Impregnation, catalyst

In an alternative industrial process, resorcinol [108-46-3] is autoclaved with ammonia for 2—6 h at 200—230°C under a pressurized nitrogen atmosphere, 2.2—3.5 MPa (22—35 atm). Diammonium phosphate, ammonium molybdate, ammonium sulfite, or arsenic pentoxide maybe used as a catalyst to give yields of 60—94% with 85—90% selectivity for 3-aminophenol (67,68). A vapor-phase system operating at 320°C using a siUcon dioxide catalyst impregnated with gallium sesquioxide gives a 26—31% conversion of resorcinol with a 96—99% selectivity for 3-aminophenol (69). 

Figure 9.20. XPS spectra of a chromium polymerization catalyst along with chromium(vi) reference compounds for comparison of the state of chromium in the catalyst. Impregnated chromate in the freshly prepared catalyst shows the same binding energy as alkali chromates/dichromates or bulk Cr03. Upon calcination the binding energy...

GL 18] [R 6a] [P 17] A sol-gel deposited catalyst used in a fixed-bed reactor gave higher conversion than a micro-channel catalyst impregnated on a porous alumina layer [17]. This was due to the higher geometric surface area of the sol-gel deposited catalyst. 

Be careful to keep track of which side is the active side of the catalyst impregnated carbon cloth. The active side has more of the carbon-platinum binder powder and is smoother. 

Keywords Total methane oxidation, Pd-ZSM-5 catalysts, impregnation, solid exchange method, pre-treatment and palladium loading. 

Very prominent pioneering work in the fundamentals of catalyst impregnation was performed by Schwarz and his group [3-7], Several seminal results can be excerpted from their four-part series on CPA impregnation of alumina [3-6], The pH dependence of CPA uptake on alumina was... 

Here again, a number of models exist in the colloid science literature, ranging from very simple to very complex. Adsorption models employed for catalyst impregnation typically contain a chemical component (see [13,14,25] and references therein) for example, the proposed uptake of CPA by alumina shown in Figure 6.16. 

The catalyst/substrate ratio is 1.5 mol% for the supported ionic liquid phase (SILP) catalyst, 3 mol% for the impregnated catalyst and 2 mol% for the homogeneous reaction aRuns 1 -4 are consecutive experiments with the same catalyst in a stirred batch reactor. bDimeric Cr (salen) catalyst impregnated on silica cHomogeneous reaction at 0-2 OC optimized for product selectivity dHomogeneous reaction at room temperature optimized for product selectivity... 

In a series of experimental runs on virgin commercial catalysts and sieves then available and some of our experimental catalysts, we quickly learned that a catalyst impregnated with vanadium, and subjected to high temperatures in steam and air deactivated rapidly. Vanadium, especially in the +5 valence state, rapidly deactivated a catalyst by destroying zeolite crystallinity (Figure 17). In the presence of sodium, the deactivation rate of vanadium was even more severe. (lA-17)... 

The catalyst impregnation on the dispersed CNFs must be carefully optimized to obtain a sufficient dispersion of noble metals. Dispersion ofthe CNF in the particular solvent is desirable for uniform impregnation ofthe catalyst. CNFs with very small diameter are very important for effective dispersion. Sophisticated procedures for dispersion must be applied. In the present study, nanodispersion at an impeller agitation of 16 500 rpm was applied to disperse the thin CNFs better. 

Hydrothermal Deactivation of Catalyst Impregnated with Different Levels of Metal... 

We have tested successfully a variant of this Mukaiyama procedure, that has been described in more detail subsequently (45-46). Our prior experience with nickel(II) catalysts impregnated on clays and nicknamed (47) "claynick" (48) and the convenience of a supported catalyst (49-50) made us opt for clay-impregnated nickel acetylacetonate as the catalyst. 

The selection of raw materials and the method of preparation of the catalyst base are important in determining the final quality of the catalyst. Impregnating almost any iron oxide with potassium hydroxide and drying it will yield a catalyst of some activity, but care must be exercised both in selecting the raw materials and in the method of preparation, if a superior catalyst is to be obtained. Generally, the purer the components the better the catalyst, but substantial quantities of impurities such as silicon dioxide, aluminum oxide, and carbon can be tolerated. Suitable raw materials are obtainable at low cost, and satisfactory methods of preparation are simple and inexpensive. 

In the process jointly developed by Bayer and Hoechst,933-935 a palladium-gold-on-silica or alumina catalyst impregnated with KOAc is used. A mixture of ethylene, acetic acid, and oxygen is converted at 150-170°C and about 5-10 atm to produce vinyl acetate with about 91-92% selectivity at about 10% conversion in a highly exothermic reaction. The only major byproduct is C02. KOAc requires continuous replenishment. A similar process was independently developed by U.S.I. Chemicals.932 936... 

