Molecular sieve manufacturer explains the latest development of aromatics conversion research on molecular sieves

For the production of many important products, aromatics are extremely important raw materials in chemical industry, polymerization, agriculture, perfume, wood engineering and other industries. Their chemical changes on molecular sieves mainly involve three main reactions, namely alkylation, isomerization, and disproportionation. To enable the reaction to proceed effectively, using molecular sieves as catalysts is the first choice, as they have high activity, excellent selectivity for the required products, are not easily deactivated, renewable, and environmentally friendly. Below, the editor of molecular sieve manufacturer will explain the latest progress in the study of molecular sieve aromatics conversion.
For the reaction of aromatic hydrocarbon conversion on molecular sieves, most recent papers have focused on toluene alkylation and methanol to xylene, including selecting different types of molecular sieves, changing the characteristics of molecular sieves, or changing the process to achieve maximum para selectivity. In principle, most of the goals of these studies can be divided into the following:
① Optimize catalyst formulations, including different methods of molecular sieve modification;
② Improve process parameters, reactor types, and establish kinetic parameter models;
③ Study the structure and chemical parameters of new molecular sieves.
The main advantage of molecular sieves in the conversion of aromatic hydrocarbons is their speed. They are aluminum silicate crystals with micropores, with pore sizes of approximately 0.4~1.0nm and controllable acidity. The structure of molecular sieves is composed of tetrahedrons of so-called basic structural units: Si04, or AI04, connected by an oxygen bridge. Four Si04 can be connected to the middle Si04 tetrahedron, but according to the Loewenstein rule, direct connection of the Al04 tetrahedron is not allowed. The further combination of the two tetrahedra, AI04 and Si04, leads to the formation of secondary structures and, through their connection, forms pore systems of different sizes and shapes. These pores are often composed of 8, 10, 12, and 14 rings, and even some peculiar or larger rings have been found.
The channels of molecular sieves can be one-dimensional (1D), two-dimensional (2D), or three-dimensional (3D), depending on their connectivity. Some zeolites have channels with different pore sizes, even channel intersections or one-dimensional channels. For the application of molecular sieves in adsorption and catalysis, the size of channels plays a decisive role. For many dynamic diameters of organic reaction, products or transition states, the size of molecular sieve channels is the same. Therefore, when the molecular size of the reactant is greater than the available space of the molecular sieve channel, the reactant cannot penetrate into the interior of the molecular sieve channel, the transition state cannot be formed inside, and the product (if already formed) cannot leave the channel. This phenomenon is called shape selectivity.
There have been many papers discussing this, especially in terms of aromatics conversion. Individual types of shape selectivity can significantly control activity and also control the selectivity of molecular sieves in different reactions. Although approximately 200 types of molecular sieves and similar molecular sieves have been recognized by the International Molecular Sieve Association, only a few of them have been used for research on aromatics conversion. Hunan Providence New Materials Co., Ltd is a professional molecular sieve manufacturer which can provide USY zeolite, NaY zeolite, REY zeolite, ZSM-5 zeolite, welcome to consult.