Catalytic test reaction

Acidic micro- and mesoporous materials, and in particular USY type zeolites, are widely used in petroleum refinery and petrochemical industry. Dealumination treatment of Y type zeolites referred to as ultrastabilisation is carried out to tune acidity, porosity and stability of these materials [1]. Dealumination by high temperature treatment in presence of steam creates a secondary mesoporous network inside individual zeolite crystals. In view of catalytic applications, it is essential to characterize those mesopores and to distinguish mesopores connected to the external surface of the zeolite crystal from mesopores present as cavities accessible via micropores only [2]. Externally accessible mesopores increase catalytic effectiveness by lifting diffusion limitation and facilitating desorption of reaction products [3], The aim of this paper is to characterize those mesopores by means of catalytic test reaction and liquid phase breakthrough experiments. 

Lercher, J.A., Jentys, A., and Brait, A. (2008) Catalytic test reactions for probing the acidity and basicity of zeolites. Mol. Sieves, 6,153-212. 

Corma, A., Chica, A., Gull, J.M., Uopis, F.J., Mabilon, G., Perigon-Melon, A., and Valencia, S. (2000) Determination of the pore topology of zeolite IM-5 by means of catalytic test reactions and hydrocarbon absorption measurements. f Catal, 189, 382-394. 

Webb, E.B., III and Grest, G. (1998) Influence of intracrystalline diffusion in shape selective catalytic test reactions. Catal. Lett., 56, 95-104. 

Several catalytic test reactions have been used for indirect characterization of acid and base properties of solids (78). Among them, decomposition of alcohols such as 2-propanol (79,80), 2-methyl-3-butyn-2-ol (81,82), 2-methyl-2-butanol (83), cyclo-hexanol (84), phenyl ethanol (55), and t-butyl alcohol (86) have been investigated. In... 

Catalytic test reactions represent an important tool for acid-basic characterization. Conversion of secondary alcohols such as isopropanol, 2-butanol, and cyclohexanol either to olefins or to ketones, is considered to be evidence of acidic and basic behavior, respectively [104],... 

Catalytic test reactions (n-hexane cracking) prove that partially crystallized biphasic ZSM-5 containing silicate materials are catalytically active composites. The activity of the prepared biphasic silicates is related to the crystalline fraction in the pellets. 

Zamaraev and Thomas provide a concise summary of work done with a family of classic catalytic test reactions—dehydration of butyl alcohols—to probe the workings of acidic molecular sieve catalysts. This chapter echoes some of the themes stated by Pines and Manassen, who wrote about alcohol dehydration reactions catalyzed by solid acids in the 1966 volume of Advances in Catalysis. 

Homogeneous catalysis is, of course, a major field in it s own right, as catalytic transformations are important synthetic tools. However, catalysis is also a potentially sensitive probe for nanoparticle properties and surface chemistry, since catalytic reactions are ultimately carried out on the particle surface. In the case of bimetallic DENs, catalytic test reactions have provided clear evidence for the modification of one metal by another. DENs also provide the opportunity to undertake rational control experiments not previously possible to evaluate changes in catalytic activity as a function of particle composition. 

Catalytic test reactions have been widely used to characterize the basicity of catalysts. The decomposition of 2-methyl-3-butyn-2-ol[291 and the conversion of... 

As a catalytic test reaction, the epoxidation of cyclooctene with t-BuOOH was studied. Although the complex leaches from an Al-containing MCM-41,... 

The chosen catalytic test reaction was the oxidation of phenol, which yields a mixture of catechol, hydro-quinonc, and 1,4-benzoquinone (Scheme I). The reaction was conducted at atmospheric pressure by continuously adding aqueous H2O2 to a mixture of catalyst, phenol, water, and a solvent (either methanol or acetone) at the reaction temperature (usually 373 K) reaction times were l-4h. Conversions and product sclectivities depended on the composition of this mixture under the best conditions, H2O2 conversion was 100%, phenol conversion 27%, and phenol hydrox-ylation selectivity 91%. The ratio of o />-substituted products (Scheme 1) was usually about unity. It was concluded that catalytic performance depended critically on calcination conditions, i.e. on the completeness of removal of the template. Many facets of the reaction remain to be investigated. 

The acid or base strength is defined by comparing the interaction between the sites and reference (probe) molecules. For example, the acid strength is the ability of the site to convert an adsorbed reference neutral base into its conjugate acid. This process may be monitored by following the colour changes of the indicators or by such techniques as IR or NMR spectroscopies. Several criteria must be considered in the selection of these probes their pK value must be adapted to the acidity or basicity of the surface under study the size of the probe molecules should ensure that all sites are readily accessible finally, the probe should be selected so that its interaction with the surface is easily studied by the available experimental techniques. Catalytic test reactions are sometimes used... 

Several methods have been used to determine the surface acidity of solid acids, but each method has its limitations. Common methods are titration with the Hammett indicators, temperature-programmed desorption (TPD), adsorption microcalorimetry, catalytic test reactions, and IR and NMR spectroscopies. These techniques exhibit several advantages and disadvantages. 

As revealed by selected catalytic test reactions, the effective pore width of zeolite MCM-22 is between those of medium pore and the very large pore materials [16-18]. Due to its very large cavities which, on the other hand, can be reached exclusively via 10-membered ring windows, this zeolite offers a remarkable potential for shape selective catalysis involving bulky transition states. 

