents a formidable analytical challenge. The catalyst particles are in the form of microspheres of 60-70 micron average diameter which are themselves composites of up to five different micron and submicron sized phases. In refinery operation the catalysts are poisoned by trace concentrations of nickel, vanadium and other contaminant metals. Due to the replacement of a small portion of equilibrium catalyst each day (generally around 1% of the total reactor inventory) the catalyst particles in a reactor exist as a mixture of differing particle ages, poisoning levels and activities. 

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