Catalytic Methanol to Hydrocarbons Transformation Particularities in Case of Micro Structured Flows Application

The methanol into hydrocarbons transformation is a complex catalytic reaction accompanied by the formation of a wide range of hydrocarbons and proceeding on the surface of acid sites of various zeolites. Zeolite H-ZSM-5 considered to be most often used catalyst for this process. H-ZSM-5 is a highly dispersed material with a crystal diameter of 1–20 microns, which complicates its direct use in reactors with a fixed catalyst bed due to the high hydraulic pressure drop of the catalytic bed. Traditionally in industry, this issue is solved by using complex reactor systems with a fluidized bed, which is justified for large-scale production. In small and medium-size plants, the use of fluidized bed systems is not economically feasible. One of the possible solutions to this problem is the use of a monolithic catalyst with a supported layer of H-ZSM-5 zeolite. This article presents a study of the catalytic activity of a zeolite-containing microstructured monolith in methanol into hydrocarbons transformation. The monolith was synthesized by pressing a zeolite-containing mass followed by drying, calcining, and secondary growth of the zeolite on the monolith surface. A sample of a monolith with an average channel diameter of 0.5, 1.0, 1.5, 2.0 mm were synthesized this way. Samples of the microstructured catalyst were tested at varying temperatures from 250 to 450 °C and at varying the specific methanol feed rate from 0.65 to 2.3 kg (MeOH)/(kg (Cat) h). For this purpose, the monolithic catalyst was placed in a reactor for testing microstructured catalysts, which consisted of a pump, a temperature controller, a catalytic reactor, a condenser, a separating funnel, and a chromatograph. Varying the conditions showed that for the preferential production of gaseous C1–C4 hydrocarbons, it is advisable to carry out the reaction under the following conditions: the average diameter of the catalyst channels is 2 mm, the reaction temperature is 350 °C, the methanol feed rate is 1.65 kg (MeOH)/(kg (Cat) h). For the predominant formation of liquid hydrocarbons of the C5–C8 fraction, it is advisable to carry out the transformation of methanol into hydrocarbons under the following conditions: the average diameter of the catalyst channels is 1 mm, the reaction temperature is 350 °C, the methanol feed rate is 0.65 kg (MeOH) / (kg (Cat) h). For the predominant formation of liquid hydrocarbons of the C9–C12 fraction, it is advisable to carry out the transformation of methanol into hydrocarbons under the following conditions: the average diameter of the catalyst channels is 0.5 mm, the reaction temperature is 350 °C, and the methanol feed rate is 0.65 kg (MeOH) / (kg (Cat) h).

PECULIARITIES OF SMALL STRAINED ALICYCLE COMPOUNDS FORMATION IN CATALYTIC TRANSFORMATION OF METHANOL OVER ZEOLITE H-ZSM-5

The article presents the results of strained hydrocarbons formation study during the catalytic transformation of methanol into hydrocarbons on zeolite H-ZSM-5. The formation of the following strained cyclic compounds was determined: 1,1-dimethylcyclopropane, 1,2-dimethyl-cyclopropane, 1,1,2-trimethylcyclopropane, 1,2,3-trimethylcyclopropane, 1,1,2,2-tetramethylcyclo-propane, 1,1,2 , 3-tetramethylcyclopropane. The non-stationary character of strained cyclic hydrocarbons formation with a pronounced hydrocarbons formation rate maximum and subsequent deactivation of the catalyst was found. The temperature effect on strained hydrocarbons yield was evaluated. Thus, with an increase in the process reaction temperature up to 400 °C, a maximum of strained hydrocarbons accumulation rate was achieved as 8-8.5 g(Hyd)/(kg(Cat)·h) on 350 h of reaction, and a further increase in the reaction temperature leads to a decrease in the strained hydrocarbons accumulation rate. The effect of the methanol feed rate on the strained hydrocarbons formation rate was also studied. An increase in the methanol feed rate from 0.02 ml/min to 0.16 ml/min results in increase in the strained hydrocarbons formation rate up to 37 g (Hyd)/(kg(Cat)·h). The article presents results of H-ZSM-5 physicochemical study used by ammonia chemisorption, nitrogen phisisorption, X-ray photoelectron spectroscopy. Physicochemical studies of catalyst samples after the methanol transformation process to form strained hydrocarbons showed a twofold decrease in the number of acid sites from 1.2 mmol(NH3)/g (sample) to 0.3 mmol (NH3)/g(sample) and a significant decrease in surface area of micropores from 294 m2/g for the initial sample to 16 m2/g for the sample after the reaction. The X-ray diffraction spectroscopy method showed that the composition of the catalysts H-ZSM-5 surface includes carbon, oxygen, silicon and aluminum. Carbon concentration was found to be 4.3 at.% on the surface of the initial catalyst. While the carbon concentration increases up to 14.1 at.% during the reaction. Also oxygen content on the catalysts surface decreases from 59.9 to 53.4 at%, silica concentration decreases from 35.5 to 32.1 at.%. The following indicates the formation of a carbon surface layer over the catalysts.