A Study On Catalytic Materials For Efficient Conversion Of Syngas

Syngas is an important raw material for chemical production.It is obtained from the conversion of carbon-containing minerals such as coal, petroleum and natural gas,which in turn can be used to synthesize a variety of chemicals such as oil and aromatics.In this paper,the study of catalytic materials for efficient conversion of syngas is divided into two parts:efficient cobalt-based molecular sieve catalysts for syngas to gasoline and efficient molecular sieve catalysts for methanation co-production of aromatics.China’s foreign dependence on oil has exceeded 50%in recent years.Therefore,China’s petroleum industry urgently needs to expand and diversify raw materials from a single crude oil,and this industry transformation has become a major trend in China’s petroleum industry.Vigorously developing modern coal chemical industry,looking for alternative energy to petroleum,and researching new technology of Fischer-Tropsch synthesis are of great significance to national energy security on the one hand,and can alleviate the problem of environmental pollution on the other.An important aspect of Fischer-Tropsch synthesis technology is the regulation of product distribution,and this study was conducted to improve the quality of gasoline synthesized by Fischer-Tropsch.The product distribution of conventional catalysts for Fischer-Tropsch synthesis is under the ASF distribution,with a theoretical maximum of about 40%for the gasoline fraction and a predominance of straight-chain hydrocarbons in the product.This study aims to design a bifunctional catalyst to improve the selectivity of gasoline fraction by secondary reaction of Fischer-Tropsch synthesis products,and to increase the isomerization ratio of gasoline fraction to improve the quality of gasoline.This study was designed in the Fischer-Tropsch synthesis of high-quality gasoline.The embedded Co@HBeta molecular sieve catalysts with better crystallinity were synthesized in one step under certain ratios using Co/Si O₂as the silica source,TEAOH as the template agent,and no metal ion basic modifier such as Na OH was added.A comprehensive characterization of the conventional Fischer-Tropsch synthesis catalyst Co/Si O₂,the impregnated Co/HBeta molecular sieve catalyst,and the new embedded Co@HBeta molecular sieve catalyst was found by XRD,TEM,STEM,NMR,Py-IR,NH₃-TPD,etc.The Co species of the embedded Co@HBeta molecular sieve were embedded in the molecular sieve as clusters from the conventional Fischer-Tropsch synthesis catalyst Co/Si O₂without significant changes,while the Co species interacted weakly with the molecular sieve chemistry.In contrast,the active center Co interacts more strongly with the molecular sieve in the impregnated Co/HBeta molecular sieve catalyst.The reaction performance of the unified Fischer-Tropsch catalyst Co/Si O₂,the impregnated Co/HBeta molecular sieve catalyst,and the new embedded Co@HBeta molecular sieve catalyst were evaluated,and it was found that the embedded Co@HBeta molecular sieve catalyst showed excellent performance in the Fischer-Tropsch synthesis of high-quality gasoline,and at 250℃ and 1Mpa,the gasoline component of the conventional catalyst was The embedded catalysts showed good catalyst activity and stability in the long reaction time of 100 h,maintaining 64.1%gasoline selectivity and 2.31 product isomerization ratio.And the catalyst characteristics such as morphological acidity were well maintained after the reaction.It has good catalytic performance for Fischer-Tropsch synthesis to produce high-quality gasoline.Aromatics are important basic raw materials for the petrochemical industry.Among the total of about 8 million known organic compounds,aromatic compounds account for about 30%,among which benzene（B）,toluene（T）and xylene（X）are second only to ethylene and propylene in terms of production and scale,and are known as the first-class basic organic raw materials.In recent years,the research on direct synthesis of aromatics from syngas has become a hot topic of interest.In the conventional synthesis of aromatics directly from syngas,a bimetallic molecular sieve bifunctional catalyst is generally used to produce oxygen-containing intermediates or hydrocarbon intermediates through methanolization reaction or Fischer-Tropsch synthesis reaction as the first step reaction.In this study,based on the previous research,we creatively use methane as the reaction intermediate and synthesize aromatics by coupling methanation reaction with methane aromatization reaction to realize reaction coupling and heat coupling in the reaction.Meanwhile,the bimetallic embedded catalyst Ni Mo@HZSM-5 was synthesized by hydrothermal synthesis through two-step impregnation of the precursor catalyst Ni Mo/Si O₂as the precursor,and no Ni,Mo miscrystallization was found from the XRD analysis.The embedded bimetallic Ni Mo@HZSM-5 catalyst has high crystallinity of molecular sieve,and the catalyst is well-formed without Ni,Mo mixed crystals.The metal species are embedded in the molecular sieve skeleton with uniform distribution and weak interaction with the molecular sieve.The specific surface area of the catalyst changed less compared with the pure phase HZSM-5,and the acidic site distribution was maintained with the pure phase HZSM-5 type catalyst,which maintained the amount of B-acid acid in the catalyst.The embedded catalyst Ni Mo@HZSM-5 showed good catalyst performance at Ni,Mo loading mass fraction percentages of 20,10,reaction temperature of 300℃ and atmospheric pressure,good stability within 50h reaction time,aromatic selectivity of 14.1%,and simple product distribution with low carbon accumulation,and excellent catalytic performance.The direct synthesis of aromatics from syngas with methane as intermediate was achieved at a lower temperature and atmospheric pressure.