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

C2 to C4 olefins are traditionally produced from steam cracking of naphtha. The necessity for alternative production routes for these major commodity chemicals via non-oil-based processes has driven research in past times during the oil crises. Currently, there is a renewed interest in producing lower olefins from alternative feedstocks such as coal, natural gas, or biomass, in view of high oil prices, environmental regulations, and strategies to gain independence from oil imports. This review describes the major routes for the production of lower olefins from synthesis gas with an emphasis on a direct or single step process, the so-called FTO or Fischer–Tropsch to olefins process. The different catalysts for FTO are outlined and compared, and the key issues and requirements for future developments are highlighted. Iron-based catalysts are prevailing for FTO, and reproducible lower olefin selectivities of 50 wt % of hydrocarbons produced have been realized at CO conversions higher than 70% for 60 to 1000 ...

Catalysts for Production of Lower Olefins from Synthesis Gas: A Review

The NH3-SCR activity of the small-pore zeolites, Cu-SSZ-13, Cu-SSZ-16, and Cu-SAPO-34, is investigated using a high-throughput reactor system. These copper exchanged small-pore zeolites have high SCR activity between 150 and 500 °C and are shown to be much more hydrothermally stable than the medium-pore zeolite, Cu-ZSM-5. The degree of copper exchange, the dimensionality of the framework, and heteroatom framework substitution all impact the SCR activity and hydrothermal stability of the materials. Of the small-pore zeolites tested, Cu-SSZ-13 and Cu-SAPO-34 display superior SCR performance, both before and after high-temperature hydrothermal treatment.

The ammonia selective catalytic reduction activity of copper-exchanged small-pore zeolites

Transition-metal ions in aluminophosphate and silicoaluminophosphate molecular sieves: location, interaction with adsorbates and catalytic properties.

IR spectroscopy in catalysis

Small-pore molecular-sieves sapo-34 and sapo-44 with chabazite structure - a study of silicon incorporation

Alkylation of phenol with t -butanol in the vapour phase on SAPO-11 catalyst has been studied. The main products are 4- t -butylphenol,2- t -butylphenol and 2,4-di- t -butylphenol, the last of these is the product of further alkylation of the 2- t -butylphenol.2- t -butylphenol easily isomerises to 4- t -butylphenol whereas the reverse reaction is not significant. Separate studies have shown that both butylphenols undergo easy dealkylation. The results of acid site poisoning by adsorption of bases as well as by sililation suggest that the reaction takes place essentially inside the zeolite pores.

Para-selective butylation of phenol over silicoaluminophosphate molecular sieve SAPO-11 catalyst

Silicoaluminophosphate molecular sieves SAPO-11, SAPO-31 and SAPO-41: synthesis, characterization and alkylation of toluene with methanol

Substitution of Al by Fe and Si in the AlPO4-5 and AIPO4-11 frameworks has been investigated by a number of experimental methods such as electron paramagnetic resonance (EPR), Mossbauer and magic-angle-spinning nuclear magnetic resonance (MASNMR) spectroscopies and temperature-programmed desorption of ammonia. There are indications that FeIII replaces AlIII and the extent of substitution increases with time of reaction. The FAPO-n formed, however, is contaminated with an amorphous phase containing FeIII. Silicon replaces phosphorus in the framework only to a limited extent and in those cases when the synthesis gel had a higher amount of silicon, the product was contaminated with an amorphous silica-containing phase. No evidence for silicon removing a phosphorus–aluminium pair has been found. The conclusions are also supported by the results of acidity measurements and the alkylation of toluene with methanol on these molecular sieve samples.

Substitution of Al in the AlPO4-5 and AlPO4-11 frameworks by Si and Fe: a study by Mössbauer, magic-angle-spinning nuclear magnetic resonance and electron paramagnetic resonance spectroscopies and chemical probes

Dipak K. Chakrabarty

Papers

Small-pore molecular-sieves sapo-34 and sapo-44 with chabazite structure - a study of silicon incorporation

Para-selective butylation of phenol over silicoaluminophosphate molecular sieve SAPO-11 catalyst

Silicoaluminophosphate molecular sieves SAPO-11, SAPO-31 and SAPO-41: synthesis, characterization and alkylation of toluene with methanol

Substitution of Al in the AlPO4-5 and AlPO4-11 frameworks by Si and Fe: a study by Mössbauer, magic-angle-spinning nuclear magnetic resonance and electron paramagnetic resonance spectroscopies and chemical probes

Conversion of syngas to light olefins over silicalite-1 supported iron and cobalt catalysts: Effect of manganese addition