scholarly journals Methanol-to-Olefin Reaction over MWW and MFI Zeolites: Effect of Pore Structure on Product Distribution and Catalyst Deactivation

2011 ◽  
Vol 49 (5) ◽  
pp. 521-529 ◽  
Author(s):  
Ki Won Song ◽  
Gon Seo ◽  
Chae-Ho Shin
Keyword(s):  
Pore Structure ◽  
Catalyst Deactivation ◽  
Product Distribution ◽  
Methanol To Olefin ◽  
Mfi Zeolites

Study of coke deposition phenomena on the SAPO_34 catalyst and its effects on light olefin selectivity during the methanol to olefin reaction

RSC Advances ◽  
2015 ◽  
Vol 5 (100) ◽  
pp. 81965-81980 ◽  
Author(s):  
Reza Bagherian Rostami ◽  
Mohammad Ghavipour ◽  
Zuoxing Di ◽  
Yao Wang ◽  
Reza Mosayyebi Behbahani
Keyword(s):  
Hydrogen Transfer ◽  
Catalyst Deactivation ◽  
Coke Formation ◽  
Great Influence ◽  
Product Distribution ◽  
Coke Deposition ◽  
Light Olefin ◽  
Methanol To Olefin ◽  
Olefin Selectivity ◽  
Transfer Index

Hydrogen transfer index was found to be a key parameter in prediction of coke deposition behavior. A good macro-model of product distribution with coke formation is provided. Temperature had a great influence on distribution of coke species and catalyst deactivation.

Optimization of Vapor Phase Pyridine Synthesis Hindered by Rapid Catalyst Deactivation

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Suresh Kumar Reddy Kuppi Reddy ◽  
Inkollu Sreedhar ◽  
Kondapuram Vijaya Raghavan ◽  
Shivanand Janardan Kulkarni ◽  
Machiraju Ramakrishna
Keyword(s):  
Catalyst Deactivation ◽  
A Priori ◽  
Coke Formation ◽  
Product Distribution ◽  
Combined Effects ◽  
Reactor Operation ◽  
Proper Selection ◽  
Pyridine Bases ◽  
Deactivation Process ◽  
Selection Of

The synthesis of pyridine bases from acetaldehyde, formaldehyde and ammonia through aminocyclization continues to provide the best prospect for meeting growing demand. A proper selection of catalyst and standardization of process parameters are vital to achieve a market friendly product distribution and reactor operation. In this work, the major responsible factors for enhancing the activity and selectivity of HZS-5 catalysts have been identified and their individual and combined effects on aldehyde conversion, coke formation and selectivity to pyridine formation have been assessed. A priori assessment of catalyst time on stream behavior has been achieved by modeling the catalyst deactivation process.

Preparation of Y Zeolite-Based Catalysts and their Catalytic Cracking Performances of Venezuelan Heavy Oil

2012 ◽  
Vol 608-609 ◽  
pp. 1407-1412
Author(s):  
Peng Hui Zeng ◽  
Bao Jian Shen ◽  
Sheng Fu Ji ◽  
Yun Liang ◽  
Xiang Hai Meng
Keyword(s):  
Pore Structure ◽  
Heavy Oil ◽  
Catalytic Cracking ◽  
Product Distribution ◽  
Pore Distribution ◽  
Oil Yield ◽  
Y Zeolite ◽  
Acidic Properties ◽  
Cracking Performance ◽  
Adsorption Desorption

Five kinds of modified Y zeolite-based fluid catalytic cracking (FCC) catalysts were prepared. The N2 adsorption desorption and NH3 temperature-programmed-desorption (NH3-TPD) were used to investigate the pore structure and acidic properties of the catalysts. The effects of pore structure and acidic properties of catalysts on the catalytic cracking performance of Venezuelan heavy oil were carried out using an advanced cracking evaluation unit. The results of N2 adsorption desorption and NH3-TPD show that CAT-A and CAT-B catalysts with rundle pore distribution have a similar pore sizes and acidSubscript textSubscript textic properties. The catalytic cracking results show that the acidic properties and the pore distribution of the catalysts have obvious effects on the conversion and product distribution. The light oil yield and total liquid oil yield can reach 58.75wt% and 73.83 wt%, respectively, under reaction temperature of 520°C.

scholarly journals Contrasting Arene, Alkene, Diene, and Formaldehyde Hydrogenationin H-ZSM-5, H-SSZ-13, and H-SAPO-34 Zeolite Frameworks during MTO

2019 ◽  
Author(s):  
Mykela DeLuca ◽  
Christina Janes ◽  
David Hibbitts
Keyword(s):  
Selective Hydrogenation ◽  
Density Functional ◽  
High Pressures ◽  
Catalyst Deactivation ◽  
Zeolite Catalysts ◽  
Functional Theory ◽  
As Species ◽  
Methanol To Olefin ◽  
Alkene Hydrogenation ◽  
Thermodynamic Instability