The catalytic test reaction, the acylation of 2-methox)maphthalene (2MN), distinguishes between the inner and outer surfaces by means of product selectivity. Absorption experiments under the same reaction conditions show that the linear ketone product 2-acetyl-6-methoxynaphthalene (2AC) can pass through the 12-ring channels of beta whereas the other product l-acetyl-2-methoxynaphthalene (lAC) is too bulky to enter into any zeolite except Y. Once formed, lAC is unstable in the presence of acids and can deacylate to give the starting material (see reaction scheme 1). Since 1 AC can only form outside the micropore space of zeolite beta, the yield can be used as a measure of the catalytic activity on the external surface, although high yields can be expected because the 1-position is the most favoured for electrophilic attack. 

The cracking of w-hexane and -butane as catalytic test reactions show unexpected results upon laser heating of the samples. Methane/coke deposits were obtained. The assignment of the intermediates which have life times of some seconds requires further work. 

Table 1 shows the results of the catalytic test reactions as well as carbon and chlorine contents. It can be noted that sanq)les regenerated with a stream containing 0.01% and 0.03% chloride show almost the same amount of chloride. In both cases these results correspond to white pellets and we can thus conclude that low amounts of chloride (e.g. 0.01%) are enough to produce particles with concentrations close to that in fresh catalysts. However in this case, some dark particles with a concentration as low as that in samples burnt without chloride are also obtained. It confirms that, in the regeneration experiments performed with the intermediate value of chloride, there is a difiiisional limitation in the outermost layers of the pellets. 

The selective oxidation of D-glucose into gluconic acid was selected as catalytic test reaction. The reactor vessel and the experimental conditions were described in detail elsewhere [8]. The pH of the reaction mixture was kept at a constant value in the range 9.25-9.45 by adding a 20 wt.% aqueous solution of sodium hydroxide with an automatic titrator (Stat Titrino 718) from METROHM. The base consumption was recorded as a function of time. 

The catalytic test reactions were carried out in a microreactor under the following conditions reaction temperature T = 330°C atmospheric pressure with 0.7 % o-xylene in air, and a space time W/F = 5.0 10 kgeat f h. Under test conditions the catalysts were diluted in quartz (1 7 wt. %). 

The selective oxidation of D-glucose into gluconic acid was selected as catalytic test reaction. The reactor vessel and the experimental conditions were described in detail elsewhere... 

The pore width of large pore zeolites like HY, HM, H6, can be characterized by proper catalytic test reactions. The isopropylation of large molecules like meta DIPB (Diisopropylbenzene) is a reaction wherein the formation of isomeric DIPB s isomeric TIPB s (Triisopropylbenzene) signify the pore dimensions and the structural properties. Thus isomerization is the major reaction in H13, whereas isomerization and alkylation of DIPB with isopropanol compete in HY. However no activity is observed in HM. It is known that bulky 1,3 DIPB does not enter the pores of HM. Similarly the formation of 1,2,4 TIPB in HY and 1,3,5 TIPB in HI3 depend on the structural features. The acidic nature of zeolite does not influence the product formation. 

Si-VPI-5 is synthesized according to a novel method using aluminium isopropoxide as source of aluminium and using a recipe from literature. The samples are compared with SAPO-5 and SAPO-11 using 27Al and 29si MAS NMR, thermoanalysis and the decane catalytic test reaction. The Si for P isomorphic substitution mechanism, which generates Brpnsted acidity in SAPO-5 and SAPO-11 is not active in Si-VPI-5. An explanation for the fiindamental difference between SAPO-n materials and Si-VPI-5 is offered. 

A V-ZSM-5 sample with a Si/V o 42 was synthetized outgoing from V0(C00)2 and Q-brand sodium silicate using TPA-Br as template. ESR spectroscopy proved that vanadium(IV) ions in the zeolitic framework exhibit a distorted square planar symmetry. Upon heat treatment a part of the framework vanadium ions migrate to extra-framework positions. After dehydration no Bronsted acidity was found. Treatment in oxygen and hydrogen above 570 K revealed the redox character of the V-ZSM-5 sample. In oxidation of n-bu-tane (as catalytic test reaction) the V-ZSM-5 zeolite exhibits selective dehydrogenation and aromatization activity. 

According to the physico-chemical characterization there are essential differences in the individual samples Investigated. Two catalytic test reactions and both nitrogen and hydrogen as carrier gases have been applied to provide some information about the effect of nickel-modification on the catalytic properties. 

By varying the exposure time to UV-light, it is found by TEM and XAFS that the Pt nanoparticles are initially formed by the photo-reduction of the impregnated Pt cations in the mesopores. Subsequently, [PtClg] - ions migrate in the vicinity of the nanoparticles and are reduced on the surface and extend into the nanowires in the confined channels of FSM-16, as represented in Fig. 10(a). Ryoo reported the thermal preparation of the Pt nanowires in MCM-41 by the stepwise H2-reduction of Pt ions that were added to the pre-reduced Pt/MCM-41 above 823 As catalytic test reactions for Pt nanowires/FSM-16, Ichikawa et al. studied... 

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