TiCl4 Purification via Tin Reaction for Arsenic Removal
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Solution Overview
Problem
The chloride process for producing TiCl4 results in arsenic contamination, which is difficult to remove due to its similar boiling point with TiCl4, leading to undesirable levels in TiO2 pigment and titanium metal, and existing methods like distillation or carbon adsorption are inefficient or not commercially viable.
Innovation Solution
Using tin metal to selectively remove arsenic from crude TiCl4 through a two-stage process, where tin reacts with arsenic to produce solid arsenic and SnCl4, allowing for effective separation and reduction of arsenic levels without significant yield loss or energy penalty.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If distillation is used to remove AsCl3 from TiCl4, then arsenic concentration is reduced, but TiCl4 yield is significantly lost and energy consumption increases
Solution Approach 1:
The invention changes the chemical state of arsenic from AsCl3 (boiling point 130°C) to solid arsenic (boiling point >1500°C) through reaction with tin metal, creating a large boiling point difference that enables efficient separation by distillation with minimal TiCl4 loss and energy consumption
Solution Approach 2:
Tin metal is introduced as an intermediary substance that reacts with AsCl3 to form solid arsenic and SnCl4, facilitating the separation of arsenic from TiCl4 through subsequent distillation without significant loss of TiCl4
2Manufacturing precision
If carbon adsorption is used to remove AsCl3 from TiCl4, then arsenic is removed to very low levels, but many other species adsorb competitively limiting the capacity and making it not commercially viable
Solution Approach 1:
The invention converts the harmful AsCl3 into solid arsenic through reaction with tin metal, transforming a difficult-to-remove gaseous contaminant into an easily separable solid that can be removed to very low levels without the competitive adsorption problems that limit carbon adsorption capacity and commercial viability
3Loss of substance
If distillation is used to produce highly concentrated AsCl3 product, then yield loss of TiCl4 is reduced, but the AsCl3 product has little commercial value and requires disposal
Solution Approach 1:
The invention converts AsCl3 into solid arsenic through reaction with tin metal, transforming a low-value disposal problem into an easily separable solid that can be removed completely, eliminating the need for concentrated AsCl3 product and its associated disposal challenges
Solution Approach 2:
The invention changes the physical state and boiling point of arsenic from gaseous AsCl3 (130°C) to solid arsenic (>1500°C), enabling complete removal through distillation and eliminating the need to produce or dispose of concentrated arsenic products
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 method efficiently reduces arsenic levels in TiCl4 to meet regulatory standards for TiO2 and titanium metal production, producing a valuable coproduct SnCl4 and reducing disposal challenges and energy consumption, while avoiding the formation of hazardous waste.
Implementation Method 1
tin reacts with arsenic to produce solid arsenic and SnCl4
Implementation Method 2
separating the solid arsenic from the purified TiCl4 and SnCl4
Data Source
AI summary
The present disclosure relates to reacting tin metal with crude TiCl4 containing arsenic to produce pure TiCl4, SnC4, and an arsenic solid co-product. In some embodiments, the contaminant vanadium is removed as well. In another embodiment, the vanadium is removed separately through a commercial process and the resulting arsenic containing commercial grade of purified TiCl4 is reacted with elemental tin, sulfur and ferric chloride to substantially reduce the arsenic. The reaction is preferably done in a continuous fashion in two stages for maximum through-put and utility at an elevated temperature. Distillation can be used to purify the TiCl4 produced and simultaneously yield a purified SnC4 product. The synthesis of SnC4 in this method utilizes waste chloride to save virgin chlorine which would otherwise be used.