<p>Co-feeding H<sub>2</sub> at high pressures increases zeolite catalyst lifetimes during methanol-to-olefin (MTO) reactions while maintaining high alkene-to-alkane ratios; however, the mechanisms and species hydrogenated by H<sub>2</sub> co-feeds to prevent catalyst deactivation remain unknown. This study uses periodic density functional theory (DFT) to examine hydrogenation mechanisms of MTO product C<sub>2</sub>–C<sub>4</sub> alkenes, as well as species related to the deactivation of MTO catalysts such as C<sub>4</sub> and C<sub>6</sub> dienes, benzene, and formaldehyde in H-MFI and H-CHA zeolite catalysts. Results show that dienes and formaldehyde are selectively hydrogenated in both frameworks at MTO conditions because their hydrogenation transition states proceed via allylic and oxocarbenium cations which are more stable than alkylcarbenium ions which mediate alkene hydrogenation. Diene hydrogenation is further stabilized by protonation and hydridation at α,δ positioned C-atoms to form 2-butene from butadiene and 3-hexene from hexadiene as primary hydrogenation products. This α,δ-hydrogenation directly leads to selective hydrogenation of dienes; pathways which hydrogenate dienes at the α,β-position (e.g., forming 1-butene from butadiene) proceed with barriers 20 kJ mol<sup>-1</sup> higher than α,δ-hydrogenation and with barriers nearly equivalent to butene hydrogenation, despite α,β-hydrogenation of butadiene also occurring through allylic carbocations. Hydrogenation of formaldehyde, a diene precursor, occurs with barriers that are within 15 kJ mol<sup>-1</sup> of diene hydrogenation barriers, indicating that it may also contribute to increasing catalyst lifetimes by preventing diene formation. Benzene, in contrast to dienes and formaldehyde, is hydrogenated with higher barriers than C<sub>2</sub>–C<sub>4</sub> alkenes despite proceeding via stable benzenium cations because of the thermodynamic instability of the product which has lost aromaticity. Carbocation stabilities predict the relative rates of alkene hydrogenation and in some cases shed insights into the hydrogenation of benzene, dienes, and formaldehyde, but cation stabilities alone cannot account for the poor hydrogenation of benzene or the facile hydrogenation of dienes, boosted by stabilization conferred by a,δ-hydrogenation. This work suggests that the main mechanisms of catalyst lifetime improvement with high H<sub>2</sub> co-feeds is reduction of diene concentrations through both their selective hydrogenation and hydrogenation of their precursors to prevent formation of deactivating polyaromatic species.</p>

scholarly journals Hierarchical H-MOR Zeolite Supported Vanadium Oxide for Dimethyl Ether Direct Oxidation

Catalysts ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 628 ◽  
Author(s):  
Wenfeng Wang ◽  
Xiujuan Gao ◽  
Ru Feng ◽  
Qi Yang ◽  
Tao Zhang ◽  
...  
Keyword(s):  
Vanadium Oxide ◽  
Pore Structure ◽  
Dimethyl Ether ◽  
Active Sites ◽  
Synthesis Method ◽  
Product Distribution ◽  
Acid Sites ◽  
Synthesis Methods ◽  
Direct Oxidation ◽  
Post Synthesis

A series of hierarchical H-MOR zeolites with different pore structure were designed and synthesized by alkaline and alkaline-acid post-synthesis methods. The catalytic performance of hierarchical H-MOR zeolite-supported vanadium oxide was investigated for dimethyl ether (DME) direct oxidation. Different pore structures apparently affect the distribution of oxidation product distribution, especially the selectivity of DMMx and CO. The formation of mesopores for 10%V2O5/deAlmm-H-MOR markedly improved the DMMx selectivity up to 78.2% from 60.0%, and more notably, CO selectivity dropped to zero compared to that of 10%V2O5/H-MOR. The hierarchical H-MOR zeolites were confirmed to be successfully prepared by the post-synthesis method. Due to the presence of mesoporous structure, the dispersion of vanadium oxide species was enhanced, which could improve the reducibility of vanadium oxide species and also make better contact with the acid sites of zeolite to exert the synergistic effect of the bifunctional active sites. More importantly, the creation of mesopores was proved to be favorable to the mass transfer of intermediate and products to avoid the occurrence of secondary reaction, which could effectively suppress the formation of by-products. This work is helpful for us to provide a novel insight to design the catalyst with suitable pore structure to effectively synthesize diesel fuel additives from DME direct oxidation.

Surface and Pore Structure Assessment of Hierarchical MFI Zeolites by Advanced Water and Argon Sorption Studies

2012 ◽  
Vol 116 (35) ◽  
pp. 18816-18823 ◽  
Author(s):  
Matthias Thommes ◽  
Sharon Mitchell ◽  
Javier Pérez-Ramírez
Keyword(s):  
Pore Structure ◽  
Structure Assessment ◽  
Mfi Zeolites

Impact of hierarchical pore structure on the catalytic performances of MFI zeolites modified by ZnO for the conversion of methanol to aromatics

2017 ◽  
Vol 7 (16) ◽  
pp. 3598-3612 ◽  
Author(s):  
Xinquan Shen ◽  
Jincan Kang ◽  
Wei Niu ◽  
Mengheng Wang ◽  
Qinghong Zhang ◽  
...  
Keyword(s):  
Pore Structure ◽  
Catalyst Stability ◽  
Hierarchical Pore Structure ◽  
Hierarchical Pore ◽  
Mfi Zeolites ◽  
Catalytic Performances

The increase in the pore hierarchy of ZnO/hierarchical H-ZSM-5 catalysts increased the catalyst stability and the yield of aromatics, particularly BTX, from methanol.

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