Lewis Acids: From Conventional Homogeneous to Green Homogeneous and Heterogeneous Catalysis

Heteropolyanions are polymeric oxoanions which are formed by the condensation of more than two different oxoanions [Eq. (1)l. Polyanions consisting of one kind of oxoanion are called isopolyanions [Eq. (2)]. Acidic elements such as Mo, W, V, Nb, and Ta are present as oxoanions in aqueous solutions and polymerize to form polyanions at low pH. Free acids (or acid forms) of these species are called heteropoly and isopoly acids, respectively. Here, the term “heteropoly compounds” is used for heteropoly acids and their salts.

Heterogeneous catalysis by heteropoly compounds of molybdenum and tungsten

Infrared spectrometric studies of the surface basicity of metal oxides and zeolites using adsorbed probe molecules

The steam reforming process converts hydrocarbons into mixtures of hydrogen, carbon monoxide, carbon dioxide, and methane 

$$C_n H_m + nH_2 O \to nCO + \left( {n + \frac{m}{2}} \right)H_2 \left( { - \Delta H_{298}^0 < 0} \right) $$

(1)



$$ CO + H_2 O \rightleftarrows CO_2 + H_2 \left( { - \Delta H_{298}^0 = 41.2kJ\,mol^{ - 1} } \right) $$

(2)



$$ CO + 3H_2 \rightleftarrows CH_4 + H_2 O\left( { - \Delta H_{298}^0 = 206.2kJ\,mol^{ - 1} } \right) $$

(3)

The expression reforming is misleading since it is used also for the well-knowm process for improvement of the octane number of gasoline [1]. In the gas industry, reforming has generally been used for “the changing by heat treatment of a hydrocarbon with high heating value into a gaseous mixture of lower heating value” [2].

Catalytic Steam Reforming

This article is an up-to-date review of the literature available on the subject of ethanol to ethylene. The process of ethanol to ethylene has broad development prospects. Compared with the process of petroleum to ethylene, ethanol dehydration to ethylene is economically feasible. Researchers have been redirecting their interest to the ethylene production process, catalysts, and reaction mechanisms. A fluidized bed reactor, together with a wear-resistant, efficient, and stable catalyst will be the focus of future research that includes a deep understanding of the large-scale activated alumina catalyst and the molecular sieve catalyst used, and will promote the development of the ethanol dehydration to ethylene process and provide strong support for the market competiveness of the process.

Dehydration of Ethanol to Ethylene

Base-strength distribution studies of solid-base surfaces

Linear free-energy relationships in heterogeneous catalysis. VI. Catalytic elimination reaction of hydrogen chloride from chloroethanes on solid acids and bases

Ethanol dehydration on alumina catalysts: I. The thermal desorption of surface compounds

When pyridine chemisorbed on silica–alumina was evacuated at 350°C, the 1460 cm−1 band due to Lewis-bound pyridine (LPY) remained while the 1540 cm−1 band due to Bronsted-bound pyridine (BPY) compl...

Nature of catalytically active sites over solid acids. I. Selective poisoning of Lewis acid sites on silica-alumina with pyridine and its application to olefin polymerization.

A new UV-spectrophotometric n-butylamine titration method was proposed for measuring acid-strength distribution of acid sites on solid acid catalysts. The method can provide information on acid-strength distribution of acid sites beyond H0=−8.2, which can not be obtained by the conventional visual n-butylamine titration method. Acid-strength distributions were measured for a series of silica-alimina catalysts differing in sodium content, using 4-benzeneazodiphenylamine (pKa=1.5), trans-benzalacetophenone (pKa=−5.6), 4-nitrotoluene (pKa=−10.5), and 2,4-dinitrotoluene (pKa=−12.8) as indicators. The results revealed that about one-half of the acid sites on an unpoisoned silica-alumina catalyst lay in the H0 region from −10.5 to −12.8, and the strongest ones in the H0 region beyond −12.8. The strong acid sites were eliminated with the modification of acid-strength distribution as the catalyst was poisoned with sodium ions. UV spectra of the above indicators in adsorbed state were discussed.

Jun-ichiro Take

Papers

Base-strength distribution studies of solid-base surfaces

Linear free-energy relationships in heterogeneous catalysis. VI. Catalytic elimination reaction of hydrogen chloride from chloroethanes on solid acids and bases

Ethanol dehydration on alumina catalysts: I. The thermal desorption of surface compounds

Nature of catalytically active sites over solid acids. I. Selective poisoning of Lewis acid sites on silica-alumina with pyridine and its application to olefin polymerization.

Measurements of Acid-strength Distribution beyond H0=−8.2 of Silica-Alumina Catalysts by UV-Spectrophotometric n-Butylamine Titration Method