Date of Award

3-2023

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

First Advisor

Abbas Khaleel

Abstract

Due to different technical challenges associated with direct use of methane, the main component of natural gas, its conversion to higher hydrocarbons has been a subject of great industrial importance. All of the known routes for methane conversion are catalytic processes, where the performance is largely dependent on the physicochemical properties of the catalyst. The catalysts that have shown promising performance in methane reforming are based on expensive metals such as Pt, Pd, and Ru. Ni, on the other hand, is a cost-effective metal and has shown promising catalytic activity. These catalysts are usually in the form of metal nanoparticles supported on an oxide powder such as Al2O3 and MgAl2O4. The support very often plays a role in surface catalytic reactions. For example, MgAl2O4, which is the support investigated in this research, has been found to be a promising support for Ni catalysts where its physicochemical properties play a role in minimizing coke formation that usually leads to catalyst deactivation. Its textural properties as well as its surface basic site density were found to play key roles in enhancing coking resistance. Since solid characteristics very often depend on the preparation method and conditions, the main aim of the research herein is to prepare MgAl2O4 as a support for Ni catalysts by different methods and correlate between the preparation methods and its final properties especially the surface acid-base characteristics and textural properties. The different preparation methods that were investigated include sol-gel, and co-precipitation. Ni/MgAl2O4 is prepared using the differently prepared supports employing wet impregnation. Correlation between preparation methods and physicochemical characteristics of the prepared catalyst as well as their coking resistance during partial oxidation of methane reaction were studied.