Amorphous and mesostructured Zr02 solid catalysts impregnated with various amounts of triflic acid were tested in the acylation of biphenyl356,357 and toluene358 (with benzoyl chloride and para-toluyl chloride, respectively, nitrobenzene solvent, 170°C and 130°C). All catalysts exhibited lower activity when compared with neat triflic acid. The mesoporous catalysts, however, showed complete selectivity in the formation of para-benzoylbiphenyl. A triflic acid-silica catalyst, in turn, prepared using an aminopropyl-modified silica, showed good characteristics in the solvent-less acetylation of anisole and 2-methoxynaphthalene with acetic anhydride.359,360 The activity of 1,1,2,2-tetrafluoroethanesulfonic acid, either neat or embedded in silica, was found to be similar to that of triflic acid in the acetylation of anisole.196... 

A detrimental effect of excess nitric acid on the ZnO support was observed, resulting in a reduced ZnO particle size and losses of surface area. This excess was present in the palladium nitrate solution that was applied for catalyst impregnation. Additionally it was found that the PdZn alloy was not only formed during the initial reduction step but also in situ in the hydrogen-rich reaction mixture of methanol steam reforming. 

Hydrocarbonization processes are characterized by three primary independent variables - temperature, hydrogen pressure, and coal type - and five other, important independent variables -solid residence time, gas residence time, reactor configuration, coal pretreatment, and catalyst impregnation. Control of these variables permits control, over a wide range, of (1) the relative yields of liquid, gaseous, and solid products, (2) the quality of one or more of these products, (3) hydrogen consumption, and, ultimately (4) product cost. 

Hydrocarbonization yields may also be influenced by catalyst impregnation and coal pretreatment. For example, the yields of liquid and gasious products may be substantially increased by impregnation of the feed coal with ZnCl2 or other catalysts. (3)... 

The operating conditions are gas phase at 170-250°C and Zn(OAc)2 catalyst impregnated on charcoal. Per-pass acetylene conversion is 60-70% with a selectivity of 93% acetylene and 99% acetic acid. High acetylene cost and safety problems make this process less competitive today. 

Gas odorant, solvent for many inorganic substances, catalyst impregnate , ... 

Figure 2. Differentiation between liquefaction and gasification by-product waters by pH and redox potential characteristics 1 and 2, waste water PETC coal liquefaction development unit, disposable catalyst, runs DCD 13B and DCD 12 3, waste water, SRC-1 plant 4, scrubber water, light oil, Blacksville No. 2 coal 5, waste water, fixed-bed gasifier, METC 6, waste water, fluidized-bed gasifier, Rosebud coal, PETC 7, gasifier condensate, 40 atm Nt, catalyst-impregnated Illinois 6 coal 8, gasifier condensate, 40 atm He, Montana Rosebud coal.

E. Reactors with Catalyst Impregnated on Reactor Walls or Placed in an Annular Basket... 

Catalyst Impregnation. The adsorption and desorption isotherm record, and the essential pore size distribution data for a small pore silica-alumina catalyst, are shown in Figure 4. The sample pore size distribution was fairly sharp, in the 15-and 30-A. radii range, and the median pore radius was 27 A. 

Figure 1-1 Various types of segmented fixed-bed gas-liquid-solid reactor, (a) Horizontal segments of bed, (h) vertical segments of bed, (c) annular segments of bed, (d) catalyst impregnated at the wall.

Several reactors are presently used for studying gas-solid reactions. These reactors should, in principle, be useful for studying gas-liquid-solid catalytic reactions. The reactors are the ball-mill reactor (Fig. 5-10), a fluidized-bed reactor with an agitator (Fig. 5-11), a stirred reactor with catalyst impregnated on the reactor walls or placed in an annular basket (Fig. 5-12), a reactor with catalyst placed in a stationary cylindrical basket (Fig. 5-13), an internal recirculation reactor (Fig. 5-14), microreactors (Fig. 5-16), a single-pellet pulse reactor (Fig. 5-17), and a chromatographic-column pulse reactor (Fig. 5-18). The key features of these reactors are listed in Tables 5-3 through 5-9. The pertinent references for these reactors are listed at the end of the chapter. 

Table 5-5 Key features of a stirred reactor with catalyst impregnated on reactor walls or placed in an annular basket...

Ilias and Govind(lO) have reviewed the development of high temperature membranes lor membrane reactor application. Hsieh(4) has summarized the technology in the area of important inorganic membranes, the thermal and mechanical stabilities of these membranes, selective permeabilities, catalyst impregnation, membrane/reaction considerations, reactor configuration, and reaction coupling. 

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