Nickel Catalyst Activation for Selective Olefin Purification
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Solution Overview
Problem
Current processes for converting ethane to liquid fuels face challenges due to the rapid deactivation of zeolite oligomerization catalysts by contaminants like acetylene and butadiene, and existing hydrogenation catalysts lack selectivity, leading to excessive hydrogenation of ethylene.
Innovation Solution
A process involving thermal activation of a nickel hydrogenation catalyst with a mixed gas containing hydrogen and hydrogen sulfide, gradually increasing temperature in increments, results in a modified catalyst with increased selectivity for acetylene and butadiene hydrogenation and decreased selectivity for ethylene, achieving over 90% removal of both contaminants while minimizing ethylene hydrogenation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing hydrogenation catalysts are used to remove acetylene and butadiene, then contaminant removal efficiency is improved, but selectivity towards ethylene hydrogenation increases causing excessive hydrogenation and loss of ethylene
Solution Approach 1:
The patent applies parameter changes by modifying the catalyst through controlled exposure to hydrogen sulfide and temperature cycling. This transforms the catalyst's chemical and physical properties, creating a modified nickel catalyst with enhanced selectivity. The specific parameters changed include: exposure to H2S gas at controlled temperatures (25-50°C initially, then ramped to 350°C), controlled temperature cycling, and controlled gas flow rates. These parameter changes result in a catalyst that selectively hydrogenates acetylene and butadiene while minimizing ethylene hydrogenation.
Solution Approach 2:
The patent uses hydrogen sulfide as an intermediary substance to modify the nickel catalyst. The H2S acts as a mediator that transforms the catalyst's properties without being the final product. During the activation process, H2S exposes the nickel catalyst to controlled conditions that create a modified surface structure. This intermediary approach allows the catalyst to achieve the desired selectivity without directly participating in the hydrogenation reaction during operation.
2Ease of manufacture
If conventional catalyst activation methods are used, then catalyst preparation is simplified, but catalyst selectivity and activity for simultaneous hydrogenation of acetylene and butadiene is insufficient
Solution Approach 1:
The patent applies preliminary action by performing a specific activation treatment on the nickel catalyst before it is used in the hydrogenation process. The activation involves exposing the catalyst to a mixed gas containing hydrogen and hydrogen sulfide at controlled temperatures, then rapidly heating to high temperature and holding for a specified time. This preliminary treatment modifies the catalyst's structure and properties, ensuring it achieves the required selectivity and activity for simultaneously hydrogenating both acetylene and butadiene while minimizing ethylene hydrogenation.
3Productivity
If zeolite oligomerization catalysts are used in cracked ethane streams containing contaminants, then oligomerization reaction proceeds, but catalyst deactivation occurs rapidly due to coking from acetylene and butadiene
Solution Approach 1:
The patent applies preliminary anti-action by removing acetylene and butadiene contaminants from the cracked ethane stream before the stream enters the zeolite oligomerization catalyst. The modified nickel catalyst selectively hydrogenates these contaminants to less reactive compounds (ethylene and butane) that do not cause rapid coking. This preliminary removal of harmful substances prevents the subsequent deactivation of the zeolite catalyst, thereby extending its operational lifespan while maintaining high oligomerization productivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The modified catalyst effectively removes over 90% of acetylene and butadiene while hydrogenating less than 3% of ethylene, significantly extending zeolite catalyst lifespan and preventing premature deactivation, thus optimizing the conversion process to liquid transportation fuels.
Implementation Method 1
selective hydrogenation of contaminants in a light olefin stream
Implementation Method 2
raising the temperature of the mixed gas in the first reaction zone until a second temperature is reached that is greater than the first temperature
Data Source
AI summary
A process for activating a hydrogenation catalyst comprising nickel to produce a selective hydrogenation catalyst, comprising contacting the hydrogenation catalyst with a mixed gas comprising and hydrogen sulfide and periodically increasing the temperature of the mixed gas in increments until the mixed gas reaches a temperature that facilities the efficient catalytic hydrogenation of both acetylene and butadiene by the modified catalyst, while the modified catalyst is simultaneously characterized by low selectivity for the hydrogenation of ethylene. The disclosure further claims a process that utilizes the modified catalyst to selectively hydrogenate acetylene and butadiene contaminants in a raw light olefin stream produced by thermal cracking, thereby extending the useful catalytic lifespan of a downstream oligomerization catalyst that converts the light olefins stream to a liquid transportation fuel, or a blend stock thereof.