Arabic Abstract

ﺴﺑﺒﺐ اﻟﺘﺤﺪﯾﺎت اﻟﺘﻘﻨﯿﺔ اﻟﻤﺨتلفة اﻟﻤﺮﺗﺒﻄﺔ ﺑﺎﻻﺳﺘﺨﺪام اﻟﻤﺒﺎﺷﺮ ﻟﻠﻤﯿﺜﺎن، اﻟﻤﻜﻮن اﻟﺮﺋيسي ﻟﻠﻐﺎز اﻟﻄﺒﯿﻌﻲ، ﻛﺎن ﺗﺤﻮﯾﻠﮫ إﻟﻰ ھﯿﺪروﻛﺮﺑﻮﻧﺎت أﻋﻠﻰ ﻣﻮﺿﻮﻋًﺎ ذا أھﻤﯿﺔ ﺻﻨﺎﻋﯿﺔ ﻛﺒﯿﺮة. ﺟﻤﯿﻊ اﻟﻄﺮق اﻟﻤﻌﺮوﻓﺔ ﻟﺘﺤﻮﯾﻞ اﻟﻤﯿﺜﺎن ھﻲ ﻋﻤﻠﯿﺎت ﺤﺗﻔﯿﺰﯾﺔ، ﺣﯿﺚ ﯾﻌﺘﻤﺪ اﻷداء إﻟﻰ ﺣﺪ ﻛﺒﯿﺮ ﻋﻠﻰ اﻟﺨﺼﺎﺋﺺ الفيزيائية الكيميائية ﻠﻟﻤﺤﻔﺰ. واﻟﻤﺤﻔﺰات اﻟﺘﻲ أظﮭﺮت أداءً واﻋﺪًا ﻓﻲ ﺗﺤﻮﯾﻞ اﻟﻤﯿﺜﺎن ﺗﺴﺘﻨﺪ إﻟﻰ ﻣﻌﺎدن ﺑﺎھﻈﺔ اﻟﺜﻤﻦ ﻣﺜﻞ البلاتين واﻟﺒﻼدﯾﻮم والروﺛﯿﻨﯿﻮم. واﻟﻨﯿﻜﻞ، ﻣﻦ ﻧﺎﺣﯿﺔ أﺧﺮى، ھﻮ ﻣﻌﺪن ﻓﻌﺎل ﻣﻦ ﺣﯿﺚ اﻟﺘﻜﻠﻔﺔ وﻗﺪ أظﮭﺮ ﻧﺸﺎطًﺎ ﺗﺤﻔﯿﺰﯾًﺎ واﻋﺪًا. وﻋﺎدة ﻣﺎ ﺗﻜﻮن ھﺬه اﻟﻤﺤﻔﺰات ﻋﻠﻰ ﺷﻜﻞ جسيمات ﻧﺎﻧﻮﯾﺔ ﻣﻌﺪﻧﯿﺔ ﻣﺪﻋﻮﻣﺔ ﻋﻠﻰ ﻣسحوق أﻛﺴﯿﺪ ﻣﺜﻞ الألومينا وأﻟﻮﻣﯿﻨﺎت اﻟﻤﻐﻨﯿﺴﯿﻮم. وﯾﻠﻌﺐ اﻟﺪاﻋﻢ دوراً ﻓﻲ التفاعلات التحفيزية السطحية. على ﺳﺒﯿﻞ اﻟﻤﺜﺎل، ﺗﻢ العثور ﻋﻠﻰ أن أﻟﻮﻣﯿﻨﺎت اﻟﻤﻐﻨﯿﺴﯿﻮم، وھﻲ ﻣﻮﺿﻮع ھﺬا البحث، داﻋﻤًﺎ واﻋﺪاً ﻟﻤﺤﻔﺰات النيكل حيث ﺗﻠﻌﺐ ﺧﺼﺎﺋﺼﮭﺎ اﻟﻔﯿﺰﯾﺎﺋﯿﺔ اﻟﻜﯿﻤﯿﺎﺋﯿﺔ دوراً ﻓﻲ ﺗﻘﻠﯿﻞ ﺗﺮﺳﺐ اﻟﻜﺮﺑﻮن اﻟﺬي ﯾﺆدي ﻋﺎدةً إﻟﻰ ﺗﻌﻄﯿﻞ اﻟﻤﺤﻔﺰ. ووﺟﺪ أن ﻛﺜﺎﻓﺔ المواﻗﻊ القاﻋﺪﯾﺔ السطحية، ﻋﻠﻰ وﺟﮫ الخصوص، ﻟﮭﺎ دور رﺋﯿﺴﻲ ﻓﻲ ﺗﻌﺰﯾﺰ ﻣﻘﺎوﻣﺔ ﺗﺮﺳﺐ اﻟﻜﺮﺑﻮن. وﻧﻈﺮاً ﻷن اﻟﺨﺼﺎﺋﺺ اﻟﺼﻠﺒﺔ ﺗﻌﺘﻤﺪ ﻓﻲ ﻛﺜﯿﺮ ﻣﻦ اﻷﺣﯿﺎن ﻋﻠﻰ طﺮﯾﻘﺔ وشروط اﻟﺘﺤﻀﯿﺮ، فإن اﻟﮭﺪف اﻟﺮﺋﯿﺴﻲ ﻟﻠﺒﺤﺚ ھﻨﺎ ھﻮ ﺗﺤﻀﯿﺮ أﻟﻮﻣﯿﻨﺎت اﻟﻤﻐﻨﯿﺴﯿﻮم كداﻋﻢ ﻟﻤﺤﻔﺰات النيكل بطرق ﻣﺨﺘﻠﻔﺔ واﻟﻌﻼﻗﺔ ﺑﯿﻦ طرق اﻟﺘﺤﻀﯿﺮ وﺧﺼﺎﺋﺼﮭﺎ اﻟﻨﮭﺎﺋﯿﺔ وﺧﺎﺻﺔ ﺧﺼﺎﺋﺺ اﻟﻘﻮاﻋﺪ واﻷﺣﻤﺎض اﻟﺴﻄﺤﯿﺔ واﻟﺨﺼﺎﺋﺺ اﻟﻨﺴﯿﺠﯿﺔ. وﺗﺸﻤل طرق اﻟﺘﺤﻀﯿﺮ اﻟﻤﺨﺘﻠﻔﺔ اﻟﺘﻲ ﺳﯿﺘﻢ ﻓﺤصها – Sol gel Co-precipitation. وﯾﺘﻢ ﺗﺤﻀﯿﺮ اﻟﻤﺤﻔﺰ Ni/MgAl2O4 باﺳﺘﺨﺪام اﻟﺪﻋﺎﻣﺎت اﻟﻤﺤﻀﺮة ﺑﺸﻜﻞ ﻣﺨﺘﻠﻒ ﺑﻮاﺳﻄﺔ Wetness impregnation. وﺗﻤﺖ دراﺳﺔ الارﺗﺒﺎط ﺑﯿﻦ طﺮق اﻟﺘﺤﻀﯿﺮ واﻟﺨﺼﺎﺋﺺ اﻟﻔﯿﺰﯾﺎﺋﯿﺔ اﻟﻜﯿﻤﯿﺎﺋﯿﺔ ﻟﻠﻤﺤﻔﺰ اﻟﻤﺤﻀﺮ وﻛﺬﻟﻚ ﻣﻘﺎوﻣﺔ ﻓﺤﻢ اﻟﻜﻮك أﺛﻨﺎء الأكسدة اﻟﺠﺰﺋﯿﺔ لتفاعل اﻟﻤﯿﺜﺎن.

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