Reverse-Flow Reactor for Non-Oxidative Hydrocarbon Conversion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current processes for producing aromatic hydrocarbons, such as benzene, face challenges in achieving high yield with low selectivity for catalyst coke and saturated hydrocarbons like methane, and often require complex and costly methods to manage catalyst deactivation.
Innovation Solution
The process involves discretizing desaturation and aromatization steps into a pyrolysis stage and a catalytic aromatization stage within a tubular flow-through reactor, using a reverse-flow reactor configuration that allows for cyclic operation between regeneration and reaction modes, reducing catalyst exposure to high temperatures and enabling the use of catalysts with greater acidic functionality and lower metal content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional processes operate at high temperature to increase aromatic hydrocarbon yield, then productivity is improved, but catalyst deactivation rate increases due to increased coking
Solution Approach 1:
The reaction process is divided into two distinct stages: a pyrolysis stage for rapid thermal decomposition and an aromatization stage for catalytic conversion. This segmentation allows the pyrolysis stage to operate at high temperature without catalyst present, avoiding coking on the catalyst while still achieving high aromatic yields through subsequent catalytic aromatization.
Solution Approach 2:
The harmful coking process is extracted from the catalytic reaction zone and placed in a separate pyrolysis stage where no catalyst is present. This removes the source of catalyst deactivation while maintaining the beneficial high-temperature conversion pathway.
2Productivity
If steam cracking is used to produce aromatic hydrocarbons, then aromatic yield is improved, but process complexity increases due to required separation and recovery systems
Solution Approach 1:
The process maintains continuous conversion of hydrocarbons to aromatics through coupled pyrolysis and aromatization stages, avoiding the need for intermittent separation and recovery operations required by conventional steam cracking. The catalytic aromatization stage continuously converts pyrolysis products to desired aromatic products.
3Productivity
If naphtha reforming is used to produce aromatic hydrocarbons, then aromatic content is improved, but feedstock utility is reduced since naphtha is needed for other purposes
Solution Approach 1:
The process changes the key parameter of feedstock type from requiring high-quality naphtha to accepting lower-quality gas-phase hydrocarbons. This parameter change enables utilization of feedstocks that would otherwise be unsuitable for aromatization, expanding feedstock flexibility while maintaining aromatic production.
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 approach enhances the selectivity for desired aromatics (BTXN) while minimizing catalyst coke and saturated hydrocarbon production, leading to a more efficient and cost-effective production of aromatic hydrocarbons with improved catalyst longevity.
Implementation Method 1
A hydrocarbon feedstock is contacted with a heated pyrolysis zone for a time and at a temperature sufficient to pyrolyze at least a portion of the hydrocarbons in the hydrocarbon feedstock
Implementation Method 2
The effluent from the pyrolysis stage is contacted with a dehydrocyclization catalyst in a catalytic aromatization stage for a time and at a temperature sufficient to form an aromatized hydrocarbon product
Implementation Method 3
catalytic dehydrocyclization (aromatization) in the same step/zone/reactor
Implementation Method 4
Heat transferred from the hot combustion products to the reaction zone reheats the reaction zone to a temperature sufficient for carrying out dehydrogenation mode operation
Implementation Method 5
The reverse-flow reaction combusts at least a portion of the catalyst coke, which decreases or substantially prevents the accumulation of catalyst coke in the reverse-flow reactor over repeated cycles
Data Source
AI summary
Methods of transforming a hydrocarbon feedstream into an aromatization product in a multi-stage reverse flow reactor (RFR) apparatus are disclosed. The methods include at least two reaction stages in series, at least one being a pyrolysis stage and at least another being a catalytic aromatization stage. Using a highly saturated hydrocarbon feedstream the pyrolysis stage focuses on desaturation, while the catalytic aromatization stage focuses on aromatization. The catalytic aromatization stage contains a aromatization catalyst that can include substantially no magnesium, scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, rhenium, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, copper, silver, gold, gallium, indium, tin, lanthanides, or actinides, or, in some cases, substantially no added active metals at all. The aromatization product can contain at least 35 mol % aromatic hydrocarbons, based on a total amount of hydrogen and hydrocarbons in the aromatized hydrocarbon product.