Composite Catalyst Bed for Selective Phenylacetylene Hydrogenation
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Solution Overview
Problem
Existing processes for removing phenylacetylene from styrene streams in pyrolysis gasoline suffer from low removal rates and high styrene loss, with existing catalysts exhibiting high reaction temperatures, short lifetimes, and inefficient hydrogenation rates.
Innovation Solution
A combined catalyst bed process using a nickel-based catalyst in conjunction with a palladium-based or copper-based catalyst, where the nickel-based catalyst is upstream and the palladium-based or copper-based catalyst is downstream, to achieve high phenylacetylene hydrogenation rates while minimizing styrene loss, with specific catalyst preparations and operating conditions optimizing catalytic activity across a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single catalyst bed with reduced copper compound on θ-alumina support is used, then the hydrogenation of phenylacetylene can be achieved, but the reaction temperature is high (at least 60°C), the hydrogenation rate is low (about 70%), catalyst lifetime is short, and styrene loss is high (about 3%)
Solution Approach 1:
The single catalyst bed is segmented into two separate catalyst beds. The first bed contains a nickel-based catalyst that selectively hydrogenates phenylacetylene to styrene at lower temperatures. The second bed contains a palladium-based or copper-based catalyst that further hydrogenates any remaining phenylacetylene. This segmentation allows each catalyst to operate under optimized conditions, achieving high phenylacetylene conversion (≥95%) while minimizing styrene loss (<0.5%) by avoiding the high temperatures and prolonged exposure required by single-catalyst systems.
Solution Approach 2:
The invention employs composite catalyst systems where different metal catalysts (nickel, palladium, or copper) are used in sequence in separate beds. Each catalyst material has complementary properties: nickel provides high activity at lower temperatures for the first stage, while palladium or copper provides high selectivity and activity for the second stage. This composite approach combines the advantages of different catalyst materials to achieve both high productivity and low styrene loss simultaneously.
2Loss of substance
If a multi-stage catalyst bed reactor with diluent is used, then phenylacetylene removal can be achieved with low styrene loss (about 0.2%), but the process is only effective for low concentration phenylacetylene (300 ppm) and the catalyst exhibits low hydrogenation rate (about 95%)
Solution Approach 1:
The invention optimizes key process parameters including operating temperature (50-150°C, preferably 80-120°C), pressure (0.5-5.0 MPa), and space velocity (0.5-5.0 h⁻¹) to achieve both high phenylacetylene conversion and low styrene loss. The nickel-based catalyst in the first bed operates at lower temperatures than conventional single-catalyst systems, while the second bed with palladium or copper catalyst completes the hydrogenation. This parameter optimization enables the process to handle higher phenylacetylene concentrations (0.03-2.0 wt%) effectively, achieving ≥95% removal with <0.5% styrene loss.
3Measurement precision
If extraction-distillation process is used to separate styrene from phenylacetylene, then separation can be attempted, but effective separation is impossible due to similar chemical structures and interactions with extraction-distillation solvent
Solution Approach 1:
The invention replaces the mechanical separation process (extraction-distillation) with a chemical transformation process (catalytic hydrogenation). Instead of attempting to physically separate phenylacetylene from styrene based on their similar physical and chemical properties, the process chemically converts phenylacetylene to styrene through hydrogenation. This substitution eliminates the fundamental limitation of extraction-distillation and achieves complete separation by transforming the impurity into the desired product.
Solution Approach 2:
The invention converts the harmful presence of phenylacetylene (an impurity that degrades polymer quality) into a beneficial outcome by hydrogenating it to styrene (the desired product). This approach not only removes the impurity but actually increases the yield of the target compound. The phenylacetylene, which would otherwise require complex separation and represent a loss, is transformed into valuable styrene, improving both purity and overall process efficiency.
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 process achieves nearly complete hydrogenation of phenylacetylene with minimal styrene loss, ensuring effective removal of phenylacetylene while maintaining high styrene recovery, even under reduced pressure and varying feedstock compositions.
Implementation Method 1
the nickel-based catalyst is upstream and the palladium-based or copper-based catalyst is downstream, to achieve high phenylacetylene hydrogenation rates
Implementation Method 2
selective hydrogenation of phenylacetylene using composite bed in the presence of styrene
Implementation Method 3
a palladium-based or copper-based catalyst, where the nickel-based catalyst is upstream and the palladium-based or copper-based catalyst is downstream
Data Source
AI summary
The present invention discloses a process for the selective hydrogenation of phenylacetylene in the presence of styrene conducted in a combined bed, which process comprises under hydrogenation reaction conditions, passing a hydrocarbon fraction feedstock containing phenylacetylene and styrene through a combined bed reactor containing a catalyst A and a catalyst B to contact the feedstock with the catalyst A and the catalyst B in turn, wherein the catalyst A is a nickel-based catalyst, the catalyst B is at least one selected from the group consisting of palladium-based catalysts and copper-based catalysts, and a weight ratio of the catalyst A loaded to the catalyst B loaded is from 0.5:1 to 5:1.