Vanadium tolerance

Dougan, T. J., Alkemade, V., Lakhampel, B and Brock, L. T., Advances in FCC Vanadium Tolerance, presented at NPRA Annual Meeting, San Antonio. Texas, March 20, 1994 reprinted in Grace Davison Catalagram No. 72, 1985. 

Figure 9 demonstrates the clear benefit of nickel encapsulation in reducing the activity for hydrogen production. The observed 2 3 effect on hydrogen production, is related to the formation of zeolite surface non-framework alumina. Progress in nickel tolerance of FCC catalyst with these new technologies is at least as dramatic as in vanadium tolerance (2). 

Figure 8. Vanadium Tolerance of FCC Catalyst Standard vs. Low O2 CPS - M A Retention with V Level...

Many of the materials used to trap vanadium by chemical reaction also share a similar chemistry with the oxides of sulfur a prevalent contaminant in FCC feed stocks. Sites which trap vanadium are thereby competed for by sulfur species. Results obtained by incorporating a feed contaminant, such as sulfur, in a competition with vanadium demonstrate the importance of including sulfur in vanadium tolerance testing and will be discussed. The ETM test offers the ability to study what happens under just such a competition. 

R. F. Uormsbecber, A. V. Peters, J. M. Maselli, Vanadium poisoning of cracking catalysts mechanism of poisoning and design of vanadium tolerant catalyst system, J. Catal, 100, (1986), pp. 130-137,... 

Figure 8. RV4+ Improves Vanadium Tolerance Figure 9. V4+ Technology Improves Activity Vanadium vs Time-Trial G. Retention-Microactivity vs. Vanadium...

An accelerated test for the vanadium tolerance of cracking catalysts involves inpregnation with a vanadium ccmpound followed by air calcination euid steam deactivation. Examination of experimental catalysts after inpregnation with 0, 1000, 3000 and 5000 ppm vcinadium shows loss of micro and meso-pore surface areas, crystallinity and catalytic activity in direct preportion to the... 

Ceramies are quite tolerant of sueh eontaminants as sodium and vanadium, whieh are present in low-eost fuels and highly eorrosive to eurrently used niekel alloys. Ceramies are also up to 40% lighter than eomparable high-temperature alloys—another plus in applieation. But the biggest plus is material eost. Ceramies eost around 5% the eost of super alloys. 

Steel is essentially iron with a small amount of carbon. Additional elements are present in small quantities. Contaminants such as sulfur and phosphorus are tolerated at varying levels, depending on the use to which the steel is to be put. Since they are present in the raw material from which the steel is made it is not economic to remove them. Alloying elements such as manganese, silicon, nickel, chromium, molybdenum and vanadium are present at specified levels to improve physical properties such as toughness or corrosion resistance. 

The alumina content, the amount of rare-earth, and the type and amount of zeolite affect catalyst tolerance to vanadium poisoning. 

A preparation of the third nitrogenase from A. vinelandii, isolated from a molybdenum-tolerant strain but lacking the structural genes for the molybdenum and vanadium nitrogenases, was discovered to contain FeMoco 194). The 8 subunit encoded by anfG was identified in this preparation, which contained 24 Fe atoms and 1 Mo atom per mol. EPR spectroscopy and extraction of the cofactor identified it as FeMoco. The hybrid enzyme could reduce N2 to ammonia and reduced acetylene to ethylene and ethane. The rate of formation of ethane was nonlinear and the ethane ethylene ratio was strongly dependent on the ratio of nitrogenase components. 

Thus there is considerable incentive to find extractants that could tolerate higher quantities of solids in H2SO4 leach liquors. Stripping of uranium from the Amex process extractant and subsequent regeneration of the amine solvent also consume considerable quantities of acid and base. Recovery of uranium from H2SO4 solutions would be simplified if a convenient neutral extractant could be found. An extractant with better selectivity for vanadium and molybdenum than HDEHP and long-chain amines is also desirable. 

ZSM-5 has been used successfully in commercial operations when processing high boiling range feedstock and resids. This is principally due to its ability to maintain activity despite the presence of a high concentration of feed metals. ZSM-5 s excellent metals tolerance has been demonstrated commercially at equilibrium catalyst metals levels up to 10,000 ppm nickel plus vanadium and 6,000 ppm sodium with very little detrimental effect. Laboratory tests show that ZSM-5 is far less affected by metals than Y-zeolite catalysts. Metals were introduced, as follows ... 

DFCr systems appear to have the necessary metals tolerance to process residual oils and the abundant, cheaper, but heavily vanadium-contaminated, Venezuelan and Mexican crudes (1-4). Therefore, the dual function fluid cracking catalyst (DFCC) concept could lead to the generation of important catalysts for U.S. refineries should Middle East politics cause another sudden escalation in crude oil prices and availability. The concept is... 

I can say, for example, that it tends to form chemical bonds to five other atoms at a time, but can tolerate fewer and, at a push, more. It is a metal, probably quite a soft one, heavier than iron but lighter than lead. Many of its compounds - its combinations with other elements - will be coloured. It will be apt to form bonds to other niobium atoms - so-called metal-metal bonds. It will behave chemically in a similar manner to the element vanadium, but will be more similar still to tantalum. 

Additionally, Aykan et al. (98) reported the results for scheelite-type systems in which A sites are occupied by divalent elements and bismuth, and M sites contain vanadium and molybdenum. The tolerance for vacancies in this system was reported to be 15% of the A cation sites. Good yields of acrolein were obained when bismuth and defects were present in the scheelite-structured catalysts. 

Several generations of vanadium metal catchers have been developed (1, 2), leading to an improved activity retention at high vanadium levels on catalyst. The recent progress in nickel tolerance with new nickel encapsulation technologies is just as dramatic. 

Catalysts for ethylene/carbon monoxide copolymerisation were initially obtained from Ni(II) derivatives, such as K2Ni(CN)4 and (w-Bu4N)2 Ni(CN)4, and Pd(II) derivatives, such as [(w-Bu3P)PdCl2]2, Pd(CN)2 and HPd(CN)3, often combined with alcohol or protonic acid as a cocatalyst [241]. It must be emphasised that, in contrast to titanium-, zirconium- or vanadium-based catalysts, nickel- and palladium-based catalysts tolerate polar functional groups (including hydroxyl, carboxylic and sulfonic groups)... 

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