Hydroconversion Process for Renewable Diesel Fuel
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Solution Overview
Problem
Existing processes for producing diesel fuel from renewable feedstocks, such as plant oils and animal fats, face challenges in catalyst deactivation due to oxygen-containing molecules like carbon dioxide and water, which are not effectively removed, leading to suboptimal isomerization performance and product quality.
Innovation Solution
A hydroconversion process involving hydrogenation, decarboxylation, and hydrodeoxygenation followed by isomerization, where a selective hot high-pressure hydrogen stripper is used to remove carbon dioxide and water, and additional rectification agents like diesel or naphtha streams are introduced to minimize n-paraffins in the overhead, thereby improving catalyst performance and product quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hydroprocessing is used to convert renewable feedstocks to diesel fuel, then hydrocarbons are produced, but oxygen-containing molecules like carbon dioxide and water cause isomerization catalyst deactivation
Solution Approach 1:
The patent applies extraction by introducing a selective hot high pressure hydrogen stripper that removes oxygen-containing molecules (carbon dioxide, carbon monoxide, and water) from the hydroprocessing effluent before it enters the isomerization zone. This extraction step separates the harmful oxygen-containing components from the hydrocarbon stream, preventing catalyst deactivation while maintaining product yield.
Solution Approach 2:
The patent applies preliminary action by performing the selective removal of oxygen-containing molecules in a hot high pressure hydrogen stripper positioned between the hydroprocessing and isomerization zones. This preliminary treatment prepares the feed stream for isomerization by eliminating substances that would otherwise deactivate the isomerization catalyst, ensuring optimal catalyst performance before the main isomerization reaction occurs.
2Reliability
If a selective hot high pressure hydrogen stripper is used to remove carbon oxides, then catalyst deactivation is prevented, but n-paraffins are carried in the overhead stream reducing product quality
Solution Approach 1:
The patent applies the intermediary principle by introducing a rectification agent (diesel range stream or naphtha range stream) into the hydrogen stripper. This intermediary substance mediates between the need to remove carbon oxides and the need to prevent n-paraffin carryover. The rectification agent facilitates selective removal of oxygen-containing molecules while the rectification zone prevents hydrocarbon products from being carried overhead, thus maintaining product composition quality.
Solution Approach 2:
The patent applies parameter changes by operating the hydrogen stripper at high pressure and elevated temperature (hot high pressure conditions). These parameter changes enable selective removal of oxygen-containing molecules while maintaining hydrocarbons in the liquid phase. The high pressure prevents n-paraffins from vaporizing and being carried overhead, while the elevated temperature facilitates the removal of carbon oxides and water.
3Manufacturing precision
If rectification agents are used to decrease overhead product carryover, then diesel fuel quality is improved, but process complexity increases
Solution Approach 1:
The patent applies multi-functionality by designing the hydrogen stripper to perform multiple functions: (1) selective removal of oxygen-containing molecules in the stripping zone, and (2) prevention of hydrocarbon carryover in the rectification zone. By combining these functions in a single unit operation using a multi-functional device, the patent avoids the need for separate strippers and rectifiers, thereby reducing overall process complexity while achieving both catalyst protection and product quality improvement.
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
This process enhances the production of isoparaffin-enriched diesel fuel by reducing n-paraffins, improving cold flow properties, and allowing operation at lower pressures, thus reducing costs and increasing throughput while maintaining high product quality.
Implementation Method 1
a selective hot high pressure hydrogen stripper is used to remove at least the carbon oxides from the hydrogenation, decarboxylation and/or hydrodeoxygenation zone effluent
Implementation Method 2
The carbon dioxide and water generated as byproducts in the first reaction zone are selectively removed from the first reaction zone product in an integrated hot high pressure stripper using hydrogen as the stripping gas
Implementation Method 3
A diesel range stream or a naphtha range stream, or a mixture of the two streams is used as an additional rectification agent in the selective hot high pressure hydrogen stripper to decrease the amount of product carried in the overhead
Implementation Method 4
treating the feedstock in a first reaction zone by hydrogenating and deoxygenating the feedstock at reaction conditions
Implementation Method 5
hydrogenation, decarboxylation and/or hydrodeoxygenation
Implementation Method 6
isomerization in one or more reactors
Data Source
AI summary
A process has been developed for producing diesel fuel from renewable feedstocks such as plant oils and greases. The process involves treating a renewable feedstock by hydrogenating and deoxygenating i.e. decarboxylating and/or hydrodeoxygenating to provide a hydrocarbon fraction useful as a diesel fuel. If desired, the hydrocarbon fraction can be isomerized to improve cold flow properties. A portion of the hydrogenated and deoxygenated feedstock is selectively separated and then recycled to the treatment zone to increase the hydrogen solubility of the reaction mixture. A diesel range stream or a naphtha range stream, or a mixture of the two streams is used as a rectification agent in the selective hot high pressure hydrogen stripper to decrease the amount of product carried in the overhead.